A virtual joint method of analytical form for parallel manipulators

Zhang, Hui; Xu, Zhenbang; Han, Hasiaoqier; Han, Chunyang; Yang, Yu; Xia, Mingyi

doi:10.1177/09544062211016076

Cited by 3 publications

(2 citation statements)

References 35 publications

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“…Pashkevich et al 16 , 17 considered the compliance of the link on this basis, and described the translational/rotational compliance of the link and the joint as well as the coupling between them by using a 6-dof virtual spring. The method is not only simple to calculate but also reliable in calculation accuracy, so it has been widely popular 18 – 24 .…”

Section: Introductionmentioning

confidence: 99%

Stiffness characteristics analysis of a Biglide industrial parallel robot considering the gravity of mobile platform and links

Guan

Zou

et al. 2023

Sci Rep

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For the machining process of industrial parallel robots, the gravity generated by the weight of mobile platform and links will lead to the deviation of the expected machining trajectory of the tool head. In order to evaluate this deviation and then circumvent it, it is necessary to perform the robotic stiffness model. However, the influence of gravity is seldom considered in the previous stiffness analysis. This paper presents an effective stiffness modeling method for industrial parallel robots considering the link/joint compliance, the mobile platform/link gravity, and the mass center position of each link. First, the external gravity corresponding to each component is determined by the static model under the influence of gravity and mass center position. Then, the corresponding Jacobian matrix of each component is obtained by the kinematic model. Subsequently, the compliance of each component is obtained by cantilever beam theory and FEA-based virtual experiments. In turn, the stiffness model of the whole parallel robot is determined and the Cartesian stiffness matrix of the parallel robot is calculated at several positions. Moreover, the principal stiffness distribution of the tool head in each direction over the main workspace is predicted. Finally, the validity of the stiffness model with gravity is experimentally proved by the comparison of the calculated stiffness and measured stiffness in identical conditions.

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Section: Introductionmentioning

confidence: 99%

Stiffness characteristics analysis of a Biglide industrial parallel robot considering the gravity of mobile platform and links

Guan

Zou

et al. 2023

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Manuscript submitted to ACM FE analysis of the robot links. The method allowed better accuracy without compromising overall computational efficiency [15].…”

Section: Introductionmentioning

confidence: 99%

Evaluation Of Deviations Due To Robot Configuration For Robot-based Incremental Sheet Metal Forming

Paul,

Bharti,

Uthama

et al. 2023

Advances in Robotics - 6th International Conference of the Robotics Society

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Industrial robot-based Incremental Sheet metal Forming (ISF) is known as Roboforming. Industrial robots are being adopted for forming operations because they allow higher tool flexibility in terms of positioning and orientating the tool and a larger workspace at a minimum cost compared to CNC-based ISF. However, the lower stiffness of the robots leads to undesirable geometrical anomalies and deviations in the formed part. Along with the externally applied forces, robot configuration changes also impact the tool's positional accuracy. An attempt has been made to study the influence of robot configurations on overall part deviations in Roboforming due to robot compliance. Understanding changes in compliance or stiffness changes owing to different robot poses is a necessary step for optimizing the transition from a traditional CNC-based ISF to a robot-assisted ISF. Robot stiffness-based deviations are evaluated using an analytical approach, and configuration-based deflections are studied using FEM-based approaches for their contribution to the overall part deviations. Results are compared to the sheet metal forming experiments conducted over conventional 3-axis CNC for forming a cone-shaped profile using a spiral toolpath. It is highlighted that the overall deviations in the formed components are influenced by robot compliance and pose.

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Systematic Elastostatic Stiffness Model of Over-Constrained Parallel Manipulators Without Additional Constraint Equations

Yang,

Yu,

et al. 2024

Chin. J. Mech. Eng.

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The establishment of an elastostatic stiffness model for over constrained parallel manipulators (PMs), particularly those with over constrained subclosed loops, poses a challenge while ensuring numerical stability. This study addresses this issue by proposing a systematic elastostatic stiffness model based on matrix structural analysis (MSA) and independent displacement coordinates (IDCs) extraction techniques. To begin, the closed-loop PM is transformed into an open-loop PM by eliminating constraints. A subassembly element is then introduced, which considers the flexibility of both rods and joints. This approach helps circumvent the numerical instability typically encountered with traditional constraint equations. The IDCs and analytical constraint equations of nodes constrained by various joints are summarized in the appendix, utilizing multipoint constraint theory and singularity analysis, all unified within a single coordinate frame. Subsequently, the open-loop mechanism is efficiently closed by referencing the constraint equations presented in the appendix, alongside its elastostatic model. The proposed method proves to be both modeling and computationally efficient due to the comprehensive summary of the constraint equations in the Appendix, eliminating the need for additional equations. An example utilizing an over constrained subclosed loops demonstrate the application of the proposed method. In conclusion, the model proposed in this study enriches the theory of elastostatic stiffness modeling of PMs and provides an effective solution for stiffness modeling challenges they present.

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A virtual joint method of analytical form for parallel manipulators

Cited by 3 publications

References 35 publications

Stiffness characteristics analysis of a Biglide industrial parallel robot considering the gravity of mobile platform and links

Stiffness characteristics analysis of a Biglide industrial parallel robot considering the gravity of mobile platform and links

Evaluation Of Deviations Due To Robot Configuration For Robot-based Incremental Sheet Metal Forming

Systematic Elastostatic Stiffness Model of Over-Constrained Parallel Manipulators Without Additional Constraint Equations

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