Rolling with minimisation of a drop in the bending force upon entry

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 (t2), 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 (t3), the stabilization time (t3) being after the actual entry time (t2), 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 (t2) and ends after the actual entry time (t2),
• 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 (t2), 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.