U.S. patent application number 11/913858 was filed with the patent office on 2008-08-28 for method for training a person while operating a vehicle.
This patent application is currently assigned to VOLVO AERO CORPORATION. Invention is credited to Olof Hannius, Thomas Johnsson, Anders Lundbladh, Dan Ring.
Application Number | 20080206719 11/913858 |
Document ID | / |
Family ID | 37532554 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080206719 |
Kind Code |
A1 |
Johnsson; Thomas ; et
al. |
August 28, 2008 |
Method For Training A Person While Operating A Vehicle
Abstract
In a method for training a person while operating a vehicle, the
vehicle has a control system for receiving vehicle operating
commands from the person for controlling the vehicle. A calculation
unit is provided for simulating a state of the vehicle and/or the
environment to which the vehicle is subjected, the simulated state
being a possible real state of the vehicle and/or the environment
which is different from the actual state of the vehicle and/or the
environment. The vehicle operating commands and the calculation
unit are used for calculating vehicle command signals. The vehicle
command signals are used for controlling the vehicle so as to cause
the vehicle to respond to the vehicle operating commands in a way
that corresponds to the state simulated by the calculation unit
instead of the actual state of the vehicle and/or the
environment.
Inventors: |
Johnsson; Thomas;
(Trollhattan, SE) ; Lundbladh; Anders;
(Trollhatan, SE) ; Ring; Dan; (Trollhattan,
SE) ; Hannius; Olof; (Trollhattan, SE) |
Correspondence
Address: |
WRB-IP LLP
1217 KING STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
VOLVO AERO CORPORATION
Trollhattan
SE
|
Family ID: |
37532554 |
Appl. No.: |
11/913858 |
Filed: |
June 14, 2005 |
PCT Filed: |
June 14, 2005 |
PCT NO: |
PCT/SE2005/000915 |
371 Date: |
November 8, 2007 |
Current U.S.
Class: |
434/37 ;
703/8 |
Current CPC
Class: |
G06G 7/48 20130101; G09B
9/00 20130101; G09B 9/44 20130101; G09B 19/165 20130101; G09B 9/02
20130101 |
Class at
Publication: |
434/37 ;
703/8 |
International
Class: |
G09B 19/16 20060101
G09B019/16 |
Claims
1. A method for training a person while operating a vehicle, the
vehicle having a control system for receiving vehicle operating
commands from the person for controlling the vehicle comprising
providing a means for simulating a state of the vehicle and/or the
environment to which the vehicle is subjected, the simulated state
being at least one of a possible real state of the vehicle and the
environment which is different from at least one of an actual state
of the vehicle and the environment, using the vehicle operating
commands and the simulation means, the vehicle operating commands
and the simulation means comprising a calculation unit, for
calculating vehicle command signals, and using the vehicle command
signals for controlling the vehicle so as to cause the vehicle to
respond to the vehicle operating commands in a way that corresponds
to the state simulated by the simulation means instead of the at
least one of the actual state of the vehicle and the
environment.
2. A method according to claim 1, comprising using the calculation
unit comprising an actual vehicle model and using the vehicle
operating commands as input to the actual vehicle model for
calculating the vehicle command signals.
3. A method according to claim 1 comprising using at least one of
key data for the simulated state of the vehicle and key data for
the actual vehicle as input to the calculation unit for calculating
the vehicle command signals.
4. A method according to claim 1, comprising using the calculation
unit comprising an inverse actual vehicle model for calculating the
vehicle command signals and calculated motion of the simulated
state of the vehicle as input to the inverse actual vehicle model
for calculating the vehicle command signals.
5. A method according to claim 1, comprising using the simulation
means comprising a load database for calculating the vehicle
command signals.
6. A method according to claim 5, comprising using the load
database to calculate at least one of key data for the simulated
state of the vehicle and key data for the actual state of the
vehicle.
7. A method according to claim 6, comprising calculating the key
data for the simulated state of the vehicle by using vehicle
operating commands as input to the load database.
8. A method according to claim 6, comprising calculating the key
data for the actual state of the vehicle by using vehicle response
as input to the load database.
