This invention relates generally to simulation vehicles and, more particularly, to adjusting of motion response characteristics of simulation vehicles.
Computer simulated aircraft motion is defined by around a dozen aerodynamic coefficients. The aerodynamic coefficients are determined based on the aircraft design and detailed aerodynamic principals. The aerodynamic coefficients are difficult to adjust if one desires to instill different flight characteristics for an aircraft. Many times, an aircraft manufacturer is requested by a customer (e.g., commercial airline or military service) to modify aircraft in order to provide certain flight characteristics.
When this occurs, the aircraft manufacturer would like to provide a simulation aircraft model that accurately reflects desired changes in the flight characteristics. The customer presents the new simulation model to its pilots to determine if this is an acceptable modification change. At present, if the aircraft manufacturer was to change the flight characteristics, it would have to change the coefficients and provide these changed coefficients to the customer in its simulation. When this occurs, the aircraft manufacturer might be giving away its valuable trade secrets or other proprietary or confidential information regarding the flight characteristics of the aircraft.
Also, because of the complexity of the flight characteristics of the aircraft as they relate to the coefficients, only an expert with extensive aerodynamic and mathematical knowledge can effectively change the coefficients. Most likely, a customer or user of the simulation model would not posses the required knowledge and therefore not be able to accurately and efficiently make any desired flight characteristic changes.
Thus, there exists a need to quickly and easily change flight characteristics of flight simulation aircraft models.
The present invention is a system and method for easily adjusting flight characteristics of a simulated aircraft. The system includes a memory that stores atmospheric temperature values and atmospheric dynamic pressure values and associated frequency response values for pitch, yaw, and roll. The system also includes a component for adjusting at least one of the stored frequency response values for the simulated aircraft. The memory includes a look up table for storing the frequency response values and corresponding atmospheric temperature and atmospheric dynamic pressure values.
The system also includes a memory that stores commanded angle of attack, yaw angle, and roll rate values with an associated atmospheric temperature value, atmospheric dynamic pressure value, and at least one of an aileron, rudder, or elevator position value, and a component for adjusting at least one of the stored commanded angle of attack, yaw angle, or roll rate values for the simulated aircraft. The memory includes a look up table for storing the commanded angle of attack, yaw angle, and roll rate values, associated atmospheric temperature values, atmospheric dynamic pressure values, and aileron, rudder, or elevator position values.
The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
In an alternate embodiment of the present invention, a plurality of users using user input devices 24 are coupled to a central server or processor 22 over a network connection (not shown). The central server 22 performs simulation calculations for each entity controlled by a user at a user input device 24 or entities that are not user controlled, such as missiles or projectiles. The user interface 28 allows a user or other operator to manipulate the aircraft flight characteristic values that are stored in the memory 30. The user input device 24 is suitably a stick/yoke and rudder pedals, but could be any other device that can generate aircraft control signals. The user interface 28 is suitably a keyboard or mouse, but could be any user interface device that allows one to access and manipulate the values stored in the memory 30.
The present invention allows one to easily adjust a response the simulation program provides in response to user input. In one embodiment, using the user interface 28 one can adjust commanded values for an angle of attack relative to elevator positions, a yaw angle relative to rudder positions, and roll rate relative to aileron positions. In another embodiment, using the user interface 28 one can adjust the frequency at which the simulation program moves the aircraft from one steady state to another steady state (i.e., the frequency the program moves the simulated aircraft from the last commanded value to the present commanded value). In still another embodiment, using the user interface 28 one can apply factors to the calculation of Thrust, Drag, Lift, or Sideforce to change flight characteristics. The following example illustrates an exemplary process used to update an image or simulation information of a simulated aircraft or update an image generated for a simulated aircraft (i.e., pilot or operator view) and to provide an easy ability to change the flight characteristics of the simulated aircraft.
