CD Control of Dilution Headboxes

1
CD Control of Dilution Headboxes

• Ben Blanchette
• Honeywell

2
Honeywell Dilution Profiling Experience

• 201 Honeywell Dilution Profiling Systems(as of
  January 2006)

Honeywell Optimizers with ProFlow 121
Honeywell Optimizers with all Actuators 201
3
Overview

• Cross-directional control issues
• Challenges/considerations
• Alignment and Nonlinear shrinkage
• Actuator response shape and tuning
• Coordinated slice lip and dilution control
• Examples

4
CD Profile Control Loop

• The pursuit of better paper quality has placed
  new demands on Cross Directional (CD) control
  systems
• smaller zone sizes
• faster response
• lower CD spreads

5
Data Acquisition
One 35 mm (1.38 in) CP headbox control
zone (Dwell 0.058 sec. _at_ 600 mm/sec scan rate)
2 mm (0.08 in) measurement zones (Dwell 3.3
msec)
Head-position reads (10 msec / read)
Sensor samples (0.5 msec / read)
117 sensor readings
6
Measurement Platform Considerations

• 10 mm (0.04 inch) minislice profile resolution
  for best control of narrow zones
• Low measurementnoise fortruest possible signal
• Full edge-to-edge sheetmeasurement for
  accurateCD profile derivation
• Fast scanning andsignal processingto minimize
  MD/CD couplingfor true CD profiles

7
Symptoms of a CD control problem
8
Classification
9
Classification
10
Trade-off is required
11
Trade-off is required
12

• Alignment and Nonlinear Shrinkage

13
Honeywell CP Optimizer
Actuators
Process
Measurement
Deadband Limit Check
Intelligent Controllers
Actuator Smoothing/Optimizer
Deconvolution/ Wave Model
Instantaneous Scan Computation
High Resolution Profiles
MD
High Resolution Deviation
IntelliMap
CD
Actuator Resolution Deviation
Profile Verification - Spike Detection -
Validation - Interpolation
Actuator Setpoints
Mapping Conversion to Actuator Zones
CD / MD Separation - DAT or Exponential
Multiple Actuator Controls - Ratio Split or -
Frequency Split
AntiAliasing Algorithm
Error Profile Generation / Apply Bias Target
To 2nd Actuator
14
CD Process Model

• Three main components
• Dynamics are important to model correctly in
  order to achieve a fast closed-loop that does not
  oscillate.
• Spatial response shape
• Modelled too narrow ? can lead to actuator
  picketing
• Modelled too wide ? can lead to streaks in
  profile
• Alignment
• Poor actuator-scanner alignment can lead to
  picketing
• Can be linear or nonlinear

15
CP Resolution Advantage

• CD Zone Width Resolution Comparison

16
Consistency Profiling

• Basis Weight Response with Dilution Control bump
• adjustment - No Zone to Zone coupling
• 1480 FPM (same as 1st bump below)
• 2.0 slice opening

• Basis Weight Response with Slice lip bump
  adjustment (adjacent Zones are coupled)
• 1150 FPM
• 2.0 slice opening
• Before Dilution Control

• Basis Weight Response with Slice Lip bump
  adjustment (adjacent Zones are coupled)
• 1480 FPM
• 2.0 slice opening
• Before Dilution Control

17
IntelliMap Automatic Setup and Tuning

• One button implementation of entire alignment
  sequence
• Short bump test duration for minimal quality
  impact and no production losses
• Grade-dependent determination of all parameters,
  including CD controller tuning
• Robust operation unaffected by variation, upsets
  and poor signal-to-noise ratio

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Alignment Model
20

• Actuator Response Shape andCutoff Wavelength

21
Consistency Profiling with Newsprint

• Given these profiles Is the CD control doing a
  good job?

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CD Control Performance

• CD control (or any control) is doing a good job
  when
• It is removing controllable variability
• It is not chasing uncontrollable variability
• Since each process is different, we will need to
  determine what is and is not controllable on a
  case-by-case basis

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Bump Test Data

• First, we need a model of the bump shape (as
  obtained earlier)

24
Typically a Bell-Shaped Response for Consistency
Profiling
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and in the Frequency Domain
Bump Response
CD position
ProcessGain
Controllable,long wavelengths
Uncontrollable,short wavelengths
CD frequency
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Definition of Cutoff Wavelength
the point at which the controller begins to
remove disturbances
cutoff wavelengthXc
1.0
DisturbanceAttenuation
Controllable,long wavelengths
Uncontrollable,short wavelengths
0.5
0.0
1/Xc
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Definition of Cutoff Wavelength
1.0
DisturbanceAttenuation
Controllable,long wavelengths
Uncontrollable,short wavelengths
0.5
0.0
1/Xc
ProcessGain
Controllable,long wavelengths
Uncontrollable,short wavelengths
CD frequency cycles/metre
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Rule of Thumb for Cutoff Wavelength
Xc
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Rule of Thumb for Cutoff Wavelength
Xc
Rule-of-thumb response shape determines cutoff
wavelength.
CD position
1/Xc
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CD Spatial Controllability

• First perform a bump test.
• Identify a process model.
• Compute the cutoff wavelength from the process
  model.
• Variablity with a CD wavelength shorter than this
  cutoff is uncontrollable.
• For dilution control, you can estimate the
  cutoff wavelength from the width of the 80-20
  point in the bump response.

