CN102609593A - Polypropylene melt index predicating method based on multiple priori knowledge mixed model - Google Patents

Polypropylene melt index predicating method based on multiple priori knowledge mixed model Download PDF

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CN102609593A
CN102609593A CN2012100550178A CN201210055017A CN102609593A CN 102609593 A CN102609593 A CN 102609593A CN 2012100550178 A CN2012100550178 A CN 2012100550178A CN 201210055017 A CN201210055017 A CN 201210055017A CN 102609593 A CN102609593 A CN 102609593A
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neural network
melt index
priori
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CN102609593B (en
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苏宏业
娄海川
谢磊
古勇
侯卫锋
荣冈
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Zhejiang University ZJU
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Abstract

The invention discloses a polypropylene melt index predicating method based on a multiple priori knowledge mixed model, which fully explores and utilizes priori knowledge of a polypropylene industrial site, and is used for organically integrating various priori knowledge, embedding the priori knowledge into a multilayer perceptron neural network in a non-linear equality constraint form, and optimizing a network weight number by means of a particle swarm optimization algorithm based on an augmented Lagrange multiplier constraint processing mechanism. Based on the multiple priori knowledge neural network model, the multiple priori knowledge neural network model is organically integrated with a polypropylene melt index simplification mechanism model into a harmonic average mixed soft-measuring model. The multiple priori knowledge mixed soft-measuring modeling method has good fitting prediction ability, and is capable of enhancing model extrapolation capacity and realizing good unity of model extrapolation and prediction accuracy of polypropylene melt indexes. Besides, the method is capable of avoiding zero gain and gain inversion and guaranteeing safety in practical polypropylene melt index quality closed-loop control application.

Description

Polypropylene melt index forecast method based on multiple priori mixture model
Technical field
The present invention relates to the soft measurement forecast of polypropylene industrial process field, especially, relate to the soft measurement forecasting procedure of a kind of polypropylene melt index based on multiple priori mixture model.
Background technology
Polypropylene (Polypropylene is abbreviated as PP) is to be the polymkeric substance that monomer polymerization forms with the propylene.Polypropylene is a kind of general-purpose plastics of function admirable, is widely used in fields such as packing, manufacturing, weaving and many civilian consumption.Melting index is one of main quality index of polypropylene product, reflects the resin flows performance, thereby is determining the trade mark of resin.The polyacrylic resin trade mark is various, reaches hundreds of from several kinds.As far as the polypropylene process units,,, stern challenge has been proposed for the modeling and the control of melting index if will produce the polypropylene product of high-quality, many trades mark because working conditions change is frequent in the operation of propylene polymerization.
The modeling difficulty of production quality control mainly contains following several aspect in the polypropylene production:
1) lack the melting index in-line analyzer, melting index can only be through hand sampling, and the off-line assay obtains, and analyzes once in general every 2-4 hour, and time lag is big, is difficult to satisfy the requirement of control in real time, causes the product quality fluctuation big.
2) the propylene polymerization processes principle is complicated, comprises multistep physics, chemical reaction; Influence factor is numerous, and is non-linear strong, the multiple dimensioned characteristic of measurement data; When producing different product, the trade mark switches frequent, and operating conditions changes greatly; For the process of such complicacy, be difficult to adopt the model of a single operating mode to describe.
3) the polypropylene production status changes, and mismatch takes place model easily in the soft instrument long-time running, needs regularly to safeguard and proofread and correct.
Traditional polypropylene soft measurement model mainly contains mechanism model and data-driven model, based on the simple rerum natura mechanism model of correlation experience exploitation, can the course of reaction approximate trend change, and precision of prediction but is difficult to guarantee.In fact; The polyolefin polymerization course of reaction exists severe nonlinear and uncertainty, is an extremely complicated chemical reaction, develop a desirable melting index quality modelling by mechanism and take time and effort; In addition the produced on-site condition is different, not promotion.Though and it is convenient to set up the melting index soft-sensing model based on the clear data driving method, and to a certain degree can satisfy modeling accuracy.But for the occasion that such polymerization process trade mark switches, the working point often changes; Leaving the operating area of modeling data, simple application data driving method not only lacks the extrapolation performance; And when the quality closed-loop control; The blindly extrapolation of training data zone causes maloperation easily, brings tremendous influence to production.
