This chapter addresses smart sensor systems. In recent years, goods identification technology using a soft magnetic barcode, radio frequency identification, and automated wheelchair guidance technology using a magnetic field usable in dirty environments as part of Robotics and Mechatronics are becoming important in many areas, such as factories, physical distribution, office, security, etc. These identification and guidance technologies are based on sensing of magnetic field. Therefore, smart magnetic sensing technologies suitable for these identification and guidance techniques are described in this chapter.
Top1. Introduction
Optical paper-based barcodes are widely used in Point Of Sale (POS) systems for the management of foods, daily necessities, and goods management in clean factories. These commercial available systems are not usable for goods in dirty factories or in outdoor environments, where it is easy to be contaminated by oil, dust, and or mud. In 1990, researchers proposed a magnetic grooved barcode detection system using a magneto-resistive sensor usable in these dirty environments (Okabe & Wakaumi, 1990). This was an experimental system, in which the detection of a grooved barcode on an iron plate was confirmed in a low detection height of 0.1 mm. Afterward, its detection performance was improved to practical levels by developing a new scanner head structure using the Tape-Automated-Bonding (TAB) technology and by developing a new MR sensor with a slant-element sensor structure for realizing highly sensitive scanners (Wakaumi, Komaoka, & Hankui, 2000; Wakaumi, Ajiki, Hankui, & Nagasawa, 2000). These systems have an ability of detecting a barcode pattern engraved on a soft magnetic substance. So, it enables us to manage by easily identifying goods contaminated by oil, dust, and/or mud. In 2000, a highly sensitive GMR spin valve sensor being currently used in hard disks has been also developed (Lenz & Edelstein, 2006). This device has an ability to realize highly stable magnetic scanners due to its high sensitivity in low magnetic fields.
Magnetic sensing technology using a magnetic field is now being used for ID tag detection. This magnetic sensing technology had been already developed for use in detection of a magnetic ferrite marker. Ferrite can be cheaply made as a sub-product of Mn-Zn core and a product generated at refinement of Fe/Ti. Ferrite marker is a solid block or soft tile of ferrite sub-product bound in place with asphalt, concrete, and resin etc. This ferrite marker is detected by a magnetic sensor consisting of a magnetic field generating exciting coil and detecting coils. As concrete examples of this technology, an automated wheelchair guidance and control system has been developed (Wakaumi, Nakamura, Matsumura, & Yamauchi, 1989). This system can be constructed at low cost because of using the ferrite sub-product. Since it is also extremely useful for protection of global environment, this system is worth to be described. In the era of 2000 after that, computer controlled wheelchairs using several kinds of sensors such as a panoramic camera, a sonar proximity sensor, and a laser range finder have been developed instead of the magnetically guided wheelchair, in which their representative is the Bremen Autonomous Wheelchair (Rofer & Lankenau, 2000). It is thought that these technologies are very important in the process of realizing fully automation control wheelchairs required in advancing aging society.
As a Radio Frequency Identification (RFID) technology, an electromagnetic induction technology using a magnetic wave of 13.56 MHz is known and is widely used. This technology is basically the same as an operation principle in magnetic sensing technology for detection of ferrite markers using the magnetic field. However, each sensor structure is different from each other. The former uses one detection unit unified an oscillating coil with its sensing coil for detecting magnetic distortion. Basically, transmitted magnetic waves to ferrite sub-product are not modulated. The latter uses reader and tag receiver antenna coils for transmitting and receiving modulated electromagnetic waves. Transmitting of waves from the reader and receiver is performed in separate time periods using a half duplex mode or in the form of frequency-modulated signals within the same time period using a full duplex mode. Mainly, an amplitude modulation signal in a transmitter and receiver consisting of antenna coils is used in this system. This RFID identification system was developed to identify concrete-mixer vehicles to monitor the running status in 2003 (Nikkei Computer, 2003; RFID Technology Editorial Department, 2004). Presently, this technology is used for identification of personal information and goods such as products.