The Automatic Control System Of Heat-treatment Technology For The Composite Brake Shoes

According to the technology and development planning of railway ministry, high-speed and heavy-duty railway will be the major direction.Brake shoe is an indispensable component in vehicle and brake system.Because of railway transport characteristics,they results in the complicated working environment of the brake shoe. The brake shoe endures high temperature,static load and dynamic load.Therefore,the reliability of brake shoe quality is directly related to the rail transport safety.The characteristics of heat-treatment processing are nonlinear,time-varying,noisy and time-delay.so it is very difficult to establish the accurate mathematical model of the object.It is also very difficult to control the temperature of the industry process using the conventional PID control theory.Since the heat-treatment instrument of the composite brake shoes has long interval time in adjustment,hard control in the time of the rising temperature and low control precision,lanzhou vehicle repairing section proposed the automatic reform to the TDL constant temperature drying oven.Against the characteristics of heat-treatment temperature control,the design of the hardware system that used ADμC812 microcontroller as the control center was discussed.ADμC812 microcontroller is a real and complete data acquisition chip.Its A/D converter has high speed,simple structure. Combined with the software,the nonlinearity hardware calibration on thermocouple and the over-zero-trigger PWM pulse width temperature control was achieved.It has the fast speed of circuit reaction and anti-jamming capability.The characteristics and control difficulty of heat-treatment processing was also analysed comprehensively.Then the essential reasons of the poor precision in the equipment which was to be improved were summarized.Considering that the control method must apply in the practical control effectively,an improved Smith predictor control method-integral separation segmentation and anti-saturation PID Control Algorithm was proposed.Overshoot was reduced;static error was decreased and the problem of heat-treatment temperature control was settled up.Hardware circuit was designed,whole software was debugged,and control algorithm was edited and debugged.It was used in the practical field operation.It shows that the control system operates steadily and has high reliability,the algorithm doesn't need the accurate mathematical model of the object.it also has good flexibility,high operational capability and strong robustness.Test shows that it has a better control effect.