Abstract
The author describes a position identification technique for tunneling machines. A three-dimensional flux measurement system is presented to conduct a remote search for the head of a tunneling machine. A transmitter is installed in the machine head, which generates a low-frequency magnetic field. A receiver, placed on the ground above the machine, accurately detects the magnetic flux. An instantaneous estimation algorithm is proposed to locate the transmitter position by evaluating three-dimensional distribution of the flux density. The estimation procedure is formulated in detail, and exemplified by concrete measurement data. A prototype measurement system is designed and manufactured to install in the tunneling machine. The receiver is equipped with a newly developed 1.3-mm-thick magnetometer which is smaller and lighter than a conventional wired coil sensor. The resolution of the magnetometer is less than 10 nT, and is more sensitive than a Hall element. Experimental results show that this system can estimate the position of a transmitter placed 5 m below it with an accuracy of about 10 mm. The measurement system was actually applied to construction of a tunnel and showed its successful performance.
