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It looks to me that the sad day we all knew would eventually come has arrived. The first person that I have heard of plotting to use R/C planes to bomb the Pentagon and the Capital building. It appears he was planning to use some kind of autopilot given that they stated the plane was to be "GPS guided". Below is a link to the CNN page that has the details. I only hope this doesn't lead to a complete lock down of the R/C and sUAS industry. It is so young and ripe for growth and innovation. 

http://www.cnn.com/2011/09/28/us/massachusetts-pentagon-plot-arrest/index.html?hpt=hp_t1

Hi guys, I just wanted to share some photos of my minimalist ArduCopter 3DR. The APM is using Jason Short's power hack, a Spektrum adapter, and a DSM2 remote Rx. the OilPan is standard except for the compass, which is one of the first ten or so HMC5883L prototype boards from a while ago. The rest of the frame is mostly stock (arms, ESCs, motors), but the stack-up is a little shorter than usual, and the legs are the never-sold easy-break kind. Flying this one outside the 3DR shop has been a blast!

Happy hacking :)

Proud to post my first blog post yay !

Well ok its only eyecandy, but i hope you'll get a 2min break of what you're doing and a little smile maybe laughing at the noob, hehe ^^ fair enough !

So today i received 2 more lipos so i could finally have a proper longer flight session and could setup some cams to finally do some video recording for post analysis (yeah, to analyse stuff , whatever ill get ^^);

So i got now 2 x4500mah 45c  and 1 x 5000mah 40c   .. circa 30min flight :))

Soldered xt60 connectors to the brand new lipos, recharged and then wiiiizzz !

Beautifull, aerial, Pure joy !

no tests, no experiment, nothing but a delicious manual free run on stabilize, aaahh :)

Well, ok, it didn't end like i wanted, but anyways , was great !!

1 and 3/4 lipo later :

Conclusion : Sharp aggressive jibe + 12" black basic propeller = heavy load, high bending  and probable snap .. lesson learned and ordered straight away 6 epoxy props.

Will retry and see what'll happen ! :D

Any comments on any aspects of all this are welcome !

Until next time, thanks for watching !

Drone specs, flight conditions: 

Arducopter 2.0.42 (stock pids) on Hexacopter 880kv
12" props (black non-epoxy) 4S 4500mah 45C 100% Stabilize mode manual
test flight on 29-09-2011 @Dusk ~6:30pm Conditions : 27c, No wind

Complete flight video rush is here : https://www.youtube.com/watch?v=g8Ge8D67AF0

I'm sure a few of you will recall the warm British summer day & BBQ promised in this Blog post a few months back, and just like any Great British summer, it did not arrive! Still we all had a great deal of fun between the rain showers. The event has now been featured in Rotor World magazine and with their permission I have added it here, there is a PDF for downloading and viewing "full screen". There are more photos from the day here. I hope to have another Drone Zone meeting later this year, I will keep you updated.

Regards

Martin

www.buildyourowndrone.co.uk

Hey everyone, I've been trying to tackle the issue of autonomous landing for a little while now, specifically restrained to optical flow techniques. I have hit a roadblock and wanted to see if anyone on here could shed some advice on the issue.

Essentially what is happening is I have a downward looking vision chip that can successfully put a Coaxial helicopter into a hover using a minimization of OF. I want that chip to now track a moving surface underneath it, particularly a landing platform. The problem lies in that the helicopter has no way of knowing the linear velocity of the thing it is tracking. Because the OF is only calculating a height/speed ratio, there is no way to know exactly how far the surface it is tracking has displaced in the X and Y direction. I am trying to avoid using other sensors that would give me height over ground because my objective is to operate using only vision chips. Therefore, unless I constrain the speed of the landing platform and keep the height of my UAV at a very fixed height to match the linear velocity of the platform, does anyone have any suggestions on how to remedy this issue?

For reference, I am programming via an Arduino board and I am using a Centeye 16X16 vision chip. 

After Chris posted about a new sonar mount on thingverse for Arducopter, I realised that everyone who purcahsed a Arducopter 3DR frame, has a potential sonar mount included in the kit.

All the kits come with a bunch of spares (arm, centreplate, stackup plate, and leg set)  We decided to use one of the spare leg sets that are included as a sonar mount. It is reccomended that you mount the sonar at least 3 inches away from the body to avoid electrical noise/interferance, the setup about is just over 3 inches away, but If you want to mount it further out, you can do so but turning the leg over.

