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.

Energy-Efficient Tristable Soft Gripper Using Shape Memory Alloy Wires for Gripping Convex and Concave Objects

Abstract

Bistable structures have been widely utilized in soft grippers to reduce the energy required for maintaining grip. Grippers have been investigated in terms of the energy efficiency and accuracy of gripping; however, the limited number of gripping states hinders the holding of objects of various shapes. In this study, an energy-efficient gripper was developed to accommodate both convex and concave shapes using a tristable structure that combines two bistable structures, with shape memory alloy wires used as actuators. Different gripping modes were designed for convex and concave shapes, based on three states of the gripper: gripping, open, and holding. The gripper consisted of a driving part with a leaf spring for a “linear snap action” and a soft finger part with an elastic ring and prestressed fingers. Geometric variables were adjusted to construct a tristable energy curve through experiments and analyses. The fabricated gripper weighed about 140 g and was capable of gripping convex objects of up to 80 g, and concave objects of about 120 g. Only a small amount of energy was consumed in the switching states, and the gripper maintained a stable state while gripping with no energy consumption. It is expected that this research will contribute to lightweight and energy-efficient grippers for application to drones, for example.

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