Improved Electric Differential System for Independent Speed Control of Brushless DC Motors Driven Electric Vehicles

Abstract

This study proposes an improved electric differential system (EDS) for an electric vehicle (EV) with separately control of two front wheels driven using brushless DC (BLDC) motors based on robust fuzzy logic speed controllers. The speeds and torques of all wheels of the EV can change on a curved road with different surface conditions. The proposed EDS not only has important features such as reduction of EV mechanical losses and weight, but is able to separately control the speed of each front motor and lock them on such mentioned road conditions in order to make safe turn and driving. To achieve this, an improved Hall sensor signal-based synchronizing EDS along with a dynamic steering model of the EV is proposed to combine the rotor positions of the motors come from the Hall sensors signals and converting them to group of common switching signals to ensure the operation of motors with identical speed during variable steering angles and wheels torques. In spite of the recent control techniques for EDS, the proposed control strategy has simple and feasible structure with no need to auxiliary controllers. The system's simulations are carried out using MATLAB/Simulink toolbox for different operation modes of the EV to illustrate the proper operation of EDS and better accuracy of the control system.