Lecture 3 Conceptual System Design PDF

Systems engineering (ISAN3070) BINOD TIMILSINA, INÊS PEIXOTO LECTURE 3: CONCEPTUAL SYSTEM DESIGN UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) Learning objectives By the end of this lecture, we will have broad knowledge of the following Definition of needs a...

Systems engineering (ISAN3070) BINOD TIMILSINA, INÊS PEIXOTO LECTURE 3: CONCEPTUAL SYSTEM DESIGN UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) Learning objectives By the end of this lecture, we will have broad knowledge of the following Definition of needs and requirements Requirement analysis Conceptual design Process of conceptual design Importance of conceptual design in systems engineering UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 2 Key terms System planning means the development of overall plan for successful system design ─ Focus is towards successful management of system design process System architecting means the development of conceptual model that defines structure and behaviour of the proposed system. ─ Focus: To understand structure and purpose ─ Shows how different components & elements interact with each other and other systems System design the process of defining system components and elements (e.g. system architecture, system models, conceptual design) and the interface between them. ─ Focus towards implementation and practice i.e. development of complete set of design characteristics that are almost ready for implementation. Note the difference between these terms, don’t mix them together. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 3  Key terms, example System planning: development of overall plan to successfully complete the SE project from need identification to phase-out of the system after its operational life. System architecting comprises: defining and selecting the concept decomposing the system and conducting a mapping of form to function Figure: Architecture of the battery electric vehicle (Makrygiorgou & Alexandridis, 2016) defining key operating parameters of system System design: defining and selecting the actual values for key operating parameters Note the difference between these terms, don’t mix them together. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 4  Conceptual design: What is it? Conceptual designs provide a clear picture of the system, i.e., the architecture, diagrams, sketches, and models help to understand and show what the system looks like, what function it serves -> forms and functions help to understand the user’s needs and requirements to develop a system that actually meets them help to make a commitment, predetermine the function, form, cost, and development schedule. Note: “Customer’s needs and requirements” and “system’s requirements” are different things. Do not mix them together. By developing system’s requirements, we define the means to meet customer’s needs and requirements. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 5  Customer’s needs and requirements Vs System’s requirements Customer’s needs and requirements: Describe the system’s function and features from a customer or user perspective. Usually expressed in natural language ………> no technical details. In defining customer needs and requirements it is essential to understand the user environment and application domain. System requirements : Precise and complete set of specifications with great technical detail - - > clearly specify what should be developed Developed after identifying customer needs and requirements Note: Sometimes customer and user can be different people; in this case, the user requirements can be given by the customer to the team who performs systems engineering. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 6 Conceptual design, example 1 We want to build a smart parking device that allows us to track the time of parking so that we can charge for the actual time used for parking. Figure: Conceptual diagram for developing smart parking place UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 7 Conceptual design, example 2 Figure: Conceptual diagram for order tracking system for a manufacturing company UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 8 Conceptual design, example 3 (a) Low cost design (c) Accurate dial design (b) Minimum input displacement design Figure: Weighing machine (Campbell, Cagan & Kotovsky, 1999) Note! Conceptual system design occurs in a dynamic environment i.e. changing user preference. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 9 Conceptual design, example 4 How about these examples? UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 10  Exercise: Conceptual design 1. Your company needs a new supplier of raw materials for manufacturing. Develop the conceptual design of a system to select the best suppliers. 2. You want to propose a student feedback system to our university. Develop the conceptual design of the system that you want to propose. 3. You want to develop an unarmed aerial vehicle. 4. You want to develop a self-driving car for the public transport system. 5. You want to develop a high-speed camera. Remember! the diagrams, sketches, 6. Think your own idea for a system. and models plays very important role in developing a system, especially at Your Task early stage. Sketch a conceptual design for one of these based on your own current understanding – don’t worry about the real outcome, it’s an exercise. