Design of dynamic and static antiwindup compensators for a three-loop autopilot

The presence of the actuator saturation in a three-loop autopilot of a flying vehicle arising from the windup phenomena leads to the performance degradation. In this paper, a dynamic anti-windup and a static anti-windup compensators are proposed. The dynamic compensator, available in some references for systems with output feedback is designed to make the controller states of the saturated system arbitrarily close to the controller states of the unsaturated system. In this paper, this compensator is developed for controllers similar to three-loop autopilot of a flying vehicle, in which, the controller is a feedback of both plant output and plant states. In order to compare with the dynamic compensator, a static compensator is also designed with a new approach in such a way that the controller output tracks the output of saturation function. With this requirement, it is expected that no windup will occur. These two compensators have been applied on the autopilot of an aerodynamic tail-controlled flying vehicle in two stable and unstable conditions and their performances have been compared to each other in terms of control performance. The results show the better performance of the static compensator compared to the dynamic compensator in tracking the desired command in both operating conditions. Moreover, through simulation of flying vehicle guidance system, it is shown that using anti-windup leads to the less miss distances. Especially, using the static compensator leads to reduction of the miss distance by about 50% in unstable conditions compared to the use of the dynamic compensator.