Displacement Amplifier Research Articles

Design and test of a compact large-stroke dual-drive linear-motion system

This paper presents the design, modelling, analysis, and test of a piezo-actuated dual-drive linear motion system, capable of millimeter stroke with nanometer resolution. The primary actuator is a two-stage bridge-type amplifier with hybrid flexure hinges, which is driven by a piezo-stack actuator and generates output stroke greater than 6 mm. The micro actuation is directly driven by an extra piezo-stack to achieve resolution of 20 nm. A very large amplification ratio of 91 is achieved, which implies not only large stroke but also compactness. An inherent characteristic for the multi-stage compliant displacement amplifier, ‘kick-back’ phenomenon, is first analyzed and eliminated by using the stiffness distribution method. The architectural parameters are optimized by genetic algorithm to find the trade-off among natural frequency, stroke and stiffness ratio. The optimized design was then fabricated and tested. The superiority of the proposed system is remarkable compared with other similar works. The concept and approach outlined are generic and can be extended to this class of actuators.

Optimal Design and Analysis for a New 1-DOF Compliant Stage Based on Additive Manufacturing Method for Testing Medical Specimens

In situ nanoindentation is extensively employed for online observing deformation and mechanical behaviors of bio-materials. However, the existing designs of the positioning stages have limited performances for testing soft or hard biomaterials. Consequently, this paper proposes a new structural design of a compliant one degree of freedom (01-DOF) stage with faster response. In addition to a new design, this article applies an analytical method to estimate the kinematic and dynamic behaviors of the stage. Firstly, the 01-DOF stage is designed with two modules, including a displacement amplifier with six levers and a symmetric parallelogram mechanism. Secondly, a kinetostatic diagram of the stage is built by pseudo-rigid-body method. Then, the dynamic equation of the proposed stage is formulated using the Lagrange method. In order to speed up the response of the indentation system, the structural optimization of the stage is conducted via the Firefly algorithm. The results showed that the theoretical first-order resonant frequency is found at about 226.8458 Hz. The theoretical consequences are nearby to the verified simulation. Besides, this achieved frequency of the presented stage is greater than that of previous stages. In an upcoming study, the prototype will be fabricated by additive manufacturing method or a computerized wire cutting method in order to verify the analytical results with experimental results.

Design of a Piezoelectric Pump Driven by Inertial Force of Vibrator Supported by a Slotted Beam

This paper introduces the design, manufacture, dynamic analysis, and experimental results of a piezoelectric pump driven by the inertial force of a vibrator supported by a slotted beam. The piezoelectric vibrator is composed of a mass block, displacement amplifier, and slotted beam fixed with both ends. In the resonant mode, the displacement amplifier drives the slotted beam to work, and produces amplitude and inertial force. In this paper, the design of the slotted beam optimizes the output of the displacement amplifier. In addition, the slotted beam supports the displacement amplifier and increases the elastic output. The pump body adopts polydimethylsiloxane (PDMS) check valves and compressible spaces to improve the output performance. This research studies the influence of stiffness and mass on the output performance by qualitatively analyzing the inertial output force of the vibrator. Nine kinds of slotted beams with different stiffnesses and different mass blocks are designed for comparison. Thereafter, an optimal structure of the piezoelectric pump is selected. The experimental results show that under a driving voltage of 700 Vpp , the maximum flowrate is 441 mL min−1 and the maximum back pressure is 25.3 kPa.

Optimized design of a compact multi-stage displacement amplification mechanism with enhanced efficiency

Mechanically amplifying micro-stroke of actuators such as piezoelectric stacks through compliant mechanisms is an effective solution for use in micro/nano manipulation, precision positioning, gripping and manufacturing with large enough workspaces. This paper proposes a novel type of hybrid three-stage compliant displacement amplifier with a compact structure by synthesizing bridge-type and lever-type compliant mechanisms. A new index is introduced to measure its displacement amplification efficiency by considering the whole size and input stiffness. To facilitate design, the dynamic stiffness model is also derived to capture its kinetostatics and dynamics on both time and frequency domain. Then, the key structural parameters are efficiently optimized with the Pareto multi-objective optimization strategy. The capacity curve in terms of the resonance frequency, displacement amplification ratio and load capacity (output stiffness) is provided as well in a form of the Pareto optimal solution set. Experimental tests of two prototypes indicate a high displacement amplification efficiency of the current design, of which one prototype exhibits the output displacement of 0.7 mm and the resonance frequency of 874 Hz with a compact size of only 57 mm × 50 mm × 10 mm.

