Simultaneous stabilizing controller with robust servo characteristic for a pair of unstable plants

In this paper, we examine a design method for simultaneous stabilizing controller with robust servo characteristic for the step signal. Several papers have been examined design methods for simultaneous stabilizing controllers. However, no paper examines a design method for simultaneous stabilizing controllers which has robust servo characteristic for the step signal. Therefore, using the simultaneous stabilizing controller which is designed by previously proposed method, the output of the control system cannot follow the step reference input without steady state error when the plant has uncertainty. Moreover, the influence of the step disturbance cannot be attenuated. In this paper, we propose a design method for simultaneous stabilizing controllers which has robust servo characteristic for the step signal. They can simultaneously stabilize a pair of unstable plants having no common unstable poles. In order to solve this problem, we use the relationship between the simultaneous stabilization and the strong stabilization. Then this problem can be reduced to the strongly stabilization problem with interpolation problem. We can obtain the parameterization of all simultaneous stabilizing controllers with robust servo characteristic for the step signal by using this idea.