Yaw with a 4-rotor machine

[macnab]

Helping out a friend. If you have rotors at the 4 corners of the aircraft, with individual throttles, pitch and roll is one thing. But how would you control yaw?

[Keith_Beef]

According to the Wikipedia article on Quadcopters:

"Yaw is induced by mismatching the balance in aerodynamic torques (i.e., by offsetting the cumulative thrust commands between the counter-rotating blade pairs)."



For pilot input, I suppose you would keep the familiar rudder pedal or jostick twist. But how to translate the control on the stick into changes in motor speed and blade angle is a different matter.

[macnab]

Thanks. Never thought of looking for an article in the wiki.

The aircraft works with a throttle per engine. The secret is to read the elevator, rudder and aileron values, and then use nasal to adjust the throttle settings for the engines. Will take quite a bit of experimentation. Or you need 4 very nimble thumbs, seeing as the guy is using a USB R/C controller.

[Alant]

There is a quadrotor jsbsim model at https://github.com/arktools/arkhangar/t ... arducopter
More details in the thesis at http://diydrones.com/profiles/blogs/che ... dupilotone.

Alan

[macnab]

Thanks. The guy I am helping is using the arducopter! Fortunately he knows how to edit files and write xml code. He just didn't realise that the model's FDM doesn't respond to flight-surface control - you need to write your own code to control the 4 engines to get it to do what you want.

If I point him in the right direction he will mostly get it right himself. Communication with him is a bit haphazzard, though - the PC with FG on it is in some lab (school/college/?).