Pub Date : 2026-03-01Epub Date: 2025-12-29DOI: 10.1016/j.mechmachtheory.2025.106336
Zecun Guo , Chuanying Wang , Dong Wang , Luwei Liu , Ziyi Ding , Kaixuan Chen , Tao Sun
The sheet metal pose adjustment equipment for stamping production lines faces three challenges: high-speed, heavy-load, and double operating modes. This paper proposes a new type of dual-robot system to meet the application requirements of sheet metal pose adjustment. The pose adjustment mechanism innovatively decouples the load inertia force from gravity through the combination of ball transfer units and a planar parallel mechanism. The pose adjustment system can complete the pose adjustment operation of a 3.2-ton load within 0.45 s. A dual-robot design method is proposed, which takes into account the elastic dynamic behavior and reliability of key structural components. The external layer of this method optimizes the scale-structure-drive parameters of the planar mechanism, while the internal layer optimizes the layout parameters of the ball transfer units for the parameter combinations determined by the external layer, achieving the integrated design of the dual-robot system. Through this optimization, the in-plane linear stiffness of the dual-robot positioning system is increased by 17.6 %, the driving force is reduced by 12.4 %, and the natural frequency is improved by 16.3 %.
{"title":"Integrated design of scale-structure-drive for high-speed and heavy-load dual-robot pose adjustment system","authors":"Zecun Guo , Chuanying Wang , Dong Wang , Luwei Liu , Ziyi Ding , Kaixuan Chen , Tao Sun","doi":"10.1016/j.mechmachtheory.2025.106336","DOIUrl":"10.1016/j.mechmachtheory.2025.106336","url":null,"abstract":"<div><div>The sheet metal pose adjustment equipment for stamping production lines faces three challenges: high-speed, heavy-load, and double operating modes. This paper proposes a new type of dual-robot system to meet the application requirements of sheet metal pose adjustment. The pose adjustment mechanism innovatively decouples the load inertia force from gravity through the combination of ball transfer units and a planar parallel mechanism. The pose adjustment system can complete the pose adjustment operation of a 3.2-ton load within 0.45 s. A dual-robot design method is proposed, which takes into account the elastic dynamic behavior and reliability of key structural components. The external layer of this method optimizes the scale-structure-drive parameters of the planar mechanism, while the internal layer optimizes the layout parameters of the ball transfer units for the parameter combinations determined by the external layer, achieving the integrated design of the dual-robot system. Through this optimization, the in-plane linear stiffness of the dual-robot positioning system is increased by 17.6 %, the driving force is reduced by 12.4 %, and the natural frequency is improved by 16.3 %.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106336"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-04DOI: 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.
{"title":"Layout optimization of compliant mechanism with embedded components using moving morphable component (MMC) method","authors":"Min Liu , Liwen Lu , Jinqing Zhan , Benliang Zhu , Hua Wang , Xianmin Zhang","doi":"10.1016/j.mechmachtheory.2025.106301","DOIUrl":"10.1016/j.mechmachtheory.2025.106301","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106301"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Design and reinforcement learning-based locomotion gait planning for an 8-bar single-loop transformable robot","authors":"Meng Zhao, Zoulang Qin, Wenxuan Cheng, Ruiming Li, Hui Yang, Yezhuo Li, Jianxu Wu","doi":"10.1016/j.mechmachtheory.2025.106304","DOIUrl":"10.1016/j.mechmachtheory.2025.106304","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106304"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-24DOI: 10.1016/j.mechmachtheory.2025.106314
Paul Milenkovic , Zinan Wang , Jose I Rodriguez
A singularity encirclement procedure determines all feasible displacement paths of a 6-axis serial-link robot radiating from isolated, coincident or nearly coincident singularities. Points on these paths supply alternative inverse-kinematic solutions of the robot in the neighborhood of these singularities. The encirclement maintains a constant sum-of-squared joint-angle distance from the associated path bifurcation. This is accomplished by following an intended displacement path of the robot in coordination with a deviation from this path. Where the encircling path crosses through zero deviation identifies a point on a feasible zero-deviation robot path radiating from the bifurcation. Differing from the prior applications of this method, which do not include robots, some but not all coincident singularity pairs require two deviation directions. A novel procedure employing matrix regularization facilitates this identification by bringing nearly coincident singularities into coincidence and by calculating multiple deviations direction corresponding to multiple coincident singularities.
