Search Results

In order to achieve maximum fuel efficiency, the SI engine of the new CVT-equipped hybrid car developed at the Swiss Federal Institute of Technology (ETH) is operated in a high power regime (such as highway driving at speeds above 120 km/h) with its throttle in its 100-percent open position. Whenever an engine power which exceeds 11 kWs is demanded, there exists an equilibrium point between the engine torque and the torque induced by the drag. Any regulation of the vehicle speed has to be performed by altering the gear ratio of the CVT. If any acceleration is required, it is necessary to increase the engine speed. This requires that the vehicle has to be slowed down for a certain short period of time. If this characteristic behaviour of the car (which is typical for a non-minimum-phase system) is not accepted by a driver who demands and expects immediate acceleration, it might lead to critical situations.

Electric vehicles today clearly represent the only solution fulfilling the zero emission vehicles (ZEV) standard. However, they are still not an equivalent alternative to gasoline driven cars due to the well known problems of today's batteries. The concept of a parallel hybrid drive line can be an optimal combination of both principles of propulsion in that the gasoline engine guarantees a wide range operation, while electric propulsion can be used within the restricted zero emission zones [20]. The parallel hybrid drive train described here has been realized at the Swiss Federal Institute of Technology (ETH), Zurich, Switzerland. For the first time a drive line consisting of a spark ignition engine, an electric asynchronous machine, a flywheel, and a wide range continuously variable transmission (CVT) is realized. An overall control system has been developed for the drive train. This drive line has been integrated in a multi purpose van for real road testing.