Abstract: In order to guarantee the welding quality of gas pipe joints and prevent serious accidents, a high performance welding control system for thermal melt pipe fittings is developed. The system uses bidirectional thyristor as the main control circuit, and uses timer interrupt technology to control the bidirectional thyristor through PWM( Pulse Width Modulation) to realize the adjustable voltage output of the thermal melt welding system. In order to improve the reliability of the system, the errors generated by the information collected by the sensor are analyzed. And the nonlinear and zero drift errors of the sensor output are reduced by the piecewise dynamic calibration of the sensor information using the least square method. The adaptive sliding filtering method is adopted to suppress the errors of noise and power frequency interference. For the control voltage, an improved PID( Proportion Integration Differentiation) fast voltage regulation algorithm is designed to improve the output response speed and output stability. The field test shows that the welding process can reach steady state quickly and effectively suppress the interference of environmental noise to the data acquisition, the voltage fluctuation is less than +-0. 1 V, lower than +-0. 5 V national standard, which meets the requirements of welding process.

Key words: control system,  , error,  ,  , sensor,  ,  , reliability