Motion control and power coordination of electric propulsion and braking distributed on multiple axles on heavy vehicles

Instantaneous allocation of power in a distributed electric powertrain reduces losses by selective usage of actuators. Such an allocation also poses a challenge of coordinating power among actuators optimally. This study explores three different approaches of motion control and power coordination of electric machines and service brakes, using an instantaneous power allocation. These approaches based on control allocation framework, are further evaluated and compared for a given use case using simulations. The distinctive strength of the power loss minimisation approach, by using regressed data of power losses from electric machine models instantaneously, is highlighted. Additionally, it is also shown that the power loss minimisation approach resulted in the lowest energy loss in actuator power losses compared to the other approaches.

I. Introduction

The propulsion system of long haul battery electric heavy vehicles (BEVs), in specific the 35 tonne tractor-semitrailer, requires around 500 kW of continuous electric power to achieve an adequate performance in all operating conditions. However, to decelerate such a vehicle during normal driving, surplus power is required from the service brakes in addition to what the electric machines can provide. For example, the deceleration of 0. 25g at a cruising speed of 85 km/h requires more than 2000 kW on a levelled road. Hence, optimal allocation of actuator usage is essential to reduce the power losses for improved efficiency and performance. Additionally, distributed powertrain with drives on multiple axles provide the opportunity to blend the usage of electric machines among the axles along with service brakes [1] –[3]. However, the previous study in [3] using control allocation (CA), is limited to the coordination of power between electric machines on different axles and excludes service brakes.