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THIS WEEK IN AEROSPACE

THE WAR ON ALUMINUM, MARCY 2 IDEAS

AIRFRAME OPTIMIZATION HELL

Mainly, going from something that flies to something worthless hoping to someday get something more efficient flying again. The fact is Marcy 1 didn't have enough lift to do what She needed to do.



Got a wing from a discontinued glider to try to improve Marcy 1's efficiency.











It looks horrible compared to the beveled sheet & it's heavier. Everything needs to grow to balance it. You need a bigger balance beam to counteract its moment of inertia. It has to be bolted. It has unnecessary winglets since we have full cyclic control. It takes full power to get off the ground & quickly falls back down.





Went back to a glued balsa sheet but an enlarged balance beam. The best monocopter is completely glued even if every broken propeller & crash is a rebuild.

That got no meaningful improvement. The larger balance beam didn't improve attitude stability either. It's not loss of lift but loss of reserve power for translation. We as hover experts don't think she has enough attitude control to hover using sonar.

Also got rid of the inductor & relied on software instead. It's actually bearable with all the filtering required for attitude sensing.

The next step is a steeper angle of attack. Angle of attack changes require rebuilding the entire Marcy 1 but it's no worse than what goes into mocking up a human rated aircraft.







The steeper angle of attack was a disaster.

Despite your intentions of achieving fixed wing efficiency out of a rotary wing, a monocopter still gets most of its lift from just the outer part of the wing. People usually make it fatter on the outside or hang it on a long boom. Next comes longer wings.





That did slightly better in the wind, climbing even with full cyclic, but we're out of calm weather until next month. Going longer means no indoor use, so next comes going wider. A wide 1/16" sheet might actually work.





Undoubtedly going to require a longer balance beam to overcome pitch. This actually seemed to work well, but there's no such thing as a calm day in Calif* in April. Can get maybe 20 seconds before she's blown down the golf course.





THE WAR ON ALUMINUM

Next, the war on aluminum nuts continues.



Any threadlock completely destroys the prop. Down to plumbing tape & just letting it strip.


Overall, the Marcy 1 program sux.

MARCY 2 IDEAS



Been thinking of a long duration hover vehicle using 2 large monocopters bolted to a fuselage or a larger monocopter for outdoor use, but some people still get excited about tri rotors. Don't feel another tri rotor is advanced enough to call a Marcy vehicle.

Long duration hover requires a larger lifting area than any propeller or helicopter rotor can give. Pitch would involve differential thrust. Roll would involve throttle modulation from Marcy 1. Yaw would involve differential roll. Bearings would come from the Corona parts.

This would give 6 degrees of freedom from only 2 PWM's. Marcy 1 gets 3 degrees of freedom from 1 PWM.

It would need 3 batteries & 3 full duplex radio links to the ground. 2 would control the monocopters which would use beam cutoff sensors instead of magnetometers & no thermopiles. An IMU on the fuselage would detect attitude. They wouldn't need balance beams.

1st step is flying a big monocopter with a larger battery, motor & a dummy balance beam. That would prove longer flights were possible.


It's hard to justify the amount of work going into thermopiles if no future vehicle is going to use them. With the payload limitation & open space requirement, Marcy 1 is never going to do more than POV lighting at night. Monocopters can't bank enough to counteract wind because their magnetometers lock up.

When the weight of the monocopter is factored in, she doesn't get much more thrust out of the motor than a bare propeller. A bare propeller + flap would probably do better but couldn't do POV.

So it's heading back to the original plan of Marcy 2 as an indoor tri rotor & Marcy 3 as a VTOL Predator. Marcy 1 would be a toy for POV, maybe autonomous but more likely manual.






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ScanEagle Video



I came across ScanEagle video on EngineeringTV that showed ffew things that I din't know about it - each wing is attached to fuselage by one pin, motor mount is very flexible ( for vibration isolation) - there is a good shot of it towards the end of the video. Video has two parts and there is comerciall in the middle ( i.e. don't close the video when commerical starts ( ~ 2 min into the video...)

http://engineeringtv.com/blogs/etv/archive/2010/03/25/scaneagle-unmanned-system.aspx
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Inverted V-tail advantages?

Did some googling on military UAVs and it came up with this nice site, listing 30 UAVs currently in use and for future deployment.

