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Dual adaptive control of chip refiner motor load Allison, Bruce James
Abstract
A characteristic of wood chip refiners is that the incremental gain between the motor load and the plate gap is subject to a slow drift due to plate wear and sudden changes in sign due to pulp pad collapse. A pad collapse can be caused by a change in operating point, or may occur suddenly due to a feed rate or consistency disturbance. This poses a problem for fixed-parameter linear controllers which may actually accelerate pad collapse and induce plate clashing as a result of getting caught in a positive feedback loop. The objective of this thesis is to develop a reliable chip refiner motor load controller and to test it out on an industrial refiner. The problem is approached from a fault detection and control viewpoint and the proposed algorithm consists of an improved parameter estimator and a controller containing "dual" features. The role of the improved estimator is to track both drifts and jumps in the parameters. The use of active learning or probing in the controller is justified by the fact that the parameter estimates are key to identifying a pad collapse, and that probing targets a portion of the input energy at continuously identifying these parameters. Since there still does not exist a general dual controller design methodology, the main challenge was to extend existing suboptimal approaches to handle realistic dynamics including deadtime and correlated disturbances. To track both slow and fast changes in the system parameters, a multi-model approach called adaptive forgetting through multiple models or AFMM is used. A method of modifying the AFMM to include information about what to expect in the event of a pad collapse is proposed. The main contribution of the thesis is the development of the active adaptive controller or AAC, which consists of a constrained certainty equivalence approach coupled with an extended output horizon to deal with nonminimum phase systems and a cost function extension to get probing. Finally, the AAC is combined with the AFMM, and the resulting combination is tested on an industrial refiner.
Item Metadata
Title |
Dual adaptive control of chip refiner motor load
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1994
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Description |
A characteristic of wood chip refiners is that the incremental gain between the motor load and
the plate gap is subject to a slow drift due to plate wear and sudden changes in sign due to pulp pad
collapse. A pad collapse can be caused by a change in operating point, or may occur suddenly due
to a feed rate or consistency disturbance. This poses a problem for fixed-parameter linear controllers
which may actually accelerate pad collapse and induce plate clashing as a result of getting caught in
a positive feedback loop.
The objective of this thesis is to develop a reliable chip refiner motor load controller and to
test it out on an industrial refiner. The problem is approached from a fault detection and control
viewpoint and the proposed algorithm consists of an improved parameter estimator and a controller
containing "dual" features. The role of the improved estimator is to track both drifts and jumps in the
parameters. The use of active learning or probing in the controller is justified by the fact that the
parameter estimates are key to identifying a pad collapse, and that probing targets a portion of the
input energy at continuously identifying these parameters. Since there still does not exist a general
dual controller design methodology, the main challenge was to extend existing suboptimal approaches
to handle realistic dynamics including deadtime and correlated disturbances.
To track both slow and fast changes in the system parameters, a multi-model approach called
adaptive forgetting through multiple models or AFMM is used. A method of modifying the AFMM
to include information about what to expect in the event of a pad collapse is proposed. The main
contribution of the thesis is the development of the active adaptive controller or AAC, which consists of a constrained certainty equivalence approach coupled with an extended output horizon to deal with
nonminimum phase systems and a cost function extension to get probing. Finally, the AAC is
combined with the AFMM, and the resulting combination is tested on an industrial refiner.
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Extent |
6735832 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-04-17
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0058582
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1994-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.