Mechanism and Machine Theory最新文献

英文中文

Discussion on: Jia Ma, Menghao Bai, Jie Wang, Shuai Dong, Hao Jie, Bo Hu, Lairong Yin, “A novel variable restitution coefficient model for sphere–substrate elastoplastic contact/impact process,” Mechanism and Machine Theory 202 (2024)

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-12 DOI: 10.1016/j.mechmachtheory.2024.105868

Itzhak Green

引用次数: 0

Double-level reconfigurable variation of Bennett-induced 8R mechanism and its evolved metamorphic 7R mechanism family

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-11 DOI: 10.1016/j.mechmachtheory.2024.105879

Xi Kang , Qia Lin , Huijuan Feng , Bing Li

Reconfigurable mechanisms are widely utilized in the design of intelligent robots and devices capable of adapting to diverse environments and requirements. While the design of reconfigurable mechanisms has garnered significant attention, previous studies have primarily focused on single types of reconfiguration, limiting the diversity and potential applications of such mechanisms. This paper introduces a double-level reconfigurable variation that integrates two reconfiguration approaches: joint rigidization and geometric constraints. This variation is derived from an 8R mechanism created by adding four joints to an equilateral Bennett mechanism. The original 8R mechanism serves as a foundation for generating a family of metamorphic mechanisms, including four distinct 7R mechanisms, through selective joint rigidization. Each of these 7R mechanisms exhibits multiple motion branches and singular configurations, which are analyzed in detail, with their metamorphic motion cycles illustrated graphically. In total, the mechanism family encompasses 39 unique motion branches. Some of these branches and singular configurations overlap, enabling transitions between mechanisms by altering rigidization patterns, thereby achieving a double-level reconfigurable variation. This study elucidates the interrelationships among the metamorphic mechanisms within this family, offering valuable insights for advancing the configuration synthesis and application of metamorphic mechanisms.

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引用次数: 0

Meshing theory of point-contact conical-envelope cylindrical worm-face worm gear drive

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-07 DOI: 10.1016/j.mechmachtheory.2024.105870

Shibo Mu , Xingwei Sun , Zhixu Dong , Heran Yang , Yin Liu , Weifeng Zhang , Qingxiang Meng , Yaping Zhao

This paper proposes further developing mismatched modification technology in meshing theory via physics-informed neural networks (PINNs). Thus, a design approach that considers meshing performance and meshing theory is presented for the mismatched parameters. On this basis, an innovative point-contact face worm gear drive with symmetric benchmark points is developed and its meshing theory is systematically developed. This study addresses high-dimensional nonlinear equation systems in tooth contact analysis (TCA) via PINN technology to convert initial value problems in conventional iterative methods into physical boundary problems. A PINN technique driven by meshing theory and meshing performance is proposed, achieving a coordinated optimization design for multiple mismatched parameters. The accuracy and feasibility of the PINN technique are proven by comparing it with the traditional iterative method. Applying the established meshing theory, TCA and error sensitivity analysis are conducted for the drive. The numerical results demonstrate that the PINN model has excellent accuracy in solving high-dimensional nonlinear equation systems. The analysis of the meshing characteristics indicates outstanding performance and a reduced susceptibility to installation errors.

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引用次数: 0

Dynamic modeling and effective vibration reduction of dual-link flexible manipulators with two-stage cascade PID and active torque actuation

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-06 DOI: 10.1016/j.mechmachtheory.2024.105867

Nitin Gupta, Barun Pratiher

Flexible manipulators, praised for their adaptability, face challenges in controlling inherent vibrations. This study introduces an advanced control strategy that employs active torque actuation to effectively mitigate tip vibrations in a dual-link flexible manipulator, enhancing stability and performance. An accurate dynamic model, developed using extended Hamilton’s principle and the assumed mode method, addresses the system’s natural frequencies and mode shapes, transforming coupled nonlinear partial differential equations into simpler ordinary differential equations with defined boundary conditions. The robust control strategy employs a two-stage cascade Proportional–Integral–Derivative (PID) controller, managing rigid and flexible motions separately to ensure precise control and stability despite the manipulator’s complexities. Analytical and experimental results show that this control strategy significantly improves transient response by reducing settling time and overshooting, with minor changes to peak time. MATLAB simulations and experiments confirm the effective damping of flexible deflections, aligning closely with dynamic model predictions. These results underscore the effectiveness of the control strategy and dynamic model in achieving superior vibration suppression and improved transient response, thereby optimizing system performance.

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引用次数: 0

Effect of redundant rollers in planetary gearbox

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-05 DOI: 10.1016/j.mechmachtheory.2024.105871

Anand Varadharajan , Pablo López García , Stein Crispel , Dirk Lefeber , Tom Verstraten

Mechanical transmission losses account for a significant portion of energy dissipation in electromechanical actuators. These actuators generally use a combination of high-speed electrical motors with a high-ratio gearbox. For such high-ratio gear transmission, even minor deviations in meshing can lead to substantial power loss. To mitigate this, rollers can be used as redundant elements along with gears. This paper highlights the importance of such redundant rollers that function in tandem with gears to facilitate optimal gear meshing through a specific gearbox design which enables to asses the contribution of rollers and gears individually and in combined manner. The findings reveal that overall, rollers significantly reduce gearbox losses both under no-load and loaded conditions. Especially at high speed and high torque regimes, where the gearbox usually suffers severe losses, the efficiency remains consistently high due to improved meshing.

