The Design Of PID Controller On-line Self-tuning Based On AVR Microcontroller

PID controller is the main controller used for process control. Because of its simple algorithm, robustness and high reliability, PID controllers were widely used in industrial process control. But it needed for experienced engineers to complete PID parameter tuning, time-consuming and laborious. Combined with the factors of delay and nonlinear in the actual system, it increased the difficulty of PID parameter tuning. It is an important subject how to on-line self-tuning PID parameters to meet the requirements of process control. It can not only reduce the burden on operators, but also get the best run.Relay auto-tuning is one of the methods proposed that how to self-tuning PID parameters now. Its basic principle is to use limit cycle oscillations caused by relay feedback to determine the critical gain and critical period, and then used Ziegler-Nichols, pole placement and other methods to tuning PID parameters. To solve these problems, we design a PID controller based on AVR microcontroller. The controller used relay auto-tuning PID control algorithm, with the ATmegal28 as the Core Chip to achieve controlling of water level on the FESTO, and used 8-bit LED digital tube to show the water level of control object and the user settings in real time.First, the domestic and international background, current situation and development trend of the PID controller were introduced simply. First, the domestic and international background, current situation and development trend of the PID controller were introduced simply. Then, in the second chapter, it focused on the basic principle of PID controller, an improved digital PID controller, and PID auto-tuning technology, and gave a detailed introduction about relay feedback self-tuning PID technology and tactics made. In the third chapter, the hardware design of self-tuning PID controller was introduced, that used modular design, and each module of design were introduced in detail. In the fourth chapter, the software design of controller was described. The software platform on the controller design and process design have been described, and completed the Matlab simulation of the relay-based PID algorithm. The effect that the design of self-tuning PID controller to control the object's control were introduced and analyzed in the fifth chapter. In the sixth chapter, the development of the self-tuning PID Control in the future were prospected.The results show that the design of the relay on-line self-tuning PID controller could be online self-tuning PID controller parameters, which were assigned to PID controller. It could get a good result to use this controller, fast, smooth control, and small overshoot.