RU2014618C1 - Method of determining the average value of the linear speed - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: method includes the division of the generated sequence of electric pulses into reference and sounding ones transformation of sounding pulses into physical marks, receiving by a detector of marks on the fixed length of the controlled section, their transformation into electrical measuring pulses, the formation of the time interval between the reference and the nearest measuring pulses, the change of the recurrence frequency of the generated pulses till the coincidence of the following reference pulse with the measuring one, the measurement of the recurrence frequency, the delay of reference pulses, the increase in the recurrence frequency of the generated pulses till the coincidence of reference pulses with measuring ones, the measurement of their recurrence frequency, the attenuation of the level of sounding pulses, the increase in the recurrence frequency of the generated pulses till the coincidence of reference and sounding ones the measurement of their recurrence frequency, the determination of the average value of the linear speed by the three values of the measured frequencies of the generated pulses and the length of the controlled section. EFFECT: enhanced accuracy of measurements. 2 dwg

Description

 The invention relates to the measurement of linear velocities by measuring the travel time of a characteristic part (mark) on a moving medium in a control section of the path and can be used to determine the average value of the speed of the rolled materials, as well as the flow rates of liquids and gases.

, где L - длина контрольного участка пути;
δT - время прохождения контрольного участка.A known method of determining the average speed [1], which consists in the excitation of the marks in a moving medium, receiving them after passing the control section of the path, measuring the passage time of the mark and determining the average speed according to the formula
U =

where L is the length of the control section of the path;
δT is the transit time of the control section.

, где U_min - минимальное значение скорости.For a given length value, δT _{max is} determined by the formula
δT _max =

where U _min is the minimum value of speed.

.The label generation frequency F is found from the condition
F <

.

Under these conditions, uniqueness of speed measurement is provided in the entire range of values from U _min to U _max according to the measured travel time of the path with a mark.

 However, in real conditions, a number of restrictions are imposed on the choice of the length of the control section L, and the condition of measurement uniqueness is violated.

 The choice of the length of the control section L depends on the duration of the label. So, ionization labels are quickly destroyed due to recombination of ions, and thermal labels due to heat transfer to the environment. In the turbulent regime of a liquid or gas flow, the mark, as it moves due to turbulent diffusion, erodes, increasing its size both in the axial and in the radial direction. Therefore, for reliable detection and indication of marks, a small value of L is advisable. But from the point of view of increasing the accuracy of measuring the average speed of a moving medium, the distance L needs to be increased. In some cases, the choice of a small value of L is complicated by design and technological features, for example, the inadmissibility of creating new holes in the pipe wall or the need to place a tag detector at the outlet of the technological apparatus. As a result of these restrictions, the length of the control section L must be chosen large, which leads to a decrease in the signal-to-noise ratio at the output of the label detector.

To increase the accuracy of the indication of labels, it is advisable to increase the frequency of generation of labels. However, this causes a measurement ambiguity, since the period of the T = 1 / F labels becomes less than the time taken for the control section, and therefore, the label generation frequency is F> 1 / δ T _max .

= L·F, где L - длина контрольного участка пути;
T - период повторения метода, равный времени прохождения контрольного участка;
F - частота следования меток.A known method for determining the average value of the linear velocity [2], which consists in generating a sequence of electrical pulses, converting electrical pulses into labels of the corresponding physical nature in a moving medium, receiving the marks on a fixed length of the control section of the path, converting them into electrical measuring pulses, forming a time interval between generated and measuring pulses, changing the pulse repetition rate until the last generating pulse with a measuring pulse, measuring the repetition rate of matching pulses and determining the average linear velocity by the formula
v =

= L · F, where L is the length of the control section of the track;
T is the repetition period of the method, equal to the time taken for the control section;
F is the label repetition rate.

 In the known method provides direct proportionality between the measured speed and the frequency of the marks.

