The Research Of Four-wheel Steering Based On Optimal Control And Co-simulation

Four-wheel steering can reduce the minimum turning radius of vehicle in a low speed steering; In a high speed steering, Four-wheel steering can reduce yaw rate and lateral movement of vehicle, and the vehicle driving attitude is controlled more easily by driver, so Four-wheel steering has handling stability and active safety, and become an important new technology of modern vehicle.The whole vehicle's two and three DOF mathematical models are built,uniting with the relationship of linear wheel's lateral force and side slip angle. A MIMO comprehensive control analysis is done to the four-wheel steering vehicle, using optimal control law. The vehicle models are simulated in high and low speed steering meanwhile. The result is compared to the vehicle whose front and rear wheel corners are in proportion and front-wheel steering vehicle. A four DOF,four-wheel steering vehicle mathematical model with steering system is built based on this. The simulation and comparison analysis are done to two, three DOF and different steering ratio respectively. The variation curve of sideslip angle, yaw rate, lateral acceleration, side rake angle, side rake angle rate and roll angle acceleration over time are obtained. The four-wheel steering vehicle mathematical model is built with ADAMS, multibody dynamics simulation software. A co-simulation experiment is done combined with magic formula tire model and MATLAB/Simulink, using the optimal control theory.The results show that sideslip angle can be zero with four-wheel steering system of optimal control theory; the minimum turning radius is reduced in a low speed steering; the response time of yaw rate and overshoot are reduced in a high speed steering; important basis is provided to the validation of theory research; vehicle maneuverability, stability and driving safety are proved.