You will need to buy some extra screws and nuts (M3 x 25mm).  I would suggest also getting some double sided tape to secure the sonar, as there is only a single hole to mount it on the end of the leg.

Hope this is usefull for anyone who has not figured this out yet.

unmannedtechshop.co.uk

PASSED !

Spotted on Thingverse, uploaded by Jag. Nice!

Nice IMU project spotted on Dangerous Prototypes with MEMS gyros and accelerometer, Cortex-M3.

"The IMU is supposed to be high-end, implementing state-of-the-art data filtering, best low-cost MEMS sensors available and many features to compete with commercial IMUs used in robotics at a fraction of the price…"

Although LED strip lighting looks more spectacular, I couldn't help but notice these little lights the other day when I was nosing my way through the aisles at Home Depot. They are called Dot-Its, by Sylvania. They are meant to be decorative note-holders, lit with SMT LED's and powered by a lithium disk cell.

These lights are really quite bright, and you can select a steady or blinking mode. They have an adhesive backing, but they also have strong magnets in them, and cling to the screw heads beneath the motors without falling off.

The pack of four cost just $ 10.00 (CAD), and although the cells would probably cost a lot to replace, it wouldn't take much to wire them in permanently with the appropriate resistors.

John

More goodness from UC Berkeley: iBird, a robotic ornithopter that can fly towards shiny targets. Starts at 1:31 in the video above (the first part is a cockroach). From Gizmodo.

Good inspiration.

I found this bird on youtube made by a man from Norway.

4.4M wingspan.

From our Wired Science blog. This team is presenting this week at the International Conference on Intelligent Robots and Systems in San Francisco this week. I'm speaking there, too, on Wed morning at 8:00 am. 

Swarms of flying robots, flocking autonomously like birds, have taken to the air near Lake Geneva, Switzerland.

At Ecole Polytechnique Fédérale’s Laboratory of Intelligence Systems in Lausanne, Sabine Hauert, Severin Leven and Dario Floreano have found a way to make small, fixed-wing machines fly together, migrate and avoid crashing. The swarms can be used for imaging and mapping the ground. In the future they may fly on search and surveillance missions.

The swarming behavior is based on a three-dimensional algorithm that represents the movements of schools of fish and flocks of birds. The algorithm, developed in 1986 by Craig Reynolds, was first used as a computer graphics tool. In the algorithm, as in real flocks, the individual agents behave simply. They respond to their close neighbors without considering the movements of the group. Yet out of the noise, larger patterns emerge, coherent and beautiful.

 

“Flocking requires three things. You need to move with the same speed and direction as your neighbors, you need to avoid hitting them and you need to stay close,” said Hauert, who is now a post-doctoral student at the Massachusetts Institute of Technology. When programming the robots, Hauert and Floreano added in a fourth ability: migration. With this ability, the robot swarm can travel to a set location, making them more useful as search and surveillance tools.

The robots were built by senseFly, a Swiss startup founded in late 2009, as a spin-off of the work done at the Floreano’s lab. The bots communicate with each other via a simple WiFi dongle connected to the on-board Linux computer that runs the autopilot program. In this project, Hauert and Floreano searched for the best balance between the robots’ weight, cost, turning ability and the range of their communications, while keeping their ability to flock.

“You can imagine two robots working together like holding hands with someone,” Hauert said. “If one of you changes direction, but the other person can’t respond quickly enough, then you break the connection.”

To perfect the technology, they tested the robots over 200 times in the field, without any crashes. The trials began simply, eventually reaching a flock of 10 autonomous fliers. More could be added, they believe. They’ve simulated up to 100 flocking robots. Next Floreano is interested in adding different kinds of sensors, such as cameras modeled on insect eyes, so the robots would be able to avoid obstacles while staying as a flock.

My 3DR quad frame is finished, and I mounted the 880 kV motors and 12" props. This thing is a BEAST! It takes off like a rocket, although the flight times are rather short. All in all, I love the frame build. Thanks, Jeff, for helping me out with the bolt issue.

John

With the Quad 3DR frame availability increasing, I wanted to take a moment to offer a "Build Quick Tip". Skip to the bottom of this post to get to the "quick" part of this tip.

