Monday, August 25, 2008, 05:19 PM - ElectronicsSparkfun is offering a new version of the Arduino: the Arduino Pro, which
is lighter, cheaper, and slightly more compact than the Decimilia.
The supply voltage is 3.3v, which makes it compatible with things like gyros and accelerometer sensors. Too bad news is that the clock is only 8MHz, instead of the 16MHz od most other Arduinos.
Monday, August 25, 2008, 01:23 PM - Flying ContraptionsThe Universal Aerial Video Platform is an open source design for a quadrocopter. The UAVP controller board is based on a PIC microcontroller, and has a number of optional sensors, such as gyros, accelerometers, and altitude sensors.
Several sites in Europe and the US sell the UAVP controller board and associated components. QuadroUFO is a US supplier of parts for DIY Quadrocopters. Most parts that they sell, except for the controller board, can be found from R/C store, such as BP Hobbies, or electronics/robotics suppliers like Sparkfun.
A fully populated controller board with all the sensors is $435. The blank PCB is only $15, but the sensors are expensive.
I'm working on a cheap Arduino-based DIY quadrorotor controller. Stay tuned.....
Monday, August 25, 2008, 01:12 PM - Flying ContraptionsQuadrocopter building has become an increasingly popular activity in Europe, particularly in Germany.
The MikroKopter Wiki has tons of information (mostly in German), equipment, instructions, and software for quadrocopters.
In particular, it has this huge list of quadrocopters with characteristics, pictures, and links to more details.
Among other things, the site has the schematics and software for a brushless motor speed control, something I have never seen anywhere else.
This other site contains a huge collection of pictures shot at the 2008 Quadrocopter meeting in Germany. There is a bunch of nice-looking QCs there.
Monday, August 25, 2008, 12:27 PM - Flying ContraptionsHartmut Kaak in Germany has produced a series of extremely impressive micro-sized quad-rotor flying contraptions over the last few years. The most impressive aspect is the size of his latest creation, the diminutive Smarty: 15g, and 80mm in length.
TheSmarty uses 4 motors and props cannibalized from a Silverlit X-Twin R/C toy airplane.
Hartmut built his own mixer/stabilizer/controller around an Atmega88 microcontroller and three ADXRS300 solid-state gyros. His software directly produces the PWM signals for the (brushed) motors. More interestingly, he was able to power the whole thing with a single 145mAh LiPo using a MAX1686 voltage pump chip from Maxim (which generates 5V from the LiPo 3.6V).
Monday, August 25, 2008, 03:20 AM - Flying ContraptionsThe 2008 Inter-Ex will take place September 6 and 7 in Boissy sous Saint Yon, a few kilometers south of Paris.
Inter-Ex is a get-together of creative R/C modeler who design and build unusual flying contraptions. There are pictures of previous editions on the web site.
Monday, August 25, 2008, 01:54 AM - Misc TechnoToysRecently, I was looking for 2.0mm wood screws, As it turns out, these little things are horribly difficult to find in the US. So, I tried to look for the closest thing to a 2.0mm wood screw in the US "system".
I stumbled on this Wikipedia page that contains a curve and a table that maps US drill bit gauge numbers to millimeters.
This makes you realize how screwed up the US drill bit system is (like many other US measurement systems I might add).
The curve that maps gauge number to mm is monotonically increasing, but other than that, it has no regularity that I can identify: it's non-linear, non-convex, and it's full of wiggles.
Now for the best part: the gauge scale is unrelated to the gauge scale for screws. However, the scale for screws, at least, is piecewise linear with only two pieces. Naturally, the coefficients aren't anything logical (that would be too much to ask). Since a number zero screw is about 1.5mm, the non-intelligent designers of this devilish systems decided to use a different notation system for smaller screws. Instead of simply using negative numbers (which would have been the least illogical thing to do), they chose to add multiple zeros as the screw gets smaller. They must have thought that simply using negative numbers would confuse the hell out of the average American machinist (then again, they didn't seem to understand the decimal notation to begin with). The formula for converting screw number to diameter is:
mm = 0.03302 x N + 0.1524
For your convenience, here is a table of US screw number to mm:
Incidentally, a 2.0mm drill bit is close to a number 47.
How could the US build an industry around this? I'll never figure out....
Saturday, August 23, 2008, 03:48 PM - Flying ContraptionsFor several years, my friend and colleague Andrew Ng at Stanford has run an autonomous helicopter project in his lab, with two of his PhD students, Pieter Abbeel and Adam Coates. They have developed new reinforcement learning techniques to automatically learn how to stabilize and control the helicopter. They reached the point where they can pretty much get their heli to perform every aerobatic figure known under the sun. There is a bunch of videos on their website, as well as on their Youtube chanel.
Interesting implementation details: they have no on-board intelligence on the heli. They use a GPS and an IMU with serial outputs directly fed into Xbee Pro modules. The signals are received by a PC on the ground, which remotely controls the heli through the training port of a conventional R/C transmitter.
