Application Research Of The Automobile Inertia-brake-test-system Based On Fast Pneumatic Servo Control

The brake's good performance is directly related to the safe operation of automobile. The automobile inertia-brake-test-system is used to test various performance of the brake by assembly bed-test through simulating the brake process of automobile, which requires achieving constant air pressure, constant oil pressure, constant torque and constant deceleration automatic control. The system adopts the driving type that fast pneumatic servo drives hydraulic cylinder, which is a typical electro-pneumatic-hydraulic, strong nonlinear, time-lagging and varying, complicated system.Using traditional single closed-loop PID, only air and oil pressure can be controlled. It can't achieve fast control of torque and deceleration. Therefore, it is of practical significance and academic value to perform research on the constant torque and deceleration automatic control of the automobile inertia-brake-test-system.Based on building the model of the automobile inertia-brake-test-system, this paper constructs a simulation platform of the system by the simulation software of MATLAB/SIMULINK; Analyses the characteristics of double closed-loop control,PID control,fuzzy control technology and some structures of Fuzzy-PI controller; Aimed at the disadvantages of traditional single closed-loop PID controlling torque and deceleration, brings forword a double closed-loop Fuzzy-PI control to the constant torque and deceleration control by combining the advantages of three control technology, and performs the simulation verification on the simulation platform;Designs the general structure of control system and human-machine interface of monitoring system based on configuration software WinCC.The technology of double closed-loop adopts inner-loop and outer-loop control.The outer-loop is a constant control system and the inner-loop is a servomechanism.This structure has better dynamic performance than traditional single closed-loop system, which can improve the work frequency of the system and increases the system's anti-interference ability greatly.Fuzzy control is a nonlinear control technology essentially,which shows superior performance to control the object that is complicated, nonlinear, time-lagging,difficult to describe by precise mathematical model,and it has a fast response speed and strong robustness. But the fuzzy control precision is not good, which makes it is necessary for introducing integral link to improve the static performance. This paper combines the technology of double closed-loop control with fuzzy control, and puts forward a new way that brake master cylinder actuating force inner-loop takes traditional PI control and torque or deceleration outer-loop takes Fuzzy-PI series compound control. In the simulation research, the inner-loop adopt PI control in all cases, the outer-loop adopt PI control, fuzzy control, Fuzzy-PI control respectively. Compareing the three control modes in the four situations of step input, different input amplitudes, system structure parameters varying and anti-interference ability, we can reach a conclusion that the double close-loop Fuzzy-PI control can achieve fast control of torque and deceleration.In the same time, it keeps good adaptability ,control precision and robustness.Considering the features of the automobile inertia-brake-test-system, the control system design adopts the distributed network technology based on PROFIBUS-DP field bus, in which monitoring stage adopts the industrial personal computer based on WinCC, control stage adopts SIMENS PLC S7-400, and field stage adopts ET200 remote I/O module.