Hey everyone - first post, so please be gentle!
I've been meaning to get into electronics for a long time and more often than not the ubiquitous UAV comes up as an ideal first project to learn many of the basics. The fact that I'm an aviation and space nut is just a bonus!
I know that putting together pre-made kits is one way of learning some of the basics, but personally I've always felt that I learn more by designing and building something from scratch. That being said, I also always seem to make things difficult for myself by (unintentionally) over complicating things due to a lack of knowledge. Just the other night I was thinking about how to use magnetic bearings to get higher performance out of propeller systems, and after several hours of thinking and research, I realised that I had ended up re-inventing the brushless motor :D
So. For my first question, I've been looking into UAVs and noticed that most, if not all, rely on the direct thrust provided by the propellers to maneuver. Although this obviously works well and is probably the way I'll end up going, I've been thinking of a potential UAV design which uses EDFs, or some similar ducted system to gather thrust and channel it all into a kind of central manifold. This manifold system would then redistribute the total available thrust to various thrust reaction "nozzles" (for want of a better word) according to the needs required by the maneuvers in progress.
So the idea is that instead of driving the aircraft off of the raw thrust of the propellers, I would refine the system through a process of collecting the total available thrust and then redistributing it in a more precise way to allow for finer control and possibly a larger range of maneuvers.
I know this idea might be a bit odd, and probably isn't viable, or practical, but I enjoy challenges and the learning that comes with them, plus I think designing and building something a little bit different from scratch will help me to learn more than just copying existing designs.
Any thoughts or suggestions? I'm open to criticism and any feedback.
Thanks in advance!
Replies
I can relate with the desire to do things the hard way. Despite the advice to start with an EasyStar, I bought several books on RC Plane design before getting my first Glider airframe. It's still in a box in a storage unit and hasn't seen any flight time. I can say in hindsight that the EasyStar+ArduPilot Mega path is the best one, but similar words did not persuade me.
My understanding is that a single large propeller is more efficient than many smaller propellers of equal total thrust. The rationale behind vehicles like this being redundancy & economies of scale cost benefits:
http://diydrones.com/profiles/blogs/how-many-brushless-motors-do-yo...
I've seen videos of VTOL ducted fan based UAVs that use a single EDF with control surfaces. I don't know if that's what you had in mind. Vectored thrust along these lines: http://en.wikipedia.org/wiki/Vernier_thruster http://hackaday.com/2011/01/18/attitude-control-for-a-really-big-ro... is something I have not seen on a UAV before.
Probably the closest thing I've seen:
http://en.wikipedia.org/wiki/BAE_Systems_Demon
I don't have the experience with fluid-dynamics to comment but you may want to pick up a text book from the library or read up on Computational fluid dynamics(CFD) so you at least can identify sources of inefficiency.
The mechanical aspects are fun to think about but you have to be able to control it. I don't know if you have any experience with programming, but if not, an ArduCopter kit is probably a good place to learn. Calibrating it would give you a chance to get familiar with PIDs, serial communications, IMU data, and the DCM algorithm.
There are some ducted fan UAVs that use vanes for control, but I haven't see anything as complex as what you describe. I suspect that's because of all the energy loss in all that redirection of flow.