CN103984873A - Method for applying digital signal processing algorithm to DSP system - Google Patents
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Abstract
The invention relates to the technical field of signal processing and application of mass flow meters based on the Coriolis principle, in particular to a method for applying a digital signal processing algorithm to a DSP system. Based on the flow time-varying characteristic, the digital signal processing algorithm based on an adaptive lattice IIR notching filter and the Hilbert transform method is designed. According to the algorithm, iterative operation is not needed, and therefore error accumulation does not occur, stability of measurement accuracy can be kept, and convergence time is saved. Finally, a Coriolis mass flow meter software and hardware system based on a digital signal processor (DSP) is designed in a modularized mode, and the algorithm is transplanted onto the DSP system on the premise that accuracy loss is reduced. By the adoption of the method, high-speed and high-accuracy calculation of parameters of Coriolis mass flow meters is realized.
Description
Technical field
The mass flowmeter signal the present invention relates to based on Coriolis principle is processed and applied technical field, the particularly application process of a kind of digital signal processing algorithm on dsp system.
Background technology
Coriolis mass flowmeters (Coriolis Mass Flowmeter, english abbreviation is CMF, hereinafter to be referred as coriolis mass flowmeters) a kind ofly according to Coriolis force principle, develop, the fluid in rotating system simultaneously moving linearly will produce a kind of Coriolis force being directly proportional to fluid mass.This flowmeter was taken the lead in succeeding in developing by Micro Motion company in 1977, and it not only has higher accuracy, stability, repeatability, and in measuring tube, there is no choked flow element, had improved to a great extent reliability and serviceable life.The clean fuel compressed natural gas (CNG) that current most of automobile is used measures with it, and also more and more in the application of the departments such as oil, papermaking, building materials, food, medicine, the energy, bioengineering, space flight.
Can only measurement volumes flow different from common flowmeter, coriolis mass flowmeters can directly be measured fluid mass flow accurately, it is external except can be used in all kinds of normal flows of measurement, can also be for measuring unconventional fluid, as batch of material stream/two-phase flow, liquid gas, slurries and compressed natural gas, therefore, the application of coriolis mass flowmeters is also more and more extensive, but because technical development is ripe not enough, measuring accuracy does not also reach people's expected effect.
Both at home and abroad the research of coriolis mass flowmeters was also made certain gains in recent years.
Beijing Aviation university research for signal processing method and the system of novel straight pipe type and class straight pipe type Coriolis flowmeter, the method is usingd fft algorithm as core, by fpga logic circuit and peripheral circuit, realize the frequency-tracking to sensor signal, adjust Direct Digital Synthesizer (DDS) and generate V-CLK, can realize the closed-loop control to sample frequency, fft algorithm can be carried out integer-period sampled, that reduces that non-integer-period causes blocks formation spectral leakage.But the error of calculation of this system is larger.HeFei University of Technology is studied the drive system of Coriolis flowmeter and digital signal processing method, in dsp system, the zero crossing of input signal is analyzed to judgement, determines the phase place of signal.And in 2010, completed and take system testing and the experimental calibration of the CMF transmitter that DSP is core, this system combines adaptive lattice type notch filter and SDTFT recursive algorithm, frequency that can accurate tracking signal.But be easily subject to noise, affect comparatively seriously, computational accuracy is difficult to reach requirement, owing to there being interative computation, its error is accumulation constantly, causes measuring accuracy to decline.
