EP1457274A2 - Method and device for avoiding vibrations - Google Patents

Abstract

Process for avoiding vibrations, especially 3- and 5-octave vibrations in a roll unit having a roll stand with provision for roll adjustment, a set of rolls, including a controller, with the aid of which the degree of adjustment, which changes with time, is determined in real time, an actuator, via which one roll of the roll set l is admitted (sic) and the degree of control is held at a specific desired value (sic) and the degree of control is held at a specific desired value. Independent claims are included for: (1) a device for avoiding the vibrations; (2) A band-like roll material of thickness variations at least 20% less than given thickness tolerances.

Description

The invention relates to a method and a device for avoiding Vibrations, especially 3rd and 5th octave vibrations, in a rolling mill at least one roll stand with roll adjustment and at least one roll set.

With rolling mills, it is known that under certain operating conditions it too unwanted oscillations or vibrations that lead to considerable damage on the system, as well as lead to defects in the rolled product. By a Superposition of vibrations, the causes of which are not yet complete in detail Clarifying vibrations, i.e. vibrations with a negative damping. One consequence of this is unstable vibration conditions or vibrations with a very high energy content. In addition to the above Damage to the system can also lead to impermissible deviations in the geometric dimensions and unwanted surface patterns or surface defects occur on the rolling stock. Both mean considerable costs for the production, because the faulty rolled products must be rejected.

Those skilled in the art are aware of the large number of vibrations occurring in rolling processes known two typical groups, which according to their characteristics, such as the frequency and their effects can be divided into 3rd and 5th octave vibrations. 3. Octave vibrations occur in a frequency range from about 100 to 350 Hz and are characterized by a very high energy content, so that also considerable mechanical damage to the rolling mill can occur. These vibrations are accompanied by a loud noise. The specified frequencies depend from time to time depending on the particular system configuration and the rolling parameters can therefore deviate from it. At the set of rollers occurs between the rollers often an oppositely directed vibration, which leads to stretching of the Scaffolding stand is coming. Stick-slip effects can also cause vibrations be, with differences in the drive torques of the rollers for which vibrations can be. A special feature of these vibrations the appearance of unstable vibrations.

5. Octave vibrations occur in a frequency range of around 500 to 800 Hz and lead to surface defects on the rolling stock and are partly only due to this Defects in the rolling stock are detected. The work rolls swing relative to the Backup rolls.

Both types of vibration have in common that there are movements of the roller set and thus there is a deviation from the target roll gap. Depending on the type of vibration the defects on the rolling stock show different degrees of surface defects, as geometrical defects or as combinations thereof.

Monitoring systems are known from the prior art. Watch these systems or measure the vibration condition of the rolling mill or the rolling stands and reduce the rolling speed in the event of vibrations, in order to reduce vibrations and avoid instabilities. A disadvantage of Procedures that use monitoring systems is a significant drop in productivity, due to a reduction in the rolling speed.

Rolling mills with passive vibration damping systems are also known. The energy of an occurring vibration is reduced and by means of dampers so the risk of damage is reduced. However, these systems can have surface defects insufficiently avoid the rolling stock, so that the task of a faultless Generate rolling stock so that it is not solved.

US 5,724,846 describes a method for combating vibrations (octave vibrations) in a rolling mill for rolling strip. The Rolling system imprinted a vibration component that is relative to an existing one Vibration is asynchronous to vertical vibrations of the rollers avoid. The solution described always goes from an existing one Vibration, which is used as the basis for the countermeasure. at This solution is not sufficient for rolling mills, because of changing operating conditions despite the countermeasure, defects still occur on the rolled strip can. Especially for resonating vibrations that are characterized by a negative Damping can be characterized by that described in US Pat. No. 5,724,846 Invention no solution can be found.

A device can be found in US Pat. No. 6,387,214 B1 measured vibration by means of an actuator the vibration state of a roller being affected. The solution only offers an indication of how the vibrations be reduced, but not how they can be avoided. In the case of unstable No solution is offered to vibration conditions.

• Kailath T.: "Linear Systems", Prentice Hall, 1980.
• Franklin G., Powell D., Emami-Naeini A.: "Feedback Control of Dynamic Systems", Fourth Edition, Prentice Hall, 2002.
• Vidyasagar M.: "Nonlinear Systems Analysis", Second Edition, Prentice Hall, 1993.

