Missouri S&T AESS UAV Team

We went out flying a few weeks ago (September 8th) with the intent of tuning the autopilot control loops better, since in their current state they were not tuned well enough for autonomous landing. We headed out to the RC field around 3 and shortly got everything together. We had also installed a camera on the vertical stabilizer to finally get some in flight video. For the most part everything was going smoothly until the third flight.

During the third flight shortly after takeoff we began a descent and then both wings suddenly tore off from the fuselage. It is important to note that this occurred under the manual control of the pilot, it should also be noted that the UAV was carrying more weight than we have had in any other flights. We had also previously suspected that the wings might be too weak to handle the weight, and it turns out they were. After the wings tore off, the airplane was still several hundred feet in the air and it quickly went into a dive and plummeted into an open field, thankfully no cows were harmed in the crash. Below are pictures of the carnage…

As you can see from the pictures above the fuselage is completely ruined, as are the wings, but thankfully all of the electronics and the engine survived. We have already begun to search for a new airframe, currently we have not been able to find an aircraft that is more suited for our purpose so we will most likely be purchasing another Sig Kadet and building our own wings in order to make them much stronger and more efficient (by using a different airfoil).

Here is some in-flight video before the airplane crashed…

Click here to download the high quality video.

Over the summer we have come to the conclusion that we will not be ready to compete in this years UAV Challenge due to a lack of progress, which is understandable considering we only had about 2 months together as a team before the summer break to build the UAV.  Instead we plan on competing in next year’s competition, by then we should have a mature platform that will be tested and ready to perform the mission.

Currently our next goal is to get the UAV put back together since all of the electronics were removed over the summer to do some testing.  The current goals are to have onboard video installed within the next few weeks, and get the control loops tuned better for autonomous landing.

We had our first few autonomous flights two weeks ago, and the UAV didn’t crash, unlike another airplane that day. We got out to the RC field in the early afternoon and it started to rain, it rained on and off all afternoon, so we were only able to fly for short periods of time in between the rain. There were also several other planes out at the field that day, including one of the senior project airplanes built entirely out of carbon fiber.

Unfortunately that airplane was extremely hard to control and on it’s first flight it crashed shortly after takeoff, shearing some nylon bolts. After replacements arrived, it took off again and the second flight lasted much longer, approximately five minutes, before the pilot lost control and it plummeted into the ground. Just as a note, the pilot was a quite experienced, and still had quite a bit of trouble controlling it. Now for the carnage…

As you can see, not much was left of that…

Thankfully our flights did not end like that. Once the runways were clear we prepared for our first autonomous navigation with the autopilot. I created a simple path in the shape of a rectangle for the UAV to fly over the RC field. The UAV took off under manual control and once it was in the air control was handed over to the autopilot. The first time it flew in autonomous navigation mode, the path that the UAV took was rather sloppy, and not very close to the waypoints that were specified. After giving a quick call to Procerus and adjusting a few parameters it flew much better and closer to the path designated. It was quite the sight seeing the UAV fly itself, a little scary at times, but also very impressive.

After flying a few simple paths and loiters, we attempted to use the autonomous landing mode of the Kestrel autopilot. The UAV began to circle down to the proper altitude and once it reached the altitude where it was supposed to come in for the landing approach, for lack of better words, it simply wandered off into the distance and we were forced to take manual control and bring it back. After a few attempts at it, all resulting in the same behavior, we decided to give up and just send the telemtry log back to Procerus to see if they can diagnose the problem.

In this picture you can see the pitot tube to measure airspeed on the wing.

That weekend we went out flying again on Sunday and attempted our first autonomous takeoff, which worked quite well the first time. Once again we attempted some autonomous navigation, this time going farther from the home location (over 1.5 kilometers or ~1 mile). Several times during those flights we had to bring the UAV back under manual control since there was real air traffic to the nearby airport and we did not want to interfere. I will be posting video of our first autonomous flight soon, as well as an update on our electrical system soon.

We had our first flight of the airplane with the autopilot installed last Tuesday (April 17th). We arrived at the RC airfield around 6PM, much to our dismay there was some light rain, which eventually stopped. Setting up the ground station was the first priority, then all of the control surfaces were tested to make sure they were functioning and deflecting the right amount, although for some reason the throttle servo was not moving, after a little bit of tweaking in the Virtual Cockpit, it worked fine. Shortly after the throttle servo was fixed, the autopilot stopped responding, it turned out that the ground connection of the battery to the autopilot had failed, since we did not have a soldering iron handy, the two wires were twisted together and wrapped securely in electrical tape, although as an interesting note, if this wire would have come lose in flight, all control of the aircraft would have been lost.

