Structure Design And Characteristics Analysis Of Piezoelectric Actuated Squeeze Film Levitation System

With rapid development of precision engineering,higher requirements are put forward for the supporting way of rotary mechanical structure.Traditional contact supporting has wear and heat between stator and rotor,which reduces working stability after long time operation,and affects the life of equipment seriously.In order to avoid the wear failure phenomenon,squeeze film effect is used to design a non-contact spindle supporting system based on piezoelectric driving technology.The levitation of precision spindle is realized by levitation force generated by high-frequency excitation of piezoelectric transducer.The support system does not require external air source,has a simple structure,and has broad prospects for development.The main research contents and results are as follows:A non-contact squeeze film system is designed based on three sets of 120° sandwich piezoelectric transducers which can completely surround the shaft in circumferential direction,which increases radiation area and improves levitation stability of shaft.As the core component of non-contact support system,piezoelectric transducer can convert the input sinusoidal AC electrical signal into high-frequency mechanical motion,squeeze the gas in levitation gap,and realize the levitation of spindle.In order to obtain a support system with larger load-bearing capacity,longitudinal vibration sandwich piezoelectric transducer with a hyperbolic function-shaped horn is designed by analytical method.The frequency equation of transducer is derived and the structural dimensions of each part of transducer are calculated.Using ANSYS finite element simulation software,the modal analysis and harmonic response analysis of sandwich type piezoelectric transducer are carried out.The resonant frequency,output mode,electrical characteristic parameters of transducer and displacement of each node of transducer under different conditions are obtained.Resonant frequency of piezoelectric transducer and ratio of front and back output amplitudes with the size of key structure and material of piezoelectric transducer are analyzed to optimize the output performance of piezoelectric transducer.Based on fluid dynamics theory,the Reynolds equation describing pressure distribution of air in the gap is established and solved by numerical analysis method.The levitation mechanism is revealed from perspective of time and space,and influence of amplitude,frequency,levitation gap and other factors on air film bearing capacity is explored.Squeeze number is an important factor affecting the bearing capacity of levitation system.Starting from squeeze number,the changes of levitation force and pressure distribution under different squeeze number are analyzed,and the squeeze characteristics of the levitation system are further studied.On the basis of theoretical research,several groups of piezoelectric transducer prototypes are made and a testing system of non-contact levitation system is built.Resonant frequency and amplitude of piezoelectric transducer are studied,and the bearing capacity of levitation system and the variation of levitation stability of spindle under different parameters are tested.Results show that both the piezoelectric transducer and the levitation system have good performance,and experimental results are in good agreement with simulation analysis and theoretical calculation.