Electric-Power-Steering system Vehicle Control Stability and Return Strategies Based on Predictive Control

Steering wheel torque may fluctuate when vehicles are making a steering return. Variation of steering wheel return torque may lead to insufficient or excessive return of vehicles, thereby influencing the steering stability of vehicles. To disclose the relationship between the performances of Electric-Power-Steering (EPS) system and vehicle control stability, a return control strategies for the entire vehicle EPS system based on predictive control algorithm was proposed. The state equation that combines the EPS system and the whole vehicle was built up through system modeling, and discretized thereafter. An EPS system-based vehicle predictive control model was constructed based on the objective yaw rate. Moreover, a system model based on the combination of MATLAB and CarSim software was constructed. Optimal values of parameters of the prediction system were determined by analyzing parameter characteristics in the predictive model. Return performances of the EPS system was improved by adjusting the power dead zone value, during which steering wheel torque signal was used as a control parameter. Validity of the predictive model and return control strategy was verified through a simulation experiment and field test. Results demonstrate that the designed control system can effectively improve control stability of vehicles and strengthen return of system. Yaw rate response time of vehicles after optimization of the control and prediction time domains in the predictive control is decreased by 4 s and the response amplitude decreased by 2 deg compared with those before optimization. The minimum return residual angle of steering wheel is 2.2 deg. The proposed method provides significantly references to explore the vehicle control stability and return control strategy of EPS. © 2022 School of Science, IHU. All rights reserved.