Displacement Amplification Ratio Research Articles

Design, Analysis and Experiment of a Bridge-Type Piezoelectric Actuator for Infrared Image Stabilization.

Piezoelectric actuators are widely used in the optical field due to their high precision, compact structure, flexible design, and fast response. This paper presents a novel piezoelectric actuator with a bridge-type mechanism, which can be used to stabilize the images of an infrared imaging system. The bridge amplification mechanism is used to amplify the actuation displacement, and its structural parameters are optimized by the response surface method. The control strategy of the image stabilization system is formulated, and the overall structure of the infrared image stabilization system is designed according to the principle of image stabilization and the control strategy. The prototype was fabricated and verified by a series of experiments. In the test, the laminated piezoelectric ceramics are used as the driving element, and its maximum output displacement was about 17 μm under a voltage of 100 V. Firstly, the performance of the piezoelectric amplification mechanism was tested, and the maximum displacement of the piezoelectric micro-motion mechanism was 115 μm. The displacement amplification ratio of the mechanism was 5.7. Then, the step distance and response time of the micro-displacement mechanism were measured by inputting the stepping signal. When the input voltage increased to 3 V, 5 V, and 7 V, the stepping displacements of the mechanism were 2.4 μm, 4.1 μm, and 5.8 μm. Finally, the image stabilization effect of the designed mechanism was verified by imaging timing control and feedback signal processing.

Development and Test of a Two-Dimensional Stacked Terfenol-D Actuator With High Bandwidth and Large Stroke

Smart material actuators (SMAs) can provide motion with high resolution and high bandwidth, but the output stroke is relatively small. Therefore, motion amplification mechanisms for SMAs have drawn considerable attentions in recent years. However, most of existing mechanisms realize the motion amplification at the expense of working bandwidth. To achieve large stroke and high bandwidth simultaneously, a novel two-dimensional stacked magnetostrictive actuator (TSMA) was developed and tested by adopting the magnetostrictive material, i.e., the Terfenol-D in this article. The U-shaped sleeves were employed to support the axial and radial two-dimensional stacking of three Terfenol-D rods. Then, an analytical model was established based on working principle of the TSMA, and a design of experiment analysis was carried out for the sensitivity study of the TSMA's key structural parameters. Next, the involved parameters of the established analytical model were obtained via system identification. Furthermore, several experimental tests of a fabricated prototype for the TSMA were carried out. The results show that the stroke of the proposed TSMA can reach 65 μ m. The displacement amplification ratio is achieved as 2.8 and the working bandwidth is kept as 500 Hz. This proves that the proposed structure can significantly increase the displacement with a little loss of bandwidth. Finally, a set of preliminary closed-loop tests using a traditional incremental proportion-integration-differentiation (PID) control were carried out to improve the motion precision. The closed-loop tracking results of 10-100 Hz sinusoid references show that the root-mean-square errors are less than 4$\%$ using a simple PID control alone.

Analytical model and experimental verification of an elliptical bridge-type compliant displacement amplification mechanism.

In this paper, an analytical model of elliptical bridge-type compliant mechanism is established. Compared with the traditional bridge mechanism, the elliptical bridge-type compliant mechanism has the advantages of light weight, high natural frequency, and more uniform stress distribution. Based on the strain energy and Castigliano's displacement theorem, a static model for calculating the displacement amplification ratio and input stiffness is established. Then, the Lagrange equation is used to establish the dynamic model to calculate the natural frequency. After that, finite element simulation and experimental test are both used to verify the proposed analytical model. The results show that the maximum error between the analytical model and finite element simulation is within 8.25% and that of the experimental results is within 6.25%. The conclusion of this paper provides an accurate prediction analytical method for the mechanical performance index design of the elliptical compliant mechanism, which has important theoretical significance.

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).

