Patent Grant
11752533
This application relates to and claims the benefit and priority to European Application No. EP21382169.7, filed Feb. 26, 2021.
The present invention relates to a method used for controlling the operation of a leveling machine for leveling sheet material, and to a leveling machine for leveling sheet material configured for carrying out said method.
When manufacturing sheet material, such as a metal strip or sheet metal, the material is generally subjected to cold and hot rolling which provides the material with mechanical properties; however, residual stresses are generated within the material. The release of residual stresses within the material can be achieved by means of processes of straightening, stretch leveling, tension leveling, or by means of the roll leveling in a leveling machine.
The leveling machine has work rolls between which the sheet material is moved following a winding path from the inlet to the outlet of the leveler. The work rolls are arranged in an upper row and a lower row between which the sheet material is moved. By means of rotation of the rolls and by the exerted friction, the sheet material is moved forward at a pre-established setpoint speed. The winding path the material follows through the rolls causes the fibers of the surface of the sheet material to be subjected to tensile and compression stresses, causing a plastic deformation that corrects the defects. Generally, 70-80% of the material exceeds the yield strength during deformation.
The shafts of the rolls of each row of rolls are parallel to one another, but the upper row of rolls is designed with a tilt, such that the deformation induced by the rolls arranged at the inlet of the leveler is greater than that induced by the rolls arranged at the outlet, and therefore the deformation of the material gradually decreases from the inlet towards the outlet as the sheet material moves forward. Therefore, the leveling process is divided into a first part in which the rolls of the inlet of the leveler subject the sheet material to elevated deformations, and a second part in which the rolls of the outlet of the leveler eliminate the curvature that the sheet material has acquired.
The rolls of the leveler can be operated with a single drive, but given that the process is divided into the two parts in which the inlet rolls generate more stress than the outlet rolls, leveling machines formed by a first group of rolls operated by means of a first drive and a second group of rolls operated by means of a second drive which is independent of the first drive, such that each group of rolls of the leveling machine can be controlled independently are known (see for example EP1951455A1, EP2058059A1, and EP2624978A1).
EP2624978A1 shows a control method of a leveling machine which comprises moving a sheet material between a first group of work rolls and a second group of work rolls following a winding path from the first group to the second group according to a setpoint speed, driving the first group of work rolls by means of a first drive, and driving the second group of work rolls by means of a second drive which is independent of the first drive.
The second drive is controlled by means of the setpoint speed and a first torsion torque value of the second drive is measured when the second drive operates at the setpoint speed. A second torsion torque value defining a relationship with the first torsion torque value is subsequently determined, and the second torsion torque value is applied on the first drive maintaining the relationship between the first and the second torsion torque value. The torsion torque value which is applied to a drive based on the torsion torque value which is measured in the other drive is thereby controlled, maintaining a constant relationship between them during the movement of the sheet material.
One aspect of the invention relates to a control method of a leveling machine which comprises:
Another aspect of the invention relates to a leveling machine comprising:
The invention allows to obtain in a simple manner an equitable distribution of the stresses generated by the drives of the groups of work rolls, and therefore to obtain an optimized energy consumption of the leveling machine. The two drives are controlled independently by means of a respective torque setpoint signal which is a function of an error signal obtained from the difference between the setpoint speed at which the drives are to be operated for moving the sheet material and the real speed of the drive. The control method thereby measures the real speed of the drives and compares it with the setpoint speed, and the obtained error signal is used for acting on the setpoint torque of the drive, said setpoint torque being directly proportional to the error signal. The second torque setpoint signal applied to the second drive is also a function of an additional torque gain, whereby the setpoint torque applied to the second drive which is arranged at the outlet of the leveling machine is greater than in a conventional leveling machine in which said additional torque gain is not applied.
Therefore, the first group of rolls is used for applying the force required for deforming the sheet material and eliminating residual stresses, whereas the additional torque gain applied to the second drive allows the second group of work rolls to eliminate the curvature the sheet material has acquired when passing through the first group of work rolls, and furthermore allows the second group of work rolls to pull on the sheet material, helping to remove it from the leveler, therefore preventing the first group of rolls from having to perform said pulling effort and being able to concentrate the efforts in the deformation.
