Force/Motion Transmissibility Analysis of Six Degree of Freedom Parallel Mechanisms

Huang, Tian; Wang, Manxin; Yang, Shuofei; Sun, Tao; Chetwynd, D. G.; Xie, Fugui

doi:10.1115/1.4026631

Cited by 32 publications

(12 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This physical criterion was already provided in [23] and can be respected through a proper robot trajectory planning. It should also be mentioned here that in the works [33,34,35], the authors used criteria based on a virtual power to characterize the motion/force transmissibility in parallel manipulators (and thus to characterize the closeness to Type 1 and Type 2 singularities). However, such criteria where never used to defined a criterion able to avoid the degeneracy of the dynamic model near singularity.…”

Section: Optimal Trajectory Planning Through Type 2 Singularitiesmentioning

confidence: 99%

Degeneracy conditions of the dynamic model of parallel robots

et al. 2015

View full text Add to dashboard Cite

Despite their well known advantages in terms of higher intrinsic rigidity, larger payload-to-weight ratio, and higher velocity and acceleration capacities, parallel robots have drawbacks. Among them, the most important one is surely the presence of singularities in the workspace which divide the workspace into different aspects (each aspect corresponding to one or more assembly modes) and near which the performance is considerably reduced. In order to increase the reachable workspace of parallel robots, a promising solution consists in the definition of optimal trajectories passing through the singularities to change either the leg working modes or the robot assembly modes. Previous works on the field have shown that it is possible to define optimal trajectories that allow the passing through the robot Type 2 singularities. Such trajectories must respect a physical criterion which can be obtained through the analysis of the degeneracy conditions of the parallel robot inverse dynamic model. However, the mentioned works were not complete: they lacked a degeneracy condition of the parallel robot inverse dynamic model which is not due to Type 2 singularity anymore, but to a serial singularity. Crossing a serial singularity is appealing as in that case we can change the robot leg working mode and then potentially access to other workspace zones. This absence is due to the fact that the authors used a reduced dynamic model which was not taking into account all link dynamic parameters. The present paper aims to fill this gap by providing a complete study of the degeneracy conditions of the parallel robot dynamic model and also by demonstrating that it is possible to cross the Type 2, but also serial singularity, by defining trajectories that respect some given criteria obtained from the analysis of the degeneracy of the robot dynamic model. It also aims to demonstrate that the serial singularities have impacts on the robot effort transmission, which is a point that is usually bypassed in the literature. All theoretical developments are validated through simulations and experiments.

show abstract

Section: Optimal Trajectory Planning Through Type 2 Singularitiesmentioning

confidence: 99%

Degeneracy conditions of the dynamic model of parallel robots

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Many indexes are proposed, such as transmission factor, generalized transmission index that can evaluate the motion/force transmissibility, local transmission index and homogeneously dimensionless local and global transmission indices. [20][21][22][23][24] Although different kinds of indexes are presented for parallel mechanism, an index which can reflect the degree of symmetry of kinematic performance of parallel mechanism is not presented. In this article, we propose an index called global symmetry index (GSI) to reflect the degree of symmetry of kinematic performance.…”

Section: Introductionmentioning

confidence: 99%

Kinematic performance evaluation of 2-degree-of-freedom parallel mechanism applied in multilayer garage

Shao

Zhang

et al. 2018

Advances in Mechanical Engineering

View full text Add to dashboard Cite

In this article, our recent work on a kind of 2-degree-of-freedom lower-mobility parallel mechanism, which has one rotation degree of freedom and one translational degree of freedom, used in multilayer garage is presented. It has the following characteristics: lower-mobility, non-symmetric structure but can realize symmetric movement and a good compatibility for different kinds of lifting work. Kinematic performance should be considered in the first of designing a new kind of mechanism, the optimal kinematic design and analysis of this lower-mobility parallel mechanism are primarily investigated. In process of study, the global conditioning index over workspace is adopted, we establish a new evaluation method for the lower-mobility parallel mechanism, called global symmetry index and simulation results are shown. In addition, the flexible workspace of this lower-mobility parallel mechanism is also proposed. The evaluation index can be also applied on other lower-mobility parallel mechanism, which needs steady and symmetric movement.

show abstract

“…At present, most of the works on kinematic analysis for mechanisms are based on the ideal joints, 4–6 which do not accurately capture the actual working conditions of mechanisms. When clearances are taken into account, collision contact, as well as contact forces must be considered in the dynamic model.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator

Shan

2018

Proceedings of the Institution of Mechanical Engineers, Part K:

View full text Add to dashboard Cite

Clearance, friction, and local elastic and plastic deformation of joint, which can be called joint effects, may cause nonlinear dynamic behaviour of mechanisms. In the paper, nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator was studied. There are 10 spherical joints in the 2(3PUS+S) parallel manipulator, and the dynamic characteristics of the spherical joints directly affect the overall output performance since they are connected to the moving platforms. Therefore, the joint effects of spherical joint and its effect are studied. To study the effect of the irregular clearance (size of the clearance varies with the attitude) of spherical joint due to manufacturing tolerance and wear, the spherical surface is approximated as an ellipsoid. In addition, the contact force models of spherical joint with variable contact stiffness were established under dry friction and lubrication condition, respectively. And then considering the contact forces of the spherical joints, the overall dynamic model of the 2(3PUS+S) parallel manipulator was established. Based on the overall dynamic model, the influence of joint effects on the dynamic characteristics of the 2(3PUS+S) parallel manipulator was studied, and the correctness of theoretical models was verified through experiments. The results from the simulation and experiments indicate that joint effects can cause nonlinear dynamic characteristics and have important influence on the dynamic performance of the 2(3PUS+S) parallel manipulator.

show abstract

Force/Motion Transmissibility Analysis of Six Degree of Freedom Parallel Mechanisms

Cited by 32 publications

References 20 publications

Degeneracy conditions of the dynamic model of parallel robots

Degeneracy conditions of the dynamic model of parallel robots

Kinematic performance evaluation of 2-degree-of-freedom parallel mechanism applied in multilayer garage

Nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator

Contact Info

Product

Resources

About