I have spent the last month laying down the groundwork for a micro VTOL aircraft, which can be flown indoors autonomously. I've chosen this type of platform because quite frankly,
1) My only experience flying rc helicopters is my blade msr, and considering my current lack of piloting talent, I want to avoid large dangerous rotors and expensive crashes,
2) I believe that current twin rotor designs can be successfully scaled down into the micro size, as long as every component is optimized for this exact application,
and
3) I am interested in designing my flight controller completely from scratch, so my options are further expanded.
I will be using two brushed motors for initial prototyping. If I need greater RPM control I will move to brushless. I will be using an ARM7 microcontroller (or simmilar) which will have serial out (am I wrong in thinking that rs232 is the lightest/most supported interface?) and accept the inputs from my sensor package. I'm not gonna kid you guys, my only experience programming microcontrollers is from a few day experiment with a STAMP Basic 2. However, I'm not too concerned, I figure I can borrow code from Arduino, right?
Either way, ignoring my lack of programming experience which is limited only to what I learned in college, I have a considerable amount of experience using LabVIEW. I hope that this will jump start data acquisition + interface development, and I should be able to port my VIs into the ARM7 with a little luck...
Looking at what's out there commercially, I have not found an ARM7 board that is minimalistic enough for me to buy outright. So I'm planning on etching my own PCB at home. *crosses fingers*
I'll skip over the boring circuitry stuff and get to the cool part, the actual UAV design!
Both motors will be boom mounted and will rotate independently in 2 axis. Motor speed will be variable and independent of one another, of course, providing the third axis of control. Plan B: if the former proves to not work for a multitude of reasons, the two motors will be linked together on a single boom so they rotate forward and back dependently, however then I will lose the ability to spin on its Z axis.
I plan to hang the circuitry and batteries between the two rotors, to maintain a central and very low center of gravity. This will hopefully provide some stability on it's own.
Autonomous flight control will use parallel processing to sort and categorize data, from which my main flight control program will read this streaming data.
I'll stop explaining here, and open myself up to your opinions.
What do you think?
Just in case I did a poor job explaining my airframe design, look here for a commercial example of a twin rotor VTOL.
You need to be a member of diydrones to add comments!
Replies
http://leaflabs.com/tiki-index.php
The smaller the physical size the greater the control and stability problems and the higher the performance of the control loops. I would be looking to use brushless motors and possibly digital servos.
I would have thought yaw and roll are controlled by tilting both the rotors (same and opposite directions) and pitch by the differential speed of the rotors.
Good luck and let us know how you get on.
Peter
am i missing anything?
I agree that the gyroscopic forces from twin rotors will be difficult to overcome. I appreciate the advice on that. The reason I chose 2 rotors over 4 was to increase maneuverability in a smaller package. I may have a solution to this, but I need to run the math. What if I switch to heavier brushless motors and mount them between the two rotors, in the center of the airframe? The gyroscopic forces of the axial mounted motors might overcome the rotors. Or maybe not. I'll be looking into this today.
I recently ordered the ARM7 dev board (http://www.futurlec.com/ET-STM32_Stamp.shtml) so I'll see what its like. The main benefit is that you can use xduino code (arduino-like functions).
I'm interested in a micro quadcopter (horizontal flight biplane/vertical flight landing/takeoff) using the same ARM7 CPU but on a custom board with integrated gyro and accel and compass (yaw). I should work on an Eagle layout with the cpu and accelerometers this weekend, I'll let you know how it goes.
Mechanically, the only issue I'd say (I saw this on an RCGROUPS post regarding an avatar-like r/c heli) is that the torque of your tilt servos will act negatively on your chassis, IE: the body will tilt instead of the rotors. At higher speeds it's more negligible since the rear H-stab will have an aero influnce (mainly drag).