Mechanism and Machine Theory最新文献

英文中文

Analysis of the tooth-root stress of external spur gears with high effective contact ratio 高有效接触比外直齿轮齿根应力分析

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-14 DOI: 10.1016/j.mechmachtheory.2024.105813

For spur gears with contact ratio close to 2, the extension of the contact interval resulting from loaded tooth deflections and local contact deformations may result in an effective contact ratio above 2. In these cases, the load is transmitted by at least two tooth-pairs, the maximum load and tooth-root stress decrease, and therefore the calculation methods of the gear rating Standards ISO and AGMA provide very conservative results. In this work, two models are applied to the calculation of the tooth-root stress of load-induced high contact ratio external gears: (i) an analytic model of load sharing, based on the minimum energy method, and (ii) a finite element model, which validates the results obtained from the previous model. Obtained values of the stress are compared with those provided by ISO and AGMA rating methods, which do not account for the stress reduction due to the higher contact ratio. A new modification coefficient is proposed to correct these conservative values, which allows the AGMA and ISO geometry factors to remain as no load-dependent factors and keep their actual calculation methods and significance.

对于接触比接近 2 的正齿轮，加载的齿挠度和局部接触变形导致的接触间隔延长可能会使有效接触比超过 2。在这种情况下，载荷至少由两个齿对传递，最大载荷和齿根应力都会降低，因此齿轮等级标准 ISO 和 AGMA 的计算方法提供的结果非常保守。在这项工作中，应用了两种模型来计算负载引起的高接触比外齿轮的齿根应力：(i) 基于最小能量法的负载分担分析模型；(ii) 有限元模型，该模型验证了前一模型得出的结果。获得的应力值与 ISO 和 AGMA 等级评定方法提供的应力值进行了比较，后者没有考虑到接触比增大导致的应力减小。我们提出了一个新的修正系数来修正这些保守值，从而使 AGMA 和 ISO 几何系数保持为不依赖载荷的系数，并保留其实际计算方法和意义。

引用次数: 0

Design and analytical modeling of a double-joint flexible surgical instrument with hand-held isomorphic actuation 手持式同构驱动双关节柔性手术器械的设计与分析建模

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-07 DOI: 10.1016/j.mechmachtheory.2024.105804

In catheter reduction surgeries, surgical instruments with multi-joint end effectors are employed to improve surgery qualities, where implementations of miniaturization design and isomorphic actuation are challenging. In this work, a miniaturized double-joint end effector is designed using a novel multi-backbone mechanism. The backbones are made of spiral-notched tubes that have good axial stiffness and large bending flexibility, and a co-placed backbone arrangement is used to avoid double-joint actuation coupling. A double-joint handle is developed to implement isomorphic actuation of the end effector, where local reinforcement design of the handle is proposed to reduce torsional disturbances on the end effector. A recursive kinematic model of the multi-backbone mechanism is firstly established by relating friction with bending angles in a beam model of the backbones, and forward kinematics from the handle to the end effector is developed. Performance tests show that the double-joint end effector has good actuation decoupling characteristics. Parameter identification is conducted and model accuracy is validated. Phantom model experiments show that the end effector can reach the target position with the double-joint configuration.

在导管缩减手术中，使用带有多关节末端效应器的手术器械来提高手术质量，而小型化设计和同构驱动的实现具有挑战性。在这项工作中，利用新型多骨干机构设计了微型化双关节末端效应器。骨干由具有良好轴向刚度和较大弯曲弹性的螺旋缺口管制成，并采用共置骨干排列以避免双关节驱动耦合。开发了一种双关节手柄，以实现末端效应器的同构驱动，其中提出了手柄的局部加固设计，以减少末端效应器受到的扭转干扰。首先，通过在骨干的梁模型中将摩擦力与弯曲角度联系起来，建立了多骨干机构的递归运动学模型，并开发了从手柄到末端效应器的前向运动学。性能测试表明，双关节末端执行器具有良好的执行解耦特性。进行了参数识别并验证了模型的准确性。幻影模型实验表明，采用双关节配置的末端效应器可以到达目标位置。

