Note: Descriptions are shown in the official language in which they were submitted.
CA 02235176 2004-11-08
METHOD AND APPARATUS FOR IMPROVED INSPECTION AND
CLASSIFICATION OF ATTRIBUTES OF A WORKPIECE
FIELD OF THE I1WENTION
This invention relates to a method and apparatus for improved inspection and
classification
of attributes of a workpiece, and in particular to automated high speed defect
assembly and
generation of a workpiece model for lumber grading.
BACKGROUND
It has become a serious consideration in the lumber industry to improve
grading of lumber
and therefore improve secondary breakdown decisions. By optimizing the
recovery of"good wood"
against a slate of desired products, the value of the lumber may be increased.
"Good wood" refers to
wood which meets a prescribed criteria. For different uses, what is considered
"good wood" may
vary. For example, for fine furniture, it may not be acceptable to have any
knots in the wood.
However, for furniture intended to have a more rustic appearance, a certain
number of knots may in I
i
fact be desirable. In general though it is desirable to identify certain
"defects" in the lumber, and to
locate them with respect to a spatial reference system. One method of doing
this is to have a human
visually inspect each piece of lumber prior to it being cut into secondary
boards. This is slow and a
prone to error. Further, even if the defect is identified, the information
must still somehow be
communicated to a saw operator in a meaningful manner to allow the defect to
be isolated, yet allow
wood recovery to be optimized against a desired product slate.
There have been some improvements in the area of grading lumber, for example
Lumber
Optimizer (US Patent 4,879,753 to Aune et al), Method of Estimating the
Strength of Wood (US
Patent 4,941,357 to Schajer), Dielectric Sensor Apparatus (US Patent S,b54,643
to Bechtel et al),
Detector for Heterogeneous Materials (US Patent 5,585,732 to Steele et al),
and Flaw Detection i
System Using Microwaves (US Patent 4,514,680 to Heikkil~ et al) which uses
microwaves to
measure lumber flaws. !
I
Defects comprise such features as knots, rot, splits, sap, skips, holes,
cracks, wane, stain and
the like. Defects may be further subclassified, for example a knot may be a
sound knot or an
unsound knot. Most defects have some attribute which allows them to be
detected by automated
scanning. For example, reflective inspection (laser or gray-scale video) can
detect stain and sap in
wood. Transmissive inspection techniques (such as x-ray) can detect density
variations, and thus
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CA 02235176 2004-11-08
knots and rot and the like. As indicated, a variety of automatic inspection
techniques exist for
determining the presence of such defects. Most of these methods give only an
indication of the
probability of a defect, and do not guarantee that the object identified by
the inspection technique is
actually a defect. However, by combining the different results of automatic
inspection into a single
model, defects can be verified and the probability that an identified object
is in fact a defect are
increased.. Further, combining inspection results allows further
characterization of a defect. For
example, a dark area identified by a visual scan can either indicate rot,
stain, or a knot. However,
verification of the visual scan with an x-ray scan can reveal the object to be
rot if the x-ray scan
indicates it is an area of low density, or a knot if the x-ray scan indicates
it is an area of high density.
It is desirable if all of the results of inspection can be combined to produce
a board model,
which in the digital realm might be more appropriately termed a "virtual
board." The board model
can then be analyzed for optimum yield against a product slate. Further,
automated handling
machines such as conveyors, and automated process machines such as saws, can
control the handling
and processing of the physical board on which the board model is based.
It is fixrther desirable to have a system which is flexible and can easily
accommodate the
addition or subtraction of additional components, such as additional
inspection subsystems, user
interfaces, computer controlled machines (saws, etc.), and additional
technology as it becomes
available.
For any such system to be effective, it is desirable that the system be able
to determine the
precise location of the board at various points throughout the system. Various
prior art tracking
systems such encoder wheels can become inaccurate due to slippage, and can
cause undesirable
marking of the product in the event of a failure. It is therefore desirable to
provide a tracking system
which is accurate and reliable.
SUMMARY OF THE INVENTION
An apparatus for detecting the probable existence, location, and type of
defects in a
workpiece is disclosed. The apparatus has a signal processor having a computer
readable memory, a
control subsystem, and a sensor subsystem. The sensor subsystem is configured
to sense a first
section of the workpiece and produce signals corresponding to ax least one
physical characteristic of
the section of the workpiece and store the signals in the computer readable
memory. The processor
is configured to read the signals from the computer readable memory, to verify
the signals, to
generate defect types by comparing the signals to a rule set, and to generate
a data model of the
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CA 02235176 2004-11-08
workpiece section. The control system is configured to generate a workpiece
section identifier to
specifically identify a workpiece section being sensed and provide the
workpiece section identifier to
the processor. The processor is further configured to receive the signals for
the first workpiece
section to a first workpiece processing thread after receiving the associated
workpiece section
identifier, and to generate a second workpiece processing thread for receiving
signals from a second
workpiece section. The signals in the first workpiece processing thread are
processed to generate the
data model of the first workpiece section prior to processing of the signals
in the second workpiece
processing thread.
The invention further includes an apparatus for detecting the probable
existence, location,
and type of defects in a workpiece wherein the apparatus includes a sensor
subsystem as described
above, a defect assembler, an optimizer, and a computer system. The defect
assembler is configured
to generate defect assembler data, subscription requests, to receive the
signals produced by the sensor
subsystem, and to generate a workpiece data model based on the signals. The
optimizer is
configured to generate workpiece segmentation recommendations based on the
workpiece data
model, and generate optimizer data subscription requests. The computer system
further includes a
processor and a computer readable memory. The computer system is configured to
receive signals
form the sensor subsystem and store them in the computer readable memory. The
processor is
configured with a first producer thread program which, in response to the
receipt of a first set of
signals by the computer system, receives one of the data subscription requests
and transmits the first
set of signals from the computer readable memory to the generator of the data
subscription request.
The processor is further configured to generate a second producer thread in
response to a storage of a
second set of signals in the computer readable memory, the second producer
thread being configured
to receive one of the data subscription requests and selectively send the
second set of signals to the
generator of the data subscription request.
The invention further includes an apparatus for characterizing a workpiece,
the apparatus
including an interface controller, a plurality of producer units, and a
plurality of consumer units. The
producer units are configured to produce data relevant to characterization of
the workplace. The
producer units are selected from the group consisting of sensor subsystems, a
defect assembler, an
optimizer, and a data controller. The sensor subsystems are configured to
sense features of the
workplace and generate signals in response thereto. The defect assembler is
configured to generate a
workplace data model. The optimizer is configured to produce a refined
workplace data model and
generate workplace segmentation recommendations based on the refined workplace
data model. The
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CA 02235176 2004-11-08
controller is configured to determine the position of the workpiece during
sensing and segmentation.
The producer units are configured to notify the interface controller the
workpiece data is available
from the producer unit. The consumer units are configured to use data relevant
to characterization of
the workpiece. The consumer units are selected from the group consisting of an
optimizer, a defect
S assembler, a host computer, and user interfaces. The optimizer is configured
to use the refined
workpiece model to generate workpiece segmentation recommendations. The defect
assembler is
configured. to use signals from the sensor subsystems to generate the
workpiece data model. The
host computer is configured to store workpiece characterization data. The user
interfaces are
configured to display workpiece characterization data. Workpiece
characterization data are selected
from the group consisting of signals from the sensor subsystems, the workpiece
data model, and the
refined workpiece data model. The consumer units subscribed to selected
workpiece
characterization data. The interface controller includes a processor
configured to generate producer
threads to respond to workpiece characterization data subscriptions from the
consumer units in
response to notification from the producer units the workpiece data is
available from the producer
unit. The processor is fiuther configured to send workpiece characterization
data to selected
consumer units in response to workpiece characterization data subscriptions
from the selected
consumer units.
The invention also includes a method for generating a workpiece model
comprising the steps
of
reading signals from a computer readable memory, the signals being
representative of at least
one physical characteristic of a first section of a workpiece;
reading a first workpiece section identifier from the computer readable
memory, wherein the
first workpiece section identifier specifically identifies the first workpiece
section associated with the
signals;
associating the signals for the first workpiece section to a first workpiece
processing thread
after receiving the associated workpiece section identifier;
generating a second workpiece processing thread for receiving signals from a
second
workpiece section; and
prior to the processing of the signals in the second workpiece processing
thread, processing
the signals in the first workpiece processing thread that generated the data
model of the first
workpiece section.
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The invention further includes a computer readable medium having computer
executable
instructions for performing.the steps of the above-described method.
The invention further includes a workpiece characterization system including
at least one
producer subsystem configured to produce a set of services relating to
physical characteristics of a
workpiece, at least one consumer subsystem configured to consume the set of
services, and an
interface controller for exchanging data between the subsystems in a generic,
scalable manner. The
interface controller includes an object-oriented producer application program
interface (API) and an
object-oriented consumer API. The APIs are configured for use on a mufti-
threaded, client-server
operating system. The producer API is configured to initialize producer server
objects and producer
client objects, to receive requests for data from a consumer subsystem via the
producer client objects,
to send acknowledgments to a consumer subsystem in response to requests from
the consumer
subsystem via the producer server objects, and to send data to a consumer
subsystem in response to
requests from the consumer subsystem via the producer server objects. The
consumer API is
configured to initialize the consumer server objects and consumer client
objects, to send requests for
data to a producer subsystem via the consumer server obj ects, to receive
acknowledgments from a
producer subsystem in response to requests from the producer subsystem via the
consumer client
objects, and to receive data from a producer subsystem in response to requests
from the producer
subsystem via.the consumer client objects.
