Modeling and Design of Soft Pneumatic Actuators

Read more about this work and access the open-source tool developed at RRL to model soft robots at Harvard University’s Soft Robotics Toolkit.  You can also download complete set of SPA Design Tool scripts here:

Soft pneumatic actuators (SPA) consisting of elastomeric matrices embedded or reinforced with flexible materials are of particular interest to the robotics community because they are lightweight, affordable and easily customized to a given application. They enable the achievement of safer and flexible interaction in a variety of applications including robotic grasping, wearable systems, versatile locomotion, and biomedical rehabilitation. These actuators can be rapidly fabricated in a multi-step molding process and can achieve combinations of extension/contraction, bending and rotary motion, as shown below. By defining motion and force profile requirements, it is possible to program these soft actuators to achieve the performance requirements with simple tunable control inputs such as air pressure.

Numerical simulation results using Finite Element Analysis (FEA) for soft actuators in
linear and bending motion. Simulations predict motion-force profiles obtained with
the actuators, enabling the design of more efficient systems.

Although the scalability, customizability, and diversity of soft actuators are widely recognized, comprehensive techniques for modeling and designing soft actuators are lacking. Characterizing and predicting the behavior of soft actuators is challenging due to the nonlinear nature of both the hyperelastic, viscoelastic material used and the large range of motions they produce. In this work, mathematical tools and new design concepts are employed to improve the performance of these actuators compared to existing designs.

A comprehensive, cohesive, and open-source simulation and design tool for soft actuators using the finite element method (FEM) has been developed, readily compatible with and extensible to a diverse range of soft materials and design parameters. This design tool can enable the generation of improved predictive models that will help us to rapidly converge on new and innovative applications of these soft actuators.

Current work is focused on the development of novel designs for soft actuators, aimed at making the fabrication of these actuators more repeatable, along with improving the actuator performance compared to the metrics obtainable with existing designs. Corresponding FEM simulation tools to predict the actuator behavior and enable better future designs are simultaneously being developed and will continue to be a focus for future study. Another direction of research in this field is aimed at customizing the actuator performance for specific biomedical applications and characterizing the mechanical behavior required.

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