极限工况车辆非线性模糊MPC控制

Nonlinear fuzzy MPC control for vehicles under extreme conditions

针对应急转向下车辆的横摆稳定性和侧倾稳定性,研究前轮主动转向(active front-wheel steering,AFS)和直接横摆力矩(direct yaw-moment control,DYC)的非线性模型预测MPC集成控制。考虑轮胎侧偏刚度非线性变化,采用Takagi-Sugeon方法(T-S)建立4个车辆横摆-侧倾线性子系统,结合模糊观测器实时获取轮胎动态参数。为消除侧倾稳定性能约束,在T-S框架下建立改进横摆理想参考模型,引入侧倾稳定指标约束期望横摆角速度。根据横摆角速度、质心侧偏角、侧倾姿态的跟踪偏差和控制输入建立二次型评价函数,以驾驶员转向扰动为评价函数附加项,构建无限预测时域MPC最优性能指标,基于分布补偿方法设计非线性系统的模糊控制器MPC-TS,并根据轮胎侧偏特性设计自适应主动转向约束。通过LMIs方法将无限时域的非线性MPC控制转化凸优化过程,推导子系统转向扰动最小值问题的线性不等式。最后联合Trucksim-Simulink软件进行仿真测试,以Sine with Dwell和Fishhook曲线为驾驶员输入模拟应急转向过程,结果表明:在驾驶员应急转向的强非线性过程,MPC-TS方法能够显著增强横摆稳定性和侧倾稳定性,并适应低附和高附着路面。

Here,aiming at yaw stability and roll stability of vehicles under emergency steering,nonlinear model prediction integrated control(MPC)of active front-wheel steering(AFS)and direct yaw moment(DYC)were studied.Considering nonlinear change of tire lateral stiffness,Takagi-Sugeon method(T-S)was used to establish 4 linear subsystems of vehicle yaw and roll,and tire dynamic parameters were obtained in real time with fuzzy observer.In order to eliminate constraints of roll stability performance,an improved yaw ideal reference model was established under T-S framework,and the roll stability index was introduced to constrain the expected yaw angular speed.According to tracking deviation and control input of yaw angular speed,mass center sideslip angle and roll attitude,a quadratic evaluation function was established,the driver steering disturbance was taken as additional item of the evaluation function,MPC optimal performance index in infinite prediction time domain was constructed,nonlinear system’s fuzzy controller MPC-TS was designed based on the distributed compensation method,and the adaptive active steering constraint was designed according to tire sideslip characteristics.Nonlinear MPC control in infinite time domain was converted into a convex optimization process with LMIs method to derive linear inequality for the minimum value problem of subsystem steering disturbance.Finally,simulation tests were conducted with Trucksim-Simulink software,and Sine with Dwell and Fishhook curves were taken as driver inputs to simulate emergency steering process.The results showed that MPC-TS method can significantly enhance yaw stability and roll stability of vehicles in strong nonlinear process of driver’s emergency steering,and adapt to low adhesion and high adhesion roads.