Research On Nonlinear Dynamics Of Wind Turbine Gear Transmission System

The multiple stage gear transmission system plays a vital role on wind turbine.Due to the nonlinear factors,the dynamics of system need to study further for steady state controlling,optimization design and fault mechanism.The multiple stage gear transmission system of wind turbine is studied mainly in this paper.The dynamic analyses of the system including the nonlinear dynamic modeling,stability and bifurcation characteristics within different parameters and gear meshing states are illustrated and discussed thoroughly.The main achievements obtained in this paper can be drawn up as follows.1.The torsional nonlinear dynamic model of wind turbine multistage gear transmission system which consists of a planetary gear stage and two parallel gear stages are established respectively with time-varying meshing stiffness,comprehensive gear errors and gear backlash to solve and analysis the dynamic behaviors of the system.2.Based on nonlinear dynamic theory and analysis methods such as global bifurcation diagram,the largest Lyapunov exponent(LLE),phase diagram,Poincaré map,time series and FFT spectra,the bifurcation characteristics and dynamic behaviors are analyzed.The excitation frequency,comprehension gear errors,gear backlash and planetary gear meshing damping are the bifurcation parameters.Analysis results show that the system motion is the complex.With the excitation frequency increasing,the dynamic behaviors such as chaos,multi-period motion,quasi-period motion are demonstrated,and the chaotic attractor at the low frequency is smaller than high frequency.Through the whole analysis,the system is sensitive to the excitation frequency.With the increase of gear errors,the motion of the system changes form chaos to periodic motion.The higher damping coefficient could suppress the region of chaos.Under the bifurcation parameter of backlash,the motions of different stage of the system are different.It is presented that the sun-planet backlash has more complex effect on the system than the ring-planet backlash.The motions of the system on backlash of parallel gear are diverse including of some different multi-periodic motions.Also,the state of the system changes from chaos into quasi-periodic behavior,which means that the dynamic behavior of the system is composed of more stable components with the increase of the backlash.Hence,parameters of the system should be designed properly and controlled timely for the better operation and enhancing life of the system.3.The transverse-torsional nonlinear model of multistage gear transmission system is established and further studied by applying excitation frequency and support stiffness as the bifurcation parameters.The motions of the system with the changes of the support stiffness are diverse including of some different multi-periodic motions.The radial max displacement of sun gear,the max/min dynamic meshing force and RMS are used to analyze the system meshing state.The range of double-sided impact is illustrated.With the support stiffness is increasing,the chaos and vibration could be decreased.This research and results will provide a theoretical reference for the design,manufacturing and reliability improvement of the gear transmission system of the wind turbine.