Basic Research On The Vibration Damping Model Of Ultrasonic Motor

Ultrasonic motor(USM)is the typical engineering application of ultrasonic vibration.Unlike traditional electromagnetic motor,USM uses the inverse pressure electric effect and ultrasonic vibration technology,having advantage of smart structure,low speed and high torque,response fast,self-locking on power off,electromagnetic compatibility,etc.,and USM has been widely used in the field of robot,precision instruments,medical instruments,aerospace,new weapons and equipment.However,USM also has its disadvantage of small power output,low efficiency,short life,and complex drive.Since the energy dissipation caused by vibration damping has direct impact on the output power and efficiency of the motor,the study of vibration damping can provide important guidance for the vibration characteristics and the energy conversion efficiency of the system.In this paper,according to the existing vibration damping theory model,and combined with single oscillator systems,two degree freedom oscillator system,USM continuous medium vibration system,we have done basic research on the vibration damping model and damping characteristic of the system from two dimensions of theoretical and experimental.For the single oscillator system(SOS),based on the physical image of free vibration,and in the viscoelastic damping,structural damping and composite damping model,we derived the formulas of energy of the system,damping energy dissipation,and mechanical quality factor(mQ).Theoretical results show that the influences of damping on vibration system are different with different damping theory model.As to structural damping model,the value ofmQ is frequency independent,which has inverse relationship of structure material damping factor(g);as to viscoelastic damping model,the value ofmQ depends on the frequency,and the higher frequency model has greatermQ value.Experimentally,we used the contact and non-contact type those two kinds of damping measurement methods,and results show that compared to viscoelastic damping,the effect of structural damping is small,which can be neglected;And the model with higher frequency,which has bigger value number of mQ.For two degree of freedom oscillator system(TDFOS),based on the SOS damping theory,we have done researches theoretical and experimental.The theoretical results show that as to the structural damping model,themQ value is still frequency independent and inversely proportional to g;as to viscoelastic damping model,mQ value depends on the frequency,and the higher frequency model,the greatermQ value.The experimental results show that there are two different models appeared in TDFOS,and the model with higher frequency has larger mQ value,which is in agreement with the theoretical model.For USM vibration system(USMVS),the theoretical formula of the mechanical quality factor of the system is derived in theory,which is based on the theory of the vibration damping of uniform beam continuous medium.In the experiment,the vibration friction damping of metal materials are tested,and the relationships between the friction and vibration amplitude of metal aluminum,copper and steel are measured.Experimental data agree well with to verify the rationality of the theoretical formula of friction vibration.