Path Tracking of Parallel Manipulators in the Presence of Force Singularity

Jui, Chia-Kai Kevin; Sun, Qiao

doi:10.1115/1.2098893

Cited by 32 publications

(3 citation statements)

References 20 publications

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“…Two strategies are possible to deal with singularities. Either special planning and control procedures are used to traverse them (Porta et al, 2012;Jui and Sun, 2005) or they are avoided (Bohigas et al, 2013). Both strategies can be based on higher-dimensional continuation and it is our future endeavor to integrate them in the planner for tensegrity structures introduced herein.…”

Section: Discussionmentioning

confidence: 99%

Path planning for active tensegrity structures

Porta

Hernández-Juan

2016

International Journal of Solids and Structures

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This paper presents a path planning method for actuated tensegrity structures with quasi-static motion. The valid configurations for such structures lay on an equilibrium manifold, which is implicitly defined by a set of kinematic and static constraints. The exploration of this manifold is difficult with standard methods due to the lack of a global parametrization. Thus, this paper proposes the use of techniques with roots in differential geometry to define an atlas, i.e., a set of coordinated local parameterizations of the equilibrium manifold. This atlas is exploited to define a rapidly-exploring random tree, which efficiently finds valid paths between configurations. However, these paths are typically long and jerky and, therefore, this paper also introduces a procedure to reduce their control effort. A variety of test cases are presented to empirically evaluate the proposed method.

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Section: Discussionmentioning

confidence: 99%

Path planning for active tensegrity structures

Porta

Hernández-Juan

2016

International Journal of Solids and Structures

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“…Over time, however, the focus has shifted more to developing methods that will enable parallel robots to pass through them. A condition to be met in this regard is that the motion equations of the robot must be consistent at the singularity to be crossed [17,25,26]. However, as shown by Özdemir [27], parallel robots may also encounter singularities that require additional conditions besides consistency in order to be passed through.…”

Section: Introductionmentioning

confidence: 99%

Path and trajectory planning of a RPRPR planar parallel robot for prevention of high-order singularities

ÖZDEMİR,

KARAKAYA

2024

Proc. Rom. Acad. Ser. A - Math. Phys. Tech. Sci. Inf. Sci.

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Parallel robots have many remarkable advantages over their conventional serial counterparts. Highly accurate positioning capability and high payload-to-weight ratio are among the main ones. The main factor underlying all these advantages is their closed-loop construction. However, this constructional feature also causes a special singularity problem, which constitutes their biggest disadvantage. Characteristic singularities classified as Type II exist inside their workspace, around which the magnitude of the inverse dynamic solution grows unboundedly. This naturally yields the saturation of the actuators and eventually in uncontrollability of the robot. Consequently, the whole workspace becomes impossible to be used. In order to pass through a Type II singularity, the consistency of the motion equations of the robot must be maintained at that singularity. However, any Type II singular configuration can transform into a high-order singularity, which, in order to be passed through, requires additional conditions other than the consistency. Therefore, full utilization of the whole workspace with a minimum number of conditions requires to avoid high-order singularities. The present article contributes to the literature by developing path and trajectory planning principles for preventing a two-degree-of-freedom planar parallel robot with RPRPR structure from experiencing high-order singularities.

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“…However, it is an expensive solution to the problem because of the additional actuators and the complicated control of the manipulator caused by actuation redundancy. Another approach concerns with motion planning to pass through singularity [18][19][20][21][22][23][24][25], i.e. a parallel manipulator may track a path through singular poses if its velocity and acceleration are properly constrained.…”

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confidence: 99%

On the dynamic properties and optimum control of parallel manipulators in the presence of singularity

Briot

Arakelian

2008

2008 IEEE International Conference on Robotics and Automation

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It is known that a parallel manipulator with a singular configuration can gain one or more degrees of freedom and become uncontrollable. That is it might not reproduce a stable motion under a prescribed trajectory. However, it is proved experimentally that there is possible passing through the singular zones. This was simulated and shown on numerical examples and illustrated on several parallel structures. In this paper, we determine the optimal dynamic conditions generating a stable motion inside the singular zones. The obtained results show that the general condition for passing through a singularity can be defined as follows: the endeffector of the parallel manipulator can pass through the singular positions without perturbation of motion if the wrench applied on the end-effector by the legs, and external efforts of the manipulator are orthogonal to the twist along the direction of the uncontrollable motion. This condition is obtained from the inverse dynamics and analytically demonstrated by the study of the Lagrangian of a general parallel manipulator. Numerical simulations are carried out using the software ADAMS and validated by experimental tests.

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Path Tracking of Parallel Manipulators in the Presence of Force Singularity

Cited by 32 publications

References 20 publications

Path planning for active tensegrity structures

Path planning for active tensegrity structures

Path and trajectory planning of a RPRPR planar parallel robot for prevention of high-order singularities

On the dynamic properties and optimum control of parallel manipulators in the presence of singularity

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