The invention further includes an apparatus for tracking sel~t kinerriatics of
a workpiece
moving at a linear velocity. The tracking apparatus includes an encoder wheel,
a drive mechanism,
and a signal generator. The encoder wheel is configured to tangentially
contact a workpiece and
rotate at an angular velocity coincident with the linear velocity of the
workpiece in response to
contact between the encoder wheel and the workpiece. The drive mechanism is
configured to drive
the encoder wheel at a first angular velocity approaching an angular velocity
of the encoder wheel
coincident with the. linear velocity of the workpiece. The signal generator is
configured to interact
with the encoder wheel and generate a signal in response to the angular
velocity of the encoder
wheel.
The invention further includes an apparatus for detecting the probable
existence, location,
and type of defects in a workpiece. The apparatus includes a sensor subsystem,
a defect assembler,
an optimizer, a computer controllable workpiece segmenter, a control
subsystem, a computer system,
and a tracking device. The sensor subsystem is configured to sense a first
section of a workpiece and
produce signals corresponding to at least one physical characteristic of the
section of the workpiece.
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The defect assembler is configured to generate defect assembler data
subscription requests, to receive
the signals, and to generate a workpiece data model based on the signals. The
optimizer is
configured to generate workpiece segmentation recommendations based on the
workpiece data
model and generate optimizer data subscription requests. The computer
controllable workpiece
segmenter is configured to segment a workpiece according to the segmentation
recommendations.
The control subsystem is configured to control the workpiece segmenter in
response to the location
of a workpiece within the apparatus and in response to the workpiece data
model and the
segmentation recommendations. The computer system includes a processor and
computer readable
memory. The computer system is configured to receive signals from the sensor
subsystem and store
them in the computer readable memory. The processor is configured with a first
producer thread
program which, in response to the receipt of a first set of signals by the
computer system, receives
one of the data subscription requests and transmits the first set of signals
from the computer readable
memory to the generator of the data subscription request. The processor is
further configured to
generate a second producer thread in response to storage of a second set of
signals in the computer
readable memory, the second producer thread being configured to receive one of
the data
subscription requests and selectively send the second set of signals to the
generator of the data
subscription request. The tracking device is configured to track selected
kinematics of a workpiece
moving in a linear velocity within the apparatus. The tracking device includes
ari encoder wheel, a
drive mechanism, and a signal generator. The encoder wheel is configured to
tangentially contact a
workpiece and rotate at an angular velocity coincident with the linear
velocity of the workpiece in
response to contact between the encoder wheel and the workpiece. The drive
mechanism is
configured to drive the encoder wheel at a first angular velocity approaching
an angular velocity of
the encoder wh~l coincident with the linear velocity of the workpiece. The
signal generator is
configured to interact with the encoder wheel and generate a signal in
response to the angular
velocity of the encoder.wheel and provide the signal to the control subsystem.
The invention provides other advantages which will be made clear in the
description of the
preferred embodiments.
BRIEF DESCRIptION OF THE DRAWINGS
The invention will be better understood by reference to drawings, wherein:
Figurel is an isometric schematic diagram showing a modern lumber mill and the
system for
determining the presence of defects in a board and making optimization
decisions based thereon.
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CA 02235176 2004-11-08
Figure 2 is a schematic diagram showing the interrelation between the various
components of the
system in a block diagram format.
Figure 3 is table showing the different attributes of a workpiece such as a
board which can be sensed
by various sensing or measuring subsystems.
Figure 4 is an end view of a workpiece such as a board showing the 9 segments
that the board may
be divided into for purposes of producing a board model.
Figure, 5 is an isometric diagram of a visual representation of a board model
or "virtual board".
Figure 6 is an end view diagram of the board model of Fig. 5 wherein the
corner vertices collapse for
a rectangular board.
Figure 7 is an end view diagram of the board model of Fig. 5 wherein the
corner vertices and the top
vertices collapse for a board exhibiting severe wane.
Figure 8 is an end elevation view of a section of a board having a knot
passing therethrough.
Figure 9 is a plan view of a defect map showing a defect sensed by two
different sensing subsystems,
and how the defects might be merged into a single defect.
Figure 10 is a side elevation view of a board tracking device.
Figure 11 is a plan view of the board tracking device of Fig. 10.
Figure 12 is an end view of the board tracking device of Fig. 10.
Fig. 13 is a schematic diagram of a model of the type of message used in the
interface control
subsystem.
Fig. 14 is a diagram of a four-point defect bounding box for external bounding
and secondary
internal feature bounding.
Fig.15 is another diagram of a four-point defect bounding box for external
bounding and secondary
internal feature bounding.
Fig. 16 is a schematic diagram of the defect assembler architecture.
DETAILED DESCRIPTION OF A PREFERRED EMBODI1VVIENT OF THE INVENTION
Referring to Fig. 1, the system 10 is made up of a number of modules or
subsystems which
beneficially work together to scan each board and produce an optimized
decision. These subsystems
detect board features and defects, optimize the board, and preferably pass the
optimized decision for
each board to the appropriate saw.
The sensing subsystem 100 can include x-ray 110, profile 120, laser profile
(not shown),
color vision 130, fluorescent mark reader (not shown), moisture (not shown) ,
and inspection and
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sensing systems (not shown). The control subsystem 13 8 include the defect
assembler 36, scheduler
(not shown), and the optimizer 38 and programmable logic controller (PLC), 42
of Fig. 2. These
subsystems get their operational instructions such as product definitions,
prices, etc., from a database
maintained by the host subsystem 46 and accessed by the graphical user
interfaces 44 and 45.
When a board enters the system 10 it is detected by a barrier photoeye 34 and
can be tracked
using an electronic encoder 136. Images of the board are collected from the
various sensors 110,120
and 130 one "slice" (data slice) at a time as the board travels through the
sensing subsystem 100.
When a number of "slices" have been acquired this is termed a "frame" of data.
Frames can then be
evaluated for the features and defects that the sensors identify as likely to
exist in the board.
As each frame is evaluated the features and defects are passed from the
sensing subsystems
100 to the defect assembler 36. The defect assembler 36 adds all of the defect
and feature
information together from the various sensing subsystems and passes the board
model on to the
optimizer 3 8.
The optimizer 38 evaluates the board for the products defined in the current
cut order and
generates an optimum decision. This decision may include fixed length
products, finger joint
(variable length) products, and re-rip products. It can place the products
towards the leading end of
the board, the trailing end of the board, or centered in the board between
defects. The decision will
be based on either recovery optimization (get the most wood possible out of
the board) or on value
(get the most money possible out of the board). Each product can be defined to
allow or not allow
certain defects in certain parts of the product cross section. This means that
products that will be
machined further can allow defects in the product where the defect will be
removed at a later step in
the process. This decision is preferable complete by the time that the board
exits the sensing
subsystem 100 and is in turn displayed on the graphical user interface 44 or
45 (real-time display)
and is passed on to the control subsystem 138 of Fig. 2.
The control subsystem 138 tracks the board through the system by assigning it
an
identification number which all of the other subsystems use to make sure that
they are referencing the
same board. Once a board decision has been made the control subsystem
communicates with a
material handling process controller (not shown and not part of the system) to
determine which saw
the cut decision is to be sent to. At the appropriate time, the cut decision
(including positions along
the board at which to cut, and which storage biri the resulting block of wood
is to be sent to) is then
transmitted directly to the computer controlled saw 50. A plurality of saws
can be fed
simultaneously by one system.
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As each board passes through the system 10 and a decision is made, the board
data. and
decision are stored in a database in computer 46. Production summazy reports
can be generated from
this data providing users with a clear picture of what product volumes were
produced. Each board's
information may also be saved in a manner that allows it to be re-optimized
later during a "what-if'
system tuning exercise. This is an effective way to tune the system without
the time and cost of
processing real wood.
In addition to using the board model generated by the system for purposes of
optimizing
board segmentation and for controlling the execution of board segmentation by
saws and the like, the
board rriodel can be saved on a computer readable medium for future use. For
example, rather than
segmenting the boards associated with a saved board model, the physical boards
might be sold to a
customer for further processing along with an accompanying copy of the board
model on computer
readable medium. This will allow the buyer to make local decisions regarding
segmenting the
boards, and can also allow the buyer to perform such segmentation of the board
with machines
capable of using the board model for machine positional control. Likewise, a
potential buyer of
. boards can preview the boards by viewing the board model to determine
whether the boards meet the
buyers needs.
Overview of the system
Fig. l shows an overview of the system 10 for grading and handling graded
lumber, including
the cutting of boards, which is generally found in a sawmill. Lumber or a
workpiece generally
advances into the plant from a planer 12 on a feed belt 14 adj acent a fence
16.
The system 10 is preferably provided with sensors to allow the tracking a
detection of
workpieces as they move through the system. Workpieces may be marked' with bar
code by bar
coder 52 , allowing the board. to be tracked as it moves through the plant or
identified in apackage of
boards for later distribution or use. For workpieces such as lumber where it
can be undesirable to
visibly mark boards, bar coding may be accomplished by using ink which can
only be read by non-
visible light frequencies (such as ultraviolet).
It is also desirable to know, ax various points in the system, the precise
location of aboard.
