Patent Publication Number: US-11656053-B2

Title: Method and apparatus for firearm recoil simulation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/127,578, filed Sep. 11, 2018, now U.S. Pat. No. 10,852,094, which is a continuation of U.S. patent application Ser. No. 15/486,443, filed Apr. 13, 2017, now U.S. Pat. No. 10,101,111, which is a continuation of U.S. patent application Ser. No. 14/808,247, filed Jul. 24, 2015, now U.S. Pat. No. 9,810,502, which is a continuation of Ser. No. 13/804,429, filed Mar. 14, 2013, now U.S. Pat. No. 9,146,069, which claims the benefit of U.S. Provisional Patent Application No. 61/650,006, filed May 22, 2012, each of which are incorporated herein in their entirety by reference thereto. 
    
    
     BACKGROUND 
     One embodiment relates to simulating of recoil for firearms. More specifically, one embodiment provides a method and apparatus for simulating the recoil of a selected conventional firearm. One embodiment additionally provides a laser to simulate the path of a bullet if the bullet had been fired from a firearm being simulated by the method and apparatus. 
     Firearms training for military personnel, law enforcement officers, and private citizens increasingly encompass role playing and decision making in addition to marksmanship. Such training often includes competing against role players and/or responding to situations projected onto a screen in front of the trainee. 
     Although self-healing screens exist, permitting the use of conventional firearms for such training, the use of such a system requires a location appropriate to the use of conventional firearms. Furthermore, such systems are expensive and can be unreliable. Alternatives to conventional firearms have been developed. These alternatives include paintball, simunitions, and the use of a laser to show the path a bullet would have taken had one been fired. 
     Such alternatives, however, do not duplicate substantially all of the characteristics of firing an actual weapon with actual ammunition, and the current alternatives limit the extent to which the training will carry over to use of actual firearms. In various embodiments the characteristics of a conventional firearm to be duplicated can include size, weight, grip configuration, trigger reach, trigger pull weight, type of sights, level of accuracy, method of reloading, method of operation, location and operation of controls, and recoil. 
     Realistic recoil is the most difficult characteristic to duplicate. The inability to get a trainee accustomed to the recoil generated by a particular firearm is one of the greatest disadvantages in the use of various firearm training simulators. Recoil not only forces the firearm shooter to reacquire the sights after shooting, but also forces the shooter to adapt to a level of discomfort proportional to the energy of the particular bullet to be fired by the firearm. Recoil is significantly more difficult to control during full automatic fire than during semi-automatic fire, making the accurate simulation of both recoil and cyclic rate important in ensuring that simulation training carries over to the use of actual firearms. 
     While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.” 
     SUMMARY 
     One embodiment provides a firearm training simulator having a recoil emulating the recoil impulse pattern of a particular firearm firing a particular size and type of bullet. In one embodiment the method and apparatus can include a laser beam projector for projecting the path of a bullet fired from the particular firearm being simulated. 
     In various embodiments the method and apparatus can also simulate additional operations of a particular firearm which operations include sighting, positioning of the firearm controls, and methods of operation of the firearm. Particular firearms that can be simulated include M-4A1, AR-15, or M-16 rifles, along with other conventional firearms. 
     In one embodiment the method and apparatus can be controlled by a combination of the trigger assembly, bolt, and linear motor. In various embodiments the method and apparatus is capable of simulating modes of semi-automatic fire and full automatic firing. In various embodiments the cyclic rate of full automatic firing mode simulation is substantially the same cyclic rate of a conventional automatic rifle. 
     One embodiment provides a laser substantially tracking the path of an actual bullet being fired from a firearm being simulated. One laser emitter can be housed within the barrel of the firearm simulating body. In one embodiment the laser emitter can be operatively connected to a controller which is also operatively connected to a recoil. One embodiment of the switch may be a roller switch structured to be actuated by a switching rod extending forward from the bolt. When the bolt moves forward in response to pulling the trigger, the switching rod engages the roller of the switch, thereby depressing the switch and actuating the laser. Another embodiment uses a proximity switch mounted in a location wherein a magnet may be brought into contact with it upon forward movement of the bolt. A preferred location is adjacent to the juncture between a barrel and upper receiver. A magnet affixed to the bolt is structured to be brought into proximity with the proximity switch when the bolt is in its forwardmost position, thereby causing the proximity switch to actuate the laser. 
     One embodiment provides a method and apparatus wherein the level of recoil imparted to the user may be programmed by the user. 
     One embodiment provides a method and apparatus capable of both semi-automatic and full automatic operation. 
     One embodiment provides a method and apparatus wherein different cyclic rate of full automatic fire may be programmed by the user. 
     One embodiment provides a method and apparatus including a laser assembly projecting laser substantially along the path of a bullet that would have been fired from the firearm being simulated. 
     One embodiment provides a method and apparatus simulating the recoil of a conventional firearm using a linear motor controlling a sliding mass and operatively coupled to a controller. 
     A linear motor can be thought of as an electric motor that has had its stator and rotor “unrolled” so that, instead of producing a torque (i.e., through rotation), it produces a linear force along its longitudinal length. The most common mode of operation for conventional linear motors is as a Lorentz-type actuator, in which the applied force is linearly proportional to the current and the magnetic field. 
     Many designs have been put forward for linear motors, falling into two major categories, low-acceleration and high-acceleration linear motors. Low-acceleration linear motors are suitable for maglev trains and other ground-based transportation applications. High-acceleration linear motors are normally rather short, and are designed to accelerate an object to a very high speed, for example see the railgun. They are usually used for studies of hypervelocity collisions, as weapons, or as mass drivers for spacecraft propulsion. The high-acceleration motors are usually of the AC linear induction motor (LIM) design with an active three-phase winding on one side of the air-gap and a passive conductor plate on the other side. However, the direct current homopolar linear motor railgun is another high acceleration linear motor design. The low-acceleration, high speed and high power motors are usually of the linear synchronous motor (LSM) design, with an active winding on one side of the air-gap and an array of alternate-pole magnets on the other side. These magnets can be permanent magnets or energized magnets. The Transrapid Shanghai motor is an LSM. 
     Linear motors employ a direct electromagnetic principle. Electromagnetic force provides direct linear movement without the use of cams, gears, belts, or other mechanical devices. The motor consists of only two parts: the slider and the stator. The slider is a precision assembly that consists of a stainless steel tube, which is filled with neodymium magnets, that has threaded attachment holes on each end. The stator, consisting of coils, the bearing for the slider, position sensors and a microprocessor board, is designed for use in harsh industrial environments. 
     A solenoid is a coil wound into a tightly packed helix. The term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. The term solenoid refers specifically to a coil designed to produce a uniform magnetic field in a volume of space (where some experiment might be carried out). In engineering, the term solenoid may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid. 
     Electromechanical solenoids consist of an electromagnetically inductive coil, wound around a movable steel or iron slug (termed the armature). The coil is shaped such that the armature can be moved in and out of the center, altering the coil&#39;s inductance and thereby becoming an electromagnet. The armature is used to provide a mechanical force to some mechanism (such as controlling a pneumatic valve). Although typically weak over anything but very short distances, solenoids may be controlled directly by a controller circuit, and thus have very low reaction times. The force applied to the armature is proportional to the change in inductance of the coil with respect to the change in position of the armature, and the current flowing through the coil (see Faraday&#39;s law of induction). The force applied to the armature will always move the armature in a direction that increases the coil&#39;s inductance. The armature is a ferromagnetic material. Free recoil is a vernacular term or jargon for recoil energy of a firearm not supported from behind. Free recoil denotes the translational kinetic energy (E t ) imparted to the shooter of a small arm when discharged and is expressed in joule(J) and foot-pound force (ft·lbf) for non-SI units of measure. More generally, the term refers to the recoil of a free-standing firearm, in contrast to a firearm securely bolted to or braced by a massive mount or wall. 
     Free recoil should not be confused with recoil. Free recoil is the given name for the translational kinetic energy transmitted from a small arm to a shooter. Recoil is a name given for conservation of momentum as it generally applies to an everyday event. 
     Free recoil, sometimes called recoil energy, is a byproduct of the propulsive force from the powder charge held within a firearm chamber (metallic cartridge firearm) or breech (black powder firearm). The physical event of free recoil occurs when a powder charge is detonated within a firearm, resulting in the conversion of chemical energy held within the powder charge into thermodynamic energy. This energy is then transferred to the base of the bullet and to the rear of the cartridge or breech, propelling the firearm rearward into the shooter while the projectile is propelled forward down the barrel, with increasing velocity, to the muzzle. The rearward energy of the firearm is the free recoil and the forward energy of the bullet is the muzzle energy. 
     The concept of free recoil comes from the tolerability of gross recoil energy. Trying to figure the net recoil energy of a firearm (also known as felt recoil) is a futile endeavor. Even if you can calculate the recoil energy loss due to: muzzle brake; recoil operated action or gas operated action; mercury recoil suppression tube; recoil reducing butt pad and or hand grip; shooting vest and or gloves, the human factor is not calculable. 
     Free recoil can be thought of as a scientific measurement of recoil energy. The comfort level of a shooter&#39;s ability to tolerate free recoil is a personal perception. Just as it is a person&#39;s, personal perception of how comfortable he or she feels to room or outside temperature. 
     There are many factors that determine how a shooter will perceive the free recoil of his or her small arm. Some of the factors are, but not limited to: body mass; body frame; experience; shooting position; recoil suppression equipment; small arm fit and or environmental stressors. 
     There are several different ways to calculate free recoil. However, the two most common are the momentum short and long forms. 
     Both forms will yield the same value. The short form uses one equation as where the long form requires two equations. With the long form you will first find for the fire arm velocity. With the velocity known for the small arm, the free recoil of the small arm can be calculated using the translational kinetic energy equation. A calculation can be done as follows: 
     Momentum Short Form:
 
