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Module 1: Introduction to System Design & Processes

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Six Functions of Design Process

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We will go through the differentsteps one by one on the design of engineering systems.(Refer Slide Time: 00:48)
As explained in the previous lectures, we start with the system design process with theidentification of needs. So, the focus here is mainly on finding out the original needs.And then based on this needs we go to the operational concept functional requirementssystem architecture and then allocated requirement for these systems once we identifythese requirement for various subsystems then we go for the detailed design and thenimplementation. And finally, we go for the test and verification. So, this is the flow ofsteps involved in the design. So, we start with the need identification.
(Refer Slide Time: 01:32)
So, we will try to see; what are the needs we are trying to identify or what are the needswe are trying to filled using this system design and what is wrong with the currentsituation and why do we need this particular situation, so that will tell us; what are theneeds to be addressed in this particular design. And, another important part is thatwhether the need is clearly articulated or clearly understood clearly mentioned or clearlyrecorded the requirements and the needs of the customer.So, once we have this needs identified we will go for the operations concept for thesystem; since it is a new design, we need to identify some kind of a Friesian conceptwhich will actually help us to develop the system based on these concepts. So, in order todo that what we tried to do is to find out; who are the intended user for this system: howthey use the products or how they actually use these products and how is this differentfrom the present system.So, if we know these things about the users and their preferences and what should bedifferent from the existing we can develop an operations concept, once we have theseoperations concept we will go to the next level of functional requirements.
(Refer Slide Time: 02:40)
So, what specific capability will be provided in this particular system to satisfy thecustomer requirement and to what level of detail we need to provide these requirementsand whether all the element interfaces are well defined within the requirements. So, oncewe have these answers to this question we are actually having our functionalrequirements ready based on that we will go for the design of the system architecture.(Refer Slide Time: 03:06)
So, here we will try to address what is the overall plan of attack what elements make upthe overall approach and are these complete logical or consistent. So, whether the overall
plan of attack is consistent whether it actually satisfy the requirement and whether theircomplete and logical will be identified and verified in the system architecture stage. Andthen we go for the allocated requirements since we have many requirements and manysystems.(Refer Slide Time: 03:34)
So, we have to allocate this requirement amongst the system components. So, we will tryto see which elements address which requirement.So, we do a mapping of the requirements with the components or the physical structure.So, there we do a mapping to identify which are the elements which actually address aparticular requirement identified by the customer. And then we see whether the allocationis appropriate whether the allocation is appropriate or we have did an over allocation oran under allocation. So, this will be analyzed and then there any unnecessaryrequirements.So, we have to go through the requirements and all the requirements are genuine andthere are no unnecessary requirements which warn an edition of additional elements intothe system. So, all this will be analyzed in this stage and once we are comfortable withthese requirements and allocation of the requirements we will go for the detailed design.
(Refer Slide Time: 04:26)
Which again is not part of the system engineering which is more of a componentengineering focus and this that the details are correct do they meet the requirements arethe interfaces are satisfied all these are done by the design engineers or componentengineers and once the components are ready and it is ready for integration again, thesystem engineer will take it over and then start the assembly. And then do theimplementation then basically we will do a testing of the implementation will be testedbasically to understand the solution be satisfactory in terms of cost and schedule.And can we reuse the existing pieces. So, this will be analyzed in the implementation ofstage and once this is completed we will go for a test and verification.
