Blogs

Tom Pycke, who is one of the more sophisticated UAV hobbyists, has a good post showing how to use the open-source Flight Gear simulator program to test your autopilot code.

He begins:

"A lot of people think they need great electronics skills, a lot of time, and embedded programming skills to experiment with Kalman filtering of IMU-data. Think again! The key to all your success stories is simulation!

One of the easiest tools that can help you with those simulations, is a great flight sim called Flight gear. It uses advanced aerodynamics simulation libraries, among which some were created by the NASA. Good enough for our purposes! On top of that, you can easily configure Flightgear to log all the data you need. I updated my config file to log the following variables:

• Roll
• Pitch
• Acceleration along the 3 axis
• Gyro reading along the 3 axis
• Heading
• Airspeed"

He includes sample VB code, too (yes, you can code a Kalman in VB!). Read it all here.

The cover of MAKE magazine this month is a how-to on "blubberbots", which are small indoor blimp UAVs (story only for subscribers for the moment--subscribe! It's worth it). You can buy a kit from the MAKE store for $99 that will allow you to build a limited UAV--it heads towards lights and has a bump sensor to retreat when it hits walls. But how much harder would it be to give them real navigation abiliites, triangulating off IR beacons or even using GPS (if your roof isn't too thick)?

Oh, and the back page feature of that issue is on me and my Lego UAV (blush).

Here's a picture of the CPU and motor assembly from the creator's website, where there are several other Autonomous Light Air Vessels (ALAVs) and robtics projects:

These scientists describe their UAV project at the South Pole. Sound familiar?

"Flying a mission is always a little scary. Tom, the project engineer and pilot, stands by with his remote control and flies it a little until a stable flight is acheived, then we engage the autopilot. The plane then turns and heads off into the distance, disappearing from view after about half a mile, and dropping out of radio contact with its computer base station after four miles or so. That part of the mission is the most scary, as we've nothing to do but wait for fifteen minutes biting our nails as the plane follows its plan.

We breath a sigh of relief when we regain the signal and see some coordinates on the screen, but only declare success once we've seen the machine, taken it smoothly back down to the snow, and downloaded the data its recorded."

Play around with Lego Mindstorms NXT enough and at some point you'll inevitably get frustrated with NXT-G, its graphical programming language of "blocks" that you drag around and connect with "wires". It's great for teaching kids the basics, but once they embark on anything remotely ambitious they're bound to run into trouble. Whether it's the crazy sprawl of blocks over the work area (even a simple loop can require screens of slow horizontal scrolling), the lack of floating point math or, perhaps worst of all, the total absence of debugging tools, sooner or later you're going to start longing for a proper programming language that uses, you know, text and stuff.

"if...then...else", "while", even "for...next" -- you won't know how much you actually like those constructs until you don't have them. For anyone who's ever programmed, there's nothing better for understanding programming logic than properly tabbed and commented code, all in a column of text as God intended. And for your kids, there's no time like the present to introduce real programming, using coding conventions that will be as relevant in the decades to come as they were in decades past.

The good news is that there are lots of replacement text-based languages for Mindstorms NXT, from Java to Lua (or, if you want to stick with visual programming, you can also use LabView, the professional-grade language that NXT-G is based on). Even better news: I'm here to tell you that one stands out from all the rest.

It's RobotC and it's simply fantastic. If you're not a C programmer, don't worry--aside from a few grammatical conventions, it could be BASIC. But where it really stands out is in the programming environment. RobotC's integrated development environment (IDE) includes real-time syntax checking, compiling and contextual help and auto-complete of functions and variables. It has an awesome debugger, allowing you to step through your program, set break points and watch variables, or just watch the code executing on the NXT brick. And its collection of instructional and sample programs is unmatched in the Mindstorms world.

To give you of sense of this, here's my Lego UAV code in NXT-G (here and here) and in RobotC (here).

RobotC got its start at Carnegie-Mellon, the nation's top robotics school, and the pedigree shows. But special credit should go to Dick Swan, who authored much of the current program. (Dick, get a home page so I can link to you!)

