直線式時柵位移傳感器的動態測量與頻譜分析

Tian-heng ZHANG，Long-bo SUO，X ing-hong ZHANG，Liang WU

(Engineering Research Center of Mechanical Testing Technology and Equipment，Ministy of Education Chongqing Key Laboratory of Time-Grating Sensing and Advanced Testing Technology，Chongqing University of Technology，Chongqing 400054，China)

1 In troduction

Measurement is sure that valuemeasurement attribute for the purpose of all operations．The position measurementmainly refers to length and Angle of the measurement．The international system of units of length is one of seven basic physical quantities(length，quality，time，current，thermodynamics temperature，amount of substance and luminous intensity)．For thousands of years，people have been length ofmeasurementmethod study．With modern industry and science technology of the development，the static measurement has not adapt to the modern measurement requirements．At present，the dynamicmeasurement is concerned by many national research institutions and scholars．Dynamic measurement technology as a new measurement technology is of being widely used in variousmeasurement occasions，the measurement technology have become bigger change，Nomatter from efficiency or technical connotation．Therefore，The Linear Typed Time Grating Displacement Sensor dynamic measurement research，no matter whether The Linear Typed Time Grating Displacement Sensor improve dynamic accuracy in high-speedmeasurement or design improvementwith important theoretical significance and practical value．

2 The p rincip le of linear grating sensor

According to the“Linear AC Motor”principle［1-2］，Linear AC Motor’s shell unfold along the line，can further design The Linear Typed Time Grating Sensor，as shown in Fig．1．After the power supply，the traveling wave magnetic field M from c point beginning to d point end，along the straight line every after time T，forward a pitch w．when traveling wave successively through the first set and a dynamicmeasurement b will has a head sine wave characteristics of the electrical signals，get the instantaneous moments value and Ti，type(1)is the measuring line of dis-placementmathematicalmodel:

Realize the use of clock pulses to measure space displacement．In a word，use type line waves can establish the mechanical way can not establish infinite long coordinate system，The Linear Typed Time Grating apply for angular displacement measurement expanded to Linear displacementmeasurement．This is The Linear Typed Time Grating Displacement Sensors principle project．

Fig．1 The linear typed tim e grating sensor p rincip le diag ram

3 Dynam ic m easu rem en t of linear typed tim e grating sensor

According to the definition of dynamic measurement，themeasurement device used in dynamicmeasurement that is for dynamic measurement．Dynamic measurement is to point to determine the amount the instantaneous and(or)the changeswith time ofmeasurement，the measurement is that over time the change．Dynamic measurement has four notable features:instant degeneration and randomicity，relevance and dynamic［3］．

Fig．2 Dynam ic m easu rem en t experim en t device d iagram

3．1 The dynamic characteristics and main dynamic error sources

The Linear Typed Time Grating Displacement Sensor dynamic measurement experiment device is shown in Fig．2．The Linear Typed Time Grating Displacement Sensor dynamic error ismain it’s actual dynamic characteristics deviation from ideal dynamic characteristics of generation，The dynamic characteristics become the dynamic error research foundation．The gratingmeasuring value as The Linear Typed Time Grating Displacement Sensor space position measurement standard amount，standard amount and grating prediction compare，thus obtains the dynamic prediction of measurement error value．Spatial Position of The Linear Typed Time Grating Displacement Sensor has timeliness and spatiality，so dynamic prediction error inevitably has time and space．In order to preciselymeasure dynamic error．The Linear Typed Time Grating Displacement Sensor need to compare synchronous displacement movement in the process，synchronous sampling grating value and predictive value of Time Grating．This requires high precision grating subdivision and counts circuit，the sine signal processing，the receive external synchronous signal locking up data，and the results are transmitted to the computer［4－5］．

Stepping motor drive the ball screw，The Linear Typed Time Grating Displacement Sensor of moving head and linear grating scanning heads of synchronous movement，in the dynamic measurement，the measurement speed will change constantly，all moving components will be affected by larger inertia force，and because themoving parts of joint stiffness of guide rail and weak of the ideal nature，moving parts will produce larger elastic deformation，because structure of the guide is not correspond the Abbe’s principle，produce Abbe’s error in themeasuring head．In addition，themeasuring head and the servo control system of dynamic characteristics and vibration，etc．Various kinds of random factorswill also bring dynamic measurement error in result of a measurement．The main dynamic error sources and mutual relationship of The Linear Typed Time Grating Displacement Sensor are shown in Fig．3．

Fig．3 Main dynam ic error source o f the linear typed tim e g rating senso r

3．2 Dynamicmeasurement data sampling

In the experiments Heidenhain company to the IBV102 LIDA101 line grating signal processing，the IBV102 is based on PCI bus subdivision and count card．In Windows XP environment，through theWDM(Windows Driver Model)device drive to visit IBV102［5］．The computer data processing and analysis software use the Visual Basic language．Use its visual graphics programming environment，use of object-oriented program designmethod to design software［4］．In Visual Basic，by calling a dynamic-link Library DLL(Dynamic Link Library)visit IBV102．Computer read grating measuring data by timing way，timing pulse automatic lock to save IBV102 displacement measurement data．By the count of time grating card，interface circuit of the output pulse has count and processing，the count card through the PCIpower supply，use lock to save IBV102 data of the timing pulse signal lock to save data of count card at the same time，and through the RS-232 interface output．Stepping motor driver continuous movement of The Linear Typed Time Grating Sensor，the computer is synchronous sampling grating value and prediction value of time grating every time，grating measuring value has the standard amount，software do automatic draw time grating of prediction error curve［6］．

