This paper reports on the mechanism design, dimension optimization, closed-loop control, and practical application of a piezoelectrically actuated fast tool servo (FTS) for the diamond turning of micro-structured surfaces. With the mechanism, a finite element based analytical model is developed to theoretically relate the working performance with its structural dimensions. Considering its application for micro/nanocutting, the structural dimensions of the mechanism are deliberately determined through evolutionarily optimizing a comprehensive objective. To ultra-finely track the cutting trajectory with a high bandwidth, a PID controller together with the dynamics inversion based feedforward compensation is optimally designed with assistance of the Nyquist diagram, and a disturbance observer is further employed to compensate for the inherent hysteresis nonlinearity as well as external cutting force disturbances. Both open-loop and closed-loop experimental tests on the prototype suggest that a stroke of 15 μm and a closed-loop bandwidth of 1730 Hz are achieved. Taking advantage of the newly developed FTS, two typical micro-structured surfaces are ultra-precisely turned, well demonstrating the effectiveness of the FTS.

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 μm 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 μm amplitude and 120 Hz frequency is obtained to be ±0.2 μm, demonstrating the capability of the FTS for high accuracy trajectory tracking.