We arrived in Brisbane on the morning of Friday September 19th after 18 hours of flying and traveling 8000+ miles.  We picked up our rental car, and with maps in hand (or on the laptop), we headed for a hobby shop to pick up some glow fuel and landing gear wheels.  At the hobby shop (Hobbyrama) they were even kind enough to let us borrow one of their 36MHz RC transmitter/receiver pairs since we could not use our 72MHz system for our failsafe.  We then headed off to Kingaroy where the competition would take place.

The view out the window of the Boeing 747-400 of the sunrise over the Pacific Ocean

After 2.5 hours of driving we arrived at our destination, Kingaroy, the peanut capital of Australia.  We checked into our hotel and drove over to the airport to get an idea for the competition site.  We then proceeded to rebuild the airplane in our hotel room, as we had to remove the engine and the empennage in order to fit it into crates.
Bright and early Monday morning we arrived at the competition site and unloaded our gear into one of the event tents.  We also had our oral presentation that morning where we discussed our design and gave an overview of our system as a whole.   The oral presentation went well and we also turned in our technical report and documentary to the judges.  The next order of business was to pass the safety inspection.  This included checking all control surface linkages, equipment mounting, structural integrity of the airframe, etc. That afternoon we were also able to perform an engine run to ensure that everything was reassembled correctly, during this test we found an air leak in the fuel system, which was quickly corrected.

Our competition paddock

The first day of competition was a success, everything going smoothly.  The organizers did a great job of keeping everybody informed of what was going on and ensuring that we had everything that we needed.  The following day (Tuesday) was the high school Airborne Delivery Challenge.  We arrived early in the morning and powered on our UAV, which we had left in the tent overnight.  We quickly noticed that something was wrong, the onboard computer was acting flaky and the 2.4GHz WiFi card in the onboard computer did not want to function properly.  Much of the morning was spent trying to remedy that problem, trying everything we could possibly think of.  Eventually early in the afternoon everything was sorted out, the condensation on the components in the morning may have been the culprit, the lesson learned from that was to not leave our electronics outside overnight.

Troubleshooting the onboard computer on the UAV

It was impressive to see all of the aircraft that the high school students had built, all of them equipped with wireless video and many of them were also equipped with “co-pilot” wing levelers.  The level of enthusiasm was also impressive.  It was definitely interesting to watch the teams’ mission attempts, unfortunately many of the attempts resulted in crashes, with the 2.4GHz RC radios being the prime suspects. There was also one really close call with a helicopter that took off, and shortly after takeoff the pilot lost control and it flew up over the sponsor tent and curved around and crashed right by the grandstands, barely missing some spectators, it then thrashed around on the ground for a bit before finally dying.

By late afternoon we had our system up and running and were ready to perform our demonstration flights.  The winds were quite high that afternoon, around 10-13 MPH, and the grass around the paved runway was not as smooth as we would have liked (we prefer grass takeoffs since it’s easier on the propellers than tarmac in the event of a prop strike).  After a couple unsuccessful attempts we were able to get the UAV in the air under manual control, we then switched over to autopilot control and flew a few circuits and dropped the water bottle to demonstrate our system.  The autopilot was not navigating very well and was oscillating in pitch, this was probably due to the fact that we had only had two days before leaving for Australia to tune our control loops to the new airframe and some of the gains were off.  But the purpose of this flight was to demonstrate to the judges that we could perform safe manual and autonomous flight, which we did.

The third and final day of competition included the actual mission attempt at finding Outback Joe.  Early in the morning we gave Procerus a call and sent them a telemetry file to try and figure out why we were oscillating in pitch and why navigation performance was not very good.  After a short discussion the cause of the problem was identified and the judges allowed us to perform a second tuning flight before our actual mission attempt.  We went out to the field to set up our gear for our second flight and we started up the engine and it turned out to have trouble idling.  After about an hour of messing around with the low-speed idle and the high-speed needle we got it working reasonably well and got the UAV in the air.  But not without several failed attempts at taking off in the windy conditions.  Once the UAV was in the air, we quickly adjusted the parameters that needed to be modified and it then handled admirably, especially considering the amount of wind that it had to fight against.

