The Yamaha Rmax
Early pictures of avionics enclosure
Hardware block
diagram
In parallel with waiting for sensor items and parts, the avionics enclosure was starting to take shape around October 2001. The payload of the Rmax is around 45 kg. This allowed the design of the box to be made flexible enough to replace sensors and add sensor / computer modules to the platform. The mass of the final avionics box was around 15 kg.
Some of our earliest tests involved tuning the navigation system. Much of this work was performed on the back of a truck where the avionics box and all sensor antennae were mounted and driven around campus correcting and tuning the nav filter.
Nav tests with truck. This is in the
YMCA parking lot behind the Aerospace building.
The control systems and navigation filter were developed and tested using an in-house simulation tool called Esim.
Simulation Tool
Simulation was used extensively from testing the navigation, control to developing device drivers and use as a ground station. Some details of the simulation tool and how it was used used may be found in \cite{johnson:mst:02}.
Navigation and Control Interaction
The helicopter uses an adaptive controller based on feedback linearization and is documented in \cite{kannan:gnc:02, kannan:dasc:02}. Some of the many uses of simulation and configurations are shown below.
Single
Computer full simulation including model, nav, control and ground
station. Usual configuration during development and testing
This
configuration is where all flight code runs on actual hardware but
sensors
are simulated. The flight computer thinks it is in the air.
This configuration shows testing where
all sensors are turned on and the flight
computer is talking to actual sensors. In the lab however, GPS is
unavailable
and hence only that signal is emulated and sent to the flight computer.
This has
the disadvantage that one may not fly maneuvers but it does test all
the sensor
drivers, and nav filter. Hence, the flight computer thinks it is
sitting still.
This configuration is the closest one comes to flight in the lab.
The original goal was to use the fast Texas Instruments DSP board and daughter card for Image Processing. In fact many of the algorithms actually worked very well. However, the TI boards interface for communication was quite cumbersome. The only truly supported interface was via the Parallel Port to Windows. Although talking via parallel port to a Linux Machine was partially achieved, in part due to an open source for BSD driver. If used, the communication path to the TI board would have become to cumbersome. TI:BSD driver:Wireless ethernet packet and finally to Ground station. We hope to master the TI board interface soon.
The final decision for aerial robotics, was to use an open source library called OpenCV from Intel. It provided many image processing primitives and runs on NT and Linux. Most of the image processing was developed on Windows but during the latter stages it was tested and run primarily on Linux. The secondary computer acted as the Image Processing system with a minimal installation of Redhat 7.3 on a 512MB flash disk. A video server from www.axis.com was used to take analog camera input and ftp images at 5Hz to a ramdisk on the secondary flight computer (linux).
Overview
of the vision system.
The vision system consisted of two parts, the image processing and tracker. The image processing was deliberately kept simple and acted on one image at any given instant. The image processor picked the best candidate for a building (rectangle) and iarc symbol, scored them and passed their location onto the tracker. The tracker kept a record of events happening temporally and kept track of confidences of building, window and symbol locations. At any given instant, the tracker, knowing the position and attitude of the helicopter and camera can estimate the expected size of the window and building. This information is then used by the image processor to pick rectangles that best matched the area criteria.
Overview of the image processing test.
A
sample of the onboard video (about 16 MB)
The image processing was tested in the lab using playback of onboard video, whereas the tracking algorithm was tested using simulated images.
Tracker
test setup
Testing the tracker in the lab
Flight configuration
The final flight configuration was essentially a small change from the hardware in the loop simulations in the lab.
| f020329e_alltest1.mpg | First loop closure (all loops) |
| f020410c_altitude.mpg | Altitude Step, rare pilot complement. The safety pilot is now redundant. |
| f020410c_firstHover.mpg | First hover |
| f020705d3_40fps10fps2.mpg | High speed dash at 40ft/s and 10 ft/s2 |
| f020705d6_racetrackPart1.mpg | Race track maneuver |
| f020714c1_pullaway.mpg | Pullaway to start Level 1 maneuver |
| f020725_hover.mpg | Hover, parked while we decide next maneuver |
| f020725_map.mpg | Heli investigates the truck then climbs and parks |
| f020725_mission.mpg | Heli goes from hover to start point and makes a turn to start searching for buildings |
| Calgary Movies | |
| f020730_hover.mpg | Long boring hover |
| f020730_hover2.mpg | Another long boring hover |
| f020730_turn.mpg | 180 degree turn |
| f020731_mission.mpg | Level 2 mission on sunny |
| f020731_turnon.mpg | Pilot is having problems with wind, the autopilot is turned on and it handles wind very well |
| f020731_windy.mpg | Wind gets much stronger, struggling to hold position and the controller does a very good job |
| f020801_mission1.mpg | Competition day mission last attempt in the hour. Heli has already found the 3 buildings and is descending towards them. Notice the helicopter automatically turns midway during descent to keep its point of interest in view |
| f020801_mission2.mpg | Round and round. Fuel Low |
| f020801_mission3.mpg | and round and round |
| f020801_mission4.mpg | Notice the fuel low light, Jeong does not do his usual crowd fly by before landing |
Calgary Olympic Park,
Calgary,
Canada.
