Dynamic Switching of Two Degree-of-Freedom Control for Belt-Driven Servomechanism

This paper proposes a new two degree-of-freedom control structure such that the robustness control of a belt-driven servomechanism is adequately addressed. In conventional design approaches, a trade-off between robust stability and robust tracking performance is unavoidable because the control engineer must take different frequency regions into consideration. In this paper, a frequency-dependent switching control structure is proposed, where the feedback connection to the external-loop controller is dynamically switched between the outputs of the controlled plant and its nominal model. The disturbance attenuation at lower frequencies by the double-loop control, as well as the robust stability at higher frequencies through the reference feedforward control, can be achieved at one fixed two degree-of-freedom control structure. The feasibility of the proposed approach is verified by theoretical analysis and experimental results.