sustainability
Article Design for Six Sigma (DFSS) Applied to a New E-Segment Sedan
Daniela Francia *, Giampiero Donnici , Gian Marco Ricciardelli and Gian Maria Santi
Department of Industrial Engineering, Alma Mater Studiorum University of Bologna, V.le Risorgimento, 2, 40136 Bologna, Italy; [email protected] (G.D.); [email protected] (G.M.R.); [email protected] (G.M.S.) * Correspondence: [email protected]
Received: 21 October 2019; Accepted: 25 December 2019; Published: 21 January 2020
Abstract: “Innovation activities” means all the scientific, technological, organizational, financial and commercial steps aimed at implementing innovation. Some innovation activities are themselves innovative, others are not new, but they are necessary for the implementation of innovation, such as Research and Development not linked to a specific innovation. Innovation has a close reference to the economic market, that is to say with the users of the innovated product: if these are not sufficiently developed they are not able to understand it and appreciate it. Innovation, making the process better, generates greater competitiveness: it is the dream of something better that translates into general well-being. This work presents an innovative hybrid car’s design, belonging to the E-segment. The choice of this segment is already innovative in its nature, as despite being currently in strong development, hybrid and electric engines are still little used for large sedans. The method we present in this paper for the car design is also innovative and is called Design for Six Sigma. It is a method used to develop new products, through the determination of customer and market needs and the transformation of these requests into the product generated.
Keywords: Design for Six Sigma; Quality Function Deployment; automotive; car; E-segment; sedan; Bench Marking
1. Introduction The Design for Six Sigma consists of a design method for the development of new products that aims to better respect the demands and expectations of the customer. This research is based on products that already exist: the aim is to succeed in eliminating defects and contradictions found in the products on the market, so as to obtain a new product that is more satisfying and innovative. Different approaches exist for the application of the method:
- DMADV; Define, Measure, Analyze, Design and Validate. - CDDOV; Concept, Define, Design, Optimization and Verification phases. - IDOV; Concept, Design, Optimize, Verify. - IDDOV; Identify, Define, Develop, Optimize, Verify. - RADIOV; Requirements, Architecture, Design, Integration, Optimization, Verification.
Although each approach follows its own guideline it is possible to identify some common steps. The basic activities that are carried out in a Design for Six Sigma approach are the following: investigation of customer requests and needs, analysis and classification of such requests, transformation of customer requests into engineering information, design development, verification performance, and implementation of processes in line with the objective to be achieved. Other design methods centered
Sustainability 2020, 12, 787; doi:10.3390/su12030787 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 787 2 of 27 on the innovation enhancement are TRIZ and Design Thinking. TRIZ is the Russian acronym for the “Theory of Inventive Problem Solving,” an international system of creativity developed in the U.S.S.R. between 1946 and 1985, by engineer and scientist Genrich S. Altshuller and his colleagues. According to TRIZ, universal principles of creativity form the basis of innovation. TRIZ identifies and codifies these principles, and uses them to make the creative process more predictable. TRIZ is most useful in roles such as product development, design engineering, and process management. For example, Six Sigma quality improvement processes often make use of TRIZ [1–7]. Design Thinking is a specific method to solve complex (wicked) problems and to generate innovative solutions, based on a user-centered approach with multi-disciplinary teams. Design thinking is becoming more and more popular among business schools, and it is applied in R and D departments of companies to foster innovation. Unlike the typical creative design process, which is usually an intuitive and individual process, design thinking consists of a flexible sequence of process steps and iteration loops, each including several tools and resulting in different artifacts. Since it is the idea of design thinking to be applied by multi-disciplinary teams instead of well-trained designers, an explicit understanding of the process is crucial [8]. Among scientific research and papers connected to the automotive industry, there may be specified few groups of issues examined from the perspective of life-cycle stage of an automobile including (i) development and manufacturing, (ii) use, and (iii) disposal (end-of-life). The recent technology development has led to challenges in the use of vehicles and their disposal (e.g., in considerably reduction of vehicles life cycles). The shortening of product life cycle in the automotive industry has resulted in a growing number of vehicles at the last stage. On the basis of research experience, it was stated that the most challenging phase is end-of-life stage. This issue could be supported by design strategies, as Design for Disassembly (DfD), that help designers to take care of the disassembly of products in order to recycle, reuse, remanufacture, correct disposal [9–11]. In addition, car spare parts play a major role in business, maintenance and repairs due to the short-term orders realization and flexible services [12]. The predictive market gives the possibility of better assessment of trends by questionnaire surveys. This is the result of asking participants not only to perceive reality, but also to estimate probability of the event appearance on the market. Considering specific factors of disassembling business, in literature predictive market has been chosen as appropriate tool for demand for reusable parts forecasting [13]. Taking into account the significance of the disassembling facility, in the context of the company’s activities, there was identified a need to support the decision-making process related to forecasting the demand for spare parts. However, these aspects are only secondary compared to the aim of these paper and they could be further explored in future works.
2. Design for Six Sigma—DMADV The DMADV approach is the most used in the field of Design for Six Sigma and is the one that will be used for our analysis [14]. As previously mentioned, this approach consists of 5 distinct phases: Define, Measure, Analyze, Design, and Validate. Each phase has its own objective; at the end of the last phase it will have come to a design in line with the Design for Six Sigma methodology. 1. Define. During the first phase, information is collected on the client’s requests and needs. Specifically, it is important to note what problems the customer encounters when approaching a specific product already on the market. 2. Measure. In this phase the Quality Function Deployment (QFD) analysis is carried out to translate the customer’s needs into engineering information. In this way it is possible to obtain those characteristics linked to the design that influence the respect or not of the customer’s requests. 3. Analyze. The key features obtained in the second phase are used to conceive the design of the new product. For this purpose, a benchmarking analysis is carried out, which allows to study similar designs of competitive models with the product in question. Sustainability 2020, 12, 787 3 of 27
4. Design. Depending on the results obtained from the analysis phase, we proceed with the design using appropriate software of the new product. In this phase, all the information obtained from
the previousSustainability points 2020 must, 12, x be FOR taken PEER REVIEW into consideration and attempts must be made to respect3 of 29 them to the best. from the previous points must be taken into consideration and attempts must be made to respect Validate. 5. themIn this to the last best. phase, it is stated with certainty that the finished product confirms the expected results.5. Validate It is possible. In this last to producephase, it isprototypes stated with certainty to be tested that the to finished ensure product that the confirms product the is in line with theexpected required results. characteristics. It is possible to produce prototypes to be tested to ensure that the product is in line with the required characteristics. All could be clearerAll could through be clearer the through image the (Figure image (Figure1) below: 1) below:
Figure 1. Design for Six Sigma (DFSS) Structure and Application. Figure 1. Design for Six Sigma (DFSS) Structure and Application. 3. DFSS: DEFINE 3. DFSS: DEFINE This phase involvesThis phase the involves collection the collection of information of informat regardingion regarding the the client’s client’s requestsrequests and and needs. needs. More specifically,More it specifically, is necessary it is necessary to obtain to data obtain on data which on which to rely to rely in in order order to understand understand what what the the product requirementsproduct mustrequirements be. must be. To this end, the use of the QFD as a tool for clarification of the task is useful. This method lends To this end,itself the to use the ofplanning the QFD of each as aph toolase and for therefore clarification can be of used the at task various is useful. levels. The This method method starts lends itself to the planningwith the ofcorrect each identification phase and of thereforeproduct needs, can an be easily used obtainable at various objective, levels. interviewing The method a limited starts with the correctnumber identification of people. of The product questions needs, to be answer an easilyed are obtainablethe following, objective, collected in interviewing Table 1. a limited number of people. The questions to be answered are the following, collected in Table1. Table 1. QFD—Six Questions.
Six Questions Table 1. QFD—Six Questions. Free Answers The product is intended for the population groups that we could identify as Six Questionsthe upper middle class. The car Freewe Answersare going to design falls into the category WHO uses/buysThe product of so-called is intended forExecutive the population cars. groups The clientele that we could is therefore identify as themostly upper composed middle class. of The adult car we are going to design falls into the category of so-called Executive cars. The clientele is therefore mostly composed of WHO uses/buys the product?the product? men over the age of 40 years old. adult men over the age of 40 years old. In addition,In carsaddition, of this kind cars are of also this attractive kind are as regards also attractive the company as car regards or taxi-limousine the company market. car or The producttaxi-limousine by its very nature market. can be identified as a long-distance car, which is ideal for long journeys in comfort WHAT are the uses of the product? and for transportingThe product passengers by its equally very comfortablynature can and be safely. identified The car couldas a thereforelong-distance easily perform car, which the function of a company machine, being suitable for long journeys, also allowing for a possible saving in consumption. WHAT are the is ideal for long journeys in comfort and for transporting passengers equally The product is mainly used outside built-up areas, given its large size and performance characteristics. Its features uses of the make it thecomfortably ideal product and for long safely. journeys The on car suburban could roads therefore and highways. easily perform the function of WHERE is the product used? product? The introductiona company of the electric machine, motor, however,being suitable allows a greaterfor long use also journeys, in the city, also where allowing traveling at lowfor speedsa the electricpossible motor would saving carry in out consumption. much of the task minimizing consumption. Its use is not subjected to seasonality and is almost unchanged throughout the year. Being a car of this type, its use WHEN is the product used? will be dailyThe and product frequent inis mostmainly cases. used outside built-up areas, given its large size and performance characteristics. Its features make it the ideal product for long It guarantees good performance and safety, combined with high comfort and low consumption compared to cars in WHY was it chosen? Why could it WHERE is thethe samejourneys segment. Being on suburban a hybrid vehicle, roads it allows and highways. you to save on fuel, road tax, insurance, and parking, also be chosen? product used?allowing The access introduction to any LTZ. of the electric motor, however, allows a greater use also in HOW is the product used? The productthe is city, used where for long traveling distances and at forlow fast speeds movements. the electric motor would carry out much of the task minimizing consumption. This interview allows the data on the customer to be made explicit, up to a complete list of needs. The list will only contain qualitative data such as ideas, opinions, perceptions, and desires, so the classical methods of relationship between numbers cannot be used to treat similar data. The tools that we are going to introduce later will allow us to treat qualitative data in the same way as numerical data, in order to be able to work on them, comparisons, and classifications. Sustainability 2020, 12, 787 4 of 27
The objective is to elaborate the qualitative data obtained in order to arrive at the product specification. To do this it is necessary to introduce the following tools:
Affinity diagrams • Interrelation matrices • Relationship matrices • Through the affinity diagram, the qualitative information obtained previously is summarized and reclassified into general themes or fundamental ideas. In this way, it is possible to determine the logical groupings of the needs. The data are then collected in homogeneous groups, following the method proposed in [15], and appropriate titles are selected for the groups. We therefore obtain a summary list of the customer’s advanced requests: PRICE: the purchase of hybrid vehicles in Italy is still very limited compared to the purchase of petrol or diesel cars. One of the reasons for this trend is the price that is usually higher than the equivalent models with petrol or diesel engines. Only in recent years has the hybrid become a more solid reality, even in Italy. “Since the beginning of 2018, there has been an increase of 33.1% compared to the same period of the previous year with over 55,000 vehicles registered equal to more than 80% of all those sold in the whole 2017”. “The main reasons that are driving hybrid car sales in recent years are precisely the benefits offered to those who own hybrid or electric cars such as exemption from stamp duty, discounts on RC cars, the possibility of driving in Limited Traffic Zone (LTZ) and parking free in urban centers. Therefore, it is clear that the price of the car and the costs deriving from its use should be minimized as much as possible”. PERFORMANCE: “If, as is true, the performance aspect of hybrid cars is of concern to some motorists, the test numbers show that the performance of hybrid cars is, in principle, similar to those obtained by the corresponding models, with diesel or petrol engines”. When it comes to a segment car from us in analysis, performance plays a fundamental role in the choice of the customer, who expects to have the advantages of a hybrid engine without having a decline in performance. COMFORT: A customer who buys a car belonging to segment E expects to be able to make long journeys in comfort, both for those who drive and for passengers. What is required is adequate space in the passenger compartment, so that the car can comfortably accommodate 5 people. Furthermore, the stresses to which the car is subjected during the journey must be taken into consideration, which in turn affect the driver. In order to offer the maximum possible comfort, it will be necessary to insert the appropriate suspensions and equip the passenger compartment with good sound insulation so as to make the journey more silent. CONSUMPTION: The purchase of a hybrid car is almost always dictated by the customer’s desire to own a car with low fuel consumption. “Beyond the official values communicated by the manufacturers, consumption also fluctuates a lot depending on your driving style, as well as the type of use you make of the car itself. On urban roads, the differential with a single-fueled vehicle will be marked. Tapering as you leave the city and frequent extra-urban contexts. That said, the mixed consumption is always lower than that of an equivalent model exclusively for internal combustion.” LOADING CAPACITY: Anyone who buys a car of this type, even if it is not a station wagon, expects to have a spacious trunk available, which allows it to contain suitcases or other bulky items. The right compromise is therefore sought between elegance of design and load capacity, generally contrasting characteristics. AESTHETICS/DESIGN: Without taking anything away from all the aspects that characterize a car and that guide its choice, the aesthetic aspect that is the car design, it is still one of the most important factors for its sale. It will therefore be necessary to give the car a sleek and elegant appearance. ACCESSORIES: From a car in this segment, for which customers are willing to pay figures of around 50,000 euros or more, the accessories certainly do not pass into the background. When choosing a car, the presence or absence of specific, standard or paid options can make the difference. Sustainability 2020, 12, 787 5 of 27
4. DFSS: MEASURE A study of the items listed in the previous list is now necessary, more precisely we try to highlight any existing dependency relationships. Evaluation matrixes can be used to estimate relative importance or independence relationships among requirements. The interrelation matrix is an instrument evaluating the relationships of dependency (first use) and/or of relative importance (second use) among various necessities or ideas; the instrument is used also to explain priorities and to establish the best arrangement of activities. The dependence between the requirements can be none, weak, medium, or strong. Instead, in the second practice, the matrix is employed to estimate relative importance among all the variables. Through the matrix employment, it is easy to understand that the highest values of the sums per rows specify which is the most important variable among all of them (i.e., those which have more influence on the others). All the matrixes have been formulated by investigating a thematic focus group that is composed by 20 people more or less, chosen among industrial experts, from different kinds of industrial reality, Professors and PhD students from University. Finally, after explanation of the task, the conceptual design starts at first, followed by the constructive one [1–7,16]. The interrelation matrices formulated in this paper provided us with the tools to create a unique ranking. The first matrix we use is the dependency matrix. To build it, perform the following steps:
(1) We put all the items of the customer’s product requirements, both in column and in line (2) We determine the cause and effect relations, the question to ask then will be: the element on the line, how does it depend on the elements on the columns? (3) We indicate by the use of numbers the dependency relation presents between the element in column and the one in line, distinguishing between: none dependence (0), weak dependence (1), average dependence (3), strong dependence (9). (4) We add the indexes of interrelation for rows and for columns.
