SELECTABLE FEEDBACK CONTROL SYSTEM

A control system includes a first estimation section for estimating a first state variable of a plant object such as a semiconductor wafer temperature control arrangement on the basis of a control input supplied to the plant object and an output from the plant object, a second estimation section for estimating a second state variable of the plant object on the basis of the control input alone, a switching section for selecting one of the first and second estimation sections, and a servo section for adjusting the control input by feeding back the state variable from the first or second estimation section to an input section of the plant object.