9. A method according to claim 6, comprising calculating the at
least one of the key data for the simulated state of the vehicle
and the key data for the actual state of the vehicle by using load
configuration for at least one of the simulated state and actual
vehicle state as input to the load database.
10. A method according to any preceding claim 6, comprising using
the simulation means comprising a vehicle model for calculating the
vehicle command signals.
11. A method according to claim 10, comprising calculating, in a
first step, motion of the vehicle in the simulated state by using
the vehicle model and the vehicle operating commands as input, and
then calculating, in a second step, the vehicle command signals by
using the calculated motion of the vehicle in the simulated state
as input to the calculation unit.
12. A method according to claim 10, comprising using the key data
for the simulated state of the vehicle as input to the vehicle
model.
13. A method according to claim 12, comprising transmitting the key
data for the simulated state of the vehicle to the vehicle model
during operation of the vehicle.
14. A method according to claim 11, comprising calculating the
vehicle command signals by using the vehicle operating commands as
input in the second step.
15. A method according to claim 11 comprising calculating the
vehicle command signals by using the key data for the actual
vehicle as input in the second step.
16. A method according to claim 1, comprising calculating the
vehicle command signals by using vehicle response as input to the
simulation means.
17. A method according to claim 16, comprising calculating the
vehicle command signals by using vehicle response as input to the
calculation unit.
18. A method according to claim 10, comprising calculating the
vehicle command signals by using vehicle response as input to the
vehicle model.
19. A method according to claim 1, comprising using the vehicle
command signals in order to simulate transient effects on vehicle
motion relating to load release.
20. A method according to claim 1, comprising using pre-calculated
data in the simulation means for calculating the vehicle command
signals, the pre-calculated data defining a relation between
certain vehicle operating commands and the vehicle command
signals.
21. A method according to claim 1, comprising using the vehicle
command signals for controlling at least one actuator of the
vehicle.
22. A method according to claim 21, comprising using the vehicle
command signals for controlling at least one actuator of an engine
of the vehicle.
23. A method according to claim 22, comprising using the vehicle
command signals for controlling power or thrust of the engine.
24. A method according to claim 21, comprising using the vehicle
command signals for controlling at least one control surface of the
vehicle.
25. A method according to claim 24, comprising using the vehicle
command signals for controlling a position of the control
surface.
26. A method according to claim 21, comprising using the vehicle
command signals for controlling at least one wheel of the
vehicle.
27. A method according to claim 26, comprising using the vehicle
command signals for controlling at least one wheel brake actuator
of the vehicle.
28. A method according to claim 1, comprising providing a simulated
state of the vehicle wherein the weight of the vehicle is different
from the real weight of the vehicle.
29. A method according to claim 1, comprising providing a simulated
state of the vehicle wherein the vehicle is loaded by a load which
is different from the real load.
30. A method according to claim 1, comprising switching between a
training mode operation in which behavior of the vehicle in the
simulated state of the vehicle is arranged to be obtained and a
normal mode operation during the same operation of the vehicle.
31. A method according to claim 1, comprising switching between
different simulated states of the vehicle during a same flight of
the vehicle, the vehicle being an air vehicle.
32. A method according to claim 1, comprising training a person
while operating an air vehicle which is adapted to be flown in
either one of a first configuration or in a second configuration,
the first and second configurations being selectable by the
operator during a flight, and using a state simulated by the
simulation means for simulating a transition from the first
configuration to the second configuration.
33. A method according to claim 1, comprising training a person
while operating an air vehicle.
34. A training system for training a person while operating a
vehicle, the vehicle having a control system for receiving vehicle
operating commands from the person for controlling the vehicle, the
training system comprising means for simulating at least one of a
state of the vehicle and the environment to which the vehicle is
subjected, the simulated state being at least one of a possible
real state of the vehicle and the environment which is different
from the at least one of the actual state of the vehicle and the
environment, means for calculating vehicle command signals using
the vehicle operating commands and the simulation means, and means
for transmitting the vehicle command signals to at least one
controllable component of the vehicle for controlling the vehicle
so as to cause the vehicle to respond to the vehicle operating
commands in a way that corresponds to the state simulated by the
simulation means instead of the at least one of the actual state of
the vehicle and the environment.
