RU2523166C1 - Generation of pulses from rpm induction transducer signals - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: proposed method comprises the steps that follow. Volt-second area S₁ of first half-wave is measured. Its maximum magnitude S_1K is memorised to generate threshold magnitude S_thres=Q·S_1K, where Q<1.S_1K is compared with threshold magnitude S_{mar. min} equal to marginal minimum permissible magnitude of volt-second area of analysed signal half-waves. Volt-second area S₂ of second half-wave is measured. In measurement, obtained magnitudes of S₂ are compared with threshold magnitude S_thres. Provided that S_1K>S_{mar. min}, S₂>S_thres comparator changeover permit signal is generated. Comparator changeover and comparator changeover permit signal reset are executed at induction transducer input signal zero-crossing.

EFFECT: higher precision.

2 dwg

Description

The invention relates to measuring equipment and can be used in automatic measurement, control and emergency protection systems, which include sensors that generate bipolar signals, in particular induction sensors of speed and flow.

A known method of generating pulses from the signals of induction speed sensors, in which volt-second areas of two adjacent bipolar signals of the same rotation polarity are measured in the same polarity of the half-wave signals, the volt-second area S1 of the first half-wave is measured first, and its maximum value S1k is stored, generate a threshold value Sпор1 = Q · S1к, where Q <1, compare S1к with a threshold value Sпр.min equal to the maximum minimum allowable value of volt-second area studied tivity of half-waves signals, then measure the volt-second area S2 of the second half wave, during the measurement value obtained is compared with a threshold value S2 Spor1 and under the conditions S1k> Spr.min, S2> Spor1 produce the desired pulse. Simultaneously with the measurement of the volt-second area S2, its maximum value S2k is stored, the threshold value Spor2 = Q · S2k is generated, which is necessary for the implementation of the next cycle of pulse formation. With the arrival of each new bipolar signal of the induction speed sensor, the process of generating the required pulse is repeated. The method found an implementation in the device [1].

This method is ineffective when changing the amplitude of the signal over a wide range, since at a low level of the input signal threshold values decrease, which, in turn, reduces the noise immunity of the formation of pulses from the sensor signals.

Of the known closest in technical essence is the method of generating pulses from the signals of induction speed sensors [2], also based on measuring the volt-second area, according to which:

1. The volt-second area of two adjacent half-waves of opposite polarity of the bipolar signals of the induction speed sensor is measured and compared, first, the volt-second area S1 of the first half-wave is measured, its maximum value S1k is stored, the threshold value Sпор1 = Q · S1к is generated, where Q < 1, compare S1k with a threshold value of Sr.min equal to the limiting minimum permissible value of the volt-second area of the studied half-wave signals, then measure the volt-second area S2 of the second half-wave, in the process and Measurements compare the obtained values of S2 with the threshold value of Ssp1 and, under the conditions S1k> Sp.min, S2> Spp1, generate the required impulse, and during the measurement of the volt-second area S1 of the first half-wave, compare the obtained values of S1 with the threshold value of Sp.min and at the moment if the condition S1> Spr.min is fulfilled, they obtain a permission to measure the volt-second area S2 of the second (opposite polarity) half-wave, which is canceled at the beginning or after the start of the issuing of the required pulse, with the arrival of each new bipolar signal of the induction speed sensor repeat the process of forming the desired pulse.

2. In addition to claim 1, that in the process of measuring the volt-second area S2 of the second (opposite polarity) half-wave of the bipolar signal of the induction speed sensor, an additional parameter Sx = (1 + Q) · S2 / 2 is generated, its maximum value Sxk is compared with threshold values Ssp1 = Q · S1k and Ssp2 = S1k and when the conditions S1k> Spr.min, Spor1 <Sxk <Spor2 (instead of the conditions S1k> Spr.min, S2> Sp1 according to claim 1) are generated, the required pulse is generated.

The disadvantage of this method is the significant instability of the switching front of the comparator, which is caused by a gentle front of the volt-second area in the switching area and the effect of various kinds of interference on the compared signals. In this case, the accuracy of measuring the rotational speed by a periodic method decreases. In addition, if there are significant noise levels (the Q value must be set closer to 1) and if the volt-second area of the input signal is very unstable, pulse skipping is also possible.

The aim of the proposed method is to increase the accuracy of the pulse shaper by increasing the stability of the switching front of the output signal.

