AU611701B2 - Markmanship training apparatus - Google Patents

Description

une uonun.Ltult~ L Lu1--r bEi- -,i

I

r 611701

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: 0000 00 0 0

C

S S Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: Divisional of 27186/84 TO BE COMPLETED BY APPLICANT Name of Applicant: AUSTRALASIAN TRAINING RAIDS (PTY)- LTD.

Address of Applicant: 16--1--69-.FALL 6 N STREET, I ,rr i 2640.

0

CO

Actual Inventor: Address for Service: WILLIAM HENRY BOWYER, BRUCE MOXLEY, LINDSAY CHARLES KNIGHT, ROBERT BARRETT

PHILLIPS

GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: MARKMANSHIP TRAINING APPARATUS The following statement is a full description of this invention including the best method of performing it known to me:i, U I I U- I ~1 i 1 MARKSMANSHIP TRAINING APPARATUS L0 a sq a a

S.

a ."i ar a.

The present invention relates to an apparatus for determining information concerning a supersonic projectile hitting a target or the passing thereof through a predetermined measurement plane.

When a projectile travels through the atmosphere with a supersonic velocity, a conically-expanding pressure or shock wave is generated, with the projectile being at the apex of the shock wave.

It has been proposed to provide apparatus for determining the position at which the trajectory of the projectile passes through a plane, employing transducers or the like to detect such a shock wave generated by a supersonic projectile. One such proposal is described in U.S. Patent No. 3,778,059 (Rohrbaugh).

Other target systems are disclosed in Swiss PaLent Specification Ch-PS 589,835, granted May 15, 1977, to Walti and German Utility Model DE-GM 77 26 275 of Walti, laid open March 16, 1978. Other prior art systems are known, as well, but none provides comprehensive training in proper marksmanship. The prior art target arrangements provide only partial information to the trainee marksman about the progress of his shooting. For example, the aforementioned prior art references provide systems which determine a location at which a projectile fired at a target passes relative to the target.

U.S. Patent No. 3,233,904 offers an automatic target apparatus having an impulse switch for detecting projectile hits on a target and initiating operation of a target mechanism which drops the target from a fully raised to a fully lowered position.

Embodiments of the present invention provide a considerably more versatile and sophisticated system for training in marksmanship than has heretofore been proposed for example in order to more effectively instruct trainees in marksmanship training, it is advantageouis to provide i 1 3 positive and negative reinforcement of shooting techniques immediately after each shot is fired. Such reinforcement may take a number of forms, but preferably comprises a plurality of indications concerning each shot fired. For example, it is desirable to provide the trainee marksman with an at least approximate indication of where a projectile fired at a target has passed relative to the target and/or a positive indication of whether the projectile has actually hit the target and/or whether the projectile has ricocheted prior to reaching the zone of the target. It is also advantageous to provide, in combination with one of the foregoing indications, information concerning whether the trainee marksman is correctly gripping the weapon being fired. The marksmanship training system is particularly effective for beginning marksmen who may not be holding the weapon correctly and who may not even be shooting sufficiently near the target to score a "hit".

Such a marksman is thus apprised of the manner in which he should change his technique to improve his shooting. The system is, however, also effective for more advanced shooters, who may wish to not only have an indication that o* the target has been hit by the projectile but whether the projectile has struck a particular region of the target.

p provides apparatus for use in marksmanship training in which a projectile travels along a trajectory from a firing point toward a target member and through a measurement plane, comprising: means for detecting and indicating a location in said measurement plane through which said trajectory passes, S thereby providing an indication of where said projectile Spasses relative to said target member; means for measuring a velocity of the projectile in the vicinity of the target member; and for II 4 comparing said measured velocity with at least one expected projectile velocity value to ascertain if said measured velocity is within an expected projectile velocity range; and for providing an indication of the result of said comparison between said measured velocity and said at least one expected velocity value, whereby a trainee marksman will also be provided with an indication of whether the projectile has passed through said measurement plane in free flightprojet!ie or from a projectile which has ricocheted prior to passing through said measurement plane.

According to one aspect the present invention provides apparatus for use in marksmanship training in which a projectile is fired at a target member, comprising:, in use,

S..

means for detecting a projectile hit on a target member; 9 means for detecting passage of said projectile 0.o through at least one predetermined zone, in use, located rlative to said target member; and computing means responsive to said means for detecting a projectile hit and said passage detecting means and operative for: determining a time difference between an instant at which said hit detecting means detects a projectile hit on said target member and an instant at which rsaid passage detecting means detects passage of said projectile through said predetermined zone; comparing said time difference with at least one expected time difference value to ascertain whether the velocity of said projectile is within an expected projectile velocity range; and oi providing an indication of the result of said comparison,

R

k ii lr ~U~x~rrrrrm~~; ii wherein said expected time difference value is selected such that a trainee marksman is provided with an indication of whether a detected projectile hit on said target has resulted from a free flight projectile hitting said target member or from a projectile which has ricocheted prior to hitting said target member.

According to one aspect the present invention provides apparatus for use in marksmanship training in which a projectile is fired at a target member, comprising: means for detecting a projectile hit on a target member; means for measuring velocity of said projectile in the vicinity of said target member; and computing means responsive to said hit detecting means and said velocity measuring means and operative for: comparing said measured velocity with at least one oo expected projectile velocity value to ascertain if said measured velocity is within an expected projectile velocity range; and for 2D providing an indication of the result of said comparison between said measured velocity and said o at least one expected velocity value, S whereby a trainee marksman will be provided with an indication of whether a detected projectile hit on said target has resulted from a free flight projectile hitting said target member or from a projectile which has ricocheted prior to hitting said target member.

According to one aspect the present invention provides apparatus for indicating the location in a measurement plane through which the trajectory of a supersonic projectile passes, the supersonic projectile travelling from a firing point toward a target zone and S through said measurement plane, comprising: oo4*oo /t ls ii 6 a target member located in said target zone; an array of at least three transducers responsive to an airborne shock wave from the supersonic projectile and located at respective predetermined positions spaced along a line substantially parallel to said measurement plane; means for measuring velocity of the supersonic projectile; means for measuring velocity of propagation of sound in air in the vicinity of the array of transducers; computing means responsive to said array of transducers, said projectile velocity measuring means, and said propagation velocity measuring means, and operative for: determining the location in said plane through which the trajectory of the supersonic projectile passes, and providing an output indicating said determined location.

It will be seen from the description which follows with reference to the examples depicted in the accompanying S drawing figures and computer program appendices that the present invention provides a comprehensive marksmanship training system which is both versatile and sophisticated, and which provides a level of training that has heretofore 25 been unknown in the field.

e S eo oo oo

L

FIGURE 1 shows in perspective view a marksmanship training range employing concepts of the present invention; FIGURE 2 shows in perspective view a target mechanism equipped with a target member, a hit sensor, and transducers for detecting an airborne shock wave; FIGURE 3 shows a coordinate system relating the positions of shock wave-sensing transducers; FIGURE 4 shows a schematic block diagram of an overall system in accordance with the invention; FIGURE 5 shows an isolator module circuit for block 66 of Figure 4; FIGURE 6 shows in block schematic form one channel of comparator 62 of Figure 4; FIGURES 7A 7F show in detail one possible form of timer interface 64 of Figure 4; r S. FIGURES 8A and 8B show a suitable circuit arrangement for the air temperature sensing unit 78 of Figure 4; FIGURE 8C shows a timing diagram for the circuits of Figures 8A and 8B; "'2E FIGURE 9 shows airboren shock waves impinging on a piezoelectric disc transducer; FIGURE 10 shows an output waveform for the transducer of Figure 9; ~FIGURES 11 and 12 show one possible form of :construction for airborne shock wave-sensing transducers; FIGURE 13 shows an acoustically decoupled mounting for the airborne shock wave transducers; FIGURES 14A nad 14B are flow charts for computer subroutine CALL(3); FIGURES 15A- 15C show flow charts for computer subroutine CALL FIGURES 16 18 show alternate transducer arrangements in plan view; FIGURE 19 shows apparatus for generating a light curtain and detecting the passage of a projectile 7.

A

tA

I

therethrough; FIGURE 20 shows an arrangement employing two such constructions as shown in Figure 19, in combination with an array of transducers for detecting an airborne shock wave; FIGURES 21 and 22 show an arrangement for sensing impact of a projectile on a target member; FIGURE 23 shows a target member construction for detecting passage of a projectile therethrough; FIGURE 24 shows an alternative arrangement for determining projectile velocity; and FIGURE 25 shows a graticule overlay used on the visual display screen of Figure 4.

*8

*S*

*t8

S

8.

-i ':iiiiiiiii i i f i i 4 Figure 1 shows in perspective view a marksmanship training range employing concepts of the present invention.

The range has a plurality of firing points 10 from which trainee marksmen 12 shoot at targets 14. Located in front of the targets 14 is, for example, an earthen embankment which does not obstruct the marksman's view of targets 14 from the firing points, but which permits the positioning of transducer arrays 18 just below the lower edge of the target and out of the line of fire. The transducer arrays will be described in more detail below, but it will be •understood that they may be connected by suitable cables S"to a computer 22 situated in a control room 24 located behind the firing points, as shown, or may alternatively be connected to a data processor or computer (not shown) 15 located near the transducer array, which is in turn coupled *eftsoo to the visual display units. As will be explained below, each transducer array detects the shock wave generated by a supersonic projectile, such as a bullet, fired at the respective target, and the compute 22 is operative to determine the location in a measurement plane in front of the target through which the bullet trajectory passes. Means (not shown in Figure 1) are provided at each target for detecting when the target has been "hit" by a projectile.

Computer 22 is coupled to suitable visual display units 26, 28, 30, located respectively in the control room 24, at S"each firing point 10, and at one or mcre other locations Provided on the visual display units may be, for example, an approximate indication, relative to a target representation, of where the projectile has passed through the measurement plane, and an indication of whether the target has been "hit" by the projectile.

Spectators 32 may observe the progress of shooting of one or more of the trainee marksmen on visual display unit The computer may be coupled with a suitable printer or paper punching device 34 to generate a permanent record 1 of the bullet trajectory location determined by the computer.

Although the targets 14 shown in Figure 1 have marked thereon representations of the conventional bull's-eye type target, the target may be of any suitable configuration, such as a rigid or semi-rigid target member 35 as shown in Figure 2 on which may be provided the outline of a soldier or the like. Means are provided for detecting when a projectile fired at the target member has "hit" the target member, and the target member may be mounted on a target mechanism 36 which is operative to lower the target out of sight of the trainee when a "hit" is detected. The "hit" detecting means may be an inertia switch 38 as shown in Figure 2, or any other suitable apparatus. Alternative "hit" detecting arrangements will be described below. The automated target mechanism may be of the type described in U.S. Patent No. 3,233,904 to GILLIAM et al (the content of which is incorporated herein by reference). Target mechanism of this type are available commercially from Australasian Training Aids Pty.Ltd., Albury, N.S.W. 2640, 9 Australia, Catalog No. 106535. Inrertia switches are commercially avaialble from Australasian Training Aids Pty.Ltd., Catalog No. 101805.