The Backstory

The ArduCopter2 frame uses narrow aluminum arms, and so the design calls for motor mounts. The 3DR frame uses 20mm, 3/4" square tube arms, much larger than those on the other frame, and so it offers a different mounting method. Included in the 3DR frame kit, for each arm, are metal screws and a bag of washers/spacers. The 3DR uses a direct mount method. Each arm has two holes spaced about 1.5 cm apart along the center line of the tube. Screws are placed up through the arm holes and connect directly to the bottom of the motors. Only two of the four motor mounting holes are used, but it is plenty solid, and the X-shaped motor mounting brackets included with most brushless motors are not used at all.

The 3DR frame assembly instructions discusses motor mounting, and I encourage you to read all of the instructions carefully, twice before picking up a single tool. Once you are done reading those instructions, I recommend you take the small bag of spacers and ... put them aside. Do not even open them. 

"But if I do not use the spacers, don't I run the chance of damaging my motors?" you might ask. The truth is, no. You will not run the chance of damaging your motors, you are virtually guaranteed to damage your motors. The screws are simply too long, "engineering variances" aside, for virtually any motor you are likely to be using. The point of my recommendation, however, is that even with the included spacers, you are still running the risk of damaging your motors. So perhaps I should explain myself?

The 3DR frame is my first "kit" built frame. It is my fourth quad, but the first frame I purchased. When yours arrives, it may well have three or four times the spacers/washers that were included in mine. I purchased one of the earliest 3DR frames available from the DIYDrones store, and it included about 20 spacer/washers. I used all the washers and supplemented some small nuts besides, and I still wasn't sure I was getting the spacing right. Ever eager, I "got by" with fewer of the spacers on one of the arms. And you can see the motor from that arm in the picture above. It is a disaster waiting to happen. It functions around 45% throttle, just enough to get the quad off the ground. Then it stops. I discovered this during routine testing, fortunately, and not during a flight test. I am confident that jDrones shipped me a good motor, so what went wrong? The screw was just long enough that, under load, there was some shorting (think, spark gap transmitter!) inside the motor that damaged part of the stator wiring. The motor will spin up and then will short and fail. Backing the screw out will not help, the motor damage is done. Fortunately for me, my last order from jDrones was a batch of sixteen. What can I say, I am an addict. 

The "Quick" Tip

The washers/spacers will be useful, so keep them. For use elsewhere. The problem is that there are just not enough of them, and even if you do have enough of them, it is a pain to count them out (you need at least five per screw, 40 in all, to be safe, and I suspect they are also heavier than this solution.)

Included in your propeller bag (and, if you are using the standard or heavy ArduCopter motors, and the 3DR frame, I really do recommend you use the 10x45 or 12x45 props; unless you know the math better, of course...) are some plastic inserts used, along with the prop adaptor, to fit the propeller to the motor shaft. You can see them in this photo.

At the top of the photo, you will see the full set of  

unadulterated spacers. You get one of these sets with each propeller.

The second set of spacers, in the middle, shows one item missing. That is the plastic insert that is pressed into the center of the propeller.

Notice on the bottom, two additional spacers are missing along the right hand side. Counted collectively, you will have four spacers of just the right size for use in your props themselves. Then, for each prop, you will have two spacer of very slightly different sizes which will work perfectly for our purposes. 

After you have fitted the correct spacer into the propeller, to avoid any mixups, remove these additional spacers, and use them, rather than the included 3DR frame washers, to back the motor screw off so that it cannot damage your motor wiring. Inspect your motors well  (we can now speak of "engineering tolerances.") It is possible that you may still need to use an extra spacer or two (rather than a minimum of five per motor.) I did not need to use any of the 3DR-included spacers when I used the propeller inserts, one insert per motor screw. 

Total (additional) cost: $0.00. Please let me know which country you are from in the comments and I will happily provide conversions for the additional cost into any currency of your choice. ;) This tip is so simple that you might just be annoyed with me for writing such a lengthy blog about it. But, I suspect, not nearly as annoyed as you would be with four secretly unreliable, damaged motors. 

I leave you with a photograph of the final product. I hope that it brings you the same peace of mind and happy motors that I now enjoy.

Following Leon's great blog post showing the use of a camera from a WII remote as a 3D position sensor for his helicopter, I've been tinkering and now have a Wii remote camera working as a sensor on my Arducopter. Thanks to Chris for encouraging me to blog this work that was previously described in the forums

Why bother
Currently the only sensor we have that tells us where we are relative to something else in our environment is the sonar. Some of the other sensors tell us where we are relative to a theoretical datum (eg GPS), or a variable datum (eg air pressure) these could both see you trying to land your aircraft below ground or off in a tree somewhere if your unlucky. The accelerometers tell us how we are oriented relative to gravity but nothing about where we are. The gyros tell us how we are moving. The recent work on optical flow which senses the surroundings also tells us how the aircraft is moving but not where it is.

