Modelling a soft composite accumulator for human mobility assist devices

Area of Science:

• Biomedical Engineering
• Materials Science
• Robotics

Background:

• Human mobility assist devices aim to reduce metabolic cost during daily activities.
• Pneumatic Artificial Muscles (PAMs) are effective energy accumulators but face challenges like pressure dissipation and limited elongation.
• A novel Soft Composite material replicates PAM behavior without internal pressurization.

Purpose of the Study:

• To develop and validate constitutive models for Soft Composite energy accumulators.
• To provide a deeper understanding of the mechanical behavior of these novel materials.
• To establish a foundation for future Soft Composite design in assistive devices.

Main Methods:

• Development of two constitutive models based on finite elasticity theory.
• Utilized Holzapfel, Gasser, and Ogden's strain energy function (structural).
• Utilized Fung's strain energy function (phenomenological).
• Experimental validation using a modified extension-inflation test.

Main Results:

• Both developed constitutive models accurately represented the experimental data.
• The models showed good agreement with the behavior of the Soft Composite material.
• The Soft Composite material demonstrated PAM-like mechanical properties without pressurization.

Conclusions:

• The proposed constitutive models offer a reliable basis for analyzing Soft Composite accumulators.
• Soft Composite materials present a viable alternative to PAMs in mobility assist devices.
• Further research into Soft Composite design models is warranted for advanced assistive technologies.