Research On Complementary Resonant Coupling Method Of PCB-based Inductive Linear Displacement Sensor

In industry,aviation,aerospace and other fields,the measurement of linear displacement becomes particularly important.In order to obtain accurate and reliable linear displacement information,a linear displacement sensor with excellent performance is needed.In the field of linear displacement measurement in harsh environment,magnetic field linear displacement sensor is preferred because of its high reliability,strong anti-interference ability and high measurement accuracy.Different magnetic field coupling methods can be obtained by combining different coils,conducting magnets and printed circuit board(PCB).These magnetic field coupling methods generate and constrain the time-varying magnetic field related to linear displacement,that is,the coupling field,so the measurement accuracy of the sensor is affected by these magnetic field coupling methods.At present,the magnetic field coupling method often used in magnetic field linear displacement sensor,namely "coil+ coil","coil + magnet" and "PCB + magnet" magnetic field coupling method,is difficult to make the sensor have high original measurement accuracy,and the measurement accuracy of the sensor is greatly affected by the movement and scale mechanical offset,and the installation requirements of the sensor are also high.In view of this situation,this subject has carried out the research on the complementary resonant coupling method of PCB electromagnetic induction linear displacement sensor,trying to improve the structure and principle of magnetic field linear displacement sensor,so as to make the sensor have high original measurement accuracy,not easy to be affected by mechanical offset,and reduce the difficulty of sensor installation,so as to meet the higher and higher requirements of magnetic field linear displacement sensor in various fields.The main research work and results of this subject are as follows:(1)By studying the magnetic field coupling method of the existing magnetic field linear displacement sensor,a complementary resonant coupling method of the magnetic field linear displacement sensor is proposed.The method comprises a bilateral sensor structure,that is,the sensor is composed of a fixed ruler and two moving rulers,both of which are PCB,and the moving ruler does not need a lead.Each moving ruler PCB has a coil,which is connected in series with the capacitor and generates series resonance during operation,which can enhance the moving magnetic field.(2)Combined with the newly designed sensor structure,the principle of incremental linear displacement measurement is deduced based on a group of sinusoidal induction coils and cosine induction coils;Combined with the structural characteristics of another group of sinusoidal induction coils and cosine induction coils,the principle of absolute linear displacement measurement by sensor is deduced.Combined with the factors that may produce measurement errors,it is inferred that the sensor may produce measurement errors once and twice in a short period.By comparing the sensors with unilateral structure,the suppression effect of complementary resonant coupling method on the adverse effects caused by the change of irregularity and gap between moving and fixed length is studied.(3)According to the structure and measurement principle of the new sensor,the simulation model of the sensor is constructed in the three-dimensional software,and it is imported into the finite element electromagnetic simulation software for qualitative analysis.The finite element electromagnetic simulation results show that at the same time,the incremental displacement of the sensor moving ruler has sinusoidal and cosine relationship with the induced electromotive force on the sinusoidal induction coil and cosine induction coil,which is consistent with the theoretical derivation.The simulation results verify the feasibility of the new sensor structure and measurement principle,that is,the feasibility of the complementary resonant coupling method.(4)In order to verify the feasibility of the complementary resonant coupling method,the prototype experiment of the sensor is carried out.The sensor prototype is made by using PCB technology,the supporting electrical system of the sensor is made according to the measurement principle,the experimental platform is built,and the comparative experiment of the prototype is carried out.The comparative experiment of prototype shows that the complementary resonant coupling method can indeed suppress the adverse effects caused by dynamic and fixed length mechanical offset.In order to improve the measurement accuracy of the prototype,the original measurement error is analyzed by fast Fourier transform,and the sensor structure,supporting electrical system and displacement calculation algorithm are improved accordingly.The accuracy improvement experiment of the prototype is carried out.Experiments show that the optimal short period original measurement error of the sensor is-4.9?m?+4.4?m,the peak to peak value is 9.3?m;Within the range of 300 mm,the long period original measurement error is-7.3?m?+5.9?m,the peak to peak value is 13.2?m.It shows that the complementary resonant coupling method can achieve ideal original measurement accuracy.To sum up,this topic first proposes a magnetic field coupling method of magnetic field linear displacement sensor,then verifies its feasibility through electromagnetic field finite element simulation,and finally verifies the practical feasibility of this method through prototype experiment,and the sensor prototype has high original measurement accuracy,is not easy to be affected by mechanical offset,and is easy to install.