Machine Gun and Minor Caliber Weapons Trainer

1. Field Of The Invention

The invention relates generally to the field of training devices, an more particularly to devices on which trainees practice firing manually aimed weapons in simulation by "firing" a demilitarized or simulated weapon at a target imaged on a video projection screen.

2. Description Of The Prior Art

Minor caliber weapons that lack a fire control system are installed on-board naval ships for close-in ship defense against high speed boats and aircraft that are used with hostile intent. The gunner must be practiced in the difficult art of manually aiming the weapon in lead angle and elevation that is closely related to being an experienced and accurate estimator of range, in order to be effective at eliminating the threat. Previously, the training that is necessary to achieve and maintain proficiency at range and lead estimation has been conducted in the classroom without the aid of a training device, and in the field at great expense with live rounds against dummy targets. Such training lacks an accurate threat simulation and fails to provide marksmanship training against an elusive target, variable daylight and sea state conditions, and training in target identification, as well as accepts a trade-off of safety for realism.

Art that is relevant to the field includes U.S. Pat. No. 4,824,374 that discloses a target trainer having a screen on which is depicted a scene, a target projector for projecting the image of a moving target on the screen, and a combination of an infra-red target beam projector and infra-red sensitive television camera, associated with a simulated weapon and the target to determine the accuracy of simulated shooting at the target. U.S. Pat. No. 4,820,161 discloses a device for simulating indirect field of fire gunnery for training artillery gunnery observers, that includes a screen for showing a photographic image of terrain overlaid with computer generated images of shell bursts at locations corresponding to commands given by a trainee. U.S. Pat. No. 4,813,682 discloses a television game using a photosensitive gun and a technique to avoid mistaking light from an outside source for the light from the target, wherein actuation of the gun's trigger causes black picture data to be displayed followed immediately by white picture data in the position of the target, which white picture data is detected and processed for use as a detection signal from the target. U.S. Pat. No. 4,789,339 discloses an attachment to a gun having a fire control system, that provides simulated scenic images to the gun's visual display and overwrites the scene with simulated target images, then computes the gunner's accuracy by computing the difference between his aim point and the location of the simulated target. U.S. Pat. No. 4,639,222 discloses a gunnery trainer having a library of video records of actual projectile trajectories and impacts for various orientations, wherein the video record is selected and displayed in a time relationship to trigger actuation. U.S. Pat. No. 4,606,724 discloses a simulator of small-bore guns that provides images of target, tracers and aim point in the gunsight.

The present invention overcomes the disadvantages of the prior art by providing a device that will train a gunner with a simulated or demilitarized weapon on a projection video system wherein a library of prerecorded video target scenarios are preselectively available to randomly present various sequences by type, and wherein each shot launched by the gunner from the weapon is graphically displayed through its trajectory to impact. Hits and misses are determined by comparing the computed point of impact with the target's location on the relevant frame of video, wherein the target's location has been previously identified frame by frame for use in the comparison, and scoring is accomplished by accumulating points that relate to proximity of impact to target. Hits are depicted by graphically burning the target; and, recoil is provided pneumatically through the weapon's handles. A sound generator having a first section for simulating the discharge of the weapon is provided, as well as a second section for simulating the sound of hits and misses delayed to simulate the lag between seeing the impact and hearing it.

Accordingly, an object of the present invention is to achieve realism for a gunner operating a simulator that represents a weapon that must be manually aimed. Another object is to provide a simulator having a projection system of prerecorded video showing scenes in which a moving target represents the threat to be removed and the trainees effectiveness is scored by comparing a digital representation of the target's location with digital computations of the trainee's shots. Another object is to provide such a simulator wherein the flight and impact of the shots are graphically superimposed on the video scenes. And, another object is for a device wherein sound, recoil and hits/misses are depicted realistically to the trainee.

FIG. 1 is a block diagram of a preferred embodiment of the invention;

FIG. 2 is a block diagram of the microprocessor of the preferred embodiment;

FIGS. 3 and 4 are a block diagram of the computer sub-assemblies;

FIG. 5 is a block diagram of the simulated or demilitarized weapon;

FIG. 6 is a block diagram of the elevation and azimuth sensors attached to the weapon for use in measuring the gunner's aim to compute trajectory;

FIG. 7 is a block diagram of the sound system; and,

FIG. 8 is a block diagram of the recoil circuit for use in pneumatically simulating recoil in the handles of the simulated weapon.

An embodiment of the present invention is shown in FIG. 1 to include projection screen 10 and video color video projector 12, computer cabinet 14 coupled to and driving projector 12, simulated or demilitarized weapon 16 and associated electronic package 18 coupled to and communicating with microcomputer 14, and compressor 20 used to pneumatically active recoil simulation in weapon 16. Instructor's terminal 22 may be included. Electronics package 18 may be enclosed in the ammo box that would accompany the weapon simulated by training weapon 16, to retain a realistic appearance to the trainee.

