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3D Robotics

Multiplex vs HobbyKing Shootout!

Posted by Chris Anderson on January 11, 2010 at 11:30pm

I'm always looking for cheaper Chinese alternatives to our standard aircraft platforms, which is why I'm a fan of the Hawk Sky (EasyStar clone) and Busy Bee (good aerial photography platform). Most of them come really ready to fly these days, with pre-installed brushless motors and ESCs, servos and sometimes even decent LiPo batteries and chargers. Since many of these aim to offer cheaper alternatives to the excellent but expensive Multiplex line that are a favorite for UAV makers, I thought I'd check out two HobbyKing clones of our tried and true Multiplex Easy Glider Pro and Funjet: the Easy Fly and the Sky Fun. They've now arrived and the jury is in: the SkyFun is great and the Easy Fly is crap. At first glance, they both look very attractive. The HobbyKing SkyFun, at $63 with servos and brushless motor included and installed, costs less than a third of what the Multiplex FunJet and power pack costs. And the HobbyKing Easy Fly, at $70 with installed brushless motor, folding prop and servos, likewise costs less than a third of the Multiplex EasyGlider Pro and power pack. But are they really such a good deal? The answer is that the HobbyKing foam RTF kit quality varies pretty widely. The right kit is as good or better than the name-brand equivalent. And the wrong kit is no bargain at any price. First the good news: the SkyFun is a terrific replacement for the FunJet. As you can see from the photo above (the SkyFun is on the right), it's a bit bigger than the Funjet, but otherwise very similar. It comes with a smaller motor, which the commentators on the product listing say leads to pretty tame stock performance, but it has a very wide flight envelope, from slow to very fast (with a bigger motor). Most importantly for UAV uses, it has a HUGE equipment area. As you can see in the picture below, it has more than twice as much interior room as the FunJet, and the FunJet is known for having a lot of interior room. You could put an autopilot, a camera, a range of sensors, and all sorts of wireless video gear in there and still have room for loads of foam padding and movement to get the Center of Gravity right.

I haven't flown the SkyFun yet, but I'm pretty sure that this one will get a lot of UAV use, and possibly a motor upgrade if I get very confident in its flight characteristics.

Now for the bad news: the EasyFly. It's a joke, at least for UAV use. The quality of the model is far below Multiplex standards, and the cockpit area is a mystifying failure of design. Although the EasyFly is bigger than the Multiplex Easy Glider Pro, it's got only half as much interior space, due to some poorly placed servos, way too much useless foam and a ridiculously thick and deep canopy. Just look at it, compared to the Easy Glider Pro (the EasyFly is on the left):

You can see even more clearly from this angle that the EasyFly doesn't even have enough room for a decent-sized battery, much less an autopilot and other electronics:

Then there is the quality of the model. The folding prop and spinner don't fit the body, so they look bad and the prop blades hit the side. The motor is tiny compared to the Easy Glider Pro (which is, to be fair, pretty overpowered). And rather than proper horns on the ailerons and rudder, the EasyFly has these ridiculous lever things (I imagine that they're designed to lower air resistance, but they just have the effect of less solid control):

The comments suggest other problems, such as an unreliable wing mounting, but I think the cramped cockpit is simply disqualifying. I may end up using it to learn slope soaring (if I crash/lose it I won't be too sorry) but I can't see ever turning it into a UAV. Where would I put the gear?
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Chad Frost shares stories from NASA's autonomous systems and robotics department and his thoughts on civilian usage of UAVs.

Posted by Tim Trueman on January 11, 2010 at 10:30pm
iTunes linksAAC: http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=330632997MP3: http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=330633212RSS feedAAC: http://feeds.feedburner.com/diydronesMP3: http://feeds.feedburner.com/diydronesmp3It's been three weeks but we're back in this action-packed hour-long episode!
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3D Robotics

Who should we invite to be a DIY Drones podcast guest?

Posted by Chris Anderson on January 10, 2010 at 11:26pm
We're starting another year of weekly DIY Drones podcasts, and we need your help in choosing guests. Who should we invite to join us for a half-hour Q&A, to be recorded for the podcast audience? Anybody who is doing something cool is a good candidate, professional or amateur--we've had everyone from NASA scientists to other hobbyists. Please give us suggestions in the comments below. Who would you like to hear from?
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3D Robotics

