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I was asked on the 'Advances in Airspeed Handling' forum to give more info on this, so here is some practical info on Pitot tubes and sense piping for Airdata measurement systems.

In general, strategically located air inlet ports are required to sense both static and dynamic air systems, feeding said pressures to the relevant sensors.

Static pressure sensing is used to compute the Barometric Altitude, and must be as immune to airflow as possible.

Dynamic pressure is related to the flow of air at the inlet of the dynamic pressure sensor, as induced by the aircraft motion through the air. This pressure is very small for low air speeds ( sub 40m/s, say) and is measured by a differential sensor. Such a sensor has both ports exposed to the static ambient air, with one port having the pressure caused by movement added to the ambient pressure. This way a low pressure sense element can be used to sense the difference between static and dynamic pressures. However, any variation on the static port input side will be seen by the sensor as a change in differential pressure, and a change in calculated airspeed will result.

It is therefore important to ensure that the static pressure sensed does not vary due to aircraft attitude, wind and wind direction, etc. Measured static pressure should only vary as a result of altitude and temperature.

These requirements place considerable constraints on the design and location of the air inlet ports for both airdata sources.

The dynamic inlet port is normally a suitably shaped orifice, facing the oncoming air. This orifice is a hole into a tube, the tip of which is rounded to coax the oncoming air to neatly part without creating vortices at the inlet. At low air speeds the 'rounding' is not critical - a hemisphere the diameter of the tube is acceptable.  At high airspeeds the shape is critical, becoming more pointed. The dynamic port is most accurate at an angle directly facing the oncoming air. Pitching or yawing the tube in the oncoming air reduces the resultant pressure with ensuing airspeed changes.

The static pressure ports are normally orifices directly side on the the airflow. These are often combined co axially in a Pitot-Static Tube, with the holes spaced evenly around the circumference of the tube, at least 10 to 15 tube diameters rearwards of the probe tip. To close to the tip results in tip vortices affecting the static pressure at the hole entrances.

Such a tube can be located in the wing tip or in the fuselage nose ( pusher prop) but the static port holes must be at least 40 to 50 tube diameters from the wing leading edge or fuse nose, to not be affected by the airflow.

The picture below shows a working tube, the larger diameter one. The thinner diameter tube static sensing performance is poor due to the static inlet holes being far to close to the tip.

The static inlet holes are spaced around the tube so that the aiflow 'balances' out when the tube is not facing directly into the airflow, eg, when pitching or yawing, or with side winds. Higher pitch/yaw angles do however result in erroneous measurements. 

An alternative static air sense port can be located directly on the straight sides of the fuselage, preferably two ports directly opposite each other, and joined in a T. 

These pictures show the making of such a tube setup:

This is the long tube, the end of which will be flush with the fuselage sides. left and right. The nick in the middle is where the hole will be, into which the T tube is soldered.

This is the T Tube, with the scalloped end.

These are the two tubes tinned and ready for soldering

Now soldered together:

This T assembly is inserted into the fuselage, from the insight, left or right side first, and then bonded in place with the ends of the tube flush with the left and right side of the fuselage. The T piece is then piped to the static and dynamic sensors.

The tube ends MUST be on a regular surface part of the fuselage, ie, not directly behind or in front of any protrusions, bumps , landing gear, etc. Also not on a tapered part of the fuselage. All these will cause vortices and pressure variations at the tube tips, rendering measurements worthless. The principle relies on a smooth airflow past the tube orifices, and if any side wind is experienced, the air enters one hole and exits the other, with little or no pressure change in the T part of the tube.

This is a picture of my SurVoyeur aircraft fuselage, showing 3 positions where I placed this tube to do measurements to see effects of the chosen position.

Location 1 is no good - was on the tapered part of the fuse and pressure changed with airspeed.

Location 2 is good, on the flat portion, and forward of the landing gear vertical struts.

