CN103203376A - Method for accurately controlling pressure of cold-rolled strip steel emulsion system - Google Patents

Abstract

The invention relates to the technical field of steel rolling process control, in particular to a method for accurately controlling the pressure of an emulsion system of cold-rolled strip steel, wherein the emulsion pressure of the emulsion system of the cold-rolled strip steel is controlled in a mode of combining a pressure bypass valve with main pump frequency conversion regulation, and the pressure of the emulsion system is kept constant by adjusting the rotating speed of a frequency conversion motor; in order to realize the purpose of accurate pressure regulation of the system, the system adopts two execution modes aiming at different processes: 1) in the starting process, when the pressure regulation of the pressure bypass valve exceeds the working range, the emulsion pressure of a main pump output system is increased by increasing the rotating speed of the variable frequency motor, so that the pressure regulation capability of the system is ensured; 2) in the normal working process, the PID control algorithm with Smith estimation is adopted in consideration of the fact that the distance between a pressure detection point of an emulsion system and a liquid path of a variable-frequency pressure regulating actuating mechanism is long and the system lag is large. The method has the advantages of accurate pressure control of an emulsion system of the cold rolling lubrication and cooling process, greatly improved quality of cold-rolled strip steel, energy conservation, consumption reduction and production cost reduction.

Description

A kind of cold-strip steel emulsion system pressure accuracy control method

Technical field

The present invention relates to a kind of steel rolling process control technology field, be specifically related to a kind of cold-strip steel emulsion system pressure accuracy control method.

Background technology

Technological lubrication and technology cooling are one of important topics of modern cold rolling technology, also are the technological difficulties in the production practices, and it has crucial effects for the control of production cost, the raising of product quality.Emulsion pressure control level directly influences the emulsion flow, the emulsion instability of flow will certainly cause technology cooling and lubricating state, and the quality of cooling and lubricating state directly influences normally carrying out of cold rolling production, as produce the problems such as milling train chatter, heat scuffing and complicated shape wave that occur in the reality, all have direct related with the lubricating status of emulsion.So from lubricated and cool off two aspects, adopting process is lubricated in cold rolling is not only necessaryly, and is to improve product production capacity and quality, the key measure of reduction energy resource consumption and production cost.

The by-pass and pressure regulator valve mode is adopted in traditional emulsion pressure adjustment; because bypass aperture voltage regulating mode; has nonlinear characteristic; this mode of operation can cause emulsion system pressure to produce big fluctuation usually even disperse; degree of regulation is low; finally also can cause the error of injection flow between the emulsion frame bigger than normal; in case deviation appears in the cooling and lubricating amount; will cause the milling train chatter; problems such as heat scuffing and complicated shape wave; and; can be owing to the deviation of cooling and lubricating amount, roller surface can be because the too high scaling that cause that thermal stress causes in the reduction of quench hardened case hardness and the roller of temperature; problems such as roll wear increase.In addition, usually adjustable range 8bar ± 5% of by-pass and pressure regulator valve is less than normal, and exceeding this adjustable range then because the main pump non-frequency is regulated can't increase-volume, then helpless to the operating differential state.

In the prior art, the fixed-voltage altering-current system is adopted in the control of cold rolling emulsion, keeps constant for the system pressure on latex dust road by the rotating speed of adjusting variable-frequency motor, but adopts frequency-converting speed-governing control system to have the problem of control lag separately.

Therefore, proposing a kind of is that variable frequency adjustment is the basis by increasing the emulsion system main pump, utilizes system pressure to regulate the mode that by-passing valve combines with variable frequency adjustment pressure, and emulsion system pressure is accurately controlled, and is the unusual technical issues that need to address.

Summary of the invention

The purpose of this invention is to provide a kind of cold-strip steel emulsion system pressure accuracy control method, the mode that adopts the pressure by-passing valve to combine with the main pump variable frequency adjustment realizes the emulsion pressure control of cold-strip steel emulsion system, this method is accurate for cold rolling emulsion system pressure control lubricated and process for cooling, improved the quality of cold-strip steel greatly, energy-saving and cost-reducing, reduced production cost.

