Abstract:
A method and apparatus for scaling a large commercial flight simulator into a more compact flight simulator, without losing the look and feel of a corresponding aircraft in-flight, by modifying movement of the motion platform to conform to the recommendations of one knowledgeable of the actual aircraft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application claims the benefit of earlier filed U.S. Provisional Patent Application Ser. No. 60/177,173, filed Jan. 20, 2000, entitled “Inexpensive Motion Base and Driver Technology for Flight Simulators.” 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to motion simulators and, more particularly, to motion simulators which mimic perceived movements of an aircraft in-flight.  
           [0004]    2. Brief Description of the Prior Art  
           [0005]    Motion simulators are generally known. Examples include U.S. Pat. No. 6,027,342 to Brown; U.S. Pat. No. 5,954,508 to Lo et al.; and U.S. Pat. No. 5,857,917 to Francis et al.  
           [0006]    As generally discussed in the Lo et al. patent, motion simulators fall into the categories of commercial motion simulators and amusement motion simulators. Commercial motion simulators are large, complex, and are generally driven by hydraulic actuators. Conversely, amusement motion simulators are scaled-down versions of the larger commercial motion simulators. The Lo et al. patent further discloses that commercial motion simulators may be transformed into less complicated amusement motion simulators by reducing range of motion.  
           [0007]    When comparing the trade-off between size, complexity, and range of motion, it is important to consider the particular application. Many aircraft motion simulators employ large hydraulic-driven actuators having a range of motion of up to three feet or more. This range of motion has historically been needed to make movement perceived by a pilot in the simulator mimic movement perceived by a pilot during actual flight conditions. This degree of realism is required to fulfill safety requirements, FAA qualification requirements, and training goals. Conversely, amusement motion simulators do not require demanding precision because the purpose of amusement is to entertain, not train. The continuing problem, however, is scaling down the cost and the complexity of a commercial motion simulator without significantly sacrificing realistic movement of the simulator, as perceived by a pilot.  
         SUMMARY OF THE INVENTION  
         [0008]    It is, therefore, an object of the present invention to provide an inexpensive motion base and driver technology for a flight simulator, which does not significantly sacrifice the realistic perceived movement of a larger, more complex commercial motion simulator.  
           [0009]    One method is to make a perceived movement of a motion platform correspond to a perceived movement of an actual vehicle in motion, the motion platform connected to a computer, includes the steps of executing simulation software programmed in the computer, transmitting an output of the computer to the motion platform, evaluating the perceived movement of the motion platform, and adjusting the output of the computer until the perceived movement of the motion platform corresponds to the perceived movement of the actual vehicle. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an elevation view of a simulated cockpit and motion base of a flight simulator according to one embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a side elevation view of the motion base shown in FIG. 1;  
         [0012]    [0012]FIG. 3 is a top view of the motion base shown in FIGS. 1 and 2;  
         [0013]    [0013]FIG. 4 is a top perspective view of a second embodiment motion base according to another embodiment of the present invention  
         [0014]    [0014]FIG. 5 is a schematic view of the flight simulator shown in FIG. 1 connected to computers and a display monitor;  
         [0015]    [0015]FIG. 6 is an elevation view of the simulated cockpit shown in FIG. 1;  
         [0016]    [0016]FIG. 7 is a flow chart of one method of making a movement response of a motion platform correspond to a movement response of an actual vehicle; and  
         [0017]    [0017]FIG. 8 is a flow chart of one method of making a movement response of a flight simulator correspond to a movement response of a corresponding actual aircraft. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The present invention is a method and apparatus for producing simulated motion, such as simulating the motion of an aircraft in-flight.  
         [0019]    [0019]FIG. 1 shows a simulator  6  having a motion base  8  and a simulated cockpit  10 , each commercially available from Servos &amp; Simulation, Inc., 111 Atlantic Annex Point, Maitland, Fla. The motion base  8 , shown in greater detail in FIGS.  2 - 3 , includes a base plate  12 . Positioned adjacent to the base plate  12  is at least one electric motor  14  having a rotatable motor shaft  16 . One suitable electric motor  14  is commercially available from Nord Gear Ltd., 800 Nord Drive, Waunakee, Wis. Fixed to the motor shaft  16  is a motor arm  18 . The motor arm  18  is also pivotally connected to one end  20  of an actuator  22 . Alternatively, the actuator  22  can be pivotally connected directly to the motor shaft  16 . As shown in FIG. 2, a motion platform  24  is pivotally connected to an opposite end  26  of the actuator  22  via a pivot joint  28 .  
