A Scalable Soft Robotic Cellbot

Abstract

In nature, cells combine into different structures to perform the task at hand. Taking inspiration from cells, we present a proof-of-concept and a prototype of a soft modular cellbot composed of simple spherical elements (cells). Locomotion is achieved by establishing and exploiting frictional asymmetries in the interaction of cells and the terrain. We explore the effect of friction coefficient, actuation forcing function, number of cells and axial robot orientation on robot movement, using both simulation model and physical robot. The robot was built using multiple inflatable balls to represent cells connected by linear actuators. The structure, softness, compliance and the ability to deflate the structure for transporting are designed to enhance robustness, fault tolerance and cost effectiveness for disaster affected areas, nuclear sites, and outer space applications. The trend of displacement versus number of cells varies for different friction values. For a surface with mid-to-high static and kinetic friction coefficient, increasing the number of cells stabilises the robot on the ground, increasing the necessary frictional asymmetry and reducing slipping. This helps the designer exploit friction conditions by specifying the robot with suitable structural materials. Understanding the effect of these parameters will help to maximise robot movement by choosing an optimal configuration with respect to orientation or by merging or splitting the cellbot, based on the frictional properties of terrain.