CN102284505A

CN102284505A - System for controlling thickness of fuzzy PI (Proportional Integral) based on ARM (Advanced RISC machines)

Info

Publication number: CN102284505A
Application number: CN2011102457249A
Authority: CN
Inventors: 齐磊; 龚涛
Original assignee: Donghua University
Current assignee: Donghua University
Priority date: 2011-08-25
Filing date: 2011-08-25
Publication date: 2011-12-21

Abstract

The invention provides a system for controlling thickness of fuzzy PI (Proportional Integral) based on ARM (Advanced RISC machines), which comprises an inlet thickness gauge and an outlet thickness gauge which are arranged at the inlet and the outlet of a hydraulic rolling mill, respectively. The inlet thickness gauge is connected with a compensator. The system is characterized that the compensator and the outlet thickness gauge are connected with a fuzzy robust regulating module, respectively, wherein the fuzzy robust regulating module comprises a fuzzy robust regulator realized through ARM; the fuzzy robust regulator is connected a position signal collecting module, a pressure signal collecting module, a thickness signal collecting module, an executing module and a signal conditioning module, respectively. The system provided by the invention improves a series of problems that instabilities occur in a traditional AGC control. In the actual cold rolling industry, a traditional PID (Proportion Integration Differentiation) control strategy is difficult to control well due to complexity of an object of the rolling mill. However, in the system provided by the invention, uncertainty of the object is not prominent to work during a control process due to nonlinearity exclusive to the fuzzy control strategy.

Description

A kind of PI type Fuzzy thickness control system based on ARM

Technical field

The present invention relates to a kind of thickness control system based on ARM and Fuzzy PI Controller, is that a kind of on-line parameter at the vertical thick difference of hydraulic pressure cold-rolling mill band in the cold rolling industry is from adjusting the thickness intelligence control system.

Background technology

Generally address to the vertical thick poor control system of band in the cold rolling industry of current hydraulic pressure is AGC(Automatic Gauge Control, i.e. automatic thickness control).The control core of hydraulic mill AGC system is the servo-control system of oil cylinder position, is called for short APC(Automatic Position Control).

As shown in Figure 1, APC adopts MTS or SSI series magnetostriction type displacement transducer, in order to measure the position signalling of oil cylinder.The action of oil cylinder provides power (energy) source by Hydraulic Station (high pressure) on the one hand, controls it by electrohydraulic servo valve on the other hand and moves up and down.Oil cylinder piston acts on backing roll, and Newton force passes to working roll (actual Rolling roller) by backing roll.In the permanent roll gap operation of rolling, computer sends control instruction (given position signal), through certain algorithm process (such as PI control), gives electrohydraulic servo valve by computer with output signal (execution command) again.The purpose of THICKNESS CONTROL is to make the actual thickness that shuts out of band steel equal setting value, band steel AGC system must preestablish a desired value and measured actual (real) thickness compares by computer, obtain deviation signal δ h, perhaps obtain deviation signal δ h by changing tension force, pressure etc., utilize device for automatically control thickness or computer function routine change depressing position or strip tension or mill speed again, band the actual of steel shut out THICKNESS CONTROL in allowed limits.

Objectively requiring the actual (real) thickness of band as controlled volume, rather than the physical location of above-mentioned oil cylinder piston.Given this plant and consider, on the basis of position ring, introduced the thickness monitoring link of band---the AGC monitoring.Fig. 2 is the control block diagram of AGC monitoring.

Above-mentioned AGC monitoring scheme, on the basis of original APC, the outlet outfit calibrator at hydraulic mill in order to the exit thickness of real-time measurement band, thus, has constituted the thickness feedback control system on the just sincere justice.In fact, but there are bigger inertia in the oil cylinder of milling train and roll thereof as mechanical part, and this just causes existing certain hysteresis on THICKNESS CONTROL.Not only so, theoretically, certain distance is arranged between calibrator and the working roll, band rolling part be not the part that calibrator is gathered thickness signal, just having one section pure hysteresis like this in the middle of reality, is not to reach very ideal control effect thereby cause the AGC monitoring.Therefore, the improvement of following Fig. 3 is proposed---hydraulic mill inlet, outlet are equipped with calibrator simultaneously.