09-rq-7.jpg


http://www.popsci.com/technology/gallery/2010-02/gallery-future-drones

I found the inverted v-tails on some of them interesting, can anyone enlighten me on the advantages they present compared to normal v-tails or even more conventional tailplanes? I've seen one or two blog posts with similar mods, but it seems all it does is save weight.


http://uavkes.blogspot.com <- our blog


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Hi, this is my first post in these forums. I'm an avionics software developer working on a CS Master's with no robotics background (beyond some Lego Logo and Mindstorms stuff way back when) but I'm looking to change that for my Thesis.

I'm looking at researching and developing a simulation environment for use in drone fleets (primarily UAV but I want it to be useful for ground and sea drones as well). While I want a reasonable basic physics handling of each unit my primary focus is going to be communications between multiple units of a BVR fleet.

Any suggestions on what I might want to consider or any research material I might find useful would be terriffic!

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The competition held on March 20 and 21 in Taiwan. There are various events in the competition. Please refer to the official site : http://www.iaa.ncku.edu.tw/~whlai/uav/2010/
One of the events is Beyond-Vision-Range Flight. The airplane should fly far away and take some pictures of ground targets. The locations of tragets in the competition are shown in the following figure. The farest waypoint is about 3 km from home location.


We used EasyStar as the vehicle and UAV devBoard as the contorller. The plane crashed twice due to EMI problem before the successful flight. Because of the strong wind, it deviated from the expected flight path and disappered in the sky for about half an hour. When we were going to give up and the referee had asked the next team to take off, it suddently showed up above the home location. The crowd cheered as the plane safely landed on the runway.

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3D Robotics

Tri/Quadcopter awesomeness


[There was a bunch of very cool Tri/Quadcopter stuff on the RCG blogs today. Here's a sampling:]


Above: A very cool custom tricopter with a Trex body so you can tell which direction is forward. Check out the post for details on the pro quality pan-tilt camera mount.


And check this next one out. Did you know that you can make a Mikrocopter amphibious? This video is mindblowing. It starts underwater, but keep watching:



Finally, a "best of" video of Mikrocopters as camera platforms. How many Hollywood movies or TV shows have you seen recently that used quads rather than cranes?



Both of those quad videos are from this post, which is great introduction to Mikrocopters. Worth reading the whole thing.

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Developing an IMU from the UAVDevBoard

Hi all!

First I wanna congratulate all of you with all the things you've achieved already!
Now I have question:
I have to do a large school project, I have almost a year to complete it, and I want to make an IMU and display the data graphically using a rotating cube. I've done a lot of reading on this site already, and this is what i came up with:

My idea is to use the UAV Dev Board as a starting point. I would make my own board based on the UAVDevBoard, and rewrite the code (Yes I know I'd be reinventing the wheel, but thats part of the assignment :P).
Because the IMU would not be moving a lot, I won't be able to use GPS data for yaw correction (Right?), so I would need to use a magnetometer (Right?). And if so, what kind of magnetometer would I have to use? I was thinking a 3-axis tilt-compensated magnetometer like this one: http://www.sparkfun.com/commerce/product_info.php?products_id=8656

Also the sparkfun description of the UAVDevBoard kind of confuses me, because it says
"dsPIC runs at 120MHz with 16MHz resonator and PLL"
Now I understand that PLL can multiply the clock speed. But my understanding is that it can only multiply by 4, 8 or 16, none of which give 120MHz. Also the datasheet says that PLL can only be used with a 4-10MHz oscillator.
And finally, in the code i can't seem to find the place where the PLL is set?
Could someone maybe explain to me how they got to 120 MHz?

With regards,
Wouter van Verre
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Rule of Thumb for Power to Lift

1 horsepower = 7 pounds

I've come across this magic number using different sized rotors, props, and engines in large RC helicopters and planes, and also researching horsepower to lift divided by time in several ultralight and light sport aircraft and rotorcraft, and this is a good rule of thumb when developing something that needs to do more than hover or drift in the wind.

Guidelines for precise calculation of lift or thrust

http://www.heli-chair.com/aerodynamics_101.html

Comparison information using UAV specialist developer information

http://www.barnardmicrosystems.com/L3_engines.htm

Be sure to click on the different links for engine type (4 stroke, wankel, turbine, etc.) In fact, Barnard Microsystems is an excellent reference for those looking to DIY a larger drone, and is highly informative reading material in all aspects of UAVs.

