CN104792379A - Coriolis mass flowmeter amplitude self-adaptation control method based on fluid state detecting - Google Patents
Coriolis mass flowmeter amplitude self-adaptation control method based on fluid state detecting Download PDFInfo
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- CN104792379A CN104792379A CN201510164860.3A CN201510164860A CN104792379A CN 104792379 A CN104792379 A CN 104792379A CN 201510164860 A CN201510164860 A CN 201510164860A CN 104792379 A CN104792379 A CN 104792379A
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Abstract
The invention discloses a Coriolis mass flowmeter amplitude self-adaptation control method based on fluid state detecting. An ultrasonic transducer is arranged at an inlet end of a Coriolis mass flowmeter detecting pipe, through the attenuation effect on ultrasonic signals from impurities such as air bubbles, whether the amplitude value of received signals is changed suddenly is detected and judged via a threshold value comparer, whether impurities exist at a fluid state is obtained, and then switching of fixed PID and fuzzy PID amplitude controllers is carried out. According to the method, by detecting on the fluid state and self-adaptation controller switching, high-precision stable state control performance can be kept, system dynamic response speed can be improved, measuring pipe vibration stopping is avoided, stable vibration is reestablished quickly, the self adaptability of Coriolis mass flowmeter measuring pipe amplitude control is enhanced, and the reliability and the metering performance of a Coriolis mass flowmeter under a complex working condition are improved.
Description
Technical field
The present invention relates to a kind of Coriolis flowmeter control method, particularly relate to a kind of Coriolis flowmeter amplitude self-adaptation control method detected based on fluid state.
Background technology
Coriolis flowmeter has high precision, wide-range ratio, reproducible feature, represents the highest level of Technologies of Direct Mass Flow Measurement, is widely used at industrial circles such as oil, chemical industry, pharmacy, food, Trade Measures.Its principle of work is, the Coriolis force be directly proportional to mass rate produced when utilizing fluid to flow in the pipeline vibrated, directly measurement quality flow.
Coriolis flowmeter is the vibration work based on measuring tube, and industry member generally believes, the accurate measurement of amplitude stability to Coriolis flowmeter of measuring tube vibration has material impact.Also find in Coriolis flowmeter site of deployment, the change (as become two-phase flow from single-phase flow) of fluid state can cause the change of measuring tube vibration damping, destroys the amplitude stability of measuring tube, and then reduces the measuring accuracy of Coriolis flowmeter.But in the various application occasions of Coriolis flowmeter; inevitably often there will be bubble flow (being namely mixed into bubble in liquid) or be mixed into other solids; now measuring tube vibrational system damping can increase one to two orders of magnitude, and occurs acutely to beat.Generally adopt positive feedback driving circuit as the drive scheme of measuring tube vibrational system in Coriolis flowmeter, directly as drive singal after being multiplied by a driving gain K by measuring tube vibration signal, thus the key of measuring tube amplitude controlling is the determination driving gain K.Gain K is driven to be using the deviation of vibration signal amplitude and setting amplitude as input signal, via what obtain after amplitude controller computing.Amplitude control method the most frequently used is at present that fixing PID controls, single at fluid media (medium), and during the parameter stability of measuring tube vibrational system, fixing PID controls to obtain highly stable amplitude, ensures the high precision advantage of Coriolis flowmeter.But change at fluid state, when the parameter of measuring tube vibrational system changes, fixing PID controls to remain on best control performance, need longer stabilization time, when changing greatly, even there will be after measuring tube failure of oscillation cannot starting of oscillation again, thus the situation causing Coriolis flowmeter to lose efficacy.
