CN110262254A - The observation of ammonia coverage rate and tracking whole design control method - Google Patents
The observation of ammonia coverage rate and tracking whole design control method Download PDFInfo
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Abstract
The invention discloses a kind of observation of ammonia coverage rate and tracking whole design control method, BROAD SUMMARY includes establishing urea-SCR system mathematic model；It is proposed ammonia coverage rate Design of Observer method；It is proposed ammonia coverage rate Tracking Control Design method.Ammonia coverage rate proposed by the present invention observation and tracking whole design control method, step is simple, Unified Model, is suitable for engineer application；With overall stability discussion, it is capable of the calibration process of simplified control parameter.
Description
Technical field
The invention belongs to diesel urea SCR discharge post-treatment system parameter estimation techniques fields, and in particular to a kind of ammonia
Coverage rate observation and tracking whole design control method.
Background technique
Compared with gasoline engine, diesel engine has higher fuel economy and higher power output.However, diesel engine
Emission problem develops always a challenge, especially NO to itxDischarge.Researcher proposes many reduction NOxThe side of discharge
Method, wherein urea selective catalytic reduction (urea-SCR) emission aftertreatment technology, has by the features such as its low cost, high efficiency
Standby some superiority.And urea-SCR system is lower to the sensibility of sulphur, according to the higher reality of sulfur content in current China's fuel oil
Border national conditions, the technology have more advantage.The basic principle of urea-SCR system work is to utilize ammonia (NH3) reduction engine generation
NOx, these ammonia generally all derive from 32.5% urea liquid (adding blue solution).Although ammonia can restore NOx, but itself
It is harmful to the human body, and has pungent smell, although not expressly provided in current emission regulation.So together
The lower NO of Shi ShixianxDischarge becomes the significant challenge of urea-SCR system research with the escaping of ammonia.
For above-mentioned challenge, there is scholar to propose some hardware modifications measures.But in practical applications, it is most of be all with
Increase cost and takes up space as cost.Currently, people it is well recognized that, by improve urea spraying technique reach above-mentioned
Target is controlled, is a kind of more convenient and economic method.Current some method for urea injection control are concentrated mainly on feedback control
It sets up on meter.Wherein, a part of feedback control is based on NOxSensor.But NOxSensor has cross-sensitivity to ammonia, causes
There are errors for measuring signal.Moreover, only taking NOxFeedback signal is also difficult to ensure that emission intensity meets standard.Although Delphi company
It is proposed NH recently3Sensor, but since it is not also by volume production, it is seldom used in actual industrial application.This allows for list
Only NOxAnd NH3Feedback is all extremely difficult to preferably control purpose.Then, scholar proposes a kind of feedback method of synthesis,
I.e. using ammonia coverage rate as Tracking Feedback Control target.
But the measurement of ammonia coverage rate can only be completed in laboratory environments at present.Although in response to this problem, there is scholar
Some observation methods have been proposed.But the current non-linear observation of ammonia coverage rate and tracking control problem, still face following
Challenge: 1, ammonia coverage rate observer and tracking control unit based on urea-SCR system model it is variant, use in conjunction is had any problem；
2, ammonia coverage rate observer and tracking control unit lack whole design and Stability.
Summary of the invention
The purpose of the present invention is to propose to a kind of observation of ammonia coverage rate and tracking whole design control method, this method has whole
Body Stability is capable of the calibration process of simplified control parameter, and this method step is simple, Unified Model, is suitable for work
Cheng Yingyong.
The object of the present invention is achieved like this, a kind of observation of ammonia coverage rate and tracking whole design control method, including
Following steps:
Step 1: establishing urea-SCR system mathematic model
Step 2: design ammonia coverage rate observer
Wherein,
Step 3: design ammonia coverage rate tracking control unit
The present invention has the advantage that compared with prior art:
1, the observation of ammonia coverage rate and tracking whole design control method proposed, step is simple, Unified Model, is suitable for work
Cheng Yingyong.
2, the observation of ammonia coverage rate and tracking whole design control method proposed, has overall stability discussion, Neng Goujian
Change the calibration process of control parameter.
Detailed description of the invention
Fig. 1 is ammonia coverage rate observation of the present invention and tracking whole design control method schematic diagram.
Fig. 2 is the control effect figure of the observation of ammonia coverage rate and tracking whole design control method of the present invention.
