Differential flatness implementation questions

[liwangGT]

Hi @blandry ,

I am thinking about implementing the differential flatness controller for crazyflie 2.0 based on Mellinger's paper. I used your code as reference, and had some questions about "crazyflie-tools/matlab/invertFlatOutputs.m". Can you give me some insights, so that I can speed up my learning curve?

1. You used [x,y,z,roll,pitch,yaw,xd,yd,zd,rolld,pitchd,yawd] as states, instead of [x,y,z,roll,pitch,yaw,xd,yd,zd,p,q,r] in Mellinger's paper. Why?
2. You get "u = omega_squared" for the controller using differential flatness. Then abandoned it, and used "u = [x(4:6);p,q,r;.25*u1/kF(1)]" instead. Why? And the dimension of u seems to be wrong, because u1 is a scaler.

Thanks,

Li