Constrained stability control with optimal power management strategy for in-wheel electric vehicles

Abstract

This paper looks into the energy management and directional stability of four-in-wheel driven electric vehicles, simultaneously. In the proposed strategy, the optimal driving torques are initially distributed between the wheels by considering the condition for minimum losses of motors using the motor efficiency model. In risky maneuvers, a novel optimal torque vectoring system is developed to intentionally change the initial optimal torques for the generation of required stabilizing yaw moment. For designing the stability controller, a new constrained control method is analytically developed based on the prediction of continuous nonlinear vehicle models. The proposed control method restricts the side-slip angle to guarantee the stability. Also, the required control torque for each motor is restricted within the admissible range according to the motor map. As another result of the constrained strategy, a small change in the optimal energy consumption is occurred for improved stability because of using minimum external yaw moment. In simulation studies, a good performance of the developed control system to provide both directional stability and drivability of electric vehicle with high energy efficiency is presented at different driving conditions using 14-degrees-of-freedom vehicle model. A comparative study with the conventional model predictive control method indicates the speed of the proposed constrained control method and the ease of its solution and implementation.