And in this lecture we will try to learn about some of theseprocesses which are being used for design of engineering systems.(Refer Slide Time: 00:42)
So, we will be discussing about the 3 major processes which are used for product orsystem development. The first one is known as a stage gate or waterfall process, which isused for mainly for product development. And then the next one is a spiral process,which is again a modification of stage gate process with the multiple stage gates. Andthen the last one is known as system vee, it is a system design process which is known assystem vee.So, let us go to the first one which is the stage gate process.
(Refer Slide Time: 01:18)
These development processes there are multiple stages in the design of a product or asystem. So, every stage of development will be passing through a gate, which actuallyverify the system the design of that particular stage and then decides whether to go aheadwith the design project or not. So, as you can see there are multiple stages or phases oractivities in the development work, followed by periodic gates which are known as thestage gate development process. Because of this stages and gate we call it as a stage gatedevelopment process. A gate is nothing but an evaluation by upper management orwithin the team structure, to ensure the next stage is worth carrying forward.Any product development process should pass through each gate to make it to the pointof product launch. So, there are stages and gates. So, every stage will pass through a gateevery design that stage will pass through a gate and if the fails at the gate the project willbe scrapped or it will be modified to suit that present requirement and that is why this isknown as a stage gate development process. Most of the project will be scrapped at theinitial stages, but not at the later stages because once we put a lot of effort in developinga product and then coming to a particular stage scrapping that project may not be viable.So, most of the cases, the scrapping of the project will be done at the early stages and atthe later stages modification of the product or adding new functionalities of the productto meet the present requirement will be undertaken. Though the project continues the
product the final product may not be the same as which is anticipated in the beginning ofthe process. This is the stage gate development process.(Refer Slide Time: 03:05)
So, the early gates ensure that there is a market for the product, and that it can bedeveloped and manufactured. So, that is the function of the early gates, which actuallyensure that there is a market for the product and the product can be developed andmanufactured. But later gates ensure detailed integration factors such as ensuring that thesoftware functions and all other integration factors are taken into account that is takencare of in the later gates.At each gate listen is to made whether to proceed with the product or kill the product orkill the some features of the product. So, depending on the product and the requirement,decision will be taken whether to kill the project or to modify the project or change someof the features of the product. So, as I mentioned only few projects are killed outright inthe later stages instead specifications are revised in the light of difficulties and budgetallocations and necessary changes are done in the gate analysis.
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This picture shows how the stage gate process proceeds; as you can see that at everystage every design of a product or system starts with the discovery of a new requirement.So, somebody identifies a need for a particular product or a discovers in opportunity todevelop a new product or a system, that is the earliest stage in the development processand it passes through an idea screen, were actually the gate the initial gate somebodyanalyzes that whether there is a good opportunity to develop the product.So, if there is an opportunity to develop the product or that opportunity identified by thediscovery of the opportunity of that particular product or a process, if it is worthproceeding then go ahead with that in the first gate it will be passed. And it will go to thenext level of product scoping, do a market survey, and try to understand what are thecustomer requirements whether there is a real need for that for a particular product, thosethings will be analyzed in the next stage. And again you will pass through a gate and thattakes it to the stage of build a business case for the particular product.
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So, building a business case is the critical homework stage, one that makes or breaks theproject. The technical marketing and business feasibility are accessed resulting in abusiness case which has three main components product and project definition, projectjustification and project plan. So, this is one of the important stages in the developmentwhere all the important factors are analyzed business aspect, a technical aspect and thefeasibility of the project is accessed and decision is taken whether to go ahead with theproject or not.So, as you can see there are multiple stages product and project definition, and I meanyou define the product and the project and then you justify the project and then you planthe project, how do we take this forward from that this to the next level. So, that is thestage 2. And again it goes through a gate where an upper management team will assessthe whole project plan.The project requirements and the feasibility of the project, and once it is satisfied it willgo to the next stage for where actually the design and development; stage 3 where thedesign and development takes place that is the development stage where stage 3 is therewhere the development plans are translated into concrete deliverables.
(Refer Slide Time: 06:16)
The actual design and development of the new product occurs the manufacturing oroperations behind is mapped out, the marketing launch and operation team plans aredeveloped and the test plans for the next stage are defined. So, all these are done in thestage 3 which is the development stage.So, once it passes gate 3 then the complete design and development takes place all thetechnical people will be involved in this particular aspect. And they design the productdevelop the product plan for testing and verification and it goes through the testing stagewhich is the gate 4 and once it passes through the stage four that is the testing andvalidation.
