Dynamic singularity avoidance for parallel manipulators using a task-priority based control scheme

Agarwal, Abhishek; Nasa, Chaman; Bandyopadhyay, Sandipan

doi:10.1016/j.mechmachtheory.2015.07.013

Cited by 36 publications

(30 citation statements)

References 22 publications

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“…This section describes the results of the application of the above formulations to the 3-RRR manipulator prototype, whose dimensions are given in ref. [12], with the manipulator base side length, b = 500 mm, length of the active links, l = 220 mm, length of the passive links, r = 170 mm, and side of the end-effector triangle, a = 125 mm. The workspace of the 3-RRR manipulator is parametrised by (x, y, α).…”

Section: Numerical Resultsmentioning

confidence: 99%

“…The same result can be achieved in a slightly different manner, in which the required redundancy is artificially created by confining the workspace of the manipulator to a lower dimension, rather than using an additional actuator. 12 While many of the above strategies have been demonstrated successfully through experiments or simulations, they have a common inherent issue -the solutions obtained are specific to the given desired path, and hence need to be computed afresh every time the desired path changes.…”

Section: Introductionmentioning

confidence: 99%

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Computation of the safe working zones of Planar and Spatial Parallel Manipulators

et al. 2019

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SUMMARYThis paper presents the computation of the safe working zone (SWZ) of a parallel manipulator having three degrees of freedom. The SWZ is defined as a continuous subset of the workspace, wherein the manipulator does not suffer any singularity, and is also free from the issues of link interference and physical limits on its joints. The proposed theory is illustrated via application to two parallel manipulators: a planar 3-R̲RR manipulator and a spatial manipulator, namely, MaPaMan-I. It is also shown how the analyses can be applied to any parallel manipulator having three degrees of freedom, planar or spatial.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Computation of the safe working zones of Planar and Spatial Parallel Manipulators

et al. 2019

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“…The extensive analysis of type II singularities presented has been incorporated in motion/force performance evaluation [18,20], path planning, and the design of reconfigurable PRs [21,22]. These analyses have been developed offline, and very little has been found about including this information in the control unit of the PR [23,24]. Abgarwal et al [24] designed a control scheme to avoid type II singularities of a planar PR by using artificial potential functions.…”

Section: Introductionmentioning

confidence: 99%

“…These analyses have been developed offline, and very little has been found about including this information in the control unit of the PR [23,24]. Abgarwal et al [24] designed a control scheme to avoid type II singularities of a planar PR by using artificial potential functions. The potential functions are activated near the singularity to alter the trajectory by means of repulsion forces.…”

Section: Introductionmentioning

confidence: 99%

Vision-Based Hybrid Controller to Release a 4-DOF Parallel Robot from a Type II Singularity

Pulloquinga

Escarabajal

Ferrándiz

et al. 2021

Sensors

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The high accuracy and dynamic performance of parallel robots (PRs) make them suitable to ensure safe operation in human–robot interaction. However, these advantages come at the expense of a reduced workspace and the possible appearance of type II singularities. The latter is due to the loss of control of the PR and requires further analysis to keep the stiffness of the PR even after a singular configuration is reached. All or a subset of the limbs could be responsible for a type II singularity, and they can be detected by using the angle between two output twist screws (OTSs). However, this angle has not been applied in control because it requires an accurate measure of the pose of the PR. This paper proposes a new hybrid controller to release a 4-DOF PR from a type II singularity based on a real time vision system. The vision system data are used to automatically readapt the configuration of the PR by moving the limbs identified by the angle between two OTSs. This controller is intended for a knee rehabilitation PR, and the results show how this release is accomplished with smooth controlled movements where the patient’s safety is not compromised.

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“…But, generally speaking, redundant parallel manipulators have some drawbacks, such as additional cost and control complexity. 44 To overcome this additional cost, Agarwal et al 45 suggested a singularity avoidance control scheme, which is based on controlling only a selected subset of the degrees of freedom of the robot.…”

Section: Introductionmentioning

confidence: 99%

High-order singularities of 5R planar parallel robots

Özdemir

2018

Robotica

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SUMMARYSingularity analysis of parallel manipulators is an active research field in robotics. The present article derives for the first time in the literature a condition under which a five-bar parallel robot encounters high-order parallel singularities. In this regard, by focusing on the planar 5R mechanism, a theorem is given in terms of the slope of its coupler curve at the parallel singular configurations. At high-order parallel singularities, the associated determinant vanishes simultaneously with at least its first-order time derivative. The determination of such singularities is quite important since in their presence, some special conditions should be satisfied for bounded inverse dynamic solutions.

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Dynamic singularity avoidance for parallel manipulators using a task-priority based control scheme

Cited by 36 publications

References 22 publications

Computation of the safe working zones of Planar and Spatial Parallel Manipulators

Computation of the safe working zones of Planar and Spatial Parallel Manipulators

Vision-Based Hybrid Controller to Release a 4-DOF Parallel Robot from a Type II Singularity

High-order singularities of 5R planar parallel robots

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