Development Of Temperature Control System For Infrared Target Simulator

Measurement and control of temperature is a common issue in daily life and manufacture. Accurate measurement and control of temperature have great significance for researching and producing new materials, promoting the development of science and technology and raising the level of production. Infrared target simulator is the equipment of detection and identification for infrared homing warhead, radar test system and many other major PV systems, so it is one of the essential equipments for military and national defense. Because of the crucial device of infrared simulator-blackbody which is easy to be influenced by temperature needs a constant work environment and few kinds of thermostat aim at it. Therefore it is necessary to develop a kind of special thermostat with high accuracy.PID control is the earliest control means. It has simple construction, good robustness and high credibility, which is wildly used in industry control systems. But the parameter's adjustment of the PID mainly depends on the human's experience and the object model, the result is normally dissatisfying. Fuzzy control which developed rapidly in recent years does not need to know accurate mathematic model of object. But the fuzzy PID which is based on human thinking and producing experience applies language rule to describe controlling process and bases on rule to modify the controlling arithmetic and parameter .So it has been one of the essential and effective forms of intelligent control. Combining PID control with fuzzy control, the system have both the accuracy of PID control and the facility of fuzzy control, and it can also make perfect effect on the nonlinear and time varying systems.By analyzing the various means of temperature measurement and studying some advanced temperature control technique, I adopted the temperature measurement of four-wire platinum resistance based on the constant current source and a scheme of fuzzy PID control for infrared target simulator. The core of the thermostat is PIC16F873A MCU with abundant on-chip peripheral equipment and the software. It has carried out some advanced functions at least hardware cost such as the channel selection, measurement and control of temperature, the temperature control value setting up, the control parameter of PID self-tuning. The software design uses the way of operating systems. The management of the system to subprograms makes subprograms independence of each other and extremely modularized, and also improves the readability and maintainability of the program.The thermostat which uses the temperature measurement circuit of four-wire platinum resistance based on the constant current has high precision and simple structure. The design of fuzzy PID control algorithm can carry out the function of PID control parameters self-tuning to reduce the overshoot and accelerate the response speed. The results of actual testing prove that the performance of the thermostat has achieved the requests of the design.