 E   tgu =0.5 *m   gu *[[( m   p   *v   p )*( m   c   *v   c )]/1000] 2   /m   gu   2  
 
Momentum Long Form:
 
 v   gu =[( m   p   *v   p )+( m   c   *v   c )]/(1000 *m   gu ) and
 
and
 
 E   tgu =0.5 *m   gu   *v   gu   2  
     Where as:
       E tgu  is the translational kinetic energy of the small arm as expressed by the joule (J).   m gu  is the weight of the small arm expressed in kilograms (kg).   m p  is the weight of the projectile expressed in grams (g).   m c  is the weight of the powder charge expressed in grams (g).   v gu  is the velocity of the small arm expressed in meters per second (m/s).   v p  is the velocity of the projectile expressed in meters per second (m/s).   v c  is the velocity of the powder charge expressed in meters per second (m/s).   1000 is the conversion factor to set the equation equal to kilograms.   
       

     In various embodiments the linear motor comprises a sliding mass/rod including a plurality of individual magnets each having north and south poles. In various embodiment the plurality of individual magnets are longitudinally aligned with like poles of adjacent magnets facing like poles. In various embodiment the plurality of individual magnets are longitudinally aligned with unlike poles of adjacent magnets facing unlike poles. In various embodiments the plurality of individual magnets in the sliding mass/rod comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 19, 20, 25, 30, 35, 40, 45, and/or 50 magnets. In various embodiments the number of magnets is between the range of any two of the above listed numbers. 
     In various embodiments the linear motor includes a plurality of magnetic coils independently controllable with respect to each other regarding timing and/or amount of current flow. In various embodiments the plurality of independently controllable magnetic coils are each independently controllable regarding the timing and/or amount of current flow and/or direction of current flow. 
     In various embodiments each of the plurality of independently controllable magnetic coils can include a plurality of sub-coil sections that are spaced apart from each other but connected electrically in series causing the electrically serially connected spaced apart sub-coil sections to form a single independently controllable magnetic coil. In various embodiments at least one sub-coil of a first independently controllable magnetic coil of the plurality of coils is intermediately spaced between two spaced apart sub-coils of a second independently controllable magnetic coil of the plurality of coils. In various embodiments the linear motor comprises a plurality of independently controllable magnetic coils which are longitudinally aligned with each other and closely spaced, wherein at least two adjacent independently controllable magnetic coils are energized to create oppositely polarized magnetic fields. In various embodiments the linear motor comprises a plurality of independently controllable magnetic coils which are longitudinally aligned, wherein adjacent independently controllable magnetic coils are simultaneously energized to create oppositely polarized magnetic fields. 
     In various embodiments the linear motor comprises a plurality of independently controllable magnetic coils which are longitudinally aligned with each other and closely spaced, slidingly connected to a sliding mass of magnets which sliding mass is comprised of a plurality of longitudinally aligned adjacent magnets, wherein the linear motor causes movement of a sliding mass of magnets by varying current through individual independently controllable coils in relation to the proximity of a particular magnet in the plurality of magnets to a particular coil in the plurality of independently controllable magnetic coils. 
     In various embodiments the plurality of individually controllable magnetic coils in the plurality of coils include at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 19, 20, 25, 30, 35, 40, 45, and/or 50 independently controllable coils. In various embodiments the number of independently controllable magnetic coils is between the range of any two of the above listed numbers. 
     These together with other objects of the invention, along with the various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
         FIG.  1    is a side view of one embodiment of a firearm training system. 
         FIG.  2    is a side view of simulated firearm body of the system shown in  FIG.  1   . 
         FIG.  3    is a perspective view of the upper assembly of the simulated firearm body of  FIG.  2   . 
         FIG.  4    is an exploded view of the simulated firearm body of  FIG.  2   . 
         FIG.  5    is a perspective view of one embodiment of a linear motor and sliding mass. 
         FIG.  6    is an exploded side view of one embodiment of a linear motor and sliding mass. 
         FIG.  7    is an assembled side view of the linear motor and sliding mass of  FIG.  6   . 
         FIG.  8    is a perspective view of one embodiment of a support bracket for the linear motor and sliding mass. 
         FIG.  9    is a side view of one embodiment of a simulated firearm body. 
         FIG.  10    is a schematic flow diagram of various operation of the simulated firearm system shown in  FIG.  1   . 
         FIG.  11    is a sequencing side view showing the sliding mass of the linear motor at an initial position relative to simulated firearm body in a simulation recoil cycle. 
         FIG.  12    is a sequencing side view showing the sliding mass of the linear motor extending the sliding shaft to the end of its rightmost movement relative to simulated firearm body in a simulation recoil cycle. 
         FIG.  13    is a sequencing side view showing the linear motor retracting the sliding mass relative to simulated firearm body in a simulation recoil cycle. 
         FIG.  14    is a sequencing side view showing the linear motor continuing to retract the sliding mass relative to simulated firearm body in a simulation recoil cycle. 
         FIG.  15    is a sequencing side view showing the linear motor after finishing the retraction of the sliding mass relative to simulated firearm body in a simulation recoil cycle so that the linear motor is ready for the next simulation recoil cycle. 
         FIG.  16    is a prophetic graph plotting recoil force versus time of a first round of ammunition along with force versus time caused by the linear motor kinematically controlling dynamics of the sliding mass. 
         FIG.  17    is a prophetic graph plotting recoil force versus time of a second round of ammunition along with force versus time caused by the linear motor kinematically controlling dynamics of the sliding mass. 
         FIGS.  18 - 21    are schematic sequencing diagrams illustrating an individual repetitively firing of a firearm with recoil causing increasing loss of accuracy with repetitive shots. 
         FIG.  22    is a perspective view of another embodiment of a linear motor and sliding mass. 
         FIG.  23    is a perspective view of a sliding mass with exemplary magnets removed. 
         FIG.  24    is an enlarged perspective view of the sliding mass with exemplary magnets. 
         FIG.  25    is a schematic diagram illustrating operation of the coils in a linear motor. 
         FIGS.  26  and  27    are schematic diagrams illustrating operation of the coils in a linear motor in two different energized states. 
         FIGS.  28  and  29    are schematic diagrams illustrating movement of magnets through a linear motor in two different energized states. 
         FIG.  30    is a diagram illustrating magnetic flux density versus voltage output. 
         FIGS.  31  and  32    are exemplar diagrams of sensor voltage response versus time for a slider moving through the linear motor. 
         FIG.  33    is a diagram of a sample wave form. 
         FIGS.  34  and  35    are exemplar diagrams of sensor voltage response versus time for a slider moving through the linear motor at two different constant linear speeds. 
         FIG.  36    is an exemplar diagrams of a force versus time plotted for recoil forces for an actual firearm, compared to simulated recoil forces by the method and apparatus using a mechanical stop, and not using a mechanical stop. 
         FIG.  37    is an exemplar diagrams of an acceleration versus time plotted for recoil acceleration for an actual firearm, compared to simulated acceleration of the sliding mass caused by the method and apparatus using a mechanical stop, and not using a mechanical stop. 
         FIG.  38    is an exemplar diagrams of a velocity versus time plotted for recoil velocity for an actual firearm, compared to simulated velocity of the sliding mass caused by the method and apparatus using a mechanical stop, and not using a mechanical stop. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed descriptions of one or more preferred embodiments are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in any appropriate system, structure or manner. 
     One embodiment provides a firearm simulator body  20  which simulates an M-4A1, AR-15, or M-16 rifle. The firearm simulator body  20  includes upper receiver  120  and lower receiver  140 . Like a conventional M-16, upper receiver  120  can be pivotally secured to lower receiver  140  by a screw or pin. 
     Lower receiver  140  can include a pistol grip  160 , a trigger  170  disposed in front of the pistol grip  160 , and a selector  450  disposed above the pistol grip  160 . A shoulder stock  220  is secured to lower receiver  140 . 
     A barrel assembly  300  is mounted to the front portion of upper receiver  120 . The barrel assembly  300  includes a barrel  310  which is directly secured to upper receiver  120 . An upper handguard  330  and lower handguard  340  are secured to barrel assembly. A front sight block  360  is disposed around barrel  310 . 
       FIG.  1    is a side view of one embodiment of a firearm training system  10 .  FIG.  2    is a side view of simulated firearm body  20 .  FIG.  3    is a perspective view of upper assembly  120 .  FIG.  4    is an exploded view of simulated firearm body  20 . 
     Firearm training system  10  can include a simulated firearm body  20  having a linear motor  500  operatively connected to a slider mass  600 , and a controller  50  operatively connected to the linear motor  500 . 
     Simulated firearm body  20  can include upper assembly  120  and lower assembly  140 . Upper assembly  120  can include barrel assembly  300 , barrel  310 , along with upper  330  and lower  340  hand guards. 
     Lower assembly  140  can include stock shoulder stock  220 , buffer tube  230 , and pistol grip  160 . Pistol grip  160  can include trigger  170 . Cartridge  250  can be detachably connectable to lower assembly  140 . 
     Linear motor  500  can be attached to upper assembly  120  via connector assembly  700 . Connector assembly  700  can include first end  710 , second end  720 , connector plates  721  and  722 , connector tube  740  having bore  750 . Connector plate  721  includes fastener openings  730 , and connector plate  722  includes fastener openings  732 .  FIG.  5    is a perspective view of one embodiment of a linear motor  500  and sliding mass  600 .  FIG.  6    is an exploded side view of linear motor  500  and sliding mass  600 .  FIG.  7    is an assembled view of the linear motor  500  and sliding mass  600 . 
     Linear motor  500  includes a plurality  520  of separately controllable energized coils  521 ,  522 ,  523 ,  524 ,  525 ,  526 ,  527 ,  528 ,  529 ,  530 , etc. which electomagnetically interact with the plurality of magnets  640  in mass  600 . By controlling the timing, direction of current, and power of magnetic attraction of particular magnetic coils in plurality of separately controllable magnetic coils  520  movement, acceleration, velocity, and position of mass  600  can be controlled to obtain a desired momentum/impulse curve over time which approximates a particular impulse curve over time for a particular firearm being simulated. 
     Linear motor  500  can include a mass  600  which is slidably connected to linear motor  500 . Mass  600  can include first end  610 , second end  620 , and bore  630 . A plurality of magnets  640  can be included inside of bore  630 . Linear motors  500  are conventionally available but have not been used in simulated firearms for controlling recoil force. 
       FIG.  8    is a perspective view of one embodiment of a support  700  for linear motor  500  and sliding mass  600 . Support can include first end  710  and second end  720 . 
     On first end can be first and second connector flanges  721 , 722 . First connector flange  721  can include a plurality of connector openings  730 . Second connector flange  722  can include a plurality of connector openings  732 . Coming from second end  720  can be tubular section  740  having a tubular bore  750 . Linear motor  500  can be mounted to support  700  via plurality of openings  730  and  732  being connected to plurality of connector openings  540 . After mounting to support  700 , linear motor  500  can cause sliding mass  600  to controllably move (e.g., slide, accelerate, etc.) inside of and relative to bore  750 . 
     In one embodiment stop  800  can be employed to increase free recoil from sliding mass  600 . A mechanical stop  800  can be employed inside the simulated firearm body  20  to “rigidly” (i.e., more quickly negatively accelerate to zero sliding mass  600  than linear motor  500  is capable of) at the end of allowed length of travel  660 . Such quick stop produces an enhanced recoil effect on user  5  by increasing the maximum generated recoil force on the user  5 . Because linear motor  500  employs a magnetic sliding mass  600  with an electromagnetic stator, there is a coupling between the two and a corresponding maximum acceleration and deceleration that the device can achieve. To such limitation, mechanical stop  800  can be employed. Since linear motor  500  normally brakes sliding mass  500  by reversing the driving magnetic field originally used to accelerate sliding mass  600  in the opposite direction, such this feature is not required for stopping at the end of the length of travel  660 . Instead braking is left up to contact between sliding mass second end  620  and mechanical stop first end  810  inside lower assembly  140 . This allows for much faster breaking times for sliding mass  600  than linear motor  500  could, with such faster braking or deceleration creating larger reactive forces from sliding mass  600  and thus a larger free recoil value produced by system  10  at this point in time and position for sliding mass  600 . 
     In various embodiments, during an emulated firing cycle, linear motor  500  can control movement of sliding mass  600  causing sliding mass  600  to continue to acceleration until the last 1 percent of the entire stroke of sliding mass  600  as sliding mass  600  moves towards collision with mechanical stop  800 . In various embodiments acceleration can be increased until the last 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, and/40 percent of the entire stroke of sliding mass  600  as sliding mass  600  moves towards collision with mechanical stop  800 . In various embodiments the control of increased acceleration can be until the range of any two of the above referenced percentages percent of the entire stroke of sliding mass  600  as sliding mass  600  moves towards collision with mechanical stop  800 . 