Location 3 is no good - it is on the flat portion, but the landing gear vertical stut ( only 5mm thick) creates sufficient disturbance to cause significant variation of pressure with airspeed ( of the order of 0.3mbar - 1mbar = approx 8meters .)

If anyone is interested in more detailed info, let me know.

Joe

The Nampilot.

Governmental use of unmanned surveillance drones has inspired a lot of concern about privacy, but Bogota City Mayor Gustavo Petro thinks the battle's already over. In a TV interview days ago, Petro said essentially that drones are an inevitable part of our future, comparing them to the thousands of cameras already located around Bogota.

The Mayor Petro, said that city will have a pilot program with aircraft of medium and small size, which according to results would be integrated into the security system of Bogotá.

Petro said that in 6 weeks would be delivered to the city the results of these studies allowed to know the effectiveness of the system.

"At the end of these studies if we report efficiency, will be an important part of our system 123(emergency line in Colombia), Civil Emergency System Security," said Mayor Petro.

The Mayor of the Colombia Capital city said that the UAV are tools that help you to: urban perimeter monitoring, emergency support system, search and rescue, monitoring the traffic of the city, massive event monitoring.

"In addition to help us with maps and mapping, in monitoring the proliferation of waste, efficiency environmental monitoring, environmental damage," said the Petro.

Finally, the Mayor said that with this technology can support the work of organizations such as: fire, police, mobility and other.

In the other hand Tecscorp CEO, company to assist the mayoralty to develop this test plan commented that the system chosen for this work will be a new version of the UAV Chronos, which has not yet been launched to the market. In the presentation to the media Tecscorp used his pilot training module, it is expected that in the course of the next few days is to unveil the new system. Messino also said that advances in the development of new and better aircraft to meet various applications and are working closely with the authorities to meet all the technical and legal issues that are required.

By Brian Dodson

Intel's Futurist and Director of Future Casting, Brian David Johnson, was at this week's Maker Faire in New York City to introduce an open source, 3D printed companion robot called Jimmie.

Johnson's job is to advise Intel as to what innovations may be expected in the active marketplace roughly a decade into the future. His use of science fiction writers as projective futurists in Intel's Tomorrow Project is well known.

With the 21st Century robot project, Johnson plans to introduce an easy to build, completely open source, human-like robot that can be built created from a kit and a home 3D printer, then stand back and see what a group of highly motivated makers do with it.

The open-source software, 3D printing files, and the kit are projected to be available next May. The vehicle for the project is a book called 21st Century robot, which combines science fiction with a how to guide for creating your own robot. A "work in progress" version of the book can be downloadedhere [PDF].

Although there are no firm details at this stage, the kit will reportedly consist of processors, memory, servos, power packs, and other parts to enable easy construction of a robot. Jimmie (Johnson's name for his prototype, which is at this stage just a shell) is roughly humanoid, about 20 inches (0.5 m) tall and has a strong family resemblance to Aldebaran Robotics Nao robot (my personal all-time favorite robot). Interestingly, Intel was one of Aldebaran's major third round VC funders.

The target for such a kit is highly focused, as only rather accomplished makers will have the 3D printing capabilities at hand, and also the electromechanical and software chops to turn a kit into a working robot to be upgraded, modified, and taught new tricks. Johnson wants to make the kit available for US$500-1000. Comparing this to Nao's $17K price tag, it's clear why such a kit may be popular.

While we can only speculate about Jimmie's base capabilities at this stage, it is being described as a companion and helper. We expect that Jimmie will be able to understand and speak some subset of a spoken language. Also, it seems likely that it will be able to walk about and have some ability to grab and manipulate objects – particularly as Jimmie appears to have inherited Nao's opposable thumb.

We'll bring you more details as they become official. In the meantime, you can watch Johnson talking about the project in this CBS News interview.

