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 pre- mium 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, vehic- les 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 dyna- mics, 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 11I2014 Volume 116 5 COVER STORY ELECTRIC MOBILITY 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 dis- play, 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