AN INVESTIGATION INTO ROBUST FORCE CONTROL THROUGH A CONSTRAINED FLEXIBLE BEAM

In this paper we consider the problem of force control through a const rained flexible beam. The H-infinity loopshaping design paradigm is us ed in an attempt to obtain controllers that are insensitive to the exa ct position of the constraint. Although the controllers generated by t his design approach possess a number of desirable features we demonstr ate how easy it is to obtain unacceptable controllers if the propertie s of the plant are not given due consideration. We then show how the d elta(nu)-gap metric introduced by Vinnicombe (1993) can be used to inc orporate parametric uncertainty into the H-infinity-loopshaping design paradigm. Using this metric, and suitable switching techniques, contr ollers are designed to cover large variations in the open-loop dynamic s that result from significant changes in the position of the constrai nt. Finally, these controllers are implemented and evaluated on an exp erimental system.