CA2204116A1

CA2204116A1 - Learning autopilot

Info

Publication number: CA2204116A1
Application number: CA002204116A
Authority: CA
Inventors: Fred M. Strohacker; Francis E. Peter
Original assignee: Individual
Current assignee: Honeywell Inc
Priority date: 1994-11-01
Filing date: 1995-10-30
Publication date: 1996-05-09
Also published as: EP0789862B1; IL115764A; DE69508783T2; IL115764A0; WO1996013765A1; EP0789862A1; US5785281A; DE69508783D1

Abstract

A learning autopilot for a vehicle provides the capability to command complex maneuvers or maneuver the vehicle when control by its ground station is not possible. A memory is used during a piloted rehearsal mission and position and time information for the aircraft is stored in the memory. This memory is incorporated into the vehicle control system, and during automatic operation of the aircraft, the recorded position and relative time information is retrieved and compared against position and relative time information occurring during automatic flight. The difference between the recorded information and the actual flight information is used to generate error signals which are converted to command signals for the vehicle. Maneuvers which were initiated and completed by the pilot during the rehearsal mission are then repeated during the automatic flight from the flight information stored in the memory.

Description

LEARNING AUTOPILOT

BACKGROUND OF THF INVENTION
Field of the Invention The present invention relates to vehicle autopilots and, more particularly, to an autopilot for nnm~nned vehicles in which portions of a mission are preprogrammed into the vehicle control computer to provide for fully automatic operation of the vehicle.
Discussion of the Related Art The use of drone vehicles is well-known. A drone is a pilotless vehicle operated0 by remote control. The more well-known types of drones are aircraft used as aerial targets, for reconn~i~q:~nce, or for ordnance delivery.
The typical drone system consists of an airborne vehicle with a specialized airborne drone control system in combination with a ground station. The airborne drone control system is adapted to provide positive control of the drone throughout the flight envelope of the air vehicle. In addition, ~plupl;ate electrical or mechanical devices on board are also controlled through the drone control system. These electrical/mechanical devices are used to actuate such things as the aircraft flight control linkages, landing gear, wing flaps, slats, wheel brakes, speed brakes, nose wheel steering, and any other electrical connections used for controlling the air vehicle. The aircraft is controlled from the ground through the use of a ground station. The ground station transmits radio frequency (RF) command signals to the remotely-piloted aircraft where the on-board drone control system provides comm~n-lc to the aircraft control eq--ipmPnt The ground station is adapted to intPrf~e with a drone controller or other ground operator, thereby allowing the remotely-piloted vehicle to execute real-time comm~n~l~
Three types of drone ground stations are typically used. In the first type (Type1), the ground station radiates to the drone from a single antenna, and using ~ntenn~
elevation angle, azimuth angle, and range, is able to determine the point at which the drone is located. For this to work, constant line-of-sight must be m~int~ined between the ground station antenna and the drone. Any time the drone flies out of direct line-of-sight with the ~nt~nn~, control of the drone is lost. The drone is typically programmed with automatic responses so that when contact is lost with the ground station, the drone will automatically climb and loiter until ground station control is reestablished.

W O96/13765 PCTrUS95/13984 In a second type of drone ground station (Type 2), a series of antennas are positioned on remote sites at surveyed positions. All ~ntçnn~ locations must be chosen so that a maximum direct line-of-sight can be m~int~ined with the drone. As the drone is flown~ it must remain in line-of-sight contact with at least three :mt~nn~c so that the s drone's position can be determined using triangulation techniques. Uplink comm~ntlc and downlink telemetry data is also provided using the RF link between the ground station ~nt~nn~c and the drone. This type of ground station can be seen in Fig. 1.
In the third type of ground station (Type 3), an on-board position estimator (e.g., global positioning system (GPS)) is used to determine drone position, and the position 0 data is downlinked to the ground station that can be either Type 1 or Type 2.
The above types of drone ground stations have several drawbacks. One drawback is that the Type 1 system is very limited by the l~n(lccape in which the drone is operated. Care must be taken so the drone does not fly into areas in which line-of-sight is lost with the single ground station ~nt~nn~ Therefore, flight low to the ground 5 or behind terrain is not possible in this type of ground station. The Type 2 ground station is capable of improving upon the Type 1 ground station, as long as enough ~ntenn~c can be properly positioned around the area in which the drone will be flown.
However, in many areas, especially in ocean areas, this is impractical. In addition, the Type 2 ground station is typically very costly due to the need for many ~nt~nn~c and 20 also because this type of ground station typically requires fast and complex co~ ulalions within the ground station, therefore re~ui~ g expensive software and hardware. The Type 3 ground station has the advantage of on-board position detçrmin~tion, but is still dependent on line-of-sight being m~int~in~cl between the drone and the ground station. Another significant drawback of all of these ground 25 stations is that they are incapable of providing complex drone maneuvers that an on-board pilot could perform.
These limitations have been especially noticeable with target drones. A typical drone training mission consists of the target drone flying in a straight line at a constant velocity. Some prior art drones have been preprogrammed with particular maneuvers 30 but these are limited and do not accurately mimic a m~nn~d aircraft in a battle situation.
None of the prior art drone systems provide a realistic training scenario in light of the fact that modern day helicopters or fighter aircraft are highly maneuverable and able to L~ -'3~ ~~ 3 ~j~~:3~ 3'Jl~ .5 - --- ----CA 02204116 1997-04-30~