Application of Grey Relational Approach and Artificial Neural Network to Optimise Design Parameters of Bridge-Type Compliant Mechanism Flexure Hinge

The investigation proposed a hybrid Grey-artificial neural network to optimise the design parameters of a two degree of freedom (2-DOF) bridge-type compliant mechanism flexure hinge (BTCMFH). The design variables play a vital role in determining the deformation and stress of the mechanism. The investigation is different from the previous studies where the hybrid method is a combination of grey relational analysis and artificial neural network based on finite element method (FEM) in ANSYS to maximise output displacement (DI) and minimise the stress (ST) of the mechanism. The simulation and ANOVA results identified the design variables have significantly affected the output displacement and stress by their contribution. The grey relational analysis and artificial neural network predicted values are in agreement with the simulation results at optimal combination parameters with a deviation error displacement and stress being 0.57% and 2.1%, respectively. The optimal combination parameters with a deviation error of displacement and stress of 0.52% and 2.1%, respectively. The optimal values of DI and ST were obtained as 0.957 mm and 104.74 MPa, respectively. The optimal value of displacement amplification ratio gained is 95.7.

Robust Optimization for Precision Product using Taguchi-RSM and Desirability Function

The Taguchi method (TM) and TM-combined methods [e.g., TM fuzzy method (TM-Fuzzy), TM data envelopment analysis (TM-DEA), TM coupled with grey relational analysis (TM-GRA), etc.] have been proven to be effective to achieve robust design performance. However, the efficient strategy to identify the significant design parameters, and the link between different quality characteristics and design parameters have not been fully studied. To fill the gaps, a combined method, i.e., TM–response surface methodology (RSM)–desirability function (DF), (TM–RSM–DF), was proposed. The significance of the TM–RSM–DF method is able to address the relationship between design parameters and quality characteristics, which facilitated to sort out the most significant design parameters precisely; besides, it also provided a robust strategy to optimize the multiple quality characteristics of the precision product. A design process of a precision amplification (PA) was taken as an example to prove the effectiveness of the TM–RSM–DF. The results showed that the TM–RSM–DF method improved the estimation performance of displacement amplification ratio (DAR) and natural frequency (NF) by 6.148% and 0.537% compared with the initial desired design. Besides, compared with others, the TM–RSM–DF method reduced the stress amount about 16% and had the lowest DAR and NF errors of 2.882% and 1.305%, respectively. Overall, the proposed TM–RSM–DF method outperformed the TM-DEA, TM-GRA, and TM-Fuzzy in the robustness of the PA design.

EAR CANAL INSERTION-TYPE PIEZOELECTRIC BONE CONDUCTION ACTUATOR OF BRIDGE STRUCTURE

Hearing loss in people is increasing because of a rise in the usage of wireless audio multimedia devices. Hearing aids are used as representative hearing rehabilitation devices. Bone conduction hearing aids are recommended for problems in the eardrum and middle ear. Bone conduction is classified according to the driving method into two types, electromagnetic and piezoelectric. Electromagnetic bone conduction causes skin disease and aesthetic problems due to transplantation, high power consumption, and external interference. Piezoelectric bone conduction converts electrical energy into mechanical vibrations, and the characteristics change linearly with size. However, the driving force of ear canal insertion of the piezoelectric body is limited because of the ear canal anatomy. In this paper, a piezoelectric actuator with a bridge structure inserted into the ear canal is proposed. The proposed method is that the displacement amplification ratio was derived using the formula of a bridge-type structure, and the displacement and resonance frequency were derived by finite element analysis (FEA) using different variables. The piezoelectric actuator was fabricated on the basis of FEA simulation results and verified through an artificial mastoid for stimulation in the ear canal. It is expected that the proposed piezoelectric actuator can be used in the various fields for sound and precision control.

Investigation of seismic response of topography under recorded excitation using boundary element method

Irregular topography induces non-uniform excitation in the supports of large structures such as dams and bridges. The present study employs the 3-dimensional boundary element method to achieve the seismic response of Pacoima Dam’s valley and compares the numerical results with the real responses recorded during the 2001 Pacoima earthquake. The horizontal components recorded on the bottom of the valley are used as the input wave for the analysis. The time history of displacements and amplifications of different points are examined. The results revealed that the amplification factor enhanced from bottom to the top of the valley for the most frequencies. The displacement amplification ratio reached approximately 3 along the valley, suggesting the necessity for considering the non-uniform motions effects on huge structures.