         [0020]    FIGS.  2 - 3  show three electric motors  14  positioned adjacent to the base plate  12 , each configured with a corresponding actuator  22 . In this arrangement, the motion platform  24  has three degrees of freedom. In aircraft simulation terminology, these degrees of freedom are referred to as roll, pitch, and heave. If more degrees of freedom are desired, such as yaw, sway, and surge in aircraft terminology, more electric motors  14  and corresponding actuators  22  can be added, such as a six degree of freedom motion base  8 ′ shown FIG. 4.  
         [0021]    Referring again to FIG. 2, each electric motor  14  and corresponding actuator  22  is designed to simultaneously move the motion platform  24  approximately four to eight inches in the D1 and D2 vertical directions, as measured from an imaginary plane IP lying coincident with the motion platform  24  when the imaginary plane IP and the motion platform  24  are both positioned parallel to a second imaginary plane IP2 lying coincident with the base plate  12 .  
         [0022]    A support rod  30  is positioned between the base plate  12  and the motion platform  24 . The support rod  30  is preferably fixed to the base plate  12  at one end and is pivotally connected to the motion platform  24  at an opposite end, preferably via a second pivot joint  32 . The support rod  30  may be further equipped with a spring  34  to absorb weight or dampen motion of the motion platform  24 . An alternating current variable frequency drive  36 , shown in FIGS. 1 and 5, is electrically connected to the electric motor or motors  14 .  
         [0023]    With continuing reference to FIG. 5, the alternating current variable frequency drive  36  is also connected to a motion computer  38  through a digital/analog serial output card  40  or other suitable device. The motion computer  38  is programmed with proprietary motion software, described below. Connected to the motion computer  38  is a simulation computer  42  programmed with a simulation program, such as the ELITE PROP 6.0 brand of flight simulation software commercially available from 617 N. Semoran Boulevard, Orlando, Fla. However, any suitable simulation program containing a flight model can be used for flight simulation applications. The motion computer  38  and the simulation computer  42  can be separate computers, or the motion computer  38  and the simulation computer  42  can be combined together into a unitary computer  50 .  
         [0024]    The simulation computer  42  is connected to the simulated cockpit  10 , and more specifically, to the simulated flight instruments  44 , simulated aircraft controls  46 , and the one or more video display screens  48 , shown in FIGS. 5 and 6. The video display screens  48  are preferably positioned so that a pilot can view the video display screens  48  directly and peripherally. The direct and peripheral video cues, along with gravitational forces and inner ear changes, help to create the perception of motion and orientation. As shown in FIG. 5, a second video display screen  52  may also be connected to the simulation computer  42  for instructor monitoring purposes.  
         [0025]    With continuing reference to FIG. 5, the simulation program, such as a flight simulator program, is executed on the simulation computer  42 . The simulation program receives movement data from the simulated flight instrumentation and simulated aircraft controls  44 ,  46  through serial ports  54  in the simulation computer  42 . The simulation program generates graphical images which are displayed on the video display screens  48  inside the simulated cockpit  10 , on the optional second video display screen  52 , and as simulated flight instruments  44 . The movement data is also sent to the motion computer  38 , preferably in the form of a code having one or more characteristics. The motion software converts the code, such as a digital code, into plus or minus 5 volt DC drive signal voltages, which are inverted by the alternating current variable frequency drive  36  and received by one or more of the electric motors  14 . Each corresponding electric motor  14  then rotates the corresponding motor shaft  16  an appropriate amount, moving the motion platform  24  via the corresponding actuator  22 .  
         [0026]    The following table shows a fifteen characteristic code corresponding to one possible flight simulator application. All values are relative to an imaginary aircraft.  
