Abstract
In this paper, we study linear time-invariant multivariable systems with two-degree-of-freedom compensators. Firstly, we parametrize all stabilizing compensators by the two independent parameters which determine the system transfer matrix and the robustness property, respectively. Based on this parametrization, a basic structure of the control system is given. This structure clarifies that both specifications on the system transfer matrix and the robustness property can be satisfied independently. Secondly, utilizing this basic structure, we give a general solution of the robust tracking problem in the two-degree-of-freedom control systems. Thirdly, the concept of basic structure is extended to the control systems with sensors whose dynamics are not negligible.
