The Networked Hybrid Concept for Sports Cars

COVER STORY ELECTRIC MOBILITY

THE NETWORKED HYBRID CONCEPT FOR SPORTS CARS

Bosch Engineering GmbH has converted a sports car with a V12 internal combustion engine and manual six-speed transmission into a vehicle with an axle-split hybrid powertrain. By doing so, the Bosch subsidiary is demonstrating the potential of electriﬁ cation for utilising cross-domain systems knowledge to reduce fuel

consumption and CO2 emissions, improve vehicle dynamics and performance, and expand customisation possibilities speciﬁ cally in the sports car segment.

4 AUTHORS MOTIVATION

The latest emissions standards to be adopted, which set the limits for 2015 and 2020, require ambitious technical progress in reducing fuel consumption. This affects mid-range and premium vehicles as well as sports cars. In order to permanently reduce ﬂ eet emissions to meet the speciﬁ ed targets, modern GABRIELE PIERACCINI vehicle development is focusing on sustainable system solu-

is Hybrid Systems Project Manager at tions. ➊ shows the weight-classiﬁ ed CO2 emissions of sports Bosch Engineering GmbH in Abstatt cars with gasoline and hybrid powertrains currently available (Germany). on the European market, alongside the emissions limits for 2015 and 2020. To get closer to these limits, sports car manu-

facturers are already employing classic engine-based CO2 reduction strategies, including IC engine displacement down- sizing, dethrottling, and cylinder deactivation. However, vehicles in the sports car segment will not reach the new emissions limits by IC (internal combustion) engine measures alone. In BODO BECKER combination with other measures targeting other parts of the is Prototype and Demonstrator Project Manager at Bosch Engineering GmbH vehicle, powertrain electriﬁ cation is a sustainable move with

in Holzkirchen (Germany). the potential to bring sports cars’ CO2 emissions below future statutory limits for the long term. With its hybrid concept car, Bosch Engineering GmbH is demonstrating the beneﬁ ts of electrifying high-performance

sports cars in terms of fuel consumption and CO2 reductions, improved vehicle dynamics, innovative HMI concepts, and per- sonalised driving functions. In a matter of months, the Bosch GÜNTHER VOGT subsidiary converted the DB9 with its IC engine and manual is Expert for Special Designs at six-speed transmission into a car with an axle-split hybrid Bosch Management Support GmbH powertrain. To do this, 30 new components were integrated in Leonberg (Germany). into the vehicle in the domains of powertrain, vehicle dynamics, body, and multimedia. These components were then networked with each other and with the base vehicle’s systems, and new driving functions were developed. The networking concept and the new functions can be adapted in subsequent series-production projects to different manufacturers’ brand concepts and their requirements with respect to the driveabi- lity, comfort, and dynamics of their vehicles.

600

500

400

300 emissions [g/km] 2 CO 200 Sports cars Hybrid sports cars

100 CO2 target 2015

CO2 target 2020

0 1000 1200 1400 1600 1800 2000 2200 Curb weight [kg]

➊ Sports car emissions values

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➋ Powertrain topology concept vehicle

