RESEARCH PAPER ON INDUSTRIAL ENGINEERING
“THE ROLE OF THERBLIGS IN AUTOMATED DESIGN PROCESS MAPPING”
Hemanth Kumar V (36)
The research
presented in this paper involves the detailed analysis of a user's
actions
whilst carrying out a design activity in a virtual reality (VR) environment.
It is
proposed that the analysis can be used to extract the design knowledge that is
generated
during the design session. By parsing and analysing the log files,
motion study
analysis and process planning can be performed automatically.
Furthermore,
IDEF0 diagrams can be automatically generated which allow the
processes
occurring during the design session to be easily described and
visualised.
The outcome of all the analysis will benefit future users by aiding them
in creating
more efficient designs that will contain fewer errors and be less time
consuming to produce.
When a
designer completes a design in a computer-aided design (CAD) environment,
the end
result contains only the solution to the design problem, but none of the design
knowledge
that is created, or learned, during the session. This means that the reasons
the designer
came up with the final solution will not be known to other users, unless that
information
was explicitly stated by the designer, either during the design session or
afterwards.
However, having to record this extra information will not only take more
time and
effort, but it will also disrupt the design process and creativity of the user.
Therefore,
it is proposed that if each individual action of the user during the design
session
could be logged and analysed, it would give the potential for formalising the
design
rationale of the designer. Rationale, in this case, refers to the user’s
reasons for
making their
design decisions during the session. Since the logging is carried out
unobtrusively
and automatically in the background, the designer will not be disrupted
and no extra
work will be required from them to record their design actions. After
obtaining
the formalised design rationale, it could then be used to aid subsequent users,
who are
carrying out a similar design task, by providing hints to them as well as
identifying
any mistakes that they have made. In the research presented in this paper,
the actions
of a user are logged while they are designing a cable assembly in a virtual
design
environment, and then various techniques that are applied to analyse the logged
data is
detailed.
The paper
starts by discussing the related research in user-logging and cable design, and
then the
immersive VR apparatus and experimental methodology used in this research is
detailed.
This is followed by a section demonstrating the potential for automatically
generating
manufacturing planning data. Furthermore, several visual techniques for
representing
the user activity from the log files are presented which aid the
identification
of signature patterns relating to design rationale. Next, the benefits of
representing
the design processes using IDEF diagrams, and a way to generate them
automatically,
is presented, before finally drawing some conclusions.
User Logging and Design Intent Identification
By
considering the thoughts of the designer, it is possible to identify how
important the
cognitive
issues associated with design, as a creative process, are. In McPhee, design
is described
as a mysterious mix of science and art that can only be understood by first
understanding
how humans think and behave. It is also mentioned that design is 3 of 18
instinctive,
as does Schöns’s “knowing-in-action” theory
Cable Harness Design Using Virtual Environments
The
designing of cable harnesses, which refers to the assembly of cable, connectors
and
clips, is a
classic design problem and, even with the application of extensive CAD based
packages available, many companies still utilise physical prototypes to create
the
cable routes
and to verify the design . In addition, human expert intervention is still
required to
make fine adjustments and verify the solutions. Therefore, it would be
advantageous
to investigate the nature of new human-driven tools to support interaction
with data in
this domain. According to integrating
the human expert into the 4 of 18
‘system’ is
crucial within VR applications because it treats the operator as an integral
part of the
system
EXPERIMENTAL PROCEDURE AND ANALYSIS
Three
constrained design tasks were developed and implemented to evaluate each
designer’s
time on the system. These covered common harness design activities such as
routing,
bundling, cable modification and choosing connectors. The log files were
subsequently
analysed to identify which areas of the virtual design system were used,
the type of
activity performed and their distribution within the total design time. The
participants
were given sufficient information about the goals of the task along with the
main boundary
conditions but were given the freedom to determine the final design
solution.
Task 1: Outline Design – This task, and
the following one, is for training and
familiarisation
purposes and involves the user generating two new electrical
interconnections
within the product model using specific connectors and a specified
cable type.
Task 2: Detailed Design – Using
pre-defined cable interconnections in a model, a
number of
which had already been routed through a sequence of cable clips, the user
had to route
the outline cables in the model through the cable clips to complete the cable 7
of 18
harness
design.
Task 3: Redesign – The key experimental
design evaluation task, this began with a
product
model containing a completed, fully designed harness assembly. The user had
to complete
some ‘engineering change requests’ requiring redesign of the cable harness.
The specific
changes required were the addition of a new cable and the removal of one
of its
associated connectors. Finally, there was another ‘undefined’ error within the
model – a
cable routed through a solid wall – which the participants were required to
locate and
fix by rerouting.
AUTOMATED LOG FILE ANALYSIS, MOTION STUDY
AND PROCESS
MODELLING
Log File Analysis
In earlier
work, the logged data generated during the VR design sessions were all
categorised
and analysed, manually, which proved to be very time consuming.
Therefore, a
spreadsheet macro was written that could carry out the analysis tasks
automatically.
The first step in the macro is to parse the log file and assign each user
action into
various categories which will aid in further analysis.
CONCLUSIONS
This paper
has presented an automated way to generate assembly plans by utilising the
data that is
logged from the user during a design activity. To give more realistic
assembly
operation times, a table of standard real-world assembly times have been
mapped onto
the corresponding virtual operation.
In addition,
two analysis methods, called therbligs and chronocyclegraphs, have been
applied to
study a user’s motion when carrying out a design task in the virtual 16 of 18
environment,
to gain a detailed understanding of the user interactions and process
activities.
Both methods have allowed any inefficiency in the user’s motion, processes
and VR
interface design to be visually identified and analysed. One potential
application
of the data obtained from the analysis is the extraction of ‘thinking time’ by
searching
for pauses in the user’s activity or changes in their behaviour. This may
highlight
areas where the user is thinking about the design, and may imply design intent,
or
reasoning, from the actions leading up to, and after, an event where a design
decision
has been
made.
Finally, it
is proposed that further analysis of the log files can allow design knowledge
to be
acquired. Once the design knowledge has been extracted, IDEF0 diagrams can be
used to
represent them, and it has been shown that they can be automatically generated.
An
additional benefit of utilising IDEF0 diagrams is that they are widely used in
industry. By
providing the design knowledge, stored in the IDEF0 diagrams, to
subsequent
users carrying out specific design tasks, it can be used to aid them in
creating
more efficient designs, more quickly.
REFERENCES
1. McPhee,
K. Design Theory and Software Design, Technical Report TR 96-26,
Department
of Computer Science, University of Alberta, Canada.
2. Schon,
D.A. The Reflective Practitioner: How
Professionals Think in Action,
Arena, 1991.
3. Guindon,
R., Krasner, H., and Curtis, B. Breakdowns and Processes During the
Early
Activities of Software Design by Professionals, Empirical Studies of
Programmers
- Second Workshop (December 1987) Washington, DC, pp 65-82.
4. Cross, N.
Design cognition: Results from protocol and other empirical studies of
design
activity, In C. Eastman, M. McCracken & W. Newstetter (eds.), Design
knowing and
Learning: Cognition in Design Education. Amsterdam: Elsevier,
2001, pp
79-103.
5. Adelson,
B., and Solway, E. The Role of Domain Experience in Software Design,
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Transactions on Software Engineering, 1985, 11:1351-1360.
6. Guindon,
R. Designing the design process:
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Human-Computer
Interaction, 1990, 5(2), pp.305-344.s
