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 of an Efficient Non-Backdrivable Mechanism With Wrap Spring for Hand Prosthesis

Abstract

The aim of this paper is to create a system that enables power transmission non-backdrivability in a hand prosthesis with a single actuator. This system allows the motor to be stopped while maintaining the gripping force to prevent the held object from being dropped. This non-backdrivability allows users, for example, to release muscle contractions while still keeping a tight grip on an object, as well as completely turning off the prosthesis to avoid unintentional commands that could lead to loosening the object. Beyond the functional aspect of non-backdrivability, the physical non-backdrivability of the transmission enables the full power of the motors to be utilized without exceeding their thermal limits. To be effectively used, the non-backdrivable system must be energy efficient. A state-of-the-art analysis of different non-backdrivable mechanisms is conducted, evaluating their functioning and maximum efficiency. A novel system is developed based on an existing principle but with a focus on simplicity of manufacturing and fewer components compared to existing systems. An analysis is conducted to understand the effect of each mechanism parameter, and a dimensioning procedure is derived. A prototype is developed to compare theoretical values with measured values. The obtained results are analyzed and discussed.

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