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Michael's Dispatches 4 U

On http://www.michaelyon-online.com/warthog.htm Michael Won wrote:

UAVs are very useful, but come with sharp limitations. They are great hammers when you need a hammer, but they’re still hammers when you need a wrench. For example, UAVs can’t guard bridges against suicide bombers. They have limited, pinprick firepower other than for small targets. They are useless in poor weather. UAVs are but one sort of tool in a great big tool chest.




IMG_1727aC-1000.jpg




The Warthogs had to wait for a Reaper to roll by. No telling where Mr. iRobot would fly to. Do these go to Pakistan? I have no idea, but it seems like you can’t read the news without seeing where these robots have hit more terrorists. There was a time when the enemy thought terror was a one-way street.

This place has gotten to be like a hornet’s nest of Predators and Reapers. A couple years ago, you’d see them every day, but now you can’t turn around without seeing an iRobot Terminator buzzing around to land or disappearing into the sunset or sunrise.


lmopar also had some more Insitu porn from the same airbase for everyone interested in that.

http://www.rcgroups.com/forums/showthread.php?t=1215717


a3138603-213-P3220047.jpg?d=1269365085




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Developer

ArduPilot 2.5.1 alpha test video

I have been busily testing ArduPilot 2.5.1 with ArduIMU and correcting bugs in the basic functionality. I now have all MODEs working well in my primary airframe configuration and will now work on verifying other configurations (radio types, shield versions, thermopiles, etc.)


If you want to help test climb aboard. There is an active thread in the Forum.

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Developer

Flight testing 2.5.03

Hi All,
I just uploaded the last version of 2.5.0(3) I wanted this one to be rock solid before 2.5.1 came out.

I got a few hours today to tweak code and gains for my EZ Star. I implemented the derivative term in the heading/navigation loop and all the other loops used just the p term. The derivative term helped reduce overshoot by about 50%. I'm not kidding about the wind. The plane was flying at a 30° angle to fight the wind.

Altitude hold was working very well. Pitch_comp reduced to .1 was about all I needed. The airspeed control needs work, but Doug is tackling that.

I have my own personal ground station in Flash and I added uploading of all of the major variables in order to tune the aircraft in flight. This worked great so I'll leave the code included for the GCS team to check out. I didn't use error checking, I had the plane echo back the values so I could see if the uploaded values worked correctly before re-entering AP. It was far less complicated to do it that way than to try and implement errror-checking through code.

I've also implemented a simple dampening system for flying into the wind based on ground speed. Doug has a much more complex version, but this one worked remarkably well. Here you can see the loiter pattern. Please note that I was flying into a terrific headwind. The plane was moving 12 mph upwind and over 40MPH downwind. Sometimes the wind would pick up and the plane would virtually stand still, hence the strange patterns. Overall the snaking was minimal and far better than before. I was able to hold the 45m radius no problem. I could have cut that down to 30.







Altitude hold with 15 loops around home, then a landing.


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A little side project...