(Refer Slide Time: 06:58)
Where the entire project is tested and the product is tested, and validated for therequirement. The product itself the production manufacturing process, customeracceptance and the economics of the project are analyzed in this gauge, which actuallydecides to on this stage, then once it passes through the gate reaches to the launchingstage of the product.(Refer Slide Time: 07:24)
That is once it passes the testing and verification validation are those procedures, it goesto the launching stage and the product is launched into the market and starts getting
earning money from the project. So, it is a very effective efficient and faster process thatimproves our product innovation results. So, because there are stages and gates actuallymake sure that, whatever you develop at every stage is meeting the requirement and thenonly it goes to the next level of design. So, it becomes efficient and a faster processwhich improves the product innovation results.(Refer Slide Time: 08:03)
Though there are good things about stage gate development process, there are a fewdrawbacks also. The main problem is that real projects rarely follow the sequential flow.As we can see the project is following a sequential procedure, where you take do the firstpart of market analysis then go through a stage gate, then analyze the designed product,then do the fed testing verification etcetera. So, it is going in a sequential way. Most ofthe times the real projects would not do go take these sequential paths. There will bemany parallel activities going on and it is very difficult to capture those activities in thestage gate process.So, this is one of the drawbacks of stage gate process. Another one is that it does notaccommodate the natural uncertainty in the design process especially at the early stages.So, there are many uncertainties in the early stages, which cannot be fully captured inthis process because every stage gate once the gate passes the gate and all of the factorswhich are considered earlier will not be considered again in the next gate. Therefore,many uncertainties are not fully accounted in this particular process; and the working
version of the system is available only towards end of the process, again you do not haveany product till we complete the whole project.So, because it is a sequential process, you need to wait till the end of the process to get ita prototype of the product or a functional prototype of the product which actually willshow you how the product will look like, what are the features and how to improve. Andagain by modification we may have to go back to the initial stage and again pass throughthe same stage gate process, to reach to the next prototype. So, this is another drawbackof stage gate process and that is why there is another process called spiral model.(Refer Slide Time: 09:44)
This is an improved stage gate process, where this methodology is implementedespecially in industries where there are lots of pressures on time delivery or delivery ofthe product in time.So, especially software companies are using this kind of a development model, where theproduct will pass through multiple stage gate process. So, it actually passed through aloop where one end to the other end you will pass through one stage gate, and you get theproduct and again it will pass through another stage gate again you would be having aproduct. So, you will be having different versions of the product that at the end of everystage though it may not be completely functional, it may not be a complete product. So,here one repeats stage gate process several times, before finishing the product to 100percent.
So, the stage gate process is repeated with several times, to get a 100 percent completeproduct and at the end of any of the stage gate processes on has a partial product thatworks that is important. So, you have a partial product that works, at the end of everyprocess it may not be fully featured, but it works. So, that is the thing the product maynot be fully featured, but still it works example is for a software for word processing.If you take the word processing software, you will see that this software will come withmultiple versions. So, the first version may not be having are the features, then after thatsometime that another person will come with the additional features, and he will keep onchanging and at some stage the company will decide to stop that process and then will goto a next product. So, this is typically a spiral process where at one stage gate process, ifthe software windows need to be released in 2010. So, they cannot wait it to 2011 for allthe features.So, the windows 2010 will be released in 2010 with limited features, and as you progressas the time progressed they will add more and more features and become the nextversions will be made available to the consumers. So, this is the way how a spiral modelworks.(Refer Slide Time: 11:51)
So, this animation shows the way in which the spiral model works. So, as you can seethere are four buttons here one is the determinate the objectives of the process of thesystem, identify and resolve risk development and test and plan for the next iteration.
So, you can see here first it will start from this quadrant, where the objectives aredetermined. It will start with the identifying the reload risk concept requirements conceptof operation requirements, plan risk analysis and prototype one. As we can see aprototype one is available once you complete one stage gate process of course, there aredifferent stages in gates in this. And once we complete this stage gate, you will be gettingat the end of this stage gate process you are having prototype one.Again if the next level it will go once we complete the prototype one, we will not stopthere again it starts the process again requirements verification development plan riskanalysis and prototype two is available made available, again it will pass through andyou will be getting prototype 3 also. So, you can see here at the end of every one stagegate process you have a prototype: prototype 1, prototype 2 operation prototype anddepending on the requirement.This will be keep on increasing once the company is satisfied with the operationprototype then it will go for detailed design code integration test and implementation. So,this is how a spiral gate process works. As I mentioned the advantages here is that youknow that you can see a prototype right at the end of the first process, you do not need towait till the end of this stage, where to the release stage to see a final product. You willbe seeing a product and then it is easy to make the changes in the product by looking atthis prototype and then you can see the improvement taking place over a period of time.As you can see in software this typically happens the first version will come, and thenagain that will go through another design process, the second version will come like thatkeep on improving on the design. This is good for time compressed industries becausethey can deliver the product even though it is not fully operational, but partiallyoperation product will be available for the consumer. This kind of process cannot beapplied for consumer products mainly because you cannot have a partially workingproduct to the customer. So, mostly if you go for a stage gate process or some otherprocess to ensure that the fully functional product is made available to the customer.
