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ME886.3 Topic 1: System and System Design (II)

ME886.3 Topic 1: System and System Design (II). Science-based design: making a better system. Introduction: System and Design. A system is a set of elements that are connected An element may further be decomposed into smaller elements; in this case, the element may be called subsystem

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ME886.3 Topic 1: System and System Design (II)

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  1. ME886.3Topic 1: System and System Design (II)

  2. Science-based design: making a better system

  3. Introduction: System and Design • A system is a set of elements that are connected • An element may further be decomposed into smaller elements; in this case, the element may be called subsystem • Design is a decision-making process starting from requirements to system structures

  4. Introduction: System and Design • Requirement consists of functional requirement (FR) and constraint requirement (CR). FR: A function or functions a device or system has to achieve or a role or roles a device or system has to play. CR: A condition or situation where a device or system achieves a required function.

  5. Introduction: System and Design • CR has two types: • A condition must be met; for instance, the pedal of a bike must be in black color • A condition has a range; for instance, the cost of a system under design must be less than X dollars

  6. Introduction: System and Design Design parameter (DP): Description of the structural element to meet both the functional and constraint requirements

  7. Science-based Design • General design phase theory • Design theory and methodology • Design modeling and optimization Towards a Better System

  8. 2. General design phase Conceptual design Embodiment design Detailed design

  9. Conceptual design Develop a technical specification. Technical specification: a document of customer’s requirement in the technical term. Example Technical specification: Be able to penetrate into the material with HRC>30 This is also called DP Customer’ s requirement: Need a drill to penetrate common steel

  10. Conceptual design Develop solution principle What is solution principle: solution versus solution principle Example Solution principle is DP Solution principle: - Crank-slider - Rack-and-pinion Requirement: Rotation to translation Remark: for machine design, it refers to kinematic design (principal dimension is given but not material and volume)

  11. Making a statement of what without including the means to achieve it Realize the rotation to translation through a linkage Means The means restrict the possibility of having the means of rack and pinion

  12. Embodiment Design Requirement: FR: To materialize a crank-slider kinematic linkage for load of 50 KN CR: To make device as light as possible Embodiment crank-slider linkage: Layout is DP

  13. Detailed Design Develop a complete specification for each individual component ready for manufacturing Requirement: FR: To specify geometrical details ready for manufacturing CR: To be easy for manufacturing and assembly Detailed piston component ready for manufacturing Details for manufacturing are DP

  14. Science-based Design • General design phase • Design theory and methodology • Design modeling and optimization Towards a Better System

  15. 3. Design theory and methodology General Axiom 1: Making what to do and how to do separately. In particular while describing what it is, not be affected by how to realize it Example (Rotation to translation) Requirement statement: When a rotary motor turns, it connects with a rod which further transfers motion to a slider to realize a translation ……. The above statement has violated Design Axiom 1

  16. Complexity Problem -1.1 Problem -1.2 Simplicity Problem -2.2 Problem -2.1 3. Design theory and methodology General Axiom 2: Divide and conquer Problem -0

  17. General Axiom 2: Divide and conquer Requirement: hold hot (~100oC) water with hand Hold hot water Grasp water Hold normal water Resist heat exchange

  18. Ceramic material Resist heat exchange Grasp water Hold normal water

  19. 3. Design theory and methodology General Axiom 3: Generalization of design Other design problems along with their solutions Generic design problem Current design problem A solution to the current design problem Remark: The above process is in fact an analogy process to lead to innovation

  20. Science-based Design • General design process • Design theory and methodology • Design modeling and optimization Towards a Better System

  21. 4. Design modeling and optimization • Mathematical model for design objects at a different level (conceptual object, embodiment object, detailed object) • Variables defined for structural features, and mathematical relations defined for the whole structure along with its behavior • Varying of the variables to seek the best behavior

  22. 5. Designer’s cognitive process • Team-based brain storm and white-box communication • Diversification in team composition and in task management • Confidence • Removal of unnecessary constraints

  23. 6. Summary • Design is a marriage of human designers and science-based processes, • Science-based processes are: general design process, design theory and methodology, and modeling and optimization, • Design theory and methodology has three general axioms. • Designer’s cognitive process includes four guidelines,

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