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引用次数: 0

A general method to synthesize planar overconstrained mechanism 合成平面超约束机制的一般方法

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-05 DOI: 10.1016/j.mechmachtheory.2024.105801

Traditionally, planar overconstrained mechanisms has been explained through special geometry, which often lacks clarity and specificity. This paper addresses this challenge by introducing two explicit criteria for analyzing and synthesizing planar overconstrained mechanisms. With the criteria, one may synthesize new planar overconstrained systematically and confidently. To create new planar overconstrained mechanisms, three approaches are employed: the parallelogram-aided approach, the stretch-rotation approach, and an optimization-based method. Given that the mobility of mechanisms is independent of the choice of the ground link and that the mathematical treatment of function generation is straightforward, this paper proposes a systematic approach for synthesizing novel function cognates. By combining these approaches, new types of overconstrained mechanisms are discovered. Leveraging advanced computational tools, a special geometric condition for function cognates of inverted slider cranks is found for the first time. Through inversion, the coupler cognates for slider cranks are also identified. The success of these results indicates that the proposed criteria are explicit and crucial for discovering new mechanisms, and the concept may be extended to spherical or spatial cases.

传统上，平面超约束机制是通过特殊几何来解释的，这往往缺乏清晰性和具体性。本文针对这一挑战，提出了两个明确的标准，用于分析和综合平面超约束机制。有了这些标准，人们就可以系统而自信地合成新的平面超约束。为了创建新的平面超约束机构，我们采用了三种方法：平行四边形辅助方法、拉伸旋转方法和基于优化的方法。鉴于机构的流动性与地面链接的选择无关，而且函数生成的数学处理简单明了，本文提出了一种合成新型函数同源物的系统方法。通过结合这些方法，我们发现了新型超约束机制。利用先进的计算工具，本文首次发现了倒置滑块曲柄功能同源物的特殊几何条件。通过反演，还确定了滑块曲柄的耦合器同源物。这些结果的成功表明，所提出的标准是明确的，对于发现新机制至关重要，而且这一概念可以扩展到球形或空间情况。

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引用次数: 0

Simulation and validation of the transmission error, meshing stiffness, and load sharing of planetary spur gear transmissions 行星直齿轮传动装置的传动误差、啮合刚度和负载分担的模拟与验证

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-05 DOI: 10.1016/j.mechmachtheory.2024.105800

Although the load sharing between planets of sequentially phased planetary gear transmissions has been studied in the past, the required solving techniques based on the Finite Element Method result in long time consuming and high computational cost. This limits the possibilities of undertaking extensive studies that take into consideration a high number of cases allowing optimal solutions to be sought or general conclusions drawn. In addition, the determination of the curves of transmission error, time-varying mesh stiffness, and load sharing among tooth pairs in simultaneous contact are also complicated. In this work an analytical model has been developed for the simulation of the time-varying mesh stiffness, quasi-static transmission error, and load sharing ratio between planets and tooth pairs of planetary spur gear transmissions. It is based on similar models for external and internal spur gears previously developed and has been validated by comparison with a hybrid model based on the Finite Element Method and theoretic-experimental correlation.

虽然过去曾对顺序相位行星齿轮传动装置的行星之间的负载分担进行过研究，但所需的基于有限元法的求解技术耗时长、计算成本高。这就限制了对大量案例进行广泛研究的可能性，从而无法寻求最佳解决方案或得出一般性结论。此外，确定传动误差曲线、时变网格刚度和同时接触的齿对之间的载荷分担也很复杂。本研究建立了一个分析模型，用于模拟行星直齿轮传动的时变啮合刚度、准静态传动误差以及行星和齿对之间的负载分担率。该模型基于之前开发的外直齿齿轮和内直齿齿轮的类似模型，并与基于有限元法和理论-实验相关性的混合模型进行了比较验证。

