Elastic Hinges Research Articles

J113031 空気圧ベローズを用いた静圧案内微動ステージの超精密位置決め

The demand for ultra precise positioning of nanometer-order is increasing with the progress of nanotechnology in biotechnology industry and especially semiconductor industry. Previously we developed the elastic hinge guide stage driven by pneumatic bellows for such a demand, and realized ultra precise positioning with accuracy of 0.02±3.9 [nm]. Then, positioning accuracy was limited by the vibration from a floor with the resonance frequency which is decided by the mass of a stage and the spring of elastic hinges. On the other hand, the measurement of exact stage position by the laser interferometer is difficult because fluctuation of air influences to the measurement. In this research, guide was changed into the air bearing from the elastic hinge, and positioning measurement was changed into the laser scale from the laser interferometer in order to solve these problems. The purpose of this research is investigated the positioning accuracy the changed stage. As a result, the positioning accuracy is improved to 0.01 ±0.9 [nm] with the positioning resolution of l [nm] and the good positioning repeatability.

A TWO-DOF Controlled Lens Drive Actuator for Off-Axis Laser Beam Cutting

This paper describes a two-degree-of-freedom (two-DOF) controlled electromagnetic actuator guided by an elastic hinge mechanism to realize off-axis laser beam cutting. In the laser beam cutting process, a focused laser beam melts and vaporizes part of the workpiece, and the molten material is blown away by an assist gas jet. The cutting speed and quality are related to the flow of the assist gas jet. In order to improve the removal capability of the molten material and to reduce gas consumption in off-axis laser beam cutting, the lens is driven radially by the proposed two-DOF actuator to generate relative motion between the assist gas nozzle and the laser. Experimental results show the prototype actuator possesses a positioning stroke of ±500µm within 3µm of tracking error and bandwidths more than 150Hz in the two-DOF directions. In the acceleration test supposed at a maximum acceleration of 2G, the prototype actuator maintains the relative displacement between the lens holder and the laser head within 10µm. Off-axis laser beam cutting by using the prototype actuator achieves high speed and less dross processing.

Seismic Response of Baihua Viaduct during the Wenchuan Earthquake and Methods of Reducing Seismic Damage

Baihua Viaduct which is an important transportation project of 213 National Highway was severely destroyed during the 512 Wenchuan earthquake. The fifth segment of the bridge suffered the most severe unrepairable damage, such as the rupture of the piers and falling of beams. It is worth to study the performance through the FEM dynamical analysis to explain the damage performance of Baihua Viaduct in the earthquake. The dynamical FE model of the Baihua Viaduct is established considering the non-liner properties of piers and bearings. Further the earthquake records of the nearest Wolong station is chosen to be as the earthquake excitation input to conduct the seismic analysis. The analysis shows that the results of damage position and damage degree of components of the bridge calculated by elastic-plastic dynamic analysis are close to the actual damage of Baihua Viaduct. The reinforcement ratio of piers is low, while there is not any shear failure on piers. The damage degree of elastic hinge is related with the arrangement of bearings. The girders’ displacement is much larger because there are not any anti-dropping devices on the bridge. Damage of the fifth segment of bridge may be caused by plasticity destroy of some piers.

Seismic Response of Baihua Viaduct during the Wenchuan Earthquake and Methods of Reducing Seismic Damage

Baihua Viaduct which is an important transportation project of 213 National Highway was severely destroyed during the 512 Wenchuan earthquake. The fifth segment of the bridge suffered the most severe unrepairable damage, such as the rupture of the piers and falling of beams. It is worth to study the performance through the FEM dynamical analysis to explain the damage performance of Baihua Viaduct in the earthquake. The dynamical FE model of the Baihua Viaduct is established considering the non-liner properties of piers and bearings. Further the earthquake records of the nearest Wolong station is chosen to be as the earthquake excitation input to conduct the seismic analysis. The analysis shows that the results of damage position and damage degree of components of the bridge calculated by elastic-plastic dynamic analysis are close to the actual damage of Baihua Viaduct. The reinforcement ratio of piers is low, while there is not any shear failure on piers. The damage degree of elastic hinge is related with the arrangement of bearings. The girders’ displacement is much larger because there are not any anti-dropping devices on the bridge. Damage of the fifth segment of bridge may be caused by plasticity destroy of some piers.