At this point the matrix is complete and provides us with important information regarding customer requests, as shown in Table2. In fact, by analyzing the table we can draw up a ranking from the most dependent to the most independent request. We can also distinguish between the one that most influences the others and the one that influences the least. The sum of the major line (25) indicates that the “low price” item is the most affected by the others, it is the most dependent. High values are also recorded for the “performance” item. The sum of the major column (24), indicates instead that the “performance” item has the greatest influence on the other quantities. At a single point of distance, we find the entry concerning the “low price”, which as was to be expected is very influential on the other requirements. We now have data relating to the link between the various customer product requirements, but we do not yet have data regarding the relative importance of the various items. To obtain them starting from qualitative data it is necessary to use a second matrix, the matrix of relative importance. The construction is similar to the previous one, but the question that now arises is the following: is the element in the row more important than the element in the column? We use numbers like this:
1 = the row element and the column element have the same importance 0 = the row element is less important than the one in column 2 = the row element is more important than the one in column Sustainability 2020, 12, 787 6 of 27
Therefore, the sum by rows classifies the absolute importance of the quantities compared in a relative way to two by two. The last column contains the values of “normalized importance” that is the values relative to the total, normalized to the maximum value. As shown by the relative importance matrix, detailed in Table3, the item that reaches the maximum value turns out to be “DESIGN” followed by “PERFORMANCE” and “COMFORT”.
Table 2. Independence matrix.
INDEPENDENCE Price Performances Comfort Consumptions Load Capacity Aesthetics/Design Accessories Total (Dependence) MATRIX Price 9 3 1 0 3 9 25 Performances 9 1 9 1 0 0 20 Comfort 3 3 0 3 1 0 10 Consumptions 1 9 1 1 0 0 12 Load capacity 3 3 0 0 0 6 Aesthetics/Design 1 0 0 0 3 1 5 Accessories 9 0 3 0 0 1 13 Total 23 24 11 10 8 5 10 91 (Independence) The color of the numerical values highlight the more important properties derived from the method application.
Table 3. Relative importance matrix.
IMPORTANCE Importance Price Performances Comfort Consumptions Load Capacity Aesthetics/Design Accessories Total MATRIX Normalized Price 1 0 0 1 1 1 1 5 4.5 Performances 2 1 1 1 2 1 1 9 8.2 Comfort 2 1 1 1 2 0 1 8 7.3 Consumptions 1 1 1 1 2 0 1 7 6.4 Load capacity 1 0 0 0 1 0 0 2 1.8 Aesthetics/Design 1 1 2 2 2 1 2 11 10.0 Accessories 1 1 1 1 1 0 1 6 5.5 The item that reaches the maximum value turns out to be “DESIGN” followed by “PERFORMANCE” and “COMFORT”. The color of the numerical values highlight the more important properties derived from the method application.
5. DFSS: ANALYZE To design an innovative hybrid executive car, it is necessary to analyze in depth the models already existing on the market. This process of study and systematic comparison between the various products on the market, takes the name of Benchmarking. Today, Benchmarking is used to indicate the methodology based on systematic comparison that allows companies that apply it to compare with the best and above all to learn from them to improve own performances. Following the benchmarking process there is usually a review of the performance target values to be achieved and the identification of the best practices to be studied and imitated. Once the benchmarking has been defined, the tool we are going to use later is called Top Flop Analysis, a tool that allows you to quickly compare a defined quantity of products on an equally defined number of chosen parameters. For each competitor we have considered pros and cons in terms of performances of each product. More in particular, for each parameter chosen for the comparison, the best and the worst cases, associated to the cars models presented, have been highlighted. At the end, for each car model, the sum of the best and the worst cases has been done, thus evidencing which car model can be considered the best (highest number of best cases) and which one can be considered the worst (highest number of worst cases). The cars being compared, correspond to all the hybrid models existing today, belonging to the Executive car segment. We are now going to illustrate the results of benchmarking in detail in the following sections.
5.1. Benchmarking
5.1.1. Brand and Models Benchmarking The benchmarking analysis highlighted the most relevant brands involved in Hybrid concepts. Sustainability 2020, 12, 787 7 of 27
Table4, that follows, resumed the models available on the market [17–22].
Table 4. Hybrid-models benchmarking.
AUDI A very elegant long sedan that combines a 3000 cc V6 Diesel engine with the Mild-Hybrid system. This system, 48 V only for 6-cylinder versions, is composed as follows: Model: A6 45 A belt start generator (BSG) and a lithium ion battery allow a reduction in fuel consumption and CO emissions thanks to greater energy 3.0 TDI four 2 recovery as well as to the engine cut-out during journeys of less than 60 km/h (inertia gear with zero emissions). tipt The permanent connection of the BSG to the combustion engine ensures comfortable starting with low vibrations. What is surprising about this machine are the high values of expressible torque, which reaches 500 Nm. BMW The latest hybrid version of the BMW 5 series, also on sale since 2018, presents the Plug-in Hybrid technology. Among the most recognizable and noteworthy driving characteristics of BMW plug-in hybrid cars is the quietness and the so-called “electricboosting”. It means that in sudden short-term accelerations, such as overtaking, the electric motor works as a support for the petrol engine, ensuring an even more dynamic drive. The propulsion system consists of a 185 kW (252 hp) 4-cylinder petrol engine with BMW TwinPower Turbo technology, a 70 kW (95 hp) electric motor and a high-voltage lithium-ion battery with a capacity of 9, 2 kWh. Model: 530e The car offers different propulsion modes: The purely electric one is perfect for the city, the hybrid one offers the best possible combination between consumption and performance, while the combustion mode serves to save the battery capacity to drive later in exclusively electric mode. Intelligent energy management optimizes the power-efficiency factor of the hybrid system by choosing the most suitable mode in advance. The most astonishing figure among those collected is the consumption declared by the house, which is practically zero in the urban context thanks to the powerful electric motor which is fitted with Plug-in Hybrid technology. KIA The first goal of KIA for this car is certainly the reduction to the minimum of consumption and the achievement of maximum efficiency. The plug-in hybrid version has several tricks to better puncture the air not only visually but also physically. It has aerodynamic bumpers, ventilation grilles for intelligent radiators, dedicated 17“ wheels for a Cx of 0.25, against 0.27 of the other Optima and 0.24 of the extremely high-profile Toyota Prius. The tricks to make the Optima PHEV more efficient do not stop there, even the air conditioning and Model: Optima heated seats (and, optional, ventilated) play their part with the Driver Only function, which optimizes the driving position and excludes 2.0 GDI Plug-in the rest of the passenger compartment. The regenerative braking system is in its third generation and is 11% more efficient. Hybrid The only engine available in a hybrid version is the 156 Atkinson 2.0 petrol engine coupled to a 68 hp electric motor, powered by a modern 9.8 kWh lithium-ion battery“. This combination makes the Optima Plug-in Hybrid, the car with the least exciting performances, among its hybrid peers, but at the same time equipping it with one of the most capacious batteries on the market, which allows it an exclusively electric range of more than 50 km. The house declares a theoretical consumption of 62.5 km/L and CO2 emissions well below the average. MERCEDES-BENZ The first E-Class with plug-in hybrid technology: the E 350e combines driving performance of surprising agility with driving at zero local emissions. With its traction system that combines internal combustion engine and electric motor, it plays a pioneering role in its category. The hybrid drive consists of a 4-cylinder petrol engine with a power of 155 kW (211 hp) and a maximum torque of 350 Nm and is integrated with an electric motor of 65 kW (88 hp) with maximum torque of 440 Nm. You can travel in pure electric mode for 33 km and reach a maximum speed of 130 km/h. The boost function adds an extra boost and the extra torque of the electric motor ensures a significant increase in agility. The battery recharging speed is the same as for other plug-in vehicles (about 90 min from a wall box/charging station or about 180 min from a domestic power outlet) and the battery can recharge even during charging in Charge Mode or for regeneration. The interaction of the electric motor and internal combustion engine can also be influenced by the mode selector. Depending on the driving program, up to four modes are available: HYBRID: all the hybrid functions of the car are available and are used automatically, depending on the driving situation and the course, to reduce consumption as much as possible. Model: E 350e E-MODE: you can travel on pure electric power, for example in historic centers or when the battery is sufficiently charged to cover the remaining route. E-SAVE: the charge level of the battery is kept constant, to allow driving with pure electric power at a later time. The electric mode is therefore only available to a limited extent. CHARGE: it is useful to recharge the battery while driving, thanks to the internal combustion engine. The electrical operating mode is not possible. Once the destination has been set, using the data provided by the COMAND Online navigation system, the charge and discharge phases of the battery are automatically adjusted to ensure ideal energy exploitation along the entire route. A further innovation presented by Mercedes is the haptic accelerator, which reduces fuel consumption and therefore also exhaust gas emissions. For this purpose, it provides two information: when traveling in E-MODE you feel a resistance point of the accelerator pedal, this means that you have reached the maximum limit of electric power that can be supplied and by pushing on the accelerator beyond this point, the internal combustion engine. LEXUS From the moment you sit behind the wheel, self-recharging batteries are ready to deliver power without the need for any prior charge. Lexus Self-Charging Hybrid technology combines the power of a petrol engine with the efficiency of an electric motor. Thanks to a dedicated control unit, the system is able to decide in complete autonomy when to use one motorization, the other, or both. The system Model: GS 300h constantly monitors the battery charge, providing to recharge it during all the driving phases. As for performance, the Lexus GS 300h is powered by a 2.5-L, 4-cylinder direct-injection petrol engine with 180 hp at 6000 rpm, and a 142-hp electric unit, for a total available power of 223 hp, discharged entirely on the rear wheels. Performance is clearly not a sports car, as reported by the House: the maximum speed is 190 km/h and acceleration from 0 to 100 km/h is completed in 9.2 s. For more sporting performance just buy the older sister, equipped with a 292-horsepower 3.5-L V6 petrol engine, coupled to the hybrid system that includes a 200 hp permanent-magnet synchronous electric motor for a total power of 345 horsepower. Model: GS 450h These propellers move an epicycle gear train to which the generator is also connected: the system then transmits the motion to the rear wheels and acts as a speed change with a continuous variation of ratio (eCvt). This more sporting set-up has a list price of around 75,000 euros, the most expensive model among those analyzed. INFINITI Equipped with a 3.5-L V6 petrol engine, coupled with an electric motor, it delivers 364 horsepower, which allows it to accelerate from 0 to 100 km/h in 5.3 s, an incredible figure considering the car’s weight 1894 Kg. But the advantages do not end there, the Q70 Hybrid is equipped with every type of comfort and cutting-edge technology such as the Model: Q70 Forest Air system that purifies the air, maintains the right level of humidity and releases a slight fragrance inside the cabin. Hybrid The boot is a bit limited for this version due to the presence of lithium ion batteries. Another positive point to note is a very large tank (70 L), which however will be emptied faster than the others, as the Q70 is the car with the highest fuel consumption declared among its peers. Sustainability 2020, 12, 787 8 of 27
Table 4. Cont.
VOLVO Starting from 2017, even S90 like other Volvo cars before, adopts Twin Engine technology. This technology, as we have already seen for other hybrid cars, is of the Plug-In Hybrid type. More than that, the Twin Engine consists of using the following system: 1. -PETROL ENGINE 2. CISG UNIT (Crank-Integrated Starter Generator) 3. REAR ELECTRIC MOTOR (ERAD—Electrical Rear Axel Drive) Model: S90 4. LITHIUM ION BATTERY AND COOLING SYSTEM But the S90 is still a step ahead, being equipped with the T8 Twin Engine AWD engine, available only for the 90 range, which guarantees absolute performance with very low emission levels even for small hybrids. The T8 Twin Engine AWD is the result of the combination of a 2-L four-cylinder petrol engine with turbocharger and volumetric compressor and an electric motor, and is capable of delivering an astonishing total power—402 hp and 400 Nm—comparable to that of engines with multiple cylinders. The petrol engine drives the front wheels while the rear ones receive traction from the electric motor, providing instant acceleration and all-wheel drive when needed. In the “Pure” mode, with the use of the electric motor only, there are zero emissions and up to 50 km of autonomy. In the “Hybrid” mode consumption is enviable and the emissions are extremely reduced.
