CN104897250B - A kind of more bit stream gauge step-by-step counting compensation methodes for resisting strong harmonic wave interference - Google Patents

Abstract

The invention provides a method for compensating fundamental wave phase pulses of multi-position flowmeters against strong harmonic interference. The method includes: obtaining the output pulse signals of flowmeters and standard meters, and extracting them with a digital Butterworth filter with adjustable pre-cutoff frequency. The fundamental wave signal y(t), using the adaptive notch filter state variable period track to calculate the fundamental wave phase at the start and end of the counting time, obtain the measured pulse number value within the measurement time, calculate the compensation count value according to the phase compensation principle, and obtain the counting compensation The final accurate count value realizes pulse count compensation. The invention realizes the correct extraction of the fundamental wave signal, the acquisition of the fundamental wave phase, and the precision compensation of multiple asynchronous pulse signals under strong harmonic interference, and can effectively improve the verification accuracy of the flowmeter.

Description

A Compensation Method for Pulse Counting of Multi-position Flowmeters Against Strong Harmonic Interference

technical field

The invention relates to the field of flow meter pulse count compensation, in particular to a multi-stage flow meter pulse count compensation method for resisting strong harmonic interference.

Background technique

With the development of modern industry, the demand for flowmeters continues to increase, especially the pulse output flowmeter (in the case of a stable flow field, the instantaneous flow rate of the pulse output flowmeter is proportional to the pulse frequency) has been unprecedentedly applied, which is of great significance for its rapid and accurate verification. major. Universal verification device, the industrial computer drives the commutator according to the phase-locked signal of the pulse signal of the flowmeter, and can intercept the pulse signal of the flowmeter for the entire period. However, in the stage device, the measurement accuracy requirement of the pulse count of another flowmeter cannot be guaranteed.

Patent CN 103176045A proposes a method for detecting coincidence of different frequencies and two phases based on coincidence pulse counting. The patent constructs phase coincidence pre-detection and phase coincidence pulse group generation circuits for inter-frequency signals, a phase deviation correction circuit for double-phase coincidence detection, and a gate time generation circuit, claiming to solve the problem that traditional phase coincidence detection is susceptible to phase noise and trigger errors. There is a disadvantage of phase coincidence detection phase deviation. In fact, the phase correction formula given by the patent (N2 and N1 correspond to the count values of the two pulses, and T2 and T1 correspond to the periods of the two pulses), which are not suitable for the application requirements of variable frequency and pulse width of the multi-position flowmeter verification device.

Other phase coincidence detection methods, such as CN 102680808A, CN 102323739 B, CN103472299 A, etc., are used in multi-position flowmeter verification devices, which have uncertain verification time, require additional complex hardware devices, and are not conducive to detection systems based on industrial computers. Integration etc.

Contents of the invention

In order to solve the above existing problems and defects, the present invention provides a method for compensating the fundamental wave phase pulse of multi-position flowmeters against strong harmonic interference. The method realizes the correct extraction of fundamental wave signals and the acquisition of fundamental The wave phase and the accuracy compensation of multiple asynchronous pulse signals can effectively improve the verification accuracy of the flowmeter.

The purpose of the present invention is achieved through the following technical solutions:

A fundamental phase pulse compensation method for multi-position flowmeters against strong harmonic interference, characterized in that the method includes:

A obtains the output pulse signal u(t) of the flowmeter and the standard meter;

B Use the digital Butterworth filter with adjustable front cut-off frequency to extract the fundamental wave signal y(t);

C Utilize the self-adaptive notch filter state variable period orbit to calculate the counting start and end time t _s , t _e fundamental wave phase

D obtains the value N _p of the measured pulses within the measurement time, calculates the compensation count value N _c according to the phase compensation principle, and obtains the accurate count value N after count compensation.

The beneficial effects of the present invention are:

It realizes the correct extraction of the fundamental wave signal, the acquisition of the fundamental wave phase, and the precision compensation of multiple asynchronous pulse signals under strong harmonic interference, which can effectively improve the verification accuracy of the flowmeter.

