NXT goes airborne (again)
I made my first test flight today with my Lego NXT AutoPilot (all the needed parts are already commercially available!!).
The test flight was a success when it comes to AutoPilot but in the middle of the flight my EasyGlider suffered an elevator servo failure. NXT, however, managed to make something like a landing and nothing was broken.
Here are some specs of my NXT AutoPilot:
Hardware:
-Mindsensors Accelerometer
-Mindsensors Servo Controller
-Mindsensors Compass Sensor (on the same input port as accelerometer)
-2x HiTechnic rate gyros
-(Homebrewed pressure-sensor for altitude control but this is not really neccessary (on the same input port as servo controller))
Software:
-Full NXT based stabilisation with PID (uses integrated gyro outputs as input and accelerometer data to set gyro bias)
-GPS navigation with the help of the compass sensor
-All coding made with RobotC
-What would you like? :)
I'm really amazed how well this assembly works. Gyro integration - and how well it works - is what amazed me most: The gyro drift is generally less than 5deg/min which accelerometer can easily compensate (I didn't even use Kalman Filter and the AutoPilot flies the EasyGlider better than I do!). As for NXT's CPU speed: only about 50-60% of CPU time is being used while all the functions of the AutoPilot are on.
Just like Chris said: "It's so cool--". ..and now you can finally make this yourself! I'll publish the source code (?) when I have translated all the commentations to english....
More to come soon! (Videos, photos and so on...)
Sami F.
The test flight was a success when it comes to AutoPilot but in the middle of the flight my EasyGlider suffered an elevator servo failure. NXT, however, managed to make something like a landing and nothing was broken.
Here are some specs of my NXT AutoPilot:
Hardware:
-Mindsensors Accelerometer
-Mindsensors Servo Controller
-Mindsensors Compass Sensor (on the same input port as accelerometer)
-2x HiTechnic rate gyros
-(Homebrewed pressure-sensor for altitude control but this is not really neccessary (on the same input port as servo controller))
Software:
-Full NXT based stabilisation with PID (uses integrated gyro outputs as input and accelerometer data to set gyro bias)
-GPS navigation with the help of the compass sensor
-All coding made with RobotC
-What would you like? :)
I'm really amazed how well this assembly works. Gyro integration - and how well it works - is what amazed me most: The gyro drift is generally less than 5deg/min which accelerometer can easily compensate (I didn't even use Kalman Filter and the AutoPilot flies the EasyGlider better than I do!). As for NXT's CPU speed: only about 50-60% of CPU time is being used while all the functions of the AutoPilot are on.
Just like Chris said: "It's so cool--". ..and now you can finally make this yourself! I'll publish the source code (?) when I have translated all the commentations to english....
More to come soon! (Videos, photos and so on...)
Sami F.
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3D Robotics Comment by Chris Anderson on November 2, 2008 at 11:55am -
Great job! Can't wait to see the source code. I'm impressed you were able to do it with the prototype HiTechnic MUX. I would have run out of ports without it!
When you're ready to post code, pictures and video I'll set up a special page for it. We've been waiting too long for the HiTechnic sensors and other gear that I used to go into production, so it will be show something that uses stuff that's already available.
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Comment by Paul Marsh on November 2, 2008 at 3:43pm -
Can't wait to see more!
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3D Robotics Comment by Chris Anderson on November 2, 2008 at 3:54pm -
Just correcting my post, I meant to say that I was impressed he did it *without* the MUX.
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Comment by Sami Finnila on November 3, 2008 at 10:55am -
Thanks! I actually had to toss some of the I2C sensors on the same port (for the basic version without barometer and compass sensor this is not needed). Didn't get off with it easy anyways: Just checked that I have produced a little over 1200 lines of (C/C++) code over the last two weeks (although some of it is not mine).. Also, I won't probably publish the current version of the NXT AutoPilot that is able to land itself (due to it's risky nature and the need of a barometer) so you'll need an additional failsafe which I forgot to list above (for which I'll publish a PCB/DIY-instructions which uses 3 relays for 5 ch failsafe estimated cost of which is about 5 to 10 euros or so).
I'm busy with some school work next weekend so the next test flight will probably be postponed by a week or so (as darkness falls at these latitudes so early that after school I'm not able to fly anymore). As soon as I have been able to make a full successfull test flight I'll post the source and so on.. Until then... ;)
Sami F.
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Comment by Sami Finnila on November 3, 2008 at 11:05am
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Oh.. I had these lying around... ;)
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3D Robotics Comment by Chris Anderson on November 3, 2008 at 11:30am -
Is there an NXT in there? I can't tell.
FWIW, here's the demo code that I used to show how the HiTechnic iGyros, accelerometers and MUX could stabilize an aircraft. It doesn't use a Kalman filter (and just uses the P term of a PID), and the BT GPS code isn't integrated, but it may be useful for those wanting some RobotC code for this sort of function. The BT GPS code is used is derived from Steve Hassenplug's code. It's here.
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Comment by Sami Finnila on November 3, 2008 at 11:34am
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:D It's there... I sort of a run out of space as the canopy is really small so I had to make a small box for the NXT and put it below the plane.
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3D Robotics Comment by Chris Anderson on November 3, 2008 at 11:39am -
Yikes! So much for soft landings ;-)
I use the NSP Viking, which has more room (although probably not enough for all that you're carrying), but isn't quite as stable and sturdy as the EasyGlider. The best choice might be a big high-wing plane, like a Senior Telemaster, which has loads of room. But that's not one for the local park...
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Comment by Sami Finnila on November 3, 2008 at 12:12pm
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Yeah.. Luckily this is not my first flying RC.. ;) The freedom of usage is defenitely what I love most in gliders: I can go to my back yard and hand launch a glider whenever I want to and landing is somewhat easy too because my gliders (generally) fly so slow. (My backyard BTW is rather a big field so no worries there.) I have also some faster aircraft available but I'd rather not risk them (yet) as one glitch in the code might cause an unrecoverable error (and damage...) to the aircraft.
That NSP Viking looks promising as for the space, price and size and it shouldn't be too unstable either by the looks of it. But I'll have to seriously consider if my budget has enough room even for that kind of investment in the near future...
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3D Robotics Comment by Chris Anderson on November 3, 2008 at 1:12pm -
PS--I like your DIY power pylon, which looks like it frees up a lot of space in the EasyGlider nose. Any tips on how to build one (or links to tutorials elsewhere)?
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