5.1.2. Benchmarking and Top-Flop Analysis Once you have gathered as much information as possible on the cars just listed, the real Top/Flop analysis begins: you decide to compare the various cars using a certain number of parameters, which give an overview of the fundamental characteristics of the car and that are relevant for a subsequent project of a similar car (Table4). For each parameter, the best and worst values are then identified, among those of the cars compared, coloring the green or red boxes respectively. The purpose of this analysis is to determine on each object compared what is innovative and what is not. This tool is very useful because, if you consider the best values of each car compared, you can get a set of starting values for the creation of an innovative car. The cars were compared using the following parameters: Length, width, height, weight, luggage capacity, number of seats, and number of doors: relating to the appearance of the car and its dimensions. Power supply, power, displacement, maximum speed, acceleration 0–100 km/h and maximum torque: related to the actual performance of the car. Theoretical autonomy, electric autonomy, battery power, and time for a complete charge: characteristics relating to the electric motorization. Price For each of these parameters, the “best value” was sought, that is, what is deemed to be preferable by the customer. Therefore, depending on the case, in green or in red we will have the highest or the lowest value. For example, regarding the dimensions (LENGTH, HEIGHT, WIDTH), we chose to consider smaller values as “better”. As regards the capacity of the tank and the boot, the highest value obtained is considered to be the best. Once the table is drawn up, we insert below it an additional table (present in the image), where we report for each car compared, the number of best values (TOP) and the number of worst values (FLOP) obtained (Table5). Making the di fference between the number of TOP values and the number of FLOP values we get DELTA. The ∆ represents the innovativeness of the car as it is obtained as a gap between the values identified as best and those identified as worst. The sedans that turn out to be the most innovative are those with ∆ greater. Creating a more innovative car will mean overcoming or equaling the found, to do so it is sufficient that the ∆ of the designed car is greater than the highest delta obtained among the cars in the table. Once the maximum is known, we take the “best values” or TOP values, relative to each parameter individually, and insert them in the column next to the table, which takes the name of innovation column and for reasons of space has not been inserted previously. SustainabilitySustainabilitySustainability 2020 2020 2020, 12, 12,, , 12 x, x,FOR, xxFOR FORFOR PEER PEER PEERPEER REVIEW REVIEW REVIEWREVIEW 11 11 11 11 of of of of 29 29 29 29 SustainabilitySustainabilitySustainability 2020 ,2020 12, 2020x, 12FOR,, x12 FORPEER, x FOR PEER REVIEW PEER REVIEW REVIEW 11 of 11 29 of 11 29 of 29 The maximum value of the sum of the column indicates which parameter is the most important The ThemaximumTheTheThe maximum maximum maximum maximum value value value ofvalue value the of of ofsumthe of the the thesum ofsum sum sumthe of of ofcolumnthe of the the thecolumn column column column indicates in in dicatesin indicatesdicates dicateswhich which which whichparameterwhich parameter parameter parameter parameter is the is is mosttheis isthe the themost mostimportant most most important important important important in order to reach the customer’s requests. in orderinin inorderinin order toorderorder order reach to to toreachto to reach thereachreach reach customer’sthe the thethe thecustomer’s customer’s customer’scustomer’s customer’s requests. requests. requests. requests.requests. requests. Now let’s highlight the parameters that have obtained the highest values of the column sums: NowNow Nowlet’sNowNow let’s highlightlet’s let’s let’s highlight highlight highlight highlight the parametersthe the the theparameters parameters parameters parameters that that have that that that have haveobtained have have obtained obtained obtained obtained the highestthe the the thehighest highest highest highest values values values values valuesof the of of ofcolumnthe of the the thecolumn column column column sums: sums: sums: sums: sums: - DISPLACEMENT, POWER, ACCELERATION, and MAXIMUM TORQUE: These four - - DISPLACEMENT,- --- DISPLACEMENT,DISPLACEMENT,DISPLACEMENT,DISPLACEMENT, POWER, POWER, POWER,POWER,POWER, ACCELERATIO ACCELERATIO ACCELERATIOACCELERATIOACCELERATION, N,andN,N, N, and andMAXIMUMandand MAXIMUM MAXIMUMMAXIMUMMAXIMUM TORQUE: TORQUE: TORQUE:TORQUE:TORQUE: These These These TheseThesefour four fourfourfour parameters are redundant, they are all related to the performance and therefore to the car’s parametersparametersparametersparametersparameters are areredundant, are are areredundant, redundant, redundant,redundant, they they theyare theythey areall are are arerelatedall all allallrelated related relatedrelated to the to to totheperformanceto the the theperformance performance performanceperformance and and thereforeand andand therefore therefore thereforetherefore to the to to tothecar’sto the the thecar’s car’s car’scar’s engine, so it will be sufficient to improve one only of them to obtain an increase of the others. engine,engine,engine,engine,engine, so it so willso so itso it willit beitwill will willsufficient be be be sufficientbe sufficient sufficient sufficient to improve to to toimprove to improve improve improve one oneon one one lyone on ofon only on themly lyoflyly of ofthemof of them to themthem them obtain to to toobtainto to obtain obtain obtainanobtain increase an an an anincreasean increase increaseincrease increase of the of of ofothers.ofthe of the thethe theothers. others. others.others. others. - PRICE - - PRICE- --- PRICEPRICEPRICE PRICE - AVERAGE CONSUMPTION - - AVERAGE- --- AVERAGEAVERAGEAVERAGEAVERAGE CONSUMPTION CONSUMPTION CONSUMPTION CONSUMPTION CONSUMPTION Then going on to analyze the line sums, we note that the larger values are obtained from the ThenThen ThengoingThenThen going going going ongoing toon on analyzeon onto to to analyzeto analyze analyze analyze the theline the the the line sums,line line line sums, sums, sums, wesums, notewe we we wenote thatnote note note that thethat that that thelarger the the thelarger larger larger valueslarger values values values valuesare areobtained are are areobtained obtained obtained obtained from from from thefrom from the the the the entries: entries:entries:entries:entries:entries: - LOW PRICE - - LOW- --- LOWLOW PRICELOWLOW PRICE PRICE PRICE PRICE - PERFORMANCE - - PERFORMANCE- --- PERFORMANCEPERFORMANCEPERFORMANCEPERFORMANCE - LOW CONSUMPTION - - LOW- --- LOWLOW CONSUMPTIONLOWLOW CONSUMPTION CONSUMPTION CONSUMPTION CONSUMPTION This means that these three requirements are the most influenced by the parameters studied and ThisThis meansThisThisThis means means means meansthat that these that that that these thesethree these these three threerequirements three three requirements requirements requirements requirements are thare aree are aremostth th eth themoste mosteinfluenced most most influenced influenced influenced influenced by the by by by parameterstheby the the theparameters parameters parameters parameters studied studied studied studied studied and and and and and therefore also easier to obtain thereforethereforethereforethereforethereforetherefore also also easier also alsoalso also easier easier easiereasierto easier obtain to to toobtainto to obtain obtain obtainobtain Based on the information collected, we aim to design an innovative hybrid sedan, improving the BasedBasedBased BasedonBased the on on on informationtheon the the theinformation information information information collected, collected, collected, collected, collected, we aimwe we we we aimto aim aim designaim to to todesign to design design designan innovative an an an innovativean innovative innovative innovative hybrid hybrid hybrid hybrid hybridsedan, sedan, sedan, sedan, improvingsedan, improving improving improving improving the the the the the followingfollowingfollowingfollowingfollowingfollowing 3 parameters: 3 3 parameters: 3 3parameters:3 parameters:parameters: parameters: Sustainability 2020, 12following, 787 3 parameters: 9 of 27 - Power (weight-power ratio) - - Power- --- PowerPowerPower Power(weight-power (weight-power (weight-power (weight-power (weight-power ratio) ratio) ratio) ratio) ratio) - Price - - Price- --- Price PricePricePrice - Average consumption Each value- - Average- will --- AverageAverageAverage beAverage consumption accompanied consumption consumption consumption consumption by a
TableTableTable 5.TableTable Benchmarking 5. 5. Benchmarking5. 5.Benchmarking Benchmarking Benchmarking and Topand and and and TopFlop Top Top Top Flopanalysis Flop Flop Flop analysis analysis analysis analysis table. table. table. table. table. Table 5. BenchmarkingTable 5. Benchmarking and Top and Flop Top Flop analysis analysis table. table. BrandBrandBrand BrandBrand AUDIAUDIAUDI AUDIAUDI BMW BMWBMW BMWBMW KIA KIAKIAKIAKIA MERCEDES MERCEDESMERCEDESMERCEDESMERCEDES LEXUS LEXUS LEXUS LEXUS LEXUS INFINITI INFINITI INFINITI INFINITI INFINITI VOLVO VOLVOVOLVOVOLVOVOLVO BrandBrand AUDI AUDI BMW BMW KIA KIA MERCEDES MERCEDES LEXUS LEXUS INFINITI INFINITI VOLVOVOLVO ModelModel A6 A6 5 Series 5 Series Optima Optima E Class E Class GS GS 300h 300h GS GS 450h 450h Q Q70 70 S90 S90 ModelModelModelModel Model A6 A6 A6 A6 A6 5 Series 5 5Series Series5 Series Optima Optima Optima Optima Optima E Class E E EClass ClassClass E Class GS GS300h GS GS 300h 300h GS 300h 300h GS GS 450h GS GS 450h 450h GS 450h 450h Q Q70 70 Q Q70 Q70 70 S90 S90 S90 S90 S90
TOPTOP FLOPTOPTOPTOP FLOP FLOP FLOP FLOP TOP FLOPTOP ANALYSIS FLOP ANALYSISANALYSIS ANALYSISANALYSISANALYSISANALYSIS Lenght [mm] 4940 4940 4860 4920 4880 4880 4980 4960 LenghtLenghtLenghtLenght [mm]Lenght [mm] [mm] [mm] [mm] 4940 4940 4940 4940 4940 4940 4940 4940 4940 4940 4860 4860486048604860 4920 4920492049204920 4880 4880 4880 4880 4880 4880 4880488048804880 4980 4980498049804980 4960 4960496049604960 WidthLenght [mm] [mm] 49401890 4940 1870 4860 1860 4920 1850 1840 4880 18404880 18504980 1880 4960 WidthWidthWidthWidth [mm] [mm] [mm] [mm] 1890189018901890 1870187018701870 1860 1860 1860 1860 1850 1850 1850 1850 1840184018401840 1840184018401840 1850185018501850 1880 1880 1880 1880 HeightWidthWidth [mm] [mm] 18901890 1460 18701870 1480 1860 1860 1470 1850 1850 1470 1840 14601840 1840 14601840 185014901850 1440 1880 1880 HeightHeight [mm] [mm] 1460 1460 1480 1480 1470 1470 1470 1470 1460 1460 1460 1460 14901490 14401440 HeightWeightHeightHeight [mm]Height [kg] [mm] [mm] [mm] 1460 1460 1900 1460 1460 1480 1480 18451480 1480 1470 1470 1470 1780 1470 1470 1470 1925 1470 1470 14601735 1460 1460 1460 1460 1825 1460 1460 1460 1490 18941490 14901490 201914401440 14401440 WeightWeight [kg] [kg] 1900 1900 1845 1845 1780 1780 1925 1925 17351735 18251825 1894 1894 20192019 TrunkWeight capacityWeightWeight Weight[kg] [dm [kg] [kg]3 ][kg] 1900 1900530 1900 1900 1845 1845 1845 410 1845 1780 1780 1780307 1780 1925 1925540 1925 1925 1735 4501735 17351735 1825 4501825 18251825 1894 350 1894 1894 1894 50020192019 20192019 TrunkTrunkTrunk capacityTrunkTrunk capacity capacity capacity capacity SupplyTrunk capacity 530 HYB.530530530530 410 410 HYB.410410410 307 307 HYB.307307307 540 HYBRID 540540540540 450 HYB 450450450450 450 HYB. 450450450450 350 HYB. 350350350350 HYB.500 500500500500 3[dm3[dm[dm3]3 33]3] 530 410 307 540 450 450 350 500 Displ.[dm [cm[dm] [dm[dm]3] ] ] 2967 1998 1999 1991 2494 3456 3498 1969 SupplySupply HYB.HYB. HYB.HYB. HYB.HYB. HYBRHYBRIDID ID HYBHYBHYB HYB.HYB.HYB. HYB. HYB. HYB. HYB. HYB. HYB. PowerSupply [Kw]SupplySupply Supply HYB. 210HYB. HYB. (286)HYB. HYB. 185HYB. HYB.HYB. (252) HYB. HYB.151 HYB.HYB. (205) HYBR HYBR 210HYBRIDHYBR (286)IDID ID HYB 164HYB (223)HYBHYB HYB. 254HYB. (345) HYB.HYB. 268 HYB. (364) HYB. HYB. HYB. 296 HYB. (402) HYB. HYB. HYB. Displ.Displ.3 [cm [cm3]3 33]3] 296729672967 199819981998 199919991999 1991 1991 1991 2494 2494 2494 345634563456 34983498 19691969 MaxDispl. Sp.Displ.Displ. [cm [kmDispl. /[cm]h] [cm [cm3] ] ] 29672967 25029672967 1998 1998 1998 2351998 1999 1999 1999 1921999 1991 1991 2501991 1991 2494190 2494 2494 2494 34562503456 34563456 34982503498 34983498 25019691969 19691969 Acceleration PowerPower [Kw] [Kw] 210 210 6.3(286) (286) 185 185 (252) 6.2 (252) 151151 (205)9.4 (205) 210 210 6.2(286) (286) 164 9.2 164 (223) (223) 254 5.9 254 (345) (345) 5.3268 268 (364) (364) 5.1296296 (402) (402) 0–100PowerPower kmPower [Kw]Power/h [s] [Kw] [Kw] [Kw] 210 (286) 210 210 210(286) (286) 185(286) (252) 185 185 185(252) (252) (252)151 (205)151 151 151(205) (205) (205) 210 (286) 210 210 210(286) (286) (286) 164 (223) 164 164 164(223) (223) (223) 254 (345) 254 254 254(345) (345) (345) 268 (364) 268 268 268(364) (364) (364) 296 (402)296296 296(402) (402) (402) Max Tor. [Nm] 500 290 189 350 221 352 350 400 MaxMax Sp. Sp. [km/h] [km/h] 250250 235235 192 192 250 250 190190 250250 250250 250250 MaxPriceMax Sp.Max [Euro]Max [km/h]Sp. Sp. Sp.[km/h] [km/h] [km/h] 250 64.000250250 250 235 235 65.000235 235 192 19244.000 192 192 250 68.000 250 250 250 190 58.000 190190 190 25075.000 250250 250 250 65.000 250250 250 73.000250 250250 250 Tank [liter] 63 46 55 66 66 66 70 50 AccelerationAccelerationAccelerationAccelerationAcceleration Av. Cons.Acceleration [L/100 km] 6.3 5.676.36.36.3 6.3 6.2 6.2 1.96.26.2 6.2 9.4 9.49.41.79.4 9.4 6.2 6.2 2.66.26.2 6.2 9.2 4.9 9.2 9.2 9.2 9.2 5.9 6.35.95.95.9 5.9 5.36.7 5.3 5.3 5.3 5.3 2.15.1 5.15.15.1 5.1 0–1000–100 0–100km/h0–1000–100 km/h km/h[s] km/h km/h [s] [s] [s] [s] 6.3 6.2 9.4 6.2 9.2 5.9 5.3 5.1 CO Em.0–100 [g /km/hkm] [s] 146 44 37 57 113 145 145 46 2 MaxMax Tor. Tor. [Nm] [Nm] 500500 290290 189189 350350 221 221 352352 350350 400 400 MaxTh.Max AutTor.MaxMax [km]Tor.[Nm] Tor. Tor. [Nm] [Nm] [Nm] 500 500500 500 290 290 2300290 290 189 1893400189 189 350 350 2380350 350 221 1400 221 221 221 3521100 352352 352 350 1127 350350 350 2500 400 400 400 400 PricePrice [Euro] [Euro] 64.000 64.000 65.000 65.000 44.00044.000 68.00068.000 58.000 58.000 75.00075.000 65.00065.000 73.000 73.000 El.Price AutPrice [Euro]Price [km]Price [Euro] [Euro] [Euro] 64.000 64.000 64.000 3 64.000 65.000 65.000 65.000 4665.000 44.000 44.00044.000 44.00054 68.000 68.00068.000 3368.000 58.000 58.000 58.000 58.000 75.000 75.00075.000 75.000 65.000 65.00065.000 65.000 73.000 40 73.000 73.000 73.000 TankTank [liter] [liter] 63 63 46 46 55 55 66 66 66 66 66 66 70 70 50 50 BatteryTankTank [liter]Tank [kWh]Tank [liter] [liter] [liter] 63 631.3 63 63 46 46 9.246 46 55 55559.8 55 66 66 6.2 66 66 66 66 66 66 66 66 66 66 70 7070 70 9.250 5050 50 ChargingAv. Cons.Av.Av.Av.Av. timesCons. Cons.[L/100 Cons. Cons. [h][L/100 [L/100 [L/100 [L/100 4 6 3 4 Av. Cons. [L/100 5.67 5.675.675.675.67 1.9 1.91.91.9 1.9 1.7 1.71.71.7 1.7 2.6 2.62.62.6 2.6 4.9 4.9 4.9 4.9 4.9 6.3 6.36.36.3 6.3 6.7 6.76.76.7 6.7 2.1 2.12.12.1 2.1 km]km] 5.67 1.9 1.7 2.6 4.9 6.3 6.7 2.1 Numberkm] of km] TOPkm]km] 2 0 7 2 2 2 3 2 Number of FLOP 4 1 5 0 1 2 3 2 CO2 COEm.COCOCO2 2[g/km]Em. 2Em.2 2 Em.Em. Em. [g/km] [g/km] [g/km][g/km] [g/km] 146 146146146146 44 4444 4444 37 3737 3737 57 5757 5757 113 113 113 113 113 145 145145145145 145 145145145145 46 46 46 46 46 DeltaCO2 Em.∆ [g/km] 1462 44 137 257 2 1113 0145 0145 0 46 − − Th.Th. Aut Aut [km] [km] 23002300 34003400 23802380 1400 1400 11001100 11271127 2500 2500 Th. AutTh.Th. Th.Aut[km] Aut Aut [km] [km]The [km] cells colored 2300 in2300 red23002300 and 3400 in3400 green34003400 evidenced 23802380 23802380 the best1400 1400 and 1400 1400 worst 1100cases.1100 11001100 11271127 11271127 2500 2500 2500 2500
After completed, the TOP-FLOP analysis is possible to collect all the targets that performances of the new car must reach, by collecting the data into an Innovation List Targets Table (Table6).
