EA022138B1 - Method for measuring amplitude of object vibration - Google Patents

Abstract

The invention relates to measuring technology and can be used for noncontact measuring vibration amplitude in heat-and-power engineering, gas industry, machinery construction, aircraft construction and other industries. The technical result is aimed at increasing accuracy of measuring vibration amplitude and simplification of design of microwave path of the noncontact measuring vibration amplitude to minimize its overall dimensions. The assigned task is characterized in that a test object is probed by a microwave signal using an antenna with alternating frequency short-wave region of millimeter range wave length, wherein a balance mixer receives a part of a probing signal and a signal reflected from the vibrating object.

Description

The invention relates to measuring equipment and can be used for non-contact measurement of the amplitude of vibration in the power system, gas industry, mechanical engineering, aircraft manufacturing and other fields.

Known non-contact radio wave method of measuring the amplitude of vibration, implemented in a radar for detecting vibration [1], which consists in probing the object under study with a microwave signal of a fixed carrier frequency G ₀ , receiving a reflected microwave signal of the form

where A ₁ is the amplitude of the reflected signal;

G ₀ - carrier frequency of the probing signal;

φ ₁ - phase shift of the reflected signal in the microwave measuring path at the output of the integrated balanced mixer;

φ _Β (ΐ) = φ _Β Μ 5J1 2πί _Β ΐ - phase change of the reflected signal under the influence of vibration of the studied object;

φ _ΒΜ is the amplitude value of the phase change of the reflected signal under the influence of vibration of the studied object;

ί _Β - vibration frequency;

they mix the reflected signal with a reference signal in a complex balanced mixer, which is used as a part of the probing signal, and, after filtering and amplifying the output of the complex balanced mixer, quadrature signals I ₁ (1) and I ₂ (1) of the form

1 /, 0) = | 4D ₂ cos [(^ | - <M + M ')]' where A ₂ is the amplitude of the reference signal;

φ ₂ - phase shift between the reference signal at the input of the complex balanced mixer and the original probing signal;

calibration procedure involves removal of a plurality of signal values and _one (1), and ₂ (1) and after homogenization (the average value of φ _Β (ΐ) tends to zero) calculated values of k ₁ and (φ _1, φ ₂₎ ; taking these calculated values into account, using an adjustable microwave attenuator and phase shifter, an additional sounding microwave signal is reproduced, which after reflection from the surface of the additional antenna has an amplitude of A! and phase shift (φι-φ ₂ ) ₀ ⁼ φι-φ ₂ + π; since this signal is combined with the reflected signal, then at the output of the complex balanced mixer there will be quadrature signals of the form

the amplitude of the output signal And ₂ (1) will be proportional to the amplitude of the vibration Ό _Μ C

-ψα> · ΐ 'where C is the speed of light.

However, this method, despite the provision of high measurement sensitivity due to the use of an integrated balanced mixer, has several disadvantages: firstly, the complexity and complexity of the calibration procedure, which should be carried out at the installation site of the vibration amplitude meter, and as a result, the measurement process cannot be automated (because for the need to use a regulatory system - adjustable microwave attenuator and phase shifter); secondly, the limitation of the upper value of the measured amplitude of the vibration due to the need to fulfill the condition of smallness of the value of φ _ΒΜ .

Closest to the proposed invention is a non-contact radio wave method for measuring vibration [2], which consists in the fact that the object is probed by an antenna with a microwave signal of a fixed carrier frequency in the short-wave part of the millimeter wavelength range using an antenna, and a signal 8, (1) of the form

they mix the reflected signal with the reference signal in a complex balanced mixer, as a part of the probing signal, and receive, after filtering and amplifying the output of the complex balanced mixer, quadrature signals and, (1) and And ₂ (1) of the form

- 1 022138

convert the signals υ, (1) and And ₂ (1) into digital form in the form of a set of instantaneous values of ID) and υ ₂ (ΐι) by means of a high-speed two-channel analog-to-digital converter, the polling frequency of which is chosen much higher than the maximum value of the vibration frequency of the studied object, for each pair of obtained values of IDO and υ ₂ (ΐ ₁ ) calculate the instantaneous values of the phase shift φι by the expression

from the obtained values of φ, determine φ _ΜΙΝ and φ _ΜΑΧ , calculate the value of φ _ΒΜ by the expression _ Ψμαχ ~ Fmm '

Ψβμ 2 'and the vibration amplitude Ό _Μ is determined by the expression

The above non-contact radio wave measurement method is free from the disadvantages inherent in the method [1]. However, the disadvantages of this method are the large dimensions of the vibration amplitude meter due to the complexity of the design of the microwave path using an integrated balanced mixer;

limitation of the accuracy of measuring the amplitude of vibration due to the non-identical channel parameters during two-channel signal conversion in a complex balanced mixer.

The objective of the invention is to increase the accuracy of measuring the amplitude of vibration and simplifying the design of the microwave path of the meter to minimize its overall dimensions.

