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.

Development of a Novel Compact Robotic Exoskeleton Glove With Reinforcement Learning Control

Abstract

This paper presents the design, optimization, control, and experimental evaluation of a novel compact exoskeleton glove aiming to assist patients with brachial plexus injuries in grasping daily used objects. The finger mechanism is based on a rigid coupling hybrid mechanism concept, which utilizes a serially connected rack-and-pinion mechanism and an offset slider-crank mechanism to couple the motions of different finger joints. The glove dimensions are synthesized based on the natural grasping motion of human hands. To better control the glove and enhance the grasping capabilities, a simulation environment was developed and reinforcement learning techniques were applied. This learning-based control trained an agent to perform different grasp types with appropriate force. The trained agent was then applied in real-world experiments with the developed exoskeleton glove. The results validated the effectiveness of the mechanical design and the real-time self-adjustable control policy, which demonstrated the glove’s functionality and capability to grasp various objects relevant to activities of daily living.

Read More

Journal of Mechanisms and Robotics Open Issues