Design and Characterisation of a Variable-Stiffness Soft Actuator Based on Tendon Twisting

The field of soft robotics aims to address the challenges faced by traditional rigid robots in less structured and dynamic environments that require more adaptive interactions. Taking inspiration from biological organisms’ such as octopus tentacles and elephant trunks, soft robots commonly use elastic materials and novel actuation methods to mimic the continuous deformation of their mostly soft bodies. While current robotic manipulators, such as those used in the DaVinci surgical robot, have seen use in precise minimally invasive surgeries applications, the capability of soft robotics to provide a greater degree of flexibility and inherently safe interactions shows great promise that motivates further study. Nevertheless, introducing softness consequently opens new challenges in achieving accurate positional control and sufficient force generation often required for manipulation tasks. In this paper, the feasibility of a stiffening mechanism based on tendon-twisting is investigated, as an alternative stiffening mechanism for soft actuators that can be easily scaled as needed based on tendon size, material properties, and arrangements, while offering simple means of controlling a gradual increase in stiffening during operation.