Research On Nonlinear Dynamic Analysis Of Ultrasonic Bearing Rotor System

As the core component of rotating machinery,rotor is widely used in various fields.And the bearing plays an important supporting role on the running machine.With the development of science and technology,the precision requirement of modern equipment is gradually increasing.So it is of great significance to reduce the system friction between the rotor and the stator.In recent years,as a novel method of restraining vibration,the near-field acoustic levitation effect is widely used,with the use of ultrasonic levitation and ultrasonic reducing friction.It has feasibility for the production of ultrasonic bearing.The research detail contents are as follows:Firstly,an ultrasonic bearing is proposed.It is consist of three ultrasonic transducers supporting rotor by radial.In this paper,the author made an ultrasonic bearing-rotor test system.Compared with the radial and axial bearing made of single ultrasonic transducer,three ultrasonic transducers ensure the rotor radial coverage area increased,uniform stress,arc design of ultrasonic vibrator ensure to increase the contact surface of the ultrasonic vibrator and the rotor,strength evenly.Secondly,the mechanism of ultrasonic levitation was studied.Based on the principle of acoustic radiation,the analytical formula of the ultrasonic levitation gas extrusion film is obtained.Based on the theory of fluid mechanics,the Reynolds equation of the gas squeeze film is derived.Starting from the angle of micro element method,dynamics of viscous fluid continuity equations is simplified to solve by using the method of numerical analysis and the finite difference method,obtaining the ultrasonic gas film force.This paper analyses that the relationship of the ultrasonic bearing force and the levitation gap,ultrasonic amplitude,ultrasonic frequency,rotor speed are close.The ultrasonic bearing force is inversely proportional to the levitation gap.The ultrasonic bearing force is proportional to ultrasonic amplitude and ultrasonic frequency.The vibration suppression effect of the ultrasonic bearing force on the rotor system is more obvious in the resonance frequency position.Thirdly,the experiment data of the rotor vibration suppression effect under different parameters is record.According to the simulation analysis of all kinds of influence factors,this paper made the related experimental procedures with a single variable principle.And it used eddy current displacement sensor monitoring signal.It used NI4431 collecting rotor vibration signal with two directions.The rotor vibration suppression effect is consistent with the theoretical simulation analysis,under different levitation gap,ultrasonic amplitude,ultrasonic frequency and rotor speed.Fourthly,the nonlinear dynamic analysis of the ultrasonic bearing rotor system is carried out.Firstly,this paper uses incremental harmonic balance method to analyze the ultrasonic intermediate bearing-rotor system and the ultrasonic supporting bearing-rotor system.Then it explored the vibration suppression effect of ultrasonic bearing-rotor system in the mass unbalance,misalignment,rubbing,loosening inhibitory vibration fault.At the same time,the rotor vibration suppression experiment of the rotor under simulated fault is also carried out.