Load Speed Control of Two-inertia System by Load Speed/Torque Estimation and Torsion Torque Compensation

We consider the speed control problem for a two-inertia system that consists of two inertias connected by a shaft. In this system, the flexibility produces torsional vibrations that usually result in limited tracking performance when employing a conventional control strategy such as PI control. Moreover, the control problem becomes far more challenging if the load-side speed and torsion torque developed in the shaft are not measurable. This paper presents a disturbance observer-based controller that suppresses vibrations due to torsion torque and external disturbance so that the load speed tracks the desired reference. This is done by constructing an observer that estimates the torsion torque, load speed, and load torque at the same time and a controller that can adjust the torsion torque as desired. The proposed idea is validated through numerical simulations.