Analysis And Experimental Research On Radial Capacity Characteristics Of An Ultrasonic Suspension Bearing

Non-contact suspension support is an essential anti-friction path for precision drive systems working at high rotary speed.Ultrasonic suspension based on piezoelectric driving principle is a new suspension support technology that can reduce friction and is easy to control.Ultrasonic suspension bearings derived from ultrasonic suspension technology overcome the limitations of traditional non-contact suspension support and show significant advantages in the field of non-contact suspension support for precision drive systems.With high working speed and low friction regarded as research goals,radial capacity characteristics of an Ultrasonic Suspension Bearing is studied by means of theoretical modeling,simulation techniques and experiments.The radial capacity characteristics of the non-uniform film is studied with the structure of the nonuniform squeeze gas film analyzed at different suspension positions.Based on the nonlinear acoustic theory,suspension mechanism is explained from the aspects of vibration form,average energy and force analysis of the acoustic proton.Based on the Reynolds equation,the numerical analysis method is used to solve the second order nonlinear parabolic partial differential equation and calculate the air pressure distribution of the nonuniform gas film.The influence of the driving characteristics of the piezoelectric transducer,the physical properties of the flow field and the contour structure of the radiating surface on the radial capacity are analyzed.The structural parameters and the working conditions of the ultrasonic suspension bearing are legitimately selected.Based on the equilibrium equation and the motion equation of the fluid micro-element,the inertia item in the motion direction is deduced to modify the Reynolds equation.The pressure drop at the boundary of the film is calculated by taking the inertial effect into account.The non-uniform gas film structure is modified through introducing the established random distribution function of surface roughness detected by Atomic Force Microscopy(AFM).Based on the average flow model,the levitation force model is deduced that considers the inertia,surface morphology and rarefaction effect.The influence of the standard deviation of the roughness and Peklenik number on the pressure flow factor and radial capacity characteristics is studied.The levitation force and dynamic friction torque are modified under the condition of high rotary speed,and the effect of rotational speed on the dynamic capacity characters is revealed.Based on the working principle and the radial capacity characteristics of the ultrasonic suspension bearings,the prototype is developed.Based on the equivalent circuit of Meissen,the equivalent network model of piezoelectric trans ducer with vertical bending is established.The approach of finite element analysis is utilized to acquire the modal parameters and harmonic response of the piezoelectric transducer.The correctness of the equivalent network model is verified by testing the driving characteristics through impedance analyzer.The impedance matching is carried out according to the impedance mode and the phase angle.The experiments of static capacity characteristics and the dynamic capacity characteristics of the ultrasonic suspension bearing are carried out to verify the correctness of the theory of levitation force and reveal the influence of the rotational speed on the rotor axis trajectory and the friction torque.