Quadrotor Design Help

[rao1995]

Hello

I am doing a project on "Quadrotor Control System in case of a propeller failure". It's aim is to make an emergency landing of the quadrotor in case of a failure of a propeller.

But I do not have any idea on how to build a quadrotor from scratch. Please do help me on how to build a quadrotor from the most basic concepts and parts.

PS : Also, any materials or links on quadrotor basic design, working and concepts would be helpful.

Thank You

 

[shaiko]

Basic parts:

Frame, 4 Motors, 4 Electronic Speed Controllers, Flight computer with orientation sensors, Radio control link,

First you have to understand the concept of how a Quad maneuvers.
Read the "Flight dynamics" section in this link:
https://en.wikipedia.org/wiki/Quadcopter

Of course you can build a Quadcopter from scratch - although, there're many pre-manufactured frames that require only assembling. What is your budget for the build ?

 

[BradtheRad]

emergency landing of the quadrotor in case of a failure of a propeller.

You'll want the craft to descend slowly. To ensure this you either need to (a) install an altimeter, or (b) spin the propellers at an rpm which you determined (by previous experiments) is the proper speed so that 3 propellers will reduce altitude.

You certainly do not want the craft to gain altitude, automatically. It will fly away.

With only three propellers operating, it is a problem for it to stay level. One of the propellers is the 'odd' propeller. It will be important to speed that one up or slow it down, so the craft stays level. You'll need to install an accelerometer, or some kind of level sensing device.

 

[shaiko]

With only three propellers operating, it is a problem for it to stay level. One of the propellers is the 'odd' propeller. It will be important to speed that one up or slow it down, so the craft stays level. You'll need to install an accelerometer, or some kind of level sensing device.

I'd approach the problem differently.

1. Detect the yaw direction. For example if one of the clockwise propellers is damaged - your gyro will show counter-clockwise angular spin.
2. Shut down both clockwise motors and increase the RPM of both counter-clockwise motors proportionally to maintain height. This will increase the counter-clockwise angular velocity even further but at least your veichle will remain stable relative to the horizon - which is the only important thing at this point.
3. Start a controllable decent by proportionally decreasing the RPM of the 2 counter-clockwise motors.

Note: implementing my solution will require all of the power required for the upward thrust to be generated by only 2 motors (until a safe landing). You have to ensure they won't overheat and burn out.

 

[Warpspeed]

Its not going to work .

Although in theory a quad rotor may be able to provide enough lift to stay up with only two diagonal motors turning, it will have absolutely no stability.
Its going to tilt sideways and crash.

Rather like asking how can I build a four wheeled vehicle that I can still drive if one wheel completely falls off.
Saying just remove the opposite diagonal wheel, and everything will be fine, is not going to work, for exactly the same reason.
Its going to fall over onto one corner, and your drone will do likewise.

 

[shaiko]

Rather like asking how can I build a four wheeled vehicle that I can still drive if one wheel completely falls off.

Hardly the same thing.
The 4 wheeled (or better say 2 wheeled) veichle doesn't spin relatively to it's center axis.
If you have a quad to play with - just remove 2 of the opposite facing props and see what happens.

Your quad will spin like a flying saucer and you'll have no directional control over it - but it WILL stay stable relative to the horizon!