Avoiding rotational speed drop during rolling bite

Abstract

And the rotating speed drop during rolling biting is avoided. A rolled stock (2) made of metal having a rolled stock front end (6) is rolled in a rolling mill (1). A control device (7) for the rolling mill (1) determines a nip time (t3), a rolling speed (vW) and a rolling torque (MW) before a rolling stock front end (6) enters the rolling mill (1). Before a starting time (t2) before the nip time (t3), the control device (7) determines a torque curve (M) of the drive device (4) for driving the rollers (3) of the rolling mill (1) via the drive chain (5) for a period of time from the starting time (t2) to the nip time (t3). The actuating device (4) is actuated during the time period according to the determined torque curve (M). The control device (7) determines a torque curve (M) on the basis of a starting state (x2) of the drive device (4), the drive chain (5) and the driven roller (3) of the rolling mill (1) present at a starting time (t2), such that the driven roller (3) of the rolling mill (1) is applied by the drive chain (5) at a nip time (t3) with a rolling torque (MW) and rotated at a circumferential speed (vU) that is coordinated with the rolling speed (vW).

Description

Technical Field

[0001] This invention relates to a method for operating a rolling mill, in which a workpiece made of metal with a workpiece tip is rolled. - Specifically, before the workpiece enters the rolling mill, the control device for the rolling mill obtains the bite time, rolling speed, and rolling torque. -The bite-in moment is the moment when the front end of the workpiece enters the rolling mill, and the workpiece must be rolled at the rolling speed and rolling torque at the bite-in moment. - Specifically, before the start time prior to the bite-in time, the control device determines the torque curve of the drive device used to drive the mill rolls via the drive chain (Antriebsstrang) for the time period from the start time to the bite-in time, and operates the drive device according to the determined torque curve during that time period.

[0002] The present invention also relates to a control program having machine code that can be processed by a control device for a rolling mill for rolling a workpiece made of metal with a workpiece front end, wherein the control device processes the machine code to cause the control device to perform an operating method.

[0003] The present invention also relates to a control device for a rolling mill for rolling a workpiece made of metal having a workpiece front end, wherein the control device is programmed by a control program to perform such an operating method during operation.

[0004] The present invention also relates to a rolling apparatus for rolling a workpiece made of metal having a workpiece tip. -The rolling equipment includes a rolling mill, in which the workpiece is rolled. The rolling mill includes a drive unit, a drive chain, and rolling rolls. -The roll can be driven by a drive unit via a drive chain. -The rolling equipment has such a control device for the rolling mill. Background Technology

[0005] The above topics are generally known. For example, see the technical article “Impact Speed ​​Drop Compensation Procedure for a new layout Wire Rod Mill” by Antonella Scaglia and Graziano Melandri, Proceedings of the 28th Annual Meeting of the Industrial Electronics Society (IECON), 2002, pp. 573-578, and JP2001150013A.

[0006] When rolling metal parts (such as steel, aluminum, brass, or copper), the quality of the final product depends on many factors. The rolled part can be, for example, a flat piece, such as strip or plate. Factors affecting the quality of the final product include material temperature, lubrication during the rolling process, proper pressure conditions of the rolls, and the rotational speed or circumferential speed of the work rolls. Whether discussing rotational speed or circumferential speed is equivalent, as they can be converted to each other using the diameter of the work rolls.

[0007] Especially regarding the working roll speed, it is crucial to adhere to the desired speed as accurately as possible. Any deviation will lead to negative consequences, such as decreased product quality, material blockage (e.g., forming strip loops), inaccuracy of relevant process variables, and difficulty in material guidance. The dimensions of the final product may also change as a result.

[0008] During stable rolling, the required precision can be ensured by using a simple and robust adjustment system. Transitioning from one stable operating range to another is much more difficult. This is especially true at the bite point, when the front of the workpiece enters the mill. At this moment, the load on the mill changes. In particular, the required rolling force and required rolling torque increase significantly. These changes occur almost abruptly (instantaneously) at the bite point.

[0009] Due to the sudden increase in required rolling torque, the rotational speed of the driven rolls in the prior art will drop. This drop is then compensated for by the associated speed regulator. However, this requires a settling time, the duration of which depends on the characteristics of the drive unit, drive chain, and regulator used. During the settling time, the quality of the final product will be compromised.

[0010] In the prior art, it is known to increase the target speed of the work roll, or typically the driven roll, shortly before the bite-in moment. For example, the aforementioned technical article by Antonella Scaglia and Graziano Melandri explains such a process. It is also known to calculate an additional torque based on the speed drop and its duration, which is then applied to a torque regulator or current regulator subordinate to the speed regulator at the bite-in moment. For example, such a process is described in JP2001150013A.

[0011] Existing technologies have failed to adequately address the problem of the driven roll speed dropping. Summary of the Invention

[0012] The purpose of this invention is to propose some possible solutions that can completely or at least almost completely avoid the drop in the rotational speed of the driven roll.

[0013] This objective is achieved by an operating method having the features of claim 1. An advantageous design of this operating method is the subject of dependent claims 2 to 12.

[0014] According to the present invention, the operating method of the type described at the beginning is designed as follows: the control device determines the torque curve based on the initial state of the mill's drive device, drive chain and driven roll at the initial moment, such that the driven roll of the mill is subjected to rolling torque by the drive chain at the biting moment and rotates at a circumferential speed coordinated with the rolling speed.

