CN102393661A - Digital closed loop control system for Coriolis mass flowmeter (CMF) - Google Patents
Digital closed loop control system for Coriolis mass flowmeter (CMF) Download PDFInfo
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Abstract
The invention relates to a digital closed loop control system for a Coriolis mass flowmeter (CMF). The system comprises an amplitude limiting circuit, an inverting amplifier, an effective value converter, an analog-to-digital converter (ADC), a processor, a multiplying digital-to-analog converter (MDAC) and an amplifier, wherein the inverting amplifier amplifies a vibration signal output by a vibration pickup, the effective value converter converts the amplified signal into an effective value, and the processor performs sampling measurement on the effective value through the ADC and compares the effective value with a preset target effective value to obtain an error value; the amplitude of a signal output by the MDAC is adjusted in real time by a nonlinear amplitude control method, the signal is amplified by the amplifier, and the amplified signal is taken as an excitation signal and transmitted to a vibration exciter, so that a measuring tube vibrates at stable amplitude; and when the measuring tube stably vibrates, the vibration frequency is the resonant frequency of the measuring tube of the CMF. The digital closed loop control system is short in response time and high in antijamming capability and adaptability and can be extended to be applied to the closed loop control of a resonant sensor.
Description
Technical field
The present invention relates to a kind of Ke's mass flowmeter digital closed-loop control system; Adopt multiplication D/A converter MDAC Coriolis mass flowmeter (Coriolis Mass Flowmeter is hereinafter to be referred as CMF) to be carried out the closed-loop control of fast and stable with the method that non-linear amplitude control combines.
Background technology
Flow metering occupies critical role in industrial process control, CMF has the performance of the incomparable brilliance of a lot of other flow sensors as a kind of measurement instrument of direct responsive fluid mass flow.Therefore, it is widely used in the fields such as food, oil, chemical industry, and the trend that continues expansion is arranged.
CMF mainly partly is made up of Sensor section and secondary instrument, and Sensor section mainly comprises vibrator, measuring tube, vibro-pickup, and the secondary instrument part comprises that mainly closed-loop control system and flow resolve system.Wherein the function of closed-loop control system is to make the measuring tube of CM F with its resonance frequency stable oscillation, provides and resolves signal for resolving system, and it is the key of CMF operate as normal, and its performance directly determines the flow calculation accuracy.
Closed-loop control system must satisfy amplitude condition and phase condition simultaneously.Traditional closed-loop control system is used Realization of Analog Circuit, complicated circuit, and generally use analog device to build; Receive temperature, noise effect bigger, poor anti jamming capability is easy to generate drift; Cause measuring accuracy lower, even make that measuring tube can't operate as normal.Therefore, in recent years, the digital closed loop control technology develops just gradually.
The digital closed loop control technology proposes by abroad taking the lead in, and develops for two more than ten years so far.The Manus P.Henry and the Mayela Zamora of Britain Oxford university have proposed a kind of control method, and this method has been described four kinds of patterns: random series pattern, zero output pattern, positive feedback pattern and digital synthesis model.At first generate the sinusoidal signal excitation measuring tube of random frequency and amplitude, after after a while, get into the zero output pattern; In the set time, pumping signal is zero always, after buret to be measured is stabilized in resonance frequency, gets into the positive feedback pattern; Processor calculates the frequency and the phase shift size of vibrating tube vibration, gets into digital synthesis model, produces pumping signal.This method utilizes ADC, DAC, FPGA and high speed processor to build the digital closed loop control system, and the vibrational state of monitoring sensor has and controls effect preferably in real time.But the modeling in advance of this method obtains the operating frequency range of measuring tube, and necessary its vibration frequency of measuring of each control, and control procedure is complicated, and processor speed is had relatively high expectations.In addition, hardware uses separate modules to build, and integrated level is low, and cost is too high, has limited it and has applied.(Manus?P.Henry，Mayela?E.Zamora.STARTUP?AND?OPERATIONAL?TECHNIQUES?FOR?A?DIGITAL?FLOWMETER[P].2006，US7146280B2；Mayela?Zamora，Manus?P.Henry.An?FPGA?Implementation?of?a?Digital?Coriolis?Mass?FloW?Metering?Drive?System[J].IEEE?Transactions?on?Industrial?Electronics，2008，55(7)：2820-2831).
Summary of the invention
Technology of the present invention is dealt with problems and is: the deficiency that overcomes prior art; A kind of Ke's mass flowmeter digital closed-loop control system is provided; Simplified circuit, the vibration frequency of real-time follow-up pipe has improved CMF closed-loop control performance; Guarantee the work of sensor normal and stable, improved the measuring accuracy of CMF to a certain extent.
