Researches on 4WIS-4WID Stability with LQR Coordinated 4WS and DYC

Four-wheel independent steering and four-wheel independent driving electric vehicle (4WIS-4WID EV) has more control degrees of freedom (DOF). It benefits to realize torque allocation and differential steering control. Therefore, four wheel steering technology (4WS) and direct yaw control (DYC) are important research direction of vehicle stability. This paper designed a kind of novel adaptive linear quadratic optimal regulator (LQR) as a coordination controller for 4WIS-4WID EV stability control with 4WS and DYC. The deviation between the real value and ideal value is obtained and delivered to LQR controller. According to different speed and road surface conditions, sideslip angle β and stable area are calculated using phase plane method. The weight matrix Q and R of LQR controller is adaptive to velocity, adhesion coefficient and the \( \beta - \dot{\beta } \) phase plane. The performance of adaptive LQR is simulated in MATLAB/Simulink and Carsim platform. Compared with no control, 4WS, DYC, and fixed LQR strategies, the results show that the adaptive LQR controller with weight matrix adaption has better performance than the outputs form DYC, 4WS and fixed LQR in stability.