Force and Speed in a Soft Stewart Platform

--Many soft robots struggle to produce dynamic motions with fast, large displacements. We develop a parallel 6 degree-of-freedom (DoF) Stewart-Gough mechanism using Handed Shearing Auxetic (HSA) actuators. By using soft actuators, we are able to use one third as many mechatronic components as a rigid Stewart platform, while retaining a working payload of 2kg and an open-loop bandwidth greater than 16Hz. We show that the platform is capable of both precise tracing and dynamic disturbance rejection when controlling a ball and sliding puck using a Proportional Integral Derivative (PID) controller . We develop a machine-learning-based kinematics model and demonstrate a functional workspace of roughly 10cm in each translation direction and 28 degrees in each orientation. This 6DoF device has many of the characteristics associated with rigid components--power, speed, and total workspace-- while capturing the advantages of soft mechanisms. Soft robots promise to be safer, more resilient, and more adaptable than their rigid counterparts. This is particularly valuable for systems that are expected to touch and interact with people. However, existing soft 6 DoF parallel mechanisms struggle to produce the forces, displacements, and response times required for mass adoption [1]-[3]. A substantial driver of this capability gap is the many limitations of soft actuator technologies.