Summary of the invention
The objective of the invention is provides a kind of based on the polypropylene melt index soft measurement forecasting procedure of multiple priori neural network with simple mechanism mixture model in order to overcome the not high deficiency that can't guarantee with clear data driving model extrapolability and security performance of existing pure mechanism model precision.This method is the harmonic average mixture model with multiple priori neural network model and the combination of polypropylene melt index simplification mechanism model; Good match predictive ability is not only arranged; Strengthened the model extrapolability; Implementation model extrapolation and to the good unification of melting index precision of prediction can be avoided zero gain and gain inversion simultaneously, guarantees the security performance of network in practical application.
Technical solution of the present invention is: fully discover and use the on-the-spot priori of polypropylene industrial; Various prioris are organically blended; And be embedded in the multilayer perceptron neural network with the form of non-linear equality constraint; Based on augmentation method of Lagrange multipliers Constraints Processing mechanism, optimize network weight simultaneously with particle swarm optimization algorithm.On the basis of multiple priori neural network model, itself and the combination of polypropylene melt index simplification mechanism model are harmonic average mixing soft-sensing model.Concrete steps are following:
The data of 1) from on-the-spot DCS station and laboratory assay platform, gathering crucial auxiliary variable of polypropylene production process and leading variable are as training sample;
2) application data pre-processing module comprises that wavelet threshold denoising, robust yardstick leave detection of value point and rejecting and minimax method for normalizing training sample is carried out pre-service, thereby obtains smooth and reliable modeling data, and step is:
(1) wavelet threshold denoising: with original signal through after flexible and the translation; Be decomposed into a series of subband signals with different spatial resolutions, different frequency characteristic and directivity characteristics; These subband signals have local features such as good time domain, frequency domain; These characteristics can be used to represent the local feature of original signal, and then realize the localization analysis to signal time, frequency, extract the waveform character of signal effectively.
(2) the robust yardstick detects and rejects from the value point:
Figure 2012100550178100002DEST_PATH_IMAGE001
; According to
Figure 169257DEST_PATH_IMAGE002
decision rule; If the situation that
Figure 2012100550178100002DEST_PATH_IMAGE003
appears in certain sample; Then this time sampled value promptly from the value point, is rejected.Wherein,
Figure 972128DEST_PATH_IMAGE004
is that intermediate value and
Figure 487817DEST_PATH_IMAGE006
of data sequence
Figure 2012100550178100002DEST_PATH_IMAGE005
is the intermediate value index of intermediate value absolute value deviation
Figure 2012100550178100002DEST_PATH_IMAGE007
(3) minimax normalization:
Figure 8928DEST_PATH_IMAGE008
Wherein,
Figure 2012100550178100002DEST_PATH_IMAGE009
is the sample data of not nominal; And minimax sample value;
Figure 196327DEST_PATH_IMAGE010
is the sample data of nominal, and the minimax sample value of nominal;
3) set up normalized mutual information time delay recognition module, utilize this recognition module to obtain time delay, the auxiliary variable of polypropylene melt index forecast model and leading variable are carried out the sequential coupling;
4) fully excavate and utilize the on-the-spot priori of polypropylene industrial, various prioris are organically blended, and be embedded in the multilayer perceptron neural network, make up multiple priori neural network model with the form of nonlinear inequalities constraint;
5) based on augmentation method of Lagrange multipliers Constraints Processing mechanism, be built with trapped particle crowd optimal module multiple priori neural network weight is carried out on-line optimization;
6) on the basis that makes up multiple priori neural network model, this model and the combination of polypropylene melt index simplification mechanism model for mixing soft measurement forecasting model, are forecast polypropylene melt index in harmonic average.