If the average thickness of band inlet represents with Gi, the outlet average thickness represents with Go, and represents the float value of band inlet thickness with △ gi, and △ go represents the float value of band exit thickness, then:

Inlet thickness=Gi+ △ gi;

Exit thickness=Go+ △ go;

Generally speaking, if △ gi be on the occasion of, then show band blocked up (with average thickness comparatively speaking), need to adjust control algolithm Gc1 so, have enough big drafts to guarantee oil cylinder; Otherwise △ gi is a negative value, shows that then band is thin excessively, then needs equally to adjust Gc1, and guaranteeing Gp(such as Fig. 2, Gp represents the difference of the value of feedback of the output of controller Gc1 and displacement transducer, and the actual input value of controller PID) not too small.Certainly, △ gi is as the function of time, can use △ gi(t) represent.△ gi(t wherein) be time dependent, so in essence as can be seen compensation control is a kind of of Self Adaptive Control, therefore, can adopt the achievement in research of artificial intelligence, designs more intelligent control algolithm.Generally speaking, the AGC pre-control is to add the strategy of compensation control on the basis of AGC monitoring.

Undeniable, conventional PI has brought into play historical effect in the special THICKNESS CONTROL in cold rolling industry of traditional industry control.But along with to strip quality improving constantly of requiring of longitudinal thickness tolerance (2 μ are to the variation of 3 μ) particularly, traditional control method is subjected to very big challenge.We will find dynamic model by the analytic liquid rolling press, unintentional nonlinearity and when slow the change factor be present in Position Control link (just existing non-linear) such as servo valve.Particularly the ubiquitous random disturbances of industry spot (electromagnetic interference is a kind of important interference type), conventional PID control does not possess the parameter self-tuning function and just is difficult to the good control effect of performance.Find that by analyzing be difficult to obtain the mathematical models of this rolling machine system, thus, the classical control theory that is based upon the controlled device mathematical models just loses due effect.

Summary of the invention

Become when the objective of the invention is and disturb uncertain characteristics, a kind of control system with fine robustness is provided at hydraulic mill non-linear, slow.

In order to achieve the above object, technical scheme of the present invention has provided a kind of PI type Fuzzy thickness control system based on ARM, comprise the inlet calibrator and the outlet calibrator that lay respectively at hydraulic mill inlet and exit, the inlet calibrator connects compensator, it is characterized in that: compensator and outlet calibrator connect fuzzy robust adjustment module respectively, wherein, fuzzy robust adjustment module comprises the fuzzy robust regulator of realizing by ARM, and fuzzy robust regulator is the link position signal acquisition module respectively, the pressure signal acquisition module, the thickness signal acquisition module, Executive Module and signal condition module;

Fuzzy robust regulator comprises automatic compensated regulator, automatic thickness adjuster and automated location adjuster, wherein,

Automatically compensated regulator constitutes feedforward regulator, and it adopts conventional proportional controller, and the deviation of compensated regulator inlet thickness value that will obtain by the inlet calibrator and thickness set-point is carried out suitable amplification or dwindled automatically;

The automatic thickness adjuster constitutes the outer shroud adjuster, and it comprises Fuzzy module and conventional PID adjuster, the absolute value of the exit thickness value that will be obtained by the outlet calibrator by the Fuzzy module and the difference of thickness set-point

And the absolute value of this difference rate of change As input, and adopt the proportionality constant of Fuzzy method to conventional PID adjuster

, integral constant

And derivative constant

On-line correction obtains output by conventional PID adjuster ,

, wherein, The integration of the exit thickness value that the outlet calibrator of serving as reasons obtains and the difference of thickness set-point;

Ring adjuster in the automated location adjuster constitutes, it adopts conventional PID adjuster, the output that is input as automatic compensated regulator of automated location adjuster and the output that obtains by the automatic thickness adjuster

The difference of sum and the positional information that obtains in order to the position sensor of the position signalling of measuring oil cylinder by hydraulic mill is controlled servo valve and then is reached the purpose of control hydraulic mill oil cylinder by the output of automated location adjuster.

The present invention is directed to a series of instability problems that occur in traditional AGC control, propose to improve.In the cold rolling industry of reality, because the complexity of milling train object, traditional PID control scheme is difficult to play excellent control effect.Because the fuzzy control strategy unintentional nonlinearity makes the uncertainty of object not have very outstanding showing in the middle of control procedure.

