Mechanism and Machine Theory最新文献

Transmission angle of planar four-bar linkages applicable for different input-output links subject to external loads 平面四杆连杆机构的传动角，适用于承受外部载荷的不同输入输出连杆机构

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-11-01 DOI: 10.1016/j.mechmachtheory.2024.105829

The transmission angle is a traditional performance indicator in planar four-bar linkages, whereby force and motion are transmitted from the input link to the output link. However, for the calculation of traditional transmission angle, it is predefined that the input and output links are connected to the fixed link, i.e., the grounded link. This brings the problem of calculating the transmission angle for other cases, for example, the coupler link being the input link. Moreover, the traditional transmission angle cannot evaluate the influence of external loads on the transmission quality. In this work, we revisit this problem and redefine the transmission angle, which allows us to investigate the effect of different selections of the input and output links and external loads on the transmission performance. A case study of transmission angle analysis of a planar four-bar linkage is included to illustrate the application of the revised performance index. Moreover, three new transmission quality indices are introduced, upon which transmission performance optimization of a planar four-bar linkage is presented. Based on the redefined transmission angle and the proposed transmission quality indices, transmission quality analysis and optimal design of general four-bar linkages can be conducted to enhance their transmission performances.

传动角是平面四杆连杆机构的传统性能指标，力和运动从输入连杆传递到输出连杆。然而，在计算传统的传递角时，输入和输出链接被预先设定为连接到固定链接，即接地链接。这就带来了在其他情况下计算传输角的问题，例如耦合器链路是输入链路。此外，传统的传输角无法评估外部负载对传输质量的影响。在这项工作中，我们重新审视了这一问题，并重新定义了传输角，从而可以研究输入和输出链接以及外部负载的不同选择对传输性能的影响。为了说明修订后的性能指标的应用，我们还对平面四杆联动装置的传动角分析进行了案例研究。此外，还引入了三个新的传动质量指标，并在此基础上对平面四杆联动机构的传动性能进行了优化。根据重新定义的传动角和提出的传动质量指数，可以对一般四杆联动装置进行传动质量分析和优化设计，以提高其传动性能。

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引用次数: 0

Optimizing natural frequencies in compliant mechanisms through geometric scaling 通过几何缩放优化顺变机构的固有频率

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-11-01 DOI: 10.1016/j.mechmachtheory.2024.105822

This work contributes to the dynamic analysis and optimization of compliant mechanisms in terms of their natural frequencies. The previously established analytical method based on Bernoulli beams and the transfer matrix method, which underlies the existing calculation tool CaTEf, is extended to enable the scaling of any specified geometric parameter or parameter set within a given mechanism to achieve a desired natural frequency. By introducing a scaling parameter, precise adjustments of selected geometric parameters are ensured while accounting for inherent dependencies. Minor discrepancies are revealed in parameter studies when comparing results obtained with our proposed analytical method to those from the Finite Element Method (FEM) regarding the resulting scaled values. Following validation, the analytical method is seamlessly integrated into CaTEf and verified against experimental data, demonstrating strong agreement. This work results in a highly efficient analytical method for optimizing compliant mechanisms in terms of their dynamic behavior, especially natural frequencies, while significantly reducing modeling and calculation time.

这项工作有助于根据自然频率对顺变机构进行动态分析和优化。之前建立的基于伯努利梁和传递矩阵法的分析方法是现有计算工具 CaTEf 的基础，通过扩展该方法，可对给定机构中的任何指定几何参数或参数集进行缩放，以实现所需的固有频率。通过引入比例参数，可确保对所选几何参数进行精确调整，同时考虑固有的依赖关系。在参数研究中，当比较我们提出的分析方法和有限元法（FEM）得出的结果时，会发现两者的缩放值存在微小差异。经过验证后，分析方法被无缝集成到 CaTEf 中，并与实验数据进行了验证，结果表明两者非常吻合。这项工作产生了一种高效的分析方法，用于优化顺从机构的动态行为，特别是自然频率，同时显著减少建模和计算时间。

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引用次数: 0

Oriblock: The origami-blocks based on hinged dissection Oriblock：基于铰链解剖的折纸块

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-30 DOI: 10.1016/j.mechmachtheory.2024.105826