Description of drawings

Fig. 1 is a flow chart of the multi-stage flowmeter fundamental wave phase pulse compensation method against strong harmonic interference according to the present invention;

Fig. 2 is a block diagram of pulse signal phase extraction process;

Fig. 3 is a Butterworth filter curve;

Figure 4 is a graph of input angular frequency estimation.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and accompanying drawings.

The present invention is an asynchronous pulse signal accuracy compensation method based on the adjustable digital Butterworth filter with pre-cutoff frequency to extract the fundamental wave signal, and the state variable period track of the self-adaptive notch filter to calculate the fundamental wave phase. As shown in Figure 1, the method includes Follow the steps below:

Step 10, obtaining the output pulse signal u(t) of the flow meter and the standard meter.

Step 20, extracting the fundamental wave signal y(t) with a digital filter with adjustable pre-cutoff frequency; wherein:

1. The frequency normalized transfer function of the digital filter with adjustable pre-cutoff frequency is:

Where b ₁ =2.6131, b ₂ =3.4142, b ₃ =2.6131 are characteristic parameters of the Butterworth filter. Suppose the sampling interval time is T _s , ω _i is the angular frequency of the i-th pulse signal, and the cut-off frequency ω _c of the Butterworth low-pass filter is set to 3ω _i , then its unnormalized transfer function is:

As shown in Fig. 2, it is a flow chart of pulse signal phase extraction.

2. Perform Z-transform discretization on the above formula, let u(k) and y(k) be the input and output of the discrete form filter at time k, then:

Among them, A ₁ , A ₂ , B ₁ , B ₂ , C ₁ , C ₂ , D ₁ , D ₂ , E ₁ , E ₂ are constants related to ω _ci , T _s , b ₁ , b ₂ , b ₃ .

Step 30, use the adaptive notch filter state variable period orbit to calculate the counting start and end time t _s , t _e fundamental wave phase The method is:

1. If the adaptive law is not considered, the transfer function of the notch filter is:

Let f be the input signal, the state variables of the second-order system are x ₁ and x ₂ , the damping ratio is ξ, the adaptive gain is γ, and the angular frequency ω transient estimate is θ (as shown in Figure 4, it is the input angular frequency estimate curve), then the adaptive notch filter can be designed as:

2. Make the periodic pulse fundamental wave signal filtered by the Butterworth digital filter be Then the discrete adaptive notch filter is (as shown in Figure 3 is the Butterworth filter curve):

3. For the i-th periodic input signal, suppose the dynamic system (4) enters its periodic orbit at time t _s , then has a unique periodic orbit:

4. According to the periodic orbit Γ _i , the state variable x ₂ is completely consistent with the input signal y, and the phase of the pulse signal at any n moment can be obtained through Γ _i :

Calculate the real-time phase of the pulse signal at the gate signal occurrence time t _s and t _e according to the above formula

Due to the formula:

It is a differential structure, and there is a requirement to keep the water supply pressure constant during the flowmeter verification process, so using this formula to calculate the compensation count value N _c does not take into account the phase loss caused by low-pass filtering.

Step 40 obtains the value N _p of the measured pulses within the measurement time, calculates the compensated count value N _c according to the principle of phase compensation, and obtains the accurate count value N after count compensation as follows:

Assuming that the period of the pulse signal is T, the phases of the pulse signal at the time t _s and t _e of the gate signal are respectively have Then the counting compensation value N _c can be obtained as:

Count according to the rising edge transition mode, set the measured pulse value N _P within the measurement time, then the accurate count value N after counting compensation is:

N _=Np + _Nc .

Although the embodiments disclosed in the present invention are as above. However, the content described is only an implementation mode adopted for easy understanding of the present invention, and is not intended to limit the present invention. Anyone skilled in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention, but the patent protection scope of the present invention, The scope defined by the appended claims must still prevail.