Such is particularly useful after a board has been optimized to identify
defects and then presented to
a saw for the cutting. Without precise location identification of the board,
defects may be left in the
board, or alternately, good wood cut out of the board. Preferred apparatus for
such tracking of
boards in a computerized optimization sawmill are described herein.
i
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Turning to Figure 2, a hierarchal block diagram is provided showing the
relationship between
the subsystem components. The system 10 includes sensing or inspection
subsystem shown as x-ray
110, profile 120, and visual 130. The x-ray inspection subsystem can determine
density defects and
shuttle profile of the workpiece. The profile sensing subsystem can determine
a geometric 3-
dimensional profile of the board or workpiece, as well as the existence of
surface defects. The visual
inspection subsystem can determine visual surface defects. As described above,
other sensing and
inspection subsystems can be added to the system. The particular system
provided makes it easy to
add additional inspection subsystems as will be described further below. The
system 1~0 fiufiher
comprises a board tracking subsystem 138 which, in addition to tracking the
position of the board
within the plant as well as the position of the board within subsystems such
as the sensing
subsystems, can determine the length of the board. The control subsystem 138
fi~rther communicates
with a computer controlled saw 50 of Fig. l as well as the programmable logic
controller or PLC 42
of Fig. 1. The sensing subsystems as well as the control subsystem communicate
directly with the
defect assembler 36. As described above, the defect assembler generates a
board model or a "virtual
board." The defect assembler is in communication with the optimizer 38. The
optimizer 38 is in
communication with the controller 138 such that the optimized decisions made
by the optimizer 38
can be communicated to the controller 138 allowing the controller to execute
the decisions. The
optimizer 38 is in further communication with the host 46 allowing the
optimizer 38 to access and
store data, including computer programs, on the computer readable medium of
the host. In
traditional network architecture, the host supports user interfaces such as
terminals 44 and 45. The
host may be in further communication with a main bus line 40 which can support
additional user
interfaces such as operator console 54 of Fig. 1 or user interface 213 of Fig.
2, as well as
communicate with the existing mill networks by node 360.
Connecting all of the subsystems is the interface controller (IFC) 200 of Fig
.2. The interface
controller 200 consists of communication links 201, 202, 204 through 212,
inclusive, and 214. The
interface controller 200 is further configured such that firture subsystems
220 can be added and
arccommodated through communication channel 221. Likewise, components such as
user interface
213 may be removed and communication channel 212 removed without difficulty,
due to the
structure of the interface controller as will be further described below. The
system 200 can further
beneficially include a communication link 214 between the defect assembler and
the host allowing
the defect assembler to store the board model on the computer readable medium
of the host 46.
CA 02235176 2004-11-08
It is understood that, while the system of the present invention is primarily
described as
having a plurality of sensor subsystems, the system can comprise only a single
sensor subsystem. An
example of single sensor subsystem use is in a primary breakdown operation
wherein large pieces of
wood (as for example, logs) are cut into primary bulk pieces for latter
processing into smaller,
commercial sized pieces. A primary breakdown operation can be performed using
only a profile
sensor to determine wane or a "no-board" condition. The resulting
inforrization can then be provided
to the optimizer and the controller for cutting of the log into primary
components. In such case the
interface controller cans still be used to integrate the optimizer and the
optimizer.
Turning to Fig. 3 a block diagram table is provided showing a variety of
sensing subsystems
and the types of data that they produce. Board data may be generally separated
into three different
categories. The first category is a profile data set which provides
information about the physical
dimensions of the board in l, 2, or 3 dimensions (represented by Cartesian
coordinates x, y and z).
The next category is defect information which may either be 2-dimensional or 3-
dimensional. For
example,. a single source x-ray system can provide 2-dimensional defect
information, particularly
relating to density variations in the work piece. A profile subsystem can
provide defect information
in 3-dimensions, but is limited to detecting such defects as gouges, holes,
and other defects which
affect the profile of the board itself. A third category is a dimensional
category. Again, different
subsystems can provide different dimensional information. For example, the x-
ray subsystem can
provide dimensional information relating to the width and length (x and y) of
the board while the
control system can only provide information relating to the length of the
board.
In Fig. 3, each of the three categories are shown with respect to four sensing
subsystems 110,
120, 130 and 238, and each category is further defined with respect to the
number of dimensions
(referenced by coordinates x, y and z) in which the category can be measured
for each of the shown
subsystems.
The information collected from the subsystem shown in Fig. 3 is used to build
a board model.
Turning to Fig. 4, an end view of a workpiece or board is shown. For modeling
purposes, it is
convenient to segment the board into eight segments. Assuming that Fig. 4
shows the end of a board
which leads travel through the system, segments 1, 2 and 3 border the top of
the board, while
segments 5, 6 and 7 border the bottom of the board. Likewise, segments 1, 8
and 7 border the port
side of the board (referenced by looking at the top facing towards the leading
edge), while segments
3, 4 and 5 border the starboard side of the board. It is convenient to segment
the board into eight of
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CA 02235176 2004-11-08
segments since such segmentation conveys the Wandefelt information relevant to
board
characterization.
i
Turning to Fig. 5, an isometric visual diagram of a board riiodel or "virtual
board" is shown.
j
The board model is preferably conshvcted using 8 vertices 301 through 308.
Eight vertices are
selected since most physical board shapes may be accommodated with an 8-point
model. Briefly
referring to Fig. 6, it is seen that when a perfectly rectangular board is
encountered that the corner
vertices will collapse, as exemplified by vertices 301 and 308.
Briefly turning to Fig. 7, it is further seen that for a board such as a piece
of wood cut near the
edge of a tree exhibiting significant roundness on one side, the vertices will
collapse even further as
shown by vertices group 302, 303, 304 and 305. I
Returning now to Fig. 5, a Cartesian coordinate system having coordinates of
x, y and z
corresponding respectively to the length, width, and height of the virtual
board is shown. Such a
reference system is useful for generating, storing, and manipulating a
computer model such as the
virtual board described herein. f
The virtual board of Fig. 5 is further shown with defects 310 on the top side,
320 on the
bottom side, 330 on the port side, and 340 on the starboard side. It is the
job of the defect assembler
to take this information and assemble it into a board model to generate a
model which is
representative of the physical board.. For example, a visual scanner may
determine only that defect
310 and defect 320 exist on the top and bottom respectively of the actual
board. However, there is i
no data-which connects these two together so it is impossible for a visual
scanning subsystem to I
i
determine whether there is any relationship between the two defects. If the
defect is a knot which i
passes through the board at an angle, as shown in Fig. 8 showing knot 350
having top 310 and f
bottom 320, an x-ray scanner will only determine that a defect of width x
exists in the board, since it
i
will not have any information regarding the location of the defect with
respect to the depth of the
board. The defect assembler can take both the visual information showing
defects 310 and 320, as
i
well as the x-ray information showing a block defect 361, and combine them
together to determine
that in fact the defect is a knot which passes through the board. This type of
data combining is .
shown graphically in Fig. 9 wherein an x-ray defect 371 is combined with a
visual defect 372
producing an overlapping defect zone 373. It is the function of the defect
assembler to compare this
information against other acquired information and determine the probable
existence, type, and
location of a real deft within the board and generate an appropriate board
model in response
I
thereto.
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The defect assembler as well as the other components and subsystems of the
system, will be
described more fully below.
SUBSYSTEMS
Iasnection and Sensing Subsystems
X-Ray
The x-ray subsystem 110 of Fig. 1 transmits x-rays through lumber as it
travels lengthwise
through the scanner 100. The x-rays are blocked according to the density of
the wood at given
locations which results in greater attenuation of x-rays at the detectors when
there is high density
wood present such as knots, and less attenuation of x-rays when there is lower
density such as clear
wood, and even less attenuation when there is extremely low density in the
cases of rot. By
evaluating the x-rays that are received, the system can locate knots, rot, and
clear wood. This
information is summarized by the system and preferably passed on to the defect
assembler 36.
Vision
The vision subsystem 130 illuminates a board with white light which is
reflected into a color
linescan camera. The amount and color of the reflected light varies according
to the type of wood
traveling through the scanner and the features or defects at a particular
location on the board. Using
this color visual information the system can locate the surface locations of
knots, cracks, holes,
stains, ix~ct damage, etc. A number of techniques are used in evaluating the
image to locate these
features which are then summarized and preferably passed on to the defect
assembler 36.
Profile
The profile subsystem 120 illuminates the sides of a board with white light
which is then
reflected to cameras above and below the board faces. The amount of light
reflected from the edge
depends on the slope of the board edge. In this way, the system determines the
presence and width
of wane along the board edges. This information is summarized and preferably
passed on to the
defect assembler 36.
Laser Profile
A laser profile subsystem (not shown) projects lines of laser light onto a
board at an angle.
The light is reflected to a camera looking at the board from a different
angle. The .difference in
13
CA 02235176 2004-11-08
projection and viewing angles of the light and the camera are used to
determine the location of the
board surface by a method such as triangulation. The resulting image
represents the range to the
board surface and the conveyor. The range image is evaluated using a number of
techniques to
locate geometric defects such as wane, holes, cracks, skip, scant, bow, etc.,
which are summarized
and preferably passed on to the defect assembler 36.
Moisture
A moisture subsystem (not shown) transmits radio waves through the board. The
radio
waves are blocked by the water in the wood. The more water there is in the
board the more the radio
waves are attenuated at the receiver. In this way the moisture profile along
the length of the board is
determined. Acceptable moisture levels are used to determine what part of the
board is likely to be
wet, and is to be cut out and/or sorted for further drying or some other type
of processing.
