Research On Absolute Angular Displacement Measurement Method Based On Cascade Of Multiple Capacitance Sensors

Angular displacement measurement devices play an important role in motion control fields such as equipment guidance,high-end CNC,and precision motors.In the field of industrial automation,there is a demand for high positioning accuracy,high resolution,and high reliability of sensors in operating environments such as mechanical vibration,dust pollution,and electromagnetic interference.Absolute angular displacement sensors have obvious advantages in the field of high-precision measurement and control.Compared to incremental angular displacement sensors,they can effectively solve problems such as power loss,position data loss,and cumulative measurement errors.In the field of absolute angular displacement measurement,grating angular displacement sensors have undergone years of research iterations and have formed a complete and modern measurement system,occupying an absolute share in the high-end manufacturing industry.The precision grating measurement technology has been restricted and blocked by foreign countries.The corresponding measurement technology in China started relatively late,and related products are only used in low-end markets with low requirements for measurement accuracy.High precision and high-resolution grating sensors rely on foreign imports and are subject to human constraints.The research team where the author works has proposed a method for constructing a uniform motion reference frame,which links spatial displacement with time changes,and achieves precise angular displacement measurement by measuring space through time.This method was early applied in the absolute angular displacement sensor,which has the advantages of absolute positioning ability and high-precision measurement.However,the sensor achieves precise measurement through the targeting structure,which leads to the problem of wire entanglement caused by rotor rotation,increasing the difficulty of using the sensor and reducing its reliability.To address the above issues,based on the high-precision electric field type time grating angular displacement sensor with independent intellectual property rights,this paper conducts research on the absolute angular displacement measurement method based on cascaded multi capacitance sensors.The main research work is as follows:1)Using two channels of single row incremental time grating sensors,a capacitance array with N and N - 1 measurement period is formed,which are used as the precise measurement and rough measurement parts respectively.The corresponding angular displacement value is obtained by using precise time scales to measure the signal phase,and the absolute position measurement is achieved by using a differential absolute positioning method.2)The sensor is a three-layer structure,which is based on a two-layer structure and achieves a multi-layer cascade structure by adding a layer of electric field coupling loops.The induced traveling wave signal obtained by coupling the first layer of stator and the second layer of rotor is transmitted to the output of the third layer of stator,and the rotor lead winding problem is avoided.3)The error theory analysis of the sensor prototype based on this method is carried out from two aspects: single cycle error and full cycle measurement error.An error theoretical model is established for the periodic error caused by unequal amplitude and non-orthogonal phase,and theoretical analysis is conducted for the entire cycle error caused by sensor installation in eccentric and inclined states.4)Test platform construction and experimental system design.The outer diameter is manufactured using a PCB process Φ = 100 mm,inner diameter Φ = 50 mm sensor prototype has been designed with a time grating sensor measurement system and a test platform built in an ultra-precision laboratory.5)Preliminary experimental data indicate that the sensor has the effect of signal crosstalk.Based on the experimental data and theoretical analysis,the sensor structure is optimized using signal time sharing and electrode multiplexing methods to avoid the impact of signal crosstalk and further increase the effective sensing area.The error theory verification and performance testing of the optimized prototype sensor are carried out.The experimental results are consistent with the error theory analysis,and can achieve highprecision absolute position output.In summary,through a combination of theoretical analysis and experimental research,this article has finally established a complete set of absolute angular displacement measurement methods based on multiple capacitive sensor cascades,improving the antiinterference ability of time gates and expanding the application scenarios of time gates.The prototype angular displacement sensor with a cascade structure has an in-pole measurement accuracy of ± 2.12 ″,a repeatability accuracy of 0.20 ″,and an original measurement accuracy of ± 3.0 ″ for the entire cycle.