For the stuff that we're now doing, including integrating GPS via Bluetooth, there's nothing for Mindstorms NXT that can match RobotC for flexibility and ease of use. Plus if you want to teach your kids real programming, why not introduce them to a real programming language? C leads to C+, C++ and C#, which is a lot more than you can say for Java ;-)

(Aside: as I was re-teaching myself how to program in C, I was reminded about the funny logic of computers. -100 is > than -90. Is this true in all languages?)

If you ask me, this is better than NASCAR. The DARPA Urban Challenge (robot cars race though a town) is being webcast live now.

Very well done live video is here, with color commentators, helicopter views and tons of team cams. Go Stanford (pic)!

How long till we see something like this for UAVs?

Well good old Google as ever comes up trumps...

http://www.rrcc.org/downloads.htm

http://pages.sbcglobal.net/limeybob/

http://www.ajdesigner.com/phpwinglift/wing_lift_equation_force.php

I'm sure there are many others that people know about.

Perhaps there should be a page of useful software here.

G

It would seem that being +30 at 4000' means something, which of course I already knew, but just what is the drop in performance on a 50 odd inch wing trainer??

What magic program or website could tell me that to lift lets say an extra 1KG of equipment at a density altitude of 7000' the aircraft would need to be X wingspan with Y power up front??

There must be something out there that will tell us such things.

As I walked into add this little bit, my wife said come and look at this, making its way across our dining room was a tiny mole snake, or thats what we think it was anyway.

I must be back in Africa!!!

Sorry if my blog posts are annoying some as they appear on the front page, very little hard core UAV and lots of off topic, but it should encourage some of the 270 other members to move me off the page ;-)

Gary Mortimer, now that the storm has passed.....

Settled back in South Africa after the glorious world cup rugby victory!! A storm is brewing outside so can't stay long!

I have been itching to get a shot of animals to start the process of getting software to spot them for me (grown ups will work that out)

It also crossed my mind whilst flying down to South Africa that a Zagi or some such flying wing would be a very robust platform to play with. Having never flown a powered flying wing I made up a balsa box for engine and battery and taped it onto my Xit flying wing.

My eldest Adam demonstrating here!!!

As you can tell another fine example of my engineering skills, still it worked it went like 5h1t off a shovel, a little two unstable for camera work. But if I could find a two metre span foam flying wing I think it would be a winner. My youngest Daniel demanded that it be turned back into a glider as he has most correctly spotted glider guiding is the finer form of model flying.

Next the Hobbico Superstar received the electric motor.

You all know what that looks like, so here we are before the off.

Anyhow that flew, but on adding my camera did'nt.

The aircraft did just not quite have the go at 4000' and plus 30C

Does anyone know a simple place for working out what a trainer type airframe might lift when temperature and density altitude have been taken into account?? I might just have to get out my E6B but have no idea what sort of thing a standard airframe would lift at ISA or how to work it out.

All rather annoying as the school that bounds the polo fields from which we fly has a small airfield, yes I said that right a small airfield. What would I have given to have an airfield at my school. Anyhow they have a few game animals, a couple of Zebra and some Blesbuck. If I can get some shots of them to my friend Lyndon Estes in the US then maybe his wizards can work out how to count them from video or stills.

I can use some ic powered airframes but I think that vibration will be an issue, maybe I will have just try that until the powers to be can be pursueded that I need a big electric glider ;-)

From inside the storm in Mooi River......

Bang

• Return to starting point when pilot looses the plane

• GPS input and parsing based on several NMEA codes
• Waypoint storage (one for now)
• SD card support
• Radio control receiver interface
• Servo control
• Video output of any GPS and microprocessor values
• As a separate unit, 2.4Ghz video downlinking.

• Video overlay on the downlink
• Google Earth Integration for setting routes (via KML file read/write)
• Pan/tilt/snap camera control integration

"Not even the bucolic Berkeley hills are immune to security concerns in a post-Sept. 11 world, as the editor in chief of Wired magazine has discovered.

Chris Anderson, a 45-year-old Berkeley resident and aerial-reconnaissance enthusiast, sparked a minor security scare Sunday when his remote-controlled plane - equipped with a camera - crashed into a tree at Lawrence Berkeley Laboratory.

Security personnel apparently didn't notice the plane until Anderson asked for help retrieving it, but they've taken notice since.