The scheme of US Patent No. 6073495 is that the differential signal of two-way sensor output signal is processed and calculated phase differential by quadrature demodulation, utilizes its component to control the amplitude size of two-way sensor signal simultaneously.The scheme of the US20020038186 of Foxboro house journal is calculated rate value, amplitude and phase differential again after first using the signal close with signal frequency to two paths of signals quadrature demodulation.Oxonian Henry proposes to adopt the two-way sensor output signal of synchronous modulation technical finesse Coriolis flowmeter.The method is by modulation signal, after filtering after the new function that obtains of structure can reflected signal amplitude and frequency information.First Freeman has proposed the two paths of signals of use digital phase-locked loop (PLL) technical finesse Coriolis flowmeter in his patent.Compare with DFT method, the real-time of the method frequency-tracking, phase difference calculating is better; Frequency-tracking has stronger inhibiting effect to random noise and fixed frequency interference.But compare with ALE method, the required sampled point of the method is more, and calculated amount is larger, and to carry out Frequency Estimation be to adopt lookup table mode, and to having relatively high expectations of internal memory, it is larger that the calculating of phase differential is simultaneously subject to random noise impact, is the main cause of error.
Summary of the invention
The object of the present invention is to provide a kind of high speed, the application process of high precision computation digital signal processing algorithm on dsp system of realizing coriolis mass flowmeters flow parameter.
For achieving the above object, technical scheme of the present invention is: the application process of a kind of digital signal processing algorithm on dsp system, comprise the steps,
Step S01: according to coriolis mass flowmeters characteristic, design a kind of digital signal processing algorithm based on adaptive lattice type IIR notch filter and Hilbert transform method composition;
Step S02: the digital signal processing algorithm that described step S01 is obtained, be transplanted on dsp system;
Step S03: transplant the dsp system that has digital signal processing algorithm by described step S02, process the digital signal of coriolis mass flowmeters.
In embodiments of the present invention, described digital signal processing algorithm, specifically comprises the steps,
Step S21: signal filtering: the input signal of coriolis mass flowmeters is carried out to digital filtering, and carry out noise filtering, obtain predetermined frequency band signal; Then, by adaptive lattice type IIR notch filter, this predetermined frequency band signal is carried out to filtering processing, output strengthens signal;
Step S22: phase difference calculating: the enhancing signal described step S21 being obtained by phase differential algorithm carries out phase difference calculating;
Step S23: flow rate calculation: the phase difference value obtaining according to described step S22, calculates mistiming and the flow of signal.
In embodiments of the present invention, described phase differential algorithm, specific implementation process is as follows,
If strengthen signal through filtered two-way, be:
In formula:
for the amplitude of signal,
,
for phase place,
for digital angular frequency; From Euler's formula
, there is Hilbert conversion:
Two paths of signals, through Hilbert conversion, obtains only containing the analytic signal of positive frequency:
By tan and poor eliminate indigestion formula, had:
Above formula is carried out to arctangent cp cp operation and can try to achieve phase differential:
。
In embodiments of the present invention, described dsp system comprises primary controller and the power management module that is used to system power supply, signal condition and the acquisition module and the human-machine interface module that are connected with this primary controller.
In embodiments of the present invention, described signal condition and acquisition module are an AD modular converter.
In embodiments of the present invention, described human-machine interface module comprises LCD module and Keysheet module.
Compared to prior art, the present invention has following beneficial effect: the inventive method is through actual test, under different initial phase difference conditions, the coriolis flow result precision that adopts self-adaptation Lattice filter, Hilbert mapping algorithm to obtain is higher, and relative error is only 0.02%.
Accompanying drawing explanation
Fig. 1 is lattice type iir filter structural drawing.
Fig. 2 is that Hilbert measure phase difference realizes block diagram.
Fig. 3 is digital signal processing algorithm process flow diagram of the present invention.
Fig. 4 is adaptive lattice type notch filter algorithm flow chart.
Fig. 5 is that Hilbert mapping algorithm calculates phase differential process flow diagram.
Fig. 6 is system hardware structure block diagram of the present invention.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is specifically described.
The application process of a kind of digital signal processing algorithm of the present invention on dsp system, comprises the steps,
Step S01: according to coriolis mass flowmeters characteristic, design a kind of digital signal processing algorithm based on adaptive lattice type IIR notch filter and Hilbert transform method composition;
Step S02: the digital signal processing algorithm that described step S01 is obtained, be transplanted on dsp system;
Step S03: transplant the dsp system that has digital signal processing algorithm by described step S02, process the digital signal of coriolis mass flowmeters.
