Protection of Cascaded Loops Against Windup and Limit Cycling

Abstract

Integral action (aka reset action) in feedback controllers is very popular among practitioners and academics. Practitioners have almost always been aware of the need to protect such controllers, or their resets, against windup during operational situations where a controller's output exceeds the actuator's range. Such windup counter-measures are easy to design for single-loop controllers that are adjacent to the actuator. Master controllers of cascaded feedback loops are not designed to be adjacent to the actuators. Here, I propose an anti-windup technique for master controllers that does not invalidate any of the linear designs and mitigates the actuator saturation-related tendency of limit cycling in cascaded control systems.