Research On Planar Absolute Time-grating Angular Displacement Sensor Based On Composite Time-varying Magnetic Field

With the continuous development of science and technology,precision measurement plays a very important role in the manufacturing industry,and high-precision measuring instruments are widely used in industrial machine tools and defense industry.Time grid displacement transducer is a displacement transducer created by Chinese people,which can achieve high precision and large range measurement.The traditional time-grid displacement sensor designs the structure of tooth slot on the stator or rotor to install the coil winding,and this processing method is often time-consuming and laborious,and the consistency of the coil winding is not high.The planar PCB type time grid displacement sensor has the advantages of strong anti-interference ability and high reliability,and the stator and rotor of the sensor are changed from winding on the gear to processing on the planar PCB,which solves the inconvenience caused by the winding type time grid,but most of the planar PCB type time grid displacement sensors have bilateral leads.Based on this paper,a planar type absolute time-grid angular displacement sensor based on compound time-varying magnetic field is proposed to carry out the research of integration of magnetic field absolute angular displacement sensor,using PCB technology to replace the traditional processing method to achieve planar type displacement measurement,using the way of constructing compound time-varying magnetic field,which makes the leads of the sensor all on the stator,the main research contents of this paper are as follows:(1)Construction of planar-type absolute compound time-varying magnetic field.According to the principle of time-grid measurement,a planar type absolute time-grid angular displacement sensor based on the composite time-varying magnetic field is proposed.According to the electromagnetic theory,the compound time-varying magnetic field is established based on the Biot-Savard law.The compound time-varying magnetic field includes and mathematical derivation of the distribution law of the plane-type compound time-varying magnetic field,and the traveling wave equation is established based on this mathematical model.(2)Structural design and model simulation of the planar absolute sensor with compound time-varying magnetic field.The first-stage sensing unit and the second-stage sensing unit are arranged on both the stator and the rotor of the sensor,and the sensed output of the firststage sensing is used as the excitation signal of the second-stage sensing,and the two-stage sensing realizes the two-stage compound modulation.The two-stage compound modulation makes the sensor input and output concentrated on the stator so that the sensor wires are led from the stator and the coil on the rotor is connected in series with the capacitor to produce resonance to enhance the signal strength.The absolute displacement measurement is achieved by combining the fine machine signal with the coarse machine signal.A threedimensional model is built and finite element simulation is performed on the model,and the simulation results are analyzed to obtain error curves and harmonic frequencies.(3)Sensor signal processing system design.The STM32H750 chip is selected as the main controller of the system,and the hardware electrical system is designed to generate a sinusoidal excitation signal with a frequency of 2.5MHz and to amplify and shape the sensing signal;the software processing system is used to collect the experimental data and to solve,display and save the data containing displacement information in real time.(4)Build the experimental platform.The experimental prototype of the sensor is fabricated,and a precision test platform is built to carry out the experimental research of the planar absolute time-grid angular displacement sensor based on the compound time-varying magnetic field.The sensor prototype is assembled with an integrated design by choosing PCB process with 180 number of pairs of poles for the fine machine and 7 number of pairs of poles for the coarse machine.The basic waveform of the sensor prototype,the fluctuation of the output signal indication value and the accuracy of the sensor at rest were tested,and the error analysis and error compensation were done on the experimental data,and the error sources were explained.In summary,based on the mechanism of the compound time-varying magnetic field,this paper establishes a mathematical model and a three-dimensional model,performs finite element simulation on the model,designs and fabricates a plane type absolute time-grid angular displacement sensor prototype based on the compound time-varying magnetic field,verifies the feasibility of the sensor through simulation experiments and prototype experiments,analyzes the error sources,and provides a basis for the subsequent improvement and optimization of the sensor.The experimental results show that the fluctuation of the sensor prototype is 0.2″,and the whole circumference error after compensation is 10″.