Abstract
The Two-Drive-Transmission is based on the idea of using an automated manual transmission (AMT) for the realization of an Extended Range Electric Vehicle (EREV) powertrain. AMT technology offers high efficiency at reasonable cost. The drawback of AMT technology, the interruption of the traction force during shifting can be avoided by using the proposed topology. The Two-Drive-Transmission consists of two parallel subtransmissions, each driven by one electrical machine. Both subtransmissions have two gear ratios, so when one subtransmission is to be shifted, the other electric machine uses its overload capacity to drive the vehicle solely while the other subtransmission is shifting. The objective of this project is to find an optimal configuration of the Two-Drive-Transmission for both high efficiency and driving performance. Early in the design process of a hybrid electric vehicle, the powertrain components have to be dimensioned. Maximum torque and speed of the electric machines and the internal combustion engine need to be determined as well as the gear ratios of the transmission. Requirements on efficiency and driving performance have to be considered. Often these requirements are conflicting, therefore a trade-off is necessary. Mathematically such a trade-off can be found by using multi-objective optimization algorithms. On the example of the Two-Drive-Transmission a multi-objective optimization is demonstrated. One of the major challenges in performing such an optimization is the implementation of a control strategy which is able to coordinate the components in such a way, that the difference of the state of charge (SOC) at the beginning and at the end of the driving cycle is zero regardless of the configuration of the powertrain. An Equivalent Consumption Minimisation Strategy (ECMS) has been chosen to fulfil this task and will be presented. By minimizing a cost function in every time step of the simulation, an optimal solution can be found. This strategy is parameterized and applied to every configuration during the optimization. This method ensures a fair comparison of different configurations. The result of the optimization is a Pareto front, which represents the optimal trade-off solutions for the Two-Drive-Transmission.
KEYWORDS – Hybrid electric vehicle; Innovative transmission, Multi-objective optimization; Component sizing; High efficiency