A Type II singularity avoidance algorithm for parallel manipulators using output twist screws

Pulloquinga, José L.; Escarabajal, Rafael J.; Valera, Ángel; Vallés, Marina; Mata, Vicente

doi:10.1016/j.mechmachtheory.2023.105282

Cited by 6 publications

(3 citation statements)

References 29 publications

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“…One approach involves locally characterising the singularity-free C-space, as done in [28], which is complete from an algorithmic point of view but very expensive. Another idea, presented in [46], focuses on moving at each step, minimising the risk of falling into singularities.…”

Section: Fk Modelling-numerical Methodsmentioning

confidence: 99%

Kinematic Modelling of a 3RRR Planar Parallel Robot Using Genetic Algorithms and Neural Networks

García-Samartín,

Barrientos

2023

Machines

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Kinematic modelling of parallel manipulators poses significant challenges due to the absence of analytical solutions for the Forward Kinematics (FK) problem. This study centres on a specific parallel planar robot, specifically a 3RRR configuration, and addresses the FK problem through two distinct methodologies: Genetic Algorithms (GA) and Neural Networks (NN). Utilising the Inverse Kinematic (IK) model, which is readily obtainable, both GA and NN techniques are implemented without the need for closed-loop formulations or non-systematic mathematical tools, allowing for easy extension to other robot types. A comparative analysis against an existing numerical method demonstrates that the proposed methodologies yield comparable or superior performance in terms of accuracy and time, all while reducing development costs. Despite GA’s time consumption limitations, it excels in path planning, whereas NN delivers precise results unaffected by stochastic elements. These results underscore the feasibility of using neural networks and genetic algorithms as viable alternatives for real-time kinematic modelling of robots when closed-form solutions are unavailable.

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Section: Fk Modelling-numerical Methodsmentioning

confidence: 99%

Kinematic Modelling of a 3RRR Planar Parallel Robot Using Genetic Algorithms and Neural Networks

García-Samartín,

Barrientos

2023

Machines

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“…One drawback of parallel manipulators is the existence of configurations inside of their workspace where the expected mobility changes instantaneously owing to the closed nature of the corresponding topologies. 56 These postures where named II-type singularities 57 and represent a potential dangerous for the architecture of the parallel manipulator. For a better comprehension of these illness configurations of robot manipulators, let us consider the planar four-bar linkage shown in Figure 4(a).…”

Section: Singularitymentioning

confidence: 99%

A novel Schönflies-motion generator parallel manipulator with decoupled rotational freedom

Gallardo-Alvarado,

Alcaraz-Caracheo

2023

Proceedings of the Institution of Mechanical Engineers, Part C:

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This paper introduces a four-legged decoupled Schönflies-motion generator parallel manipulator, free of passive limbs, provided with three linear actuators and one rotary actuator. The displacement analysis problem leads to closed-form solutions, thus avoiding the application of numerical methods for their solution, an unusual feature for most parallel manipulators. Subsequently, the theory of screws allows for solving the velocity, acceleration, and jerk analyses. Canceling the passive joint rates of the limbs is an indisputable advantage of the reciprocal-screw algebra. Moreover, upon the velocity analysis, the singularity analysis of the parallel manipulator is carried out by investigating the nature of the Jacobian matrices of the parallel manipulator. Then, we conclude that the robot at hand is free of type I and III singularities. Numerical examples enhance the correctness of the kinematic analysis method employed in the contribution. As far as the authors are aware, the topology of the parallel manipulator investigated here is original.

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“…An algorithm for Type II singularities avoidance by modifying the trajectory of a subset of the actuators is seen to be presented. 22 Type II singularity leads to the addition of redundancy in the mechanism, where the Jacobin-based approach for singularity analysis is found to give unreliable solutions. When it is applied to planar mechanisms where kinematic redundancy occurs, there is an inherent probability to miss out on certain singularities and incorrectly identify the singularities at other configurations in the workspace of the mechanism as seen in the literature.…”

Section: Introductionmentioning

confidence: 99%

Study on transmission angle and singularity in 5R planar mechanism

Jawale,

Choudhari,

Thorat

2023

Proceedings of the Institution of Mechanical Engineers, Part C:

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Transmission angle is one of the important design criteria to be considered for the effective force and motion transmission of a mechanism. Poor transmission angles are detrimental to the performance of a mechanism as they exaggerate the effect of friction and clearances. In addition, the torque required to overcome external load tends to increase and the required torque capacity of the drive increases unnecessarily. The singularity positions in a workspace are closely related to the transmission angle of the manipulator configuration. For achieving a large singularity-free area, the configuration dimension needs to be increased. Even though the objective is to design a compact five-bar planar mechanism, the link dimensions are likely to increase to some extent while achieving the desired transmission angles. This paper deals with estimating the singularity-free area of a five-bar mechanism by considering variations in transmission angles for different link lengths. The generalized methodology presented in this work demonstrates the estimation of singularity-free largest reachable area and link proportions at which intra-link transmission angles are confined. A dimensionless singularity-free workspace index is proposed to quantify performance at various transmission angles.

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A Type II singularity avoidance algorithm for parallel manipulators using output twist screws

Cited by 6 publications

References 29 publications

Kinematic Modelling of a 3RRR Planar Parallel Robot Using Genetic Algorithms and Neural Networks

Kinematic Modelling of a 3RRR Planar Parallel Robot Using Genetic Algorithms and Neural Networks

A novel Schönflies-motion generator parallel manipulator with decoupled rotational freedom

Study on transmission angle and singularity in 5R planar mechanism

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