Latest Papers

ASME Journal of Mechanisms and Robotics

  • Dynamic Modeling and Simulation of a Hybrid Robot
    by Shen N, Yuan H, Li J, et al. on May 12, 2022 at 12:00 am

    AbstractThe unique structure of hybrid robot makes its dynamic characteristic different from that of the traditional machine tools. Therefore, the dynamic model is crucial to both designing and application of hybrid robot. In this paper, a new type of five-degrees-of-freedom (5DoF) hybrid robot is introduced, and its dynamic model is established. First, the kinematic formulas are derived for all the component, and then, the inertia forces or moments are calculated. Second, the active forces or moments in the joints are assumed as variables and the number of variables is reduced by analyzing joint types. Then, an equation set of 36 equilibrium equations with 38 variables is obtained using D'Alembert's principle. Based on the spatial deformation compatibility analysis of two branches, two supplementary equations are derived to determine the solution of dynamic model of the hybrid robot with redundant constraints in its parallel mechanism. Several cases are studied by comparing with ADAMS simulation. The result shows the good accuracy of the proposed dynamic model, which provides a practical method to calculate the reaction force or moment in any joint at any instant for the hybrid robot and thus facilitates dimensional synthesis, trajectory optimization, and smoothing control.

  • Feasibility Design and Control of a Lower Leg Gait Emulator Utilizing a Mobile 3-Revolute, Prismatic, Revolute Parallel Manipulator
    by Soliman A, Ribeiro GA, Gan D, et al. on May 12, 2022 at 12:00 am

    AbstractDesign and control of lower extremity robotic prostheses are iterative tasks that would greatly benefit from testing platforms that would autonomously replicate realistic gait conditions. This paper presents the design of a novel mobile 3-degree-of-freedom (DOF) parallel manipulator integrated with a mobile base to emulate human gait for lower limb prosthesis evaluation in the sagittal plane. The integrated mobile base provides a wider workspace range of motion along the gait direction and reduces the requirement of the parallel manipulator’s actuators and links. The parallel manipulator design is optimal to generate the defined gait trajectories with both motion and force requirements using commercially available linear actuators. An integrated active force control with proportional integral derivative (PID) control provided more desirable control compared to traditional PID control in terms of error reduction. The novelty of the work includes the methodology of human data-oriented optimal mechanism design and the concept of a mobile parallel robot to extend the translational workspace of the parallel manipulator with substantially reduced actuator requirements, allowing the evaluation of prostheses in instrumented walkways or integrated with instrumented treadmills.

  • Announcing the 2021 Best Paper Award and Honorable Mention
    by Krovi V. on May 12, 2022 at 12:00 am

    Together with the Editorial Board of the Journal of Mechanisms and Robotics (JMR), I am pleased to announce the winner of the journal's 2021 Best Paper Award:P. Reinier Kuppens, Miguel A. Bessa, Just L. Herder, and Jonathan B. Hopkins, 2021, “Compliant Mechanisms That Use Static Balancing to Achieve Dramatically Different States of Stiffness,” ASME J. Mech. Robot., 13(2), p. 021010. https://doi.org/10.1115/1.4049438

Spring Configurations and Attachment Angles Determination for Statically Balanced Planar Articulated Manipulators

Abstract

Admissible spring configurations for statically balanced planar articulated manipulators have been investigated in previous studies. However, in these spring configurations, springs are only identified by the connection between links. The attachment angles and distance for springs to be properly installed remain unaddressed. In this study, a method to determine attachment angles and distance for springs is developed to ensure all the springs are acting for the benefit of static balancing. Here, the gravitational and elastic potential energies are represented in stiffness matrix form, it is shown that term by term compatibility exists between the first row of gravitational stiffness matrix and the first row of the elastic stiffness matrix. In accordance with these compatibility conditions, the admissible spring attachment angles are found to ensure all the ground-connected springs are acting for the benefit of gravity balancing. And the remained components below the first row of the elastic stiffness matrix are offset by the non-ground-connected springs. In accordance with the compatibility between the remained components and the elastic stiffness matrix of non-ground-connected springs, the spring attachment angles to ensure all the non-ground-connected springs acting for the benefit of elastic balancing are found. The determination of the admissible spring configurations is revisited in addition to the connection between links, and the attachment angles of springs are also specified. The admissible spring configurations of statically balanced planar articulated three- and four-link manipulators are derived. A four-link planar manipulator is used as an example for illustration.

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