In the arrangement of Figure 2, transducers Sl-S4 are mounted on a rigid support member 40, which is in turn mounted on the target mechanism 36. Although the transducer arrays 18 may be supported seperately from the target mechanism beneath targets 14 (as in Figure 1), affixing the transducer array to the target mechanism as in Figure 2 assure correct alignment of the measurement plane relative to target member 35. Transducers Sl-S4 (Figure 2) preferably each comprise a disk-shaped piezoelectric element of 5 mm diameter mounted on a hemispherical aluminum dome, the hemispherical surface of the dome being exposed for receiving the shock wave from the bullet. The airborne shock wave generated by the bullet is represented by the series of expanding rings 42, the bullet trajectory by a line 44, and the acoustic vibrations induced in the target member 35 on impact of the bullet by arc segments 46.

Figure 3 shows a three-dimensional coordinate system in which the positions of the four transducers Sl-S4 are related to a reference point 0, The transducer array illustrated is similar to that shown in Figure 2, with a row of three transducers S1, S3, S4 situated at spaced locations along the X axis and with a fourth transducer S2 situated at a spaced location behind transducer Sl along the Z-axis. A portion of target member 9 35 is also shown for reference purposes, as is an arrow 44 representing the bullet trajectory. The distance along the X-axis from transducer S1 to transducers S3 and S4, 9.9.

lrespectively, is represented by distance d. The distance a• along the Z-axis between transducers Sl and S2 is represented by d' The X-Y plane intersecting the origin of the Z axis of the coordinate system shown in Figure 3 is considered to be the measurment plane in which the location of the trajectory is to be determined.

fe 'Transducers Sl-S4 provide output signals in response to detection of the shock wave of the bullet, from which 000the location in the measurement plane through which the projectile trajectory passes can be determined. A mathematical analysis is provided below for a relatively simple case in which it is assumed that: 1) The transducer array is as shown in Figure 3; 2) The measurement plane has its X-axis parallel to the straight line joining transducers Si, S3, S4; 3) The projectile trajectory is normal to the measurement plane; 4) The projectile travels with constant velocity; Air through which the shock wave propagates to strike the transducers is 11.

oi i m i H a) of uniform and isotropic shock wave propagation velocity, and b) has no velocity wind) relative to the transducer array; and 6) The shock wave propagation velocity and projectile velocity are separately measured or otherwise known or assumed.

It is noted that small departures from the above-stated conditions have in practice been found acceptable, since the resulting error in calculated location in the measurement plane through which the projectile passes is tolerably small for most applications.

The respective times of arrival of the shock wave at transducers Sl, S2, S3, S4 are defined as Tl, T2, T3, and *15 T4. All times of arrival are measured with respect to an arbitrary time origin. V s is defined as the propagation velocity of the shock wave front in air in a direction normal to the wave front, while VB is defined as the velocity .of the supersonic projectile along its trajectory.

The velocity VB of the bullet in a direction normal to the measurement plane can be determined from the times of arrival T 1

T

2 of the shock wave a, transducers Sl and S2 and from the distance d' between transducers Sl and S2: o SV d' (1) T2 T 1 Then the propagation velocity of the shock wave front in a direction normal to the projectile velocity may be defined as:

V

V =B N (2) i vB The differences between the times of arrival of the shock wave may be defined as: I itea;LI Z L U.a t--U U IC L Ity "IL t 1A-.A L.L measurement plane through which said trajectory ;asses, thereby providing an indication of where said projectile passes relative to said target member; means for: measuring a velocity of the projectile in the vicinity of the target member; and for comparing said measured velocity with at least onek /2 t T T 1 (3) t T T 1 (4) The X-axis coordinate of the intersection point of the projectile trajectory with the measurement plane is: X= (l-t2) (VN2 t t2 d2 2d (t 1 t2) The distance in the measuremnet plane from sensor Sl to the point of intersection of the projectile trajectory with the measurement plane is: 15 2d 2

V

2 2 2 .N (t 1 t 2 1 0 (6) 2 VN (t 1 t 2 The Y-axis coordinate of the intersection point of 20 the bullet trajectory with the measur -ent plane is: y 10 x 2 (7) It is possible to construct a mathematical solution for the above-described transducer system which incorporates such effects as: 1) Wind; 2) Non-equally spaced transducers along the X-axis; 3) Non-colinear arrays; 4) Decelerating projectiles; and Non-normal trajectories.

However, most of these corrections require more complex arithmetic, and in general can only be solved by iterative techniques.

It can be seen that the tra.isducer arrangements shown 13.

i" .0#00 040 020 300 3..5 L .00000 a 0

S.

0 00 in Figures 1-3 form, when viewed in plan, a configuration with at least three transducers on the crossbar of the and one transducer at the base of the The stem of the is substantially aligned with the expected bullet trajectory. The error created if the stem of the is not precisely aligned with the anticipated projectile trajectory is relatively minor and thus the alignment of the can be considered substantially insensitive to error. However, when the stem of the (that is, '--he Z-axis of Figure 3) is aligned parallel to the expected projectile trajectory, the effect is to cancel substantially any shock wave-arrival-angle dependent time delays in the transducer outputs.

Referring now to Figure 4, a plan view of the transducers Sl-S4 in a configuration is illustrated schematically. Each transducer is coupled by an appropriate shielded cable to a respective one of amplifiers 54-60.

The outputs of amplifiers 54-60 are provided through coupling capacitors to respective inputs of a multi-channel comparator unit each channel of which provides an output when the input signal of that channel exceeds a predetermined threshold level. Thus, a pulse is provided at the output of each of channels 1, 2, 3, and 6 of comparator unit 62 at respective times indicating the instants of reception of the shock wave at each of the transducers Sl-S4. In the presently-described form of the invention, channel 4 of the six-channel comparator unit is unused. The outputs of channels 1-3 and 6 of comparator unit 62 are provided to inputs of a timer interface unit 64. Timer interface unit 64 serves a number of functions, including conversion of pulses from comparator unit 62 into digital values representing respective times of shock wave detection which are conveyed via a cable 68 to a minicomputer The output of channel 1 of comparator unit 62 is coupled to the inputs of channels 0 and 1 of timer interface

L

V- -i~wiiI La.ulLn is a ru±n aescription of this invention including the best method of performing it known to me:- ^rrirr-nT 1 11 unit 64, the output of channel 2 of the comparator unit is coupled to the input .f channel 2 of the timer interface unit, the output of channel 3 of the comparator unit is coupled to the inputs of channels 3 and 4 of the timer interface unit, and the output of channel 6 of the comparator unit is coupled to the input of channel 6 of the timer interface unit. The channel 5 input of the timer interface unit is coupled via comparator unit channel 5 to an air temperature sensing unit 78 which has a. temperaturesensitive device 80 for measuring the ambient air temperature.

The output of amplifier 54 is also provided to air temperature sensing unit 78, for purposes described below with reference to Figures 8A-8C.

Figure 4 also shows schematiclly the target mechanism *rr 36 and the inertia switch 38 of Figure 2, which are interconnected as shown for the units avai2able from Austral- 6 asian Training Aids Pty.Ltd. Coupled to terminals A, B, C of the target mechanism/inertia switch interconnection be is an isolator module 66 which provides a pulse similar in *8 form to the output pulses of comparator unit 62 when inertia switch 38 is actuated by impa-t of a projectile on the rigid target member 35 of Figure 2. The output of isolator module 66 is supplied to two remaining inputs of timer interface unit 64, indicated in Figure 4 as channels &2 7 and S*,i Minicomputer 70 of Figure 4 may be of type LS1-2/20G, available from Computer Automation Inc. of Irvine, California, Part No. 10560-16. The basic LSI-2/20G unit is preferably equipped with an additional memory board available from Computer Automation, Part No. 11673-16, which expands the computer memory to allow for a larger "BASIC" program.

Minicomputer 70 is preferably also equipped with a dual floppy disk drive available from Computer Automation, Part No. 22566-22, and a floppy disk controller available from Computer Automation, Part No. 14696-01. Minicomputer I_ is coupled to a terminal 72 having a visual display screen and a keyboard, such as model "CONSUL 520" available from Applied Digital Data Systems Inc. of 100 Marcus Boulevard, Hauppauge, New York 11787, U.S.A. The CONSUL 520 terminal is plug-compatible with the LSI-2 minicomputer.

Other peripheral units which may employed to provide greater flexibility in marksmanship training, include a line printer 72' for generating permanent output records, and a graphics generator/visual display unit combination 72" which permits the coordinates of the intersection point of the projectile trajectory with the measurement plane to be displayed relative to a representation of the target, as *5 well as an indication of whether the target has been "hit" s. and a tally of the trainee marksman's "score." Graphics generator/visual display unit 72" may be, for example, do 0 Model MRD "450", available from Applied Digital Date Systems, Inc., which is plug-compatible with the LSI-2 minicomputer.

Also shown in Figure 4 is a thermometer 76, which .30 preferably a remote-reading digital thermometer such as the Pye-Ether series 60 digital panel meter Serial No.

60-4561-CM, available from Pyrimetric Service and Supplies, 242-248 Lennox St., Richmond, Victoria 3221, Australia, equipped with an outdoor air temperature sensor assembly (Reference Job No. Z9846). The remote-reading digital thermometer may have its sensor (not shown) placed in the region of the transducer array and, if the system is not equipped with the air temperature sensing unit 78 shown in Figure 4, the operator of terminal 72 may read the remote-reading digital thermometer 76, and input a value for the air temperature.

An approximate value for the spped of the shock-wave front propagation in ambient air can be readily calculated from the air temperature using a known formula as described below.

vicinity of the target member; and for r I I 1 Figure 5 shows a circuit diagram of the intertia switch isolator module 66 of Figure 4, having inputs A, B, C coupled as in Figure 4 to the commercially-available inertia switch. The isolator module provides DC isolation for the inertia switch output signal and presents the signal to timer interface unit 64 of Figure 4 in a format comparable to the output signals from comparator unit 62.

Suitable components for isolator module 66 are: o* S o 82,84 86 88 90 92 94 96 98 100 102 IN914 47uF BC177 10K4 8204V 5082-4360 4704 6. 8K4O 10U F 74LS 221N Monostable Multivibrator with Schmitttrigger inputs DS8830N Di.fferential line driver 0.22yF 474 4a a ar 2,e.

