Continuum Robot Proprioception: The Ionic Liquid Approach

Slender continuum robots are uniquely placed to address inspection and intervention tasks in difficult-to-access environments. Tasks such as minimally invasive surgery and
in situ
maintenance of complex machinery require dexterous robots with accurate motion control, and benefit from instruments with small diameters and large internal passages for services. Intrinsic proprioception, or built-in position sensory feedback, has been described in prior work on continuum and soft robots but seldom employed for motion closed-loop control. In this research article, we present a novel tubular resistive stretch sensor with ionic liquid conductors to enable closed-loop position control of low-cost, 3-D printed continuum robots. We describe a methodology for sensor characterization and calibration drawing from a model of their behavior under strain, allowing us to apply four stretch sensors as proprioceptive feedback for motion control of a four-axis slender continuum manipulator. We demonstrate a substantial (approximately 65%) improvement in position control accuracy and repeatability over open-loop methods and show a promising step toward low-cost, scalable position feedback for slender continuum robots.