The task is achieved by the fact that in the known non-contact radio wave method for measuring the amplitude of vibration there is no complex balanced mixer, and to ensure the measurement of the amplitude of vibration, the spectrum of the vibration signal is linearly transferred to the intermediate frequency with its subsequent processing in a digital quadrature mixer. To do this, the object under investigation is probed by means of an antenna with a microwave signal with a periodically changing frequency in the short-wave part of the millimeter wavelength range, while part of the probing signal of the form enters the mixer

5 ,, (/) = 4, SSCR-GD /)], where P _n (1) is the law of change in the frequency of the probe signal, described by the expression Pn (1) = Go + P (1);

G0 is the constant component of the carrier frequency of the probe signal;

'- a variable component of the carrier frequency of the probe signal, changing over a period T the frequency value from 0 to R _m ;

P _m - the magnitude of the frequency deviation, which is calculated and provided on the basis of the known distance to the test object b according to the formula = - ^A '2 /.

and the signal reflected from the vibrating object

5, (/) = Л, cos [2l-Г „(ί) + φ _ν (/) + φ _ί (ί)], where Α ₀ , Α ₁ are the amplitudes of the part of the probing and reflected signals;

φι, (Ι) is the phase shift of the reflected signal in the microwave measuring path at the output of the balanced mixer, determined by the distance to the test object b and the value of the carrier frequency P _n (1);

the signals δ ₀ (ί) and δ, (1) are mixed in a balanced mixer, and a difference component is extracted at its output, while the total component having a double carrier frequency is filtered out. The extracted signal will have the form (0 = 4-, and cos [2l-G _{/ 71} , G + φ, ₀ + φ _Β (/)], where A _SM is the signal amplitude at the mixer output;

- 2 022138. 4τί, / ₀ С <Ри>

- a constant phase incursion of the reflected signal at a frequency G; the signal 8 _C m (t) is converted into digital form in the form of a set of instantaneous values § _cm (£) by means of a single-channel high-speed analog-to-digital converter, the sampling frequency of which is chosen at a much higher frequency P _IF ;

digitally generate the instantaneous values of the reference stresses of the form C (/,) = ¢ 08 (2 ^, /,), (() ~ нп (2я · Р _pc 1,), and multiplying them with instantaneous values of the signal of 8 _cm (th) followed by digital filtering to obtain quadrature signals containing phase information

for each pair of obtained values and ₃ (1 ₁ ) and υ ₄ (ίι) calculate the instantaneous values of the phase shift φ, according to the formula

L (A

A,) 'from the obtained values of φ _; , determine φ _ΜΙΝ and φ _ΜΑΧ , calculate the value of φ _ΒΜ by the expression:

_ 'T: <- Ά ¹ ?.

'and the amplitude of the vibration And _m is determined by the expression C

-fwm

A comparative analysis with the prototype shows that the inventive method differs in the principle of generating a probe microwave signal, the carrier frequency of which R _n (1) periodically linearly changes to the frequency P (1) in the short-wavelength part of the millimeter wavelength range, which allows digital quadrature processing signal, instead of a complex balanced mixer with two outputs, using a conventional mixer with one output and a single-channel high-speed analog-to-digital converter, as well as Hovhan digitally reference voltages and _one (1 ₁₎ and υ ₂ (ΐ,) for obtaining the quadrature components of the signal and measuring the amplitude of the vibration and _m, to ensure their precise phase shift of π / 2.

This makes it possible to reduce the error in measuring the amplitude of vibration by eliminating the non-identity of parameters during analog two-channel quadrature signal processing due to the exact digital generation of reference signals υ ₁ (ί;) and υ ₂ (1ί) in a digital quadrature detector, and to significantly simplify the design of the microwave path and, accordingly, significantly reduce the overall dimensions of the meter by using a conventional mixer instead of the complex balanced mixer used in the meters given in [1, 2].

The proposed method is illustrated in the drawing, which shows a structural diagram of a vibration amplitude meter with which the proposed method can be implemented.

The meter, with which the proposed method can be implemented, contains a microwave generator (G) 1 with electrical frequency tuning, the output of which is connected to the input of a power divider (DM) 2, the first output of which is connected through a directional coupler (BUT) 3 to a horn antenna (A ) 4, oriented in the direction of the object under study (ИО) 5 and irradiating and receiving the microwave signal reflected from (ИО) 5, supplied to the first input of the balanced mixer (BS) 6, to the second input of which the reference signal from the second output of the DM , in the course of the balanced mixer (BS) 6 is connected to the analog input of a high-speed analog-to-digital converter (ADC) 7, the digital output of which is connected to the digital input of the ΌδΡ processor (ΌδΡ) 8, the digital inputs and outputs ΌδΡ 8 are connected to the inputs and outputs of the ADC 7, digital-to-analog converter (DAC) 9, personal computer (PC) 10; the analog output of the DAC 9 is connected to the control input of the microwave generator 1.

