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Android Phone Center of Gravity Calculator.

Posted by Graham Dyer on October 15, 2010 at 7:12am

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Android Phone Center of Gravity Calculator.


Here is a free Android Phone CGC (Center of Gravity Calculator) for planes.

It will calculate the position of the center of gravity of an airplane
using the tip chord, root chord, sweep and required CG in percent,
measured back from the leading edge at wing root.

It's free, released as donationware, just download the .apk file below
and use Astro File Explorer or Estrongs File Explorer (or equiv.) to
install it. (I'm busy working on getting it onto the Android Market.)

It's pretty intuitive but instructions are behind the 'Instructions' button

Comments and suggestions welcome!

Please try it out and send it to anyone who might be able to use it! (or point them to this post)

CGcalc.apk (Right Click > Save Link As: )

Thanks

Graham Dyer

(RCGroups: http://www.rcgroups.com/forums/showthread.php?t=1322984&pp=100#post16295945)
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Super early demo of FreeSpace video overlay system

Posted by Tj Bordelon on October 15, 2010 at 7:05am


Super early demo of my video overlay code. This is a post process that occurs after the mission to overlay the data on top of the video from my cheap Chinese camera. Note that the video is not in sync with the data, and is off by approx 250 ms. This is due to a reboot that occurred during the flight (cause unknown).

The code that draws the instruments is the same code that runs on my ground station. That happens to be displaying on a 256x128x1 vacuum flourescent display, hence the rather low resolution instruments.

This is the same flight I posted earlier, but with the video overlay.
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Arducopter photos followup

Posted by Matt White on October 14, 2010 at 8:00pm

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As a response to the requests for details on cost, etc + photos, here goes:

KDA 20-20L ($12.88) x 4: $51.52

HK SuperSimple 18-20 ESC: x 4: $31.20

Zippy 4000 mah 40C battery: $24.74

Zippy 500mah 20C battery: $6.43
Optional, but I like having a separate flight pack as opposed to powering via an ESC. It may be superstitious, but I'd really hate to have a brownout mess with my APM in flight.

HK-T500 Landing Gear: $3.78

Mikrokopter 500mm frame: $72.95
The MK frame is pretty pricey, and replacement aluminum riggers are pretty spendy. This will definitely be a step up with the Arducopter frame, when released.

Oilpan: $159.95

Ardupilot Mega: $59.95

Break away headers: $4.95

APC 10x4.7 Slow Flier x 2: $5.86

APC 10x4.7 Slow Flier Pusher x 2: $8.78

Spektrum AR6110E: $49.99

Radio Shack Project Enclosure: $3.99

JST Male connectors x 10: $1.99

JST Female connectors x 10: $1.55

F/F Servo Wires x 8: $12.00
I made these myself with some bare-end female servo cables from Hobbyking. But these are better :).

Optional Xbee
Adafruit Xbee adaper: $10.00

Xbee Explorer USB: $24.95

Xbee Pro RSPMA 900mhz: $44.95

Xbee Pro 900mhz Wire Antenna: $42.95

F/F Jumper Wires: $4.50
For connecting the Xbee to the Oilpan...

Total of the above: $614.98

I'd highly recommend getting an Xbee setup, since there are issues with blowing outputs on the APM when connecting speed controls and USB at the same time. That means that tuning PID values and testing is a MAJOR pain, since it requires unplugging your ESCs every time you want to plug in the USB. With Xbee you don't even have to open the electronics housing to make changes. Plus you get to look cool because you bring your laptop when you fly :P.

I also made some super-short servo extensions for my ESCs that have the voltage line cut (the red one). This prevents the ESCs from providing power to the board, since I wanted to use a separate flight battery. I found out afterwards that this may be also done by removing a solder jumper on the APM? If so, oh well... I already made the extensions.

There's a few other miscellaneous bits and pieces, such as Deans connectors for the main battery, and rubber grommets and nylon bolts that I bought for vibration isolation for the electronics platform. You can see those between the box and the platform in the pictures below. It's tough to say if they are effective or not yet, because I was having major vibration problems on my aeroquad setup (same frame, just a different box), and I haven't re-tested the aeroquad stuff after getting arducopter finished. It may just be that the Arducopter gyros and accels are less vibration sensitive. It can't hurt, though, and the Mikrokopter frame itself doesn't do much for vibration if you directly attach the electronics to it with the nylon standoffs.