Fluorescent Mark
A fluorescent marks reader subsystem (not shown) detects crayon marks placed
on the wood
surface. These marks can be used to indicate special grade zones to the
optimizer 3 8. As the board
passes through the scanner 100 this system detects the crayon mark locations
along the length of the
board, and summarizes and passes this information to the defect assembler.
Other Sensor Sub-systems
Other sensor subsystems, both existing and prospective, can be used in the
system 10 of the
present invention. For example, the three dimensional color imaging system
disclosed in U.S. Patent
No. 5,708,498 to Rioux et al can be employed to essentially replace the two
separate Profile and
Vision sensor subsystems.
Defect Assembler
The defect assembler 36 collects all of the board feature and defect
information from the
sensing subsystems 100 and adds them together into a single board model for
the optimizer to
evaluate. More than one sensing subsystem can detect the same defect type and
it is the defect
assembler 36 that referee's and decides how to summarize the information in
the most meaningful
manner.
i
f
14
CA 02235176 2004-11-08
Scheduler
The scheduler (not shown) controls the production and inventory levels by
monitoring the
production of each prnduct. The current production levels are compared with
the order size to be
filled and the current recovery of the product for the raw material being
processed. This comparison
is used to adjust the product weighting so that the order is filled without
overproducing the product.
This affects the product values used by the optimizer. The scheduler can be
incorporated into the
host 46.
Optimizer
The optimizer 38 uses a model of each board prepared by the defect assembler
and a set of
product definitions and cut order to determine the best way to cut the board
into product components.
The optimizer can be configured for each defect type and size category to
expand the defect bounds
to ensure that the defect fringes are not included in "good wood." Once these
"back offs" have been
applied to the defect, the optimizer starts fitting the longest and highest
valued products that it can
into the board based on the board size, wane profile, and defect locations.
This process continues
until the defined products have been considered and then the combination that
results in the highest
volume or value is determined. The decision is then passed to the host 4G,
graphical user interface
44 or 45, and control subsystems 13 8. Alternately, a report may be produced
which can accompany
the boards if sold or sent to another location for processing. Additionally,
the resulting decisions
from the optimizer can be saved on a computer readable medium and sold with
the boards in order to
enable the buyer to optimize yield or value from the purchased boards, or to
enable a potential buyer
to determine the value of the boards. The optimizer results, if stored on a
computer readable
medium, can also be modified according to factors not within the scope of the
optimizer's
optimization program. All of the optimizer functions can be accomplished by a
computer program or
programs. Such optimizers and optimizer programs are known in the art and will
not be described
further herein.
Control
The control subsystem 138, of Fig. 2 tracks each board as it passes through
the system,
conveys the board decisions to the appropriate saws, and interfaces with the
material handling
process control system. Data processing elements of the control subsystem can
be incorporated into
the host 46.
CA 02235176 2004-11-08
Programmable Logic Controller (PLC)
Once the optimizer has made a decision regarding a particular workpiece, the
decision is
preferably communicated to the programmable logic controller (PLC) 42 for
execution. The PLC 42
preferably includes computer readable medium for storing computer programs.
Examples of
computer readable medium include, without limitation, ROM, RAM, a hard drive,
a diskette and
diskette drive, a CD ROM and CD drive, a tape and tape drive, and an EPROM.
The logic controller
42 can decide whether the board is to be cut or not, and if so, by which saw.
Typically a plant for
processing boards has a plurality of computer controllable saws. Such ensures
that the sawing of the
boards do not become a bottleneck for throughput through the plant. Further,
depending on the type
of cut to be made (for example, rip or cross-cut), one saw may be preferably
configured over the
other. Boards can be routed to a selected saw via a conveyor interchange (not
shown) which can be
for example a pneumatically actuated conveyor interchange system actuated by
the PLC 42. The
conveyor interchanger can move a workpiece from a first conveyor to a second
conveyor.
Host
The host subsystem 46 comprises a computer-readable medium such as a hard
drive, and acts
as an "information warehouse" to store the product def nitions and save the
board production
statistics. The host subsystem controls the other subsystems and monitors
their status. An
uninterntptible power supply preferably communicates with the host, informing
of a pending loss of
power with enough time to save working data and shut down the system securely.
A service modem
access can be connected to the host permitting remote diagnostic and
troubleshooting, and allowing
software upgrades to be transferred to the system from remote locations.
The host or network server 46 can also perform other known functions such as
communication with remote devices through modem 48, and interfacing with other
computer
systems in the sawmill or other facilities through line 360. For example, the
network server 46 can
provide production information to an accounting or shipping office.
It should be appreciated that the control system, including the DFA 36, the
PLC 42, the
control module 38, and the host 46 can be considered as a "computer."
Alternately, each of the
components such as the DFA 36, the PLC 42, the control subsystem 38 module and
the network
server 46 can also properly be considered separately as computers. While the
control scheme is
describe herein in a particular configuration, it should be appreciated by one
skilled in the art that the
16
CA 02235176 2004-11-08
necessary functions of the invention, as described fuller herein below, can be
accomplished with any
one of a variety of control system configurations.
Graphical User Interface (GUn
The graphical user interface 44 and 45 allows a human/machine interface with
the system.
Each board decision can be displayed on the GUI as it is processed, with the
capability of displaying
prior board decisions. The GUI can also display boards with their solutions
based on where they are
in the material handling system at aay given moment. Production reporting,
diagnostics, setup, and
alarm monitoring can all be bandied through the GUI. The system preferably
supports multiple
GUI's simultaneously, permitting the machine operator to view real-time
decisions at the machine
while a supervisor can define products from an office off the shop floor.
Board Tracking Apparatus
Since inspection of the board by the system results in a board model having
spatial reference
to locations on the board, it is important to have a reference point on the
board when scanning the
board such that the physical measurements accurately represent the board in
the board model.
Further, when the board is provided to alternate systems, as for example a
computer controlled saw,
it is important that the board be capable of being aligned such that a board
defect in the physical
board which is represented in the board model is accurately located with
respect to the saw such that
optimization decision are effectively carried out by the saw. Data from the
tracking system is
provided to the control system 38 of Fig. 2. Preferably, the system 10 is
provided with a plurality of
tracking devices such that the location of a workpiece within the system can
generally be known at
any time, as well as specifically known within a subsystem itself, as for
example within the sensor
subsystems 100 or the saw 50.
One method of tracking the board is with a laser dopier velocimeter 136 of
Fig. 1. Such are
available for example firm Canon T~ as model LV-20Z. The laser dopier
velocimeter pen~nits
contact-free measuring of the velocity of the board within the system,
movement distances of the
board, speed irnegularities, and rotation irregularities. Contact-free
measurement of the parameters
outlined is desirable since contact tracking devices can be prone to slippage
or other mechanical
problems. An alternate workpiece tracking apparatus is shown in Figs. I O
through 12. Fig. IO
shows a side elevaxion view of the apparatus which comprises a plurality of
encoder wheels 20.
Encoder wheels are configured such that a rotation of the wheel produces a
signal, preferably a
17
CA 02235176 2004-11-08
digital signal, which can be provided to the control subsystem 38 of Fig. 2.
In operation, a encoder
wheel is in contact with a workpiece and the workpiece is moved past the
encoder wheel. The
friction of the workpiece on the encoder wheel causes the encoder wheel to
rotate. Since the outside
diameter of the encoder wheel 20 is known, travel of the encoder wheel over a
workpiece can be
measured by the number of rotations or partial rotations of the encode wheel,
and converted into a
lineal distance.
In order to reduce the potential slippage between the encoder wheels 20 and
the workpiece,
the apparatus 250 is preferably provided with a mechanism for driving the
encoder wheels at speed
approximating, but slightly less than, that at which the workpiece is expected
to move across the
encoder wheels. In this manner the encoder wheels have only a slight
differential driving force
applied to them by the workpiece, reducing wear on the encoder wheels acid
slippage which can
contribute to error. Preferably, the encoder wheels 20 are provided with a
unidirectional clutch (not
shown) allowing the encoder wheels to be driven at a predetermined minimum
percentage of the
corresponding speed of the belt 139, but not less than this speed. Thus, if
there is slippage of the
I 5 board relative to the belt 139, the encoder wheels will still rotate at
the predetermined percentage. If
the board is moving faster than the predetermined minimum percentage of the
corresponding speed,
the encoder wheels will track the faster velocity.
The mechanism for driving the plurality of encoder wheels is shown in Fig. 11.
An electric
motor 22 drives a series of belts 139. The belts are attached to pulley
assemblies 150. The pulley
assemblies are driven by the belt 139 at a first end and have the encoder
wheel 20 at a second end.
Turning to Fig. 10, the belt and pulley assembly 150 is shown in side view.
Preferably, the first
pulley 142 drives the encoder wheel 20 by a secondary belt 146. The pulley
assembly 150
comprising pulley 142, encoder wheel 20, and secondary belt 146 is configured
to pivot about pivot
point 152. In this manner, the encoder wheel 20 can move through an arch to
effectively raise and
lower the encoder wheel, allowing the encoder wheel to encounter workpieces of
varying thicknesses
and to maintain contact with the board notwithstanding height irregularities
in the board surface.
Belts 139 are preferably provided with tensioners 166 as shown in Fig.10.
Since rotation of
the encoder assembly 150 about pivot point 152 can alter the geometry of the
belt 139 and produce
slack in the belt, tensioners 166 are provided to ensure that the drive belts
maintain the proper
tension against the pulleys 142 during such rotation.
In order to accommodate various heights of boards which can be encountered by
the tracking
mechanism, the tracking mechanism 250 can be provided with a manual board
height adjustment
18
CA 02235176 2004-11-08
mechanism comprising linkage 19 which, when moved to the left as shown in Fig.
