Electromagnetic system determining the position of tunnelling robots

The authors describe a newly developed thin arrayed-magnetometer system and a 1.3 mm thick highly sensitive magnetometer device especially designed for it. The system uses a sensor sheet spread over the ground above the tunnel construction site. Each magnetometer in the sheet is a planar coil made using a printed-circuit-board photofabrication process and includes built-in amplifier and filter circuits. The magnetic flux, generated by a transmitting coil which is contained in a tunnelling robot, is detected by the sensor sheet and the system estimates the magnetic field distribution and conjectures the coil position. Experiments proved that the system accurately determines where the tunnelling robot is travelling at a precise moment