The said normalized mutual information time delay recognition module of setting up, the concrete steps that obtain time delay
Figure 2012100550178100002DEST_PATH_IMAGE011
are:
(1) sampling period
Figure 2012100550178100002DEST_PATH_IMAGE013
of setting leading variable polypropylene melt index
Figure 617819DEST_PATH_IMAGE012
; The sampling period of auxiliary variable
Figure 865260DEST_PATH_IMAGE014
is
Figure 2012100550178100002DEST_PATH_IMAGE015
; Confirm that maximum hysteresis step-length
Figure 811351DEST_PATH_IMAGE016
is
Figure 2012100550178100002DEST_PATH_IMAGE017
, wherein
Figure 292186DEST_PATH_IMAGE018
;
(2) arrange again according to the sample data of each auxiliary variable of big young pathbreaker
Figure 131967DEST_PATH_IMAGE014
of hysteresis step-length;
Figure 2012100550178100002DEST_PATH_IMAGE019
,
Figure 550310DEST_PATH_IMAGE020
is time delay to be determined.Again the arrangement of process data is equivalent to and each variable is converted into
Figure 2012100550178100002DEST_PATH_IMAGE021
individual sub-variable, and wherein the sample number of each variable equals leading variable sample number
Figure 575214DEST_PATH_IMAGE022
in
Figure 718117DEST_PATH_IMAGE021
individual sub-variable;
(3) utilize following formula normalized mutual information method to obtain the normalized mutual information of
Figure 705719DEST_PATH_IMAGE021
individual sub- variable and leading variable
Figure DEST_PATH_IMAGE023
Figure 294963DEST_PATH_IMAGE024
Can get the corresponding time delay step-length of auxiliary variable
Figure 340280DEST_PATH_IMAGE014
does
Figure DEST_PATH_IMAGE025
Then obtain time delay ;
The step of the multiple priori neural network model of described structure module:
(1) makes up multiple priori neural network
Figure DEST_PATH_IMAGE027
In the formula, non-linear latent node adopts non-linear Sigmoid activation function,
Figure 598796DEST_PATH_IMAGE028
Linear latent node adopts linear activation function
Figure DEST_PATH_IMAGE029
This network structure is three layers of feedforward network with single latent layer; Direct annexation has been set up in input and output; More can reflect the I/O relation of process, zero gain occur for fear of real process simultaneously, latent layer is made up of non-linear and linear latent node two parts.
(2) excavate the on-the-spot priori of polypropylene, comprise process gain and characteristic thereof, the monotonicity of process, and process characteristic curve concavity and convexity are concrete by obtaining as follows:
1) process gain and characteristic thereof: for process gain
Figure 624521DEST_PATH_IMAGE030
Given constraint
Mi, MiMinimum and maximal value for gain provide according to scene or practical experience.
In addition; Can guarantee during as
Figure 829238DEST_PATH_IMAGE032
monotonic decay that gains can guarantee the level and smooth increase that gains during as
Figure DEST_PATH_IMAGE033
.
2) monotonicity of process: work as monotone increasing;
Figure 402039DEST_PATH_IMAGE034
is described; When monotone decreasing then,
3) process characteristic curve concavity and convexity: the family curve between process variable, generally can find out the concavity and convexity of curve.For ; During as ; The process characteristic curve shows concavity; Otherwise during as
Figure 939648DEST_PATH_IMAGE038
, be convexity.
(3) design object function.Objective function imposed restriction to be embedded into priori in the neural network, and on the basis of error term, various prioris are directly retrained with nonlinear inequalities represent as objective function,
Described augmentation Lagrange multiplier particle group optimizing module step:
(1) sets initial value: the maximum update times of Lagrange multiplier and penalty factor, the maximum iteration time of particle cluster algorithm, population population, population dimension, inertia weight W, cognitive coefficient c 1With the c of coefficient of association 2,Initial Lagrangian, initial penalty factor.In independent variable space initialization particulate random site and speed.
(2) according to the adaptive value of the Augmented Lagrangian Functions of each particle of computes; To each particulate; If adaptive value is greater than its desired positions, then with it as current desired positions
Figure 70808DEST_PATH_IMAGE040
; If adaptive value is then reset overall optimum position
Figure DEST_PATH_IMAGE041
greater than full crowd's desired positions
Figure 745503DEST_PATH_IMAGE042
Wherein,
Figure DEST_PATH_IMAGE043
;
Figure 144255DEST_PATH_IMAGE044
is target function value;
Figure DEST_PATH_IMAGE045
is variable (following is population);
Figure 10317DEST_PATH_IMAGE046
inequality constrain for violating;
Figure DEST_PATH_IMAGE047
is Lagrange multiplier, and
Figure 861730DEST_PATH_IMAGE048
is penalty factor.
