Study On Magnetostrictive Cable Force Measurement Based On Pseudo Saturation Of High Frequency Transformer

Steel cable has been widely used in engineering facility(ships,bridges,construction,water conservancy)and civil equipment(protective fence,floor,foundation)because of its characteristics of bearing large force,good toughness,high hardness,strong seismic resistance and light weight.Cable can apply in gym,cable-stayed bridge,suspension bridge,cable barrier(slope protection network)and so on.On the one hand,in the process of using the cable,it is the main force of the center and the center of gravity of the whole bridge structure.If the stress of cable force is too large,internal,corrosion,self-fault,and the decline,will lead to unforeseen consequences.Therefore,the tension or pull of the steel cable must be measured accurately.On the other hand,the long-term monitoring changes of the cable can not only quickly and accurately carry out the maintenance,but also achieve the maximum useful life to improve own value in the use of the process.Therefore,the on-line monitoring of cable tension is the effective method for judging the state of cable structure.The cable measuring method based on magnetostrictive effect has become the researching emphasis at home and abroad.According to the principle of cable force measurement with magnetostrictive effect method,researchers have chosen the magnetic field strength in the vicinity of the maximum permeability.However,the fact is that the change of signal and the variation of permeability in the vicinity of the maximum permeability are not conducive to the observation of the experiment and the analysis of the experimental results.Therefore,the magnetic field strength should be selected in the vicinity of the quasi saturation region with the largest variation rate of the output signal and permeability.Now,the way of saturation of frequency has been used to make the magnetic field work in the quasi saturation region.In order to make the frequency reach saturation,high-frequency transformer had been widely used.So it is necessary to establish a theoretical system based on the magnetostrictive effect of the high-frequency transformer with quasi saturation,and complete the tensile test.This paper proposed a method based on the cable force measurement of the magnetostrictive effect of the high-frequency transformer with quasi saturation on the basis of cable force measurement method at home and abroad,completed theoretical research based on the cable force measurement of the magnetostrictive effect of the high-frequency transformer with quasi saturation,created the experimental programs and the experimental platform,and finished experimental study on tensile force under AC excitation.Specific research contents are as follows:(1)By introducing commonly used cable type,model,and the relationship between the variation of permeability and cable tension.The results show that the cable tension is in direct proportion to the variation of permeability,and derived perfectly the measurement of permeability.(2)The paper clarified the characteristics,principle and model of high-frequency transformer,and deduced further the phenomenon of the magnetic saturation of the high frequency transformer and the cause of magnetic saturation.The analyses show how to choose magnetizing operating point under the condition of high-frequency transformer with quasi magnetic saturation.(3)According to establishing a theoretical model based on the magnetostrictive effect of the high-frequency transformer with quasi saturation,the relationship among the cable force and temperature,induced voltage,material permeability,air gap and so on was deduced.The relationship between the induced voltage and the cable tension in quasi magnetic saturation is summarized.The theory suggests that cable tension can be obtained by measuring the output induced voltage under AC excitation,and the induced voltage is approximately linear with the cable tension.(4)Designed experimental program based on the cable force measurement of the magnetostrictive effect of the high-frequency transformer with quasi saturation,and finished tensile test under AC excitation.The results show that the induced voltage is approximately linear with the cable tension.At last,this dissertation reviews the whole research work and the outlook of the future research.