Evolution of Material Properties and Gripping Strategy in Soft Robotic Jamming Devices

We consider the problem of design of granular materials for optimal gripping behaviour in soft robotic devices. This represents a highly challenging multi-dimensional design problem, requiring consideration of material, geometry and control strategies. Our system consists of a bag gripper composed of a flexible balloon attached to a vacuum pump, filled with granular material of non-spherical particles. At atmospheric pressure the bag is soft, flexible and deforms around a target object. When the vacuum is then applied, the granular material within the gripper densifies, freezing into a rigid shape and gripping the target object. The morphology of the particles within the granular material play a crucial role in determining the dynamics of the gripping behaviour and the overall performance of the gripper in terms of its interaction with the target object and the strength of the grip (quantified as the pull off force). In this work we consider both a real world physical gripper and a corresponding computational model (based on the Discrete Element Method), and employ NSGA-III to optimise the design of both the complex structure of the granular material within the gripper and also an optimal gripping strategy to achieve maximum gripping performance for multiple fitness criteria.