引用次数: 0

Kineto-static analysis of a hybrid manipulator consisting of rigid and flexible limbs with locking function for planar shape morphing 对由具有锁定功能的刚性和柔性肢体组成的混合机械手进行运动静态分析，以实现平面形状变形

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-05 DOI: 10.1016/j.mechmachtheory.2024.105802

The incorporation of lockable passive backbones into active compliant morphing systems efficiently results in lightweight, high-load, and large deformation systems. However, there exist challenges in kineto-static analysis due to the interaction between rigid reconfigurable kinematic constraints and the nonlinear deformation of actuated flexible limbs. This paper addresses these issues by developing a kineto-static method to analyze the motion in a novel planar 3-DOF shape-morphing manipulator. The manipulator features two actuated flexible limbs with a lockable variable geometry truss (LVGT). In this study, two isostatic topologies are selected for reconfigurable motion control under external tip loads. A multi-step sequential control strategy is proposed to maneuver the manipulator's platform for desired poses. Then, a constrained-trajectory-based kinematic model is proposed for an inverse kinematic solution considering motion planning. Subsequently, a kineto-static model is introduced, considering constraints from rigid and flexible limbs, aiming to distribute distributing redundant actuation forces. Finally, nonlinear finite element analysis (FEA) and experiments are carried out to validate the effectiveness of the proposed method.

将可锁定的被动骨架纳入主动顺应变形系统，可有效地实现轻质、高负载和大变形系统。然而，由于刚性可重构运动学约束与致动柔性肢体的非线性变形之间的相互作用，运动静力学分析面临着挑战。本文针对这些问题，开发了一种运动静力学方法，用于分析新型平面 3-DOF 形状变形机械手的运动。该机械手具有两个带可锁定可变几何桁架（LVGT）的致动柔性肢体。在这项研究中，选择了两种等静态拓扑结构，用于外部顶端负载下的可重构运动控制。研究提出了一种多步骤顺序控制策略，以操纵机械手平台实现所需的姿势。然后，提出了一个基于约束轨迹的运动学模型，用于考虑运动规划的逆运动学解决方案。随后，考虑到来自刚性和柔性肢体的约束，引入了运动静态模型，旨在分配多余的驱动力。最后，进行了非线性有限元分析（FEA）和实验，以验证所提方法的有效性。

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引用次数: 0

Non-inertial dynamic modeling and gear mesh characteristic analysis of planetary gear train system 行星齿轮传动系统的非惯性动态建模和齿轮啮合特性分析

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-10-01 DOI: 10.1016/j.mechmachtheory.2024.105794

Floating offshore wind turbines experience periodical platform motions due to waves and currents, which intensify vibrations in wind turbine gearboxes. In these gearboxes, the gear mesh characteristics of the planetary gear train system (PGTS) are vulnerable to vibrations caused by platform motions. However, many PGTS models lack attention to gear mesh characteristics affected by platform motions. This study introduces a novel instantaneous multi-teeth contact model that integrates a loaded tooth contact analysis model with dynamic displacements. A rigid-flexible coupling dynamic model of PGTS that accounts for platform motions is established, and then an efficient iterative solution scheme is developed. The model is validated using the Finite Element Method, and gear mesh characteristics of PGTS are thoroughly analyzed. Simulation results show that resonance exacerbates dynamic gear meshing force and stiffness fluctuations, leading to significant deviations from static values. Platform motions disturb contact force distribution, increase peak forces and fluctuations, and pose a risk of tooth disengagement. The axial vibration frequencies and amplitudes of the ring gear tooth correlate with base motions, suggesting potential applications in gear mesh state monitoring.

