Research On The Methods Of PID Parameters Self-tuning And Development Of The Controller

PID (Proportional-Integral-Derivative) control is one of the control methods which are widely used in process industry at present. However, the simple PID control can not meet the optimal control requirements when the object system changes its characteristics, while manually adjusting PID parameters can not meet the control accuracy and adjusting frequency. There are a variety of PID controllers with self-tuning function at present, but the tuning methods of them are usually complicated and have bad influence on the actual control. In view of PID control method is still widely used at present, research on the methods of PID parameters self-tuning will have good application values. Based on the current application situation, this paper puts forward and realizes the design of a kind of PID controller with parameters self-tuning function based on embedded technology.This paper first simply introduces digital PID control and analyzes the current research on PID self-tuning methods, then focuses on the study of the principle and design methods of PID parameters self-tuning based on correlation coefficient identification method and fuzzy self-tuning method. Then this paper carries out simulation experiments using Matlab.Based on the study of theory, this paper realizes a PID self-tuning controller using an AVR single-chip microcomputer based on correlation coefficient method, and shows the details of hardware and software designs. The self-tuning process is mainly divided into two parts including the model identification and PID parameters optimization. This paper describes the basic procedure of modeling using correlation coefficient method, establishs the FOPDT (first order plus delay time) model, then optimizes PID parameters using H-J searching method. This controller can sample exactly a variety of sensor input signals while outputting two kinds of control signals:4～20 mA current or PWM pulse whose period and duty cycle can be adjusted, to adapt to different applications. At the same time, this controller expands the digital input and output interfaces, to have the capability of satisfying different control requirements. The software design uses modularization method to enhance the scalability of the program.At last, the controller is applied to temperature control system, and the parameters of the controller could be displayed and modified online using the monitoring and control interface in PC. The actual application shows that the control system has a fast response and good accuracy and stability, and the control effect is well.