Nonlinear Dynamics of an All-Movable Rudder System with Freeplay Nonlinearity

The freeplay nonlinearity will reduce the supporting stiffness of the rudder system, affect the accuracy of the position control and reduce its response speed. These set obstacles to modal parameters identification of the rudder system by using traditional ground vibration modal tests. For this problem, a piecewise-linear nonlinear dynamic model is presented in this paper to investigate nonlinear dynamics of an all-movable rudder system with freeplay nonlinearity. Time histories of rotation angle and angular speed, phase portrait and corresponding Poincaré section graph of the rudder system are calculated by means of the seam method. The evolution of different motion modes such as the periodic motion, chaotic motion and period-doubling bifurcation that vary with structural parameters including excitation frequency and damping ratio are discussed. Additionally, influences of parameters including excitation frequency, excitation amplitude, damping ratio and initial position are examined. This study can help instruct ground vibration tests and the corresponding modal parameters identification of the rudder system.