Digital Motion Control And Its Application to Camshaft Turning

Tsu-Chin Tsao
Associate Professor
University of Illinois at Urbana-Champaign
Department of Mechanical And Industrial Engineering

Non-Circular Turning Process for automotive camshaft machining can potentially reduce or replace the present grinding process with many benefits. It presents a challenging motion control problem where a fast response linear actuator carrying the cutting tool must generate a cam lobe profile precisely in synchronization with a rotating workpiece and subject to cutting force disturbances. Digital motion control algorithms for an electrohydraulic actuator will be presented for this task. Because of the large range of motion required, the nonlinear behavior of the hydraulic actuator must be accounted for to ensure stability and tracking performance. Exploiting the problem's special characteristics, a successive linearization approach, which combines periodic system identification, robust performance linear feedback, off-line repetitive control for feedforward input generation, and on-line periodic time varying repetitive control is developed to achieve the performance objective. Control issues and solutions of using another actuator -- voice coil motor will also be presented if time permits.