Stiffness Modelling and Performance Evaluation of a Large Loading SCARA Parallel Robot

doi:10.3901/JME.2025.21.213

Abstract

Abstract: Addressing the demands for high-speed, high-precision, and heavy-load operation equipment in fields such as textiles, food processing, and logistics, a refined stiffness modeling method and performance analysis for a SCARA parallel robot featuring closed-loop substructure within branches is investigated. Firstly, the structure and position of the robot are described and analyzed. Subsequently, within the framework of the screw theory, the virtual spring method is employed to determine the stiffness matrix of the active/passive parallelogram substructure, thereby deriving the stiffness model of the branch chain. Subsequently, the overall stiffness model of the robot is established through the principle of stiffness superposition. A comparison of linear stiffness and torsional stiffness under six typical poses is conducted using both the numerical calculations and finite element simulation. The results indicated that the relative errors are all within 10%, validating the accuracy and effectiveness of the theoretical stiffness model. Furthermore, the stiffness distribution within different planes of the workspace is visualized when the attitude angle is set at 0°, and the relevant change patterns of stiffness is elucidated. Ultimately, to effectively harmonize the dimensions of linear and torsional deformations, a stiffness performance index with distinct physical significance is defined based on instantaneous energy, by which, an analysis of stiffness performance within the task workspace under varying attitude angles is conducted, laying a theoretical foundation for the high-speed, high-stiffness integrated design and prototype development of this robot.

Key words: SCARA parallel robot, screw theory, stiffness matrix, virtual spring method, finite element analysis

CLC Number:

TH112

LIANG Dong, HAN Zhiqiang, SONG Yimin, CHANG Boyan. Stiffness Modelling and Performance Evaluation of a Large Loading SCARA Parallel Robot[J]. Journal of Mechanical Engineering, 2025, 61(21): 213-226.

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