Removing the wing from the UAV and preparing to refuel

The tuning flight lasted approximately 15 minutes and we brought the UAV down and prepared for the actual mission attempt.  This included filling up both of our fuel tanks and recharging the LiPo batteries for our electronics.  In the mean time Team Telemaster made their attempt at the mission.  They took off and began circling above, and appeared to be having trouble with their system, then all of a sudden the UAV started circling down, clearly the flight termination mode had engaged.  It was definitely disappointing to see their UAV circle down into the ground, fortunately for them; it was a relatively “soft” landing, with only minor damage to the airframe.

We were up next; we went out to the field and the clock started (we had an hour for our attempt at the mission).  We took our time to make sure everything was set up and configured correctly and started up the engine.  By this point in the afternoon the winds had picked up even more than earlier in the day, wind readings were about 12-15 knots steady, with gusts.  We taxied down the field and prepared for takeoff.  The engine revved up and the UAV started down the field parallel to the tarmac runway, the wind started to push the airplane on to the tarmac and then as the wind picked up a wing tip caught on the tarmac, and the airplane flipped over on it’s back.  We had had this happen on grass before so we ran over to flip it over and start it up again, but when we got there we knew something was wrong.  The fuselage was broken in two.  The judges deemed the damage too structural to attempt repairing it in the one hour allotted for the mission attempt.  It was over.  We were so close, had we gotten in the air, we would have almost certainly found Outback Joe.

The UAV after the crash

We ended up receiving second place overall, with Team Telemaster placing first, and QUT (Queensland University of Technology) placing third.  Overall the competition was definitely an excellent learning experience, and the camaraderie between the teams was excellent, we all helped each other out and offered up tools and help when needed.  The judges were also very helpful and understanding when we had issues, allowing us to resolve the issues and helping us in any way that they could.  The next competition should definitely be much more competitive, it was rather unfortunate that all three teams crashed this year, especially considering any one of the teams could have successfully completed the mission.

Accepting the prize

And now for some pictures after the competition:

Note: Sorry for the late update, I was really busy catching up with school after returning from the competition and then forgot to post an update…

Sig Kadet Senior before the crash.

On August 29th we were performing some long range testing with the UAV (Sig Kadet Senior) and everything appeared to be going smoothly.  It was navigating beautifully and maintaining altitude and airspeed very well.  When slowly the link quality started to decrease, it then lost the communication link, but not without the notification that it was “landing now.”  It ended up landing in a tree, which did not bode well for the UAV.
It turns out that the failsafes had been programmed incorrectly so instead of “flying home” it immediately tried to “Land Now” since the trigger time was set to 0 seconds instead of a couple minutes.  This was a rather unfortunate fact, and could have easily been avoided.  The decision then had to be made of whether or not to rebuild, with only 18 days left until we left for Australia.  If we were to rebuild we also had to decide whether or not to stick with the Sig Kadet, which was quickly ruled out due to the fact that the stock wing could not handle our payload.  So instead we selected an ARF Senior Telemaster, which had a much stronger stock wing and more spacious fuselage, this also meant that we needed to upgrade to a larger 1.20 O.S. Four-Stroke engine.

Remains of the Sig Kadet Senior

We scrambled to order the parts and to get the Telemaster together.  Fortunately all of the electronics survived the crash and we were able to get the Telemaster flying within a week.  Leaving a little more than a week to test the new airframe and UAV configuration.

The new Senior Telemaster UAV

Then to add even more to the drama, during early testing with the Telemaster, it was getting late and visibility was quickly diminishing so we decided to bring it in to land.  As the pilot came in for the approach, the airplane was much further out than expected and it dropped below the horizon and control was lost.  We feared for the worst, we expect the airplane to be in thousands of pieces, with no time for us to rebuild once again.  We quickly hopped in the car and tried to find it.  As we drove to the adjacent field we found the Telemaster sitting in the grass as pictured below (the wing was attached when we arrived, but was removed to inspect the internal damage):

Senior Telemaster after minor crash

This was probably the best crash we could have hopped for, one broken wheel hub, bent landing gear, and a few broken bulkheads inside the fuselage.  The repairs were quickly performed later that evening and we were back to testing within a day.

Note: This post has been backdated to reflect the order of actual events.