HYBRID CONCEPT power-assisted steering and air conditio- in the dependencies and interactions of ning by powering the belt drive at the IC the powertrain and vehicle-dynamics Performance, effi ciency, and vehicle engine. Both these functions were trans- domains along with their respective sub- dynamics are key factors in developing planted unmodifi ed from the base systems. To use simulation to good effect high-performance sports cars. When vehicle. The third electric motor can also in system design, Bosch Engineering electrifying the powertrain, not only be operated as a generator in conjunction developed a software platform that pro- must no compromises be made in these with a specially developed overrunning vides a fast and effi cient comparison crucial areas, it is also important for cus- clutch on the crankshaft and supplies the between different powertrain topologies tomer acceptance reasons to actually vehicle’s 12-V electrical system via an with regard to fuel consumption, CO2 improve them via a suitable hybrid con- intermediate DC-to-DC converter. Three emissions, and basic longitudinal dyna- cept. Moreover, a hybrid powertrain Bosch Invcon 2.3 power electronics units mics performance. In order to include should allow automakers to adapt the serve as central interfaces between the vehicle dynamics characteristics, corres- driving characteristics of their predomi- electric motors and the high-voltage ponding sub-models were added to the nantly rear-wheel drive sports cars to battery. simulation platform, ➌. The vehicle specifi c brands to a great extent. To meet simulation also reproduces powertrain these requirements, the conventional components’ thermal behaviour, taking CROSS-DOMAIN VEHICLE powertrain of an Aston Martin DB9 was into consideration power losses from DEVELOPMENT converted into an axle-split hybrid pow- energy storage. By using cross-domain ertrain with two separate wheel-specifi c All the additional components together simulation, it was possible to simulate electric motors (Bosch SMG 180/120) on with their wirings made the concept car and evaluate the boundaries of dynamic the front axle, ➋. A general advantage of 280 kilograms heavier than the base performance over defi ned parameters this topology is that it makes it easier to vehicle, so the challenge when conver- while taking account of lateral dynamic integrate the requisite hybrid compo- ting the powertrain was to observe the performance and to compare them nents into existing powertrain architec- CO2 limits despite the additional weight directly with those of the series produc- tures based on conventional IC engines; while also improving performance. Even tion model [1]. The results showed the the vehicles do not have to be developed though drive power was increased by hybrid concept car consuming 50 % less from scratch. Installing two wheel-speci- 169 kW and the hybridisation delivers fuel compared to the conventional power- fi c electric motors on the front axle also high torque, it is the extra weight along train. At the same time, there was a sig- allows for additional vehicle dynamics with the change in center of gravity and nifi cant improvement in vehicle dyna- functions, such as torque vectoring, inte- suspension characteristics that deter- mics performance, measured by accele- grated vehicle dynamics control, and mine the sports car’s handling. Conse- ration time, ➍. Initial validation results temporary four wheel drive. In addition, quently, the focus was on implementing are confi rming the simulation fi gures: the concept car was fi tted with a third a system design that incorporated all in test drives, acceleration time from electric motor (Bosch SMG 138/80) on vehicle domains right from the start of 0 to 100 km/h was reduced by 21 % the drive belt, which facilitates both the development process, so as to factor and from 0 to 200 km/h by 19 %. More 6 Controls manufactured new attachments. For the electrical powertrain components, Bosch Ascet Load profiles Matlab/ of components Engineering developed an independent Simulink cooling circuit along with an additional autonomous cooling system for the high- voltage battery. The latter was integrated Powertrain Integration into the concept car instead of the fuel GT-Suite platform Vehicle systems Post processing tank, and a prototype solution was also Matlab/ simulation of results developed for the tank system together Simulink Matlab/Simulink with its pumps, hoses, level sensors, and purging mechanisms, ➎ [2]. Besides converting the powertrain, the Vehicle dynamics developers in Holzkirchen also integra- Verification of customer ted the components of the new HMI con- CarMaker requirements CarSim cept with its 7-inch head unit, 12-inch instrument cluster with fully digital display, and 10-inch tablet computer, as well as the control unit and networking architecture behind the user interface. Vehicle and component configuration Simulation and concept verification based on validated libraries As regards vehicle dynamics, the base vehicle’s existing brake system was ➌ Simulation platform replaced with a Bosch ESP system in order to implement – in combination with the separate wheel-specifi c drives on the front axle – new torque vectoring results are to follow. In other vehicles, rate the powertrain components into the functions and integrated vehicle dyna- these values can vary depending on the base vehicle. For each front wheel, it mics control. capacity of the installed battery, the connects the electric motors to the wheel To enable the conversion of the con- recovery capacity, and the operating with a gear ratio of approx 1 : 6 and a 90 ° cept car to be accomplished within just strategy. rerouting for reasons of installation ten months, a total of 75 developers and space. The scarcity of installation space engineers worked together in a simulta- available inside the unchanged base- neous engineering team at two locations. MECHANICAL INTEGRATION vehicle body was the biggest challenge Mechanical integration of the car’s 30 for the developers when it came to deve- OPERATING STRATEGY AND new components was carried out by loping and integrating the gearbox. As a MODULAR HYBRID PLATFORM Bosch Engineering at its Holzkirchen site solution, they modifi ed components such near Munich. The engineers and develo- as the chassis frame in the engine com- The operating strategy for the concept pers converted the powertrain by instal- partment, adjusted the position of the car was developed with numerous diffe- ling the separate wheel-specifi c drives on engine, sub-frames, and further compo- rent driving modes in order to meet cus- the front axle and the third electric nents (including in the steering), and tomer demand for the greatest possible motor on the drive belt. To do this, they integrated a combination of available Bosch components, third-party provider