These and other advantages and features will become apparent in view of the figures and detailed description.
The sheet material 1 can be supplied in the form of a continuous strip, as shown in
The drive rolls 30 are a pair of rolls between which the sheet material 1 is forced to pass. As shown in
The leveling machine 10 comprises a first group of work rolls 11 and a second group of work rolls 12 defining a winding path for moving the sheet material 1 from the first group 11 to the second group 12 according to a setpoint speed V*, a first drive 13 for driving the first group of work rolls 11, a second drive 14 for driving the second group of work rolls 12, which is independent of the first drive 11, and a controller 15 of the drives 13 and 14.
The first drive 13 is a first motor for driving the first group of work rolls 11. The second drive 14 is a second motor for driving the second group of rolls.
The first motor 13 is coupled to the shafts of the rolls of the first group of work rolls 11 by means of a first system of gears and first transmission rods. The second motor 14 is coupled to the shafts of the rolls of the second group of work rolls 12 by means of a second system of gears and second transmission rods. The shaft of the first motor 13 is connected to the first system of gears driving the first transmission rods connected to each roll of the first group of work rolls 11. The shaft of the second motor 14 is connected to the second system of gears driving the second transmission rods connected to each roll of the second group of work rolls 12. The transmission between a motor and the rolls by means of gears and transmission rods is known in leveling machines and not depicted in the figures.
As can be seen in
The shafts of the rolls of each row of rolls are parallel to one another, and one of the rows (generally the upper row) is tilted with respect to the other row, such that the separation between the rolls arranged at the inlet of the leveler 10 is less than the separation between the rolls arranged at the outlet of the leveler 10. Therefore, the deformation induced by the rolls arranged at the inlet of the leveler is greater than the deformation induced by the rolls arranged at the outlet; therefore, the deformation of the sheet material 1 gradually decreases from the inlet towards the outlet of the leveling machine as the sheet material 1 moves forward.
Therefore, the leveling process is divided into two parts, the first part corresponds to the one which occurs in the first group of work rolls 11, and the second part corresponds to the one which occurs in the second group of work rolls 12. In the first part, the force exerted by the rolls 11 on the sheet material is greater, and the sheet material 1 develops areas of plastic deformation which increase as the sheet material 1 is bent between the rolls 11, until reaching a maximum plasticized thickness. Due to the strong bends in this first part, a stress profile is generated in the thickness of the sheet material. For that purpose, after the first part, the force exerted on the sheet material 1 decreases until, at the outlet, the rolls 12 barely deform the sheet material 1. The purpose of the second part is to gradually eliminate the curvature of the sheet material 1 and reduce the stress gradient generated in the first part.
It has experimentally been found that when the two drives 13 and 14 are operating at the same speed, the first group of work rolls 11 performs a greater effort than the second group of work rolls 12, such that the torsion torque exerted by the first drive 13 of the first group of work rolls 11 is greater than the torsion torque exerted by the second drive 14 of the second group of work rolls 12. To that end, the purpose of the invention is to obtain a more equitable distribution of the stresses generated by the drive 13, 14 of each group of work rolls 11 and 12, such that the first group 11 carries out its function of deforming the sheet material 1, and the second group 12 carries out its function of eliminating the curvature, but furthermore the second group 12 performs an additional effort for pulling the sheet material 1, helping to remove it from the leveling machine 10.
The control method of the leveling machine 10 comprises:
The setpoint speed V* is pre-established and is the speed at which the drives 13 and 14 are required to operate for moving the sheet material 1 in the forward movement direction A of the leveling line.
Speeds V1 and V2 of the first and second drives 13 and 14 can be measured with encoders coupled to the shafts of the drives, such as magnetic encoders, optical encoders, etc. Alternatively, other detection elements instead of encoders can be used for measuring the speed of the drives.
The speed V1 is the speed measured in the shaft of the first motor 13. The speed V2 is the speed measured in the shaft of the second motor 14.
The torque setpoint signal T* of each drive 13 and 14 is directly proportional to the error signal e(t) according to the following expression:
T*(t)=Kp·e(t)
wherein Kp is a constant.
The constant Kp is the constant characteristic of proportional controllers P, and it is the same for the two drives.
