PowerFlow Paper Solutions

Data Flow Pipeline

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Pipeline Overview

The Dilution Control System processes data through a well-defined pipeline that transforms raw scanner measurements into precise actuator commands. This pipeline executes continuously at the configured control interval.

1

Scanner Profile

Raw basis weight measurements

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2

Edge Detection

Find valid measurement region

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3

Data Cleaning

Spike removal & hole filling

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4

Filtering

Exponential smoothing

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5

Zone Mapping

Databoxes to actuator zones

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6

Error Calculation

Target minus measured profile

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7

Control Algorithm

Calculate position changes

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8

Actuator Output

Send setpoints to PLC

Data Acquisition

The system acquires measurement data from the QCS scanner system. The scanner traverses across the paper web, measuring basis weight at many points.

Scanner Profile Structure

Parameter Typical Value Description
Databoxes 200 Number of measurement points across the web
Scan Time 15-30 seconds Time for one complete traverse
Profile Width Web width Measurement coverage
Update Rate 15-60 seconds New profile availability
Scanner Configuration

The number of databoxes is determined by the QCS scanner system configuration and is typically 100-300 for most paper machines.

Profile Processing

Raw scanner data requires processing to remove noise and artifacts before use in the control algorithm.

Edge Detection

The system automatically detects the valid measurement region by identifying where the paper web starts and ends. This handles:

  • Variable web widths
  • Edge trim changes
  • Scanner overshoot at edges

Spike Removal

Measurement spikes from sensor glitches or web breaks are detected and removed. The algorithm:

  1. Calculates the profile average
  2. Identifies points exceeding a threshold deviation
  3. Replaces spikes with interpolated values

Hole Filling

Invalid or missing data points (holes) are filled using linear interpolation from neighboring valid points.

Exponential Filtering

A configurable exponential filter smooths the profile to reduce noise while maintaining responsiveness:

Filter Depth Parameter

  • Range: 0.0 to 1.0
  • 0.0: No filtering (raw data)
  • 0.3: Light filtering (typical)
  • 0.5: Medium filtering
  • 0.8: Heavy filtering (slow response)

Zone Mapping

The processed scanner profile (in databoxes) must be mapped to actuator zones for control. This mapping accounts for the physical relationship between measurement points and actuator locations.

Mapping Configuration

Parameter Description
Front Side Offset Offset from scanner edge to first actuator zone
Back Side Offset Offset from scanner edge to last actuator zone
Zone Width Number of databoxes averaged per zone
Mapping Direction Front-to-back or back-to-front numbering
Mapping Tip

Correct zone mapping is critical for control performance. Use the profile visualization to verify that scanner peaks correspond to the correct actuator zones.

Control Calculation

The control engine calculates the required actuator position changes based on the error profile (difference between target and measured profiles).

Error Calculation

For each zone, the error is calculated as:

Error = Target Profile - Measured Profile

Control Modes

Mode Behavior Use Case
Integrating Accumulates error over time for gradual correction Standard operation (recommended)
Static Proportional response to current error Fast response needed
Manual No automatic control; operator sets positions Troubleshooting, commissioning
Dynamic Adaptive control with correlation analysis Variable process conditions

Response Matrix

The response matrix defines how each actuator zone affects the profile. It accounts for:

  • Zone influence width
  • Cross-zone effects
  • Physical actuator spacing

Constraint Handling

Before output, position changes are constrained:

  • Position Limits: Min/max actuator positions
  • Stepping Limits: Maximum change per control cycle
  • Bending Limits: Maximum difference between adjacent zones
  • Deadband: Minimum error before action is taken

Output to Actuators

Final setpoints are sent to the PLC for zones in AUTO mode. The output process includes:

  1. Mode Check

    Only zones in AUTO mode receive calculated setpoints. MANUAL and LOCAL zones retain their current positions.

  2. Setpoint Update

    New setpoints are written to the PLC via the configured communication protocol (Modbus TCP, S7, etc.).

  3. Feedback Verification

    Actuator feedback positions are read to confirm valve movement.

  4. Status Update

    Zone status is updated based on setpoint/feedback deviation and any error conditions.

Timing & Synchronization

Proper timing ensures stable control performance.

Control Interval

Setting Value Range Recommendation
Control Interval 15-120 seconds 60 seconds (typical)
Scan Read Rate 5-30 seconds Match scanner traverse time
PLC Write Rate 100-500 ms 500 ms (default)
Feedback Read Rate 100-500 ms 500 ms (default)
Control Interval Selection

The control interval should be at least equal to the scanner traverse time to ensure new profile data is available. Setting it too short can cause oscillations; setting it too long slows response to disturbances.

Synchronization

The system synchronizes control actions with scanner data updates:

  • Waits for new profile data before control calculation
  • Uses profile timestamp to detect stale data
  • Suspends control if scanner communication is lost