Search Results (31)

This paper presents the development of a compact nanopositioning stage with long-range capabilities and six-degree-of-freedom (DOF) closed-loop control. The system, referred to as NPS6D100, provides Ø100 mm planar and 10 mm vertical travel range while maintaining direct force transfer to the moving platform (or slider) in all DOFs. Based on an integrated planar direct drive concept, the system is enhanced by precise vertical actuation and full 6D output feedback control. The mechanical structure, drive architecture, guiding, and measurement subsystems are described in detail, along with experimental results that confirm sub-10 nm servo errors under constant setpoint operation and in synchronized multi-axis motion scenarios. With its scalable and low-disturbance design, the NPS6D100 is well suited as a nanopositioning platform for sub-10 nm applications in nanoscience and precision metrology. Full article

Flexure-based linear stages have become prevalent in precision engineering; however, most designs suffer from parasitic shifts that degrade positioning accuracy. Conventional solutions to mitigate these parasitic motions often compromise support stiffness, reduce motion range, and increase structural complexity. This study presents a novel family of flexure-based rectilinear-motion stages using coupled n-RRR planar parallel mechanisms, achieving extremely low parasitic shifts while addressing the forementioned limitations. Four design variants are selected and analyzed via Finite Element Method (FEM) simulations, evaluating parasitic shifts, stroke, and support stiffness. The most precise configuration, a 4-RRR rectilinear stage having kinematic chains coupled via two Watt linkages, exhibits a lateral shift smaller than 0.258 µm and an in-plane parasitic rotation smaller than 12.6 µrad over a 12 mm stroke. Experimental validation using a POM prototype confirms the high positioning precision and support stiffness properties. In addition, a silicon prototype incorporating thermally preloaded buckling beams is investigated to reduce its translational stiffness. Experimental results show a translational stiffness reduction of 98% in the monostable configuration and 112% in the bistable configuration (i.e., negative stiffness), without support stiffness reduction. These results highlight the potential of the proposed mechanisms for a wide range of precision applications, offering a scalable and high-accuracy solution for micro- and nano-positioning systems. Full article

A novel over-constrained XYθ_z nano-positioning stage with a high load-bearing capacity is proposed. This serially connected displacement stage adopts an embedded structural design that integrates a translation stage with a rotation stage in series. The Z-axis amplification mechanism employs out-of-plane actuation, realising a compact solution for three-axis independent motion. The hybrid amplification mechanism designed in the translation stage ensures enhanced output displacement and structural stiffness. The hybrid-parallel amplification mechanism comprises a lever-type displacement amplifier and a Scott–Russell displacement amplifier connected in series, which is then connected in parallel with a bridge-type displacement amplifier. An over-constrained mechanism is introduced to impose redundant constraints along the Z-axis, effectively suppressing parasitic displacement in the Z-direction while enhancing resistance to out-of-plane deformation. A quasi-static model of the XYθ_z motion stage was established to comprehensively characterise the deformation behaviour of the stage, which was verified by finite element simulations and experiments on the prototype. The experimental results indicate that the XYθ_z stage achieves a large motion range (up to 152.22 μm × 151.3 μm × 2.885 mrad) while maintaining excellent anti-deformation capability 200 nm at 4 kg loading. Full article

This paper presents an adaptive sliding mode control (ASMC) scheme based on strain gauge position feedback for compensating for motion errors in a piezoelectric nanopositioning stages and ensures precise and reliable motion tracking control. The innovation of this scheme lies in calibrating the relationship between the feedback voltage of the strain gauge and the actual stage displacement. Thus, the calibrated feedback displacement is directly used as the position feedback signal for the ASMC scheme. Adaptive rules are employed to adjust the control gains, thereby eliminating the requirement to determine the upper bound of the disturbance. The stability of the ASMC strategy is theoretically proven within the Lyapunov framework. Comparative experiments under external disturbances have confirmed the superiority of the proposed control scheme. Results demonstrate that the proposed control scheme exhibits superior robust tracking performance compared to the traditional sliding mode control (SMC) scheme. Full article

This work presents the new development of a nanopositioning machine for a large operating range. The machine, called NPS6D200, provides Ø200 $\mathrm{m}$$\mathrm{m}$ planar and 25 $\mathrm{m}$$\mathrm{m}$ vertical travel range and applies a 6D closed loop control with all drive forces applied directly to the same moving part. The stage architecture evolves from an integrated planar direct drive which is extended by high precision vertical positioning capability. The setup of the machine and the characteristics of the different subsystems are presented together with investigations into the positioning performance that is achieved with the NPS6D200. In constant setpoint operation as well as in synchronized multiaxial motion tasks over three orders of magnitude, the system shows servo errors only in the low nanometer range and proves suitable as positioning platform for nanoscience applications. Full article