Change for fluid state and cause the fast-changing situation of the parameter of measuring tube vibrational system, existing solution is fuzzy amplitude control method.The method is according to the change of vibration amplitude, with reference to the experience of adjusting of industry member pid parameter, adjust pid parameter in real time, to respond to the Parameters variation of measuring tube vibrational system, avoid the failure of oscillation of measuring tube, and the fast quick-recovery of amplitude is stablized, improve Coriolis flowmeter at bubble flow or containing the reliability in other impurity situation and measuring accuracy.But fuzzy-adaptation PID control is when measuring tube Vibration Parameters is stable, compared with controlling with fixing PID, frequently beating of pid parameter can be caused on the one hand, reduce the steady-state behaviour of amplitude controlling, negative effect is caused to the metering of Coriolis flowmeter, weakens its high precision advantage; On the other hand, fuzzy PID control method needs to calculate pid parameter in real time and adjust, and calculates and data storage capacities requires high to the data of system, and long luck guild significantly increases system power dissipation, improves the application cost of Coriolis flowmeter.
Summary of the invention
In order to obtain the amplitude stability of Coriolis flowmeter measuring tube under complex fluid state, the invention provides a kind of Coriolis flowmeter amplitude self-adaptation control method detected based on fluid state, different amplitude control methods is adopted for different fluid states, strengthen the adaptivity of amplitude controlling, while the high precision advantage keeping Coriolis flowmeter under stable state, improve its dynamic response performance, improve the reliability of Coriolis flowmeter under complex working condition and metering performance.
The step of the technical solution adopted for the present invention to solve the technical problems is as follows:
1) between the inlet end and fluid line of Coriolis flowmeter measuring tube, install fluid state pick-up unit, convection cell state detects; Fluid state pick-up unit comprises liquid ultrasonic wave launcher, liquid ultrasonic receiver and threshold comparator, liquid ultrasonic wave launcher, liquid ultrasonic receiver are arranged on the both sides of installing pipeline section symmetry respectively, liquid ultrasonic receiver connect threshold comparer;
2) ultrasound wave that liquid ultrasonic wave launcher is launched is received by liquid ultrasonic receiver after installing the fluid in pipeline section, compare detection ultrasound wave Received signal strength amplitude by threshold comparator whether to undergo mutation, if do not undergo mutation, not containing impurity in fluid, if undergo mutation, containing impurity in fluid;
3) whether contain the result of impurity in real time according to the fluid state of above-mentioned steps, be fixed the real-time switching of PID and fuzzy amplitude controller, realize the adaptive control of flowmeter amplitude.
In described fluid, impurity comprises bubble or solids.
When within a ultrasonic signal cycle, there is rising edge in described threshold comparator, and expression fluid state is stable state, and ultrasound wave Received signal strength amplitude is not undergone mutation wherein not containing impurity; When within least one ultrasonic signal cycle, there is not rising edge in described threshold comparator, and ultrasound wave Received signal strength amplitude is undergone mutation wherein containing impurity.
Described step 2) threshold comparator adopts analog single threshold comparer.
The end of oppisite phase of described threshold voltage access threshold comparator, the in-phase end of ultrasound wave Received signal strength access threshold comparator.
Described step 3) in the switching mode of amplitude controller specific as follows: to obtain if detect in fluid containing impurity, then the mode of operation of single-chip microcomputer being switched to fuzzy amplitude controller; Obtain if detect in fluid not containing impurity; Then the mode of operation of single-chip microcomputer is switched to fixing PID amplitude controller.
Described threshold comparator is connected with single-chip microcomputer, the timer of cycle timing during single-chip microcomputer is connected with and judges for ultrasound wave Received signal strength amplitude, single-chip microcomputer is connected through the control end of driver module with Coriolis flowmeter measuring tube, and single-chip microcomputer drives gain signal to be sent to Coriolis flowmeter measuring tube by the controller generation switched and controls.
The beneficial effect that the present invention has compared with background technology is:
The present invention uses a pair liquid ultrasonic wave transducer to detect fluids within pipes state at Coriolis flowmeter measuring tube inlet upstream, and utilize threshold comparator process ultrasound wave Received signal strength and compare, convection cell state carries out anticipation.
When fluid is the impurity such as stable state bubble-free, the fixing PID controller obtained of adjusting under adopting Steady Experimental carries out amplitude controlling, obtains the high precision control performance under stable state; When containing the impurity such as bubble in fluid, the fuzzy controller adopting bubble flow simulation optimization to obtain carries out amplitude controlling, improves system dynamic responding speed, avoids the failure of oscillation of measuring tube, and Fast Reconstruction stable oscillation.