     In various embodiments, during an emulated firing cycle, linear motor  500  can control movement of sliding mass  600  causing sliding mass  600  to continue acceleration until 1 millisecond before sliding mass  600  collides with mechanical stop  800 . In various embodiments acceleration can be increased until 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, and/or 20 millisecond before sliding mass  600  collides with mechanical stop  800 . In various embodiments the control of increased acceleration can be until the range of any two of the above referenced time periods before sliding mass  600  collides with mechanical stop  800 . 
     Simulated firearm body  20  can include a selector switch  450  operatively connected to controller  50  for controlling the type of operation firearm training system  10 . For example, selector switch  450  can have a plurality of modes of simulation such as: (1) safety; (2) semi-automatic firing mode; (3) fully automatic firing mode; and (4) burst firing mode. 
     To use firearm training system  10  a user selects the position of selector switch  450 , aims simulated firearm body  20  at a target, and pulls trigger  170 . When trigger  170  is pulled, controller  50  will cause linear motor  500  to kinematically control sliding mass  600  to create reactionary forces which will be transmitted to user holding simulated firearm body  20 . The reactionary forces created by controlling sliding mass  600  can be controlled to be substantially similar in time and amount for particular ammunition being simulated as being fired from the firearm being simulated. 
     In one embodiment a time versus force diagram of a particular round of ammunition being fired from a particular firearm to be simulated can be identified, and controller  50  can be programmed to control linear motor  500  to control movement of sliding mass  600  to create substantially the same forces over time by controlling the acceleration versus time of sliding mass. Because force is equal to the product of acceleration multiplied by mass, controlling acceleration versus time also controls force versus time. 
     In one embodiment a plurality of simulation data point sets (such as force versus time values) can be generated. In one embodiment a particular type of ammunition can be tested in a firearm to be simulated and a data set of apparent recoil force versus time can be generated. In one embodiment a plurality of measurements are taken over a plurality of times. In one embodiment a program for linear motor can be created to cause reaction forces of sliding mass  600  to substantially match in both time and amplitude such emulated force diagram for a plurality of points. In one embodiment at least 3 points are matched. 
     In various embodiments at least 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, and/or 100 simulation point data sets can be substantially matched. In various embodiments a range of between any two of the above specified number of simulation point data sets can be substantially matched. 
     In one embodiment system  10  can be used to emulate a force versus time curve that is estimated to occur with a particular firearm firing a particular size and type of ammunition being simulated. 
     Recoil can be thought of as the forces that a firearm places on the user firing the firearm. Such recoil forces are dependant upon the size and construction of the firearm, along with the characteristics of the bullet being fired from the firearm. The recoil imposed on a user of the same firearm can be different when the firearm fires a first type of ammunition compared to a second type of ammunition. 
     In one embodiment linear motor  500  and sliding mass  600  combined have a total mass which approximates the mass of the particular firearm being simulated. In one embodiment simulated firearm body  20  which includes linear motor  500  and sliding mass  600  combined have a total mass which approximates the mass of the particular firearm being simulated. In various embodiments either the linear motor  500  and/or sliding mass  600  combined have a total mass (and/or the simulated firearm body  20  which includes linear motor  500  and sliding mass  600  combined) have a total mass which is about 65, 70, 75, 80, 85, 90, 95, and/or 100 percent of the mass of the particular firearm being simulated. In various embodiments a range between any two of the above referenced percentages can be used. 
     In one embodiment is provided a substantially balanced simulated firearm body  20 . By locating linear motor  500  in the front portion of simulated firearm body  20 , better weight balance as well as a more realistic starting position for the simulated reactive force vector can be achieved. By positioning sliding mass  600  movement in this way, barrel  300  weight and center of gravity of simulated firearm body  20  will be more realistic to user  5  when system  10  is idle and trigger  170  is not being pulled. This is due to the starting position of sliding mass  600 . In one embodiment barrel  310  material being used in upper assembly  120  will not be steel, upper assembly  120  may feel unrealistic to user  5  due to a change in weight distribution compared to an upper assembly for an actual firearm being simulated. To solve this problem, during the initial stage of a recoil simulation cycle, a portion of sliding mass  600  can rest inside barrel  310 . Such portion of sliding mass simulates this extra “missing” weight in barrel  310  with the extra weight from the stator of linear motor  500  assisting as well. When user fires system  10 , sliding mass  600  moves from barrel  310  towards the rear of simulated firearm body  20  and is stopped by stop  800  that is even with the beginning of the stock. Sliding mass  600  then returns to its initial position and creates a seamless effect for user  5  that the weight distribution of the gun “feels” correct when the gun is not being fired. 
     In different embodiments, the location of linear motor  500  can be moved from the hand grip position, such as in stock  220 , or farther up into the receiver if necessary.  FIG.  9    is a side view of one embodiment of a simulated firearm body  20 . The amount of linear travel of sliding mass is  600  is schematically indicated by arrows  660 . In this view, the actual position  666  of second end  620  of sliding mass  600  is schematically shown by “time dependent” vertical line  666 ′″ indicating the transient position of second end  620  of sliding mass  600  in length of travel  660 . Arrow  1320  schematically represents a time dependent recoil force which is created by time dependent acceleration of sliding mass  600  by linear motor  500 . Clip  650  can be removed from sliding mass  600  before or after installation of linear motor  500  to allow, if desired, during control of sliding mass  600 , first and second ends  610 ,  620  of sliding mass  600  to enter plurality of coils  520  of linear motor  500  between first and second ends  530 , 534  of plurality of coils  520 . 
       FIG.  10    is a schematic flow diagram of various operation of the simulated firearm system shown in  FIG.  1   . In one embodiment controller  50  can be programmed to control linear motor  500  to control kinematic movement of sliding mass  600  within length of free travel  660  of sliding mass  600  to cause sliding mass to create a desired reactionary force versus time curve, where such force versus time curve simulates a force versus time curve of a particular bullet fired in a particular firearm being simulated. Linear motor  500 , which includes controlled sliding mass  600  along with motor logic controller  504 . Motor logic controller  504  is operatively connected to controller  50 . A power supply  60  (e.g., 24 volts) can be connected to both linear motor&#39;s logic controller  504  and controller  50 . Because of the larger current demand of the linear motor  500  stator, a separate power supply  60  (e.g., 72 volts) can be connected to linear motor  500 . 
     Sequencing 
       FIGS.  11 - 15    are sequencing side views showing the sliding mass  600  of the linear motor  500  at four different positions relative to simulated firearm body  20 . In one embodiment system  10  is programmed to simulate recoil for different ammunition types that a user  5  may use in a particular rifle. Programming of system  10  can be accomplished by measuring the force vs. time of an actual round in a particular weapons system to be simulated by system  10  and by using the “free recoil” formula to determine the energy produced by the actual firearm system to be simulated. Once the force vs. time of the actual firearm system to be simulated is known and the free recoil of this actual system is known, then system  10  can be programmed to cause sliding mass  600  to create reactionary forces to substantially match in at least a first plurality of preselected data points the same or similar force vs. time and free recoil energy can be delivered to user  5  giving the same perceived recoil as the live ammunition fired from the actual firearm being simulated. 
     Accordingly, by changing the stroke distance, velocity, acceleration, and/or deceleration at preselected time intervals or points of sliding mass  600 , the reactive recoil force imparted to user  5  from simulated firearm body  20  can be controlled. This reactive recoil force can be controlled to mimic or simulate: 
     the recoil force generated by a particular type of ammunition round in the particular firearm being simulated; 
     the recoil force generated by different types of ammunition rounds in the particular firearm being simulated; which different types of ammunition rounds may use more gun powder/less gun powder or use a higher weight bullet/lower weight bullet or some combination of both. 
     The different types of recoil forces can be simulated by merely having linear motor  500  change the dynamic movements of sliding mass  600  over time. For example if a larger force is desired at a particular point in time during the recoil time period at such particular point in time linear motor merely increases the instantaneous acceleration of sliding mass  600  to cause such reactionary force. 
       FIG.  16    is a graph plotting hypothetical recoil force versus time (shown in green with the square tick marts) of a first round of ammunition along with force versus time caused by the linear motor kinematically controlling dynamics of the sliding mass (shown in brown with the triangular tick marks).  FIG.  16    can be compared to sequencing  FIGS.  11 - 15   . At time zero second end  620  of sliding mass  600  is as shown in  FIG.  11    at position  666 , and has just started to accelerate in the opposite direction of arrow  1300  (causing a reactive force in the direction of arrow  1300  to be imposed on simulated firearm body  20  and user holding body  20 ). Linear motor  500  causes second end  620  of sliding mass  600  to accelerate and move in the opposite direction of arrow  1300  until second end  620  reaches position  666 ′ (shown in  FIG.  12   ) having contact with first end  810  of stop  800 . Immediately preceding reaching  666 ′ acceleration of sliding mass  600  causes a reactive force in the direction of arrow  1300  (shown at time 16 milliseconds in  FIG.  16    and in a negative reactive force). However, immediate after impact between second end  620  and first end  810 , such collision/contact causes an acceleration of sliding mass  600  in the opposite direction of arrow  1310  creating a reactive force in the direction  1310  (shown between times 16 and 36 milliseconds in  FIG.  16    and being a positive reactive force). During this same time period of contact/collision between second end  620  and first end  810 , linear motor  500  can independently accelerate sliding mass in the opposite direction of arrow  1310  (adding to the reactive force  1310  shown in  FIG.  12    by force vectors). From times 36 to 66 milliseconds on the graph shown in  FIG.  16   , controller  50  can be programmed to cause linear motor  500  to control acceleration of sliding mass  500  to create the desired simulated recoil reactive forces. 
       FIG.  13    shows second end  620  at position  666 ″ where linear motor could cause sliding mass  600  to accelerate to create a reactive force shown at 41 milliseconds in  FIG.  16   .  FIG.  14    shows second end  620  at position  666 ′″ where linear motor could cause sliding mass  600  to accelerate to create a reactive force shown at 56 milliseconds in  FIG.  16   .  FIG.  15    shows second end  620  at starting position  666  for the next recoil cycle. Now between possible  666 ′″ shown in  FIG.  14    to position  666  shown in  FIG.  15    linear motor  500  will have to accelerate sliding mass in the direction of arrow  1330  (to eventually slow and then stop sliding mass  600  at position  666  to be ready for the next recoil cycle). However, such slowing acceleration can be controlled to a minimum to minimize the amount of negative reactive force imposed on simulated firearm body  20  and user  5 . Such negative reactive force is not shown in  FIG.  16    and can be relatively small. In such manner the amplitudes and timing of such amplitudes of recoil forces experienced by a user firing a particular type of bullet in a particular firearm can be simulated by programmed kinematics of sliding mass  600  being controlled by linear motor  500 . 
     To simulate multiple firing cycles, the linear motor  500  can control dynamic movement of sliding mass  600  to create repeated force versus time patterns/diagrams of kinematic movement of sliding mass  600  the desired number of times or cycles. 
       FIG.  17    is a graph plotting hypothetical recoil force versus time (shown in green with the square tick marts) of a first round of ammunition along with force versus time caused by the linear motor kinematically controlling dynamics of the sliding mass (shown in brown with the triangular tick marks).  FIG.  17    shows a different bullet with different force versus time curve to be simulated by programmed linear motor  500  controlling kinematic movement of sliding mass  600 . Additionally, the overall period of the curve can be different from 66 millisecond and can change depending of the recoil characteristics of the firearm being simulated firing a particular bullet. 
     The ability of linear motor  500  to create reactive forces with sliding mass  600  is further enhanced by the alternating of the mass of sliding mass  600 . In one embodiment the different overall lengths for sliding mass  600  can be used (with the longer length option having a greater mass). With a greater mass for a given acceleration of such mass the reactive force created is found by the formula force equals mass times acceleration. In various embodiments sliding mass  600  can be 270 mm in length slider, or can be 350 mm in length, and such optional sliding masses  600 , 600 ′ can be interchanged with linear motor  500  to modify: 
     The mass of the sliding mass  600 . The 270 mm sliding mass  600  has a mass of 215 grams and the 350 mm sliding mass  600 ′ has a mass of 280 grams. The change in mass gives rise to different reactive forces caused by acceleration, and different free recoil energies, which can be used to better approximate the force vs. time curve produced by certain rounds of ammunition. 
     Additionally, the length of sliding mass  600  changes the overall acceleration and length of travel  660  linear motor  500  has to approximate the force vs. time curve produced by particular rounds of ammunition. 
     With a shorter sliding mass  600 , linear motor  500  can achieve higher velocities due to the longer acceleration time and thus give larger values of free recoil energy to the user. 
     The maximum reactive forces for different sliding masses  600 , 600 ′ can be computed as follows:
 