Saturday, August 23, 2008, 03:31 PM - Flying ContraptionsThere are a few YouTube videos of an interesting VTOL flying contraption that seems to be using contra-rotating propellers, most likely based on a Himax co-axial contra-rotating motor pair from MAXX Products. The plane appears to be very maneuverable (thanks to Bertrand for the pointer).
More videos are available here, here, here, and here.
UPDATE (2008-09-08): Chris Good, the builder of this nice flying contraption, pointed us to his rcgroups forum post describing the construction. The post has several pictures of the innards, and details of the channel mixing. Contrary to what I guessed, Chris used two separate motors (mounted in a push-pull fashion), rather than a co-axial double motor. The motors are geared brushless in-runners.
Tuesday, July 1, 2008, 12:11 AM - Flying ContraptionsDrone manufacturer Lite Machines Inc. has a video of their latest drone called the Voyeur.
It's a cigar-shaped drone, 686mm in length, 63.5mm in diameter, with two counter-rotating rotors, 762mm in diameter. It seems to be using bushless outrunner electric motors powered by a 3-cell LiPo battery.
The total mass is 1.4kg. The cruising speed is 30 knots and the autonomy 30 minutes.
There is a cool video on YouTube
This must be the same Lite Machines Inc. that got started by producing the first gas-powered micro-helicopter many years ago. It used a Cox 0.8 cubic cm motor and had a really clever mechanical system on the tail rotor to stabilize the yaw. This was a kind a mechanical gyro, before the days of cheap and light solid-state gyros.
Monday, June 16, 2008, 11:03 AM - Flying ContraptionsThe Rencontres Electriques de Crespiere, an annual electric flight meeting took place near Paris last week-end. A particularly interesting design was shown this year: the Verti4. It is the simplest and most successful electric VTOL design I have ever seen. It looks like a fairly conventional trainer-style airplane with four motors on each side of the wing (two in front of the wing, two aft of the wing). The motors can pivot 90 degrees (all together) from facing up to facing forward (V22 Osprey-style), allowing a transition from hovering to translational flight. Is with other quad-rotor contraptions, two rotors turn clockwise, and two counter-clockwise on a diagonal. From what I gather from Jean-Claude and Bertrand (my dad and brother) who attended Crespiere, the stabilization and control is not done with some sort of custom electronics, but with a combination of conventional gyros, and channel mixing.
There are a few videos on YouTube:
Others have built quad-rotor or quad-ducted fan electric VTOL planes before (like this F35 or this strange-looking quad-EDF contraption), but not with this simple way of transitioning to translational flight.
Monday, June 16, 2008, 12:48 AM - Flying ContraptionsKyosho has a series of ready-to-fly R/C airplanes called the Minium that come with a complete 2.4GHz radio set.
Until recently, the only Minium plane was a small Cessna (38cm wingspan, 18 grams). The plane has been available (and very successful) in Japan, Europe and Australia under the Kyosho/Minium name. In the US, a very similar plane (if not exactly identical) has been distributed by Horizon Hobby under the ParkZone brand. It sells for $120
Now Kyosho has announced a new Minium: the Piper Cherokee. The main difference is that the Cherokee has ailerons. The plane is advertised for pre-orders for $180 on Kyosho's US e-commerce web site, but the availability date is unspecified.
What's strange is that the same web site does not have the Cessna (probably because of some exclusive contract with Horizon Hobby).
Even stranger, Kyosho's Japanese website used to have a page on the Cherokee, but it has been taken down....
Monday, June 16, 2008, 12:38 AM - Flying ContraptionsAerovironment has apparently received 0.5e6 US$ to develop a nano-UAV that flaps it wings. I'm guessing Aerovironment's Matt Keenon (an micro R/C enthusiast and pioneer) must be involved in this project.
It looks like the plane could be designed to take off vertically.
The advantage of flapping wings for hovering is that you don't get a reaction torque, as with a helicopter rotor. The solutions are few: contra-rotating rotors, or oscillating blades (flapping wings).
The mechanical design, the control system, and the aerodynamic efficiency will all be challenging.
Monday, June 16, 2008, 12:28 AM - Misc TechnoToysThis French furniture store sells what looks like oversized LEGO blocks called LunaBlocks, with which one can build furniture. Cool concept.
Monday, June 16, 2008, 12:22 AM - Flying ContraptionsEagleTree Systems have introduced two new sensors to their telemetry and flight recording product line: an altimeter with 1 meter resolution, and an airspeed sensor (with Pitot tube).
They cost around $40 each, and include an 7-segment LED display.
They can run standalone and display the maximum value observed during a flight, or they can plug into one of EagleTree's flight recording systems.
Monday, June 16, 2008, 12:18 AM - ElectronicsThe Drum Master is a DIY "brain" for an electronic drum pad.
The web site has some data on how to process the output of piezo-electric sensors used in drum pads.
Monday, June 16, 2008, 12:11 AM - RoboticsThe arduino.cc forum has an entry describing a nice little robot that can solve mazes written on the ground with a black marker. There is a link to a YouTube video showing the robot in action.
The author used the Arduino IDE to program the ATmega-168 used on his robot. He mentions using a Pololu 3PI robot platform. This platform is not yet available from Pololu, but apparently will be soon.