Research On Predictive Auto-coupling PID Control Method For Large Time-delay System

The time-delay systems are widely existed in temperature change process and chemical reaction process.Its characteristic is that the system has no effective output during the period of delay.Therefore,problems such as overshoot,oscillation,slow response speed and low control accuracy appear.For the control of large time-delay processes,thesis propose a control method independent of the controlled object model by combining the auto-coupling PID(AC-PID)with the Smith predictor.The tuning rules of velocity factors are designed for first-order and second-order systems with large time-delay.An advanced control method independent of the controlled object is realized and the problem of PID gain tuning is solved effectively.AC-PID eliminates errors based on errors as same as several classical control methods.Based on the concept of the extended state of active disturbance rejection control(ADRC),all unknown complex factors of the system are defined as the sum disturbance,and then the nonlinear uncertain system is mapped to linear uncertain system.With the introduction of the Smith predictor,a dynamic error system under the reverse excitation of summation disturbance without time delay is formed.The proportion,integration and differential of error are closely coupled by means of velocity factor independent of the precision model of the controlled object.Thus,a cooperative control system with different functions but consistent control objectives is formed.The global robust stability and anti-disturbance robustness of the control system are proved by time domain and complex frequency domain analysis.The features and innovations of the paper are as follows:1)Inherit the simple structure of AC-PID,the Smith delay prediction compensation link in parallel with the controller and then advanced compensation is adopted to control the system with large time delay.By means of the defined sum disturbance and the predicted compensation output,the control problem of time-delay system is transformed into the control problem of time-delay-free dynamic error system under the inverse incentive of the sum disturbance.2)The tuning rules of velocity factor are designed for the first-order and second-order systems with large time delay and the rules are only related to the estimation of time constant or transitional time and delay time.Thus the controller model and the parameter tuning rules are only related to the velocity factor.For it does not depend on the exact model of the controlled object and without parameter online optimization and real-time disturbance estimation,the problem of PID gain tuning is effectively solved.In order to verify the effectiveness of the proposed method,simulation experiments are carried out by using the designed controller,PADRC and the composite algorithm formed by the combination of traditional PID and Smith predictor.The simulation results show that the comprehensive control effect of the proposed a control method in static error,overshoot,tracking speed and anti-disturbance recovery speed is better than the other two algorithms.