基于变权重系数的LQR车辆后轮主动转向控制研究

为提高4WS汽车LQR后轮主动转向控制器的性能与适用范围，分析不同路面附着条件下质心侧偏角、横摆角速度对汽车稳定性的影响，提出一种基于路面附着系数调整最优控制中半正定矩阵Q权重系数策略.利用模糊控制理论设计变权重系数调节器，实现最优控制参数的自适应调整.通过Matlab/Simulink软件进行闭环双移线仿真试验，结果表明，在不同附着路面上行驶时，所提出的变权重系数LQR后轮主动转向控制器能够改善车辆的稳定性与安全性，保证车辆按照驾驶员预期的理想轨迹行驶，顺利完成双移线试验；相比于LQR后轮主动转向控制器，与标准双移线轨迹之间的误差降低了28.25%.通过硬件在环试验验证了这一控制系统的可行性与实时性.

Study on rear wheel active steering control based on variable weight coefficient of LQR

To improve the application and performance for rear active steering system of four wheel steering (4WS) vehicles with linear quadratic regulator (LQR), the effects on vehicles' stabilities which caused by side slip angle and yaw rate with different road-adhesion conditions were analyzed, and the adjustment strategy of optimum control positive semi-definite matrix Q weight coefficient based on the road adhesion coefficient was proposed. Variable weight coefficient regulator with fuzzy control theory and achieved adaptive adjustment for optimum control parameters were designed. The simulation which tested closed-loop double lane change through Matlab/Simulink reveals that the LQR rear active steering system could not only improve the stability and esecurity of vehicles but also ensure that vehicles follow the ideal trajectory for the driver's expectation. Results show that the double lane change simulation was completed successfully. Comparing to LQR rear wheel active steering controller, the error between ideal trajectory and actual path is reduced by 28.25%. The hardware in the loop test has verified the feasible and the real-time performance of this system.