It is a fundamental feature that unstable vibration states can only be eliminated and thus stabilized by regulating, that is to say by returning the information signal. A detailed explanation of this fact can be found in the publications below:

• Kailath T .: "Linear Systems", Prentice Hall, 1980.
• Franklin G., Powell D., Emami-Naeini A .: "Feedback Control of Dynamic Systems", Fourth Edition, Prentice Hall, 2002.
• Vidyasagar M .: "Nonlinear Systems Analysis", Second Edition, Prentice Hall, 1993.

It is an object of the invention a method according to the preamble of Claim 1 to develop further, so that damage to the rolling mill or defects avoided or excluded on the rolling stock due to oscillations or vibrations become.

The object is according to the inventive method according to the characterizing Part of claim 1 solved. By the method according to the invention is the generation of vibrations that lead to malfunctions of the rolling operation or Defects in the rolling stock can be avoided and a vibration and trouble-free Operation ensured. Based on at least one permanently measured Size, a controller, a mathematical control law and submodels, the Parts of the system describe, includes, is supplied, the determination is made at least one temporally variable manipulated variable in real time, the manipulated variable being Input signal for at least one actuator to act on at least one Roll of the roll set of a roll stand and / or the rolling stock is used.

To predict the behavior of the controlled system is next to a sufficiently precise Acquisition of the operating status including a precise description of the system or of system behavior necessary. The system behavior is determined by a mathematical Description, all relevant physical influences and relationships and the material behavior of system components and rolling stock taken into account, by linear or non-linear or from combinations of linear and non-linear sub-models are described, creating one for the controlled system sufficiently accurate simulation is achieved.

The controller takes into account the essential system nonlinearities, such as. the rolling force model, actuator etc., the energy required for Raising of the vibration leads, withdrawn or it is achieved that in the system Rolling mill stored energy takes a minimum. With the math Control law is based on linear and / or non-linear equations and / or Differential equations and / or differential equations the manipulated variable (s) as Function of the measured variable (s) determined. A control scheme for this is shown in FIG. 1.

In the case of unstable working points, the energy stored in the system increases and thus also the amplitudes of the vibrations over time. Without acting on the system through a targeted control intervention, or as with known systems by reducing the belt speed, belt tears can cause serious damage on the plant, plant downtimes and thus very high costs occur. By a The belt speed is reduced so that the system becomes stable again and the amplitude decreases, but under the disadvantage already described one reduced productivity.

The sub-models include the modules and the system behavior a hydraulic and / or a mechanical and / or a rolling force model. through of the sub-models, the rolling mill is adequately described and in the regulatory law mapped, in addition to the behavior of the system parts and the system load the behavior of the entire rolling mill is mapped with high accuracy.

• Kugi A.: "Nonlinear Control Based on Physical Models", Lecture Notes in Control and Information Sciences 260, Springer, 2000.
• Merritt H. E.: "Hydraulic Control Systems", John Wiley & Sons 1967.

A possible hydraulic sub-model is described in detail in the publication below.

• Kugi A .: "Nonlinear Control Based on Physical Models", Lecture Notes in Control and Information Sciences 260, Springer, 2000.
• Merritt HE: "Hydraulic Control Systems", John Wiley & Sons 1967.

• Kugi A., Schlacher K., Keintzel G.: "Position Control and Active Eccentricity compensation in Rolling Mills", at - Automatisierungstechnik S. 342-349, Oldenbourg, 1999.

Further descriptions of possible models for hydraulics and rolling force determination can be found in the publication:

• Kugi A., Schlacher K., Keintzel G .: "Position Control and Active Eccentricity compensation in Rolling Mills", at - Automatisierungstechnik pp. 342-349, Oldenbourg, 1999.

• Grabmair G., Schlacher K., Kugi A.: "Coupling effects in multi stand rolling mills", Metal Forming 2000, pp. 295-301, 2000.
• Bland D., Ford H., Ellis F.: "Cold rolling with strip tension", Part I, Journal of the Iron and Steel Institute, pp. 57-72, 1951.
• Bland D., Ford H., Ellis F.: "Cold rolling with strip tension", Part II, Journal of the Iron and Steel Institute, pp. 239-245, 1952.
• Bland D., Ford H.: "Cold rolling with strip tension", Part III, Journal of the Iron and Steel Institute, pp. 245-249, 1952.
• Jortner D., Osterle J., Zorowski C.: "An analysis of cold strip rolling", Int. J. Mech. Sci., Vol.2, pp. 179-194, 1960.