fly at ~ny speed at very low aitiludes. Modcm day helicopters or fighters also can pcll'u,l.~ a mlmber of evasive maneuvcrs in order to avoid a ground altack. The possibility of irlcorpor~tin~
co~nrl~ maneu~ s and low-altitude flight illtO a tar~et drone mission would be o~ gTeat ad~antage in training grou~d troops arld testirlg anti-aircraf~ systems.
Prior a~ f~L~ CCj include the following: U.S. Patent 3,G~8,257 which discloses ana~ri~ on~l system which ~im-~lt~ Qu51y displ~$~s discr~tc navi~ n~l coordinate signals ~ld records thesc siE~nals in a moving memo~y ~s a ~/chicle movcs along 3 path. These signals are recallet from memory during fiuture use.
U.S. Patent 4,51~,7;3 descr~bes a te~a~n contour matç~in~T ~dance syst~m. Points o:~
the terrain are stored ill a memory, ~d tl:lis data is later used to guide an aircr~.
IJ.S. Patent 5,331,561 des~ribes a system which guides a v~hicle ~Long a ~redPfine~ path by correlating v~hiclc sidc rangc profilcs. A lead vehicle gathOEs data and provi~es this data to a ~ollow~ng ~/el~icle. The following vehiclc correlates the data firon~ the le~d vehicle with the terrain currently around the vehicle.
U.S. Patent 5,~04,8 l4 describes an automa~c, self propelled Iawn movver. The lawn mower cuts the ~rass throu~h use of eIec~onIcally stored path and terrail~ inr~ ;o~ as a prima~y navi6~t~on system, and se~s~ a nonm~r etic, non current carrying m~t~llic ~uide path as a seconda~y navig~tion system.
Th~refore, it is an object of the present invention to provide a drone contro1 system which enables the vehicle to a l~ Ollll complex maneuvers I-lt~ t;c~lly with ~r without the vehicle being in cont~ct ~th a gro~d station.
Otller ob3ects, fieatures and ad~ ges of the invent~on will beco.-~e appa~e.~t to ~ose skilled in the art from the descriptio~l ofthe ~r~r~ emb~diment, c~aims and ~ d~Ul~ hereof, whercin l~ke num~ refe~ to lilce el~nts.
~U~fMA~Y OF T~. lNVl~N~ON
Disclosed he~eln is a l~mir~ autopil~t which provides ~to~tic con~ol for a vehicle.
The autopilot ~ s inrlu~s a position estirn~tion syste~ which proYides posi~on inf.n~nn for ~e vchicle with~: a known ~efcl~,ce frame. A memory contains position infi~ tion ~o~ l:hc vehicle which was stored during a piloted r~ s~l micei~n- The position infonnation ~as ~cqu~ed by pcnodically sampling s~gn~ls ou~put b$~ the p~qitilm A~3'.~ D SHE~T