On mechanical properties of planar flexure hinges of compliant mechanisms

Abstract. The synthesis of compliant mechanisms yield optimized topologies that combine several stiff parts with highly elastic flexure hinges. The hinges are often represented in finite element analysis by a single node (one-node hinge) leaving doubts on the physical meaning as well as an uncertainty in the manufacturing process. To overcome this one-node hinge problem of optimized compliant mechanisms' topologies, one-node hinges need to be replaced by real flexure hinges providing desired deflection range and the ability to bear internal loads without failure. Therefore, several common types of planar flexure hinges with different geometries are characterized and categorized in this work providing a comprehensive guide with explicit analytical expressions to replace one-node hinges effectively. Analytical expressions on displacements, stresses, maximum elastic deformations, bending stiffness, center of rotation and first natural frequencies are derived in this work. Numerical simulations and experimental studies are performed validating the analytical results. More importance is given to practice-oriented flexure hinge types in terms of cost-saving manufacturability, i.e. circular notch type hinges and rectangular leaf type hinges.

Theoretic Analysis of Inner Force of Shield Tunnel According to Elastic Hinge Model

Elastic hinge model is one kind of reasonable models to analysis shield tunnel. However, no formulas are valid to calculate inner force caused by load of water pressure and elastic reaction. Mechanical equations of two kinds of load are built and inner force formulas are deduced. Results calculated by homogeneous ring model are contrasted with those by elastic hinge model and conclusion is derived. The contrast shows that the results according to elastic hinge model are more reasonable.

3376 A TWO-DOF Controlled Lens Drive Actuator for Off-Axis Laser Beam Cutting

This paper describes a two-degrees-of-freedom (two-DOF) controlled electromagnetic actuator guided by an elastic hinge mechanism to realize off-axis laser beam cutting. In the laser beam cutting process, a focused laser beam melts and vaporizes part of the workpiece, and the molten material is blown away by an assist gas jet. The cutting speed and quality is related to the flow of the assist gas jet. In order to improve the removal capability of the molten material and to reduce gas consumption in off-axis laser beam cutting, the lens is driven radially by the proposed two-DOF actuator to generate relative motion between the assist gas nozzle and the laser.

Deployable Trusses Based on Large Rotation Flexure Hinges

Formulations for the strength, stiffness, mass efficiency, and packaging of deployable trusses using flexure hinges are developed and comparedwith the experimentwithin. The equations are based on classical buckling theory, Euler buckling with engineering approximations, and finite element-based models to predict the column and bending strengths of solid rod and tubular trusses with slender flexure hinges. Flexure hinge material performance metrics are derived and used to show that, while bothmass efficient trusses of solid rods and trusses of tubes are feasible with existing materials, trusses of solid rods are significantly more strain limited. A representative high compaction ratio deployable truss with pultruded carbon fiber reinforced plastic rods and super elastic nickel-titanium alloy flexure hinges was fabricated and tested. The compressive strength of the truss was 48% less than predicted and the compressive stiffness of the truss was 12% less than predicted.

Molecular determinants of coupling between the domain III voltage sensor and pore of a sodium channel

In a voltage-dependent sodium channel, the activation of voltage sensors upon depolarization leads to the opening of the pore gates. To elucidate the principles underlying this conformational coupling, we investigated a putative gating interface in domain III of the sodium channel using voltage-clamp fluorimetry and tryptophan-scanning mutagenesis. Most mutations have similar energetic effects on voltage-sensor activation and pore opening. However, several mutations stabilized the activated voltage sensor while concurrently destabilizing the open pore. When mapped onto a homology model of the sodium channel, most localized to hinge regions of the gating interface. Our analysis shows that these residues are involved in energetic coupling of the voltage sensor to the pore when both are in resting and when both are in activated conformations, supporting the notion that electromechanical coupling in a voltage-dependent ion channel involves the movement of rigid segments connected by elastic hinges.

