Research On Nonlinear Dynamics And Fault Identification Of Gear Transmission System With Stochastic Disturbance

In modern mechanical equipment, such as gearbox, robot, aviation engine, fan, water pump, higher requirements on dynamic characteristics and safety of gear transmission system are put forward. In addition, the fault diagnosis, for protecting the safety of equipment operation, avoiding catastrophic accidents and reducing the occurrence of the great economic losses, has very important significance. The research on nonlinear dynamics of gear transmission system is generally concerned by scholars at home and abroad. Therefore, this dissertation has deeply investigated the nonlinear dynamics and fault identification technology of gear transmission system with non-smooth, nonlinear and stochastic. The main contents are as follows:1. Numerical simulation, for the stochastic disturbance of gear mesh frequency, damping ratio, gear meshing stiffness, backlash and random disturbance caused by input torque, is carried out using Monte-Carlo method and the central limit theorem.2. Considering the random disturbance of gear mesh frequency, damping ratio, gear meshing stiffness, backlash and stochastic disturbance caused by input torque, the stochastic nonlinear dynamics model of gear transmission system and the model of system with wear fault are established. The 4-5 order variable step size Runge-Kutta method is applied for numerical analysis of kinetic equations, and its effectiveness is verified.3. Integrated using time history curve diagram, phase diagram, Poincare map, power spectrum and Lyapunov exponent, the dissertation discusses the influence of the stochastic disturbance of the gear transmission system internal parameters and external incentives to produce bifurcation and chaotic vibration on the system; analyzes the influence of load ratio, frequency ratio, damping ratio, gear backlash, meshing stiffness and other random parameters on dynamic characteristics of the system under different operation conditions; discusses how to match parameters to make the system in the stable state.4. Chaotic vibration of gear transmission system is effectively controlled or suppressed by using the linear and nonlinear feedback control method and three non-feedback control method such as additional periodic signal method, plus constant load method and phase method.5. For gear wear failure, a fault identification method is proposed based on Symlets A wavelet family morphological denoising and frequency slice of wavelet transform. Simulation analysis and experimental test results are consistent, which verifies the correctness of the surface wear fault model and the validity of the method.6. For rolling bearing pitting fault, a fault identification method is proposed based on autocorrelation morphological filtering and empirical mode decomposition. The effectiveness and superiority of the method is verified by experiment.