 A disadvantage of the known methods is the ambiguity of the results of determining the speed in the case when the pulse repetition period is a multiple of the time the label passes through the control section. In this case, the mark highlighted by the detector may coincide with the first subsequent mark, as well as with the second, third, and later marks. Due to the appearance of ambiguity in fixing the coincidence of marks following a high repetition rate, the range of unambiguous determination of speed narrows and the measurement accuracy decreases significantly when the range of measured velocities is expanded.

 The aim of the invention is to increase accuracy and expand the range of measured speeds.

, где F1, F2, F3 - частоты следования генерируемых импульсов соответственно при первом, втором и третьем измерениях;
L - длина контрольного участка пути.This goal is achieved by the fact that in the method for determining the average value of the linear velocity of a moving medium, including generating a sequence of electrical pulses, dividing this sequence into reference and probing pulses, converting the probing pulses into physical marks in a moving medium, the detector receiving marks on a fixed length of the control section of the path , converting them into electrical measuring pulses, forming a time interval between the reference and the nearest measuring and pulse, changing the repetition rate of the generating pulses until the subsequent reference pulse coincides with the measuring pulse, measuring their repetition frequency F1 and determining the average linear velocity from the frequency of the generated pulses and the length of the control section of the path, additional reference pulses are delayed for a time shorter than the half-period of the probing pulses, after which increases the repetition rate of the generated pulses to a value at which the reference pulses coincide with the measuring pulse they themselves measure the frequency F2 of their repetition, then weaken the level of the probe pulses to the level of the measuring pulses, increase the repetition rate of the generated pulses until the reference and probe pulses coincide, and measure the frequency F3 of their repetition, while the average linear velocity U is determined as
v =

where F1, F2, F3 are the repetition frequencies of the generated pulses, respectively, in the first, second and third measurements;
L is the length of the control section of the path.

 In FIG. 1 is a structural diagram of an apparatus for implementing a method for determining an average value of a linear velocity of a moving medium; figure 2 - voltage waveforms explaining the operation of the device.

 The device comprises an adjustable frequency pulse generator 1, to which a frequency meter 2 and a pulse distributor 3 are connected. To the first input of the pulse distributor 3, series-connected pulse amplifier 4, a tag source 5, a moving medium 6, a tag detector 7, a switch 8, a pulse amplifier 9 are connected and a pulse shaper 10, and to the second input a single-shot 11 and a pulse shaper 12. The outputs of the pulse shapers 10 and 12 are connected to the inputs of the trigger 13, to which a low-pass filter 14 and an indicator are connected OP 15. The device also contains an attenuator 16 connected to the first input of the pulse distributor 3, while the output of the attenuator is connected to the second input of the switch 8.

 The determination of the average linear velocity is as follows.

 The sequence of the output pulses of the generator 1 is divided into reference and probe pulses (Fig. 2a) using a pulse distributor 3. The probe pulses are amplified in the amplifier 4 and act on the source of labels 5. As a source of labels use electrodes, coils, emitters when creating ionization, dielectric , magnetic marks or dispensers when introducing or applying an indicator substance to a moving medium. Labels moving with the medium 6 are read by the detector 7 and converted into electrical measuring pulses (Fig.2b). Electrodes, coils, particle counters, low-inertia thermal converters, photocells, etc. can also be used as tag detectors. Measuring pulses through the Converter 8 are fed to the amplifier 9 where they are amplified to a constant level. Short pulses are created from the amplified pulses by the shaper 10, which are fed to one of the inputs of the trigger 13. The reference pulses excite a single-shot 11 with an adjustable delay time. From the delayed output pulses of the single vibrator, the shaper 12 creates short pulses arriving at the second input of the trigger 13.

The measuring pulses are delayed relative to the reference pulses during the passage of the control section of the path between the source 5 and the detector 7 marks
δt = L / U (1) where δt is the travel time of the control section of the track;
L is the length of the control section of the path;
U is the velocity of the medium (marks).

