Large Travel Range Research Articles

A Novel Monopolar Cross-Scale Nanopositioning Stage Based on Dual Piezoelectric Stick-Slip Driving Principle.

The precise characterization and measurement of new nanomaterials and nano devices require in situ SEM nanorobotic instrumentation systems, which put forward further technical requirements on nanopositioning techniques of compact structure, cross-scale, nanometer accuracy, high vacuum and non-magnetic environment compatibility, etc. In this work, a novel cross-scale nanopositioning stage was proposed, which combined the advantages of piezoelectric stick-slip positioner and piezoelectric scanner techniques and adopted the idea of macro/micro positioning. A new structure design of a single flexible hinge shared by a small and large PZT was proposed to effectively reduce the size of the positioning stage and achieve millimeter stroke and nanometer motion positioning accuracy. Then, the cross-scale motion generation mechanism of the dual piezoelectric stick-slip drive was studied, the system-level dynamics model of the proposed positioning stages was constructed, and the mechanism design was optimized. Further, a prototype was manufactured and a series of experiments were carried out to test the performance of the stage. The results show that the proposed positioning stage has a maximum motion range of 20 mm and minimum step length of 70 nm under the small piezoceramic ceramic macro-motion stepping mode, and a maximum scanning range of 4.9 μm and motion resolution of 16 nm under the large piezoceramic ceramic micro-motion scanning mode. Moreover, the proposed stage has a compact structure size of 30 × 17 × 8 mm3, with a maximum motion speed of 10 mm/s and maximum load of 2 kg. The experimental results confirm the feasibility of the proposed stage, and nanometer positioning resolution, high accuracy, high speed, and a large travel range were achieved, which demonstrates that the proposed stage has significant performance and potential for many in situ SEM nanorobotic instrument systems.

6-DoF Magnetically Levitated Rotary Table With Dynamic Numerical Force and Torque Regulator

Multiaxis motion control over a large travel range is still difficult for magnetic levitation positioning systems because the accuracy of the magnetic force model deteriorates when both translation and rotation of the moving part take place. To overcome this issue, this paper studies a dynamic force and torque regulating method based on the numerical wrench model and validates it with a 6-degree-of-freedom (DoF) magnetically levitated (maglev) rotary table. In each sampling cycle, the current-wrench transformation matrix (CWTM) is determined by the numerical wrench model, and then it is employed to decide the exciting currents for each coil phase by solving the overdetermined equation. A field programmable gate array (FPGA) is used as the processor to meet the real-time requirement of the control system by taking advantage of the fine-grained parallelism in the numerical wrench model. A high level synthesis (HLS) tool, general intellectual property core, a very-high-speed integrated circuit hardware description language (VHDL) component, and a MicroBlaze processor are employed simultaneously to develop the controller. By utilizing the numerical regulator, the maglev rotary table realizes stable multiaxis motions. Comparative experiments with the existing analytical method illustrate that the numerical wrench model improves the static decoupling effect, decreases the positioning fluctuations, and enlarges the travel range.

Displacement Linearity Improving Method of Stepping Piezoelectric Platform Based on Leg Wagging Mechanism

It is difficult to obtain linear output displacements for stepping piezoelectric platform due to their discontinuous outputs. Inspired by the theory that the maximum static friction force is greater than the sliding friction force, in this letter, we propose a bipedal alternating inertial actuation mode (BAIAM) to improve the displacement linearity of the stepping platform. The output displacements are measured, the linear fitting is carried out by the least square method, the correlation coefficient and linear fitting function are used to evaluate the displacement linearity, and the correlation coefficients of the forward and backward motions are calculated as 0.9998 and 0.9999 in BAIAM, respectively, which verifies the effectiveness of the proposed method. The closed-loop experiments in BAIAM are also carried out, and the steady-state errors for the target position of ±40 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m within ±0.2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m in the point-to-point positioning control experiments are achieved. The experimental results confirm that the developed platform can be applied to precision fields requiring a large travel range, planar two-degree-of-freedom motion, and linear outputs.