The inventive method enhances the adaptivity of Coriolis flowmeter measuring tube amplitude controlling, improves the reliability of Coriolis flowmeter under complex working condition and metering performance.
Accompanying drawing explanation
Fig. 1 is fluid state pick-up unit scheme of installation of the present invention.
Fig. 2 is the ultrasound examination schematic diagram of fluid state of the present invention.
Fig. 3 is amplitude self-adaptation control method process flow diagram of the present invention.
In figure: 1, fluid line; 2, fluid state pick-up unit; 3, Coriolis flowmeter measuring tube; 4, bubble; 5, threshold comparator; 6, single-chip microcomputer; 7, timer; 2_1, installation pipeline section; 2_2, liquid ultrasonic wave launcher; 2_3, liquid ultrasonic receiver; 2_4, pad.
Embodiment
Below in conjunction with drawings and Examples, the present invention will be further described.
The inventive method comprises the following steps:
1) as shown in Figure 1, between the inlet end and fluid line 1 of Coriolis flowmeter measuring tube 3, install fluid state pick-up unit 2, convection cell state detects; As shown in Figure 2, fluid state pick-up unit 2 comprises liquid ultrasonic wave launcher 2_2, liquid ultrasonic receiver 2_3 and threshold comparator 5, liquid ultrasonic wave launcher 2_2, liquid ultrasonic receiver 2_3 are arranged on the both sides of installing pipeline section 2_1 symmetry respectively, liquid ultrasonic receiver 2_3 connect threshold comparer 5; Threshold comparator 5 connects single-chip microcomputer, single-chip microcomputer is connected with timer, single-chip microcomputer is connected through the control end of driver module with Coriolis flowmeter measuring tube 3, and liquid ultrasonic wave launcher 2_2, liquid ultrasonic receiver 2_3 are arranged in the endoporus installing pipeline section 2_1 both sides by pad 2_4;
2) ultrasound wave that liquid ultrasonic wave launcher 2_2 launches is received by liquid ultrasonic receiver 2_3 after installing the fluid in pipeline section 2_1, whether compare detection ultrasound wave Received signal strength amplitude by threshold comparator 5 to undergo mutation, whether ultrasound wave can make ultrasound wave Received signal strength amplitude change and then judge wherein containing impurity after impurity decay in fluid; If do not undergo mutation, not containing impurity in fluid, if undergo mutation, containing impurity in fluid; In its fluid, impurity refers to and may comprise bubble or solids.
Whether ultrasound wave Received signal strength of the present invention is undergone mutation and is judged by rising edge, and in the event of rising edge, amplitude is not suddenlyd change; If there is not rising edge, then signal amplitude has diminished, and there occurs sudden change.
Fluid state pick-up unit 2 of the present invention comprises a liquid ultrasonic wave launcher and a liquid ultrasonic receiver, and they are arranged on the inlet end upstream of Coriolis flowmeter measuring tube 3; The ultrasound wave that liquid ultrasonic wave launcher is launched is propagated in the liquid of uniform density does not almost have energy loss, and the impurity such as bubble or other particle has attenuation to ultrasonic signal, can cause the reduction suddenly of ultrasound wave Received signal strength amplitude.
Preferred threshold comparator 5 adopts analog single threshold comparer.The end of oppisite phase of threshold voltage access threshold comparator 5, its threshold voltage is compromised by the amplitude of ultrasound wave Received signal strength in steady-state fluid experiment and bubbles fluid experiment and is determined.The in-phase end of ultrasound wave Received signal strength access threshold comparator 5; When ultrasound wave Received signal strength is higher than threshold voltage, threshold comparator 5 exports high level, on the contrary output low level.
When within a ultrasonic signal cycle, there is rising edge in threshold comparator 5, and expression fluid state is stable state, do not undergo mutation wherein not containing impurity; When within least one ultrasonic signal cycle, threshold comparator output signal 5 is always low level, does not occur rising edge, undergos mutation wherein containing impurity.