Table 6. Innovation list targets table.
Innovation Column Ideal Car Lenght [mm] <4860 Width [mm] <1840 Height [mm] <1440 Weight [kg] <1735 Trunk capacity [dm3] >540 Supply HYBRID Displacement [cm3] >3500 Power [Kw (hp)] >296 (402) Max Speed [km/h] >= 250 Acceleration 0–100 km/h [s] <5,1 Max Torque [Nm] >500 Price [Euro] <44.000 Tank [liter] >70 Average Consumptions [L/100 km] <1.7 CO2 Emissions [g/km) <37 theoretical Autonomy [km] >3400 Electric Autonomy [km] >54 Battery [kWh] >9.8 Charging times [h] <3
Moreover, in order to understand which of these parameters is most advantageous to improve, we use an additional tool, the what-like matrix. Sustainability 2020, 12, 787 10 of 27
The customer’s requirements (what) are compared to the designer’s answers (how) (Table7).
Table 7. What/how matrix. ] 100 km] h [s] ] 3 / / 3 h] km) / / Total Supply Tank [L] Weight [kg] Width [mm] Price [Euro] Emissions [g Height [mm] Lenght [mm] Battery [kWh] 2 Power [Kw (hp)] Max Torque [Nm] Max Speed [km Charging times [h] Displacement [cm Trunk capacity [dm CO WHAT-HOW MATRIX Electric Autonomy [km] Acceleration 0-100 km theoretical Autonomy [km] Average Consumptions [L
Price 1 9 9 3 9 9 9 1 1 1 1 53 Performances 3 3 3 9 9 9 9 3 9 3 1 3 1 1 66 Comfort 9 9 9 1 3 3 1 35 Consumptions 3 3 9 3 1 1 1 9 9 9 9 3 1 61 Aesthetics/Design 1 1 1 1 3 3 10 Total 10 10 10 9 6 6 21 21 13 19 19 18 0 19 12 11 13 5 3
A matrix is then prepared with in line the requirements to be satisfied and in column the means that make the realization of that requirement possible. In line we then insert the customer’s needs and in the column the parameters used to perform the Top Flop Analysis, modifying which, it will be possible to meet the customer’s requests. The client’s requirements listed above will not all be entered in the table, but will be filtered so as to insert only the items that have obtained the highest values in the interrelation matrices. Also, in this case numerical evaluations on the type of relation will be used: nothing (empty box, equivalent to 0), weak (1), medium (3), strong (9). We then found the sums by rows and by columns: The maximum value of the line sum indicates which requirement is the most influenced by the parameters in the column. The maximum value of the sum of the column indicates which parameter is the most important in order to reach the customer’s requests. Now let’s highlight the parameters that have obtained the highest values of the column sums: - DISPLACEMENT, POWER, ACCELERATION, and MAXIMUM TORQUE: These four parameters are redundant, they are all related to the performance and therefore to the car’s engine, so it will be sufficient to improve one only of them to obtain an increase of the others. - PRICE - AVERAGE CONSUMPTION Then going on to analyze the line sums, we note that the larger values are obtained from the entries: - LOW PRICE - PERFORMANCE - LOW CONSUMPTION This means that these three requirements are the most influenced by the parameters studied and therefore also easier to obtain Based on the information collected, we aim to design an innovative hybrid sedan, improving the following 3 parameters: - Power (weight-power ratio) - Price - Average consumption A more detailed study of the possible viable solutions is now necessary in order to improve the parameters. Sustainability 2020, 12, 787 11 of 27 Sustainability 2020, 12, x FOR PEER REVIEW 13 of 29
Power The choice of power as a parameter to be increased was dictated by its strong influenceinfluence on the performance of thethe machinemachine bothboth inin termsterms ofof acceleration,acceleration, maximummaximum speed,speed, torque,torque, etc.etc. What is is going going to to affect affect power power is isclearly clearly the the choice choice of the of thepropulsion propulsion group. group. The choice The choice of a high- of a high-performanceperformance heat engine heat engine can be can ideal be idealfor achieving for achieving high hightorque torque and acceleration and acceleration values, values, which which give givethe car the a carsportier a sportier character. character. At thethe same same time, time, a very a very heavy heavy engine engine would worsenwould theworsen car’s performancethe car’s performance in terms of consumption.in terms of Theconsumption. right compromise The right must compromise therefore must be sought therefore that be allows sought good that allows results good to be results achieved to be in achieved terms of performance,in terms of performance, without a substantial without a increasesubstantial in theincrease price in and the consumption price and consumption of the car. of the car. This leads us to an important firstfirst choice,choice, whichwhich typetype ofof hybridhybrid shouldshould bebe used?used? Depending on the degree of hybridization, threethree didifferentfferent typestypes ofof hybridhybrid cancan bebe defined:defined: a. Full hybrid or full hybridization cars: this this type type of hybrid cars adopts the classic heat engine, petrol or diesel, one or more electric motors of rather high power, a 400 Volt electricelectric system and batteries of such a capacity as to allow the car to travel a few kilometres in purely electric mode i.e., zero emissions.emissions. TheThe twotwo motorsmotors are are normally normally coupled coupled via via a a CVT CVT continuously continuously variable variable transmission transmission or viaor via a converter a converter or double-clutch or double-clutch automatic automatic transmission. transmission. The symbiosis The symbiosis of the twoof the engines, two engines, the thermal the andthermal the electricand the one, electric is then one, guaranteed is then guaranteed by the electronics by the that electronics manage theirthat manage operation, their allowing operation, both enginesallowing to both obtain engines and guarantee to obtain and the bestguarantee total e ffitheciency. best total Precisely efficiency. for this Precisely reason fullfor hybridthis reason cars full are ablehybrid to movecars are forward able to using move only forward the heat using engine only or the just heat the electricengine motoror just or the the electric combination motor of or both the (Figurecombination2). of both (Figure 2).
Figure 2. Full hybrid car architecture [[23].23].
The same heat engine, in case it was needed, can be declined in addition to traction even when recharging the samesame batterybattery pack.pack. Furthermore, Furthermore, th thee heat heat engine is always switched off off when not necessary, suchsuch asas duringduring stops, or the car can be left sailing with both engi enginesnes disconnected. Finally, Finally, in the deceleration and braking phases, the electric motor is used as a current generator to implement regenerative braking so as to recharge the batterybattery pack by exploitingexploiting the kinetic energy that would otherwise be lost in heat in the brakes. b. Mild hybrid or light hybridization vehicles vehicles:: t thishis type of hybrid cars adopts the classic heat engine, petrol or diesel, an electric motor/generato motor/generatorr of modest or reduced power (replacing the classic alternator), aa 4848 VoltVolt electrical electrical system system and and lithium-ion lithium-ion batteries batteries of of smaller smaller capacity, capacity, separated separated from from the restthe rest of the of electricalthe electrical system, system, which which allows allows the car the to car travel to severaltravel several hundred hundred meters meters with only with electric only tractionelectric traction (Figure 3(Figure). The real3). The novelty real novelty of the mild of the hybrid mild systemhybrid issystem the 48 is Volt the electrical48 Volt electrical system which,system replacingwhich, replacing the high the voltage high systemvoltage (400system Volt) (400 of theVolt full) of hybrid the full systems, hybrid goessystems, alongside goes alongside the classic the 12 classic 12 Volt electrical system. This design choice has allowed on the one hand to adopt 48 Volt motors and battery packs so up to 4 times more powerful than the 12 Volt ones, on the other hand to Sustainability 2020, 12, 787 12 of 27
Volt electrical system. This design choice has allowed on the one hand to adopt 48 Volt motors and Sustainability 2020, 12, x FOR PEER REVIEW 14 of 29 battery packs so up to 4 times more powerful than the 12 Volt ones, on the other hand to limit the limitvoltages the voltages so as to reduce so as to the reduce cable sizethe cable by as size much by as as 75% much so as to75% contain so as costs,to contain dimensions costs, dimensions and weight andof the weight wiring. of the As wiring. with full As hybrids, with full if hybrids, more power if more is required,power is required, the electric the motor electric/generator motor/generator gives its givesadditional its additional boost to the boost heat to engine. the heat In deceleration engine. In ordeceleration braking, on or the braking, other hand, on the the other engine hand,/generator the engine/generatoracts as a brake to acts charge as a the brake battery to charge with energythe battery that wouldwith energy otherwise that would be lost. otherwise be lost.
Figure 3. Mild hybrid car architecture [24]. Figure 3. Mild hybrid car architecture [24]. c. Plug-in hybrid cars: This type of hybrid cars fully reflects those just described of the full hybrid type,c. withPlug-in the hybrid only di cars:fference This thattype they of hybrid add a cars power fully socket reflects for those recharging just described the battery of the pack full hybrid via the type,mains with (home the oronly post) difference and a battery that they pack add of a greater power capacitysocket for allowing recharging in this theso battery the hybrid pack via car the can mainstravel (home a greater or distancepost) and in a purely battery electric pack of mode, greater that capacity is to say allowing with zero in emissions. this so the For hybrid the restcar theycan travelare identical a greater to distance full hybrid in carspurely and electric therefore mode, share that their is to strengths say with and zero weaknesses emissions. inFor addition the restto they the areconstruction identical to scheme full hybrid (Figure cars4). and therefore share their strengths and weaknesses in addition to the constructionCase Study scheme Choice. (Figure After 4). the above mentioned analysis, project choice falls on a full Hybrid petrol engine, which does not require an external recharge and is therefore more suitable for long journeys without the need for frequent recharges. Furthermore, having to design an E-segment sedan, which will be used more frequently in suburban areas, the high electrical autonomy of Plug-In hybrids is not necessary. This choice makes it possible to minimize the size and weight of the electric motor by optimizing the efficiency of the machine in terms of consumption and performance. As for the type of engine, it was decided to use the same engine as the Lexus 450 h, which is capable of delivering 345 horsepower. Therefore, the actual power of the car will not be the highest among those analyzed, because the use of an even more powerful engine would lead to a further increase in costs and consumption. For this reason, the parameter that we propose to improve will be the weight-power ratio.