 E   tgu =0.5 *m   gu   *v   gu   2  
 
     since there will be no powder or velocity of the powder charge, these values (v c  &amp; m c ) go to zero and we have the standard kinetic energy formula K=(0.5*m*v2). The maximum values achieved for E tgu  are as follows for both sliders: 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                 Sliding Mass 
                 Sliding Mass 
                 Sliding Mass 
                 Overall Mass 
                 Free 
               
               
                 Length 
                 Mass 
                 Acceleration 
                 of Firearm 
                 Recoil 
               
               
                   
               
             
            
               
                 270 mm 
                 215 grams 
                 7.35 m/s 2   
                 1.5 kg 
                 2.539 J 
               
               
                 350 mm 
                 280 grams 
                  7.4 m/s 2   
                 1.5 kg 
                 4.071 J 
               
               
                   
               
            
           
         
       
     
       FIGS.  18 - 21    are schematic sequencing diagrams illustrating an individual  5  repetitively firing of a firearm simulating body  20  with recoil causing increasing loss of accuracy with repetitive shots. In these figures is schematically shown a simulating training exercise via semi-auto-burst fire modes with electronic recoil to training an individual  5  for accuracy. 
     One embodiment uses firearm simulating body  20  with linear motor  500  simulating an M4A1 rifle firing a particular type of bullet (although other types of firearms and bullets are envisioned in different embodiments). In one embodiment selector switch can have three modes of operation (1) semiautomatic  454 , (2) burst  456 , and (3) fully automatic  458 . Schematically show in  FIGS.  18 - 21    is a user fire after selecting burst  452  mode. In burst mode (2) a series of three simulated bullet firings will be performed by system  10 . 
     Individual  5  selects which type of simulation for this particular firearm is desired by using selector switch  450 . As schematically shown in  FIG.  18   , user  5  aims simulated firearm body  20  at target area  1400 . User next pulls on trigger  170  which is connected to trigger switch  172  sending a signal to controller  50 . Controller  50  controls linear motor  500  which in turn controls sliding mass  600 . Controller  50  also controls laser emitter  1200 . 
     Controller  50  causes linear motor  500  causing sliding mass  600  to traverse a pre-programmed kinematic movements creating reactionary forces in accordance with a predefined reactionary force versus time in an effort to simulate the recoil forces that an individual would experience actually simulating the particular bullet for the particular gun. Controller  50  is also connected to an infrared laser system  1200  which can be in phase with user  5  pulling trigger  170 . 
     Laser  1200  simulates on the target screen (area  1400  or  1410 ) where a bullet would have traveled from simulated firearm body  20 . 
     In  FIG.  19   , the first of the three simulated burst rounds, laser  1200  shoots laser line  1220  and has a hit  1221  in target area  1400 . In  FIG.  20   , the second of the three simulated burst rounds, laser  1200  shoots laser line  1230  and has a hit  1231  in target area  1400  (but closer to non-target area  1410 ). In  FIG.  21   , the second of the three simulated burst rounds, laser  1200  shoots laser line  1230  and has a hit  1231  in non-target area  1410 . 
     Arrow  1350  schematically represents the simulated recoil placed on body  20  causing user&#39;s  5  aim to degrade. With repeated use of system  10 , user  5  can become accustomed to the simulated recoil and adjust his aim. 
     In an actual training exercise, the projection system will simulate “target space” and “non-target” space for user  5 . If user  5  fires off of the screen  1400 , this counts as “non-target” space  1410 . These targets  1400  can be either moving or stationary and may vary greatly in size and shape. However, the projection system will count the total number of bullet strikes (e.g.,  1221 ,  1231 ) in target space and non-target space and add them. This enables the following formula to be used: 
     Accuracy=[Total−(non-target space)]/Total]*100% to determine accuracy for user  5 . 
     For example, if the user fired a total of 10 shots, corresponding to 4 shots in the target space  1400  and 6 shots in the non-target space  1410  the formula would read:
 
Accuracy=[[10−6]/10]*100%.
 