~ CA 02204116 1997-04-30 ~

est;m~tion system. Duril~g automatic operation of thc Yehic~c whcn the leasnin~ autopilot is ~ngagcd, the position infolmation stored in thc memory is co~pal~ to ace ul positi~n informatiorl received f~om the position estim~t on systcm and a plurality of cITor si~ als is ge"e,atct. The er~or si~als are p~o~o~l;onal to ~he di~.~"lce between the storcd and act~Lal positio~ info~m~ion. A co~ltrol system in the vchicle convcrts thc error si~nals to control signals which provid~ dire~tion~l and ~vclocity control for the vehicle.
The fiTst stepinILsing the leaming autopiloe is m~n~ ly pilotin~ thc vchiclc ~ough al mission. Durirl~ ~is r,~ I flight, position in~ormation is ge~ L~d for tlle vehicle and stored in a memory at predet~nnin~ or adaptive L~tervals. I~uri~g automatic opera~ian of tlle vehicle, the posi~do~ i~LCu~ ion stoled in mernory is retrieved aIld co.np~ed to actu~l posi~on inrn~ ion fortl~e vehicle ~ t~ by the position e~ ;on syster~ A
co"~ ;.cnn~s made between the actllai and recorded position i~ ioll auld error si~nals ar~ g~ w~ich are~r~portional to the 3a - hi~ S~EET

W O96/13765 PCTrUS95/13984 difference between the actual and recorded position information. The error signals are converted to control signals for operation of the vehicle. The recorded positioninformation allows for automatic operation of the vehicle through a predetermin~cl mission without the direct control of a ground station.
s BRTFF DFSCRrPTION OF THF DRAWINGS
Fig. 1 is a diagram of a prior art drone control system.
Fig. 2 is a diagram of an embodiment of the learning autopilot system.
Fig. 3 shows the transfer of information between the position estimator and the 0 memorv during the m~nnecl rehearsal flight.
Fig. 4 shows the generation of the error signals for directional and velocity control during the automatic flight.
Fig. 5 shows the transfer of information between the vehicle controls detector and the memory during the m~nnecl rehearsal flight.
Fig. 6 shows the generation of the error signals for flight control during automatic flight.

DESCRrPTION OF THE PREFFRRFn Fl~BOr)IMF.NT(S) Shown in Fig. 2 is a diagram of the basic components of the learning autopilot system described herein. Included in the system is target 30, which in this case is shown as an aircraft, either a helicopter or an airplane. In the preferred embodiment of the invention, the learning autopilot will be described in relation to an aircraft, however, it is within the scope of this invention to include other vehicles, such as ground vehicles or boats. In the present embo-liment, the aircraft is a drone which can either be flown 2s m~m-~lly or remotely through ground station 20. Ground station 20 includesappro~l;ate hardware and software so that cont~ol signals can be sent to the drone aircraft. Ground station 20 is also equipped to receive downlink telemetry while the aircraft is in operation. Also included on the aircraft 30 is a position estimation system, such as a global positioning system (GPS) unit, which receives and tr~n.cl~tec positional information transmitted from GPS satellites 24. Through use of GPS, the aircraftsystem and ground station are able to monitor location of the aircraft 30.

s The learning autopilot disclosed herein provides for automatic operation of the drone aircraft even when it is out of contact with the ground station. In order to provide more realistic maneuvers for ground forces, or to test anti-aircraft guns or missiles, it is desirable to have a drone aircraft which can pclr~Jllll complex maneuvers, or fly at low 5 altitude and is not limited by the l~n~lcc~pe of the area in which the exercises are being pclrolllled. A drawback of modern day drone control systems is that the drone must always stay in contact with the ground station, either through a direct line of sight link, or through relay ~ntenn~ strategically placed in and around (or above) the exercise area.
With the learning autopilot incorporated into the drone aircraft, automatic comm~n~l~
0 are stored in a memory and complex maneuvers are performed without direct contact with the ground station.
The first step in providing automatic control for the drone aircraft is creating a memory which contains position information for performing the desired maneuvers. In the preferred embodiment of the invention, the drone aircraft 30 is provided with an 5 electronic nonvolatile memory. Stored in the memory is four--limton.~ional (4-D) location and time data for the aircraft within a known reference frame. In the pler~ d embodiment of the invention, the four dimensions are lonEit~l~le, latitude, altitude, and time. If it is so desired, time can be replaced with velocity.
The system for generating the 4-D data for the drone aircraft is shown in detail20 in Fig. 3. The 4-D data for the drone aircraft is established with the position estim~tor.
In the ~lcfclled embodiment of the invention, as shown in Fig. 2, GPS is used for this purpose. Although GPS is used in the plcr~ d embodiment, it is conceivable that other systems, such as inertial guidance, Doppler radar, or other position estimators, may be employed to generate 4-D data for the aircraft. The position estim~tor is connected to 25 memory bank 36 through a series of switches and sampling devices such as the zero order hold (ZOH) devices 34. The switches are closed at a predetermined or adaptive sampling rate in order to fully reconstruct the mission. The ZOH devices 34 m~int~in the value of the incoming signals after the switches have been opened. In one embodiment, the 4-D data is stored in a non-volatile memory onboard the aircraft. In 30 another embodiment of the invention, the 4-D data is downloaded to the ground station which records the 4-D data in real time.