Price The total price of the motorcycle will be determined both by the quality and quantity of the components used, which affect variable costs, and by project and management costs, or fixed costs, compared to the number of volumes, all multiplied by a coefficient k (typically values less than 3 are not used). Unit Price = [Variable Costs + Fixed Costs Sales Volumes] k Figure 4. Plug-in hybrid car architecture× [25]. ×
Case Study Choice. After the above mentioned analysis, project choice falls on a full Hybrid petrol engine, which does not require an external recharge and is therefore more suitable for long journeys without the need for frequent recharges. Furthermore, having to design an E-segment sedan, which will be used more frequently in suburban areas, the high electrical autonomy of Plug-In hybrids is not necessary. This choice makes it possible to minimize the size and weight of the electric Sustainability 2020, 12, x FOR PEER REVIEW 14 of 29
limit the voltages so as to reduce the cable size by as much as 75% so as to contain costs, dimensions and weight of the wiring. As with full hybrids, if more power is required, the electric motor/generator gives its additional boost to the heat engine. In deceleration or braking, on the other hand, the engine/generator acts as a brake to charge the battery with energy that would otherwise be lost.
Sustainability 2020, 12, 787 13 of 27
In particular, under the heading of fixed costs all expenses related to the phases of research and development must be included, therefore costs of prototyping, analysis of the materials and work of the engineers, then the expenditure on production plants and the cost of services, electrical, logistics and marketing. Among all the items that are part of the costs, we are able to intervene exclusively on the expenses related to the design and construction of the car itself. The elements that can determine a price increase/decrease are mainly the following:
- Presence of accessories - Engine Figure 3. Mild hybrid car architecture [24]. - Use of expensive materials c. Plug-in hybrid cars: This type of hybrid cars fully reflects those just described of the full hybrid type,It with will the therefore only difference be necessary that they to design add a apower car that socket has thefor recharging necessary accessoriesthe battery forpack a via saloon the ofmains this (home type, butor post) without and ana battery excess ofpack technology of greater that capacity would allowing lead to in a risethis inso prices.the hybrid As alreadycar can mentioned,travel a greater the distance right compromise in purely electric between mode, performance that is toand say costwithof zero the emissions. propulsion For system the rest will they be sought.are identical Finally, to full it will hybrid be necessary cars and therefore to study solutionsshare their that strengths allow to and achieve weaknesses optimal in results addition with to the useconstruction of low-cost scheme materials. (Figure 4).
Figure 4. Plug-in hybrid car architecture [[25].25].
AverageCase Consumptions Study Choice. After the above mentioned analysis, project choice falls on a full Hybrid petrolThe engine, presence which of thedoes hybrid not require engine generallyan external allows recharge to save and more is therefore than 25% more of fuel suitable compared for long to a petroljourneys engine. without To makethe need our for car frequent even cheaper, recharges. it will Fu berthermore, essential having that the to electric design motoran E-segment and the sedan, petrol enginewhich will are managedbe used asmore effi cientlyfrequently as possible in suburban by the areas, electronics, the high so aselectrical to exclusively autonomy use theof Plug-In electric motorhybrids whenever is not necessary. possible This and choice save the makes battery it possible instead whento minimize on suburban the size roads. and weight of the electric An innovative solution already used by Mercedes could be the haptic accelerator, which by providing a resistance on the accelerator pedal, indicates that the maximum limit of deliverable electric power has been reached and pushing the accelerator beyond this point the engine would start to operate internal combustion. This would allow a more informed guide by the user, followed by a not inconsiderable reduction in consumption. Even the size of the rims is not negligible in a maximum efficiency optic, the use of smaller rims leads to lower consumption but less rigidity and road holding. The weight of the car will be even more important in this respect. Reducing it would have benefits in all areas that we set out to improve. Therefore, a further study will be required to reduce the weight of the car as much as possible. Sustainability 2020, 12, x FOR PEER REVIEW 16 of 29 doesSustainability not require 2020, 12 the, x FOR maximum PEER REVIEW possible machining precision, however the dimensions that 16define of 29 the attachment points of the various organs must be scrupulously respected. During vehicle operation,does not require the frame the ismaximum subjected possibleto various machining and complex precision, mechanical however stresses, the dimensions which cannot that always define Sustainabilitybethe accurately attachment2020 ,assessed12 ,points 787 duringof the thevarious design organs phase. must In principle, be scrupulously the frame respected. must meet During the following vehicle14 of 27 requirements:operation, the frame is subjected to various and complex mechanical stresses, which cannot always be accurately(1) Be built assessed with material during having the design high fatiguephase. resistance.In principle, the frame must meet the following 6.requirements: DFSS:(2) Having DESIGN a shape that offers good resistance to deformation. After(3)(1) HaveBe collecting built a relatively with some material low information weight having so necessaryhigh as tofatigue keep for theresistance. the weight-power design of the car, ratio we low. move on to the design of the chassis,The(2) Having types choosing of a framesshape the thattypeused offers that for road best good suitsmachinery resistance the type are to of deformation.the car. following: InFRAMES(3) general, Have aWITH relatively the frame LONGWAYS low has weight the dual AND so purposeas toCROSSPIECES keep of the ensuring weight-power (lad theder connection frame): ratio low. It ofconsists the various of a groupspair of makingparallelThe upspars types the connected vehicleof frames and usedtogether carrying for roadby the simple machinery body crossbars. and theare load.the The following: The side construction members and of across frame members of this type are doesfitted notFRAMES with require appropriate WITH the maximum LONGWAYS brackets, possible brackets AND machining and CROSSPIECES supports precision, for attaching(lad howeverder frame): the suspensions dimensions It consists thatand of definefora pair fixing the of attachmenttheparallel various sparspoints groups connected of making the various together up the organs vehicleby simple must itself. be crossbars. scrupulously Depending The respected. onside the members type During and and shape vehicle cross of operation, themembers body and theare framethefitted loading iswith subjected appropriateand use to conditions, various brackets, and the brackets complex side members and mechanical supports take different stresses, for attaching forms which the(Figures cannot suspensions always5 and 6). beand accurately for fixing assessedthe variousAdvantages: during groups the This designmaking type phase. ofup frame the In vehicle principle,is simple itself. and the Depending frameinexpensive must on meet to the design thetype following and build;shape requirements: presentsof the body a great and versatilitythe loading as and different use conditions, bodies can the be side mounted members on thtakee same different frame. forms It has (Figures good flexural 5 and 6). strength and (1)stiffnessBeAdvantages: built and withdiscreet materialThis torsional type having of framestiffness high is simple fatigue when andequipp resistance. inexpensiveed with suitable to design reinforcements. and build; presents It is used a great in (2)vehiclesversatilityHaving suitable as a different shape for heavy that bodies o fftransport,ers can good be resistancewithmounted high on tovertical deformation.the same loads frame. supported It has by good sturdy flexural side members,strength and or (3)instiffness allHave those and athat relatively discreet do not lowtorsionalrequire weight excellent stiffness so as todriv when keeping theequippprecision weight-powered within their suitable use ratio (off-road low.reinforcements. or SUV). It is used in vehiclesDisadvantages: suitable for Asheavy long transport, as the structure with high remain verticals two-dimensional, loads supported bythat sturdy is without side members, calculating or The types of frames used for road machinery are the following: thein all additional those that strength do not andrequire stiffness excellent of the driv body,ing evenprecision if properly in their rein useforced (off-road it has or a SUV).torsional stiffness FRAMES WITH LONGWAYS AND CROSSPIECES (ladder frame): It consists of a pair of parallel muchDisadvantages: lower than that As of alllong the as other the structuretypes of known remain frames.s two-dimensional, that is without calculating spars connected together by simple crossbars. The side members and cross members are fitted with the additionalWith equal strength rigidity, and the stiffness weight isof 10–15% the body, higher even thanif properly the monocoque. reinforced it has a torsional stiffness appropriatemuch lower brackets, than that brackets of all the and other supports types of for known attaching frames. the suspensions and for fixing the various groupsWith making equal up rigidity, the vehicle the weight itself. is Depending 10–15% higher on the than type the and monocoque. shape of the body and the loading and use conditions, the side members take different forms (Figures5 and6).
Figure 5. Ladder frame, first configuration. Figure 5. Ladder frame, first configuration. Figure 5. Ladder frame, first configuration.
Figure 6. Ladder frame, second configuration Figure 6. Ladder frame, second configuration Advantages: This type of frame is simple and inexpensive to design and build; presents a great versatilityBACK as SPROCKET different bodies (chassis canFigure bebackbone) 6. mounted Ladder: frame,This on the type second same of configurationframe frame. consists It has good of a flexuralcentral tunnel strength with and a stirectangularffness and section discreet or torsional a tube frame. stiffness The when so-called equipped “backbone” with suitable connects reinforcements. the front axle with It is usedthe rear in vehiclesaxle andBACK suitable provides SPROCKET for all heavy the mechanical(chassis transport, backbone) with strength high: verticalThisof the type car loads ofby frame supporteditself. consistsThe bysubstructures sturdy of a central side members,supporting tunnel with or the in a allsuspensions,rectangular those that section domasses not requireor and a tubeengine excellent frame. are integral drivingThe so-called to precision the tunnel.“backbone” in their The useBackbone connects (off-road theChassis or front SUV). is axle very with suitable the rear for carsaxle withDisadvantages: and twoprovides and four all As the seats, long mechanical where as the the structure strength size of remainsthe of tunnelthe car two-dimensional, can by beitself. used The as ansubstructures that armrest is without between supporting calculating the seats. the theThesuspensions, additional greater the masses strength height and andof enginethe sti fftunnelness are of integralthe the greater body, to the eventhe tunnel. torsional if properly The stiffness Backbone reinforced (in Chassis any it has case a is torsional greatervery suitable than stiffness the for muchladdercars with lower frame). two than and that four of seats, all the where other the types size of of known the tunnel frames. can be used as an armrest between the seats. The Withgreater equal the rigidity,height of the the weight tunnel is the 10–15% greater higher the thantorsional the monocoque. stiffness (in any case greater than the ladderBACK frame). SPROCKET (chassis backbone): This type of frame consists of a central tunnel with a rectangular section or a tube frame. The so-called “backbone” connects the front axle with the rear axle and provides all the mechanical strength of the car by itself. The substructures supporting the suspensions, masses and engine are integral to the tunnel. The Backbone Chassis is very suitable for cars with two and four seats, where the size of the tunnel can be used as an armrest between the seats. Sustainability 2020, 12, 787 15 of 27
The greater the height of the tunnel the greater the torsional stiffness (in any case greater than the Sustainability 2020, 12, x FOR PEER REVIEW 17 of 29 ladder frame). Advantages: The “chassis backbone” or tunnel frame is strong enough for small sports cars. It Advantages: The “chassis backbone” or tunnel frame is strong enough for small sports cars. It has a torsional stiffness that is not very high but still superior to that of the “ladder frame”. Simple to has a torsional stiffness that is not very high but still superior to that of the “ladder frame”. Simple to build by hand and economically for small production volumes. build by hand and economically for small production volumes. Disadvantages: Does not protect against side impacts. It requires additional reinforcements in the Disadvantages: Does not protect against side impacts. It requires additional reinforcements in bodywork and is inconvenient for high production volumes (Figure7). the bodywork and is inconvenient for high production volumes (Figure 7).
FigureFigure 7.7. ChassisChassis backbone.backbone.
TUBULARTUBULAR FRAMEFRAME (space (space frame) frame): In: someIn some sports sports cars of verycars limitedof very production limited orproduction competition, or framescompetition, with a frames high sti withffness a/ weighthigh stiffness/weight ratio are obtained ratio by are joining obtained tubes. byIf joining the frame tubes. has If been the frame designed has correctly,been designed the forces correctly, coming the from forces the suspension coming from attachments the suspension are discharged attachments on several are pipes,discharged lowering on theseveral amount pipes, of mechanicallowering the stress. amount The tubesof mechanical can have distress.fferent The sections tubes depending can have ondifferent the direction sections of thedepending stress: a on round the direction section is of used the tostress: withstand a round possible section impacts is used havingto withstand an unknown possible direction, impacts insteadhaving elliptical,an unknown square direction, or rectangular instead sectionselliptical, are square used whenor rectangular the stress sections is known are or used slightly when variable the stress in the is directionknown or to slightly favor resistance variable orin thethe sti directionffness of to the favor pipe inresistance one direction or the over stiffness another. of the pipe in one directionThese over cars another. have a remarkable lightness also because it is possible to use bodies built with low-densityThese cars metal have alloys a remarkable (aluminum-based) lightness oralso with because very lightit is possible complex to polymeric use bodies materials built with that low- do notdensity have metal a load-bearing alloys (aluminum-based) function in most or cases. with very light complex polymeric materials that do not haveA a tubularload-bearing frame, function in its simplest in most configuration, cases. consists of a welded tube truss and does not alone performA tubular the task frame, of withstanding in its simplest all stresses; configuration, even the consists engine of and a welded some bodywork tube truss wallpaper and does not can alone have aperform supporting the task function. of withstanding A tubular frame all stresses; “space frame”even the is byengine definition and some a reticular bodywork structure wallpaper formed can by tiehave rods a andsupporting struts connected function. togetherA tubular so asframe to form “space triangular frame” geometries. is by definition This frame, a reticular in its currentlystructure moreformed complex by tie configuration,rods and struts consists connected of various together types so as of elementsto form triangular of different geometries. materials and This processing frame, in technologies,its currently more which complex can be theoretically configuration, independently consists of various designed. types Whether of elements it is a simpleof different tubular materials frame orand space processing frame, thetechnologies, structure is which designed can to be have theore a verytically high independently stiffness. designed. Whether it is a simpleAdvantages: tubular frame The or tubular space frame, frame isthe very structur resistante is designed compared to tohave the a frame very high with stiffness. longitudinal and crossAdvantages: members or toThe the tubular monocoque frame frame is very (see resistant next paragraph) compared for to thethe sameframe weight; with longitudinal it also has high and sticrossffness members/weight or ratios, to the exceeded monocoque only frame by carbon (see next fiber pa frames.ragraph) for the same weight; it also has high stiffness/weightDisadvantages: ratios, Complex exceeded and only expensive, by carbon it requiresfiber frames. long manufacturing times. Not robotically feasible.Disadvantages: Raise the lower Complex threshold and ofexpensive, the doors, it making requires living long spacemanufacturing difficult (Figures times. 8Not and robotically9). feasible.LOADING Raise the BODY lower (unibody) threshold: of The the bearing doors, making body in living pressed space steel difficult sheet has (Figures for decades 8 and been 9). the most adopted solution by all the automotive industries for standard production cars, so much so that it is used by 95% of the vehicles currently in production. The main reason lies in the general qualities, in the cheapness and in the great adaptability to the automated production, coupled to the good level of the obtained performances [26–30]. The body is defined as a carrier when it has a mechanical resistance such as to support its own weight and that of the various groups making up the vehicle. In this way, a single structure is created to which the engine and the other vehicle groups are applied directly. What we try to achieve in any case is a high torsional rigidity, to prevent the deformation of the monocoque affecting the road holding. In fact, if the body is subjected to forces that subject it to torsion, the vibrations have a similar frequency Figure 8. The space frame, first configuration. Sustainability 2020, 12, x FOR PEER REVIEW 17 of 29
Advantages: The “chassis backbone” or tunnel frame is strong enough for small sports cars. It has a torsional stiffness that is not very high but still superior to that of the “ladder frame”. Simple to build by hand and economically for small production volumes. Disadvantages: Does not protect against side impacts. It requires additional reinforcements in the bodywork and is inconvenient for high production volumes (Figure 7).
