Improving local anti-windup performance: preliminary results on a two-stage approach

To obtain improved local performance while retaining the property ofglobal stability, this paper proposes a new two-stage approach toanti-windup compensation for systems containing input saturation.The method ensures that (i) if no saturation occurs, then linear operation continues unhindered; (ii) if mild saturationoccurs, an aggressive local anti-windup compensator becomes active and; (iii) if severe saturation occurs a globally stabilisinganti-windup algorithm enters the fray. A notable feature of the scheme is that, for stable plants, a two-stagecompensator will always exist. Another interesting aside, is that simple, possibly ad hoctechniques can be combined to yield a good two-stage compensatorwhich may perform better, locally, than many `optimal' schemes.