Digital signal processing back biased hall effect muzzle velocity measurement system

Abstract

A system for precisely measuring muzzle exit velocity of a “muzzle loaded” mortar projectile fired from a mortar tube using two back-biased Hall effect sensors for projectile gas ring channel detection. The system includes a back-biased Hall effect sensor block, a digital resolver electronic circuit and a computer software interface. The back-biased Hall effect sensors are located in a calibrated sensor block attached to a mortar tube. As the projectile metal casing passes a face of the sensors, the sensors trigger and release, providing two electronic pulses. The pulse edges are captured in the resolver electronics, containing a discriminator circuit for filtering all input pulses to distinguish between a projectile loading event and a projectile firing event. Once a valid firing event is detected, an output of precision timers is presented serially to a computer where it is processed and displayed by a computer software interface.

Description

GOVERNMENT RIGHTS [0001] The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of DAAE30-03-D-1004, awarded by the Department of the Army.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention (Technical Field) [0003] The present invention relates to measuring systems and more specifically to a method and apparatus for measuring a mortar muzzle exit velocity. [0004] 2. Background Art [0005] This present invention solves the problem of providing accurate primary instrumentation for the measurement of the velocity of a projectile at the muzzle point of exit. Many variables affect muzzle velocity. Examples include, but are not limited to barrel wear, propellant temperature, unique propellant burn rate, and air density. While some of these variables can accurately be accounted for individually, when taken in total, it is most efficient to simp...

AI Technical Summary

Benefits of technology

This patent describes a system for accurately measuring the velocity of a fired projectile by detecting the ferrous metal casing of the projectile as it moves past sensors at the muzzle point of exit. The system uses back-biased digital Hall effect integrated circuit sensors and a thin film laser-trimmed resistor network to set and control the sensor's offset voltage and operate point. A discrete value capacitor is used to store a reference voltage that is directly proportional to the sensor's off state at the targets threshold magnetic field strength. The trigger circuit uses this reference voltage to establish the reference level for the operate point. The output of the sensor electronics is fed through a cable into the input stage of the digital resolver electronics where both the leading and trailing edges of each sensor output pulse are captured asynchronously. These captured pulse edges start and stop two 16-bit, precision timers, which count at a frequency of 60 MHz. The output of the timer circuits along with the captured pulse edges are simultaneously fed into a discriminator circuit that logically filters the data to distinguish between a projectile loading event and a projectile firing event. The system is lightweight, low power consumption, small in size, and low cost. It can be battery operated remotely and without attachment from a continuous power supply. The system is designed to operate for extended lengths of time.

Problems solved by technology

Radar systems presently are used to analyze the ballistic path but do not provide an actual point of exit measurement.

The inductive approach exhibits a characteristic reduced frequency response while optical and fiber optic systems are not suitable to the combat environment or are not practical for fielding.

RF injection requires that the barrel be penetrated at multiple locations which violates the military standard for barrel structural integrity.

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