Latest Papers

ASME Journal of Mechanisms and Robotics

  • Investigation on a Class of 2D Profile Amplified Stroke Dielectric Elastomer Actuators
    on September 24, 2024 at 12:00 am

    AbstractDielectric elastomer actuators (DEAs) have been widely studied in soft robotics due to their muscle-like movements. Linear DEAs are typically tensioned using compression springs with positive stiffness or weights directly attached to the flexible film of the DEA. In this paper, a novel class of 2D profile linear DEAs (butterfly- and X-shaped linear DEAs) with compact structure is introduced, which, employing negative-stiffness mechanisms, can largely increase the stroke of the actuators. Then, a dynamic model of the proposed amplified-stroke linear DEAs (ASL-DEAs) is developed and used to predict the actuator stroke. The fabrication process of linear DEAs is presented. This, using compliant joints, 3D-printed links, and dielectric elastomer, allows for rapid and affordable production. The experimental validation of the butterfly- and X-shaped linear DEAs proved capable of increasing the stroke up to 32.7% and 24.0%, respectively, compared with the conventional design employing springs and constant weights. Finally, the dynamic model is validated against the experimental data of stroke amplitude and output force; errors smaller than 10.5% for a large stroke amplitude (60% of maximum stroke) and 10.5% on the output force are observed.

Design, Modeling, and Manufacturing of a Variable Lateral Stiffness Arm Via Shape Morphing Mechanisms

Abstract

In this article, we present a continuously tunable stiffness arm for safe physical human–robot interactions. Compliant joints and compliant links are two typical solutions to address safety issues for physical human–robot interactions via introducing mechanical compliance to robotic systems. While extensive studies explore variable stiffness joints/actuators, variable stiffness links for safe physical human–robot interactions are much less studied. This article details the design and modeling of a compliant robotic arm whose stiffness can be continuously tuned via cable-driven mechanisms actuated by a single servo motor. Specifically, a 3D-printed compliant robotic arm is prototyped and tested by static experiments, and an analytical model of the variable stiffness arm is derived and validated by testing. The results show that the lateral stiffness of the robot arm can achieve a variety of 221.26% given a morphing angle of 90 deg. The variable stiffness arm design developed in this study could be a promising approach to address safety concerns for safe physical human–robot interactions.
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