Mechanically Programmable Jamming Based on Articulated Mesh Structures for Variable Stiffness Robots

Abstract

Soft robots are capable of effortlessly adapting to their environment using elastic materials that impart structural compliance into their designs, allowing them to execute complex tasks with minimal sensing and control. However, soft robots cannot exert high forces and can only handle low deformation forces. These characteristics typically limit their applicability to tasks that require delicate interactions. In this work, we present a mechanically programmable, variable stiffness, jamming actuator based on an articulated mesh structure. The proposed actuator can elastically bend when it is not activated but compresses to attain a pre-programmed shape that is determined by the mesh geometry of the multi-layer jamming architecture when pressure is applied to the silicone pouch containing it. Unlike traditional jamming structures the utilisation of the articulated mesh structure facilitates elastic deformations past the yield point when jammed. The actuator can become >27 times stiffer than its relaxed configuration when exposed to only 90 kPa pressure. We demonstrate the efficiency of this actuator by developing variable stiffness joints that can be used to create: i) underactuated, tendon driven robotic grippers and soft, disposable robotic grippers that exhibit increased dexterity and ii) wearable, affordable, lightweight elbow exoskeleton systems that can assist humans in holding heavy objects with minimal effort.

Design and implementation of an underactuated gripper with enhanced shape adaptability and lateral stiffness through semi-active multi-degree-of-freedom endoskeletons

“…This relatively small pinch force is mainly due to the compliance of the palm and thus could be enhanced by adding the locking endoskeleton into the palm actuators. Also, vacuum has been widely used to tune and enhance stiffness by enveloping rigid pieces with a sealed skin (Wang et al, 2021; Gao et al, 2022). Simply introducing a vacuum besides the positive pressure to our gripper’s soft skin actuator and palm actuator may further increase its grasping stability and stiffness.…”