Attitude Control of Nanosatellites by Paddle Motion Using Elastic Hinges Actuated by Shape Memory Alloy

Recent research has been extending the applications of small satellites called microsatellites, nanosatellites, or picosatellites. To further improve capability of those satellites, a lightweight, active attitude-control mechanism is needed. This paper proposes a concept of inertial orientation control, an attitude control method using movable solar arrays. This method is made suitable for nanosatellites by the use of shape memory alloy (SMA)-actuated elastic hinges and a simple maneuver generation algorithm. The combination of SMA and an elastic hinge allows the hinge to remain lightweight and free of frictional or rolling contacts. Changes in the shrinking and stretching speeds of the SMA were measured in a vacuum chamber. The proposed algorithm constructs a maneuver to achieve arbitrary attitude change by repeating simple maneuvers called unit maneuvers. Provided with three types of unit maneuvers, each degree of freedom of the satellite can be controlled independently. Such construction requires only simple calculations, making it a practical algorithm for a nanosatellite with limited computational capability. In addition, power generation variation caused by maneuvers was analyzed to confirm that a maneuver from any initial attitude to an attitude facing the sun was justifiable in terms of the power budget.

713 弾性ヒンジ機構を用いたワイヤレス光学ひずみゲージの開発(OS7. 逆問題解析手法の開発と最新応用(3),オーガナイズドセッション講演)

713 弾性ヒンジ機構を用いたワイヤレス光学ひずみゲージの開発(OS7. 逆問題解析手法の開発と最新応用(3),オーガナイズドセッション講演)

Fast drive of displacement magnification mechanism with flexure hinge using loading type impact damper

A displacement magnification mechanism which uses flexure motion guide using elastic hinges can realize smooth frictionless motion but has poor vibration damping capability. An impact damper is a damping mechanism which uses collision energy to dissipate vibration energy. If the damper is used for vibration control of the flexure mechanism, it may be able to dissipate unexpected vibration without killing the merits of the flexure mechanism. In the paper, a loading type impact damper is applied to settle down transient vibration of a displacement magnification mechanism. We investigate differences of damping effect by setting conditions of the damper. It is shown that the impact damper can eliminate residual vibration at step response effectively without steady state error. The experimental displacement magnification mechanism with impact damper can settle down less than 1/5 of the response without the damper under appropriate setting conditions. Influence of natural frequency ratio between damper and displacement magnification mechanism is investigated. Influences of indentation at impact point are also examined.

103 剛体-弾性体リンク系・振動特性(機械力学・計測制御I)

103 剛体-弾性体リンク系・振動特性(機械力学・計測制御I)

Displacement amplifier for piezoelectric actuator based on honeycomb link mechanism

This study proposes a compact and array-type design of a mechanical amplifier for piezoelectric actuators. The amplifier emulates in-plane deformation of a specific honeycomb having bow-tie-type reentrant cells. When a multilayer piezoelectric actuator causes the elongation of a cell of the amplifier in the longitudinal direction, the cell causes expansion in the transverse direction with amplification depending on its geometry. For ease of fabrication of the amplifier, a plate having periodic patterns of two holes and a slit is proposed, in which all walls and corners of the cell are replaced with rigid links and elastic hinges, respectively. Compactness of an amplified piezoelectric actuator based on the honeycomb link mechanism is demonstrated by using prototypes of uniaxial actuators and XY stages. Furthermore, theoretical formulas are discussed, which are used in the design of the amplified actuators.

The new INRiM nanoangle generator

At the angle metrology laboratory of the Istituto Nazionale di Ricerca Metrologica (INRiM, formerly IMGC), an instrument to generate very small angles has been recently developed. It is a sine-bar angle generator based on an elastic hinge and a piezocapacitive device. The facility can be used to calibrate precise angle measuring instruments (levels, autocollimators, etc) in a range of 120 µrad with an uncertainty of about 20 nrad and a sensitivity of fractions of a nanoradian. The working principle and metrological characterization are presented.

Forward and inverse analyses of smart compliant mechanisms for path generation

In this paper, an open loop compliant mechanism consisting of two elastic links actuated through piezoelectric actuators has been analyzed. The links may be joined through rigid or elastic hinge connection. The effect of piezoelectric actuators placed on an elastic beam is considered as two concentrated self-balancing moments acting on the beam at the edges of the actuator. Considering the large deflection of the two links of the mechanism under these self-balancing moments as well as end loads, the forward and inverse analyses of the mechanism are carried out. Two numerical schemes, namely, non-linear shooting (NLS) and Adomian decomposition methods (ADM) have been used for solving these problems. Numerical results are included to demonstrate the potential of the proposed methods.