On May 10th we attempted our first bottle drop from 400 feet.  The bottle had an aluminum tab attached to it which was held by small servo at the center of gravity of the UAV.  We took off under manual control and gained altitude, as the UAV flew it’s oval path autonomously, the bottle was released over the field.  The first bottle we dropped was a 500mL Nalgene bottle, which failed miserably (see picture below).

With the water bottle attached, the flight characteristics were not affected, although takeoff distance was increased, the autopilot’s ability to control the UAV was not affected noticably.  During these flights the winds were relatively high, ranging from 10 to 15 MPH, which made navigation for the UAV difficult, but the autopilot performed admirably.  Though at times it was blown off the path, it returned quickly to the intended flight path.  Several autonomous test flights were performed in the windy conditions, further demonstrating the robustness of our UAV platform.

Three more test flights were performed on May 15th, all of which included water bottle drops with different bottle designs that took into account lessons learned from the first test.  Enclosures were developed for subsequent bottles that allowed them to survive the 400-foot drop.  Data was also gathered about where the bottles landed and at what point they were released.  With this data the theoretical and actual horizontal distance traveled were compared.  After analysis it turned out that the horizontal distance traveled from two of the drops was consistent, this allowed a simple model to be developed for the trajectory of the bottle.  During the final flight, aerial video of the bottle being released was also obtained from the onboard digital camera (see the video below).

These test flights provided valuable data about how the bottle’s trajectory is affected by the wind resistance, as well as about how the UAV platform handles moderate winds.  The next crucial step will be to integrate the onboard computer along with the camera into the aircraft to allow testing of the system as a whole.

I would like to thank all of our sponsors that have helped us get to this point, and will help us finish strong.  Our current list of sponsors includes IEEE, AESS, Boeing, Procerus, and Garmin.  We’re still a little short on funding for the year, but we’re almost there.  If you or your compnay may be interested in sponsoring our team in anyway (financially, with equipment, with publicity, etc.) please contact David Erdos at sponsors@aessuav.org for more information.  Also, check back next week for another update (we plan on doing some more testing early next week).

On Saturday (April 5th) we flew the airplane for the first time with the autopilot since it got the new wing.  But before we went out to the RC airfield we had to physically install the autopilot in the fuselage, which went well.  We then performed all of the flights necessary to tune the autopilot in HIL (Hardware In the Loop) simulation mode.

Using HIL simulation allowed us to all to get a better of idea of what we had to do once we got out to the airfield.  In the end performing the HIL simulation in the lab saved us a lot of time and allowed me to get more familiar with tuning the PID control loops for the autopilot.  Previously we had not used the PID window in Virtual Cockpit, but after using it in the HIL simulation it proved to be invaluable for properly tuning the autopilot, it allows you to see the actual, desired, and effort of a certain control parameter (i.e. pitch, roll, yaw, altitude, etc.).  Previously we had had issues seeing a change in the behavior from the ground after changing a certain PID gain.

On the first flight soon after takeoff the aircraft became unstable and began to become uncontrollable and began oscillating wildly, fortunately our pilot Kyle was able to get it back on the ground without any damage.  It turns out that our CG was too far aft, but after adjusting the CG we were able to continue with testing.  Using the PID window and the having performed the same process of tuning the autopilot in HIL mode, the first few flights went quickly and we were able to quickly tune the level 1 control loops within two 15-minute flights.  A graph of the autopilot’s roll performance is shown below, ideally the two lines should match, and they are in fact very close.

We then moved on to the level 2 control loops (i.e. pitch from airspeed, pitch from altitude, airspeed from throttle, etc.).  These were slightly more difficult, and took several passes over the airfield to complete, but we were able to get them tuned to a reasonable level.  The ability of the autopilot to maintain a constant altitude is shown below, there are slight oscillations in the altitude (+/- 3 meters), these are reasonable, but might be improved at a later time with more tuning.

Just as my laptop battery was about to give out we moved on to the final flight of the day.  The purpose of the final flight was to verify that the autopilot is able to navigate accurately and safely.  The first test was simply placing a loiter waypoint above the center of the RC airfield; although there were some oscillations in altitude, the overall performance was quite good (note the 4 m/s wind speed).