FIG. 2 shows the contents of computer cabinet 14 to include microcomputer 24 coupled to training weapon 16 and providing image data to projector 12, video disk player 26 responsive to computer 24 for providing frames of prerecorded video, sound system 28 responsive by way of computer 24 to trigger actuation of training weapon 16 and to computed hits/misses. Included is time base corrector 30 that is necessary for purposes of synchronization to overcome the mechanical deviations inherent in video disk players that would cause jitter. It corrects the video data coming from video disk player 26. Also, included in FIG. 2 are speaker or headphones 32 for use to audibilize the output of sound system 28 for the gunner-trainee.

For purposes of the embodiment a training device for the military's MK-19 minor caliber weapon will be used as an example. The MK-19 is a 40 mm machine gun that fires grenades at the rate of 375 rounds per minute. The weapon can saturate an area with lethal fragments so a scoring system that accumulates points as a measure of proximity is most suitable. The effective range of the weapon is 1500 meters, with the round being visible to the gunner during at least part of its trajectory. At a maximum range the time of flight of the round can be 10 seconds, with the round achieving a maximum elevation of 100 meters. The gunner must manually aim the weapon without the assistance of a fire control system. Accordingly, the gunner derives the fire control solutions mentally by taken into account what he sees to be the location of where the fired rounds are falling as well as the portion of their trajectory that is visible to him.

The present invention shows the rounds in flight as they are fired by the gunner's actuation of the weapon's trigger, as well as the impact of the rounds on the water or target. The display is shown on large screen 10 which may be the 72 inch screen used by projection television systems, such as are available from SONY, for example. The system uses computer graphics and video disk technology to simulate the rounds in flight as well as the explosions of rounds hitting the water or target. Target areas are stored on the video disk and can represent various sea states as well as lighting conditions, etc. Explosions and rounds in flight are inserted by a frame buffer on the video scene. Computer 24 may be an INTEL 386 single board computer with a 387 math coprocessor, for example. FIG. 3 and FIG. 4 show sub-assemblies of computer 24 wherein the components are listed by source for a configuration that uses the INTEL computer as the example in an operational embodiment for the MK-19 trainer.

Training weapon 16 is a simulated or demilitarized weapon and is located for training in front of screen 10. When the gunner fires weapon 16 by actuating its trigger, he feels a recoil enabled by computer 24 and energized by compressor 20. Also, the gunner hears the weapon's report, provided by sound system 28. The elevation and azimuth of the weapon are measured to calculate the trajectory of the round and determine its point of impact. Horizontal and vertical potentiometers 34 and 36, respectively, on the cradle of gun 16 as shown in FIG. 5 provide the values for measuring the position of weapon 16 by elevation and azimuth. Voltages from pots 34 and 36 are filtered as shown in FIG. 6 by four-pole low pass filters 38 and 40, respectively, implemented on the horizontal/vertical potentiometer driver circuit included in electronics package 18. After filtering, the horizontal and vertical position signals are converted to digital values by data translation analog input board 42 on FIG. 4. The horizontal and vertical potentiometer circuit supplies two independent analog signals to computer 24 that correspond to the horizontal position and vertical position of weapon 16. The two channels may be identical. Each channel places the potentiometer between a bipolar dc voltage supply in a voltage divider arrangement. The voltage at the wiper of the potentiometer is coupled to a buffer and voltage scaler to limit the output to a preselected maximum, and filtered. Filters 38 and 40 may be Butterworth filters with a center frequency of 600 Hz. The cut-off frequency is selected to minimize phase delay before the signal is coupled to computer 24.

The computation to describe the flight of the round is performed by computer 24 using a fourth order equation that defines the trajectory associated with the weapon that is being simulated. Likewise, other weapons will have equations that define the trajectory of rounds fired from them. The equation associated with the MK-19 is included in Annex A, which is a source code of the programs prepared for the operational embodiment used in the example. As shown in Annex A at line 371 of the source code, the fourth order equation appropriate for the application of the invention to the MK-19 weapon system is, fprange=(6.987623E-07 times the elevation in mils to the fourth power) minus (3.080162E-04 times the elevation in mils to the third power) plus (3.422262E-02 times the elevation in mils to the second power) plus (5.386276 times the elevation in mils) plus 215.3749. The elevation in mils is translated in lines 364 et seq from the elevation in pixels between y values 150 and 410, with y value 210 denoting that the gun is level. A second fourth order equation that computes the time of flight, is listed at line 373. And, the round is displayed initially at the y value computed at line 376, with a velocity of drop at the value computed at line 377.

Switch 44 in FIG. 5 is operated by actuation of the trigger and is used to control recoil/pulse generator circuit 46 located in ammo canister 18. The circuit both provides an interrupt signal to computer 24 over trigger interrupt connector 48, and allows control of the weapon's recoil mechanism over recoil enable connector 50.