6* *r 104 106 108 Figure 6 shows a block diagram of one channel of comparator unit 62. The output signal from one of amplifiers 54-60 is provided through a high pass filter 110 to one input of a differential amplifier 112 which serves as a threshold detector. The remaining input of differential amplifier 112 is provided with a preset threshold voltage of up to, for example, 500 millivolts. The output of threshold detector 112 is supplied to a lamp driver circuit 114, to one input of a NAND gate 116 and to the trigger input of a monostable multivibrator 118 which provides an output pulse of approximately 50 millisecond duration. A shaped output pulse is therefore provided from NAND gate 116 in response to 17.

comparison, /q M$ vrt" h 4r 'P i I weo 0 t p w 0.)

I

*00*iO n 0 wO *0 *0 detection of the airborne shock wave by one of transducers Sl-S4. Lamp driver circuit 114 may optionally be provided for driving a lamp which indicates that the associated transducer has detected a shock wave and produced an output signal which, when amplified and supplied to threshold detector 112, exceeds the preset threshold value.

The logic output signals of comparator unit 62 cause counters in timer interface unit 64 to count numbers of precision crystal-controlled clock pulses corresponding to the differences in times of arrival of the logic output signals, which in turn correspond to the times of arrival of the shock waves at the transducers. Once this counting process is complete and all channels of the timer interface u:nit have received signals, the counter data is transferred on command into the computer main memory. Following execution of a suitable program (described below), the resulting projectile trajectory data is displayed on the visual display unit 72 and/or units 72', 72" of Figure 4.

Figure 7A-7F show in detail one possible form of a timer interface unit 64, which converts time differences between the fast logic edge pulses initiated by the transducers into binary numbers suitable for processing by minicomputer 70. Figure 7A shows the input and counting circuit portions of the timer interface unit, which accept timing edges from respective comparator unit channels and generate time difference counts in respective counters. The timer interface unit has eight channel inputs labeled Ch0-Ch7 and one input labeled receiving signals as follows: 18.

Timer Interface Input Channel No. Receives Signals initiating from Transducer Sl S1 S3 Air Temperature Sensing Unit 78, if equipped; otherwise Transducer S4 Transducer S4 Inertia Switch Isolator Module 66 it ti it i, 1i 0 *0 0 10 0 0r** u 6 6 7

S.S.

The input signals to each of timer interface inputs Ch0-Ch7 comprise logic signals which are first buffered and then supplied to the clock input CK of respective latches FFO-FF7. The latch outputs LCHO+through LCH7+ are provided, as shown, to exclusive OR gates EOR1-EOR7, which in turn provide counter enabling signals ENAl- through ENA7-.

Latches FF0-FF9 are cleared upon receipt of clear signal CLR. The input and counting circuits also include a respective up/down counter for each of eight channels (indicated for channel 1 as "UP/DOWN COUNTER Each up/down counter comprises, for example, four seriesconnected integrated circuits of type 74191. Each of up/down counters 1-8 thus has 16 binary outputs, each output coupled to a respective one of terminals TBO0- through a controllable gate ci.m:uit (indicated for channel 1 as "GATES on receipt of a command signal (indicated for channel 1 as Up/down counter 1 is connected to receive latch signal LCH1+, enable signal ENAl- a clock signal CLK, and a clear signal CLR, and to provide a ripple carry output signal RC1- when an overflow occurs. Up/down counters 2-8 each receive a respective one of enable signals ENA2- through ENA8-. Counter 2 receives its clear signal CLB from counter 1; counters 3 and 5 receive clear signal CLR and provide clear signals CLB to counters 4 and 6, respectively; counter 7 receives clear signal CLR; and counter 8 receives clear signal SEL2-. The up/down inputs of counters 2-7 receive latch signals LCH2+ through LCH7+, respectively, while the up/down input of counter 8 is permanently connected to a +5 volt source. Counters 2-8 each receive clock signal CLK, while each of counters 2-7 provide a ripple carry signal (RC2- through RC7-, respectively) when the respective counter overflows. Gates 2-8 are .r coupled to receive respective command signals IN1- through IN7- for passing the counter contents to terminals TB00- S. through TB15-. Figure 7A also shows a gate NAND 1 which receives the latch outputs LCH0+ through LCH7+ and provides an output signal SEN7+, the purpose of which is explained below.

Figure 7B shows a circuit for providing clear signal 0. CLR, which resets input latches FFO-FF7 and up/down counters When one of ripple carry outputs RC1- through RC7of up/down counters 1-7 goes to a logic low level, indicating that a counter has overflowed, or when a reset signal 6* SEL4- is provided from the computer, gate NAND 2 triggers a monostable element which then provides clear signal CLR in the form of a logic pulse to clear up/down counters 1-7 4..

and input latches FFO-FF7 of Figure 7A.

Up/down counters 1-7 are reset by signal SEL4- from the computer before each shot is fired by a trainee marksman.

When a shot is fired, each counter will count down or up depending on whether its associated channel triggers before or after a reference channel, which in this case is input channel Ch0.

Figure 7C shows the input circuitry for input of the timer interface. Latch FF8 is coupled to receive reset signal SEL4- and preset signal SELl- from the interface controller of Figures 7E and 7F in response to k FIGURE 19 shows apparatus for generating a light curtain and detecting the passage of a projectile 7.

computer commands. Timer interface input receives "hit" indication signal VEL- from the inertia switch isolator module 66, and provides a counter enable signal ENA8- for up/down counter 8.

The computer communicates with the timer interface unit by placing a "device address" on lines AB03- AB07 (Figure 7D) and a "function code" on lines ABOP- AB02 (Figure 7F). If the computer is outputting data to the timer interface, signal OUT is produced; if the computer is inputting data, signal IN is produced.

Figure 7D shows exclusive OR gates EOR11-EOR15 which decode the "device address." A "device address" can also be selected manually by means of switches SW1-SW5. The address signal AD- from gate NAND3 is then further gated 5 as indicated with computer-initiated signals IN, OUT, EXEC, and PLSE, to prevent the timer interface from responding to memory addresses which also appear on the address bus.

Figure 7F shows a latch 2A which holds the function code of lines AB00-AB02 when either the IN or OUT signal is produced. The input/output function signals from latch 2A are labeled IOF0 through IOF2.

If the computer executes an IN instruction to receive data from the timer interface, the combination of IOFO through IOF2 and ADIN- (Figure 7D) produce one of signals INO- through IN7- at BCD/decimal decoder 5A of Figure 7E.

Each of signals INO- through IN7- enables data from one of up/down counters 1-8 to be placed on data bus terminals TBO- through If the computer is executing a "select" instruction for the timer interface, the combination of signals IOFO IOF2 and ADEXP- (Figure 7D) produce one of select signals SELO- through SEL7- at BCD/ decimal decoder 5B of Figure 7E.

The select signal functions employed in the presentlydescribed invention are: 21.

*I~

I _4 SELl- enables triggering of latch FF9 (Figure 7C) SEL2- resets up/down counter 8 (Figure 7A) SEL4- resets latch FF8 (Figure 7C) and triggers monostable element 328 via NAND2 (Figure 7B) If the computer is executing a sense instruction from the timer interface, the combination of signals IOFo IOF2 (Figure 7F) and AD- (Figure 7D) allow one of sense signals SENO+ through SEN7+ to be placed on the SER- line (Figure 7F). This allows the computer to examine the state of one of these sense signals. The only sense signal employed Sin the presently-described embodiment is SEN7+, which indicates that the timer interface has a complete set of time data for a single shot fired at the target as explained more fully below.

The theory of operation of tiner interface unit 64 is as follows. Channel Cho is the reference channel. Each channel triggering will clock a respective one of latches I. FFO FF7, producing a respective one of signals LCHo+ through LCH7+. Signals LCH1+ through LCH7+ each control the ap/down line of one of counters 1-7 and are also provided to OR gates EOR1 through EOR7 to produce a respective counter enabling signal ENAl- through ENA7-.

Exclusive OR gates EOR1 through EOR7 each achieve two functions. First, the counters of any channel that Striggers before reference channel Cho will be enabled until reference channel ChI triggers. This has the effect of causing the counters to count down because the associated LCH+ input line is high. Second, the counters of any channels that have not triggered by the time reference channel 3 Cho triggers are all enabled by the reference channel until each individual channel triggers. This has the effect of causing the counters to count up, since the associated LCH+ lines are low while the counters are enabled.

Initially, the computer resets up/down counter 8 with signal SEL2- and then causes a general reset with signal 22.

'1 SEL4-. Signal SEL4- causes gate NAND2 (Figure 7B) to trigger monostable element 328, producing clear signal CLR, which resets latches FFO FF7 and up/down counters 1-7 (Figure 7A). Reset signal SEL4- also clears latch FF8 (Figure 7C). Latch FF9 (Figure 7C) is preset by the computer with signal SEL which puts set steering onto FF9. Latch FF9 is thus clocked set when a signal VELis received at the input from inertia switch isolator module 66, indicating that the target has been "hit." Thus, prior to a shot being fired, counters 1-8 are reset, input latches FFO FF7 are reset, and la-tch FF9 is "armed." All resets occur when the computer executes controller BASIC statement CALL described fur:ther below.

At this stage, none of channels Cho through Ch7 or the channel 8 has been triggered. Since channel Ch0 has not yet triggered, signal LCH0+ is low. The remaining input of gate EOR0 is permanently high, so the output of gate EORO is high. Since signals LCH1+ through LCH7+ are all low, signals ENAl- through ENA7-- are all high, disabling all of up/down counters 1-7. Signal ENA8- is also high, disabling up/down counter 8.

Assume now that a shot is fired to the left of the target, missing the target, and to the left of the transducer array shown in Figure 4. Channel 3 of Figure 7A triggers 2irst, so that signal LCH3+ goes high, causing signal ENA3- to go low and thereby causing up/down counter 3 to begin counting down. Reference channel Ch0 and channel Chl then trigger simultaneously. Signal LCH0+ goes high, so the output of gate EOR0 goes low. This makes signal ENA3- go high, while signals ENA2- and ENA4- through ENA7go low. Signals ENAl- and ENA8- remain high. Counter 3 will thus stop counting, counter 1 remains disabled and has no count, and counters 2, and 5-7 will start counting up.

23.

receiving the shock wave from the bullet. The airborne shock wave generated by the bullet is represented by the l e E L.: 9.

As each successive channel triggers, its respective LCH+ signal will go high, removing the associated ENAsignal and stopping the associated counter. When all LCH+ signals are high (indicating that all counters have been disabled), signal SEN7+ at the output of gate NAND1 in Figure 7A goes from high to low. The computer monitors signal SEN7+ to wait for all timing edge counts to be completed.