CO2/ fuel reduction (ECE R101) Acceleration performance [0 to 100] components, and new, specially develo- and vehicle mass [%] and vehicle mass [%] ped components into an overall system. +20 All three of the car’s electric motors and 120 +17 +17 the power electronics are Bosch pro- ducts. The commercially available, 100 series-produced components from third- party providers are the charger, the 80 charge plug, and the power distribution 60 unit (PDU). A third-party provider’s -50 high-voltage battery was developed and CO emissions and 40 2 built as a prototype following the speciﬁ - fuel consumption cations. For power transmission from the 20 Acceleration two drive shafts to the front wheels, Vehicle mass

Bosch Engineering developed and proto- 0 typed an adapted the suspension geome- Base Hybrid concept Base Hybrid concept vehicle vehicle vehicle vehicle try. The team also developed a new gearbox with a disconnecting clutch to integ- ➍ Simulation results

11I2014 Volume 116 7 COVER STORY ELECTRIC MOBILITY

of the operating strategy and the driving modes and functions. For example, it simulated certifi cation driving cycles such as the NEDC for the EU market and FTP75/US06 for the U.S. market. To provide more effi cient support for the development of hybrid and all-electric powertrains for small-scale series customers in future, Bosch Engineering has developed a modular hybrid software platform. With this software, users can quickly and effi ciently adapt a self-developed platform operating strategy to a variety of powertrain topologies. To do this, the software platform integrates the electric motors contained in the respective topology on the one hand and the interfaces ➎ Mechanical integration of numerous control units – including from the driving dynamics, body, and multimedia domains – on the other. The vehicle’s thermal system is also integra- degree of vehicle personalisation. In drivers can be notifi ed via a signal in the ted into the development process for the addition to fully IC engine and fully elec- pedal as soon as the electric motors have operating strategy, along with the res- tric modes, various hybrid forms are also reached maximum output. This enables pective temperatures of the IC engine, possible. The standard hybrid mode, drivers to instinctively recognise that the electric motors, and catalytic converter, which is called Hybrid Eco, prioritises IC engine will be activated if they do not the battery’s state of charge, and the spe- effi ciency and low fuel consumption. In ease up on the accelerator. In other cifi c torque of the electric motors. Hybrid Sport mode, by contrast, drive words, they can directly infl uence chan- torque distribution is designed for spor- ges in the operating modes of the hybrid VEHICLE DYNAMICS tier, more agile driving. The IC-engine is system. In addition, drivers can deter- activated at all times and the boost func- mine the pedal’s feedback by means of A big advantage of the concept car’s hyb- tion is used for support at certain times, various fi xed settings, including a “kick- rid powertrain topology is the power it such as when overtaking or when star- down mode” and various profi les with gives drivers to infl uence driving dyna- ting the vehicle. The Hybrid Race mode constant force balance [3]. mics. This power is exercised via the two was developed for use on closed racing The Bosch Engineering simulation new wheel-specifi c electric motors in circuits. If, in addition to standard infor- platform, which was already introduced conjunction with the newly integrated mation such as vehicle model, battery at the systems development stage for the ESP system. The integrated vehicle dyna- state of charge, recovery potential, and vehicle, was also used for development mics control function, developed and the power of the electric motors, infor- mation is available on the routes of the circuits, the operating strategy calculates an optimum boost strategy to minimise lap times. The Custom hybrid mode allows drivers to select their personal preferences for all personalisable characteristics. They can also save their prefer- red confi gurations and access them at any time. In addition, the concept car includes various functions that allow drivers to personalise the vehicle’s driving behaviour to meet their personal preferences. This includes the ability to set a custom recuperation level as soon as the driver’s foot lifts from the accelerator. To this end, a force feedback pedal has been integrated into the vehicle, whereby an electric motor generates a resistance force that presses against the driver’s foot. When driving in all-electric mode, for example, ➏ Graphical user interface of the tablet-PC for vehicle dynamics adjustments 8 patented by Bosch Engineering, connects these actuators with each other. In this Electrical energy management topology, the function can achieve soft- Adjustable Adjustable ware-based improvements in vehicle hybrid strategy traction control dynamics behaviour that not even chassis adjustments could deliver. The wheel- specifi c electric motors on the front axle Gear shift Adjustable are networked with the IC engine and assist torque vectoring wheel-specifi c braking to optimise lateral dynamics. As a result, the application of integrated vehicle dynamics control in Adjustable Adjustable this vehicle comprises three pre-set dri- recuperation strategy pedal map ving programs as well as a freely adjustable mode, which satisfi es customers’ need to be able to personalise the vehicle Adjustable Adjustable as much as possible [4]. In addition to boost strategy regenerative braking integrated vehicle dynamics control, the concept car can also implement torque ➐ Overview of tunable functions vectoring and temporary four-wheel drive functions.

