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Description  |
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The present invention relates to a computer-based assembly system, and more
specifically, to a computer implemented process and system which generate
a bill-of-material for existing as well as new articles and automatically
configure product assemblies.
BACKGROUND OF THE INVENTION
Speed, simplicity and self-confidence are important elements in becoming
and maintaining a competitive business. As competitiveness in a
marketplace increases, quickly responding to specific demands within the
market becomes increasingly important. If one competitor fails to quickly
respond to a consumer's demand, then the consumer's demand may
substantially decrease, at least with regard to products of the one
competitor. The consumer may use a suitable substitute product from
another competitor.
Many factors contribute to slowing the process of bringing a product to
market, thereby weakening the competitiveness of a business. Complexity of
a product contributes to the difficulties in meeting specific consumer
demands in a timely manner. The complexity of world-wide production, the
changing nature of competition, and even the complexity internal to
production companies, generally slow the process of bringing a new or even
modified product to market.
For example, motors generally are complex products, and in order to meet
specific consumer demands, a complex design and implementation process
must be completed. For the consumer, however, the time period required for
delivery may be too long. The consumer may therefore resort to substitute
products of another competitor.
In order to speedup the pace at which consumer demands for a new or
modified product are satisfied, manufacturers utilize bill-of-material
systems. The term "bill-of-material", as generally understood in the art
and as used herein, refers to a parts explosion listing. Specifically, a
product may have many subassemblies, some or all of which may have further
subassemblies. A bill-of-material is a printed-out parts list having
indentations where the indentations correspond to a depth of hierarchy of
each product in each subassembly. The bill-of-material traditionally has
been utilized during the manufacturing process of an assembly to provide a
reference for the relationship of each component to other components in
the assembly.
An example of a system for generating a bill-of-material is described in
Ferriter et al., U.S. Pat. No. 4,847,761. In the Ferriter et al. system, a
bill-of-material generation process begins by producing a functional model
of a product design. In order to generate the functional model, the user
must know each part required to meet the design specifications, i.e. the
user must formulate and apply rules to determine proper subassemblies. The
functional model is in the form of a hierarchy tree structure. The tree
structure is assigned an item number and stored in a database. Once a tree
structure for a product is established, a user can view the hierarchical
tree, check it for correctness and modify it, if necessary. From this tree
structure, the Ferriter et al. system generates a bill-of-material.
With known systems, such as the system described in the above-identified
patent, in order to generate a bill-of-material for a specific assembly, a
user must first input a functional model into a database. Inputting
functional models for each assembly is a time-consuming process. For
example, in a motor context, each motor contains many subassemblies such
as a rotor assembly, stator assembly, frame, end shield, and other parts.
Many components, such as the rotor assembly, further decompose into more
subassemblies, such as a shaft, laminations, nuts, and bolts. In practice,
therefore, full automation for bill-of-material generation for all model
designs would take many man-years to implement. By the time such a
complete system was implemented, the models probably would be partially
out of date and require additional modeling.
Design accuracy and consistency with these known systems is highly
dependent upon the expertise of a person who creates and enters the
functional model for each new product. These known systems therefore also
are susceptible to errors and inconsistent design techniques. Further, in
order to implement a new design technique, each model must be reanalyzed
and structured. This process also is very time-consuming and increases the
cost and time required to bring a product to market.
Moreover, and importantly, although identifying component parts aids in
speeding the process of bringing a product to a market, until now, no
known system provides generation of an assembly hierarchy from design
specifications alone. Specifically, no known bill-of-material system
provides that a new or modified product can be automatically designed
using assembly hierarchy information of previously designed products.
Further, no known system automatically acquires rules which guide
construction of a new product and its bill-of-material. Automatically
constructing assembly hierarchies and generating rules to guide
construction of a new product further reduces the time required to bring
new and modified products to market.
It is therefore an object of the present invention to provide an automated
bill-of-material generation system which generates a bill-of-material from
design specifications.
Another object of the present invention is to provide an automated
bill-of-material generation system which facilitates bringing a new or
modified product to a market within a short period of time.
Still another object of the present invention is to provide an automated
bill-of-material generation system which enables electronic storage of all
variations of a specific assembly.
Yet another object of the present invention is to provide an automated
bill-of-material generation system which enhances the accuracy and
consistency of design techniques.
Still yet another object of the present invention is to provide an
automated bill-of-material generation system which automatically generates
assembly hierarchies and automatically generates rules to guide
construction of new or modified products.
