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.

Motion Modeling of a 5-Axis Delta Robot with Telescopic Shafts

Abstract

This paper deals with motion modeling of a 5-axis industrial Delta robot. The robot has extra rotational two degrees-of-freedom (DoF) realized with a wrist arm driven through two co-axial telescopic shafts as compared to the basic 3-DoF Delta robot. The kinematic model is derived with fully symbolic Jacobian matrices. Using the derived Jacobians, a novel simplified dynamic model is proposed based on the virtual work principle and the trajectory dependent artificial mass distribution. As compared to the existing literature, the proposed dynamic model does not require Lagrangian multiplier calculation or recursive and parallel computing so that it provides advantage for model-based control design. Also a linear regression model is provided to identify the dynamic parameters. The presented models are suitable to be employed for basic Delta and the extended Delta robots with parallel telescopic shafts as well. The derived models are verified through a Simulink model where the 3D CAD files of robot bodies having the information of real dimensions, masses and moments of inertia are used. The adequate agreement of the proposed dynamic model with the simulation results is illustrated via performing three different generated trajectory profiles. We also demonstrate the better accuracy of the proposed dynamic model as compared to a simplified and widely employed model for basic 3-DoF Delta robot. The simulation model is shared online to serve as a research and test platform for performing tasks such as motion planning, model prototyping, and control design.

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