August 2, 2002.
Sent: Friday, August 02, 2002 3:59 PM
Subject: Results from the Aerial Robotics Competition
All,
This is a brief summary of the Georgia Tech experience at the 2002
International Aerial Robotics Competition in Calgary, Alberta.
The first major event was a chance to create new case law for the import/export
of UAVs - obviously not one of our goals. By sheer chance, we got a U.S. customs
inspector who had just become a "specialist in UAVs" and detained our vehicle
at the border. After a massive effort by Gary Wolovick, Dan Schrage,
Robert Michelson, the team, and many others we received word from the State Department that
we were free to go and legal (as in we had done nothing wrong, although they
recommended that we seek prior approval next time) 28 hours after it was detained.
To my knowledge, this is a new requirement for this class of vehicle,
and it appears to be at least partially due to 9/11 that this occurred.
The team caught up fast, actually getting in a few practice flights the
same day the vehicle was released. The following day was "static judging",
which is used to prioritize flight times for contest day. Georgia Tech was fourth,
which was good enough to allow the team to pick its favorite time slot:first, 7am.
Practice flights that afternoon included flight in windy and gusty conditions,
and the vehicle performed beautifully. Discovery channel was filming these
flights, so look for this in the future.
Contest day: The GTMax was in the air for virtually the entire 1 hour of
Georgia Tech's allotted time (because a mission attempt can start
and end in the air). The team's goal
was to achieve the Level 2 mission, which includes
locating a particular building in a group of three buildings, and then
locating at least one entry point in that building. This must be done with a
completely automated air vehicle and image processing system.
The bad news for everyone was that there were a number of emitters at the
site (radio stations and other functions) which led to degraded
GPS and datalink performance. Loss of GPS signal and
datalinks led to at least 6 aborted mission attempts. Three of the attempts
proceeded far enough to successfully automatically locate all three buildings.
Two of the attempts proceeded far enough for the vehicle to descend and circle
the buildings, obtaining "close up" pictures of
the windows and identifying the correct building. Just to keep things dramatic,
it was on the final attempt during the allotted time that the GPS and datalinks
held out long enough to map all three buildings. .and just to make it extra
dramatic the low fuel light came on while mapping that last building.
After several hours of looking at the data produced during the two mission
attempts that included results for entry points, the following was determined:
On the first, the mission was aborted (due to GPS on that one) before the
vehicle got to even try to map the correct building. On the one mission attempt
that got to map all three buildings, the correct building
was identified based on a specified symbol (about 1 meter in diameter) located
on the building. This building was only 12 feet from another building, and the
automated system unfortunately picked an entry point from this neighboring
building as its solution. In summary: The vehicle and autopilot flew great, the
buildings were located automatically several times, window mapping was quite
precise in position, but due to GPS and datalink dropouts only one full mission
attempt was completed - and due to a stroke of bad luck it picked a window from
a building 12 feet away.
Additional completed mission attempts almost certainly would have made it.
Due to the interference problems mentioned above, no other team did any
notable flight attempts on the contest day. Most didn't leave the ground
because they couldn't use their GPS and/or their manual control links were not
achieving enough range.
Although we didn't get Level 2, we did achieve plenty - in fact, far more
than enough to finish in first place for the second year in a row.
Thank you to all of you for supporting the team, including our
sponsors:
Lockheed Martin, NovAtel, Bahr Avionics, Texas Instruments and Guided Systems Technologies
Here are some pictures of the team after the competition and of Alison and Mike on their return trip.
Sumit and the Royal canadian mounted police.
Jeong doing his flyby
Early morning, competition day
Yet another heli pic
Henrik, Suresh and Jeong at Banff
The only tree in Kansas
Alison and Mike on detour to Mount Rushmore on their way back with the truck
Protecting our one and only safety pilot