35. An air vehicle comprising a training system according to claim
34.
36. A land vehicle comprising a training system according to claim
34.
37. A space vehicle comprising a training system according to claim
34.
38. A marine vehicle comprising a training system according to
claim 34.
39. A control unit comprising a computer and a computer program
stored in an internal memory of the computer, the computer program
being used for instructing a processor to accomplish the steps
according to claim 1 when the computer program is executed in the
computer.
40. A computer program product comprising software code portions
for instructing a processor to accomplish the steps according to
claim 1 when the program is run in a computer.
41. A computer program according to claim 40 provided at least
partly via a network such as the internet.
42. A computer readable medium having a stored program thereon
intended to cause a computer to control the steps according to
claim 1.
Description
BACKGROUND AND SUMMARY
[0001] The present invention relates to a method for training a
person while operating a vehicle.
[0002] The invention is applicable to different types of vehicles,
in particular air vehicles such as aircraft for training pilots.
Although aspects of the invention will be exemplified by describing
an aircraft application, the invention can also be applied to other
vehicles, such as cars, boats, trains etc. Thus, by the word
"vehicles" is meant airborne vehicles, land vehicles as well as
marine vehicles.
[0003] Training of pilots includes flying with heavily loaded
aircraft. A modern aircraft can carry loads weighing at least as
much as the weight of the empty aircraft. Therefore, such flights
are expensive to perform because the engines have to run at high
rating and fuel consumption is high. In addition, the high engine
rating means significantly increased engine wear resulting in
higher cost for engine maintenance. Furthermore, the stress levels
(fatigue) of the aircraft structure are higher in a loaded aircraft
resulting in a shorter life span and higher maintenance cost.
Training with heavily loaded aircraft also means a flight safety
hazard, in particular during the take off phase. A heavy aircraft
has less margins and in case of an engine fault, a bird strike or
any other incident there will be a higher risk for a catastrophic
situation which could result in serious injuries among the
crew.
[0004] The high cost and risk for training with heavily loaded
aircraft often leads to the fact that such training is avoided and
thus, the pilots receive less realistic training than desired.
[0005] Ground-based flight simulators are sometimes used for the
above-mentioned training but in many aspects they cannot provide
sufficiently realistic conditions.
[0006] Another type of training which provides more realistic
situations is the use of airborne simulation systems used in real
aircraft during flying. Such simulation systems use software for
imposing power output limits on an engine for simulating an engine
failure. A method for simulating an engine failure in a
multiple-engine aircraft is described in US 2002/0133322. The
engine failure is simulated by placing a software output limiter on
one or more engines. This could be combined with fictitious gauge
readings on the pilot's instrument panel. However, such a method,
which only means that there is an option mode conferring an
impaired performance of the engine which is usable for simulating a
specific engine failure, does not support general training with
heavily loaded aircraft of the type discussed above.
[0007] It is desirable to provide a method of the kind referred to
in the introduction, which method makes it possible to train
persons, such as aircraft pilots, to operate a vehicle during
trying conditions in a realistic and safe way and at reasonable
costs.
[0008] By a method according to an aspect of the present invention,
a pilot/driver of the vehicle can experience the behaviour of the
vehicle in a certain state without actually operating the vehicle
in this certain state. Realistic training can be performed to a
lower cost while still using a real vehicle. For example, the
vehicle can be selected to behave as if the load configuration was
different from the actual conditions. In other words; a simulation
of a heavily loaded aircraft can be performed by flying an unloaded
(light) aircraft. According to an aspect, an unloaded and light
aircraft can be caused to behave like it really was loaded and
heavy. This in turn can save costs and improve safety
[0009] The method and system according to an aspect of the
invention may be used for simulating many different states of the
vehicle and/or the environment to provide training situations for a
person. The term "a simulated state which is a possible real state
of the vehicle and/or the environment" refers to a state which can
very well occur during other conditions while using the same
vehicle but which state is simulated to avoid operating the vehicle
in such a state and still provide the desired training. The term
"different states" does not comprise different designs of the
vehicle, or other kinds of vehicle, beyond modifications associated
to the loading of the vehicle. As an example, the real state of an
air vehicle could be an unloaded state and the simulated state of
the air vehicle could be a state where the same air vehicle is
loaded with weapons, such as missiles or similar. In another
example a simulated fuel quantity is different from the actual fuel
quantity carried by the vehicle.
