KINEMATIC ANALYSIS OF TWO DEGREES-OF-FREEDOM PLANAR SEVEN-BAR MECHANISMS WITH PRISMATIC PAIRS

Mingquan Yang, JunWang, and Yizhe Huang

Keywords

Prismatic pair, singularity curve, dead center position, branch, branch point, sub-branch

Abstract

The two-degrees-of-freedom (DOF) planar seven-bar mechanism is a complicated mechanism because of its two closed kinematic chains and two input joints that lead to its motion’s complexity. The majority of previous research in this area primarily focuses on the mechanism with only revolute pairs. Since the revolute pair only produces rotational motion, the need for translational movement is unaddressed. Translational motion created by a prismatic pair where the prismatic pair moves in the same direction at the same speed is needed in numerous mechanical structures. Therefore, kinematic analysis of the two-DOF planar seven-bar mechanisms with a prismatic pair and with two prismatic pairs is necessary. Paired with three-dimensional (3D) simulation, the method for the analysis is algebraic. Firstly, singularity curves, dead center positions, branches, and branch points of the two proposed mechanisms were identified via mathematical analysis; so was the rotational or translational displacement of each joint in each proposed mechanism. Secondly, the singularity configurations of the mechanisms at branch points were simulated and verified via the mechanisms’ 3D models. Lastly, the sub-branches of each mechanism were identified mathematically and described by demonstrating different configurations of the mechanisms in different sub-branches via their 3D models.

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