Research On Magnetic Induction Linear Displacement Sensor Based On PCB Coil

With the transformation of China's manufacturing from a big country to a manufacturing power,the traditional manufacturing industry has become an inevitable trend toward automation and intelligent development.As a cornerstone of intelligent manufacturing,precision measurement is also an important indicator to measure a country's industrial manufacturing level and technology level.The displacement sensor based on the principle of electromagnetic induction is widely used in industrial automation production because of its advantages of good stability,high reliability,strong anti-interference ability and low working environment requirements.However,most of the high-precision displacement sensors on the market are expensive,and low-precision displacement sensors are difficult to meet the high-precision and low-cost requirements of position sensors in modern manufacturing.The research team has been working on a low-cost,high-precision magnetic field time grating displacement sensor.Since the conventional magnetic field time grating is restricted by the manufacturing process,the consistency of the coil winding is difficult to be ensured,and the production efficiency is difficult to be improved.For this situation,the time grating measurement technology is combined with the more mature PCB process.This paper studies the magnetic induction linear displacement sensor based on PCB coil.The main research contents are as follows:(1)The electromagnetic field theory is used to analyze the magnetic field distribution of the planar coil.Based on the principle of electromagnetic induction and the design rule of the time grating displacement sensor,the induction coil is designed as a sinusoidal shape to restrict the coupling area of magnetic field and make full use of the effective area of magnetic field.The measurement model of double-row linear displacement sensor and single-row linear displacement sensor are established,and the working principle and the system error rule are deduced theoretically.(2)The two sensor models are modeled in 3D and simulated by the electromagnetic field finite element simulation software Ansys Maxwell.According to the simulation results of the movable ruler and the fixed ruler at different air gaps,the harmonic error components of the measurement error are analyzed separately.Combined with the repetition rule of space period,the four-harmonic errors appearing in the opposite poles of the two sensor models are suppressed by the multi-pole winding spatial offset phase shifting method,and then the two sensor models are optimized and separately simulation comparison verification.(3)The excitation coil and the induction winding of the two sensor models were designed by using the PCB coil,and the sensor prototype was fabricated by the PCB process.The electrical system of the sensor is designed with EP4CE6E22C8 as the MCU,which mainly includes the hardware circuit and software program design of the excitation source and data acquisition.In the design of data acquisition program,a multi-path parallel doubleedge counting method is proposed to improve the clock pulse resolution and reduce the quantization error.(4)The experimental platform was built and the two sensors prototypes were tested,compared and verified.The error correction experiments of the optimized two sensors prototypes were carried out by using the Fourier series harmonic correction method.The experimental results show that the measurement accuracy of the double-row linear displacement sensor is ±10?m in the measurement range of 108 mm,and the measurement accuracy of the single-row linear displacement sensor is ±8?m.