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 11  Principles of conceptual design, mechatronic systems 1. The two key characteristics of any system aimed 4. In pursuing the goal of increasing the system at operating in a dynamic environment should be value, units may, at their discretion and with the agility and autonomy. Here, approval of affected units, Agility means the ability to rapidly change Compete and/or co-operate with each other the system behavior in response to, or in (autonomy) anticipation of changes in its environment, and Construct, deconstruct and reconstruct links with each other (self-organisation) Autonomy means the ability to decide when and how to change the system behavior Disconnect units considered ineffective and without waiting for external instructions. connect new promising units, temporarily or long-term (evolution). 2. Systems should be designed as networks of autonomous units, rather than hierarchies. 5. During the conceptual design stage, considerations of concepts related to the three 3. All decisions on system behavior should be fundamental elements of a mechatronics system, made through negotiation among affected namely, processing of information (communication constituent units. Negotiations must lead to the and control), conversion of energy, and movement increase of the specified overall system value. of materials should be done concurrently and interactively. (Rzevski, 2003) Note: In mechatronics, electrical and software engineering are combined to solve a wide range of problems. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 12  Process of conceptual design Customer needs and requirements System architecture/Design concept Design review/assessment Concept for further development Figure: A novel model of conceptual design process (Chong, Chen & Leong, 2009) UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 13  1. Problem definition & need identification Problem definition The gap between ‘as is’ and ’to be’ states - based on a real deficiency, e.g., system not meeting performance requirements ─ The gap may exist, but not be the priority (in relation to other gaps) Should reflect the customer needs and requirements Helps to focus system development and planning, keep track of efforts, and validate the system Need identification Identifying customer’s true requirements and possible constraints Reflects the issues that a customer must solve ………> level of priority Customer wants are translated into more specific system level requirements System requirements Set of features and behaviors of a system that must be fulfilled Clearly define problem - > Identify actual need -> Develop system requirements (what is needed to solve problem) For example: In manufacturing, one defect rate is 10/100, and another is 25/100, but tolerance limit is set at 5%. In the second case, the defect rate is much higher than the tolerance limit (i.e., real priority to solve soon) Otherwise manufacturing costs become much higher than the expected value. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 14  Problem Definition In system design: identify and describe customer’s needs and requirements -> Requirement Analysis. Needs and requirements define something that the system must do …….> ”must-have” feature Defining actual needs and requirements is one of the main inputs in a systems engineering process. ✓ Reminder: Systems engineering process ─ comprehensive, iterative, and recursive problem-solving, implemented in a top-down approach ─ transforms user needs and requirements into a set of system requirements, generates information for decision-makers, and provides input for the next level of development. ─ applied sequentially, level by level, adding detail and definition with each level of development. Different process models can be appropriate (e.g., Waterfall model, Spiral model, Vee (V) model, Iterative model, Agile product development model, etc.) ─ There is no single common model for the systems engineering process. Each project is different - the systems engineer adapts the process to meet project needs. Regardless of the model used, the process starts with systems engineering process inputs (SEP). UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 15  Systems engineering process inputs (SEP) Recap: Systems engineering process: Conceptual system design …….> preliminary design …….> detail design and development …….> test, evaluation and validation …….> production, utilization, disposal. For conceptual design, the most important step is to identify systems engineering process inputs (SEP) i.e., the most important in the whole process ─ SEP includes a whole range of information and matrices ─ Goal: understand the context, project goals, key success factors, available resources and so on. ─ Understand well the problem before moving forward in the design process. SEP inputs include ─ Customer’s actual needs and requirements ─ Project constraints and limitations ─ Functional requirements Among these SEP “customer’s actual needs and requirements” ─ Performance requirements and “project constraints and limitations” are the major inputs ─ Design requirements to systems engineering process. ─ Derived requirements ─ Allocated requirements UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 16  Need identification, a closer look How to identify customer’s actual needs and requirements? By asking questions, e.g.,, What is required of the system in “functional” terms? ─ What does the system must do? What are the “primary and secondary (functions that depends on other functions)” functions? ─ Functional flow block diagrams might be useful What could be done to alleviate the stated deficiency? ─ There might be different alternatives to meet the deficiency ………> what are they? When must this be accomplished? ─ Time frame Where is it to be accomplished? How many times and at what frequency must this be accomplished? Remember! at conceptual system design we are focused on what to address, not how to address. We develop a concept based on which we make further decisions, e.g., what technology to adopt, what subsystems and components are needed, how to develop an interface between them, etc. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 17 Who are the customers? Primary functions of systems engineering: ─Development ─Manufacturing/production/construction The customers are people who ─Deployment perform these primary functions ─Operations of systems engineering. ─Support Among these is the key ─Disposal customer, who defines the ─Training system’s operational ─Verifications requirements. ─……………… Also relevant: investors, regulatory bodies, board members, suppliers etc. i.e., “stakeholders” - any person who can influence the system’s life cycle. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 18  Basic questions to operational requirements Basic questions that help to define operational requirements: Where will the system be used? - -> Operational distribution or deployment How will the system accomplish objectives? - -> Mission profile or scenario What are the critical parameters? - -> Performance and related parameters How will various system components be used? - -> Utilization environments How effective the system is in performing mission? - -> Effectiveness requirements How efficient the system is in performing mission? - -> Efficiency requirements How long the system will be in use? - -> Operational life cycle What are the environments where effective operation is expected? - -> Operating environments UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 19 User defined Vs System engineer defined concept Design solutions (based on user defined functional Fuzzy requirements (or functional specification) specification) Figure: User defined weighing machine Figure: Systems engineer defined weighing machine (Campbell, Cagan, & Kotovsky, 1999) Note: In the original source these figures are has been defined a bit differently. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 20 Examples of key requirements in systems engineering 1. Functional requirements --> define systems behavior and operation, i.e. Input --> process (system behavior) --> output --> what system must do. 2. Non-functional requirements --> help a system to operate efficiently --> not mandatory --> but typically increase a system’s overall reliability and quality, e.g., security feature, portability, compatibility requirements, legal requirements etc. --> constraints in system design and manufacturing. 3. Performance requirements --> set of criteria that defines how things should perform in a specific set of circumstances or operating environment. E.g., response speed, throughput time, storage capacity, etc. 4. System technical requirements --> set of factors required to deliver a desired function or behavior to satisfy a user's needs and standards. --> define how the system is built --> specifications for technology. 5. Operational requirements --> set of criteria that define system’s operating environment, e.g., the system must run at 240 volt, 50Hz, 16 Amp --> also defines a series of actions needed to obtain desired results. 6. System specifications --> set of criteria that describe the operational and performance requirements. Note: Specifications include many things, e.g., material, product, packaging specifications etc. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 21 Requirement analysis Requirement analysis is an iterative process and can be identified at different levels, level 0, level 1, level 2, level 3, etc. Level 0: Identify top level requirement (i.e., system level requirement) Level 1: Identify subsystem level requirements Level 2: Identify component level requirements, …. In conceptual design we focus on system-level requirements (we have not done the system design yet) and it is too early – and difficult – to define requirements at lower level. The iterative nature of requirement analysis is not visible in different process models (e.g., Waterfall, Vee (V), Spiral, etc.) but we must consider it, it exists in practice. 22 Characteristics of good requirements Well-formulated requirements are: Achievable Verifiable Unambiguous Complete Consistent Important! Requirements must be expressed in terms of need, not solution --> they should address “why” and “what” questions not “how”. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 23 Models for elicitation of customer needs and requirements There are four basic models for elicitation of customer needs and requirements 1. Scenario based models, e.g., use cases, user stories 2. Class based models, e.g., class diagrams, collaboration diagrams 3. Behavioral based models, e.g., state diagrams, sequence diagrams 4. Flow based models, e.g., functional flow block diagrams, data models UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 24 2. Advanced system planning and architecting Recap: System planning: develop overall plan for successful system design. System architecting: develop conceptual model to define structure and behaviour of system. Both tasks start when problem definition and need identification have been completed Primary focus: To bring a new or improved capability into existence System planning and architecting includes ❖ Programme requirement definitions ✓ = Operational and functional requirements, which leads to the development of Programme management plan ✓ Describes how different managerial and technical activities will be managed, controlled, and tracked ✓ Leads to the development of technical requirements and system engineering programme requirements UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 25 Development of technical requirements Technical requirements: Functional characteristics that the system must have for successful execution of the system’s mission, e.g., performance, reliability, availability… Can be developed in different ways, e.g., by Further examining the operational and functional architecture Proposing and analyzing alternative technical concepts Performing feasibility analysis Selecting maintenance and support approaches, etc. Remember! Technical requirements establish the ground for developing system specifications at lower levels System specifications: operational and performance requirements UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 26 Development of system engineering programme requirements System engineering programme requirements: The configuration of the system necessary for a smooth and efficient running of the system. They are developed by: ─Confirming system engineering designs, and answering questions like √ How does the system work? √ What are the qualities and properties of the system needed to meet the solution objectives? They help in the preparation of the system engineering management plan ─which describes the overall management approach for the different activities, e.g., processes, tools, and control measures. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 27 Advanced system planning and architecting, summary Type A: System specification Functional characteristics that the system must have for the Technical and performance characteristics successful execution of the proposed system and product. Operational requirements Maintenance and support concepts Functional descriptions Design requirements Subsystem allocation etc. System engineering management plan describes overall management approach Operational and functional in regards to different activities, e.g., requirements processes, tools, and control measures. System engineering programme requirements are the How different managerial and technical activities will be managed, configuration of the system which is must for smooth and controlled, and tracked? efficient running of the proposed system. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 28 3. System design and feasibility analysis Recap: System design: Process of defining characteristics of components and elements of a conceptual model and the interface between them. Feasibility analysis: preliminary examination of whether the system can be taken into further consideration or not – is it feasible? Why to conduct feasibility analysis? To identify feasible alternatives --> A need can be addressed in several ways. To avoid mistakes --> Choices have impact on lifecycle cost, operational and design characteristics Challenge: How to reduce the number of solutions and identify the best option Identify various system level design approaches or alternatives Evaluate feasible alternatives in terms of performance, effectiveness, maintenance and support, and life cycle economic criteria, Recommend preferred course of actions --> the best solution. Remember! The user need should dictate and drive the technology, and not vice versa. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 29 4. Identifying system operational requirements Operational requirements: capability of a system that has significant impact on the level of performance, system reliability, availability, maintainability etc. For example: Once the battery is fully charged it should last for 5 hours. The system should have provision for improvement The system should be compatible to ………. Operational requirements Defined on the basis of identified needs and selected technology Should be developed at an early stage, as detailed as possible Presented as operational scenario or as set of operational requirements UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 30  Operational requirements, example The bridge next to our university: Have you thought of its operational requirements? Operational requirements for a bridge can include: Traffic information - - > Helps in deciding the number of lanes. ◦ The bridge should be operational 24/7 and should be able to handle along one day: ◦ 2000 cars These are ◦ 120 taxis, 20 busses assumption ─ 200 commercial vehicles, 20 large trucks values, only for ─ 300 cyclists, 500 pedestrians learning purpose. Operational life: 50 years - -> determines the quality of construction materials. Maintenance downtime: 1 day or less. Rate of waterflow and estimated rain fall (based on history) - -> to decide waterway openings. Remember! Operational requirements are basis for preliminary design. We will come back to this example in the next lecture. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 31 Factors influencing operational requirements Factors that influence operational requirements: Mission definition Performance and physical parameters Operational deployment or distribution Operational life cycle (horizon) Utilization requirements Effectiveness factors Environmental factors UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 32  Factors influencing operational requirements (cont) Mission definition (scenario) Describes core purpose of system i.e. What should it accomplish? How will it accomplish objectives? Performance and physical parameters Define operating characteristics of system, e.g., size, weight, speed, range, capacity, etc. Help to identify critical performance parameters and their relationship to the mission Operational deployment or distribution Identify equipment quantities, software, personnel, facilities, and so on. Which location? When does the system become fully operational? Operational life cycle (horizon) Anticipated time that the system will be in operational use Who will be operating the system and for what period of time? UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 33 Factors influencing operational requirements (cont..) Utilization requirements Anticipated time of system and its elements to be in operational use, e.g. hours of operations per day, use of total capacity etc. How is the system to be used by customer, operator, or operating authority in the field? Effectiveness factors Define the effectiveness of system Can be measured against cost of operation, operational availability, maintenance downtime, and so on. Environmental factors Environment in which the system is expected to operate (e.g. temperature, humidity etc.) Transportation (how to handle in transit?), storage modes, and so on. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 34 5. System maintenance and support Refers to planning and analysis of maintenance and support activities ─Purpose: To guarantee well-functioning of the system throughout its lifecycle ─Well-functioning depends on effectiveness of maintenance and support infrastructure Beneficial to plan maintenance and support early during the conceptual design ─Maintenance and support system should be planned for the entire system System maintenance and support plan includes ─Level of maintenance ─Repair policies ─Organizational responsibilities ─Maintenance support element ─Effectiveness requirements, and ─Environment UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 35  System maintenance and support plan Levels of maintenance ─ Maintenance and support activities can be carried out in different levels ─ E.g., site where the system is functioning, nearby workshops or manufacturer’s facilities Organizational level ─ Carried out at the operational site where the system is functioning ─ Includes very minor servicing ─ Performed by persons with low level of maintenance skills Intermediate level ─ Carried out through mobile units or at a fixed workshop. ─ Major servicing, e.g. parts repair, detail inspection, system adjustments and calibrations ─ Performed by personnel with intermediate level of maintenance skills Manufacturer level ─ Carried out at the place of manufacturer ─ Performed by specialized personnel with high level of maintenance skills UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 36 System maintenance and support plan, cont.….. Repair policies ─Indicate what kind of system maintenance to be developed ─ e.g., non- repairable, partially repairable, or fully repairable ─Provide early guidelines in designing system components ─Developed and established during conceptual design phase, and subsequently updated as the design progresses Organizational responsibilities ─Define who is responsible for maintenance ─ e.g., customer, producer, third party or a combination of these ─Defined in early phase of system design -> impacts activities like repair policies, warranty and guarantee provisions. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 37  System maintenance and support plan, cont.….. Maintenance support elements ─ Describe equipment needed for maintenance and support activities ─ e.g., spare and repair parts, test equipment, trainings etc. ─ It’s an input to design, test provisions (built in Vee model’s external test requirements) packaging, transport, personnel and skill level, constraints etc. Effectiveness requirements ─ Clarify how effective the maintenance and support system should be ─ E.g., availability of spare parts, training times, reliability of training equipment, item processing time etc. Environment ─ How external factors impact the design of maintenance and support provision ─ E.g., temperature, shock, vibration, humidity, noise, ground conditions etc. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 38 6. Identifying and prioritizing technical performance measures (TPMs) Recap: TPMs: quantitative values (estimated, predicted, or measured) that describe system performance, e.g., process time, speed, size, weight, range etc. Derived from design dependent parameters (DDPs) ✓ Characteristics to be inherent in the design and impacts the operational outcomes ✓ Example: Design life, reliability, producibility, maintainability etc. Serve as foundation to the system design Help ensure that the system to be designed will serve the desired needs TPMs hierarchy can be developed on the basis of ✓ Prioritization ✓ Quality function deployment (QFD) UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 39 TPMs hierarchy: Prioritization Prioritization: method of evaluating and arranging activities according to the level of importance Can be done considering several factors: economic, available technology, environmental impacts, etc. Designer should identify, understand and make tradeoffs between TPMs ✓ E.g., speed Vs size, production quantity Vs quality, range Vs clarity of message etc. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 40  TPMs hierarchy: Quality function deployment (QFD) Team approach for defining & translating customer needs & requirements into technical solutions Identified needs are prioritized & summarized to matrices called house of quality ✓ Enables better correlation between customer needs (what) and the proposed solution (how) Challenges to identify: ✓ Good set of requirements (what & how) ✓ Exact relationship between customer needs and proposed solution Recommended reading: Hauser, J. R. & Clausing, D. (1988). The House of Quality. Harvard Business Review, 66 (May–June), 63–73. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 41 Quality function deployment (QFD),cont.… UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 42  Quality function deployment (QFD), an example Scale for roof (correlation between how i.e. design specification) ++ Strong positive How? + Positive What? None - Negative -- Strong negative Scale for body (relationship between what & how) ʘ Strong 9 օ Moderate 3 ∆ Weak 1 None 0 Customer importance can be evaluated in 1-5 scale, where 1 = least important and 5 = most important Similarly, competitors benchmarking can be done in 1-5 scale (1 = weak and 5 = strong in comparison to competitors) UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 43 7. Functional analysis and requirements allocation to subsystem and components Functional analysis: Iterative process of translating system requirements into lower-level requirement as far as possible, which is the basis for ─ Translating system requirements into detail design criteria ─ Identifying resources necessary for realizing and supporting the functioning of system, e.g. reliability, maintainability, human factor, and supportability requirements. ─ Identifying operational conditions and system maintenance activities Divide system level requirements into subsystem level, as far as possible --> to identify system design input criteria and constraints. Presents system’s functional architecture --> baseline for system physical resource requirements. The process of functional analysis and allocation can be enhanced through: ─ Functional flow block diagram ─ Functional allocation ─ The system architecture UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 44 Functional flow block diagram Block diagrams that define the functions and their interrelationship in a system. They help: to decompose top level functions into second level function, second level functions into third level functions, and so on, e.g. main equipment, system elements, spare parts etc. to identify the relationship between functional requirements and resource needs to establish sequence, design relationship and interface among different activities UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 45  Functional allocation Process of confirming whether a particular function can be accomplished or not. ─ It helps in minimizing the use of extra physical resources For the purpose, functions are grouped according to related functions, and then the search is made for solutions that can serve multiple functions Each group should be designed in such a way that if necessary one group can be removed without impacting other The communication between each group should be avoided as far as possible; this helps in reducing the complexity of the system. One of the important objectives of the functional allocation is to practice open architecture approach, so that, if necessary, the system can be upgraded or degraded without disturbing other subsystems. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 46 The system architecture The formal description of systems structure, including system components, their interrelationship, and operational requirements Represents top level system requirements Describes how system elements interact in moving from what (problems) to how (solutions) UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 47 8. System trade-off analysis Trade-off analysis: Method of selecting one alternative over other based on facts. Performed on the basis of factors like ─ Commercial off-the-shelf components Vs self manufacturing ─ Manufacturing process ─ Cost of resources ─ Material phase-out ─ Logistic and transportation ─ Maintenance and support, and so on. First define evaluation criteria and follow through accordingly. Iterative process of synthesis, analysis, and evaluation against functional base line e.g., TPMs UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 48  Concept generation Vs Concept selection Concept generation: find systems that do right thing Concept selection: develop the best systems that do right thing and do it well. Remember! Concept selection develops the most promising concept, e.g., combine