[0010] Further examples of simulated states are the simulation of a
transient disturbance of an air vehicle due to releasing loads
although no actual loads are released, and the simulation of
special wind and temperature conditions although the actual weather
is different. The consequence of the simulated states is that the
weight of the simulated vehicle is different from the actual weight
of the vehicle, that the centre of gravity of the simulated vehicle
is different from the actual centre of gravity of the vehicle
and/or that the moment of inertia the simulated vehicle is
different from the actual moment of inertia of the vehicle Further
consequences may be that the relationship between the angle of
attack and sideslip and the drag and lift of the simulated vehicle
is different from the actual relationship between said angles and
the drag and lift of the vehicle
[0011] Particularly, the method according to an aspect of the
invention may be used for training a pilot/driver by the simulation
of a state, which state is created by controlling dynamic
properties of the vehicle and/or controlling an engine of the
vehicle, such as the position of one or more air vehicle control
surfaces and/or the setting of engine thrust and/or thrust
vectoring.
[0012] According to an aspect of the invention, the motion of the
vehicle in the simulated state is calculated in a first step by
using a vehicle model and the vehicle operating commands as input,
and then the vehicle command signals are calculated in a second
step by using the calculated motion of the vehicle in the simulated
state as input to the calculation unit. Hereby, the controller for
training mode operation can be designed using the controller for
normal mode operation and the equations of motion.
[0013] The vehicle model, which can handle different load
configurations and environmental conditions for instance, can be
either in its simplest form a tabulated vehicle description, but
preferably a real time dynamic model for the vehicle motion based
on the equations of motion.
[0014] The calculated vehicle command signals used for controlling
the vehicle are ordinary vehicle control signals and any additional
vehicle control signals produced by the training system during
training mode only. However, in both cases the calculated vehicle
command signals are based on the vehicle operating commands and
designed to cause the vehicle to respond to the vehicle operating
commands in a way that corresponds to the state simulated by the
vehicle model instead of the actual state of the vehicle and/or the
environment.
[0015] A control unit comprised in the simulation system may be
achieved based on known electrical and/or mechanical control
components and corresponding software. A computer program
comprising an instruction set stored in an internal memory of the
computer may be used to instruct a processor for accomplishing the
steps of the method when the instruction set is executed in the
computer. The computer program can be provided at least partly via
a network such as the Internet. The control unit may be designed
for receiving a computer readable medium having a stored program or
data thereon intended to cause the computer to control the steps of
the method according to an aspect of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] With reference to the appended drawings, below follows a
more detailed description of preferred embodiments of the invention
provided merely as non-limiting examples.
[0017] In the drawings:
[0018] FIG. 1 is a block diagram schematically illustrating one
embodiment of a simulation system for carrying out the method
according to an aspect of the invention,
[0019] FIG. 2 is a variant of the system in FIG. 1 adapted for an
aircraft,
[0020] FIG. 3 is a view of an aircraft illustrating the forces
acting on an aerial vehicle while flying,
[0021] FIG. 4 is a graph illustrating the acceleration and the
velocity of a loaded and unloaded aircraft for a certain pilot
command, and
[0022] FIG. 5 is a graph illustrating the acceleration of a loaded
aircraft as in FIG. 4 and the acceleration of an unloaded aircraft
controlled by the system and the method according to an aspect of
the invention for simulating a loaded aircraft (to the left), and
pilot PLA-command (Power Lever Angle) and calculated actual engine
PLA-command (to the right).
DETAILED DESCRIPTION
[0023] A general vehicle simulator system for carrying out the
method according to an aspect of the invention is illustrated for a
general vehicle in FIG. 1. A pilot/driver normally issues vehicle
operating commands 01 for controlling a vehicle 12 and uses the
vehicle response 13 as feedback. The vehicle may be provided with a
propulsion system comprising one or more engines. In many
applications the vehicle is provided with control surfaces. The
engines and the control surfaces are to be controlled by the
pilot/driver by means of the vehicle operating commands received by
a control system of the vehicle.
