In my mind there was a project growing up for a few years now. But now it's getting to the point of realizing it.
There are a few requirements for this UAV.
Here is a shorter list:
- extended range
- full autonomous flight
- VTOL
- simple maintenance and service
- extended durability for repeated flights
- nonexistent cargo capacity
I'll try to justify and explain every one of the items on the list below. And for the use of this UAV, it will stay with me for now, only thing to know is that i has to support an IR camera and additional AVR32 cpu or something with a lot of processing power in floating point operations, but low power requirements. There has to be no real time video link, just photo sending possibility, but that's the last thing the project will get.
First of all is VTOL. I know that most of you are launching UAVs from hand, but due to shear size of this thing assisted launch is not an option. I'm thinking about a VTOL airframe with twin tilt rotor design.
Tilt rotor design presents a vibration problem, so i'm looking at all electric UAV, and here is the range problem, and durability. Batteries are good now, but for a vehicle of that size and autonomous flight time, they might be a huge problem. Did anyone tried fuel cell power source?
Just to clarify I'm looking for at least few hours of flight time. Four hours of flight time would be nice. Speed is not a factor here, just range. The slower the better is the word of my idea, but it has to have range.
It has to be completely autonomous. It can have a backup RC link for testing and development, but it has to be a pure UAV at the end. For autopilot / flight control system I'm looking for a custom made device. ATXmega cpu, with a custom board, and custom software written in ASM just as a proof of concept, and that software will be OpenSourced from it's beginnings.
Maintenance has to be simple, service in long intervals, refueling has to be short (for electric power battery replacement is an option), and it has to be capable to spend as little time as possible on the ground.
For the cargo, it has to carry its fuel and additional small computer.
I'm thinking about a larger wing span, with rotors enclosed in casings near wings, probably close to the fuselage, to escape hell of from rotating wingtip rotors, or tilt wing designs.
Replies
Some options exist for extended duration flight but I think you may run into a snag with 4 hours of flight. When I considered the construction of my UAV system I was looking for the same things. I came up with several ideas that seemed to answer some of these concerns. Since Nitro powered engines seem reliable and common to most helicopter airframes I selected one that was able to accomodate an engine larger than specified for the model. In my case I chose the Quick 30 airframe because it combined many of these features. My video link was a small board camera, channel 16 ATV transmitter, and linear amp. I chose an inverted egg beater antenna for the video transmit antenna and added a OSD card to supply the on screen display of GPS data. This was relayed back to a Sony GV-200 video walkman to record the data and also provide heads up video. From there I designed a master voltage regulator board and supplimented the radio batteries with a small generator (made from a slot car motor) geared to the rotor head drive gear. That satisfies the draw of most of the electronics. But.....It takes a lot of electronics for a UAV copter.
In my case I also needed CCPM mixing for the rotor head and a way to marry this to the throtle. What I found was an onboard mixer that satisfied this problem. Of course fuel is fuel. It takes quite a bit to go 4 hours. What I would do is look at weed eater motors for your power plant. Clutches are fairly easy to make for these things and from there it is just a matter of scaling up the mechanics. Make good use of your blade loading and plan your power use for the fuel you need to make your flights. A weed eater will run about 45 minutes on its tank of fuel so you can estimate it from there.
Gas is still a cheaper way to go on these things and most of the fuel tanks used for models will also hold gasoline without a problem. That would be my suggestion.
Regards,
Skip
Seattle, WA
FYI , a 350+ cc of fuel in .50 or 8 cc nitro engined heli lasts between 10-15 minutes. That's approximately 2 liters/hour,
You may want to lookup a simple but tested single rotor commercial solution like yamaha R-Max to get an idea on price , size etc. Like Chris and Gary mentioned, IMHO you should start with simple solution and then scale it up.
I'm intrigued why does it have to be rotary? We have a fixed wing solution that can fly for three hours.
Fuels cells have been used in fixed wing solutions.
You are going to butt up against regulation in some parts of the world. Several places are proposing no autonomous flights that last more than 30 minutes as a risk mitigation.
You've picked pretty much the hardest UAV challenge possible, combining pretty much all of the most difficult technical problems in this area. This is the sort of thing that the largest defense contractors spend millions of dollars trying to solve. I suggest you start with something simpler and tacking one problem at a time. You might want to begin with the Paparazzi Booz project.
you have come to right place to learn , it is mostly DIY forum , so you will have to learn, understand, source, build , ask and share. But once in a while you will find posts from commercial UAV builders or off the shelf components ready for integration too. Fun is guaranteed , Good luck with you project.