Claims (4)

1. A kind of 1. more bit stream gauge fundamental phase impulse compensation methods for resisting strong harmonic wave interference, it is characterised in that methods described Including：

   A obtains flowmeter and standard scale output pulse signal u (t)；

   B extracts fundamental signal y (t) with preposition cut-off frequency adjustable digital Butterworth wave filters；

   C utilizes adaptive notch filter state variable periodic orbit count start/stop time t_s、t_eFundamental phase

   D is obtained in time of measuring and is measured pulse number value N_p, compensation count value N is calculated according to phase compensation principle_c, obtain Accurate metering value N after to count compensation.
2. 2. resist more bit stream gauge fundamental phase impulse compensation methods of strong harmonic wave interference, its feature as claimed in claim 1 It is, preposition cut-off frequency adjustable digital Butterworth filter frequencies normalized transfer functions are in the step B：

   <mrow> <msub> <mi>H</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mrow> <msup> <mi>s</mi> <mn>4</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>3</mn> </msub> <msup> <mi>s</mi> <mn>3</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>2</mn> </msub> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>1</mn> </msub> <mi>s</mi> <mo>+</mo> <mn>1</mn> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow>

   Wherein b₁、b₂、b₃For the characterisitic parameter of Butterworth wave filters；If sampling interval duration is T_s, ω_iFor the i-th tunnel pulse Signal angular frequency, if Butterworth low pass filter cutoff frequencies ω_cFor 3 ω_i, then its non-normalized transmission function be：

   <mrow> <msub> <mi>H</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <msubsup> <mi>&amp;omega;</mi> <mi>c</mi> <mn>4</mn> </msubsup> <mrow> <msup> <mi>S</mi> <mn>4</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>1</mn> </msub> <msub> <mi>&amp;omega;</mi> <mi>c</mi> </msub> <msup> <mi>s</mi> <mn>3</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>2</mn> </msub> <msubsup> <mi>&amp;omega;</mi> <mi>c</mi> <mn>2</mn> </msubsup> <msup> <mi>s</mi> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>b</mi> <mn>3</mn> </msub> <msubsup> <mi>&amp;omega;</mi> <mi>c</mi> <mn>3</mn> </msubsup> <mi>s</mi> <mo>+</mo> <msubsup> <mi>&amp;omega;</mi> <mi>c</mi> <mn>4</mn> </msubsup> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow>

   Using transform to formula (2) discretization, input, output that u (k), y (k) are k moment discrete form wave filters are made, then is had：

   <mrow> <mtable> <mtr> <mtd> <mrow> <mi>y</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <msub> <mi>A</mi> <mn>2</mn> </msub> </mfrac> <mo>&amp;lsqb;</mo> <msub> <mi>A</mi> <mn>1</mn> </msub> <mi>u</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>B</mi> <mn>1</mn> </msub> <mi>u</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> <msub> <mrow> <mo>+</mo> <mi>C</mi> </mrow> <mn>1</mn> </msub> <mi>u</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>2</mn> </mrow> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>D</mi> <mn>1</mn> </msub> <mi>u</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>3</mn> </mrow> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>E</mi> <mn>1</mn> </msub> <mi>u</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>4</mn> </mrow> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>-</mo> <msub> <mi>B</mi> <mn>2</mn> </msub> <mi>y</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> <mo>-</mo> <msub> <mi>C</mi> <mn>2</mn> </msub> <mi>y</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>2</mn> </mrow> <mo>)</mo> </mrow> <mo>-</mo> <msub> <mi>D</mi> <mn>2</mn> </msub> <mi>y</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>3</mn> </mrow> <mo>)</mo> </mrow> <mo>-</mo> <msub> <mi>E</mi> <mn>2</mn> </msub> <mi>y</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>-</mo> <mn>4</mn> </mrow> <mo>)</mo> </mrow> <mo>&amp;rsqb;</mo> </mrow> </mtd> </mtr> </mtable> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow>

   Wherein, A₁、A₂、B₁、B₂、C₁、C₂、D₁、D₂、E₁、E₂For with ω_ci、T_s、b₁、b₂、b₃Related constant.
3. 3. resist more bit stream gauge fundamental phase impulse compensation methods of strong harmonic wave interference, its feature as claimed in claim 1 It is, in the step C, utilizes adaptive notch filter state variable periodic orbit count start/stop time t_s、t_eFundamental phaseMethod be：