(3) judge whether to satisfy the population maximum iteration time; As do not reach; Then press following formula and upgrade
Figure DEST_PATH_IMAGE049
individual particle's velocity and position, return (2); Otherwise, forward next step to
Figure 779263DEST_PATH_IMAGE050
Wherein: subscript "
Figure DEST_PATH_IMAGE051
" the expression particulate the
Figure 298101DEST_PATH_IMAGE051
Dimension, tExpression the tGeneration,
Figure 570950DEST_PATH_IMAGE052
Be particulate iCurrent location,
Figure DEST_PATH_IMAGE053
Be particulate
Figure 736090DEST_PATH_IMAGE049
Current flight speed,
Figure 752588DEST_PATH_IMAGE040
Be particulate
Figure 188248DEST_PATH_IMAGE049
The individual desired positions that is experienced,
Figure 631999DEST_PATH_IMAGE054
Be overall desired positions.
Figure DEST_PATH_IMAGE055
is two separate random functions.In order to reduce during evolution; Particulate leaves the possibility of search volume;
Figure 236766DEST_PATH_IMAGE056
is defined in the certain limit usually; If in promptly the search volume of problem is limited to
Figure DEST_PATH_IMAGE057
, then can set .
(4) judge whether to satisfy stopping criterion for iteration, if satisfy, stop calculating the output optimal value; Otherwise the following formula of pressing of Lagrange multiplier and penalty factor upgrades, and returns (2)
Figure DEST_PATH_IMAGE059
Figure 783340DEST_PATH_IMAGE060
Described harmonic average mixes the step of soft measurement forecasting model:
(1), optimizes the simple mechanism model parameter of polypropylene melt index with unconstrained optimization algorithm (genetic algorithm or method of steepest descent algorithm) by the on-the-spot leading variable and the auxiliary variable data of gathering;
(2) by the on-the-spot leading variable and the auxiliary variable data of gathering, according to the objective function of setting up, optimize multiple priori neural network weight parameter with augmentation Lagrange multiplier particle group optimizing module, obtain multiple priori neural network model;
(3) make up harmonic average mixing soft-sensing model
Figure DEST_PATH_IMAGE061
Wherein, ;
Figure DEST_PATH_IMAGE063
;
Figure 976872DEST_PATH_IMAGE064
is respectively multiple priori neural network model, the simple mechanism model of melting index and harmonic average mixing soft-sensing model; is the weight of multiple priori neural network model, the simple mechanism model of melting index; Adopt the harmonic average method to obtain, promptly
Figure 774320DEST_PATH_IMAGE066
Two submodel variances
Figure DEST_PATH_IMAGE067
wherein,
Figure 184573DEST_PATH_IMAGE068
Can guarantee that like this mixture model
Figure 970127DEST_PATH_IMAGE064
does not have when estimating partially its variance .
In this harmonic average mixing soft-sensing model, melting index is simplified the general trend that mechanism model is held process, and multiple priori neural network model guarantees the overall performance of prediction through local accuracy's compensation.This method simple, intuitive when guaranteeing the effective accuracy of prediction, strengthens the model extrapolability, with the implementation model extrapolation with to the good unification of melting index precision of prediction.
Beneficial effect of the present invention mainly shows: 1, use normalized mutual information time delay recognition module is carried out the sequential coupling to the auxiliary variable and the leading variable of soft-sensing model, has guaranteed the precision of model prediction to a great extent; 2, fully excavate and utilize the on-the-spot priori of polypropylene industrial; Various prioris are organically blended; And be embedded in the multilayer perceptron neural network with the form of nonlinear inequalities constraint, optimize network weight based on augmentation Lagrange multiplier particle swarm optimization algorithm module simultaneously.Good match predictive ability is not only arranged, can avoid zero gain and gain inversion simultaneously, guarantee the security performance of model in practical application; 3, on the basis of multiple priori neural network model; Itself and the combination of polypropylene melt index simplification mechanism model are multiple priori harmonic average mixing soft-sensing model; Strengthened the model extrapolability, implementation model extrapolation and to the good unification of melting index precision of prediction.
Description of drawings
Fig. 1 dicyclo plumber liquid propylene bulk polymerization schematic diagram of device of planting
Fig. 2 is a theory diagram proposed by the invention
The multiple priori of Fig. 3 is mixed the online application synoptic diagram of soft measurement forecasting model
Fig. 4 is conventional softer measuring method and the inventive method value of forecasting comparison diagram
Fig. 5 is that traditional data drives flexible measurement method (not being with the priori constraint) and the inventive method (constraint of band priori) gain security comparison diagram.