Abe and Jonathan starting the airplane

The moment of truth came and we fired up the engine and began the to takeoff (on manual control), the airplane was able to takeoff in a relatively short distance and was quickly in the air. The radio link between the autopilot and the ground station was quite strong and the Virtual Cockpit provided us with the airspeed, height above ground, and the attitude of the aircraft. The first order of business was to calibrate the dynamic and static air pressure sensors on the airplane. The next few flights consisted of tuning the control loops with the correct parameters, this was fairly straightforward, but rather time consuming. Once the roll and yaw loops were configured, it was interesting to see how the airplane quickly straightened itself when the pilot attempted to roll it. Although we were not able to finish tuning the control loops since it began getting dark.

Overall the first flight with the autopilot was a great success. We plan on flying the airplane again this Sunday, and will hopefully finish tunning the control loops and have our first autonomous flight.  For more pictures you can visit our flickr site.

This weekend we began installing the Kestrel autopilot in the airplane, which consisted of wiring up all of the servos and GPS, as well as configuring the servos in the Virtual Cockpit software. This took a surprisingly long time, although most of the time was spent on making the wiring harnesses and troubleshooting why the servos were not function properly. Once everything was powered up, the servos didn’t want to move, which it turns out was because I did not use the autopilot’s power rails since I had completely bypassed them and sent only the PWM signal wire from the autopilot to the servos, and powered the servos independent of the autopilot. Once that autopilot’s power rails were hooked up the servos started working, although they were quite jittery and very rough when on manual control, possibly from some kind of interference from the radio or other electronics. Below are some pictures of the autopilot installed in the airplane.

The autopilot

The GPS unit.

Now that the autopilot is installed, and as long as there is good weather this week, we should be able to have the first few flights with the autopilot. According to the manual, it will only take about four flights to tune the control loops for fully autonomous flight. We will also probably end up purchasing an embedded computer this week for the image processing, which will allow us to start developing the image processing algorithm.

Last week the the Kestrel Autopilot from Procerus arrived, and I have to admit, I was quite surprised by the size of it. It’s literally smaller than a deck of cards (slightly taler but less area). Reading over the documentation was first step in learning how to use this powerful little thing. Thankfully the documentation was quite good, and after 5 minutes of soldering a few wires together, it was ready to be powered on for the first time. The accompanying software was quite straightforward and surprisingly once both the autopilot and ground station unit were powered, they instantly acquired a wireless link, and began feeding data into the Virtual Cockpit software.

One really cool and amusing feature was that there was an artificial horizon with a 3D model of an airplane that rotated in whichever direction the autopilot was oriented. After everything was configured roughly how it should be, I began to setup the HIL (Hardware In the Loop) simulation. This allows the autopilot to fly an airplane in a simulator on the computer, allowing the simulation of an entire flight from takeoff to landing. The HIL simulation was quite easy to setup, and was running within minutes. Of course there were several minor details that were overlooked, due to the fact that I had not read the entire manual yet and did not understand the various modes of the autopilot, so the UAV kept crashing, but eventually after playing around with it, it all worked great.

Overall I was rather impressed with how straightforward and easy it was to start using the autopilot right out of the box. From my experience I’ve rarely had such complicated systems up and running in such a short amount of time. Now the next step is to install the autopilot in the airplane, which is quite a task in itself. Hopefully we will be able to have it installed by the end of this weekend, and maybe perform the first flight with the autopilot this weekend, or sometime next week, weather permitting.

And now for some pictures:

The autopilot itself.

The communications box.

To see more pictures of our UAV you can visit our flickr site. We will be updating our the flickr site frequently with new pictures of our progress.

We have also just recently purchased the autopilot, which should be coming in within the next week or so. After extensive searching and comparisons of various autopilot solutions, the autopilot we decided to go with is the Kestrel by Procerus Technologies. It is quite the feature packed autopilot and should allow us to get the plane up and flying autonomously rather quickly. And we are still in the process of determining what we will use for our video link back to the ground station, the biggest issue is the range, whatever we decide to use must be able to achieve a maximum range of seven miles (line of sight), and lots of bandwidth would be nice too.

As a note we are still looking for sponsors please contact me (derdos (at) ieee.org) if you might be interested in sponsoring our team.

Welcome the UMR AESS UAV Team blog. We are currently in the process of building an Autonomous UAV (Unmanned Aerial Vehicle) to compete in this competition, we will be competing in the Search and Rescue Challenge component of the competition. The goal is to build a UAV that will takeoff, fly to a grid that is roughly 2 miles by 2 miles, search the grid for a missing person (Outback Joe), and drop a bottle of water near him, then return and land. All of this must be done autonomously to maximize the number of points awarded. There is also a technical report and oral presentation that must be submitted.

Yesterday we performed the first manual test flight of the airplane, and thankfully everything worked perfectly, even though it was a little windy at times, which resulted in the ability to hover the plane into the wind. It seemed to have plenty of power, and easily performed loops and barrel rolls. Although in the process of transporting the plane back to the Electrical Engineering building one of the wings was damaged, although we were able to repair. Below are some pictures of the first flight of our airplane.