Displacement Amplification Mechanism Research Articles

Seismic vulnerability analysis of a high‐rise steel frame structure equipped with novel displacement‐amplified viscoelastic dampers

SummaryThe energy dissipation capacity of conventional viscoelastic dampers (VEDs) cannot be fully exerted due to the relatively small inter‐story displacement of building structures. Thus, a novel VED with a displacement amplification mechanism based on the lever principle is developed in this study to achieve small displacement but high energy dissipation ability. First, the structural layout of an amplified viscoelastic damper (AVED) system is briefly introduced, and then the displacement amplification effect is described in detail. According to the working principle of the AVED and the relationship of force and geometric displacement in an actual frame structure, the restoring force theoretical formula of the corresponding amplified damper is derived. Based on the restoring force of the AVED and in combination with the secondary development function of the ABAQUS unit, a VUEL subroutine suitable for the explicit algorithm is programmed with the FORTRAN language. Then, the correctness of the subroutine is verified through a comparative analysis of the ABAQUS simulation and theoretically calculated results. Consequently, the vulnerability analysis of a high‐rise steel frame structure is conducted by using the incremental dynamic analysis (IDA) method, and the influence of the AVED on the seismic performance of the steel frame structure is quantitatively analyzed from the perspective of probability statistics. The analysis results show that compared with the VED structure, the failure probability of the AVED‐2 and AVED‐3 structures reaching the ultimate failure state at all levels is reduced by approximately 43% and 57%, respectively, and the collapse margin ratio (CMR) of structures under large earthquakes is increased by approximately 35% and 68%, respectively. This indicates that the AVED structures with displacement‐amplified dampers have a better effect on the seismic stability of tall steel frame structures under random seismic excitations. This study aims to provide comprehensive information for the seismic‐resistant design of tall buildings in earthquake‐prone regions.

Design and analysis of novel microelectromechanical system based microgripper for manipulating microbiological species and micro objects

Design and analysis of a pair of novel microelectromechanical system (MEMS) microgrippers having single and multiple sets of jaws respectively, incorporated with displacement amplification mechanism and electrostatic force sensor is presented in this research work. The novelty of the proposed microgrippers is their unique and efficient designs, having the versatility of gripping ranges. The size of the microgripper is 3.2 × 3.7 mm2 in both cases and has one and three sets of jaws with gripping ranges of 30–64 µm, 175–200 µm, and 350–380 µm respectively. The three jaw sets are application-specific to the multicellular small organism, eukaryotic cells, and microcells, respectively. The microgrippers are being actuated by an optimized V-shaped thermal chevron actuator whose input is amplified by using a pantograph displacement amplification mechanism with an amplification factor of 54. The force applied to the gripping object is sensed by a rotary comb electrostatic force sensor. Special attention has been paid to the structural design, and detailed stress analysis has been discussed. This research work includes static, electrostatic, parametric, and electrothermal analysis carried out using Finite Element Method (FEM) techniques and analytical modeling. The results show that the operating voltage range of the devices is from 4 to 9.25 V, having a maximum operational temperature of 380 °C with a factor of safety of 1.026. The maximum capacitance change with the full operational range of microgrippers is 0.63 µf, having a capacitive sensitivity of 19.6 nf/µm. The microgrippers can be used as an instrument to grip not only the microbiological species but also can be beneficial to carry out manipulations at the micro-level like micro-assembly. The proposed microgripper has a substantial structural stability, has a high amplification factor and accommodates manipulation of a wide range of microorganism.

Development, modeling and analysis of a differential lever-bridge amplification mechanism

The displacement amplification mechanism is commonly utilized in micro/nano-manipulating systems to enhance the output stroke of piezoelectric actuators. Aiming at large amplification ratio, this paper proposes a symmetrical dual-stage amplification mechanism consisting of a differential lever mechanism and a half-bridge mechanism. With consideration of the coupling effect between the dual-stage amplification mechanism, a kinematic modeling method is developed for the symmetrical differential lever-bridge hybrid (SDLBH) mechanism on top of the static balance and constraint conditions of the branch chain. In particular, the force-deformation relationship of the flexible hinge is derived according to the flexibility matrix method. Based on the path constraint conditions of the branch chain, the static equilibrium equation as well as the displacement constraint conditions are obtained. Consequently, the input-output model of the SDLBH mechanism is established, which is capable of accurately predicting the amplification ratio and the mechanical stiffness. Finite element simulations and real time experiments on the SDLBH prototype effectively validate the mechanical performance as well as the accuracy of proposed modeling method. The performance sensitivity of the developed SDLBH mechanism is further analyzed by the Taguchi method, aiming to offer the optimization guideline for real applications.