3) whether contain the result of impurity in real time according to the fluid state of above-mentioned steps, be fixed the real-time switching of PID and fuzzy amplitude controller, realize the adaptive control of flowmeter amplitude.
In step 3, the switching mode of amplitude controller is specific as follows: obtain if detect in fluid containing impurity, then the mode of operation of single-chip microcomputer is switched to fuzzy amplitude controller, namely within a ultrasonic signal cycle, threshold comparator 5 outputs signal and does not occur rising edge, switch to fuzzy amplitude controller at once during this end cycle, its parameter is by obtaining bubble flow simulation optimization; Obtain if detect in fluid not containing impurity; Then the mode of operation of single-chip microcomputer is switched to fixing PID amplitude controller, namely within a ultrasonic signal cycle, there is rising edge in threshold comparator 5, switches to fixing PID amplitude controller during this end cycle at once, and its parameter obtains by adjusting under Steady Experimental.
The present invention is based on the impurity such as bubble to hyperacoustic attenuation, detected by ultrasonic transducer convection cell state; By threshold comparator transducer receiving end signal processed and compare, whether judging in fluid containing bubble; According to the result of determination of fluid state, switch different amplitude control methods.
The control procedure of the inventive method is as shown in Figure 3: 1. Coriolis flowmeter measuring tube amplitude control system is in completion system initialization, after timer initialization n=N; (ratio of N=ultrasonic signal cycle length and time Singlechip clock signal period)
2. from measuring tube vibration signal
place reads vibration amplitude; 3. then read comparer from threshold comparator 5 to export; 4. and to carry out decision signal be rising edge: if 5. signal is rising edge, then timer reset, n=N; If 6. there is not rising edge signal, then the counting n=n-1 of timer.7. continue to judge whether n meets n>0 in the following ways:
If 8. n>0, then judge that fluid is as stable state, 9. enables fixing PID controller simultaneously,
obtain driving gain K; In other words, if 10. n≤0, then judge there is bubble in fluid,
enable fuzzy controller simultaneously,
obtain driving gain K.
then driving gain K is passed to measuring tube positive feedback driving circuit,
finally obtain the measuring tube vibration signal after modulating.
Specific embodiments of the invention and implementation process as follows:
As shown in Figure 1, in concrete enforcement, Coriolis flowmeter measuring tube 3 adopts double-U-shaped measuring tube, single tube diameter is 6mm, threshold comparator 5 adopts analog single threshold comparer, fluid state pick-up unit 2 is installed between fluid line 1 and Coriolis flowmeter measuring tube 3, before fluid enters Coriolis flowmeter measuring tube, fluids within pipes state is detected, for Coriolis flowmeter provides fluid state anticipation information.
As shown in Figure 2, fluid state pick-up unit 2 comprises installation pipeline section 2_1, liquid ultrasonic wave launcher 2_2 and liquid ultrasonic receiver 2_3.Liquid ultrasonic wave launcher 2_2 and liquid ultrasonic receiver 2_3 installs so that correlation mode is symmetrical on installation pipeline section 2_1, is connected by taper thread.Liquid ultrasonic wave launcher 2_2 launches ultrasonic signal, final arrival liquid ultrasonic receiver 2_3 after passing over fluid media (medium).Ultrasound wave Received signal strength accesses threshold comparator 5 in-phase end subsequently, threshold voltage V
taccess threshold comparator 5 end of oppisite phase, threshold voltage V
tfor 0.8V: when in fluid during bubble-free 4, ultrasound wave Received signal strength peak value is that 1V is greater than threshold voltage V
t0.8V, threshold comparator 5 exports high level, and high level signal is 3V, and when there is bubble 4 in fluid, ultrasound wave Received signal strength peak value is less than threshold voltage V
t0.8V, threshold comparator 5 continues output low level, and low level signal is 0V.Single-chip microcomputer 6 is sampled to the output signal of threshold comparator 5 under the effect of clock signal, when there is signal rising edge, and reset timer 7, otherwise the counter of timer 7 subtracts one.When there is bubble 4 in fluid, within a period of time threshold comparator 5 output signal in all there is no rising edge, the count value of timer 7 reduces to 0, and be determined with bubble 4 and occur, amplitude control method switches to fuzzy-adaptation PID control.
