Research Of Nonliner Crack Rotor Vibration And Crack Propagation Control

Rotor system is an important part of the rotating machinery,such as large steam turbine generator,aviation,aerospace engine and compressor,etc.It develops fast towards high speed,large load and precision and has played an increasingly important role.Due to differences in the material,there will be a small defect and the micro-cracks on the rotor surface in the process of casting the rotor.Those tiny mutations will generate serious concentration stress,which withstand in the cycle of stress,high-temperature environment and external shocks for a long time.It easily induced fatigue crack and crack propagation,even property loss and engineering accident.So it is important to diagnosis early rotor cracks and to explore the impact factor of crack opened and closed,but that appears to be more practical significance to control vibration of cracked rotor and delay crack propagation,which can support mechanical systems of industrial,military,aerospace and other large equipment to work safely and operate stably,and to apply the battle field self-help.Based on the domestic and overseas research techniques of nonlinear cracked rotor dynamics,the mathematic model of the crack rotor system,the crack stiffness model,the nonlinear model under the support of ball bearing and the electro-magnetic force model have been selected and the electromagnetic actuator using the FUZZY-PID controller with the fitness function of the variable width and variable geometric shapes has been designed,the simulation results is verified by using experimental methods.The main content of this paper are shown below.First,the vibration characteristics of the rotor system and the crack breathing state are researched in different parameters(include linerity,nonlinerity,damp,eccentricity,stiffness variation,shaft asymmetry)through the numerical simulation.Hilbert Huang and higher-order spectrum method apply for characteristic analysis of micro nonlinear cracked rotor.For the vibration control of the nonlinear rotor system and the processing the nonlinear restoring force,the main harmonic region and fractional harmonic region are accomplished completely and crack propagation is delayed based on the electro-magnetic actuator.In addition,this paper compare this tactics difference on the traditional PID controller,the FUZZY-PID controller with the fitness function of the variable width,variable geometric shapes and single geometric shapes for vibration control of rotor.Finally,electro-magnetic actuator is made to achieve the complete nonlinear vibration control of rotor system based on experiments method.This paper summarizes the effects of different parameters on the crack opened and closed of the rotor system and research the mechanism of delaying crack propagation.The results confirm that active control system based on electro-magnetic actuator can effectively control the amplitude of the nonlinear vibration of cracked rotor and delay crack propagation.Through comparing with the control methods of the traditional PID and the FUZ ZY-PID and their results,the simulation results show the proposed FUZZY-PID controller canprocess the model of the nonlinear restoring force by the self-study and the nonlinear vibratio n control in the vicinities of the major critical speed and sub-harmonic critical speed and the r otor system was improved with a stronger ability of the interference rejection.