     This simulation would give the user an accuracy of 40%. Since a real recoil effect will be produced and knock the user&#39;s sights off of the target space  1400  for which he is aiming, system  10  this will help to train user  5  to become more accurate in firing actual firearm system but without the need to fire live ammunition. 
     Located inside barrel  310  can be laser emitter  1200 . A preferred laser emitter assembly is available Laser Shot, located in Stafford, Tex. Laser emitter  1200  assembly includes a circuit board, a battery box, a switch, and a laser emitter. Laser emitter  1200  is preferably housed within barrel  310 , and is oriented to emit a laser beam substantially parallel to and coaxial with the longitudinal centerline of barrel  310 . A typical cyclic rate for full automatic fire with a low cyclic rate is approximately 600 rounds per minute. A typical cyclic rate for full automatic fire at a high cyclic rate is approximately 900 rounds per minute, approximately simulating the cyclic rate of an M-4A1, AR-15, and/or M-16 rifle. 
     The firearms training simulator therefore simulates the recoil, cyclic rate, configuration, controls, and mode of operation of the firearm for which it is intended to be used to train a shooter. The training simulator therefore provides the opportunity to conduct decision-making training scenarios projected on a screen, with the safety and reduced facilities cost of using a laser instead of live ammunition, while duplicating a sufficient number of the characteristics of a conventional firearm so that the training will effectively carry over to a conventional firearm. 
       FIG.  22    is a perspective view of another embodiment of a linear motor  500  and sliding mass  600 . Linear motor  500  can include sensors  550  and  552 , which can be Hall Effect sensors.  FIG.  23    is a perspective view of a sliding mass  600  with exemplary plurality of magnets  640  removed.  FIG.  24    is an enlarged perspective view of the sliding mass  600  with exemplary magnets  640 . In  FIGS.  23  and  24    the plurality of magnets  640  (e.g., magnets  642 ,  644 ,  646 , etc.) can be comprised of neodymium. Additionally, between pairs of magnets  640  can be spacers (e.g., spacer  643  between magnets  642  and  644 , and spacer  645  between magnets  644  and  645 ). In a preferred embodiment the spacers can be comprised of iron (such as ferromagnetic iron). In a preferred embodiment plurality of magnets  640  are aligned so that like poles are facing like poles (i.e., north pole to north pole and south pole to south pole). In  FIGS.  23  and  24   , starting from the left hand side, magnet&#39;s  642  pole to the left is north and pole to the right is south, and magnet&#39;s  644  pole to the left is south and pole to the right is north. 
     Thus, the plurality of magnets  640  contained in slider/driven mass  600  have similar poles facing each other creating a repelling force. In a preferred embodiment the outer shell of sliding mass  600  longitudinally holds the plurality of magnets  640  and spacers securely together. In preferred embodiment the outer shell can be stainless steel which can be non-magnetic of a material that does not substantially interfere with the magnetic forces between plurality of coils  520  of linear motor  500  and plurality of magnets  640  of sliding mass  600 . 
       FIGS.  25 - 29    schematically show operation of linear motor  500  and sliding mass  600  as the plurality of magnets  640  are driven by the plurality of coils  520 .  FIG.  25    is a schematic diagram illustrating operation of the plurality of coils  520  in a linear motor  500 .  FIGS.  26  and  27    are schematic diagrams illustrating operation of the coils  520  in a linear motor  500  in two different energized states. 
     In  FIG.  25   , coils  521 ,  523 , and  525  in the stator of linear motor  500  can be wired in series and labeled as phase 1 (when wired together in series these coils of phase 1 can be considered sub-coils of a single independently controllable magnetic coil). Coils  522  and  524  are also wired in series and are labeled as phase 2 (when wired together in series these coils of phase 2 can be considered sub-coils of a single independently controllable magnetic coil). The plurality independently controllable magnetic coils  520  of linear motor  500  can be wound in the same or different direction depending on design. 
     Each independently controllable coil in phase 1 and 2 produces its own magnetic field when energized. This allows for independently controllable magnetic coils of phase 1 and 2 the plurality of coils  520  to repel each other or for phase 1 and phase 2 coils to attract each other depending on the way the phases are polarized and the coils wound. These alternative states of polarization are shown in  FIGS.  26  and  27   . In  FIG.  26    phase 1 and phase 2 are polarized in the same direction so that coils in the two phases are attracted to each other. In  FIG.  27    phase 1 and phase 2 are polarized in the opposite direction so that coils in the two phases repel to each other. It can be seen that by varying the polarization of phases in the plurality of independently controllable magnetic coils  520  of linear motor  500 , sliding mass  600  can be controllably moved as desired through the plurality of coils  520  so as to create the desired reactive forces user  5  such as time dependently controlled force, acceleration, velocity, position, and/or momentum; or overall impulse. 
       FIGS.  28  and  29    are schematic diagrams illustrating movement of the plurality of magnets  640  of sliding mass  600  through the plurality of coils  520  a linear motor  520  in different energized states. 
       FIG.  28    schematically indicates initial movement of sliding mass  600  with plurality magnets  640  through plurality of coils  520  of linear motor  500 . In  FIG.  28   , the first magnet  642  of sliding mass  600  enters plurality of coils  520  of linear motor  500 . Plurality of coils  520  can then be energized with phase 2 polarized as shown and phase 1 not being energized (or OFF). This causes magnet  642  (and sliding mass  600 ) to be pulled deeper into plurality of coils (schematically indicating by the arrow towards the right). As schematically shown in  FIG.  29   , when first magnet  642  moves halfway into coil  522 , phase 1 can be energized (or turned ON) creating a pulling force on magnet  642  and speeds the second magnet  644  to the center of coil  521  while at the same time repelling the magnet  642 . The movement of sliding mass  600  eventually stops when the plurality of magnets  640  reach steady state with the plurality of coils  520 , which in this case means that the north pole of coils  521  and  522  are respectively aligned with the north poles of magnets  642  and  644 ; and coil  522  is aligned with magnet  644 ′s south pole and coil  521  is aligned with the magnet  644 ′s south pole. Thus, the magnetic forces are in equilibrium and movement ceases while phase 1 and 2 remain energized with this polarization. So, by switching the coils ON/OFF and by alternating the coils polarization the slider (filled with neodymium magnets) can be pushed or pulled through the stator (made up of many coils). Furthermore, the number of coils depicted in  FIGS.  25  through  29    through can be increased to have a larger accelerating cross section. 
     The velocity, acceleration, and linear distance of sliding mass  600  can be measured as a function of Hall Effect sensors  550  and  552  that are 90 degrees out of phase. Out of phase Hall Effect sensors  550  and  552  can each produce a linear voltage in response to increasing or decreasing magnetic field increases.  FIG.  22    can show the mechanical alignment in linear motor  5000  and sensors  550 , 552 . The response that sensors  550  and  552  give as a function of magnetic field strength (flux through the sensor) versus voltage (out of the sensor) is depicted in  FIG.  30   , which is a diagram illustrating magnetic flux density versus voltage output. 
       FIGS.  31  and  32    are exemplar diagrams of sensor  550  and  552  voltage response versus time for a slider moving through the linear motor. When sliding mass  600  is moved through the plurality of coils  520  of linear motor  500 , 90 degree out of phasesensors  550  and  552  provide a voltage response versus time falling into a Sine or Cosine function as indicated in  FIG.  31    (sine(x) for sensor  550 ) and  FIG.  32    (cosine(x) for sensor  552 ). These resultant waves are generated by sensors  550  and  552  because generated magnetic flux for the plurality of magnets  640  inside sliding mass  500  are most powerful at their magnetic poles. So as the north poles of two magnets approach, the wave goes positive and peaks when directly above those poles. Continuing in the same direction, as the south poles approach, the wave goes negative and peaks when directly above those poles. Thus, one sensor  550  gives a function of Sin(x) and the other sensor  552  gives a function of Cos(x). As can be seen these functions are 90 degrees out of phase. Two sensors  550  and  552  are used for better precision feedback and control of sliding mass  600  through the plurality of coils  520  of linear motor  500 , and as a method to make sure sliding mass is continually tracked accurately. 
     To provide additional explanation, sensor  550  generating a sin wave is plotted in  FIG.  31   , and will be further examined regarding how this graph can be used to track velocity, acceleration, and displacement of sliding mass  600 .  FIG.  33    is a diagram of a sample wave form which illustrates the various components of a wave form generated by sensor  550 . The wavelength (λ) relates to the velocity of sliding mass  600  through plurality of coils  520  of linear motor  500 . As the wavelength shortens, the frequency can be calculated by f=1/λ, and the frequency will increase as the wavelength shortens. 
       FIGS.  34  and  35    are exemplar diagrams of sensor voltage response versus time for a sliding mass  600  moving through the linear motor  500  at two different constant linear speeds. For example, in  FIG.  34    sliding mass  600  can be said to be moving through plurality of coils  520  at 1 meter per second and generating this wave. As sliding mass  600  speeds up to 2 meters per second,  FIG.  35    is generated. It can be seen that this increase in wave frequency corresponds to the velocity with which sliding mass  600  is moving through the plurality of coils  520  of linear motor  500 . Furthermore, the change in waveform from  FIG.  34    to  FIG.  35    relates to the acceleration of sliding mass  600 .  FIGS.  34  and  35    each individually represent constant velocities of sliding mass  600  (although the constant velocity in  FIG.  35    is twice that of the constant velocity in  FIG.  34   ) so that in each of these two figures, there is no acceleration; however, as sliding mass  600  slider approached 2 meters per second linear speed shown in  FIG.  35   , the frequency increased to the value in  FIG.  35   : that frequency change over time can be used to compute acceleration of driven mass  600 . Lastly, distance traveled by driven mass  600  can be calculated by knowing the length of the plurality of magnets  640  in sliding mass, and counting the number of wavelengths that go past sensor  550 . Each wavelength corresponds to the full length of the permanent magnet inside the body of sliding mass  600 . Accordingly, velocity, acceleration, and distance can be calculated from sensors  550 ,  552  voltage versus magnetic flux graphs. 
     Emulating Overall Recoil Impulse 
     In one embodiment linear motor  500  and sliding mass  600  can be used to emulate total recoil impulse for a particular firearm firing a particular form of ammunition. “Actual recoil force” is the force generated by a particular type of firearm firing a particular type of ammunition at any point in time after firing where such force is transmitting to the user. Such actual recoil force can be plotted over a particular period of time from initial firing of the ammunition in the firearm to the end of any actual recoil force following such firing. 
     On the other hand, “generated recoil force” is the reactive force generated by linear motor  500  controlling movement of sliding mass  600 . Such generated recoil force will be transmitted to a user  5  holding simulated firearm body  20  of simulator system  10 . 
     Actual recoil impulse is the area under a force versus time diagram where the force is generated by a particular type of firearm firing a particular type of ammunition. Generated recoil impulse is the area under a force versus time diagram  1600  of a reactive force generated by linear motor  500  controlling movement of sliding mass  600  (e.g., acceleration, velocity, and distance) over time. 
       FIG.  16    shows prophetic examples of diagrams for actual recoil force  1500  versus time, along with generated recoil force  1600  versus time. The area under the actual recoil force versus time diagram  1500  is the actual recoil impulse. The area under the generated recoil force versus time diagram  1600  is the generated recoil impulse. Note how the area under the generated recoil impulse can be both positive (above the zero), and negative (below the zero). In a preferred embodiment the negative area would be subtracted from the positive area in calculating total impulse. In other embodiments the negative area can be ignored in calculating total impulse. 
