A method of measuring the displacement

 

(57) Abstract:

The invention relates to the field of automation and can be used to convert non-electrical quantities in an electrical signal. The technical result is to increase the accuracy. The method is based on the fact that the form of the reference signal with a known spectrum, determine the range of the output signal, compare the spectra of the reference and output signals and, if they are identical, is determined taking into account the inverse Fourier transform spectrum of the excitation signal. 1 Il.

The invention relates to locating method of converting non-electrical quantities in an electrical signal, namely, the measuring device is moved.

Known location method based on measuring the travel time of the measured displacement (distance) radiation, the speed of which is known and remains unchanged during the measurement process [see Spector, S. A. Electrical measurement of non-electrical quantities: measurement Methods: Educational. manual for schools. HP: Energoatomizdat. Leningrad. separa-tion, 1987, S. 172-178].

The disadvantage of this method is the low accuracy due to the heterogeneity of the properties along the length of the sections ol the Directors (temperature and so p. ), which leads to changes in the velocity of propagation of the radiation and the dependence of its time and coordinates.

Closest to the invention is also a locating method for motion measurement based on measuring the time of passage of the elastic wave section of the waveguide is equal to the measured displacement, from the moment of its initiation until the reception, in order to obtain high precision measurements of the shape of the excitation signal is chosen such that the output signal after passing through the waveguide path had maximum amplitude under normal conditions, and for one of the characteristic points of the output signal, we take the point of maximum [see Artemiev E. A., Druzhinin Century A. optimization of the shape of the probing signal magnetostrictive linear displacement sensor. Abstracts of all-Union scientific-technical conference "Theory and practice of simulation and create simulators". M. : 1985. - 95 S.] (hereinafter, the characteristic point will be called a point of reference level).

However, the accuracy of this method is also low due to the action of influencing factors on the properties of the waveguide path and, consequently, the speed of propagation of the light.

It is known that the incorporation method of measuring the time interval t between the characteristic points of the excitation signal SVASB(t) and the output signal SO(t) depends keemah complex frequency response K():

t=F1(x,K(),...). (1)

When the wave propagation in the waveguide due to the heterogeneity of its properties along the length, different length of the section of the waveguide, the phenomena of dispersion and changes of parameters of the medium of propagation of the radiation caused by the action of influencing factors (temperature, etc.), changes of the complex frequency response K() section of the waveguide:

< / BR>
where SO() and SVASB() - respectively the spectra of the output signal and the excitation signal;

x - measured displacement [m];

frequency [Hz];

- ambient temperature [oI];

with the average speed of wave propagation on the section of the waveguide in the current time [m/s].

When you change To() eventually change the shape of the output signal and its spectrum) and accordingly the position of the characteristic points in time relative to the characteristic points of the excitation signal, resulting in measurement errors.

Characteristic points (XT) input and output signals may be the position of their extremum on the time axis, the moments of their passage through zero, the position of the point on their fronts corresponding to a certain percentage of the amplitude, combinations thereof, etc.,()=SFL()=const, (3)

the position of the characteristic point on the time axis for the output signal will be constant and at a constant position of characteristic points of the excitation signal time interval t is uniquely determined measured move:

t=x/c. (4)

The current value KCH Ki(a) plot of the waveguide path corresponding to the measured displacement x at the current time t, must comply with the following range of excitation signal:

< / BR>
The spectra of the excitation signal SVASB() and the output signal SO()=SFL() correspond to the signals which form taking into account the inverse Fourier transform is:

< / BR>
The spectrum of the received signal due to the delay while passing through the waveguide path (range delayed signal) will be:

< / BR>
where SWYH(a) spectrum of the output signal received in the system in the absence of displacement of the receiver relative to the emitter (ti);

ti- the period of time between the launch and reception of the signal [s].

Thus, it is possible to determine the period of time tibetween the characteristic points of excitation and signal reception on the time axis, and the distance XNoi (SO()= SFL()), then the characteristic point, for example, the position of the extremum of the output signal relative to the zero crossing of the excitation signal will be unambiguously measured move independently from the action of influencing factors on the parameters of the waveguide path, and achieves the technical effect.

