Control Feedback

Dear everyone,

I have done the control logic by Simulink,and I add the feedback of tower A-F acceleration for 5MW,when I don’t add the feedback ,the damping is 0.0597.So I give the gain G,the damp get bigger,if the G get bigger ,the pitch angle have some fluctuation :

damping of the picture above is 0.152 by giving G=0.04,
Do you think how to give a appropriate valve for G? In order to keep steady pitch angle ,do I need get G samller or get G bigger for large Damping?

Hope your answer!

Best Regard!