This is pretty much the exact set of gear that is on my quad... Probably way more than anyone here wanted to know :).

Photos


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It's ALLIIVE!! (My Arducopter, that is)

Posted by Matt White on October 14, 2010 at 10:30am
I got my quad off the ground this morning and it worked perfectly with NO tuning needed! NONE! And I'm not using a stock frame either, I'm using a Mikrokopter 50cm frame with some modifications for vibration isolation (just an extra platform with some rubber grommets + nylon bolts)...

Setup:
APM/Oilpan
KDA motors from Hobbyking
HK SuperSimple ESCs with high-rate Quax PPM firmware
Turnigy 5000 3cell
Turnigy 1000 2cell battery for electronics
Spektrum DX7 + AR6100
Mikrokopter 50cm frame
APC 10x4.7 props
Electronics are housed in a Radio Shack project box... I've landed upside down before and really don't want to break anything :)

The system was very easy to get up and running (especially when compared to AeroQuad, which requires a lot more assembly work with the shield, etc). Wireless telemetry via XBee was a snap, and the configurator worked awesome as always (well done, Mikro!).

Stable mode was absolutely amazingly stable... It's less "noticeable" than other stable modes I've dealt with, too. It just seems to do what it should, without any fuss... Acro flew well too, very predictable without any obvious jitter or wobbliness.

Overall, I'm totally stoked, and super excited to get a chance to try all of the position holding stuff once it's released! Again, thanks, well done, and keep up the good work!

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Developer

ArduPilot v2.7.4a JLN version test with GPS Emulator

Posted by Jean-Louis Naudin on October 14, 2010 at 7:14am

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Hello ArduPilots,

Here you will find my latest updated version of the ArduPilot (v2.7.4a JLN) successfully tested in autonomous flights with a Multiplex Cularis (GPS Ublox and ArduIMU v1.6). This version runs very well with the GPS Emulator v1.1.45 and you may test it yourself at home.

More photos at : http://diydrones.com/photo/albums/ardupilot-and-arduimu-on-a

The full software can be downloaded at: http://code.google.com/p/ardupilotdev/downloads/list

Here the test procedure with the GPS Emulator:

Required material: Ardupilot with or without shield, it works also with Arduino board "Duemilanove"

1) Compile and upload the ArduPilot_2_7_4_JLN software to your ardupilot board
2) Download a flight plan with PlanifMission.exe (v 1.4.14), i.e. upload the flight plan "fieldtest4"
3) Run the GPSEmulator.exe (v 1.1.45):
a) choose the ardupilot comm port: i.e. COM10 then click 'Connect'
b) Select File/Run ArduPilot Mission
c) Selected Mission 'fieldtest4'
d) GPS Data Source 'GPS Emulator w/ArduPilot'
e) check 'Listen to Throttle'
f) Click on the 'Start' button on the main window

Enjoy,
Jean-Louis Naudin

Main JLN DIY Drones page: http://diydrones.com/profile/JeanLouisNaudin

Google code: http://code.google.com/p/ardupilotdev/

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UAVs and the Human Element: Why Army UAV Technology is Breaking Stereotypes

Posted by Andrew Van Der Plaats on October 14, 2010 at 3:30am
Glenn Rizzi is the Deputy Director of the US Army UAS Center of Excellence. In this video, he discusses the Army's deployment of unmanned technology at the tactical echelon level. Listen to him describe the US Army's Roadmap development programme with short term, medium term, and long term project goals. Swarming technologies, improved commonality and autonomy are all topics broached here, as well as the US Army's vision of what capacity the 'human element' should fulfill within the role of UAVs in a combat environment.


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Autopilot control in Xplane

Posted by erenzokko on October 14, 2010 at 3:00am

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Hello... I have small problem with autopilot.I try to make simulation on xplane9.Before I activate autopilot everything is good.But when autopilot is on ,plane flies strait forward and climbing slowly,instead of
flying to waypoints.Ardusimulator working properly.GPS and plane IMU datas
updating well.I couldn’t figured out what is the problem.Could you help me
plese???