                             TABLE 1                           Example of a Fifteen Characteristic Code for a Flight Simulation       Application            Characteristic   Description   +/− Values               A   Header   Identifies program       B   True airspeed   N/A       C   Angle of attack in degrees   +/−       D   Pitch acceleration in degrees per   +up, −down           second 2         E   YAW acceleration in degrees per   +right, −left           second 2         F   Roll acceleration in degrees per   +right, −left           second 2         G   X axis acceleration in feet per   +up, −down           second 2         H   Y axis acceleration in feet per   +up, −down           second 2         I   Z axis acceleration in feet per   +forward           second 2         J   If/Then statement   If 1, gear on ground       K   Pitch   Up in degrees       L   YAW angle   +right, −left       M   Roll angle   +right, −left       N   Last ASCII code entered   N/A       O   Check sum   N/A                  
 
         [0027]    As an example, the character of the code corresponding to angle of attack has a numerical value, which is either zero, positive, or negative. If the numerical value is positive, one or more of the electric motors  14  and the corresponding actuator or actuators  22  move the motion platform  24  to create the perception of an aircraft moving in a nose-up orientation. Conversely, if the numerical value of the character is negative, the motion platform  24  moves to create the perception of an aircraft moving in a nose-down orientation. An example of the characteristic code is as follows:  
                                                           TABLE 2                           Example Codes for T1 and T2                Time 1   Character   Time 2   Character                            A1   −425.000   A2   −425.00           B1   64.5297   B2   72.6613           C1   4.5344   C2   3.1067           D1   0.0558   D2   1.1832           E1   −0.1733   E2   4.7004           F1   2.4731   F2   3.3943           G1   0.1151   G2   −0.0405           H1   31.3273   H2   31.7748           I1   5.1007   I2   4.0096           J1   0.0000   J2   0.0000           K1   13.5849   K2   −30.3394           L1   0.3091   L2   1.0233           M1   −4.0029   M2   −62.1991           N1   93.000   N2   112.0000           O1   −779.1511   O2   −848.7253                      
 
         [0028]    As shown in FIG. 2, the actuator or actuators  22  only move the motion platform  24  approximately four to eight inches in the D1 and D2 directions. Therefore, motion perceived by a person inside the simulator  6  does not accurately mimic the motion that would actually be perceived if the person were operating a corresponding actual device, such as an actual aircraft in-flight. However, this problem can be corrected by adjusting the motion software, through trial and error, by someone skilled at operating the corresponding actual device.  
         [0029]    In general, one method of making perceived movements of a motion platform  24  correspond to perceived movements of an actual vehicle in motion is shown in FIG. 7. FIG. 8 shows a method of making perceived movements of a flight simulator correspond to perceived movements of a corresponding actual aircraft, such as the type generally discussed above. Perceived movements are movements which are gathered by sensory organs, such as the eyes and inner ear, and transmitted to the brain. Stated another way, perceived movements are what a person in the simulator  6  or actual corresponding vehicle, such as an aircraft would see and feel.  
         [0030]    As shown in FIG. 7, the method generally includes (S1) executing simulation software programmed in the computer; (S2) transmitting an output of the computer to the motion platform; (S3) evaluating the perceived movement of the motion platform; and (S4) adjusting the output of the computer until the perceived movement of the motion platform corresponds to the perceived movement of the actual vehicle. As stated earlier, the computer  50  can be one computing device or more than one computing device.  
         [0031]    As an example, a pilot or other person familiar with the actual flight characteristics of a CESSNA 172 can execute a CESSNA 172 flight model software program in a simulator  6 , perform various maneuvers in the simulator  6 , and compare the perceived movement of the simulator  6  to what the pilot actually perceives while flying the same maneuvers in an actual airborne CESSNA 172. In the angle of attack example discussed above, if the character corresponding to angle of attack is a positive numerical value, a pilot in the simulator and a pilot flying the actual corresponding aircraft should each perceive a nose-up orientation, although the magnitude of the perceived motion will generally be different. Any difference between the movement perceived in the simulator  6  and the movement perceived while flying the actual corresponding aircraft is then corrected by adjusting the numerical value of the appropriate character of the code corresponding to angle of attack.  
         [0032]    Another example is washout. If a passenger in an airborne CESSNA 172 closes his or her eyes and a pilot enters into a turn by banking the aircraft, the passenger would feel centrifugal force as the turn was initiated. However, once the turn is established, the passenger would not know he or she was in a turn. To simulate this effect, the numerical value of the character of the code corresponding to the roll axis is decreased while the numerical value of the character of the code corresponding to pitch is kept sufficiently large to simulate the gravitational effects which would be felt during actual flight. Other flight characteristics of the flight model can also be adjusted, as appropriate, to provide a realistic perceived movement.  
         [0033]    Once modifications to the code have been determined, the adjustments can be assigned to the particular flight model simulator software being run in the simulator  6 , based on the manufacturer and the program type. For example, a MICROSOFT brand of flight simulation software can be executed and the motion software adjusted, as discussed above. The adjusted motion program can then be loaded with the corresponding flight model software each time the flight model program is run.  
         [0034]    The present invention provides a compact, realistic simulation device. The electro-servo motors eliminate the need for complex hydraulic systems, and the maintenance which such systems require. Despite a movement range of approximately four to eight inches, the present invention can provide the feel of a simulator having much longer hydraulic actuators. An important aspect to the decrease in size without a loss of realism is in the modified motion program which is developed based on the difference between the calculated simulated input and what the input should really look and feel like if flying an actual aircraft. By making these modifications, the present invention handles similarly to the prior art hydraulically operated larger and more expensive simulation machine.  
         [0035]    The invention has been described with reference to the preferred embodiment. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.