Reliable control using hidden sub-controllers and their realization as sampled-data controllers

This paper proposes a new method for reliable control: addition of a hidden sub-controller. It enables us to make the provided control system reliable without affecting the control performance that has been attained originally by the main controller. This paper states when we can use this method and gives parametrization of all the admissible hidden sub-controllers. Moreover, we show advantages and limitations in realizing the controllers as sampled-data ones. For accuracy of treatment, some efforts are spent to clarify the basic properties of multi-operator systems, which frequently appear in this paper