Performance Assessment Of Predictive PI Control System Based On Relay Feedback

The performance of control system will be degenerated without periodic maintenance along with time. So how to assess the performance of control system through acquiring information from operation production process is a problem that the field engineers concerned. The research of control system performance assessment has been highly promoted by requirement of the control system performance enhancing.Time-delay is a very common phenomenon in industry. The stability of system is severely influenced by the existence of long time-delay, cased the big overshoot, long regulating time, even oscillation and divergence. In this kind of situation, the ordinary PID auto-tuning method can hardly satisfy the demand of control system, even can't stabilize the system. Predictive PI is a control structure based on the combined model predictive control and PID. The controller has the characteristic that simple structure, less parameters and strong robust, and the impaction of the long time-delay to system can be eliminated by it, too.Firstly, in this thesis, the background of the research is introduced, which includes the control system performance assessment and model identification based on relay feedback. Secondly, the predictive PI control structure used in control of plant with long time-delay has been analyzed. The predictive PI control system is introduced specially, a performance assessment method is proposed based on the relay feedback model identification technology, the performance assessment benchmark is got by combined the integral absolute error and the indicator of robustness. This method could make the controller both have good setting point change tracking and disturbances restraining performance. Simulation has shown the effectiveness and feasibility of this method. Finally, the further prospect of the research work is present.