Analyzing structural nonlinear flutter characteristics for a rudder with dynamic stiffness considered

Two new methods which can analyze the rudder's flutter characteristics are used respectively for structurally nonlinear hydraulic booster with its dynamic stiffness considered. The component mode substitution method is used to establish the nonlinear governing equations respectively in time domain and frequency domain based on the fundamental dynamic equations of the hydraulic booster and rocker arm. The flutter characteristics containing preload freeplay nonlinearity are obtained respectively with the existing describing function method and a proposed iterative method when control command is zero. A comparison between the results of time domain and those of frequency domain is studied. The results show that the amplitude and phase of the control command have also an influence on the flutter characteristics under the nonlinear condition.