Research And Simulation On Control Method Of The ABS

ABS can prevent wheels from locking in emergency braking situation by predicting and controlling the brake pressure, it also ensures the tyres work near the peak of the “tire longitudinal force-slip rate” curve. So it has become a standard part on cars because it can effectively avoid lots of dangerous situations, such as the tire wear、unable to rotate the steering wheel and so on. Since ABS has strong nonlinear, with time-varying parameters and no precise mathematical model and so on, this paper chooses a sliding mode control method, with the tire slip rate as control object and brake torque as the control variable in an optimal closed loop control system online.Unlike the diagnosis methods, this paper adopts a kind of searching optimization extreme method to get the peak of the “tire force”-“slip ratio” curve automatically on online, which can ensure the largest tire longitudinal force, the shortest straight line braking time and distance at the same time. Since the longitudinal force and inner lateral force coupling, when a vehicle steers, the largest longitudinal force corresponds to smaller lateral force, leading to the instability of turning, so this paper takes the steering angle into account and uses the offset function to avoid algorithm following optimal value and leading unacceptable lateral force when the car starting turning. Thus, when a car steers, these methods can ensure it’s stability by enlarging the tire lateral forcesMany models which are based on engineering experimental parameters are built in Matlab. The correctness of the extremum-seeking algorithm is verified through experiments. Through the comparison of experiments, it verifies the effectiveness and importance of ABS. Finally, in the case of multi degree of freedom vehicle model experiments that include straight line braking and lateral motion, the correctness of the extremum-seeking algorithm is proved, and the practicability of the scheme is verified by the simulation results.