A proportional controller P is thereby used for applying the torque setpoint signal T* to each drive which is directly proportional to the error signal e(t). The very nature of the proportional controller P means that there is always an error signal e(t) that generates a torque setpoint T* with which it is possible to control the drives 13 and 14. If a proportional integral controller PI is used for generating the torque setpoint signal based on said error signal e(t), the controller PI would tend to achieve zero error in speed (permanent regimen), such that it would not be possible to control the stresses generated by the two drives, whereby in practice the first drive 13 would end up performing a greater effort than the second drive 14.
The speed V1 of the first drive 13 is controlled by means of the first torque setpoint signal T1* which is a function of the first error signal e1 according to the following expressions:
T1*(t)=Kp·e1(t)
e1(t)=V*(t)−V1(t)
wherein:
The speed V2 of the second drive 14 is controlled by means of the second torque setpoint signal T2* which is a function of the second error signal e2 according to the following expressions:
T2*(t)=Kp·e2(t)
e2(t)=V*(t)−V2(t)
wherein:
As shown in
T2**(t)=T2*(t)+K2T2*(t)
wherein:
As shown in
Alternatively, for applying the additional torque gain, it is possible to directly modify the constant Kp of the proportional controller P of the second drive 14 and obtain the second desired torque setpoint signal T2*.
An example of the control method for a time instant in which the setpoint speed V* is 500 rpm, the real speed V1 measured in the first drive 13 is 400 rpm, and the real speed V2 measured in the second drive 14 is 405 rpm is shown below, the constant Kp of the proportional controller for both drives being 8. By applying the control method without the additional torque gain, a first torque setpoint signal T1* of 800 Nm and a second torque setpoint signal T2* of 760 Nm would be obtained.
V*(t)=500 rpm;Kp=8 (the same for the two drives)
V1(t)=400 rpm→e1(t)=100 rpm and T1*(t)=Kp*e1(t)=800 Nm
V2(t)=405 rpm→e2(t)=95 rpm and T2*(t)=Kp*e2(t)=760 Nm
In this case, the second torque setpoint signal T2* is greater than the first torque setpoint signal T1*. According to this example, an increase in torque in the second drive 14 with respect to the first drive 13 is achieved by adding the additional torque gain to the second drive 14. For example, by applying a constant K2 of 0.3, a second additional torque setpoint signal T2** of 988 Nm would be obtained for the previously indicated time instant, whereby the second drive 14 would perform 23.5% more torque than the first drive 13, as shown below.
K2=0.3
T2**(t)=760+760*0.3=988 Nm
Additionally, if an increase in torque in the first drive 13 is to be obtained, another additional torque gain can be applied to the first torque setpoint signal T1* in the same way that has been described for the second drive 14. To that end, as shown in the example of
T1**(t)=T1*(t)+K1T1*(t)
wherein:
Generally, K1=0; nevertheless, based on the conditions of the leveling line it may be necessary to apply the other additional torque gain to modify the torque applied to the first drive 13, K1 also being a constant which is determined beforehand based on the conditions of the leveling line.
The leveling machine comprises:
The controller 15 of the leveling machine is configured for carrying out the control method depicted in
| Number | Date | Country | Kind |
|---|---|---|---|
| 21382169 | Feb 2021 | EP | regional |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7812558 | Mori | Oct 2010 | B2 |
| 8127580 | Polatidis | Mar 2012 | B2 |
| 10232419 | Imanari | Mar 2019 | B2 |
| 20120047977 | Smith | Mar 2012 | A1 |
| 20160271669 | Bergman | Sep 2016 | A1 |
| Number | Date | Country |
|---|---|---|
| 201175737 | Jan 2009 | CN |
| 104801572 | Jul 2015 | CN |
| 1951455 | Aug 2008 | EP |
| 2058059 | May 2009 | EP |
| 2624978 | Aug 2013 | EP |
| H01317620 | Dec 1989 | JP |
| Entry |
|---|
| English translate (CN104801572A), retrieved date Jan. 22, 2023. |
| European Search Report, EP21382169.7, dated Jul. 22, 2021, 7 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220274148 A1 | Sep 2022 | US |