{"title":"Encircling singularities of a serial robot to find alternative inverse-kinematic solutions","authors":"Paul Milenkovic , Zinan Wang , Jose I Rodriguez","doi":"10.1016/j.mechmachtheory.2025.106314","DOIUrl":"10.1016/j.mechmachtheory.2025.106314","url":null,"abstract":"<div><div>A singularity encirclement procedure determines all feasible displacement paths of a 6-axis serial-link robot radiating from isolated, coincident or nearly coincident singularities. Points on these paths supply alternative inverse-kinematic solutions of the robot in the neighborhood of these singularities. The encirclement maintains a constant sum-of-squared joint-angle distance from the associated path bifurcation. This is accomplished by following an intended displacement path of the robot in coordination with a deviation from this path. Where the encircling path crosses through zero deviation identifies a point on a feasible zero-deviation robot path radiating from the bifurcation. Differing from the prior applications of this method, which do not include robots, some but not all coincident singularity pairs require two deviation directions. A novel procedure employing matrix regularization facilitates this identification by bringing nearly coincident singularities into coincidence and by calculating multiple deviations direction corresponding to multiple coincident singularities.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106314"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The precise control of ship-mounted rotary cranes is critically challenged by their inherent underactuation, strong nonlinear coupling between boom motion and payload swing, and persistent wave-induced ship disturbances. While advanced control strategies (e.g., sliding mode control, adaptive control) have been developed, many existing designs either rely on model linearization, lack rigorous finite-time stability guarantees for the fully coupled system, or exhibit limited robustness against compound time-varying disturbances. To address these gaps, this paper proposes a novel adaptive non-singular fast terminal sliding mode (ANFTSM) controller. Its core innovation is a newly constructed sliding surface that explicitly integrates errors from both actuated and underactuated states, ensuring the finite-time convergence of all system variables. Enhanced robustness is achieved through adaptive laws that estimate and compensate for unknown friction and wind disturbances in real time, without requiring prior knowledge of disturbance bounds. Importantly, the controller is derived directly from the full nonlinear dynamics, forgoing any linearization, and its global stability is rigorously proven via Lyapunov theory. Extensive comparative experiments demonstrate that the proposed controller outperforms established benchmarks (PD-SMC, OFC, BBC). Under nominal conditions, it achieves the fastest convergence times (8.06 [s] for luffing, 8.56 [s] for rotation) and superior swing suppression, limiting the maximum radial sway to merely 2.05 [deg]. Furthermore, it maintains excellent robustness against significant parameter variations (e.g., load mass, cable length) and non-zero initial swing angles. These performance gains are accomplished with the lowest total control effort (70 [N · m · s]) among all compared methods, confirming its superior energy efficiency alongside outstanding control performance.
船载旋转起重机固有的欠驱动、臂架运动与载荷摆动之间强烈的非线性耦合以及持续的波浪扰动对其精确控制提出了严峻的挑战。虽然先进的控制策略（如滑模控制、自适应控制）已经开发出来，但许多现有的设计要么依赖于模型线性化，对完全耦合系统缺乏严格的有限时间稳定性保证，要么对复合时变扰动的鲁棒性有限。为了解决这些问题，本文提出了一种新的自适应非奇异快速终端滑模控制器（ANFTSM）。其核心创新是新构建的滑动面，该滑动面明确地集成了驱动和欠驱动状态的误差，确保了所有系统变量的有限时间收敛。增强的鲁棒性是通过自适应律来实现的，该律实时估计和补偿未知的摩擦和风扰动，而不需要事先知道扰动边界。重要的是，控制器是直接从完全非线性动力学推导出来的，放弃了任何线性化，并通过李雅普诺夫理论严格证明了其全局稳定性。大量的对比实验表明，所提出的控制器优于既定的基准（PD-SMC， OFC， BBC）。在标称条件下，它实现了最快的收敛时间（变幅8.06 [s]，旋转8.56 [s]）和优越的摆幅抑制，将最大径向摆动限制在2.05[度]。此外，它对重大参数变化（例如，负载质量，电缆长度）和非零初始摆角保持出色的鲁棒性。在所有比较的方法中，这些性能增益是以最低的总控制努力（70 [N · m · s]）完成的，证实了其优越的能源效率和出色的控制性能。
{"title":"Improved non-singular fast terminal sliding mode control for 4DOF ship-mounted rotary cranes","authors":"Zijie Wu , Huimin Ouyang , Menghua Zhang , Tongtong Liu","doi":"10.1016/j.mechmachtheory.2025.106329","DOIUrl":"10.1016/j.mechmachtheory.2025.106329","url":null,"abstract":"<div><div>The precise control of ship-mounted rotary cranes is critically challenged by their inherent underactuation, strong nonlinear coupling between boom motion and payload swing, and persistent wave-induced ship disturbances. While advanced control strategies (e.g., sliding mode control, adaptive control) have been developed, many existing designs either rely on model linearization, lack rigorous finite-time stability guarantees for the fully coupled system, or exhibit limited robustness against compound time-varying disturbances. To address these gaps, this paper proposes a novel adaptive non-singular fast terminal sliding mode (ANFTSM) controller. Its core innovation is a newly constructed sliding surface that explicitly integrates errors from both actuated and underactuated states, ensuring the finite-time convergence of all system variables. Enhanced robustness is achieved through adaptive laws that estimate and compensate for unknown friction and wind disturbances in real time, without requiring prior knowledge of disturbance bounds. Importantly, the