Traditional origami, a well-known art of paper-folding, does not account for material thickness. Subsequently, several thickness-accommodation techniques have been developed, considering the non-negligible thickness of materials, which enables the application of origami to a wide range of mechanisms. Although these techniques prevent self-intersections and preserve kinematics after accommodating panel thickness, they are limited by their reliance on initial zero-thickness origami patterns in two dimensions. To address this issue, this study proposes a novel technique, the volume-accommodation technique in three-dimensional space, which allocates non-coplanar origami creases based on solid geometry to allow a greater variety of shape-changing motions. Typical solid geometries, such as a pyramid and a prism, are selected as examples to demonstrate the design procedures. Closure equations of the obtained oriblock are used to analyze the kinematic properties. Additionally, Bennett and Myard Linkages are derived from oriblocks based on their kinematic equivalence to strengthen their connections. As a result, this new type of origami can offer a variety of mechanisms for designers and facilitate potential applications in origami-inspired metamaterials and robotics.

传统折纸是一种著名的折纸艺术，但它并不考虑材料的厚度。后来，考虑到材料的厚度不可忽略，人们开发了几种厚度适应技术，从而使折纸能够应用于多种机械装置。虽然这些技术在适应面板厚度后可以防止自相交并保持运动学特性，但由于它们依赖于二维的初始零厚度折纸图案，因此受到了限制。为解决这一问题，本研究提出了一种新技术--三维空间体积容纳技术，该技术根据实体几何形状分配非共面折纸折痕，从而允许更多的形状变化运动。我们选择了典型的实体几何图形，如金字塔和棱柱，作为演示设计程序的示例。获得的oriblock 的闭合方程用于分析其运动特性。此外，还根据运动学等效性，从口部模块推导出 Bennett 和 Myard 连接器，以加强它们之间的连接。因此，这种新型折纸可以为设计者提供多种机制，并促进折纸启发的超材料和机器人技术的潜在应用。

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引用次数: 0

A comprehensive study of the effect of thermal deformation on the dynamic characteristics of the high-speed spindle unit with various preload forces 不同预紧力下热变形对高速主轴单元动态特性影响的综合研究

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-30 DOI: 10.1016/j.mechmachtheory.2024.105820

In this paper, based on the multi-degree-of-freedom (M-DOF) finite element and 2-dimensional transient thermal network methods, a novel thermo-mechanical coupling model of the high-speed spindle-bearing system by comprehensively considering the radial coupling deformations of supporting ball bearings and rotor is proposed, and the effects of the temperature rise and thermal deformation on its dynamic characteristics are discussed. Then a non-contact electromagnetic loading device is designed to test the dynamic amplitude-frequency response of a hydraulic variable preload experimental spindle system. The studies show that, the results calculated by proposed thermo-mechanical coupling model are highly consistent with the experimental results of the spindles system, and the temperature rise and thermal deformations have an important influence on its mechanical behavior, and the linear resonant frequency of the high-speed spindle under the constant pressure preload mechanism continues to increase until the system reaches its thermal equilibrium state.

本文基于多自由度（M-DOF）有限元和二维瞬态热网络方法，综合考虑支撑球轴承和转子的径向耦合变形，提出了一种新型的高速主轴-轴承系统热机械耦合模型，并讨论了温升和热变形对其动态特性的影响。然后设计了一种非接触式电磁加载装置，用于测试液压变预载实验主轴系统的动态幅频响应。研究表明，提出的热机械耦合模型计算结果与主轴系统的实验结果高度一致，温升和热变形对其机械行为有重要影响，恒压预紧机构下高速主轴的线性共振频率持续上升，直至系统达到热平衡状态。

引用次数: 0

Analysis of nonphysical attraction force and new coefficient of restitution based on a nonlinear viscoelastic contact model in cohesionless granular system 基于非线性粘弹性接触模型的无内聚力颗粒体系中的非物理吸引力和新的恢复系数分析

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-28 DOI: 10.1016/j.mechmachtheory.2024.105821