Source: 21st Century Robot via All Things D

By Travis Good

Jaws drop when makers see a five-axis CNC at work. That’s what happened to me when I saw PocketNC performing its magic. I peered closely and saw a spindle moving along two axes milling a piece of plastic mounted on a trunnion moving along/around three axes. The result of a three-year, four-prototype development effort of husband and wife team Matt and Michelle Hertel,PocketNC is getting ready for market.

Machinists and mechanical engineers, this couple loves building things. After participating in many Instructables contests and putting in up to 30 hours per week on their entries, they eventually decided to channel their energies into something which they could sell as a product. Matt had wanted a mini mill but couldn’t find what he wanted at the price he was willing to pay. Over the course of their research, they found that many others wanted the same thing so they decided to build their own but jumped straight to five-axes.

While their prototyping efforts started in the house they quickly converted a 10×10 shed to a workshop where they worked. From the start, the mill’s frame was built of aluminum but they are always working to reduce weight, presently at 25 pounds. The mill uses stepper motors and they can cut dependably to a tolerance of +/- 1/5000th of an inch, the spindle turns at 500-6000 rpm for plenty of range for speeds and feeds of various materials. The millable volume is  5″ diameter by 4″ tall. This gem can mill plastic and aluminum and they’re confirming that it can also mill steel and titanium

World Maker Faire was their first big public showing of PocketNC and they found it invigorating. After years spent working on the project in isolation it was exciting to see so many positive reactions from the maker community. They’ve come a long way after multiple prototypes. They still want to test more materials, switch their controller to Synthetos, and then go to market but with measured organic growth till they get it totally right.

Cost? They’re shooting for around $3,000.

Paparazzi Apogee is new generation of Paparazzi Autopilot

• STMicroelectronics STM32F405RGT6 Cortex M4 168MHz processor featuring a Floating point unit (FPU), up to 192k of RAM and 1024k of FLASH.
• 9(6) DOF integrated IMU MPU-9150(6050) based
• 1 x Barometer/altimeter MPL3115A2 (I2C, MPU slave capability)
• 1 x MicroSD card slot, 4 bit SDIO interface (high speed data logging)
• 1 x USB : DFU mode (download) or USB storage (direct access to MicroSD card)
• 6 x Servo PWM outputs
• 1 x R/C receiver PPM frame input
• 1 x R/C receiver serial input with inverter (Futaba S.BUS, Spektrum, etc.)
• 3 x UART
• 2 x I²C bus
• 1 x SPI bus
• RTC with backup capacitor
• SWD(ARM download/debug interface)
• 4 x Auxiliary I/O (General Purpose and/or ADC and/or servo PWM)
• 5v / 1.5A switching power supply (input voltage range 5.5V min → 17.0v max)
• 3.3v / 1A linear regulator
• 1 x 5v / 500mA power switch
• 4 x status LEDs
• 10.4 grams (0.37 oz)
• 53 x 25mm (2.1" x 0.98"), shares the same external dimensions and mounting points as UmarimLite
• 4 layers PCB design

http://paparazzi.enac.fr/wiki/Apogee/v1.00

It is available at following link.

http://www.droneasy.com/index.php/electronics/flight-controllers-2/paparazzi-apogee.html

This is it... all of FrSky Taranis batch #1 packaged and all ready for Canada Post pickup! 

Also got to meet a lot of you for local pickup, it was busy!  For one night it felt like HobbyKing in here (all remaining units exceeding the pre-orders got sold in 14 minutes after the very late newsletter!) Thanks again!  

I know a lot of you (if not all of you) waited quite a long time for this shipment, well FrSky fixed the gimbal issues from test batch 1 (shipped to USA but not Canada) and now this is the time for us to also get our hands on some updated/revised units. I did test them out and no more gimbal sticking off center. 

There is still a small buzzing sound on the speaker, apparently there is a Cap/reisstor? fix... (post it if you know, hard to stay up to date and ship at the same time!) 

