Electromagnetic navigation displacement transducer based on magnetic gradiometer

Summary form only given. Electromagnetic navigation is a complementary guiding technique often used in navigation systems in conjunction with optical, GPS, and visual navigation techniques. It is especially important for smart vehicles working in severe environments and requiring high accuracy, reliability, and cost-effectiveness. In most cases, magnetic sensing arrays are assembled in the vehicles to pick up magnetic fields generated by cables buried in prescribed paths. By optimizing the position and response of the sensors in the arrays, the displacement of the vehicles to the cables can be determined and adjusted by steering systems. Though the navigation accuracy could be improved by increasing the number of sensors in the arrays, the reliability decreases with increasing the sensor number. The nonlinearity caused by discrete signals from the arrays also imposes challenges on the control systems. In this paper, an electromagnetic navigation linear displacement transducer is proposed and evaluated theoretically and experimentally based on a magnetic gradiometer made of two counter-wounded coils . Figure 1 shows the experiment results of the gradiometer output at different heights of 2-10 cm when the base-line length is 18cm . The best linear response occurs at a height of 6cm, in accordance with the theoretical derivation of height/length=0 .354 . Figure 2 compares the theoretical and experimental results under an optimal condition with an error of <;3% . Our proposed linear displacement transducer can overcome the discontinuous response and nonlinearity problem intrinsic in traditional magnetic sensor arrays, and provide a continuous displacement (movement) feedback with an accuracy of within several millimeters.