Nanopositioning stages with piezoelectric actuators have been widely used in fields such as precision mechanical engineering, but the nonlinear start-up accuracy problem under open-loop control has still not been solved, and more errors will accumulate, especially under open-loop control. This paper first analyzes the causes of the starting errors from both the physical properties of materials and voltages: the starting errors are affected by the material properties of piezoelectric ceramics, and the magnitude of the voltage determines the magnitude of the starting errors. Then, this paper adopts an image-only model of the data separated by a Prandtl-Ishlinskii model (DSPI) based on the classical Prandtl-Ishlinskii model (CPI), which can improve the positioning accuracy of the nanopositioning platform after separating the data based on the start-up error characteristics. This model can improve the positioning accuracy of the nanopositioning platform while solving the problem of nonlinear start-up errors under open-loop control. Finally, the DSPI inverse model is used for the feedforward compensation control of the platform, and the experimental results show that the DSPI model can solve the nonlinear start-up error problem existing under open-loop control. The DSPI model not only has higher modeling accuracy than the CPI model but also has better performance in terms of compensation results. The DSPI model improves the localization accuracy by 99.427% compared to the CPI model. When compared with another improved model, the localization accuracy is improved by 92.763%. Full article

In this manuscript, a compact electromagnetic dual actuation positioning system (CEDAPS) based on the Lorentz force principle that features a 10 mm range and nanometer-scale resolution with flexure guides is presented. Firstly, the stiffness of the flexure mechanism is modelled. Secondly, based on it, the primary coil is designed, and from its performance, a suitable secondary coil is made to compensate for the deficiency of the primary actuation subsystem. The characteristics of the forces generated by these coils are also evaluated by an electromagnetic FEA simulation. Thirdly, a control scheme is presented that combines the performances of these two actuators, and finally, a prototype is fabricated to evaluate the performance. The results show a 10 nm resolution for a 10 mm (±5 mm) stroke with low sub-micron sinusoidal tracking errors and nanometer accuracy for step tracking under the proposed control scheme. The thermal properties of the system are also presented. Full article

Piezo-actuated stage (P-AS) has become the topic of considerable interest in the realm of micro/nanopositioning technology in the recent years owing to its advantages, such as high positioning accuracy, high response speed, and large output force. However, rate-dependent (RD) hysteresis, which is an inherent nonlinear property of piezoelectric materials, considerably restricts the application of P-AS. In this research paper, we develop a Hammerstein model to depict the RD hysteresis of P-AS. An improved differential evolution algorithm and a least-squares algorithm are used to identify the static hysteresis sub-model and the dynamic linear sub-model for the Hammerstein model, respectively. Then, a hysteresis compensator based on the inverse Bouc–Wen model is designed to compensate for the static hysteresis of the P-AS. However, the inevitable modeling error presents a hurdle to the hysteresis compensation. In addition, external factors, such as environmental noise and measurement errors, affect the control accuracy. To overcome these complications, a hybrid adaptive control approach based on the hysteresis compensator is adopted to increase the control accuracy. The closed-loop system stability is analyzed with the help of the Lyapunov stability theory. Finally, experimental results indicate that the raised control approach is effective for the accurate positioning of P-AS. Full article

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. Full article

Nanopositioning technology is widely used in high-resolution applications. It often uses piezoelectric actuators due to their superior characteristics. However, piezoelectric actuators exhibit a hysteresis phenomenon that limits their positioning accuracy. To compensate for the hysteresis effect, developing an accurate hysteresis model of piezoelectric actuators is very important. This task is challenging, requiring some considerations of the multivalued mapping of hysteresis loops and the generalization capabilities of the model. This challenge can be dealt with by developing a machine learning-based model, whose inverse model can be used to efficiently design an accurate feedforward controller for hysteresis compensation. However, this approach depends on model accuracy and the type of data used to train the model. Thus, accurate prediction of the hysteresis behavior may not be guaranteed in the presence of disturbances. In this paper, a machine learning-based model is used to design a hysteresis compensator and then combined with a robust feedback controller to enhance the robustness of a nanopositioning control system. The proposed model is based on hysteresis operators, the least square support vector machine (LSSVM) method, and particle swarm optimization (PSO) algorithm. The inverse model is used to design the feedforward controller, and the RST controller is employed to develop feedback control. Our main contribution is the introduction of a hybrid controller capable of compensating for the hysteresis effect, and at the same time, eliminating remaining modeling errors and rejecting disturbances. The performance of the proposed approach is evaluated through MATLAB simulation, as well as through real-time experiments. The experimental results of our approach demonstrate superior tracking performance compared with the PID-LSSVM controller. Full article

