Industrial-Engineering-Research-Paper (HEMANTH)

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,

IEEE Transactions on Software Engineering, 1985, 11:1351-1360.

6. Guindon, R.  Designing the design process: Exploiting opportunistic thoughts,

Human-Computer Interaction, 1990, 5(2), pp.305-344.s