Mechanism and Machine Theory最新文献

Derailment mechanism analysis of subway vehicles under air spring failure 空气弹簧失效下地铁车辆脱轨机理分析

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-11 DOI: 10.1016/j.mechmachtheory.2025.106316

Bo Wang , Qing Wu , Hailiang Yu , Weihua Ma , Feng Lin , Xiangyu Li , Xueqiang Zhang

To analyze the derailment mechanism of a subway train under air spring failure conditions and to identify improvement measures, this study first establishes a dynamic train model according to the actual train formation. Subsequently, equivalent models for air spring failure are introduced. Finally, based on wheel–rail derailment theory and vehicle system dynamics, a comparative analysis is conducted under both normal (inflated) and failed air spring conditions to investigate key factors influencing the derailment mechanism. Corresponding improvement measures are then proposed. The results indicate that: (1) with air spring failure, curve transition derails the train; (2) multiple factors can effectively lower derailment risks; (3) large lateral creep force and attack angle are not necessary conditions for flange climbing; and (4) installing guard rails at curve exits and applying lubrication to the rails can effectively reduce flange climbing risk under air spring failure. This study provides valuable insights for subway track design and for mitigating derailment risks in the event of air spring failure.

为了分析空气弹簧失效条件下地铁列车的脱轨机理，确定改进措施，本研究首先根据实际列车编队建立了动态列车模型。随后，介绍了空气弹簧失效的等效模型。最后，基于轮轨脱轨理论和车辆系统动力学，对正常（充气）空气弹簧和失效空气弹簧进行了对比分析，探讨了影响轮轨脱轨机理的关键因素。并提出了相应的改进措施。结果表明：(1)空气弹簧失效时，曲线过渡使列车脱轨；(2)多因素有效降低脱轨风险；(3)侧向蠕变力大、攻角大不是法兰爬升的必要条件；(4)在弯道出口处安装护栏并对护栏进行润滑，可有效降低空气弹簧失效时法兰爬升的风险。该研究为地铁轨道设计和减少空气弹簧失效时的脱轨风险提供了有价值的见解。

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引用次数: 0

Driving rotational motion with Euler parameters: a constraint formulation for multibody systems 用欧拉参数驱动旋转运动：多体系统的约束公式

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-10 DOI: 10.1016/j.mechmachtheory.2025.106315

Madalena Antunes, João Folgado, Carlos Quental

The formulation of rotational driving constraints using angular variables (angle-based formulation) may introduce numerical instabilities and redundancy among kinematic constraints, which can compromise the robustness of multibody analyses. This study proposes an alternative Euler-based formulation, in which Euler parameters, describing the relative orientation between joint-connected bodies, are used to define rotational driving constraints. This formulation avoids singularities, enables full range of motion evaluation, and eliminates redundancy. Both angled-based and Euler-based formulations were applied to different joints within both open and closed kinematic chains using an in-house multibody model of the human body. Kinematic and inverse dynamic analyses were conducted across several movements from multiple subjects, and the results were compared between the two formulations and literature data. The Euler-based formulation provided independent kinematic constraints and showed good agreement with joint kinematics and torques from established methods. In addition, it improved computational efficiency. Overall, the use of Euler parameters offers a robust and efficient alternative to angle-based formulations for rotational driving constraints in multibody system dynamics.

使用角度变量的旋转驱动约束公式（基于角度的公式）可能会引入数值不稳定性和运动约束之间的冗余，从而影响多体分析的鲁棒性。本研究提出了一种基于欧拉的替代公式，其中欧拉参数用于描述关节连接体之间的相对方向，以定义旋转驱动约束。这个公式避免了奇点，使全范围的运动评估，并消除了冗余。使用人体内部多体模型，将基于角度和基于欧拉的公式应用于开放和封闭运动链中的不同关节。运动学和逆动力学分析在多个受试者的几个运动中进行，并将结果与两种公式和文献数据进行比较。基于欧拉的公式提供了独立的运动学约束，并与现有方法的关节运动学和扭矩具有良好的一致性。此外，它还提高了计算效率。总的来说，欧拉参数的使用为多体系统动力学中旋转驱动约束的基于角度的公式提供了一种鲁棒和高效的替代方案。

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引用次数: 0

Type synthesis of reconfigurable single-loop mechanisms based on transitional configurations 基于过渡构型的可重构单环机构类型综合