Piezoelectric actuators (PEAs) and compliant parallel mechanisms (CPMs) are advantageous for designing nanopositioning stages (NPSs) with multiple degrees of freedom (multi-DOFs). This paper proposes a new NPS that uses PEAs and CPMs with multiple spatial DOFs. First, the design of the mechanism is introduced. Six parallel kinematics revolute-revolute-revolute-revolute (RRRR) branched chains were used to create a 6-RRRR CPM for superior mechanical performance. Three in-plane and three out-of-plane chains were combined using a two-in-one structure to ensure fabrication feasibility. A two-in-one 6-RRRR CPM was employed to build the proposed NPS. Second, the mechanical performance was analyzed. High-efficiency finite-element modeling approaches were derived using the compliance-based matrix method (CMM) and a pseudo-rigid body model (PRBM). The model included both 6-RRRR CPM and NPS. The simulation results validated the static and dynamic performance, and the experimental results verified the kinematics. Based on the newly designed mechanism and verified mechanical performance, the proposed 6-RRRR NPS contributes to the development of spatial multi-DOF NPSs using PEAs and CPMs. Full article

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. Full article

The paper proposes a three-degrees-of-freedom flexible nano-positioning stage constructed from compliant flexures and piezoelectric thin-sheet actuators, featuring a compact size and fast dynamic responses, which can be extensively applied to the typical micro/nano-positioning applications. Meanwhile, the dynamic model of the flexible PZT nano-positioning with distributed parameter characteristics is established to distinctly reflect the piezoelectric–mechanical coupling relationship between the four flexible PZT actuators and the three outputs of such a system. Furthermore, the attitude decoupling control for the 3-DOF flexible piezoelectric nano-positioning stage is achieved by the Active Disturbance Rejection Control (ADRC) method to compensate for the positioning errors in the actual positioning process. After this, a real-time experimental apparatus with two Position-Sensitive Detectors (PSDs) is also proposed and fabricated to test the three outputs of the flexible piezoelectric thin-sheet (PZT-5A) nano-positioning stage and validate the effectiveness of the dynamic modeling method and attitude decoupling control in the piezoelectric nano-positioning stage ranges. Full article

This paper presents a flexure-based displacement reduction mechanism driven by a voice coil motor to improve the motion resolution and eliminate the hysteresis nonlinearity of the traditional piezo-actuated micropositioning/nanopositioning stages. The mechanism is composed of three groups of compound bridge-type displacement reduction mechanisms, which adopt distributed-compliance rectangular beams to reduce the concentration of stress and improve the dynamic performance of the mechanism. The symmetrical distribution of the structure can eliminate the parasitic displacement of the mechanism and avoid the bending moment and lateral stress applied to the voice coil motor. Firstly, the analytical model of the mechanism is obtained by the stiffness matrix method. The theoretical displacement reduction ratio, input stiffness, and natural frequency of the displacement reduction mechanism are obtained by solving the analytical model. Then, through the static analysis and modal analysis of the mechanism with the Ansys software, the accuracy of the analytical model is verified, and the experimental prototype is also constructed for performance tests. The results show that the maximum stroke of the mechanism is 197.43 μm with motion resolution of 40 nm. The natural frequency is 291 Hz, and the input stiffness is 28.50 N/mm. Finally, the trajectory tracking experiment is carried out to verify the positioning performance of the mechanism. The experimental results show that the designed feedback controller has good stability, and the introduction of the feedforward controller and disturbance observer can greatly reduce the tracking errors. Full article

This paper presents a novel parallel dual-stage compliant nanopositioning system (PDCNS), aimed at nanoscale positioning for microscale manipulation. In the developed PDCNS, the coarse stage actuated by the voice coil motor and the fine stage driven by the piezoelectric actuator are integrated in a parallel manner by a specially devised A-shaped compliant mechanism, which leads to many excellent performances, such as good resolution and large stroke and broadband. To enhance the closed-loop-positioning capability of the proposed PDCNS, a double-servo cooperative control (DSCC) strategy is specially constructed. The performance of the proposed PDCNS is evaluated by analytical model, finite element analysis, and experimental research. Results show that the first-order resonance frequency of the designed A-shaped compliant mechanism can reach 99.7 Hz. Combined with the designed DSCC, the developed PDCNS prototype is demonstrated to provide a stroke of 1.49 mm and a positioning resolution of ≤50 nm. Full article