Acceleration feedback control for direct-drive motor system

Classical PD control for a direct drive motor system is enhanced to suppress disturbing torque by incorporating an acceleration feedback loop. This is intended to achieve a stable and high stiffness control without the need of adjusting the PD controller, either the structure or the parameters. The acceleration feedback control is presented with a focus on designing the acceleration closed-loop in terms of its stability and ability in resisting the dynamic disturbances. The sensing and modeling of angular acceleration via servo-type linear accelerometers is dealt with from the viewpoint of practical implementation. Extensive experiments are conducted on the second joint of a three-link direct drive robot. Results are compared to those obtained by classical PD control without the acceleration feedback loop, to mainly investigate the ability of the acceleration feedback control in resisting disturbing torque, and its influence on conventional PD control