Design and Control of a Flexure-Based Dual Stage Piezoelectric Micropositioner

AbstractIn the field of advanced manufacturing technology, there is a growing need for high-precision micro/nano positioners. The traditional single stage actuated positioners have encountered performance limitation in achieving longer travel range and higher precision. This motivates us to develop a novel dual stage piezoelectric-actuated micropositioner presented in this paper. The micropositioner incorporates displacement amplification mechanisms to overcome the limited range of piezoelectric actuators. Design considerations such as flexure characteristics and material selection are discussed, and structural analysis is performed using finite element analysis (FEA). For precise positioning, the dual stage control strategy is investigated and compared with the conventional proportional-integral-derivative (PID) single stage control method. In the proposed positioner, a combination of parallelogram and bridge mechanisms is utilized. The bridge mechanism works to amplify the piezoelectric actuator displacement output. The parallelogram mechanism, integrated within the system, helps mitigate resonance modes and contributes to the achievement of linearized motion. The characteristics of the micropositioner were evaluated using analytical modelling and FEA. Multiple analysis was used to optimise the positioner’s design parameters. Furthermore, experimental studies were carried out to validate the characteristics of the micropositioner performance in terms of achievable output travel range and sustained positioning accuracy.

Displacement amplification mechanism in passive capacitive bolt axial force sensors to suppress manufacturing variations

Abstract We present a method of minimizing manufacturing variations in passive capacitive sensors for noncontact bolt inspection using a displacement amplification mechanism. This inspection mechanism uses electromagnetic coupling to eliminate the need for contact, making it particularly suitable for inspections using unmanned aerial vehicles. Analysis by the finite element method and prototype testing verified the capability of the mechanism to amplify displacement changes due to axial force. The prototype exhibited an 80% increase in displacement relative to the bolt head, effectively halving variation effects. Despite the design challenges, the mechanism significantly improved the effectiveness of the sensor.

Development of two types of in-plane motion actuators with modular design and application to morphing wings

This study explored the design, performance evaluation, and application of two types of in-plane motion actuators that were scalable to larger sizes—that is, the extension-type electrothermal actuator (ExACT) and retraction-type electrothermal actuator (ReACT). These actuators were based on the displacement amplification mechanism (DAM) principles and regularly arranged structures in mechanical metamaterials. A modular design approach allowed these actuators to be easily configured to the desired size and scaled to create large-scale in-plane motion actuators. Studies were conducted to assess the performance of the ExACT and ReACT, focusing on the actuator displacement and blocking force. The actuation displacements for the 3 × 1 ExACT and ReACT matrices were measured at 2.0 and 0.8 mm, respectively. Similarly, the blocking forces achieved by the actuator matrices were 2.24 and 3.78 N for the ExACT and ReACT, respectively. Subsequently, the ExACT and ReACT were applied to implement large deformable morphing wings, referred to as the ExMOW and ReMOW, respectively. These wings incorporated an additional thickness amplification mechanism resembling an elliptical bridge-type DAM. The wing thickness of the ExMOW increased by approximately one-third of its initial value, whereas that of the ReMOW decreased to approximately one-quarter of its original thickness.

A novel bridge-type compliant displacement amplification mechanism under compound loads based on the topology optimisation of flexure hinge and its application in micro-force sensing

The design and modelling of bridge-type compliant displacement amplification mechanisms (CDAMs) are key components in precision engineering. In this study, a bridge-type CDAM under compound loads with an optimum flexure hinge configuration is designed, analysed, and tested. For the case when the flexure hinge configuration is unknown, the internal force distribution for a bridge-type CDAM under compound loads is analysed, and the topology of the flexure hinge is optimised. By applying different volume constraints, the optimised flexure hinge configurations are all V-shaped. Subsequently, a static model of the V-shaped flexure hinge is established. For a bridge-type CDAM with V-shaped flexure hinges, the compliance matrix of the flexure hinge is combined with the relationship among the local compliance matrices in a serial mechanism; consequently, the analytical relationship between the output displacement, output force, and input force is derived. The CDAM is parametrically optimised to further improve the output performance. Simulations and experiments verify the topology optimisation result, static model, and parametric optimisation result. Finally, the CDAM and its static model are applied to the tensile manipulation and micro-force sensing in a microfiber tensile test.