The final test was to create an oval over the airfield that the UAV would have to navigate.  The first time around the circuit the UAV did not adhere to the waypoints too strictly, but after adjusting some of the navigation parameters the performance was significantly improved (see image below).  After completing these flights the telemetry was reviewed and we were better able to analyze the performance of the autopilot and its navigation.

Overall the testing went well and we were able to tune the autopilot control loops better than we had previously been able to with the old wing, this is most likely due to our use the PID window and the HIL simulation which allowed our time at the airfield to be spent much more efficiently.

And now for some video of the flight and the telemetry from the navigation flights:

Sorry about the lack of updates, there are many new updates coming shortly so bear with us.  The first update being that we completed the new wing and completed the first flight with the new wing and it performed very well even in windy conditions.  Unfortunately there are no pictures of the actual flight but here are some pictures of the new wing on the airplane.  This new wing is significantly stronger allowing us to carry our large payload, it also has less drag allowing us to fly at greater speeds.

Although you can’t see from this picture the entire trailing edge consists of the control surfaces for the flaps and the ailerons, we plan on using the flaps during landing to allow us to land slower at slower speeds.

We have also been working on the onboard computer for the airplane, below are some pictures of it and the new enclosure that we had rapid prototyped out of polycarbonate on campus.  The onboard computer is a single-board-computer (SBC) with a 1.8GHz Pentium M processor, 1GB of RAM, and 4GB of flash running Ubuntu Linux.  This computer will handle all of the image acquisition and some or all of the image processing.

Since we have the UAV in flying condition again we will be slowly integrating the all of the electronics into the actual airframe and there should be more frequent updates now that we will be back in the testing/development phase.

We began construction of the new wing on Friday (January 25th) after all the ribs were waterjet. The new wing is build out of plywood and balsa and hardwood rib caps. So far it seems to be significantly stronger than our previous wing. Building a wing from scratch can be a rather tedious and time consuming process, in the last two days we have put in 20+ hours building the wing, and it’s now nearing completion. The control surfaces are the last major component left to build. Below are some pictures of the wing (for more pictures visit our flickr).

The left wing panel.

The complete three panel wing.

By having a three panel wing, transportation is greatly simplified.

I recently started assembling a test rig to integrate all of the electronics that will be going in the UAV. By performing all of this integration on test bench, the final installation and configuration will be performed much faster. This will also allow us do our HIL (Hardware In the Loop) simulation with all of the components connected.

You may have noticed that there are two large NiHM battery packs, these will soon be replaced by two (11.1V 3200mAh) Lithium Polymer battery packs, saving us about half a pound of weight and significantly increasing our power capacities. Although for bench testing all of the electronics will be powered of off a standard ATX computer power supply. The next step is the get the HIL simulation working with the autopilot and the it’s simulator, this part has been a bit finicky but it should be resolved now.

As a team we have also discussed possible strategies for image acquisition and processing. We had previously planned on simply acquiring VGA resolution video at 30 frames per second, but after reconsidering what altitudes we will be required to fly at to cover the search area in a reasonable time we quickly realized that VGA video would not provide the resolution we need to identify a human target on the ground from an altitude of 400 feet. We have since decided it would be best to use a much higher resolution still camera taking images at set intervals and tagging them with the GPS coordinates and the orientation of the UAV.

Starting January 1st, 2008, the University of Missouri-Rolla will be officially known as the Missouri University of Science and Technology (Missouri S&T), more about that here. As a result of this we will also be changing our name to MS&T AESS UAV Team.

Since our crash several months ago we have been developing a new wing specifically designed to meet our requirements for our mission. Since speed is high priority in our mission we have designed a wing that is smaller and more aerodynamic allowing us to fly faster in order to cover the search area in less time. Two of our excellent Aerospace Engineers have been working on the design of our wing, performing various calculations and CFD (Computational Fluid Dynamics) analysis. Unfortunately due to everybody’s busy schedules we have been slightly behind schedule in the construction of the new wing, but we plan to be back in the air by late January or early February. Below are a few images of our current design and a screenshot of our UAV flying in the X-Plane flight simulator.

We are also currently in the process of evaluating our strategy for acquiring and processing the images, we are working to decide what approach would be best suited and the most efficient for our mission. Our second revision of the power distribution board for the UAV is also nearing completion (see below).