Precision positioning systems with large working stroke (millimeter or more) and micro/nano-scale positioning resolution are widely required in both scientific research and industries. For this kind of applications, piezoelectric materials based actuators show unique advantages and have been widely employed. To overcome the demerit of the limited working stroke for single piezoelectric element, various stepping motion principles have been proposed in the past years, and accordingly, stepping piezoelectric actuators with various structures have been designed and evaluated. This review is aimed to summarize the recent developments and achievements in stepping piezoelectric actuators with large working stroke. Especially, the emphasis is on three main types of stepping piezoelectric actuators, i.e., inchworm type, friction-inertia type, and parasitic type. The motion principles of these three types of piezoelectric actuators and the corresponding developments of various actuators are discussed respectively, followed by pointing out the existing problems in these three types of piezoelectric actuators and proposing some potential research directions in this topic. It is expected that this review is helpful for relevant researchers to understand stepping motion principles as well as piezoelectric actuators, and to successfully select and design stepping piezoelectric actuators for specific applications.

Stepping piezoelectric actuators with large working stroke for nano-positioning systems: A review

A piezoelectric-driven actuator based on coupling motion has been proposed and tested to achieve a large linear working stroke with high resolution. “Z-shaped” flexure hinges are exploited for the symmetric flexure hinge mechanism to reduce the structural stress. Coupling motion is obtained by placing this symmetric flexure hinge mechanism with an angle of $\theta =20^\circ $ to the slider. Experimental results indicate that linear motion with a large working stroke is effectively obtained by this coupling motion; the maximum motion speed is $V_{s}=$ 6057 μm/s and the maximum output force is $F_{g}=$ 350 g. Additionally, the influences of input frequency $f$ and input voltage $U_{e}$ are investigated, and the system kinetic model is established to better analyze the performance of this designed piezoelectric-driven linear actuator.

A Piezoelectric-Driven Linear Actuator by Means of Coupling Motion

\n Flexure-based compliant mechanisms are becoming increasingly promising in precision engineering, robotics, and other applications due to the excellent advantages of no friction, no backlash, no wear, and minimal requirement of assembly. Because compliant mechanisms have inherent coupling of kinematic-mechanical behaviors with large deflections and/or complex serial-parallel configurations, the kinetostatic and dynamic analyses are challenging in comparison to their rigid-body counterparts. To address these challenges, a variety of techniques have been reported in a growing stream of publications. This paper surveys and compares the conceptual ideas, key advances, and applicable scopes, and open problems of the state-of-the-art kinetostatic and dynamic modeling methods for compliant mechanisms in terms of small and large deflections. Future challenges are discussed and new opportunities for extended study are highlighted as well. The presented review provides a guide on how to select suitable modeling approaches for those engaged in the field of compliant mechanisms.

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Kinetostatic and Dynamic Modeling of Flexure-Based Compliant Mechanisms: A Survey

A novel hybrid actuation mechanism based XY nanopositioning stage with totally decoupled kinematics

Fast tool servo (FTS) in ultra-precision machining (UPM) is an enabling and efficient technology for fabricating optical freeform surfaces or microstructures with submicrometric form accuracy and nanometric surface finish. There are many kinds of FTS in the different driving principle to present their various performances currently. Their kernel technologies influence the machining ability and accuracy of freeform surfaces, consequently receiving much research attention and interest. These technologies are generally summarized as the development of FTS structure, the advanced control algorithms, tool path planning, machining condition monitoring, and surface measurement and error compensation. This paper aims to survey the current state of the art in machining freeform optics by FTS. An analysis of the principle, performance, and application of FTS machining with regard to freeform optics is presented. And the key machining technologies for optical freeform surfaces by FTS are then introduced in detail. The challenges and opportunities for further studies are concluded according to the FTS machining difficult of optical freeform surfaces finally.

