Locking electric differential for brushless DC machine-based electric vehicle with independent wheel drives

The stability of vehicles under certain driving conditions is improved by forcing the wheels to turn at the same speed regardless of the available traction under individual wheels. For conventional vehicles this can be achieved by locking the mechanical differential system. This paper proposes an innovative approach for locking the electrical differential system (EDS) of electric vehicles (EV) with independent brushless DC (BLDC) machine-based wheel drives. The proposed method locks the active wheels of the vehicle as if they were operating on a common shaft. The locking algorithm is implemented by processing the Hall sensor signals of the considered motors and driving them with a single set of “averaged” Hall signals, thereby operating the motors at the same speed and angle. A detailed switch-level model of the EDS embedded with the proposed sync-lock control (SLC) along with the BLDC propulsion motors has been developed and compared against the measurements for the considered BLDC propulsion motors. The proposed technique is shown to achieve better results compared to a conventional speed control loop as the considered motors are locked directly through the corresponding magnetic fields.