Embodiment
Below in conjunction with accompanying drawing the present invention is further described.
With reference to Fig. 2, Fig. 3, a kind of polypropylene melt index forecast method based on multiple priori mixture model, the practical implementation method is following:
(1) off-line modeling
The polypropylene melt index forecast model based on multiple priori mixture model is set up in elder generation's off-line initialization, and detailed process is following:
1) from the annular tube type liquid propylene bulk polymerization field device (Fig. 1) of certain petro-chemical corporation of China, sets up the needed data of soft-sensing model through two approach collections.According to dicyclo pipe liquid propylene bulk polymerization production technology and reaction mechanism; The auxiliary variable of confirming soft-sensing model is density of hydrogen , hydrogen feed amount , propylene monomer inlet amount
Figure 368933DEST_PATH_IMAGE072
, jacket water (J.W.) temperature
Figure DEST_PATH_IMAGE073
and the catalyzer flow rate etc. of two endless tubes, and leading variable is the melting index of R202 endless tube.Gather device process data (6 minutes sampling times of DCS record in real time from the data server that utilizes manufacturer's information station; Several 4600 groups of original sample) with the laboratory assay data (per 4 hours by laboratory personnel's chemical examination once, totally 115 groups) of the hand-kept R202 endless tube melting index of time period as training sample;
2) application data pre-processing module comprises that wavelet threshold denoising, robust yardstick leave detection of value point and rejecting and minimax method for normalizing training sample is carried out pre-service, thereby obtains smooth and reliable modeling data, and step is:
(1) wavelet threshold denoising: original training sample through after flexible and the translation, is decomposed into a series of tools
The subband signal that different spatial resolutions, different frequency characteristic and directivity characteristics are arranged, and then realize localization analysis to signal time, frequency, extract the waveform character of signal effectively.
(2) the robust yardstick detects and rejects from the value point:
Figure 357191DEST_PATH_IMAGE001
; According to decision rule; If the situation that appears in certain sample; Then this time sampled value promptly from the value point, is rejected.
(3) minimax normalization:
Figure 589086DEST_PATH_IMAGE008
Wherein,
Figure 480556DEST_PATH_IMAGE009
is the sample data of not nominal; And minimax sample value;
Figure 318062DEST_PATH_IMAGE010
is the sample data of nominal, and the minimax sample value of nominal;
3) set up normalized mutual information time delay recognition module, utilize this recognition module to obtain time delay, the auxiliary variable of polypropylene melt index forecast model and leading variable are carried out the sequential coupling, step is following:
(1) sampling period of setting leading variable endless tube R202 melting index is
Figure DEST_PATH_IMAGE075
; Auxiliary variable (density of hydrogen, hydrogen feed amount, propylene monomer inlet amount, jacket water (J.W.) temperature and the catalyzer flow rate that comprise two endless tubes) sampling period is
Figure 759539DEST_PATH_IMAGE076
, then maximum hysteresis step-length
Figure 234776DEST_PATH_IMAGE016
is confirmed as
Figure DEST_PATH_IMAGE077
.Leading variable is
Figure 798613DEST_PATH_IMAGE078
with the ratio of auxiliary variable sample number;
(2) arrange again according to the sample data of big each auxiliary variable of young pathbreaker of hysteresis step-length;
Figure DEST_PATH_IMAGE079
,
Figure 61098DEST_PATH_IMAGE020
is time delay to be determined.Again the arrangement of process data is equivalent to and each variable is converted into
Figure 165320DEST_PATH_IMAGE080
individual sub-variable, and wherein the sample number of each variable equals leading variable sample number
Figure DEST_PATH_IMAGE081
in
Figure 757713DEST_PATH_IMAGE080
individual sub-variable;
(3) utilize following formula normalized mutual information method to obtain the normalized mutual information of
Figure 430134DEST_PATH_IMAGE080
individual variable and leading variable
Figure 976653DEST_PATH_IMAGE024
Then can get the corresponding time delay step-length
Figure 150146DEST_PATH_IMAGE082
of each auxiliary variable does
Figure DEST_PATH_IMAGE083
Each variable time delay
Figure 525939DEST_PATH_IMAGE026
then;
4) fully excavate and utilize the on-the-spot priori of polypropylene industrial, various prioris are organically blended, and be embedded in the multilayer perceptron neural network, make up multiple priori neural network model with the form of nonlinear inequalities constraint;
Concrete performing step is following:
(1) makes up multiple priori neural network
In the formula, 12 non-linear latent nodes adopt non-linear Sigmoid activation function,
Figure 465393DEST_PATH_IMAGE028
1 latent node of linearity adopts linear activation function
Figure 347636DEST_PATH_IMAGE029
(2) excavate the on-the-spot priori of polypropylene, comprise process gain and characteristic thereof, the monotonicity of process, and process characteristic curve concavity and convexity are concrete by obtaining as follows:
1) process gain and characteristic thereof: given gain constraint
Figure 478404DEST_PATH_IMAGE084
Wherein Mi, MiMinimum and maximal value for gain are respectively 0.1 and 1 according to the scene value of providing.
