FBG-based shape sensing tubes for continuum robots

Fiber Bragg gratings (FBG)-based optical sensors are a promising real-time technique for sensing the 3D curvature of continuum robots. Existing implementations, however, have relied on embedding optical fibers in small-diameter metal wires or needles. This paper proposes polymer tubes as an alternative substrate for the fibers. This approach separates the sensors from the robot structural components while using a minimal amount of the robot's tool lumen and providing the potential of inexpensive fabrication. Since the fibers are stiffer than the polymer substrate, however, design challenges arise in modeling strain transfer between the fibers and the tube substrate. To investigate the potential of this approach, a strain transfer model is derived and validated through simulation and experiment.