A Study Of Robust Control Method For Pneumatic Brake ABS On Commercial Vehicles

Anti-lock brake system (ABS) as active safety carborne equipments of automobile, which guarantees good performance of braking, handling ability and direction stability, has become the mandatory configuration. The factors of the dynamic characteristics of pneumatic brake system and the strongly nonlinear and dynamicity of the tire and so on, take more difficulties to ABS control. Therefore, developing robust theory actively for pneumatic brake ABS on Commercial Vehicles has practical significance.According to the principle of dynamics, quarter vehicle model is built as the foundation of researching robust control method of pneumatic brake ABS on commercial vehicles, and then the vehicle mode is built on the basis of the quarter vehicle model; On the basis of comparing and analyzing a few kinds of tire models accepted widely, the "magic formula" tire model is selected as the tire model in the vehicle brake which is suitable for dynamic simulation; pneumatic brake system model that is identified by experiment is built for the disadvantages of theoretic modeling .A class of nonlinear continuous predictive controller is proposed by researching on the control methods which is on the basis of slip ratio for commercial vehicles. T A nonlinear predictive controller was designed based on the slip ratio of ABS. The predictive model is acquired by truncating appropriately the Taylor series for system state. This paper designed the reference trajectory model by the ABS road identification and the theory of predictive control. When the road traffic changes, reference trajectory also changes. The quadratic predictive control law is modified. The integral feedback of slip ratio is also employed to increase the robustness of the designed controller. The simulation results indicate that the system could obtain perfect braking performance and lateral stability than logic threshold controller even with the model bias and load changes.The brake principle of ideal state is studied and the dynamic characteristics of the actuators are analyzed in this paper from the working principle and control target of ABS. According to the dynamic characteristics of actuators and strongly nonlinear problem in the process of braking, a self-tuning control algorithm is put forward which is practical and robust. The proposed strategy shows that it is possible to track the optimal slip value just by measuring the wheel speed, which dispenses with vehicle speed estimation modules to avoid the error of speed estimation. And according to the nonlinear characteristics of actuators in the braking process, this paper sets the compensation state in special. The proposed approach is robust with respect to the load variations and the nonlinear of the tire, take into account the dynamics of the actuators, and it is also has good adaptability.An ABS hardware-in-the-loop simulation platform is designed for a quarter commercial vehicle based on the self-tuning control which has good practicability and low cost and the common logic threshold control. This paper take the semi-object simulation on the dry asphalt road that is high adhesion coefficient road and ice road that is low adhesion coefficient road, comparing with off-line simulation in Matlab/Simulink. The results show that the established quarter vehicle model is precise, and can reflect the operating condition of vehicles; the self-tuning control has better adaptability and robustness than logic threshold control, which only takes into account of the dynamics of actuators, and is more convenient to set the threshold.Finally, in order to further validation the practicality and robustness of self-tuning control algorithm, the decorating form of ABS is designed on the vehicle. The self-tuning controller and logic threshold controller is applied to the braking model of the vehicle to compare and analyze the vehicle simulation in different braking conditions. The research indicates that, in the ABS control of the vehicle, self-tuning controller can obtain good braking performance and manipulation stability, and has better adaptability and robustness compared with logic threshold controller.