Robust Control System Design for Multivariable Plants With Lightly Damped Modes

A robust controller design is proposed for the active suspension system bench-mark problem. The CRONE control system design used is extended to unstable multivariable plants with lightly damped modes and RHP zeros. Decoupling and stabilizing controller K, is achieved for the open-loop transfer matrix. Fractional order transfer functions are used to define all the components of the diagonal open-loop transfer matrix, β. In defining the fractional open-loop transfer function β0i some elements of the plants, G0 and its inverse must be considered to achieve the stable controller. Optimisation provides the best fractional open-loop βopt. Finally, frequency domain system identification is used to find controller K=G0−1 βopt.