[0024] Examples of vehicle operating command parameters in an
aircraft application are power lever angle and control stick
deflection. Examples of vehicle response parameters in an aircraft
application are altitude, angle of climb, speed, accelerations,
g-load and pitch/yaw/roll rates. The system comprises a switch 11
or similar for pilot/driver selection, i.e. for activating the
simulation system, or for automatic safety disengagement of the
simulation. When the switch is set at the position for training
mode operation illustrated in FIG. 1, the system is activated and
the pilot/driver can use the method according to an aspect of the
invention This means that at least one of the vehicle operating
commands 01 is used for creating at least one vehicle command
signal 10 to be used by the control system. However, if the switch
is moved to another position for normal mode operation, the
simulator system is disconnected and the vehicle operating commands
are treated by the control system in the ordinary manner.
[0025] To create the vehicle command signals 10 a simulation means
00 is used for transformation of the vehicle operating commands 01
into the vehicle command signals 10 The simulation means comprises
a calculation unit 09 for calculating vehicle command signals 10.
In its simplest form the calculation unit 09 may comprise a means
for receiving the vehicle operating commands 01, a pre-calculated
table or similar for converting the vehicle operating commands 01
to vehicle command signals 10, and a means for emitting the vehicle
command signals 10 to the vehicle 12 The vehicle command signals 10
are then used for controlling the vehicle so as to cause the
vehicle 12 to respond to the vehicle operating commands 01 in a way
that corresponds to the state simulated by the simulation means 00
instead of the actual state of the vehicle and/or the
environment.
[0026] In more advanced applications the simulation means 00 may
comprise a load database 04, a vehicle model 07 and a more advanced
calculation unit 09. The load database 04 contains data for all
vehicle loads, the current configuration for the vehicle and how
the loads affect the vehicle The vehicle model 07 predicts the
motion of the vehicle based on loads and operating commands. The
calculation unit 09 converts the calculated motion of the simulated
vehicle 08 into vehicle command signals 10 so that the vehicle 12
follows the motion of the simulated vehicle. The calculation unit
09 can be a controller that makes the measured motion of the actual
vehicle the same as the simulated vehicle. If measurements of the
vehicle motion are not available or if better confidence in
measurements is needed, the calculation unit 09 can also use an
actual vehicle model to generate the motion of the actual vehicle
In another implementation, the calculation unit 09 can comprise an
inverse actual vehicle model i.e. a model with the calculated
motion of the simulated vehicle 08 as input and the vehicle command
signals 10 as output.
[0027] A load selection unit 02 may contain data for load
configuration 03 for the vehicle to be simulated and for the actual
vehicle. The load data base 04 provides key data 05 for the
simulated vehicle as input to the vehicle model 07, and provides
key data 06 for the actual vehicle as input to the calculation unit
09.
[0028] The term "key data" may comprise the mass, position of the
centre of gravity and the moments of inertia and the aerodynamic
properties of the vehicle. The aerodynamic properties are given by
the functions of the vehicle's speed, angle of attack and sideslip
and angular velocities yielding the aerodynamic forces and
torques.
[0029] The vehicle model 07 uses the key data 05 and the vehicle
operating commands 01 for calculating the motion of the simulated
vehicle 08. In addition, vehicle response 13 can be used in the
vehicle model 07. The calculating unit 09 calculates the vehicle
command signals 10 by using the calculated motion 08 of the
simulated vehicle and the key data 06 for the actual vehicle as
input. In addition, the vehicle operating commands 01 and/or the
vehicle response 13 can be used as input to the calculation unit 09
for calculation of the vehicle command signals 10.
[0030] By using the vehicle command signals 10 to control the
vehicle 12, the vehicle responds to the propulsion provided by the
propulsion system and/or the settings of the control surfaces to
behave like the simulated vehicle 08. The resulting motion of the
vehicle 12 is used as feedback to the system and results in the
data for the vehicle response 13 changing continuously during the
training.