Design and Analysis of a Compact Piezo-Actuated Microgripper With a Large Amplification Ratio

Abstract This article presents a piezo-actuated microgripper characterized by large amplification ratio and compact structure size. The microgripper is actuated by a piezo-stack actuator that is integrated with a two-stage displacement amplifier to achieve large travel range. A new design methodology “flexure hinge individualized design” (FHID) was proposed to realize large amplification ratio. According to this methodology, each flexure hinge was designed personally based on force condition of the piviot to reconfigure the motion stiffness of the compliant microgripper so that the parasitic motion and displacement loss could be eliminated. Consequently, a 52-amplification ratio amplifier was obtained. The developed microgripper was modeled via kinematics and Castigliano’s displacement theorem, respectively. Finite element analysis and the experimental studies were conducted to evaluate the characteristics of the microgripper. The results show that the motion stroke of the gripper tip is 917 μm, and the structure dimension is 62 mm × 42 mm × 12 mm. The design methodology FHID is generic and can be extended to other compliant mechanisms.

A 3-DOF piezoelectric driven nanopositioner: Design, control and experiment

In this paper, a novel 3-degree-of-freedom (DOF) nanopositioner was investigated in order to position objects with nanometer scale accuracy. Nanopositioners are used in a variety of real-world applications, e.g. biomedical technology and nanoassembly. In this work, a nanopositioner was firstly designed with the flexure diaphragm guider, capacitive sensors and walking piezoelectric actuators. The specifically designed monolithic flexure diaphragm guider was able to significantly restrict motions in the other unwanted directions. The walking piezoelectric actuator can enable the developed nanopositioner to have nanometer scale positioning accuracy and a large travel range. Then a closed-loop sliding mode control strategy was developed to overcome the effect of the actuator’s speed nonlinearity and its stability was analysed based on Lyapunov theory. Finally, experiments focused on coupling displacement and point-to-point movement were conducted. The observed results revealed that the ratio of coupling displacement to Z displacement was less than 0.1%, which means that the coupling displacement was less than 120 nm during the Z direction travel range of the nanopositioner from −80 μm to 80 μm. Moreover, the positioning accuracy in the Z direction of point-to-point movement was within 10 nm and the dynamic response settled within 0.2 s. Therefore, the experimental results showed that the novel piezoelectric driven nanopositioner has excellent performance in terms of coupling displacement and nanometer scale accuracy for point-to-point movement.

Development of a Nanopositioning Platform With Large Travel Range Based on Bionic Quadruped Piezoelectric Actuator

A piezoelectric platform driven by a bionic quadruped piezoelectric actuator is developed. It uses the operating principle of combining bionic walking and swinging actuation modes to achieve nanopositioning in a large travel range. The mechanical structure is introduced, the operation principle is illustrated, and the dynamic model and control method are developed. The open-loop performances are first tested to verify the effectiveness of the operating principle and the dynamic model, and the simulation results agree well with the experimental results. Then, the closed-loop experiments in bionic walking and swinging actuation modes are carried out, respectively, and the controllers are designed based on the dynamic model. In the point-to-point positioning control experiments, the steady-state errors for the target position of ±1000 μm in axes X and Y are within ±1 μm in bionic walking actuation mode, and they are within ±20 nm for the target position of ±2 μm in bionic swinging actuation mode. The closed-loop experiments under the combination of the bionic walking actuation mode and swinging actuation mode are performed, and a switched controller is developed to obtain the switching of the two modes automatically; the steady-state errors are within ±20 nm. The experimental results confirm that the method combining bionic walking and swinging actuation modes and switched control is valid in enhancing the positioning precision and travel range for the nanopositioning platform.

Development of a Resonant Scanner to Improve the Imaging Rate of Astigmatic Optical Profilometers

An astigmatic optical profilometer provides numerous advantages such as compact size, low cost, and high resolution. In 2018, a z-axis modulation mode of the astigmatic optical profilometer was developed to realize quantitative height measurement for a surface comprising complex materials. However, the current imaging rate of the z-axis modulation mode is time-consuming. In this article, a resonant scanner was proposed to execute a high-speed z-axis scanning motion. By inducing the resonant mode, the resonant scanner enabled both a large travel range of over 87 μm and high oscillation frequency of 1.576 kHz. Additionally, a data analysis process was proposed to calibrate the nonlinear movement of the resonant scanner. Experimental results demonstrated that the developed optical profilometer successfully captured the quantitative height and reflectivity of the complex material comprising chrome patterns on a glass substrate. Furthermore, an imaging rate of 256 s/frame was achieved, which was approximately 50 times faster than that of a previous system employing a commercial flexure-guided scanner.

