Exoskeletal Force-Sensing End-Effectors With Embedded Optical Fiber-Bragg-Grating Sensors

Abstract

Abstract-Force sensing is an essential requirement for dexterous robot manipulation. We describe composite robot end-effectors that incorporate optical fibers for accurate force sensing and estimation of contact locations. The design is inspired by the sensors in arthropod exoskeletons that allow them to detect contacts and loads on their limbs. In this paper, we present a fabrication process that allows us to create hollow multimaterial structures with embedded fibers and the results of experiments to characterize the sensors and controlling contact forces in a system involving an industrial robot and a two-fingered dexterous hand. We also briefly describe the optical-interrogation method used to measure multiple sensors along a single fiber at kilohertz rates for closed-loop force control.Index Terms-Biologically inspired robots, dexterous manipulation, fiber Bragg grating (FBG), force and tactile sensing, force control, shape-deposition manufacturing.

Subwavelength Resonant Gratings for Micrometric Strain Sensors

“…The resulting sensitivity in both cases is 7.5 pm/µε (120 nm/16000 µε). In comparison with other proposed sensors based on lambda shifts [1] [2] (1.21 pm/µε and an order of magnitude higher), the sensitivity is considerably high in a broad range of elongations (16000 µε). In this case, the interrogation would require the use of spectrometers and tunable lasers.…”

“…Commercially, the most prevalent technology today is based on fiber Bragg gratings (FBG). The sensitivity for standard FBG strain gauges is well known to be 1.21 picometers (pm) of wavelength shift per µε applied to the fiber (pm/µε) [1]. These are fabricated in conventional 125 µm silica fiber with a Bragg wavelength at 1550 nm.…”

Fiber Bragg Gratings as e-Health Enablers: An Overview for Gait Analysis Applications

“…Although there is a shortage of studies regarding the adaptation of FBG sensing technologies to exoskeletons, for gait aid there are already some reports focusing on its application in robot fingers and glove-based devices [95][96][97]. Park et al presented an FBG-based solution to monitor the force in exoskeleton fingers [95].…”

“…Although there is a shortage of studies regarding the adaptation of FBG sensing technologies to exoskeletons, for gait aid there are already some reports focusing on its application in robot fingers and glove-based devices [95][96][97]. Park et al presented an FBG-based solution to monitor the force in exoskeleton fingers [95]. The authors embedded the optical fiber sensors in a finger-like plastic 3D mesh, inspired in the design of arthropod limbs, near the fingers base, for enhanced sensitivity.…”

“…The authors embedded the optical fiber sensors in a finger-like plastic 3D mesh, inspired in the design of arthropod limbs, near the fingers base, for enhanced sensitivity. With the developed structure, it is possible to detect forces down to 0.02 N, with a resolution of ~0.15 N. The robot hand instrumented by Park et al was able to be operated in a hybrid control scheme, with the fingers being capable to sense small forces, with the advantage of being able to have all the FBG sensors in one single fiber, due to FBGs multiplexing ability [95].…”