This investigation implements systematical research on the coefficient of restitution (CoR) and nonphysical attraction force. Firstly, a characteristic length is redefined based on energy conservation. On this basis, a new general CoR model is derived through characteristic length. Subsequently, a new constraint equation of the power exponents is proposed from the new CoR model. The new CoR model is validated by experimental data regardless of whether the initial impact velocity is very low or high speed. Secondly, we systematically analyze the real reason for the nonphysical attraction force in the viscous damping loop. The simulation shows the nonphysical attraction force cannot be removed from the viscous damping loop. The real reason for the nonphysical attraction force lies in the natural property of the viscous damping factor. Finally, to eliminate the effect of the attraction force on the motion status of colliding particles after impact, a balance coefficient is introduced to compensate for the deficiency of nonphysical attraction force and original damping factor. The simulation proves that the post-impact velocity of colliding particles can be precisely captured using a viscous contact force model with a balance coefficient.

本研究对弹性模量（CoR）和非物理吸引力进行了系统研究。首先，基于能量守恒重新定义了特征长度。在此基础上，通过特征长度推导出新的通用 CoR 模型。随后，根据新的 CoR 模型提出了一个新的功率指数约束方程。无论初始冲击速度是很低还是很高，新的 CoR 模型都得到了实验数据的验证。其次，我们系统地分析了粘性阻尼回路中产生非物理吸引力的真正原因。模拟结果表明，粘性阻尼回路中的非物理吸引力无法消除。非物理吸引力的真正原因在于粘性阻尼因子的自然属性。最后，为了消除吸引力对碰撞后粒子运动状态的影响，引入了平衡系数来弥补非物理吸引力和原始阻尼系数的不足。仿真证明，使用带有平衡系数的粘性接触力模型可以精确地捕捉到碰撞后粒子的速度。

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引用次数: 0

Design and optimization of a planar anti-buckling compliant rotational joint with a remote center of motion 设计和优化具有远程运动中心的平面抗弯曲顺应旋转接头

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-28 DOI: 10.1016/j.mechmachtheory.2024.105816

Compliant mechanisms (CMs) exhibit some excellent mechanical properties and provide numerous innovative solutions for many existing mechanical applications. Among them, planar compliant rotational joints have made substantial contributions to precision engineering. To achieve high-precision positioning with a compliant rotational joint, it is essential to study characteristics such as anti-buckling and constant stiffness. The remote center of motion (RCM) mechanism, with its compact structure and ease of precise control, is expected to enhance overall rigidity and reduce parasitic displacements. Here, we propose a planar anti-buckling compliant rotational joint with a RCM. Static modeling and model validation are conducted for different geometric configurations, including single and combined structures. A distributed configuration with bidirectional anti-buckling properties is selected for optimization. Using a global parameter optimization model, single-objective optimization studies are conducted for three distinct characteristics. Subsequently, a multi-objective optimization model for constant stiffness and high precision is established. Based on the optimization results, a compliant rotational joint with bidirectional anti-buckling, constant rotational stiffness, and high precision is designed. Finally, the effectiveness of the optimization method is validated through physical experiments.

顺应机构（CM）具有一些优异的机械特性，为许多现有的机械应用提供了大量创新解决方案。其中，平面顺应旋转接头为精密工程做出了巨大贡献。要利用顺应旋转接头实现高精度定位，必须研究其抗弯曲和恒定刚度等特性。远程运动中心（RCM）机构结构紧凑，易于精确控制，有望增强整体刚度并减少寄生位移。在此，我们提出了一种带有 RCM 的平面抗弯曲顺应旋转接头。我们针对不同的几何配置（包括单一结构和组合结构）进行了静态建模和模型验证。选择了具有双向抗屈曲特性的分布式结构进行优化。利用全局参数优化模型，针对三个不同的特征进行了单目标优化研究。随后，建立了恒定刚度和高精度的多目标优化模型。根据优化结果，设计出了具有双向抗屈曲、恒定旋转刚度和高精度的顺应旋转接头。最后，通过物理实验验证了优化方法的有效性。