10, causes the
encoder wheel 20 to pivot about the pivot point 152, thereby raising the
encoder wheel relative to a
workpiece on conveyor 14. In one embodiment the linkage 19 is manually
adjusted to accommodate
a know height of boards to be encountered by the tracking apparatus 250. In a
preferred
embodiment, the tracking apparatus 250 is provided with an automatic actuating
mechanism to
automatically raise the encoder wheels 20 to a height approximating that of
the workpiece as the
workpiece approaches the apparatus 250. The automated actuating mechanism can
comprise a
photoeye 21 which is attached to a cylinder 156 having a piston 154. Attached
at a second end ofthe
piston 154 is a linkage 19 which is attached to the encoder wheel assembly 150
in a manner such.that
as the piston 154 is retracted into the cylinder 156, the linkage 19 moves to
the left as shown in Fig.
I0, causing the encoder wheel 20 to pivot about the pivot point 152, thereby
raising the encoder
wheel relative to a workpiece on conveyor 14. The amount of retraction of
piston 154 into cylinder
156 is governed by the photoeye 21 which determines the height of the
workpiece.
Taming to Fig. 12, the tracking apparatus 250 is preferably mounted at an
angle with respect
1 S to the grade 2 such that a workpiece supported on conveyor 14 is urged by
gravity towards fence 16
against which the workpiece can rest. This assures that he workpiece will be
oriented to a fixed
plane, being the fence 16, as it passes through~the sensor system. Such
essentially establishes a
"y = 0" reference point for the (x, y) Cartesian coordinate system used to
generate the board model.
Returning to Fig. 10, in the preferred embodiment the tracking apparatus 250
comprises a
feed conveyor 158 which urges a workpiece toward the sensor system 30, an
intermediate conveyor
162, and a discharge conveyor 164. This allows the first conveyor 158 to be
separated from the
intermediate conveyor 162. Separation of the conveyors can be useful in
providing a separation
between workpieces to allow a photoeye or other detection system to determine
the leading edge of
the workpiece.
In as alternate embodiment, a laser dopier tracking device and the tracking
apparatus 250
may be used together to confirm each other.
19
CA 02235176 2004-11-08
Defect Assembler (DFA)
The defect assembler (DFA) 36 of Fig. 1 is driven by a computer prograrrl
which is
configured to perform the necessary functions of the board model assembler.
The purpose of the
DFA subsystem is to build a board model using information (for example, the
defect and profile list)
from any number and combination of sensor subsystems, including a single
sensor subsystem. When
a single sensor subsystem is employed, it is more appropriate to refer to the
defect assembler
subsystem as a "data modeler", since it uses data (albeit from a single sensor
subsystem) to model a
board. In the following discussion, the expression "defect assembler" or "DFA"
maybe used to refer
to the program which drives the defect assembler subsystem. "DFA" or "defect
assembler" will also
be understood to include a data modeler in a single-sensor or no-sensor
configuration.
The defect assembler program is constructed in a classical "producer-consumer"
architecture,
wherein certain subsystems are producers of information and other subsystems
are consumers of
information. For example, sensor subsystems 110,120 and 130 are considered
producer subsystem
since they produce information relating to the physical attributes of the
board, while the saw is a
consumer of information since it uses or consumes the board model to cut the
board into finished
product. Some components, such as the defect assembler, are both producer and
consumer. That is,
with respect to the defect assembler, it consumes the information produced 6y
the sensing systems
and produces a board model which is used by other subsystems. The defect
assembler (DFA)
functions primarily as a consumer of incoming data from scanning subsystems
and as a producer of
board model data to subscribers, including the optimizer subsystem (OPT).
As boards travel through a scanner, each scanning subsystem generates a list
of defects and
other attributes to describe the board. These lists are sent to DFA 36 where
they are combined into a
single board model. The board model is then passed from DFA to OPT 38 where
the "best cut"
solution is determined. The DFA 36 is configured to generate board models from
any combination
of scanning subsystem data produced in the system. In some cases, more than
one scanning
subsystem will report the same defect. It is the responsibility of DFA to
rationalize these instances
into the single board model according to a set of arbitration rules.
The DFA's hardware consists of a processor, preferably one having multiple
network
connections to other subsystems. An exemplary operating system is Windows IVT
TM available from
Microsoft Corporation.
CA 02235176 2004-11-08
Board Model Framework
The foundation of the defect assembler subsystem's operation lies in a board
model
framework that is common to the defect assembler subsystem and the various
scanning subsystems.
The board model geometry is a combination of three-dimensional (x , y, z)
Cartesian coordinates and
two-dimensional (x, y) and (x, z) coordinates with reference to the board face
as shown in Figure 5
The principle of datum referencing is used to relate geometrical features to
the reference
surface of the ideal board model, and maintain functional similarity of the
scanning subsystems to
the saw. A datum indicates the origin of a dimensional re I ationship between
a tolerance feature and
a reference surface of the wood, i.e., bottom, port, and lead side. The
reference surface serves as a
datum feature, whereas its true geometric counterpoint establishes the datum.
Figure 5 illustrates the construction of reference surfaces defined by the
scanning system
datum. The continuous belt conveyor 14 of Figure 1 is a datum plane
establishing the bottom
surface, the fixed fence 16 of Figure 1 is a datum plane establishing the port
surface, and the
photoeye 34 is a datum line establishing the lead surface of the board model.
The photoeye datum
line also establishes the trail surface of the board model, as further
described below.
The true geometry of the board referenced from the three datums deft nes the
board model as
follows: Three-dimensional Cartesian (x, y, z) coordinate system referenced to
lead surface, bottom
surface and port surface whereby the origin is the hypothetical intersection
of the these three
surfaces. Visually, the coordinate system is determined by looking into the
scanner from the outfeed,
assuming that the board contacts the belt and fence at thi s point, and
applying the "right hand rule"
for x, y and z coordinates along the line where the fence and conveyor meet,
as indicated by the axes
in Fig. 5. At least six two-dimensional faces {top, bottom, port, starboard,
lead, trail) comprise a
volume describing length, width, and thickness of the board model in x, y, and
z Cartesian space,
respectively. Leading and trailing faces of the board are defi ned here for
future use. An ambiguous
volume within the board (internal) where only two Cartesian coordinates are
known (usually x, y)
and thickness is defined externally as nominal. Base line dimensioning is used
for all coordinates
with respect to the datum origin.
The photoeye datum line is preferably used to establish both the lead and
trail surfaces ofthe
board model. Each subsystem can receive the photoeye hi/lo signal and the
encoder pulses from the
conveyor. The photoeye 34 will transition from lo/hi to hi/lo (or visa versa)
when a moving board
breaks the photoeye beam. Each subsystem will define the lead surface and
coordinate origin from I
this mark. Encoder pulses are recorded and used to measure the distance the
conveyor moves the
21
CA 02235176 2004-11-08
board for a given constant conveyor speed. The photoeye will transition from
hi/lo to lo/hi (or visa
versa) when the board gasses the photoeye and the beam is restored. Each
subsystem will define the
trail surface and total length from this mark. Because each subsystem
preferably measures board
length the same, i.e., accoiding to the precision of the encoder pulse train,
each subsystem passes a
standardized total board length to the defect assembler subsystem.
The photoeye (34 of Fig. 1) is preferably upstream of the sensor subsystems
110, 120 and
130, and each subsystem preferably uses encoder pulses to determine the board
lead surface with
respect to the constant conveyor speed. That is; as the board moves along the
conveyor, each
subsystem can determine when the board lead surface passes through the
scanning apparatus and
when to begin recording data by offsetting the virtual lead surface a pre-
defined number of encoder
pulses.
If a subsystem determines that a board's lead surface has slipped ahead or
behind the expected
or virtual lead surface, the subsystem preferably does not re-position the
board's lead surface or
origin to the determined mark. Preferably, the subsystem will begin sending
board data at the
determined mark with coordinates referenced to the expected or virtual origin.
That is, board data
may have negative x-axis coordinates. In addition, the subsystem will
preferably record the
difference between the mark and the expected lead surface as pre-slippage. If
a subsystem
determines that a board's trail surface has slipped ahead or behind the
expected or virtual trail
surface, the subsystem will preferably not re-position the board's trail
surface to the determined
mark, but will instead continue sending board data after the expected or
virtual trail surface, and will
also record the difference between the mark and the expected trail surface as
post-slippage. The total
board length as determined by counting encoder pulses preferably will not
change; total length is a
data parity check for out-of sequence defect recognition.
Preferably, each subsystem records the maximum amount of data obtainable for
each board.
The defect assembler subsystem arbitrates differences in measurements when
building the board
model from each subsystem's data. The defect assembler subsystem uses pre- and
post-slippage
information when combining defects from different subsystems and when adding
buffer zones
around defect features.
Each subsystem preferably sends the defect assembler subsystem exact measured
coordinates
with respect to the coordinate system described above. Other than mechanical
board handling,-which
is assumed to be similar to the saw, a subsystem preferably does not remove
board warp, bow, twist,
or cup geometry to produce similitude with nominal board dimensions, nor does
a subsystem add ;'
i
22
CA 02235176 2004-11-08
buffer material to defect features. Each subsystem preferably measures and
bounds features as
closely as possible, within the constraints of the subsystem. Note that each
subsystem preferably
removes measurement distortion effects, for example, x-ray point-source
triangulation through the
board center and Lens barrel correction on the board surflce.