Design and investigation of a resonant piezoelectric pump with high output pressure using a displacement-amplifying vibrator

A resonant piezoelectric pump using a displacement-amplifying vibrator is proposed in this paper to improve the output pressure of the piezoelectric pump. The piezoelectric pump is composed of a displacement-amplifying vibrator and a pump body. The displacement-amplifying vibrator consists of two amplifiers and two piezoelectric stacks. The pump body comprises a piston shaft, an orifice plate, a valve body, check valves and a runner plate. A clearance exists between the piston shaft and the orifice plate. A groove is designed on the piston shaft, and the pump body is sealed by O-rings. The displacement-amplifying vibrator works in the resonant state, which has a large output amplitude. In this paper, the working principle of the piezoelectric pump is introduced and the influencing factors of output pressure of the piezoelectric pump are theoretically analyzed. The resonant frequency and stiffness of check valves with different thicknesses are simulated and compared, and three displacement amplifiers are designed and simulated. Prototypes of piezoelectric pump are made, and the effect of valve thickness, the diameter of piston shaft, and the displacement-amplifying vibrator is experimentally investigated. The experimental results show that the piezoelectric pump prototype with displacement-amplifying vibrator 3, 10 mm piston shaft and 0.05 mm-thick check valve has the maximum output pressure. Under the driving voltage of 500 Vpp, the maximum output pressure is 4.73 MPa, and the maximum flowrate is 65.7 ml min−1.

Structural optimization and experiment of a semi-active hourglass-type electromagnetic isolator with negative resistance shunt circuit

The present work proposed a semi-active electromagnetic isolator with negative resistance shunt circuit to improve isolation performance on micro-vibration. By an innovative combination of an hourglass-type displacement amplifier and electromagnetic mechanism with negative resistance shunt circuit, the proposed isolator can not only solve the difficulty for electromagnetic isolators to isolation micro-amplitude vibration but also achieve a significant electromechanical coupling effect to obtain excellent vibration isolation performance by a self-sensing method. First, the design of the isolator and motion relationship are presented. Then, the electromechanical coupling dynamic model of the isolator is established. Moreover, the angle of the hourglass-type displacement amplifier is optimized, and the influence of the negative resistance on the additional damping ratio and system stability is explored. Finally, the isolator was manufactured and several experiments were carried on. The experiment results demonstrated that the isolator has an excellent isolation performance. And meanwhile, the comparison between experiment and simulation also indicated the correctness of the model.

On-demand direct printing of tin microdots by a piezoelectric microjet: design, simulation, and experimental evaluation

Metal microdot precision printing is widely applied in flexible circuit manufacturing, ball grid array and additive manufacturing, etc. Compared with indirect metal microdot printing, direct printing can realize high efficiency printing by directly ejecting hot-melt metal droplets. While, due to the compressibility of the driving gas, uniform printed microdots are hardly to be obtained by using the existing direct printing method. In this work, a piezoelectric microjet, which can print tin microdots directly by the drive of piezoelectric actuator without complex pneumatic system, is designed. Optimization analyses of the displacement amplifier are carried out to obtain high amplification efficiency for realizing hot-melt droplet ejection and effective heat insulation. The forming, spreading, and solidification processes of the ejected hot-melt tin droplets are discussed, and the printing mechanism is revealed. Based on experimental research, the influences of the excitation parameters and the target surface characteristics on the morphology and size of the printed tin microdots are studied, and the methods to meet different printing requirements are proposed. Tin microdot diameter of 340 μm can be printed on the surface with temperature of 120 °C when voltage pulse with amplitude of only 16 V is applied on the designed piezoelectric microjet with the nozzle diameter of 200 μm. The feasibility and controllability of the tin microdot printing methods are verified by two-dimensional printing and three-dimensional deposition printing test. This work can provide important reference for on-demand printing of metal microdots.

