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'[PICLIST] Autonomous Aircraft Project'
2000\11\02@012332 by matt.currie

picon face
Hello List,


   This is my first post.  I have been following the discussions over
the last week or so and felt I should introduce myself and my project.
I am currently in a promising stage of an autonomous aircraft.  I have
been an avid R/C Pilot for the last couple years while spending time
with robotics, electronics, and information technology.  With the
removal of SA from the GPS signals, I realized a dream.  My plan was to
build an airplane that could, once airborne, be switched into autonomous
mode and fly to determined way points via a laptop and radio link.  Once
at the point, the plane could do any number of tasks including taking 35
mm photos.

   Without getting into too much detail I will try and explain where I
am at this point.  Over the last couple of weeks I have developed an
entire guidance system consisting of a PIC16F877 with a serial
bootloader.  A modified version of the Mini-SSC is interfaced to a
software created serial port.  A 16x2 Character LCD display shows
debugging information.  I reused the same serial interface for the
bootloader to communicate with a PC, which will simply be replaced with
a TTL lever radio transceiver when time and funding permit.  I have
successfully interfaced analogue sensors to the 10-bit A/D converters
and an oscilloscope to one of the PWM channels.  A third serial port is
awaiting a GPS receiver.  The code is laid out via an interrupt that
will take the GPS information as a stream and parse it into separate
chunks of data.  I hope to get away from polling methods and use the
interrupt capabilities of the 877 to create a somewhat efficient
multitasking environment.

   Sensory will consist of a GPS Receiver (Pos., Heading, Altitude,
Ground Speed), Peizo Rate Gyros for 3-axis of attitude, and other
minimal but equally important actuators.

   Hopefully one can picture where I am!  I will be using one of my
model airplanes as a test-bed for the current prototype.  I currently
have 6 control surfaces moving under software control.  It is hard for
me to actually believe that I am so close to my goal.  All this in the
spare time I can find between a ~30 hour/week job and Grade 12 courses
;p

I will be glad to hear any comments, ideas, maybe even some criticism ;)

I also threw up a quick page during class today at:
http://project.complexminds.com


Yours,
Matt Currie
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2000\11\02@013820 by Sean H. Breheny

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Hi Matt,

Wow! I have to say it again, Wow! Matt, that is amazing. I am a senior in
EE at Cornell University and the team leader for a roughly similar project,
except that it is a helicopter and uses a computer vision system instead of
GPS (although we looked into GPS). We have spent more than ten times your
projected total cost already, and have 5 team members plus an advisor with
a PhD in control systems. With all this, we are only a little ahead of you! :-)

Please keep us updated, I'm very interested.

Sean

At 10:22 PM 11/1/00 -0800, Matt Currie wrote:
{Quote hidden}

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2000\11\02@014650 by matt.currie

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Sean,

   Thanks for that shot of motivation ;)  I can't stress enough how serious I am
about this project.  I literally have almost everything minus the more expensive
equipment like GPS receiver ( I am debating a Differential input ) and laptop. In
the meantime I use my small network I setup with a couple of computers.  I just
picked up a 1800mAh NiMh pack that weighs as much as a 500mAh would, this will run
my control surfaces for about 10 solid hours!  I am awaiting my Warp-13 programmer
so I can return my Picstart Plus to the lender.  I just interfaced my friend's
grandpa's GPS receiver to his laptop for marine purposes so I even have that under
my belt.


Matt Currie
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"Sean H. Breheny" wrote:

{Quote hidden}

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2000\11\02@022649 by Russell McMahon

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I also am interested in making an autonomous model aircraft (as I have noted
on PICList at various times in the past) and while I have done lots of
thinking about it I have done no practical work thereon whatsoever.

1.    I assume that you (Matt) are aware of the magnificent Australian
autonomous meteorological craft (Aerosonde?)
Their website has much description of capability and some wonderful photos.

2.    You may not be aware of a 1995/96 vintage effort by a Stanford
university student which used differential GPS, 3 rate gyros (to allow
temporary loss of GPS signal) true autonomous control, auto landing and
more. Details below. Locating and talking to this man may be useful. His
positional accuracy of 0.5 meters over a 1km course should be adequate for
most purposes.

It seems likely that others have done or are doing this as the usefulness
and fun involved are manifest but there is little else useful that I could
find on the web.




