Coupled Vibration Analysis And Dynamic Performance Optimization Of Multi-stage Planetary Transmission Of Lifting Gearbox

Lifting gearbox is the important component of lifting device of jack-up drlling platform,of which mechanical capacity and dynamic characteristic attract extensive attention.The gearbox may cause violent vibration easily,because of severe offshore working condition,requirement of synchronous operation with dozens of gearboxs on the drilling platform,being installed on slim and flexible leg,action of multi-source excitation,and complex coupling effect among components of planetary gear transmission system.Thus,carrying out coupled vibration analysis and dynamic performance optimization of lifting gearbox have important theoretical significance and engineering value for improving its comprehensive performance.Fousing on the lifting gearbox of offshore platform,research on the load sharing characteristic of multi-stage planetary gearbox,vibration reponse analysis of coupled system,finite element simulation of vibration noise,and dynamic performance optimization of coupled system are conducted.The main research work in this thesis can be summarized as follows:(1)The supporting stiffness of bearing and mesh stiffess of gear pairs are calculated with the Romax software.The dynamic model of four-stage planetary gear transmission of lifting gearbox with consideration of time-varying mesh stiffness,transmission error,backlash and so on is established.By solving the dynamic equation with Runge-Kutta method,vibration displacement and dynamic meshing force of gear pairs are obtained.The load sharing coefficients of planetary gear trains are calculated,and effects of eccentric errors on dynamic meshing forces and load sharing characteristic of four-stage planetary gear transmission is studied.(2)A lumped parameter model for four-stage planetary gear coupled system with consideration of time-varying mesh stiffness,transmission error,mesh damping,backlash,friction moment,combined stiffness and damp is established.The vibration response of all components weather considering nonlinear factors such as backlash and friction moment or not is calculated with Runge-Kutta method,and comparing with the experimental vibration,the calculated vibration response considering nonlinear factors is more accurate.(3)A finite element model for the gearbox coupling four-stage planetary gear train,bearings and housing is established by ANSYS software,and natural modes of vibration of the gearbox are analyzed.The calculated internal dynamic excitations of gear pairs before and after tooth modification are loaded on finite element model,vibration responses of the gearbox before and after tooth modification are solved by mode superposition method,accordingly radiation noise is predicted for the gearbox by acoustic boundary element method,and the simulation results of vibration noise have a good agreement with test values,which verifies the correctness of simulation.(4)On the basis of lumped parameter model of lifting gearbox,a dynamic optimization method of multi-stage planetary coupled system is developed by harmonic balance method.A mixed discrete optimization model with objectives of minimizing RMS value of vibration acceleration and total mass is established by taking structural parameters of housing and gear pairs as design variables,and the optimal design variables are obtained through writing optimization program based on the branch-bound algorithm.Comparing with taking parameters of transimission system or structural system as design variables separately,the optimization model of coupled system has a better effect.