Quantifying Dynamic Shapes in Soft Morphologies

Unlike in the case of rigid bodies, it is not trivial to describe the shape of a soft deformable body. A quantitative measure to describe body shape is therefore extremely useful in the design and analysis of soft robots. Abstraction is a key step in bioinspired design and identifying the key features of a shape could influence design choices such as the material of construction or actuation technology. In this article, we use a method based on elliptic Fourier descriptors to describe soft deformable morphologies. We perform eigenshape analysis on the descriptors to extract key features that change during the motion of soft robots, showing the first analysis of this type on dynamic systems. We apply the method to both biological and soft robotic systems, which include the movement of a passive tentacle, the crawling movement of two species of caterpillar (Manduca sexta and Sphacelodes sp.), the motion of body segments in the M. sexta, and a comparison of the motion of a soft robot with that of a microorganism (euglenoid, Eutreptiella sp.). In the case of the tentacle, we show that the method captures differences in movement in varied media. In the caterpillars, the method illuminates a prominent feature of crawling, the extension of the terminal proleg. In the comparison between the robot and euglenoids, our method quantifies the similarity in shape to ∼85%.

This work is now published in the Soft Robotics journal. Access the paper on the publisher’s website.

A simplified demo of the MATLAB code used in the paper can be found here.