Ahh!! CRASH and BURN!!
I had planned to use the Pico-Pilot and Pico-GPS for the autopilot in my UAV, but I have now discovered that since Jan 2007, they have been classed as MILITARY technology and are controlled by US Export License regulations. Specifically theregulations cover,
a. “UAVs” having any of the following:
a.1. An autonomous flight control and navigation capability (e.g., an autopilot with an Inertial
Navigation System); or
a.2. Capability of controlled flight out of the direct visual range involving a human operator
(e.g., televisual remote control).
b. Associated systems, equipment and components as follows:
b.1. Equipment specially designed for remotely controlling the “UAVs” controlled by 9A012.a.;
b.2. Guidance or control systems, other than those controlled in Category 7, specially designed for
integration into “UAVs” controlled by 9A012.a.;
b.3. Equipment and components specially designed to convert a manned “aircraft” to a “UAV”
controlled by 9A012.a.
Note: 9A012 does not control model aircraft.
Despite the last sentence, UNAV, who make the Pico Pilot have now told me that none of the applications for export licenses they have made thisyear have yet been granted. Back to the drawing board.
The other common low cost option for an autopilot seems to be based on the FMA Co-Pilot for flight stability with an additional board suchas the RCAP2 plus a GPS receiver for navigation. While a cheaperalternative, I had already discounted this approach because it isbased on thermopile sensors. For my terrain, I cannot get a clear360degree view of the horizon to calibrate the system before launch.In addition, the various different terrain types , forest, grassland,lakes etc. could give problems in flight, irrespective of thetemperature differences that can occur if different parts of a valleyare in sunlight or shade.
During my initial research into autopilots, I also looked at the Paparazzi project. While there is a wealth of open source stuff there, thecurrent Tiny autopilot still uses thermopile sensors for stability,although it does have an on board GPS unit for navigation. An all singing, dancing IMU with gyro's , mangetometers etc. is under development. Althoughall the designs are published, there is still no commercial source ofassembled units or PCB's.
A recent post on this forum (can't find it now), talked about the the UAV development board from Sparkfun. I had a brief look at this, butinitially discounted as they claim that the firmware is a guidelineonly. It is also written in assembly code and I am far to old tostart writing in assembler again. Still I shall have another look atthis over Christmas, as the board does have a proper IMU with 2 gyrosand a 3 axis accelerometer.
Conclusions and Questions
- I cannot use my prefered autopilot option owing to US export regulations.
- What other, non US manufactured, commercial autopilots are people using?
- Any other suggestions for a home built unit with an IMU rather than thermopiles?
Building a UAV for phot mapping - Previous Posts
Comments
And that's the point. Thermopiles are working good if you provide a biological pilot to the autopilot to land/takeoff the whole thing. This diminishes the number of potential users by few orders of magnitiude. The problem is, you really need a MSc in applied maths/physics/related to make a good IMU at home.
We use the FMA thermopile on GeoCrawler 1-3 and have no problems with heat-radiating areas at close range. That's because we only engage the autopilot after we're at an altitude of 100m or so. I assume you'll be doing the same thing--taking off and landing manually, with the autopilot disengaged--so I don't think you have to worry about this.
That said, the Paparazzi hardware/software is technically challenging to get right, so the Picopilot is by far the easier path.
Having not yet tried any form of autopiot, my comments were not based on any practical experience - just trying to think through the issues. Certainly in the FMA instructions in the calibration section, it states.
" Measure the temperature difference between earth and sky.
a. Take the model to a spot (grass is best) representative of the area where you will be flying. The aircraft should be atleast 100 feet (30 meters) from anything that radiates heat (heat from buildings or parking lots can affect calibration)."
If you look at my launch/landing area photo in the first post , you can see I have the house to one side and trees on the other - both closer than 30m. This combined with the steep hills and valleys and the great variety of terrain types led me to think that I would have problems with any system that uses thermopiles.
If, based on your experience, you are saying that these factors are not important, then that is very useful to know. I have also not seen any mention of them being more accurate than IMU systems - do you have a reference?
Paul
Except for very certain conditions(ie forest fires etc) they are as accurate or more accurate than IMUs(gyro,mag,accel) in the equivalent price range or even far above.
thought you might like to know
gwen - researcher
I am too am embarrassed by the outmoded laws that only keep the honest honest!
Paul
That sucks, and I'm once again embarrassed by my government. If you'd like we can talk offline about ways to get around this. No harm, no foul, etc.... Use the private messaging system (envelope icon above) to ping me if you'd like to discuss.