controller is derived directly from the full nonlinear dynamics, forgoing any linearization, and its global stability is rigorously proven via Lyapunov theory. Extensive comparative experiments demonstrate that the proposed controller outperforms established benchmarks (PD-SMC, OFC, BBC). Under nominal conditions, it achieves the fastest convergence times (8.06 [s] for luffing, 8.56 [s] for rotation) and superior swing suppression, limiting the maximum radial sway to merely 2.05 [deg]. Furthermore, it maintains excellent robustness against significant parameter variations (e.g., load mass, cable length) and non-zero initial swing angles. These performance gains are accomplished with the lowest total control effort (70 [N · m · s]) among all compared methods, confirming its superior energy efficiency alongside outstanding control performance.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106329"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-16DOI: 10.1016/j.mechmachtheory.2025.106322
Yu Liu , Xinyuan Li , Hao Liu , Hui Ma
This study investigates the coupled deformation mechanism and time-varying meshing stiffness of thin-walled ring gears with integrated idler gear bearings in aerospace planetary transmission systems. Based on a self-balanced virtual support model and thin-walled ring theory, influence coefficient formulas for the radial displacement and rotation at the gear root were derived, and an analytical model of ring gear deformation considering roller phase relations was established. By formulating the nonlinear relationship between radial displacement, rotation, and roller rotation angle, a foundation stiffness model of the gear–idler gear bearing system was developed. Furthermore, a time-varying meshing stiffness model was proposed using the potential energy method. Comparison with finite element results validated the proposed approach. The findings reveal that roller support significantly enhances the ring gear foundation stiffness; an increased speed ratio between the cage and ring gear increases meshing stiffness, whereas a higher roller rotational speed increases stiffness due to centrifugal effects. This work provides theoretical guidance for stiffness optimization and dynamic design of thin-walled ring gear planetary systems with idler gear bearings.
{"title":"Time-varying meshing stiffness model of the idler ring bearing in planetary gear train","authors":"Yu Liu , Xinyuan Li , Hao Liu , Hui Ma","doi":"10.1016/j.mechmachtheory.2025.106322","DOIUrl":"10.1016/j.mechmachtheory.2025.106322","url":null,"abstract":"<div><div>This study investigates the coupled deformation mechanism and time-varying meshing stiffness of thin-walled ring gears with integrated idler gear bearings in aerospace planetary transmission systems. Based on a self-balanced virtual support model and thin-walled ring theory, influence coefficient formulas for the radial displacement and rotation at the gear root were derived, and an analytical model of ring gear deformation considering roller phase relations was established. By formulating the nonlinear relationship between radial displacement, rotation, and roller rotation angle, a foundation stiffness model of the gear–idler gear bearing system was developed. Furthermore, a time-varying meshing stiffness model was proposed using the potential energy method. Comparison with finite element results validated the proposed approach. The findings reveal that roller support significantly enhances the ring gear foundation stiffness; an increased speed ratio between the cage and ring gear increases meshing stiffness, whereas a higher roller rotational speed increases stiffness due to centrifugal effects. This work provides theoretical guidance for stiffness optimization and dynamic design of thin-walled ring gear planetary systems with idler gear bearings.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106322"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-18DOI: 10.1016/j.mechmachtheory.2025.106327
Qi Yang , Kaiwen Hu , Xincui Shi , Jinzhu Zhou
Achieving a high load-to-mass ratio is a critical yet challenging goal for multi-locomotion tensegrity robots, as it dictates their practical load-carrying capacity but is difficult to optimize due to the complex model and redundant parameters of the robots. In this study, we propose an optimal design method that significantly enhances load-to-mass ratio for a class of multi-locomotion tensegrity mobile robots. Our key innovation lies in a holistic approach that integrates a finite element-based stiffness model, which is derived from force-deformation mapping. The effect of key parameters of the robot on stiffness is clarified. The established stiffness model subsequently guides a multi-constrained optimization framework, which is tailored to acquire high load-to-mass ratio across the entire locomotion process. In particular, the complex method is employed to solve the optimization model. The result is a groundbreaking improvement: our optimized design achieves a load-to-mass ratio of up to 7.60, which significantly surpasses all previously documented values for comparable mobile robots. Finally, experiments on the load-to-mass ratio of a prototype are conducted to demonstrate the correctness and rationality of the proposed optimal design method.