Comprehensive, the present invention adopts a pair liquid ultrasonic wave transducer, bubble before fluid enters Coriolis flowmeter measuring tube in convection cell carries out detection provides anticipation, realize the timely switching of Coriolis flowmeter measuring tube amplitude control method, enhance the adaptivity of Coriolis flowmeter measuring tube amplitude controlling, improve the reliability of Coriolis flowmeter under complex working condition and metering performance, there is outstanding technique effect.
Above-mentioned embodiment is used for explaining and the present invention is described, instead of limits the invention, and in the protection domain of spirit of the present invention and claim, any amendment make the present invention and change, all fall into protection scope of the present invention.
Claims (7)
1., based on the Coriolis flowmeter amplitude self-adaptation control method that fluid state detects, it is characterized in that the method is as follows:
1) between the inlet end and fluid line (1) of Coriolis flowmeter measuring tube (3), install fluid state pick-up unit (2), convection cell state detects; Fluid state pick-up unit (2) comprises liquid ultrasonic wave launcher (2_2), liquid ultrasonic receiver (2_3) and threshold comparator (5), liquid ultrasonic wave launcher (2_2), liquid ultrasonic receiver (2_3) are arranged on respectively installs the symmetrical both sides of pipeline section (2_1), liquid ultrasonic receiver (2_3) connect threshold comparer (5);
2) ultrasound wave that liquid ultrasonic wave launcher (2_2) is launched is received by liquid ultrasonic receiver (2_3) after installing the fluid in pipeline section (2_1), compare detection ultrasound wave Received signal strength amplitude by threshold comparator whether to undergo mutation, if do not undergo mutation, not containing impurity in fluid, if undergo mutation, containing impurity in fluid;
3) whether contain the result of impurity in real time according to the fluid state of above-mentioned steps, be fixed the real-time switching of PID and fuzzy amplitude controller, realize the adaptive control of flowmeter amplitude.
2. a kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state monitoring according to claim 1, is characterized in that: in described fluid, impurity comprises bubble or solids.
3. a kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state monitoring according to claim 1, it is characterized in that: when within a ultrasonic signal cycle, there is rising edge in described threshold comparator (5), expression fluid state is stable state, and ultrasound wave Received signal strength amplitude is not undergone mutation wherein not containing impurity; When within least one ultrasonic signal cycle, there is not rising edge in described threshold comparator output signal (5), and ultrasound wave Received signal strength amplitude is undergone mutation wherein containing impurity.
4. a kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state monitoring according to claim 1, is characterized in that: described step 2) threshold comparator (5) adopts analog single threshold comparer.
5. a kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state monitoring according to claim 1, it is characterized in that: the end of oppisite phase of described threshold voltage access threshold comparator (5), the in-phase end of ultrasound wave Received signal strength access threshold comparator (5).
6. a kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state monitoring according to claim 1, it is characterized in that: in described step 3), the switching mode of amplitude controller is specific as follows: obtain if detect containing impurity in fluid, then the mode of operation of single-chip microcomputer is switched to fuzzy amplitude controller; Obtain if detect in fluid not containing impurity; Then the mode of operation of single-chip microcomputer is switched to fixing PID amplitude controller.
7. a kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state monitoring according to claim 1, it is characterized in that: described threshold comparator (5) is connected with single-chip microcomputer, the timer of cycle timing during single-chip microcomputer is connected with and judges for ultrasound wave Received signal strength amplitude, single-chip microcomputer is connected through the control end of driver module with Coriolis flowmeter measuring tube (3), and single-chip microcomputer drives gain signal to be sent to Coriolis flowmeter measuring tube (3) by the controller generation switched and controls.
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