good features from different concept. Some concept generations tools: Many tools facilitate concept System architecture generation and selection. Mapping function to form A learning mindset of “let’s just Logical decomposition of function and form try everything, let’s go forward with this” might be useful in early Brainstorming stages of concept generation and Mind map selection. Morphological matrix Some concept selection tools: Key idea is to answer these: Weighted rating method -> Weights given to evaluation criteria In how many different ways we can address customer needs Pug matrix -> Criteria scoring based on reference values and requirements? Analytical hierarchy process -> Pairwise comparison What is the best system design concept to move forward? Quality function deployment ✓ Selecting a concept requires defining the evaluation criteria first! UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 49 9. System specification In conceptual system design, System specifications (Type A) represent top level system requirements, which can be further qualified into lower level requirements. For example ─ Product specification ─ Process specification ─ Technical and performance characteristics ─ Operational requirements ─ Maintenance and support concepts ─ Functional descriptions ─ Design requirements ─ Subsystem allocation etc. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 50  System specification, example of Level 0 Example: passenger car Example: elevator Body type: Metal frame Capacity (person): 12 Dimension: Power rating: 75 KW ─ Length = 3.5 m Speed: 1.5m/second ─ Width = 1.5 m Time for door opening and closing: 2 second ─ Height = 1.6 m Minimum weight: 1500 Kg Engine size: 1794 cc Maximum weight: 2000 Kg Engine type: Petrol Height: 5 m Weight: 6 tons Width: 2.5 m Performance (full load): 170 Km/hr Floor distance: 5 m Transmission: Manual six gears Note: These specifications may not be true but it’s a good example to understand system specification at Level 0. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 51 10. Conceptual design review Process of validating system’s operational requirements, maintenance and support concept, specified TPMs, functional analysis, and allocation of system-level requirements. ◦ Needs are justified and verified against system’s requirements ◦ e.g. performance, reliability, maintainability, supportability etc. ◦ Requirements satisfied? --> Approve design --> Otherwise: Revision and corrective actions Main goal: To identify the best option for system design and examine cost effectiveness Other purposes of conceptual design review: ─ Formal check of design with system and subsystems operational requirements ─ Confirm that the system elements acts as a system, in conceptual phase ─ Provide justification for various decisions made UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 52  Exercises: Conceptual design 1. Your company needs a new supplier of raw materials for manufacturing. Develop the conceptual design of a system to select the best suppliers. 2. You want to propose a student feedback system to our university. Develop the conceptual design of the system that you want to propose. 3. You want to develop an unarmed aerial vehicle. 4. You want to develop a self-driving car for the public transport system. 5. You want to develop a high-speed camera. Remember! the diagrams, sketches, 6. Think your own idea for a system. and models plays very important role in developing a system, especially at Your Task early stage. Sketch a conceptual design for one of these based on your own current understanding – don’t worry about the real outcome, it’s an exercise. How do you view this system design problem now? What was missing in your initial ideas? UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 53  Assignment Three (Voluntary) Completing these exercises will improve your understanding of lecture topics, help with exam preparation, and support project work. Try to answer the following questions: 1. Go through the lecture slides in your own speed and time and try to understand all the provided information. 2. What is the relevance of conceptual design in systems engineering? Describe the process of conceptual design in your own words. 3. Define the following terms in your own words with suitable example. Technical performance measures Operational requirement Functional requirement Performance requirements System specification UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 54 Any questions, comments, or concerns? UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 55  Sources 1. Campbell, M. I., Cagan, J., & Kotovsky, K. (1999). A-design: an agent-based approach to conceptual design in a dynamic environment. Research in Engineering Design, 11(3), 172-192. 2. Chong, Y. T., Chen, C. H., & Leong, K. F. (2009). A heuristic-based approach to conceptual design. Research in Engineering Design, 20(2), 97-116. 3. Rzevski, G. (2003). On conceptual design of intelligent mechatronic systems. Mechatronics, 13(10), 1029-1044. 4. Makrygiorgou, J. J., & Alexandridis, A. T. (2016, June). Dynamic analysis of induction machine driven electric vehicles based on the nonlinear accurate model. In 2016 24th Mediterranean Conference on Control and Automation (MED) (pp. 479-484). IEEE. UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 56 UNIVERSITY OF VAASA / SYSTEMS ENGINEERING (ISAN3070) 57