Description of drawings

Fig. 1 is the APC block diagram;

Fig. 2 is the control block diagram of band AGC monitoring;

Fig. 3 is a milling train control schematic diagram;

Fig. 4 is improved AGC control system block diagram;

Fig. 5 is a PI type Fuzzy parameter adjustment block diagram;

Fig. 6 is based on the intelligent AGC thickness control system of ARM and respectively forms module;

Fig. 7 is a hydraulic mill PI type Fuzzy THICKNESS CONTROL block diagram.

The specific embodiment

For the present invention is become apparent, now with a preferred embodiment, and conjunction with figs. is described in detail below.

The antijamming capability of tradition AGC system can not adapt to the needs of modernized metallurgical automation, and therefore, the stability and the interference rejection ability that how to improve system are the design of robust controller cores.Having its source in of problem, conventional PID does not possess the parameter self-tuning function, can not make the auto-adaptive parameter adjustment at complex environment.The scheme that the present invention proposes adopts idea of modular, set up with the ARM chip be bottom hardware core cell, PI type Fuzzy algorithm be upper strata control software kernels unit, peripheral modules (image data and output conditioning thereof) " satellite-type " around embedded solution, the function of at utmost separating each several part is to reach the purpose of each module degree of coupling minimum.

Hardware configuration of the present invention such as Fig. 4 and shown in Figure 6 comprise the inlet calibrator and the outlet calibrator that lay respectively at hydraulic mill inlet and exit, and the inlet calibrator connects compensator, and compensator and outlet calibrator connect fuzzy robust adjustment module respectively.

As shown in Figure 6, fuzzy robust adjustment module comprises the fuzzy robust regulator of realizing by ARM, and fuzzy robust regulator is link position signal acquisition module, pressure signal acquisition module, thickness signal acquisition module, Executive Module and signal condition module respectively.

Comprise that in conjunction with control software kernels unit, Fig. 7 upper strata (English abbreviates ACA as to automatic compensated regulator, full name is Automatic Compensation Adjuster), (English abbreviates ATA as to the automatic thickness adjuster, full name is Automatic Thickness Adjuster) and automated location adjuster (English abbreviates APA as, and full name is Automatic Position Adjuster).

As shown in Figure 7, upper strata control software kernels unit is the multiplex control system that is made of ACA, ATA, APA.Wherein, ring adjuster in APA constitutes; ATA constitutes the outer shroud adjuster; ACA constitutes feedforward regulator.Inner and outer ring constitutes the tandem control of two-stage, adds FEEDFORWARD CONTROL, constitutes above-mentioned hybrid system jointly.Below each adjuster is explained respectively.

ACA adopts the deviation of inlet calibrator and given thickness as its input signal.Based on following idea: the tube inlet calibrator does not still export calibrator, and its installation site and roller are that the position exists certain space length.In order to satisfy the real-time of control, must take the strategy that compensates, ACA just being based on this design.ACA adopts proportional controller, so that the deviation of thickness set-point and inlet thickness value (this numerical value is recorded by the inlet calibrator) is carried out suitable amplification and dwindled.Feedforward regulator ACA designs at the control accuracy that improves system.As shown in Figure 3, the actual rolling position of calibrator installation site and band also has suitable distance, in other words, is benchmark with the thickness of rolling position, and inlet calibrator institute measured value is greater than a reference value, and outlet calibrator institute measured value is less than a reference value.Thus, the inaccuracy of measured value just causes the control accuracy of whole hydraulic mill thickness control system to reduce.Be taken into the mean value of mouthful thickness and exit thickness, and compare with the thickness set-point.If the former greater than the latter, then should strengthen the output of controller; Otherwise should reduce the output of controller.This is the design criteria of ACA.

ATA is the core adjuster of this system.In view of the parameter of outer shroud adjuster need rely on concrete technology and decides, consider design Fuzzy PID parameters self-adjusting caliper profiler.The key of this design is the online self-adjusting of pid parameter, and guarantees that this system possesses the stability of technical grade.Improving the consideration of stability of a system this respect, with the noise in the filtering collection signal at forward path design filter unit.The filter unit here also needs to adjust its cut-off frequency flexibly, to adapt to different complicated scenes.In fact, the problem of filtering is the problem of the information flow that has recovered as far as possible by noise jamming, just predict a seasonal effect in time series problem of having been mixed up by noise, so filtering problem promptly is a forecasting problem.The so-called prediction removed to estimate the statistical parameter of whole assemblage exactly from a time series past data from mathematics.Consider the problems referred to above, claim that this system is intelligent robust servo adjustment system.

