Latest Papers

ASME Journal of Mechanisms and Robotics

  • Theoretical Analysis of Workspace of a Hybrid Offset Joint
    on December 19, 2024 at 12:00 am

    AbstractOffset joints are widely used in robotics, and literature has demonstrated that axial offset joints can expand the workspace. However, the hybrid offset joint, which incorporates offsets in three orthogonal directions (x, y, and z axes), provides a more flexible and comprehensive range of motion compared to traditional axial offset joints. Therefore, a comprehensive understanding of the workspace of hybrid offset joints with three-directional offsets is essential. First, through a parameter model, the interference motion of hybrid offset joints is studied, considering three different directional offsets and obtaining analytical expressions. Next, based on coordinate transformations, the workspace of this joint is investigated, resulting in corresponding theoretical formulas. In addition, the influence of offset amounts in various directions on the joint’s workspace is examined. Finally, the application of hybrid offset joints in parallel manipulators (PMs) is introduced, highlighting their practical engineering value. Through comparative analysis, it is found that lateral offsets on the x- and y-axes adjust the maximum rotation angles, while the z-axis offset expands the rotational range of these joints. Moreover, by increasing the limit rotation angle of the passive joint in a specific direction, the application of hybrid offset joints in PMs can impact the workspace. These findings offer valuable insights for the design of hybrid offset joints and their applications in robotics.

  • A Novel Delta-Like Parallel Robot With Three Translations and Two Pitch Rotations for Peg-in-Hole Assembly
    on December 19, 2024 at 12:00 am

    AbstractThis paper presents a novel 5-degree-of-freedom (5-DOF) delta-like parallel robot named the double-pitch-delta robot, which can output three translations and two pitch rotations for peg-in-hole assembly. First, the kinematic mechanism of the new robot is designed based on the DOF requirements. Second, the closed-form kinematic model of the double-pitch-delta robot is established. Finally, the workspace of the double-pitch-delta robot is quantitatively analyzed, and a physical prototype of the new robot is developed to verify the effectiveness of the designed mechanism and the established models. Compared with the existing 5-DOF parallel robots with two pitch rotations, the double-pitch-delta robot has a simpler forward displacement model, larger workspace, and fewer singular loci. The double-pitch-delta robot can be also extended as a 6-DOF hybrid robot with the full-cycle tool-axis rotation to satisfy more complex operations. With these benefits, the new robot has a promising prospect in assembly applications.

Modeling Method for Static Large Deflection Problem of Curved Planar Beams in Compliant Mechanisms Based on a Novel Governing Equation

Abstract

Slender beams serve as typical flexible components to transfer motion, force, and energy in compliant mechanisms. Therefore, the accurate and efficient kinetostatic modeling for the slender beams is highly needed in the synthesis and analysis of compliant mechanisms. Several impressive and great modeling methods have been completed by the pioneering researchers based on the governing equation of slender beams, which can solve the deflection of the beam while the beam-tip loads are known. However, parts of the beam-tip loads are unknown in some scenarios and the traditional governing equation becomes inefficient in these scenarios. The aim of this paper is to propose a novel modeling method for the compliant mechanism, which can solve the large deflection problem without iterative algorithm. In this research, a novel governing equation of slender beams has been established based on Castigliano’s principle and simplified by the differential geometry. In the proposed governing equation, the statically force equilibrium equations and geometric constraint equations between different slender beams can be established in the boundary conditions, therefore the model of compliant mechanisms can be solved directly even if parts of the beam’s tip loads and displacements are unknown. The proposed governing equation provides the deformed shapes and cross-sectional loads of the slender beams, which help the designer to check the mechanical interference and strength in the design process. The numerical examples are presented to demonstrate the feasibility of proposed method.

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