When the computer senses signal SEN7+, indicating that a complete set of counts is present in counters 1 through 7, it generates address signals ABO0-AB07 and the IN signal which cause BCD-to-decimal decoder 5A (Figure 7E) to issue signals INI- through IN7- in sequence so that the computer will sequentially "read" the state of each counter (on output lines TBOO-through The computer has thus received counts representing times as follows: Tl zero count from counter 1 (transducer 31) T2 positive count from counter 2 (transducer S2) T3 negative count from counter 3 (transducer S3) T4 negative count from counter 4 (transducer S3) positive count from counter 5 (air temperature sensing module as explained below with reference to Figure 10, or, if none, the output of channel 6 amplifier 60 goes to input channel of the timer interface unit and the output of transducer S4 triggers counter T6 positive count from counter 6 (transducer S4) T7 positive count from counter 7 (inertia switch) A2 zero count from counter 8 (inertia switch) The zero count in A2 indicates that the inertia switch was not operated, thus showing that the shot fired has missed the target. Had the bullet struck the target a non-zero count would be recorded in A2 because signal ENA8would have gone low upon receipt of signal VEL- (Figure 7C).

t Air through which the shock wave propagates to strike the transducers is l

I:I

The computer is programmed to operate on the received "time" signals Tl through T7 and A2 in a manner which will be described below such that the coordinates of the bullet trajectory in the X-Y measurement plane of Figure 3 are determined.

If any channel of the timer interface unit triggers spuriously the inertia switch may be triggered by a stone shower, one of the transducers may detect noise from other target lanes or other sources, etc.), the associated counter will continue counting until it overflows, causing a ripple carry signal (RCl-through RC7- All of the ripple carry signals are supplied to gate NAND2 (Figure 7B) which fires the associated monostable element 328, causing generation of clear signal CLR which resets latches FFV -FF7 and up/down counters 1-7.

Figures 8A and 8B show in detail a suitable circuit arrangement for the air temperature sensing unit 78 of Figure 4. Figure 8C shows wave forms of various points in the circuit of Figures 8A and 8B. The effect of the air temperature sensing unit is to generate a pulse at a time t 1 following the time to at which channel Chl of comparator unit 62 is triggered (allowing of course for propagation delays in connecting cables).

Referring to Figure 8B, a temperature sensor ICI 4"25 mounted in a sensor assembly, assumes a temperature substantially equal to that of ambient air in the vicinity of the transducer array. Temperature sensor ICI may be, for example, Model AD590M, available from Analog Devices Inc., P.O. Box 280, Norwood, MA 02062. Temperature sensor ICI permits a current IIN to flow through it, current IIN being substaDtially proportional to the absolute temperature (in degrees Kelvin) of the semiconductor chip which forms the active element of temperature sensor IC1.

Referring again to Figure 8A, when transducer Sl detects a shock wave generated by the bullet, a wave form v (2) 1 s 2 I

B

The differences between the times of arrival of the shock wave may be defined as: 12.

similar to that shown at A in Figure 8C is produced at the output of its associated amplifier 54 (Figure Integrated circuit chip IC3B of Figure 8A forms a threshold detector, the threshold being set equal to that set in channel Chl of comparator unit 62 of Figure 6.

Integrated circuit chip IC3 may be of type LM 319, available from National Semiconductor Corporation, Box 2900, Santa Clara, California 95051. When wave form A of Figure 8C exceeds the preset threshold, wave form D is generated at the output of circuit chip IC3B. The leading edge (first transition) of wave form B triggers the monostable multivibrator formed by half of integrated circuit chip IC4 of Figure 8B and the associated timing components R8 and C3.

Circuit chip IC4 may be of type 74LS221N, available from Texas Instruments, Inc., P.O. Box 5012, Dallas, Texas 75222.

The output of this monostable multivibrator is fed via buffer transistor Q1 to the gate of metal oxide semi-conductor Q2, the wave form at this point being depicted as C in Figure 8C. Transistor Ql may be of type BC107, available 2 0 from Mullard Ltd., Mullard House, Torrington Place, London, and semiconductor Q2 may be of type VN 40AF, available from Siliconix Inc., 2201 Laurelwood Road, Santa Clara, California 95054.

When wave form C, which is normally high, goes low, metal oxide semiconductor Q2 changes from a substantially ooo low resistance between its source S and drain D to a very high resistance. As a result of the current flowing through temperature sensor IC1 (proportional to its absolute temperature), the voltage at the output of integrated circuit chip IC2 starts to rise, as shown at D in Figure 8C. The rate of rise in volts per second of wave form D is substantially proportional to the current flowing through temperature sensor IC1 and thus is proportional to the absolute temperature of temperature sensor IC1. Integrated circuit chip IC2 may be of type CA3040, available from RCA Solid State, Box 3200, Summerville, New Jersey ,08876.

26.

.LU Ucl iUe s'een na rne rraiisaucer arrangements shown 13.

4

'C

When the voltage of wave form D, which is supplied to the inverting input of comparator IC3A, rises to the preset threshold voltage VTH2 at the non-inverting input of comparator IC3A, the output of comparator IC3A changes state as indicated in wave form E at time tl. This triggers a second monostable multivibrator formed of half of integrated circuit IC4 and timing components C4 and R9. The output of this second monostable multivibrator is sent via a line driver circuit chip IC5 to a coaxial cable which connects to the channel 5 input of the comparator unit 62.

The operation of the air temperature sensing .unit 78 of Figures 8A and 8B may be mathematically described as follows (assuming that the ramp at wave form D of Figure 8C is linear and ignoring offset voltages in the circuit, which will be small): T TH2 (8) dt where Vo voltage of wave form D, Figure 8C, and d I d. V IN (9) dt o where I current through IC1 IIN C e K where C is a constant of proportionality and 9Kis the absolute temperature of ICI combining and V Cl t (11) 1

C

27.

1 The output of channel 1 of comparator unit 62 is coupled to the inputs of channels 0 and 1 of timer interface 1 14.

I

or V TH2C1 e TI-12 K t (12) Ct1 Timer interface unit 64 can then measure time t 1 by the same procedure that is employed for measuring the time differences between transducers Sl-S4. It will be recalled that timer interface unit 64 will start counter 5 counting up upon receipt of a pulse on channel CHO, which is responsive to shock wave detection by transducer Sl. Counter 5 will 4 roA stop counting upon receipt of the pulse of wave form G from g* the air temperature sensing unit at time t

I

Thus, the count 9 on counter 5 of the timer interface unit will be directly proportional to the reciprocal of the absolute temperature of sensor ICl.

Each of transducers Sl-S4 may be a flat disk 530 of piezoelectric material (Figure If a bullet 532 is fired to the right of the transducer 530, the shock wave 532 will impinge on the corner 534 of transducer 530, and the transducer output will have a wave form as illustrated in Figure 10. It is desired to measure the time T illustrated in Figure 12 but it is difficult to detect this accurately since the amplitude of the "pip" 542 depends upon the position [9 "of the bullet relative to the transducer, is difficult to .e distinguish from background noise and can even be absent under some circumstances.

The minicomputer is provided in advance with the position of each transducer; all calculations assume that the transducer is located at point 536 and that the transducer output signal indicates the instant at which the shock wave arrives at point 536.

However, the distance between the transducer surface and each of the trajectories of bullets 532, 538 is equal to a distance L. Since the transducer provides an output as soon as the shock wave impinges on its surface, the times between the bullet passing and the output signal being generated 2 28.

d

K

No. 22566-22, and a floppy disk controller available trom Computer Automation, Part No. 14696-01. Minicomputer are equal. Therefore, the output of the transducer would suggest that the trajectories of the bullets 532, 538 are equispaced from point 536 which is not correct.

This disadvantage can be overcome by disposing the transducers in a vertical orientation so that the transducers are in the form of vertical disks with the planar faces of the disks directed toward the trainee marksman. As a bullet passes over the disks and the resulting shock wave is generated, the shock wave will impinge on the periphery of each disk and the point of impingement will be 60040: an equal distance from the center of the disk. A constant ."timing error will thus be introduced, but since only time 0 differences are used as a basis for calculaticn of the bullet trajectory location, this error will cancel out.

"15' However, orienting the disks vertically will not *0e00: 0 obviate the problem of the positive pip 542 at the beginning of output signal 540. It is therefore, preferred to provide seeeach transducer with a dome ofasolid material having a convex surface exposed to the shock wave, the planar base of the dome being in contact with the transducer disk and being suitable for transmitting shock waves from the atmosphere to the transducer disk. Shock waves generated by projectiles fired at the target will always strike the hemispherical *0 dome tangentially, and shock waves will be transmitted radially through the dome directly to the center of the transducer. The constant timing error thereby introduced will cancel out during calculation of the bullet trajectory location.

The hemispherical dome prevents or minimizes generation of positive-going pip 542 so the output of the transducer more closely resembles a sinusoidal wave form.

The instant of commencement of this sinusoidal wave form must be measured with great accuracy, so the transducer must have a fast response.

It is advantageous to utilize a piezoelectric disk 29. I Iri having a diameter of about 5 mm, which provides a fast response time and a relatively high amplitude output signal.

Referring now -to Figures 11 and 12 of the drawings, one possible form of transducer for use in connection with the present invention comprises a transducer element consisting of a disk 550 of piezoelectric material such as, for example, lead zirconium titanate. The disk 550 is about I mm thick and 2-5 mm in diameter, and maybe part No. MB1043, available from Mullard Ltd., Torrington Place, London, U.K.

The opposed planar faces of disk 550 are provided with a coating of conductive material 552, which may be vacuumdeposited silver.