Nxn+1=Thrust−Drag*cos(βn)*cos(αn)−Sideforce*sin(βn)*cos(αn)+Lift* sin(αn) (1)
Axn+1=Nxn+1−sin(θn) (2)
Nyn+1=−Drag*sin(βn)+Sideforce*cos(βn) (3)
Ayn+1=Nyn+1+cos(θn)*sin(φn) (4)
Nzn+1=−Drag*cos(βn)*sin(αn)−Sideforce*sin(βn)*sin(αn)−Lift*cos(αn) (5)
Azn+1=Nzn+1+cos(θn)*cos(φn) (6)
At a block 116, the processor 22 determines temporary axial velocities at time equals n+1 based on the beginning simulation values and the determined n+1 axial acceleration values. See equations 7–9 below:
Un+1=Un+(Axn+1+Qn*Wn−Rn*Vn)*dt (7)
Vn+1=Vn+(Ayn+1+Rn*Un−Pn*Wn)*dt (8)
Wn+1=Wn+(Azn+1+Pn*Vn−Qn*Un)*dt (9)
At a block 120, the processor 22 determines a total velocity value at time equals n+1 based on the determined temporary axial velocities. See equation 10 below:
Vtn+1=sqrt(Un+12+Vn+12+Wn+12) (10)
The process 90 then continues to a block 180 in
At a block 186, the simulation application program determines forcing coefficients (kf) and resistance coefficients (kr) for Hook's Spring equation for each of angle of attack, yaw angle, and roll rate based on the simulation frequency and the corresponding angle of attack frequency, yaw frequency, and roll rate frequency. At block 190, the simulation application program determines angle of attack, yaw angle, and roll rate at time n+1 based on the angle of attack, yaw angle, roll rate at time n, the retrieved commanded angle of attack, yaw angle, roll rate, and the determined corresponding coefficients (kf, kr). See equations 11–19 below:
{dot over ({dot over (α)}n+1=(αcom
{dot over (α)}n+1={dot over (α)}n+{dot over ({dot over (α)}n+1*dt (12)
αn+1=αn+{dot over (α)}n+1*dt (13)
{dot over ({dot over (β)}n+1=(βcom
{dot over (β)}n+1={dot over (β)}n+1{dot over ({dot over (β)}n+1*dt (15)
βn+1=βn+{dot over (β)}n+1*dt (16)
{dot over ({dot over (P)}n+1=(Pcom
{dot over (P)}n+1={dot over (P)}n+{dot over ({dot over (P)}n+1*dt (18)
Pn+=Pn+{dot over (P)}n+1*dt (19)
Next, at a block 194, the simulation application program determines axial velocities and acceleration values at time equals n+1 based on the determined angle of attack, yaw angle, total velocity, and simulation frequency at time equals n+1. See equations 20–25 below:
Un+1=Vtn+1*cos(αn+1)*cos(βn+1) (20)
Vn+1=Vtn+1*sin(βn+1) (21)
Wn+1=Vtn+1*sin(αn+1)*cos(βn+1) (22)
{dot over (U)}n+1=(Un+1−Un)*f (23)
{dot over (V)}n+1=(Vn+1−Vn)*f (24)
{dot over (W)}n+1=(Wn+1−Wn)*f (25)
At the block 196 in
{dot over (Q)}n+1=({dot over (W)}n+1−Azn+1+Pn+1*Vn+1)/Un+1 (26)
{dot over (R)}n+1=(−{dot over (V)}n+1+Ayn+1+Pn+1*Wn+1)/Un+1 (27)
In order for one to further understand the behavior of the simulation aircraft and fidelity of the simulation, the products of the following equations are used:
{dot over (Q)}n+1=(Qn+1−Qn)*f (23)
{dot over (R)}n+1=(Rn+1−Rn)*f (24)
At a block 198, the simulation application program updates or generates a new image of the simulation vehicle based on the determined pitch and yaw rate values (Q,R) at time equals n+1. At this point, the simulation application program has completed an update of the simulated aircraft.
If at a decision block 200, the user does not desire to change the aircraft's flight characteristics, the process returns to the block 108 for calculating the next aircraft position using the just calculated values of angle of attack, yaw angle, and roll angle. The flight characteristics include commanded values (angle of attack, yaw angle, and roll rate) and frequency at which the simulation aircraft attains the commanded value.
At the decision block 200, if a user desires to change any flight characteristics of the simulated aircraft, such as commanded values, frequency of attaining a commanded value, or other variables, the simulation for that aircraft is stopped, see a block 208. At a block 210, the user desiring to change the aircraft characteristics changes at least one of the stored values in the tables in the memory 30 associated with commanded angle of attack, yaw angle, and roll rate, values in the table associated with angle of attack frequency, yaw angle frequency, or provides a factor to the determination of Lift, Thrust, Drag, or Sideforce. Then, the user will restart the application program for the aircraft, at block 100 of
In order to make changes to the stored commanded values and frequency values, a user accesses the tables in the memory 30 using the user interface 28 by one of many known methods for database access.
In an alternate embodiment of the present invention, changes are made to stored values in the tables in the memory 30 while the application program continues to operate.
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
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