Described digital signal processing algorithm, specifically comprises the steps,
Step S21: signal filtering: the input signal of coriolis mass flowmeters is carried out to digital filtering, and carry out noise filtering, obtain predetermined frequency band signal; Then, by adaptive lattice type IIR notch filter, this predetermined frequency band signal is carried out to filtering processing, output strengthens signal;
Step S22: phase difference calculating: the enhancing signal described step S21 being obtained by phase differential algorithm carries out phase difference calculating;
Step S23: flow rate calculation: the phase difference value obtaining according to described step S22, calculates mistiming and the flow of signal.
Described phase differential algorithm, specific implementation process is as follows,
If strengthen signal through filtered two-way, be:
In formula:
for the amplitude of signal,
,
for phase place,
for digital angular frequency; From Euler's formula
, there is Hilbert conversion:
Two paths of signals, through Hilbert conversion, obtains only containing the analytic signal of positive frequency:
By tan and poor eliminate indigestion formula, had:
Above formula is carried out to arctangent cp cp operation and can try to achieve phase differential:
。
Described dsp system comprises primary controller and the power management module that is used to system power supply, signal condition and the acquisition module and the human-machine interface module that are connected with this primary controller; Described signal condition and acquisition module are an AD modular converter; Described human-machine interface module comprises LCD module and Keysheet module.
Be below embodiments of the invention.
The application process of a kind of digital signal processing algorithm of the present invention on dsp system, implementation procedure is as follows.
one, the digital signal processing algorithm main contents based on adaptive lattice type IIR notch filter and Hilbert transform method composition:
1) for the feature of time varying signal and the non-time varying signal of coriolis flow, set up flow probabilistic model.In actual measurement application, every physical parameter of coriolis mass flowmeters signal can not change on each sampled point;
formula (1)
formula (2)
formula (3)
formula (4)
In formula:
,
,
the amplitude, frequency, the phase place that represent respectively time varying signal,
,
with
for the white noise that Normal Distribution, average are 0, variance is 1,
,
,
with
determine the amplitude of moving about of corresponding parameter,
be called the coefficient that moves about, the 0-1 that obedience probability is P distributes, and determines the variation of corresponding parameter, and when P trends towards 1, every some variation of parameter, is exactly Time-varying Signal Model; When P trends towards 0, this model is non-time varying signal;
2) adaptive lattice type IIR notch filter
The structure of lattice type iir filter as shown in Figure 1, forms full zero point lattice type trapper and full limit lattice type trapper cascade.Its transport function is:
formula (5)
,
be respectively denominator part and the molecular moiety on equation right side,
be a FIR wave filter, therefore by being fixed on its zero point on unit circle, to reduce, calculate, so only need to regulate a parameter just can realize adaptive notch.
for weight coefficient, for calculating frequency input signal,
for offset parameter, its value determines the trap bandwidth of wave filter, and
press formula (6) convergence;
formula (6)
3) flow signal phase differential is asked in Hilbert conversion,
Hilbert measure phase difference realizes block diagram as shown in Figure 2, establishes through filtered two-way enhancing signal to be:
formula (7)
In formula:
for the amplitude of signal,
,
for phase place,
for digital angular frequency.From Euler's formula
, there is Hilbert conversion:
formula (8)
Two paths of signals, through Hilbert conversion, obtains only containing the analytic signal of positive frequency:
formula (9)
By tan and poor eliminate indigestion formula, had:
formula (10)
Above formula is carried out to arctangent cp cp operation and can try to achieve phase differential:
formula (11).
