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Hi there.

This being my first post and all please bear with me.

Having read through an number of posts on airframes for armature UAV's i'm left a bit baffled.
I do understand that some people are more into electronics and software than building airframes but i find it quite odd that a modified Easystar seems to be the "donor" plane of choice.

I know that the mods are endless and there's even a guy that writes about building and selling Easystar carbon fuselages here but from what i can tell the fuselage and the fact that ailerons are not standard
is the Achilles heel of the Easystar.

Obviously threes no reason to reinvent the wheel so i was thinking along the lines of combining the wings of something like a "BMI Arrow", "AXN Floater jet" or "Dynam Hawksky" (they are all Easystar type planes

but with ailerons) with the fuselage of something like "Penguin-B UAV" or "Team Javelin" which should basically result in a platform as stable as the Easystar but with a lot more room and freedom for payload placement.

Anyways... My point being (although a bit obscured). How about a joint venture. There's loads of brilliant people with tons of experience in here. Why not define a "standard" DIY Drone platform that will suit the majority of projects?

Please let me know you thoughts.

Lets get a list of requirements together and see what happens.

Kindest Regards

/Stig

ARDUROV T100
- PRELIMINARY PROJECT ANALISYS -

Overview

ArduRov is an under water electrical vehicle controlled by the surface trough an umbilical cable, operator drive the Rov by the image of a camera and with the help of various sensors.
The goal of the project is the realization of a cheap ROV, a rock solid open source software, a modular design for a safe and easy use
The project could be divided in different parts, to be discussed and developed.

Surface Electronics

A small box with the power supply , Surface telemetry electronics and the video output
Options:
BASIC: A Simple Plastic Box with Input/Output connectors, PC or R/C Joystick
Advanced: A Case with LCD Monitor ,Telemetry Overlay or second LCD, A PlayStation JoyPad
PRO: A Consolle with HD Monitor, Overlay, DigitalRecording, Custom JoyStick etc

Umbilical Cable

To maintain a low cost the umbilical cable will be a standard multipolar PVC cable with at least 8 conductors, section of the conductor is to be defined depending to the final amps consumption.
My Idea is start with 50 mt of umbilical cable to avoid the needed of a winch to handle the cable.
All parts of the ArduRov Basic must be projected for a pressure of 20 bars (-200 mt)
Options:
BASIC: 30 mt of PVC 8 Conductor Industrial cable
Advanced: 100 mt of Kevlar armoured cable with hand winch
PRO: 200 mt of Kevlar armoured cable with motorized winch


ROV Frame

The frame must be as modular as possible, corrosion free, and with a low water drag.
For my experience the best way is use two polypropylene mono-block shoulder connected by Anticorodal Anodized “U” profiles. Carbon Fiber will be the next spet to reduce weight in air.
The profiles will be used to fix the thrusters, the underwater electronic pod, camera, lights etc
Options:
BASIC: polypropylene / Anticorodal frame
Advanced: Carbon Fiber/ Anticorodal frame
PRO: Full Carbon Fiber Frame with hydrodynamics surfaces
Buoyant System
To Compensate the weight of the ROV a buoyant system is needed, there are different method to add buoyancy but the most reliable will be the use of block of a special close-cell polymer.
A cheap solution could be polystyrene but it will fault at more than 5 bars (-50mt)

Options:
BASIC: polystyrene
Advanced: close-cell polymer
PRO: close-cell polymer with Carbon Fiber Coating

Thrusters

Propulsion is one of the most important thing in an ROV, We plan to use 3 , 5 or 6 thrusters to control the vehicle. Basically One or two thrusters are vertical and controls only the depth and eventually the tilt of the ROV and two or four thrusters are disposed on the same plane as in the following scheme:

This configuration allow Reverse , Forward , Left, Right and Rotation movements, to archive more thrust rear propulsion could be oriented differently.
The main problem of the thruster is the design of the underwater housing to resist at the pressure and at the same time not reduce the mechanical power, there are several different techniques to do this:
- Direct Shaft output with O-rings (cheap but with poor performance and frequently maintenance)
- Ceramic Shaft Seal with Oil Compensation ( Expensive and need special tools to fill oil )
- Magnetic Coupling with Dry Motor and magnetic Follower ( A bit more complicated design and project costs but virtually no maintenance and good efficiency )

Motor type should be Brushless sensorless, this type of motor can be controlled by an Electronic Driver and perform a good torque and a good power/dimensions balance.
We need to find a good motor with a very low Kv to have the maximum torque and reduce the RPM.
A good rpm speed could be around 2500 Rpm at full thrust.