For achieving the above object, the present invention is achieved through the following technical solutions:

A kind of cold-strip steel emulsion system pressure accuracy control method, the mode that adopts the pressure by-passing valve to combine with the main pump variable frequency adjustment is accurately regulated emulsion system pressure; In start-up course, the rotating speed initial value at first is set and according to pressure-regulating valve aperture amplitude limit value, the rotating speed of adjusting variable-frequency motor keeps the initial pressure of emulsion system constant; In course of normal operation, the pressure by-passing valve keeps aperture at 45-55%, by automatic adjusting variable-frequency motor rotating speed, comes accuracy-control system pressure;

At system starting process, main pump variable-frequency motor initialization is the output of 80% rated speed, when pressure-regulating valve aperture＞95%, illustrate that the higher pressure-regulating valve aperture bypass regulating system pressure that utilizes separately of emulsion system pressure has been difficult to realize reducing, have only this moment the rotating speed with variable-frequency motor to reduce, the rotating speed of variable-frequency motor is made as 60% rated speed, just can effectively reduce system pressure; When pressure-regulating valve aperture＜5%, illustrate that emulsion system pressure is higher, utilize pressure-regulating valve aperture bypass regulating system pressure to be difficult to realize increasing separately, have only this moment the rotating speed with variable-frequency motor to increase, be made as 100% rated speed, could effectively increase system pressure; When rolling mill speed is zero, be to save the energy to keep the basic self-loopa of emulsion system, be that the output of 50% rated speed reaches this ability and gets final product with the speed setting of variable-frequency motor.

In system's course of normal operation, by automatic adjusting variable-frequency motor rotating speed, come accuracy-control system pressure; Because the frequency conversion voltage adjusting mode has the large time delay characteristics, so adopt PID control in conjunction with Smith predictive compensation mode, wherein the PID equation is as follows:

$u\left(t\right)=K_{P}e+K_d\frac{\mathrm{de}}{\mathrm{dt}}+K_i\∫\mathrm{edt}---\left(1\right)$

System's setting parameter is: K _P=0.15, K _d=0.001, K _i=0.0027.

G _p(s) e ^{-τ s}The transfer function of indicated object, G _c(s) transfer function of expression adjuster, wherein G _p(s) be controlled device, do not comprise the transfer function of the pure part that lags behind, e ^{-τ s}The transfer function of the part that lags behind for controlled device is pure includes pure lag system e in the ssystem transfer function denominator ^{-τ s}, the stability of system is reduced, if τ is enough big, system is unsettled.In order to improve the control effect of this class large time delay object, introduce a compensator in parallel with object, i.e. so-called Smith prediction device, its transfer function is G _τ(s), the transfer function after compensation is:

$\frac{Y^{\′}\left(s\right)}{U\left(s\right)}=G_p\left(s\right)e^{-\mathrm{\τs}}+G_{\mathrm{\τ}}\left(s\right)---\left(2\right)$

If will then require by means of the pure hysteresis of compensator full remuneration object:

$\frac{Y^{\′}\left(s\right)}{U\left(s\right)}=G_p\left(s\right)e^{-\mathrm{\τs}}+G_{\mathrm{\τ}}\left(s\right)=G_p\left(s\right)---\left(3\right)$

So be compensated the transfer function expression formula of device be:

G _τ(s)＝G _p(s)(1-e _-τs) (4)。

Compared with prior art, the invention has the beneficial effects as follows:

Take Different Strategies in emulsion system startup and normal course of operation, large time delay problem at frequency conversion voltage adjusting, the mode of PID control in conjunction with the Smith predictive compensation proposed, improve the control accuracy of emulsion system pressure, can satisfy production Automobile Plate and the high-grade household electrical appliances needs of plate fully, improve the quality of cold-rolled products.The mode that adopts the pressure by-passing valve to combine with the main pump variable frequency adjustment realizes the emulsion pressure control of cold-strip steel emulsion system, this method is accurate for cold rolling emulsion system pressure control lubricated and process for cooling, improved the quality of cold-strip steel greatly, energy-saving and cost-reducing, reduced production cost.

Description of drawings

Fig. 1 is that emulsion system pressure is regulated schematic diagram;

Fig. 2 is that control chart is coordinated in by-passing valve system and the pressure regulation of speed governing unsteady flow;

Fig. 3 is emulsion system Flow-rate adjustment figure;

Fig. 4 is that the by-passing valve aperture is regulated and the discharge relation curve;

Fig. 5 is that the bypass aperture is estimated Regulation Control figure in conjunction with Smith;

Fig. 6 is emulsion system pressure control result curve.

