Displacement Amplification Mechanism Research Articles

Design and experiment of a large displacement linear piezoelectric actuator

To increase the output displacement of the linear piezoelectric actuator, a linear piezoelectric actuator with large displacement and three operation modes is proposed. The operating principle of the piezoelectric actuator is presented. The magnification factor of the displacement amplification mechanism is deduced and verified by finite element analysis. To improve the output precision of the actuator, a feedforward PID control model is established. Based on the experimental test platform, the output characteristics of the piezoelectric actuator are tested. Results show the maximum output displacement of the piezoelectric actuator is 558.3 μm under a driving voltage of 150 V with two piezoelectric stacks. When the driving frequencies are less than 3 Hz, the control accuracy of feedforward PID is higher than that of PID, and the error between the measured displacement and the ideal value is less than 10% after applying the control to the piezoelectric actuator.

Shaking table test and seismic behaviour evaluation of viscous damping wall with amplification mechanism

Methods to improve the damping efficiency of dampers have been widely investigated. This study introduces a shaking table test on a viscous damping wall (VDW) with a displacement amplification mechanism. A mechanical model was developed and validated using a model test. Then, shaking table tests were conducted on five-story steel frames equipped with an VDW and a viscous damping wall with amplification mechanism (AVDW). The AVDW was confirmed to be effective in mitigating the structural acceleration, inter-story displacement, and shear forces. Finally, a numerical simulation of a seven-story structure was performed to characterise the seismic behaviour of the AVDW system. By comparing the structural responses and performance state, the efficiency of the AVDW in mitigating the structural responses and improving seismic safety was confirmed.

Biomorphic Actuation Driven Via On‐Chip Buckling of Photoresponsive Hydrogel Films

AbstractRemotely controllable photoresponsive hydrogel actuators are promising for applications in multiple fields. However, simple deformation mechanisms, which rely on the general swelling/deswelling, limit their performance and application. Herein, we report a displacement amplification mechanism based on the buckling deformation of photoresponsive hydrogel film. The on‐chip buckled architecture of the hydrogel enables actuation between a flat 2D shape and tubular 3D buckled shape with remarkable performances, including high deformation ratio (height ratio: ≈360%), tunable cycle motion frequency (0.1—1 Hz) and high cyclic stability. Moreover, localized buckling deformation, such as tube opening and closing, can be controlled in response to photostimulation. Inspired by these biomorphic shapes and motions, an intestine‐mimetic device and demonstrate segmentation with substance crushing and peristalsis motion with substance propelling were further fabricated. This study will provide a useful design principle for hydrogel actuators and shed light on diverse applications in soft robotics, dynamic microfluidics and organs‐on‐chips.

MAXIMUM SEISMIC RESPONSE PREDICTION BASED ON CAPACITY SPECTRUM METHOD FOR VIBRATION-CONTROLLED CEILING STRUCTURE EMPLOYED PULLEY MECHANISM

This paper proposes a new procedure for predicting the maximum seismic response based on the capacity spectrum method (CSM) for the passively controlled suspended ceiling structures named “Pulley Damper Ceiling System (PDCS)”. The structural system has a supplemental nonlinear viscous damper and a bilinear hysteretic damper in parallel with displacement amplification mechanisms of block and tackle pulley system. The single degree-of-freedom model of the PDCS is initially discussed. The accuracy of a simplified calculation method for obtaining the structural equivalent damping coefficient, determined by the sum of the inherent damping and the square root of sum of squares (SRSS) of each damping provided by the nonlinear viscous damper and the bilinear hysteretic damper, is verified by comparing with the full-scale shake table test results of the PDCS. Then, the pseudo capacity curve of the structure is generated by continuously plotting the transition of maximum force and displacement values under different amplitudes of sinusoidal waves. Finally, the availability of the response prediction based on proposed CSM procedure considering floor response spectrum (FRS) is examined by the comparison of time history analysis results, and the sufficient accuracy to evaluate the seismic response is confirmed.