(Refer Slide Time: 05:12)
Basically, we are try to understand or identify what is our evidence of success and willthe customer be happy with this particular system or will the users need; whether the allthe needs of the users are matched. So, we will do a test and verification the end of thedesign process to ensure that it actually satisfy the customer requirements. So, these arethe various steps involved in the design of the system.(Refer Slide Time: 05:41)
So, in order to achieve this we have divided this whole process of the system design in to6 process or the 6 functions of design process. So, these 6 functions are applicable across
life cycle and the first one is define system level design problem. So, here we try tounderstand the whole problem from the customer’s point of view or the stakeholder’spoint of view; try to develop concepts for the system and try to identify the systemboundaries try to identify the requirements and then prepare a originating requirementdocument.So, the purpose of the first level of a design process or the first function of designprocess is basically to define the system level design problem let second function isbasically to develop the system functional architecture. So, here once we have these arethe requirements identify; we try to identify their functions to be provided in the system.And then provide a hierarchical structure for the functions and identify all the functionsand make sure that this functions are sufficient to meet the customer requirements thethird one is to develop the system physical architecture. So, once the functions areidentified, we try to identify the components or the physical systems which actually willprovide these functions in the system this stage is the physical architecture developmentstage and the fourth one is the system operation architecture.So, once we have the system the physical system in place we need to find out how thesystem will be operated what are the operational requirements for the system and thenwe develop an operation architecture which will satisfy the customer requirements thenwe development an interface architecture since we have many sub systems in place. So,we go for an interface architecture which will try to identify are the interfaces needed forthe sub system as well as to the external system, and ensure that there is compatibilitywith the standards. And other requirements identified in the system and make sure thatthere is no loss of data or no loss of data in the communication systems.And finally, once the system is ready developer qualification system for the systemwhere we ensure that the developed system is qualified to meet the requirements of thecustomer. So, in this process this course what will try to do is to go through all thesesteps in details try to identify; what are the tasks involved in each stage or the eachfunction. And then finally, we will develop the qualification system for the main systemwhich will actually satisfy requirements as I mentioned earlier this is applicablethroughout the lifecycle of the system.
(Refer Slide Time: 08:12)
So, for any life cycle of the system these 6 functions are applicable. So, if you take thedevelopment phase or the manufacturing phase or deployment phase we need to identifythe requirement we have to define the problem we need to define the functionalarchitecture we need to define the physical architecture we need to identify the interfaceswe need to identify the qualification system. So, across the life cycle these processes areapplicable. So, we will develop these 6 functions for each life cycle separately and thenidentify the requirement for each life cycle and the function and the architecture for eachlife cycle.(Refer Slide Time: 08:50)
So, to come to the first process which is the define system level design problem which isthe out of the 6 function this is the first one; so here in this stage.We try to develop the operation concept for the system we try to identify the externalsystems which are external to the system being developed. And will try to identify theoriginating requirements we try to identify what are the objectives of the system and howdo we develop the objectives hierarchy and then how to we how to make thedocumentation for the requirements, and then how do we manage the requirements. So,this are the steps involved in defining the system level design problem, we will go
through one by one what are the steps and how do we actually do all these stages in toachieve the system level design problem.(Refer Slide Time: 09:39)
So, as you can see here the system level design problem the major input is stakeholdersinput. So, we have stakeholders it can be the customer, it can be the purchaser or who arethis using it. So, there this input is the major input for the system level design problemthey states the requirements their application their expectation from the system based onthat the output will be coming as originating requirements and operational concepts.So, the major input is the stakeholders input and then the major output from thisparticular stage is the originating requirements we make a document which is calledoriginating requirements document or ORD. And we have few operational conceptswhich can be developed further to satisfy the stakeholders requirements.
(Refer Slide Time: 10:23)
So, this chart actually explains the various stages and what are the inputs and outputs forthe each stage in the first function. Thus, you can see here develop operational conceptthis is the first stage where we have the stakeholders input as the major input and wehave an output from this particular stage as the operational concept. So, we developoperational concept very top level operational concept very abstract and without anymuch details. So, this will be the output from the first stage of develop operationalconcept and once we have this we use this as an input operational concepts as an inputand defend the system boundary.With external systems since every system is interacting with the external system we needto identify what is our focus. So, which one we are trying to focus here. So, that becomesour main focus and that becomes our system of interest and everything which isinteracting with the system will define as external system help us to make boundarywithin which we need to design the system. So, the second stage of defining the systemboundary will help the external system diagram, it help you identify the system boundarythe inputs and outputs. So, the main output from this particular stage is the definition ofthe system boundary the inputs to the system and what the outputs going out of thesystem then we use the operational concept as well as the system boundary inputs andoutputs and this operation concept and stakeholders input will be used to develop thesystem objectives hierarchy. So, every system will be having some object used to be met