The demand is still crazy but this will satisfy quite a few customers! 

For those of you who have already started to tweak and mod your Taranis Radio, please post your settings, firmware update or tweaks that you applied! I did not see a lot of threads around here but I know there is a very long one on RCGroups. Would be nice to see some here too! 

Get on the Batch #2 pre-order list

Dany

Hi Everyone! I just wanted to share my bad experience with the DJI legs. I bought a few weeks ago, the addon landing gear for the F450 from DJI (Link here). The looked really cool :-D (at first). Look:

So I wen't to the park very happy to test my new altitude hold algorithm. After a while I have a bad measurement on the ultrasonic sensor, and the system performed a very hard landing. The result: the four arms of the F450 broke on the same place in the same way. I think this is due to a very bad design of the landing gear attachment.

Canadian company - Rinnovated Design has created an innovative concept, that is really worth seeing. Their original approach to the matter allows creators to offer a printer for no more tha $100. By the use of blender software, sound card (!) and dripping water (!!) owners will be able to print 3D parts, that are cheap as they possibly can.

more info:

http://www.kickstarter.com/projects/117421627/the-peachy-printer-the-first-100-3d-printer-and-sc

http://www.3ders.org//articles/20130921-the-peachy-printer-the-world-first-100-dollar-3d-printer-scanner.html

I really like the approach of Rinnovated Design, completely out of the box thinking. It's a pitty that they don't develop drones. They could over come some present personal drones development issues :)

See for your self:

Sory if my post isn't top quality. It's my first one and English is not my main language. Anyway, hope you like the finding! :)

Hi all,

The recently released SF02 laser "altimeter" from http://lightware.co.za/ has sparked a lot of discussion in the forum thread here. I asked if I could get a sample to review, and to use on my gas powered 100cc homemade drone. They said yes, and promptly shipped one to me, so here is my first (ground based) review. I'm not affiliated with the company in any way, and they have not read nor approved (nor disapproved) of this review. If I get anything wrong, I am sure they will clarify in the comments section!

Frankly I was doubtful whether it would work very well at all. The laser it uses is a class 1M, which means it is less powerful than most cheap laser pointers on the market, which are mostly class 2 or above. But I was assured that the secret was in the sensitive receiver optics and electronics, which meant that the power of the laser could be limited to a very low (and safe) level.

Now I use the word "altimeter" in quotation marks, because it's not an altimeter. It's more of an electronic tape measure. Point it anywhere, and it will shoot off a small infra-red laser. The time it takes for the laser light to be received is then calculated into a distance, which can be read using a serial port, USB or analog voltage. So it could be used as an altimeter, an object detector, or more intriguingly, it could be mounted on a servo and be used as a crude 2D laser range finder. It takes 12 readings per second, so that should be good enough on a slow moving servo.

Make no mistake, this is a Time of Flight (TOF) device. It measures the time it takes for the beam to bounce back. So unlike those cheap IR distance measures, it does not depend on an angle measurement, and the distance error should not be any different for close or far objects. Also, as it doesn't use sonar (sound waves) it should work over far longer distances and in many varied conditions and varied surfaces.

Opening the box, I was pleased to see a very professional bit of kit. The PCB is surface mount, and double loaded. (components on both sides). One side has a very large and powerful Actel SmartFusion Arm processor, and the other side has mostly sticky-tape components and some regulators. Pinouts are through a very small 10 way screw terminal header. Not the best option for my vibration prone plane, but I can always solder to the pins directly and run a hard wired cable lead to the connector of my choice. 

You can see in the photo above, that the business end of the PCB which houses the laser diode, and pickup, is sandwitched with the optics assembly. There is a good 10mm of PCB overlapping the optics assembly. The result is a very rugged union which suggests the designer spent some time making sure that the board would stand up to a bit of abuse.

