Robust H∞, H2/H∞ controller for rotational/translational actuator (RTAC)

In this paper, robust controllers have been proposed for oscillation suppression in the RTAC benchmark problem. A nominal plant and an uncertainty model are extracted out of varieties of linear models, identified for the nonlinear system and the generalized plant for the unstructured uncertainty problem has been presented. Based on passivity, a cascade controller has been designed to reduce amount of uncertainty in lower frequencies. It is verified that through a nonlinear feedback controller in the inner loop, the uncertainty of linear estimates of the system reduces significantly, and becomes plausible to use linear robust techniques such as mixed sensitivity and H2/H∞ to design controller for the system. Finally H∞ and H2/H∞ controllers have been designed for new generalized plant and results are compared with the previous reports in literature.