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UBC Theses and Dissertations

Fiber optic interferometric torque sensor with applications to milling Richardson, Douglas Harvey


To make unmanned machining viable it is necessary to monitor the machining process. The currently available sensor technology is not adequate to monitor all of the required aspects of the machining process. In this thesis a fiber optic milling machine torque sensor is proposed and experimentally analyzed. The initial tests, at low torque amplitudes, performed on the experimental prototype indicate that the proposed sensor may have performance characteristics which are superior to the characteristics of the currently used milling machine sensors. The proposed sensor has the advantages of small size, immunity to electromagnetic interference, micro-torque resolution, a dynamic range greater than 100000, and a useful minimum frequency bandwidth limited only by the first natural frequency of the spindle. Two sensors were constructed, one a bench top test sensor and the other a milling machine sensor. Two electrical signal processing schemes, which remove the inherent ambiguities of the sensor technology used, were investigated for each sensor. The milling machine sensing system had the fiber optic components mounted on the milling machine's drawbar. Before the drawbar sensor could be mounted on to the milling machine the laser diode source was damaged. Using the results of the tests performed on the bench top sensor and the drawbar sensor, the milling machine sensor was predicted to have a frequency bandwidth of 780 Hz, a resolution of 20 µNm, and a dynamic range greater than 100000.

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