Russell McMahon

_____________________________________________


One or other of the following should lead you to the site.
If you can't find it ask me and I'll look further.

       http://aero.stanford.edu/adg.html#StdAtm.html

Possibly

http://www.stanford.edu/news/gif/snewshd.gif
http://www.stanford.edu/group/GPS/
http://www.stanford.edu/news/gif/news.home.gif
http://www.stanford.edu/news/gif/help.gif
http://www.stanford.edu/news/gif/b_currel.gif
http://www.stanford.edu/news/gif/search.gif


____________________________________________


1/16/96

CONTACT: Stanford University News Service (415) 723-2558
COMMENT: Paul Montgomery, Aeronautics/Astronautics (415) 322-1946
Prof. Brad Parkinson, Aeronautics/Astronautics (415) 725-4105

Model aircraft flies by itself using satellite navigation sensors

STANFORD -- Using a 12-foot model, doctoral student Paul Montgomery has
shown that an aircraft can take off, fly a specified course and land
automatically without relying on hundreds of thousands of dollars of
sophisticated equipment.

It took him more than three-and-a-half years, but the Stanford aeronautics
and astronautics student has managed to fully control a model aircraft using
only the guts of a typical laptop computer, simple onboard wind speed and
direction indicators, and receivers that track signals from Global
Positioning System (GPS) navigation satellites - equipment that costs a few
thousand dollars.

Low-cost automatically piloted aircraft might replace manned aircraft for
purposes such as aerial photography, crop spraying and police surveillance.
They also could be used in place of weather balloons for gathering
meteorological data: Unlike weather balloons, they would not be restricted
to certain altitudes. There are also a number of potential military
applications.

"Paul has shown marvelous innovation in providing a very inexpensive
solution," said Bradford W. Parkinson, the Edward C. Wells Professor of
Aeronautics and Astronautics and Montgomery's adviser. "His results are
startling, in the sense that he has shown the ability to perform precise
control to better than a meter. This is noteworthy because it represents the
next wave of GPS - accurate control using navigation satellites."

Montgomery's research is just one facet of a large program at Stanford
designed to develop new GPS applications. Research at the GPS Laboratory,
which comprises three faculty members and 22 students, includes efforts to
develop a satellite-based, all-weather automatic landing system for
commercial aircraft; a GPS-based system that can provide a regional or
wide-area aircraft navigation and landing system; a pseudo-GPS system for
robot navigation on the factory floor; and an auto-pilot for farm tractors
based on satellite navigation.

Although the GPS-controlled aircraft has been Montgomery's project, he
received substantial assistance from Hiro Uematsu, an engineering research
associate at Stanford's Gravity Probe B project, and Andrew Conway, who
recently received his doctorate from Stanford's aeronautics and astronautics
department.

The first successful autonomous flight of the model aircraft took place on
Nov. 27 at a special airfield for radio-controlled aircraft in Fremont,
Calif. On that day and in subsequent flights, Montgomery showed that a
technique called carrier differential GPS can provide the position
information needed to control an aircraft with extreme precision. (Carrier
differential GPS uses a signal from a ground station at a known location to
increase the accuracy of the position that can be determined from the
satellite signals.)

Before a flight, Montgomery programs into a laptop computer the path that he
wants the aircraft to follow. This information then is downloaded into the
airplane's onboard computer. After placing the plane on the runway and
starting the engine, he pushes a single button, the aircraft takes off,
flies the preprogrammed course and then lands all by itself.

Averaged over a kilometer course, the deviation in the aircraft's position
from the programmed course was typically less than 0.5 meter horizontally,
0.25 meter vertically and 0.25 meters per second in air speed, Montgomery
reported.

"Carrier differential GPS is accurate enough for most purposes, so you don't
need a lot of expensive equipment," he said.

One of the biggest problems in using satellite navigation for this purpose
is that as the plane banks and turns it can lose temporarily the signals
from some of the satellites. Normally, six GPS satellites are in view at one
time. A minimum of four is required to calculate the aircraft's position
with the degree of precision needed to control it. To guard against falling
below this number, test flights were made during periods when the maximum
number of satellites was visible.

To address the problem of signal loss, Montgomery also equipped the small
aircraft with a set of three inexpensive gyros that cost about $400. This
kind of gyro normally is used for purposes such as stabilizing camera
mounts. But Montgomery used them to keep track of the aircraft's attitude
after it lost the GPS signal.

To test how well the gyros worked, Montgomery used the aircraft's remote
control to perform a series of barrel rolls. In this maneuver the plane
rotates through 360 degrees as if it were moving along the surface of a
rotating cylinder. During this maneuver, the airplane typically lost GPS
signal lock for five or six seconds. During these outages the gyros kept
track of the airplane's attitude with sufficient accuracy so that when the
GPS signals were reacquired the airplane's attitude could be reestablished
without going through a prolonged period of computation.

