Integrated Control Of AFS And DYC Based On Higher-order Sliding Mode Control Theory

Either gas car or electric cars,the research on active and passive safety of vehicles to improve vehicle handling stability and comfort has always been the focus and hot spot of research.Domestic and foreign research institutions and car companies have done a lot of research and development on this,and designed many control systems to improve vehicle safety.With the development and popularity of the electronic control technology,used in vehicle active safety technology becomes rich and diverse.But the vehicles control system which should play a security role Improve handling stability become unsafe because of the mutual interference and mutual coupling between the various systems.So,the integration of various control systems in the chassis becomes an inevitable trend.In particular,the integration of the control systems to maintain the lateral stability of the vehicle mainly consists of active front steering(AFS)and direct yaw moment control(DYC).Aiming at the coordination problem of functionally coupled active front steering and direct yaw moment control in vehicle handling stability control,front wheel slip angle,rear wheel slip angle and the difference between the two are used to characterize the lateral stability of the vehicle characteristic quantity.Establishes the front wheel slip angle-rear wheel slip angle phase plane and the front wheel slip angle-difference between front wheel slip angle and rear wheel slip angle phase plane.Integrates the front and rear wheel lateral force characteristics into the established the phase plane.The stable region division in the optimized phase plane method divides the vehicle lateral state into three types: stable,critically stable,and unstable,so as to establish the coordination criteria between AFS and DYC to achieve a more accurate description of the real-time state of the vehicle and coordinate control more reasonable,effective and accurate.Taking into account the fact that vehicle state variables such as wheel slip angle are difficult to obtain through sensors in practice,and the state variables that can be obtained by sensors such as yaw rate cannot be accurately obtained due to noise and disturbance.A higher-order sliding mode observer based on super-twisting algorithm was designed,which can observer the yaw rate,the side-slip angle of the vehicle mass center,the front wheel slip angle,the rear wheel slip angle and other state variables.The observer has the characteristics of strong robustness and strong anti-interference.The accuracy of the data obtained under the influence of noise and disturbance can provided,accurate information guarantee for the calculation of coordination criteria in real time.For AFS and DYC control,a higher-order sliding mode controller based on the adaptive super-twisting algorithm was designed respectively to eliminate chattering phenomenon in the control system during the stability control process.So that the control output of the controller is smoother and more beneficial Improve the control effect and control accuracy,avoid the high frequency switching of the actuator,thus increase the service life of the actuator,and enable the proposed coordination criterion to better realize the coordination control effect of AFS and DYC.The test results shown that the coordination criterion established through the precise division of the front wheel slip angle-rear wheel slip angle phase plane can better coordinate AFS and DYC.So that the vehicle can still maintain stability under extreme conditions,and has a high longitudinal performance at the same time.