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-06 DOI: 10.1016/j.mechmachtheory.2025.106306

Jun Cai , Wang Yu , Bing Li , Sen Wang , Fujun Peng

This paper presents a general type synthesis methodology for reconfigurable single-loop mechanisms (RSLMs). Unlike conventional approaches that derive RSLMs from classical configurations, this study investigates constraint system variations during transitional configurations of RSLMs. When the RSLM is in transitional configuration, the order of wrench systems reaches its peak. Utilizing this characteristic, we categorize wrench systems according to their order and type, then construct the original single-loop mechanism through the closure of the corresponding wrench system's open-loop kinematic chains. Subsequently, while maintaining the original wrench system configuration, kinematic pairs are added. Further analysis of inactive joints and mechanism reconfiguration characteristics, the optimized RSLM configuration is synthesized. The proposed method generates more generalized RSLM configurations and ensures that the RSLM created is in transitional configurations, thereby facilitating subsequent motion pattern analysis. As validation, multiple novel 6R and 7R RSLMs with single DOF reconfigurability have been successfully synthesized, demonstrating the method's feasibility and effectiveness. Finally, optimization strategies for eliminating inactive joints and structural refinement are proposed. Two application-oriented prototypes are presented to exemplify the practical potential of the synthesized RSLMs.

本文提出了可重构单环机构的一般类型综合方法。与从经典构型推导rslm的传统方法不同，本研究考察了rslm过渡构型中的约束系统变化。当RSLM处于过渡构型时，扳手系统的顺序达到峰值。利用这一特性，对扳手系统按顺序和类型进行分类，并通过闭合相应扳手系统的开环运动链来构造原始的单环机构。随后，在保持原有扳手系统配置的同时，增加了运动副。进一步分析了非活动关节和机构重构特征，综合了优化后的RSLM构型。该方法生成了更一般化的RSLM构型，并确保所创建的RSLM处于过渡构型，从而便于后续的运动模式分析。作为验证，成功合成了多个具有单自由度可重构性的新型6R和7R rslm，验证了该方法的可行性和有效性。最后，提出了消除非活动关节和结构精细化的优化策略。提出了两个面向应用的原型，以说明综合rslm的实际潜力。

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引用次数: 0

Layout optimization of compliant mechanism with embedded components using moving morphable component (MMC) method 基于移动可变形构件法的嵌入式柔性机构布局优化

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-04 DOI: 10.1016/j.mechmachtheory.2025.106301

Min Liu , Liwen Lu , Jinqing Zhan , Benliang Zhu , Hua Wang , Xianmin Zhang

This paper proposes a single explicit topology optimization method based on the moving morphable component framework for the integrated design of the movable components and compliant mechanism. The core of this method lies in the unified use of explicit geometric parameters (size and pose) to describe the topological configuration and layout of the mechanism and embedded components, avoiding the model complexity and dual sensitivity analysis issues associated with hybrid description frameworks. Based on this unified description framework, a topological description function for the compliant mechanism with embedded components is constructed, and finite element analysis is performed using the ersatz material model. Under the volume constraint of the host structure, an optimization model is established with the goal of maximizing the output displacement. Sensitivity analysis is done analytically, and the design variables are updated using the method of moving asymptotes approach. Numerical examples verify the effectiveness of this method in the integrated design of embedded components and compliant mechanisms.

提出了一种基于可动构件框架的单显式拓扑优化方法，用于可动构件与柔性机构的集成设计。该方法的核心在于统一使用显式几何参数（尺寸和位姿）来描述机构和嵌入式部件的拓扑构型和布局，避免了混合描述框架的模型复杂性和双灵敏度分析问题。在此统一描述框架的基础上，构建了嵌入式构件柔性机构的拓扑描述函数，并利用伪材料模型进行了有限元分析。在主体结构体积约束下，以输出位移最大化为目标，建立了优化模型。采用解析法进行灵敏度分析，并采用移动渐近线法更新设计变量。数值算例验证了该方法在嵌入式构件与柔性机构集成设计中的有效性。

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引用次数: 0

Closed-form forward kinematics, singularity, dexterity and workspace analyses of a special class of 3-RRR spherical parallel mechanisms 一类特殊的3-RRR球面并联机构的闭式正运动学、奇异性、灵巧性和工作空间分析