In order to create the desired mission in memory, a pilot will take the drone aircraft on a rehearsal flight. As needed, the pilot will take the craft through a series of preplanned maneuvers. During these maneuvers, the 4-D signals from the position estimator signals are sampled at a predetemmined or adaptive rate and the signals are s stored in memory 36. An adaptive rate means that the sampling rate can be changed depending on the complexity of the maneuver (i.e., more sampling would be needed for a tum and roll maneuver than simply flying in a straight line). Once the rehearsal mission is complete, the 4-D data stored in memory can be used in a drone aircraft.
The system configuration for the drone aircraft is shown in Fig. 4. Included in 0 the system is the position estimator 32, memory 36, and 4-D guidance and control 40.
The position estimator 32 is the same unit described above for the rehearsal mission.
The position estim~tor 32 also outputs 4-D data for the drone aircraft during its nm~nn~d missions. The memory 36, as described above, contains 4-D data for the aircraft generated during the rehearsal mission. The 4-D data for the automatic maneuvers to be perfommed are associated with particular mission waypoints. The position estimator 32 outputs actual 4-D data for the drone aircraft which is subtracted from the 4-D data output from memory 36. A link is also provided between the actual time output by the position çstim~tQr and the recorded time in memory so that the two sources of 4-D infommation are syncl~o~ ed. This synchronization is necessary because the automatic mission in most cases will not occur at the same time of day as the rehearsal mission was recorded. If desired, the position data can also be synchronized to the initial position of the automatic maneuver, such that the difference between each incremlont~l waypoint during automatic flight is added to the current position. This provides for perfomming a particular sequence of maneuvers at locations other than where they were pclro,l,led. The error signals generated from the subtraction of the 4-D
signals are then fed into the 4-D guidance and control computer 40, which has software commonly known in the industry, which converts the magnitude of the error signals into control signals which provide direction, ~ttitl-~le, and speed control for the drone aircraft.
During a drone mission in which the learning autopilot is employed, the drone isfirst remotely piloted to the first preprogrammed mission waypoint which was established during the rehearsal mission. Once the waypoint is reached, the automatic guidance is engaged and automatic flight begins. While in the automatic mode, the memory 36 outputs 4-D (waypoint) information which is 1 time increment ahead of the previous 4-D (waypoint) information output by the memory bank 36. The differencebetween the current waypoint and the current output of the position estimator 32, will 5 always exist between the two signals, which acts to lead the drone aircraft through the desired maneuvers. The magnitudes of the error signals are proportional to the difference between the monitored location of the aircraft and the desired location. As was described above, these error signals are then converted into control comm~n(l~ for the drone aircraft. From the continual comparisons made between the stored 4-D
0 (waypoint) information and the actual 4-D information, the drone aircraft is able to complete the programmed maneuvers almost exactly as they were performed during the rehearsal mission. After the maneuvers are complete, the drone aircraft will reach a preprogrammed waypoint at which ground control will be reestablished and the drone aircraft will be flown back to its starting point.
An alternate embodiment of the invention is shown in Figs. 5 and 6. In this embodiment, the 4-D (waypoint) information which was previously gathered throughGPS or other means, is replaced by a system in which pilot movements of the aircraft control mech~ni~m~ are monitored over time. Using the system shown in Fig. 5, the vehicle control detector system 50 detects the pilot's movement of the control stick 20 during a rehearsal mission and these movements are recorded in memory 36 in relation to the mission time. As shown in Fig. 5 these movements are associated with pitch, roll, yaw, and throttle control movements of the aircraft.
The drone control system for the drone aircraft is shown in Fig. 6. In this system, the signals output from memory 36 are compared to the actual movements of 2s the control me~h~ni~m~ to generate a series of error signals which are transmitted to the control system 60. Once again, means are provided to synchronize the recorded movement times and actual time. The control system 60 converts the error signals to control signals for the aircraft.
During the automatic operation, the drone aircraft is flown to a predetermined 30 waypoint where the autopilot is then engaged. The stored pilot movement information is then output and the preprogrammed maneuvers are begun. As in the preferred embodiment, the recorded pilot control movement information is output l time . ~ . ~ . .

