Multi-Physical Design and Resonant Controller Based Trajectory Tracking of the Electromagnetically Driven Fast Tool Servo

In this paper, a voice coil motor (VCM) actuated fast tool servo (FTS) system is developed for diamond turning. To guide motions of the VCM actuator, a crossed double parallelogram flexure mechanism is selected featuring totally symmetric structure with high lateral stiffness. To facilitate the determination of the multi-physical parameters, analytical models of both electromagnetic and mechanical systems are developed. The designed FTS with balanced stroke and natural frequency is then verified through the finite element analysis. Finally, the prototype of the VCM actuated FTS is fabricated and experimentally demonstrated to achieve a stroke of +/- 59.02 mu m and a first natural frequency of 253 Hz. By constructing a closed-loop control using proportional-integral-derivative (PID) controller with the internal-model based resonant controller, the error for tracking a harmonic trajectory with +/- 10 mu m amplitude and 120 Hz frequency is obtained to be +/- 0.2 mu m, demonstrating the capability of the FTS for high accuracy trajectory tracking.