Simulation Study on Position Control Strategy of a Three-Phase Permanent Magnet Synchronous Motor for Steer-By-Wire Application

Vehicle intelligence with more precision and reliable steering mechanism for safety, comfort, and energy-saving is the recent key technology in the automobile industry. Due to its merits, the permanent magnet synchronous motor (PMSM) has been utilized in automation industries to serve as the servo system and is introduced in the vehicle field as the engine for the steering system. To avoid the complexity of computing and the current coupling effect of vector control which is easily affected by motor parameters changes, and to ensure that the steer-by-wire motor precisely tracks position, this paper adopts the sliding mode direct torque control method and proportional feedforward integrated with the fuzzy-proportional integral (PI) controller to address this issue. The proposed method is simulated and used to analyze the PMSM uncertainties changes due to the road condition and ensure the steer-by-wire motor tracking precision. The vehicle model is established in CarSim and combined with the simulated model under double-lane shift and step angle signal scenarios to verify the precision and steadiness of the steer-by-wire system. The steering resistance moment is considered as the load for the steering actuator due to the road condition, and the load observer is studied to mitigate the loading effect on the actuating motor. The results demonstrate that the following curve angle under the proposed method coincides highly with the reference signal with no fluctuation, and the tracking position accuracy is improved by 78.3% compared to the traditional proportional integral derivative (PID) controller. Moreover, through the realistic design of the steer-by-wire system control strategy, the vehicle handling stability is realized, which is beneficial to relieve driving fatigue and improving steering efficiency.