RU2599602C1 - Method for compensation of error of measurement of ultrasonic locator - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention can be used for measurement of depth of wells by means of an ultrasonic locating device. Core of the invention is that ultrasonic radar measurement error compensation method involves emission, reception of ultrasonic signals and measurement of time intervals between the emitted and the received ultrasonic signals at two frequencies with different periods with their subsequent correction. In addition, the time interval is measured, in which the instantaneous value of amplitude of the received ultrasonic signal of the first frequency exceeds the threshold level, and basing on the said time interval duration a correcting time interval is determined, which is used to determine the time coordinate of the beginning of the received ultrasonic signal of the first frequency and further determination of a distance to the reflecting surface by multiplying the ultrasound propagation speed in the controlled medium by half of the obtained time interval.

EFFECT: reducing the error of measurements at waveguide propagation of ultrasonic signals.

1 cl, 2 dwg

Description

The invention relates to ultrasonic location devices used to measure the depth of wells in the mining industry, shipping and other sectors of the economy.

A known method of compensating for errors of an ultrasonic level gauge (RU 2389982 C1, IPC G01F 23/28 (2006.01), publ. 05/20/2010), including emitting an ultrasonic signal, receiving it, measuring the time interval between two signals, converting it to a digital code, measuring not less than three time intervals in which the instantaneous value of the amplitude of the received ultrasonic signal exceeds the threshold level. The value of the threshold value and the change in the duration of these time intervals determine the time coordinate of the beginning of the response signal and use it when calculating the distance to the reflecting surface by multiplying the propagation velocity of ultrasound in the controlled medium by the measured time interval.

The disadvantage of this method is the low accuracy and stability of the measurement, due to a change in the shape of the received ultrasonic signal during waveguide propagation, as a result of which the duration of the measured three time intervals can vary non-monotonously, for example, the duration of the third time interval may be less than the duration of the first time interval, or the duration of all measured time intervals may be the same. This makes it impossible to determine the time coordinate of the beginning of the received ultrasonic signal.

A known method of compensating for errors of acoustic location level gauges (RU 2544310 C1, IPC G01N 29/36, published March 20, 2015), selected as a prototype, in which radiation, reception of ultrasonic signals and measurement of time intervals between emitted and received ultrasonic signals are performed on two frequencies with different periods, then compare these time intervals and their correction in accordance with the expression:

,

,

where T ₁ - the period of oscillation of the ultrasonic wave of the first frequency,

T ₂ - the period of oscillation of the ultrasonic wave of the second frequency,

i is the correction number,

Δt ₁ - the first measured time interval,

Δt ₂ - the second measured time interval, the obtained value of the time interval (Δt ₁ -i · T ₁ ) is used in determining the distance to the reflective surface.

The disadvantage of this method is the low accuracy of the measurement, due to the inability to determine the phase of the threshold device, which can vary from 0 to π / 4.

The objective of the invention is to provide a method for reducing the measurement error during the waveguide propagation of ultrasonic signals.

The problem is solved due to the fact that the method of compensating for the measurement error of the ultrasonic locator, as in the prototype, includes radiation, reception of ultrasonic signals and measurement of time intervals between emitted and received ultrasonic signals at two frequencies with different periods, comparison of these time intervals and their correction in accordance with the expression:

,

,

where T ₁ - the period of oscillation of the ultrasonic wave of the first frequency,

T ₂ - the period of oscillation of the ultrasonic wave of the second frequency,

i is the correction number,

Δt ₁ - the first measured time interval,

и расстояния до отражающей поверхности.Δt ₂ - the second measured time interval, the determination of the time interval $$\Delta t_{\mathrm{one}}^{\text{'}\text{'}}=\left(\Delta t_{\mathrm{one}}-i\cdot T_{\mathrm{one}}\right)$$

and distance to reflective surface.

