Multiobjective Topology Optimization for a Piezo-Actuated Fast Tool Servo

A novel piezo-actuated fast tool servo (FTS) is reported for the diamond turning of microstructured surfaces. The structure and its dimensions for its compliant mechanism are concurrently derived based on the velocity field level-set (VFLS) topology optimization. To address the evolution instability in simultaneously optimizing the static and dynamic performance for diamond turning, a two-stage robust optimization strategy is proposed. Performance of the achieved optimum compliant mechanism is verified through finite element simulations. The prototype exhibits a stroke of 50.17 mu m and a first-order resonant frequency of 2745 Hz, which are in good agreement with the theoretical design. A proportional-integral controller with a high-gain controller is designed for the FTS that is actively damped by an innerloop positive feedback controller. Using the optimized FTS, a typical sinusoidal microgrid surface was turned to have a surface roughness of Sa = 5.2 nm and a peak-to-valley form error of 0.26 mu m.