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-04 DOI: 10.1016/j.mechmachtheory.2025.106288

Shuai Zhang , Wei Li , Huayan Pu , Rui Chen , Jun He , Jun Luo

3-RRR spherical parallel mechanisms (SPMs) are capable of producing three-DOF spherical motion, which can find applications in various fields. This paper investigates the kinematics and workspace performance of a particular class of 3-RRR SPMs, characterized by coaxial input-joint axes, coplanar distal-joint axes, and six orthogonal links. First, two novel formulations are proposed for the forward kinematics (FK) of this robot class, both resulting in linear univariate polynomials that significantly streamline the FK formulation and reduce the computational complexity. Moreover, this robot class exhibits minimal and physically interpretable singularity loci in both the orientation workspace and the input joint space, greatly facilitating singularity avoidance and path planning. Furthermore, local and global dexterity indices are employed to analyze the mechanism’s performance, from which the architectural parameters yielding optimal dexterity are identified. Finally, the robot class demonstrates a considerably large tilt-torsion orientation workspace when the architectural parameters and link shapes are appropriately selected, allowing for infinite torsional motion when pointed within almost a hemisphere. The foregoing features make the robot class potentially promising in a wide range of applications.

3-RRR球面并联机构（SPMs）具有三自由度球面运动的能力，在各个领域都有广泛的应用。本文研究了一类具有同轴输入关节轴、共面远关节轴和六个正交连杆的3-RRR SPMs的运动学和工作空间性能。首先，对该类机器人的正运动学（FK）提出了两种新颖的公式，均得到线性单变量多项式，大大简化了FK的公式，降低了计算复杂度。此外，该类机器人在姿态工作空间和输入关节空间中都具有最小且物理可解释的奇异轨迹，极大地促进了奇异避免和路径规划。此外，采用局部和全局灵巧度指标分析机构的性能，从而确定最优灵巧度的结构参数。最后，当适当选择结构参数和连杆形状时，机器人类展示了相当大的倾斜-扭转方向工作空间，当指向几乎一个半球时，允许无限扭转运动。上述特点使得该类机器人具有广泛的应用前景。

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引用次数: 0

Optimal control approach for trajectory determination to suppress residual frame vibrations of delta robots in pick and place tasks delta机器人拾取任务中抑制机架残余振动的轨迹确定最优控制方法

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-02 DOI: 10.1016/j.mechmachtheory.2025.106302

Nils Brückmann , Christian Mirz , Mathias Hüsing , Yukio Takeda , Burkhard Corves

This paper proposes an optimal control approach to reduce frame vibrations in robotic pick and place tasks, caused by rapid acceleration and deceleration of the robot. The objective of the proposed optimal control approach is to determine time-optimal trajectories that cancel out residual frame vibrations after trajectory execution. The control problem is defined for a delta robot but can be adapted to any type of robot used for pick and place tasks. To solve the optimal control problem numerically, it is transformed into a nonlinear programming problem using the Legendre-Gauss-Lobatto collocation method. To validate the approach, experiments are conducted to compare the residual frame vibrations of optimized trajectories with typical pick and place trajectories. The novelty of the paper is the vibration reduction with an optimization-based approach on a complex multi-degree-of-freedom robot system whose dynamic parameters are identified with experimental data. In addition, a mathematical description of all constraints required for a robotic pick and place task is proposed for the optimization.

本文提出了一种最优控制方法，以减少机器人在拾取和放置任务中由于机器人的快速加减速而引起的机架振动。所提出的最优控制方法的目标是确定时间最优的轨迹，以消除轨迹执行后残留的框架振动。控制问题是为delta机器人定义的，但可以适用于任何类型的机器人用于拾取和放置任务。采用legende - gaas - lobatto配置法将最优控制问题转化为非线性规划问题，实现了最优控制问题的数值求解。为了验证该方法，通过实验将优化后的轨迹与典型的拾取轨迹的残余框架振动进行了比较。本文的新颖之处在于利用实验数据识别复杂多自由度机器人系统的动态参数，并采用基于优化的方法进行减振。此外，提出了机器人拾取和放置任务所需的所有约束的数学描述，以进行优化。