According to the invention, after receiving an ultrasonic signal of a first frequency, a time interval t is measured in which the instantaneous value of the amplitude of the received signal of the first frequency exceeds a threshold level. The corrective time interval is determined in accordance with the expression:

, $$t_{\mathrm{to}}=\left(\frac{T_{\mathrm{one}}}{2}-t\right)/2$$

,

определяют временную координату начала принятого сигнала ультразвуковой волны первой частоты в соответствии с выражением:where t is the time interval in which the instantaneous value of the amplitude of the received signal of the ultrasonic wave of the first frequency exceeds the threshold level. After receiving the value of the time interval $$\Delta t_{\mathrm{one}}^{\text{'}\text{'}}=\left(\Delta t_{\mathrm{one}}-i\cdot T_{\mathrm{one}}\right)$$

determine the time coordinate of the beginning of the received signal of the ultrasonic wave of the first frequency in accordance with the expression:

, $$t_0=\Delta t_{\mathrm{one}}^{\text{'}\text{'}}-t_{\mathrm{to}}$$

,

which is used to determine the distance to the reflective surface.

By measuring the time interval in which the instantaneous amplitude of the received ultrasonic signal of the first frequency exceeds the threshold level, it is possible to determine the correcting time interval and then determine the time coordinate of the beginning of the received ultrasonic signal of the first frequency, which made it possible to compensate for the measurement error of the ultrasonic locator.

The proposed method allows to determine the distance to the reflecting surface with an error of not more than λ / 8, since the threshold device (comparator) is triggered on the first quarter of the period of the received ultrasonic signal of the first frequency, the maximum value of which corresponds to λ / 4, and taking into account the phase of the threshold device reduce the error by half to λ / 8.

In FIG. 1 shows a diagram of a device for implementing the proposed method.

In FIG. 2 is a diagram illustrating the proposed method.

A device that implements the proposed method contains a control unit 1 (CU) connected to the first 2 (G1) and second 3 (G2) generators (Fig. 1). The output of the first generator 2 (G1) is connected to the first emitter 4 (I1), the output of the second generator 3 (G2) is connected to the second emitter 5 (I2). The first receiver 6 (P1) is connected to the first amplifier 7 (U1), the output of which is connected to the input of the first threshold device 8 (PU1). To the other input of the first threshold device 8 (PU1) is connected a reference voltage source 9 (ION). The output of the first threshold device 8 (PU1) is connected to the input of the first measurement unit of the time interval 10 (BIVI1) and to the input of the first block of the formation of the time interval 11 (BFVI1), to the other input of which the control unit 1 (BU) is connected. The output of the first block of the formation of the time interval 11 (BFVI1) is connected to the input of the second block of measurement of the time interval 12 (BIVI2), the output of which is connected to the control unit 1 (BU). The output of the first measurement unit of the time interval 10 (BIVI1) is connected to the control unit 1 (CU). The second receiver 13 (P2) is connected to a second amplifier 14 (U2), the output of which is connected to the input of the second threshold device 15 (PU2), to the other input of which a reference voltage source 9 (ION) is connected. The output of the second threshold device 15 (PU2) is connected to the input of the second block for the formation of the time interval 16 (BFVI2), to the other input of which the control unit 1 (BU) is connected. The output of the second block for the formation of the time interval 16 (BFVI2) is connected to the input of the third block for measuring the time interval 17 (BIVI3), the output of which is connected to the control unit 1 (BU). The control unit 1 (CU) is connected to the display unit 18 (BI).

The control unit 1 (CU) can be performed on the ATMEGA16 microcontroller. Generators 2 (G1) and 3 (G2) can be made according to the scheme with the discharge of the storage capacitance on KU104G thyristors. Emitters 4 (I1) and 5 (I2), receivers 6 (P1) and 13 (P2) can be made of any piezoceramics, for example, TsTS-19. Amplifiers 7 (U1) and 14 (U2) can be performed on operational amplifiers, for example K544UD2. As threshold devices 8 (PU1) and 15 (PU2), K521CA3 comparators can be used. The blocks for the formation of the time interval 11 (BFVI1) and 16 (BFVI2) can be performed on standard K1554TM2 microcircuits. The time interval measuring units 10 (BIVI1), 12 (BIVI2) and 17 (BIVI3) can be performed on standard microcircuits, for example, K1554IE7. The reference voltage source 9 (ION) is selected as standard REF 192 from ANALOG DEVICES in a standard connection. The display unit 18 (BI) is made on seven-segment indicators of the type DA56-11SRWA.

