Efficiency optimization of electric buses through transmission control

Our research is about the optimization of the transmission control system of electric buses equipped with a dual electric drive system, that contain two motors and two identical Automated Manual Transmissions, driving the same output shaft, thus providing a “drop-in” replacement for the outdated internal combustion engines in city-, or long distance buses, extending the vehicle’s lifespan significantly. The main goal of the research is to create a transmission control algorithm, which can operate the electric motors with the highest efficiency, while maintaining the dynamics required by the field of application. In conventional electric vehicles, there is only a fixed reduction gear attached to the motors, but in the case of a bus (or any heavy commercial vehicle), better results can be achieved by including a multi-speed gearbox. In our research, we examined single and twin motor drives, using a MATLAB/Simulink environment. We found that the twin-engine design has many advantages, as a really high amount of torque can be achieved by using the two engines together, or the shifting process can be done without power loss on the output shaft, but to exploit the full potential of the system, special control methods are required.