   If not considering adaptive law, the transmission function of trapper is：

   <mrow> <msub> <mi>H</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>&amp;xi;</mi> <mi>&amp;theta;</mi> </mrow> <mrow> <msup> <mi>S</mi> <mn>2</mn> </msup> <mo>+</mo> <mn>2</mn> <mi>&amp;xi;</mi> <mi>&amp;theta;</mi> <mi>s</mi> <mo>+</mo> <msup> <mi>&amp;theta;</mi> <mn>2</mn> </msup> </mrow> </mfrac> </mrow>

   It is input signal to make f, and second-order system state variable is x₁、x₂, damping ratio ξ, adaptive gain γ, angular frequency wink State estimate is θ, then can design adaptive notch filter is：

   <mrow> <mfenced open = '{' close = ''> <mtable> <mtr> <mtd> <mrow> <msub> <mover> <mi>x</mi> <mo>&amp;CenterDot;</mo> </mover> <mn>1</mn> </msub> <mo>=</mo> <msub> <mi>x</mi> <mn>2</mn> </msub> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mover> <mi>x</mi> <mo>&amp;CenterDot;</mo> </mover> <mn>2</mn> </msub> <mo>=</mo> <mo>-</mo> <mn>2</mn> <msub> <mi>&amp;xi;&amp;theta;x</mi> <mn>2</mn> </msub> <mo>-</mo> <msup> <mi>&amp;theta;</mi> <mn>2</mn> </msup> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>+</mo> <mn>2</mn> <mi>&amp;xi;</mi> <mi>&amp;theta;</mi> <mi>f</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mover> <mi>&amp;theta;</mi> <mo>&amp;CenterDot;</mo> </mover> <mo>=</mo> <mo>-</mo> <msub> <mi>&amp;gamma;x</mi> <mn>1</mn> </msub> <mi>&amp;theta;</mi> <mrow> <mo>(</mo> <mi>f</mi> <mo>-</mo> <msub> <mi>x</mi> <mn>2</mn> </msub> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>

   Recurrent pulse fundamental signal is after making Butterworth digital filtersThen Discretization adaptive notch filter is：

   <mfenced open = '{' close = ''> <mtable> <mtr> <mtd> <mrow> <msub> <mi>x</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> <msub> <mi>x</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>x</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>x</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> <mo>=</mo> <mrow> <mo>&amp;lsqb;</mo> <mrow> <mn>1</mn> <mo>-</mo> <mn>2</mn> <mi>&amp;xi;</mi> <mi>&amp;theta;</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mo>&amp;rsqb;</mo> </mrow> <mi>x</mi> <mtext> </mtext> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <mi>&amp;theta;</mi> <msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> <msub> <mi>x</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> <mo>+</mo> <mn>2</mn> <mi>&amp;xi;</mi> <mi>&amp;theta;</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>y</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mi>&amp;theta;</mi> <mrow> <mo>(</mo> <mrow> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> <mo>=</mo> <mo>-</mo> <msub> <mi>&amp;gamma;x</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>&amp;theta;</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mrow> <mo>&amp;lsqb;</mo> <mrow> <mi>y</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <msub> <mi>x</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mo>&amp;rsqb;</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> <mo>+</mo> <mi>&amp;theta;</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mfenced>

   For the i-th road periodic input signal, if dynamical system is (4) in t_sMoment enters its periodic orbit, then With unique periodic orbit：

   Thus, according to periodic orbit Γ_i, state variable x₂It is completely the same with input signal y, and Γ can be passed through_iTry to achieve pulse signal In any n moment phase：

   Signal strobe is (6) tried to achieve by formula moment t occurs_s、t_eWhen pulse signal real-time phase be respectively
4. 4. resist more bit stream gauge fundamental phase impulse compensation methods of strong harmonic wave interference, its feature as claimed in claim 1 It is, in the step D, obtains in time of measuring and measure pulse number value N_p, benefit is calculated according to phase compensation principle Repay count value N_c, the method for obtaining the accurate metering value N after count compensation is：

   If pulse signal cycle is T, in signal strobe occurs for pulse signal moment t_s、t_ePhase be respectivelyHaveIt can must then count offset N_cFor：

   Counted by rising edge Hopping Pattern, be located in time of measuring and measure pulse number value N_P, then it is accurate after count compensation Count value N is：

   N=N_p+N_c。 ⑻