Another object of the present invention is to provide an automated
bill-of-material generation system which reduces the cost in bringing a
product to market.
Still another object of the present invention to provide an automated
bill-of-material generation system which facilitates speed, simplicity and
self-confidence in bringing a product to market.
SUMMARY OF THE INVENTION
The present bill-of-material configuration system provides that a system
user need only input design specifications into the system, and from the
design specification alone, a bill-of-material for an assembly which
satisfies the design specifications is generated. In accordance with the
present invention, assembly tables and partially-ordered selection
criteria tables populated with assembly data are generated. The selection
criteria tables express assembly data as rules and control selection of
proper components which will result in an assembly that satisfies the
desired design specifications.
In operation, when a system user inputs design specifications, the system
scans the selection criteria tables, applies rules expressed in the
selection tables, and determines component parts, including subassemblies,
which satisfy the required design specifications for the particular
assembly. The system then scans the assembly table, identifies the
determined component and its relationship to other components, and
generates a bill-of-material for the assembly. The component parts are
then made available to the system user, for example, in a bill-of-material
format to guide construction of the assembly.
The present invention does not require that a system user input a
functional model for each product. Rather, using on-line operations, the
system user only enters design specifications for an assembly. Moreover,
design accuracy and consistency of the present system are not dependent
upon the expertise of a system user entering the design specifications.
The present system therefore reduces errors which may result from
inconsistent design techniques. Also, in order to implement a new design
technique, the present system can be easily modified so that the stored
data and rules conform to the new design technique.
The present bill-of-material system, by providing that new and modified
products can be automatically designed from design specifications alone,
reduces the time required to bring a new or modified product to market.
The present system thus increases competitiveness and allows a
manufacturer to meet specific demands of a consumer in a more timely
manner. Importantly, the present system facilitates speed, simplicity and
self-confidence in bringing a product to market.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the present invention, together with further
features and advantages thereof, will be apparent from the following
detailed specification when read together with the accompanying drawings,
in which:
FIG. 1 is a high level block diagram of the present bill-of-material
generation system:
FIG. 2a and 2b is a flowchart illustrating the present system;
FIG. 3 is an example of a hierarchal representation for a lawn mower;
FIG. 4 is an object oriented representation of a lawn mower;
FIG. 5 illustrates populated assembly model tables in accordance with the
present invention;
FIG. 6 illustrates typical rules which would be utilized by the present
invention in a lawn mower context;
FIG. 7 illustrates empty selection criteria tables in a lawn mower context;
FIG. 8 illustrates an assembly table and populated selection criteria
tables in accordance with the present invention;
FIG. 9 illustrates one alternate method for operation of a user interface
in accordance with the present invention;
FIG. 10 illustrates another alternate method for operation of a user
interface in accordance with the present invention;
FIG. 11 illustrates alternate print-out methods in accordance with the
present invention; and
FIG. 12 illustrates an object structure which may be utilized in generating
selection tables in accordance with the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
The present invention is directed to a system architecture and method for
automated generation of a bill-of-material, and the present invention is
not directed to any particular set of rules for carrying out a particular
bill-of-material generation process. Therefore, although the present
invention may be described herein with reference to, for example, motors
and lawn mowers, such examples are for illustrative purposes only. The
present invention may be utilized to generate a bill-of-material for many
other assemblies and process, including even computer software. Further,
the present system architecture and method are to be practiced on a
computer. The present invention, however, is not limited to practice on
one specific computer.
Referring now more particularly to the drawings, FIG. 1 illustrates, in a
high-level block diagram, a bill-of-material configuration system in
accordance with the present invention. Specifically, as shown in FIG. 1, a
system user supplies design specifications to a bill-of-material
generation system identified at block 100. The term "system user" as used
herein refers to a human operator, another computer, or a combination
human-computer operator. It should be understood, therefore, that the term
"system user" is not limited to meaning a human operator. The term "design
specification", as known in the art and as used herein, means desired
characteristics of an assembly. For example, in a lawn mower context, one
design specification may be the width of the mower. Output from the
present bill-of-material generation system, as shown in FIG. 1, comprises
an indented list of parts, i.e. a bill-of-material.