A novel piezoelectric linear actuator designed by imitating skateboarding movement

By imitating skateboarding movement, a novel stick–slip piezoelectric linear actuator was proposed in this study. A specific flexure driving foot mechanism (FDFM) was designed to realize the bionic driving function, and theoretical analysis was conducted to calculate the displacement amplification ratio of the FDFM which was further confirmed by finite element simulation. Being different from most of previous design that the slider moved and the driving mechanism was fixed, here the FDFM was integrated with the slider and they moved together along the guide rail. Being similar to that the train moved along the tracks, this kind of layout would facilitate the realization of larger working stroke of the actuator. By experiments, output characteristics of the designed actuator under various driving frequencies and voltages were tested. The results showed that by changing the waveform of driving voltage, both forward and reverse motions with good linearity and stability could be easily achieved. The speed of reverse motion was higher than that of forward motion because of the relatively larger backward motion during forward motion, which was due to the promotion of deformation recovery of the FDFM. Furthermore, the resolution and loading capacity were characterized. The resolutions of forward and reverse motions were 47 nm and 45 nm, respectively, and the actuator could achieve a relatively stable speed when the vertical load was in the range of 0–2 N. This study is expected to provide a new idea for designing piezoelectric actuators with features of high speed, high stability and large working stroke.

Computational parametric analysis and experimental investigations of a compact flexure-based microgripper

This paper presents a flexure-based piezoelectric actuated microgripper for high precision grasping/releasing tasks. The design of the microgripper consists of a three-stage amplification and transmission mechanism, and the parallel grasping technique. A bridge-type mechanism and two sequential lever-type mechanisms are symmetrically connected to amplify the output displacement of the embedded piezoelectric actuator. The parallelogram mechanisms assist in linearizing the output displacement of both jaws of the microgripper. The computational analysis is conducted to investigate the effect of the dimensional parameters on the characteristics of the microgripper. A computational parametric optimization methodology is established to achieve the required attributes of the microgripper. The design optimization resulted in a compact design, a high displacement amplification ratio, and a large output displacement of the microgripper. The experimental studies are conducted to investigate the key characteristics of the microgripper such as the displacement amplification ratio, the output displacement, tracking performance. Further, the parasitic motion, input-end and output-end motion resolution of the microgripper are identified. The experimental results indicate that the compact microgripper can achieve a high displacement amplification ratio and large output displacement with a high positioning accuracy.

Design, analysis and experimental investigations of a high precision flexure-based microgripper for micro/nano manipulation

In this paper, a flexure-based piezoelectric actuated microgripper is presented for high precision micro/nano manipulation tasks. A new design of microgripper based on a three-stage displacement amplification mechanism is utilized to magnify the piezoelectric actuator displacement. A bridge-type mechanism with a two-sided output port is serially connected with two consecutive lever mechanisms. The output motion on both sides is linearized by parallelogram mechanisms. The single-notch and double-notch circular flexural hinges were used in lever, bridge-type and parallelogram configuration. The displacement amplification and transmission mechanisms are arranged symmetrically to obtain stability of shape and compact layout of the entire microgripper. Analytical modeling was performed to establish an input and output displacement relationship. Finite Element Analysis (FEA) method was utilized to evaluate the performance of the microgripper. The design parameters of the microgripper were optimized through FEA method. The simulation results of the FEA method were validated through experimentation on the established design. The experimental results show that the total displacement amplification ratio of the microgripper is 12.76. The microgripper jaws have a high precision positioning accuracy. The microgripper also achieves a high-level working mode frequency of 1044 Hz, which is capable of accommodating rapid transient responses.

Experimental Performance Evaluation of Displacement Amplification Damping Systems Using Cables and Pulleys

The vibration control device such as the damper can be used to reinforce the seismic performance of structures. The damper is activated by the deformation of structures during earthquake; however, the deformation of structures is extremely small, causing difficulty in using the damper. Therefore, there is a need for a method capable of amplifying small deformities and transmitting them to the damper. The purpose of this paper is to develop and evaluate a displacement amplification seismic system using cable-pulley. The appropriate cable was selected through a cable tensile performance test and the results of the frame experiment were compared with theoretical displacement amplification ratio values. As a result, it may be said that the proposed system using cable-pulley is useful for displacement amplification.

