Design Of Fuzzy Self-tuning 2DOF-PID Controller And Its Application In Grinding-Classification

Because of its simple mechanism and flexible structure, the conventional PID control is widely used in the mineral processing and even in the whole industrial areas (as a fundamental control method). But on the one hand, the conventional PID control can not keep the system tracking and the anti-interference performance in good condition simultaneously, on the other hand, the parameters of P^ L D must be tuned by the accurate model of system: The more accurate mathematical model is got, the more appropriate parameters are obtained, and the better control results are reached.But the mineral processing has a big lag, a very long transient time, many influence factors, and strong interacting among the variables, it is a non-linear, time-varying process. All these make it difficult to create an accurate practical mathematical model. Aimed at these features of mineral processing, in this thesis, the two-degree-of-freedom(2 ?DOF) PID control is introduced, one of the intelligent control - fuzzy technique is studied ,and the approach using both 2-DOF PID and fuzzy control is provided.. Several control schemes are presented as follows:(1) To improve the conventional PID control which can not keep the system tracking and the anti-interference performance in good condition simultaneously, the necessity to use the new type of 2 ?DOF PID control in mineral processing and even in industrial area is explain. Furthmore, the methods of the Advanced-two-degree-of-freedom PID and the Super-two-degree-of-freedom PID are provided. The simulation results demonstrate that these two methods solved the mentioned problem of the conventional PID control.(2) In the mineral processing, there has many fuzzy variables, These variables are analyzed based on the concepts of the fuzzy control, and a control rule - adaptive fuzzy controller is designed. In this controller, the input signals are categorized at first, and then controlled. Simulations verify its effectiveness.(3) Using both the Super-two-degree-of-freedpm PID control and fuzzy techniques simultaneously, a self ?tuning PID controller is designed. Using fuzzy inference method, the PID parameters can automatically be adjusted on-line for the vary conditions of the grinding-classification in mineral processing. After doing many simulation experiments in which this controller is used in the mineral processing, it is proven that this controller has adaptability to the processes and environment, and robustness.