大行程快速反射镜的结构设计及带宽特性

大行程快速反射镜的结构设计及带宽特性

Design, Modeling, and Experimental Evaluation of a Compact Piezoelectric XY Platform for Large Travel Range.

A novel piezoelectric XY platform driven by a single actuator was presented for a large travel range and compact structure. The actuator operated at the inertial mechanism and moved the output platform step-by-step. A dynamic model of the piezoelectric actuator was established based on the Timoshenko beam theory and Galerkin procedure, which was used to aid the structure design. The dynamic model of the platform system was established based on the dynamic model of the actuator and the LuGre friction model. A prototype was fabricated and its experimental system was established; the total size was 100 × 100 × 93.5 mm3 and the travel range was 15 × 15 mm2. The measured stepper motions agreed well with the simulation results, and the correctness of the dynamic model was confirmed. The proposed platform achieved maximum speeds of 2.13 and 3.11 mm/s along the axes X and Y , respectively, and a carrying capacity of 20 kg was achieved. Furthermore, the closed-loop control experiments, including the positioning resolution and the sinusoidal trajectory tracking, were carried out, and a positioning resolution better than [Formula: see text] and a tracking error rate of 4% were achieved, which revealed the potential of the proposed piezoelectric platform in field of manipulating heavy objects with submicrometer accuracy and large travel range, especially for some specific fields including microparticle manipulation, ultraprecision manufacturing, and optical device posture adjustment where large travel range, high accuracy, and multidimension are expected.

Development of a Planar Piezoelectric Actuator Using Bending–Bending Hybrid Transducers

A planar piezoelectric actuator with large travel range is presented in this paper. The actuator is composed of four uniform piezoelectric transducers, and each transducer can bend along the horizontal direction or vertical direction independently. Trapezoidal-wave signals are used to excite the hybrid bending of the transducers and form rectangular movements on their driving feet. The actuator can move step by step by the static friction forces in nonresonant mode, and a long reliability life is obtained as there is no wear and tear problem. The operating principle is simulated by finite-element method, which reveals the generation of rectangular trajectory on each driving foot and the large structure stiffness of the actuator. A prototype is fabricated and its experiment system is established. A resolution of 16 nm is achieved at the quasi-static mode, a minimum step distance repeatability error rate of 1.06% is obtained at the stepper mode; the maximum output speed and carrying load of 300 μm/s and 35 kg are achieved at voltage of 400 V $_{{\text{p-p}}}$ and frequency of 40 Hz. The experiments also shows that the output speed is linearly related to the exciting voltage; the motion along any direction in the platform is achieved by controlling the voltage signals.

The design and kinetostatic modeling of 3PPR planar compliant parallel mechanism based on compliance matrix method.

Compliant Parallel Mechanisms (CPMs) are widely used in micro/nano-positioning systems. In recent years, CPMs with a large travel range (≥1 mm) have been getting increasing attention. In this paper, a 3 Prismatic-Prismatic-Revolute (3PPR) planar CPM with a motion range of 5 mm × 5 mm × 5° is designed. The mechanical structure is characterized by the application of three joints based on a compliant four-bar mechanism, which guarantees the motions along/about the specific axes to improve motion accuracy. A double blade rotary pivot is served as a revolute joint to decrease the drift of pivot and produce a large rotation range without loss of compactness. The compliance matrix method is implemented to kinetostatic modeling, and the input coupling effect, which is always neglected or modeled complicatedly in 3-Degree-of-Freedom planar CPMs, is involved with the principle of superposition. The feasibility of the mechanical design and the accuracy of the developed kinetostatic model are validated by finite element analysis and experiments, respectively. The results indicate that the modeling method based on the compliance matrix method is concise, effective, and accurate, and can be extended to other more complicated CPMs.

Fast positioning for X-ray scanning microscopy by a combined motion of sample and beam-defining optics.

Scanning X-ray microscopy such as X-ray ptychography requires accurate and fast positioning of samples in the X-ray beam. Sample stages often have a high mobile mass as they may carry additional mechanics or mirrors for position measurements. The high mobile mass of a piezo stage can introduce vibrations in the setup that will lead to imaging quality deterioration. Sample stages also require a large travel range which results in a slow positioning step response and thus high positioning overhead. Moving lightweight X-ray optics, such as focusing Fresnel zone plates, instead of the sample can improve the situation but it may lead to undesired variations in the illumination probe which may result in reconstruction artifacts. This paper presents a combined approach in which a slow sample stage mechanism covers the long distance range for a large field of view, and a light-weight optics scanner with a small travel range creates a superimposed motion to achieve a fast step response. The step response in the ptychographic tomography instrument used was thereby improved by an order of magnitude, allowing for efficient measurement without loss of imaging quality.