select predefi ned driving dynamics developed and integrated. The interfaces PERSONALISATION CONCEPT setups. However, the concept also gives are controlled via a body computer A variety of personalisation strategies them the option of continuously adjus- module, a central, domain-independent that allow drivers to infl uence vehicles’ ting driving characteristics such as over- control unit; this in turn is connected to driving behaviour are already on the and understeer via intuitive, easy-to-use the vehicle systems in all domains, such market – especially in the premium seg- digital controllers, ➏. The integrated as the hybrid ECU, the battery management. For this purpose, automakers often vehicle dynamics control then translates ment system, the inverters and the elec- offer fi xed, internally coordinated the driver’s commands into action by tric motors, the ESP, and the navigation vehicle confi gurations that affect several setting the available actuators and func- system. Consequently, the concept car’s systems in the vehicle. If drivers choose tions in optimum confi gurations to deli- electrical and electronic systems illust- eco or sport mode, for example, the gear- ver the desired driving behaviour. In the rate the integrated development of the box, steering, damping, and ESP are all concept car, the new personalisation system architecture particularly well. set, coordinated, and preconditioned concept was implemented for driving A particular challenge when develo- accordingly. Drivers are often unaware dynamics functions and hybrid pow- ping the concept car’s E/E system was of the specifi c settings made for the sys- ertrain functions, ➐. how to expand an existing architecture tems and they cannot control these set- consisting of the on-board communica- tings individually. The hybrid concept tion and energy systems without making HMI CONCEPT AND E/E SYSTEM car’s personalisation concept gives dri- extensive alterations to the control units vers control over these settings. As a The diverse range of personalisable and components of the base vehicle. It result, they can use the capacity and vehicle functions in the concept car was important here for the changes not performance provided by the vehicle sys- requires ergonomic control and display to impair existing functions. Compre- tems to their full potential. concepts with HMIs that are easy to ope- hensive cross-system simulations were First of all, drivers can activate or rate and that provide an intuitive experi- one of the tools used to evaluate the vari- deactivate all personalisable functions ence. It is through these interfaces that ous possible approaches for resolving by selecting various user profi les. A dis- the complex technical interrelationships this challenge. These simulations made tinction is made here between two cate- are communicated to drivers, so it is it possible to analyse the effects of the gories of driver: those who want to use vital that they enable clear, easy-to- expanded and adapted subsystems and predefi ned vehicle setups as before and understand driver-vehicle interaction. components at the level of the overall those who want to adjust individual dri- For the concept car, the team developed vehicle [5]. ving functions precisely to refl ect their an operating and display concept with a Beyond its system boundaries, the personal preferences. In the area of dri- uniform visualisation design containing concept car is also connected to digital ving dynamics, this means that drivers a 12-inch fully digital instrument cluster, infrastructure and cloud-enabled data can make their own individual settings a 7-inch head unit, and a 10-inch tablet platforms. On the one hand, this lets dri- for features such as the control threshold computer as output media. Feedback to vers implement additional driving func- for traction control, steering behaviour, drivers takes the form of visual, tactile, tions by integrating predictive navigation cornering stability, and the accelerator and acoustic signals. In addition to the data (electronic horizon), including pre- performance curve. Drivers who do not visible components in the vehicle’s inte- dictive hybrid strategies that adapt to the want to make detailed settings for perso- rior, the underlying control unit architec- route ahead and real-time synchronisa- nalisable functions can continue to ture and the E/E system were also newly tion with traffi c data.

