Principles of
Engineering System Design
Dr T Asokan
asok@iitm.ac.in
Principles of
Engineering System Design
Originating Requirements Development: Examples
Dr T Asokan
asok@iitm.ac.in
044-2257 4707
T Asokan
Air bags, safety device appearing in automobiles
in the early 1990’s, became the cause of death for a
noticeable number of individuals.
There were severe flaws in the
design, testing and deployment
requirements envisaged.
Case Study: REQUIREMENT ANALYSIS
-Air Bag System Failure in the 90s• The requirements defined only a single safety scenario
on which to base the design
• No requirement that the airbag remain undeployed
during accidents at sufficiently slow speeds that no lives
are in danger
• Test condition requirements were wrongly identified.
• Pre-impact braking was not taken into account
• Injuries due to collision with the airbag was not
considered
• Requirements of disposal of unused or partially used
bags were not identified
Self Study
• Analyse the causes of Apollo 13 disaster as an
engineering system design failure and find out the faults
in the requirements identification that led to the failure.
Tutorial
A leading financial company has decided to develop a
multipurpose ATM to deliver cash, accept cash, pay bills,
and print pass book. For the operational phase of this
machine:
(a) Identify at least few operational scenarios and
explain them in detail.
(b) Develop an input/output trace for two scenarios.
(c) Develop an external system diagram
(d) Develop a set of originating requirements and
prepare the ORD for the operational phase.
Operational Concept Scenario
Scenario 1. Customer makes deposits
Scenario 2
Scenario 3
Emergency situation
Fire
Unauthorised attempt
Scenario 4
Breakdown
Theft
Scenario 5
maintenance
ORIGINATING REQUIREMENTS
• The system shall give an indication of the status
• The system shall prompt for an identification and
provide opportunity to prove the identity
XYZ Bank
Customer
Credit Card
Customer
Another Bank's
Customer
Log in /
Request
Response
Log in /
Request
ATM Admin
Response
Response
Response
Log in /
Request
Transaction
Request
Response
Log in /
Service
Diagnostic
Response
ATM System
Transaction
Request
Log in /
Request
Diagnostic
Response
HW Maint.
Response
Retrieve
Deposits
Service
XYZ
Network
Transaction
Request
Fill up w/ Cash
ATM Service
Providers
Customer
Account
DB
Fraud / Break-in
Response
Transaction
Request
Reports
Bank
Management
ABC
Network
Unfriendly
Customer
PQR
Network
Group ASSIGNMENT II
A leading electronics gadget manufacturer has decided to
develop a multipurpose gadget to store/deliver music,
store/retrieve data like address, phone number etc.,
and provide information on location/navigation etc. For
the operational phase of this device:
(a) Identify at least 10 operational scenarios and explain
them in detail.
(b) Develop an input/output trace for three scenarios and
identify I/O requirements.
(c ) Develop the external system diagram
(d )Develop a set of originating requirements and prepare
the ORD for the operational phase.
(e) Prepare an objective hierarchy for the operational
phase
Summary
• Six functions of system design process
• Define system level design problem
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Operational Concept
External Systems
Originating Requirements
Objectives hierarchy
Documentation
Requirement management
• ORD
Principles of
Engineering System Design
SOFTWARE TOOLS FOR SYSTEM
ENGINEERING
Dr T Asokan
asok@iitm.ac.in
044-2257 4707
T Asokan
SysML
• SysML is a general purpose modeling language for
systems engineering applications. It is a dialect of
UML™, the industry standard for modeling
software-intensive systems.
• It supports the specification, analysis, design,
verification and validation of a broad range of
systems and systems-of-systems. These systems
may include hardware, software, information,
processes, personnel, and facilities
• The SysML open source specification is publicly
available for download, and includes an open
source license for distribution and use.
Reproduced with permission from M/s Vitech corporation
Summary
• IT enabled system design procedures increase
the efficiency of design process
• Commercial software are available for system
design
• CORE, SysML etc. are standard software
available for this purpose