Control And Study Of PID Self-tuning

Up to now, PID controller has already undergone the dozens of year history, and is still the most widespread controller in the industrial automation domain because of the fine performance. Whether the PID controller can keep the control performance good is due to the tuning of the PID parameter. These methods have brought the energy for the research of the tuning of PID parameter .Such as: Z-N method, relay self-tuning and so on.Because its simple principle, practical also the good control effect, PID self-tuning method based on relay feedback is widely applied in the industry control. But it is still a one tuning method, But most of industrial process is non-linear, dynamic parameter and time-lag in fact, the general methods couldn't keep the good control performance. So, for getting the good control performance, it is needed that not only the tuning of PID parameter doesn't rely on the process model, but also the PID parameter can be adjust on-line.For this reason, this paper proposed the tuning strategy that PID self-tuning method based on relay feedback tuning the PID parameter starting value , then online to adjust the PID parameter value by the fuzzy control. Therefore, this method not only has realized an one online tuning simply, but also has realized the online real-time self-tuning. In order to prove the superiority of the fuzzy PID control, this paper designs closed-loop system of direct current machine PWM control based on STC89C52. After the hardware debugging, we obtains the conclusion that the fuzzy PID control surpasses the ordinary PID control.