PLC를 이용한 온도제어에서 선형함수와 시그모이드함수 제어기 성능 비교

Comparison of Linear and Sigmoid Functions for Controlling Temperature Using PLC System

Temperature control using Programmable Logic Controller(PLC) was normally implemented as Proportional Integral Derivative(PID) controller. While establishing the PID parameter, increasing the Proportional(P) gain to improve the response characteristics resulted in a smaller linear control region. When the linear region becomes smaller, the control changes from the desired PID control to the undesired on/off switching control. As a solution to this problem, a new control method using sigmoid function has been applied. To validate the new control method, an experiment was conducted to compare the sigmoid function control by controlling the P gain parameter. The experimental set-up comprised a heater, a cooler(fan), a temperature sensor, the PLC input and an ADC-modules. A TCP/IP communication was implemented using a communication socket for transferring data from the PLC to the PC. The data from the PLC was supplied to the PC using LabVIEW. With this experimental set-up, the resulting temperature variation was displayed graphically on the PC screen. Simultaneously, the data from each PLC was stored and analyzed in the PC. From the experimental results, the control performance as determined by the sigmoid function was found to be better than that by the linear function.