Stability properties and effects of measurement disturbances on antiwindupPI- and PID-control

Different forms of discrete time controllers with integral action, control signal saturation and antiwindup feedback (i.e. PIaw, PIawD, PIaw-P cascade , I-aw with observer based feedback) are investigated. It is shown that high gain antiwindup is not required and that low antiwind up gain does not significantly diminish the stability properties as long as it is not lower than a given threshold. Results are given for the steady state control error offset induced by stat ionary high frequency measurement disturbances while operating the control loop close to the saturation. It is demonstrated that a derivative action s hould be avoided in this context, and how it can he replaced by other bette r performing structures. It is also shown how the effect of the high freque ncy disturbance may be further reduced by appropriate observer based feedba ck.