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3D Robotics

Book review: Skunk Works

I just finished a terrific book that should be an inspiration to aircraft engineers everywhere. It's called Skunk Works, and it's an inside story of the peak years of Lockheed's now-famous secret development lab, which created the U2, SR-71, and Stealth Fighter. Although first published in 1994, it's still a totally gripping read, full of anecdotes of Cold War air battles and engineering heroics. Think "Soul of A New Machine" but about spy planes. I couldn't put it down.

They also created the first reconnaissance UAV, a jet-powered Mach 3+ drone called the D-21 that was launched from a B52 and designed to overfly Russia or China, dropping its film canister by parachute to be recovered before self destructing. This was before GPS, so the drone used a sophisticated star-tracker for navigation. Although it flew five missions over China, problems with the film recovery process led it to be cancelled.

A couple cool tidbits: the big breakthrough on stealth was the discovery (from an obscure Russian scientific paper) that the radar signature of a flat object was the same (and small) regardless of its size. Thus the faceted shape of the Stealth Fighter, shown on the cover at right. The fact that computers in the 1970s could only calculate shapes with big polygons also contributed to its distinctive shape.

It's co-written by Ben Rich, the chief of the lab for much of that period. Highly recommended!


Here's the Publisher's Weekly description:

"Lockheed's Advanced Development Project has set standards for the aerospace industry for half a century. Under its presiding genius,
Clarence "Kelly" Johnson, the Skunk Works produced America's first jet
fighter, the world's most successful spy plane (U-2), the first
three-times-the-speed-of-sound surveillance aircraft and the F-117A
stealth fighter. Rich was Johnson's right-hand man and succeeded him as
director in 1975, retiring in 1990. In an entertaining style, the
authors describe Johnson's tyrannical managerial style, his thorny but
productive relationship with the Air Force and the stealth-technology
breakthrough that revolutionized military aviation. Writing with
freelancer Jonas, Rich also recounts Skunk Works' failures, including
experiments with liquid hydrogen as a propellant and spy-drone flights
over China's remote nuclear test facilities. He has much to say about
the Defense Department bureaucracy and warns, "Everyone in the defense
industry knows that bureaucratic regulations, controls, and paperwork
are at critical mass... and... in danger of destroying the entire
system." This is a significant book for those interested in aerospace
research and development."
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Moderator

Dear Friends,
this is the first video of Java GS by Riccardo Ferrari (Fox Team) in action.
Java GS using RPC Server architecture implemented in Arducopter Redfox74 branch.
This is new approach to Groundstation for people that prefer completly opensource architecture instead to use labview. In the next revision of Arducopter i think that we implement this code as experimental , activable by DEFINE .
Regards
Roberto N.
FoxTeam : www.virtualrobotix.com


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Around the world with no fuel!

Hi Guy's,

Way off topic but.... How cool is this!

These guys have built a solar plane that has the potential to stay up for ever with no fuel!!

The will attempt to fly it through the night in the next week or so.

Here is a little video from their YouTube channel. Cheers!

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My New AGV



You might remember the old one, which was just a prototype, this one is much better.


The new really big difference is the vehicle (you can see the name of it on the truck every where). I am pleased with the truck, a lot better than my $20 Rc hummer i was using before. This one has plenty of power to drive up inclines and through grass even though i still would only like to drive it on concrete or asphalt.


Also i made some custom PCBs for this purpose



If your interested in a PCB, i have extras i want to get rid of for $6 and free postage in the USA. If you want one then send me a message.


Here are the parts that go on the board:


I will be working on the code for the next few days. I have ran test code and rough AGV code and my custom board is working fine.

I bought a 3"x 2" x 1" plastic project box from Radio Shack and cut a few different holes for cables to go through. My custom AGV PCB goes inside.

The ESC, servo, and UBEC wires go through a hole in the top of the truck that was meant for the antenna.

The box is attached to the bed of the truck using velcro and the GPS is attached to the box using velcro

Here it is all finished. Just like before, the compass is mounted high in the air away from any magnetic interference from the electronics and motor.



I will post some video hopefully next week.