Characterization of a compact piezoelectric actuated microgripper based on double-stair bridge-type mechanism

This paper presents a compact flexure-based microgripper for grasping/releasing tasks. The microgripper is based on a double-stair bridge-type mechanism and consists of a bridge-type mechanism for amplifying the input displacement and the integrated parallelogram mechanisms for linearizing the motion at the microgripper jaws. The displacement transmission, amplification, linearization are accomplished in a single-stage. Stiffness modeling is established to characterize the output displacement, the displacement amplification ratio, and the input stiffness of the mechanism. The right-angle flexure hinges are utilized in the displacement amplification and transmission mechanisms to maintain the input stiffness of the mechanism. The structural design of the microgripper is optimized in such a way that a large output displacement can be achieved. Finite element analysis and experiments are conducted on the microgripper to verify the results of the analytical modeling. The proposed microgripper achieves a large output displacement of 543.8 μm with a displacement amplification ratio of 19.3. The experimental results indicate that the microgripper will be able to accommodate a grasping/releasing task.

Design and development of compliant mechanisms for electromagnetic force balance sensor

Compared with the lever-type amplifier, the rhombus-type amplifier has attracted more attention by virtue of large displacement amplification ratio, compact structure, and linear output displacement. In this paper, a novel electromagnetic force balance sensor (EFBS) based on the rhombus-type amplifier is presented to measure the mass with high precision. First, the structure and operating principle of the EFBS are described, and the requirements for the design and manufacture of the amplifier are put forward. Then, the analytical models of the two-stage rhombus-type amplifier are given out, and two guiding mechanisms are analyzed and modeled. Furthermore, the validity of the established model is verified by finite element analysis (FEA). Thanks to the theoretical guidance, an electromagnetic force balance sensor based on the two-stage rhombus-type amplifier and double parallelogram flexure mechanism is designed and tested. The experimental results demonstrate that the developed EFBS can measure the mass of the objects with high precision, and also verifies the correctness of the analytical model. This provides a new concept for the structural design of the EFBS.

Engineering a Compliant Mechanical Amplifier for MEMS Sensor Applications

In this paper, we introduce a compliant mechanical amplifier (mechAMP) suitable for the sensitivity enhancement in MEMS sensor applications. The design, fabrication and characterization of a planar compliant amplifier mechanism is presented with special focus on the kinematic and static system modelling of the displacement and force amplification. We show that the proposed system can also be applied as mechanical stiffness transformer for the adaption of mechanical signals or as mechanical transformer for MEMS actuators. Based on a kinematic model, a compact mechanism with a system size of 930 $\mu \text{m}\,\,\times2080\,\,\mu \text{m}$ and a displacement amplification ratio of 200 with an output displacement in a range of 100 $\mu \text{m}$ was designed. The fabrication of the system was carried out using silicon-on-insulator (SOI) technology. Experimentally, we could verify an amplification ratio of 197.9 for the designed and fabricated system which corresponds to the analytic model by a deviation of about 1%. [2019-0228]

Design, analysis, and experimental investigation of a single-stage and low parasitic motion piezoelectric actuated microgripper

The demand for high precision micro/nano manipulation is increasing for advanced manufacturing technology. The precise motion of the microgripper jaw is required to achieve high performance micromanipulation tasks. The parasitic motion of the microgripper reduces placement accuracy during pick and place tasks. This paper presents an asymmetric design of piezoelectric actuated microgripper. It investigates key characteristics including parasitic motion, output displacement, and displacement amplification ratio. The microgripper is designed with a single-stage displacement amplification mechanism to form a compact layout. The design of the microgripper integrates the bridge-type mechanism and the parallelogram mechanisms. The bridge-type mechanism amplifies the piezoelectric actuator output and the parallelogram mechanisms offer linear motion of the gripper jaw. The analytical modeling and finite element analysis were conducted to evaluate the characteristics of the microgripper. The design parameters of the microgripper were optimized through several finite element analysis. Further, experimental studies were conducted to verify the characteristics of the microgripper. The parasitic motion of the jaw was obtained as less than 0.18% of the microgripper jaw motion in the x-direction. The mechanism of the microgripper also achieves a high positioning accuracy. Further, a high displacement amplification ratio and large output displacement can be achieved.