which is defined by the customer something like the operational cost or the operationalefficiency.So, these things need to be given a particular hierarchy. So, we cannot have sameimportance to all these objectives. So, based on the operational concept and thestakeholder input an object is hierarchy will be developed which will help us to havesome trade off at a later stage in the design. So, the output from this stage is the object ishierarchy which is the input for operational concept and the stakeholder input now usingall these output from the previous stags we develop analyze and refined requirements.So, this is an important stage where we need to develop all the requirements and analyzeand refined the requirement for the customer now we have an operational concept wehave the stakeholder input. And we have an objective hierarchy based on this we willidentify all the requirements needed for the system and then prepare the originating andsystem requirements. So, there are 2 types of requirement one is the originatingrequirement the other one is the system requirements we will see what are thisrequirements at a later stage. So, this will be the output from this particular stage.Then we go for analysis of this requirement to ensure that they are feasible and they meetthe requirements. So, that stage is the ensure requirements feasibility. So, here the systemengineering team input will be important because that system engineers know whatactually the system requirements really meet the customer needs. So, the systemengineering team input as well as the originating and the system requirements becomethe an input here and when do a design feasibility analysis once this satisfied we gofurther qualification system requirement because every system has to be qualified tosatisfy the requirement.So, we define the qualification system requirements and the output will be the testsystem requirement document and once this is done we will get obtain the approval ofthis system documentation from the higher ups and at the end of this we will be gettingthe originating and system requirements documents. So, this process function of systemlevel design problem we start with the stakeholder’s inputs and within originating andsystem requirements document.So, this is the final output of this particular stage of development this is importantbecause the requirements need to be clearly defined and understood by the stakeholders
as well as the developed the system engineers any constraining requirement will be aproblem at the latest stage of design. So, we should make sure that the requirements areflexible. So, that we can have some freedom at the later stage to make sure that thatproper trade of can be carried out and the system designers are not too much constraint indevelopment of the operational concept as well as the functional and their physicalarchitecture of the system.(Refer Slide Time: 14:40)
So, as I mentioned the first stage is operational concept development. So, in operationalconcept is a vision for what the system is it is a statement of mission requirements anddescription of how the system will be used. So, that is a very preliminary or very abstractlevel of concept where we just define a vision.For what the system is and it is a very simple description of how the system will be usedit will include the information about how the system will be developed operated andretired from the perspective of the system stakeholders and collection of scenarios andsystems interaction with other system. So, in order to develop an operational concept weneed to have to develop preliminary analysis or preliminary concept how the system willbe operated and used and try to identify different scenarios of operation. So, what are thescenarios under which the system will be operated? So, that that will give us some inputon the requirements different various kinds of requirements and their systems interaction
with the other system which is basically an external system diagram. So, these are thethings to be included in the operational concept.(Refer Slide Time: 15:51)
For example, if you take the operational concept for landing on the moon it is again at avery top level concept you can have different concepts to do this.You can have a direct ascent where the vision will start from the earth and it will go onaround the earth and then again will take off to the moon directly from the orbit and landdirectly on the moon and then take off from the moon and then again come directly andcome to the earth. So, this is one way of doing it is a director ascent or you can have anearth orbits and print out where the earth orbit will be the first stage and then it godirectly to the moon and then land on the moon.And then come back from the moon directly take off from the moon, go one roundaround the earth and then land on the earth. So, this is the another possibility anotherconcept which can be employed or the other one is lunar orbit; orbit round out where thealong with the earth orbit it will go one round around the moon and moons orbit and thencome back to the land on the moon then take off from the moon and then come back tothe earth.So, this are the different operational concepts for landing on the moon this is the wayhow we start with the system design because we do not have any concepts to follow it is
a totally new mission the we need to identify what are the possible options for thepossible concepts we can employee then take one of these concepts. And then, developthe next level were we try to develop the operational scenarios based on which we canidentify the requirements to be provided or the functions to be provided in the system.(Refer Slide Time: 17:23)