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This week in aerospace



Monterey flights were pre flighted but the fog never cleared. Then attempted a failed flight over Tomales Bay in which we discovered 2 years of vectoring motors to aim the camera had worked the mounting tape completely loose. Monterey would have been a disaster in that case.

Almost time to invest the $30 in an arducopter. Wait long enough & commercial technology eventually can take over what only custom systems did years ago. Would prefer a 32 bit processor on the smallest board possible, without all the extra stuff or fragile hirose connectors.



The trick with the Vika 1 airframe is real cheap crashes. All the parts are easy to make with hand tools. $10 of wood lasts 1 year of crashes. Who knows what CNC aluminum & landing gear would cost.



Did snap a video of the moon over the valley during a mounting tape test flight. It seems the wind is always going to tilt the propellers slightly.






MediaTek didn't materialize. Wasn't optimistic about it from the beginning. In the interview could tell #1 they were looking for someone with a formal education in computer science & not a jack engineer. #2 they obviously knew someone else & we were just a sales pitch from a recruiter.

However, probably going to start another job in 1 week not in aerospace mind you. Vacation fail.





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T3

Made a successful flight 21 June with the Easy Star and ardupilot 2.6
The flight was autonomous from the start of the video to 20:43:06 (time on video).

For this flight I forgot to install the gps tracker, so no nice flight path graphics:(

Header file used for this flight:AP_2_6_header.h (details on airframe are below)

Here is the video of the flight showing the Dutch polders.
Enjoy

Part 1


Part 2

This was the mission plan.

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The airframe

3689358756?profile=original

Details:

Ardupilot 2.6 with shield v2 (mounted in the first opening under the wing)

XY and Z IR sensors

Ublox GPS (Mounted on the tailboom on top of the xy sensor)

900mHz xbee for telemetry

Turnigy B2835-2700 Motor with 30A ESC (mounted in the second opening)

Turnigy camera from Hobby King

3689358808?profile=original

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Got any great ideas of how to use a flexible board Arduino - these guys are making "a few for inspiration" and sound like they are willing to share their new toys with people with awesome ideas!!

http://www.seeedstudio.com/blog/2010/06/29/seeeduino-film-maybe-the-first-arduino-board-on-fpc/

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I just thought I'd share a quick video (and picture.) This is a movie I made of a replay of a real flight a couple days ago. I collected the data remotely while the flight was in progress via a maxstream radio modem connection between the aircraft and the ground station. I saved the flight data on the ground station and then can replay it later in FlightGear. The display is a "glass cockpit" style display I'm just beginning to develop.

https://www.youtube.com/watch?v=vTZ7b-uiTgU

Disclaimer: I have really noisy inertial sensors rigged up at the moment, 10 bit ADC's, you'd laugh if I described my IMU calibration procedure, probably very non-optimally tuned kalman filter for these sensors, windy day (yeah that's it, blame it all on the wind) :-)

But the really cool stuff (I think) if you can look past some of the less smooth flying, is to see all the elements of a very dynamic system playing together in one view.

For instance: the altitude tape shows the current altitude and the target altitude (via a magenta altitude bug.) If you are below the target altitude, the VSI will show a target climb rate (or decent rate if you are too high.) The autopilot tries to match the target rate of climb by manipulating pitch. The green vbars show the target pitch angle. The yellow bird shows the actual pitch angle. The autopilot manipulates the elevator to try to achieve the target pitch angle ... and you can see all these elements working together to achieve the goal.

There is a similar process with route navigation. The system computes a target ground track heading using wgs84 based math. The target heading is marked by a magenta heading bug on the horizon heading tape. There is a white "V" indicator that floats on the horizon heading tape which indicates the ground track heading. The actual heading shown is "true" heading as computed by a 15-state kalman filter. (The filter converges to true heading, independent of wind, side slip, etc.) So the autopilot computes a target roll angle to try to line the white "V" ground track indicator up with the magenta heading bug. And finally the ailerons are manipulated to try to match the target roll angle. If you watch the video you can probably see that I need to increase the gains a bit on my ailerons (maybe the end point limits as well.) What do you think? You can see the actual roll angle often lags pretty far behind the target, and this leads to some excessive serpentining as the aircraft flies towards the target. But if I dial up the gains too much, I may start over reacting to my filter's attitude estimate correction jumps. I think there is a balancing act that needs to be made between tracking your targets quickly and accurately versus slowing things down a bit to help smooth out the flight.