{"title":"Optimal design of high load-to-mass ratio for a class of multi-locomotion tensegrity mobile robots","authors":"Qi Yang , Kaiwen Hu , Xincui Shi , Jinzhu Zhou","doi":"10.1016/j.mechmachtheory.2025.106327","DOIUrl":"10.1016/j.mechmachtheory.2025.106327","url":null,"abstract":"<div><div>Achieving a high load-to-mass ratio is a critical yet challenging goal for multi-locomotion tensegrity robots, as it dictates their practical load-carrying capacity but is difficult to optimize due to the complex model and redundant parameters of the robots. In this study, we propose an optimal design method that significantly enhances load-to-mass ratio for a class of multi-locomotion tensegrity mobile robots. Our key innovation lies in a holistic approach that integrates a finite element-based stiffness model, which is derived from force-deformation mapping. The effect of key parameters of the robot on stiffness is clarified. The established stiffness model subsequently guides a multi-constrained optimization framework, which is tailored to acquire high load-to-mass ratio across the entire locomotion process. In particular, the complex method is employed to solve the optimization model. The result is a groundbreaking improvement: our optimized design achieves a load-to-mass ratio of up to 7.60, which significantly surpasses all previously documented values for comparable mobile robots. Finally, experiments on the load-to-mass ratio of a prototype are conducted to demonstrate the correctness and rationality of the proposed optimal design method.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106327"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Torsional rigidity and lost motion are critical performance indicators for evaluating the load capacity, motion stability, and positioning accuracy of the rotating vector (RV) reducer. This paper presents a dynamic modeling method for the RV reducer’s hysteresis curve and evaluates its torsional rigidity and lost motion based on the hysteresis curve. Firstly, the method provides the contact dynamic model of the RV reducer, including the influence of geometric errors in components. Secondly, the simulation control strategy for torque loading is developed based on the hysteresis curve test scheme. Besides, the validity of the calculation results is verified by experiment. Moreover, the effects of contact stiffness, bearing preload and clearance, and geometric errors of components on the hysteresis curve, as well as the torsional rigidity and lost motion, are discussed in detail. The results show that support bearing contact stiffness has the most significant influence on the torsional rigidity; radial clearance of the swivel arm bearing has a significant impact on the lost motion; and geometric errors of components will reduce the torsional rigidity and increase the lost motion.
{"title":"Modeling of hysteresis curve and study of torsional rigidity and lost motion characteristics of the RV reducer","authors":"Lixin Xu , Tianyu Zhao , Jianwei Geng , Yunqing Deng","doi":"10.1016/j.mechmachtheory.2025.106335","DOIUrl":"10.1016/j.mechmachtheory.2025.106335","url":null,"abstract":"<div><div>Torsional rigidity and lost motion are critical performance indicators for evaluating the load capacity, motion stability, and positioning accuracy of the rotating vector (RV) reducer. This paper presents a dynamic modeling method for the RV reducer’s hysteresis curve and evaluates its torsional rigidity and lost motion based on the hysteresis curve. Firstly, the method provides the contact dynamic model of the RV reducer, including the influence of geometric errors in components. Secondly, the simulation control strategy for torque loading is developed based on the hysteresis curve test scheme. Besides, the validity of the calculation results is verified by experiment. Moreover, the effects of contact stiffness, bearing preload and clearance, and geometric errors of components on the hysteresis curve, as well as the torsional rigidity and lost motion, are discussed in detail. The results show that support bearing contact stiffness has the most significant influence on the torsional rigidity; radial clearance of the swivel arm bearing has a significant impact on the lost motion; and geometric errors of components will reduce the torsional rigidity and increase the lost motion.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106335"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-06DOI: 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.
{"title":"Type synthesis of reconfigurable single-loop mechanisms based on transitional configurations","authors":"Jun Cai , Wang Yu , Bing Li , Sen Wang , Fujun Peng","doi":"10.1016/j.mechmachtheory.2025.106306","DOIUrl":"10.1016/j.mechmachtheory.2025.106306","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":49845,"journal":{"name":"Mechanism and Machine Theory","volume":"219 ","pages":"Article 106306"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-04DOI: 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.
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