Tactile sensors using the distributed optical fiber sensors

This paper describes two kinds of the tactile sensors using the optical fiber sensors. One is the tactile sensor using fiber Bragg grating (FBG) sensor. Bragg grating inscribed in an optical fiber causes reflect of a spectral component at the Bragg wavelength. This sensor can detect external force using change of the reflective wavelength. The other is the tactile sensor using the microbending optical fiber (MBOF) sensors. The microbending of the optical fiber drives the light transmission loss from the optical fiber. Using the light loss, this sensor can also detect the external force. The structures of these type tactile sensors are very simple. The tactile sensor using FBG sensor consists of an optical fiber which has a Bragg grating and bridge type transducers, and using MBOF sensors is composed of crossed fibers in the silicone rubber. In this paper, we fabricated and evaluated both tactile sensors. The performances of both tactile sensors were verified.

1 Introduction

Recently many researchers have studied to apply the five senses of human such as the sense of sight, hearing, smell, taste, and touch to the intelligent robot system. Among them, the tactile sensor for sense of touch is one of the essential means for interfacing between human and robots [1]. Several tactile sensors are introduced for intelligent robots and haptic interfaces to detect the contact force, the texture and the temperature, etc. Some tactile sensors using MEMS (Micro Electro Mechanical System) technology have been introduced [2]–[5]. However, in this paper, the optical fiber sensors are used for the tactile sensors. The optical fibers have attractive characteristics such as flexibility and relative immunity to many environmental disturbances, especially electromagnetic and electrostatic fields existing commonly near industrial machinery. The optical fiber sensors are not affected by even humid environment. In this paper, we designed two types of tactile sensor elements using the optical fiber sensors. One is tactile sensor using FBG sensor. This type of tactile sensor has simple wiring for application of the wavelength division multiplexing method with a broadband light source and some FBGs, which have different Bragg wavelength in a given optical fiber. The other is the tactile sensor using MBOF sensors with the structure of crossed fibers in the silicone rubber. This type of tactile sensor has also simple wiring by using optical fiber bundle. The optical measuring system for this sensor has compact design with a single light source and a detector.