Specific embodiment
1, the ammonia coverage rate observation of whole design of the present invention and tracking and controlling method, the specific steps are as follows:
(1), urea-SCR system mathematic model is established
Wherein,
Tables 1 and 2 respectively illustrates the related definition and parameter name reference value of all constants and variable in model,
1 constant nomenclature of table
2 variable naming method of table
State is in ammonia coverage rate observer and tracking control unitControl inputsControl exportsModel is suitably simplified are as follows:
(2), ammonia coverage rate observer is designed
Other than ammonia coverage measure is difficult, NOxMeasurement is also by sensor to NH3Cross-sensitivity influence, because
This, the measurement problem of urea-SCR system faces very big difficulty, and effective estimation method is necessary, and has in urea-SCR system
Complicated chemical reaction, NH3Concentration dynamic all has an impact to the observer and controller of ammonia coverage rate, therefore, by x2Regarding as can essence
Really measurement, devises a sliding mode observer, and be discussed under Lyapunov's theory frame, such as formula (4) and (5)
It is shown:
Wherein,
Wherein,kΘWithFor observer gain；
As shown in formula (5), it is substantially one based on ammonia coverage rate estimated valueAmmonia density (x2) sliding formwork sight
Survey device, it is contemplated that ammonia density dynamic, ammonia density estimated valueThe error of observerIt may be expressed as:
Wherein,About evaluated errorLiapunov functionIts time leads
Number are as follows:
WhenWhen, it can guaranteeThat is evaluated error?
Finite-time convergence is to 0；
For a preferable urea-SCR system controller, it can guaranteeConvergence, moreover, sliding mode controller can be protected
Card dynamic is on sliding-mode surfaceBased on equivalent control method, in sliding formwork control finite time, can obtain:
According to formula (6), can also derive
With reference to Tables 1 and 2 and a2(T) and a3(T) definition, it is known that x2a2(T)+a3(T) 0 >, have becauseKnown to
For evaluated error x1And x2, choosing a liapunov function isIts time-derivative is
Wherein, It is obvious that 0 He of α >Therefore, kΘSelection to guarantee β < 0, to guaranteeAnd evaluated error is having
0 is converged in limited time, due toGain kΘMust be sufficiently large, i.e.,
(3), ammonia coverage rate tracking control unit is designed
Based on formula (3), this chapter devises a dynamic ammonia of observer that is based on and covers under Lyapunov's theory frame
Lid rate tracking control unit, the controller can complete the tracking of ammonia coverage rate target, definition under the conditions of ginseng becomes nonlinear system
Ammonia coverage rate observationWith dreamboat valueBetween tracking error beSelect its Liapunov
Function isIts derivation can be obtained:
Formula (4) are substituted into formula (12), can be obtained:
By x2Regard control input as, defining a virtual controlling target isIt can obtain:
Wherein, k1> 0 is controller gain, available negative definite
Therefore, tracking error z1In Finite-time convergence to 0, estimated value is definedWith virtual controlling targetBetween
Error isChoosing liapunov function isIt, can be with further according to formula (14)
Obtain its time-derivative are as follows:
According to formula (5), pass through
Available negative definite
Therefore, available final control law is
Wherein, k2> 0 is controller gain, meanwhile, by deriving
Wherein, VcNumber decaying is referred to the time, and the upper limit of attenuation rate is 2min { k1, k2}。
A kind of whole observation of ammonia coverage rate and tracking and controlling method proposed by the present invention, specific embodiment such as Fig. 1
It is shown, comprising the following steps: 1) to acquireAnd T signal, send ammonia coverage rate observer module to；2),
Ammonia coverage rate observer module estimatesWithParameter value sends ammonia coverage rate tracking control unit module to；3), ammonia
Coverage rate tracking control unit module utilizes dreamboat valueAnd estimated valueBetween error, be calculated urea spray
The amount of penetrating urea.Under FTP75 transient-cycle in point state test, the observation of ammonia coverage rate and the tracing control side of the whole design of proposition are demonstrated
The control effect of method.NH is converted into consideration urea3Uncertainty and NOxSensor is to NH3Cross-sensitivity before and after, it is right
Emission effect is compared.NOxTransformation efficiency and NH3The variation difference of escape is as shown in Figure 2.The ammonia of whole design proposed by the present invention
Coverage rate observation and tracking and controlling method, can transient condition interfere and actuator and sensor condition of uncertainty under,
Meet emission control demand.Average NOxConversion ratio is 90.8%, effectively reduces discharge.It is more than in addition to putting individually
23ppm, average NH3Escape is 20ppm.Since urea cannot be fully converted to NH3, the maximum respond quilt of urea nozzle
It reduces.Therefore, this will spray full the moment in urea nozzle, lead to NH3It reduces.NH3Cross-sensitivity is to NOxThe feedback of sensor
Signal plays the role of amplification, so that the demand of urea injection is increased by.Meanwhile NOxTransformation efficiency is increased by,
NH3Escape can also be increase accordingly.However, being converted into NH compared to urea3Uncertainty, NOxSensor is to NH3Intersection it is quick
Perception is to NH3The influence of escape is unobvious.Therefore, by considering that it is proposed by the present invention whole that the comparison of uncertain front and back shows
The ammonia coverage rate observation of body design and the emission effect variation of tracking and controlling method are unobvious, can satisfy emissions requirements, and
There is robustness to the uncertainty of actuator and sensor.
