A design method for modified PID control systems for multiple-input/multiple-output plants to attenuate unknown disturbances

The Proportional-Integral-Derivative (PID) controller structure is the most widely used one in industrial applications. However, PID controller cannot stabilize any plant. In order to overcome this problem, Yamada and Hagiwara proposed a design method for modified PID controllers such that the modified PID controller makes the control system for unstable plants stable and the admissible sets of P-parameter, I-parameter and D-parameter are independent from each other. When modified PID control systems are applied to real plants, the influence of disturbance in the plant must be considered. In many cases, the disturbance in the plant is unknown. It is comparatively easy to attenuate known disturbances, but it is difficult to attenuate unknown disturbances. From a practical viewpoint, it is desirable to design a modified PID control system to attenuate unknown disturbances. Recently, a design method for modified PID control systems for to attenuate unknown disturbances was proposed. However, no paper examines a design method for modified PID control systems for multiple-input/multiple-output plants to attenuate unknown disturbances. In this paper, we propose a design method for modified PID control systems for multiple-input/multiple-output plants to attenuate unknown disturbances.