Control optimization of electromagnet coil driver for electromagnetic groundwater measurement.

As a part of New Zealand’s National Science Challenge, a novel groundwater measurement device was developed by a team of researchers from various institutions, including the University of Canterbury. A prototype device was built during this research. However, several improvements are required to bring the device out from the laboratory to the field. This master’s thesis aims to improve the performance and integration of the prototype. To measure the groundwater flow, a magnetic field is generated by a trapezoidal current driving a large coil. However, due to the proximity effect, the coil current first overshoots and then reaches the steady-state slowly. The changing current produces an interference signal which obscures the measured flow signal. Furthermore, due to the slow operation of the microcontroller that controls the coil driver prototype, timing jitter appears in the magnetic field. This project improves the hardware architecture of the controller, with the aid of an FPGA, and a control algorithm to achieve a steady current after the overshoot. The modifications reduce the coil current variation while improving the level of integration compared to the prototype. The project was funded by the National Science Challenge of New Zealand