Nonlinear H _∞ -output regulation of a nonminimum phase servomechanism with backlash

Nonlinear H _∞ control synthesis is extended to an output regulation problem for a servomechanism with backlash. The problem in question is to design a feedback controller so as to obtain the closed-loop system in which all trajectories are bounded and the load of the driver is regulated to a desired position while also attenuating the influence of external disturbances. Provided the servomotor position is the only measurement available for feedback, the proposed extension is far from trivial because of nonminimum phase properties of the system. Performance issues of the nonlinear H _∞-output regulator constructed are illustrated in an experimental study.