Magnetic Tensor Sensor for Gradient-Based Localization of Ferrous Object in Geomagnetic Field

This paper presents a gradient-based method, along with the design concept, characteristics, and operating range of a magnetic tensor sensor (MTS), for locating and identifying a ferrous/magnetic object in the presence of geomagnetic field. This method characterizes the magnetic moment M and position vector R of a ferrous/magnetic object in terms of two scalar parameters (an orientation-insensitive P and a distance-insensitive.) derived from the measured magnetic tensor data. These scalar parameters offer an excellent alternative to the traditional (M and R) in characterizing a magnetic object with an arbitrary shape for some applications when the dipole model is a poor approximation. With a prototype MTS that has been developed and experimentally validated, the effectiveness and accuracy of the gradient-based method are demonstrated with two different types of compact objects. The first object is a uniformly magnetized cylindrical permanent magnet, commonly used as an engineered landmark for machine applications, where the interest is to accurately determine M and/or R. The second object is an example of a general ferrous object with a non-uniform shape to illustrate the detection and approximate localization of a ferrous object for applications such as visually impaired assistance.