Finite-Difference Time-Domain Analysis of Currents from a Human Electro-Muscular Incapacitation Device
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Date
2010-04-27
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Abstract
This research studies the currents generated within the human body when subjected to a Human Electro-Muscular Incapacitation (HEMI) device – commonly known as a Stun Gun. The currents are calculated using the grid based Finite-Difference Time-Domain (FDTD) method of computational electromagnetics.
The FDTD technique consists of first defining the Computational Domain - in this case the model of a human torso and a HEMI device. Then the electromagnetic source is defined and the FDTD algorithm and boundary logic is applied to the computational domain to calculate the magnetic and electric fields within the model. In this research, changes were made to the model of the electromagnetic source and to the model of the human torso in order to determine the changes’ effects on the peak currents observed at key observation points within the body.
The electromagnetic source was modeled as both a gap current source and a magnetic frill source. The input signal waveform and the length of wires connecting the HEMI device to the subject were changed. In addition, the probe penetration depth, probe separation width, and probe contact locations were all changed. Finally, changes to the human torso model were made, including modeling the skin in wet and dry conditions, as well as adding clothing of various thickness and electromagnetic properties.
This research shows that modeling the source as a gap source or magnetic frill are equivalent and the length of the wires connecting the HEMI device to the subject has no impact on the currents within the body. It also shows that probe penetration and probe separation increase the current penetration into the body. Wet skin, or any slightly conductive layer, reduces current penetration to a greater degree than clothing with no conductive properties. However, the greatest impact on the currents at set observation points within the body was the location of the contact probes. This suggests that when a person is shot with a HEMI device, the location of impact of the probes has more of an effect on the currents that a person is subject to than the depth or separation of the probes, or whether the person was wet or wearing clothes.
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Keywords
HEMI, electromagnetics, FDTD
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Degree
MS
Discipline
Electrical Engineering