     In these two diagrams the force versus time diagrams  1500 ,  1600  of actual recoil over time versus reaction forces generated by linear motor  500  and sliding mass  600  over time closely track each other so that the impulse and reactive impulse are approximately equal. However, in different embodiments the actual recoil over time diagram  1500  versus reaction forces generated by linear motor  500  and sliding mass over time  1600  can substantially vary as long as both calculated impulses (from the areas under the diagrams) are close to each other at the end of the firing cycle. 
       FIG.  36    shows a single diagram with three force versus time plots: (1) force versus time of actual forces  1500  (first plot for an M16/AR-15 type rifle firing a 0.223 Remington bullet/round having an overall weight of about 7.5 pounds), and (2) force versus time of generated reactive forces from linear motor and sliding mass in combination with a mechanical stop  1600 , and (3) force versus time of generated reactive forces from linear motor and sliding mass without using a mechanical stop  1600 ′. A positive value of force indicates that a force pushing user  5  backward. As can be seen by the time, a firing cycle of about 90 milliseconds is used. 
     Diagram  1600  includes a spike  1610  when the slider  600  hits the mechanical stop  800 , and the areas under each plot  1500 ,  1600  should be roughly the same to get the same overall impulse. For diagram  1600 , time  1700  indicates the initial contact between sliding mass  600  and mechanical stop  800 . In different embodiments, because the time period for the collision between sliding mass  600  and mechanical stop  800  is so short (about less than 5 milliseconds), time of initial contact  1700  can also be calculated using the time of peak reactive force  1620 . 
     In  FIG.  36    is shown the peak  1520  of actual recoil force  1500  which is compared to the peak  1620  of generated recoil force  1600 , and the difference  1630  between such peaks. In various embodiments mechanical stop  800  can be used to generate a spike  1610  in the generated recoil force which spike  1620  has a difference of  1630  compared to the peak  1520  of actual recoil force  1500 . 
     In various embodiments peak  1620  can be such that the difference  1630  can be minimized. In various embodiments, during an emulated firing sequence, the difference  1630  is less than 50 percent of the peak  1620 . In various other embodiments the difference  1630  is less than no more than 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, and/or 1 percent of the peak  1620 . In various embodiments the difference  1630  can be within range between any two of the above referenced percentages peak  1620 . 
     In various embodiments, the average generated recoil force by linear motor  500  controlling slider  600  during a particular simulated firing sequence before initial contact of sliding mass  600  with mechanical stop  800  at time  1700  can be calculated by calculating the impulse up to initial impact at time  1700  divided by the time at time  1700 . In various embodiments the peak  1620  of generated reactive force is at least 50 percent greater than the average generated recoil force by linear motor  500  controlling slider  600  during a particular simulated firing sequence before initial contact of sliding mass  600  with mechanical stop  800  at time  1700 . In various embodiments the peak generated reactive force  1620  is greater than 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 175, 200, 225, 250, 275, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1500, and/or 2000 percent greater than the average generated recoil force by linear motor  500  controlling slider  600  during a particular simulated firing sequence before initial contact of sliding mass  600  with mechanical stop  800  at time  1700 . In various embodiments a range between any two of the above referenced percentages can be used for such comparison. 
     In various embodiments, the average generated recoil force by linear motor  500  controlling slider  600  during an entire particular simulated firing sequence can be calculated by calculating the impulse during the entire firing sequence and dividing the time for such entire firing sequence. In various embodiments the peak  1620  of generated reactive force is at least 50 percent greater than the average generated recoil force by linear motor  500  controlling slider  600  during an entire particular simulated firing sequence (i.e., both before and after initial contact of sliding mass  600  with mechanical stop  800  at time  1700 ). In various embodiments the peak generated reactive force is greater than 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 175, 200, 225, 250, 275, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1500, and/or 2000 percent greater than the average generated recoil force by linear motor  500  controlling slider  600  during an entire particular simulated firing sequence. In various embodiments a range between any two of the above referenced percentages can be used for such comparison. 
     In various embodiments, the average generated recoil force by linear motor  500  controlling slider  600  during a particular simulated firing sequence after initial contact of sliding mass  600  with mechanical stop  800  at time  1700  can be calculated by calculating the impulse following initial impact at time  1700  divided by the time following time  1700 . In various embodiments the peak  1620  of generated reactive force is at least 50 percent greater than the average generated recoil force by linear motor  500  controlling slider  600  during a particular simulated firing sequence subsequent initial contact of sliding mass  600  with mechanical stop  800  at time  1700 . In various embodiments the peak generated reactive force is greater than 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 175, 200, 225, 250, 275, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1500, and/or 2000 percent greater than the average generated recoil force by linear motor  500  controlling slider  600  during a particular simulated firing sequence subsequent to initial contact of sliding mass  600  with mechanical stop  800  at time  1700 . In various embodiments a range between any two of the above referenced percentages can be used for such comparison. 
       FIG.  37    is an exemplar diagrams  1502 ,  1602 ,  1602 ′ of an acceleration versus time plotted for recoil acceleration for an actual firearm  1502 , compared to simulated acceleration of the sliding mass caused by the method and apparatus using a mechanical stop  1602 , and not using a mechanical stop  1602 ′. Force from the acceleration diagrams can be calculated using the formula force equals mass times acceleration. 
       FIG.  38    is an exemplar diagrams  1504 ,  1604 ,  1604 ′ of a velocity versus time plotted for recoil velocity for an actual firearm  1504 , compared to simulated velocity of the sliding mass caused by the method and apparatus using a mechanical stop  1604 , and not using a mechanical stop  1604 ′. 
     In one embodiment stop  800  can be employed to modify the generated recoil force diagram from linear motor  500  controlling sliding mass  600  by sharply increasing the reactive force at the point of collision between sliding mass  600  and mechanical stop  800 . A mechanical stop  800  can be employed inside the simulated firearm body  20  to “rigidly” (i.e., more quickly negatively accelerate to zero sliding mass  600  than linear motor  500  is capable of) at the end of allowed length of travel  660 . Such quick stop produces an enhanced recoil effect on user  5 , and higher generated reactive force. In one embodiment, the reactive force generated by sliding mass  600  colliding with mechanical stop  800  is greater than any force generated by linear motor  500  accelerating sliding mass  600  during an emulated firing sequence. 
     In various embodiments, during an emulated firing sequence, the maximum reactive force generated by linear motor  500  accelerating sliding mass  600  is no more than 50 percent of the reactive force generated by sliding mass  600  colliding with mechanical stop  800 . In various other embodiments the maximum reactive force generated by linear motor  500  accelerating sliding mass  600  is no more than 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, and/or 100 percent of the reactive force generated by sliding mass  600  colliding with mechanical stop  800 . In various embodiments the maximum reactive force generated by linear motor  500  accelerating sliding mass  600  can be within range between any two of the above referenced percentages of the maximum reactive force generated by linear motor  500  controlling sliding mass  600 . 
     In various embodiments either actual recoil impulse and/or the generated recoil impulse by linear motor  500  controlling sliding mass  600  are within about 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and/or 100 percent of each other. In various embodiments a range between any two of the above referenced percentages can be used. 
     In various embodiments the total time for an emulated firing cycle by linear motor  500  controlling sliding mass  600  can be less than about 200 milliseconds. In various embodiments the maxim time for an emulated firing cycle can be less than about 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and/or 200 milliseconds. In various embodiments the maximum time can be between any two of the above referenced times. 
     Emulating a Force Versus Time Plot of Firearm 
     In one embodiment an actual firearm with actual ammunition can be tested and the actual recoil force over time plotted. In this embodiment linear motor  500  and magnetic mass/shaft  600  movement (e.g., acceleration, velocity, and position) can be programmed so as to emulate the actual force versus time diagram that was obtained from test. In different embodiments the emulated force versus time can be within 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, and/or 50 percent of the plot. In different embodiments the variation can be within a range between any two of the above referenced values. In different embodiments total impulse (which is the integral or sum of the area under the force versus time diagram) can be emulated for relatively short time sequences as it is believe that users have difficulty perceiving changes in force over time for very short time intervals regarding recoil forces, and effectively feel the overall impulse of the recoil force in firearms. 
     Changing the Strength of the Magnetic Field of Linear Motor 
     In one embodiment, the strength of the magnetic field generated by the plurality of coils  520  of linear motor  500  as a magnet in magnetic mass/shaft  600  passes by and/or is in touch with a particular coil generating a magnetic field can be increased from an initial value. In different embodiments the strength of the field can be changed by 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, and/or 50 percent of the initial value. In different embodiments the variation can be within a range between any two of the above referenced percentages. 
     Using Sensors To Directly/Indirectly Measure Dynamic Properties of Sliding Mass and Have Linear Motor Control Dynamic Properties of Sliding Mass Based on Sensor Input 
     In one embodiment, the acceleration, velocity, and/or position versus time of the magnetic mass/shaft  600  can be measured directly and/or indirectly (such as by sensors  550  and/or  552 ), and linear motor  500  can change/set the strength of the magnetic field generated by plurality of coils  520  to achieve a predetermined value of acceleration, velocity, and/or position versus time for sliding mass  600 . In different embodiments the predetermined values of emulated acceleration, velocity, and/or position versus time can be based on emulating a force versus time diagram obtained from testing an actual firearm (or emulating impulse). In different embodiments the emulated diagram can be within 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, and/or 50 percent of the plot. In different embodiments the variation can be within a range between any two of the above referenced values. 
     Options to Program in Different Variations for Firearm to be Simulated 
     In various embodiments, a user of system  10  is provided one or more of the following options in using system  10  regarding changes in a type of firearm for which recoil is to be simulated by system  10 .
         a) different size/caliber/type of ammunition in actual type of firearm to be simulated with particular type of ammunition.   b) adding/removing a muzzle suppressor to actual type of firearm to be simulated with particular type of ammunition.   c) different size/type of bolt springs for actual type of firearm to be simulated with particular type of ammunition.       