[0015] Before the bite-in moment, there is no workpiece in the rolling gap of the mill. Therefore, only a very low applied torque is needed to maintain the rotational speed of the driven rolls, which is much smaller than the rolling torque required to roll the workpiece. The applied torque is the torque used to drive the driven rolls of the mill. Since the torque output from the drive unit cannot arbitrarily increase to the rolling torque, before the bite-in moment, the torque increases to the rolling torque required to roll the workpiece, which causes the driven rolls of the mill to accelerate. The degree of acceleration is determined by the moving mass or associated moment of inertia and the rolling torque. Therefore, shortly before the bite-in moment, the circumferential speed of the driven rolls must also be lower than the circumferential speed corresponding to the rolling speed. However, due to acceleration, the circumferential speed reaches the desired circumferential speed corresponding to the rolling speed at the bite-in moment. The deviation between the circumferential speed and the rolling speed before the bite-in moment is not critical because no material is being rolled in the rolling gap of the mill during this period.

[0016] The rolling speed and the circumferential speed of the driven rolls are not necessarily the same. Specifically, when rolling a workpiece, the workpiece enters the mill at an entry speed lower than the circumferential speed of the driven rolls. Similarly, when rolling a workpiece, the workpiece exits the mill at an exit speed higher than the circumferential speed of the driven rolls. The corresponding speed relationship is known in the art by the terms lag and lead. Depending on the specific context, the term "rolling speed" can refer to the entry speed, the exit speed, or a value between the entry and exit speeds. However, regardless of the specific definition of rolling speed, a fixed relationship exists between rolling speed and circumferential speed.

[0017] For example, the control device can determine the bite-in time based on conventional path tracking combined with (constant or time-varying) rolling speed. Path tracking is generally known to those skilled in the art and therefore requires no detailed explanation. The bite-in time is typically determined indirectly by defining the length of a time period.

[0018] The driven rolls of a rolling mill are usually the work rolls. However, in special cases, the support rolls or intermediate rolls of the rolling mill may also be driven.

[0019] Preferably, the control device determines the torque curve such that at the bite moment, the drive device, drive chain, and driven rolls of the mill rotate at corresponding speeds, and the change in speed is zero. This ensures that the transient state that still exists before the bite moment decays completely at the bite moment.

[0020] Currently, a particularly preferred approach is to use a model based on mathematical physics equations to model the drive unit, drive chain, and the rolls driven by the driven unit of the rolling mill to determine the torque curve. This method allows the control unit to flexibly handle virtually any boundary conditions.

[0021] In the simplest case, the drive unit, drive chain, and driven rolls of the mill are modeled as a rigid system. In this case, the rotational speed of the drive unit is in a fixed ratio to the rotational speed of the driven rolls, and this ratio has the same value at all times. However, in practice, torsion often occurs, for example, between the drive unit and drive chain, and between the drive chain and the driven rolls. Therefore, it is preferable to model the drive unit, drive chain, and driven rolls of the mill as a multi-mass vibration system with multiple interconnected damped elastic elements. This allows such torsion to be accounted for.

[0022] The number of interconnected damping elastic elements can be determined as needed. Typically, there are at least three: the drive unit, the drive chain (considered a unit in this case), and the driven roll. However, if necessary, the drive chain can also be subdivided into multiple segments. In this case, the number of interconnected damping elastic elements increases accordingly.

[0023] One possible approach to determining the torque curve is for the control device to establish an optimization problem, incorporating the corresponding torque of the drive unit as an input variable for multiple discrete time points or moments within the time period. In this case, the control device determines the torque curve by solving the optimization problem. By establishing and solving the optimization problem, other conditions, such as limits or other boundary conditions that need to be met, can also be considered in a simple way.

[0024] Alternatively, the control device can use tables stored in the control device to determine the torque curve, with the bite time, rolling speed, rolling torque, and the initial states of the drive unit, drive chain, and driven rolls of the mill as input variables. Alternatively, the torque curve can be provided to the control device by a parameterizable time function stored in the control device, and the control device determines the parameters of this function based on the bite time, rolling speed, rolling torque, and the initial states of the drive unit, drive chain, and driven rolls of the mill.

[0025] These methods are sometimes as flexible as using models and can often be completed in a shorter time, thus improving online capabilities. These tables can be determined, for example, by pre-determining the corresponding entries in the table offline with model assistance for a large number of possible numerical combinations, and storing the model-assisted calculation results in the control unit. Similar methods can be used to determine the dependence of parameters on possible numerical combinations.

[0026] Preferably, in the initial state, the drive unit, drive chain, and driven rolls of the rolling mill rotate at corresponding speeds, and the change in speed is zero. In this case, the drive unit, drive chain, and driven rolls of the rolling mill are in a stable state at the initial moment. This method facilitates the determination of the torque curve.

[0027] As previously stated, the method according to the invention implies that the driven rolls of the rolling mill are accelerated at least shortly before biting in. Therefore, at some point before biting in, the circumferential speed of the driven rolls must be less than the circumferential speed of the driven rolls that is coordinated with the rolling speed. It is possible that this condition is not yet met at the initial moment. In this case, the driven rolls of the rolling mill must first decelerate and then accelerate during that time period. However, it is preferable that this condition is already met at the initial state. This method reduces both energy consumption and wear. For example, after a piece has been rolled in the rolling mill, i.e., after the rear end of the piece has left the mill, the driven rolls can be allowed to run slowly until they rotate at the desired (lower) circumferential speed required for the next piece at the initial moment.

[0028] Preferably, the control device determines a torque curve such that, throughout the entire time period, the torque generated and / or applied by the drive device is greater than a predetermined minimum value. As previously mentioned, the applied torque is the torque used to drive the driven rolls of the rolling mill.

