Traffic Flow and Vehicle Speed Measurements using Anisotropic Magnetoresistive (AMR) Sensors

Vehicles with ferrous material composition change the distribution of uniform earth magnetic field around them. The anisotropic magneto-resistive (AMR) sensor usually has magnetic field detection range within ±10 Oe, which is suitable to detect the earth magnetic field at 0.25~0.65 Oe as a low cost solution. The AMR sensor is able to sense the vehicle induced magnetic field change and can be utilized as vehicle detection sensor. This work uses two AMR sensor nodes to measure the vehicle velocity on the road. Signal processing is applied to remove noise and to get clean signal for precise speed calculation. The vehicle speed measured by AMR sensor is validated by a high speed camera at 250 fps. The AMR sensor at low cost and low power is a promising vehicle speed sensor for traffic flow and density management in the intelligent transport system.