User`s guide

9 Design Case Studies
9-32
This shape is impressed by two pairs of rolling cylinders (one per axis)
positioned by hydraulic actuators. The gap between the two cylinders is called
the roll gap.
The objective is to maintain the beam thickness along the x- and y-axes within
the quality assurance tolerances. Variations in output thickness canarisefrom
the following:
• Variations in the thickness/hardness of the incoming beam
• Eccentricity in the rolling cylinders
Feedback control is necessary to reduce the effect of these disturbances.
Because the roll gap cannot be measured close to the mill stand, the rolling
force is used instead for feedback.
The input thickness disturbance is modeled as a low pass filter driven by white
noise. The eccentricity disturbance is approximately periodic and its frequency
is a function of the rolling speed. A reasonable model for this disturbance is a
second-order bandpass filter driven by white noise.
-axis
incoming beam shaped beam
rolling cylinders
rolling mill stand
x