Review on Multi-Degree-of-Freedom Piezoelectric Motion Stage

Multi-degree-of-freedom (multi-DOF) piezoelectric motion stage is an important part of modern manufacturing industry. In order to perform high precision outputs in a large travel range, various multi-DOF piezoelectric motion stages have been proposed and applied for decades. This paper is concentrated on reviewing the research on a piezoelectric motion stage. It involves the major components, operating principles of different actuation modes, design schemes, and structures of the multi-DOF piezoelectric motion stages. In this paper, the summary and classification of the actuation modes used in the multi-DOF piezoelectric motion stages are presented, mainly including the resonance actuation mode, inertial actuation mode, clamping and feeding actuation mode, and direct actuation mode; the multi-DOF piezoelectric motion stage is divided into multi-actuator type and single-actuator type according to the number of actuators used in the motion stage, in which the multi-actuator type includes series, parallel, and series–parallel types from the viewpoint of structure mechanism; in addition, the output performances of the stages are compared, and the state of the arts of the stages are discussed and summarized; the further efforts and future research perspectives are highlighted.

Design and modeling of a novel monolithic parallel XY stage with centimeters travel range

Since most of XY positioning stages with large travel range proposed by former researchers suffer from loose structure and low out-of-plane payload, this article presents a novel monolithic paralle...

Compact design of a novel linear compliant positioning stage with high out-of-plane stiffness and large travel

Since most of the XY positioning stages with large travel range proposed in previous studies suffer from low out-of-plane stiffness and loose structure, this paper presents a novel two degrees-of-freedom large travel linear compliant positioning stage with high out-of-plane stiffness and compact size. The linear guide compliant mechanism of the stage takes spatial leaf spring parallelograms as the basic units, which are serially connected to obtain large travel, high out-of-plane stiffness, and compact size simultaneously. The theoretical static stiffness and dynamic resonant frequency are obtained by matrix structural analysis. Finite element analysis is carried out to investigate the characteristics of the developed stage. The analytical model is confirmed by experiments. It is noted that the developed stage has a workspace of 4.4 × 7.0 mm2, and the area ratio of workspace to the outer dimension of the stage is 0.16%, which is greater than that of any existing stage reported in the literature. The results of out-of-plane payload tests indicate that the stage can sustain at least 20 kg out-of-plane payload without changing the travel range. And the positioning experiments show that the developed stage is capable of tracking a circle of radius 1.5 mm with 10 µm error and the resolution is less than 2 µm.

Mechatronic design of a novel linear compliant positioning stage with large travel range and high out-of-plane payload capacity

Most of the XY positioning stages proposed in previous studies are mainly designed by considering only a single performance indicator of the stage. As a result, the other performance indicators are relatively weak. In this study, a 2-degree-of-freedom linear compliant positioning stage (LCPS) is developed by mechatronic design to balance the interacting performance indicators and realize the desired positioning stage. The key parameters and the coupling of the structure and actuators are completely considered in the design. The LCPS consists of four voice coil motors (VCMs), which are conformally designed for compactness, and six spatial leaf spring parallelograms. These parallelograms are serially connected for a large travel range and a high out-of-plane payload capacity. The mechatronic model is established by matrix structural analysis for structural modeling and by Kirchhoff’s law for the VCMs. The sensitivities of the key parameters are analyzed, and the design parameters are subsequently determined. The analytical model of the stage is confirmed by experiments. The stage has a travel range of 4.4 mm × 7.0 mm and a 0.16% area ratio of workspace to the outer dimension of the stage. The values of these performance indicators are greater than those of any existing stage reported in the literature. The closed-loop bandwidth is 9.5 Hz in both working directions. The stage can track a circular trajectory with a radius of 1.5 mm, with 40 mm error and a resolution of lower than 3 mm. The results of payload tests indicate that the stage has at least 20 kg outof- plane payload capacity.

A novel flexure-based vertical nanopositioning stage with large travel range.