Figure 7. Chassis backbone.
TUBULAR FRAME (space frame): In some sports cars of very limited production or competition, frames with a high stiffness/weight ratio are obtained by joining tubes. If the frame has been designed correctly, the forces coming from the suspension attachments are discharged on several pipes, lowering the amount of mechanical stress. The tubes can have different sections depending on the direction of the stress: a round section is used to withstand possible impacts having an unknown direction, instead elliptical, square or rectangular sections are used when the stress is known or slightly variable in the direction to favor resistance or the stiffness of the pipe in one direction over another. These cars have a remarkable lightness also because it is possible to use bodies built with low- density metal alloys (aluminum-based) or with very light complex polymeric materials that do not have a load-bearing function in most cases. A tubular frame, in its simplest configuration, consists of a welded tube truss and does not alone perform the task of withstanding all stresses; even the engine and some bodywork wallpaper can have a supporting function. A tubular frame “space frame” is by definition a reticular structure formed by tie rods and struts connected together so as to form triangular geometries. This frame, in Sustainabilityits currently 2020 more, 12, x complexFOR PEER configuration,REVIEW consists of various types of elements of different materials 18 of 29 and processing technologies, which can be theoretically independently designed. Whether it is a simple tubular frame or space frame, the structure is designed to have a very high stiffness. Advantages: The tubular frame is very resistant compared to the frame with longitudinal and Sustainabilitycross members2020, 12 or, 787 to the monocoque frame (see next paragraph) for the same weight; it also has16 high of 27 stiffness/weight ratios, exceeded only by carbon fiber frames. or at theDisadvantages: limit coinciding Complex with that and of expensive, damping the it requires suspensions, long formanufacturing this reason there times. is a Not negative robotically effect forfeasible. stability. Raise the lower threshold of the doors, making living space difficult (Figures 8 and 9).
Figure 9. The space frame, second configuration.
LOADING BODY (unibody): The bearing body in pressed steel sheet has for decades been the most adopted solution by all the automotive industries for standard production cars, so much so that Sustainability 2020, 12, x FOR PEER REVIEW 18 of 29 it is used by 95% of the vehicles currently in production. The main reason lies in the general qualities, in the cheapness and in the greatFigure adaptability 8. The space to the frame, automated first configuration. production, coupled to the good level of the obtained performances [26–30].Figure 8. The space frame, first configuration. The body is defined as a carrier when it has a mechanical resistance such as to support its own weight and that of the various groups making up the vehicle. In this way, a single structure is created to which the engine and the other vehicle groups are applied directly. What we try to achieve in any case is a high torsional rigidity, to prevent the deformation of the monocoque affecting the road holding. In fact, if the body is subjected to forces that subject it to torsion, the vibrations have a similar frequency or at the limit coinciding with that of damping the suspensions, for this reason there is a negative effect for stability. Figure 9. The space frame, second configuration. Advantages: The monocoqueFigure 9. frame The space (steel frame, unibod secondy) configuration.generally has a very economical base materialAdvantages: (low carbon The steel monocoque sheet: 0.8% frame by (steel weight). unibody) A great generally economy has for a very high economical productions, base with material high (low carbon steel sheet: 0.8% by weight). A great economy for high productions, with high investments investmentsLOADING only BODYin the initial (unibody) phase: Theof production bearing body (high in costpressed of the steel molds). sheet Fullhas adaptabilityfor decades beento mass the only in the initial phase of production (high cost of the molds). Full adaptability to mass production. production.most adopted Good solution behavior by all to the crash. automotive Excellent industri use of esspace, for standard with high production habitability cars, and so accessibility. much so that Good behavior to crash. Excellent use of space, with high habitability and accessibility. it is usedDisadvantages: by 95% of the Intrinsic vehicles heaviness, currently with in production. the same torsionalThe main stiffness, reason lies compared in the general to the qualities, tubular Disadvantages: Intrinsic heaviness, with the same torsional stiffness, compared to the tubular frame,in the cheapnessdue to the andquantity in the of great material adaptability used. High to the costs automated for vehicles production, with low coupled to medium to the production good level frame, due to the quantity of material used. High costs for vehicles with low to medium production volumesof the obtained (Figure performances 10). [26–30]. volumes (Figure 10). The body is defined as a carrier when it has a mechanical resistance such as to support its own weight and that of the various groups making up the vehicle. In this way, a single structure is created to which the engine and the other vehicle groups are applied directly. What we try to achieve in any case is a high torsional rigidity, to prevent the deformation of the monocoque affecting the road holding. In fact, if the body is subjected to forces that subject it to torsion, the vibrations have a similar frequency or at the limit coinciding with that of damping the suspensions, for this reason there is a negative effect for stability. Advantages: The monocoque frame (steel unibody) generally has a very economical base material (low carbon steel sheet: 0.8% by weight). A great economy for high productions, with high investments only in the initial phase of production (high cost of the molds). Full adaptability to mass production. Good behavior to crash. Excellent use of space, with high habitability and accessibility. Figure 10. Unibody. Disadvantages: Intrinsic heaviness, Figurewith the 10. sameUnibody. torsional stiffness, compared to the tubular frame,CARBONCARBON due to the FIBER quantity SHELL: of material Carbon used. fiber fiber Highis the costs most for sophisticated vehicles with material low to available medium productiontoday; today; it it is is usedusedvolumes for for high-class high-class(Figure 10). or or competition competition sports cars. Th Thee carbon carbon fiber fiber bodies bodies have have the the highest highest performance performance ever,ever, at least as regards the stistiffness-to-weightffness-to-weight and strength-to-weight ratio; but their adoption on on standardstandard cars cars presents presents some some problems problems both both from from the the economic economic point point of view of view determined determined by the by cost the ofcost the of material, the material, and andfrom from the theproductive productive one one det determinedermined by by the the impossibility impossibility of of automating automating the the production process itself causing in fact a a great great sl slownessowness of of processing; processing; moreover moreover the the recyclability recyclability of of thethe material material in in the the event event of of a a collision is also difficult. difficult. Advantages:Advantages: The The carbon carbon fiber fiber body body is is the the lightest lightest and and most most rigid rigid structure structure available available today today for for a car.a car. Disadvantages: The basic raw material is very expensive and the manufacturing process is very slow, therefore, it is not suitable for mass production (Figure 11).
Figure 10. Unibody.
CARBON FIBER SHELL: Carbon fiber is the most sophisticated material available today; it is used for high-class or competition sports cars. The carbon fiber bodies have the highest performance ever, at least as regards the stiffness-to-weight and strength-to-weight ratio; but their adoption on standard cars presents some problems both from the economic point of view determined by the cost of the material, and from the productive one determined by the impossibility of automating the production process itself causing in fact a great slowness of processing; moreover the recyclability of the material in the event of a collision is also difficult. Advantages: The carbon fiber body is the lightest and most rigid structure available today for a car. Sustainability 2020, 12, x FOR PEER REVIEW 19 of 29
SustainabilityDisadvantages:2020, 12, 787 The basic raw material is very expensive and the manufacturing process is17 very of 27 slow, therefore, it is not suitable for mass production (Figure 11).
Figure 11. CarbonCarbon fiber fiber shell.
6.1. Choice Choice of of the the Frame Frame Type Type Once allall thethe possibilities possibilities have have been been analyzed, analyzed, a tubular a tubular type type frame frame is chosen. is chosen. This choice This choice is driven is drivenby the needby the to need design to adesign car that a car has that a high has power a high/weight power/weight ratio; the ratio; tubular the frame tubular in fact,frame for in the fact, same for theweight, same is weight, more resistant is more than resistant all other than types all other of frame. types These of frame. features These allow featur us toes create allow a us lighter to create frame, a lighterwithout frame, weakening without the structureweakening and the maintaining structureadequate and maintaining stiffness for adequate the car’s stiffness required for performance. the car’s required performance. 6.2. Choice of the Material 6.2. ChoiceThe choice of the ofMaterial the material of which the frame will be made, will be influenced by the needs and objectives that we have set before: The choice of the material of which the frame will be made, will be influenced by the needs and objectives- Decrease that inwe the have price set ofbefore: the car - Decrease in consumption - Decrease in the price of the car -- DecreaseIncreased in power consumption/weight ratio - IncreasedIt is clear thatpower/weight a reduction ratio in the weight of the car positively influences 2 of the 3 objectives we set ourselves. It is clear that a reduction in the weight of the car positively influences 2 of the 3 objectives we In fact, in the normal urban/highway cycle only 25% of the engine power is needed to overcome set ourselves. the air resistance, instead 70–75% is related to the weight of the car. The inertia forces that manifest In fact, in the normal urban/highway cycle only 25% of the engine power is needed to overcome themselves in the acceleration or braking phase, the resistant components in uphill routes, the rolling the air resistance, instead 70–75% is related to the weight of the car. The inertia forces that manifest friction forces and the friction in the transmission mechanisms depend on the weight. The reduction themselves in the acceleration or braking phase, the resistant components in uphill routes, the rolling in the weight of the car would therefore allow a simultaneous improvement in performance and a friction forces and the friction in the transmission mechanisms depend on the weight. The reduction reduction in consumption. in the weight of the car would therefore allow a simultaneous improvement in performance and a We must not forget that even the price of the car is among the objectives to be minimized, so it will reduction in consumption. be necessary to choose a relatively cheap material. Once the required properties of the material that We must not forget that even the price of the car is among the objectives to be minimized, so it will make up the machine frame have been identified, the vehicle is equipped with an aluminum frame. will be necessary to choose a relatively cheap material. Once the required properties of the material The choice is mainly guided by the lightness properties of aluminum, which has a density equal to that will make up the machine frame have been identified, the vehicle is equipped with an aluminum one third of that of steel, as shown in Table8. This feature makes it possible to build lighter structures, frame. although the weight of the structure will not respect the proportion between the densities. This will The choice is mainly guided by the lightness properties of aluminum, which has a density equal be due to the use of larger and therefore heavier diameter pipes, to guarantee greater rigidity to the to one third of that of steel, as shown in Table 8. This feature makes it possible to build lighter aluminum frames. Nevertheless, weight reduction will be significant, bringing the desired benefits. structures, although the weight of the structure will not respect the proportion between the densities. Furthermore, aluminum does not suffer from the problem of rust or even the typical weakening of This will be due to the use of larger and therefore heavier diameter pipes, to guarantee greater rigidity the areas affected by welding. Or rather, the welding weakens the frame anyway, but it is possible to to the aluminum frames. Nevertheless, weight reduction will be significant, bringing the desired return practically to the original resistance values with appropriate treatments, which, unfortunately, benefits. Furthermore, aluminum does not suffer from the problem of rust or even the typical cannot be carried out for steel. weakening of the areas affected by welding. Or rather, the welding weakens the frame anyway, but it is possible to return practically Tableto the 8. originalMaterials’ resistance density comparison.values with appropriate treatments, which, unfortunately, cannot be carried out for steel. DENSITY
Material d kg/dm3 Aluminum 2.70 Titanium 4.50 Steel 7.80 Sustainability 2020, 12, 787 18 of 27
These properties, combined at a cost that is still more limited than more valuable materials, such as carbon fiber or titanium, make aluminum the best material for the tubular frame that we’re going to design. Clearly the material that will make up the frame will not be pure aluminum, but its alloy, this solution will allow us to have better mechanical properties and to choose from a wide range of alloys. Now let us list the main aluminum alloys and their properties in Table9.
Table 9. The main aluminum alloys’ properties.
ALLUMINIUM ALLOYS’ CHARACTERISTICS This composition is characterized by excellent corrosion resistance, high thermal and electrical Series 1000 conductivity, low mechanical properties and excellent workability. It is possible to have hardenings for cold working. The presence of copper allows for an increase in properties following heat treatment, which can be further Series 2000 improved with artificial aging. These alloys are often plated with high purity 6000 and 7000 alloys which give physical and electrolytic protection to the heart and increase the resistance to corrosion Manganese is the most common alloy; they are thermally untreatable alloys and possess a high resistance Series 3000 to corrosion and high formability. Series 5000 Magnesium gives good weld ability and excellent corrosion resistance. The simultaneous presence of silicon and magnesium determines the possibility of heat treatment; they Series 6000 have good formability, high resistance to corrosion with high mechanical properties. Series 7000 It has good mechanical properties but a high cost.