Detailed references to the rolling force models and the specific tasks for coupled rolling stands in rolling mill systems can be found in the references:

• Grabmair G., Schlacher K., Kugi A .: "Coupling effects in multi stand rolling mills", Metal Forming 2000, pp. 295-301, 2000.
• Bland D., Ford H., Ellis F .: "Cold rolling with strip tension", Part I, Journal of the Iron and Steel Institute, pp. 57-72, 1951.
• Bland D., Ford H., Ellis F .: "Cold rolling with strip tension", Part II, Journal of the Iron and Steel Institute, pp. 239-245, 1952.
• Bland D., Ford H .: "Cold rolling with strip tension", Part III, Journal of the Iron and Steel Institute, pp. 245-249, 1952.
• Jortner D., Osterle J., Zorowski C .: "An analysis of cold strip rolling", Int. J. Mech. Sci., Vol. 2, pp. 179-194, 1960.

In conjunction with the regulatory law, it succeeds on the basis of a precise forecast the system behavior to determine one or more manipulated variables and at least an actuator to influence the operating state of the rolling mill in such a way that the creation of 3rd and 5th octave vibrations for all operating states of the System can be prevented. This ensures that, for example, for high Rolling speeds and low rolling stock thicknesses give rise to octave vibrations is prevented.

Through permanent monitoring of the system status, over at least one permanently measured size, a continuous supply of the size to the controller and the determination of at least one time-variable manipulated variable in real time, becomes a permanent monitoring and a permanent intervention in the plant behavior reached. Due to the application of the system via at least one Actuator, energy is continuously withdrawn from the oscillatory system, so that the formation or generation of octave vibrations is reliably prevented. The measured size is used as an indicator of the system condition and kept at defined values.

According to a particular embodiment, the vertical is measured Acceleration of the roller set used. The vertical acceleration has turned out to be a good indicator of the vibration condition in the roll stand, because thereby information about the current movement situation of the rollers and thus the Load roll gap is given. The operating status can be determined using a simple measurement installation be recorded precisely and inexpensively.

Another simple embodiment of the invention sees the measured variable as Use the cylinder pressure of the roller adjustment before. Through this configuration the current operating state is very good via the cylinder pressures, for example the positioning cylinder, shown, so that an exact Prediction of the system behavior and avoidance of a control intervention Octave vibrations are possible.

In a special embodiment of the method, the measured variable is vertical position of the piston of the roller adjustment. Because the vertical Position of the roller set or the rollers of the roller set the load roll gap define, is the vibration behavior from deviations from a position easily derivable.

Another embodiment is through the use of the tension condition achieved in the rolling stock as the measured size. In particular, this also Coupling the stands of the rolling mill over the rolling stock and the overlapping ones Vibrations shown in the rolling stands.

In a preferred embodiment of the method according to the invention several permanently measured variables are used as input variables for the controller. By combining two or more measured quantities, the current operating status recorded very precisely, so that a the best possible influence on the vibration behavior is achieved. In doing so Combinations of at least two measured quantities, e.g. the vertical Acceleration and / or the cylinder pressure of the roll adjustment and / or the vertical position of the piston of the roll adjustment and / or the tension condition used in the rolling stock, the execution meeting the needs of Rolling plant is chosen accordingly. An adaptation of the invention Regulation of the respective system situation is thus possible even more precisely.

In a further embodiment of the method according to the invention, the Acting on the roller of the roller set in the or the directions of the Roll set. Through this measure we have a targeted influence the vibration behavior and thus the load roll gap reached. It is advantageous also the possibility to use the existing employment in the respective scaffolding, additional units can thus be avoided.

An extension of this inventive idea for applications with special high demands is placed on the roller of the roller set in reached in several directions. Since the 3rd and 5th octave vibrations are sometimes not to assign a single direction of movement, but three-dimensional Cause effective movements by the action of the actuators in prevention of vibrations even more efficiently in several directions. In particular is therefore for any roll arrangements or roll stand configurations a solution for a control procedure to avoid 3rd and 5th octave vibrations given.

The admission provides a particularly advantageous embodiment of the method at least one roller before the adjusting device of the roller set. by virtue of this feature is avoided by coupling employment and intervention of vibrations in a superimposed process a very simple and inexpensive Solution found.

Another possible embodiment of the method according to the invention is seen in FIG Actuation of the roller via the axial roller displacement device of the roller set in front. By using one that is standard in many rolling stands existing actuator can be found a very simple solution. Through the Combination of this solution with an application via the roller adjustment achieved a very flexible solution that meets all requirements.

The method according to the invention provides for the avoidance of 3rd and 5th octave vibrations through a permanent reduction in vibrational energy, i.e. one Continuous energy dissipation from the vibrating mill stand system, especially the roller set. Due to the continuous energy dissipation ensures that there are no oscillations or vibrations, especially those train with high energy content, which leads to significant system damage or too Errors in the rolling stock.