Zeptometer Metrology Using the Casimir Effect

In this paper, we discuss using the Casimir force in conjunction with a MEMS parametric amplifier to construct a quantum displacement amplifier. Such a mechanical amplifier converts DC displacements into much larger AC oscillations via the quantum gain of the system which, in some cases, can be a factor of a million or more. This would allow one to build chip scale metrology systems with zeptometer positional resolution. This approach leverages quantum fluctuations to build a device with a sensitivity that can’t be obtained with classical systems.

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 Koiter reduction technique for the nonlinear thermoelastic analysis of shell structures prone to buckling

AbstractThe multi‐modal Koiter method is a reduction technique for estimating quickly the nonlinear buckling response of structures under mechanical loads requiring a fine discretization. The reduced model is based on a quadratic approximation of the full model using a few linear buckling modes and their second order corrections, followed by the projection of the equilibrium equations onto the modal subspace. In this article, the method is reformulated for geometrically nonlinear thermoelastic analyses of shell structures. The starting point is an isogeometric solid‐shell discretization with an accurate modeling of thermal strains, temperature‐dependent materials and general temperature distributions. The equilibrium path is defined as a displacement versus temperature amplifier curve, while mechanical loads are kept constant. The strain energy nonlinearity with respect to the temperature amplifier is the main obstacle in the definition of an accurate reduced model. This task is achieved by coherent asymptotic expansions in mixed form using independent stress variables at the integration points and accurate linear buckling modes obtained by a two‐point mixed eigenvalue problem. Structures made of isotropic and multi‐layered composite materials, including variable angle tow laminates, are considered to show the accuracy of the proposed method.

A novel compliant XY micro-positioning stage using bridge-type displacement amplifier embedded with Scott-Russell mechanism

This paper presents a new bridge-type compliant displacement amplifier embedded with Scott-Russell mechanism. Based on this design, a novel compliant XY micro-positioning stage is also designed, analyzed and tested to illustrate the advantages of the proposed amplifier. The main feature of the new amplifier is to employ Scott-Russell mechanism to replace one arm of the compound bridge-type mechanism, aiming to improve its lateral stiffness and the natural frequency in the working direction. The compliant XY micro-positioning stage is driven by two novel bridge-type amplifiers with orthogonal distribution. Double parallelogram guide mechanisms are added at the output ends of the bridge-type mechanisms to further lower the parasitic movements of the XY stage. Then, an analytical model based on the stiffness matrix transfer method is established for the static and dynamic characteristics of stage, which are also verified by performing finite element analysis. Finally, an experimental prototype is manufactured and its static and dynamic performances are tested. The test results demonstrate that the stage can realize a workspace of 181.0 μm × 179.5 μm with motion resolution of 20 nm and a maximum coupling error of 1.07%. The natural frequencies of XY stage along the working direction are 178 Hz and 248 Hz respectively when the PZTs are not installed or installed. Additionally, the trajectory tracking performance of the stage is also preliminarily evaluated. All of the results obtained from the analytical model, finite element analysis and experimental tests verify the effectiveness of the novel bridge-type displacement amplifier and the compliant XY micro-positioning stage.

The Effect of Spool Displacement Control to the Flow Rate in the Piezoelectric Stack-Based Valve System Subjected to High Operating Temperature

This work investigates the effect of spool displacement control of the piezoelectric stack actuator (PSA) based valve system on the flow motion of the pressure drop and flow rate. As a first step, the governing equations of the structural parts of the displacement amplifier and spool are derived, followed by the governing equation of the fluid part considering control volume and steady flow force. Then, an appropriate size of the valve is designed and manufactured. An experimental apparatus to control the spool displacement is set up in the heat chamber and tracking control for the spool displacement is evaluated at 20 °C and 100 °C by implementing a proportional-integral-derivative (PID) feedback controller. The tracking controls of the spool displacement associated with the sinusoidal and triangular trajectories are realized at 20 °C and 100 °C. It is demonstrated that the tracking controls for the sinusoidal and triangular trajectories have been well carried out showing the tracking error less than 3 μm at both temperatures. In addition, the flow motions for the pressure drop and the flow rate of the proposed valve system are experimentally investigated. It is identified from this investigation that both pressure drop and flow rate evaluated 20 °C have been decreased up to 18% at 100 °C. This result directly indicates that the temperature effect to control performance of the structural part and fluid part in the proposed PSA based valve system is different and hence careful attention is required to achieve the successful development of advanced valve systems subjected to a wide range of the operating temperature.