As you can see from image.When I activate ardupilot , it adjust plane IMU roll=0 and Pitch=between
1.5 to 4.İt doesnt control heading.it gets fix when autopilot on condition.



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GPS News for October

Posted by Ken on October 13, 2010 at 4:30pm
Registration is now open for The Institute of Navigation (ION) Eighth Annual Robotic Lawn Mower Competition to be held June 2-4, 2011, at Siebenthaler’s Beaver Valley Garden Center near Dayton, Ohio.

"The purpose of the competition is for universities and colleges to design and operate a robotic unmanned lawnmower using the art and science of navigation to rapidly and accurately mow a field of grass.



If you thought that the MediaTek MT3329 GPS was small -- (the DIYdrones store claims it to be 16mm x 16mm but I would have guessed 12mm myself) -- Round Solutions, based in Neu-Isenburg, Germany, is offering the ORG4472 GPS module, based on the SiRF IV chipset is only 7mm x 7mm). But you do have to stick an antenna on it.

"The module has an integrated interface for accelerometers, gyrometers, or other sensors to make dead reckoning easy, the company said.

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Tilt-Wing Stall Landing Technique Inspired by Birds

Posted by Shannon Morrisey on October 12, 2010 at 10:30am

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A team of researchers from the Massachusetts Institute of Technology (MIT) has recently demonstrated an innovative landing control system that allows planes to land similarly to birds. Since this method allows quick changes of speed and fast landings, it might improve future aircraft...



From The Future of Things: "Airplanes’ landing procedure is common knowledge. First, the plane maneuvers slowly into an approach pattern; then, there is the long descent, and finally, the wheels touch the ground and the pilot applies the brakes until the plane comes to a full stop. In comparison, birds switch from barreling forward at full speed to lightly touching down on a target as narrow as a telephone wire. Now, a team of scientists tried to understand this difference in order to improve landing technique for airplanes.

According to this recent study, birds’ ability to land precisely depends on a complicated physical phenomenon called "stall." In fluid dynamics, a stall is a reduction in the lift coefficient generated by an airfoil as angle of attack increases. This occurs when the critical angle of attack of the airfoil is exceeded; typically, about 15 degrees, but it may vary.

When a commercial airplane is changing altitude or banking, its wings are never more than a few degrees away from level. Within that narrow range of angles, the airflow over the plane's wings is smooth and regular, like the flow of water around a small, smooth stone in a creek bed. However, when a bird approaches its perch it will tilt its wings back at a much sharper angle; it makes the airflow over the wings turbulent, and it creates large vortices — whirlwinds — from behind the wings. The effects of the vortices are hard to predict; for instance, if a plane tilts its wings back too far, it can stall and fall out of the sky (hence its name).

The newly designed control system is based on mathematics, and developed by MIT associate professor Russ Tedrake, a member of the Computer Science and Artificial Intelligence Laboratory, and Rick Cory, a PhD student in Tedrake's. Their challenge was to describe the stall phenomenon mathematically; although most engineers understand it, modeling it is time-consuming, in terms of computation.

The developed model enabled Professor Tedrake and Cory to guide a foam glider to its perch, but executing a fluid landing was not that simple "It gets this nominal trajectory," Cory explains. "It says, 'If this is a perfect model, this is how it should fly.' But, because the model is not perfect, if you play out that same solution, it completely misses."

The imperfections of the initial model drove Cory and Tedrake to develop a set of error-correction controls that could nudge the glider back onto its trajectory when location sensors determined that it had deviated from it. By using innovative techniques developed at MIT's Laboratory for Information and Decision Systems, they were able to calculate precisely the degree of deviation that the controls could compensate for.

The control system ends up being a bunch of tubes pressed together like a fistful of straws. The addition of the error-correction controls make the trajectory look like a tube snaking through space; the center of the tube is the trajectory calculated using Cory and Tedrake's model, and the radius of the tube describes the tolerance of the error-correction controls. Once the glider launches, it just keeps checking its position and executing the command that corresponds to the tube in which it finds itself. The ultimate solution found allows the glider to constantly be in one of the possible courses; if it goes so far off course that it leaves one tube, it will still find itself in another.

