Control of Constrained Multivariable Systems using the Conditioning Technique

The conditioning technique is first reviewed as a particular case of Aström and Wittenmark\´s anti-windup method [11]. Then it is reformulated in terms of a "realizable" reference signal. Using this notion, a method to handle limitations on the manipulated variables of a multivariable control system is presented. The basic idea is to introduce a mapping between the space of manipulated variables and the space of reference signals, using the conditioning technique. The limits on the manipulated variables can be translated into limits on the reference signals. Thus a domain of achievable reference signals corresponds to the domain of achievable control signals. When the control signals issued by the controller yield a point outside the corresponding achievable domain, this point must be projected on the domain boundary. In the proposed method, this projection is performed so as to follow a desired strategy in the corresponding achievable space of reference signals.