DIY Drones live chat/podcast with NASA's Chad Frost tonight at 9:00pm PST

Posted by Chris Anderson on January 10, 2010 at 7:42pm
Free video streaming by Ustream Tonight (Sunday) we'll do podcast #13, which everyone here is welcome to participate in by listening to the chat live above and commenting and asking questions via the DIY Drones chat function. We'll be starting at 9:00 PM PST and will probably go about 40 minutes. This week we'll by joined by Chad Frost, manager of the NASA Autonomous Systems and Robotics department at the Ames research center. We'll be talking about civilian applications of UAVs. As always you can subscribe to the podcast here. Tonight's livecast will be recorded and available as a podcast on Monday.
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3-axis Geomagnetic Sensor with Angular Velocity Detection

Posted by Matt on January 10, 2010 at 4:18pm
Here is a new sensor which could improve stabilisation of our drones.It is purely a Geomagnetic Sensor however it can output rotation rate just like a gyro. It might even be possible to create an IMU type module using only this sensor and an accelerometer. That would be economical!

HSCD.jpg

Features- Angular velocity detection and electronic compass functions in a single component made compatible by utilizing ALPS’s proprietary software.- Achieves high resistance to external interference with its proprietary shield structure."By processing data detected on three-directional geomagnetic axes using proprietary software developed by ALPS, the HSCD Series realizes an angular velocity detection function through triangulation, namely a gyro function. Combining these angular velocity detection and electronic compass functions in a single package reduces the size of the mounting area, as fewer components need to be installed "" resistance to external interference has been improved by building ALPS’ proprietary shield structure into its sensor element. As the number of functioning components increases in such products as mobile phones, and as progress continues in making circuit boards more compact, it is becoming easier for geomagnetic sensors to be affected by parts that generate magnetic fields, such as speakers. The proprietary shield, however, minimizes the effects of the magnetic fields emanating from other components."
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3D Robotics

Paparazzi-based Quadcopter/Biplane hybrid transitions to and from horizontal flight

Posted by Chris Anderson on January 9, 2010 at 10:30pm
This awesome display of VTOL --> horizontal flight -> vertical landing is accomplished by the Booz Paparazzi-based quad project. Although many people have tried VTOL aircraft that are meant to transition to wing-based horizontal flight, it's very hard to accomplish the transition, especially the transition from horizontal flight back to vertical. This one does it very naturally. Impressive!
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Features you would like to see in ArduPilot GCS

Posted by automatik on January 9, 2010 at 2:00pm
I am pleased to report that ArduPilot ground station ( LabVIEW ) team is getting up and going.Our first objective is to clean-up the code a bit, make it more robust, and easier to add new functionality.Over time request for ground station features have been mentioned in few threads, and I would like to consolidate them in one place.What ground station features would you like to see or change?For example:1. kml logging : log lat, lon, alt2. voice synthesis : periodically announce status (way point, alt, speed); announce status through selected flight levels3. A choice of different graphic layouts, specially for the Horizon Indicator, something that would resemble more real aircraft instruments4. Change colors to get more contrast on sunny days5. Label baud rate settings for different GPSs so you don't have to remember (uBlox=38k; EM406 = 57k)6. Distribute the executable as a .app (not just .exe) so that Mac users can try it.7. Object tracking - once we have video support8. Show a 3d model representation of the plane9. online & offline maps support (google maps, OziExplorer,...)10. Data logging - preferably user selectable parameters- add your request
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Arduino/AutoPilot based on UB32

Posted by Tim Michals on January 9, 2010 at 11:02am
Goals for this projectHave UBW32 on order, the next version has 128K of RAM so... that will be nice1) UBW32 Software porting- Use open source 4.4.x gcc compiler http://www.codesourcery.com/- Gives better code generation then current 3.3.x- Follow the general setup an ARM process has... (more on this later)- Support C++, in order to support Wiring as is the AVR supports basic C++, so need to do this...- FreeRTOS port (This is done, but, using newer gcc- USB Host support- Support wifi USB dongle ( ordered dongle, it is a 1000mw 802.11b/g)- Support Ad-doc and infrastructure mode)- Video (USB) using off the self web camera- Support of Wiring- New boot loader based on LUFA (http://www.fourwalledcubicle.com/LUFA.php also with mass storage device)- similar to mbed.org, allows users to update firmware via mass storage...- once mode USB is working... need a way to switch between the two... OTG?- SPI SD flash support.2) Simple controller (more to follow)3) Lua scripting support (allows setting simple scripting without writing a bunch of c++/c code
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3D Robotics

AeroQuad--an Arduino-powered Quadcopter

Posted by Chris Anderson on January 8, 2010 at 9:30pm
I don't know how I missed this before, but there is a pretty mature project for a Arduino-powered quadcopter, called AeroQuad (also known in RC Groups as Quadrino, which is a much better name IMO!). Rather than using a custom board, they use a standard Arduino devboard and off-the-shelf Sparkfun sensors (although they did make a custom Arduino shield to solder them on to, although that doesn't seem to be available anymore)
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Goals and First Start