Claims (2)
1. a kind of ammonia coverage rate observation and tracking whole design control method, it is characterised in that the following steps are included:
Step 1: establishing urea-SCR system mathematic model
Step 2: design ammonia coverage rate observer
Wherein,
Step 3: design ammonia coverage rate tracking control unit
2. a kind of ammonia coverage rate observation according to claim 1 and tracking whole design control method, it is characterised in that: tool
Steps are as follows for body:
(1), urea-SCR system mathematic model is established
Wherein,
Tables 1 and 2 respectively illustrates the related definition and parameter name reference value of all constants and variable in model,
1 constant nomenclature of table
2 variable naming method of table
State is in ammonia coverage rate observer and tracking control unitControl inputsControl exportsModel is suitably simplified are as follows:
(2), ammonia coverage rate observer is designed
Other than ammonia coverage measure is difficult, NOxMeasurement is also by sensor to NH3Cross-sensitivity influence, therefore,
The measurement problem of urea-SCR system faces very big difficulty, and effective estimation method is necessary, and has in urea-SCR system multiple
Miscellaneous chemical reaction, NH3Concentration dynamic all has an impact to the observer and controller of ammonia coverage rate, therefore, by x2Regarding as can be accurate
Measurement, devises a sliding mode observer, and be discussed under Lyapunov's theory frame, such as formula (4) and (5) institute
Show:
Wherein,
Wherein,kΘWithFor observer gain；
As shown in formula (5), it is substantially one based on ammonia coverage rate estimated valueAmmonia density (x2) sliding mode observer,
In view of ammonia density dynamic, ammonia density estimated valueThe error of observerIt may be expressed as:
Wherein,About evaluated errorLiapunov functionIts time-derivative are as follows:
WhenWhen, it can guaranteeThat is evaluated errorLimited
0 is converged in time；
For a preferable urea-SCR system controller, it can guaranteeConvergence, moreover, sliding mode controller can guarantee it is dynamic
State is on sliding-mode surfaceBased on equivalent control method, in sliding formwork control finite time, can obtain:
According to formula (6), can also derive
With reference to Tables 1 and 2 and a2(T) and a3(T) definition, it is known that x2a2(T)+a3(T) 0 >, have becauseIt can
Know
For evaluated error x1And x2, choosing a liapunov function isIts time-derivative is
Wherein, It is obvious that 0 He of α >Therefore, kΘSelection to guarantee β < 0, to guaranteeAnd evaluated error is having
0 is converged in limited time, due toGain kΘMust be sufficiently large, i.e.,
(3), ammonia coverage rate tracking control unit is designed
Based on formula (3), this chapter is devised a based on the dynamic ammonia coverage rate of observer under Lyapunov's theory frame
Tracking control unit, the controller can complete the tracking of ammonia coverage rate target under the conditions of ginseng becomes nonlinear system, define ammonia and cover
Lid rate observationWith dreamboat valueBetween tracking error beSelect its liapunov function
ForIts derivation can be obtained:
Formula (4) are substituted into formula (12), can be obtained:
By x2Regard control input as, defining a virtual controlling target isIt can obtain:
Wherein, k1> 0 is controller gain, available negative definite
Therefore, tracking error z1In Finite-time convergence to 0, estimated value is definedWith virtual controlling targetBetween error
ForChoosing liapunov function isIt is available further according to formula (14)
Its time-derivative are as follows:
According to formula (5), pass through
Available negative definite
Therefore, available final control law is
Wherein, k2> 0 is controller gain, meanwhile, by deriving
Wherein, VcNumber decaying is referred to the time, and the upper limit of attenuation rate is 2min { k1, k2}。
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Cited By (1)
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| CN112596474A (en) * | 2020-11-23 | 2021-04-02 | 山东微立方信息技术股份有限公司 | Uniformity optimization method for SCR denitration system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112596474A (en) * | 2020-11-23 | 2021-04-02 | 山东微立方信息技术股份有限公司 | Uniformity optimization method for SCR denitration system |
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Application publication date: 20190920 |