The claimed method in this meter can be implemented as follows.

The microwave generator (G) 1 generates a probing signal with a periodically changing frequency, which is fed through the power divider (DM) 2 and the primary channel of the directional coupler (HO) 3 to the horn antenna (A) 4, which is both transmitting and receiving. The signal reflected from the studied object (IO) 5 through the secondary channel of the directional coupler (BUT) 3 (the directional coupler (BUT) 3 is oriented to the reflected signal) is fed to the first input of the balanced mixer (BS) 6. The second input of the balanced mixer (BS) 6 through the power divider (DM) 2, a part of the probing signal is supplied 3 022138. In the balanced mixer (BS) 6, the interference of these signals is carried out, the output signal at the intermediate frequency that carries information about the phase of the signal, its filtering and amplification is extracted. A single-channel high-speed analog-to-digital converter (ADC) 7 converts the signal from the output of the balanced mixer (BS) 6 into digital form. A known value b of the distance from the antenna (A) 4 to the test object (IO) 5 is entered into a personal computer (PC) 10, which is used to provide the conditions for the formation of P _IF and the formation of digital reference voltages And ₁ (1 ₁ ) and and ₂ (C) and the parameters of the signal that controls the frequency tuning of the microwave generator (G) 1. In the IBR processor (IDB) 8, the instantaneous values of the reference signals and the signal from the digital output of the analog-to-digital converter (ADC) 7 are digitally multiplied and generated digital waveform control the frequency of the microwave generator (G) 1. The last signal is converted in a digital-to-analog converter (DAC) 9 into an analog form and serves to adjust the frequency using the varactor of the microwave generator (G) 1. In a personal computer (PC) 10, mathematical processing is performed signals, calculation and indication of the measured vibration amplitude.

The meter based on the proposed method is implemented in the Center 1.9 Scientific and Innovative Center for Microwave Technologies and their metrological support of the Belarusian State University of Informatics and Radioelectronics. The carrier frequency of the probe signal is 94 GHz, the frequency range is 1.5 GHz, the output power is at least 10 mW, the operating range of the vibration frequency is from 0 to 31250 Hz, the range of measured vibration amplitudes is from 1 μm to 10 mm (divided into sub-bands), the basic error measurements (according to the results of experimental studies) no more than 2-3%.

Information sources

1. Radar for detecting vibration: Patent of the United Kingdom of Great Britain 2310099 A, 1996.

2. A method of measuring the amplitudes of vibration of an object: Patent RB No. 13974, IPC O01N 9/00, 2010.

Claims (1)

CLAIM A method of measuring the amplitude of vibration, characterized in that the object under measurement is probed by means of an antenna with a microwave signal with a periodically changing frequency of the shortwave part of the millimeter wavelength range, while the balanced mixer receives a part of the sounding signal of the form and is reflected from a vibrating object where A ₀ , A ₁ - amplitudes of the part of the probe and reflected signals; Р _Н (1) - the law of change of the probing signal frequency, described by the expression Р _Н (1) = Г ₀ + Р (1); Go is the constant component of the carrier frequency of the probing signal; '- the variable component of the carrier frequency of the probing signal, changing over the period T the frequency value from 0 to P _m ; P _m - value of frequency deviation, calculated and provided based on the known distance to the test object according to the formula L p ₍₁₎ = p _im δίη 2πί _Β ΐ - change in the reflected signal phase under the influence of vibrations of the test object; <p _VM - the amplitude value of the change in the phase of the reflected signal under the influence of the vibration of the object under study; G _in - the frequency of vibration; t = -! - T '- during the frequency changes of the probing signal, whose value is provided based on the requirements of _IF F> T _in; which are mixed in a balanced mixer, and after filtering and amplification, a signal of the form is extracted at its output А'М (0 4ч / со02тгР _т (1) + φ, _α + <ζ » _β (/)]; where А _СМ is the amplitude of the signal at the output of the mixer; с - constant phase shift of the reflected signal at the frequency Г ₀ ; - 4 022138 8 _cm signal (1) is converted into digital form in the form of a set of instantaneous values of 8 _CM (f) by means of a single-channel high-speed analog-to-digital converter, the sampling frequency of which is chosen much higher than the frequency P _n ; make digital formation of instantaneous values of reference voltages ί7 ₂ (/,) = δΐη [2 ^ /,], and multiplying them with instantaneous values of the 8 _cm signal (f), followed by digital filtering to obtain quadrature signals containing information about the phase k ) = | Hm + <p _in (0]; k) = | Hm [^ o + bs')]; for each pair of obtained values ϋ ₃ (ί;) and ϋ ₄ (ί;), calculate the instantaneous values of the phase shift φ; by the formula of the obtained values of φ _; determine φ _ΜΙΝ and φ _{определяют} , calculate the value of φ _ΒΜ by the expression and the amplitude of the vibration E _m is determined by the expression