Research And Development Of Planar Inductance Sensitive Components For Linear Displacement Detection

The design of planar inductive linear displacement sensor is inspired by eddy current sensor and inductosyn.Eddy current sensor is limited by the interior coil structure of the probe,which can only measure the distance from the plane of the probe,and cannot measure the horizontal distance.Although the inductosyn can measure the relative displacement of the two modules,it needs to arrange winding on the two modules,which makes the application of inductosyn limited.Planar inductive displacement sensor ingenious overcomes the shortcomings of the two sensors.Its excitation coil and receiving coil are on the same piece of PCB board(Antenna).The measured displacement object is a piece of metal,which can be embedded in an object or a part of an object.Measured piece of metal under the influence of Eddy current effects in alternating magnetic field produce eddy currents at the surface.By Lenz's law,the new magnetic field excited by the eddy current is opposite to the direction of the original magnetic field.The receiving coil,which is Tandem reverse connection on the Antenna,generates the induced electromotive force under the superimposed magnetic field in different area by the electromagnetic induction effect,thereby measuring the horizontal displacement of the Target.In this paper,it mainly studies the working principle,design method,simulation process and contrast experiment of plane inductance linear displacement sensor.In this paper,the theoretical model of the excitation coil is established.The calculation formula of the magnetic induction intensity of rectangular excitation coil is derived,and the calculation formula of the Z axis direction field strength Bz of the arbitrary point of the rectangular excitation coil is obtained.In the theoretical modeling of the receiving coil,a analysis is made on the factors that generate the induced electromotive force in the coupled electromagnetic field by the variation of the flux linkage.It provides a theoretical basis for the structure design of the receiving coil.Maxwell ANSYS software is used to simulate the theoretical model in this paper.The simulation results of the rectangular excitation coil are consistent with the theoretical calculation.Both get the magnetic field along the rectangular symmetricaldistribution.The electromagnetic coupling simulation test results of the Antenna and the Target verify the feasibility of the theoretical design.A magnetic field strength amplitude step is appeared below the Target.The peak value of induced electromotive force generated on the receiving coil varies with the change of the position of the amplitude step.In this paper,it designs the Antenna and the Target used for comparison experiment,and sets up the experimental platform.In the process of debugging the experiment platform,the low pass filter is added.After detecting the frequency characteristics of the low pass filter,the frequency of the excitation signal is determined by using 3.6MHz in the electromagnetic coupling experiment of the Antenna and the Target.Through the electromagnetic coupling experiment of the Antenna and the Target,it is found that the farther the vertical distance is between the Antenna and the Target,the smaller the amplitude of the receiving voltage is,and there is a linear relationship between the two.The greater the amplitude of the excitation signal is,the greater the amplitude of the received voltage is,the two also showed a linear relationship.After the completion of the horizontal displacement experiment,according to each experiment data,there can get a graph about the relationship between the Target displacement and receiving coil voltage amplitude.Through the contrast analysis,it is found that the receiving coil sine winding can obtain bigger induced electromotive force than diamond winding.Two groups receiving coil in series can increase the received voltage amplitude.With the number of excitation coil decreasing,receiving coil amplitude will decrease.The smaller the Target area is,the smaller the receiving coil voltage amplitude is.These factors which affect the output voltage amplitude are found to provide guidance for the design of planar inductive linear displacement sensor in the future.