A cruising plane tries to minimize its drag coefficient—the measure of air resistance against a body in flight. Usually, when an aircraft is trying to slow down, it tilts its wings back in order to increase drag. Ordinarily, they cannot tilt back too far, for fear of stall. However, because Cory and Tedrake's control system takes advantage of stall, the glider has a drag coefficient that is four to five times that of other aerial vehicles

There are several potential applications for the new system. For one, the U.S. Air Force has been interested in the possibility of unmanned aerial vehicles (UAVs) that could land in confined spaces; therefore, it has been funding and monitoring Tedrake and Cory’s research. "What Russ and Rick and their team is doing is unique; I don't think anyone else is addressing the flight control problem in nearly as much detail," says Gregory Reich of the Air Force Research Laboratory. More accolades come from Boeing, who gave Cory the 2010 Engineering Student of the Year Award for the system’s development.

Still, current design interferes with the military’s plans: In the conducted experiments Cory and Tedrake used data from wall-mounted cameras to gauge the glider's position, and the control algorithms ran on a computer on the ground that transmitted instructions to the glider. "The computational power that you may have on board a vehicle of this size is really, really limited," Reich says.

Despite the drawbacks mentioned Tedrake is optimistic, saying that in a few years’ time computer processors will be powerful enough to handle the control algorithms. In the meantime, his lab has already begun to address the problem of moving the glider's location sensors onboard. On a humorous note, Cory concludes: "I visited the Air Force, and I visited Disney, and they actually have a lot in common: the Air Force wants an airplane that can land on a power line, and Disney wants a flying Tinker Bell that can land on a lantern."

TFOT has also covered CyberQuad, a UAV capable of vertical take-off and landing, and Deep Throttling, a technology developed by NASA to make smoother landings.

For more information about the technology that allows planes to land like birds, see MIT’s press release."
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PIXHAWK pxIMU available! Hardware and Firmware

Posted by pixhawk on October 12, 2010 at 10:00am
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We proudly announce the launch of the pxIMU Autopilot! The boards, which are priced at 400 chf (about $420) each, will only be made in batches of at least 30, so when we get that many orders we'll put them into production. We have also released the pxIMU Autopilot Firmware.

You can register to the PIXHAWK user forums to hook up to other users, use the forums and help to push this open-source project.


Please note that PIXHAWK is currently evolving from a research system to a open-source community platform. We offer you the best combination of weight (8g), high-performance processing and sensor precision of any current open-source IMU. But you should be experienced enough or ready to learn to handle and to program the device. Our system is targeted at high-end hobbyists and research use. Of course the whole project is well-documented in our wiki, so it will be convenient to work with. Look for example at the excellent wiki articles onpxIMU, flashing the firmware or the Intel CORE 2 DUO baseboard for MAVs. We expect this user wiki to improve even further as more and more users are joining in. If you just want to get started and are looking for a very affordable system, we recommend to look at the projects on DIYDrones as well.

The pxIMU code is available at the PIXHAWK downloads page. You can browse it online or download a ZIP file.

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Bug in NMEA parsing code for ArduPilot and ArduIMU (it's been there since the beginning)

Posted by Paul Mather on October 11, 2010 at 10:00am

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As a fan of inexpensive GPS units I've always been interested in keeping NMEA GPS's compatible with ArduPilot and ArduIMU. So last night and today, while I was incorporating Remzibi's OSD code into the AP2.7.1 source I did some testing with my new GPS Emulator navigation logic. During this test, I had problems with the plane waffling back and forth around 0 degrees (due north). I have seen this before during testing with AP2.6 and my old Emulator. For a while, I attributed this to an error in my program and spent a good 2 hours searching for the cause. Finally, I tried the same exact test using uBlox for my GPS_PROTOCOL... and what do you know? It worked like a dream!?!? So I went back to NMEA and upped the Hz. I tried everything from 5-30Hz and nothing made it any better.

Any time the plane approached or passed 0 degrees the AP would tell my emulator to turn hard left, then hard right, then hard left and sometimes would get stuck in this cycle (not the sine wave I posted yesterday) but a very tight sine wave only varying about 10 to 40 degrees before snapping back hard the other direction.

