Nonlinear fuzzy MPC control for vehicles under extreme conditions

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. © 2023 Chinese Vibration Engineering Society. All rights reserved.