Design and Control of a Piezoelectrically Actuated Fast Tool Servo for Diamond Turning of Microstructured Surfaces

This article 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 microstructured 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 ultrafinely track the cutting trajectory with a high bandwidth, a proportional-integral-derivative 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 18 $ \mu$m and a closed-loop bandwidth of 1730 Hz are achieved. Taking advantage of the newly developed FTS, two typical microstructured surfaces are ultraprecisely turned, well demonstrating the effectiveness of the FTS.