A creative wide-frequency and large-amplitude vibration isolator design method based on magnetic negative stiffness and displacement amplification mechanism

Negative stiffness vibration isolation devices have attracted significant attention and research interest for their ability to enhance the low-frequency vibration isolation performance of passive vibration isolators. However, their narrow linear negative stiffness region has hindered their broader application. To address this limitation, a novel design method for vibration isolators is proposed, integrating the permanent magnetic negative stiffness device (NSD) with the displacement amplification mechanism (DAM). The paper begins by presenting a specific vibration isolator design method and analyzing the kinematic relationship. Next, a single-degree-of-freedom (SDOF) nonlinear equivalent model of the vibration isolator is established using the pseudo-rigid-body model (PRBM) approach. Numerical simulations are then conducted to obtain the transmissibility of the isolator. Furthermore, two isolators—one with the displacement amplification effect and another without—are manufactured, and experimental investigations are carried out. The experimental results confirm that the incorporation of the displacement amplification mechanism effectively expands the linear negative stiffness region of the negative stiffness magnet pair, enabling wide-frequency and large-amplitude vibration isolation. Notably, these experimental findings align well with the simulation results. In summary, this paper proposes a creative design method for wide frequency and large amplitude vibration isolators, and proves it through theoretical analysis and experimental validation.

A new cockroach-like compliant mechanism with SLA-3D printing for micromanipulation and micropolishing of biomaterials

The traditional compliant mechanisms often employ displacement amplification mechanisms to magnitude the workspace but their displacements are still smaller than 1 mm. Unlike previous studies, the present paper proposes a new conceptual design of compliant mechanism which is inspired from biomechanics of cockroach animal. The developed compliant mechanism for two specific functions, such as microgripper and micropositioner which can handle biomaterials. It can permit a large stroke over 1 mm. Modeling of the performances of the proposed mechanism are built by a couple of adaptive neuro fuzzy inference system (ANIFS) and particle swarm optimization (PSO) where PSO is to optimize the ANFIS. To enhance the performances of the mechanism, accelerated particle swarm optimization (APSO) is utilized to search the optimal design parameters. Lastly, the optimized mechanism is printed by Stereolithography (SLA) 3D technique, and the experimental verifications are performed. The results indicated that circumstance #1, the stroke is about 1.5279 mm, the frequency is 49.02103 Hz, the crosstalk error is 0.01108 mm, and the stress is 8.50514 MPa. In circumstance #2, the stroke is 1.44544 mm, the frequency is 54.51361 Hz, the crosstalk error is 0.0248 mm, and the stress is 8.35604 MPa. In last circumstance, the optimized results are achieved the stroke of 1.62369 mm, frequency of 51.62278 Hz, crosstalk of 0.028141 mm, and stress of 7.71713 MPa. The results indicated that the safety factor of three cases are over 2.5 to ensure a safe operation. The tested results are well satisfied with the simulated results.

Design and characterization of non-linear electromagnetic energy harvester with enhanced energy output

This paper presents design, analysis, and characterization of a compliant non-linear electromagnetic energy harvester operating on the principle of bi-stability incorporated with a displacement amplification mechanism. The energy harvester engenders energy from ambient vibrations at multiple modes and with frequencies ranging from 80 to 120 Hz. The energy harvester is analytically modeled using the mechanic’s elastic beam theory. Finite Element Analysis (FEA) has been carried out using commercial Finite Element Method (FEM) based software to perform static, fatigue, dynamic and electromagnetic analysis. Bi-stable mechanism has been used to harness energy at a wider frequency bandwidth while lever mechanism is acting as a displacement amplifier for enhancing low frequency vibration amplitude with the amplification factor of 6.24. With such amplification factor, the energy harvester can be deployed to extract vibrations of diminutive level and recast them into electrical energy in the form of generated voltage. Spring steel material, owing to its structural sensitivity, stiffness and higher value of ultimate stress, was used for its fabrication. The use of Neodymium (N52) magnets, copper coils and shaker were put into practice for testing of this device. The coil resistance is 2.5 Ω with number of turns kept at 350. The maximum output voltage of 1.86 V was generated at 106 Hz with root mean square value of 548 mV. Testing results are in accordance with the results obtained through simulations and thus useful electrical power of 11.1 mW can be generated from ambient vibrations at a wider bandwidth of 18 Hz with operating frequency ranging from 99 to 117 Hz.

Modeling and Analysis of a Conical Bridge-Type Displacement Amplification Mechanism Using the Non-Uniform Rational B-Spline Curve.