A particular embodiment sees the reduction of vibrations in particular in the direction of the rollers. This simplified solution leaves vibrations with a direction other than the direction of attack. This will make it easy Solution for the procedure found that meets the requirement for safe avoidance 3rd and 5th octave vibrations.

The device according to the invention for avoiding vibrations, e.g. Third and 5th octave vibrations, in a rolling mill with at least one rolling stand with roller adjustment and at least one roller set comprises at least one Measuring device for the permanent measurement of a size of the rolling mill, one Controller that characterizes a mathematical control law and the state of the system Includes sub-models to which the measured size can be supplied, with the help this controller can determine at least one time-variable manipulated variable in real time is, and furthermore at least one actuator to which the manipulated variable can be fed and via the at least one of the rolls of the roll set and / or the rolling stock can be acted upon.

This simple structure provides an inexpensive solution that largely based on robust and reliable components. Through the The controller solution according to the invention ensures that the rolling mill has the desired behavior given by the target size.

According to a special embodiment, a hydraulic is used as the actuator Control element used. Due to the combination with existing in scaffolding, other hydraulic actuators, e.g. the hydraulic roller adjustment or the axial roller displacement becomes a robust and safe solution with high Flexibility achieved regardless of the system type.

A further special embodiment sees a piezoelectric actuating element as Actuator that is characterized by high dynamics and high energy density distinguished, so that a very high precision is achieved in the control intervention. The Actuator is installed in the rolling mill in such a way that it is dynamic, not but static loads can act on the piezoelectric actuator. This ensures that overloads do not damage the piezo-electric actuator being able to lead.

The combination makes a particularly advantageous embodiment of the device achieved by different actuators because of the different Characteristics of the actuators partial frequencies are very well covered can.

Oscillations or vibrations represent a disruptive effect for rolling processes that appears as a defect in the rolling stock. Mostly surface defects occur in particular and thickness deviations on the rolling stock.

Deviations from the target thickness of the rolling stock cause great costs because they are always a minimum thickness must be guaranteed by the manufacturer. All positive thickness deviations that is, thicknesses greater than the guaranteed minimum thickness a very significant cost factor as this affects the total production quantity of the rolling mill must be moved. A reduction in thickness deviations, tighter thickness tolerances means a lot for the mill operator high savings potential. For many processing steps cause too large thickness deviations on the rolling stock, especially when forming, do not acceptable disturbances, so that larger thickness deviations an elimination of the Make rolling good necessary. This leads to very high reject costs.

By using the method and the device according to the invention Rolling processes for the production of rolling stock is in addition to avoiding damage an overall more stable rolling process on the system and defects on the rolling stock reached. This allows tighter thickness tolerances on the rolling stock to be maintained and failures can be avoided by surface defects. Thickness tolerance is understood those rolling stock thicknesses that are a permissible deviation from a target thickness represent, i.e. do not exceed certain predefined deviations. usual Information is given as a percentage of the rolling stock thickness or in absolute terms of the permissible deviations in ± amount from the nominal thickness, the information being frequent in µm.

The achievable thickness tolerances represent an essential development step since these are not shown with the methods and facilities available today can.

Compared to the prior art, the more stable rolling conditions make it possible to set thickness tolerances that are at least 20% narrower than the technically usual tolerances such as in tandem cold rolling mills today. Tab. 1 shows typical thickness tolerances of a tandem cold rolling mill. These thickness tolerances apply to strip-shaped rolling stock with the exception of short sections at the strip head and at the strip foot, whereby the lengths of these sections are defined by guarantee formulations that take into account the specific characteristics of a system and can therefore vary. strip thickness tolerance 0.25 - 0.50 mm ± 1.2% 0.50 - 0.89 mm ± 1.0% 0.89 - 1.60 mm ± 0.9% 1.60 - 2.54 mm ± 0.8%

Especially for thin and wide tapes, the technologically the highest Make demands, offers the solution according to the invention, one compared to State of the art completely new idea and technical embodiment.

The invention is explained below using the figures as an example.

Fig .: 1 control diagram of the controlled system

Fig .: 2 system diagram

Figure 1 shows the basic structure of the controlled system, but not here Controller mathematics or the sub-models is discussed.

Sizes 2 are measured using sensors or the sensors 1 required for this Rolling system recorded. These measured variables 2 are fed to a controller 3. The Controller 3 contains a mathematical control law and the system status characterizing sub-models. With the help of the controller 3 is at least in real time a time-variable manipulated variable 4 is determined and fed to the actuator system 5. By the actuator system 5 is applied to the rolling system (section) 6, whereby the vibration state of the rolling mill 6 is influenced in a targeted manner. acting Disturbance variables 7 are taken into account via the measured variables 2. In one Comparison of the measured variables 2 with the target variables 8 is carried out Target state or the control intervention in the oscillatory system of Rolling mill 6.