As an example, consider the determination of distance by the proposed method. In a 250-cm-long pipe filled with water, emitters 4 (I1) and 5 (I2) were installed, as well as receivers 6 (P1) and 13 (P2). A reflector was mounted at the opposite end of the pipe. The frequency of the ultrasonic signals of the first emitter 4 (I1) and the first receiver 6 (P1) was 600 kHz, respectively, the wavelength λ ₁ = 2.5 mm, and the oscillation period T ₁ = 1.67 μs. The frequency of the ultrasonic signals of the second emitter 5 (I2) and the second receiver 13 (P2) was 900 kHz, respectively, the wavelength λ ₂ = 1.67 mm, and the oscillation period T ₂ = 1.11 μs.

The control unit 1 (BU) generated a start signal for the first generator 2 (G1), with the same signal, the first block of the formation of the time interval 11 (BFVI1) was set to the state of a logical unit. The first generator 2 (G1) excited the first emitter 4 (I1), which emitted ultrasonic signals with a period of T ₁ . The emitted ultrasonic signal propagated through the controlled medium and was received by the first receiver 6 (P1), amplified by the first amplifier 7 (U1) and fed to the input of the first threshold device 8 (PU1). The second input of the first threshold device 8 (PU1) was supplied with voltage U1 from the reference voltage source 9 (ION). As soon as the voltage at the output of the first amplifier 7 (U1) exceeded the voltage U1, the output of the first threshold device 8 (PU1) switched to logical 1, which reset the first block of the formation of time interval 11 (BFVI1) to a logical zero state (point t ₁ in FIG. .2). Thus, at the output of the first block of the formation of the time interval 11 (BFVI1), a signal is obtained whose duration is equal to time

Δt ₁ = t ₁ -t ₀ ,

where t ₀ - the initial time of the radiation of the ultrasonic signal.

This signal was received in the second measurement unit of the time interval 12 (BIVI2). Data on the duration of the second time interval was received in the control unit 1 (CU). In addition, the logical 1 at the output of the first threshold device 8 (PU1) allowed the operation of the first measurement unit of the time interval 10 (BIVI1) (point t ₁ in Fig. 2). As soon as the voltage at the output of the first amplifier 7 (U1) became less than the voltage U1 (point t ₃ in Fig. 2), the output of the first threshold device 8 (PU1) switched to the logical 0 state, which stopped the operation of the first measurement unit of the time interval 10 (BIVI1 ) Data from the first measurement unit of the time interval 10 (BIVI1) was received in the control unit 1 (BU), which calculated the correction value:

, $$t_{\mathrm{to}}=\left(\frac{T_{\mathrm{one}}}{2}-t\right)/2$$

,

where T ₁ is the period of oscillation of the ultrasonic wave of the first frequency,

t is the time interval in which the instantaneous value of the amplitude of the received ultrasonic signal of the first frequency exceeds the threshold level.

Then the control unit 1 (BU) generated a start signal for the second generator 3 (G2), with the same signal the second block for the formation of the time interval 16 (BFVI2) was set to logical 1. The second generator 3 (G2) excited the second emitter 5 (I2), which emitted ultrasonic signals with a period of T ₂ . The emitted ultrasonic signal propagated through the same controlled medium and was received by the second receiver 13 (P2), amplified by the second amplifier 14 (U2) and entered the input of the second threshold device 15 (PU2). The second input of the second threshold device 15 (PU2) was supplied with voltage U1 from the reference voltage source 9 (ION). As soon as the voltage at the output of the second amplifier 14 (U2) exceeded the voltage U1, the output of the second threshold device 15 (PU2) switched to the logical 1 state, which reset the second block of the formation of the time interval 16 (BFVI2) to the logical 0 state (point t ₂ in FIG. . 2). Thus, at the output of the second block for the formation of time interval 16 (BFVI2), a signal is obtained whose duration is equal to time

Δt ₂ = t ₂ -t ₀ ,

This signal entered the third block of measurement of the time interval 17 (BIVI2). Data on the duration of the third time interval was received in the control unit 1 (CU).

