An LQG/H∞ controller for a flexible manipulator

An LQG/H_∞ controller synthesis is presented for a flexible one-link manipulator with noncolocated sensing. The challenge of the problem lies in the nonminimum phase characteristics and the ill-conditioned nature of the plant. The inner-loop LQG controller provides adequate damping to the flexible modes and numerically conditions the system while the outer-loop H_∞ controller provides stability in the face of unstructured perturbation. With only tip position sensing and using a fourth-order model, a controller is synthesized. It is tested with an eighth-order model of the plant and is found to satisfy both performance and stability requirements