Research on a hydraulic displacement amplifier for a piezoactuator

A piezoactuator-based hydraulic displacement amplifier with two flexible diaphragm spools and one rigid chamber is designed. The elastic characteristics and effective area of the diaphragm spool are theoretically and numerically analyzed. The influencing factors on the effective area of the diaphragm spool are studied by the finite element analysis method. On this basis, a proto-type is produced, and its measurement and control system is built. Experimental results show that the hydraulic amplifier prototype can achieve a stroke range of 540 μm and its amplification ratio is approximately 6.

Technical Note: Internal Second-Order Stiffness: A Refined Approach to the Rm Coefficient to Account for the Influence of P-? on P-?

One component of the B2 amplifier method of addressing second-order effects is the RM coefficient, which represents the influence of P-? on P-? effects. This paper presents the background for RM based on LeMessurier’s paper, “A Practical Method of Second-Order Analysis: Part 2—Rigid Frames,” (1977), and makes explicit the simplifications entailed in the AISC Specification for Structural Steel Buildings (AISC, 2016b) formulation for this coefficient. These simplifications, while providing for reliable strength design, can overestimate the P-? effect for typical building applications, especially if applied to drift. A simple formula for RM based on the work of LeMessurier permits a more precise estimate, which can be used as a component of both force and displacement amplifiers presented in this paper. This explicit approach to the RM coefficient provides the basis for clear presentation of the relationships first-order and second-order stiffness (both internal and external), including the distinct effects of P-? and P-? stiffness reductions on equilibrium at the second-order displacement.

Design and investigation on a piezoelectric screw pump with high flowrate

A novel piezoelectric screw pump is proposed in this study to improve the output flowrate of piezoelectric valveless pump. Piezoelectric screw pump is composed of a piezoelectric driving system and a screw pump body, which could realize the separation of driving and pump body. The driving system consists of two groups of piezoelectric vibrators and a ring hinge. The piezoelectric vibrators are made of four displacement amplifiers and four piezoelectric stacks. The screw pump body consists of an outer cylinder, a threaded pipe and a screw. The threaded pipe and screw are designed with rectangular threads. A certain clearance exists on their matching surface as the liquid flow channel. The screw pump body is made by 3D printing. This paper introduces the operating principle of the piezoelectric screw pump, and analyzes the factors influencing the output performance by finite element simulation. Four groups of piezoelectric screw pump prototypes with different parameters are made. The simulation results are verified by experiments. The experimental results show that under the driving voltage of 600 V pp, the maximum back pressure of the prototypes is 5.3 kPa, and the maximum flowrate is 71.4 ml min−1.

Simulation on an electro-hydrostatic actuator controlled by a high-pressure piezoelectric pump with a displacement amplifier

PurposeThe purpose of this paper is to provide a new hydrostatic actuator controlled by a piezoelectric piston pump and to reveal its characteristics.Design/methodology/approachIn this paper, a piezoelectric pump with passive poppet valves and hydraulic displacement amplifier is designed as a new control component in a hydrostatic actuator for high actuation capacity. A component-level mathematical model is established to describe the system characteristics. Simulation verification for cases under typical conditions is implemented to evaluate the delivery behavior of the pump and the carrying ability of the actuator.FindingsBy using the displacement amplifier and the passive distributing valves, simulation demonstrates that the pump can deliver flow rate up to 3 L/min, and the actuator controlled by this pump can push an object weighing approximately 50 kg. In addition, it is particularly important to decide a proper amplification ratio of the amplifier in the pump for better actuation performance.Originality/valueThe piezoelectric pump presented in this paper has its potential to light hydrostatic actuator. The model constructed in this paper is valid for characteristic analysis and performance evaluation of this pump and actuators.

