I spent some time on the software for the ground control station lately and did some telemetry flights with my UAV Flying Wing.Nothing special but I thought I'll post this anyway so people know that I'm still alive. The software is a work in progress and I'll post some information about it later.Ground control station- XBee Pro (RP-SMA)- Duck Antenna (RP-SMA)- XBee USB adapterIn flight- Arduino Mega microcontroller- DIY shield for the Arduino- GPS module EM-406A- XBee Pro with wire antenna- XBee Pro adapterThe XBee modules I'm using for the tests are surprisingly easy to setup and use. They act just like a regular serial interface and I'm using my SimpleSerialization library for the Arduino to transfer the telemetry data.
Posted by Pekka Ahola on October 17, 2009 at 3:11am
Just came across a "new" module from Sparkfun, that promises 10Hz update rate and has a binary protocol. Does anyone in the community have any experiences working with one of these?
Just a reminder that entries are due at 12:00 midnight PST on Sunday for the current T3 contest. Right now we've got six entries, and it would be great to get a few more in today or tomorrow. I'd hoped to enter an ArduPilot and AttoPilot, but I had three straight bad weather weekends and now I'm in Italy (boohoo!)
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Posted by Nathan Woody on October 16, 2009 at 7:13pm
I'm currently trying to connect a Sparkfun logomatic v2 serial datalogger (WIG-08627) to the ardupilot card. I understand how to do it using anolog connections ,but I can't figure out how to do it through a serial connection. Does anyone know how to connect the ardupilot with the datalogger using a serial connection?
Read more…3D Robotics
This team of 17 years olds designed this RC blimp from scratch, and learned a lesson in weight control and using optimal components, since this seems to be based on heavy Vex parts. Next up: autonomy. If they want a Blimpduino, we'd be happy to send them one!
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See: http://www.opti-logic.com/industrial_rangefinders.htm Pricing from $495 for the 100 yard unit to $595 for the 400yard one.7-9VDC conditioned required and Current draw @ full power (~ 1.8W)Range (Minimum 4 Yards)Resolution 0.2mDimensions: 32x78x84mmWeight: < 8oz
is a long long long drive from the east bay on 25mph roads. Then on weekdays you're greeted with permit parking only, anywhere within 1/2 mile of the lake bed. Fortunately, U can park in the golf course parking & walk 1/2 a mile to get in.It has scattered tall weeds, making landings tricky.
It's a very large area with spectacular views from 400ft, if you've come prepared as we have.
These R all 8 megapixel images. Because we're using a very aggressive takeoff program, sometimes these overshoot to 426ft before settling at 400ft.
SOme time back (within the last two or three months) I recall seeing a ground station setup where a guy was using a graphical LCD module similar to the one proposed for the NEW ArduStation Mega, and he had a very cool interface, even had an artificial horizon on the screen - DOES ANYONE ELSE REMEMBER SEEING THIS?? Wa it here or on some other forum??
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Sparkfun has just announced that registration is open for its second annual Autonomous Vehicle Competition (which we won last year). It will be held on April 17th. New this year: separate air and land categories, so the UAVs don't blow the rovers away again ;-) We're already registered. See you there!
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I am looking to make an electronic steering system for my magnet steered free flight model aircraft. GPS is not allowed by the rules. A gyro compass seems to be the answer, but I have not found any at a reasonable price. A gyro updated by an electronic compass to correct drift would also work I think. The aircraft dynamics are too much for a tilt compensated magnetometer.
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Can anyone give any advice on an autonomous landing setup. What should I use to sense change in altitude and do you think it could possibly work to land on water. Do you think laser or ultrasonic will work over water?