4 Two electrically conductive wires 554, 556 of, for A:example, copper or gold, are connected to the center of the :lower surface of the disk and to the periphery of the upper surface of the disk, res Dectively, by soldering or by ultrasonic bonding. Disk 550 is then firmly mounted in a housing which comprises a cylindrical member 558 having recess 560 in one end thereof, the recess 560 having a depth of about mm and a diameter adapted to the transducer disk diameter, and being aligned with an axial bore 562 extending through member 558 to accomodate wire 554 provided on the lower surface of the piezoelectric member. A second bore 554, parallel to bore 562, is formed in the periphery of member 558, bore 562 accommodating wire 556 and terminating in an .:open recess 566 adjacent the main recess 560. Member 558 may be formed of Tufnol, which is a phenol2.c resin bonded fabric, this material being readily obtainable in cylindrical form. The housing may be machined from this material, although the housing may be alternately formed of a two-part phenolic resin such as that sold under the trademark Araldite, the resin being retained in a cylindrical aluminium case 568 and subsequently being machined. If th latter construction is employed, aluminium case 568 may be g~rounded to provide a Faraday cage to minimize noise. The piezoelectric of approximately 50 millisecond duration. A shaped output pulse is therefore provided from NAND gate 116 in response to 17.

material and wires are bonded into member 560 with an adhesive such as Araldite or a cyano-acrylic impact adhesive. Two small bores 570, 572 are provided in the lower surface of member 558 and electrically conducting pins are mounted in the bores. Wires 554, 556 protrude from the lower ends of bores 562, 564 and are soldered to the pins in bores 570, 572, respectively. An adhesive or other suitable setting material is employed to retain all the elements in position and to secure a solid hemispherical dome 574 to the transducer element 550. The dome 574 may be machined from aluminium or cast from a setting resin material such as that o sold under the trademark Araldite. The dome 574 preferably has an outer diameter of about 8 mm, which is equal to the diameter of the housing 568. A centrally-disposed projection 'J 576 on the base of the dome member 574 contacts and has the same diameter as the piezoelectric disk 550. Alternatively, dome 574 and member 558 may be cast as a single integral unit, surrounding the transducerdisk.

The assembled transducer with housing as shown in c Figure 12 is mounted, as discussed elsewhere herein, in front of the target. It is important that both the housing and a coaxial cable coupling the transducer assembly to the associated amplifier be acoustically decoupled from any support or other rigid structure which could possibly receive 4** the shock wave detected by the transducer before the shock wave is received by the hemispherical dome provided on top of the transducer Thus, if the transducers are mounted on a rigid horizontal framework, it is important that the transducers be acoustically decoupled from such framework.

The transducer may be mounted on a block of any suitable acoustic decoupling medium, such as an expanded polymer foam, or a combination of polymer foam and metal plate. A preferred material is closed-cell from polyethylene, this material being sold under the trademark Plastizote by Bakelite Xylonite, Ltd, U.K. Other suitable acoustic decoupling materials may 31.

t:

L

be used, as well, such as glass fiber cloth, or mineral wool.

The transducer may be mounted by taking a block 580 of acoustic decoupling medium as shown in Figure 13 and forming a recess 582 within the block of material for accomodating the transducer assembly of Figure 12. The entire block may be clamped in any convenient way, such as by clamps 584, to a suitable framework or support member 586, these items being illustrated schematically. Other suitable mounting arrangements for the transducer assembly will be described later below.

To summarize briefly, the system described above includes: Transducers Sl, S3, S4 for detecting shock wave arrival times along a line parallel to the measurement plane, which is in turn substantially parallel to the target.

Transducers Sl, S2 for detecting shock wave arrival times along a line perpendicular to the measurement plane *5 and substantially parallel to the bullet trajectory.

An inertia switch movnted on the target for detecting actual impact of the bullet with the target.

A unit for detecting the ambient air temperature in the region of the transducer array.

The outputs of the transducers, inertia switch, and air temperature sensing unit are fed through circuitry as described above to the timer interface unit, which gives counts representing times of shock wave arrival at the transducers, representing the inertia switch trigger time, and representing the air temperature. This information is fed from the timer interface unit to the minicomputer. Provided that the minicomputer is supplied with the locations of the transducers relative to the measurement plane, it may be programmed to: Determine the speed of sound in ambient air in the vicinity of the transducer array (to a reasonable 32.

li 1 U l U Wl' counters 2-8 each receive a respective one of enable signals ENA2- through ENA8-. Counter 2 receives its clear signal 19.

approximation) by a known formula V V 0 T K 0.09 (13) SoE CIJ273 where V Sis the speed of sound in air at the given temperature T, and V s0 is the speed of sound at zero degrees Celsius.C -Determine the velocity of the bullet in the direction perpendicular to the measurment plane and substantially parallel to the bullet trajectory, and -Determine the location of the trajectory in the measurement plane.

However, the information provided from the timer 0. :interface unit permits still further and very advantageous "az..:features to be provided in the system for marksmanship training. The system can be made to discriminate between direct (free flight) target hits by the bullet, on the one 0 hand, and target hits from ricochets or -target hits from stones kicked up by the bullet. striking the ground or spurious inertia switch -triggering due to wind or other factors, on the other hand. In the embodiment employing timer interface unit 64, spurious inertia switch triggering will cause counter 7 to count until ripple carry signal RC7- is produced, thereby causing the system to automatically reset. The *0 system can be further made to discriminate between ricochet hits on the target and ricochet misses. These features further enhance the usefulness in training as the trainee can be apprised, immediatcdly after a shot is fired, of the Joc-, 2.

of the shot relative the target in the measurment p. 1-,2 whether the target was actually hit by the bullet, the: shot ricocheted, and even of a "score" for the The present embodiment described so far contemplates at least three possible techniques for processing the information from the timer interface unit for the purpose of providing ricochet and stone hit discrimination.

33.

reset signal SEL4- and preset signal SELl- from the interface controller of Figures 7E and 7F in response to a) Electronic target window. For a hit to be genuine, the hit position determination system should have recognized a projectile as having passed through a target "window" in the measurement plane approximately corresponding to the outline of the actual target being fired upon.

The target outline is stored in the computer and is compared with the location of the projectile as determined from the transducer outputs. If the calculated projectile trajectory location is outside the "window", then the "hit" reported by the inertia switch or other hit registration device cannot be valid and it can be assumed that no actual impact of the o bullet on the target has occurred.

S•b) Projectile velocity. It has been found experimentally that, although there is a variation in velocity of bullets from round to round, any given type of ammunition yields projectile velocities which lie within a relatively narrow band, typically or It has also been found that when a projectile ricochets, its apparent velocity component as measured by two in-line sensors along its original line of flight is sustantially reduced, typically by 40% or more. It is therefore possible to disting:ish a genuine direct hit from a ricochet by comparing the measured velocity component with a preset lower limit representing an expected projectile velocity (which will generally be $["different for different ammunitions and ranges). If the S.detected projectile velocity does not exceed this threshold limit, then the associated mechanical hit registration (inertia switch) cannot be valid and can be ignored. The computer may be supplied with a minimum valid threshold velocity for the type of ammunition being used, and the appropriate comparison made. It is to be noted that this technique does not require a capability to measure position, but only projectile velocity, and can be implemented using only an impact detector in combination with two sensors positioned relative to the target for detecting the airborne 34.

:2 0 S15 eeo o.5 20 .25 shock wave generated by the projectile at two spaced locations on its trajectory.

c) Hit registration time. For a "hit" detected by the inertia switch to be genuine, it must have occurred within a short time period relative to the time at which the projectile position determining system detected the projectile. It has been found from theory and practice that this period is very short, not more than or -3.5 milliseconds for a commonlyused "standing man" target as illustrated in Figure 2. By suppressing all target impacts detected by the inertia switch outside of this time, many otherwise false target impact detections are eliminated. The position in time and the duration of the period varies with different targets, with position of hit positions sensors airborne shock wave responsive transducers) relative to the target, with nominal projectile velocity and velocity of sound in air, and, to a small extent, with various target materials. All these factors are, however, known in advance and it is therefore possible to provide the system with predetermined limits for-the time period. It is to be noted that this last technique does not require a capability to measure position or even projectile velocity, and can be implemented using only an impact detector in combination with a single sensor positioned relative to the target for detecting the airborne shock wave generated by the projectile.

Appendix A attached hereto is a suitable program written in "BASIC" programming language which may be directly used with the Computer Automation LSI 2/206 minicomputer.

The program is used for performing the position calculations indicated above, generating required reset signals for the timer interface unit, calculating the speed of sound and bullet velocity, performing threshold checks for bullet velocity, determining whether the inertia switch has detected a "hit", determining a ricochet hit and providing appropriate output signals for the printer and display units.

It will be recognized from the foregoing that the computer programs of Appendlix A employ the "projectile velocity" and "hit registration time period" techniques for ricochet and stone hit discrimination. Those skilled in the art will readily recognize the manner in which the programs of Appendix A may be modified to employ the "electronic target window" technique for ricochet and stone hit discrimination. That is, a mathematical algorithm defining the boundaries of. the target outline in the measurement plane may be included in the program and compared with the X, Y coordinates of the calculated bullet trajectory location in the measurement plane to determine whether the calculated location lies within the target "window". Assum- *9 9 ing for example that the target is a simple rectangle, the .151. window" may be defined in the program as XA'\Xl-\XB, YA(Y1(YB, whece XA and XE represent the left and right edges of the target "window" and YA and YB represent the lower and upper edges of the target "window", respectively.

Assembly Language subroutine facilities are provided in the programming described above. They are: 0 .0 CALL Execution of this DASIC statement resets *the timer interface unrit 64 and readies the circuitry for use. This subroutine is assigned the Assembly Language label RESET.

CALL (4 Z0, A2, T7, T6, T5, T4, T3, T2, Tl): $see Execution of this BASIC statement transfers the binary numbers of counters 1-8 of the timer interface unit to BASIC in sequence. This subroutine is assigned the assembly language label IN: HIT in the Controller BASIC E~vent Handler Subroutine Module.

Figure 14A and 14B show flow chart sections for the subroutine RESET. Appendix B provides a program listing for this subroutine. The subroutine RESET starts on line 40 of the listing of Appendix B. It saves the return address to BASIC and then tests that CALL has only one parameter.t 36.

W. ii. _LII 5 U 5 LUP UUII L±II lJJ LAJ LUILt1 I L .Lta..CQL11 U.LCUJ:- &LJ _L no count, and counters 2, and 5-7 will start counting up.

23.

Another subroutine labeled RST (line 31) is then called which contains the instructions to reset the timer interface unit circuits. Subroutine RESET ends by returning to BASIC.

Figures 15A, 15B, and 15C provide a flow chart for the subroutine IN:HIT, while Appendix B contains a program listing for this subroutine.

Those skilled in the art will recognize that the configuration of the transducer array in Figures 2 and 4 may be modified within the spirit and scope of the present invention. For example, Figures 16-18 show alternate embodiments of arrays in which the transducers may be positioned.

Still further modifications may be made in accordance with the present invention, as will be recognized by those s. skilled in the art. For example, one or more light curtains may be generated for detecting passage of the bullet through an area in space, for the purpose of determining the velocity of the bullet. Such apparatus may be of the type disclosed in U.S. Patent No. 3,788,748 to KNIGHT et al.. the content of which is incorporated herein by reference. Figure 2 shows an apparatus for generating a light curtain and detecting the passage of the bullet iLhrethrough. A continuous wave helium-neon laser 600 generates a beam 602 which is directed onto an inclined quartz mirror 603 having a 25 mirror coating on the second surface thereof, relative to Sbeam 602, such that a portion of beam 602 is transmitted therethrough to form beam 604. Beam 604 is passed into a lens 605. Lens 605 is shaped as a segment of a circle cut from a sheet of material sold under the trade name Perspex.