The high level block diagram in FIG. 1 is shown to illustrate and emphasize
that the present invention, from design specifications alone,
automatically generates a bill-of-material and automatically configures
product assemblies. As explained in more detail hereinafter, the present
system utilizes assembly model tables and selection criteria tables
comprising rules and assembly data to automatically generate the
bill-of-material. On the other hand, with known bill-of-material systems,
a system user inputs a functional sketch of an assembly such as in the
form of a hierarchy tree structure, and from this tree structure, a
bill-of-material for the assembly is generated. Known systems do not
utilize or extract rules from past design and previously stored data for
more automated bill-of-material generation. By requiring the system user
to only input design specifications in order to generate
bills-of-material, as in the present invention, the time required to bring
a new product to market may be substantially reduced.
FIG. 2 illustrates, in a more detailed flow diagram 200, the sequence of
process steps required to make and use the present bill-of-material
generation system. Specifically, a sequence of steps required to make the
present system is illustrated in "off-line" section 202 and a sequence of
steps required to use the present system is illustrated in "on-line"
section 204. As used herein, the term "off-line" means independent in time
from actual generation of a bill-of-material, and the term "on-line" means
in substantially or near real-time with actual generation of the
bill-of-material.
To further facilitate a better understanding of the present invention, the
sequence of process steps is described herein with reference to an example
illustrated in FIGS. 3 to 8. The example shown in FIGS. 3 to 8 illustrates
how the present invention would be made and used in a lawn mower context.
The example is shown for illustrative purposes only.
Referring now more specifically to FIG. 2, once the off-line process is
initiated as indicated at "START" block 206, an assembly table generation
process 208 and a selection table generation process 210 are begun.
Although shown as being performed in parallel, these processes could be
performed in series in any sequential order.
In assembly table generation process 208, and as indicated at block 212, a
system user first models product structure and determines which parts,
i.e. subassemblies, compose a complete assembly. In a lawn mower context,
and as shown in FIG. 3, many parts would compose the assembly and only one
level of subassemblies is shown in FIG. 3. Many other subassemblies are
contemplated in the lawn mower context. Note that the model created by the
system user may be in one of many forms and, for example, may even be in
hierarchical tree form described in Ferriter et al., U.S. Pat. No.
4,847,761.
The next step in the assembly table generation process, as indicated at
block 214, is to convert the assembly model into tables. The preferred
table format results from utilizing a technique known as the Object
Modeling Technique described in Blaha et al., "Relational Database Design
Using An Object-Oriented Methodology," Communications of the ACM, 31, 4,
April, 1988, which is incorporated herein, in its entirety, by reference.
In the lawn mower context, the tables which would be created by using the
Object Modeling Technique for the model shown in FIG. 3 are illustrated in
FIG. 4. Each box in FIG. 4 denotes an object class and each object class
corresponds to part of a relational database management system table. The
model includes connectivity in a hierarchal format, illustrated as lines
with arrows at their ends. Specifically, a blade, an engine, a deck and
wheels each compose a lawn mower. A lower portion of each box sets forth
attributes for each object class. Attributes which are underlined are the
primary, i.e. uniquely identifying, attributes.
The specific configuration for the assembly tables for each assembly may be
in one of many forms, and the present invention is not limited to any
particular format. For example, as shown in FIG. 5 and in the lawn mower
context, the table labelled "Lawn mower" may include information from the
"Lawn mower" block in FIG. 4, and information related to the primary
attribute of each subassembly. Each subassembly, as shown in FIG. 5, may
also be represented in a respective block, i.e. a "Blade" block, a "Deck"
block, an "Engine" block and a "Wheel" block.
The next, and generally final, step in the assembly table generation
process is to load assembly data into the generated tables as indicated at
block 216. If the assembly data is stored electronically, the assembly
table could be populated through an electronic transfer of data. If,
however, the assembly data is not stored in a compatible or electronic
format, the assembly data may have to be manually entered such as through
a keyboard interface or by scanning a printout of the data with an optical
character recognition system.
For the lawn mower example, the populated assembly tables which would be
generated are illustrated in FIG. 5. In this example, six different mower
models having different model numbers are shown. Some of the
subassemblies, e.g. blade and wheel, would include components which may be
utilized in more than one mower model, and therefore, less than six
subcomponents of blades and wheels would be shown in their respective
tables. For example, "blade num" B16M may be utilized in both mower model
numbers LM16G and LM16E. In the blade subassembly, only one entry for
"blade num" B16M would be required.
The selection table generation process, as indicated at block 218, begins
by determining selection criteria. Selection criteria are the factors
which determine a part to be selected, and the selection criteria
generally are elicited from experts in a particular technological field.