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引用次数: 0

Enhanced obstacle-crossing capability of redundantly actuated wheel-legged robot through dynamic stability and actuation pattern analyses 通过对冗余驱动轮腿机器人的动态稳定性和驱动模式分析，增强了其越障能力

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-02 DOI: 10.1016/j.mechmachtheory.2025.106305

Bike Zhu, Jun He, Feng Gao

The exploration of challenging terrains requires robotic systems with advanced mobility and adaptability. However, maintaining stability and maneuverability while traversing obstacles remains a significant challenge for such systems. Redundantly actuated wheel-legged rovers present a promising solution by introducing additional degrees of actuation, enabling more optimized motion strategies and enhanced overall performance. This paper focuses on enhancing the obstacle-crossing capability of these systems by analyzing the dynamic stability criteria and actuation patterns, using the TAWL rover as demonstration. Firstly, the dynamic models of the TAWL rover’s individual leg and the whole body are established, and the dynamic stability criteria are introduced. Secondly, the actuation patterns of the redundant system are analyzed to identify feasible actuation patterns and evaluate associated energy consumption. Thirdly, enhanced obstacle-crossing strategies are proposed, consisting of two components: increasing the rover’s maximum obstacle-crossing height and improving its stability when traversing specific obstacles. Finally, the proposed method is validated on the TAWL rover. The results demonstrate that the proposed method enables the rover to achieve maximum obstacle-crossing height and exhibit superior stability margin while traversing obstacles.

探索具有挑战性的地形需要具有先进机动性和适应性的机器人系统。然而，在穿越障碍物时保持稳定性和机动性仍然是这种系统面临的重大挑战。冗余驱动轮腿漫游者通过引入额外的驱动度，实现更优化的运动策略和增强的整体性能，提供了一个有前途的解决方案。本文以TAWL探测车为例，分析了该系统的动态稳定性准则和驱动模式，重点研究了如何提高该系统的越障能力。首先，建立了TAWL漫游车单腿和整体的动力学模型，并引入了其动态稳定性准则；其次，对冗余系统的驱动模式进行了分析，确定了可行的驱动模式，并对相关能耗进行了评估。第三，提出了增强的越障策略，包括提高漫游车的最大越障高度和提高漫游车在穿越特定障碍物时的稳定性两部分。最后，在TAWL漫游车上对该方法进行了验证。结果表明，该方法能使漫游车在越障过程中获得最大越障高度和优越的稳定裕度。

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引用次数: 0

Knowledge-enhanced optimization of a mobile parallel robot considering topological structure and dimensions 考虑拓扑结构和尺寸的移动并联机器人的知识增强优化

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-12-01 DOI: 10.1016/j.mechmachtheory.2025.106303

Binbin Lian , Qiqi Dong , Xinming Huo , Zihou Yuan , Qi Li , Tao Sun

Mobile parallel robots, formed by mounting parallel mechanisms on AGVs, combine merits of both automatic transporting and high-precision operation of large-scale parts. Optimal design of mobile parallel robots faces two key challenges: (1) co-optimizing topology of AGV frame and dimension of parallel module, (2) difficulty in embedding domain knowledge to the conventional “black-box” optimization. To address these, we propose a knowledge-enhanced optimization framework. Kinematic, stiffness, and mass models of parallel module, as well as surrogate model of AGV frame are established. A knowledge base is built by explicit knowledge from engineering and knowledge extraction through cluster analysis. Hard and soft constraints are defined, in which soft constraints are embedded to objective. Initial population of optimization searching is determined by preference-domain cluster, and a knowledge-guided multi-objective algorithm is developed. Comparative study to the optimization without knowledge injection show that Pareto front solutions of our method concentrate densely in designer-preferred regions. It achieves 36.45 % higher preference-aligned performance and shows accelerated convergence with stabilized HV progression curves. The framework effectively addresses co-optimization challenges by knowledge fusion and preference guidance.

