Guizhen Yu

Estimation of brake pressure and tyre–road friction during ABS activation

Anti-lock Braking System (ABS) control algorithm and diagnostic function rely heavily on information of road friction coefficients and brake cylinder pressure. To provide a more efficient and reliable means of friction and pressure estimation, an algorithm based on wheel speed signals and control commands for hydraulic valve operation is proposed. Estimated results are achieved by comparing the sums of squared speed errors between the measured wheel speeds and those based on a brake pressure model and wheel dynamics. Performance of the algorithm is evaluated using ABS test data under various braking conditions.

Research and Comparison of Control Methods of Vehicular DYC System

Direct Yaw-Moment Control(DYC) can enhance the vehicle lateral stability significantly. Studying its control methods is a hot spot of vehicle dynamics. Based on the in-depth study of the vehicular handling dynamics and the advanced control theory, the PID, fuzzy and intelligent integral fuzzy-PID controllers for DYC system are designed and simulated with the vehicle model. The fuzzy control theory has great superiority in some systems that need a lot of experiment knowledge and experience such as DYC. The structure of fuzzy-PID controller is proposed by Bialkowski in 1983 and it is proved that it can eliminate the error of fuzzy system. The intelligent integral is introduced to avoid the limitation of normal integral. Simulation results of the controllers are compared and indicate that all the controllers can realize the effective control of DYC, and have their own characteristics. Intelligent integral fuzzy-PID has more rapid response and higher control precision, and has much better applying prospect. Intelligent integral module can reduce the side effect of integral function, so the control effect of fuzzy-PID is further improved. The research provides important basis for applying intelligent integral fuzzy-PID to an actual DYC system.