= E

, (2) где F = 1/T - частота следования импульсов (меток);
E[A] - целая часть числа A.The duration of the output pulses of the trigger 13 will be determined by the difference in the arrival times of the reference pulses and the nearest delayed measuring pulses. Initially, the delay introduced by the single-shot 11 is set to zero. If the pulse repetition period is T, then the reference pulse and the corresponding measuring pulse will be separated by the number of pulses
n = EL

= E

, (2) where F = 1 / T is the pulse repetition rate (marks);
E [A] is the integer part of A.

- n·T =

- E

T. (3)
Из последовательности выходных импульсов триггера 13 фильтром 14 нижних частот выделяют постоянную составляющую напряжения, которую регистрируют индикатором 15. Частоту следования импульсов F предварительно устанавливают такой, чтобы обеспечить стабильные показания индикатора 15. Это обеспечивается повышением частоты следования меток, при котором возрастает отношение сигнал/помеха на выходе фильтра до требуемого значения.The duration of the output pulses of the trigger 13 (pigv) is proportional to the fractional part of the delay time labels
δT1 =

- n · T =

- E

T. (3)
From the sequence of output pulses of trigger 13, the low-pass filter 14 extracts the DC component of the voltage, which is recorded by indicator 15. The pulse repetition rate F is pre-set so as to provide stable indicator readings 15. This is achieved by increasing the label repetition rate at which the signal / noise ratio increases by filter output to the desired value.

After achieving stable readings of the indicator 15, the pulse repetition rate F is smoothly changed until the subsequent reference pulses coincide with the received measuring pulses (Fig. 2d). Upon reaching δ t1 = 0 get
δt = L / U = n ˙ T1 = n / F1, (4) where F1 is the repetition rate of coincident pulses.

- δT0 -

, (5) где δт0 - дополнительная задержка, вносимая одновибратором.The pulse repetition rate F1 of the pulses (marks) is measured by the frequency meter 2. Additionally, the reference pulses are delayed by the single-shot 11 for a time that exceeds the sensitivity threshold of the indicator 15, but less than the pulse repetition half-period (Fig.2d). To do this, smoothly increase the time constant of the single-shot 11 until the indicator reaches maximum readings 15. Then the time constant is reduced to a value at which the indicator reads reach half the value. As a result of the additional delay, the duration of the output pulses of the trigger 13 (Fig.2E) takes on the value
δT2 =

- δT0 -

, (5) where δt0 is the additional delay introduced by the single-shot.

- δT0 = n·T2 =

, (6) где F2 - частота следования импульсов (меток) при втором совпадении.Next, the pulse repetition rate is increased to a value at which the coincidence of the pulses is restored (FIG. 2g). When δ t2 = 0 get

- δT0 = nT2 =

, (6) where F2 is the pulse repetition rate (marks) at the second coincidence.

. (7)
Увеличивают частоту следования импульсов до достижения совпадения (фиг. 2к). Так как дополнительная задержка δт0 < <Т2/2, совпадение будет иметь место при условии
δT0 =

= T3 , (8) где F3 - частота следования импульсов при третьем совпадении.The frequency value F2 is measured by the frequency meter 2. Then, the switch 8 is transferred to the opposite state. In this case, the probe pulses through the attenuator 16 directly go to the amplifier 9 (fig.2z). The attenuation introduced by the attenuator 16 is chosen equal to the attenuation experienced by the probe pulses during conversion to tags, receiving tags and converting them into measuring pulses. As a result of the formation of short pulses from attenuated probe pulses, pulses are generated at the output of trigger 13 (FIG. 2i) with a duration
δT3 = δT0 <

. (7)
Increase the pulse repetition rate until a match is achieved (Fig. 2k). Since the additional delay δt0 <<T2 / 2, a coincidence will take place under the condition
δT0 =

= T3, (8) where F3 is the pulse repetition rate at the third coincidence.