In Fig. 2 is a frame of a rolling mill 6 with the schematically indicated main components shown. Via a controller 3 and a servo valve 12 an actuator 5, indicated here as a hydraulic cylinder, is acted upon. So that is done in addition to the positioning movement also the application to avoid Vibrations. Signals of a path or Position measurement 9, a pressure measurement 10 or an acceleration measurement 11 indicated with an accelerometer 13. In addition, you can Input variables that affect the rolling stock, e.g. Stress conditions in the rolling stock 14.15 or combinations of these sizes are used. to Determination of the stress conditions in the rolling stock can e.g. not shown here Measuring devices that measure touching the rolling stock are used. Actuators for application e.g. of the hydraulic cylinder are not closer here shown, their corresponding arrangement represents for the expert due to his Knowing, however, is not a problem. In a possible embodiment, as here shown, the hydraulic cylinder for roller adjustment is also used Avoidance of vibrations.

Claims (19)

Method for avoiding vibrations, in particular 3rd and 5th octave vibrations, in a rolling mill with at least one roll stand with roll adjustment and at least one set of rolls, characterized in that at least one permanently measured size of the rolling mill is a controller (3) which has a mathematical The control law and the partial models characterizing the system status include, supplied, with the help of this controller (3) determining in real time at least one time-variable manipulated variable (4), supplied to at least one actuator (5) and by the actuator (5) at least one of the rollers of the roller set and / or the rolling stock is loaded, the controlled variables being kept at defined target values. A method according to claim 1, characterized in that linear and / or non-linear sub-models are used. Method according to one of the preceding claims, characterized in that the partial models comprise a hydraulic model and / or a mechanical model and / or a rolling force model. Method according to one of the preceding claims, characterized in that the vertical acceleration of the roller set is used as the measured variable. Method according to one of the preceding claims, characterized in that the cylinder pressure of the roll adjustment is used as the measured variable. Method according to one of the preceding claims, characterized in that the piston position of the roller adjustment is used as the measured variable. Method according to one of the preceding claims, characterized in that the tension state in the rolling stock is used as the measured variable. Method according to one of the preceding claims, characterized in that combinations of the vertical acceleration and / or the cylinder pressure of the roll pitch and / or the vertical position of the roll set and / or the tension state are used as measured quantities. Method according to one of the preceding claims, characterized in that the application of pressure to the roller of the roller set takes place in the setting direction. Method according to one of the preceding claims, characterized in that the roller of the roller set is acted upon in several directions. Method according to one of the preceding claims, characterized in that the roller is acted upon by the adjusting device of the roller set. Method according to one of the preceding claims, characterized in that the application of pressure to the roller takes place via an axial roller displacement device of the roller set. Method according to one of the preceding claims, characterized in that the energy content of vibrations in the setting direction is reduced and / or eliminated by the application of the roller. Device for avoiding vibrations, in particular 3rd and 5th octave vibrations, in a rolling mill with at least one roll stand with roll adjustment and at least one roll set for carrying out the method according to one of Claims 1 to 13, characterized in that at least one measuring device (9 , 10, 11), for the permanent measurement of a size of the rolling mill, and a controller (3) which comprises a mathematical control law and partial models characterizing the condition of the plant, to which the measured size (2) can be supplied, are provided and with the aid of this controller ( 3) at least one temporally variable manipulated variable (4) can be determined, and further comprises at least one actuator (5) to which the manipulated variable (4) can be fed and via which at least one of the rolls of the roll set and / or the rolling stock can be loaded / are. Apparatus according to claim 14, characterized in that the actuator (5) is designed as a hydraulic and / or servo-hydraulic control element. Apparatus according to claim 14, characterized in that the actuator is designed as a piezoelectric actuator. Device according to claim 14 to 16, characterized in that the actuator comprises combinations of different adjusting elements. Process for the production of rolling stock according to a method accordingly one of claims 1 to 13. Strip-shaped rolling stock produced by a method, characterized according to at least one of claims 1 to 14 and claim 18, characterized in that the rolling stock has thickness deviations which are at least 20% less than the following thickness tolerances. strip thickness tolerance 0.25 - 0.50 mm ± 1.2% 0.50 - 0.89 mm ± 1.0% 0.89 - 1.60 mm ± 0.9% 1.60 - 2.54 mm ± 0.8%

Images