由于波浪和水流的影响，漂浮的海上风力涡轮机会经历周期性的平台运动，这加剧了风力涡轮机齿轮箱的振动。在这些齿轮箱中，行星齿轮传动系统（PGTS）的齿轮啮合特性很容易受到平台运动引起的振动的影响。然而，许多 PGTS 模型缺乏对受平台运动影响的齿轮啮合特性的关注。本研究引入了一种新颖的瞬时多齿接触模型，该模型集成了加载齿接触分析模型和动态位移。建立了考虑平台运动的 PGTS 刚柔耦合动态模型，然后开发了高效的迭代求解方案。利用有限元法对模型进行了验证，并对 PGTS 的齿轮啮合特性进行了深入分析。仿真结果表明，共振加剧了动态齿轮啮合力和刚度波动，导致与静态值的显著偏差。平台运动扰乱了接触力分布，增加了峰值力和波动，并带来了轮齿脱离的风险。环形齿轮齿的轴向振动频率和振幅与基座运动相关，这表明齿轮啮合状态监测具有潜在的应用价值。

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引用次数: 0

Exact constraint design of bridge-type displacement flexure amplifier 桥式位移挠性放大器的精确约束设计

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-09-25 DOI: 10.1016/j.mechmachtheory.2024.105799

Bridge-type amplifiers are commonly used to increase the effective actuation stroke of piezoelectric stack actuators owing to their compact size. However, the traditional bridge-type amplifier has an unconstrained degree-of-freedom, which yields large parasitic motions when subject to offset loads and induces dynamic performance losses related to underconstrained resonance. This work presents an exact constraint design (ECD) of bridge-type amplifier, in which a semi-bridge is introduced for both the lower bridge and the upper bridge on the basis of the traditional bridge-type amplifier. A holistic theoretical model is established for the whole bridge-type amplifier without reducing it to a half or even a quarter by taking advantage of structural symmetry. The model is generalized so that it can be used for modeling the traditional, the compound and the ECD amplifiers. Based on the model, three different bridge-type amplifiers considering manufacturing errors are modeled and compared, and the results show that the ECD amplifier is more precise in achieving desired motion and more robust against manufacturing imperfections. All the results are verified by those of the finite element models.

桥式放大器由于体积小巧，通常用于增加压电叠层致动器的有效致动冲程。然而，传统的桥式放大器具有无约束自由度，在承受偏移负载时会产生较大的寄生运动，并导致与无约束共振有关的动态性能损失。本研究提出了桥式放大器的精确约束设计（ECD），在传统桥式放大器的基础上，为下桥和上桥引入了半桥。利用结构对称性，为整个桥式放大器建立了一个整体理论模型，而没有将其简化为半桥甚至四分之一桥。该模型具有通用性，可用于传统、复合和 ECD 放大器的建模。结果表明，ECD 放大器在实现理想运动方面更加精确，对制造缺陷的抵抗能力更强。所有结果都得到了有限元模型的验证。

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引用次数: 0

Application of instantaneous invariants to Cardan positions for two parameters complex plane motion 将瞬时不变式应用于双参数复平面运动的卡丹位置

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-09-23 DOI: 10.1016/j.mechmachtheory.2024.105798

This paper aims to represent the Cardan position in the complex plane using Bottema’s instantaneous invariants for two parameters motions. The study provides unchanging and simple quantities that simplify the analysis of complicated mechanical systems by determining complex number representations of Bottema’s instantaneous invariants for Cardan motions with two parameters. The method involves illustrating invariants based on two parameters in the complex plane, defining cycloidal and Cardan motions of two parameters, and deriving the conditions for the Cardan positions. The key results are the necessary and sufficient conditions for the Cardan position for two-parameter motions in the complex plane obtained based on these instantaneous invariants.

本文旨在使用双参数运动的 Bottema 瞬时不变量来表示复平面中的万向位置。该研究通过确定双参数卡丹运动的 Bottema 瞬时不变量的复数表示，提供了不变的简单量，从而简化了复杂机械系统的分析。该方法包括在复平面上说明基于两个参数的不变量，定义两个参数的摆线运动和卡丹运动，并推导出卡丹位置的条件。主要结果是基于这些瞬时不变式得到的复平面内双参数运动的卡丹位置的必要条件和充分条件。

引用次数: 0

Dynamic inversion and optimal tracking control on the ball-plate system based on a linearized nonholonomic multibody model 基于线性化非整体多体模型的球-板系统动态反转和优化跟踪控制