[0029] Similarly, the control device preferably determines the torque curve such that the rotational acceleration used to change the speed of the drive device and / or the rotational acceleration used to change the speed of the driven roll is greater than their respective predetermined minimum values ​​throughout the entire time period.

[0030] In each of the above cases, the corresponding minimum value can be zero.

[0031] By taking these minimum values ​​into account, the load on the driven rolls of the drive unit, drive chain, and rolling mill can be balanced.

[0032] This method is particularly advantageous when combined with a design where the circumferential speed of the driven roll in the initial state is less than the circumferential speed of the driven roll that is coordinated with the rolling speed.

[0033] Preferably, the control device determines the torque curve so that the energy consumption of the drive device is minimized during that time period.

[0034] Preferably, this time period is between 50 milliseconds and 200 milliseconds, particularly between 75 milliseconds and 150 milliseconds. This makes the time period long enough to allow the load torque required for the bite moment to be established in accordance with the invention.

[0035] This objective is also achieved by a control program having the features of claim 13. According to the invention, this control program is processed such that the control device executes the operating method according to the invention.

[0036] This objective is also achieved by a control device having the features of claim 14. According to the invention, the control device is programmed with a control program according to the invention, causing the control device to execute the operating method according to the invention during operation.

[0037] This objective is also achieved by a rolling mill having the features of claim 15. According to the invention, in a rolling mill of the aforementioned type, the control device is configured as a control device according to the invention. Attached Figure Description

[0038] The features, characteristics, advantages, and implementations of the present invention described above will become clearer and easier to understand in conjunction with the following detailed description of embodiments, taken in conjunction with the accompanying drawings, wherein: Figure 1 The rolling equipment is shown. Figure 2 The drive system is shown. Figure 3 A flowchart is shown. Figure 4 The model is shown. Figure 5 The system of differential equations is shown. Figure 6 The system of differential equations in matrix representation is shown. Figure 7 The optimization problem is shown, and Figures 8 to 23 A timeline is shown. Detailed Implementation

[0039] according to Figure 1 The rolling equipment includes a rolling mill 1. A workpiece 2 is rolled in the rolling mill 1. The rolling mill 1 is typically part of a multi-stand rolling production line. However, this is not absolutely necessary. Regardless of the number of further rolling mills, the following only addresses... Figure 1 The method of the rolling mill 1 shown will be described in more detail. In this example, this is also possible and sufficient because... Figure 1The operation mode of intermediate mill 1 is independent of other mills (e.g., Figure 1 The mill upstream of mill 1 shown in the figure is a mill or Figure 1 The operating mode of the mill downstream of the mill 1 shown is illustrated. If there are multiple mills 1, the operating mode of the mill 1 according to the present invention can also be similarly implemented in other mills.

[0040] Figure 1 The rolling mill 1 has rolls 3, which—see also Figure 2 —Driven by drive unit 4 via drive chain 5. The driven roll 3 is usually the work roll of mill 1. If mill 1 has other rolls besides the work roll, in some cases the other rolls may also be driven roll 3. But usually, even in this case, the driven roll 3 is also the work roll of mill 1. The drive unit 4, drive chain 5 and driven roll 3 as a whole are referred to as the drive system below.

[0041] It is possible that the driven upper roll 3 and the driven lower roll 3 each have their own drive unit 4 and their own drive chain 5. However, as Figure 2 As shown, there is typically only one common drive unit 4, and the drive chain 5 is divided such that the drive unit 4 drives two driven rolls 3. Regardless of which of the two methods described above is used, it is secondary within the scope of this invention.

[0042] The rolled piece 2 is made of metal. In most cases, the rolled piece 2 is made of steel. However, it can also be other metals, such as aluminum, copper, or brass. Furthermore, the rolled piece 2 is typically a flat rolled piece, i.e., rolled into strip or plate. However, in some cases, it can also be a bar-shaped rolled piece, particularly a steel bar. Regardless of shape and material, the rolled piece 2 always has a front end 6. The front end 6 is the region of the rolled piece 2 that first reaches and enters the mill 1.

[0043] Figure 1 This illustrates the situation at time t1 where the front end 6 of the workpiece has not yet reached the mill 1. At this time, the front end 6 of the workpiece is located at a distance in front of the mill 1. Figure 1 The distance in front of mill 1 is also shown by dashed lines. The front end 6 of the workpiece reaches the corresponding position at time t2. Furthermore, the front end 6 of the workpiece reaches the rolling gap of mill 1 at time t3, that is, it enters mill 1 at this time. Time t1 is referred to as the information time below. Time t2 is referred to as the start time below. Time t3 is referred to as the bite time below by common convention. The start time t2 is usually between 50 milliseconds and 200 milliseconds before the bite time t3, and especially between 75 milliseconds and 150 milliseconds before the bite time t3, for example, about 100 milliseconds before the bite time t3.

[0044] The rolling mill 1 is controlled by a control device 7. The control device 7 is programmed via a control program 8. The control program 8 has machine code 9 that can be processed by the control device 7. The control device 7, through programming with the control program 8 or by processing the machine code 9, causes the control device 7 to execute the operating method described in detail below.

[0045] This invention relates to a process performed before the front end 6 of the rolled piece enters the rolling mill 1. To implement the operating method according to the invention, the control device 7 needs to obtain the start time t2 and the bite time t3 in a timely manner so that the calculations required for the operating method according to the invention can be completed no later than the start time t2. For this purpose, the information time t1 is before the start time t2. The degree to which the information time t1 precedes the start time t2 can be determined as needed. Crucially, the calculations performed by the control device 7 for correctly controlling the rolling mill 1 from the start time t2 must be completed before the start time t2.