In addition, set
Figure 554944DEST_PATH_IMAGE032
and can guarantee the monotonic decay that gains.
2) monotonicity of process: by the relation of density of hydrogen and polypropylene melt index; Can this process be monotone increasing, i.e.
Figure 76055DEST_PATH_IMAGE034
.
3) process characteristic curve concavity and convexity: by the family curve between the process variable; Can find out that curve is a convexity, i.e.
Figure 263454DEST_PATH_IMAGE038
.
(3) design object function.Objective function imposed restriction to be embedded into priori in the neural network, and on the basis of error term, various prioris are directly retrained with nonlinear inequalities represent as objective function,
Figure 687875DEST_PATH_IMAGE039
5) based on augmentation Lagrange multiplier particle group optimizing module network weight is optimized, concrete steps are:
(1) set initial value: the maximum update times of Lagrange multiplier and penalty factor is 10, and the maximum iteration time 100 of particle cluster algorithm, population population are 35, population dimension 93, inertia weight WBe 0.9, cognitive coefficient c 1Be 2.3 with the c of coefficient of association 2.Be 2.0.Initialization Lagrangian and penalty factor are in independent variable space initialization particulate random site and speed.
(2) according to the adaptive value of the Augmented Lagrangian Functions of each particle of computes; To each particulate; If adaptive value is greater than its desired positions, then with it as current desired positions ; If adaptive value is then reset overall optimum position
Figure 6041DEST_PATH_IMAGE041
greater than full crowd's desired positions
Figure 997131DEST_PATH_IMAGE042
Wherein, ;
Figure 691472DEST_PATH_IMAGE044
is target function value;
Figure 983913DEST_PATH_IMAGE045
is variable (following is population);
Figure 778694DEST_PATH_IMAGE046
inequality constrain for violating;
Figure 410664DEST_PATH_IMAGE047
is Lagrange multiplier, and is penalty factor.
(3) judge whether to satisfy the population maximum iteration time; As do not reach; Then press following formula and upgrade
Figure 484372DEST_PATH_IMAGE049
individual particle's velocity and position, return (2); Otherwise, forward next step to
Figure 879582DEST_PATH_IMAGE050
(4) judge whether to satisfy stopping criterion for iteration, if satisfy, stop calculating the output optimal value; Otherwise the following formula of pressing of Lagrange multiplier and penalty factor upgrades, and returns (2)
Figure 366058DEST_PATH_IMAGE059
Figure 391783DEST_PATH_IMAGE060
6) on the basis that makes up multiple priori neural network model module, this model and the combination of polypropylene melt index simplification mechanism model module are mixed soft measurement forecasting model for harmonic average.
(1), optimizes the simple mechanism model parameter of following formula polypropylene R202 endless tube melting index with unconstrained optimization algorithm (genetic algorithm or method of steepest descent algorithm) by the on-the-spot leading variable and the auxiliary variable data of gathering;
Figure DEST_PATH_IMAGE085
get the coefficients to be determined?
Figure 32717DEST_PATH_IMAGE086
.
