The Control Method About Four Wheels Steering Car Based on LQR Theory

In this article, the bigger tire cornering stiffness and the smaller tire cornering stiffness were connected with the weighted functions to synthesize a nonlinear equation of state of vehicle. The optimal theory of linear quadratic regulator was used to design a synthetic controller to control the four wheels steering car, considering the nonlinear character of tire cornering stiffness. The software of Matlab/Simulink and Carsim were used for a co-simulation to test the performance of the controller. The results of the simulation show that, when the car is carrying out a double lane change on the low adhesion coefficient road, the four wheels steering car controlled by LQR method can give a better handling performance than front wheels steering car, and the four wheels steering car controlled by LQR synthetic controller which considers the non-liner tire stiffness can give good handling performance than LQR controller which considers only the liner tire stiffness.