Control synthesis versus saturation compensation for systems with rate and amplitude constraints

A control synthesis theory was proposed by Horowitz (1984) to design a `three degrees of freedom´ controller for rate and amplitude constrained systems. Following anti-reset windup techniques, we (1997) proposed a saturation compensation structure to design compensators for given linear controllers. It is shown that the compensator can be reformulated in terms of the control synthesis theory. Conversely, the `three degrees of freedom´ controller is a special case of the compensator construction. From this analysis, shortcomings of the control synthesis theory are exposed and improvements using the compensator structure are discussed and illustrated by an example