(2) by on-the-spot leading variable melting index of the polypropylene of gathering and auxiliary variable data; According to the objective function of setting up; Optimize multiple priori neural network model weighting parameter with augmentation Lagrange multiplier particle group optimizing module, obtain multiple priori neural network model;
(3) make up harmonic average mixing soft-sensing model
Figure 966038DEST_PATH_IMAGE061
Wherein,
Figure 572600DEST_PATH_IMAGE062
; ; is respectively multiple priori neural network model, the simple mechanism model of melting index and harmonic average mixing soft-sensing model;
Figure 637398DEST_PATH_IMAGE065
is the weight of multiple priori neural network model, the simple mechanism model of melting index, adopts the harmonic average method to obtain.
(2) online forecasting
Above-mentioned steps is for mixing soft measurement off-line modeling process.After the modelling, obtain each weights and weight coefficient after, can realize online forecasting, may further comprise the steps:
8) read auxiliary variable data up-to-date in the production run;
9) online forecasting;
10) regularly the normal point of process status is added in the training set, repeats 4)~6) training process so that upgrade model in time.
For the polypropylene melt index forecast method based on multiple priori mixture model that the present invention proposes better is described; Through to the on-the-spot real data modeling of endless tube technology polypropylene, itself and traditional clear data driving model and pure mechanism model are compared.Here set up the multiple priori harmonic average mixing soft-sensing model (MPKNN-SFPM) that least square method supporting vector machine (LSSVM) soft-sensing model, melting index simplification mechanism model (SFPM) and the present invention propose respectively; And adopt performance evaluation index (comprising average square error function, normalization square error function) that each soft-sensing model is made synthetic performance evaluation
Figure DEST_PATH_IMAGE087
Figure 36150DEST_PATH_IMAGE088
Table one, Fig. 4 and Fig. 5 have provided both forecast results.The result shows that the method that the present invention proposes has better prediction ability, and is no matter still regional in extrapolation at total test zone, all measures forecasting procedure than conventional softer and has better precision and tracking trend.The generation that can avoid simultaneously zero gain or gain to reverse guarantees reliability and security in the actual application.
 

Claims (4)

1. based on the polypropylene melt index forecast method of multiple priori mixture model, it is characterized in that may further comprise the steps:
The data of 1) from on-the-spot DCS station and laboratory assay platform, gathering crucial auxiliary variable of polypropylene production process and leading variable are as training sample;
2) application data pre-processing module comprises that wavelet threshold denoising, robust yardstick leave detection of value point and rejecting and minimax method for normalizing training sample is carried out pre-service, thereby obtains smooth and reliable modeling data;
3) set up normalized mutual information time delay recognition module, utilize this recognition module to obtain time delay, the auxiliary variable of polypropylene melt index forecast model and leading variable are carried out the sequential coupling;
4) fully excavate and utilize the on-the-spot priori of polypropylene industrial, various prioris are organically blended, and be embedded in the multilayer perceptron neural network, make up multiple priori neural network model module with the form of nonlinear inequalities constraint;
5) based on augmentation method of Lagrange multipliers Constraints Processing mechanism, be built with trapped particle crowd optimal module the priori neural network weight is carried out on-line optimization;
6) on the basis that makes up multiple priori neural network model, this model and the combination of polypropylene melt index simplification mechanism model module for mixing soft measurement forecasting model, are forecast polypropylene melt index in harmonic average.
2. the polypropylene melt index forecast method based on multiple priori mixture model as claimed in claim 1; It is characterized in that the described normalized mutual information time delay recognition module of setting up, the concrete steps that obtain time delay are:
(1) sampling period of setting leading variable polypropylene melt index
Figure 2012100550178100001DEST_PATH_IMAGE004
is
Figure 2012100550178100001DEST_PATH_IMAGE006
; The sampling period of auxiliary variable
Figure 2012100550178100001DEST_PATH_IMAGE008
is
Figure 2012100550178100001DEST_PATH_IMAGE010
; Confirm that maximum hysteresis step-length
Figure 2012100550178100001DEST_PATH_IMAGE012
is
Figure 2012100550178100001DEST_PATH_IMAGE014
, wherein ;
(2) arrange again according to the sample data of each auxiliary variable of big young pathbreaker
Figure 676296DEST_PATH_IMAGE008
of hysteresis step-length; ,
Figure 2012100550178100001DEST_PATH_IMAGE020
is time delay to be determined; Again the arrangement of process data is equivalent to and each variable is converted into
Figure 2012100550178100001DEST_PATH_IMAGE022
individual sub-variable, and wherein the sample number of each variable equals leading variable sample number
Figure 2012100550178100001DEST_PATH_IMAGE024
in
Figure 845634DEST_PATH_IMAGE022
individual sub-variable;
(3) utilize following formula normalized mutual information method to obtain the normalized mutual information of
Figure 500737DEST_PATH_IMAGE022
individual sub- variable and leading variable
Figure 2012100550178100001DEST_PATH_IMAGE026
Figure DEST_PATH_IMAGE028
Wherein and
Figure DEST_PATH_IMAGE032
is respectively the probability of sub-variable and leading variable melting index, and
Figure DEST_PATH_IMAGE034
is joint probability;
Can get the corresponding time delay step-length of auxiliary variable
Figure 459728DEST_PATH_IMAGE008
does
Then obtain time delay
Figure DEST_PATH_IMAGE038
.