[0046] It is readily feasible to properly define and adhere to the information time t1, as the position of the workpiece tip 6 can be detected well in advance of time t1, and the control device 7 can acquire this position. Subsequently, based on the detected position and the constant or time-varying workpiece speed v of the workpiece 2, conventional path tracking of the workpiece tip 6 is performed. The current and future workpiece speed v can be easily acquired by the control device 7. All of this is generally known to those skilled in the art and therefore will not be explained in detail below. In this example, the workpiece speed v is not referred to as the rolling speed. The reason is that the workpiece speed v in this example refers to the time period during which the workpiece tip 6 has not yet arrived at the mill 1, i.e., before rolling has occurred in the mill 1.

[0047] according to Figure 3 In step S1, the control device 7 learns the bite-in time t3, the rolling speed vW, and the rolling torque MW. The rolling speed vW is the speed at which the workpiece 2 will be rolled in the mill 1 at least at the bite-in time t3. The rolling torque MW is the corresponding torque that the driven roll 3 must be driven by the drive device 4 via the drive chain 5. It is possible that the values ​​t3, vW, and MW are preset to the control device 7 from an external source. Alternatively, they may be determined by the control device 7 itself. The determination of the bite-in time t3, rolling speed vW, and rolling torque MW is not explained in detail here. They are generally known to those skilled in the art. Step S1 is executed by the control device 7 at the information time t1.

[0048] In step S2, the control device 7 determines the torque curve M of the drive device 4 for the time period from the initial time t2 to the bite time t3. The torque curve M is a function of time t. Possible implementations of step S2 will be explained in more detail later. However, in any case, the control device 7 determines the torque curve M starting from the initial state x2 of the drive system. The initial state x2 is the state x that the drive system exists in at the initial time t2. In any case, the determination in step S2 is also performed such that the driven roll 3 is subjected to a rolling torque MW by the drive chain 5 at the bite time t3 and rotates at a circumferential speed vU coordinated with the rolling speed vW. The circumferential speed vU is associated with the rolling speed vW by leading or lagging, depending on whether the rolling speed refers to the rolling speed on the inlet side or the outlet side. Preferably, the torque curve M is determined such that at the bite time t3, the drive device 4, the drive chain 5, and the driven roll 3 of the mill 1 rotate at corresponding rotational speeds, and the value of the speed change is zero. Step S2 is performed by the control device 7 before the biting time t3, or more precisely, even before the start time t2.

[0049] It is possible that the initial state x2 is preset to the control device 7. Alternatively, it is possible that the control device 7 determines the initial state x2 and manipulates the drive device 4 such that the initial state x2 exists at the initial time t2. It is also possible that the initial time t2 is preset to the control device 7. However, the control device 7 usually knows how long the time interval between the initial time t2 and the bite time t3 should be, therefore the control device 7 can determine the initial time t2 itself.

[0050] In step S3, control device 7 waits for the start time t2. Step S3 is repeated until the start time t2 is reached. Starting from the start time t2, control device 7 repeats steps S4 and S5.

[0051] In step S4, the control device 7 operates the drive device 4 according to the determined torque curve M corresponding to each time t. For example, according to... Figure 1 The control device 7 can operate the drive device 4 by outputting a corresponding control signal to the converter 4', which supplies electrical energy to the electric motor 4". Figure 1 The representation of converter 4' as thyristor-controlled is merely exemplary. Transistor control can also be used.

[0052] In step S5, the control device 7 checks whether the bite time t3 has been reached. If the bite time t3 has not been reached, the control device 7 returns to step S4. Therefore, steps S4 and S5 are repeatedly executed by the control device 7 until the bite time t3 is reached. Each time step S4 is executed, the control device 7 naturally considers the progress of time t.

[0053] Once the bite-in time t3 is reached, control device 7 proceeds to step S6. In step S6, the workpiece 2 undergoes "normal" rolling. Step S6 can be implemented in the same manner as in the prior art.

[0054] During step S2, the drive unit 4, drive chain 5, and driven roll 3 can, in the simplest case, be considered as being completely rigidly connected. In this case, the rotational speed of the drive unit 4 at any time t (considering the transmission ratio if necessary) corresponds to the rotational speed of the driven roll 3. In this case, it is even possible to analytically determine the torque curve M. However, in any case, the control unit 7 can use model 10 (see [reference missing]) which models the drive system based on mathematical physics equations. Figure 4 To determine the torque curve M.

[0055] Within the framework of Model 10, it is generally assumed that the drive unit 4 is connected to the drive chain 5 via coupling 11, and the drive chain 5 is also connected to the driven roll 3 via coupling 12. These two couplings 11 and 12 are damped flexible couplings, such as... Figure 4 The respective spring element 13 and respective damper element 14 are shown in the middle.

[0056] therefore, Figure 4 One design is shown in which the drive system is modeled as a three-mass oscillator. In some cases, one of the two couplings 11 and 12 can be neglected. In this case, the drive system can be modeled as a two-mass oscillator. If both couplings 11 and 12 are neglected, the drive system is modeled as a completely rigid system. In other cases, it is subdivided into more than three mutually coupled damped elastic elements. In this case, in addition to the two couplings 11 and 12, there are other damped elastic couplings.

[0057] When modeled as a multi-mass oscillator, the drive system can be combined as follows: Figure 5 The modeling process is described above.

