Acceleration Feedback for Suppression of Friction Induced Limit Cycles in Direct Drives Available to Purchase

This paper presents describing function analysis and control solution for a friction related problem encountered during the development of a voice coil actuated direct drive for use in turning of automotive camshafts. It is observed that the addition of a high accuracy tracking (repetitive) controller results in a system that is susceptible to limit cycle oscillations induced by Coulomb friction. A local acceleration feedback loop is utilized to shape the system response to disturbance forces and is shown to improve the drive stiffness and prevent performance deterioration due to friction.