Slip-ratio-based torque distribution control strategy for electric vehicles over split friction regions

This paper addresses a novel slip-ratio-based torque distribution strategy for electric vehicles (EVs) to avoid slippage when driving over a split friction surface. With the combination to an upper and middle controller, the desired driving force and yaw moment can be distributed to four driving wheels by utilizing the proposed lower controller. Stability analysis by using Lyapunov theorem is presented to show that the distribution method can equalize the slip ratios for the wheels on the same side of EVs. In addition, we also propose two torque distribution parameters for driving force K_F and moment K_M so that it is more flexible and easier to design a lower controller for EVs. This distribution method is able to equalize the slip ratios for wheels on the same side of EVs, so that the slipping motion can be avoided. Simulation results by using CarSim and MATLAB/Simulink are presented to show the performance of the proposed methods.

I. Introduction

Due to the problems of pollution and shortages of energy, electric vehicles (EVs) have become an important issue to research and been invested for automotive companies. By comparing to vehicles with internal combustion engine, EVs have the following advantages [1], [2]: •

The torque response of driving motor is accurate and 10–100 times faster than engines.

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All wheels can be controlled independently with an in-wheel motor.

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The output driving torque can be easily measured accurately from the motor current.