[0058] For the most front-end component of the drive system (here, drive device 4), a differential equation of the following form can be established: For all elements located between the foremost and last elements (e.g., drive chain 5), a differential equation of the form can be established as follows: For the last element of the drive system (i.e., the driven roll 3), a differential equation of the following form can be established: The symbols used in the equations have the following meanings: -Ji It is the moment of inertia of the i-th element.

[0059] -ω i It is the angular velocity of the i-th element.

[0060] -M is the torque applied by the drive unit 4, also referred to below as motor torque M.

[0061] -c i It is the spring constant for the coupling between the i-th element and the immediately following element.

[0062] -Δ i It is the rotation angle of the i-th element relative to the element immediately following it.

[0063] -d i It is the material damping of the coupling between the i-th element and the immediately following element.

[0064] -D i It is the friction coefficient of the i-th element.

[0065] -ML is the torque that acts on the driven rolls 3 and thus drives them, also referred to below as the applied torque ML.

[0066] The above ignores any transmission mechanisms (including their transmission ratios). These can be considered at any time. Considering them only results in scaling. The angular velocity ω of the element. i It is related to its rotational speed by a factor of 2π. Therefore, rotational speed and angular velocity will not be distinguished in the following text.

[0067] The following is based on Figure 6 As shown, using and Representing substates, and using Let x represent the state of the driving system being modeled. In this case, the system of differential equations determined by equations (1) to (3) can be expressed in matrix form: .

[0068] Matrix A ω , , It is known and constant. Vector b ω The same applies to 'e', ​​they are made by and Given. This representation is equivalent to Figure 5 This is known and familiar to those skilled in the art.

[0069] When determining the torque curve M, various conditions must be considered. One of the most important conditions is the rotational speed ω of the work roll 3 at the bite moment t3. n Equal to the target rotational speed ω*: .

[0070] The target rotational speed ω* corresponds to the circumferential speed vU that the driven roll 3 must have to achieve the desired rolling speed vW.

[0071] Another condition is that, at the bite-in time t3, the applied torque ML must be equal to the desired rolling torque MW. These conditions can be expressed using equation (3) as follows: .

[0072] Strictly speaking, equation (11) only applies to the case where the rotational speed of the driven roll 3 is to remain constant after the bite-in time t3. If the driven roll 3 is to be accelerated or decelerated after the bite-in time t3, then in addition to the rolling torque MW, an additional torque can be considered on the right side of equation (11).

[0073] As mentioned above, the motor torque M applied by the drive unit 4 cannot be changed arbitrarily or rapidly. Furthermore, as described in equations (1) to (3), there are usually certain elasticity, damping, and losses. Therefore, the torque curve M of the drive unit 4 must be determined in an appropriate manner to satisfy the conditions according to equations (10) and (11).

[0074] Furthermore, the transients during the acceleration of the driven roll 3 to the target speed ω* should be eliminated. Therefore, it can be required, as a further condition, that at the bite time t3, the angular velocities ω of all upstream components of the drive system are... i They all reached the target rotational speed ω*, thus satisfying the equation: (where i = 1, 2, ..., n-1), and angular acceleration, i.e. angular velocity ω i The time derivatives are all zero. This allows us to determine the rotation angle Δ at the biting time t3. i The condition that the motor torque M must satisfy is: (where i = 1, 2, ..., n-2) and .

[0075] Therefore, at the bite-in time t3, the required state x3 of the drive system—hereinafter referred to as the target state x3—is uniquely determined. However, since the front end 6 of the workpiece is still located before the mill 1, rather than inside the mill 1, immediately before the bite-in time t3, there is still acceleration in the drive system immediately before the bite-in time t3. Therefore, it is necessary to determine the corresponding torque curve M starting from the initial state x2 of the drive system, and to transfer the drive system to the target state x3 through this torque curve.

[0076] The initial state x2 is known to the control device 7. Typically, the initial state x2 is a stable state, meaning that the drive device 4, drive chain 5, and the driven rolls 3 of the rolling mill 1 operate at corresponding rotational speeds ω. i The state where the rotational speed change is zero. In principle, the circumferential speed vU of the driven roll 3 can have any value in the initial state x2. Theoretically, the circumferential speed vU of the driven roll 3 can be greater than the value coordinated with the rolling speed vW, its value can be 0, or even negative. However, in practice, it is generally advantageous for the circumferential speed vU of the driven roll 3 to be positive, but less than the circumferential speed vU of the driven roll 3 coordinated with the rolling speed vW. The reason for this will become clear from the explanation below. The state of the drive system before the initial time t2 is irrelevant here.

[0077] Determine the torque curve M (i.e., execute) Figure 3 Step S2) can be approached in various ways. In some simple cases, it is possible to analytically determine the torque curve M. This is especially possible when the drive system is assumed to be a rigid system. It is also possible to determine the torque curve M using so-called flatness-based trajectory calculations. Such calculations are known to those skilled in the art. However, in any case, an optimization problem can be established to determine the torque curve M, such as... Figure 7 As shown: .

[0078] x' is the ideal state to be achieved. The ideal state x' can be constant or time-varying. State x' can influence the torque curve M. Q is a weight matrix used to weight the deviations of each state x(t) from the ideal state x'. The weight matrix Q is positive definite (semi-positive definite). M' is the ideal motor torque to be achieved. The ideal motor torque M' can be constant or time-varying. The torque curve M can also be influenced by the ideal motor torque M'. In the case of a general optimization problem, R is a positive definite weight matrix, here with positive weighting factors used to weight the deviations of the motor torque M(t) from the ideal motor torque M'.

