Glossary of Terms
A
- Actuator
- A device that converts control signals into mechanical motion. In dilution control, typically refers to proportional valves that control water flow.
- ADS (Automation Device Specification)
- Beckhoff TwinCAT communication protocol for exchanging data with PLCs and I/O devices.
- Auto Mode
- Operating mode where the control system automatically adjusts valve positions based on profile measurements.
B
- Basis Weight
- The mass per unit area of paper, typically measured in grams per square meter (g/m²) or pounds per ream.
- Bending Limit
- Maximum allowed difference in position between adjacent actuator zones to prevent mechanical stress on the dilution header.
C
- CD (Cross Direction)
- The direction across the width of the paper web, perpendicular to the machine direction.
- Control Gain
- A parameter that determines how aggressively the control system responds to profile errors. Higher gain = faster response but risk of instability.
- Control Interval
- The time between successive control calculations, typically 30-120 seconds.
D
- Databox
- A measurement point in the scanner profile. The web width is divided into many databoxes (typically 100-300) for detailed profiling.
- Deadband
- A threshold below which profile errors are ignored to prevent unnecessary valve movements.
- Dilution
- The process of adding water to stock in specific zones of the headbox to adjust local basis weight.
- DIU (Digital Interface Unit)
- ABB/Accuray interface device that provides access to QCS data.
E
- Edge Detection
- Algorithm that identifies the boundaries of the paper web within the scanner profile.
- Error Profile
- The difference between the target profile and the measured profile, used by the control algorithm.
F
- Feedback
- The actual position of a valve, typically measured by a position sensor and reported back to the control system.
- Filter Depth
- Parameter controlling the exponential filter applied to profile data. Higher values = more smoothing.
- Flushing
- A maintenance procedure that cycles valves through their full range to prevent buildup and ensure smooth operation.
G
- Grade
- A specific paper product type with defined properties. Grade changes require different control parameters.
- GSM (Grams per Square Meter)
- Standard unit of measurement for paper basis weight.
H
- Headbox
- The component of a paper machine that distributes stock uniformly across the forming fabric. Dilution water is added here.
- Heartbeat
- A periodically updated counter used to verify communication is active between systems.
I
- Integrating Mode
- Control mode where position changes are accumulated over time to eliminate steady-state error. Recommended for dilution control.
- I/P Converter
- Device that converts electrical current (4-20mA) to pneumatic pressure for valve actuation.
M
- Manual Mode
- Operating mode where operators directly set valve positions without automatic control.
- Mapping
- The correspondence between scanner databoxes and actuator zones.
- Modbus
- A serial communication protocol commonly used for industrial control systems. Available in TCP (Ethernet) and RTU (serial) variants.
P
- PLC (Programmable Logic Controller)
- Industrial computer that controls the actuator valves based on setpoints from the Dilution Control System.
- Profile
- The measured values (e.g., basis weight) across the width of the paper web.
- Proportional Valve
- A valve that can be positioned anywhere in its range, not just fully open or closed.
Q
- QCS (Quality Control System)
- System that measures paper properties (basis weight, moisture, caliper, etc.) as the paper is produced.
R
- Response Matrix
- A mathematical model describing how each actuator zone affects the profile at each measurement point.
- RTU (Remote Terminal Unit)
- Modbus variant using serial communication (RS-232/RS-485).
S
- Scanner
- Device that traverses across the paper web taking measurements. May measure basis weight, moisture, caliper, etc.
- Setpoint
- The desired position for a valve (0-100%), sent from the control system to the PLC.
- Sigma (2-Sigma)
- Statistical measure of profile variation. Lower 2-sigma indicates better uniformity.
- Stepping Limit
- Maximum change in valve position allowed per control cycle to ensure smooth operation.
T
- Target Profile
- The desired basis weight profile that the control system tries to achieve.
- TCP (Transmission Control Protocol)
- Network protocol used for reliable Ethernet communication.
Z
- Zone
- A section of the paper web controlled by a single actuator. The web is typically divided into 24-96 zones.
- Zone Mode
- The operating mode of an individual zone: Auto, Manual, Remote, or Local.