Rolling with minimisation of a drop in the bending force upon entry
In a roll stand, the working roll inserts are pressed apart by a bending system. A base set-point value (FBB*) is supplied to a bending controller to determine a resultant set-point value (FB*). An actual value (FB) of the bending force is also supplied to the bending controller to determine a base controlled variable (SB) for the bending system so that, when the bending system is actuated with (SB), (FB) is brought as close as possible to (FBB*). From a stabilisation time (t 3 ) after an entry time (t 2 ), the bending controller determines (FB*), additionally taking an actual rolling force (F) into consideration. During an entry time period before (t 2 ) and ending at (t 3 ), an additional set-point value (FBZ*) is supplied to the bending controller for determining (FB*). (FB) is thus greater than (FBB*).
1 . An operating method for a roll stand for rolling a flat rolling stock made of metal, the rolling stock having a head,
wherein the roll stand has at least working rollers and support rollers,
wherein the working rollers are mounted in working roller chocks and a bending system that presses the working roller chocks apart acts on the working roller chocks,
wherein the head of the rolling stock reaches the roll stand at an actual entry time (t 2 ), the operating method comprising:
supplying a base setpoint (FBB*) to a bending feedback controller to determine resultant setpoint (FB*) taking into account the base setpoint (FBB*),
supplying the bending feedback controller with an actual value (FB) of the bending force,
determining with the bending feedback controller a basic manipulated variable (SB) for the bending system, so that when the bending system is controlled with the basic manipulated variable (SB), the bending feedback controller the basic manipulated variable (SB) by means of the resultant setpoint (FB*) and the actual value (FB), the actual value (FB) being approximated to the resultant setpoint (FB*), and
the bending feedback controller determining the resultant setpoint (FB*) as from a stabilization time (t 3 ), the stabilization time (t 3 ) being after the actual entry time (t 2 ), taking into account an actual rolling force (F) occurring during the rolling of the flat rolling stock,
during an entry period which begins before the actual entry time (t 2 ) and ends after the actual entry time (t 2 ),
supplying the bending feedback controller with an additional setpoint (FBZ*) in addition to the base setpoint (FBB*), so that the bending feedback controller during the entry period determines the resultant setpoint (FB*) taking into account the base setpoint (FBB*) and the additional setpoint (FBZ*), and as a result the actual value (FB) of the bending force is greater than the base setpoint (FBB*) immediately before the actual entry time (t 2 ), and/or
determining, by applying an additional manipulated variable (SZ) to the basic manipulated variable (SB), a resultant manipulated variable (SR) and supplying the resultant manipulated variable (SR) to the bending system, and the bending system being thereby controlled in such a manner that the resultant manipulated variable (SR) is greater than the basic manipulated variable (SB), and/or
supplying a selection member with the basic manipulated variable (SB) and a minimum manipulated variable (SM), and the selection member supplying the maximum of basic manipulated variable (SB) and minimum manipulated variable (SM) to the bending system.
2 . The operating method as claimed in claim 1 , wherein the additional setpoint (FBZ*), or the additional manipulated variable (SZ), or the minimum manipulated variable (SM) is raised monotonically from zero to a maximum value (FBZO*) from a beginning (t 5 ) of the entry period with a finite gradient and/or is reduced monotonically from the maximum value (FBZO*) to zero at an end (t 6 ) of the entry period with a finite gradient.
3 . The operating method as claimed in claim 2 , wherein an expected entry time (t 7 ) is determined by means of path tracking for the rolling stock, and the beginning (t 5 ) of the entry period is before the expected entry time (t 7 ) by a predetermined early time span (T 1 ).
4 . The operating method as claimed in claim 2 , wherein the end (t 6 ) of the entry period is after the actual entry time (t 2 ) by a predetermined late time span (T 2 ).
5 . The operating method as claimed in claim 1 , wherein before the rolling stock is rolled in the roll stand, a maximum value of the additional setpoint (FBZ*) and/or the additional manipulated variable (SZ) and/or the minimum manipulated variable (SM) are determined as a function of properties of the rolling stock and/or as a function of an expected rolling force (FE).
6 . The operating method as claimed in claim 1 , wherein the maximum value of the additional setpoint (FBZ*) and/or the additional manipulated variable (SZ) and/or the minimum manipulated variable (SM) is determined in such a manner that the resultant manipulated variable (SR) assumes a maximum value (MAX) at the actual entry time (t 2 ).
7 . The operating method as claimed in claim 1 , wherein the additional setpoint (FBZ*) and/or the additional manipulated variable (SZ) and/or the minimum manipulated variable (SM) are determined in such a manner that a drop in the actual value (FB) of the bending force at the actual entry time (t 2 ) is compensated for by at least 50%.
8 . A rolling unit for rolling a flat rolling stock made of metal, the rolling stock having a head, the rolling unit comprising:
a roll stand and a bending feedback controller,
working rollers mounted at least in working roller chocks, and support rollers,
a bending system that presses the working roller chocks apart, and
a selection member,
wherein the bending feedback controller actuates the bending system,
wherein the head of the rolling stock reaches the roll stand at an actual entry time (t 2 ),
wherein a base setpoint (FBB*) is supplied to a bending feedback controller and the bending feedback controller determines a resultant setpoint (FB*) taking into account the base setpoint (FBB*),
wherein the bending feedback controller is supplied with an actual value (FB) of the bending force,
wherein the bending feedback controller by means of the resultant setpoint (FB*) and the actual value (FB) determines a basic manipulated variable (SB) for the bending system, so that when the bending system is controlled with the basic manipulated variable (SB), the actual value (FB) is approximated to the resultant setpoint (FB*),
wherein the bending feedback controller determines the resultant setpoint (FB*) as from a stabilization time (t 3 ) after the entry time (t 2 ), taking into account an actual rolling force (F) occurring during the rolling of the flat rolling stock,
wherein during an entry period which begins before the actual entry time (t 2 ) and ends after the actual entry time (t 2 ),
the bending feedback controller is supplied with an additional setpoint (FBZ*) in addition to the base setpoint (FBB*), so that the bending feedback controller during the entry period determines the resultant setpoint (FB*) taking into account the base setpoint (FBB*) and the additional setpoint (FBZ*), and as a result the actual value (FB) of the bending force is greater than the base setpoint (FBB*) immediately before the actual entry time (t 2 ), and/or
by applying an additional manipulated variable (SZ) to the basic manipulated variable (SB), a resultant manipulated variable (SR) is determined and supplied to the bending system, and the bending system is thereby controlled in such a manner that the resultant manipulated variable (SR) is greater than the basic manipulated variable (SB), and/or
the selection member is supplied with the basic manipulated variable (SB) and a minimum manipulated variable (SM), and the selection member supplies the maximum of basic manipulated variable (SB) and minimum manipulated variable (SM) to the bending system.