Design And Optimization Of Electrical System For Time Grating Angular Displacement Sensor Based On Planar Coils

The magnetic field type time grating displacement sensor is a displacement sensor independently developed by our research group.Time grating realizes displacement measurement by magnetoelectronic coupling,which has the characteristics of high measurement accuracy,strong anti-interference ability and low manufacturing cost.Previously developed magnetic field sensor has some shortcomings,such as huge volume,bulky magnetic conductive material,inconsistent processing process and low production efficiency.In order to solve these problems,a planar magnetic field type time grating angular displacement sensor based on PCB technology is developed.The PCB technology,which is mature at present,is used to replace the previous processing technology of magnetic field type time grating slotted winding.It not only improves the measurement accuracy of time grating by improving the magnetic field coupling efficiency,but also lays a foundation for the industrialization process of time grating.The design structure of the planar magnetic field time grating is quite different from that of the magnetic field time grating developed earlier,so a matching electrical system is needed.Time grating electrical system is an important guarantee for high accuracy and stability of sensors.The errors of each module in the electrical system will affect the measurement results of time grating and affect the measurement accuracy.This paper designs an electrical system for circular time grating with planar magnetic field.Based on the sensing principle of time grating angular displacement sensor with planar magnetic field,the method of loading excitation signal with planar magnetic field and forming induction traveling wave signal is analyzed.The error generating mechanism of signal transmission circuit and each module of electrical system and the influence of electrical error on measuring accuracy of time grating are analyzed.A complete electrical system for planar magnetic field circular time grating is designed,which mainly includes excitation signal generation module,induction signal processing module and time measurement module.The excitation signal generating module is designed to generate twophase sinusoidal excitation signals with equal amplitude,same frequency and orthogonal phase,and to generate time-varying magnetic field for measuring stator windings.According to the error analysis of the excitation module,a closed-loop feedback circuit is designed to ensure the accuracy and stability of the excitation signal;the induction signal processing module is used to adjust the weak signal output from the time grating sensing unit and shaping the signal to ensure the accuracy of phase difference acquisition;the time measurement module uses the time digital conversion circuit to optimize the previous time measurement method.The time information of the processed phase difference signal is extracted.Aiming at the design of closed-loop feedback circuit and time measurement circuit,the excitation feedback signal detection method,closed-loop control method and time measurement method are studied.An experimental platform of circular time grating electrical system with planar magnetic field is built.Waveform experiment,stability and precision experiment are carried out for the whole time grating measuring system.The causes of various error harmonics are analyzed according to the experimental data.The experimental results show that,without considering the mechanical transmission error,the original measurement accuracy of the time grating can reach ±16.4 angular seconds).