Read more…T3
Posted by Ryan Beall on October 14, 2009 at 3:30pm
In Bill's recent pod cast he talked about how the imudevboard experienced a random nose dive or extreme over estimation in the pitch (theta) axis. His theory was that the noise due to engine/aircraft vibration was causing the gyros to give inaccurate readings. He said that he put the imu in foam and the problem went away. I don't know how repeatable his experience was or how many test vehicles this "technique" was run on, but I find it no coincidence that I experienced the exact same effect on my imu.Here is my theory:I did some quick number crunching on some equations and found that it totally makes sense that pitch would "depart reality" more-so than roll and very rapidly as both him and I have both observed.(edit)For a 30deg AOB turn at about 1.5g's total the attitude solution if improperly estimated would be off in roll a couple of deg and about 30deg in pitch causing this nose dive affect.(correction)For a 60deg AOB turn at 2G's the estimation in pitch was off by 10 deg if centripetal was incorrectly calculated. The error would be in the positive direction causing the stabilty loop to push the nose over causing the "imu nose dive problem"I was extremely surprised at how quickly pitch departed at very shallow angles of bank. So this lead me to suspect one thing beings my math modeled exactly what I was seeing in the air....centripetal. Here are the pitfalls I evaluated:Gps latencyGps bandwidthPropper velocity mapping into componentsSo I will discuss in orderLatency. GPS has it...big surprise well how much is it and how much can it affect the solution. Depending on the module I have read 10seconds to about 0.5. Well for my Ublox it was about 0.75 to 1.5 depending upon the rep rate selected and positional accuracy (number of sats). I plotted it out and you can see how poorly the centripetal was accounted for in my "car test run". It's ok but in its worst case scenario could be off as much as 13 deg....which is better than 45deg with no centripetal at all for the runs I did. However 13 off and 1.5 seconds late quickly would cause things to go southGPS bandwidth. Its at best 4Hz....need I say more. You are going to miss changes in speed quite a bit and loose a lot of accuracy. Also note the graph where GPS clearly is reporting the wrong speed at the wrong timeVelocity mapping: This is how you map the velocity into the actual body velocities. Most people assume that the speed reported from the GPS is always out of nose of the airplane. This is mostly true except for in climbs. It is safe to assume that the v velocity (out the wing) is zero but not the w (out the belly of the aircraft). The total of u and w are the SOG from GPS and you must break them up. I'm pretty sure the imudevboard code does this but if it doesn't this is another large source for mis calculation----------------------------------------------------All of these things together are issues that can clearly throw off one thing....Centripetal estimation which was why we determined there was a 30deg offset in our crappy estimation. So with that solved (use airspeed instead) the problem goes away. I have hours of flight time on my IMU both with and without GPS and the nonGPS filter has yet to diverge from reality under self stabilized flight. GPS filter on the other hand....it depended on the airplane the autopilot....amongst a lot of other random variables that never made sense like calendar day. Some days it was fine and others it wasn't on the same aircraft which leads me to my next topic.
<Noise/Vibration:Gyro drift is due to temperature. When I tried to follow the drift using an integrator in software we had issues. Same idea and same effects and just as random. Some days fine and some days not. The filter DCM or what have you is a very dynamic thing and if you try to model a temperature drift with an integrator (in my humble opinion) it will only work assuming that your other estimations are perfect. Else the other errors will map into your temp compensation.....which does happen no denying it. Its ok if your gyros don't move that much with temperature and you keep an eye on the integrator however its way too unpredictable of a problem to assume your error state is a fixed target....It simply isn't.I run a temperature comp on my gyros and get repeatable results every time. With my comp equations the end result is a gyro that will hold itself +- 5 deg for 5 min or so. There are a lot of other tricks here like circuit noise reduction and oversampling that can be done but this is huge if you want to keep your solution converged.As far as vibration.....If a gyro gave crap results because of vibration then it wouldn't be any use in a 6dof filter. Your accelerometers produce noise with vibration and hence the reason we use gyros. I just don't see any room for allowance of gyros to be noisy in vibration. Pick good gyros and temp comp them and so many problems dwindle away very quickly-----------------------------------------------------------------------------------------------------------------update: addressing the airspeed questionMy acceleration model
<Best Regards and good luck in the IMU world-Ryan
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Posted by Josh Hathaway on October 14, 2009 at 7:17am
I just wanted to say hello to everyone on this great website and I can't wait to get started on my project!I'm out in Orlando, FL and me and a few guys are looking at pricing components for our system. I want to work with the UAVDevBoard b/c I'm familiar w/ programming PICs. Any suggestions for data recorder boards that work well with it?Is it really possible to control an aircraft just from a single microcontroller? Don't autopilots need inertial navigation, guidance, and control algorithms? That seems like a lot of number crunching for these little guys...
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Just a FYI: we're doing an average of 15,000 page view a day here, with around 4,000 unique visitors/day. Total membership will hit 6,000 in the next week. The site's traffic has more than doubled over the past year!
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http://cbs5.com/local/skeletal.remains.found.2.1244063.htmlGetting freaked out? Maybe he was in 1 of these shots & we didn't know it. Maybe he lost an airplane in the toxic waste area & didn't make it back. How many skeletons R near your flying area?
Posted by Tj Bordelon on October 12, 2009 at 9:09pm
This Saturday I had 15 mph winds gusting to 25 mph.. Still landed without issue. Wind is coming from the top of the image towards the bottom. You can see the aircraft try to land down the runway (right to left) but fighting the wind made the path a bit weird. But impressive given that the wind was something I wouldn't have flown in myself. Here's the plot:I have to say that windy flights are far more impressive. I had a nice crowd watching the airplane land in the crazy winds. One guy complimented me on my flying skills, at which point I had to tell him I wasn't flying at all ;-)
Here's today's video. Only 5mph today, but this is the only video I have showing a full flight from takeoff to land. Unfortunately my flare angle was accidentally set to -5 degrees!So with a working autopilot... windy days are actually more fun. I'm 90% there. Still a bug where my integral terms wind up if it can't punch through the wind. 2 good flights, one not so good.
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