Robust controller synthesis for the coupled mass benchmark problem

Some robust controller designs for the coupled mass benchmark problem are presented in this paper and the results are compared. This benchmark problem is a non-minimum phase system, and since in all practical systems the friction exists, a detailed nonlinear friction model is considered in the design procedure. This challenging problem is the subject of robust controller schemes applied in this paper, namely Hinfin control, mixed H₂/Hinfin and mu-synthesis using modified D-K iteration. It is shown through simulations that the mu design provides superior robust performance in the presence of modeling uncertainty. Moreover, for the cases with bounded energy control efforts, H₂/Hinfin design provides a better compromise for the performance and actuator limitations.