Principles of Engineering System Design Dr T Asokan n

INTRODUCTION TO SYSTEMS DESIGN Dr T Asokan Operational Architecture Development

Six functions of Design Process 1.Define System Level Design Problem :- Originating requirements developmentDefine System Level Design Problem 2.Develop the system functional architecture 3.Develop the system physical architecture 4.Develop the system operational architecture 5.Develop the interface architecture 6.Define the qualification system for the system T Asokan ED309

Operational Architecture Development The development process for the operational architecture ( also known as allocated architecture) is the activity during which the entire design comes together. It integrates the requirements decomposition with the functional and physical architectures It provides a complete description of the system design and provides the raw materials for the interface definition as well as trade - off decisions.

1. Allocate functions and system-wide requirements to physical subsystems 2.Allocate functions to components 3.Trace system-wide requirements to system and derive component-wide 4.Define and analyze functional activation and control structure 5.Conduct performance and risk analysis 6.Document architectures and obtain approval T Asokan ED309 Major activities involved in allocated architecture Development

Global Combat Support System T Asokan ED309

Any box is the benefit of a Common Operating Environment (COE) to provide compatibility among different operating systems from a single workstation. Any user refers to the operator authorized to access relevant support data and information. One net refers to the availability of all Warfighter information via a global (web based) network. One picture refers to the capability to integrate information across combat support functional areas and command and control. Data quality relates to the availability and ready access to timely, reliable, accurate, and complete source data and derived information. T Asokan ED309

Allocation of engg. functions to components T Asokan ED309

Mapping of functions to components is chosen rather than mapping of components to functions Allowing two components to be mapped to same function must be avoided While allocation: –Try to maximise the fundamental objective –Try to minimize the number and complexity of interfaces –Maximise early critical testing opportunities –Equalize risks across the physical architecture or –Localize risks in a single element of the physical architecture

Objectives for functional allocation costs Suitability issues Error rates on key tasks Timing on key tasks Task1 Task2 Task1 Task2 MTBF MTTR Manuf. Operati onal T Asokan ED309

Approaches for solving allocation problem Distribution of responsibility between human and computer [Sheridian and Verplank 1978] – Human does all planning, scheduling, optimisation etc.; computer merely does deterministic execution –Computer provides options, but the human chooses between them and plans the operation –Computer helps to determine options and suggest one for use, which human may or may not accept –Computer selects action and carries it out if human approves –Computer does entire task and informs human of what it has done –Computer does entire task and informs human only if requested –Computer performs entire task autonomously, ignoring human supervisor who must completely trust the computer in all aspects of decision making

Distribution of functions between humans and machines [Price 1985] –There is no formula for allocation; imagination is crucial to allocation –Allocation can be systematized; combining imagination and systematization yields superior results –Make use of analogous technologies building upon allocation decisions and their results –Consider future technologies; allocation decision cannot be solely based on what exists now –Do it in stages and iterate –Provide interaction between the three design decisions- Physical resources, functional allocation and detailed design –Assure interdisciplinary communication

Design Structure Matrix (DSM) for allocation –Design structure matrix is meant to capture interactions of all sorts between functions so that intelligent combinations of functions into components can be derived –This is a bottom-up approach to the allocation problem –Information in the matrix provides a clue as to how to rearrange the items to form clusters

ABCDEFGHI Engine blockAA Cylinder head BB Cam shaftCC PistonsDD Connecting rods EE Crank shaftFF Fly wheelGG lubricationHH Water pump/cooli ng II DSM for v-8 engine [ Eppinger, 1997]

AFGDEH Engine blockAA Crank shaftFF Fly wheelGG PistonsDD Connecting rods EE lubricationHI