Posted by Jason Lyons on January 8, 2010 at 5:30pm
I thought I'd start out by outlining the goals of this project. Several years ago, I bought a remote control helicopter from Hong Kong, it's a Walkera Dragonfly fixed pitch helicopter (pretty much identical to the E-Sky Honey Bee Micro, or the Twister). It was pretty difficult to fly, and almost impossible if there was any wind. After I started getting into microcontrollers and control systems at uni (I'm now in the final year of an Elec engineering and Comp Science double degree), I started playing around with an Arduino and after awhile decided that I'd like to build a PID (or LQR) stabilization controller for my helicopter to make it easier to fly if I ever had the time (and then evolve into full automation if I can). This was a year ago, and in the mean time I haven't really had time to do much about it. Now it seems I finally have time (or, at least, the willpower to make time for it).I already had an Arduino Duemilanove, so I bought my first sensors a couple of months ago when I was all cashed up. I got these:ArduIMU Main board (4 DOF with room for 2 more gyros)http://www.sparkfun.com/commerce/product_info.php?products_id=93722x ArduIMU Daughter boardshttp://www.sparkfun.com/commerce/product_info.php?products_id=9373I got these about a week later, and assembled them no problems. I was surprised just how small the unit was. I managed to do some basic coding (getting the values from the Arduino to serial) but decided to save the rest for the summer uni break.Fastforward to now: I started working on it again about a week ago, and due to full-time work experience I only really have evenings with which to chip away at this project. I've got the sensors connected to the Arduino and I'm scaling the ADC values to units of gravity and degrees/sec, then calculating the gyro angle (in radians) through integration and acceleration angle using arctan2.Here's the setup:

Then I recorded a sample, rolling right & left then pitching down and up and yawing right then left. The X-axis is time in seconds.

As you can see, there is quite a bit of drift on the gyros, so I'm going to implement a Kalman filter to hopefully eliminate this.
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$69 1000mW FHSS Transceiver (900MHz)

Posted by Faisal Shah on January 8, 2010 at 1:29pm

* 900 MHz Frequency Hopping Spread Spectrum Transceiver* Point-to-Point and Point-to-Multipoint Network Topologies* Transmitter Power Configurable from 1 mW to 1 W* RF Data Rate Configurable from 38.4 to 500 kb/s* Serial Port Rate up to 460.8 kb/s for Streaming Applications* 128-Bit AES Encryption* Separate Serial Port for Diagnostics* Analog and Digital I/O for Sensor Applications* FCC and Canadian IC Certified for Unlicensed Operationhttp://www.rfm.com/products/dnt900.shtmlIs this too good to be true? Anyone try this out yet?How does it compare to the Digi Xtend module (1W as well): http://www.digi.com/products/wireless/long-range-multipoint/xtend-module.jsp
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EVOLUTION OF MARCY-1

Posted by Jack Crossfire on January 8, 2010 at 10:00am
Still no idea how to protect the propeller without a plastic injection molded shroud. This is 1 area where a $1000 makerbot would come in handy. Just don't have a $130,000,000 government real estate loan to store it on.

Marcy-1 came in just as heavy as Vika 3. The surface mount board, integrated radio, & new name made no difference. She has a lot more wood than Vika 3 but is more balanced.http://www.rcgroups.com/forums/showthread.php?t=1044312Tried spinning up on a table to ensure stability before lifting off. Didn't have enough thrust to break free of the rod & spinning was unbalanced.

On the test stand for Her 1st revolutions.

Now a test stand video for posterity.Finally, a full power liftoff on the golf course led to this.

Then tried this to get more moment of inertia, unsuccessfully.

She's too unstable. They seem to require precise balance like a propeller. The balance requirement means she needs a 2nd PWM to translate horizontally.The Bladestar must not have used imbalance for translation but relied on the fact that its engines blew sideways. Another point for monocopters.Steve Morris did indeed make a spin copter & it required 2 PWM's for horizontal motion.Also, since the Bladestar appeared, all monocopters have switched from photodiodes to single axis magnetometers for position sensing, making the Marcy 1 aircraft board already busted. Magnetometers would be much easier than photodiodes but we figured their update rate was too slow. Not anymore.Instead of computing north, they just sense an arbitrary sine wave on a single axis magnetometer & rely on a hard coded point in the sine wave to determine where North is.So a silly spin copter is a much harder problem than first envisioned. Marcy 1 needs to be a monocopter.MONOCOPTER NOTESMonocopters use a "balance beam" to keep the angle of attack level. There are no photographs of the Lockheed Samurai but the low resolution video shows it probably uses a gyro instead of balance beam to control angle of attack.It also has a winglet to make it more stable.Predictably, the Goog has nothing on sizing a monocopter since there are no monocopter Adsense hits. Nothing to do but cut some wood.