Modified IWO algorithm for topological optimum synthesis of the displacement amplifying compliant mechanism

The conventional mechanisms transmitted force and displacement through rigid members (high stiffness) and traditional joints (with high softness), where recently, researchers have come up with new systems called compliant mechanisms that transfer power and mobility through the deformation of their flexible members. One of the most frequently used approaches for designing compliant mechanisms is topology optimization. Extracting the optimal design of a displacement amplifying compliant mechanism using the modified Invasive Weed Optimization (MIWO) method is the current study's main novelty. The studied mechanism is a compliant micro-mechanism that can be used as a micrometric displacement amplifier. The goal of this synthesis is to maximize the output-to-input displacement ratio. In this research, a new random step is added to the Invasive Weed Optimization (IWO) method; the new seeds can be spread farther from their parents, which can be improved the algorithm's abilities. The results show that the use of the modified IWO algorithm for this problem has led to a significant improvement over the results from similar articles.

Adapting ant colony optimization of compliant structures using elements with linearly varying cross-sections

This work addresses the design of miniature compliant displacement amplifiers. The optimum design of the compliant mechanism is generated through topology optimization of two-node frame elements with linearly varying cross sections using the Ant Colony Optimization technique. First, stiffness matrices that account for the change in the cross-section dimensions are formulated. Then, each element is assigned 5 independent ants that represent its design variables defined as the width and thickness of each of the two peripheral cross-sections in addition to the material density. Three case studies with customized cost functions are furnished; the first maximizes the amplification ratio, the second maximizes the output displacement, while the third maximizes both amplification ratio and output displacement simultaneously. The resulting micro-compliant amplifiers are more compact in volume and surpass their constant cross-section counterparts in terms of amplification ratio and output displacement while keeping relatively low internal stresses. The performances of all optimized topologies are verified through ANSYS.

Design and modeling of an improved bridge-type compliant mechanism with its application for hydraulic piezo-valves

Bridge-type compliant mechanisms have been frequently utilized as the micro displacement amplifier for a variety of precision manipulation applications. However, the inertial movement of internal actuators (e.g. piezo-stacks) limits the system’s dynamic bandwidth in some traditional design. This paper presents an improved bridge-type compliant mechanism with double output ports that can generate homodromous bi-motions actuated by only one group of piezo-stacks. The inertial motion of piezo-stacks is avoided and the dynamic bandwidth is enhanced. The two-port dynamic stiffness model is established to straightforwardly capture its kinetostatic and dynamic characteristics from the perspective of input and output ports. The displacement amplification ratio, input stiffness, fundamental frequency and dynamic response spectrum of the improved bridge-type compliant mechanism are curved against key geometric parameters, then the optimal performance can be confirmed. Of particular interest for the mechanism application is applying it to develop a new type of piezoelectric two-stage flow control valve with relatively fast dynamic response and large flow rate. The inner leakage and oil contamination is effectively overcome in contrast to traditional nozzle-flapper servovalves. The presented piezoelectric flow control valve is fabricated and experimentally measured with the step response time of 8.5 ms, frequency bandwidth of 120 Hz, and stroke of ±0.8 mm (corresponding to the flow rate of 180 L/min at the supply pressure of 210 bar).

Artificial neural network base on grey relational analysis estimate displacement of bridge-type amplifier

The power of complaint mechanisms is able for a dramatic reduction in the number of parts required to compass a specified task. It may reduce manufacturing and assembly time and cost. Reduce the number of joints can also increase mechanism precision. The output displacement must be larger than input displacement with lower stress. Thus, Optimize geometry-shape for besting parameter design of the structure was investigated in this paper. The part was designed by Autodesk Inventor and determined displacement amplifier and stress by FEM in ANSYS. We estimate the displacement of a bridge-type amplifier using Artificial Neural Network (ANN) and regression method (RM) base on Grey relational analysis (GRA). The variability of the thickness, the incline angle, the length and the width of the flexure hinges (FH) affects the variability of target displacement (DI) and stress (ST). The influence of the width and the area of the location force is very small and not clear. The result of the simulation is verified by ANOVA and also compared with the predicted value of ANN, GRA, and RM. The displacement of a bridge-type amplifier is reached 0.95 mm with displacement input 0.01 mm. The ratio amplifier is got 95 times.