引用次数: 0

Certified kinematic tools for the design and control of parallel robots

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-05 DOI: 10.1016/j.mechmachtheory.2024.105865

Alexandre Lê , Fabrice Rouillier , Guillaume Rance , Damien Chablat

This paper presents a methodology for the design and control of Parallel Kinematic Robots (PKRs). First, one focuses on the problematics of design. In particular, given a parallel mechanism defined by its design parameters and its kinematic modeling as well as its prescribed workspace, the idea is to certify the absence of any numerical instabilities (computational and physical singularities) that may jeopardize the integrity of the robot. This is achieved through two complementary approaches: a global method using symbolic computation and a local one based on continuation techniques and interval calculus, accounting for uncertainties in the design. The methodology is then applied to real PKR examples. Secondly, the paper proposes a control strategy that limits the active joint velocities to ensure the robot remains within its certified workspace. It will be applied to a special class of parallel robots: Spherical Parallel Manipulators (SPM) with coaxial input shafts (CoSPM).

引用次数: 0

Achieving high-quality and large-stroke constant torque by axial force release

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-04 DOI: 10.1016/j.mechmachtheory.2024.105869

Ruiyu Bai , Nan Yang , Zhiwei Qiu , Shane Johnson , Ke Wu , Bo Li , Guimin Chen

Compliant constant-torque mechanisms (CCTMs) maintain constant-torque without the need for complex closed-loop feedback systems, broadening their applications in rehabilitation devices, surgical tools, and cooperative robotic arms. However, CCTMs present considerable design challenges due to the pronounced nonlinearities that arise due to large deflections and multi-axial loadings. Traditional CCTM design strategies focus on managing post-buckling phenomena, often leading to increased stresses and an imbalance in positive and negative stiffness, compromising torque consistency and stroke capacity. This study introduces a novel CCTM that effectively decouples the multi-axial loadings and releases axial forces, isolating beam bending forces. This decoupling is achieved by incorporating a parallel-guided compliant mechanism at the fixed end of the beam, which reduces stress and enhances torque stability throughout the operational range. Through the partical swarm optimization of geometric design parameters using the chained beam constraint model, this research has produced a CCTM capable of maintaining torque fluctuations below 0.39% over a rotational range of 18° to 68°. Experimental validations confirm the design’s superiority in providing an extended constant torque stroke and improved consistency, distinguishing it from conventional straight-beam CCTMs.

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引用次数: 0

A new reciprocating straight propulsion for high propulsive hydrodynamic efficiency 一种新型往复直推进装置，具有较高的推进水动力效率

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-12-03 DOI: 10.1016/j.mechmachtheory.2024.105833

Zhibin Song , Yuanhao Zhang , Yifan Wu , Shiyu Li , Lixuan Zhao , Hongyu Cao , Rongjie Kang , Liwei Shi , Jian S. Dai

The majority of underwater vehicles currently use screw propellers as propulsion method. Despite screw propellers are being promoted to increase the efficiency through better designs and technologies, the circumferential flow caused by the rotation of screw propeller results in wasted energy. This paper proposes an ideal reciprocating straight propulsion paradigm that eliminates this waste by implementing straight backward thrust based on a foldable mechanism. This mechanism can implement a maximized propulsion during the propelling stroke and a minimized resistance during recovery by folding and unfolding the mechanism, which can be adjusted passively via the relative motion between the thruster mechanism and water avoiding using sensors and actuations. This principle makes the reciprocating straight propulsion simple and reliable to be achieved in practice. Besides, a modularized propulsion system with four identical independently thrusters based on the proposed mechanism was proposed, achieving various motion modes in underwater vehicles. The proposed propulsion mechanism was theoretically analyzed and verified through simulations and prototype tests. In mooring tests, the thrust provided by the proposed mechanism is similar to the simulation results. The propulsion performance indicator of an underwater vehicle with the proposed propulsor reached 66 %. The mechanism could turn even with one-sided propulsion.

