むだ時間要素で結合されたシステムに対するモデル予測制御

—フィードバック制御とフィードフォワード制御の統合設計—

抄録

This paper describes control design methods based on model predictive control for a system consisting of subsystems connected by time-delay elements. When the output of the upstream subsystem is measured in the middle of the time-delay element, it can be used for both feedback (FB) control of the upstream subsystem and feedforward (FF) control of the downstream subsystem. Since FB control requires offset-free characteristics and FF control requires fast transient response, a control system that has these different characteristics needs to be integrally designed. To this end, we propose two design methods. The first is to evaluate the control output with the smoothed error between the measured and predicted values. The second is to decompose the system into a FB control system and a FF control system and to evaluate the sum of performance indexes set for each system. Although the system is decomposed in terms of design, the input of each system does not affect the performance index of the other system. Consequently, the manipulated variable can be directly calculated as the sum of both controls. We also discuss a method of suppressing the violent oscillation of the manipulation reference so as to cancel the response delay of the actuators. By adding penalty terms of the reference change between the control steps and change from the previous control step to the performance index, the oscillation of the manipulation reference is reduced and the desired control response is achieved.