Beam 604 is directed to bisect the angle of the segment and passes centrally thereinto at a circular cut-out portion 606. Cut-out portion 606 causes beam 604 to project as beam 608, which is of substantially rectangular cross-section shown by the dotted lines and which has no substantialy transverse divergence.

37.

LI

a non-zero count would be recorded in A2 because signal ENA8would have gone low upon receipt of signal VEL- (Figure 7C).

24.

Lens 605 comprises a generally triangular slab of light transmitting material having two substantially straight edges which converge, and having a part in the form of a part cylindrical notch 606 adjacent to te apex confined by the converging edges, which is adapted to diverge light entering the lens at the apex. The two straight edges of the lens, not being the edge opposite the apex at which light is to enter the lens, are reflective to light within the lens.

For example, the edges may be mirrored. Such a lens is adapted to produce a fan-shaped beam of light (a light curtain) having an angle which is equal to the angle included by the edges of the slab adjacent the apex at which light is to enter the slab.

If a projectile such as a bullet should pass through beam 608, it will be inclined by beam 608. Since the projectile cannot be a perfect black body, a portion of the beam will be reflected thereby, and a portion of that reflection will return to lens 605 where it will be collectec and.directed at mirror 603 as beam 609. Beam 609 is reflected by mirror 603, which is first-surface coated, with respect to beam 609, as beam 610. The cd'ating of mirror 603 is such 0 that beam 610 will be approximately 50% of beam 609. Beam 610 passes through an optical band pass filter 612 which prevents light of frequency substantailly different to that of laser 601 from passing, so as to reduce errors which may arise *from stray light such as sunlight. Beam 610 emerges as beam 613, which then passes through lens 614. Lens 614 focuses beam 613 onto to the center of a photoelectric cell 615, which emits an electrical signal 617. Signal 617 thus indicates the time at which the projectile passed through the light curtain.

Figure 20 shows schematically a system which may be employed for determining the velocity of the bullet in a direction normal to the measurement plane and the location in the measurement plane. A target 596 is mounted on a target Referring again to Figure 8A, when transducer Sl detects a shock wave generated by the bullet, a wave form mechanism 598 (which may be as shown in Figure An array of, for example, three transducers Sl, S2,S3 is provided in front of and below the edge of target 596. Two arrangements as shown in Figure 19 are located in front of target 596 to generate respective light curtains 608, 608' and produce output signals 618, 618' indicating the time at which the bullet passes through the respective light curtains.

Since the spacing between the light curtains 608, 608' is known in advance, the time difference may be employed to determine the velocity of the bullet in a direction normal to the measurement plane. The calculated velocity and the speed of sound in air (as separately measured or determined) may be employed with the output signals from transducers Sl-S3 to determine the location at which the bullet trajectory passes through the measurement plane. An inertia switch or other target impact detector may be used, as described above, for registering an actual hit on the target.

Those skilled in the art will readily recognize f o the manner in which the BASIC programs of Appendix A may 20 be modified for use with an arrangement as shown in Figure The skilled artisan will also recognize that, for example, light curtain 608' may be deleted and the velocity of the bullet may be determined from the output 618 of photoelectric cell 615 and the output of transducer S2 of Figure These skilled in the art will also recognize that marksmanship training may be further enhanced by combining the use of the arrangments described herein with a rifle equipped with pressure sensors at critical points as described in U.S.

A<o. -?57 77/5 Patent -Applicatin No. 835,4-31, filed September 21, 1977 (the content of which is incorporated herein by reference).

For example, the rifle used by the trainee may be equipped with pressure sensitive transducers located at the parts of the rifle that are contacted by the trainee marksman when the rifle is being fired. Thus, a transducer is located at the butt of the rifle to indicate the pressure applied by the 39.

/v 9 4' 7) 1 o.- 3 5 circuit chip IC2 may be of type CA3040, available from RCA Solid State, Box 3200, Summerville, New Jersey 08876.

26.

shoulder of the trainee marksman, a transducer is provided at the cheek of the rifle to indicate the Pressure applied by the cheek of the trainee marksman, and transducers are provided at the mrain hand grip and the forehand grip of the rifle. The outputs of the transducers are coupled to suitable comparator circuits as described in U.S. Patent Application No. 835,431 and the comparator output signals then indicate whether the pressure applied by the trainee marksman at each critical point on the rifle is less than, greater than, or within a predetermined desired range. While a dis- Play as described in U.S. Patent NElca±cnSrilU. 835 431 may be employed for indicating whether tha pressure applied by the trainee marksman to the rifle at each point is correct, it will be understood that the comparator output signals may alternatively be provided to minicomputer 70 in a suitable format so that the -visual display unit 72 of Figure 4 will display agraphic representation of the rifle and indication thereon of the pressure applied by the trainee marksman to the rifle. This graphic display may be in addition eo. to a graphic display of the target being fired upon and repr-asentations thereon of the location at which each bullet has struck or passed by the target. Such an arrangement provides the trainee marksman with an almost instantaneous indication of the manner in which he is holding the rifle and of his shooting accuracy, and permits rapid diagnosis of any diff- 9' iculties he may be having with his shooting. If a switch is mounted on the rifle for actuation when the trigger is Nr'. 4-571 71S_ Pulled as described in U.S. Patent plctnSri 4~ 835,-434,- the visual display unit 72" may be made to indicate the pressure applied to the various pressure transducers on the rifle at the precise instant of firing the rifle.

The display may be maintained on the display unit for a predetermined period of time and then erased so the trainee may proceed with firing a further round.

The addition of the pressure sensitive system ';A/vs

VTH

2 Cl t (11) C9

K

27.

enables the simultaneous display of pressure indications together with the projectile position and for positive target hit indication and/or ricochet indication. Such a simultaneous display has unique advantage in providing the trainee immediately not only with an indication of where the projectile has passed in relation to the target, but why the projectile passed through its displayed position.

This information provides immediate positive and negative reirforcement of marksmanship techniques with respect to the correct grip and aim of the weapon to permit rapid learning of correct skills.

It is not necessary to employ an inertia switch S, to detect "hit" of the projectile on a target member.

•Other apparatus may also be employed for this purpose.

For example, Figures 21-22 show an arrangement for sensing impact of a projectile on a target member 700 employing a sensor assembly 702 positioned in front of the rigid target member 700. The rigid target member 700 may be of any desired shape and may be constructed, for example, of plywood or ABS material. Sensor 702 includes a transducer mount-.d within a shrouded housing which prevents any airborne shock wave of foe a supersonic projectile from being detected. The output of the shrouded sensor assembly 702 is provided through an amplifier 704.

S235" The output of amplifier 704 is provided through a suitable signal processing circuit 706, which provides a "hit" output indication. Signal processing circuit 706 may comprise essentially a threshold detector. Shrouded sensor assembly 702 may comprise a transducer 709 (as described above with reference to Figures 11-12) mounted in a block of acoustic isolating material 708 (such as described above with reference to Figure 13). The block of acoustic isolating material is, in turn, mounted in a housing or shroud 710, with the transducer 709 recessed to provide a restricted arc of sensitivity of the transducer which is 41.

i I appropriate to just "see" the face of target 700 when sensor assembly 702 is appropriately positioned relative to the target member 700. A coaxial cable from transducer 709 passes through an opening in shroud 710 and may be isolated from vibration by a silicone rubber ring 712 or the like.

It will be understood that the threshold level of detector 707 in Figure 21 is to be appropriately set so that disturbances of the target detected by transducer 709 will produce a "hit" output indication from signal processing circuit 706 only when the amplitude of the detected disturbance is sufficiently great to indicate that the disturbance of the target was caused by a projectile e* e* impacting on or passing through target member 700.

S.i Still another apparatus for detecting a projectile "hit" passage through a target member) is illustrated in Figure 23. In this embodiment, the target member comprises eo a sheet of suitable electrically insulating spacer material 730 which may be of any desired size. Metal meshes 732, 734 are cemented to the insulating spacer sheet 730. As a bullet passes through the "sandwich" target comprising bonded-together members 730-734, electrical contact between metal meshes 732, 734 is established, so that the voltage at point 736 drops momentarily from +5 volts to 0 volts, thereby indicatingpassage of the bullet through the target 2 "sandwich".

Still other apparatus is possible for determining the velocity of the projectile, such as shown in Figure 24.

A projectile fired from a weapon 740 travels along a trajectory 742 toward a target member or target zone 744. An array of transducers Sl, S2, S3 is located below one edge of the target member or zone 744. For determining the velocity of the projectile, a detector 746 is positioned to sense the time of discharge of the projectile from the weapon and provide a signal which starts a counter 748. Counter 748 is supplied with pulses from a clock generator 750 and counts the clock 42.

.4 L a last response.

It is advantageous to utilize a piezoelectric disk 29.

i _I .j.

10 pop$, 15 0 2 6" 15 S..Poo 5* 0 pulses until a signal is received from transducer S2 through an amplifier 752 for stopping the counter.

It is known that projectiles, such as bullets, decelerate in a well-defined and consistent manner. This deceleration can be expressed in terms of loss of velocity per unit distance travelled along the trajectory, the deceleration being substantially constant from sample to sample of high quality ammunition (such as most military ammunition) and being substantially independent of velocity.

At any point along its trajectory, the projectile velocity

V

t is:

V

t

V

m d.k.

where Vt projectile velocity at point in question V nominal velocity of projectile at weapon or known origin d distance from muzzle (or known origin) to point in question k above-mentioned "deceleration" constant Dy simple algebra, it is possible to find an expression for distance travelled in a given time, which is: -kt d(t) V where t is the independent variable of time. For good quality ammunition the constant is well controlled, and can be predetermined with good accuracy. Thus, the only "unknown" is Vm which will vary from round to round.

The arrangement according to Figure 24 operates to determine a notional value for V by measuring the time of flight of the projectile from the weapon to the array.

The preceding equation permits V to be computed and, once obtained, permits V obtainedt in the vicinity of the transducer array to be calculated. Detector 746 may be an optical detector sensing the weapon discharge muzzle flash, or an acoustic device responding to the muzzle blast and/or supersonic 43.

struction is employed, aluminium case 568 may be grounaeca to provide a Faraday cage to minimize noise. The piezoelectric projectile shock wave.

Figure 25 shows a graticule overlay used on the visual display screen 72" of Figure 4. A target T is orovided as well as a separate score column for each shot.

