Design of stable actuator saturation compensators in the frequency domain

Many saturation compensation techniques, widely known as antiwindup schemes, have been proposed, but few guidelines for the design of these techniques are available. Here, frequency domain methods for the design of a class of general saturation compensators are proposed. It is shown that the design of saturation compensators simply reduces to the design of a first order filter. Two methods, the phase shift method and the gain reduction method, are proposed to design the first order filter. The choice between these two methods depends on the shape of the frequency response of the system. An example is presented to illustrate the performance of the proposed methods. Although the proposed design methods are relatively simple, it is shown in the example that they may perform as good as, if not better than, the computational more complex `optimal´ controller that includes actuator saturation in its design, and that they are also more robust as actuator saturation becomes more severe