two, the digital signal processing algorithm of adaptive lattice type IIR notch filter and Hilbert conversion composition is transplanted on dsp system:
Digital signal processing algorithm mainly carries out the computing of mass data, is divided into filtering, phase difference calculating and flow rate calculation three parts.First input signal is carried out to digital filtering, noise is carried out to filtering, obtain the signal in certain frequency band, then this part signal is carried out to self-adaptation Lattice filter, before operation, need elder generation according to the feature of input signal, set the parameters of sef-adapting filter.Enhancing signal after filtering calculates phase differential by phase difference measurement algorithm, then according to formula (12) and formula (13), calculates mistiming and the flow of signal, and algorithm process flow process as shown in Figure 3;
formula (12)
In above formula,
for two paths of signals phase differential,
for signal digital angular frequency,
for sample frequency;
formula (13)
In above formula,
for flow,
for the angle elastic modulus of pipeline, r is the radius of U type pipe sweep, from formula (13), the mass rate of detected fluid and two-way flowtube vibration signal mistiming
there is proportional relation;
4) self-adaptation Lattice filter
The process flow diagram of adaptive lattice type notch filter algorithm as shown in Figure 4.The calculated amount of adaptive lattice type IIR notch filter algorithm is little, and tracking frequencies subtle change, and tracking accuracy is in time high, and the precision of tracking frequencies estimated value is better than 0.01%.This algorithm has the feature of flexible Application, can carry out frequency-tracking by adjusting initial value and the final value of parameter, is applicable to the complicated Coriolis flowmeter signals such as two-phase flow, batch of material stream.It should be noted that adaptive lattice type notch filter has filter function and obtains is the enhancing signal of input signal, the phase place that strengthens signal can change.Therefore, in use, guarantee that the parameter value of two trappers is just the same, two paths of signals produces same phase shift, does not affect phase differential result and calculates;
5) Hilbert mapping algorithm
Fig. 5 is that Hilbert mapping algorithm calculates phase differential flow process, two-way enhancing signal is after filtering carried out respectively to Hilbert conversion to be obtained after corresponding value, two paths of signals and figure signal calculate the tan wait until phase differential by formula (10), finally use formula (11) to carry out to this function the value that arctangent cp cp operation obtains is the phase differential of two paths of signals;
Algorithm also needs to average processing through the value calculating, otherwise can take a large amount of resources and produce very large calculated amount according to data such as the phase difference calculating mistiming of each point and flows.We adopt simple average mode to carry out phase difference value processing, first obtain each time 450 data are sued for peace and are got average, then mean value result in 1s are weighted to average computation.The benefit of doing like this can reduce calculated amount videlicet, can keep again the tracking velocity of algorithm.
three, the digital signal processing algorithm based on coriolis mass flowmeters and digital signal processing circuit (DSP) system realizes:
For high-speed computation and the real-time of implementation algorithm, adopt TMS320F28335 as core herein, by DSP minimum system, AD module, SARAM, LCD module, Keysheet module, EEPROM module and 4 ~ 20mA pulse output module form;
As shown in Figure 6, DSP minimum system mainly comprises jtag circuit, crystal oscillator, power supply etc. to the structured flowchart of digital information processing system (DSP).System is mainly used buffer memory serial port McBSP, DMA, SPI and the general input/output port GPIO on dsp chip, has also used the external expansion interface XINTF monocycle of DSP simultaneously and has accessed random access memory SARAM, the data that are used in storage algorithm operational process.In system, configured EEPROM, for preserving parameter setting and the postrun measurement result of algorithm of algorithm.For observing system operation result intuitively and change parameter configuration, added human-machine interface module, comprise a LCD and mechanical key keyboard, the I/O by configuration DSP realizes.System also has watchdog module for DSP being detected and resetting.
Through actual test, under different initial phase difference conditions, the coriolis flow result precision that adopts self-adaptation Lattice filter, Hilbert mapping algorithm to obtain is higher, and relative error is only 0.02%.
Be more than preferred embodiment of the present invention, all changes of doing according to technical solution of the present invention, when the function producing does not exceed the scope of technical solution of the present invention, all belong to protection scope of the present invention.