[0031] With reference to FIG. 2 an aspect of the invention is
exemplified when applied in an aircraft load simulator system for
training pilots to perform various kinds of missions and to deal
with various kinds of situations by flying the actual aircraft in
one configuration, normally being the unloaded basic
configuration.
[0032] FIG. 2 illustrates an aircraft load simulator system
according to an aspect of the invention The functional blocks; a
load database 04, an aircraft model 07 for the simulated aircraft
and a calculation unit 09 for calculation of vehicle command
signals, represent the aircraft load simulator system. The
remaining blocks represent the aircraft with associated control
functions, pilot commands and inputs.
[0033] In this example, it is assumed that the aircraft which is to
be equipped with the aircraft load simulator system has a control
system comprising a system computer, a fly-by-wire control and an
engine control system, such as a full authority digital engine
control system.
[0034] Furthermore, it is assumed that the system computer can
provide information and data to the flight and engine control
computers and further enables the flight and engine control systems
to communicate with each other Although, the simulator system
according to an aspect of the invention is preferably partly or
totally integrated in the ordinary system computer of the vehicle,
the simulator system could be a separate system communicating with
the system computer.
[0035] Information 03 of the load configuration of the aircraft to
be simulated is transferred into the software function load
database 04 Loads can be in terms of internal loads, such as
passenger weight, cargo weight and distribution, and fuel quantity.
Loads can also be in terms of external loads such as number, type
and placement of weapons, or in terms of any other internal or
external loads such as extra fuel tanks, etc.
[0036] Software functions within the load database 04 will
calculate the weight, centre of gravity, moments of inertia,
aerodynamic properties such as drag and aerodynamic moments and
performance limitations such as maximum allowed g-loads (or the
g-load envelope if applicable). These calculated data are referred
to as key data for the simulated aircraft 05 in FIG. 2.
[0037] The actual aircraft system computer is assumed to have the
ability to identify the loads for the actual aircraft configuration
to be flown during the training mission This function provides the
actual aircraft with the same information as the load database does
for the simulated aircraft (this information is named key data for
the actual vehicle in FIG. 1). In this illustrating example of an
aspect of the invention the actual aircraft is unloaded.
[0038] When the aircraft load simulator system has been activated
for initiating a training flight, key data for the simulated
aircraft 05 is calculated by the load database 04 and may be
updated with respect to changes in simulated and actual loads. Such
changes can be because of fuel consumption and the effect of
weapons being fired. Fuel consumption during the flight is in this
example calculated within the aircraft model 07.
[0039] Key data for the simulated aircraft 05 is, during the
training mission, continuously transferred to a software function
called aircraft model 07. The key data is used together with
aircraft operating commands 01 from the pilot and aircraft motion
for calculating the motion of the simulated aircraft 08 in terms of
e.g. angle of climb, acceleration and rotation rates (pitch, yaw,
roll) by means of the aircraft model 07. The information about the
actual aircraft motion is obtained from motion measurements 21
which measure the aircraft response 13.
[0040] The motion data for the actual aircraft from the motion
measurements 21 is, during the training mission, continuously
transferred to a calculation unit or software function called
calculation of new commands 09. The data of the motion of the
simulated aircraft and data for the actual flight condition are
used for calculating the vehicle command signals 10. The vehicle
command signals 10 comprise the actual aircraft motion commands
10a, in terms of stick, pedals and other performance-affecting
settings such as trim and flaps settings, and/or the actual engine
commands 10a b in terms of thrust setting. In another embodiment of
an aspect of the invention, the engine control 31 and engine
actuators 32 loop would be modified, to improve the simulation
fidelity. In addition to the vehicle command signals 10, other
command signals could also be used. These command signals are not
limited to the type of signals which are based on signals issued by
the operator, i.e. vehicle operating commands 01. For example, the
transient thrust response can be improved for a gas turbine engine
if both the exhaust nozzle area and the PLA (Power Lever Angle) are
used as inputs to the vehicle 12. This would make it possible to
improve the simulation fidelity for some manoeuvres such as the
simulation of weapons release or quick turns. New command signals
require that the engine control 31 and engine actuators 32 loop is
modified.
