Twisted and Coiled Sensor for Shape Estimation of Soft Robots

Abstract

Soft robots with inherent compliance have been recently investigated intensively for locomotion or manipulations. A critical problem for soft robots is the capability to estimate their shapes to enable closed-loop control for precise motion. In this paper, we propose a new low-cost sensor that can be leveraged for shape estimation of soft robots. This sensor, recently discovered as an artificial muscle, can be conveniently fabricated from low-cost conductive sewing threads. We recently find that the resistance will increase if the fabricated sensor is elongated due to an external force. Since the sensor is inherently soft, it can be embedded into soft robots to estimate the shape. We establish a physics-based model to predict the external force and the displacement if the resistance is given and experimentally validate its correctness. Moreover, to demonstrate the sensing capability, we embed the proposed sensor into soft materials and successfully measure two curvatures of a two-segment soft robot. Therefore, the proposed sensor has the potential to estimate complicated shapes of soft robots to enable closed-loop control.