     In each of the above options system  10  causes linear motor  500  to control sliding mass  600  to generate a recoil force versus time diagram (or generate an impulse) which is different from the simulation for the type of firearm without the option selected, and which approximates the recoil of the firearm having such option. 
     Using Same Core Simulation System with Different Firearm Model Attachments to Provide User with Option of Better Simulating Different Types of Firearms 
     Same core simulation system but having different firearm attachments for simulating different firearms. Here, using the same controller  50  and attached linear motor  500 , have different firearm attachments (e.g., AR-15 rifle unit attachment, and Glock pistol unit attachment). Here the magnetic mass/shaft  600  slidably connected to the linear motor  500  can also be changed but keep same linear motor  500 . 
     In various embodiments simulator  10  can include a plurality of different body attachments  20 ,  20 ′,  20 ″, etc. for simulating recoil patterns from a plurality of different type firearms, each of the plurality of body attachments being interchangeably operably connectable with linear motor  500 . In various embodiments, each of the plurality of body attachments  20 ,  20 ′,  20 ″, etc. can include unique identifiers that inform controller  50  in the selection of one of a plurality of predefined sets of recoil simulating kinematic movements of sliding mass  600  in order to simulate a recoil pattern for the particular type of firearm that the particular body attachment represents. Based on the unique identifier of the particular body attachment  20 ,  20 ′,  20 ″, etc, operably connectable to linear motor, controller  50  can select one of the plurality of predefined sets of kinematic movement to control linear motor  500  in controlling sliding mass  600  to create a series of predefined movements for sliding mass  600  and emulate recoil for the particular type of firearm that the particular connected body attachment represents. In various embodiments the individual identifiers can be microcontrollers which, when a body attachment  20  is connected to linear motor  500 , communicate with microcontroller  50  (shown in  FIG.  10   ), and identify the particular type of firearm for which recoil is to be simulated. In one embodiment the plurality of interchangeable different type body attachments  20 ,  20 ′,  20 ″, etc. includes at a plurality of different type rifles. In one embodiment the plurality of interchangeable different type body attachments  20 ,  20 ′,  20 ″, etc. includes at a plurality of different type shotguns. In one embodiment the plurality of interchangeable different type body attachments  20 ,  20 ′,  20 ″, etc. includes at least one rifle body type and at least one shotgun body type and/or at least one pistol body type. In one embodiment the plurality of interchangeable different type body attachments  20 ,  20 ′,  20 ″, etc. includes a plurality of different type rifles and different type shotguns and/or pistols. 
     As to a further discussion of the manner of usage and operation of the present invention, the same should be apparent from the above description. Accordingly, no further discussion relating to the manner of usage and operation will be provided. 
     The following is a list of reference numerals: 
     LIST FOR REFERENCE NUMERALS 
     