Options:
BASIC: cheap R/C Brushless motor with direct shaft output with O-ring
Advanced: Industrial Brushless motor with hall effect position sensors and magnetic traction system
PRO: Custom Brushless Motor with hall effect position sensors and magnetic traction system


E-POD

Basically the epod in the brain of the ROV, is an Anticorodal cylinder with connection on both sides.
One side receive the umbilical cable and the other side have all output (Thrusters , camera ,lights etc).
In the e-pod there is the electronic board and the Power conversion board to power-up the brushless motors and to convert Voltage to an appropriate value for all the equipment installed.
One part of the e-pod side will be reserved for sensors (Depth sensor, compass, temp sensor etc )

Options:
BASIC: Anticorodal cylinder with cast resin cable connections without sensors
Advanced: Anticorodal cylinder with underwater connectors + depth sensor and compass
PRO: Anticorodal vaacum cylinder with underwater connectors + depth sensor , compass , temp sensor , altimeter , and Lipo Power pack optional connector for UAV conversion.

Camera

Camera is the underwater “eye” of the pilot, could be standard 640x480 resolution or HD depending on the scope of the ROV. It is composed by an Anticorodal or Derlin Cylinder with a correction lens at one side and a connection cap at the other side. For standard resolution we will use a video-baloon converter/amplifier and a twisted pair to send video to surface.
Camera could be static or remote tilted to allow a panoramic view

Options:
BASIC: Standard 640x480 b/w camera with fixed focus and fixed iris
Advanced: Standard 640x480 color camera with fixed focus and fixed iris with remote tilt possibility
PRO: HD Camera with remote zoom , focus , Iris with pan and tilt possibility

Light

Lighting is very important underwater, especially in sweet water where you will be in the dark at few meters deep. A natural light is required for a good view and we can use halogen or led source for our purpose.

Options:
BASIC: 2 x halogen light with on/off control
Advanced: 2 x halogen light with dimmer control
PRO: 3 x halogen light with dimmer control

________________________

This is a very preliminary and personal analysis, feel free to comment, add, contest everything... and sorry in advanced for errors.

Taborelli Flavio

Original blog post : http://www.virtualrobotix.com/profiles/blogs/ardurov-project-remote/

Together with the Laboratory for Energy Conversion of the ETH Zürich we have adapted their multi-hole air flow probe to Paparazzi and integrated it into our meteo Funjets. It is used to measure wind vectors/turbulences around wind turbines for a more efficient planning of wind parks. The goal is to reduce the impact that a turbine causes to the ones downstream. Swiss television has an article (in German).

Eagle Files:

ArduPilotMegaShield_H_v10.brd

ArduPilotMegaShield_H_v10.sch

Ardupilot Mega test flight report.
Today i did my first test flights with the APM installed in my Multiplex Twinstar II.

I tested the Stabilization mode and the Auto mode with six waypoints in a 1,4 km
long track.

Equipment
* Multiplex Twinstar with brushless motors.
* 35 MHz RC
* APM with shield
* Airspeed sensor
*U-blox GPS
* Aerocomm 868 MHz radio modem (Not used)

AP config
*Running software built 2010-09-07
* Custom config file exceptincreasing cruise speed and cruise throttle.
* Altitude mixing set to50%
* Air speed sensor enabled

Weather
* Wind about 10knots with gusts up to 16 knots. Moderate turbulence.

Result
Stabilizationworked great with standard settings. Maybe it responded to stick
movement a bit to abruptly, but it was really steady in the quite
turbulent air.

Auto mode worked fine. The plane flew the coursewithout any real problems and then started to loiter above the home
position. One strange thing i noticed was that the plane changed
direction during loiter after a few turns. Could it be that at first it
tried to reach home position but never came close enough and then when
it reached home it started circling in the other direction?

Altitudeholding worked fine and it was fascinating to see the AP cut the
throttle to zero when the plane reached some thermals when fighting
against the wind to reach a waypoint. You could really hear the throttle
going up and down during the flight.

The only thing that didn'twork was downloading the log files after flying. I could only read a
few lines before i got an error. I will file this as an issue at Google
Code.

Over all this was a real success. I now feel that i have aplatform that is easy to setup, maintain and fly.

Next time iwill add telemetry so i can log things as well so i can show off nice
maps.

Dear Friends,
FoxTeam after the development project Fox Hybrid , HG3.2 and support Arducopter with Hexafox project is' working on a new exciting project.
Ardurov, followed some pictures of the first rendering of the ROV we're doing.

There 's a lot of work to do, if someone wants to join the development team of the project can' contact me at my skype address: virtualrobotix

For more info follow the project on : http://www.virtualrobotix.com/profiles/blogs/foxteam-present-ardurov-the?xg_source=activity

I have been tinkering with solar powered RC planes this summer. The photos above shows the latest incarnation.

This model uses the Parkzone Vapor's radio gear and motor ( http://www.parkzone.com/Products/Default.aspx?ProdID=PKZ3380 ), plus five Powerfilm solar cells ( http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_228056_-1 ). The motor/prop are quite well matched to the cells, delivering about 2.5 watts in direct sunlight. Here are some test data:

All up weight is 38g, 18g in solar cells. It has a tiny 20mAh battery (1g) in parallel with the solar cells that acts to smooth out the voltage. Before I flew, I ran the motor using battery power until the voltage dropped too low to run the motor, then I plugged in the solar cells. That way, when I flew, I knew I was really running on solar power alone. I flew it for about 5 minutes or so, but it was a pain to fly because the wings were too torsionally floppy. I am planning the next revision that should address some of this design's shortcomings.

