How can I tune PID with this structure ?

Hello.

Now, I'm modeling Quad Copter on Simulink.

Quad Copter has 12 state as a output.

and 4 Input and therefore, Controller also exist 4 controllers include Phi, Theta, Psi, Altitude.

But, Still I can't find a solution to find a best gain for this PID controllers.

I can't use PID tunner because it is not PID block that Matlab provide in simulink.

and "Check Step Response Characteristic" also not working.

How can I tune this PID controllers ?