Design of a Compliant Mechanism Based Four-Stage Amplification Piezoelectric-Driven Asymmetric Microgripper.

The existing symmetrical microgrippers have larger output displacements compared with the asymmetrical counterparts. However, the two jaws of a symmetrical microgripper are less unlikely to offer the same forces on the two sides of a grasped micro-object due to the manufacture and assembly errors. Therefore, this paper proposes a new asymmetric microgripper to obtain stable output force of the gripper. Compared with symmetrical microgrippers, asymmetrical microgrippers usually have smaller output displacements. In order to increase the output displacement, a compliant mechanism with four stage amplification is employed to design the asymmetric microgripper. Consequently, the proposed asymmetrical microgripper possesses the advantages of both the stable output force of the gripper and large displacement amplification. To begin with, the mechanical model of the microgripper is established in this paper. The relationship between the driving force and the output displacement of the microgripper is then derived, followed by the static characteristics’ analysis of the microgripper. Furthermore, finite element analysis (FEA) of the microgripper is also performed, and the mechanical structure of the microgripper is optimized based on the FEA simulations. Lastly, experimental tests are carried out, with a 5.28% difference from the FEA results and an 8.8% difference from the theoretical results. The results from theoretical calculation, FEA simulations, and experimental tests verify that the displacement amplification ratio and the maximum gripping displacement of the microgripper are up to 31.6 and 632 μm, respectively.

A novel amplification ratio model of a decoupled XY precision positioning stage combined with elastic beam theory and Castigliano's second theorem considering the exact loading force

Abstract A novel mathematical model which can precisely calculate the amplification ratio of a bridge-type amplification mechanism has been proposed. The elastic beam theory and the Castigliano’s second theorem were utilized to establish the mathematical model with consideration of the deformation of input beams, output beam, connecting beams and flexure hinges. The proposed model was compared with existing theoretical models and finite element model (FEM), and the results validated that the proposed model featured a better performances and was the most proximal model to the FEM analysis. With the interval of the adjacent flexible hinges changed, the error at the peak of amplification ratio with the FEM was limited to 6.76%, which was lower than most of the typical existing models. To further verify the effectiveness and expansibility of the proposed method, a decoupled XY precision positioning stage was investigated. Considering the influence of the loading force exerted on amplification mechanism, the displacement amplification ratio model of the positioning stage was established, and the results were further proved through the finite element simulation. The experimental results presented that the amplification ratios for X-direction and Y-direction motions are 5.83 and 5.71, the measured workspace of the stage is 174.9 μm × 171.3 μm, and the cross-coupling error was evaluated to less than 3%.

Empirical compliance equations for conventional single-axis flexure hinges

In consideration of the stress concentration, unified compliance equations for conventional single-axis hinges are presented. The relationship between the stress concentration and the compliance of corner-filleted flexure hinges is first analyzed. Considering the stress concentration, coupled with a wide range of geometrical parameters, empirical compliance equations for conventional flexure hinges, are then obtained by using the exponential model. Subsequently, the proposed equations are unified. To verify the validity and accuracy of these equations, the characteristics of a bridge-type flexure-based mechanism are then analyzed by the proposed equations and finite element analysis, respectively. The results of compliances and displacement amplification ratios obtained by these two methods are in good agreement. It demonstrates that the empirical compliance equations could be obtained by exponential model, and these equations can be unified.

Nonlinear characteristics of compliant bridge-type displacement amplification mechanisms

Compliant bridge-type mechanisms have been extensively utilized as displacement amplifiers, but most of the existing mathematical models were developed based on linear assumptions, incapable of revealing nonlinear characteristics. In this paper, an arm is regarded as a variable thickness beam that covers both lumped and distributed configurations, and thus a nonlinear closed-form model of compliant bridge-type mechanisms is developed through considering load effect. Then, application limitations, displacement amplification ratio, input compliance, and influence of actuator are discussed to quantitatively evaluate the influences of design parameters and capture the nonlinear characteristics of compliant bridge-type mechanisms. Finally, the analytical model is verified by finite element analysis (FEA) and experiments, and the results show that the proposed model can accurately predict the deformation of compliant bridge-type mechanisms.