Abstract: As compared with traditional vehicles，four-wheel steer/drive vehicles have very good active dynamics control performance，ensuring that the four-wheel steering /torque is independently controllable． This article proposed a time-varying LQR control system based on genetic algorithm for the coordinated control of the steering angle-torque of four-wheel steer/drive vehicles． Different from the traditional linearized tire reference model，it established a linear time-varying system considering the variable stiffness characteristics of the tire，and the control weight matrix of the state quantity was optimized with the genetic algorithm． The simulation results show that under a given corner step input，the time-varying LQR control considering the non-linear characteristics of the tire is better than the linearized model control system in zeroing the center of mass sideslip angle，and the tracking accuracy of the yaw rate with ideal value is improved by 3. 01% ． The simulation of the double line change under high speed and low road conditions shows that the time-varying LQR control system based on genetic algorithm ensures a better trajectory tracking ability of the vehicle，and the maximum lateral displacement error control effect is improved by 44% ，compared with that of front-wheel steering vehicles．

Key words: four-wheel steer-drive vehicle, steering angle-torque coordinated controlgenetic algorithm, LQR control