Formulation for a practical implementation of electromagnetic induction coils optimized using stream functions

Mark A. Reed; Waymond R. Scott Jr.

doi:10.1117/12.2224214

3 May 2016 Formulation for a practical implementation of electromagnetic induction coils optimized using stream functions

Mark A. Reed, Waymond R. Scott Jr.

Author Affiliations +

Proceedings Volume 9823, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XXI; 982304 (2016) https://doi.org/10.1117/12.2224214
Event: SPIE Defense + Security, 2016, Baltimore, MD, United States

Abstract

Continuous-wave (CW) electromagnetic induction (EMI) systems used for subsurface sensing typically employ separate transmit and receive coils placed in close proximity. The closeness of the coils is desirable for both packaging and object pinpointing; however, the coils must have as little mutual coupling as possible. Otherwise, the signal from the transmit coil will couple into the receive coil, making target detection difficult or impossible. Additionally, mineralized soil can be a significant problem when attempting to detect small amounts of metal because the soil effectively couples the transmit and receive coils. Optimization of wire coils to improve their performance is difficult but can be made possible through a stream-function representation and the use of partially convex forms. Examples of such methods have been presented previously, but these methods did not account for certain practical issues with coil implementation. In this paper, the power constraint introduced into the optimization routine is modified so that it does not penalize areas of high current. It does this by representing the coils as plates carrying surface currents and adjusting the sheet resistance to be inversely proportional to the current, which is a good approximation for a wire-wound coil. Example coils are then optimized for minimum mutual coupling, maximum sensitivity, and minimum soil response at a given height with both the earlier, constant sheet resistance and the new representation. The two sets of coils are compared both to each other and other common coil types to show the method’s viability.

Citation Download Citation

Mark A. Reed and Waymond R. Scott Jr. "Formulation for a practical implementation of electromagnetic induction coils optimized using stream functions", Proc. SPIE 9823, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XXI, 982304 (3 May 2016); https://doi.org/10.1117/12.2224214

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