Minimization of State Deviations Using Perfect Indirect Control

An important issue in control structure selection is the plant ”stabilization”. By the term ”stabilize” we here include both modes which are mathematically unstable (modes with RHP poles) as well as ”drifting” modes which need to be kept within limits to avoid operational problems. By this definition, we can include the states x as variables that should be ”stabilized”, i.e., we want to avoid them to drift too far away from their desired (nominal) values. An advantage of this approach is that we are able to avoid problems resulted from nonlinear effects. Therefore, as the objective function can, usually, be considered as a combination of the states, the control system obtained by this approach is not tied too closely to a particular primary control objective (which may change with time) because it allows the designer to change the control objective. This paper presents a way to reduce the effects of disturbances and measurement errors in the states and the results show the effectiveness of this approach.