[0079] In all cases, the initial state x2 and the target state x3 are pre-defined as boundary conditions that must be followed in the optimization problem: and .

[0080] In addition, the optimization problem includes the motor torque M as a boundary condition, which is the output of the drive device 4 at the biting time t3: .

[0081] The motor torque M3 is uniquely determined by the set of equations (10) to (15).

[0082] Furthermore, the optimization problem includes the motor torque M as a boundary condition, which is the output torque that the drive device 4 should produce at the initial time t2: .

[0083] The numerical value can be freely chosen within certain limits, but a value must be specified.

[0084] As a further condition, it is generally considered that the motor torque M is within the allowable limits at every time t between the initial time t2 and the engagement time t3, that is, it cannot be lower than the minimum value Mmin and cannot exceed the maximum value Mmax: .

[0085] In general, additional equality and inequality constraints g and h can be preset, which must be satisfied by the state x between the initial time t2 and the biting time t3: and .

[0086] Examples of possible inequality constraints h could be, for instance, specifying that the angular velocity ω does not exceed a certain value. i Specific changes or specific rotation angles Δ i Alternatively, it can be stipulated that the torques acting between consecutive elements in the modeled drive system do not exceed a specific limit.

[0087] In the recursive solution of state x, consider the modeling of the driving system, for example, according to equation (24), which is a modification of equation (7): .

[0088] The optimization problem based on equation (16) can be solved analytically where possible. It can always be solved numerically. Numerical solution means that equation (16) is not solved on a time continuum, but rather the time interval from the initial time t2 to the biting time t3 is subdivided into small time steps (discretization). The result is an optimization problem established, with the corresponding torque M of the driving device 4 introduced as an input variable for multiple discrete time points or times t within this time interval. The found solution corresponds to the desired torque curve M. Therefore, the torque curve M is determined by minimizing or solving this optimization problem.

[0089] The optimal solution is model 10, as shown below. Figure 1 The solution is implemented within control device 7, thus the optimization problem is also solved by control device 7. Alternatively, as shown... Figure 1 As shown, control device 7 can also use table 15 stored in control device 7 to determine the torque curve M. In this case, bite time t3, rolling speed vW, rolling torque MW, and the initial state x2 of the drive system are input to table 15 as input variables. The distance between the initial time t2 and bite time t3 may be known in advance by control device 7. Alternatively, as shown, it may also be a function of time t f. a It is stored in the control device. In this case, the function f a Parameterization can be performed using parameter a. In this case, the torque curve M is provided to the control device 7 by the function fa. In this case, the control device 7 determines the function f based on the bite time t3, rolling speed vW, rolling torque MW, and the initial state x2 of the drive system. a The parameter a.

[0090] Various modifications can be made within the framework of the method according to the invention. For example, it is possible that the control device 7 determines the torque curve M such that the torque M generated by the drive device 4 and / or the applied torque ML applied to the driven roll 3 are greater than their respective predetermined minimum values ​​throughout the entire time period from the starting point t2 to the bite moment t3. This does not mean first observing the results of the "torque curve M" or the "curve of applied torque ML", then determining their respective minimum values, and thus concluding that the entire corresponding curve lies above its respective minimum value. This is tantamount to "shooting the arrow first, then drawing the target." Instead, before determining the torque curve M, i.e., before executing... Figure 3 Before step S2, each minimum value is preset. Then, the moment curve M is determined to comply with each minimum value. Therefore, the preset minimum value is the condition that the moment curve M must comply with. If the moment curve M is solved... Figure 7 To determine the optimization problem, for example, a preset minimum value can be introduced into equation (21) as the minimum value Mmin. The minimum value can be 0 or greater than zero.

[0091] Similarly, it is also possible that the control device 7 determines the torque curve M, causing the rotational acceleration of the drive device 4 to vary by its rotational speed ω1 and / or the rotational speed ω of the driven roll 3. n The varying rotational acceleration, throughout the entire time interval from the initial time t2 to the engagement time t3, exceeds its predetermined minimum value. Again, this is a condition that the torque curve M must satisfy, not merely a naturally occurring result. Again, the minimum value can be 0 or greater than zero.

[0092] Alternatively, the control device 7 may determine the torque curve M such that the energy consumption of the drive device 4 is minimized during the time period from the initial moment t2 to the engagement moment t3. This can be achieved, in particular, by appropriately presetting the motor torque M'.

[0093] The following presents experimental results determined by simulating typical methods of the prior art and methods according to the present invention. In all cases, the drive system is modeled as a three-mass oscillator.

[0094] exist Figures 8 to 23 In the diagram, the horizontal axis represents time in seconds, where the bite-in moment t3 occurs at 1.0 second. Therefore, from moment t3 onwards, the rolling torque MW must be applied. Before the bite-in moment t3, only a lower torque needs to be applied to ensure that the driven roll 3 rotates uniformly. Figures 8 to 23 The vertical axis in the figure represents the rotational speed or torque, both of which have been normalized.

[0095] Figures 8 to 11 The results of the prior art method are shown. These results occur before the bite-in time t3 by maintaining the drive system at a target speed ω* corresponding to the rolling speed vW, and after the bite-in time t3 by torque and speed regulation of the mill 1 to compensate for the speed drop that occurs at the bite-in time t3. Figure 8 The time curves of the rotational speed or angular velocity ω1 of the drive device 4 are shown. Figure 9 The rotational speed or angular velocity ω of the driven roll 3 is shown. n The time curve. Similarly, Figure 10 and 11 The time curves of motor torque M and applied torque ML are shown. It can be seen that the rotational speed ω of the driven roll 3... n The speed drops off after the engagement moment t3. A delayed drop also exists for drive unit 4. It takes more than 0.2 seconds to compensate for the speed drop.

