In one more attempt to test the abilities and push the limits of Bill's UAV DevBoard, I removed the winglets from my tailless design so now there are no horizontal or vertical stabilizers.The video is in three segments; the first showing manual flight with stabilization disengaged. You can see the difficulty I had flying a tight figure eight pattern. The next segment displays flight in stabilized mode which is noticeably smoother and the last shows turns at three waypoints.Even without the vertical stabilization, there is some yaw stability due to the wing sweep but it is obvious and pretty impressive that the DevBoard firmware can still handle a plane with marginal roll, pitch and yaw stability. Enjoy the cheesy music-----Note: cheesy music replaced with cool music.Read more…
After my last UAV project went up in flames (literally!) I’ve shifted gears and designed a dedicated autopilot (AP) test vehicle. She is a tailless plane with removable wings for transportation and has plenty of room in the fuselage with easy access.
For the autopilot, I’m using Bill’s UAV DevBoard with a modified AileronAssist code for handling the elevons. This modification is a work in progress by Ben Levitt and he is including a lot of great features. You can check out the latest versions of the code here. The tailless had her first autonomous flights this weekend and I’ll be posting all of the flight logs on this blog. So far, I’m really pleased with the AP’s performance. Not only does the DevBoard and software perform well, but Bill also provides a wealth of information on the theory of his methods as well as the “how to” to get the hardware and software installed and running. I know this is beginning to sound like a commercial for Bill’s stuff but if you do a search on this website, you’ll find nothing but praise for Bill and his accomplishments. And to top it all off, he’s always willing to immediately chime in and help whoever asks for assistance.
I’ve started flight tests with the latest Ardupilot code and hardware and will post my findings in this blog post. Info on my plane and set up can be found HERE. I’ve found the EG 2.2 has similar flight characteristics to the original EasyGlider including the same “reverse roll” and “reverse pitch” settings in the code so these results should help anyone flying the stock glider.A few notes on what I have discovered so far---The throttle immediately kicks in when you switch to WP or RTL mode. There is no “safety” coded into the throttle command such as, no throttle activation below a given altitude or a given speed, so be prepared if you switch from manual mode at the flying field. Also, in the .h file under Throttle gains the throttle_max variable is defined twice. I’m not sure which is used by the code. There are also some corrections to the manual that I posted HERE that may help others in their set ups. Good Luck!
At this point, the only way to get my plane flying with Ardupilot is to buy a different FTDI cable which may or may not work with my setup(I don’t have the programming skills to bypass the configuration utility and add waypoints directly into the code). I’m running Windows Vista on my laptop and have the latest Ardupilot board with the shield kit as shown below. I’ve also installed the latest code, configuration utility and the newest version of the Arduino IDE.Before I invest any more money in this project, can I get some feedback from anyone running a similar setup to mine but with the newly recommended FTDI cable where they are successfully downloading code, read/writing from the configuration utility and flying autonomously with Ardupilot?I’m sure there are success stories out there and they would really help those of us that are struggling to hang in there. I believe in the Ardupilot project and Chris' clear approach to explaining concepts and products has helped me immensely in understanding autonomous systems and in choosing the best equipment. This is a fascinating hobby and always a challenge.
I first started flying with Ardupilot before the configuration utility (CU) was created. At the field, I’d pull up the Arduino IDE on my lap top, make the changes I wanted in the code (waypoints, altitude, tuning parameters, etc.), upload to my Ardupilot, then fly. After seeing how the flight was affected, I’d go back to the IDE make another change and fly again.Then the CU was created and it looked cool but, at the field, it just created another step to go through before flying. I now had to also pull up the CU program to enter my waypoints, altitude and other parameters and upload to the board, then open the IDE, make my changes and upload a second time.Now, for a lot of us, the CU is the single break in the chain that is keeping us from flying. We have the Sparkfun FTDI cable that works fine with the old and new versions of Ardupilot for uploading code and it works with the old version for reading and writing from the CU. The problem is that the CU doesn’t allow you to use this cable with the current Ardupilot and there is no other way to upload waypoints.As you can tell, I’m not a big fan of the Configuration Utility! Since an .h file was created as an interface between user and code, couldn’t this same file be used for entering waypoints? This sounds more user friendly since you wouldn’t have another program (CU) to open, make changes to, and upload. Also, the current problem with Sparkfun FTDI’s wouldn’t exist!
This is my latest modification of the EasyGlider to coincide with the official release of Ardupilot 2.2.I call her the “EG 2.2”. The last modification, found here,involved increasing the fuselage volume but this is a little more ambitious and includes standard tail conversion to an inverted V-tail, moving the motor to the rear in a pusher configuration, moving all servos to the control surfaces and extending the nose by two inches. The nose was extended to get the CG set without having to add nose weight and to make room for the larger autopilot and data logger.The booms are made from collapsible fishing pole segments and house the elevator cables. The elevator servos are joined with a Y connector that contains a reverser for one of the servos. The ailerons are joined with a simple Y connector.She had her maiden flight yesterday and she flies fine. As soon as the new Ardupilot and shield arrive, I’ll get them installed and restart my flight tests. I’m predicting much better success this time since there will be throttle management and I have a better feel for how the code changes effect flight.
There has been some recent interest in using the EasyGlider as a flying platform so I've included some updated pictures. Space was increased beneath the canopy by removing the rudder servo since it's not being used and grinding/cutting into the right fuselage wall. This area was reinforced with fiberglass and the increased space allowed addition of the EagleTree datalogger and extra GPS. The rudder is now locked in place by the horn and a piece of balsa glued to the vertical fin.
I posted an earlier blog with pictures on how I placed the avionics in an EasyGlider Pro for autonomous flight. I found out that was the easy part! Now I’m performing flight tests to hone in on the code mods for stable flight ( as Jordi states, the latest code is optimized for the EasyStar). My method has been:Fly and observe performance in autonomous mode – record observations – make code modifications on laptop – remove GPS and upload code – replace GPS – fly again. Laborious but also fun since physical computing yields immediate effects that you get to see.I’ve attached a table I made in Excel to organize my iterations and keep me on track. Maybe this will help others in the same situation. One mistake I made was getting in a hurry to go fly. I could have found out about the reversed servo throws and IR sensor placement by just walking the plane around on the ground and changing its attitude by hand. This would have avoided the “death spirals” I experienced on that first day of flying!Bryan
I chose the Easyglider for its size, high L/D and ease of modification/construction with Elapor foam. There is plenty of room to slide in up to a 3000mAh Lipo pack under the wing but, as Chris has mentioned, there isn't a lot of room under the canopy. I modified the canopy with a tab in the front and magnet aft for attachment. The original, forward canopy hold down tabs were left off and it turned out ArduPilot was almost a perfect fit in their place (see pictures).Just waiting for weather to improve for her maiden voyage. Has anyone flown this plane yet with ArduPilot 2.0? If so, any recommendations on setting the gains?