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-09-21 DOI: 10.1016/j.mechmachtheory.2024.105795

This paper addresses the optimal control of the ball-plate system, a well-known nonholonomic system in the context of nonprehensile manipulation, using a multibody dynamics approach. The trajectory tracking control of a steady-state circular motion of the ball on the plate, for any radius and potentially off-centric with respect to the plate’s pivoting point, is achieved by designing a Linear-Quadratic Regulator. A spatial multibody model of the ball-plate system is considered. A key contribution is the analytical computation of the circular steady motion of the ball by dynamic inversion, including the control actions to achieve this reference solution. This enables the analytical computation of the linearized equations along this reference motion, resulting in a periodic linear time-varying (LTV) system, and the application of linear controllability criteria for LTV systems. A controllable linear system, involving the Cartesian coordinates of the contact point and the yaw angle of the sphere, is obtained using a convenient coordinate partition in the linearization. Compared to existing results on the same problem, closed-loop stability about the desired trajectory is achieved for any radius of the circular trajectory.

球-板系统是一种著名的非全局系统，本文采用多体动力学方法对其进行优化控制。通过设计一个线性-二次调节器，可实现对球在板上的稳态圆周运动的轨迹跟踪控制，该运动的半径不限，且可能相对于板的支点偏离中心。考虑了球-板系统的空间多体模型。其主要贡献在于通过动态反演分析计算了球的圆周稳定运动，包括实现该参考解的控制行动。这样就能分析计算出沿着该参考运动的线性化方程，从而形成周期性线性时变（LTV）系统，并应用 LTV 系统的线性可控性标准。在线性化过程中，利用方便的坐标分割，得到了一个涉及接触点笛卡尔坐标和球体偏航角的可控线性系统。与关于同一问题的现有结果相比，在圆轨迹的任何半径上都能实现对所需轨迹的闭环稳定性。

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引用次数: 0

Analytical determination of the optimal effective regular workspace of a 6-6 Stewart platform manipulator for a specified orientation workspace 分析确定指定方向工作空间的 6-6 斯图尔特平台机械手的最佳有效规则工作空间

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-09-20 DOI: 10.1016/j.mechmachtheory.2024.105791

This article presents an analytical method to identify the largest effective regular workspaces (ERWs) of a class of 6-6 Stewart platform manipulators for a given orientation workspace. The ERWs are modelled as spheres. The orientation workspace is specified in terms of ranges of Euler angles, as is the standard practice in the parallel robot industry. The radius of the said sphere is maximised through an optimisation problem, which is solved analytically. Consequently, the results obtained are exact in nature. The analytical formulation of the problem and its exact solutions constitute the novel theoretical contributions of this article. Moreover, since the results hold good over a given subset of

SO (3)

, the proposed method obviates the need for numerical scanning of the orientation workspaces in design-related computations, thus improving the accuracy, robustness, as well as computational efficiency. Finally, the significance of the neutral height in harnessing the desired extents of position and orientation workspaces has been established through parametric studies. The formulations are illustrated via applications to Stewart platform manipulators of three distinct platform dimensions.

本文提出了一种分析方法，用于确定一类 6-6 斯图尔特平台机械手在给定方向工作空间内的最大有效规则工作空间（ERW）。ERW 以球体为模型。按照并联机器人行业的标准做法，以欧拉角的范围来指定方向工作空间。所述球体的半径通过一个优化问题达到最大化，该问题通过解析法求解。因此，得到的结果是精确的。问题的分析表述及其精确解构成了本文新颖的理论贡献。此外，由于结果适用于 SO(3) 的给定子集，因此在与设计相关的计算中，所提出的方法无需对方位工作区进行数值扫描，从而提高了准确性、稳健性和计算效率。最后，通过参数研究确定了中性高度在利用位置和方向工作空间的理想范围方面的重要性。这些公式应用于三种不同平台尺寸的斯图尔特平台机械手。

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引用次数: 0

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