3. the polypropylene melt index forecast method based on multiple priori mixture model as claimed in claim 1 is characterized in that the step of the multiple priori neural network model of described structure module:
(1) makes up multiple priori neural network
Figure DEST_PATH_IMAGE040
In the formula, Ii, Jj, kBe respectively input node, latent node, output node number;
Figure DEST_PATH_IMAGE042
,
Figure DEST_PATH_IMAGE044
Corresponding model input and output respectively;
Figure DEST_PATH_IMAGE046
,
Figure DEST_PATH_IMAGE048
,
Figure DEST_PATH_IMAGE050
With
Figure DEST_PATH_IMAGE052
Be respectively input layer to latent layer, latent layer is to output layer, and input layer is to the weights and the output layer threshold value of output layer; Non-linear latent node adopts non-linear Sigmoid activation function,
Linear latent node adopts linear activation function
Figure DEST_PATH_IMAGE056
(2) excavate the on-the-spot priori of polypropylene, comprise process gain and characteristic thereof, the monotonicity of process, and process characteristic curve concavity and convexity, specific as follows:
1) process gain and characteristic thereof:
Figure DEST_PATH_IMAGE058
, and given gain constraint
Figure DEST_PATH_IMAGE060
With
Figure DEST_PATH_IMAGE062
, wherein,
Figure DEST_PATH_IMAGE064
Be hidden node, Mi, MiBe respectively gain minimum and maximal value, provide according to scene or practical experience; When
Figure DEST_PATH_IMAGE066
The time guarantee the gain monotonic decay, when
Figure DEST_PATH_IMAGE068
The time guarantee that gain-smoothing increases;
2) monotonicity of process: when the process monotone increasing; Then
Figure DEST_PATH_IMAGE070
; Work as monotone decreasing, then
Figure DEST_PATH_IMAGE072
;
3) process characteristic curve concavity and convexity:
Figure DEST_PATH_IMAGE074
; During promptly as
Figure DEST_PATH_IMAGE076
; The process characteristic curve shows concavity; Otherwise during as
Figure DEST_PATH_IMAGE078
, be convexity;
(3) design object function; On the basis of error term, various prioris are directly retrained with nonlinear inequalities represent as objective function:
Figure DEST_PATH_IMAGE080
4. the polypropylene melt index forecast method based on multiple priori mixture model as claimed in claim 1 is characterized in that described harmonic average mixes the step of soft measurement forecasting model:
(1) by on-the-spot leading variable of the polypropylene of gathering and auxiliary variable data, with the simple mechanism model parameter of unconstrained optimization algorithm optimization polypropylene melt index;
(2) by the on-the-spot leading variable and the auxiliary variable data of gathering, according to the objective function of setting up, optimize multiple priori neural network weight parameter with augmentation Lagrange multiplier particle group optimizing module, obtain multiple priori neural network model;
(3) make up harmonic average mixing soft-sensing model
Figure DEST_PATH_IMAGE082
Wherein,
Figure DEST_PATH_IMAGE086
;
Figure DEST_PATH_IMAGE088
; is respectively multiple priori neural network model, the simple mechanism model of melting index and harmonic average mixing soft-sensing model;
Figure DEST_PATH_IMAGE090
is the weight of multiple priori neural network model, the simple mechanism model of melting index, adopts the harmonic average method to obtain.
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