Review on fast tool servo machining of optical freeform surfaces

The limited degrees of freedom (DOFs) of servo motions is an inherent deficiency in conventional, fast-tool-servo-(FTS)-assisted, diamond-turning, highly blocking applications of the FTS technique. In this paper, the concept of two-DOF FTS (2-DOF FTS)-assisted diamond turning is proposed and demonstrated. A piezoelectrically actuated 2-DOF FTS mechanism is developed to enable the cutting tool to move along two directions with decoupled motions. A novel guidance flexural mechanism constructed using the newly proposed Z-shaped flexure hinges (ZFHs) is introduced to generate motions along the z -axis, which is based on the bending deformation of the beams of the ZFHs. Additionally, using the differential moving principle (DMP), bi-directional motions in the x -axis direction can be achieved. Using the matrix-based compliance modeling method, the kinematics of the mechanism are analytically described, and the dynamics are also modeled using the Lagrangian principle. The theoretical results are then verified using finite element analysis (FEA). Certain increases in performances over conventional two-DOF flexural mechanisms are achieved: (a) a more compact structure with lower moving inertia, (b) theoretically decoupled motions of the output end, and (c) less than one actuator per DOF. To investigate the practical performance of the 2-DOF FTS system, both open-loop and closed-loop tests are conducted. Finally, the developed 2-DOF FTS technique is implemented to realize an innovative Pseudo-Random Diamond Turning (PRDT) method for the fabrication of micro-structured surfaces with scattering homogenization. The cutting results demonstrate not only the superiority of the concept but also the efficiency of the developed 2-DOF FTS system.

Development of a piezoelectrically actuated two-degree-of-freedom fast tool servo with decoupled motions for micro-/nanomachining

The utility model relates to an FTS (Fast Tool Servo) device with two decoupled shafts, and belongs to the technical field of cutting process of optical curved surface parts and ultra-precise parts. A diamond cutter is fixedly connected with a cutter seat on a flexible hinge base body through a fixing screw; two ends of an X-axis piezoelectric stack are respectively connected with an X-axis drive end and the flexible hinge base body; the X-axis piezoelectric stack is connected with the flexible hinge base body through a pre-tightening bolt; a first Z-axis piezoelectric pack and a second Z-axis piezoelectric pack are respectively connected with a Z-axis drive end and the flexible hinge base body; a displacement detecting block is arranged on the backside of the cutter seat of the flexible hinge base body, and is fixedly connected with the flexible hinge base body through a fixing screw. The fast tool servo device with two decoupled shafts has the advantages of being novel in structure, reducing inert quality of motion part of the flexible hinge mechanism as a mode in which piezoelectric drivers are connected in parallel to drive a flexible mechanism is adopted, being good for adding the working bandwidth of an FTS device, and improving the processing efficiency of the FTS device.

FTS (Fast Tool Servo) device with two decoupled shafts

The invention relates to a quick cutter servo device with two decoupled shafts, and belongs to the technical field of cutting machining of optical curved surface parts and ultraprecise parts A diamond cutter is fixedly connected with a cutter seat on a flexible hinge base body through a fixing screw, and the two ends of an X-axis piezoelectric stack are connected with the flexible hinge base body and an X-axis driving end respectively The X-axis piezoelectric stack is connected with the flexible hinge base body through a first pre-tightening bolt, and a first Z-axis piezoelectric stack and a second Z-axis piezoelectric stack are connected with the flexible hinge base body and a Z-axis piezoelectric stack respectively A displacement detection block is mounted behind the cutter seat on the flexible hinge base body, and the displacement detection block is fixedly connected with the flexible hinge base body through a fixing screw The quick cutter servo device with the two decoupled shafts has the advantages that the structure is novel, the mode that a piezoelectric actuator is in parallel connection with a flexible mechanism is used, the inertia mass of the movement part of a flexible hinge mechanism is reduced, the operation bandwidth of an FTS device can be better increased, and the machining efficiency of the FTS device is improved

Liu Zhiwei

Papers

Development of a piezoelectrically actuated two-degree-of-freedom fast tool servo with decoupled motions for micro-/nanomachining

FTS (Fast Tool Servo) device with two decoupled shafts

Quick cutter servo device with two decoupled shafts