The specific embodiment

A kind of cold-strip steel emulsion system pressure accuracy control method, the emulsion pressure of cold-strip steel emulsion system is controlled the mode that adopts the pressure by-passing valve to combine with the main pump variable frequency adjustment, keeps the constant pressure of emulsion system by the rotating speed of adjusting variable-frequency motor; When the adjusting of pressure by-passing valve pressure exceeds working range, by improving the variable-frequency motor rotating speed, increase main pump output system emulsion pressure, guarantee the system pressure regulating power;

1, emulsion system start-up course, main pump variable-frequency motor initialization is the output of 80% rated speed, when pressure-regulating valve aperture＞95%, illustrate that the higher pressure-regulating valve aperture bypass regulating system pressure that utilizes separately of emulsion system pressure has been difficult to realize reducing, have only this moment the rotating speed with variable-frequency motor to reduce, the rotating speed of variable-frequency motor is made as 60% rated speed, just can effectively reduce system pressure; When pressure-regulating valve aperture＜5%, illustrate that emulsion system pressure is higher, utilize pressure-regulating valve aperture bypass regulating system pressure to be difficult to realize increasing separately, have only this moment the rotating speed with variable-frequency motor to increase, be made as 100% rated speed, could effectively increase system pressure; When rolling mill speed is zero, be to save the energy to keep the basic self-loopa of emulsion system, be that the output of 50% rated speed reaches this ability and gets final product with the speed setting of variable-frequency motor.

2, emulsion system course of normal operation, control by-passing valve aperture 45-55% comes indirect Adjustment System pressure mode by main pump variable frequency adjustment rotating speed, keeps stable for newborn system pressure.Because variable frequency adjustment has the hysteresis problem, so adopt PID control in conjunction with Smith predictive compensation mode, wherein the PID equation is as follows:

$u\left(t\right)=K_{P}e+K_d\frac{\mathrm{de}}{\mathrm{dt}}+K_i\∫\mathrm{edt}---\left(1\right)$

System's setting parameter is: K _P=0.15, K _d=0.001, K _i=0.0027

Single loop control system as shown in Figure 5.G among the figure _p(s) e ^{-τ s}The transfer function of indicated object, G _c(s) transfer function of expression adjuster, wherein G _p(s) be controlled device, do not comprise the transfer function of the pure part that lags behind, e ^{-τ s}The transfer function of the part that lags behind for controlled device is pure includes pure lag system e in the ssystem transfer function denominator ^{-τ s}, the stability of system is reduced, if τ is enough big, system is unsettled.In order to improve the control effect of this class large time delay object, introduce a compensator in parallel with object, i.e. so-called Smith prediction device, its transfer function is G _τ(s), the transfer function after compensation is:

$\frac{Y^{\′}\left(s\right)}{U\left(s\right)}=G_p\left(s\right)e^{-\mathrm{\τs}}+G_{\mathrm{\τ}}\left(s\right)---\left(2\right)$

If will then require by means of the pure hysteresis of compensator full remuneration object:

$\frac{Y^{\′}\left(s\right)}{U\left(s\right)}=G_p\left(s\right)e^{-\mathrm{\τs}}+G_{\mathrm{\τ}}\left(s\right)=G_p\left(s\right)---\left(3\right)$

So be compensated the transfer function expression formula of device be:

G _τ(s)＝G _p(s)(1-e ^-τs) (4)

Example: be for example Fig. 1 with Anshan iron and steel plant 1450 cold rolling emulsion control systems, the by-pass governing and the variable frequency adjustment system pressure that adopt this patent to propose concern as Fig. 2,4, the accurate control mode of flow such as Fig. 3, with frequency conversion combine with bypass mode regulating system pressure model such as Fig. 5, emulsion system pressure output effect such as Fig. 6 by comparative analysis as can be known, adopt the pressure flow after optimizing to regulate model, increase substantially the pressure flow precision, guarantee the at a high speed effective Rolling Production of milling train.

In actual applications, frequency-converting speed-governing control system pressure has the effect that reduces the wastage, but use variable frequency regulating speed control separately and have the control lag problem, therefore, the accurate control of finishing emulsion system pressure jointly of frequency-converting speed-governing control system and by-pass and pressure regulator valve, response speed is fast, and can realize saving energy and reduce the cost.In the present embodiment, frequency converter adopts MICROMASTER 440 Series Frequency Converter of SIEMENS, adaptive motor power (output) 250kW, output frequency 50Hz.

