Abstract
Keywords: power train, hybrid system, simulation
Hybrid electric power trains have already been used in the past to overcome the limitations of the combustion engine. For example Ferdinand Porsche introduced 1900 a study for a hybrid vehicle (`Lohner-Porsche´) (TU Braunschweig, 2002). As the operational reliablitiy of the combustion engine increased, hybrid electric propulsion has been displaced to special purposes like trucks for surface mining.
Recently hybrid electric powertrains have been integrated in series production cars as one possibility to decrease the fuel consumption of passenger cars. As a first manufacturer Toyota released the Prius in 1997 in Japan and later in the USA. When the vehicle was introduced in the european market already 120,000 cars were sold worldwide (Naunin, 2004). Another hybrid vehicle is manufactured by Honda, the Civic Hybrid. In the first year it was sold over 35,000 times worldwide. Although the number of sold hybrid vehicles is small compared to the number of manufactured passenger cars, which is over 50 Millions according to the VDA (VDA, 2006), the market for hybrid vehicles is increasing.
Thus other car manufacturers like BMW or DaimlerChrysler have announced passenger vehicles with a hybrid power train.
Main influence on the fuel saving capabilities of hybrid propulsion system has the control unit. Depending on constraints like the configuration of the power train or the maximum torque of the electric engine it operates the combustion engine at optimum working conditions or turns the engine off, f.e. at slow speeds in cities. Therefore the algorithms implemented in the control unit need special tests and must be optimized for the given power train configuration. With the help of models this can be done at the engineer´s desk with less time-consuming test drives.
The model presented in this paper evaluates the energy flow between the components of the hybrid power train. The losses of each component can be derived and different control approaches can be evaluated. Due to the modular architecture of the model power train configurations as well as the replacement of single components can be compared and the impact on the fuel consumption can be evaluated.