Depending on the sensing method at each scanner and what is necessary for
optimization,
feature coordinate locations may be described in any of the following ways: (1
) three-dimensional
coordinates in (x, y,z) format; (2) face and two-dimensional coordinates in
(port,x, z), (top, x, y),
(starboard' x, z), (bottom, x, y), (leaa~ y; z), or (trail, y, z) format; or
{3) unknown volume and
two-dimensional coordinates in (internal, x, y) format. This last model
facilitates the combination of
two-dimensional data from subsystems including the visi on subsystem, the x-
ray subsystem, and the
moisture subsystem, with three-dimensional data from the profile subsystem.
Because the
coordinates available from a given scanning subsystem are typically fixed,
some of this infonmation
is not required in data lists sent to the defect assembler subsystem. For
example, all defects bounded
by the x-ray subsystem are described in the board model as (internal, min. x,,
min. yt, max. xl, max.
yl, min. x2, min. y2, max. x2, max. y2) where the z value (internal) remains
constant. Therefore, the z
value is implied and not sent from the x-ray subsystem for each defect
element, but is assumed to be
nominal thickness at the defect assembler subsystem when constructing the
board model without z
data from other scanning subsystems.
Defect coordinate information from each subsystem is defined in Figs. 3, 5,
and 14 and as
follows:
Tme Imn)sed Sent
all XRY defects internal type, (xi, y,), (x2, y2)
profile data from PRF x value same for all x, yi, z1, y2, z2, y3, y3, z3, ya,
za, Ys~
Zs~ '
8 {Y. z) P~rs Y6~ z6~ Y~~ z~~ Ys~ zs
face defect data from PRF none type, face (top, bottom), min. x,
min. y, max. x, max. y
all VIS defects none [ type, face (top, bottom), min, x, min. I
y, max. x, max. y ] or [ type, face (port,
starboard), min. x, min. y, max. x;
max. y]
1
all MST defects internal type, min. x, min. y, max. x, max. y
I
23
CA 02235176 2004-11-08
Defect Model Definition
The defect assembler subsystem preferably combines 2 and 4-point surface and
internal
defect boxes of the same type, defined in the above table, into a single
defect set. If two or more
defect types occupy the same coordinates, e.g., a split inside a knot, two or
more defect sets will be
defined to represent each defect type so no information is lost. In the case
of a boundary dispute, i.e.,
when one or more subsystem reports a maximum or mini mum boundary different
from the principle
boundary, the subsystem with the highest basic resolution as determined by the
host will prevail.
Because most defects in boards are elliptical in nature, each subsystem
preferably minimizes
the non-defect wood included as a defect and preserves the true geometry of
the defect. Preferably,
no subsystem performs defect grouping operations. Each subsystem is preferably
configured to
convey as much information possible about the true defect shape to the defect
assembler.
Board Model Definition
The defect assembler subsystem subscribes to subsystem data as instructed by
the host. All
subsystem's board data is preferably provided to the defect assembler
subsystem in asynchronous
frames. A frame is a contiguous length of analyzed area of a scanned board.
For example, the first
frame of data the defect assembler subsystem could receive contains a surface
feature box located at
(top,105.0, 8.0,106.0, 9.0) and the second frame could contain (top,10.0,
6.0,11.0, 7.0). The defect
assembler subsystem can provide a board model divided into frames or, less
preferably, can hold or
buffer the frames until all subscribed subsystem frame data is received.
Providing aboard model by
frames allows for faster processing of the data. Note that frames may be
overlapped for verification
purposes and other data processing conveniences. The defect assembler
subsystem will then
combine the subsystem fi~ame data into the standardized board model and
release board model
fi~ames to all subscribed consumers.
The defect assembler subsystem advantageously combines and arbitrates frame
data
according to a hierarchy determined by the host. Frame data includes subsystem
features of the
outside 8-point profile box of Fig. 4, for each frame sent from each
subsystem. The hierarchy of
defect combination is as follows:
(1) If a subsystem subscription fails or frame data is not sent within the
allotted time
limit, a "critical error" message is sent, and the DFA goes to a command
state,
24
CA 02235176 2004-11-08
waiting for intervention. If any single subsystem fails, the defect assembler
subsystem issues an alarm to the host and stops processing.
(2) . The subsystem with the higher pre-configured hierarchy determines the
feature
boundary for the board model.
(3) The subsystem with the greater feature recognition reliability determines
the presence
of a feature. For example, if the vision subsystem determines a knot defect
but the x-
ray data does not correlate the existence and the host's hierarchy is the x-
ray over the
vision subsystem, and the vision subsystem defect is not included in the board
model.
Releasing A Board Model To "Consumers"
The defect assembler subsystem. advantageously issues the board model in
frames of
contiguous length. The frames are numbered in consecutive order starting with
Frame#1 containing
the (O,X,~ origin or lead surface. A frame is generated when a section of
contiguous length is
collected from all subsystems; frame length is determined by the subsystem
issuing the
shortest-length board frame. If a consumer misses a board frame, the board
model cannot be
assembled, and a time-out occurs to stop DFA activity. if a consumer misses
the last frame closing j
the board and the allotted time to process the board expires, the consumer is
responsible for issuing
alarm events and handling real-time operations. The defect assembler subsystem
advantageously f
saves the raw data and board model from each subsystem in a memory device such
as a virtual FIFO
board queue as blocked threads. Saved data can facilitate debugging of the
system and allow
simulation of alternative solution methods.
Defect Assembler Subsystem (DFA) Interface
The defect assembler subsystem operates as both consumer and producer of
information, as
described below under the section about the subsystem interface. As a
consumer, the defect i
i
assembler subsystem subscribes to data from any combination of scanning
subsystems including the
x-ray subsystem, the profile subsystem, the moisture subsystem, and the vision
subsystem. The
defect assembler subsystem also subscribes to board identification data from
the controls subsystem.
As a producer, the defect assembler subsystem provides board models to
subscribers including the
optimizer subsystem for cut solution processing, and to the host subsystem for
saw outcome
simulations.
CA 02235176 2004-11-08
Scanning Subsystem Interface Requirements
The defect assembler subscribes to measurement and defect data from each
available
scanning subsystem in the saw optimizer. Because the sensing technology among
scanning
subsystems is inherently different, it is desirable to standardize their
output and facilitate board
model assembly. To accomplish this, each scanning subsystem preferably
produces data using the
coordinate system described above. Additionally, each scanning subsystem
preferably provides three
basic data subscriptions to the defect assembler subsystem including defect,
dimension, and profile
categories (as indicated in Fig. 3), for each scanning subsystem. Basic
requirements for these
subscriptions are as follows.
DEFECT CATEGORY
Each scanning subsystem is advantageously capable of reporting certain defect
types. Some
defect types can be measured by multiple scanning subsystems (e.g. the vision
subsystem and the x-
ray subsystem both report knots) while others can only be detected by a single
subsystem.
Regardless of defect type, a common structure is used be used when sending
these data to the defect
assembler subsystem. Defect coordinates define a bounding box containing two
or four non-zero
points depending on the type of defect and sensing ability of the scanning
subsystem.
Two-Point Bounding Box
Two points are used to define a single box containing the entire defect. For
example, in Fig.
5, x?z2 andxjz~ points define the upper-left and lower-right corners (with
respect to the figure view)
of the entire box 340. This method is sufficient for defects where varying
degrees of severity are not
useful during optimization. In Figure 5, box 340 shows b tue stain defect that
is entirely bounded by
the defect box on either the port or starboard board face. 't:'he box 310
shows a knot with grain swirl
entirely bounded on either the top or bottom board face.
Less preferably, four points can be used to define an outer box containing the
entire defect,
and an inner box containing a region with significantly different defect
attributes such as grain swirl
or density. Referring to Figs.14 and 15, points X1Y1, X2Y2 define the outer
box while points X3Y3,
X4Y4 define the optional inner box. While computationally more complex, this
method of defect
bounding can provide better calculation of three-dime~~sional defects, such as
spike knots, and
maximum optimization of possible cut products. For the x-ray subsystem, inner
and outer box
classification is preferably obtained using two threshold levels. Using two
threshold levels also
26
CA 02235176 2004-11-08
increases the certainty of correctly bounding the geometry of solid defects
because denser core
material is tightly bound by the inner box thus permitting fast detection of
defects with fixed
thresholding. Less dense cross grain around knots is bound by the second outer
box thus allowing
more accurate, localized, statistically-adaptive thresholding. In Figure.14, a
spike knot defect is
shown where the inner box 650 bounds defect material 652 which is solid
through the entire
thickness of the board and the outer box 651 bounds material 653 which is less
dense. Fig. l S shows
a straight knot 660 bound by the inner box 661 and less dense cross grai n 662
bound by the outer box
663. Fig. 5 shows a solid dense defect 370 having non-determinable cross grain
(perhaps from a
rapid growth tree) and is bound by a single box 310. Por the vision subsystem,
four points are
preferably used to define knot-type defects comprising solid defect (knot)
material and cross grain.
Two-point boxes are preferably used for all other defects. An outer box bounds
the entire defect, and
an inner box bounds the knot. As in Fig. 14, points X~Y,, X2Y2 define the
outer box while points
x3y3~ X4Y4 define the optional inner box. This rilethod of defect bounding
allows better calculation
of three-dimensional defects and maximum optimization of possible cut
products. For visual
subsystem, Fig.14 shows a straight knot 652 bound by the inner box 650 and
less dense cross grain
bound 653 by the outer box 651. Fig. 5 shows a solid dense defect 370, such as
a ring knot, having
non-determinable cross grain and is bound by a single box 310.