So, in order to develop operational concept scenarios we will try to identify variousoperational scansions which we can think of for example, if you take the case of anelevator which is very common in most of our buildings if you want to develop a systemfor elevator system for a particular building with multiple elevators or a single elevatorwe will try to make a simple concepts scenario, where we will say that we have 2elevators in 2 sides of the building or 2 different locations and then this will be serving 2different floors at particular frequency
frequency is a particular efficiencies or the performancecharacteristics.And once we have this then we will try to identify what are the different scenarios underwhich this lift will be operated. So, we will try to define this scenarios in detail as muchas detail as possible. So, that it will include almost all the details what we need to knowabout the requirements to be provided in the system for example, we take the scenario ofa elevator passenger lift. So, we try to define the scenario in detail. So, we will try toexplain it that the passengers including mobility hearing and visually challenged requestup service. So, we are trying to include the disabled or the differently abled people also
into this so that the requirements to be met in the elevator will be different if we are notproviding this particular requirement. So, we are including that also here we areproviding the passengers including the differently abled people they request the upservice and the down service they receive a feedback that their request was accepted. So,unless they receive a feedback they will not be knowing whether the elevator is workingor not.So, it is necessary to provide a feedback to the passenger saying that yes your request hasbeen accepted and we will give a feedback that request was accepted and then receive aninput that elevator car is approach. So, not only that the request was accepted it will alsogive an input that the elevator car is approaching and then that an entry opportunitiesavailable, so it should be informed to the passengers that an entry opportunity is alreadymade available this is important especially because of visually challenged people theymay not be knowing that has it has reached at the door is open. So, we need to ensurethat in entry opportunities available and then the passenger will enter the elevator car andthen request the floor and once the passenger requests for the floor the they should getthe feedback that their request was accepted and then receive feedback that the door isclosing receive feedback about what floor the elevator is toping we receive the feedbackthat an.Accent opportunities available and exit elevator with no physical impediments. So, itclearly explains the whole scenario of using an elevator by a passenger from the momenthe requests for a service to the action where he actually comes out of the elevatorwithout any physical impediments it is important to say all these words like includingmobility hearing visually challenged as well as exit elevator with no physicalimpairments all this will define the actual requirements to be provided in the elevator.So, this is just one scenario there will be multiple scenarios like this which will help us toidentify various requirements for example.
(Refer Slide Time: 20:42)
We can define different scenarios like emergency situation. So, what will happen if thereis emergency in the lift that inside the lift door outside the lift? So, what are the things tobe taken care of under this situation and that is a fire in the building. So, if there is a firewhat will be the way in which the elevator should function whether it should provide theservice or it should stop at the point where it is point inside the lift what should be theaction to be taken. So, for that what are the other requirements to be needed what kind ofcommunication system to be provided between the elevator and the building between theelevator and the emergency response team.So, all those things will be identified in this scenario description similarly auto closebreakdown overload maintenance all this scenarios can be clearly explained using thescenarios then we can identify those requirements for to meet such requirements. So, thiswill ensure that we are taking care of all the requirements all the scenarios and ensuringthat the lift which is being this designed we meets the requirements of the customer
meet the various requirement under various operating scenarios.
(Refer Slide Time: 21:52)
So, to describe the scenario we can actually use method called input output trace. So,here the input output trace.Basically gives a picture will representation of the scenarios here we the vertical linesrepresents the interacting people the passenger and the elevator or the systemcomponents the system or the external system and the horizontal represents thecommunication between system and the external system. So, here the passenger is anexternal system and the elevator system is the main system which we are interested. So,we can identify what are the request going from the passenger what kind of feedback iscoming back to the passenger and then what information is being sent from the passengerto the elevator based on the feedback given by the elevator.So, all this can be represented in a pictorial way. So, that it is easy to understand forothers especially the design engineers. So, anyone going through this will understandthat the kind of interaction taking place between the system and its sub system or theexternal systems. So, this is the input output trace for the scenario one which wediscussed we explained in the previous slide.
(Refer Slide Time: 23:02)
So, that was the about the input output trace for identifying the requirements foroperational concept and another factor we need to take care is the external systemdiagram. So, as I mentioned the system interacts with the environment and anothersystem. So, we need to identify the boundary in which the where we need to concentrateour design efforts for that we need to have the external systems diagram which is themodel of the interaction of the system with other systems in the relevant context; thusproviding a definition of the systems boundary in terms of the system inputs and outputs.So, here we are define the system boundary in terms of the systems inputs and outputsthe purpose of this one is basically to explicitly define the system boundary and neededinterfaces. So, using this external system diagram will be able to define the boundary andthe defined interfaces for