(Refer Slide Time: 14:15)
Another process is known as the system engineering Vee. So, we saw that stage gateprocess and spiral process. So, both this got their own problems and difficulties inimplementing for a complex engineering system that is why we go for a another processcalled a system engineering Vee.(Refer Slide Time: 14:36)
This is coming the name it comes from; the shape of this particular as the process it lookslike a Vee where the activities involved in this process development are taking placesome of them are a sequence and some of them are parallel. So, you can see many
parallel activities in this a completely sequential, since there are some parallel activitiestaking place that I why these looks like a v shape and that is why it is known as Veemodel of system development.This actually starts with the system user requirements and concepts of operation thensystem requirements and architecture component design, then fabrication assembledintegration and test and system demonstration validation. So, the horizontal line hereactually shows the difference or the domains of system engineers and the componentengineering domain. It will go a little bit more into this process by taking another case.(Refer Slide Time: 15:26)
So, here you can see all the processes involved in the system vee engineering process;the left hand of the vee actually represents the decomposition and definition stage ofsystem design, which actually it starts with the customer need. So, you identify thecustomer need at the top and then go through the different stages of identifying thesystem performance specification and expand the performance into components anddesign specs to see a verification plans and then gives this to the domain experts, whoactually define the system and then assemble and integrate and then again pass it to righthand side of the Vee which is the integration and qualification plan.So, here you can see it is a decomposition and here it is an integration. So, we aredecomposing a problem into sub tasks and then going ahead with the design, and oncethe design is completed we start making the system and then integration. So, this stage is
a decomposition stage and this is a integration stage. As you can see here, we start withthe customer need then understand the system requirement from the customerperspective and develop the performance specifications, then go to the performanceconfiguration items into design to specs and configuration item verification plan. So, weidentify the performance specification and identify the systems and components neededfor this particular performance, and then parallely develop the verification plan also andthen pass it to the technology domain experts to design the actual components andsubsystems.So, the horizontal line again represents the division of job between the system engineersand domain experts here. So, once this is completed, this design performanceconfiguration items and design to specs are identified, then the design engineers willdevelop the components and integrate them fabricate assemble and integrate and inspectto build to documentation.There will be a documentation which actually specify what are the requirements or thespecifications the component should satisfy for the build to system. And then we will goto the integration stage, where the configuration items are assembled and theperformance is verified then again the system is integrated with all the sub componentsand sub assemblies, and then you demonstrate and validate the system to the customerand then once the customer accept it goes to the customer. So, this is how the systemdesign process takes place in an engineering system.As you can see here this is the timeline you can see there are many activities taking placeparallel. Here you can see there as the process of understanding the customerrequirements going on, you start the developing the system performance specificationsalso and it keeps on modifying as we progress with the time. And once it is finalized Imean as the system performance specification being developed performance here intodesign two specs and see a verification plan that is configuration item verification planalso will be developed. So, many parallel activities take place along with
the sequentialactivities also, that is why we have a v shape for this particular system design.
(Refer Slide Time: 18:42)
And these are the interactions between different stages in V as I told you thedecomposition stage and integration stage, here we can see that at the mission analysis orthe identification of requirement stage or the need stage, there will be a continuousquality improvement plan depending on the operation and requirement.So, as we final system test is done and then the operation of the system is going on,based on the feedback the requirement will be modified. So, that the next level ofdevelopment will be incorporating the requirements identified from the operation. Thenthere will be a final test the validation plan will be checked if the system requirements.So, as we develop the system requirement a validation plan also will be developed andthe system will be tested against this validation plan or validated against the plan alreadyworked out. Similarly there is a verification plan for the components and subsystems andthe system so that will be the verification plan will be coming from this stage and it willbe going, and it will be the system will be verified against this plan.Similarly the component decomposition the physical decomposition and the test plan willbe developed at this stage, which will be tested again the components which are beingdeveloped by the design engineers. So, there will be lot of interaction between this thetwo arms of the V and that actually helps to continually improve the design process.So, this is the design down stroke and the manufacturing and assembly upstroke is thisone.