This goal is achieved by the fact that in the method of generating pulses from the signals of the induction speed sensors, in which volt-second areas of two adjacent half-waves of bipolar signals of the rotational speed sensors are measured and compared, the volt-second area S _{1 of the} first half-wave is measured first, and it is stored the maximum value of S _1K, S generate threshold _thresh ⁼ Q * S _1K, where Q <1, S _1Q compared with a threshold value S _{pr. min,} equal to a minimum permissible limiting value of volt-second n oschadi investigated half-waves signals, then measure the volt-second area S ₂ of the second half wave, during the measurement compares received values S ₂ with the threshold value S _long, according to the inventive method under the conditions of S _1K> S _{pr. min,} S _2> S _then produce the comparator switching enable signal, and the comparator switching and resetting the comparator switching enable signal is performed when the input signal of the induction sensor passes through zero.

In the proposed method, the output signal of the driver is switched not when the volt-second area of its threshold value is reached, as in the prototype, but when the signal from the sensor passes through zero. When the volt-second area of its threshold value is reached, the proposed method only removes the blocking of the switching of the comparator, which forms the output signal of the shaper.

Blocking the switching of the comparator at the level of the volt-second area below its threshold value allows, as in the prototype, to eliminate false response of the driver in the presence of interference in the input signal from the sensor with a level of up to 80-90% of the level of the useful signal. Switching the output signal of the shaper when the signal from the sensor passes through zero, i.e. in the region of the maximum gradient of the input signal of the comparator, it allows to stabilize the switching front of the shaper, which increases the accuracy of the shaper.

Thus, the proposed method provides a technical effect and improves the accuracy of the shaper in the presence of various kinds of interference.

In the embodiment of the proposed method shown in FIG. 1, the signal e _{from the} induction speed sensor is supplied to the comparator 1 and the analog-to-digital converter (ADC) 2, the output code of which is sent to the processor 3, which calculates the volt-second half-wavelength of the input signal and simultaneously performs comparator control functions 1. The output of the comparator is the output of the shaper circuit, and is also connected to the input of the processor 3.

The comparator 1 switches when the input signal passes through zero with an enable signal from the processor 3. The ADC 2 together with the processor 3 determine the volt-second area of the current half-wave of the input signal, the processor 3 calculates the threshold level S _then . According to the results of comparison, the volt-second area of the current half-wave of the input signal with thresholds S _{ave. Min} and S _then processor 3 generates a resolution signal for comparator 1.

All elements that make up the device can be implemented as separate functional units or by hardware and software of a microcontroller equipped with a comparator and ADC.

The device operates as follows (figure 2). When adjusting the shaper, depending on the parameters of the input signal and the expected level of interference, the value of the coefficient Q is set, the minimum threshold of the comparator S _{pr min} ; the value of the current threshold S _{then is} set equal to S _{PR min} . After turning on the shaper, the ADC 2 cyclically selects the input signal e _s from the speed sensor, converts it into a digital code and sends it to the processor 3 with a frequency substantially higher than the frequency of the input signal. In the initial state, the operation of comparator 1 is enabled by the control signal En = 1 of processor 3. When the input signal passes through zero for the first time, comparator 1 is activated and processor 3 prohibits switching of comparator 1 on this signal (En = 0). Simultaneously with the transition of the input signal through zero, the processor 3 begins to summarize the samples of the ADC 2 and compare the received current sum S with the threshold S _min . After reaching the conditions S> S, _{etc. min} and S> S _then, processor 3 enables the switching of comparator 1 (En = 1).

Input signal at the subsequent transitions e _to zero crossing comparator 1 operates, the CPU 3 forbids switching comparator 1 (En = 0) and the largest accumulation value S for the entire previous half-wave input signal calculates the current threshold S _then = Q · S, then begins to accumulate Samples in the new amount S.

In the case of interference with an S value of less than S _{then the} input signal passes through zero with the locked comparator 1 and does not switch.

Thus, the pulse shaper does not perceive interference in the input signal with an S value of less than S _then ≥S sp _. Min and ensures stability of the switching front regardless of the level of blocked pulses, which allows to increase the accuracy of measuring the speed.

Information sources

1. Patent RU 2173022 C2, IPC7 Н03К 5/153, publ. August 27, 2001

2. Patent RU 2352058 C1, IPC Н03К 5/153, publ. 04/10/2009

Claims (1)

A method of generating pulses from signals from induction speed sensors, in which volt-second areas of two adjacent half-waves of bipolar signals of an induction speed sensor are measured and compared, first, volt-second area S is measured_one the first half-wave, remember its maximum value S_{1 TO}generate a threshold value S_since= Q_{1 TO}where Q <1, compare S_{1 TO} with threshold value S_minequal to the limiting minimum permissible value of the volt-second area of the studied half-wave signals, then measure the volt-second area S₂ the second half-wave; during the measurement, the obtained values of S are compared₂ with threshold value S_sincecharacterized in that under the conditions S_1K> S_{etc. min}, S₂> S_sincea comparator switching enable signal is generated, and the comparator switching and reset of the comparator switching enable signal are performed when the input signal of the induction sensor passes through zero.

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