The Structure of Sheet Thickness Control System
A typical process control system that may be used to control the thickness of sheet produced by rollers is illustrated in the diagram below:
A block diagram of sheet thickness control system describing the above system is shown below:
Operation of Sheet Thickness Control System
The thickness of the sheet is monitored by a sensor such as a linear variable differential transformer (LVDT). The position of the LVDT sensor probe is set so that when the required thickness sheet is produced, there is no output from the LVDT. The LVDT produces an alternating current output, the amplitude of which is proportional to the error. This is then converted to a DC error signal which is fed to an amplifier (all this is accomplished by the AC to DC converter). The amplified signal is then used to control the speed of a DC motor, typically being used to vary the armature current. The rotation of the motor is likely to be geared down and then used to rotate a screw which alters the position of the upper roll, hence changing the thickness of sheet produced.
Related articles:
- A Digitally Controlled Drill Press
- Industrial Process Temperature Control System
- What is Process Control?
- Ratio Control
- Principles of Control Systems
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