Looking for a compromise between alloys with good mechanical properties and low price, we discard the alloys of the 6000 and 7000 series, which despite having excellent mechanical properties, have too high a cost that would meet our goal of containing the price. We then choose a 2000 series alloy, which will be subjected to heat treatment, in order to obtain an improvement in mechanical performance.
6.3. Design of the Frame After choosing the material, all that remains is to start with the actual design of the frame. For a correct design it is necessary to know first the height, length, and width of the car. With these data it is possible to make a first sketch of the car’s floor, equipped exclusively with side members, flame arrester, luggage compartment, and special spaces for the wheels [31–33].
6.3.1. Static Verification Every time a sketch is completed, a static analysis of the structure created must be carried out, to verify that it responds adequately to the loads and that there are no points of weakness or errors in the design. All this is accomplished through a simulation software, which will allow to have information about:
- Stress - Deformation - Moving
The following loads are applied to the structure:
- Motor weight - Weight of frame + body + windows (estimated) - Weight of the 2 front passengers (75 kg each) - Weight of the 3 passengers behind (75 kg each) - Full tank weight - Full boot weight Sustainability 2020, 12, x FOR PEER REVIEW 21 of 29
The following loads are applied to the structure: - Motor weight - Weight of frame + body + windows (estimated) - Weight of the 2 front passengers (75 kg each) - Weight of the 3 passengers behind (75 kg each) - Full tank weight - Full boot weight Once all the calculations and estimates have been made, it is possible to apply the individual loads to the relative components of the frame on which they rest. Once this is done, the constraints are imposed on the structure, consistent with the wheel-frame Sustainability 2020, 12, 787 19 of 27 coupling. The study is then carried out which will highlight the tensions, deformations, and displacements to whichOnce the all structure the calculations is subjected. and estimates have been made, it is possible to apply the individual loads to the relative components of the frame on which they rest. FrameOnce without this Plates is done, the constraints are imposed on the structure, consistent with the wheel-frame coupling. The initial sketch of the frame includes the insertion of the platform, the firewall, the tubes that The study is then carried out which will highlight the tensions, deformations, and displacements will make up the bonnet and the rear part relative to the trunk. The first sketch is certainly the most to which the structure is subjected. difficult to make as it is necessary to be able to match all the frame sizes, so as not to have any Framesurprises without later when Plates going to perform the verification in Layout, inserting seats, mannequins, and wheels (Figure 12). TheAs you initial can sketch see, in of fact, the framethe three includes crossbars the insertion that extend of the over platform, the entire the firewall,length of the the tubes platform that will are makedeliberately up the bonnetat different and thedistances rear part from relative each toother, the trunk.this because The first when sketch we is would certainly later the go most to insert difficult the toseats, make it aswill it isbe necessarynecessary to to be have able more to match space all av theailable frame underneath sizes, so as passengers’ not to have anyfeet. surprises This solution later whenallows going us to toinstall perform the seats the verification lower down, in Layout, gaining inserting space in seats,height. mannequins, and wheels (Figure 12).
FigureFigure 12.12. Frame without plates designed.
AsWe you will can now see, proceed in fact, theto the three analysis crossbars of thatthe extendstructure over following the entire the length parameters of the platform previously are deliberatelyindicated (Figures at different 13–15) distances [32,33]. from each other, this because when we would later go to insert the seats, it will be necessary to have more space available underneath passengers’ feet. This solution allows us to install the seats lower down, gaining space in height. We will now proceed to the analysis of the structure following the parameters previously indicated (Figures 13–15)[32,33]. All of the analyses are displayed in the “deformed state” function of the program that helps the understanding of the user by highlighting the structure deformation. From the first analysis we can consider ourselves very satisfied, in all three fields in fact, the frame reacts well to the loads to which it is subjected. The maximum load is in fact 13.8 MPa, an acceptable value considering that the chosen material has a yield strength of 290 MPa. As expected, the most stressed area appears to be the platform that has the maximum displacements. Even in this case, however, the result is more than acceptable. In addition to verifying the most stressed areas, it is equally important to check which areas are less subject to loads and deformations so as to be able to perform a possible under sizing that allows to reduce the weights and the overall dimensions. As we can see, in fact, the upper beams that make up the trunk are practically free of loads, so you choose to eliminate the rear beam, so as to have easier access to the trunk and a lower weight of the structure. Although the structure has achieved reasonable results, it is clear that further reinforcement and stiffening is required in specific areas. Therefore, some sheets are added to connect the various beams, so as to have a more uniform distribution of the loads and a greater rigidity of the structure. Sustainability 2020, 12, 787 20 of 27
Sustainability 2020, 12, x FOR PEER REVIEW 22 of 29 SustainabilitySustainability 20202020,, 1212,, xx FORFOR PEERPEER REVIEWREVIEW 22 22 of of 29 29
Figure 13. Maximum load: 13.8 MPa. FigureFigureFigure 13. 13.13. MaximumMaximum load:load: 13.813.8 MPa.MPa.
Figure 14. Maximum deformation 0.0001. FigureFigure 14.14.14. MaximumMaximum deformationdeformation 0.0001.0.0001.
Figure 15. Maximum displacement: 1.4 mm. Figure 15. Maximum displacement: 1.4 mm. FigureFigure 15.15. Maximum displacement: 1.4 mm. All of the analyses are displayed in the “deformed state” function of the program that helps the FrameAllAll with ofof thethe Plates analysesanalyses areare displayeddisplayed inin thethe “deformed“deformed state”state” functionfunction ofof thethe programprogram thatthat helpshelps thethe understanding of the user by highlighting the structure deformation. understandingunderstanding ofof thethe useruser byby highlihighlightingghting thethe structurestructure deformation.deformation. FromThe the structure first analysis (Figure 16we) presentscan consider the sheets ourselves exclusively very satisfied, in the fundamental in all three points, fields theirin fact, presence the FromFrom thethe firstfirst analysisanalysis wewe cancan considerconsider ourselvesourselves veryvery satisfied,satisfied, inin allall threethree fieldsfields inin fact,fact, thethe framein fact reacts influences well to significantly the loads to the which weight. it is The subjec thicknessested. The and maximum the position load of is thein sheetsfact 13.8 were MPa, decided an frameframe reactsreacts wellwell toto thethe loadsloads toto whichwhich itit isis subjecsubjected.ted. TheThe maximummaximum loadload isis inin factfact 13.813.8 MPa,MPa, anan acceptablefollowing value various considering static analyses that the of chosen which wematerial are now has going a yield to showstrength the of final 290 results MPa. (Figures 17–19). acceptableacceptable valuevalue consideringconsidering thatthat thethe chosenchosen materialmaterial hashas aa yieldyield strengthstrength ofof 290290 MPa.MPa. As expected, the most stressed area appears to be the platform that has the maximum AsAs expected,expected, thethe mostmost stressedstressed areaarea appearsappears toto bebe thethe platformplatform thatthat hashas thethe maximummaximum displacements. Even in this case, however, the result is more than acceptable. displacements.displacements. EvenEven inin thisthis case,case, howevehowever,r, thethe resultresult isis moremore thanthan acceptable.acceptable. In addition to verifying the most stressed areas, it is equally important to check which areas are InIn additionaddition toto verifyingverifying thethe mostmost stressedstressed areas,areas, itit isis equallyequally importantimportant toto checkcheck whichwhich areasareas areare less subject to loads and deformations so as to be able to perform a possible under sizing that allows lessless subjectsubject toto loadsloads andand deformationsdeformations soso asas toto bebe ableable toto performperform aa possiblepossible underunder sizingsizing thatthat allowsallows SustainabilitySustainability 20202020,,, 1212,,, xxx FORFORFOR PEERPEERPEER REVIEWREVIEWREVIEW 23 23 23 of of of 29 29 29 toto reducereduce thethe weightsweights andand thethe overalloverall dimensions.dimensions. AsAs wewewe cancancan see,see,see, ininin fact,fact,fact, thethethe upperupperupper beamsbeamsbeams thatthatthat makemakemake upup thethe trunktrunk areare practicallypractically freefree ofof loads,loads, soso youyou choosechoose toto eliminateeliminate thethe rearrear beam,beam, soso asas toto havehave easiereasier accessaccess toto thethe trunktrunk andand aa lowerlower weightweight ofof thethe structure.structure. AlthoughAlthough thethe structurestructure hashas achievedachieved reasonablereasonable resuresults,lts, itit isis clearclear thatthat furtherfurther reinforcementreinforcement andand stiffeningstiffening isis requiredrequired inin specificspecific areas.areas. Therefore,Therefore, somesome sheetssheets areare addedadded toto connectconnect thethe variousvarious beams,beams, soso asas toto havehave aa moremore uniformuniform distributiondistribution ofof thethe loadsloads andand aa greatergreater rigidityrigidity ofof thethe structure.structure.
FrameFrame withwith PlatesPlates TheThe structurestructure (Figure(Figure 16)16) presentspresents thethe sheetssheets exclusivelyexclusively inin thethe fundamentalfundamental points,points, theirtheir presencepresence inin factfact influencesinfluences significantlysignificantly thethe weigweight.ht. TheThe thicknessesthicknesses andand thethe positionposition ofof thethe sheetssheets Sustainabilitywerewere decideddecided2020 following,following12, 787 variousvarious staticstatic analysesanalyses ofof whichwhich wewe areare nownow goinggoing toto showshow thethe finalfinal resultsresults21 of 27 (Figures(Figures 17–19).17–19).
FigureFigure 16.16. FrameFrame with with plates plates designed. designed.
FigureFigure 17.17. MaximumMaximum load:load: 10.6 10.6 MPa. MPa.
Figure 18. Maximum deformation 0.0001. FigureFigure 18.18. MaximumMaximum deformation deformation 0.0001.0.0001.
As expected, the results are better than the previous ones, all three analyses show lower maximum values. In order to perform an initial test, the thickness of the plates had been uniquely placed at 5 mm, giving more than excellent results in all three tests. This solution gave the structure a hyper-rigidity that is not always a positive factor. For this reason, in order to minimize the weight of the car, a value of 3 mm was chosen for the thickness of the sheets. A separate discussion must be made for the sheet relative to the motor housing, the latter in fact showed unacceptable deformation and maximum load values, for this reason its thickness was increased to 10 mm. For the same reason the sheet relative to the rear trunk has been designed keeping the thickness of 5 mm. Having thus achieved the goal in terms of resistance and weight optimization, we now complete the frame structure by inserting the uprights that will form the upper part of the car and the longitudinal tunnel that will house the crankshaft. Sustainability 2020, 12, x FOR PEER REVIEW 24 of 29
Sustainability 2020, 12, 787 22 of 27 Sustainability 2020, 12, x FOR PEER REVIEW 24 of 29 Figure 19. Maximum displacement: 1 mm.
As expected, the results are better than the previous ones, all three analyses show lower maximum values. In order to perform an initial test, the thickness of the plates had been uniquely placed at 5 mm, giving more than excellent results in all three tests. This solution gave the structure a hyper-rigidity that is not always a positive factor. For this reason, in order to minimize the weight of the car, a value of 3 mm was chosen for the thickness of the sheets. A separate discussion must be made for the sheet relative to the motor housing, the latter in fact showed unacceptable deformation and maximum load values, for this reason its thickness was increased to 10 mm. For the same reason the sheet relative to the rear trunk has been designed keeping the thickness of 5 mm. Having thus achieved the goal in terms of resistance and weight optimization, we now complete the frame structure by inserting the uprights that will form the upper part of the car and the longitudinal tunnel that will houseFigureFigure the 19.19. crankshaft. Maximum displacement: 1 mm.
CompleteAs expected, Chassis the results are better than the previous ones, all three analyses show lower maximumAs anticipated, values. In the order frame to wasperform also completedan initial test, in the the upper thickness part, andof the was plates then had closed been by uniquely inserting placedAs at anticipated, 5 mm, giving the framemore thanwas alsoexcellent completed results in in the all upper three part,tests. and This was solution then closed gave the by insertingstructure the imperial (Figure 20).20). Since Since the the car car is is rear-wheel rear-wheel drive drive it it was was necessary necessary to to provide provide for the the presence presence ofa hyper-rigidity a space for the that passage is not of always the crankshaft a positive and factor. of the For wiring this reason, to the rearin order wheels. to minimize In the upper the weight part of ofof athe space car, fora value the passage of 3 mm of was the chosencrankshaft for theand thickness of the wiring of the to sheets. the rear A wheels.separate In discussion the upper must part beof the frame have been added fittings fittings in all the the faces, faces, in in order order to to avoid avoid possible possible concentrations concentrations of tension tension andmade also for for the aesthetic sheet relative purposes. to the motor housing, the latter in fact showed unacceptable deformation andand alsomaximum for aesthetic load values, purposes. for this reason its thickness was increased to 10 mm. For the same reason the sheet relative to the rear trunk has been designed keeping the thickness of 5 mm. Having thus achieved the goal in terms of resistance and weight optimization, we now complete the frame structure by inserting the uprights that will form the upper part of the car and the longitudinal tunnel that will house the crankshaft.
Complete Chassis As anticipated, the frame was also completed in the upper part, and was then closed by inserting the imperial (Figure 20). Since the car is rear-wheel drive it was necessary to provide for the presence of a space for the passage of the crankshaft and of the wiring to the rear wheels. In the upper part of the frame have been added fittings in all the faces, in order to avoid possible concentrations of tension Figure 20. Complete chassis. and also for aesthetic purposes. Figure 20. Complete chassis. 7. DFSS: DFSS: VALIDATE VALIDATE Once the design of the frame has been completed it is necessary to carry out the checks checks that that show show that the product hashas respectedrespected the the objectives objectives that that had had been been set set and and that that it it does does not not present present problems problems of ofany any kind. kind. The static check is carried out one last time to observe the reaction of the complete frame to the loads and to establish which are the actual rigidityrigidity andand resistance.resistance.
