Triply damped servo drive positioning with high-order DOB, model-free observer, and virtual damping injection

This paper proposes an observer-based output feedback controller that enforces triply damped dynamics in servo drives. This makes transients softer as well as the model less dependent. The primary contributions are as follows: (a) The observer gain, structured by virtual damping (VD) and a convergence rate, enables the estimation loop to be governed by a first-order transfer function without requiring any system model information; (b) a high-order disturbance observer (HODOB) exponentially estimates high-frequency disturbances in accordance with the triple-damping transfer function; and (c) a proportional–integral-type controller based on the observer and HODOB, incorporating VD terms, guarantees exponential recovery of the desired triply damped performance. Experimental results on a commercial servo drive confirm the practical effectiveness of the proposed method across varying load conditions.