PROFILE CATEGORY
Each scanning subsystem is configured to be capable of measuring board profile
to some
extent. Because of differences in scanning technology, there is significant
variance among the
subsystems ability to measure profile in all planes and their relative
resolutions. Regardless ofthese
differences, a common structure can be used when sending these data to the
defect assembler
subsystem. Profile data are measured at regular x-axis intervals, or cross
sections ofthe board. At
each cross section, the subsystem determines an eight-point structure that
describes board profile
according to the following rules:
(1 ) All data points preferably follow the datum-referenced Cartesian
coordinate system
defined above.
(2) A flat segment is defined as planed and roughly vertical or horizontal.
Some angular
variance is expected in boards with twist, warp, and/or cup.
(3) An irregular segment is defined as not planed, even though it may be
reasonably flat.
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CA 02235176 2004-11-08
(4) A vertex is defined as the transition point between either two flat
segments, one flat
segment and one irregular segment, the widest point at which an irregular
outside
segment (port or starboard) has vertical slope, the thickest point at which an
irregular
top or bottom segment has horizontal slope, or the thinnest point at which an
irregular top or bottom segment has horizontal slope. Vertex examples are
shown iw
in Figs. 5, 6 and 7.
(5) Eight (8) vertexes can be used to describe the board profile at a given x
location as
shown in Fig. 5.
(6) Vertexes 1 through 4 are defined from bottom scanner data, and vertexes 5
through 8
I O are defined from top scanner data.
(7) Vertex numbering begins with the origin (x = 0, y = 0) coordinate and
proceeds
counter-clockwise to describe all coordinates. If a board is twisted,
numbering
begins with the bottom scanner's vertex closest to the fence datum and not
defined by
the top scanner's vertex.
(8) Au vertexes are used.
(9) Linear interpolation to the basic resolution is allowed between all data
points.
Once the eight-point perimeter has been determined, it is described in a
dimension data
structure.
When a given subsystem (the x-ray subsystem, for example) cannot measure all
portions of
the complete profile data set, nominal values are substituted in those fields
before being sent to the
deft assembler subsystem.
DIIVVIENSION CATEGORY
Each scanning subsystem is preferably configured to receive identical scanner
encoder and
photoeye information. Therefore, each scanning subsystem will "measure"
standardized gross board
lengths. It is possible for a scanning subsystem's own sensors to report lead
and trail board edges
that are different from those reported by the photoeye and encoder. The defect
assembler subsystem
handles these cases separately. In addition to gross length, scanning
subsystem can report to the
defect assembler subsystem the gross width and gross thickness of each board.
When these
quantities can be directly measured, the measurements are used. Otherwise,
nominal width and
thickness values are used.
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CA 02235176 2004-11-08
Data Flow
Under normal operation the defect assembler subsystem offers services to the
following
subscribers: optimizer (OPT); and host {HST).
Under normal operation the defect assembler subsystem subscribes to services
from the
following producers: vision (VIS); x-ray (XR~; profile (PRF); and moisture
(MST). The defect
assembler subsystem external data flow is generally depicted below in Figs. 2
and 13.
The following services allow other subsystems to subscribe to, or request data
from the defect
assembler subsystem.
Board model rules are used to control how the defect assembler subsystem will
process
lumber from various board quality or stock grades. For example, users might
choose to place less
confidence in knot boundaries reported by the vision subsystem in certain
types of lumber because
they know that the x-ray subsystem will do a better job of bounding these
defects. The solution is to
develop a list of defect assembly rules for that paradigm which will produce
the correct board model.
The types of rules can comprise the following: hierarchy used to select best
profile measurements
when in conflict; valid defect types used to build board model from subsystem
information;
hierarchy used to select best defect measurements when in conflict;
probability that standard defect
has been correctly identified by the specified scanning subsystem; the minimum
editable defect; the
maximuxweditable defect; the maximum x-axis separation between defects of same
type for grouping
into common set; the maximum y-axis separation between defects of same type
for grouping into
common set; scalable x-axis adjustment to defects reported by the specified
scanning subsystem; and
scalable y-axis adjustment to defects reported by the specified scanning
subsystem.
The following description describes individual functioning units that make up
the defect
assembler subsystem.
Scanning LAN Interface
A scanning LAN connects the defect assembler to all scanning subsystems
including, for
example, x-ray, profile, moisture, and vision. The scanning LAN is, for
example, an Ethernet
network intended primarily to transfer defect list elements from scanning
subsystems to the defect
assembler. Additional LAN traffic can include pass-through information from a
machine center
LAN, and board 1D messages from machine controls subsystem. The defect
assembler gains access
to the scanning LAN through a network adapter card. Software access can be
provided via TCP/IP
and BSD sockets at the operating system level, wherein the connections are
preferably message
29
CA 02235176 2004-11-08
based stream sockets. A board model LAN connects the defect assembler to the
optimizer subsystem
and machine controls subsystem. The board model LAN is, for example, an
Ethernet network
intended primarily to transfer board models from the defect assembler to the
optimizer, and cut
solutions from the optimizer to the machine controls. The defect assembler
gains access to the board
model LAN through a network adapter card similar to the scanning LAN.
Operation
Under running conditions, the defect assembler subsystem operates per the
following
description.
For each board processed, the defect assembler subsystem can receive the board
identification
from machine controls subsystem and the defect list elements and overall
length from each sensing
(defect detecting) subsystem. For each board processed, the defect assembler
produces a board
model to the optimizer subsystem and other optional subscribers.
It is the defect assembler's responsibility to track synchronization of each
scanning subsystem
as boards are processed. If the defect assembler determines that one or more
scanning subsystems
have failed, a message is sent immediately to the Host Subsystem indicating
the nature of the failure.
Synchronization is handled according to the following rules:
(1) When a new Board lD is received from machine controls, the defect
assembler
creates the new board model list node.
(2) The board-specific node is responsible for receiving and compiling defect
elements
from each configured scanning subsystem until all defect lists are complete.
(3) A new node may be created before the nodes for the previous (n) boards
have
completed, where n is configurable.
(4) A node for a new board can be created if the node for board (n-1) is not
completed.
This indicates a problem and is cause for sending an alarm event to the host.
The following sequence is typical for operations involving a single board:
(1) Board enters scanner and is seen by tracking photoeye.
(2) Machine controls subsystem issues board CD to scanning subsystems and the
defect
assembler.
(3) The defect assembler creates board model node in the list to generate
board model
and waits for data from scanning subsystems.
CA 02235176 2004-11-08
(4) Scanning subsystems send asynchronous messages containing defect elements
and
overall board length. The defect assembler generates boaid model as defect
elements
arrive.
(5) When the defect assembler receives overall board length from all operating
scanning
subsystems, board model is completed and the node is removed from the list.
(6) The defect assembler sends board model to subscribers.
Due to the asynchronous nature of incoming defect data and variable processing
delays from
each scanning subsystem, the defect assembler preferably is capable of
overlapping the above
sequence for multiple boards.
Conflict Resolution
Depending on the configuration of scanning subsystems, the defect assembler
subsystem may
receive conflicting information from two or more sources. For example, the x-
ray subsystem and the
vision subsystem are both capable of detecting knots but are unlikely to bound
a given knot with
identical coordinates. The following description outline rules used by the
defect assembler
subsystem to resolve defect data conflicts during board model assembly.
Knots: Most knot boundary conflicts will arise from differences between the
vision subsystem and
the x-ray subsystem data. A small number of knots exhibiting tear-out might
also be detected by the
profile subsystem as face defects, but probably won't be classified as knots.
In order to define
conflict resolution rules between the vision subsystem and the x-ray
subsystem, it is important to
understand relative performance advantages of each subsystem. For example, the
x-ray subsystem
has the highest certainty of detecting absolute knot presence, but is less
capable of correctly
hounding knots due to an inability to "see" surrounding grain swirl and
differentiate between
opposite board faces. Conversely, the vision subsystem has lower certainty of
detecting knot
presence because of false readings caused by heavy grain patterns or foreign
matter on the board
surface, but has greater ability to measure grain angle and detect boundaries
on any board face.
Based on these considerations, rules for adding knot defects to the board
model can be developed.
For example
Seen by X-rav Seen by Vision Resolution
Yes No Knot is added to board model with identical
top and bottom boundaries as reported by x-
r ay.
31
CA 02235176 2004-11-08
Yes Yes Knot is added to board model with all face
boundaries as reported by vision.
No No No knot added to board model.
No Yes No knot added to board model.
Implementation
The defect assembler subsystem architecture consists of several threads and
their associated
functions as shown in Figure 16 for an x-ray subsystem 820. When a board
arrives at the control
subsystem photoeye, the defect assembler subsystem 800 receives board
identification (1D) data from
the control (CTL) subsystem 801. As long as the new board thread 802 receives
the board
identification data from the defect assembler subsystem's control subsystem
consumer call back
function 805, it will save the data into the "board processi ng thread working
buffer" 803 and assign a
board identification to the waiting board processing thread 804. The board
processing thread will
then spawn another board processing thread 806 to wait for the next board.
To minimize the x-ray consumer callback function 809 from being blocked too
long by
received defect/profile data frames, two named pipes 807 and 808 are used to
write received
defect/profile data into the named pipes by x-ray consumer callback functions.