Modeling of properties and motions of an inhomogeneous one-dimensional continuum of a complicated Cosserat-type microstructure

We consider an approach to modeling the properties of the one-dimensional Cosserat continuum [1] by using the mechanical modeling method proposed by Il’yushin in [2] and applied in [3]. In this method, elements (blocks, cells) of special form are used to develop a discrete model of the structure so that the average properties of the model reproduced the properties of the continuum under study. The rigged rod model, which is an elastic structure in the form of a thin rod with massive inclusions (pulleys) fixed by elastic hinges on its elastic line and connected by elastic belt transmissions, is taken to be the original discrete model of the Cosserat continuum. The complete system of equations describing the mechanical properties and the dynamical equilibrium of the rigged rod in arbitrary plane motions is derived. These equations are averaged in the case of a sufficiently smooth variation in the parameters of motion along the rod (the long-wave approximation). It was found that the average equations exactly coincide with the equations for the one-dimensional Cosserat medium [1] and, in some specific cases, with the classical equations of motion of an elastic rod [4–6]. We study the plane motions of the one-dimensional continuum model thus constructed. The equations characterizing the continuum properties and motions are linearized by using several assumptions that the kinematic parameters are small. We solve the problem of natural vibrations with homogeneous boundary conditions and establish that each value of the parameter distinguishing the natural vibration modes is associated with exactly two distinct vibration mode shapes (in the same mode), each of which has its own frequency value.

Recursive Algorithm with Efficient Variables for Flexible Multibody Dynamics with Multiloop Constraints

An algorithm is given to reduce computer time for simulation of motion of hinge-connected flexible multibody systems with multiple structural loops. The algorithm is based on using efficient motion variables for elastic motion and hinge rotation in a recursive formulation for an articulated system of bodies in a tree configuration. This formulation is then used for multiloop systems by cutting the loops at joints and exposing unknown constraint forces. A new development is given of the intertwining of the effects of the constraint forces on the accelerations of the bodies, with constraint force contributions requiring a two-stage update. Explicit expression of the accelerations in terms of the constraint forces leads to a particularly simple form for the evaluation of the latter. Numerical efficiency of the algorithm is shown by examples comparing to a standard, nonrecursive formulation using customary motion variables. Examples include large-angle slewing of a flexible solar sail, flexible multiantenna spacecraft with prescribed motion for internal loads calculation, a whirling chain of flexible bodies with two ends pinned, and a multiloop, flexible multibody mechanism. All the examples demonstrate the relative computational efficiency of the new formulation, with efficiency increasing with increased number of modes per flexible body.

Experimental analysis of the wet flexural mode response of an NPL 6A hydroelastic segmented model

This paper investigates the effects of stiffness and mass distribution on the longitudinal flexural natural frequency response of an NPL 6A segmented monohull model in still water at zero speed. Experimental tests were undertaken in order to establish the parameters that affect the whipping frequency at model-scale so as to replicate the vibratory response of a full-scale vessel subject to slamming. The model was cut into two halves at the longitudinal centre of buoyancy and connected by a backbone beam with an elastic hinge joining the two segments. Wet vibration tests conducted on the model showed significant influences on the flexural natural frequency response through variations in stiffness and ballast mass distribution. The whipping frequency was predicted with a two degree of freedom theoretical model using an added mass approximation to provide good correlation with measured experimental data. Damping ratios of the wet transient response are also presented with respect to variations in the condition of the void separating the two model halves.

Analytical and numerical results for vibration analysis of multi-stepped and multi-damaged circular arches

This paper investigates the in-plane linear dynamic behaviour of multi-stepped and multi-damaged circular arches under different boundary conditions. Cracked cross-sections are modelled as massless elastic rotational hinges. In damaged configuration, cracks can be located both at the interface between two adjacent portions as well as inside the portion itself. For each arch portion bounded by two cracks, the differential equations of motion have been established considering axial extension, transverse shear effects and rotatory inertia. The equilibrium equations of arch portions are combined in the coupled fundamental system in terms of radial displacement, tangential displacement and rotation. Analytical and numerical solutions for multi-stepped arches, in undamaged as well as in damaged configurations, are proposed. The analytical solution is based on the Euler characteristic exponent procedure involving the roots of characteristic polynomials, while the numerical method is focused on the Generalized Differential Quadrature (GDQ) method and the Generalized Differential Quadrature Element (GDQE) technique. Numerical results are shown in terms of the first 10 analytical and numerical frequencies of multi-stepped and multi-damaged arches with different boundary conditions. Finally, convergence and stability characteristics of the GDQE procedure are investigated. The convergence rate of the natural frequencies is shown to be very fast and the stability of the numerical procedure is very good.