7.1. Static Verification As expected, we get further reinforcement and stiffening of the structure, which now has excellent performance, with a maximum load ofFigure only 20. 4.4 Complete Mpa and chassis. a maximum displacement of only 0.28 mm, as shown in Figures 21–23. 7. DFSS:The structureVALIDATE compared to the previous analysis improves its performance especially in the central area, where the insertion of the tunnel for the crankshaft and the closure of the structure have given Once the design of the frame has been completed it is necessary to carry out the checks that show greater resistance. The frame therefore satisfies the requirements of rigidity and resistance. that the product has respected the objectives that had been set and that it does not present problems of any kind. The static check is carried out one last time to observe the reaction of the complete frame to the loads and to establish which are the actual rigidity and resistance.
Sustainability 2020, 12, x FOR PEER REVIEW 25 of 29 Sustainability 2020, 12, x FOR PEER REVIEW 25 of 29 7.1. Static Verification 7.1. Static Verification As expected, we get further reinforcement and stiffening of the structure, which now has As expected, we get further reinforcement and stiffening of the structure, which now has excellent performance, with a maximum load of only 4.4 Mpa and a maximum displacement of only excellent performance, with a maximum load of only 4.4 Mpa and a maximum displacement of only 0.28 mm, as shown in Figures 21–23. 0.28 mm, as shown in Figures 21–23. The structure compared to the previous analysis improves its performance especially in the The structure compared to the previous analysis improves its performance especially in the Sustainabilitycentral area,2020 where, 12, 787 the insertion of the tunnel for the crankshaft and the closure of the structure23 have of 27 central area, where the insertion of the tunnel for the crankshaft and the closure of the structure have given greater resistance. The frame therefore satisfies the requirements of rigidity and resistance. given greater resistance. The frame therefore satisfies the requirements of rigidity and resistance.
Figure 21. Maximum load: 4.4 MPa. FigureFigure 21.21. Maximum load: 4.4 MPa.
Figure 22. Maximum deformation 0.00003. Figure 22. Maximum deformation 0.00003.
Figure 23. Maximum displacement: 0.283 mm. Figure 23.23. Maximum displacement: 0.283 mm. 7.2. Lay-Out Verification (VLO) 7.2. Lay-Out Verification Verification (VLO) The bulkiest and spacious components are inserted inside the car, so as to check its habitability The bulkiest and spacious components are inserted inside the car, so as to check its habitability and capacity. Thus we begin by inserting the batteries, whose seat has been inserted under the rear and capacity. Thus we begin by inserting the batteries,batteries, whose seat has been inserted under the rear seats, so as not to lose space in height inside the passenger compartment (Figure 24). seats, so as not to lose space inin heightheight insideinside thethe passengerpassenger compartmentcompartment (Figure(Figure 2424).). After that, insert the seats in front and behind inside the passenger compartment to check if there is enough space for them (Figure 25). Once inserted in the right positions it is necessary to evaluate the comfort of the 5 seats, for which 5 mannequins are inserted, whose dimensions are deliberately slightly oversized, so as to verify if the car is able to contain 5 adult males in comfort (Figure 26). Mannequins height: 1.82 m. As can be seen, from this image and from the previous one, there is enough space for 5 adult males, both in regards to the place for the feet and the width of the rear seat (Figure 27). Sustainability 2020, 12, x FOR PEER REVIEW 26 of 29
Sustainability 2020, 12, x FOR PEER REVIEW 26 of 29
Sustainability 2020, 12, x FOR PEER REVIEW 26 of 29
Sustainability 2020, 12, 787 24 of 27 Sustainability 2020, 12, x FOR PEER REVIEW 26 of 29
Figure 24. Verification of lay-out (VLO): battery set up.
After that, insert the seats in front and behind inside the passenger compartment to check if there Figure 24. Verification of lay-out (VLO): battery set up. is enough space for them (Figure 25). After that, insert the seatsFigure in 24. front Verification and behind of lay-out inside (VLO): the passenger battery set compartment up. to check if there is enough space for them (Figure 25). After that, insert the seats in front and behind inside the passenger compartment to check if there is enough space for them Figure(Figure 24. 25). VerificationVerification of lay-out (VLO): battery set up.
After that, insert the seats in front and behind inside the passenger compartment to check if there is enough space for them (Figure 25).
Figure 25. Verification of lay-out (VLO): seats set up.
Once inserted in the right positions it is necessary to evaluate the comfort of the 5 seats, for which Figure 25. Verification of lay-out (VLO): seats set up. 5 mannequins are inserted, whose dimensions are deliberately slightly oversized, so as to verify if the carOnce is able inserted to contain in the 5right Figureadult positions males 25. VerificationVerification in it comfort is necessary of lay-out(Figure to (VLO): evaluate 26). Mannequins seats the set comfort up. height: of the 1.82 5 seats, m. for which 5 mannequins are inserted, whose dimensions are deliberately slightly oversized, so as to verify if Once inserted in the right positions it is necessary to evaluate the comfort of the 5 seats, for which the car is able to contain 5 adult males in comfort (Figure 26). Mannequins height: 1.82 m. 5 mannequins are inserted,Figure whose 25. dimensionsVerification of are lay-out deliberately (VLO): seats slightly set up. oversized, so as to verify if the car is able to contain 5 adult males in comfort (Figure 26). Mannequins height: 1.82 m. Once inserted in the right positions it is necessary to evaluate the comfort of the 5 seats, for which 5 mannequins are inserted, whose dimensions are deliberately slightly oversized, so as to verify if the car is able to contain 5 adult males in comfort (Figure 26). Mannequins height: 1.82 m.
Figure 26. VerificationVerification of lay-out (VLO): fivefive mannequins set up.
WhatAs can we be want seen, to from highlight this image with the and last from image the is previous that despite one, the there use ofis 1.82enough m height space mannequins, for 5 adult Figure 26. Verification of lay-out (VLO): five mannequins set up. theremales, is both still ain lot regards of space to forthe theplace head for insidethe feet the and passenger the width compartment, of the rear seat making (Figure the 27). car suitable also for tallAs passengers. can be seen, Then Figurefrom there this 26. Verification isimage the capacity and of from lay-out of the (VLO): trunk,previous five which mannequinsone, can there comfortably is set enough up. hold space 4 suitcasesfor 5 adult of 55males,40 both20 in (black) regards and to two the suitcasesplace for ofthe 40 feet30 and 20the (gray) width size. of the rear seat (Figure 27). × As ×can be seen, from this image and from× the× previous one, there is enough space for 5 adult males, both in regardsFigure to the 26. place Verification for the offeet lay-out and the(VLO): width five of mannequins the rear seat set (Figureup. 27).
As can be seen, from this image and from the previous one, there is enough space for 5 adult males, both in regards to the place for the feet and the width of the rear seat (Figure 27).
Figure 27. Verification of lay-out (VLO): five mannequins set up lateral view.
What we want to highlight with the last image is that despite the use of 1.82 m height FigureFigure 27. VerificationVerification of lay-out (VLO): five five mannequins set up lateral view. mannequins, there is still a lot of space for the head inside the passenger compartment, making the ItsWhat capacity we Figurewant is around to27. Verificationhighlight 510 L, with upof lay-out to the more (VLO):last than image five 1200 mannequins is Lthat if thedespite set rear up seatsthelateral use are view. of lowered 1.82 m and height the compartmentmannequins, there separating is still the a lot trunk of space from for the the passenger head inside compartment the passenger is removed compartment, (Figure 28 making). the What we want to highlight with the last image is that despite the use of 1.82 m height mannequins, thereFigure is still27. Verification a lot of space of lay-out for the (VLO): head five inside mannequins the passenger set up lateralcompartment, view. making the
What we want to highlight with the last image is that despite the use of 1.82 m height mannequins, there is still a lot of space for the head inside the passenger compartment, making the Sustainability 2020, 12, x FOR PEER REVIEW 27 of 29 car suitable also for tall passengers. Then there is the capacity of the trunk, which can comfortably hold 4 suitcases of 55 × 40 × 20 (black) and two suitcases of 40 × 30 × 20 (gray) size. SustainabilityIts capacity 2020, 12 ,is x FORaround PEER 510REVIEW L, up to more than 1200 L if the rear seats are lowered and 27 ofthe 29 compartment separating the trunk from the passenger compartment is removed (Figure 28). car suitable also for tall passengers. Then there is the capacity of the trunk, which can comfortably Finally, all that remains is to insert the wheels in the appropriate spaces, for the designed model hold 4 suitcases of 55 × 40 × 20 (black) and two suitcases of 40 × 30 × 20 (gray) size. Sustainabilitywe consider2020 as, 12standard, 787 20’’ rims, then insert the tires and check their correct positioning (Figure25 of29). 27 Its capacity is around 510 L, up to more than 1200 L if the rear seats are lowered and the (Batteries remain exposed for illustrative purposes only). compartment separating the trunk from the passenger compartment is removed (Figure 28). Finally, all that remains is to insert the wheels in the appropriate spaces, for the designed model we consider as standard 20’’ rims, then insert the tires and check their correct positioning (Figure 29). (Batteries remain exposed for illustrative purposes only).
Figure 28. Verification of lay-out (VLO): trunk capacity. Figure 28. Verification of lay-out (VLO): trunk capacity.
Finally, all that remains is to insert the wheels in the appropriate spaces, for the designed model we consider as standard 20” rims, then insert the tires and check their correct positioning (Figure 29). Figure 28. Verification of lay-out (VLO): trunk capacity.
Figure 29. Verification of lay-out (VLO): wheels set up.
8. Discussion: Characteristics and Innovations
Once both checks haveFigure been 29. completed, Verification the of lay-out frame (VLO):can be wheelsconsidered set up. definitive. Let us now summarizeFigure the 29.featuresVerification and innovations of lay-out (VLO): of this wheels new setcar. up. 8.- Discussion:(BatteriesThe designed remainCharacteristics car exposedis of the and forfull illustrative InnovationsHybrid type, purposes with a only).3.5 L gasoline engine with rear-wheel drive Oncethat coupled both checks to the have electric been motor completed, provides the a frame power can of 345be considered horsepower. definitive. 8. Discussion: Characteristics and Innovations - LetThe us trunk now has summarize a capacity the of features about 510 and L, innovations which can become of this new around car. 1200 L, knocking down the rear seats. - OnceThe designed both checks car is have of the been full completed, Hybrid type, the framewith a can 3.5 beL gasoline considered engine definitive. with rear-wheel drive - The car measures 4.90 m in length, 1.80 in width (considering the mirrors) and 1.48 m in height. Letthatus coupled now summarize to the electric the featuresmotor provides and innovations a power of of 345 this horsepower. new car. - Aluminum alloy frame: This choice made it possible to obtain a better power/weight ratio - The trunk has a capacity of about 510 L, which can become around 1200 L, knocking down the - comparedThe designed to all car existing is of the cars full in Hybrid the same type, segm withent. a 3.5This L gasolineallows for engine high withperformance, rear-wheel without drive rear seats. penalizingthat coupled consumption. to the electric motor provides a power of 345 horsepower. - The car measures 4.90 m in length, 1.80 in width (considering the mirrors) and 1.48 m in height. -- LighterThe trunk frame has than a capacity all currently of about existing 510 L, cars which in canthe same become segment. around 1200 L, knocking down the - Aluminum alloy frame: This choice made it possible to obtain a better power/weight ratio - Therear built seats. frame is able to withstand high stresses, thanks to a very high stiffness and resistance. compared to all existing cars in the same segment. This allows for high performance, without -- ConsumptionThe car measures is very 4.90 low, m in thanks length, to 1.80 the in heavy width weight (considering reduction the and mirrors) the use and of 1.48 large m inbatteries, height. penalizing consumption. - especiallyAluminum in alloycities frame:where the This electric choice motor made does it possible most of tothe obtain work. a better power/weight ratio - Lighter frame than all currently existing cars in the same segment. - Positioningcompared to the all battery, existing its cars positioning in the same under segment. the re Thisar seats, allows allows for higha better performance, exploitation without of the - The built frame is able to withstand high stresses, thanks to a very high stiffness and resistance. spacepenalizing inside consumption. the passenger compartment in terms of height. - Consumption is very low, thanks to the heavy weight reduction and the use of large batteries, - High comfort, the frame allows to comfortably accommodate 5 people of medium–large build. - especiallyLighter frame in cities than where all currently the electric existing motor cars does in the most same of the segment. work. - The price is kept low thanks to the use of not too expensive materials and the lightening of the -- PositioningThe built frame the battery, is able to its withstand positioning high under stresses, the thanksrear seats, to a allows very high a better stiffness exploitation and resistance. of the structure. - spaceConsumption inside the is passenger very low, compartment thanks to the heavyin terms weight of height. reduction and the use of large batteries, - Highespecially comfort, in cities the frame where allows the electric to comfortably motor does accommodate most of the work. 5 people of medium–large build. -- ThePositioning price is kept the battery, low thanks its positioning to the use of under not too the expensive rear seats, materials allows a betterand the exploitation lightening of the structure.space inside the passenger compartment in terms of height. - High comfort, the frame allows to comfortably accommodate 5 people of medium–large build. - The price is kept low thanks to the use of not too expensive materials and the lightening of the structure. Sustainability 2020, 12, 787 26 of 27
9. Conclusions This work presented an innovative hybrid car’s design, belonging to the E-segment. The Design for Six Sigma was applied in order to develop a new product, through the determination of customer and market needs and the transformation of these requests into the product generated. The result was that a new full hybrid type car was designed that presents high performances and low consumption, together with high comfort. The method adopted made it possible to develop a reliable study of possible product enhancements. Only a few constraints and limitations can be foreseen, by the translation of this conceptual study into a constructive design, linked to the material and the manufacturing process selection, which have not been specifically discussed here. Further studies could be deepened, focusing on the method application to the ambit of Logistics in the context of Industry 4.0 [34].
Author Contributions: For this research article the individual contributions have to be considered as follows: conceptualization, G.M.R.; methodology, D.F.; software, G.M.S.; data curation, G.D. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest.
References
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