increment ahead of the previous output of the memory bank 36. The dift'erence between the current pilot control reference and the actual position of the aircraft controls, acts to lead the drone aircraft through the maneuver. Once the desired maneuvers are complete, ground control is reestablished and the drone aircraft is returned.
In the embo~1im~nt~ described above, the recorded tlight int'ormation becomes a permanent record and can be used indefinitely. The recorded flight data does not necessarily have to be used with the aircraft used in the rehearsal tlight. This information recorded in memory can be used in other aircraft which have similar size and performance. If one particular rehearsed mission is t'ound to be particularly effective, it can be stored over time and can be used over and over again in a lirnited variety of aircra~.

G~D S~

Claims

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. An apparatus for providing automatic control of a vehicle comprising:
a global positioning system (GPS) mounted on the vehicle which generates 4 dimensional (4-D) information of longitude, latitude, altitude, and time information memory means (36) with stored position information for the vehicle, where the stored information is created by operating the vehicle on a rehearsal mission, and in conjunction with the means for providing the vehicle position information, identifying the position of the vehicle and storing the vehicle position information during the rehearsal mission in said memory means at predetermined intervals;
means for comparing the stored vehicle position information from the rehearsal mission with actual position information from said means for providingvehicle position information during automatic operation of the vehicle and generating a plurality of error signals, each of the error signals has a magnitude proportional to the difference between the stored vehicle position information and actual vehicle position information; and vehicle control means (40) which receives the plurality of error signals from said means for comparing and converts the error signals to control signals whichcontrol the movements of the vehicle, where the vehicle moves according to the vehicle position information stored in the memory means.

2. The apparatus for providing automatic control of a vehicle of claim 1 whereinthe vehicle is an aircraft.

3. The apparatus for providing automatic control of a vehicle of claim 1 whereinthe time of the vehicle is replaced by velocity of the vehicle.

4. The apparatus for providing automatic control of a vehicle of claim 1 whereinoperator movements of control surfaces of the vehicle are measured and stored during the rehearsal mission instead of the vehicle position, and said movements are compared against actual control surface movements during automatic operation of the vehicle.

5. The apparatus for providing automatic control of a vehicle of claim 1 whereinthe memory means (36) is a non-volatile memory.

6. The apparatus for providing automatic control of a vehicle of claim 5 whereinthe vehicle position information is downlinked to a ground station (20) for storage in real time.

7. The apparatus for providing automatic control of a vehicle of claim 2 whereinthe vehicle is a helicopter.

8. A method of providing automatic control of a vehicle comprising the steps of;providing a global positioning system (GPS) mounted on the vehicle which generates 4 dimensional (4-D) information of longitudes, latitude, altitude, and time information;
manually operating the vehicle on a rehearsal mission according to a predetermined plan;
recording the position information during the rehearsal mission for the vehicle in a memory (36) at predetermined intervals;
during automatic operation of the vehicle, generating a plurality error signals which are proportional to the difference between the recorded position information from the rehearsal mission and actual position information for the vehicle; and converting said error signals into control signals which provide for automatic operation of the vehicle.

9. The method of providing automatic control of a vehicle of claim 8 wherein thevehicle is an aircraft.

10. The method of providing automatic control of a vehicle of claim 9 wherein the vehicle is a helicopter.

11. The method of providing automatic control of a vehicle of claim 9 wherein the vehicle is a land vehicle.

12. The method of providing automatic control of a vehicle of claim 8 wherein the vehicle is a water-going vessel.

13. The method of providing automatic control of a vehicle of claim 8 wherein velocity is included in the 4-D position.

14. The method of providing automatic control of a vehicle of claim 8 wherein the vehicle position information is replace with measured movements of the vehicle controls by the pilot at the predetermined intervals.

15. The method of providing automatic control of a vehicle of claim 8 wherein the predetermined interval is adaptive depending on the type of maneuver the vehicle is making.

16. The method of providing automatic control of a vehicle of claim 12 wherein maneuvers performed during the automatic operation of the vehicle are performed at a different absolute time from maneuvers in the recorded data, with elapsed time of the recorded maneuvers remaining the same.