(9)
Решив систему (9) относительно скорости движения меток U получают
U =

·L. (10)
Таким образом, по трем значениям частоты следования меток определяют среднее значение линейной скорости при заданном значении сигнал/помеха. При этом исключается неоднозначность измерений при длительности периода следования меток меньше времени прохождения метками контрольного участка пути (Т<<δt).From relations (4), (6) and (8), a system of equations

(9)
Having solved the system (9) with respect to the speed of movement of the marks U get
U =

· L. (10)
Thus, the average value of the linear velocity at a given signal / noise value is determined from the three values of the label repetition rate. At the same time, the ambiguity of measurements is excluded when the duration of the marks following period is less than the time the marks cover the control section of the track (T << δt).

 As an example of the implementation of the proposed method for determining the average linear velocity, the results of controlling the speed of movement of the tape drive of a tape recorder are presented. The sequence of marks on the tape was applied using a magnetic head excited from an E6-26 pulse generator, the repetition rate of which was measured by a frequency meter of the type Ch3-65. The length of the control section of the path based on the design features of the mechanism for pulling the tape selected equal to 0.05 m Magnetic tags were read using a magnetic head. The speed of the tape was controlled in the sound reproduction mode.

·L = 9,64 cm/c.The determination of speed was carried out in the following sequence. The pulse generator 1 set such a pulse repetition rate (in this case, at least 45 Hz) at which the readings of indicator 15 became stable. Then the pulse repetition rate was gradually increased until the zero readings on the indicator 15 were established, which indicated that the reference pulses coincided in time with the received measuring ones. After reaching zero readings with a frequency counter 2, the first value of the frequency of coincident pulses F1 was recorded, which amounted to 49.38 Hz. Then, using a single vibrator 9, made on a K155AG1 microcircuit, the reference pulses were delayed for a time shorter than the pulse repetition half-cycle. The readings of indicator 15 differed from zero. By gradually increasing the frequency of the generator 1, the zero readings of the indicator 15 were restored and the second frequency value F2 was recorded, which amounted to 49.88 Hz. After that, switch 8 was set to position b, the readings of indicator 15 due to the delay of pulses in the reference channel again became nonzero. The pulse repetition rate from generator 1 was increased until the delayed reference and probe pulses coincided. The moment of coincidence was recorded according to the zero readings of indicator 15 and the third value of the frequency F3 was recorded, which amounted to 192.31 Hz. Further, according to formula 10, the average value of the speed of the tape was determined:
U =

L = 9.64 cm / s.

After that, the tape speed mechanism of the tape recorder set a different speed of movement of the magnetic tape and, according to the method described above, frequency measurements were carried out, which resulted in:
F1 = 207.36 Hz; F2 = 209.86 Hz; F3 = 322.58 Hz.

 The average speed of the magnetic tape in the second mode of operation of the tape recorder was 19.21 cm / s.

 As a result of eliminating the ambiguity in determining the average value of the speed, the proposed method compared to the prototype method can significantly expand the range of measured speeds and improve the accuracy of measurements in the presence of interference.

Claims (1)

METHOD FOR DETERMINING THE AVERAGE VALUE OF LINEAR SPEED OF A MOVING MEDIA, including generating a sequence of electrical pulses, dividing this sequence into reference and probe pulses, converting probe pulses to physical marks in a moving medium, receiving the marks on a fixed length of the control part of the path, converting them into electrical measuring pulses , the formation of a time interval between the reference and the nearest measuring pulses, the frequency change is followed I generated pulses to match subsequent reference pulse with the measuring pulse, the measurement frequency F ₁ of the journey, and determining an average value of linear velocity of the frequency of the generated pulses, and the length of the monitored track section, characterized in that, in order to increase the accuracy and expand the measured velocity range, the reference the pulses are delayed for a time shorter than the half-period of the following pulsing pulses, and then increase the repetition rate of the generated pulses to a value at which the support The pulses coincide with the measuring pulses and measure their repetition rate F ₂ , then weaken the level of the probe pulses to the level of the measuring pulses, increase the repetition rate of the generated pulses until the reference and probe pulses coincide, and measure their repetition frequency F ₃ , with the average linear value speeds v are determined from the expression
v =

,
where F ₁ , F ₂ , F ₃ - repetition frequencies of the generated pulses, respectively, in the first, second and third measurements;
L is the length of the control section of the path.

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