Absolute Long-Range Linear Position System With a Single 3-D Magnetic Field Sensor

The range of magnetic linear position detection is limited by the field amplitude of the permanent magnetic source, which must exceed external stray fields or sensor limitations. We propose a novel implementation with a specially designed magnetic source and a single 3-D sensor to improve the performance. The source is based on an array of magnets, arranged in a string parallel to the mechanical motion, and can be implemented using only simple, commercially available permanent magnet geometries. A theoretical analysis shows that the proposed system can boost the range by a factor of two when compared with the state-of-the-art 2-D implementations with similar total magnetic volume. An experimental validation was successfully carried out.