An Improved Dynamic Model and Matrix Displacement Model for Distributed-Compliance Bridge-Type Amplification Mechanism

This paper establishes a matrix displacement model and an improved dynamic model for the static and dynamic performances analysis for a kind of bridge-type displacement amplification mechanism with distributed-compliance, which has better performances than traditional lumped-compliance bridge-type mechanisms. In the matrix displacement model, the stiffness matrix for two rigid bodies connected by flexures is first obtained by regarding the displacements and the forces on two mass centers of the rigid bodies as the node displacements and node forces. By extending and superimposing each elemental stiffness matrix, the global stiffness matrix for the flexure mechanism can be obtained to calculate the displacement amplification ratio and input stiffness of the bridge-type mechanism. In the improved dynamic model, in order to establish the Lagrangian dynamic model more accurately, the deflectional, axial, and rotational velocities of any point on the beam flexure are calculated by solving the derivatives of the deformation curves of beam flexures versus time to obtain the expression of the kinetic energy in the vibrating beams. On this basis, the three-degree-of-freedom vibration differential equation for the bridge-type mechanism is established by using the Lagrange method, and the natural frequency in the working direction is obtained accurately. The presented models are compared with the finite element analysis, and experiments for two case studies of the bridge-type distributed-compliance mechanism are presented. The comparisons results demonstrate the high prediction accuracy of the improved dynamic model.

A Structure Load Performance Integrated Model Method for the Bridge-Type Displacement Amplification Mechanism

The modeling of compliant bridge-type displacement amplification mechanisms has challenges due to the intrinsic coupling of kinematic and mechanical behaviors. A structure load performance integrated model method for the bridge-type displacement amplification mechanism is presented. The established modeling based on Castigliano’s second theorem considers the deformations of all members, the effect of external load and the nonlinear shear effect. Compared to the finite element model (FEM) and existing models, the established modeling precisely predicts significant nonlinearity of the displacement amplification ratio (DAR) with the driving force, strong sensitivity of DAR to the external load and corresponding relationships of structural parameters with DAR, which is the closest to the FEM result over existing models. The variance-based sensitivities of structural parameters to DAR are thoroughly analyzed, indicating that sensitive structure parameters need to be focused on. Modeling applications further prove the reliability and expandability of the proposed model method. The proposed model method can provide support for the design, optimization and control of compliant systems with bridge-type displacement amplification mechanisms.

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.

Parameter optimization of magnetostrictive bistable vibration harvester with displacement amplifier

The vibration harvester can transform the ambient vibration energy into electrical energy for the use of microelectronic equipment. Currently, the introduction of bistable structure in magnetostrictive harvester makes the system have two equilibrium states, thus the output capacity of the system is improved. In order to further improve the working ability and its ability to harvest vibration of magnetostrictive bistable harvester with displacement amplification mechanism, the identification of the key parameters of the magnetostrictive bistable vibration harvester's mathematical model are first proposed in the paper. The accurate values of system damping, electromechanical coupling factor, piezomagnetic coefficient and permeability are obtained. On this basis, bistable structure and displacement amplification mechanism in the harvester are optimized, including the repulsive permanent magnets distance in the bistable structure, mass ratio and stiffness ratio between the bistable structure and the displacement amplification mechanism. Finally, the working ability of the optimized prototype is tested through experiments. The results show that the output voltage and electrical power of the optimized prototype are increased by 2∼4 times and 4∼15 times compared with the unoptimized prototype. Under the excitation amplitude of 7.84 m/s2, the voltage of the optimized prototype reaches 2.96 V, and the electrical power reaches146.032 mW.

