Muzzle Reference System

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The Princeton Scientific Instruments Automatic Muzzle Reference System (AMRS)* accurately measures the angular motion of the muzzle of a tank mounted cannon relative to its trunnion at any elevation angle, while the
tank is in motion and as the round exits the muzzle. This instrument can continuously measure muzzle pitch and yaw with a dynamic range of ±5 milliradians and precision of 5 microradians at a bandwidth of 1000 Hz. The Princeton Scientific Instruments AMRS has used to evaluate tank cannon, ammunition, and fire control concepts, and will be incorporated in future tank and artillery fire control systems.

The basic approach taken to measure cannon muzzle angular motion on a moving tank is based on viewing the muzzle from the cannon trunnion. The optics assembly consists of an autocollimator type instrument mounted on the trunnion of the gun and a mirror rigidly fastened to the muzzle. A beam of light projected by the autocollimator telescope reflects off the muzzle mirror and passes back through the telescope to be reimaged on a solid state position sensitive detector located in the focal plane. The output of the electronics are analog signals representing muzzle azimuth and elevation.

Figure 1

Figure 1 shows data taken at Aberdeen Proving Ground by the AMRS instrument while mounted on an M1A1 tank traveling over a rough terrain "washboard" course at a speed of 25mph. The graph shows a small sample of the data set plotted sequently in time on a grid where the x and y axis are scaled in milliradians and represent the horizontal and vertical components of the muzzle pointing angle, respectively. Each data point displayed represents a measurement by the AMRS of the pointing angle of the cannon relative to the trunnion. The data clearly shows the intricate meanderings of the muzzle over time. The range of angular motion for this test was found to be on the order of 3 milliradians. The scale for the grid in Figure 1 is in milliradians. A milliradian is 1 meter at 1000 meters. The capability to continuous follow the motion of the tank cannon muzzle to within fractions of a milliradian as shown in this film significantly increases the probability of hitting a tank sized target several thousand meters away.

The Princeton Scientific Instrument's AMRS can monitor muzzle motion while the cannon is firing. The ability of the AMRS to continuously monitor muzzle pointing can yield information to the ballistics researcher concerning the dynamics of the gun tube and ammunition, and allow ammunition test results to be corrected for muzzle pointing angle variation on a shot by shot basis.

Figure 2

Figure 2 displays two graphs showing the muzzle pointing angle during 2 separate test firings of the tank cannon. The round in the plot on the left was actually fired a half hour later than the round on the right. The general path the muzzle takes is similar for both rounds. More importunately, the muzzle angle at shot exit, indicated by the yellow data point, is nearly the same for both shots. The significance of this is the possibility of using pointing angle information gained at shot exit from one firing of the cannon as a predictor to the pointing angle at shot exit for the second firing. This information could be incorporated into the ballistic solution for aiming the second round, significantly improving its accuracy.

The Princeton Scientific Instrument's Automatic Muzzle Reference System can enhance the firing accuracy of the M1A1 under all firing conditions, providing the capability to continuously correct for bending of the tank cannon due to tank motion, thermal heating, and firing of ammunition.

* Note that Automatic Muzzle Reference System (AMRS), Continuous Muzzle Reference System (CMRS), and Dynamic Muzzle Reference System (DMRS) are synonymous.

Princeton Scientific Instruments

 

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