Video disk player 26 is interconnected with computer sub-assembly board 52 and provides target scenarios recorded previously with a video camera, preferably from the same level that the weapon occupies in the operational environment in order to provide a realistic perspective of the target image on replay. Disk player 26 is controlled over interface 54, which for the example is a serial port of computer 24. Each frame of the video is individually digitized for target size, location and range. Computer 24 computes the trajectory of the round fired from weapon 16 by reading the settings on potentiometers 34 and 36 on the gun cradle, and graphics board 56 on FIG. 4 generates the graphics for the round in-flight and the impact explosions. The graphics data is superimposed on the video disk target scene, and the result is displayed by video projector 12.

FIG. 7 shows sound system 28 that is used to generate sound effects by playing back a digitized recording of the weapons actual muzzle blast, and actual hit and miss explosions. First and second microcontrollers 58 and 60, respectively, reproduce sounds by transferring data stored in eproms 62 and 64, respectively, to converters whereat the data is converted from digital to analog form. First microcontroller 58 generates the sound of the muzzle blast, while microcontroller 60 generates the miss and the hit explosions through program controlled operational amplifiers 66 and 68, respectively. Range and sound delay of the explosions are accounted for in the program. These sound effects may be mixed in summer 70 to create simultaneous sound effects. Power amplifier 72 provides the output to audibilizer 32, such as a speaker or headphones.

The section of sound system 28 that has microcontroller 58 can work independently of the section that has microcontroller 60, but not vice versa. Accordingly, there can be a muzzle blast without an impact, but not an impact explosion without a muzzle blast. The first section, i.e., having microcontroller 58, supplies both an interrupt signal and the digital-to-analog transfer pulse required by the second section. Sound delay is determined by matching the shot's range to predetermined segments, wherein the maximum range for the weapon is divided into multiple segments with each progressively more distant segment having a greater delay.

FIG. 8 shows the recoil circuit. Recoil is caused by moving the handles of weapon 16 with a pneumatic cylinder. Compressed air is provided by compressor 20 and controlled by air valve 74 on FIG. 5. Valve 76 is shown as high speed solenoid valves 76 and 78 on FIG. 8. When trigger 44 is held down in an actuation position the recoil circuit generates a continuous pulse train for both recoil drivers 76 and 78, and computer 24. Trigger switch is debounced and used to control the enable oscillator that may be configured as a monostable multivibrator designed to oscillate at 262 Hz. Its output is coupled to a first one-shot that adjustably divides it to produce the rate required by computer 24. A second one-shot adjustably controls the pulse width of the signal that is being applied to the solenoid drivers. In return an enable signal is generated by computer 24 to disable the recoil signal, although the interrupt signal will continue to be received as trigger 44 is held down. Also, the enable signal is applied to sound system 28 to indicate status.

The software of Annex A was written using INTEL's PLM-286 compiler under the iRMX 286 operating system. The high level language and real-time capabilities of the operating system permits expeditious development of the application software. The ballistic characteristics of the round are used to determine the ballistic model for the weapon. The model is used to calculate a solution for the projection of the round in flight. Using this information graphical rounds and explosions are superimposed over the video disk image giving the gunner a visually correct perspective. Graphical sequences of hit and miss explosions are stored in the display buffer of computer 24 for block transfer during program execution. These images are loaded from hard disk 80 during initialization of the program. The graphics are updated at the frame rate of video disk player 26 using a double buffer technique.

The data on the video disk may be separated into numerous sequences, which in the case of the operational example was 35 scenarios. Each scenario shows a different range, speed attitude of direction of the target. The target was a boat. Ranges varied between 75 meters and 700 meters with boat speeds from stop to 35 miles per hour. Different training sessions are available from the scenarios, such as a session of lateral moving targets displayed in a random order. Files that describe the outline and range of the target for each frame of the scenario are stored on hard disk 80. Before a scenario is played the description file is loaded into memory for fast access by the program. Target hits are determined by comparing current impact location with target location for the current frame.

At the end of the training session a complete gunner assessment may be printed on screen 10. Gunner performance is determined by averaging the number of rounds the gunner takes to destroy the target over the scenario. A target is destroyed or disabled if a preselected point total is exceeded. Points are accumulated by proximity to the target. Each impact within 60 meters is given a value, an impact within 15 meters is given a greater value, and so on. For example, according to the program of Annex A the operator's menu provides flexibility to the scoring system and performance rating by offering several setup parameters. The instructor can selectively activate from the menu each scoring distance through a skill level parameter. A skill level 1 activates only the 5 meter impact distance, a skill level 2 activates both 5 meter and 15 meter impact distances, and a skill level 3 activates the greatest number of impact distances. The manner of measuring performance by tallying the average number of rounds per target destroyed, also can be varied for each rating classification. Once the parameters are selected they may be saved as system startup parameters, which permits the instructor to configure the system as desired.

From the foregoing description, it may readily be seen that the present invention comprises a new, unique, and exceedingly useful weapons trainer that constitutes a considerable improvement over the prior art. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described. ##SPC1##