[0041] The actual aircraft motion commands are transmitted to the
ordinary flight control functions, i.e motion and stability control
22, 23, where they are used for affecting the aircraft control
surfaces 24. Correspondingly, the actual engine commands are
transmitted to the ordinary engine control 31 where they are used
for controlling the engine actuators 32.
[0042] The aircraft thus responds to the thrust provided by the
engine 31 and the settings of the aircraft control surfaces 24 to
behave like the simulated aircraft. The resulting motion of the
aircraft is used as feedback to the system and results in the data
for the aircraft response 13 being continuously changed during the
flight.
[0043] To illustrate an aspect of the invention in more detail, a
simplified calculation example where an aircraft initially flies at
a certain constant speed and altitude, and the pilot then wishes to
accelerate as quickly as possible at the same altitude, is
described. Furthermore, the pilot is training for a mission that
requires a certain load configuration of the aircraft, but for
economical or safety reasons or other reasons, the loads are not
included during training Thus, the training aircraft has a smaller
total weight than the aircraft would have in a corresponding real
situation where the loads are carried by the aircraft.
[0044] The following definitions of physical conditions related to
an aircraft have been used. The motion of an aircraft is described
by four basic forces, see FIG. 3 illustrating the forces acting on
an aerial vehicle. Theses forces are lift L, thrust T, drag D and
gravity G. The drag force is directed backwards and opposite to the
velocity vector v of the aircraft. The lift force is directed
perpendicular to the drag force and dependent on an attack angle
.alpha. between an x-axis of the aircraft (A/C x-axis) and the
velocity vector v. Gravity G is directed downwards and given by the
mass m of the aircraft and the gravity constant g. The pitch
attitude .theta. is an angle between the aircraft x-axis and a
fixed horizontal x-axis.
[0045] This particular example is limited to longitudinal control
of the aircraft. The primary control surface for movement in the
vertical plane is the elevator and the canards are used for
stability. The elevator creates a rotational momentum around the
y-axis of the aircraft. The velocity of the aircraft is controlled
by the engine thrust setting. Thus, in this example the relevant
aircraft operating commands are the stick angle affecting the
elevator angle and the power lever angle PLA affecting engine
thrust T. All forces acting on the aircraft are dependent on
parameters such as pressure, temperature, altitude, velocity, angle
of attack, aircraft aerodynamics and loads such as remaining amount
of fuel, passengers, weapons etc. All these parameters are denoted
p in the equations (2) and (3) which equations are described
hereinafter.
[0046] The aircraft has controls for affecting control functions of
the aircraft by means of vehicle operating commands. In this case a
control stick can be used for affecting a flight control surface,
such as the elevator angle. A power lever can be used for affecting
the engine thrust. If the power lever angle PLA is increased, the
throttle of the engine is opened and this will result in different
accelerations dependent on aircraft loads. In this regard,
reference is made to FIG. 4 illustrating the acceleration and
increase in velocity of a loaded and unloaded aircraft for a power
lever angle step from PLA.apprxeq.54.degree. to a maximum value of
100.degree. at the time point t=4s.
[0047] The continuous curve represents the unloaded training
aircraft without using the simulation method according to an aspect
of the invention. The dotted curve represents same training
aircraft if loaded. It appears from the curves that the
acceleration and increase in velocity of the unloaded aircraft are
very high compared to the loaded aircraft, making such pilot
training less realistic and not so efficient.
[0048] As already mentioned, according to an aspect of the
invention a model for simulating a certain state of the aircraft
and/or the environment is provided. The simulated state is a
possible real state which is different from the actual state of the
aircraft and/or environment. In this example, it is desired that
the acceleration of the unloaded aircraft during training becomes
the same as if the aircraft actually would have been loaded. The
aircraft operating commands are received from the controls; in this
case the thrust power lever and the elevator angle stick, and the
aircraft operating commands and key data for the desired simulated
state are used as input to the aircraft model for calculating
vehicle command signals.
[0049] These vehicle command signals, which are different from the
signals which would be expected based on the actual aircraft
operating commands if the load simulator system was not in use, are
then used for controlling the aircraft so as to cause the aircraft
to respond to the aircraft operating commands in a way that
corresponds to the state simulated by the aircraft model instead of
the actual state of the aircraft.