The drawing shows a structural diagram of a magnetostrictive transducer movements (CMP) that implements the proposed method.

CMP consists of a waveguide path (W) and block processing and management (BOU).

W contains ferromagnetic waveguide 1, the ends of which are placed in the dampers 3, the driver signals of excitation (PE) 6, the causative agent of elastic waves (HC) in the waveguide 2, the inverter 4 HC EMU and the amplifier output signal 5, the latter together form a receiver HC.

The object, the movement of which is measured, is rigidly connected with the exciter 2.

The BOW contains shaper 7 the spectrum of the reference signal (PV), spectrum analyzers (SA) 8 and 9, respectively, the output and input signals, the unit 10 comparison of the spectra of the reference and output signals, the transmitter CCH (VK) 11, function generator (FG) 13 that implements the function (5) and g="ptx2">

WFP works as follows.

On the "start" command with output 2 BOW to the inputs PV 6 and SA 9 receives the signal of a given shape (with known spectrum). The PV 6 it is amplified with the help of agent 2 as the direct effects of magnetostriction excites the waveguide 1 HC, which is distributed in the past with the speed c(t) in both directions from the place of excitation. Reaching dampers 3, this wave is absorbed by them.

HC, extending to the right from the place of excitation passes under the transducer 4 and at this moment at its output (because of the opposite effect of magnetostriction) is formed EMF, which is amplified by the amplifier 5 and supplied to the inputs of the VI 12 and SA 8. The time interval between initiation of HC in the waveguide 1 and the moment of occurrence of the EMF at the output of the Converter 4 determines the measured displacement x.

Output SA 8 is formed range of SO() the output signal, which is supplied to the second input of the BS 10. Simultaneously, at the first input of the BS 10 receives the spectrum of the reference signal SFL() from the output unit 7. In the BS 10 by comparing the spectra of the reference and output signals and when they are equal, a signal is generated startup VI 12, which calculates the measurement result is another advantage of the signal, who goes to BU 14, and outputs 1 and 4 it appears the control signals, which, firstly run CA 9 on the definition of the spectrum of the excitation signal, and secondly, to calculate CCH WATTS calculator VK 11.

The calculated current value CCH W K() is supplied to the first input of FY 13. Simultaneously to the second input of FY 13 receives the signal output from the PV 7, after which the team from BU 14 output FG 7 is formed by the excitation signal, the spectrum (and shape) which is determined by the expression (5).

Next cycle CMP repeats.

The positive effect is due to the fact that the form of the output signal SO(a) remains unchanged (SO()=SFL()) and the characteristic point will be uniquely measured move independently from the action of influencing factors on the parameters of the waveguide path.

Sources of information

1. Spector, S. A. Electrical measurement of non-electrical quantities: measurement Methods: Educational. manual for schools. HP: Energoatomizdat. Leningrad. separa-tion, 1987, S. 172-178.

2. Artemiev E. A., Druzhinin Century A. optimization of the shape of the probing signal magnetostrictive linear displacement sensor. Abstracts of all-Union scientific-technical is>Method for motion measurement, implemented waveguide path, consisting of a waveguide, shaper of the excitation signal and the receiver, namely, that form the excitation signal, to excite a wave in the waveguide, take wave after passing through the section of the waveguide is equal to the measured displacement, and convert the wave into an output signal, characterized in that the form of the reference signal with a known spectrum, determine the range of the output signal, compare the spectra of the reference and output signals and, if they are identical, is determined taking into account the inverse Fourier transform spectrum of the excitation signal, calculate the complex frequency response plot of the waveguide path corresponding to the measured movement at the current time, as the ratio of the spectrum of the output signal to the spectrum of the excitation signal, calculate the range of the new excitation signal as the ratio of the spectrum of the reference signal to the mentioned complex frequency response and repeat the cycle of measurement, the measured displacement corresponds to the time interval between the characteristic points of the excitation signal and the output signal when the identity of the spectra of the output and atalo the

 

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