A Method for Recovering Linear Performance in Feedback Systems With Nonlinear Instrumentation

The problem of controller design in linear systems is well understood. Often, however, when linear controllers are implemented on a physical system, the anticipated performance is not met. In some cases, this can be attributed to nonlinearities in the instrumentation, i.e., sensors and actuators. Intuition suggests that to compensate for this instrumentation, one can boost, i.e., increase, the controller gain. This paper formally pursues this strategy and develops the theory of boosting. It provides conditions under which the controller gain can be modified to offset the effects of instrumentation, thus recovering the performance of the intended linear design. Experimental verification of the technique developed is reported using a magnetic levitation device.