[0096] Figures 12 to 15Results of the prior art method are also shown. These results involve maintaining the drive system at a target rotational speed ω* above the roll circumferential speed vU corresponding to the rolling speed vW before the bite-in time t3, and reducing the target rotational speed ω* to a value corresponding to the rolling speed vW approximately 50 milliseconds after the bite-in time t3. Figure 12 The time curves of the rotational speed or angular velocity ω1 of the drive device 4 are shown. Figure 13 The rotational speed or angular velocity ω of the driven roll 3 is shown. n The time curve. Similarly, Figure 14 and 15 The time curves of motor torque M and applied torque ML are shown. The rotational speed ω of the driven roll 3 can also be seen here. n It fell, although not like Figures 8 to 11 The process is as drastic as shown. The angular velocity ω1 of drive unit 4 also drops with a delay. Here, a period of more than 0.2 seconds is needed to compensate for the drop in speed. The transient change in motor torque M that occurs when the target speed ω* decreases is particularly unfavorable.

[0097] Figures 16 to 19 The results of the method according to the invention are shown. These results occur before the start time t2, maintaining the drive system at a target rotational speed ω* corresponding to the rolling speed vW. The start time t2 is approximately 0.1 seconds before the bite-in time t3. Figure 16 The time curves of the rotational speed or angular velocity ω1 of the drive device 4 are shown. Figure 17 The rotational speed or angular velocity ω of the driven roll 3 is shown. n The time curve. Similarly, Figure 18 and 19 The time curves of motor torque M and applied torque ML are shown. It can be seen that the rotational speed ω of the driven roll 3... n There was no drop at the biting moment t3. The same applies to the angular velocity ω1 of the drive unit 4. It can also be seen that the rotational speed ω of the driven roller 3... n It increases shortly before the bite-in time t3, and the maximum amplitude of the motor torque M is lower than according to Figures 8 to 11 and according to Figures 12 to 15 The maximum value of the method.

[0098] exist Figures 16 to 19 During the process, the drive unit 4 and the driven roll 3 must be temporarily braked shortly after the initial time t2. Therefore, shortly after the initial time t2, both the motor torque M and the applied torque ML become negative. This can be achieved through… Figures 20 to 23 The process is avoided, and these figures also show the results of the process according to the invention.

[0099] exist Figures 20 to 23In the process shown, the initial time t2 is also approximately 0.1 seconds before the bite-in time t3. However, prior to the initial time t2, the drive system is maintained at a target speed ω* significantly lower than the speed corresponding to the rolling speed vW, specifically approximately 70% of that speed. The corresponding speed reduction can be easily achieved, for example, by gradually slowing down the drive unit 4 after the workpiece rolled before the currently considered workpiece 2 has left, until the drive system reaches the desired (low) target speed ω*.

[0100] Figure 20 The time curves of the rotational speed or angular velocity ω1 of the drive device 4 are shown. Figure 21 The rotational speed or angular velocity ω of the driven roll 3 is shown. n The time curve. Similarly, Figure 22 and 23 The time curves of motor torque M and applied torque ML are shown. It can be seen that this not only avoids the driven roll 3 rotating at speed ω at the biting moment t3, but also... n The drop. Furthermore, the rotational speeds ω1 and ω2 of the drive unit 4 and the driven roll 3 can be controlled. n As the applied torque ML continuously increases, the motor torque M remains above 0 at every time t. The maximum value of the motor torque M is still lower than... Figures 8 to 11 and Figures 12 to 15 The maximum value of the method. Figures 20 to 23 The method is superior to existing technologies and techniques. Figures 16 to 19 The method is more stable and energy-efficient.

[0101] This invention offers numerous advantages. In particular, within the scope of this invention, the speed drop during biting is not compensated for retrospectively, but rather ensured from the outset through appropriate pre-control that at biting time t3, the circumferential speed vU of the driven roll 3 and the load torque ML acting on the driven roll 3 are already set so that they precisely correspond to the desired values ​​vW and MW. This is guaranteed by the invention's predictive determination of the torque curve M over the time interval from the initial time t2 to biting time t3. The method according to the invention can completely or almost completely avoid speed drops during biting. The method of the invention can also be easily implemented as an add-on to existing rolling mills. This method is independent of the regulation system on which the control device 7 is based. For example, commissioning and stability testing can be performed independently of other regulation systems.

[0102] Although the invention has been described and described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and those skilled in the art can derive other variations therefrom without departing from the scope of protection of the invention.