Technical solution of the present invention: a kind of Ke's mass flowmeter digital closed-loop control system comprises: amplitude limiter circuit, inverting amplifier, effective value converter, analog-digital converter (ADC), processor, multiplication D/A converter (MDAC) and amplifier; The vibration signal of vibro-pickup output amplifies through amplitude limiter circuit amplitude limit, inverting amplifier, and the conversion of signals after will being amplified by the effective value converter is an effective value, and ADC carries out sampled measurements to said effective value and delivers in the processor; Processor compares said effective value and predefined target effective value and obtains error amount; And utilize non-linear amplitude control method to adjust the amplitude of MDAC output signal in real time; Its implementation procedure is: measuring tube is in vibration processes; When error amount is higher than a certain threshold value, the pumping signal of processor control MDAC output maximum amplitude; When error amount during less than this threshold value, operation parameter is regulated the amplitude of pumping signal from the PI control method of adjusting; The amplitude of said MDAC output signal reaches vibrator as pumping signal after amplifier amplifies, make measuring tube with stable amplitude vibration; The reference voltage of MDAC is directly provided by the vibration signal after amplifying through inverting amplifier simultaneously; Said MDAC is set as anti-phase output, i.e. output voltage and reference voltage anti-phase is after twice anti-phase; Realize 360 ° of fixed phase drifts on the hardware; Satisfy the phase condition of closed-loop control, make the sinusoidal signal frequency of MDAC output and the signal frequency of vibro-pickup output be consistent simultaneously, with the vibration frequency of tracking measurement pipe; When the measuring tube stable oscillation, the vibration frequency of this moment is the resonance frequency of the measuring tube of coriolis mass flow sensor.
In order to shorten the response time of this closed-loop control system; According to the error amount size; The scale-up factor Kp and the integral coefficient Ki of the PI link of adjustment PID controller make pick-up signal effective value can reach setting value fast, thereby make closed-loop system can get into steady-working state sooner.
Principle of the present invention: the present invention uses MDAC to realize the CMF closed-loop control with the method that non-linear amplitude control combines.Use MDAC and processor to produce pumping signal on the hardware; Because the reference voltage of MDAC directly provides after being amplified by the vibration signal process anti-phase of measuring tube, and MDAC is set to anti-phase output, twice anti-phase makes the exciting signal frequency of output and the vibration signal of phase place and measuring tube be consistent; Therefore; Can satisfy the phase condition of closed-loop system on the hardware, software only need be controlled excitation signal amplitude, and the amplitude condition that satisfies closed-loop system gets final product.Utilize the effective value change-over circuit to convert sinusoidal signal into effective value; Use high-precision A/D to measure the effective value of this sinusoidal vibration signal; Compare with predefined effective value, try to achieve error amount, and according to its size; Adopt the output drive signal amplitude of non-linear amplitude control method adjustment MDAC, make it satisfy the amplitude condition.
The present invention's advantage compared with prior art is:
(1) the present invention adopts MDAC output CMF pumping signal; This MDAC reference voltage is to provide after vibro-pickup output signal amplifies through anti-phase by the measuring tube vibration signal; And MDAC is set to anti-phase output; Twice anti-phase makes the exciting signal frequency of output and the vibration signal of phase place and measuring tube be consistent, and can satisfy the phase condition of closed-loop control on the hardware, simplified the design of software section;
(2) the present invention adopts non-linear amplitude control method to adjust the digital quantity of MDAC in real time, makes the suitable pumping signal of its output amplitude.Promptly when error amount reaches a certain threshold value, the sinusoidal signal of MDAC output maximum amplitude, in case error less than this threshold value, then operation parameter is from the amplitude of adjusting PI control method adjustment MDAC output signal.For improving the performance of closed-loop control system; Shorten the response time, make the measuring tube rapid adjustment to setting amplitude, according to the error amount size with the resonance frequency stable oscillation; Suitably adjust the coefficient of each link of PI controller; PI control method than common has greatly shortened the response time, has improved antijamming capability;
(3) the present invention is simple in structure, uses device less, and major part is a digital device, has avoided analog device to introduce the situation of too much noise, has reduced noise source, has stronger antijamming capability, has also reduced cost simultaneously, has certain marketing potentiality.
