The Robust Servomechanism Problem with Input Saturation Constraint

A limitation in achieving effective control for disturbance rejection/set point tracking in a multivariable plant is often associated with the operating range of the control input signals associated with the plant, i.e. control input saturation, and maximum rates of input change constraints. This paper proposes a LTI controller, called an "unsaturated controller", for a stable linear time invariant plant, which has the property that it solves the robust servomechanism problem for control disturbances/set-points, and maximizes the operating range of the controller for the plant, subject to any given maximum rate of change constraints, which may be imposed on the control inputs of the plant. Some application studies are included to illustrate the behaviour of the controller.