[0050] In this case the vehicle command signals are used for
controlling an engine control function, the throttle of the engine,
obtaining an engine thrust which is adapted to keep the
acceleration (and velocity) the same for the unloaded training
aircraft as it would have been for the loaded aircraft for the same
instrument setting and pilot commands without calculation of said
vehicle command signals.
[0051] Assuming that the engine thrust is aligned with the aircraft
x-axis, the aircraft motion expressed in fixed x-z coordinates is
described below by the following relations:
x . = v cos ( .theta. - a ) , z . = v sin ( .theta. - a ) ( 1 ) x =
[ T ( p ) cos .theta. - L ( p ) sin ( .theta. - a ) - D ( p ) cos (
.theta. - a ) ] / m ( 2 ) z = [ T ( p ) sin .theta. - L ( p ) cos (
.theta. - a ) - D ( p ) sin ( .theta. - a ) - mg ] / m ( 3 ) P L A
= P L A O + k [ ( x sim - x ) + 1 T i .intg. ( x sim - x ) t ] ( 4
) ##EQU00001##
[0052] Thus, the exemplified simulation is designed to keep the
acceleration (and velocity) the same for the training aircraft as
it would be for a loaded aircraft. A matching of the acceleration
along the x-axis is performed in equation (4) by the use of for
example a Pi-controller. By the Pi-controller the actual engine
command PLA is calculated. Tj and k are the controller time
constant and gain, respectively. PLA.sub.o denotes the stationary
thrust demand for training and will result in the same stationary
velocity as for the simulated aircraft with the actual pilot
command.
[0053] Although it is not explicitly described herein how the
aircraft control surfaces, such as the elevator, have been
controlled so as to maintain the altitude of the training aircraft,
vehicle command signals are also calculated for affecting the
aircraft control surfaces as desired. Of course different
algorithms are required when simulating different states of the
aircraft and/or the environment to the aircraft. In many
applications a six dimensional problem has to be addressed, which
means that flight manoeuvres in the lateral direction would also be
included.
[0054] Furthermore, changes in important parameters such as the
angle of attack, pitch attitude, or moments of inertia have not
been explicitly addressed in this description. However, these
parameters have been included in the exemplified simulation
illustrated in FIG. 5 and are represented by p in equations (2) and
(3).
[0055] The following sequence describes how the pilot commands may
be transformed by means of the system and the method according to
an aspect of the invention. [0056] a) The pilot selects the
appropriate training mode for the aircraft, [0057] b) The moment of
inertia around the y-axis of the aircraft, the aircraft mass, and
the centre of gravity from the load database are used together with
current values and immediate history of the measured inputs to
calculate the drag, lift, gravity and momentum for the simulated
aircraft through the use of an aircraft model, and [0058] c) The
motion of the simulated aircraft can then be calculated using the
equations (1), (2) and (3). The system controls the aircraft such
that the actual aircraft follows the simulated aircraft trajectory.
By using the pilot commands and the difference between the
simulated aircraft trajectory and the actual flight condition as
input, the actual aircraft motion commands and the actual engine
commands can be produced as output. These vehicle command signals
are then used for controlling the aircraft
[0059] On the left in FIG. 5, it is shown how the real acceleration
of the unloaded aircraft follows the simulated acceleration (see
also dashed curve in FIG. 4) expected for the simulated loaded
aircraft. The aircraft is tracking the model very well, which means
that its performance is very similar to the performance of the
simulated loaded aircraft.
[0060] In the example, the pilot command is a step from
PLA.apprxeq.54.degree. to the maximum PLA angle of 100.degree.,
which is shown by the dashed curve on the right in FIG. 5. The
calculated actual engine PLA-command used during the flight, which
command corresponds to the pilot command and which actually affects
the engine thrust, follows the lower continuous curve and makes the
aircraft response similar to the response which is expected by a
loaded aircraft. This concludes the simplified example.
[0061] It is to be understood that the present invention is not
limited to the embodiments described above and illustrated in the
drawings; rather, the skilled person will recognize that many
changes and modifications may be made within the scope of the
appended claims. For example the algorithms of the model used in
the method may be varied in many ways.
* * * * *