If the positive hit indication (inertia switch) is not actuated, a score is indicated, otherwise a non-zero point score is displayed. The positive hit indication is particularly advantageous for borderline cases, as for example, shot No. 6. In such cases, it may not be clear from the position display alone whether a "hit" occurred.

Shot No. 1 is shown as a clear miss; shot No. 2 as a ricochet hit, shot No. 5 as a ricochet miss and shot numbers 3, 4 and 7 as hits having different poin- values.

9 *0 a 9* a go 4.to ease

S.

0 00 0 *0 ,i oigsoic uncter tne tracemar( Piastizore ny ba~eiie \yiLunLLu, Ltd, U.K. Other suitable acoustic decoupling materials may 31.

APPENDIX "A" 2 REM INTERMEDIATE RANGE PROJECTILE POSITION CALCULATION PROGRAMj~ 7 REM INCLUDING INTEGRATED VELOCITY OF SOUND IN AIR ESTIMATION 1010 R=4998000 1015 R0=1/R 1020 DATA 0.0,0.5,0.0,0.29,-0.5,0.0.5,-0.5,0.0.5,0-5,0.0.5,0.5,0.0.5 1025 DIM C(6.3) 1030 M4AT READ C 1035 MAT PRINT C '1037 PRINT "MINIMUM BULLET VELOCITY, METRES/SEC.?" *1040 INPUT VO 1045 K=0 001 0 1120 CALL (4,20, A2 ,T7 ,TG,TST4 ,T3 ,T2 ,Tl) .4,09,112 5 Tl=Tl*RO .~1130 T2=T2*RO 1135 T3=T3*R(O 114 *4* 1140 T4=T4*RO ~~1150 T6=T6*RO 1155 T7=T7*RO 1157 GOTO 1450 1160 1165 1170 IF Vl>VO GOTO 1180 1175 N1-Nl+2 1180 IF A2= GOTO 1210 1185 IF N1<2 GOTO 1200 Determine the speed of sound in ambient air in the vicinity of the transducer array (to a reasonable 1190 1195 1200 1210 1250 1255 1260 1265 70 :0*127 5 1300 1301 1302 1305 10 1315 1325 a..33 1340 1345 1350 1355 1360 1365 1370 1375 1380 1385 IF T7=T1>0 002 GOTO 1400 IF T7-T1<-0 0005 GOTO 1400 Nl=N1+1 IF NI>1 GOTO 1400 B1=BO J=3 K= 6 T8=T3 T9=T6 Z3BO*BO G1=G* (T9-T1) G2=2*G1 G4=0 1) -C 1) G3=2*G4 G1=G1*CT9+T1)-G4*(C(K.1)+O*1.1)) H 1=G* (T1-T8) H 2 =2 *H1 H4=C 1) -C 1) H3=2*114 lI1H1i* T1+T8) -H4* 1. 1) ±0 1) .Xl= (H2*G1-li1*G2) /(1-3*G2.-H2*G3) B3= (G1+G3*Xl) /G2 Y1=Tl-B3 Y1=G*Y1*Y1 G4=X1-C(1. 1) Y1=Y1-G4 *G4 Yl=SQR(Y1) 2) GOTO 1110 at least three possible techniques for processing the information from the timer interface unit for the purpose of providing ricochet and stone hit discrimination.

33.

1400 1405 1410 1420 1425 1430 1435 1440 ~..:1450 1455 :1460 1500 Do0* xl= Q Y PRINT Xl; Y1; "S11OT STATUS NO";Nl PRINT"Nl=O FOR MISS" PRINT "N1=l FOR HIT" PRINT"N1=2 FOR RICOCHET MISS" PRINT "Nl-3 FOR RICOCHET HIT" GOTO 1500 K1=K/ (T5-T1) BO=331. 45*SQR(K/273)+oo 9 GOTO 1160

END

I le.

0003 0004 0005 0006 0007 0008 0009 0010 0011 0012 0013 0014 0015 0016 0017 0018 0019 S 0020 0021 0022 '.:0023 0024 :0025 .0026 *0027 0028 0029 0030 0031 '.",0032 S 0033 0034 .0035 0036 0037 0038 0039 0040 :0041 0042 0043 0044 0045 0046 0047 0048 0049 0050 0051 0052 0053 0054 0055 0056 0057 APPENDIX 'B' RESI:T RESET SYSTEM IN:IIIT=SHIFT HIT DATA FROM MEMORY TO BASIC OP:BIN= OUTPUT HIT/MISS FROM BASIC TO V.D.U.

8 OFF 16 BIT WORDS WILL BE INPUT TO MIEMORY FOR EVERY HIT 001A 0022 005A 0000 0000 0001 0002 0003 0004 0005 0006 0007 0008 0009 000A 000B 000C 000D 000E 000F 0010 0011 0012 0013 0014 0015 0016 0017 0018 0019 00.11 001B 001C 001D 001E 001F 0020 0021 0022 0023 0024 0025 0026 0027 0028 0029 002A 002B NAN RESET,IN:HIT, OP:BIN 0000 0018 58CO 0800 0000 44C'7 44C2 44C4 44C1 58C7 0A00 F708 0011 0800 FF1B 0000 C601 FF18 0005 FEOD 0011 0110 9E12 OOOE F71E 0003 0800 FF23 0000 C60A FF20 0005 5801

COOE

F203 002C 49C7 F215 0040 F605 0026 PSH

FLT:

OPDEND

POP:

STR:

VAC:

ERR:

ACC1 ACC2 Bccl BCC2

PTT:

EVL:

FIX:

FLAG

COUNT

Ml1

INA

RST

RESET

IN:HIT

HOLD

REL

REF

REF

REF

REF

REF

REF

REF

REF

REF

REF

REF

REF

REF

REF

RES

RE S

EQU

IN A

ENT

NOP

SEA

SEA

SEA

SEA

INA

EIN

RTN

ENT

CALL

LAP

CALL

JST

ZAR

STA

JMP

ENT

CALL

LAP

CALL

ISA

CAI

JMP

SEN

JMP

JMP

0 1 24 MI. 0 Ml. 7 MI. 2 Ml. 4 M1.7 Ml. 7

RST

RESET INTERRUPTS 1 to 8 RESET TIMER 1 to 8 CLEAR COUNTERS 1 to 8 ARM TIMER *PSH 1

*VAC:

RST

FLAG

*POP:

*PSH:

*VAC:

14

ESCAPE

Ml. 7 P :NEXT

HOLD

SAVE RETURN CHECK PARAMETER COUNT CLEAR TO SHOOT SAVE RETURN CHECK COUNT I/P CONSOLE SENSE REG CHECK FOR "E" GET OUT IF IT IS MODULE READY? DATA AVAILABLE NO. GO ROUND AGAIN a "nit", determining a JluuUi-eL IL-L aL UieV---, -rr output signals for the printer and display units.

0058 0059 0060 0061 0062 0063 0064 0065 0066 0067 0068 0069 0070 0071 0072 0073 0074 :0075 0076 **."0077 S.0078 .:0079 0080 0081 :0032 :0082 0083 0084 0085 .*..,0086 0087 S. *0088 0089 0090 *,.0091 0092 0093 0094 *....0095 ""0096 1)097 S"098 0099 0100 0101 0102 0103 0104 0105 0106 0107 0108 0109 0110 0111 0112 0113 0114 002C 002D 002E 002F 0030 00.31 0032 0033 0034 C.70 7 9E1E 0110 FA1E DE21 F603 B624

FAIA

F731

ESCAPE

000F 004E OOOF 000F 002E 000E 004E 0003

LAM

STA

ZAR

JST

IMS

JMP

LDA

JST

JMP

8

COUNT

PASSV

COUNT

$-3

FLAG

PASSV

*POP

END

BACK TO BASIC *PASS 9 VALUES TO BASIC 0035 C708 0036 9E27 OOOF PASS LAM 8 STA COUNT 0037 003.8 0039 003A 0033 003C 003D 003E 003F B627 0010 9A00 0039

HERE

AA2E FA12 DE03 DE2E F6.05 F60D 0069 004E 0039 000F 0039 0032

LDA

STA

RES

XOR

JST

IMS

IMS

JMP

JMP

INA

HERE

1 MAS K1

PASSV

HERE

COUNT

HERE

END

P:NEXT DETECTS IF COUNTERS FITTED 0040 0041 0042 0043 0044 0045 0046 0047 0048 0049 004A 004B 004C 004D 004E 004F 0050 0051 0052 0053 0054 0055 0056 0057 0058 0059 005A 005B 005C 005D 005E 58C1 AA27 0069 314D 0035 58C2 AA24 0069 3150 0035 58C3 AA21 0069 3153 0035 58C4 AA1E 0069 3156 0035 58C7 F627 0026 0800 FF4E 0001 FF45 0008 3106 0058 FF46 000C B74A 0009 9C00 0000 B74B 000A 9C01 0001 F709 004E FF52 0006 C6D7 0800 FF5R 0000 C602 FF58 0005 FF53 0008

P:NEXT

PASSY

ER

INA

XOR

JuAN

INA

XOR

JAN

INA

XOR

JAN

INA

XOR

JAN

INA

JMP

ENT

CALL

CALL

JAN

CALL

LDR

STA

LDA

STA

RTN

CALL

DATA

OP :BIN

CALL

LAP

CALL

CALL

l. 1 IMASK1

PASS

Ml. 2 MASK1

PASS

Ml. 3 M1.3 MAS K 1

PASS

Ml. 4 MASK1

PASS

Ml. 7

HOLD

*FLT:

*PTT:

ER

*EVL:

*BCC1 @0 *DCC2 @1

PASSV

*ERR:

FW

ENT

*PSH:

2

*VAC

*PTT:

_L1< the listing of Appendix B. It saves tne return aooreb.:iu BASIC and then tests that CALL has only one parameter.

36.

0115 005F 31 011.6 0060 FF 0117 0061 FF 0118 0062 B7 0119 0063 49 0120 0064 F6 0121 0065 6C 0122 0066 49 0123 0067 F6 0124 0068 F7 0125 0069 7F 0126 0000 ERRORS 0000 WARNING .08 0068 '54 OOOC '54 OOOD 5B3 0007 313 01 0063 38 313 01 0066 65 0003

FF

JAN

CALL

CALL

LDA

SEN

imp

OTA

SEN

J M) imLp

DATA'.

END

ERROR

*EVL:

*FIX:

*ACC1 7. 3 1 7. 3 s-i 7FFF

ERROR

MJXSKI

INVERT 15 BITS

S

S

4* 55 5 0

S

OS S 0e t~ Op..

S P OS S p

S

05 U U

S*

S.