Design of compliant mechanisms: An explicit topology optimization method using end-constrained spline curves with variable width

In this study, an approach using moving end-constrained spline (ECS) curves with variable widths is presented for the explicit topology optimization of compliant mechanisms. The proposed approach uses a series of spline curves to represent the topology of the compliant mechanism. Instead of using a fixed width, we let the width of such spline curves vary along the curve. The optimized design is obtained by optimizing the width of the spline curves and the position of the control points. To avoid infeasible solutions in the design process, the end points of several specific spline curves are constrained according to the design region. The validity of the proposed method is demonstrated using different types of splines, such as the Bézier curve and B-spline curve, for the design of a force inverter, a compliant gripper and a compliant orthogonal displacement amplification mechanism.

Design and Analysis of a 2-D Piezoelectric Platform Based on Three-Stage Amplification and L-Shaped Guiding

In piezoelectric micro-positioning platforms, the displacement amplification mechanism can solve the small output displacement of the platform; the displacement coupling will also increase when the displacement is amplified. To solve the problem of multistage displacement amplification and displacement coupling after multistage displacement amplification, this study proposes a two-dimensional piezoelectric platform based on three-stage amplification and L-shaped guiding. First, the structure of the two-dimensional piezoelectric platform is designed and its working principle is described. Next, the two-dimensional piezoelectric platform is analyzed theoretically, and the static and dynamic characteristics of the structure are analyzed by the finite element method. Finally, a prototype of the two-dimensional piezoelectric platform is fabricated, and the theoretical and simulation results are analyzed experimentally. The experimental results reveal that the platform has a motion range of 31.8 μm × 41 μm. The multistage displacement amplification ratio is 21.8, and the displacement coupling error is less than 4.2%. The positioning error of the closed-loop control platform is less than 0.5%, and the trajectory tracking error is less than 1.6%. Compared with the traditional piezoelectric micro-positioning platform, the three-stage amplification and L-shaped guiding mechanism can effectively improve the displacement magnification and decoupling performance of the piezoelectric micro-positioning platform as well as the positioning ability and trajectory tracking ability of the platform under closed-loop control, which is expected to be utilized in fields such as multi-stage amplification micro-positioning platforms and dynamic optical systems.

An Optimized Design of New XYθ Mobile Positioning Microrobotic Platform for Polishing Robot Application Using Artificial Neural Network and Teaching‐Learning Based Optimization

Compliant mechanisms with flexure hinges have been widely applied for positioners, bioengineering, and aerospace. In this study, a new optimized design method for the mobile microrobotic platform was developed for the polishing robot system. A metaheuristic‐based machine learning technique in combination with finite element analysis (FEA) was developed. The designed platform allows three degrees of freedom with two x‐and‐y translations and one z‐axis rotation. A new hybrid displacement amplification mechanism was also developed using Scott‐Russell and two‐lever mechanisms to magnify the workspace of the platform. The leaf hinges were employed due to their large rotation, and the right circular hinges were adopted because of their high accuracy. In modeling the behaviors of the developed platform, the artificial neural network is formulated in combination with the teaching‐learning‐based optimization (TLBO) method. The ANN architecture was optimized through TLBO to a better approximation. And then, three optimized case studies were conducted by the TLBO. The data is collected through FEA simulation. The modeling results from the TLBO‐based ANN were well established with excellent metrics of R, R2, and MSE. The optimized results found that the proposed MPM platform achieves a max‐y stroke of 1568.1 μm, max‐x stroke of 735.55 μm, and max‐θ rotation angle of 2.26 degrees. The proposed MPM platform can operate at a high displacement amplification ratio of over 9.

Design, Analysis and Experimental Test of the Bridge-type Displacement Amplification Mechanism Based on the Topology Optimization of Flexure Hinge

Design, Analysis and Experimental Test of the Bridge-type Displacement Amplification Mechanism Based on the Topology Optimization of Flexure Hinge

Metadamping enhancement and tunability via scissor-like electromechanical metamaterials

