Magnetoresistors for vehicle detection and identification

A magnetoresistor sensor is proposed as an alternative to the conventional magnetic loop for automobile detection and traffic control. Underground magnetic loops have been used to detect the presence of vehicles at the roadway intersections for the past few decades. The detection scheme is based on the principle that the magnetic flux linking the buried loop changes whenever a vehicle is present above the plane of the loop. However, it has long been recognized that these magnetic loops are intrusive, expensive to install, and costly to maintain. Besides not very reliable, they are incapable of detecting the differences between cars, trucks, and motorcycles. In addition to the permanent magnetism inherent to a vehicle, the Earth's magnetic field also induces in it a magnetic dipole field. The vector sum of the induced and permanent fields may be exploited by a vehicle recognition and identification system or device. By means of systems modeling and computer simulation, the paper analyzes and evaluates such a vehicle sensing device.