         
         (Reference No.) (Description) 
           5  user 
           10  firearm training simulator system 
           20  simulated firearm body 
           50  controller 
           54  connecting wire bus 
           60  power supply or supplies 
           100  receiver 
           120  upper receiver 
           140  lower receiver 
           160  pistol grip 
           170  trigger 
           172  trigger switch 
           180  charging handle 
           200  sight rail 
           210  rear sight 
           220  shoulder stock 
           230  buffer tube 
           250  cartridge 
           254  cartridge release 
           280  the adjustment lever 
           300  barrel assembly 
           310  barrel 
           320  barrel bore 
           330  upper handguard 
           340  lower handguard 
           350  rail 
           360  front sight 
           370  flash hider 
           400  bolt 
           450  selector interface switch 
           452  off position 
           454  semi automatic position 
           456  burst position 
           458  fully automatic position 
           500  linear motor 
           504  linear motor logic controller 
           510  driving portion 
           520  plurality of controllable energized coils 
           521  controllable coil 
           522  controllable coil 
           523  controllable coil 
           524  controllable coil 
           525  controllable coil 
           526  controllable coil 
           530  first end of plurality of coils 
           534  second end of plurality of coils 
           540  fastener openings 
           550  sensor 
           552  sensor 
           600  driven mass 
           610  first end 
           620  second end 
           630  bore 
           640  plurality of magnets 
           641  spacer 
           642  magnet 
           643  spacer 
           644  magnet 
           645  spacer 
           646  magnet 
           650  stop 
           660  length of travel for driven mass 
           666  position of second end of driven mass with respect to length of travel 
           700  support for linear motor 
           710  first end 
           720  second end 
           721  first connector flange 
           722  second connector flange 
           730  openings 
           732  openings 
           740  tubular section 
           750  bore 
           800  stop 
           810  first end 
           820  second end 
           1000  trigger switch 
           1100  clip switch 
           1200  laser emitter 
           1210  wires 
           1220  first laser path 
           1221  location of hit for first laser path 
           1230  second laser path 
           1231  location of hit for second laser path 
           1240  third laser path 
           1241  location of hit for third laser path 
           1300  arrow 
           1310  arrow 
           1320  arrow 
           1330  arrow 
           1350  arrow 
           1400  target area 
           1410  non-target area 
           1500  actual recoil force diagram 
           1502  actual acceleration diagram 
           1504  actual position diagram 
           1520  peak actual recoil force 
           1522  value of peak recoil force 
           1600  simulated recoil force diagram 
           1602  simulated acceleration diagram 
           1604  simulated position diagram 
           1610  spike in force diagram caused by mechanical stop 
           1620  peak force 
           1630  difference between peak actual recoil force and peak generated recoil force 
           1700  time at which slider first impacts mechanical stop 
       
    
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.