According to The Linear Typed Time Grating Displacement Sensor of basic principles，measurement results is the software process after the concrete value，not the general dynamic measurement system changes with time of time sequence．When measurement head work in point condition，obtain the result is often measured specific valve，discrete values．considering dynamic error component，but simple and high speed and low speed ofmeasurement difference has dynamic error for processing．If it makes further research on dynamic error，research the measurement of original data characteristics．Research found that dynamic error has repetitive in certain conditions，this is many dynamic error compensation method of premise．The conditions have same measuring conditions，the same measurement process，the samemeasured，with speed parameters as parameter［7-8］．

Dynamicmeasurementoriginal error of Linear Typed Time Grating Sensor spatial position has 139．6 mm(only take one over ten of the sampling points)．Becausemany unknown factors involved in，original errors peak-peak is bigger than the static measurement．

4 Pretreatm ent in the dynam ic m easurem ent

In order to separate error composition，establish the error model，data of dynamic measurement has pretreatment in the dynamic measurement［9］．

4．1 Abnormal data eliminated

In the dynamicmeasurement in original datawill be mixed in with some false data，called abnormal data or different points．Different point ismeasured bulky error of the cause，must first eliminate the abnormal data．The vision is the key point out properly detect different points，although means is not very perfect，but there are still somemethod．If Tulcey proposed 53 H method，can detect different points．Detection of different points basic idea is to think is normal data is“smooth”，and different point is“mutation”．If the first original data smooth estimate，and set the coefficient for K，says normal data estimates ranging from smooth．If some of the original data numerical outside this range，the judge this number is different points．Thismethod，the key is that produce a smooth estimation and select K．

Use“median”method can produce a smooth estimate:

First of all the original data from{yi}(I=1，2，…，n)to construct a new sequence{yi(1)}:take the firstnumber5 yi，y1，y2，y3，y4，according to the numerical size rearrange y5for y(1)or(2)y than y(3)，y(4)than y than y(5)，from which the digits y(3)，recorded for y3(1)，and then eliminated y1join y6，take y2，y3，y4，y5，y6themedian y4(1)，So on get5 in double digits，and the adjacent five original data of themedian sequence{yi(1)}，i=3，4，…，n－2．

In a similarway again from sequence{yi(1)}constitute three data of adjacentmedian sequence

K is data processing according to the circumstances of the set the appropriate value．If︱yi-yi(3)︱ ＞K，yishould be eliminated，and according to the adjacent data smoothing hypothesis，with a interpolation(such as Linear interpolation)instead of it．

4．2 Spectrum analysis

According to the dynamicmeasurement data prepro-cessingmethod of sampling length 16937 points and eliminate the abnormal data，get 14000 points．Using MATLAB in FFT transform，dynamic error of spectral analysis，extracting them corresponding amplitudes and phase［10］．

Fig．4 Am p litude and phase spectrum o f original curve

Get through every harmonic of superpositionmethod to realize its harmonic revise，so as to use software to realize harmonic modifying method，to avoid the The Linear Typed Time Grating Displacement Sensor test device for existing hardware changes．After the operation of the spectrum of figure as shown in Fig．4(a)，4(b)shows:from the Fig．4(a)，4(b)can see exist2，5，and 6 times error，but also has the 0，1，12 times．Fitting to 180 times error，will the random sampling parameters compensation，obtain the curve Fig．5 shows，the integrated error was only 6．7 μm，realize The Linear Typed Time Grating Displacement Sensor no Linear error automatic revise．Obtain the curve Fig．5 shows，the integrated error was only 6．7 μm，realize The Linear Typed Time Grating Displacement Sensor no Linear error automatic revise．

5 Conclusions

This article get through The Linear Typed Time Grating Displacement Sensor of dynamic measurement and data processing research，themain dynamic error source，data pretreatment and spectrum analysis，The Linear Typed Time Grating Sensor’s error revise by software，the idea that reduce the influence of dynamic error infuse The Linear Typed Time Grating Displacement Sensor structure design．decreasing hardware costs at the same time，in the designing phase noticed each component of the dynamic characteristics of the improved，so as to improve the accuracy of The Linear Typed Time Grating Displacement Sensor．With the rapid development of modern science and technology dynamicmeasurement has become the core ofmodern measuring technology，so the dynamic accuracy ismore and more attention by people．

Fig．5 Error curve after fitting

Acknow ledgem ents

This paper is supported by National Natural Science Foundation of China (No． 51205434，51405049，51435002)

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