11I2014 Volume 116 9 COVER STORY ELECTRIC MOBILITY

On the other hand, drivers can also REFERENCES download individual driving profi les, [1] Appel, C.; Freudenstein, S.; Temmen, C.: Durch- gängige Simulation zur Elektrifizierung des Antriebs. vehicle setups, and functions via cloud- In: MTZ 75 (2014), No. 2, pp. 22-28 enabled data portals. Telemetry data [2] Buchner, P.; Pieraccini, G.; Frauenkron, H.; Herz- about laps driven on racing tracks can be hauser, E.; Lingenfelser, C.; König, L.; Windisch, G.; evaluated online and exchanged with Becker, B.: Innovations in Powertrain and Vehicle Personalization for Sports Cars. 22nd Aachen Collo- other drivers. This external connectivity quium Automobile and Engine Technology 2013 allows automakers to offer additional [3] Bihr, B.; Pieraccini, G.; Hofmann, H., Freuden- software functions, setting them even stein, S.: Performance and efficiency – technical solutions for high-performance sports cars to achieve further apart from the competition. th future CO2 limits. 14 Stuttgart International Sympo- sium for Automotive and Engine Technology, 2014 [4] König, L.; Gutmayer, B.; Merlein, D.; Walter, T.: SUMMARY Integrierte Fahrdynamikregelung – ein neuer Effi cient, high-performance, customis- Ansatz zur Vernetzung querdynamischer Stell- glieder. 14th Stuttgart Symposium 2014 able, and networked: electrifying the [5] Windisch, G.; Pieraccini, G.; Schmidt, R.: Ver- powertrain of sports cars is more than netzt, elektrifiziert: Elektroniksysteme eines Hybrid- just a means of slashing emissions to Konzeptfahrzeugs. In: ATZelektronik 9 (2014), No. 5, pp. 10-16 comfortably meet future statutory limits. It also opens up new brand differentia- tion possibilities for vehicle manufacturers in the areas of driving dynamics, multimedia, and personalisation. THANKS Mastering this additional complexity requires overarching systems knowledge about the interplay between the different The authors would like to thank all 75 Bosch energy storage and powertrain systems Engineering GmbH associates at the Abstatt and and the vehicle domains of powertrain, Holzkirchen locations for their hard work and vehicle dynamics, body, and multimedia. dedication on this project. In addition, the whole In addition, intelligent functional and Bosch Engineering project team expresses its software development can resolve the gratitude to the staff at Aston Martin Lagonda Ltd., challenges of electrifi cation. Innovative which provided the Aston Martin DB9 that served control and display concepts help drivers as the base vehicle, for the support provided to to manage the increased complexity and this unusual project. The concept sports car with give them a completely new driving hybrid powertrain was developed as a demonstra- experience. What is more, the techno- tion vehicle. It does not form part of any prepara- logy gives manufacturers the power to tions for series production by Aston Martin. create distinctive unique selling points.

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