As shown in Figure 5, ATA adopts the Fuzzy method to carry out the automatic thickness adjuster of pid parameter on-line correction just.Conventional PID control formula is

, wherein,

Represent the output of PID,

, And

Represent the exit thickness value and the difference of thickness set-point, the rate of change of this difference and the integration of this difference that obtain by the outlet calibrator respectively,

,

With

Represent proportionality constant, integral constant and the derivative constant of PID adjuster respectively.

From the essence of Fuzzy control, three undetermined parameters of APA adjuster

,

With

Be respectively

With

Binary function, that is:

,

,

It is carried out generality analysis has: when

When big, have preferably tracking performance fast, should get bigger for making system

With less

, for bigger overshoot appears in the response of avoiding system, the reply integral action is limited, and gets usually simultaneously

=0.When

When being in median size, have less overshoot for making system,

Should obtain smaller; In this case,

Value bigger to the influence of system,

Value want suitably.When

Hour, have steady-state behaviour preferably for making system,

,

All should obtain big, simultaneously for avoiding near system's appearance setting value to shake,

Selection very important.

As previously mentioned, the linguistic variable of Fuzzy controller has two, promptly

,

, discuss earlier

(1)

Basic domain, that is the absolute value of thickness error, in the cold rolling field of reality, always wish band thick difference control heal little good more, but error is an objective reality, it also is impossible reaching error and be zero.Require the thick difference of finished product to be controlled in the reality | 10| μ m, perhaps better situation | 5| μ m.But the supplied materials tolerance is bigger in general, here with | 60| μ m analyzes.So | the basic domain of e| is [0,60] (μ m).Below with | e| is corresponding

Domain be X={0,1,2,3,4,5,6,7,8,9,10,11,12}, thereby draw quantizing factor

(2) be Error Absolute Value

This linguistic variable is selected six language values: greatly (Extremely), very big (Very), quite big (Largely), bigger (Some), bigger (A little), (Slightly) a little greatly.Be defined as respectively: EB, VB, LB, SB, AB, SLB.

(3), determine domain X goes up in order to the membership function of describing Fuzzy subclass EB, VB, LB, SB, AB, SLB to represent it is more rational with normal distribution according to practical experience.The membership function expression formula:

, might as well make

(4) linguistic variable

The assignment table just can be expressed as following sheet form:

?	0	1	2	3	4	5	6	7	8	9	10	11	12
														SLB	0.9394	1.0000	0.9394	0.7788	0.5698	0.3679	0.2096	0.1054	0.0468	0.0183	0.0063	0	0.0005
AB	0.7788	0.9394	1.0000	0.9394	0.7788	0.5698	0.3679	0.2096	0.1054	0.0468	0.0183	0.0000	0.0019
														SB	0.3679	0.5698	0.7788	0.9394	1.0000	0.9394	0.7788	0.5698	0.3679	0.2096	0.1054	0.0000	0.0183
LB	0.1054	0.2096	0.3679	0.5698	0.7788	0.9394	1.0000	0.9394	0.7788	0.5698	0.3679	0.0000	0.1054
														VB	0.0183	0.0468	0.1054	0.2096	0.3679	0.5698	0.7788	0.9394	1.0000	0.9394	0.7788	0.0000	0.3679
EB	0.0019	0.0063	0.0183	0.0468	0.1054	0.2096	0.3679	0.5698	0.7788	0.9394	1.0000	0.0000	0.7788

Hypothesis is as universe of a fuzzy set { SLB, AB, SB, LB, VB, EB}={1,2,4,6,8, the 10} of the absolute value of error in last table.

In like manner can draw linguistic variable

The assignment table.So far, the assignment table of two of the Fuzzy module input language variablees is set up.Adopt same principle, also can obtain three output language variablees of Fuzzy module

,

With

The assignment table.So far, that is set up database in the Fuzzy module knowledge base, it comprises the assignment table of input, output language variable.