The emulsion pressure of cold-strip steel emulsion system is controlled the mode that adopts the pressure by-passing valve to combine with the main pump variable frequency adjustment, keeps the constant pressure of emulsion system by the rotating speed of adjusting variable-frequency motor; Main pump variable-frequency motor initialization is the output of 80% rated speed, when pressure-regulating valve aperture＞95%, illustrate that the higher pressure-regulating valve aperture bypass regulating system pressure that utilizes separately of emulsion system pressure has been difficult to realize reducing, have only this moment the rotating speed with variable-frequency motor to reduce, the rotating speed of variable-frequency motor is made as 60% rated speed, just can effectively reduce system pressure; When pressure-regulating valve aperture＜5%, illustrate that emulsion system pressure is higher, utilize pressure-regulating valve aperture bypass regulating system pressure to be difficult to realize increasing separately, have only this moment the rotating speed with variable-frequency motor to increase, be made as 100% rated speed, could effectively increase system pressure; When rolling mill speed is zero, be to save the energy to keep the basic self-loopa of emulsion system, be that the output of 50% rated speed reaches this ability and gets final product with the speed setting of variable-frequency motor.The emulsion system course of normal operation, control by-passing valve aperture 45-55% comes indirect Adjustment System pressure mode by main pump variable frequency adjustment rotating speed, keeps stable for newborn system pressure.Because variable frequency adjustment has the hysteresis problem, so adopt PID control in conjunction with Smith predictive compensation mode.

This method is accurate for cold rolling emulsion system pressure control lubricated and process for cooling, has improved the quality of cold-strip steel greatly, and is energy-saving and cost-reducing, reduced production cost.

Claims (2)

1. a cold-strip steel emulsion system pressure accuracy control method is characterized in that, the mode that adopts the pressure by-passing valve to combine with the main pump variable frequency adjustment is accurately regulated emulsion system pressure; In start-up course, the rotating speed initial value at first is set and according to pressure-regulating valve aperture amplitude limit value, the rotating speed of adjusting variable-frequency motor keeps the initial pressure of emulsion system constant; In course of normal operation, the pressure by-passing valve keeps aperture at 45-55%, by automatic adjusting variable-frequency motor rotating speed, comes accuracy-control system pressure;

At system starting process, main pump variable-frequency motor initialization is the output of 80% rated speed, when pressure-regulating valve aperture＞95%, illustrate that the higher pressure-regulating valve aperture bypass regulating system pressure that utilizes separately of emulsion system pressure has been difficult to realize reducing, have only this moment the rotating speed with variable-frequency motor to reduce, the rotating speed of variable-frequency motor is made as 60% rated speed, just can effectively reduce system pressure; When pressure-regulating valve aperture＜5%, illustrate that emulsion system pressure is higher, utilize pressure-regulating valve aperture bypass regulating system pressure to be difficult to realize increasing separately, have only this moment the rotating speed with variable-frequency motor to increase, be made as 100% rated speed, could effectively increase system pressure; When rolling mill speed is zero, be to save the energy to keep the basic self-loopa of emulsion system, be that the output of 50% rated speed reaches this ability and gets final product with the speed setting of variable-frequency motor.

2. according to right 1 described a kind of cold-strip steel emulsion system pressure accuracy control method, it is characterized in that, in system's course of normal operation, by automatic adjusting variable-frequency motor rotating speed, come accuracy-control system pressure; Because the frequency conversion voltage adjusting mode has the large time delay characteristics, so adopt PID control in conjunction with Smith predictive compensation mode, wherein the PID equation is as follows:

$u\left(t\right)=K_{P}e+K_d\frac{\mathrm{de}}{\mathrm{dt}}+K_i\∫\mathrm{edt}---\left(1\right)$

System's setting parameter is: K _P=0.15, K _d=0.001, K _i=0.0027.

G _p(s) e ^{-τ s}The transfer function of indicated object, G _c(s) transfer function of expression adjuster, wherein G _p(s) be controlled device, do not comprise the transfer function of the pure part that lags behind, e ^{-τ s}The transfer function of the part that lags behind for controlled device is pure includes pure lag system e in the ssystem transfer function denominator ^{-τ s}, the stability of system is reduced, if τ is enough big, system is unsettled.In order to improve the control effect of this class large time delay object, introduce a compensator in parallel with object, i.e. so-called Smith prediction device, its transfer function is G _τ(s), the transfer function after compensation is:

$\frac{Y^{\′}\left(s\right)}{U\left(s\right)}=G_p\left(s\right)e^{-\mathrm{\τs}}+G_{\mathrm{\τ}}\left(s\right)---\left(2\right)$

If will then require by means of the pure hysteresis of compensator full remuneration object:

$\frac{Y^{\′}\left(s\right)}{U\left(s\right)}=G_p\left(s\right)e^{-\mathrm{\τs}}+G_{\mathrm{\τ}}\left(s\right)=G_p\left(s\right)---\left(3\right)$

So be compensated the transfer function expression formula of device be:

G _τ(s)＝G _p(s)(1-e ^-τs) (4)。

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