|Dec 28, 2007, 07:09 AM|
G. Heights, Illinois
Joined Feb 2006
Over a year later...
...the 401 is still grounded and I have given up on my build-the-whole-plane approach. Numerous problems with what I was thinking before. I could design and build the whole plane, but the amount of learning and extra cost and time it would require to make the electronics is vast. Especially when everything I need is sitting in a box somewhere for like $150.
On the positive side, the idea of this UAV is much more solid in my head. I have sorted out the obvious issues, and just have to get to work to find the ones I don't know about. I've done a lot of research and thinking, and this is what I've got it down to.
The general idea is a remote controlled airplane that I can fly up to about ten miles away using a live video and telemetry feed. This will consist of five systems on the plane, and four on the ground. The first three systems are common to both the plane and the ground; video, telemetry and control. The plane has two additional systems, an airframe and an autopilot. The ground also includes a base station.
This is obvious, it is a video link from the plane to the ground. WirelessVideoCameras.com sells video camera and Tx/Rx packages for around $700 - $1000. They have ranges varying from 1000' to 25 miles, and are built specifically for RC aircraft. The camera is also optimized for the conditions it will mostly see: pointing at the sky. The Rx on the ground has a simple yellow RCA video connector, and is NTSC compliant so I can use whatever video screen I want.
Remote measurement of airspeed, altitude, battery voltage, etc. There are several systems out there already, complete with live laptop (or pocket PC) display of virtual instruments. RCAT Systems and Eagle Tree Systems are my top choices. A gray area here is that the range I need is very, very expensive; about $2500. If I knock the proposed range to about 5 miles, this would only cost me $900 or so. What I plan to do at this point, is to write those two companies and see if it is possible to use my own transmitters. That way I can use their cheapest package, (the measuring equipment is the same no matter what the range) and still get the range I want. I would have to use the control system radio to also send data back. No idea as to how this will affect bandwidth, but I imagine I should have plenty. On the ground, I'll have a laptop presenting the information.
This system will consist of two radio modems for sending and receiving, two microcontrollers for encoding control input and sending it to the radio, and for decoding signals and controlling servos. The radios are Digi XTend OEM modules, with a range of up to 40 miles and a rate of up to 115kbps. I don't know what microcontrollers to use, but they will likely be from Parallax. Ground side, I have no idea what controller I will use. Nothing USB (a bit more complicated then I need), which means I need some kind of serial controller, or possibly a USB to serial converter.....another gray area to explore.
This I will design and build myself. I believe it will not be too difficult to design a plane that will both fly and be able to carry the electronics. It will likely take the most time, and effort of the whole deal, but will probably be the most enjoyable. If this task seems too daunting, I can always switch to an existing platform. The Hobby-Lobby Telemaster line looks appealing.
The BTA AS-07G will satisfy my needs perfectly. The autopilot will take over when radio contact is lost or when engaged. It will then fly the plane back to its initial GPS starting point and circle until control is reestablished. It also has a feature that will smooth the user inputs somewhat. You can climb, but not stall. You can bank but not roll, descend but not dive. The autopilot is totally independent of all other aircraft systems, and uses its own internal sensors to navigate.
A place to power and shelter the ground systems. IE: my car.
A few other things I will include on the plane will be a remote start, retracts, large fuel capacity, flaps, lights, possibly a four-stroke diesel.
Altogether, there are only a few issues to resolve:
- Can my telemetry also use the control modem?
- What microcontroller should I use?
- What HID will I use and how can I interface it with the microcontroller?
- Will all this crazy $4!t come together and work?
Probably the most important item of research. Good news is that I can do this, with few restrictions. The FAA has two documents on UAVs: AFS-400, and AC 91-57. AFS-400 deals with the certification and training of UAVs and their pilots. Very difficult (if not impossible) for me to meet these standards with my funds and governmental connections (little and none). However, section 6, subpart 13 states if I meet the rules stated in AC 91-57, I am exempt from AFS-400 and must obey AC 91-57. That circular states five things:
1. Do not fly above populated or noise-sensitive areas.
2. Fly below 400 feet AGL, and three miles from any airport.
3. Do not operate unproven aircraft around spectators.
4. Full size aircraft have right-of-way. Avoid full size aircraft.
5. Ask for help in obeying these rules if needed.
Furthermore, the FCC also has rules concerning operating aircraft by remote control. If unlicensed, I must only use 26-27 or 72-76 MHz bands, and only FCC approved devices(which means off-the-shelf, no modification). This is obviously not nearly good enough for my purposes. If I get an amateur radio license, I may operate on any amateur band up to one watt. Surprise, surprise, the radio modem I chose operates exactly on one of those bands, and not exceeding a watt.