This paper presents a new analytical model of a conical bridge-type displacement amplification mechanism (DAM) considering the effect of external loads and a piezostack actuator (PSA). With the merits of simple implementation and better fitting, the non-uniform rational B-spline (NURBS) is employed to parameterize conical connecting beams of the DAM, and an analytical model of the displacement amplification ratio and input stiffness is established based on Castigliano's second theorem. After that, considering the interactions with elastic loads and PSA, the actual displacement amplification ratio of the conical DAM is obtained, and the effect of the shape of connecting beams in the performance of the DAM is further analyzed. The proposed analytical model is verified by finite element analysis (FEA), and the results show a maximum error of 6.31% between the calculated value and FEA results, demonstrating the accuracy of the proposed model. A prototype of the conical DAM with optimized shape is fabricated and experimentally tested, which further validates the effectiveness and accuracy of the proposed analytical model. The proposed model offers a new method for analysis and shape optimization of the bridge-type DAM under specific elastic loads.

Design and mechanical modeling of high-magnification and low-parasitic displacement microgripper with three-stage displacement amplification

The common point of multi-stage displacement amplification mechanisms (DAMs) is that the output end of the upper-stage DAM is connected to the input end of the next-stage DAM. Therefore, the input stiffness of the next-stage DAM will have an impedance effect on the output displacement of the upper-stage DAM. Based on this, the paper introduces a three-stage amplification microgripper, which is driven by a piezoelectric actuator. The three-stage DAM is composed of a compound rhombic mechanism, a bridge mechanism and two parallelogram mechanisms. Based on Cartesian second theorem and flexure beam theory, the mechanism's displacement magnification model, input force and output force relationship model, force-displacement relationship model, input stiffness model and parasitic displacement compensation model are established. The correctness of mechanical modeling is verified by simulation analysis and experiments. The results show that the mechanical model has high prediction accuracy.

Two types of morphing wing designs based on multistage displacement amplification mechanisms

Two types of morphing wing designs based on multistage displacement amplification mechanisms

Design and optimization of a decoupled serial constant force microgripper for force sensitive objects manipulation

AbstractTo address coupling motion issues and realize large constant force range of microgrippers, we present a serial two-degree-of-freedom compliant constant force microgripper (CCFMG) in this paper. To realize a large output displacement in a compact structure, Scott–Russell displacement amplification mechanisms, bridge-type displacement amplification mechanisms, and lever amplification mechanisms are combined to compensate stroke of piezoelectric actuators. In addition, constant force modules are utilized to achieve a constant force output. We investigated CCFMG’s performances by means of pseudo-rigid body models and finite element analysis. Simulation results show that the proposed CCFMG has a stroke of 781.34 ${\unicode[Times]{x03BC}}\mathrm{m}$ in the X-direction and a stroke of 258.05 ${\unicode[Times]{x03BC}}\mathrm{m}$ in the Y-direction, and the decoupling rates in two directions are 1.1% and 0.9%, respectively. The average output constant force of the clamp is 37.49 N. The amplification ratios of the bridge-type amplifier and the Scott–Russell amplifier are 7.02 and 3, respectively. Through finite element analysis-based optimization, the constant force stroke of CCFMG is increased from the initial 1.6 to 3 mm.

Performance enhancement of snap-through vibration energy harvester with displacement amplifier

Vibration energy harvesters (VEH) based on bistable and snap-through mechanisms are being widely employed to harvest energy from different vibration sources. However, under weak ambient excitation, the performance of these systems is marginal. Multi-stability and enhancement techniques, such as displacement amplifier, are being used with bistable VEH to improve its performance. Similar to this, multi-stable snap-through VEH has also been developed; however, the usage of a displacement amplifier in the context of snap-through VEH has not yet been investigated. In this novel study, a displacement amplifier/ displacement amplification mechanism (DAM) is integrated into a snap-through VEH, and the enhanced performance under weak excitation is investigated. A generalized transformation is applied to develop a reduced-order model of the proposed system, and its dynamics and performance under harmonic and random excitation are investigated analytically and numerically. The frequency–amplitude relationship is derived under harmonic excitation, and a detailed investigation of the influence of system parameters on the frequency and force responses is performed. It is observed that by adjusting the mass and stiffness ratio between the VEH and DAM, it is possible to harvest more energy under harmonic excitation of low intensity. In the case of Gaussian white noise excitation, effective potential, and stochastic averaging methods are used to obtain marginal, joint, and stationary probability density functions and mean square power. The influence of noise intensity and other system parameters on the aforementioned measures is thoroughly investigated. It is observed that for specific parameter values, the proposed VEH can harvest 3.3 times more power under harmonic excitation and four times more power under random excitation compared to the snap-through VEH without DAM.

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.