Description of drawings
Fig. 1 is a structured flowchart of the present invention;
Fig. 2 is processor realization flow figure of the present invention;
Fig. 3 is parameter self-tuning PI control structure figure of the present invention;
Fig. 4 is typical U type pipe CMF structural drawing.
Embodiment
As shown in Figure 1, Ke's mass flowmeter digital closed-loop control system 2 of the present invention comprises amplitude limiter circuit 3, inverting amplifier 4, effective value converter 5, analog-digital converter (ADC) 6, processor 7, multiplication D/A converter (MDAC) 8 and amplifier 9.Wherein amplitude limiter circuit 3, inverting amplifier 4, effective value converter 5, analog-digital converter (ADC) 6 are formed the effective value detecting device, detect the vibration signal effective value of measuring tube 11; Multiplication D/A converter (MDAC) 8 is formed excitation signal generator with amplifier 9, produces the variable pumping signal of amplitude and drives measuring tube 11 vibrations.
As shown in Figure 2; Processor 7 of the present invention is through the target effective value of serial port setting measuring tube 11 vibration signals, and effective value converter 5 carries out effective value with ADC6 to the sinusoidal signal of vibro-pickup 12 outputs and detects, and processor 7 compares detected effective value signal and predefined target effective value; If error is greater than a certain threshold value; Then control the maximum sinusoidal signal of MDAC 8 output amplitudes, otherwise then operation parameter is from the digital input amount of the PI control method adjustment MDAC 8 that adjusts; Processor 7 control MDAC8 produce the sinusoidal signal of respective magnitudes; Reach vibrator 10 through amplifying the back as pumping signal, adjust the vibrational state of measuring tube 11 repeatedly, sentence constant amplitude vibration in its resonance frequency up to measuring tube 11.
As shown in Figure 3, the present invention adopts parameter self-tuning PI control method, according to the error amount size; The scale-up factor Kp and the integral coefficient Ki of the PI link of adjustment PID controller; Promptly when Error Absolute Value big (scope of the invention is got more than or equal to 50), Kp gets higher value (the present invention gets 25), and Ki gets zero; When Error Absolute Value was median size (scope of the invention is got more than or equal to 10, less than 50), Kp got medium value (the present invention gets 20), and Ki gets smaller value (the present invention gets 0.0005); When Error Absolute Value continued to reduce (scope of the invention is got more than or equal to 1, less than 10), Kp should get smaller value (the present invention gets 5), and Ki gets medium value (the present invention gets 0.01); When Error Absolute Value reaches minimum (scope of the invention is got less than 1); Kp should get medium value (the present invention gets 10); Ki gets maximal value (the present invention gets 0.02); Make pick-up signal effective value can reach setting value fast, thereby make closed-loop system can get into steady-working state sooner, this method is faster than traditional P I control method response speed.
The effective value measuring ability is mainly realized by inverting amplifier 4, effective value converter 5 and analog-digital converter 6; Effective value converter 5 can adopt AD637 etc.; Analog-digital converter 6 can adopt ADS7816 etc., and inverting amplifier 4 realizes that enlargement factor is 7.4 times.
Pumping signal generation function realizes that by multiplication D/A converter (MDAC) 8 and amplifier 9 wherein the characteristics of MDAC are that reference voltage can be adjusted, and like the AD5429 of AD company etc., amplifier 9 realizes that enlargement factors are 11 times.
The present invention does not set forth the known technology that part belongs to those skilled in the art in detail.
Claims (2)
1. a Ke's mass flowmeter digital closed-loop control system is characterized in that comprising: amplitude limiter circuit (3), inverting amplifier (4), effective value converter (5), analog-digital converter (ADC) (6), processor (7), multiplication D/A converter (MDAC) (8) and amplifier (9); The vibration signal of vibro-pickup (12) output amplifies through amplitude limiter circuit (3) amplitude limit, inverting amplifier (4), and the conversion of signals after will being amplified by effective value converter (5) is an effective value, and ADC (6) carries out sampled measurements to said effective value and delivers in the processor (7); Processor (7) compares said effective value and predefined target effective value and obtains error amount; And utilize non-linear amplitude control method to adjust the amplitude of MDAC (8) output signal in real time; Said non-linear amplitude control method implementation procedure is: measuring tube (11) is in vibration processes; When error amount is higher than a certain threshold value, the pumping signal of processor (7) control MDAC (8) output maximum amplitude; When error amount during less than this threshold value, operation parameter is regulated the amplitude of pumping signal from the PI control method of adjusting; The amplitude of said MDAC (8) output signal reaches vibrator (10) as pumping signal after amplifier (9) amplifies, make measuring tube (11) with stable amplitude vibration; The reference voltage of MDAC (8) is directly provided by the vibration signal after amplifying through inverting amplifier (4) simultaneously; Said MDAC (8) is set as anti-phase output, i.e. output voltage and reference voltage anti-phase is after twice anti-phase; Realize 360 ° of fixed phase drifts on the hardware; Satisfy the phase condition of closed-loop control, make the sinusoidal signal frequency of MDAC (8) output and the signal frequency of vibro-pickup (12) output be consistent simultaneously, with the vibration frequency of tracking measurement pipe (11); When measuring tube (11) stable oscillation, the vibration frequency of this moment is the resonance frequency of the measuring tube (11) of coriolis mass flow sensor (1).