Related Work

There have been many successful solar airplanes. I found the following efforts particularly interesting because they are not military or NASA scale projects, and they are well documented.

Andre Noth's (ETH Zurich) 3.2m span Sky-Sailor, which flew 27 hrs in 2008

www.asl.ethz.ch/research/asl/skysailor

Carl Engel and Adam Woodworth's (MIT) 3.1m Aphelion, which has flown over 7 hrs

http://www.rcgroups.com/forums/showthread.php?t=572000&pp=15

Solar Cell Selection

In many applications, solar cell performance is measured by efficiency. In my experiments with the Powerfilm cells, I got about 70 watts per square meter. Using a fairly standard irradiance value of 1000 watts per square meter puts the cell efficiency at something like 7%. This is not particularly good compared to the state of the art (see e.g. http://en.wikipedia.org/wiki/File:PVeff%28rev100414%29.png).

The Aphelion uses an array of 18 A-300 Sunpower Solar Cells. The total encapsulated array weighs about 350 grams and can deliver 55 watts of power. These cells are reported to be upwards of 20% efficient. BTW, if you dig deep enough into the Aphelion thread referenced above, Carl reveals his secret supplier of these cells:

<quote>

Also, here is the contact info for our solar array supplier, now that he has given permission for it to be posted. One note that he wants to be made clear: he is very busy, and it's a small operation, so there can be a serveral month lead-time on ordering an array. With that, here is his info:

SunCat Solar is the name of the comany, and our contact in Alain Chuzel(pronounced "Allen"). His email address is
ahmchuzel<at>aol<dot>com. (replace the <at> with @and <dot> with . )

He can fabricate pretty much any size or confguration of array, given a good drawing (and enough money )

</quote>

The weight of solar cells accounted for 47% of the total weight of my airplane. Therefore, I would argue that for a solar powered airplanes, an important performance measure of performance is watts per gram. I measured about 0.27 watts per gram for the Powerfilm cells. This compares favorably to the Sunpower cells at 0.16 watts per gram.

Some other attractive things about the Powerfilm cells is that they are reasonably priced, and readily available in small quantities. I have not contacted Suncat Solar to determine the cost/availability of the Sunpower cells.

Scaling Arguments

I think it would be very cool to build a solar powered drone that could stay up all day, and possibly all night. My little airplane has essentially no payload capacity. Presumably, a larger airplane would be required to carry up a GPS, IMU, two way radio, etc.

As the airplane gets bigger, we have more area for solar cells, but the weight gets larger too. So how does the power budget work out with a bigger airplane? Here are some scaling arguments to help answer that question objectively.

Definitions:

Preq: required power

Pavail: available power

Rp: the ratio of available power (Pavail) to required power (Preq)

D: drag

V: flight speed

W: weight

g: acceleration due to gravity

rho: air density

S: wing area

CL: lift coefficient

Kcell: power output of solar cell per area

LOD: lift/drag (or glide ratio)

WOS: wing loading, weight per area

Relationships:

(1) Pavail = K * S (assuming the entire wing is covered with cells)

(2) Preq = D * V

(3) V = sqrt( 2 * W * g/ (rho*S*CL) )

(4) D = W * g / LOD

Combining (2), (3), and (4) gives

(4) Preq = W * g/ LOD * sqrt( 2*W *g/ (rho*S*CL) )

Combining (1) and (4) gives

(5) Rp = K * S ^ (3/2) * LOD * sqrt(rho * CL) / ( (W*g) ^ 3/2 * sqrt(2*g) )

Finally, simplifying (5) gives

(6) Rp = K * (1/WOS) ^ (3/2) * LOD * ( sqrt(rho*CL/ 2) * g^(-3/2) )

There are four terms in (6). The first term depends only on the solar cell. The second term depends only on the wing loading. The third term depends on the aerodynamic efficiency of the airplane, and the fourth term we can treat as a constant. Thus, starting from my little airplane, as we increase the size of the airplane, if we use the same solar cells, maintain the same wing loading, and maintain the same LOD, then we should still have enough power to fly.

The bad news is that as airplanes are scaled up, their weight usually goes up faster than their area, thus their wing loading goes up. Stated another way, bigger airplanes usually have higher wing loading than smaller airplanes given similar structural technologies.

The good news is that as we increase the size of the airplane, we can expect the LOD to improve. The LOD of my airplane is around 7. Doubling or even tripling this value should be possible ( see e.g. http://www.rc-soar.com/tech/perfanal.htm ). The wing loading of my airplane is 540g/m^2. If we double the LOD, we can increase the wing loading (WOS) to 850g/m^2 (i.e a factor of 1.58) and maintain the same power ratio.

Also, as we make the motor and propeller larger, we might expect an improvement in propulsive efficiency, meaning that we fly with a reduced power ratio.

Considering these factors, building a bigger solar airplane is probably harder than building a small solar airplane. Based on the successes referenced above, I must conclude that it is possible, but not easy (or cheap).