This paper presents the design of a novel flexure-based vertical (or Z-axis) nanopositioning stage driven by a piezoelectric actuator (PZT), which is capable of executing large travel range. The proposed stage consists mainly of a hybrid displacement amplification mechanism (DAM), a motion guiding mechanism, and a decoupling mechanism. The hybrid DAM with amplification ratio of 12.1 is developed to transfer the transverse motion of the PZT actuator into the vertical motion. The motion guiding mechanism is introduced to avoid cross coupling at the output end. The decoupling mechanism can significantly reduce the cross coupling at the driving end to protect the PZT. The stiffness and dynamics of the proposed stage are improved by these mechanisms. Analytical modeling and finite element analysis (FEA) are then adopted to optimize dimensions of the stage. Finally, a prototype of the stage is fabricated and tested for verification. The results of static and dynamic tests show that the proposed stage is capable of vertical travel range of 214 μm with resolution of 8 nm, and the first two resonance frequencies are 205 Hz and 1206 Hz, respectively. Cross coupling tests under various lateral loads (0 g-1000 g) show that the maximum variances of the lateral and angular cross couplings are less than 0.78 μm and 95 μrad, respectively, indicating good decoupling capability. In addition, the low-profile structure of the stage is well suited to be used in limited vertical space.

Displacement Sensing With Silicon Flexures in MEMS Nanopositioners

We report a novel piezoresistive microelectromechanical system (MEMS) differential displacement sensing technique with a minimal footprint realized through a standard MEMS fabrication process, whereby no additional doping is required to build the piezoresistors. The design is based on configuring a pair of suspension beams attached to a movable stage so that they experience opposite axial forces when the stage moves. The resulting difference between the beam resistances is transduced into a sensor output voltage using a halfbridge readout circuit and differential amplifier. Compared with a single piezoresistive flexure sensor, the design approximately achieves 2, 22, and 200 times improvement in sensitivity, linearity, and resolution, respectively, with 1.5-nm resolution over a large travel range exceeding 12 μm.

Long-Stroke Nanopositioning Stage Driven by Piezoelectric Motor

This paper reported a biaxial nanopositioning stage single-driven by piezoelectric motor. The employed piezoelectric motor can perform two different driving modes, namely, AC drive mode to drive in long-stroke and at high-speed and DC scanning mode with the high-resolution of several nanometers, which satisfies the requirements of both long-stroke and nanoresolution. To compensate for the effects of the variable friction force and some unpredictable disturbances, a novel backward error compensation (BEC) positioning control method integrated of the two driving modes and a double closed-loop PID controller system are proposed to obtain a high-accuracy positional motion. The experiment results demonstrate that the nanopositioning stage with large travel range of 300 mm × 300 mm has a fine speed characteristic and resolution is 5 nm. In the experiments of different travels up to 15 mm, calibrated by a commercial laser vibrometer, the positioning accuracy is proved within 55 nm inx-axis and 40 nm iny-axis with standard deviation less than 40 nm inx-axis and 30 nm iny-axis and the final position locking can be limited to 10 nm, meeting the requirements of micromanipulation technology.

Design, analysis and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage

This paper presents the design, analysis, and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage driven by piezoelectric stack actuators. The stage is designed with two kinematic chains. In each kinematic chain, the end-effector of the stage is connected to the base by two symmetrically distributed flexure modules, respectively. Each flexure module comprises a fixed-fixed beam and a parallelogram flexure serving as two orthogonal prismatic joints. With the purpose to achieve high resonance frequencies of the stage, a novel center-thickened beam which has large stiffness is proposed to act as the fixed-fixed beam. The center-thickened beam also contributes to reducing cross-coupling and restricting parasitic motion. To decouple the motion in two axes totally, a symmetric configuration is adopted for the parallelogram flexures. Based on the analytical models established in static and dynamic analysis, the dimensions of the stage are optimized in order to maximize the first resonance frequency. Then finite element analysis is utilized to validate the design and a prototype of the stage is fabricated for performance tests. According to the results of static and dynamic tests, the resonance frequencies of the developed stage are over 13.6 kHz and the workspace is 11.2 μm × 11.6 μm with the cross-coupling between two axes less than 0.52%. It is clearly demonstrated that the developed stage has high resonance frequencies, a relatively large travel range, and nearly decoupled performance between two axes. For high-speed tracking performance tests, an inversion-based feedforward controller is implemented for the stage to compensate for the positioning errors caused by mechanical vibration. The experimental results show that good tracking performance at high speed is achieved, which validates the effectiveness of the developed stage.