[mechanic conventions] rotation orientation #mechanics

quadrotor_pitches.txt

from the rotor center:

	the pitch surface in phase II and IV: up rotation produce up thrust on the body
    
    the pitch surface in phase I and III: up rotation produce down thrust on the body
    
	up rotation always produce down torque
    
    down rotation produce up torque

rotation.txt

counter clockwise about an axis a means:

	1. conter clockwise looking down against the arrow direction of a
    
    2. rotate by defined by right hand rule of axis a
    
clockwise rotation about an axis means the opposite