Two threads, x-ray
profile handle 810 and defect data handle 811, are used to read the data from
the named pipes, then
deposit it into the frame data buffer of the "board processing thread working
buffer" 803 and notify
the synchronized data dispatcher thread 812 that defectlprofile data has
arnved. The synchronized
data dispatcher thread 812 then verifies that data in the "board processing
thread working buffer" 803
is available to be assembled into a board model data teame. The dispatcher
thread 812 then moves
the available data elements to a synchronized data buffer 821 and sends a
semaphore 822 or 823 to
the related board processing thread 804 or 806to notify i t that the
synchronized data is ready.
While the defect assembler subsystem has multiple board processing capability,
preferably
only the major board processing thread 804 is configured to construct board
model data frames and
send them to the optimizer subsystem 813. Other board processing threads 806
and 814 will merge
their synchronized data into a temporary board model data buffer and wait for
their turn.
The defect assembler subsystem architecture is preferably scalable for futtue
development.
32
CA 02235176 2004-11-08
Subsystem Interface
Overview
The subsystem interface (IFC) 200 of Fig. 2 is a mechanism to exchange data
between
subsystems in a generic, scalable manner. The mechanism is based on a
producer/consumer model
where one component produces a set of services and other components) consume
the services. The
subsystem interface is composed of a producer API (application program
interface) and a consumer
API. Both APPs are designed for use on a mufti-threaded operating system. The
producer API
consists of routines to initialize the producer server and client objects,
receive requests from the
consumer, and send acknowledgment and data to the consumer in response to the
requests. The
consumer API consists of routines to initialize the consumer server and client
objects, send requests
to the producer, and receive acknowledgment and data from the producer in
response'to the requests.
The subsystem interface functions as a static library to he linked into the
subsystems that require
data exchange.
The following description is with particular focus on the interface between
all subsystems
within the saw optimizer, although it is to be appreciated that such reference
is for exemplary
purposes only, and the general concept can be applied to other subsystems.
Interface
Messages between the producer/consumer components beneficially include a
message
protocol for message handling. An example of a protoco i used in one example
is as follows. Each
message sent between subsystems beneficially contains a header with the
following information:
system-wide unique subsystem number, subsystem-wide; unique service number;
service qualifier
(what is being performed (subscribe, unsubscribe, reques t, acknowledge,
reply}); and length of data
{in bytes) to follow the header.
The header is created and consumed by the subsystem interface, and defines the
data buffer
that is exchanged between the subsystems. The subsystem, service, and service
qualifier fields
together uniquely identify the message in the system. The consumer provides
the subsystem, service,
and service qualifier values, along with the data and data length to the
consumer server. The
consumer server packages the subsystem, service, service qualifier and data
length values into a
header structure and sends it to the producer server. The data is sent to the
producer server after the
header. The producer server first reads the header to determine the size of
the data that follows. The
producer server then reads the data into a data buffer. Then the subsystem,
service, service qualifier,
33
CA 02235176 2004-11-08
data, and data length are passed to the producer through the producer callback
function. The
producer preferably copies the data to its own daxa space before retiuning
from the.producer callback
function, as the buffer will be reused on the next data read. The same occurs
when the producer
sends data to the consumer.
The service qualifier determines what action is to be taken on a service for a
subsystem. The
action can be one of the following: subscribe to a conti n uous feed of data;
end subscription to a
continuous feed of data; request a single reply (oneshotj; acknowledge the
receipt of a subscribe,
unsubscribe, or request (a return status in the data portion determines the
success of the action); or
buffer containing the results of a subscription or request (a return status in
the data portion
determines the validity of the data).
A data buffer can be sent with any type of message (subscribe, unsubscribe,
request,
acknowledge, and reply). The length of the data is set i:-: the dataLen field
of the header and caa
range in value from zero, for no data, to the maximum sic; expected depending
on the service. The
amount and structure of the data is determined by the service.
The subsystem interface uses a subscription-based model to send/receive data.
A model of
this system in shown in Fig. 13. A consumer (e.g., 501 or 502) subscribes to a
feed of data from a
producer 503. When the producer generates the data, it sends the data to all
consumers that have
subscribed to that data (if any).
Consumer
The consumer thread 504, 505, or 506 subscribes to data and consumes the data
upon reply
from the producer 503. This thread must first initialize a consumer client
object and attach it to the '
consumer server object. All subsequent actions {subscribe, unsubscribe,
request) require the
consumer client object. The consumer may consist of several threads all using
one consumer server
507 or 508. In this case, each consumer thread must ir~irialize its own
consumer client object to
mutually exclude other consumer threads. This metho;i shares one consumer
callback function
between all consumer threads.
Alternately, each consumer thread create its own consumer server connection to
the producer.
This method is typically used when the consumers reside in separate tasks or
on separate machines
3 0 and cannot easily share a consumer server. This method causes.the producer
server to do more work
in that it must send data to multiple consumer servers. 'this method also
allows each consumer
thread to have its own consumer callback function.
34
CA 02235176 2004-11-08
The consumer API 511 or 512 is the Consumer's interface to the message passing
mechanism.
The Consumer API contains the following set of routines:
- Initialize a consumer server object. The consumer server thread is started.
A consumer
callback function is recorded for use by the consumer server upon receipt of
data.
- Close the consumer server object. The socket is closed which forces the
consumer server
to shut down. This routine is called prior to terminating the consumer task.
- Initialize a consumer client object. The consunoer server object is passed
as a parameter in
order to link the consumer client object to the consumer server object. The
consumer
server object is initialized first. All further acW~ns (subscribe,
unsubscribe, request) use
this consumer client object. Each consmner thread initializes its own consumer
client
object in order to mutually exclude each other.
- Close the consumer client object. If any subscri ptions are still
outstanding, they will not be
i
unsubscribed.
- Allow the consumer to subscribe to a continuous feed of data from the
producer. When
the data is generated, the producer will send a reply message containing the
data.
- Allow the consumer to end subscription of a ct ~ntinuous feed of data from
the producer
This is performed before closing the consumer client object.
- Allow the consumer to request a oneshot reply of data from the producer.
Often this
request contains data for the producer to use. The producer sends. a reply
message in
response to the request.
The consumer server 507 or 508 is a thread that is started from.an "initialize
a consumer
service object" API call. This thread monitors the connmtion status of the
socket or data port and
receives acknowledge and reply messages from the prod uue:r and passes them to
the consumer via the
consumer callback function 509 or 510. The consumer callback is a function
that is used by the
consumer server to alert the consumer threads) 504 through 506 of receipt of
data or change in
connection status from the producer server 513. This function is offered by
the consumer when
initializing the consumer server object. One consumer callback is associated
with one consumer
server. When data is passed to the consumer callback it is preferably copied
to the consumer's space
as the buffer is reused when control is returned from the consumer callback.
35
CA 02235176 2004-11-08
Producer
The producer thread 514 or 515 replies to subscriptions from the consumer 501
or 502. This
thread first preferably initializes a producer client object, v is an
"initialize a consumer client object"
consumer API, and attaches it to the producer server objet t. All subsequent
replies use the producer
client object. The producer may consist of several threads all using one
producer server 513. In this
case, each producer thread 514 or 515 preferably initializes its own producer
client object to
mutually exclude other producer threads. This method shares one producer
callback function
between all producer threads.
The producer API is the producxr's interface to the message passing mechanism.
The producer
API contains the following set of routines:
- Initialize a producer server object. T'he producer server thread is started.
A producer
callback function is recorded for use by the producer server upon receipt of
requests.
- Close the producer server object. All connecting sockets are closed which
forces the
producer server to shut down. This routine i s ca l led prior tb terminating
the producer task.
I S - Initialize a producer client object. The producer server object is
passed as a parameter in
order to link the producer client object to the producer server object. The
producer server
object is initialized first. All replies preferally use this producer client
object. Each
producer thread preferably initializes its own producer client object in order
to mutually
exclude each other.
- Close the producer client object.
- Allow the producer to reply to a continuous or oneshot subscription to.
data. If the
subscription is a oneshot request, the subscripts on is removed from the
subscription table.
This message usually contains data and a return status to qualify the data.
The producer server is a thread that is started from a ''initialize a producer
server object" API
call. This thread monitors the connection status of the data socket and
receives subscribe,
unsubscribe, and request messages from the conswner 501 or 502 and passes them
off to the
producer 503 via the producer callback function 516. lJpc>n connection of a
consumer server, a new
producer server thread is spawned to handle the nex a consumer server
connection. When a
connection is broken or dropped, the producer server tluead 514 or 515
associated with this
connection is cleaned up and terminated. All references to this connection are
removed from the !
i
subscribe tables 517.
r
36
CA 02235176 2004-11-08
The producer callback S I 6 is a function that is used by the producer server
to alert the producer
threads) 514 and 515 of receipt of data from the consumer server 507. This
function is offered by
the producer 503 when initializing the producer server object. One producer
callback is associated - i
with one producer server. When data is passed to the prod racer callback it is
preferably copied to the
producer's space as the buffer is reused when control is r~ turned from the
producer callback.
There are two subscribe tables 517: client and message. The client table
consists of
information about all consumer server connections. The message table consists
of information about
all service subscriptions. Together, these tables enable the producer 503 to
send reply messages to
all consumers 501 and 502 that have subscribed to services.
While the invention is described above as being particular to lumber, it is
understood that the
invention is equally practical for any workpiece having p«;ential defects, and
is particularlypractical
where such workpieces are non-homogeneous.
It is apparent then that variaxions and modifications of the invention can be
made without
departing from the spirit or scope thereof. Such variations and modifications
are meant to be
comprehended within the scope of the invention.
37
