Research Of Temperature Controller Based On MODBUS

The temperature is one of important parameters in the industry. The object temperature of furnace, heat treatment furnaces, reactor, used in metallurgy, machinery, food, chemical industry, often requests to control strictly. The introduction of temperature control module is significant to improve the control precision so that it has been widely used in many industrial production processes. However, general PID temperature controller is adjusted PID parameters by experience of engineering staff and circuit precision also need to adjust by potentiometer, which lead to great trouble to engineer and limit the actual application of temperature control module. In view of this situation and considering the requirement of the temperature control for the small and medium-sized enterprises, this research develops the temperature control module which has PID parameter auto-tuning function.First, this paper introduces the development of temperature control system, the development situation of PID controller and PID parameter auto-tuning. And then this paper designs hardware and software circuit. Finally, this paper researches the system of PID auto-tuning and verifies the precision and affection of the PID auto-tuning by experiment.The temperature control module with isolated RS485 communication interface supports MODBUS RTU/ASCII and multiple sensor input, improve the protection function, automatically compensate lead resistance, calibrate zero-point and full by software, and overcome the time-drift and temperature-drift of system by the technology of digital zero calibration. The temperature control module has good reliability, stability and universality without adjusting potentiometer. Using the weighted least-square parameters estimation method find the A/D conversion for nonlinear optimal parameters circuit. Thus, the temperature control module realizes the PID parameter auto-tuning, and supports fuzzy control. Generally, this research provides practical solutions for the development of small and medium-sized enterprise.