KEYWORDS: Sensors, Electric field sensors, Acoustics, Weapons, Firearms, Signal to noise ratio, Detection and tracking algorithms, Signal processing, Environmental sensing, Signal detection
Research and experimental trials have shown that electric-field (E-field) sensors are effective at detecting charged projectiles. E-field sensors can likely complement traditional acoustic sensors, and help provide a more robust and effective solution for bullet detection and tracking. By far, the acoustic sensor is the most prevalent technology in use today for hostile fire defeat systems due to compact size and low cost, yet they come with a number of challenges that include multipath, reverberant environments, false positives and low signal-to-noise. Studies have shown that these systems can benefit from additional sensor modalities such as E-field sensors. However, E-field sensors are a newer technology that is relatively untested beyond basic experimental trials; this technology has not been deployed in any fielded systems. The U.S. Army Research Laboratory (ARL) has conducted live-fire experiments at Aberdeen Proving Grounds (APG) to collect data from E-field sensors. Three types of E-field sensors were included in these experiments: (a) an electric potential gradiometer manufactured by Quasar Federal Systems (QFS), (b) electric charge induction, or "D-dot" sensors designed and built by the Army Research Lab (ARL), and (c) a varactor based E-field sensor prototype designed by University of North Carolina-Charlotte (UNCC). Sensors were placed in strategic locations near the bullet trajectories, and their data were recorded. We analyzed the performance of each E-field sensor type in regard to small-arms bullet detection capability. The most recent experiment in October 2013 allowed demonstration of improved versions of the varactor and D-dot sensor types. Results of new real-time analysis hardware employing detection algorithms were also tested. The algorithms were used to process the raw data streams to determine when bullet detections occurred. Performance among the sensor types and algorithm effectiveness were compared to estimates from acoustics signatures and known ground truth. Results, techniques and configurations that might work best for a given sensor platform are discussed.
Sensors capable of measuring the quasi-electrostatic field of traveling projectiles have been developed to detect the
passage of a bullet in flight. These sensors provide an alternative to existing optical chronograph technologies, which are
sensitive to variations in environmental lighting, and magnetic chronographs, which require close proximity to the
bullet’s path. In contrast, electric field sensors are insensitive to lighting changes and prior testing has demonstrated the
ability to reliably detect bullets at distances of at least three meters. A linear array of these sensors has been used to
measure the time of flight between the sensors, which with the known distance between the sensors can be used to
calculate the projectile’s velocity. These velocity measurements are compared to established chronograph technology as
a measurement validation. By extending this array of sensors along the projected path of the projectile, a profile of the
projectile’s position and velocity through flight can be calculated. This expected utility of this data is in refining the
calculations that are performed to determine a ballistic solution, particularly in long range engagements, where there has
been limited availability of accurate projectile velocity measurements. This robust sensor array that can easily be
deployed represents an inexpensive way to experimentally investigate numerous phenomena related to ballistics
modeling.
As part of the continuing reduction of half-pitch line widths, the International Technology Roadmap for Semiconductors
(ITRS) forecasts an increasing number of issues with electrostatic discharge (ESD) related phenomena
and the need for improved electrostatic charge control in semiconductor wafer processing. This means that wafer
metrology should encompass charge measurements as a routine operation. Additionally, with the increasing complexity
of wafer processing, in-line measurements including surface voltage and charge detection and analysis are
becoming more important. One of the instruments utilized in such measurements is a non-contacting electrostatic
voltmeter (ESVM). In this paper the authors would like to introduce a new design for the ESVM probe which
allows for the measurement of surface voltages with DC stability and millivolt sensitivity. The construction of
the probe utilizes a gold plated sensor that is mounted on a vibrating tuning fork which is electromechanically
excited by a piezoelectric driver.
In this paper, we study the no-load behavior of a lightweight piezo-composite curved actuator (LIPCA) subjected
to voltage and charge control. First, we examine the effect of hysteresis and creep when the actuator is voltage
controlled at a slow scan speed. The experimental results show that creep increases the displacement hysteresis by
over 25% when scanning at 1/60 Hz. Afterwards, we discuss the design and implementation of a charge-feedback
circuit to control the displacement of the actuator. The hysteresis curves between voltage- and charge-control
modes are compared for the scan frequencies of 1 and 5 Hz. The results show that charge control (compared to
voltage control) of a LIPCA device exhibits significantly less hysteresis, over 80% less.
In this paper authors examine the design and implementation of a
cantilever beam-style probe for non-contacting electrostatic
voltmeter. The beam is driven by a piezoelectric actuator with a
feedback loop controlling amplitude of the electrostatic sensor
displacement. Choice of the vibration mode and placement of the
actuator and sensor are discussed. A simple model for the first
three natural frequencies of the beam is constructed and compared
with the experimental results.
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