In a lawn mower context and as shown in FIG. 6, a deck of a lawn mower,
i.e. "deck num", would be selected based upon the "mower width" and the
"LM motive power". Therefore, "mower width" and "LM motive power" are the
"deck num" selection criteria. Likewise, and as also shown in FIG. 6,
selection criteria for "wheel num" would be "mower width" and "deck matl".
Selection criteria are determined for each subassembly.
Once the selection criteria are determined, the criteria are converted into
a table format as indicated at block 220. As with the assembly model, the
selection criteria model preferably is in the form generated by utilizing
the Object Modeling Technique. In the lawn mower context, the selection
criteria model which would be created is shown in FIG. 7. At this point,
the selection tables would be empty, i.e. no assembly data is in the
table. It should be apparent that while the assembly model tables would
describe a wheel, the selection model tables would provide a format for
choosing a wheel.
The next step, as indicated at block 224, is to determine a partial
ordering for the selection tables. This partial ordering must be
determined on an application specific basis. For example, in a motor
context, one subassembly of a motor is an end shield. Generally, screws
are utilized to mount the end shield to another part of the assembly.
Before the type and number of screws can be selected, the type of end
shield must be known. Therefore, the end shield selection process must be
performed prior to the screw selection process. The partial ordering
process may be performed by a human operator or may be automated. An
automated partial ordering process, for example, may be performed by a
computer implemented process. Expert knowledge generally is not required
to perform the ordering process.
As a result of the above-described selection table generation process, a
sequence of empty, partially ordered, selection database tables are
generated. Further, as a result of the assembly table generation process,
populated assembly database tables will have been generated. The next step
as indicated at block 226 is to generate populated selection database
tables. This step may be performed by determining all possible
combinations of subassemblies utilizing the assembly table and selection
table. For example, referring to FIG. 7 and in a lawn mower context, the
deck selection table actually would be an expression of a logic rule. In
the deck selection operation, the rule would be expressed as:
If "mower width"=A and "LM motive power"=B, then "deck num"=C.
For example, if the mower width is "16", and LM motive power is "gas", then
the selected deck num will be "D16". By utilizing the "deck num" rule, and
scanning the assembly table for all encountered combinations of the rule
elements, e.g. "mower width" and "LM motive power", the selection tables
would be populated.
More specifically, to populate the selection tables, e.g. the deck
selection table, each combination of subassemblies which comprise rule
elements of each rule would be determined. For example, for the deck
selection rule, each combination of "mower width" and "LM mower power"
would be copied from the assembly table to the selection table for deck
selection.
Referring to FIG. 8, to populate the selection database tables, each row of
the assembly tables would be scanned. Beginning with "model number"
"LM16G", and with reference to the "Deck Selection" table, the computer
would scan the first row of the table from left to right. During the first
scan operation of the first row, the first rows of the "Deck Selection"
and "Wheel Selection" tables would be populated. Once the scan operation
for the first row is completed, the second row of the table would be
scanned and the second row of the "Deck Selection" table would be
populated.
In the "Wheel Selection" table, however, no row would be created during the
second scan. Since the first and second scan operations contain identical
information with regard to the "Wheel Selection" table, there would be no
need for a new row in the "Wheel Selection" table for the second scan.
This scanning process would be repeated for each row in the assembly table
until all the rows have been scanned. The same process would be performed
for each selection table. It should be understood that many more tables
would be necessary to describe a lawn and necessary selection criteria.
The result of these off-line operations would be a sequence of partially
ordered, populated selection database tables.
The off-line process, as described above, may require a relatively long
time period, e.g. weeks, to complete as compared to the time required for
the on-line processes, e.g. minutes. The off-line processes of the present
invention may, for example, be performed on and/or by a computer known in
the art as a VAX 11/785, and generally are controlled by a human system
user. The present invention may be utilized with most all commercially
available computer systems, and it is contemplated that artificial
intelligence techniques may be utilized in combination with the
human-performed steps.
Briefly, during on-line operations, if a system user requires a
bill-of-material for an assembly, the system user inputs into the system,
through a user interface, design specifications. The selection rules are
then applied to the input specifications as indicated at block 228. For
example, and in a lawn mower context, a system user would enter the
desired "mower width" and "LM motive power." From these design
specifications, the system would select, from the selection tables, a
"deck num" and "wheel num". If the design specifications include a "mower
width" of "16" and a "LM motive power" of "gas", "deck num" "D16" would be
selected and "wheel num" "W3" would be selected. Other subassemblies may
require that further design specifications be entered by the system user
to select a proper component.