I’ve been working on a little side project. I originally wanted a case and / or a stand for my Xbee and Xbee Explorer module, so I ordered a couple from Polycase and strapped it together. It looked nice enough and attached to the back of my laptop with Velcro so it was an OK solution. Then I started getting lazy and didn’t want to lug out my laptop and everything every time I wanted to log a flight, so I went to a couple of the different on-board loggers, but never really found a solution I liked (picky, I know.) So that brings me to my little project. I have just finished the schematic, layout and specs and I have a few boards on the way.Here’s what it is: It functions in four possible modes; logger only (you can use it as an onboard data logger without the case and additional modules,) logger plus data pass-through on the USB port (with an Xbee module attached - for when you want to log data to the microSD card AND pass it through to a PC,) stand-alone receiver / logger (with an Xbee module onboard – utilizing the onboard battery, no PC required.) So if you took the best attributes of an XBee Explorer module and combined it with a really good data logger with a battery and charger…this would be the love child.I actually have two versions: one for those of us who like elegant solutions, and another for those who believe in extreme simplicity, but require fewer features. I call them LinqLogger, basically because they were designed to log downlinked data.The first design consists of the following components and features:Components:It uses an ARM7 LPC2148 (512K user flash and a ton of GPIO pins,) includes both a USB and Barrel plug LiPO charger (MAX1555,) On/Off switch, RTC (facilitates date / time stamping of logs,) Xbee socket (pick your own or use one you already have,) external reset, and start / stop recording buttons, USB link and logging status LEDs, microSD card slot (up to 2 GB FAT 16 formatted for PILES of data)Features:Not only does it do a nice job of data logging, but it also has a USB mass storage device profile built in - so when you attach USB, you get a mounted drive on your PC where you can see the actual files on the SD card; nice because you don’t need a separate microSD card reader / writer.The external battery connector makes the board a very independent data logger; you don’t need another microcontroller. It comes with SD+USB boot loader that allows the end user to tweak firmware to their project specifications. Configuration is done through an on-board configuration file, so there is no need to type in initialization commands. When the module is switched on and logging is initiated, everything received by the Xbee module is recorded.The second (simpler) design consists of the the following components and features:Components:It uses an ATMega 328 (16MHz, 3.3v), USB LiPo Charger (No barrel plug – MAX1555, charging LED,) microSD card slot (up to 2 GB FAT 16 formatted for PILES of data,) no RTC, On/Off switch, simple FTDI to USB (just like Xbee Explorer,) Program / Log Switch (used only when programming the ATMega328 via an FTDI – this is done so that the USB used for charging and data pass-through is NOT used for programming.)Features:This model uses the basic serial STK500 boot loader which comes pre-installed so that you can tweak the firmware, but has very few additional features. The system is the equivalent of combining an OpenLog logger interfaced to an Xbee Explorer with an on-board power source and charger.If either of these sound interesting to you feel free to drop me a line. I will be posting pictures, schematics etc., and of course it will all be available as Open Source. I have breadboarded these and they both work well. The boards and the cool little cases will both be here in the coming weeks...if anyone else wants one, I'd be willing to sell them at cost as kits or something. Any ideas you guys have for additional development are obviously welcome too!
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Developer
Poll - how do you want FBW to work?

Jason Short came up with a great flight mode, FLY BY WIRE, in ArduPilot 2.5. This mode differs from STABILIZE. In STABILIZE the autopilot constantly tries to return the plane to 0 pitch and roll, while you give stick inputs that tell the plane to do something else. It feels a bit like you are arm wrestling against the autopilot sometimes. With FLY BY WIRE if you move the right(*) stick half way to the right then the plane will bank half of the maximum amount defined. As long as you hold that stick position the plane will hold that bank. If you center the stick, the plane will go to zero bank.

* - All references to right stick assume a mode 2 RC setup where the right stick controls pitch and roll.

That is all great! You are not arm wrestling the autopilot. You are telling it what roll you want and it is giving you exactly that roll.

But what about throttle and elevator? Jason had a scheme where if you moved the right stick then you would get both a pitch and throttle response. In 2.5.1 I have been trying an alternate scheme involving both pitch and throttle increasing or decreasing together. I am convinced that these schemes are not the best. But what is? It really comes down to user preference.

I think the two best alternatives are:
  1. Have the throttle remain under manual control and have the right stick up and down control pitch angle. This setup is great for tuning your servo PID gains (both roll and pitch), and is a really fun way to fly.
  2. Have the elevator maintain a constant airspeed and have moving the right stick up and down increase or decrease throttle from a cruising throttle. This setup is probably the ideal setup for new pilots. You can hand the transmitter to anyone and they can fly. Can't stall because airspeed is controlled. Want to turn, move the stick to the side. Want to go up or down, move the stick up or down. Of course they still have to deal with what up and down is and what left and right are while coming and going, but if you let go the plane will always take care of itself.
What do you think is best??? Maybe something else?

I can't seem to get the poll to embed - please go here

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Commercial Quadrotor Recommendations?

I am setting up a lab this summer for some student research that will be similar in most ways to this one at MIT: http://vertol.mit.edu/

I would like to buy 6-8 commercially available trirotor or quadrotor helicopters in the $1000 - $1500 price range that would be similar in capabilities to the old Draganflyer V Ti. I've looked around and I would be very happy using Parrot AR Drones, but they have not set a date for releasing them or published a price. Likewise, Draganfly's web site says they will release their E4 in 2010, but no price or date of availability either. I could swear their web site used to say the E4 was coming in 2009.

I will only have the students for 10 weeks, so I would rather have them doing higher-level research using copters that work out-of-the-box and have available spare parts than have them spend a big part of their summer testing and debugging copters that they have built from scratch. Any suggestions?

Garry

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