Claims (6)
1. the application process of digital signal processing algorithm on dsp system, is characterized in that: comprise the steps,
Step S01: according to coriolis mass flowmeters characteristic, design a kind of digital signal processing algorithm based on adaptive lattice type IIR notch filter and Hilbert transform method composition;
Step S02: the digital signal processing algorithm that described step S01 is obtained, be transplanted on dsp system;
Step S03: transplant the dsp system that has digital signal processing algorithm by described step S02, process the digital signal of coriolis mass flowmeters.
2. the application process of a kind of digital signal processing algorithm according to claim 1 on dsp system, is characterized in that: described digital signal processing algorithm, specifically comprise the steps,
Step S21: signal filtering: the input signal of coriolis mass flowmeters is carried out to digital filtering, and carry out noise filtering, obtain predetermined frequency band signal; Then, by adaptive lattice type IIR notch filter, this predetermined frequency band signal is carried out to filtering processing, output strengthens signal;
Step S22: phase difference calculating: the enhancing signal described step S21 being obtained by phase differential algorithm carries out phase difference calculating;
Step S23: flow rate calculation: the phase difference value obtaining according to described step S22, calculates mistiming and the flow of signal.
3. the application process of a kind of digital signal processing algorithm according to claim 2 on dsp system, is characterized in that: described phase differential algorithm, and specific implementation process is as follows,
If strengthen signal through filtered two-way, be:
In formula:
for the amplitude of signal,
,
for phase place,
for digital angular frequency; From Euler's formula
, there is Hilbert conversion:
Two paths of signals, through Hilbert conversion, obtains only containing the analytic signal of positive frequency:
By tan and poor eliminate indigestion formula, had:
Above formula is carried out to arctangent cp cp operation and can try to achieve phase differential:
。
4. the application process of a kind of digital signal processing algorithm according to claim 1 on dsp system, is characterized in that: described dsp system comprises primary controller and the power management module that is used to system power supply, signal condition and the acquisition module and the human-machine interface module that are connected with this primary controller.
5. the application process of a kind of digital signal processing algorithm according to claim 4 on dsp system, is characterized in that: described signal condition and acquisition module comprise AD modular converter.
6. the application process of a kind of digital signal processing algorithm according to claim 4 on dsp system, is characterized in that: described human-machine interface module comprises LCD module and Keysheet module.
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| CN104280047A (en) * | 2014-09-10 | 2015-01-14 | 天津航天中为数据系统科技有限公司 | Gyroscope shift filtering system and method integrating multiple sensors |
| CN104792379A (en) * | 2015-04-08 | 2015-07-22 | 浙江大学 | Coriolis mass flowmeter amplitude self-adaptation control method based on fluid state detecting |
| CN109687842A (en) * | 2018-12-24 | 2019-04-26 | 陕西航天时代导航设备有限公司 | A kind of filter for flexure gyroscope noise |
| CN113093510A (en) * | 2021-02-26 | 2021-07-09 | 山东师范大学 | Clock frequency signal error measuring instrument and method |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104280047A (en) * | 2014-09-10 | 2015-01-14 | 天津航天中为数据系统科技有限公司 | Gyroscope shift filtering system and method integrating multiple sensors |
| CN104792379A (en) * | 2015-04-08 | 2015-07-22 | 浙江大学 | Coriolis mass flowmeter amplitude self-adaptation control method based on fluid state detecting |
| CN104792379B (en) * | 2015-04-08 | 2018-01-12 | 浙江大学 | A kind of Coriolis flowmeter amplitude self-adaptation control method based on fluid state detection |
| CN109687842A (en) * | 2018-12-24 | 2019-04-26 | 陕西航天时代导航设备有限公司 | A kind of filter for flexure gyroscope noise |
| CN113093510A (en) * | 2021-02-26 | 2021-07-09 | 山东师范大学 | Clock frequency signal error measuring instrument and method |
| CN113093510B (en) * | 2021-02-26 | 2022-07-22 | 山东师范大学 | Clock frequency signal error measuring instrument and method |
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