目前大多数水下航行器采用螺旋推进器作为推进方式。尽管螺旋螺旋桨的设计和技术不断提高，但螺旋螺旋桨旋转引起的周向流动造成了能量的浪费。本文提出了一种理想的往复式直线推进模式，通过实现基于可折叠机构的直向后推力来消除这种浪费。通过折叠和展开该机构，该机构可以在推进行程中实现最大的推进力，并在恢复过程中实现最小的阻力，这可以通过传感器和驱动装置通过推力器机构和防水机构之间的相对运动被动调节。这一原理使往复直推进在实际中实现简单可靠。在此基础上，提出了一种由四个相同的独立推进器组成的模块化推进系统，实现了水下航行器的多种运动模式。对所提出的推进机构进行了理论分析，并通过仿真和样机试验进行了验证。在系泊试验中，该机构提供的推力与仿真结果相似。采用该推进器的水下航行器的推进性能指标达到66%。这种装置即使在单侧推进的情况下也能转动。

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引用次数: 0

Kinematics and kinetics of a knee assistance exoskeleton for sit-to-stand and stand-to-sit motions with energy storage and regeneration: A bond graph approach 具有能量储存和再生功能的从坐到站和从站到坐的膝关节辅助外骨骼的运动学和动力学：键合图方法

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-11-30 DOI: 10.1016/j.mechmachtheory.2024.105866

Vivek Soni, Anand Vaz

A bond graph model for the kinematics and kinetics of a knee assistance exoskeleton for sit-to-stand (SiTSt) or stand-to-sit (StTSi) motions is presented. The exoskeleton is actuated by a wire rope connected to a lead screw and slider nut assembly driven by an electric motor. An energy storage spring (ESS) is used for energy storage and regeneration. The ESS and wire rope apply opposite forces on the slider nut resulting in switching of contact surfaces. The kinematics of the lead screw and slider nut assembly is discussed and a bond graph model for the same is developed considering switching of contact surfaces and friction. Kinetics equations are derived from the model and verified by free body diagram (FBD) analysis. The efficacy of the developed model is demonstrated through simulations, where the switching and effects of friction are captured elegantly. Further, mechanics of wrapping is discussed considering the friction between the wire rope and the pulley. Finally, the bond graph model of the proposed exoskeleton is developed. Simulations are carried out by varying the stiffness of ESS and friction coefficients. A reduction in the assistance motor torque, power and energy requirements due to ESS and wrapping is demonstrated.

提出了一种膝关节辅助外骨骼的坐立（SiTSt）或站坐（StTSi）运动的运动学和动力学键合图模型。外骨骼由连接到由电动机驱动的丝杠和滑块螺母组件的钢丝绳驱动。储能弹簧（ESS）用于储能和再生。ESS和钢丝绳对滑块螺母施加相反的力，导致接触面的切换。讨论了丝杠和滑块螺母组合的运动学，建立了考虑接触面和摩擦切换的丝杠和滑块螺母组合的键合图模型。在此基础上推导了动力学方程，并通过自由体图（FBD）分析进行了验证。通过仿真证明了所开发模型的有效性，其中切换和摩擦的影响被优雅地捕获。在此基础上，考虑了钢丝绳与滑轮之间的摩擦力，讨论了钢丝绳缠绕的机理。最后，建立了该外骨骼的键图模型。通过改变ESS的刚度和摩擦系数进行了仿真。减少了辅助电机的扭矩，功率和能量要求，由于ESS和包裹被证明。

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引用次数: 0

A model to study the effect of micropitting on the dynamic behaviour of a geared system 研究微点蚀对齿轮传动系统动态特性影响的模型

IF 4.5 1区工程技术 Q1 ENGINEERING, MECHANICAL

Mechanism and Machine Theory

Pub Date : 2024-11-30 DOI: 10.1016/j.mechmachtheory.2024.105854

S. Portron, Pedro M.T. Marques

Geared transmission systems operate under increasingly severe conditions that tend to promote micropitting on the gear flanks. Micropitting leads to an increased local coefficient of friction, in particular due to an increase in the average roughness of the damaged surfaces. Micropitting is hard to predict, but also hard to detect, since it mainly affects the contact conditions, which affect friction forces. On global signals such as input/output torque, these friction forces are one to two orders of magnitude lower than the normal forces and tend not to be detectable due to the noise in the experimental setup. This paper aims at studying the effect of micropitting on the vibrational levels of a geared system, by coupling the gear dynamics model developed by Osman and Velex with the roughness-dependent coefficient of friction formulation from Xu et al., and by representing micropitting by a local increase of the composite roughness. The simulations show that micropitting has a clear impact on the system dynamic behaviour, especially in the direction perpendicular to the plane of contact. Finally, it was shown that the bearing forces and the pinion acceleration are suitable candidates for micropitting detection, even with noisy signals.

齿轮传动系统在日益严峻的条件下运行，往往会促进齿轮侧面的微点蚀。微点蚀导致局部摩擦系数的增加，特别是由于损坏表面的平均粗糙度的增加。微点蚀很难预测，也很难检测到，因为它主要影响接触条件，而接触条件又影响摩擦力。在输入/输出扭矩等全局信号上，这些摩擦力比正常力低一到两个数量级，而且由于实验装置中的噪声，往往无法检测到。本文旨在研究微点蚀对齿轮系统振动水平的影响，方法是将Osman和Velex开发的齿轮动力学模型与Xu等人的摩擦粗糙度依赖系数公式相结合，并用复合粗糙度的局部增加来表示微点蚀。仿真结果表明，微点蚀对系统的动力学行为有明显的影响，特别是在垂直于接触面方向上。最后表明，即使在噪声信号下，轴承力和小齿轮加速度也是微点蚀检测的合适候选者。

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