2. Ke's mass flowmeter digital closed-loop control system according to claim 1; It is characterized in that: the PI control method that described PI control method is a parameter self-tuning; Promptly according to the residing scope of Error Absolute Value, adjust the scale-up factor Kp and the integral coefficient Ki of PI link, concrete implementation procedure is: when Error Absolute Value is big; Kp gets higher value, and Ki gets zero; When Error Absolute Value was median size, Kp got medium value, and Ki gets smaller value; When Error Absolute Value continued to reduce, Kp got smaller value, and Ki gets medium value; When Error Absolute Value reaches hour, Kp gets medium value, and Ki gets maximal value.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104764559A (en) * | 2015-03-20 | 2015-07-08 | 西北工业大学 | Closed-loop control circuit of silicon resonant pressure sensor and realization method thereof |
| CN105865554A (en) * | 2015-02-05 | 2016-08-17 | 横河电机株式会社 | Resonance circuit used for measurement device and measurement device |
| CN108072411A (en) * | 2016-11-18 | 2018-05-25 | 克洛纳测量技术有限公司 | For running the method for Coriolis mass and flow measuring instrument and Coriolis mass and flow measuring instrument |
| CN111141333A (en) * | 2020-01-20 | 2020-05-12 | 陕西四海测控技术有限公司 | Multichannel integrated form sensor data collection station |
| CN115962768A (en) * | 2023-03-16 | 2023-04-14 | 中国人民解放军国防科技大学 | Harmonic oscillator closed-loop excitation phase shift control method, device and equipment |
| CN117516666A (en) * | 2023-11-16 | 2024-02-06 | 北京首科实华自动化设备有限公司 | Quality factor measuring equipment and method for coriolis flowmeter |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105865554A (en) * | 2015-02-05 | 2016-08-17 | 横河电机株式会社 | Resonance circuit used for measurement device and measurement device |
| EP3054270B1 (en) * | 2015-02-05 | 2020-11-04 | Yokogawa Electric Corporation | Resonance circuit for measurement device and measurement device comprising such a resonance circuit |
| CN105865554B (en) * | 2015-02-05 | 2021-08-10 | 横河电机株式会社 | Resonant circuit for a measuring device and measuring device |
| CN104764559A (en) * | 2015-03-20 | 2015-07-08 | 西北工业大学 | Closed-loop control circuit of silicon resonant pressure sensor and realization method thereof |
| CN104764559B (en) * | 2015-03-20 | 2017-04-26 | 西北工业大学 | Closed-loop control circuit of silicon resonant pressure sensor and realization method thereof |
| CN108072411A (en) * | 2016-11-18 | 2018-05-25 | 克洛纳测量技术有限公司 | For running the method for Coriolis mass and flow measuring instrument and Coriolis mass and flow measuring instrument |
| CN108072411B (en) * | 2016-11-18 | 2020-11-10 | 克洛纳测量技术有限公司 | Method for operating a coriolis mass flow measuring device and coriolis mass flow measuring device |
| CN111141333A (en) * | 2020-01-20 | 2020-05-12 | 陕西四海测控技术有限公司 | Multichannel integrated form sensor data collection station |
| CN115962768A (en) * | 2023-03-16 | 2023-04-14 | 中国人民解放军国防科技大学 | Harmonic oscillator closed-loop excitation phase shift control method, device and equipment |
| CN117516666A (en) * | 2023-11-16 | 2024-02-06 | 北京首科实华自动化设备有限公司 | Quality factor measuring equipment and method for coriolis flowmeter |
| CN117516666B (en) * | 2023-11-16 | 2024-06-04 | 北京首科实华自动化设备有限公司 | Quality factor measuring equipment and method for coriolis flowmeter |
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