We report on a novel scissor-like electromechanical metamaterial (SEMM) with enhanced and tunable damping properties, stemming from its electromechanical resonant effects. The displacement amplification mechanism of the scissor-like structure in SEMM is exploited to amplify the damping ratio for stronger vibration mitigation through the enhanced electrical dissipation of the amplified voltage of the piezoelectric element. The relative dissipation performance, termed as metadamping, is quantified based on complex band structures, which allow frequencies to be complex valued. Using different shunting circuits, the overall damping performance of SEMM is demonstrated to be higher than a statically equivalent traditional systems, such as acoustic metamaterials and monatomic lattices. The dissipation performance of SEMM is numerically verified via finite structure analysis and found to be in an excellent agreement with Bloch’s wave analysis. Furthermore, the electromechanical nature of the piezoelectric material in SEMM provides a convenient way to tune the metadamping by adjusting the piezoelectric shunting circuit.

Design of Fast Steering Mirror Based on Displacement Amplification Mechanism

Design of Fast Steering Mirror Based on Displacement Amplification Mechanism

Experimental investigation on displacement amplification mechanism of steel wire rope-pulley damping systems with viscous damper

In this study, a new displacement amplification damping system was proposed for maximizing the performance of a damping device, even in a stiff structural system. The proposed damping system comprises steel wire ropes, pulleys, and a viscous damper; the damper displacement is amplified on the basis of the working principle of a block and tackle system. Full-scale experiments were conducted to investigate the operating mechanism of the proposed damping system and evaluate its performance. The test results demonstrated that, when compared to the amplification efficiency of the theoretically expected value, that of the proposed system was reduced by 10–25% owing to elastic deformation of the steel wire ropes and a lag in pulley operation due to friction between the pulleys and pins. However, the magnification factors (ratio of damper displacement to interstory drift of frame) measured during the pulley operation were almost equal to the theoretical values; a maximum value of 5.77 was confirmed. Despite the lag in the pulley operation, the maximum operating velocity of the damper rod was almost the same as the theoretically predicted value. A velocity-dependent damping device was used in the experiments; thereby, the damper force corresponding to the maximum velocity was developed and amplified by the theoretical magnification factor. Ultimately, this contributed to the lateral force resistance of the frame for the proposed system.

Nonlinear analysis, optimization, and testing of the bridge-type compliant displacement amplification mechanism with a single input force for microgrippers

For piezoelectric-driven compliant microgrippers, realizing flexible, stable, and accurate manipulation simultaneously is a key challenge. The bridge-type compliant displacement amplification mechanism (CDAM) with a single input force can enable stable parallel grasping and enlarge the grasping stroke by matching the output performance of typical piezoelectric actuators used in microgrippers. In this study, a nonlinear analysis of the bridge-type CDAM with a single input force was conducted to improve the prediction accuracy of the output displacement, and nonlinear optimization and testing were performed. For the expected and parasitic output displacements, a two-step nonlinear modelling method was proposed to conduct the nonlinear analysis. Using Castigliano's second theorem, small deflection-based finite element analysis (FEA), and numerical fitting, small deflection-based modelling considering the shearing effect was first performed. Then, the correction coefficients for the geometrical nonlinearity were modelled by combining geometrical nonlinear FEA and numerical fitting. By restricting the parasitic output displacement, a nonlinear constraint was derived. Thereafter, geometric parameter optimization and structural optimization of the bridge-type CDAM with a single input force was performed. Model analysis indicates that for the optimal CDAM, the expected output displacement increases with the input force, whereas a negative correlation exists between the growth rate and the input force. Finally, simulations and experimental tests were conducted to verify the effectiveness of the nonlinear models, optimization, and model analysis.

