Automatic Temperature Control Design for Thermal Vacuum Tests Based on Fuzzy PID Control

Thermal vacuum test is an essential procedure for spacecraft to ensure the flight reliability. The automatic temperature control design based on fuzzy PID (Proportional-Integral-Differential) control is conducted to solve the problems of low temperature control rate, serious thermal hysteresis of cold-plate cooling and unexpectable temperature overshoot for the oil-heat-sink thermal vacuum simulator. An automatic temperature control method is developed combined fuzzy logic control and PID control. The control object model is identified with parameter identification and the initial PID parameters are set by Cohen-Coon tuning method. Then the PID parameters are adjusted in real time by fuzzy rules due to the deviation and deviation change rate between the measured temperature and the target temperature of the product. Hence the control performance is optimized. The proposed method can increase the precision of fuzzy logic control and enhance the adaptability of the PID system at the same time. The method has been applied in the thermal vacuum tests and these results indicate that the proposed method is applicable for products of different shapes with or without heat source. It obviously increases the temperature control rate and precision, decreases the overshoot and improves the test efficiency.