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A high-performance tri-axial fast tool servo (FTS) with the hybrid electromagnetic-piezoelectric actuation and the hybrid parallel-serial-kinematic structure is reported. Featuring the balanced and uniform actuation, a novel axis-symmetric linearized reluctance actuator is proposed to generate the planar motion in parallel, and the piezo-actuated vertical motion is then serially carried by the planar motion within a limited space. Verified by the finite element analysis, a two-stage design strategy is developed to optimally determine the multi-physical system parameters for the tri-axial FTS, assisted by an analytical model of the electromagnetic circuit as well as the mechanical mechanism. As for the trajectory tracking, the loopshaping tuned PID controller with a feedforward compensator is employed for each axis, and a damping controller is additionally designed for the planar motion. Finally, both open-loop and closed-loop performance of the prototype are carefully demonstrated.

This paper reports on a dual-axial tool servo diamond turning method for the one-step fabrication of hierarchical micro-nano-structured surfaces. With respect to the dual-axial servo motion (XZ), the z-axis motion can generate the primary surface with a complex shape, and the x-axis motion is used to synchronously form the secondary structure via controlling the residual tool marks. The toolpath determination algorithm for the developed turning method is described in detail, and the effect of the machining parameters on the basic feature and sizes of the generated secondary structures is investigated through conducting the numerical simulation for both toolpath and surface generation. The simulation result indicates that the additional x-axial motion is effective for the deterministic generation of a variety of secondary structures. Finally, taking advantage of an ultra-precision lathe with a self-developed tri-axial FTS, a hierarchical surface with high accuracy is practically generated.

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