Finally, I started looking at the NMEA parsing code in the AP source. It turns out, there are 2 atoi() function calls for ground_speed and ground_course in the GPRMC parsing routine. Simply changing atoi to atof completely solves the problem. I assume it's a rounding issue and since the GPS sends one decimal place after the degrees, this decimal place was getting rounded to an integer and then multiplied by 100. I believe this bug has been there since the very beginning when the NMEA parsing routine was first written. I wouldn't have guessed that one decimal point would make such a difference!



Simulation_NMEA_NoFix.gif

Simulation_NMEA_Fix.gif
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Sine Wave Flight Pattern with AP 2.7.1 and my GPS Emulator

Posted by Paul Mather on October 10, 2010 at 1:30pm

I'm having fun today incorporating my changes to the uBlox, NMEA and EM406 code to better manage the blue blinking light as well as the output for Remzibi's OSD in the AP 2.7.1 code. I re-wrote the trajectory function in my Emulator because there was a bit of an offset in my old code. Here's what I'm finding with the new code

Simulation_SineWaves.gif

Does anyone know what changes I need to make to the gain settings (or something like that) to cut down on this pattern?

Thanks!!!

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Slightly better mouse sensor position hold video

Posted by Marko Kleine Berkenbusch on October 10, 2010 at 11:08am

After some more PID tuning, here is another video of my quadcopter trying to hold its position via the hacked mouse sensor (plus an ultrasound range finder for altitude control).
This was shot about 2 hours before sunset and the sensor already started having some trouble on my dark and fairly featureless driveway in the shadow - that's why I tried to make it hover over a sandy spot that stuck out...
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Solving PPM issues with APM boards

Posted by Scott Findlay on October 10, 2010 at 10:30am

So I get my new APM in the post, excitedly open it connect a few servos, upload the dancing firmware test and.... nothing. Jitter and a crazy flashing mux led.

Anyway to cut a long story short it seems the PPM chip has not been programmed right by Sparkfun. I tried following the steps here,
using the manual process, but found that even though the source from here,
compiles and uploads fine, the chip still doesn't work.

Seemed to me that it may be the brown out protection that is the issue here since the servos probably drop the +v rail when doing stuff, and it looks like there isn't much filtering to the servo +5v rail.
So reading the fuses I notice that the brown out was set to 4.3v which seems quite high, more than likely the issue. So I set it to 1.8v hit program and voilà it all works nicely.

Looking through Jordi's batch file confirms this as this is the setting used in the batch.

Here is the old settings:

>
And the new:


So the process is this:
  • Connect up the APM to your programmer (follow the guide for programming firmware)
  • Go to the fuses tab and click read
  • It should show the extended fuse setting as 0xFC and brown out show as 4.3v (as the first image)
  • You can then either set the drop down to 1.8v OR change the setting directly to 0xFE in the lower section
  • Then hit program, check all the status messages are ok
  • For double confirmation, click read again
  • The settings should now be 1.8v / 0xFE
For me this fixed the PPM chip and now the dancing servos program works fine.

Powering the APM is something of an avoided topic. Seems to me like from the guide someone may blow the board by connecting things up wrong.
My personal preference is to de-solder SJ1 and power the radio gear & APM separately.
On the desk the APM uses the usb (for power and serial debug) and I use a bench supply for the servos (connected to input channel 8).
In the air, I use one of the ESCs (quadrotor) to power the radio etc and a separate BEC/regulator connected to the battery for the APM (connected to the power header).

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Robot cars invade California, on orders from Google

Posted by ionut on October 10, 2010 at 12:00am

CNet article:

Google has been testing self-driving cars on roads in California, according to a report, and so far they've avoided everything but a minor fender bender--caused by a human-driven car.

The New York Times reports that seven test cars have traveled 1,000 miles without need for human intervention (a driver has been stationed behind the wheel just in case, accompanied by a technician to monitor the navigation system), and that they've covered more than 140,000 miles with the human chaperone stepping in only occasionally. One of the cars was even able to safely make its way down Lombard Street in San Francisco, the fabled "crookedest street in the world," the Times says.



Read more: http://news.cnet.com/8301-11386_3-20019136-76.html?tag=cnetRiver#ixzz11wC79QRi
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