Acceleration feedback design for voice coil actuated direct drive

Development of a servo-control system for a voice coil actuated direct drive used in turning of automotive camshafts is presented. The drive must possess low inertia, in order to satisfy motion bandwidth requirements for cam turning with a small actuator. Reduced inertia, however, makes the system more sensitive to the external forces acting on the drive, and may lead to chatter during cutting. High dynamic stiffness must be established by the control system to minimize the effects of the additional dynamics introduced by the machining process. This work presents a systematic approach to design of local acceleration feedback to increase the dynamic stiffness of the drive. An acceleration loop is added to the drive´s servo-controller, that consists of an aggressive position feedback and a feedforward controller, resulting in a five-fold improvement in the system´s performance