Fixed-structure /spl mu/-synthesis - an evolutionary approach

This paper considers the design of robust controllers using the structured singular value mu. mu-synthesis is usually based on DK-iteration, which minimizes an upper bound on mu. A drawback is that controllers designed using DK iteration are typically of high order, which makes this approach less attractive. This paper presents a novel technique of designing low-order and fixed-structure controllers that minimize an upper bound on the structured singular value mu, using a DK-iteration type of algorithm with an evolutionary search for controller and low-order scaling in the K-step. Two advantages of this approach are that: (i) the controller order is independent of the order of the multiplier D(s); and (ii) that in contrast to standard DK-iteration where the multiplier D(s) is completely frozen within the K-step, the proposed algorithm allows D(s) to be free within the K-step. Two numerical examples show that this approach performs well compared with standard DK-iteration and is computationally efficient