Parallel hybrid electric system energy optimization control with automated mechanical transmission

Abstract

Energy optimization control for a parallel hybrid electric system with automated mechanical transmission (AMT) can be divided into two steps in this paper. First, the AMT shift is not optimized and the optimal torque distribution strategy is proposed to minimize the powertrain equivalent specific fuel consumption by considering the power conversion efficiency, which distributes the vehicle single torque request into separate torque requests for the internal combustion engine (ICE) and the electric motor (EM). The distribution results are expressed in a table format and can be found from the simple process of looking up the table using the vehicle torque request, the ICE speed, and the battery state of charge (SOC). Then, the AMT shift control is suggested to maximize the powertrain system efficiency and optimizes the speed as the basis for the above-mentioned torque distribution, in which the ICE efficiency, the EM efficiency, and the battery efficiency are all explicitly taken into account. The AMT optimal shift control law and the EM optimal torque are essentially look-up-table-based control according to the ICE power, the EM power, the vehicle velocity, and the battery SOC after offline calculations. Simulation results reveal that potential fuel economy improvement has been achieved by using the energy optimization control.