All electrical drivers have certain frequencies at which it cannot act, since the impedance of the component drops to zero. How would i get an LQG system to overlook those frequencies when trying to dampen oscillations, instead of trying to pump as much power as possible into it to correct the system (adjusting the input cost matrix does not help this problem).

 

don't think you've provided enough information about the system you are trying to model and control for a meaningful response.