The LightWare software for USB control installed quickly and without fuss. I plugged in the SF02 and hit connect. Immediately the screen filled with a string of measurements. The software also allows simple datalogging recording to a text file, and some other parameters can be changed, but nothing very interesting.

So I started pointing it at things around the room, and the SF02 had no issues at measuring any surface I could find. I thought I could trick it with surfaces that had a 45 degree angle, or a shiny metallic surface, but it didn't have a problem with any of them. So with my plane still being about a week away from its maiden flight, I thought I would strap the SF02 to my car and drive around taking distance measurements. 

The following video shows the SF02 mounted to the side of my car. I think it is a good test of what a copter or fixed wing plane would see as it rushed past varying terrain. Actually, since there are a lot of shiny cars, glass windows, and the chance of direct sunlight, not to mention bushes and trees, I think it could be classified as an extreme test. 

For those that are interested in crunching the data, you can see in the video when I hit "log data" and when I hit "stop logging data". If you are nerdy enough, you can play back the data at the corresponding rate of the video, and you can therefore measure the distance to everything that I pass.

Here is the measurement data  t1.txt.

And here is the video:

It was a nice sunny day today, so perfect weather to see if the sun had any influence on the measurements.

Results: Very good. Where you see a "--" in the data, the sensor did not receive enough photons to trigger a calculation. This occurs often, but not enough to be a problem. There is a longer stretch of bad data as I drive along the beach, where obstacles are more than 40m away. There are two problems that I see: The range of 40m is probably just ok for a copter, but not enough for a plane. Our laws here in Australia allow RC flights up to 400 feet altitude, so I would like to have a sensor that would be able to do that sort of distance. Naturally that may mean a more powerful laser that may then require eye protection, but maybe there is a nice tricky way of souping up the existing laser and optics to stay within the safety limits as well as having about 100m range?

The second problem is that I could not get the SF02 to work well through glass. It would work, but the range and reliability was severely reduced. Being in a gasoline powered plane, I would have liked for it to work through glass so that it would be protected from the elements, oil, gasoline, and dirt. 

All in all, a great bit of kit. I see its use best as an aid in auto-landings and FPV landings, where a precise altitude could be used to flare just before touchdown. I'm also very surprised to see it works very well detecting complex structures such as bushes, leaves, grass... Thanks to Laser Developer for sending me the sample!

I'll have my drone up in the air soon, and hopefully (if it doesn't crash on it's maiden,) I'll have some more data from the air. I'll see if I can write a text to speech program for real time altitude updates, similar to what airliners use as they come in to land! That would be cool. I'm also interested in what tasks others are putting the SF02 to work in. Leave a comment!

I think this is a first: drone monitoring via smartwatch! Kevin Hester, the Andropilot, is adding support for the cool Pebble smartwatch. It's a sunlight-readable watch that works with your smartphone. I've got one and love it. 

Right now it just displays GCS data and status, but some limited control from the watch may be possible, too. So cool!

Here's a shot of the Iris production line, with some of the first batch of Developer Editions getting ready to go out last week. The first shipments started on Friday. They come in a cool box -- here's mine, which just arrived!

The Iris Developer Edition is for users who want the first hands-on experience with our next-gen autopilot, Pixhawk, and the suite of upgraded technologies, from software to radios, that are at the core of Iris. As part of this Developer program, these brave early users have access to a special support and feedback list, where they will be working directly with the engineers and software developers to ensure that the ultimate consumer experience is as good as possible. They'll also get a discount on the Iris Consumer Edition, which should be out before Thanksgiving (mid-Nov).

As these first Iris Developer units reach customers, we'll start revealing more of what's inside them and the full suite of technologies, from cross-platform ground stations and mobile apps to autopilot controlled camera gimbals, that are coming as part of the new Iris/Pixhawk platform.  This reflects more than a year of development and is designed to combine fly-out-of-the-box ease of use with the power of real UAV autonomy, allowing a totally new experience in aircraft control.