UC Berkeley police are investigating and federal authorities may be notified about the breach at the hillside lab, which is owned by the U.S. Department of Energy and managed by the university. Unlike UC-managed labs at Livermore and Los Alamos, Berkeley is not involved with nuclear weapons and does not conduct classfied research.

It does have important equipment that needs to be protected, said Dan Lunsford, who manages lab security.

"I think, post-9/11, when we see an event that is out of the ordinary, those are things that gain our interest," Lunsford said. "The greatest thing right now in the war on terrorism is prevention."

Anderson, who lives within walking distance of the lab, does not appear to have broken any laws, Lunsford said. In fact, Anderson said, firefighters helped him get the 4 [ed: that should actually be around 40] -ounce foam plane back when he came calling at the lab's front gate.

"They were incredibly nice about it," he said.

The flight was an attempt to take photos of the unusual architecture of the lab's cyclotron, a mostly round particle accelerator. The photos were to be posted on his personal Web site, diydrones.com, devoted to unmanned aerial vehicles, or drones.

Instead, Anderson, whose children took turns piloting the plane, ended up with a partial photo of the cyclotron and a blog entry titled: "Lesson: Don't fly planes over secure national labs!"

Anderson, who worked at Los Alamos lab in New Mexico, acknowledged he should have known better than to take the close-up aerial photos.

"I promise not to fly over secure national labs anymore," he said."

I had the wackiest near-catastrophe this weekend. My kids and I were running aerial mapping patterns over the Lawrence Berkeley Labs cyclotron (which is very distinctive from the air) and testing some ISO settings on the Pentax A30. Because we were over a built-up area and had to hand launch and recover from a hillside, we were using the Mutiplex EasyStar, which is just an RC plane, not a UAV. Which means that it's all up to the pilot to keep things in hand.

Unfortunately I was the pilot for one run where the sun was in exactly the wrong position and I got momentarily blinded. When I found the EasyStar again I couldn't tell what it's orientation was. Needless to say, ten seconds later it was in the top of the highest tree inside the gate of a super-secure National Laboratory. Yikes.

I dropped the kids off at home and went to the main gate of the lab and explained what happened. To my astonishment, they neither laughed at me nor arrested me. Instead, the head of security escorted me to the cyclotron and we started looking around. I went and got the transmitter and gunned the motor, and eventually we were able to find the plane by following the sound. Sure enough, it was 60 ft off the ground in the tree and really wedged in.

There wasn't much to be done, but at least we'd located it. I left my contact details and we agreed to have me come by the next weekend and see if the wind had budged it at all. Then I went home.

Half an hour later I got a call from the lab. "How would you feel about us using a hose to knock it down?" Needless to say, the risk of water damage seemed a lot better than losing the whole thing, camera, GPS, radio and all. "Go for it!" I said and dashed down the hill again to see what I could do.

When I got there it looked like the scene of a real airplane crash. A lab fire engine with lights flashing was at the base of the tree and searchlights had pinpointed the plane. Hoses snaked across the road and emergency radios were squawking. A fireman was braced against the truck and was about to let loose a high-pressure stream at the plane.

It actually turned out to be harder than it looked, given how high the plane was and how dense the tree was. They had to replenish the water tank once from a fire hydrant before they finally knocked it to the ground. The foam wings and tail were torn off (that's okay--they're just $20 to replace), but the fuselage and the all-important electronics were all there. I thanked everyone profusely and took it all home to dry things out and gauge the damage.

Right now the radio, motor and GPS look fine. The camera is going to have to dry out more before I can tell if it's going to be okay [UPDATE: It's fine!] , and so too for the LiPo battery. But I'm so pleased to get the rest back that I hardly care. Meanwhile, the image data on the card was really pretty good (a PTGui stitch of one pass is above).

Thanks LBL guards and firemen! I promise not to fly planes over your super-secure lab again!

Why you ask why.

Check out this great post from the winners of the Australian amateur UAV contest--the guys at Dionysus Designs, a Chico, CA-based team who focus on advanced RC technology, aerial photography and now amateur UAVs. They built their own airframes, then modded a beautiful powered glider (shown here neatly packed into a golf case to make the trip) to win best in show. Loads of helpful links in that post, too. Get in touch guys! We can use that sort of initiative here ;-)

Meanwhile, if you want other shots of contestents and UAVs from what sounds like a really sucessful contest, check out the photo archive here.