Once each subassembly has been selected, a bill-of-material can be
generated from the selected information and a print-out of the assembly
model can be obtained as indicated at block 230. The assembly model
print-out may be in one of many forms including in the form of a
bill-of-material. Alternate print-out methods are described later with
reference to FIG. 11. It is contemplated that rather than printing out the
bill-of-material, the output of the present system could be electronically
transferred to other computers for further processing. For example, in an
assembly line, a number of computers may be located along the assembly
line and portions of the bill-of-material, including assembly
instructions, related to specific components could be transferred to
computers at the respective locations where assembly of the specific
components will occur.
Referring now to FIG. 9, a more detailed and one alternative method 300 for
on-line operations is described. Method 300 illustrates the on-line
operations in a batch mode. This means that user supplied design
specifications are placed in memory, and then the design specifications
are supplied to the system from the system memory. Specifically, the first
step in method 300 is to form an empty assembly parts explosion (APE) in
memory as indicated at step 302. An APE is a computer data structure
having a memory location for every possible part that may be represented
in the assembly. Then, user supplied design specifications are loaded into
designated memory locations as indicated at step 304. Once the design
specifications are loaded into memory, a selection table counter is set to
equal 1 as indicated at block 306. Batch mode operation of the system then
begins.
Specifically, the current selection table as indicated at block 308
receives the user supplied design specifications. From the rules expressed
in the current selection table, the system determines the required input,
i.e. design specifications, to select a component. If a required input to
process the current selection table is missing, as indicated at block 310,
then the system indicates to the user that the design specifications are
bad, i.e. incomplete, or that a selection table (ST) error has occurred.
If all of the input are available but an ambiguous answer results as
indicated at block 312, then the system indicates to the user that an
error has occurred and that the error is in the assembly model or is a ST
error. If all of the inputs required for selection table operation are
provided and if no ambiguous answer results, and if the system then fails
to choose a required part as indicated at block 314, the system indicates
to the user that an error has occurred and that the error is in the
assembly model or an ST error. If an error occurs, the system user should
then edit the assembly model and/or selection table to correct the error.
Other results subsequent to application of the current selection table also
are contemplated. For example, in some assemblies, some components may be
identified as "optional" components, and the selection table may include
an "optional" or "don't need" indication for each optional component in
each assembly. An example of an optional component in a motor context is
"extra end turn insulation". Although required in some motor assemblies,
the insulation is not required in all motor assemblies. An optional legend
will be included in the selection table during selection table generation,
and after application of a selection table for a motor assembly wherein
insulation is not required, the system will provide an indication that the
insulation is optional.
Further, it is contemplated that in some contexts, such as when a new
combination of selection tables is being utilized, the system may not
identify all required components, i.e. the location in the APE
corresponding to the component will be empty. If this situation arises,
then an expert in the technological area of the specific assembly, e.g.
lawn mower expert, motor expert, etc., generally must provide information
regarding the component which should be selected. The system user can then
edit the selection table in accordance with the expert provided
information.
If all the inputs required to process the current selection table are
provided, and if the assembly model and selection table are properly
generated as described above, the system processes the current selection
table and identifies a component which meets the design specification.
Processing a selection table comprises comparing the required input design
specifications with the elements of the current selection table.
For example, and referring to FIG. 8, assume the wheel selection table is
the table to be processed, i.e. the current selection table. Further,
assume that design specifications requiring that the "mower width" be "20"
and the "deck matl" be "steel" have been entered. The system then scans
the selection table until it encounters a row which satisfies the design
specifications, and then identifies the wheel corresponding to that row.
In the present example, the design specifications match the row
corresponding to "wheel num" "W5P" and therefore, wheel type "W5P" would
be selected. This wheel type selection would then be transferred to the
APE memory location corresponding to wheel type.
More specifically, if a required part is selected from processing the
current selection table as explained above, the system then adds the
selection table output to the APE as indicated at block 316. The system
then proceeds to determine whether all the selection tables have been
processed as indicated at block 318. This operation is determined by
comparing the selection table counter to a predetermined number which
indicates the number of selection tables which must be processed. The
predetermined value is set to equal the number of selection tables to be
processed, and the value may, for example, be assigned by the user after
completion of generating populated selection tables, i.e. in off-line
operations. If all the selection tables have been processed, then the
operation is finished. At this point, the APE is loaded with all the
design specifications and the chosen parts as indicated at block 320. If
all the selection tables have not been proce | | |