That lasted about 4 hours. At full power she couldn't exit the launch rod. Shortened the launch rod enough for her to fall off & she went straight into the ground, probably due to insufficient RPM.Tried increasing angle of attack, grinding down the launch stand, & suspected imbalance was causing her to hang up on the launch stand.BALSA TERRORISM

Finally made a number of monocopter variations & a symmetric blade design just to see what would happen if we got her as balanced as possible. The monocopter is very hard to balance because of the limited payload room.The symmetric Marcy 1 finally worked. She lifted off the stand & into a stable hover before running out of room & crashing. Here's the video of the tests leading up to & including success.Balance is everything. A monocopter has to be perfectly balanced about the axis of rotation & the point the launch stand attaches to.

Note that Steve Morris also did this many years ago. He seemed to start over when switching from aerodynamics research to autonomous flight. Here's his monocopter.

Meanwhile, more Marcy-1 evolutions reduced her size, returned her to asymmetry & increased her RPM to achieve useful POV illusions someday, though her disk radius is fixed & limited by weight. The asymmetric wing is seen as important for achieving horizontal translation.That's basically a Bladestar for a lot more money & made by a strange country. The extremely fine traces on Marcy 1 are plagued by dirt. Don't be surprised if the radio appears dead after a landing.In addition to balance, a loss of control after exiting the launch stand can be caused by insufficient power. Move the motor farther from the CG to increase power. There is an optimum distance from the CG at which the motor provides maximum power yet the counterweight is not so far away that the wing is symmetric. The Goog has nothing on this.A test without the balance beam showed it is indeed required for a stable angle of attack. The Goog has nothing on the optimum balance beam size.Suspect Marcy-2 will be a large monocopter. A very large monocopter using a foam wing promises the longest hover time of any VTOL & complete control with only 1 PWM signal.SI4421 VS MRF49XA

Meanwhile, conversion from 72Mhz to 900Mhz isn't going so well. The Si4421 is pin compatible with the MRF49XA but seemingly not electrically compatible. Briefly got SPI out of it due to no particular code change & it went away. It's generating SPI but the PIC isn't receiving it.SPEAKING OF MARCY-1Going to try approaching the AIR FORCE HEROINE again so if we suddenly stop flying you'll know it was another DISASTER.
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My Ardupilot Funjet

Posted by Max on January 8, 2010 at 12:00am
Here is the latest vid, code changes are in the video... anyone have any comments?? :PWell a long time has passed since my "ardustar" flew.Been flying more FPV then anything but I pulled my finger out and slapped my ardu in the funjet - been meaning to do it for so long.Anyway it hasnt flown yet but all the gear is installed and ground tests have been completed!So tomorrow morning is the big day...Im using the stock standard 2.4 ardu code but setup for v tail mixing of course.Im assuming its going to be very twitchy... ill have a play with the code at the park but I think 2.5 will be getting installed as soon as its released.Also put a complete FPV system on the funjet along with 180 degree pan, ill tune the autopilot according to what the camera see's on the plane, should be easy to see if any oscillation problems are resolved that way...Anywho here are the pictures I just took :)Hopefully it will still look this nice tomorrow after the tests hehe...

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My Ground station Beta 2 modding

Posted by Mark B on January 7, 2010 at 9:22am
About MeI'm a LabVIEW programmer/user by profession and I'm also a keen hobbyist/maker so I came across DIY Drones on my hunt for my next project. (Possibly a quadrotor heli...)I saw the groundstation program and downloaded the code to have a look. I couldn't resist modifying the code to be more efficient and 'proper' and I tinkered with the UI.Ground station Beta 2, MB mod v1 UI Preview

Just a little preview mind, I'm in the middle of refactoring the code to make it scalable. This is my way of giving back to the open source community. I am interested in any comments about desired features in the ground station code, such as integration with google maps, custom controls that look like airplane controls, etc is possible.Credit is due to automatik for the current version of the ground station code that I based my mod on.
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UAV inspired by maple seed

Posted by jaron on January 7, 2010 at 6:59am
Lockheed Martin has test flown the Samarai prototype UAV monocopter late last year. Its design is inspired by the maple seed and couldn't be more minimalistic.It's got a 760 mm (30") wingspan, is electrically powered and was built by using off-the-shelf components.
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