The time intervals between the emitted and received ultrasonic signals, measured by time interval measurement units 12 (BIVI2) and 17 (BIVI3), had durations

Δt ₁ = 328.7 μs,

Δt ₂ = 326.8 μs.

The control unit 1 (BU) made the first correction of these time intervals in accordance with the expression:

where T ₁ is the period of oscillation of the ultrasonic wave of the first frequency,

T ₂ - the period of oscillation of the ultrasonic wave of the second frequency,

i is the correction number,

- первый скорректированный временной интервал,

- the first adjusted time interval,

- второй скорректированный временной интервал.

- the second adjusted time interval.

After that, the control unit 1 (BU) has compared the results of the correction:

After correction according to formulas (1) and (2), we obtained the following set of values:

.

.

As a result, a value exceeding a quarter of the period of ultrasonic vibrations was obtained.

The control unit 1 (BU) carried out the second correction of these time intervals:

After the second correction (i = 2), a value exceeding a quarter of the period of ultrasonic vibrations was obtained.

The control unit 1 (BU) carried out the third correction of these time intervals:

.

.

After the third correction (i = 3), we obtained the time difference of the first and second interval, which is less than a quarter of the period of ultrasonic signals of the first frequency.

The time interval in which the instantaneous value of the amplitude of the received ultrasonic signal of the first frequency exceeds the threshold level measured by the measuring unit of the time interval 11 (BIVI1), had the duration:

t = 0.4 μs.

Then the control unit and display 1 (BU) determined the duration of the corrective time interval in accordance with the expression:

.

.

After that, the control unit 1 (BU) determined the time coordinate of the beginning of the received signal of the ultrasonic wave of the first frequency:

Using this time coordinate, the control unit 1 (BU) determined the distance to the reflector h and transmitted the data to the display unit 18 (BI) for display.

h = C ₀ · t / 2 = 1500 · 333.48 * 10 ^-6 / 2 = 250.11 cm

where C is the speed of propagation of ultrasound in water.

The error in measuring the level Δh was:

Δh = 250-250.11 = 0.11 mm.

Thus, it was experimentally established that the error in measuring the distance to the reflector was λ / 22.

Claims (1)

A method of compensating for the measurement error of an ultrasonic locator, in which the radiation, the reception of ultrasonic signals and the measurement of time intervals between the emitted and received ultrasonic signals are performed at two frequencies with different periods, these time intervals are compared and corrected in accordance with the expression:

,
where T ₁ is the period of oscillation of the ultrasonic wave of the first frequency,
T ₂ - the period of oscillation of the ultrasonic wave of the second frequency,
i is the correction number,
Δt _i is the first measured time interval,
Δt ₂ - the second measured time interval, determine the value of the time interval $$\Delta t_{\mathrm{one}}^{\text{'}\text{'}}=\left(\Delta t_{\mathrm{one}}-i\cdot T_{\mathrm{one}}\right)$$

and a distance to the reflective surface, characterized in that after receiving the ultrasonic signal of the first frequency, measure the time interval t in which the instantaneous amplitude of the received signal of the first frequency exceeds the threshold level, and determine the correcting time interval in accordance with the expression:
$$t_{\mathrm{to}}=\left(\frac{T_{\mathrm{one}}}{2}-t\right)/2$$

,
where t is the time interval in which the instantaneous amplitude of the received signal of the ultrasonic wave of the first frequency exceeds the threshold level, and after receiving the value of the time interval $$\Delta t_{\mathrm{one}}^{\text{'}\text{'}}=\left(\Delta t_{\mathrm{one}}-i\cdot T_{\mathrm{one}}\right)$$

determine the time coordinate of the beginning of the received signal of the ultrasonic wave of the first frequency in accordance with the expression:
$$t_0=\Delta t_{\mathrm{one}}^{\text{'}\text{'}}-t_{\mathrm{to}}$$

,
which is used to determine the distance to the reflective surface.

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