A high-performance triaxial 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, in this article, a novel axis-symmetric linearized reluctance actuator is proposed to generate the planar motion in parallel, and the piezoactuated 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 multiphysical system parameters for the triaxial FTS, assisted by an analytical model of the electromagnetic circuit as well as the mechanical mechanism. As for the trajectory tracking, the loop-shaping 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 article reports on the design, modeling, control, and testing of a novel compliant nanopositioning stage driven by a self-developed normal-stressed electromagnetic actuator. To facilitate the parameter selection for the stage to achieve the desired stroke and natural frequency, an analytical model of both the electromagnetic circuit and flexure mechanism is established, which is then systematically verified through finite element analysis. By combining a proportional—integral—differential (PID)-based main controller with a system dynamics inversion-based feedforward compensator, a closed-loop control system for the stage is constructed with the main controller being tuned through Bode’s ideal transfer function-based loop-shaping method. The experimental result shows that a stroke of ${\pm } 95 ~\mu \text{m}$ and a first natural frequency of 743 Hz are achieved for the designed stage. Finally, taking advantage of the constructed control system, the nanopositioning capability is demonstrated by finely tracking the harmonic and nanostair commands. Note to Practitioners—Piezoelectric actuators (PEAs) and voice coil motors (VCMs) are commonly adopted for the actuation of nanopositioning stages. In general, constrained by the inherent small strain, PEA is more suitable for the generation of dynamic motions in dozens of micrometers. Meanwhile, VCM has a theoretically infinite motion range but a slow response due to its low force density nature. Taking advantage of a newly developed normal-stressed electromagnetic actuator (NSEA), we demonstrate the design, modeling, control, and testing of an NSEA-based nanopositioning stage with a relatively long motion range, high bandwidth, and compact size. Considering the high force density and relatively large motion range only constrained by the effective air gap, the NSEA-based stage is demonstrated herein to be very promising to achieve highly dynamic motions within hundreds of micrometers.

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 μm 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 μm.

Taking advantage of the concurrent stretching and bending property of corrugated flexure hinges, a sinusoidal corrugated flexure linkage was proposed and applied for the construction of a corrugated dual-axial mechanism with structural symmetry and decoupled planar motion guidance. Castigliano’s second theorem was employed to derive the complete compliance for a basic sinusoidal corrugated flexure unit, and matrix-based compliance modeling was then applied to find the stiffness of the sinusoidal corrugated flexure linkage and the corrugated dual-axial mechanism. Using established analytical models, the influence of structural parameters on the stiffness of both the corrugated flexure linkage and the dual-axial mechanism were investigated, with further verification by finite element analysis, with errors less than 20% compared to the analytical results for all cases. In addition, the stiffness of the corrugated flexure mechanism was practically tested, and its deviation between practical and analytical was around 7.4%. Further, the feasibility of the mechanism was demonstrated by successfully applying it for a magnetic planar nanopositioning stage, for which both open-loop and closed-loop performances were systematically examined. The stage has a stroke around 130 $\mathsf{\mu }$m for the two axes and a maximum cross-talk less than 2.5%, and the natural frequency is around 590 Hz.

A novel dual-axis piezoelectric system designed for elliptical vibration cutting (EVC) is reported. The system features a topology-optimized compliant mechanism for transmitting the motion of parallel-arranged stacked piezoelectric actuators (SPAs). Static and dynamic analyses of the mechanism were conducted using the solid isotropic material with penalization (SIMP) approach with hexagonal-element. A comprehensive optimization model was developed to guide the topological evolution, incorporating constraints related to resonance frequencies, motion coupling, fatigue durability, and manufacturability. The performance of the designed compliant mechanism was validated via finite element simulations. The fabricated prototype achieved strokes of $\mathbf{13.04}$ and $\mathbf{12.55}\,\boldsymbol{\mu}\mathbf{m}$ in two directions, respectively, with corresponding resonance frequencies of 4357 and 3178 Hz. A decoupled control strategy combining a proportional and integral (PI) controller and model-based feedforward compensation was implemented, yielding minimal inter-axis crosstalk. Trajectory tracking experiments demonstrated the effectiveness of the designed closed-loop system.

This article presents a novel approach to enhancing the performance of scanning tunneling microscopes using a dual-mode stick–slip piezoelectric nanopositioning stage. Robust approaching and high-resolution tunneling current tracking are, respectively, accomplished by adopting a single stage working in stick–slip and continuous scanning mode. In addition, taking advantage of the contact force regulation, a motion resolution enhancement strategy is proposed for scanning mode, which theoretically improves motion resolution from 0.638 to 0.192 nm without modifying any mechanical or circuit structures. Experiment result demonstrates that the proposed strategy can effectively track tunneling currents in a more accurate and more stable manner.