A Flexible Dual-Core Optical Waveguide Sensor for Simultaneous and Continuous Measurement of Contact Force and Position

Having the merits of chemical inertness and immunity to electromagnetic interference, light weight, small size, and softness, optical waveguides have attracted much attention in making tactile sensors recently. This paper presents a new design of waveguide using two layers of cores, one of which has an uniform width and the other has an incremental width. It is deduced and verified that the contact force can be derived from the light power loss in the uniform-width core, while the contact position can be derived from the light power loss in the other core together with the estimated force. By this dual-core design, a single waveguide can simultaneously and continuously measure the contact force and position along it, which makes it very suited for integration on some thin long robotic parts, such as robotic fingers. A hardware experiment has been conducted to demonstrate its effectiveness on a two-finger gripper in an assembly task. The dual-core waveguide achieves 2 mm spatial resolution and 0.1 N sensitivity.