My hypothesis is that a combination of an optical sensor such as the wii camera and ground based beacons could be used for accurate relative position determination to allow for precision navigation. This could be useful for landings, take offs, indoor navigation and loitering without GPS.

The Theory
The Wii Camera can track up to four infra red blobs. By sensing the location of a set of predefined IR beacons we can, through simple trigonometry, determine our height above the beacons, our displacement from the beacons and our rotation (yaw) relative to the beacons. This information could then be used to control the navigation algorithms to control the aurducopter. An example, would be to a precise landing on a 'helipad'.

Something similar to this has been done before by the University of Tubingen - have a look at their video

The Wii camera has its limitations.

• You have to sacrifice a Wii remote to obtain one - there is no known alternative source for the camera - mine cost $1.99 on ebay.
• The Field of View is quite narrow (+/- 20 deg). Leon has hot glued a small lens on his camera to get a wider field of view.
• The camera has an I2C interface - great - at 3 volts - not so great. It also needs a 24Mhz clock signal - all do-able with off the shelf components.

The calculations required to determine position from camera data are relatively simple - less complex than the optical flow calculations by the look of them.

The results
I've mounted a wii camera to my arducopter, created an arduino library to communicate with it, modified the arducopter code to work with it and done some test flying. The test flying so far is "hand flying" (with and without motors running) as the back yard is too small for free flight and it was getting late.

The "flights" are above a simple IR target that is just two IR leds approx 15cm apart. (Cost per target is less than a dollar). I've logged Sonar, Baro and Wii camera altitudes. Here is the graph of the three altitude/range sensors - click for a bigger view

The blue line is the Wii sensor output - note when the algorithm can't see both the target leds it outputs a zero value. The only "calibration" required is to know the distance between the target LEDs.  - in theory this could be eliminated if you used sonar range to 'calibrate' the target when you first see it.

The correlation between sonar and IR ranging is pretty darn good! In fact one could argue that - in this very limited test - the sonar shows noise (probably due to the BBQ cover flapping in the AC down wash) while the Wii altitude is either rock steady or nil.

The code also calculates x/y displacement from a position vertically above the target in millimetres and rotation (yaw) relative to the target. I'm not using any of this just yet.

I need to do some further work to cope with aircraft roll and pitch effects (currently the code assumes the aircraft is always level) I assume I can use the optical flow code as an example of how to sort this out.

Next steps for me
* free flying and Alt-hold tests
* clean up the code
* have a look at modifying loiter to use the targets
* find and use a lens to get a wider field of view
* come up with an precision guidance to landing concept and convince someone to help me code it

What do you think?

I'm keen to hear what people think of this type of sensor being used with arducopters.

Is it useful? How could you use it?

A couple of outside the box ideas to kick you off:

1) fit the aircraft with an IR illuminator (from a security camera) and use IR reflective markers on the ground.

2) get the aircraft to carry IR beacons and drop them when it wants to loiter for precision loiter ability. Or drop a trail of cheap beacons Hansel and Gretel style to find its way 'home' without GPS

APM_WiiCamera.zip

Research published by the good doctors at LBNL (Lawrence Berkeley National Laboratory) in Advanced Materials into alternative anode materials for Li-Ion batteries suggests that polyfluorene-based conducting polymers (PF) are showing good promise, and might cycle well over time.

Might we soon benefit with 360g 35200 mAh batteries? Six hour ArduPilot and two-and-a-half hour ArduCopter flights? Has anyone successful added a beverage holder to their fatsharks? It may be time to start the prototypes...

From the Berkeley press release: 

"The icing on the anode cake is that the new PF-based anode is not only superior but economical. 'Using commercial silicon particles and without any conductive additive, our composite anode exhibits the best performance so far,' says Gao Liu. 'The whole manufacturing process is low cost and compatible with established manufacturing technologies.'"

Finally my first frame for my first quadcopter is ready!

cut myself pretty good l;art night on a new hexacopter I just finished. I even had the props off while I tuned the ESC's and the KK control board gyros. Then I put the props on and did one test inside where I held the middle of the copter and had it take off while I held it just to make sure it was all good. My wife got home right while I was doing this and I looked away for a second and the hex got away from me and I instinctively reached for it... Big mistake I realized as the props sliced through my left palm...