Finally you can also watch airspeed. Right now the autopilot is configured to try to match the target airspeed by manipulating the throttle, so you can watch the throttle move up and down to try match airspeed. Of course as you fly the course and bank into turns, encounter up and down drafts, and work around filter estimation errors everything is changing all at once.

On the one hand, I would like to see much smoother and tighter control, but on the other hand I have to sit back in a bit of wonderment just watching all the pieces working together and doing what they are supposed to do.

I think this is evolving into a really powerful system for evaluating how well an autopilot system is tuned and how well it is tracking it's targets. If your PID gains are inducing oscillations, you can quickly see that. If the PID gains are too low, you can see the system react too slowly. You can see your controls throws max out at their preset limits (or not if that is the case.)

And for what it's worth, this display can also be fed from real-time telemetry data so you could optionally have this running during the flight ... I'm not sure why you'd want it ... maybe during the design and development phase or to impress your wife or girl friend.
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It's been a bit overdue but I've posted a number of updates on the Project Andromeda blog detailing our recent progresses with the manufacturing of the airframe, autopilot development and some software tips. The articles are as follows:


The Perseus Autopilot:

http://www.projectandromeda.com.au/blog/?p=131


This article details the Perseus Autopilot and the recent developments. It also details the hardware and some of the software on board.



Interrupt Based Programming for Microcontrollers

http://www.projectandromeda.com.au/blog/?p=143

A small article which I hope will be useful to people looking to write programs for microcontrollers using interrupts.


Airframe Developments

http://www.projectandromeda.com.au/blog/?p=149

A picture-heavy update on how we are developing the airframe of the Andromeda vehicle.


All of these are available on the Project Andromeda blog:


http://www.projectandromeda.com.au/blog/


I hope you find them useful and I'd love to hear your feedback.


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Developer

Ardupilot 2.6.2 Beta

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This beta brings support for the new MediaTek GPS unit. The MTK works great and it's very light.

I've also added some bug fixes including:


  • Auto Trim - (on by default) When you enter any flight mode from Manual, you'll save your current trim values. Great for trimming your plane in the air.
  • FBW issues (turning too much in one direction) caused by incorrect or unset radio limit - fixed with new algorithm
  • Radio Mixing - lowered the mix value for more responsive sticks
Let me know if you have issues, and I'll update the release version.
Jason


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3D Robotics

I know, it's been messy. One Xbee adapter for the ground, another for the air. Why can't one Xbee adapter do it all? Now it can! Jordi's really outdone himself on this one. The newest addition to the DIY Drones store: the ultimate all-in-one Xbee adpater--just $24.95. From the product description:


"

This is the most advanced and competitive XBee interface board you will find! It's breadboard compatible, has 4 status LED's (one selectable to display ASC or RSSI), built-in 3.3V power regulator, configuration solder jumpers and an unique feature that allows you set the device as Master or Slave FTDI mode with a simple slide of a switch!

In master mode you will be able to attach any USB FTDI cable/board and send/receive data like the rest of the average XBee adapters do (normal use mode), but if you slide the switch to "Slave mode" you will be able to attach the XtreamBee to any FTDI compatible device, like Arduinos, ArduIMU and Ardupilot's. So you only need two XtreamBee's, one master and other slave to create a both-ways wireless FTDI communication (or one XtreamBee set in "Slave Mode", if you already have another third party XBee adapter). You can even tweak the board to "wirelessly" emulate CTS and RTS signals. This board was under development for about 1 and 1/2 years! But finally after many failures I made it work with cheap/passive components. Great isn't it?

For more information please click here.

Features
-Includes 2 x 2mm female receptor headers to correctly place the XBee module.
-Includes 1 x right angle 6 position male pin headers.
-3.3V regulator build-in.
-ON Led, Tx/Rx Led's, ASC and RSSI Led (Jumper selectable).
-Master/Slave selector
-Solder jumper allow you to supply the board directly with 3.3V (Only recommended in Slave Mode).
-Breadboard compatible!
-Screw holes for easy mounting. "

(Xbee module not included)

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