The inference rule of Fuzzym module: rule statements adopts better simply IF---the THEN statement, that is:

；

；

；

Corresponding The reasoning results has:

,

,

With

It is respectively set

,

Apply obtain behind the corresponding fuzzy rule about ratio , integration

And differential

Fuzzy relation, they are a kind of of fuzzy set in essence.Wherein

Be the fuzzy set of Error Absolute Value, Be the fuzzy set of error rate absolute value,

Represent the compose operation of fuzzy set, it is identical with common multiplication of matrices calculating process, just the oeprator difference.Fuzzy control rule has identical structure, but at be different objects

,

With

, so the gained result is also just different.

Fuzzy judgement: adopt average weighted way that the fuzzy data that draws is being carried out anti-quantization (promptly divided by quantizing factor at last

), just can carry out online adjustment to parameter.

APA adopts traditional PID regulation technology, and it is input as the output and the output that obtains by the automatic thickness adjuster of automatic compensated regulator

The anti-analysis of electromagnetic interference of ARM system:

Modern hydraulic mill is the automated system that integrates plant equipment, Electrified Transmission, AGC THICKNESS CONTROL, hydraulic drive.Power line and control line, holding wire are in factory's overall situation, and so, the antijamming capability that improves the particularly embedded controller of control appliance seems particularly important.The interference protection measure of ARM chip:

The first step, partly add savings electric capacity and decoupling capacitance, can improve the ability of Electric Circuit Electromagnetic Compatibility at the power supply of chip.Savings electric capacity plays the effect of stablizing chip power supply voltage, and decoupling capacitance then is to provide the interchange fire escape for system noise (interference).

Second step, the following method of employing can reduce or weaken ground return circuit and disturb:

The cross-sectional area of---shorten ground wire or increase ground wire;

---photoelectricity is isolated;

---add filter network at the signal input circuit.

The 3rd step, the following method of employing can reduce or weaken common impedance disturbances:

The resistance value of the common ground wire of---reduce circuit;

---partly take suitable circuit connecting mode (optimum Match) at sensitive circuit adopted different ground wires such as big power line with the low signal line; Simulation ground and digitally separate, or the like.

Claims

1. PI type Fuzzy thickness control system based on ARM, comprise the inlet calibrator and the outlet calibrator that lay respectively at hydraulic mill inlet and exit, the inlet calibrator connects compensator, it is characterized in that: compensator and outlet calibrator connect fuzzy robust adjustment module respectively, wherein, fuzzy robust adjustment module comprises the fuzzy robust regulator of realizing by ARM, and fuzzy robust regulator is link position signal acquisition module, pressure signal acquisition module, thickness signal acquisition module, Executive Module and signal condition module respectively;

Figure 2011102457249100001DEST_PATH_IMAGE001

And the absolute value of this difference rate of change

As input, and adopt the proportionality constant of Fuzzy method to conventional PID adjuster , integral constant

And derivative constant

Figure 2011102457249100001DEST_PATH_IMAGE005

On-line correction obtains output by conventional PID adjuster ,

Figure 2011102457249100001DEST_PATH_IMAGE007

, wherein,

The integration of the exit thickness value that the outlet calibrator of serving as reasons obtains and the difference of thickness set-point;

Ring adjuster in the automated location adjuster constitutes, it adopts conventional PID adjuster, the output that is input as automatic compensated regulator of automated location adjuster and the output that obtains by the automatic thickness adjuster The difference of sum and the positional information that obtains in order to the position sensor of the position signalling of measuring oil cylinder by hydraulic mill is controlled servo valve and then is reached the purpose of control hydraulic mill oil cylinder by the output of automated location adjuster.

2. a kind of PI type Fuzzy thickness control system based on ARM as claimed in claim 1 is characterized in that: the method that improves the antijamming capability of the described fuzzy robust regulator of realizing by ARM is:

The first step, partly add savings electric capacity and decoupling capacitance at the power supply of ARM chip, improve the Electric Circuit Electromagnetic Compatibility ability, wherein save electric capacity and play the effect of stablize chip power supply voltage, decoupling capacitance then is to provide the passage that exchanges evacuation for system noise;

The cross-sectional area of second step, shortening ground wire or increase ground wire, output adopts photoelectricity to isolate, and reduces or weaken the loop interference of beating at signal input circuit interpolation filter network;

The 3rd goes on foot, adopts and reduce or weaken the common impedance interference.