Research On Amplitude Control Of Rotating Ultrasonic Machining System

With the great demand of hard and brittle materials and all kinds of composite materials in the fields of electronics,national defense,aerospace and biological engineering,rotary ultrasonic processing,as a kind of high and new processing technology,came into being in modern industry.In order to process these special materials with high efficiency,high precision and high quality,the study and control of amplitude has become an important research object in rotary ultrasonic machining.Because the transducer is a kind of nonlinear system,and the complexity and variability of the working conditions in the actual machining process,the resonant frequency drift and amplitude attenuation are caused.Some studies show that when the frequency tracking function of ultrasonic power supply is good,the dielectric loss and impedance characteristics of the transducer change with the change of actual working conditions,and the amplitude of the transducer is still attenuated.Therefore,current detection and feedback method can not always reflect the actual situation of amplitude in real time.In this paper,the effects of voltage,frequency,compensation network and load on amplitude control are analyzed in detail from the two aspects of electricity and load,and the relationship between vibrator vibration force,amplitude and electrical parameters is discussed.It is verified by experiments.In this paper,the vibration force signal is detected to feedback the vibration amplitude in real time,and the amplitude control is realized by adjusting the power.The following are the main contents of the study:Firstly,the research background and significance of this paper are briefly described,the development of rotary ultrasonic machining technology is described in detail,and amplitude control is introduced.Secondly,the ultrasonic machining vibration system is introduced.Based on the series resonant model of ultrasonic transducer,the electrical model and the electromechanical equivalent model are analyzed,and the transfer function of the dynamic model under the condition of no load and load of ultrasonic transducer is deduced.The relationship between frequency,load and amplitude is discussed.Thirdly,the admittance and impedance characteristics of ultrasonic transducers are analyzed comprehensively by model analysis and experimental demonstration,and their laws are discussed and verified under varying loads.Then,the influence factors of amplitude are analyzed in all directions.The mathematical model between load and electrical parameters is derived,the influence of voltage and frequency on amplitude is analyzed,the necessity of compensation network for amplitude control is analyzed in detail,and three common different topologies are proposed.The design scheme of compensation network which can adapt to maximum efficiency and maximum amplitude control is put forward through modeling analysis and experimental verification.Finally,the measuring platform of ultrasonic transducer vibration force signal,electric signal and amplitude is built,and the relationship between the vibration characteristic and electric signal of the transducer is analyzed respectively in the case of no-load and no-load.The experiments were carried out in many groups and in many directions.Finally,the interrelation among current,vibration force and amplitude is obtained,which provides the basis for realizing the feasibility of real-time feedback control of amplitude by monitoring vibration force signal.