Design of a rhombus-type stick-slip actuator with two driving modes for micropositioning

This paper proposes a novel liner stick–slip actuator with compact structure which can achieve forward and backward motion. A novel rhombus-type displacement amplification mechanism (RTDAM) with symmetric structure is used to generate lateral motion to improve the actuator performance. Theoretical analysis and finite element analysis (FEA) are carried out to calculate the coupling ratio and natural frequency of the system. In addition, a new driving method in which two driving feet act together is proposed, which can improve the load capacity of the actuator. A prototype is fabricated and experimental tests are conducted to investigate its performance. The results indicate that the maximum speed of forward and backward motion are 428.5 μm/s and 443.2 μm/s, respectively. Compared with the single foot driving method, the load capacity of the actuator is increased from 1.2 N to 1.6 N by adopting the new driving method. Finally, a micropositioning stage is built utilizing the proposed stick–slip actuator and the experimental results indicate that the stage can work stably.

AN OPTIMUM FIRST MODAL SHAPE FREQUENCY FOR FLEXIBLE DISPLACEMENT AMPLIFIER MECHANISMS

This investigation analyzed the influence of design variables of a new flexible hinge displacement amplification mechanism such as variable L, y, t, x on the first modal shape frequency of thismechanism. The Taguchi method is based on finite element analysis in ANSYS to optimize the first modal shape frequency of this mechanism. The FEA outcomes indicated that design variables have significantly affected the first modal shape frequency of this mechanism. And the problem was verified by analysis of variance, analysis of the signal to noise, and regression analysis of frequency. The optimal outcomes of frequency obtained 85.268 Hz. While the predicted outcomes of the frequency of the regression equation and the Taguchi method achieved 82.213 Hz and 82.459 Hz, these results are good agreement with error deviation percent of 3.47% and 3.29%, respectively.

Design and characteristic analysis of magnetostrictive bistable vibration harvester with displacement amplification mechanism

The working frequency of a traditional cantilever magnetostrictive vibration harvester is often higher than ambient vibration frequency. In order to make it better applied to the actual ambient vibration and improving its harvesting capacity, a bistable Fe-Ga alloy vibration harvester with displacement amplification mechanism is systematically studied in this paper. On the one hand, a bistable structure is designed based on its two unique restoring force potential wells. On the other hand, a displacement amplification mechanism is added. Utilizing magnetic dipole model theory, harmonic balance theory, etc., a nonlinear lumped-parameter coupled model of the entire system is established. Moreover, the output characteristics of the system are simulated and experimentally tested. Simulation results show that when the distance of repulsive permanent magnets is 8 mm, bistable phenomenon is the most obvious. When the stiffness ratio is 1.852, the entire system has better output characteristics. Experimental results show that when excitation level is 6.272 m/s2, the first-order resonance frequency is reduced from 60 Hz to 22 Hz, and the peak voltage is increased from 51 mV to 510 mV. In addition, two lower second-order and third-order resonance frequencies appear, which are respectively 28 Hz and 34 Hz. Currently, the voltages are also larger, reaching 590 mV and 550 mV. It is concluded that the bistable vibration harvesting system with displacement amplification mechanism can work well in the low and wide frequency region and greatly increase the voltage. Compared with a traditional cantilever magnetostrictive vibration harvester, it has better dynamic response.

Development of a low-voltage driven non-resonant three-DOF eyeball-like piezoelectric actuator

In this work, a low-voltage driven non-resonant three degree-of-freedom (DOF) eyeball-like piezoelectric actuator is proposed. Elliptical motions on the driving feet are formed from the pushing and pulling actions of the flexible displacement amplification (FDA) mechanism in the piezoelectric actuator. There are three types of elliptical movements to drive the spherical rotor around three coordinate axes while driving the different groups of piezoelectric stacks. The principles of the three-DOF rotations are analysed by theoretical and simulation methods. Fabrication of a miniature piezoelectric prototype of 34mm × 34mm × 34mm is conducted. Under a driving voltage of 40 the maximum rotary velocities of the rotor around X, Y and Z axes reach to 62.5 r min−1, 65 r min−1 and 46 r min−1 at 1.5 kHz. High resolutions around X and Y axes up to 2.5 and 5 are obtained. The remarkable comprehensive performances enable much potential applications of this three-DOF eyeball-like piezoelectric actuator in precision pointing, attitude adjustment and bionic eye positioning systems.