Showing papers in "Mechanism and Machine Theory in 2021"

TL;DR: A purely torsional dynamic model of planetary gear with gear wear is proposed wheregear wear is evaluated by Archard's equation and it is incorporated into the dynamic model through time-varying mesh stiffness, unloaded static transmission error and gear backlash.

TL;DR: In this article, a fractal contact model suited for gear pair contact has been established, and the asperity contact stiffness is calculated, thus the fractal compliance compliance can be obtained.

TL;DR: In this paper, an improved method for disconnection and re-connection of a six-DOF manipulator with simple geometry is proposed. But the method is not suitable for the case of the wrist joint variables.

TL;DR: This work is aimed at presenting a new investigation based on the LuGre friction foundation capable of overcoming limitations of these models and includes a stiffness coefficient to adjust and accommodate the variations of the normal contact forces in dynamical systems.

TL;DR: The proposed model can calculate time-varying mesh stiffness accurately under non-stationary conditions and is shown that the gear mesh stiffness is load-dependent.

TL;DR: A combined methodology for type and size optimization is proposed and applied to a cable driven parallel robot, which is intended for upper-limb rehabilitation exercises, and four different topology solutions have been considered for LAWEX robot.

TL;DR: Simulation and experimental results show that the energy efficiency is improved by using the proposed load-adaptive actuator-powered ankle exoskeleton compared with using an exoskeletons driven by linear SEAs.

TL;DR: In this paper, a wear prediction model for external spur gear (ESG) was established according to the Archard's wear equation, and a modified analytical time-varying mesh stiffness (TVMS) model was derived by the potential energy method.

TL;DR: In this article, a two-degree-of-freedom (2DOF) compliant nano-positioning scanner with compound decoupling-guiding mechanism is presented, which features with the combination of separated prismatic joint and parallelogram, through which the parasitic displacement of scanner can be reduced and the motion guiding is obtained.

TL;DR: An end-effector pose and arm-shape synchronous planning method for a hyper-redundant manipulator passing through space narrow parallel slits based on extended Jacobian matrix redundancy decomposition EJMRD is proposed.

TL;DR: A new signal decomposition algorithm, nonlinear sparse mode decomposition (NSMD), is proposed in this protocol, and the analysis results of simulation signals and planetary gearbox fault signals indicate that the proposed NSMD method is effective for raw vibration signals.

TL;DR: Different types of models are used to establish the mesh stiffness of parallel axis cylindrical gears, namely, analytical, finite element, hybrid and approximated analytical models, providing a broad range of information in great detail.

TL;DR: In this paper, the influence of the variations related to the manipulator components and geometric parameters onto the motion accuracy, including the parallelogram, is studied by means of the variational method.

TL;DR: A practical set of new tools for identifying and mapping the natural frequencies and damping ratios of dominant vibration modes of a robot arm with the commercial UR5e as a case and a new dynamic map based on a physical interpretation of the robot arm, followed by strategic simplification are presented.

TL;DR: The article presents joint control methods minimizing the influence of friction in the closed-loop Bowden cable conduit system and the methods of estimating the torque of interaction with the operator based on the ExoArm 7-DOF exoskeleton dynamics model.

TL;DR: In this paper, a modeling method and algorithm for point contact non-smooth multibody system based on the 2D LuGre friction model is presented, and the effectivity of the parameter identification method is verified by a numerical simulating example.

TL;DR: Considering the influence of cage and oil lubrication, the authors proposed a complete multi-degree-of-freedom (DOF) dynamic model for defective angular contact ball bearing by analyzing the full multi-body interactions.

TL;DR: A novel cooperative compensation method (CCM) to compensate for return stroke of stick-slip actuators is proposed that uses two signals of specific initial time gap (ITG) to reduce the return stroke to improve speed.

TL;DR: This work aims at presenting, in a comprehensive manner, several approaches to model and simulate closed loop topologies using the classical Lagrangian formulation, and the main results are compared with those obtained with the well-established Newton-Euler method for constrained multibody systems.

TL;DR: The microgripper design is optimized through the computational method to achieve high performance in terms of the low parasitic motion and large output displacement and achieves a high precision motion resolution.

TL;DR: In this paper, a penetration-based gear contact model for accurate and numerically efficient tooth contact analysis of spiral bevel gears is used to investigate the simulation of gear alignment errors, and a novel strategy to parametrically redefine the gear contact element's surfaces of roll angles in function of a gear pair's instantaneous misaligned state is developed to further increase the accuracy of the contact algorithm.

TL;DR: Simulations and experimental tests on two typical types of planetary gear trains show good consistency at crack fault frequency features, which effectively validates the proposed models.

TL;DR: A compact mechanism is proposed to achieve a large workspace and a high motion accuracy and a robust control technique is designed to improve tracking performance.

TL;DR: This study presents a systematic optimum dimension design strategy named after multi-mode synergistic optimization (MMSO), utilizing the functional sequences and kinematic decoupling to simplify the complex optimization issue into sub-issues of sub-mechanisms in sub-modes from landing to walking.

TL;DR: An indirect solution of the optimal control problem for path planning of the hexarotor system with different cost functions under different wind loads is proposed by using a modified artificial potential field which overcomes the local minima issue and finds a practical trajectory for robot path planning.

TL;DR: In this paper, a rigid-flexible coupling dynamic model was proposed to analyze the transmission error (TE) of a gearbox, where the meshing pair, flexible shaft, and bearing are established by a lumped mass element, beam element, and spring element, respectively.

TL;DR: A tightening force model for winding PAMs is presented in this paper, which can be used to evaluate the pressing force of the untethered soft gripper on the surface of an object.

TL;DR: The results demonstrate that the proposed method provides a better performance than the existing methods in terms of accuracy and efficiency for kinematic reliability analysis.

TL;DR: This review article aims to summarise results obtained by other researchers and formalise gear optimisation process, while also providing some details on micro-geometry, aiming to present a comprehensive optimisation procedure.

TL;DR: This paper presents the design of a new partial-state feedback controller by using the port-Hamiltonian formulation and develops a variation of the Integral Interconnection and Damping Assignment Passivity Based Control methodology for a class of soft continuum manipulators.