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引用次数: 0

Modelling of the objects' positioning process on the conveyor with the positioning rectilinear barrier and the system of driven oblique rollers 利用定位直线屏障和驱动斜辊系统对输送机上的物体定位过程进行建模

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-25 DOI: 10.1016/j.mechmachtheory.2024.105817

The paper deals with the positioning process modelling of the cuboidal objects along the conveyor edge by means of an oblique friction force field with a rectilinear barrier. The friction field is created by a system of driven oblique rollers. A modified nonlinear Kelvin model was used to describe the normal reaction forces at the contact points of the object with the conveyor and barrier. There were taken into account two 2D vector friction models: the LuGre and the Bengisu-Akay, representing the dynamic and static groups of friction models, respectively. The LuGre model has been modified to overcome the limitations of the classic model in terms of the invariability of the normal contact forces. The use of scaling of the stiffness coefficient (due to the normal contact force) allows the friction simulation while bodies collision, i.e. when the normal contact force shows rapid changes in value and the initial sliding velocity is non-zero. A method for determining the dynamic parameters of the LuGre model is proposed. The results of numerical and experimental research on the positioning process show acceptable compliance and validity of the adopted assumptions.

本文论述了通过带有直线障碍物的斜向摩擦力场，沿传送带边缘对长方体物体进行定位的过程建模。该摩擦力场由一个斜辊驱动系统产生。修正的非线性开尔文模型用于描述物体与传送带和障碍物接触点的法向反作用力。其中考虑了两个二维矢量摩擦模型：LuGre 和 Bengisu-Akay，分别代表动态和静态摩擦模型组。对 LuGre 模型进行了修改，以克服经典模型在法向接触力不变性方面的局限性。利用刚度系数（由于法向接触力）的缩放，可以在物体碰撞时进行摩擦模拟，即法向接触力值快速变化且初始滑动速度不为零时。提出了一种确定 LuGre 模型动态参数的方法。定位过程的数值和实验研究结果表明，所采用的假设符合要求且有效。

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引用次数: 0

Development of an analytical model and method for analyzing deformation in planar load cells 开发用于分析平面称重传感器变形的分析模型和方法

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-23 DOI: 10.1016/j.mechmachtheory.2024.105812

Due to their advantageous properties, compliant mechanisms are widely used in various technical fields. Strain-based deformation bodies, a particular type of these mechanisms, are often used in weighing technology. They are used in conjunction with strain gauges for force measurement, among other applications. Until now, such weighing mechanisms have been designed using finite element simulations or empirical studies, which are often time-consuming and costly. Therefore, this article presents an analytical calculation model based on the theory of large deformations of rod-like structures, which simplifies the calculation of such weighing mechanisms. Key elements in this calculation are the transversally symmetric hinges required for the description. Investigations show that, due to the geometry of these cells, tensile and compressive deformations are not negligible and must be included in the analytical model. The validity and accuracy of the analytical model are verified through parameter studies and show deviations of less than 6% compared to the FEM. Finally, the model is integrated into a graphical user interface to allow an easy application to analyze load cells.

由于顺变机构具有良好的特性，因此被广泛应用于各个技术领域。基于应变的变形机构是这类机构的一种特殊类型，通常用于称重技术。除其他应用外，它们还与应变片一起用于力测量。迄今为止，此类称重机构的设计都是通过有限元模拟或经验研究来实现的，而这些方法往往费时费力且成本高昂。因此，本文基于杆状结构大变形理论提出了一种分析计算模型，简化了此类称重机构的计算。该计算模型的关键要素是描述所需的横向对称铰链。研究表明，由于这些单元的几何形状，拉伸和压缩变形不容忽视，必须纳入分析模型。通过参数研究验证了分析模型的有效性和准确性，与有限元模型相比，偏差小于 6%。最后，该模型被集成到一个图形用户界面中，便于应用于分析称重传感器。

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引用次数: 0

The friction-limited end-effector motion resolution of tendon-actuated and continuum robots 腱驱动机器人和连续机器人的摩擦限制末端执行器运动分辨率

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-23 DOI: 10.1016/j.mechmachtheory.2024.105814

