Hello, I would like to ask your comments and help with regards to our thesis project in school. Our project is to make an unmanned helicopter. It will be controlled by a microcontroller.

Our problem is in selecting the design or shape of the helicopter. Initially we have proposed designing an electric helicopter (to be flown in a gym) based on a coaxial rotor design. But instead of tilting the blades, we were proposed of putting four motor/props in four quadrants to provide tilt and direction change by changing its motor speed.
We will be building the body of the aircraft unless there is a rc model of this kind. In this setup, the batteries of the motors will be tethered to reduce load. The helicopter will only fly low heights. Below is a rough design of the helicopter.

But we dont have that much idea about flight and aerodynamics (but we are researching more ).

Then, we thought about purchasing a single rotor helicopter kit and from there, we will construct the navigation system and computer system to make it fly unmanned.

I'd like to ask your help, ideas and comments on which approach would be better and more feasible. If possible please add theories/discussions or mathematical computations to support it.

We are actually leaning on choosing the 2nd option of purchasing a single rotor heli so any proofs, ideas that will show that the 1st option is not feasible (stability, design, capability to turn/tilt, etc) is ok.

Thanks! Any help will be appreciated

Don't underestimate the value of knowing you at least have something that flies. I spent the last few months trying to get a small electric delta (http://uavfun.tripod.com/temp/IMAGE0007.JPG) to fly. I never really got a chance to work on the electronics. It took ages to get it to fly at all; it started out VERY unstable. Then I changed some small little thing yesterday (I don't even know what) and it went from being a little wobbly to not flying at all. I wasted a LOT of time fixing all the electronic parts that got broken every time it crashed. There was also no way it would lift the little digital camera I wanted to put in it. It just wasn't worth it; I'll make a more conventional plane and move everything to that.

What are you planning to use for sensors and so on to tell what the vehicle is doing? It takes quite a bit (see http://autopilot.sourceforge.net/ for an example). With a plane you can 'cheat' a little bit (for example, measuring angle of attack and monitoring altitude instead of keeping track of pitch), but that won't work with a heli. You will need to constantly keep track of pitch and roll at the very least, and probably also heading and altitude.

Our helicopter/aircraft will only do navigation between to level points. First, data (heading, altitude, distance) will be programmed to the microcontroller. Then the microcontroller takes over and flies the aircraft.

For our sensors, we are planning to use three accelerometers (x,y and z), three gyroscopes (x,y and z) and a magnetometer. These will serve as inputs to a microcontroller which computes the aircraft's orientation, altitude, acceleration. And the microcontroller will control the outputs to the motors so that the aircraft will move towards the correct direction.

Our concern is about the stability of the first design and if it will fly and turn to its direction with the use of the four motors in each quadrant.

and also our problem is that our panel would like us to present some theories or computations that will tell that the first design might not be able to fly or stabilize and that given the time frame of one year, we might not be able to finish it.

thanks!

This goes a long way toward clarifying your questions of Feb.13th. Last fall I was visiting the Georgia Tech School of Aeronautics and a class there was working on a similar project. They had chosen a helicopter of conventional configuration with a large main rotor and tail rotor. Part of the decision seemed to be that there were enough problems to solve in the control design without trying at the same time to invent another kind of flying machine.

Efficiency of the coaxial configuration is the least of your problems. By tethering the batteries and keeping things light, you should have no problem producing enough lift to hover. The biggest problems I see are the mechanical complexity and problems of stability.

There is nothing indicated in your sketch that would provide any inherent stability. A microprocessor would have to be dedicated to providing stability in addition to the control functions you describe. This is certainly possible. It is similar to the problem faced by the inventor of the Segway People Mover. But you are biting off a lot to be accomplished in a school year with limited resources.

Although differential power on the outriggers will tilt the machine, they won’t supply a force to rotate it about the axis. Therefore, at least two of the outboard engines would have to be mounted on gimbals to supply directional control. Igor Sikorsky’s first successful helicopter (the VS-100 I believe) had a single main rotor with a tail rotor and four smaller vertical outriggers similar to your proposed layout except they were open rather than ducted. Although it flew after a fashion, only when he provided cyclic pitch control for the main rotor and eliminated the outriggers could it be considered a practical flying machine.

If I were on your team, I would vote to use a helicopter of more or less conventional configuration. My reasons would be:

1. The proposed machine is not inherently stable and would require design of a stability augmentation system
2. The numerous fans and motors are an unnecessarily complex solution to the assigned problem
3. Inventing a new type flying machine is a different task than designing an autonomous control system and the increase in scope makes it unlikely that it could be completed in the allotted time.

I hope this helps.

Is this a 500 level course? I am interested in your project. As an aerodynamics student several years ago, I spent many hours discussing a similar project with a true genious aerodynamacist. email me at [email protected] I would like to hear more about your project.