"The gyros are complementary to the GPS. They are fast acting but have the
problem of drift, while GPS is slower acting but does not drift," Montgomery
said. "Much of the cost in making precision gyros comes from reducing drift.
But if you use GPS information to continually calibrate the gyros, then
drift isn't a big problem for the brief periods when the GPS signal is lost.
That's why you can use low-cost gyros."

The system that he has developed lacks the "robustness" required for
commercial applications, Montgomery said. But his work indicates that a
system that combines inexpensive inertial instruments and GPS could have the
added reliability that is needed.




Paul Montgomery with model airplane




Model plane on runway

-dfs-

960116gpsplane.html



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2000\11\02@023516 by Jan Lund

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Hi Matt.

> plan was to build an airplane that could, once airborne, be switched into
> autonomous mode and fly to determined way points via a laptop and radio

Cool project!!!

>     Sensory will consist of a GPS Receiver (Pos., Heading, Altitude,
I guess you mean Course instead of heading. Due to factors like wind
currents, the airplane won't necesarily point in the direction it is flying.
In order to get the heading, you need a compass.

Have you done any tests with your track controller yet ?
I don't know if the same factors applies for planes as it does for ships,
but in order to steer a ship correctly you need a PID controller, where :

The P-element controls the proportional amplitude of the "rudder" (ie. how
much rudder you need to apply to make a "n"-degrees turn),

The "I" controls the integral part (such as compensating for wind and water
currents - a ship (container vessels and oil tankers) will sail up towards
the wind because of the wind pressure on the steering house), and

The "D"-part controls the differential part (such as taking the rudder back
towards zero and to compensate for overshoot when making a turn - ships does
not stop to turn just because you turn the rudder back to zero position, so
an auto pilot will actually apply counter rudder in order to stop the
turning in time)

The thing is that each type of ship has its own characteristics which means
you have to adjust the PID controller for every type of ship you put the
controller on.

The goal of the controller adjustment is to get the most correct steering,
but without using too much rudder, since that increases fuel consumption.

Another adjustment seen on autopilots and tracking systems is the weather
control (no it does not control the weather ;-) but controls if the steering
should bee loose or tight (ie. how much are you allowed to get "off course"
before you compensate). Generally you would use loose steering in bad
weather because you will have bad heading signal due to yaw and pitch.

Another thing is the speed control. It has influence on the PID contoller
since the characteristics of the steering changes with speed. The ships
turns faster with increasing speed, and it also uses a larger turn radius,
since it tends to "slide" through the water.

And last (but not least) the turn rate control (how fast are you allowed to
turn - before dropping containers into the sea - but i guess that this does
not apply for planes ;-) (normally you can choose to use either turn rate or
turn radius limitations in tracking systems)

> I will be glad to hear any comments, ideas, maybe even some
> criticism ;)
As i said when i started - i don't know if it is the same that applies to
planes, but now you got some input.

And keep us posted. It is a very interresting project.

Rgds
Jan

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2000\11\02@110103 by matt.currie

picon face
I apologize for posting this again but I originally omitted the proper
[EE] tag, which means many would have missed it due to
software/subscription filters.

Hello List,


   This is my first post.  I have been following the discussions over
the last week or so and felt I should introduce myself and my project. I
am currently in a promising stage of an autonomous aircraft.  I have
been an avid R/C Pilot for the last couple years while spending time
with robotics, electronics, and information technology.  With the
removal of SA from the GPS signals, I realized a dream.  My plan was to
build an airplane that could, once airborne, be switched into autonomous
mode and fly to determined way points via a laptop and radio link.  Once
at the point, the plane could do any number of tasks including taking 35
mm photos.

   Without getting into too much detail I will try and explain where I
am at this point.  Over the last couple of weeks I have developed an
entire guidance system consisting of a PIC16F877 with a serial
bootloader.  A modified version of the Mini-SSC is interfaced to a
software created serial port.  A 16x2 Character LCD display shows
debugging information.  I reused the same serial interface for the
bootloader to communicate with a PC, which will simply be replaced with
a TTL lever radio transceiver when time and funding permit.  I have
successfully interfaced analogue sensors to the 10-bit A/D converters
and an oscilloscope to one of the PWM channels.  A third serial port is
awaiting a GPS receiver.  The code is laid out via an interrupt that
will take the GPS information as a stream and parse it into separate
chunks of data.  I hope to get away from polling methods and use the
interrupt capabilities of the 877 to create a somewhat efficient
multitasking environment.