Force and motion transmission losses can significantly affect the kinematics and performance of wire-actuated robots. In addition to degrading the kinematic model, they can produce hysteresis (dead-zone) effects whereby the motion of the actuators produces no motion of the end effector. This paper presents a modeling framework that can be used at the design stage to evaluate the effects of these transmission losses. Considerations for modeling the dead-zone effects of end-effector motion are used to define a performance measure that quantifies the quality of a given design within a workspace. This design measure should be used in conjunction with the traditional kinematics and statics-based measures to reflect the expected performance of an integrated wire-actuated robot with its actuation lines and actuation unit. To illustrate our approach, we present a model of a wire-actuated snake-like robot with an articulated backbone made up of ball-and-socket joints. The results and methodology reported in this paper can guide the design of wire-actuated robots in selecting wire-parameters and determining their effects on the expected uncertainty, limiting the friction-limited minimal motion resolution of the end effector.

力和运动传输损耗会严重影响线控机器人的运动学和性能。除了降低运动学模型的性能外，它们还会产生滞后（死区）效应，即执行器的运动不会产生末端效应器的运动。本文介绍了一种建模框架，可在设计阶段用于评估这些传输损耗的影响。建模末端执行器运动死区效应的考虑因素被用来定义一种性能指标，以量化工作空间内给定设计的质量。该设计衡量标准应与传统的运动学和静力学衡量标准结合使用，以反映集成线控机器人及其执行线和执行单元的预期性能。为了说明我们的方法，我们展示了一个线控蛇形机器人模型，该机器人的骨干由球窝关节组成。本文所报告的结果和方法可以指导线控机器人的设计，选择线参数并确定其对预期不确定性的影响，从而限制末端效应器的摩擦极限最小运动分辨率。

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引用次数: 0

Reducing backward motion of stick-slip piezoelectric actuators using dual driving feet designed by asymmetric stiffness principle 利用非对称刚度原理设计的双驱动脚减少粘滑压电致动器的后向运动

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-21 DOI: 10.1016/j.mechmachtheory.2024.105810

Stick–slip piezoelectric actuators (SSPEAs) have drawn attention for their features of simple structure and high positioning accuracy. However, the backward motion has always been a major problem that limits driving speed and smoothness. Existing methods mainly focus on control methods and driving signal optimization, while few efforts emphasize mechanical structure optimization. To address this problem from the root of structure design, a novel SSPEA based on the principle of asymmetric stiffness is developed. A dual-driving feet configuration generates phase differences between two feet when feeding sawtooth driving signals. The core idea is that the backward motion of one driving foot can be compensated by another foot making full use of the phase difference due to the asymmetric stiffness compliant mechanism (ASCM). Kinematic and static models are built and the structural dimensions are then determined. Finite element analysis is conducted preliminarily to test the output performance. A physical prototype is fabricated and experimentally verified. Experimental results show the proposed actuator with ASCM achieves smaller backward motion and larger step size ranging from 250 to 1400 Hz driving frequencies compared with traditional triangular compliant mechanism (TTCM). The maximum speed is obtained as 47.2 mm/s with a resolution of

0.07 μ m

.

粘滑压电致动器（SSPEA）因其结构简单、定位精度高而备受关注。然而，后向运动一直是限制驱动速度和平稳性的主要问题。现有方法主要集中在控制方法和驱动信号优化上，而很少有人关注机械结构优化。为了从结构设计的根源上解决这一问题，我们开发了一种基于非对称刚度原理的新型 SSPEA。当输入锯齿驱动信号时，双驱动脚配置会在两个脚之间产生相位差。其核心思想是，由于非对称刚度顺应机构（ASCM）的存在，一个驱动脚的后退运动可由另一个脚充分利用相位差进行补偿。建立运动和静态模型，然后确定结构尺寸。初步进行了有限元分析，以测试输出性能。制作了一个物理原型并进行了实验验证。实验结果表明，与传统的三角形顺从机构（TTCM）相比，带有 ASCM 的拟议致动器实现了更小的后向运动和更大的步长，驱动频率范围从 250 Hz 到 1400 Hz。最大速度为 47.2 mm/s，分辨率为 0.07μm。

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引用次数: 0