Latest Papers

ASME Journal of Mechanisms and Robotics

  • Design of Reconfigurable Articulated Walking Mechanisms for Diverse Motion Behaviors
    on March 20, 2025 at 12:00 am

    AbstractLegged robots are able to move across irregular terrains and those based on 1-degree-of-freedom planar linkages can be energy efficient but are often constrained by a limited range of gaits which can limit their locomotion capabilities considerably. This article reports the design of novel reconfigurable parallel linkages that not only produce different walking patterns but also realize behaviors beyond locomotion. Experiments with an implemented wearable device able to guide the lower extremity through multiple human-like walking trajectories are presented and the preliminary results validate the proposed approach.

  • Modeling, Kinematics, and Dynamics of a Rigid-Flexible Coupling Spring-Cable-Driven Parallel Robot
    on March 20, 2025 at 12:00 am

    AbstractConventional parallel robots are made of rigid materials for the purpose of fast and accurate localization, exhibiting limited performance in large-scale operations. Inspired by the softness and natural compliance of biological systems, this article proposes a rigid-flexible coupling cable-driven parallel robot. The concept of flexible cable and spring hybrid and working principle are introduced. The kinematics of single module and multiple modules connected in series are analyzed and equations are given, and the Lagrange equation is used to establish dynamic models. Finally, two methods are used to validate the kinematics and dynamics. One is to draw the specific structure with the posture of the end-effector and measure the cable length to compare it with the analytical solution in the kinematic model. The other is to build the structure and joint characteristics in simulink, given the posture of the end-effector and the external force/torque, the cable length and the force applied are compared with those obtained from the dynamic model. The reasonableness of the mechanism and the feasibility of the kinematic and dynamic models are verified.

A Micro-Deformation Model of Parallel Manipulators in the Gravity Field

Abstract

Establishing a microelastic deformation (micro-deformation) model of parallel manipulators (PMs) in the gravity field is of great significance for improving the calibration accuracy. Gravity affects the limb constraint wrenches space of PMs, resulting in the end-point micro-deformation, which damages end-point accuracy. A modeling method was proposed for the micro-deformation analysis of PMs with the consideration of gravity and the flexibility of rods and actuators based on the screw theory to fix this issue. First, the mechanism was considered an open-loop structure by cutting joints at the connection between limbs and moving platform. The limb constraint wrenches system and limb stiffness matrix were determined based on the screw theory and strain energy methods. Then, the limb gravity-additional constraint wrenches induced by gravity were established based on the reciprocity product of the twist screw and the constraint wrenches being zero. Meanwhile, the projection of limb deformations caused by gravity in the direction of the constraint wrenches system was established. Finally, an analytical methodology of the end-point micro-deformation of PMs with the consideration of gravity was built by means of the virtual work principle. The work decoupled the influences of gravity and the external load on the micro-deformation of the mechanism. The comparison between the results of the analytical model and finite element model of the line body and solid body of the 3PRRR over-constrained PM showed that the maximum error of the linear micro-deformation was within 3% and 11%, respectively.

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