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This shows the afford product development system. So, Ford Company uses this kind ofa development system for their products. So, it starts with the customer must send onceas you know that what are the requirements of the customer for a particular car or aparticular vehicle from a Ford motor company. So, they look at these customerrequirements, and then take this input and develop the purchase and owner operatorrequirements regulatory requirements and corporate requirements of the system. So, allthese requirements are identified at this stage, and for this input the corporate knowledgewhat is the knowledge base what they have will be used to improve on this one. Alreadythe company will be having a lot of data base from different correct customers anddifferent products that will be used to define these customer requirements and thatcustomer requirement will be the final checkpoint where when you have the system.Then once the requirements are identified, then it will go to the vehicle levelrequirements that is more like this is customer requirement and then it go to the vehiclelevel requirements, identify the vehicle attributes, vehicle system specifications and allother requirements related to the vehicle. And once it is identified it will go to the nextlevel of system and subsystem level system specification.So, the company will develop specifications, based on the requirements are to beidentified from the customer as well as from the vehicle requirements. Once that isidentified it will go to the fabrication part design and fabrication plan and this will be
done by the domain experts. So, this will be the job of system engineer and again once itthe part design is completed and fabrication is completed, it will go to the verificationplan and once it is will be verified against the requirements or the specificationsidentified at this stage, and again it will go to the vehicle verification.Verified against the vehicle level requirements and goes to the purchase or commercialaspect or the go to the customer, and that will be verified against the customerrequirements and once that satisfied, we will go to the customer where the customer willbe satisfied with the system. So, this is the flow of process in a system vee model ofengineering system development which is widely practiced in industry.(Refer Slide Time: 22:27)
That was about the V-model; and there is another model which is not so, popular, but stillfor your information again I just mentioned it here it is known as N model. So, the downstroke of V-model in the previous case which is this will be split into two components toemphasize the difference between functional and physical models because in theprevious V we have a requirement identification, development of the functionalconcepts, and then developing the design and then manufacturing of this. So, everythingis in the left arm of the V.So, in this case in N model, I try to change or try to split this into two components whichactually will be one will be for the functional model another one will be the physical
model, that is only difference here; which is not very popular N model is not verypopular, but the most of the companies still use the V-model only.(Refer Slide Time: 23:23)
So those were the system design methods, used for development of complex engineeringsystems.(Refer Slide Time: 23:31)
So, let us discuss about how actually a system design process takes place, in a realengineering world. So, this again from an up level view, I will be giving a top level viewof how this is done, so because we will be going into the details at a later stage, but some
of the basic activities taking place in the design of an engineering system. So, thisactually shows the process involved in the designing of a satellite system.(Refer Slide Time: 24:06)
So, as you can see the say first stage we will develop the establish the purpose of themission here, and then we try to find out what are the boost phase missiles required andprovided right theater communication requirement, all those things will be established inthe mission. Then we go to the next level, where the decade orbit, attitude, lifetime,payload, mass for etcetera are gathered. So, the key requirements like this are gathered inthis stage and then define a concept of operation that is defined the conops. Conops isconcept of operation.So, based on these two purpose of the mission and the key requirements identified forthis project, a concept of operation will be defined. Where actually how many what willbe the constellation of this particular system, what is the launch strategy what are theground networks needed for this one, what are the availability of different system andwhat is the method of data return or what is a data rate needed for this. So, these are thethings done in the initial stage. Then, we will go to the next level where the subsystemdevelopment will take place.
(Refer Slide Time: 25:11)
So, consult the subsystem develop an initial design concept. So, have different conceptfor this and term. Once you identify the best approach identify the data models identifythe constraints and performing initial subsystem trades, develop an initial design conceptfor the whole system.(Refer Slide Time: 25:31)
So, here you define the spacecraft configuration, the combined subsystem expert datamodels perform preliminary sizing of the system. And once you do the preliminaryconcept will go to the next level of Conceptual design process.
(Refer Slide Time: 25:42)
So, we have a converged design after many iterations of concepts, where we capture theripple effects of having multiple iterations has generated an internally consistent designand look for system drivers potential system trade off.So, what are the drivers for this particular system design and what are the potential tradeoff, you need to have to define this system. And once you have this design process iscompleted, we will document the system the whole design process where therequirements and assumptions are documented. The results of the design conceptdevelopments are recorded and then record any other outstanding issues. So, this is thefirst level of design process, where we develop at document for recording all therequirements design concepts.And whatever the information we gathered from the process through this process ofdeveloping a particular system, where we follow a process were identify the purpose ofthe mission, then identify the requirements and then develop the concept of operations,
initial concepts, refine the concepts, and finalize a particular concept to launch thesystem; that is how a typical top level process works.
(Refer Slide Time: 26:55)
So, let us design some of the important key terms, which we may be using frequently inthe design of the system. Definition of the system we already saw, which is a collectionof entities that interact to generate behavior not found in the individual entities, and thereare the entities make up a system are usually referred to as subsystems. And eachsubsystem may be a system in its own right and a system takes inputs and generatescorresponding outputs.(Refer Slide Time: 27:22)