Input/output selection for robust control

Two new Input/Output (IO) selection methods are proposed. The aim is to find the IO sets for which there exists a controller that achieves robust performance. IO selection could thus be based on mu-synthesis, but to avoid this often time-consuming process H-infinity controller existence conditions are used instead. To reduce conservatism, the structure in the combined uncertainty/ performance block Delta is "eliminated." The first (sufficiency-based) method augments the plant by diagonal scalings, whereas the second (necessity-based) method absorbs an uncertainty representation into the plant. An active suspension control problem illustrates both methods.