U

*S

SO

S

550 I

Claims (6)

1. 2. Apparatus according to claim i, wherein said detecting and indicating means comprises: p means for detecting said location and providing an output indicative thereof, and means responsive to said output for providing a visual representation of said target member and for graphically displaying said detected location relative to S said target member representation. o
2. 3. Apparatus according to claim 2, wherein said graphic display means comprises a visual display screen fitted with a graticule bearing said target representation, said visual LeR et SA j4r O ritl e i s n e in g ziLu -II butt of the rifle to indicate the pressure applied by the
3. 39. I a ~-I p display screen displaying a visible mark relative to said graticule to indicate said detected location. 4. Apparatus according to claim 3, wherein said graphic display means is further responsive to a hit detecting means for displaying a positive visual indication of whether said projectile has hit said target member. Apparatus according to claim 3 or 4, further comprising comparing means for comparing said detected location with a predetermined range of locations representing a target window in said measurement plane, said graphic display means being further responsive to said comparing means for providing a visual indication of whether said detected location is within said predetermine. range of locations. 6. Apparatus according to claim i, wherein said projectile velocity measuring means comprises means for detecting passage of said projectile past two points spaced apart at a known distance along a line substantially parallel to said trajectory, and means responsive to said passage detecting means for calculating at least an approximate value of said projectile velocity in the region of said target member. 7. Apparatus according to claim 6, wherein at least one of said passage detecting means comprises a transducer responsive to an airborne shock wave from a supersonic velocity projectile. 8. Apparatus according to claim 6, wherein at least one of said passage detecting means comprises a hit detecting means. 9. Apparatus according to claim 6, comprising means for detecting a time of discharge of said projectile from a weapon fired at said target member from said firing point, said calculating means taking into account deceleration of said projectile from said firing point to the region of said target member to determine an expected approximate value of said projectile velocity in the region of said target I'I t may proceed with firing a further round. The addition of the pressure sensitive system (v member, to enable distinguishing of projectile velocities detected in said region outside said expected approximate value, whereby there can be distinguishing of a free flight hit of said projectile from said firing point or a ricocheted hit. Apparatus as claimed in claim 9 wherein the expected time of passing of said projectile past said region is determined from said detection of the time of discharge of said projectile from said weapon to provide further distinguishing of a free flight hit of said projectile from said firing point or a ricocheted hit. 11. Apparatus for use in marksmanship training in which a projectile is fired at a target member, comprising:, in use, means for detecting a projectile hit on a target member; means for detecting passage of said projectile eeoeo S through at least one predetermined zone, in use, located S relative to said target member; and computing means responsive to said means for detecting a projectile hit and said passage detecting means and operative for: determining a time difference between an instant at •which said hit detecting means detects a projectile hit on said target member and an instant at which said passage detecting means detects passage of said projectile through said predetermined zone; comparing said time difference with at least one ee* expected time difference value to ascertain whether the velocity of said projectile is within an expected S"projectile velocity range; and providing an indication of the result of said comparison, S° wherein said expected time difference value is S selected such that a trainee marksman is provided with an MtW isolating material is, in turn, mounted in a housing or shroud 710, with the transducer 709 recessed to provide a restricted arc of sensitivity of the transducer which is r re S. 0* S S indicatiun of whether a detected projectile hit on said target has resulted from a free flight projectile hitting said target member or from a projectile which has ricocheted prior to hitting said target member. 12. Apparatus for use in marksmanship training in which a projectile is fired at a target member, comprising: means for detecting a projectile hit on a target member; means for measuring velocity of said projectile in the vicinity of said target member; and computing means responsive to said hit detecting means and said velocity measuring means and operative for: comparing said measured velocity with at least one expected projectile velocity value to ascertain if said measured velocity is within an expected projectile velocity range; and for providing an indication of the result of said comparison between said measured velocity and said at least one expected velocity value, whereby a trainee marksman will be provided with an indication of whether a detected projectile hit on said target has resulted from a free flight projectile hitting said target member or from a projectile which has ricocheted prior to hitting Said target member. 13. Apparatus for indicating the location in a measurement plane through which the trajectory of a supersonic projectile passes, the supersonic projectile travelling from a firing point toward a target zone and through said measurement plane, comprising: a target member located in said target zone; an array of at least three transducers responsive to an airborne shock wave from the supersonic projectile and located at respective predetermined positions spaced along a line substantially parallel to said measurement plane; ~i; a signal which starts a counter 748. Counter 748 is supplied with pulses from a clock generator 750 and counts the clock
4. 42. means for measuring velocity of the supersonic projectile; means for measuring velocity of propagation of sound in air in the vicinity of the array of transducers; computing means responsive to said array of transducers, said projectile velocity measuring means, and said propagation velocity measuring means, and operative for: determining the location in said plane through which the trajectory of the supersonic projectile passes, and providing an output indicating said determined location. i4. Apparatus according to claim 13, further comprising means responsive to said computing means output for graphically displaying said detected location relative to said target member representation. 15. Apparatus according to claim 14, wherein said graphic S display means comprises a visual display screen fitted with S: a graticule bearing said target representation, said visual :r display screen displaying a visible mark relative to said S graticule to indicate said determined location. S 16. Apparatus according to claim 15, wherein said computing means is further operative for comparing said detected location with a predetermined range of locations Srepresenting a target window in said measurement plane, said *00000 graphic display means being further responsive to said S computing means for providing a visual indication of whether Ssaid detected location is with said predetermined range of locations. 17. Apparatus according to claim 16, wherein said Sprojectile velocity measuring means comprises first and S second means for detecting passage of said projectile past 0 respective points spaced apart at a known distance along a I$'7 ThC~ obtfined, permits V t in the vicinity of the transducer array to be calculated. Detector 746 may be an optical detector sensing the weapon discharge muzzle flash, or an acoustic device responding to the muzzle blast and/or supersonic
5. 43. 59 0. 0 0 0 S 0 line substantially parallel to said trajectory, and means responsive to said passage detecting means for calculating at least an approximate value of said projectile velocity in the region of said target membt.r. 18. Apparatus according to claim 17, wherein said passage detecting means comprises a pair of transducers responsive to an airborne shock wave from said projectile and spaced apart along said line substantially parallel to said trajectory. 19. Apparatus according to claim 18, wherein one of said pair of passage detecting transducers comprises one of said at least three transducers of said array. Apparatus according to claim 17, wherein one of said passage detecting means comprises means for detecting a time of discharge of said projectile from weapon fired at said target member from said firing point, said calculating means taking into account deceleration of said projectile from said firing point to the region of said target member to determine an expected approximate value of said projectile velocity in the region of said target member, to enable distinguishing of projectile velocities detected in said region outside said expected approximate value, whereby there can be distinguishing of a free flight hit of said projectile frr-n said firing point or a ricochet hit. 21. Appara cording to claim 20, wherein the expected time of passii said projectile past said region is determined from said detection of the time of discharge of said projectile from said weapon to provide further distinguishing of a free flight hit of said projectile from said firing point or a ricochet hit. 22. Apparatus according to claim 13, wherein said projectile velocity measuring means measures said velocity in the region of said target zone and said computing means is further operative for: comparing said measured velocity with at least one expected projectile velocity value to ascertain if said
6. 44. 57 measured velocity is within an expected projectile velocity range, and providing an indication of the result of said comparison between said measured velocity and said at least one expected velocity value, whereby a trainee marksman is provided with an indication of whether said projectile has ricocheted prior to reaching the region of said target zone. 23. Apparatus according to claim 13, wherein each said transducer of said array provides signals to said computing means representing respective instants of detection of said airborne supersonic shock wave. 24. Apparatus according to claim 23, wherein said computing means determines time difference between said instants of detection. Apparatus according to claim 13, wherein said S propagation velocity measuring means comprises means for measuring and providing to said computing means a value representing at least one parameter of ambient air in the vicinity of said array of transducers. 26. Apparatus according to claim 25, wherein said S parameter measuring r-ans comprises means for measuring temperature. 27. Apparatus according to claim 13, wherein each said transducer comprises a disk shaped member of piezoelectric material, and a member of rigid material having a convex S surface exposed to said airborne shock wave, said member of rigid material being acoustically coupled to said S disk-shaped member of piezoelectric material for transmitting to said disk-shaped. member of piezoelectric material vibrations induced by said airborne shock wave. S 28. Apparatus according to claim 27, further comprising means for mmunting each said transducer at a said respective predetermined position, said mounting means comprising an acoust'ic decoupling material. 01 "Pi; Id 1180 IF A2= GOTO 1210 1185 IF N1<2 GOTO 1200 29. Apparatus according to claim 13, wherein said computing mans is further operative for: comparing the determined location in said plane through which said supersonic projectile passes with a predetermined range of locations in said plane representing a target window in said plane; and indicating whether the determined location in said plane through which said supersonic projectile passes is within said target window in said plane. Apparatus according to claim 29, wherein a target of predetermined shape and dimension is provided in said target zone, and said predetermined range of locations in said plane corresponds to said predetermined shape and dimension of said target. 31. Apparatus according to claim 13, wherein each said transducer provides an output representing a time of S detection of said airborne shock wave, and said computing means comprises means responsive to said transducer outputs for registering said time of detection for each said transducer, relative to an arbitrary time origin. 32. Apparatus according to claim 31, wherein said S detection time registering means comprises: a source of clock pulses; and a plurality of counters, each said counter associated with one of said transducers and responsive to said source of clock pulses and to the output from said associated one S of said transducers for counting a number of said clock 0090 S pulses representing said time of detection relative to an arbitrary time origin. S 33. Apparatus according to any one of claims 1 to 32 comprising: a weapon to be gripped and fired at said target e oee S member by raid trainee marksman; means for detecting pressure applied to a plurality of locations on said weapon by said trainee marksman as said weapon is being fired; and I means responsive to said pressure detecting means for indicating when the pressure applied to the weapon at said plurality of locations is within a predetermined optimal range, wherein the trainee marksman is further provided with an indication of whether the weapon has been correctly gripped when fired at said target member. 34. Apparatus for use in marksmanship training as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings. Apparatus for use in marksmanship training as claimed in claim 11 and substantially as hereinbefore described with reference to the accompanying drawings. 36. Apparatus for use in marksmanship training as claimed in claim 12 and substantially as hereinbefore described with reference to the accompanying drawings. 37. Apparatus for use in marksmanship training as claimed in claim 13 and substantially as hereinbefore described with reference to the accompanying drawings. DATED THIS 11TH DAY OF FEBRUARY, 1991 AUSTRALIAN DEFENCE INDUSTRIES LTD. By Its Patent Attorneys: GRIFFITH HACK CO., Fellows Institute of Patent Attorneys of Australia C C C~ CC C CC A C C C A i