Research Of The Nonlinear Vibration And Bifurcation Characteristic Of Rotor-Bearing System

Rotor-bearing system as an important part of the rotating machinery,which running stability and safety is directly related to the safe operation of the whole mechanical system. There are many nonlinear factors in the rotor-bearing system,such as electromagnetic force,rub impact and so on,in which the rub impact is a main factor causing nonlinear motion of the rotor system.Magnetic bearing play a decisive role in rotor system,compared with the traditional sliding and rolling bearing which has many advantages,such as no pollution,without lubrication,high driving and so on.These advantages to meet the modern rotor-bearing system developing requirements,are widely used in future production.This article mainly studies the dynamic behavior of the flexible rotor system,double rotor system and double rotor system supported by the magnetic bearing.To set up the dynamic models of each rotor system,according to Newton’s second law,the differential equations of motion of the system is abtained,the numerical simulation of the rotor system is carried out by 4 Runge-Kutta method,simulating the actual woking condition of the rotor system,abtaining two parameter bifurcation diagram, bifurcation diagram,axis orbit diagram and Poincare evolution process diagram.The dynamic characteristics of a crack to system is considered,the article has studied the influence of stiffness variation,damping coefficient,eccentricity and all kinds of parameters to the rotor system under both crack and no crack.Through the analysis of all kinds of figures,this article has also discussed the periodic motion,almost periodic motion,period doubling bifurcation,inverse period doubling bifurcation,chaos and a variety of complex dynamic behavior of the rotor system,described the evolution process of the rotor system from periodic motion to almost periodic motion.The result shows:rotor system presents rich dynamics behavior by the change of stiffness coefficient, stiffness coefficient is bigger,the system will tend to chaotic motion.With the increasing of damping coefficient,the rotor system tends to periodic motion, chaotic motion is decreasing.Eccentricity is bigger, the system will tend to chaotic motion.The influence of the change of the friction coefficient for system dynamic characteristic is not very big.The emergence of crack increases chaotic motion of the system in low speed range,while the influence is not very big for rotor system in high speed range. Chaotic motion is harmfull in the practical operation of rotor system,so we should try to avoid the chaotic motion area on the parameter design of rotor system and the actual work. This article has also pointed out the optimal working range of system under certain parameter conditions,which provides some theoretical basis to the design parameters and fault identification and exclusion in actual work of the rotor-bearing system.