[0103] List of reference numerals 1. Rolling Mill 2 Rolled parts 3 Driven rolls 4. Drive unit 4' converter 4'' electric motor 5. Drive chain 6. Front end of the rolled piece 7. Control device 8 Control Procedure 9 Machine Code 10 models 11 and 12 couplings 13 Spring elements 14 Damping elements Table 15 a parameter A、A ω , , matrix b ω vector e c1、c i c n-1 Spring constant d1, d i d n-1 Material damping D1、D i D n coefficient of friction f a function J1, J i J n Moment of inertia M-torque curve Mmin minimum value Mmax maximum value M, M2, M3, M' Motor torque ML applies torque MW rolling torque Q weight matrix R weighting factor Steps S1 to S6 t Time / moment (general) Time intervals t1, t2, and t3 T time period V Rolling speed vW Rolling speed x, x2, x3, x', x ω , state Δ 1. Δ i Δ n-1 Corner ω*、ω1、ω i ω n angular velocity

Claims

1. A method of operating a rolling mill (1), in which a workpiece (2) made of metal and having a workpiece front end (6) is rolled, -in, Before the front end (6) of the workpiece enters the mill (1), the control device (7) for the mill (1) learns the bite time (t3), rolling speed (vW) and rolling torque (MW). - Wherein, the bite-in time (t3) is the time when the front end (6) of the workpiece should enter the rolling mill (1), and the workpiece (2) should be rolled at the bit-in time (t3) with the rolling speed (vW) and the rolling torque (MW). - Wherein, before the start time (t2) before the bite time (t3), the control device (7) determines the torque curve (M) of the drive device (4) for driving the roll (3) of the mill (1) via the drive chain (5) for a time period from the start time (t2) to the bite time (t3), and operates the drive device (4) according to the determined torque curve (M) during the time period. Its features are, The control device (7) determines the torque curve (M) based on the initial state (x2) of the drive device (4), the drive chain (5) and the driven roll (3) of the mill (1) present at the initial time (t2), such that the driven roll (3) of the mill (1) is subjected to the rolling torque (MW) by the drive chain (5) at the bite time (t3) and rotates at a circumferential speed (vU) coordinated with the rolling speed (vW).

2. The operating method according to claim 1, Its features are, The control device (7) determines the torque curve (M) such that at the bite moment (t3), the driven device (4), the drive chain (5) and the driven roll (3) of the mill (1) rotate at corresponding speeds and the change in speed is zero.

3. The operating method according to claim 1 or 2, Its features are, The control device (7) uses a model (10) to determine the torque curve (M), which models the drive device (4), the drive chain (5), and the rolls (3) of the mill (1) driven by the drive device (4) based on mathematical physics equations.

4. The operating method according to claim 3, Its features are, The model (10) models the drive device (4), the drive chain (5) and the driven roll (3) of the mill (1) as a multi-mass vibration system with multiple interconnected damping elastic elements.

5. The operating method according to claim 3 or 4, Its features are, The control device (7) establishes an optimization problem to determine the torque curve (M), and introduces the corresponding torque (M) of the drive device (4) as an input variable for multiple discrete time points (t) within the time period into the optimization problem, and determines the torque curve (M) by solving the optimization problem.

6. The operating method according to claim 1 or 2, Its features are, The control device (7) uses a table (15) stored in the control device (7) to determine the torque curve (M), the table taking the bite time (t3), the rolling speed (vW), the rolling torque (MW), and the initial state (x2) of the driven rolls (3) of the drive device (4), the drive chain (5), and the mill (1) as input variables, or The torque curve (M) is a parameterized function (f) of time (t) stored in the control device (7). a The function (f) is provided to the control device (7), and the control device (7) determines the function (f) based on the bite time (t3), the rolling speed (vW), the rolling torque (MW), and the initial state (x2) of the driven roll (3) of the drive device (4), the drive chain (5), and the mill (1). a The parameter (a) of ).

7. The operating method according to any one of the preceding claims, Its features are, In the initial state (x2), the driven rolls (3) of the drive device (4), the drive chain (5) and the mill (1) rotate at corresponding speeds and the value of the speed change is zero.

8. The operating method according to any one of the preceding claims, Its features are, In the initial state (x2), the circumferential speed (vU) of the driven roll (3) is less than the circumferential speed (v) of the driven roll (3) that is coordinated with the rolling speed (vW).

9. The operating method according to any one of the preceding claims, Its features are, The control device (7) determines the torque curve (M) such that the torque (M) generated by the drive device (4) and / or the applied torque (ML) of the driven roll (3) used to drive the mill (1) are greater than their respective predetermined minimum values ​​throughout the entire time period.

10. The operating method according to any one of the preceding claims, Its features are, The control device (7) determines the torque curve (M) such that the rotational acceleration of the rotational speed change of the drive device (4) and / or the rotational acceleration of the rotational speed change of the driven roll (3) are greater than their respective predetermined minimum values ​​throughout the entire time period.

11. The operating method according to any one of the preceding claims, Its features are, The control device (7) determines the torque curve (M) so that the energy consumption of the drive device (4) is minimized during the time period.

12. The operating method according to any one of the preceding claims, Its features are, The time period is between 50 milliseconds and 200 milliseconds, especially between 75 milliseconds and 150 milliseconds.

13. A control program having machine code (9) processable by a control device (7) for a rolling mill (1) for rolling a workpiece (2) made of metal having a workpiece front end (6), wherein, The control device (7) processes the machine code (9) to cause the control device (7) to perform the operating method according to any one of the preceding claims.

14. A control device for a rolling mill (1) for rolling a workpiece (2) made of metal having a workpiece front end (6), wherein, The control device is programmed by the control program (8) according to claim 13, so that the control device executes the operating method according to any one of claims 1 to 12 during operation.

15. A rolling apparatus for rolling a piece (2) made of metal having a front end (6). -in, The rolling equipment has a rolling mill (1) in which the workpiece (2) is rolled. -The rolling mill (1) has a drive device (4), a drive chain (5) and rolling rolls (3). -The roller (3) can be driven by the drive device (4) through the drive chain (5). -The rolling equipment has a control device (7) for the rolling mill (1). - wherein the control device (7) is configured as the control device (7) according to claim 14.

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