DESIGN OF STABLE ACTUATOR SATURATION COMPENSATORS IN THE FREQUENCY-DOMAIN

An important practical control problem is the compensation for actuato r saturation. Many saturation compensation techniques, widely known as antiwindup schemes, have been proposed, but few guidelines for the de sign of these techniques are available. Here, frequency domain methods for the design of a class of general saturation compensators are prop osed. It is shown that the design of saturation compensators simply re duces to the design of a first order filter. Two methods, the phase sh ift method and the gain reduction method, are proposed to design the f irst order filter. The choice between these two methods depends on the shape of the frequency response of the system. An example is presente d to illustrate the performance of the proposed methods. Although the proposed design methods are relatively simple, it is shown in the exam ple that they may perform as good as, if not better than, the computat ional more complex 'optimal' controller that includes actuator saturat ion in its design, and that they are also more robust as actuator satu ration becomes more severe.