移动并联机器人是将并联机构安装在agv上形成的，兼具大型零件自动输送和高精度操作的优点。移动并联机器人的优化设计面临两个关键挑战：(1)AGV框架拓扑与并联模块尺寸的协同优化；(2)传统的“黑箱”优化难以嵌入领域知识。为了解决这些问题，我们提出了一个知识增强的优化框架。建立了并联模块的运动学模型、刚度模型和质量模型以及AGV车架的代理模型。从工程中获取显性知识，通过聚类分析提取知识，构建知识库。定义了硬约束和软约束，其中软约束嵌入到目标中。利用偏好域聚类确定优化搜索的初始种群，提出了一种知识引导的多目标算法。与无知识注入优化的对比研究表明，该方法的Pareto前解密集地集中在设计人员偏好的区域。在稳定的HV级数曲线下，该算法的优先对准性能提高了36.45%，收敛速度加快。该框架通过知识融合和偏好引导有效地解决了协同优化挑战。

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引用次数: 0

Design and reinforcement learning-based locomotion gait planning for an 8-bar single-loop transformable robot 基于强化学习的8杆单回路可变形机器人运动步态规划设计

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-11-30 DOI: 10.1016/j.mechmachtheory.2025.106304

Meng Zhao, Zoulang Qin, Wenxuan Cheng, Ruiming Li, Hui Yang, Yezhuo Li, Jianxu Wu

Transformable robots with closed-chain mechanisms that exhibit underactuated and nonlinear dynamics pose a formidable challenge in gait planning. This paper introduces a two-stage reinforcement learning (RL) framework that bypasses the need for accurate system modeling to autonomously discover and refine locomotion gaits. We apply this method to an 8-bar single-loop transformable robot, whose kinematic analysis confirms its reconfigurability and variable degrees of freedom (DoF) nature. Our approach successfully generating two distinct and functional gaits: a stable peristaltic gait and a dynamic rolling gait that strategically leverages singular configurations. Extensive experiments on a physical prototype validate the gaits’ effectiveness across various terrains, with the robot achieving displacements of up to 870 mm at speeds of 8.7 mm/s. This work demonstrates a learning-based paradigm for planning complex locomotion in reconfigurable robotic systems.

具有闭链机构的变形机器人表现出欠驱动和非线性动力学特性，对步态规划提出了严峻的挑战。本文介绍了一种两阶段强化学习（RL）框架，该框架不需要精确的系统建模来自主发现和改进运动步态。将该方法应用于一个8杆单回路可变形机器人，运动学分析证实了该机器人的可重构性和可变自由度。我们的方法成功地生成了两种不同的功能性步态：稳定的蠕动步态和动态的滚动步态。在物理样机上进行的大量实验验证了步态在各种地形上的有效性，机器人在8.7毫米/秒的速度下实现了高达870毫米的位移。这项工作展示了一种基于学习的范式，用于规划可重构机器人系统中的复杂运动。

引用次数: 0

Flank modification and meshing analysis of harmonic drives with controlled backlash 可控间隙谐波传动的侧面修正与啮合分析

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2025-11-27 DOI: 10.1016/j.mechmachtheory.2025.106296

Xinzi Li, Chaosheng Song, Hailan Song

To address the challenge of correlating tooth flank modification design with meshing performance in harmonic drives, this study proposes an optimization method for meshing characteristics based on the control of meshing backlash. First, geometric models of the flexspline (produced by hobbing) and circular spline (produced by power skiving) are established. Subsequently, a computational procedure for determining meshing backlash in harmonic drives, incorporating tooth flank modification, is developed based on kinematic modeling. Finite element analysis is then employed to investigate the relationship between tooth flank modification, backlash distribution, and contact characteristics. The results indicate that controlling the meshing backlash through tooth flank modification shifts the contact pattern on the flexspline tooth surface from the heel to the toe region, reducing the maximum contact pressure by approximately 33.75% under rated torque and 31.03% during start-stop torque. This approach effectively mitigates the stress concentration and uneven load distribution observed in zero-backlash modification designs.

针对谐波传动中齿面修形设计与啮合性能之间的关系，提出了一种基于啮合间隙控制的啮合特性优化方法。首先，建立了柔键（滚刀加工）和圆花键（动力刨削加工）的几何模型。随后，在运动学建模的基础上，建立了包含齿面修正的谐波传动啮合间隙的计算方法。采用有限元分析方法研究了齿面修形、齿隙分布和接触特性之间的关系。结果表明：通过齿侧修形控制啮合间隙，使柔花键齿面接触模式由足跟区转移到趾部，最大接触压力在额定转矩下降低约33.75%，在启停转矩下降低约31.03%。这种方法有效地缓解了应力集中和不均匀荷载分布观察到的零侧隙修改设计。

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引用次数: 0