Simple and Scalable Soft Actuation Through Coupled Inflatable Tubes

The manufacturing and assembly of soft actuators may seem like a straightforward affair, but various tools, equipment and specific know-how are required to build these actuators. Assembling them into soft robots can sometimes lead to numerous difficulties and often requires permanent assemblies of the components. Similarly, minimizing the number of components in more complex designs and the scaling of component to build larger structures can often require significant redesigns. There is a need for an easy to assemble and disassemble soft robotic actuator that helps minimize the number of components and is easy to scale in size. This paper introduces a simple assembly method for a soft inflatable joint capable of bidirectional motion that uses a rigid constriction with parallel slits in which inflatable tubes are inserted and whose ratio of pressures determines the bending angle of the joint. This concept enables the non-permanent and reversible assembly of inflatable robots, is highly scalable, and can help minimize the number of parts in a soft robot by placing multiple constriction-based joints on a single load-bearing inflatable tube. This concept is then implemented in a robotic manipulator with three degrees of freedom and a robotic hand as well as a large-scale quadruped robot with a leg length exceeding one meter.