   Sensory will consist of a GPS Receiver (Pos., Heading, Altitude,
Ground Speed), Peizo Rate Gyros for 3-axis of attitude, and other
minimal but equally important actuators.

   Hopefully one can picture where I am!  I will be using one of my
model airplanes as a test-bed for the current prototype.  I currently
have 6 control surfaces moving under software control.  It is hard for
me to actually believe that I am so close to my goal.  All this in the
spare time I can find between a ~30 hour/week job and Grade 12 courses
;p

I will be glad to hear any comments, ideas, maybe even some criticism ;)

I also threw up a quick page during class today at:
http://project.complexminds.com


Yours,
Matt Currie
RemoveMEmatt.curriespamTakeThisOuThome.com

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2000\11\02@114029 by Dan Michaels

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Sean Breheny wrote:
..........
>except that it is a helicopter and uses a computer vision system instead of
>GPS (although we looked into GPS). We have spent more than ten times your
>projected total cost already, and have 5 team members plus an advisor with
>a PhD in control systems. With all this, we are only a little ahead of you! :-)
>


Hi Sean, just curious. Are you guys by any chance using fuzzy
logic in your helicopter's control system? I understand one
Japanese lab did this with good success.

- dan michaels

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2000\11\02@114642 by James R. Cunningham

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Jan Lund wrote:

> Cool project!!!

It sure is !  I've added some additional comments (you guys probably already
know all of this, but what the heck).

> >     Sensory will consist of a GPS Receiver (Pos., Heading, Altitude,
> I guess you mean Course instead of heading. Due to factors like wind
> currents, the airplane won't necesarily point in the direction it is flying.
> In order to get the heading, you need a compass.

For an aircraft, track and course will suffice.  you don't actually need to know
the yaw angle, so you can get by without the heading (though it would be a nice
thing to have).

> but in order to steer a ship correctly you need a PID controller, where :

It's needed for aircraft too.

> The P-element controls the proportional amplitude of the "rudder" (ie. how
> much rudder you need to apply to make a "n"-degrees turn),

In aircraft, you use the ailerons to establish a turn rather than the rudder
(the rudder is mostly used only for coordinating the turn (slip vs. skid)).
Once the turn is established at the desired rate, the controls are neutralized
and then opposite control is used to stop the turn.

> The "D"-part controls the differential part (such as taking the rudder back
> towards zero and to compensate for overshoot when making a turn - ships does
> not stop to turn just because you turn the rudder back to zero position, so
> an auto pilot will actually apply counter rudder in order to stop the
> turning in time)

In aircraft, ailerons mostly, but same procedure.

> The thing is that each type of ship has its own characteristics which means
> you have to adjust the PID controller for every type of ship you put the
> controller on.

Same.

> The goal of the controller adjustment is to get the most correct steering,
> but without using too much rudder, since that increases fuel consumption.

Not too much of a factor for aircraft -- the controls are constantly working
anyway.

> Another thing is the speed control. It has influence on the PID contoller
> since the characteristics of the steering changes with speed. The ships
> turns faster with increasing speed, and it also uses a larger turn radius,
> since it tends to "slide" through the water.

I would suggest making normal turns at either standard rate, or half standard
rate.  I'd let the throttle control altitude, and the elevators control airspeed
(do it the other way, and the plane will stall rather than glide if the engine
quits).

> And last (but not least) the turn rate control (how fast are you allowed to
> turn - before dropping containers into the sea - but i guess that this does
> not apply for planes ;-) (normally you can choose to use either turn rate or
> turn radius limitations in tracking systems)

It is pertinent.  Again, I'd suggest either standard or half-standard rate.

> And keep us posted. It is a very interresting project.

It sure is.  As some of you know, I'm plugging away on a design for a full-scale
flying 'Quetzalcoatlus species',  which functions as a powered (by flapping)
motorglider, and am slowly plugging away at some of the same problems.

I wish you well in you project, Matt, and apologize if my comments are too
simple to be of interest.

Jim Cunningham

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2000\11\02@123500 by Andrew Kunz

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>In aircraft, you use the ailerons to establish a turn rather than the rudder
>(the rudder is mostly used only for coordinating the turn (slip vs. skid)).
>Once the turn is established at the desired rate, the controls are neutralized
>and then opposite control is used to stop the turn.

Use of a rate gyro on rudder makes for nicely-coordinated turns.  A lot of the
"pro" contestants use this for their giant-scale planes.  Rudder is only needed
by the pilot on the ground, the rest of the time he leaves the stick in neutral
and lets the gyro fly it.

Andy

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