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Example Consistency Profiling with Newsprint
Actuator positions
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Example Consistency Profiling with Newsprint
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Example Consistency Profiling with Newsprint
Xc 10cm
10cm
1/10cm
original tuning X90 30cm
1/30cm
1/10cm
aggressive tuning X90 16cm
1/16cm
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Tuning Results

• Achieved 26.5 reduction in CD 2s
• with only 8.7 increase in Actuator 2s

35
Tuning Results

• Frequency domain tells the story better.
• Once we knew the achievable bandwidth, it was
  possible to improve control at mid-range
  wavelengths.

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• Multivariable Control

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Multivariable Control Challenges
Calendizer
InfraZone
InfraTrol
Devronizer
AutoSlice
AquaTrol/Aqualizer
Calcoil
ProFlow
ProCoat
Designed for weight, can also affect moisture
and caliper
Designed for moisture, can also affects caliper,
gloss and smoothness
Designed for caliper, can also affect
smoothness and gloss
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AutoSlice Affects Weight Moisture Caliper
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Multivariable Control Overview
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Coordinated Decoupled Control

• Future direction coordinated decoupled control
  of fibre orientation and weight profile

Fibre orientationsetpoint profile
-

Multivariable CD Controller

Weight setpoint profile
-
Weight measurement profile
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Summary

• Effective tuning of a dilution profiling system
  requires to model
• Alignment
• CD response shape
• Dynamics (not discussed today)
• Coordinated multiple CD actuator control is now
  within practical reach.

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Real World Examples
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Mill A - Fine Paper
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Mill B Fine Paper
45
Mill C Fine Paper
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Results Base Stock LWC

• CD basis weight 2s reduced from 1.29 - 0.24 g/m²
  (0.79 - 0.15 lb/3000 ft2)
• Excellent CD profile stability
• Reduced recovery time after process upsets
• Reduced operator involvement
• Improved fiber orientation profiles

CD Weight Variation Reduction
1.4
1.2
81
1
2s (g/m²)
0.8
0.6
0.4
0.2
0
Old Headbox
Concept IV-MH with
Consistency Profiling

• Machine Information
• CD System ProFlow
• Headbox Beloit Concept IV-MX
• Zones 136 zones
• Zone Width 35 mm (1.4)
• Basis Weight 38 g/m² (25.7 lb/3300 ft²)
• Controls Honeywell
• Measurement Honeywell

47
Results Container Grade

• CD 2s reduced by 95 from 10.89 to 0.52 g/m²
• Steady-state basis weight CD 2s ranges from 0.3
  to 0.5 of process

• Machine Information
• CD System ProFlow
• Headbox Allimand
• Zones 72
• Width 5300 mm (212)
• Basis Weight 150 g/m² (30 lb/1000 ft²)
• Controls MXOpen

48
Results Base Stock LWC

• CD basis weight variation reduced 46, from 0.59
  to 0.33 g/m², (0.40 to 0.22 lb/3300 ft²)
• CD moisture variation reduced 50, from 0.42 to
  0.21
• CD caliper variation reduced 50, from 1.52 to
  0.76 mm (0.06 to 0.03 mils)

Beloit Concept IV MX Headbox Startup
1.60
1.40
1.20
1.00
2s
0.80
0.60
0.40
0.20
0.00
CD Caliper (micron)
CD Basis Weight (gsm)
CD Moisture ()
Before MXOpen
After MXOpen

• Machine Information
• CD System ProFlow
• Headbox Beloit Concept IV-MX
• Zones 168 zones
• Zone Width 35 mm (1.4)
• Basis Weight 40.7 g/m² (27.5 lb/3300 ft²)
• Control MXOpen

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Results LWC

• CD weight 2s reduced by 86, from 2.57 to 0.37
  g/m²

2s Dry Weight Variation (73 g/m² sheet)
3
2.5
86
2
2s (g/m²)
1.5
1
0.5
0

• Machine Information
• CD System ProFlow
• Headbox Voith Sulzer ModuleJet
• Speed 400 - 900 m/min
• Width 3800 mm
• Zones 67 zones/linear valves
• Basis Weight 55 - 150 g/m²
• Controls MXOpen

Voith
ProFlow
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Results Fine Paper

• 58 improvement in reel dry weight profile

Reel Dry Weight Variation Reduced
0.8
58
0.7
0.6
0.5
2s (g/m²)
0.4
0.3
0.2
0.1
0

• Machine Information
• CD System ProFlow
• Headbox Beloit Concept IV-MX
• Speed 700 m/min
• Zones 145
• Width 5150 mm
• Basis Weight 40 - 120 g/m²

Before ProFlow
After ProFlow
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Results Coating Base Stock

• CD weight 2s reduced by 44, from 0.16 to 0.09
  g/m²

2s Dry Weight Variation Reduced
0.18
0.16
44
0.14
0.12
2s (g/m²)
0.1
0.08
0.06
0.04
0.02

• Machine Information
• CD System ProFlow
• Headbox Beloit Concept IV-MX
• Speed 1051 m/min
• Width 6400 mm trim
• Zones 193 zones
• Dry Weight 38 g/m²
• Controls MXOpen

0
Conventional
ProFlow
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Results CP Optimizer

• CP control
• Honeywell controls competitors actuators
• CD weight 2s reduced by 83, from 2.20 to 0.39
  g/m²

• Machine Information
• System MXOpen
• Headbox Beloit Concept IV-MX
• Zones 164
• Basis Weight 48 g/m²

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Thank You