Thanks in advance to the Developer Edition users, whose input will be invaluable in polishing off any rough edges and otherwise ensuring that the Iris Consumer Edition will arrive ready for everyone, expert or not. 

I was sorry to see that the SkyDrone long-range FPV radio project didn't make their $80,000 Indiegogo target (they just got to $30,000), but encouraged to hear from the team that they're going to continue with the product anyway and are sticking to their end-2013 target. This could be an excellent solution to bringing high-def video and two-way telemetry to mobile devices without additional ground hardware. 

Very cool. Now let's see how it handles the transitions to/from forward flight.

Ferdinand aka. EndOfDays did it again!

His latest project is an X8 with 8x T-Motor U8 with 29" propellers.

To test the motors' performance and efficiency, he fixed up an X4 quad frame from aluminum. His first test was already impressive: 4kg frame, 4kg batteries (8S) and 4kg payload = 12kg TOW - overall flight time: 44 minutes.

Follow his progress on RC Groups: http://www.rcgroups.com/forums/showthread.php?t=1994599

This is the quad that a friend and i are working now.

Its a Turnigy Thalon quad frame, with some mods. It has a pvc tubing landing gear.

Motors are NTM 3530 prop

drive.

FC: Naza-M with GPS

ESC HK 40 A opto esc.

It is equiped with the gopro black edition.

battery its 4s 5.8 Ah, zippy compact

I am getting 9 minutes of flight time.

The AUW its 2 kg

 or  ?

Hi, when i fly multirotors one of my main worries is to avoid it from crashing. Mechanically I've practically solved it because I usually fly an octocopter (motor, prop and ESC redundancy). My main concern right now is how to power the flight controller safely.

Initially I've connect all my 8 linear becs (in parallel) to my flight controller because I thought that if one fails, the rest would supply the required power. Later on I found out that a linear regulator may fail and may supply voltages higher than 5v and that would burn the flight controller.

A fuse is the easiest approach to solve this but I've read that sometimes it doesn't work well (fast enough). So i found the Crowbar Circuit.

So, i would use 2 linear BECs for redundancy and the crowbar circuit after each of the becs so in case it fails it will not burn the flight controller:

Another option:

I had the idea to use a switching BEC but i don't know if it's the best alternative. I've read that you cannot put 2 switching BECs in parallel because the voltage is generated in waves that may interference each other. So to solve this, one switching bec would be in use and if it fails, the backup switching BEC would take place.

The diagram for this is shown below:

If the SBEC number 1 fails, the Schottky diode would alternate to the SBEC number 2. I think that using 2 diodes would be better for the redundancy (i don't know if it's ok to do that). Could I use a relay instead of this diode?

What do you guys think? Will it work? Any idea is very welcome! ;D

Does anybody have the part list to do a crowbar circuit for the APM? I think it should supply 5v and 500mA, is that right?

Best regards

Woohoo!

Ok, upgraded my TBS Disco to 4S today, along with CF 955 props from RCtimer (balanced). Since I also had it in pieces the other week to change from Moongel to Zeal, I thought I'd better re-run compassmot.

And got 0% again! I had expected a worsening of the score, given the increased voltage, but no - I ran it 4 times, and got 0% on all tests. Ran throttle all the way to 100%, pausing for 5 seconds at each 10% increment (only 955 on MP, so my throttle radio calibration needs re-run) and all was well!

*Note: Picture is from very first test when I stopped halfway through...I managed to delete the "full throttle" one (taken on 3rd run) instead of this one <facepalm>.

Hello All,

I have had the great pleasure to talk to the guys from RangeVideo and hear their story regarding the RVJET they have created.

Enjoy.

Someone strapped a GoPro to an eagle. It's inspiring to think that as technology improves, we'll be able to get closer to this type of flight.

1st post.  Nothing novel revealed, but it's friggin CBS, the big league.  Personally would have been ecstatic just to get that close to Molly Wood.