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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology


CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

Introduction ďƒ˜ Design is defined as creation of new things and Synthesis is the creative step itself in conceiving new solutions to solve a problem. Engineering is a subset of these design activities and it focuses more on the technical aspects of performance of designed systems. Engineering Design Synthesis is therefore key to defining effective methodologies and selection of appropriate software tools.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

Different Stages of CDEDS Design Synthesis  The methodology has recognized two stages of Design Synthesis, Namely: •

Concept Phrasing (non-detail)

Concept Detailing

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing:  During the creative stage of “Concept Phrasing”, an engineer is interested in answering the “how” of the problem.  Multiple concepts are to be invented and evaluated.  Conditions of acceptance typically relate to form and function and less to fit, physics or performance.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing:  Using a office cabinet door flap example, lets look into the functional requirements

Specification Requirement: •

Design a door flap for a wall mounted office cabinet measuring Height =3’ x Width =2’ x Depth =2’.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concept 1: Design a swing door flap that can swing 90 degree for complete cabinet access.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: • The large swing radius of Concept 1 is not convenient on cabinet doors that are taller than 2.5’ (or more than average arm length). • We need a door flap with smaller swing radius and yet provide full access to inside of cabinet.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concepts 2A and Concepts 2B: Below images shows two candidate concepts.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concepts 2A and Concepts 2B: From the image we can conclude that,  Concept 2A uses a sliding door flap.  Concept 2B uses a split door flap that folds on itself.  Both provide reduced swing radius but suffer from reduced access to the top shelf.  We need clear passage to all the cabinet shelves in addition to reduced swing radius.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concept 3: It Shows a shorter swing radius.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concept 3:  The door flap is moved vertically up by a parallelogram mechanism.  It also provides clear passage to the all the shelves.  Since the door flap is at least 3’ tall and opens upwards.  The installation of this mechanism demands a high roof clearance not usually available in offices with false roofing.  So we now need a design that has reduced swing radius. http://cadvisionengineers.com/


CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concept 4: Key take-away from “Concept Phrasing� example:

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concept 4: Key take-away from “Concept Phrasing” example:  The first three concepts above, differ vastly from one another on how they approach the problem and so the mechanisms are also different.  The fourth one, is a variation of the parallelogram concept 3.  It clearly shows that in the early stages of phrasing we need variety and also a bulk of ideas.  Seeing the operational constraints early during ideation saves time and cost compared to seeing them later in the project life cycle. http://cadvisionengineers.com/


CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

1. Concept Phrasing: Concept 4: Key take-away from “Concept Phrasing” example:  One can also notice that different working mechanisms result from different functional constraints being overlaid on the basic specification.  These constraints, more so during Phrasing, can be translated to fundamental physical parameters like dimensional height, weight, area etc.  The concepts can be sketched by hand or drawn using software but the key requirements are – variety and bulk.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

2. Concept Detailing:  In “Concept Detailing”, one (or more) concepts from phrasing stage are typically subjected to Engineering rigor.  They are integral to making concepts practical beyond just dimensional requirements.  Depending on where you would want to stop, this step can actually end in well-conceived design solutions. •

This are practical, meet engineering rigor and meet marketing specifications.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

2. Concept Detailing: Take Excavator example: ďƒ˜ This example shows the selection of appropriate tools to address this stage of Engineering Design Synthesis.

Design Specification:  Design an excavator work group for a 23 ton tracked excavator that includes a boom, a dipper arm and a 1.2 cu.m bucket that delivers the range dimensions given.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

2. Concept Detailing: Take Excavator example: Design Specification: •

The boom pivot point on the turntable should be at least 1200 mm from ground and at least 100 mm from slew centre to provide clearance for other machinery:

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology 2. Concept Detailing: Take Excavator example:  The Engineering Manager can be in three different situations relating to this requirement and he would react differently for each situation: •

Situation 1: The specification is an extension of an existing design within the factory: then the kinematic lengths of boom, dipper and bucket are almost known and the problem reduces to iterating the four-bar mechanism at the bucket end and arriving at the cylinder sizes.

Situation 2: The specification is of a competing machine not within the factory: then the manager would conduct a competitive bench-mark exercise and arrive at starting lengths from the study.

Situation 3: Specification is not a known configuration anywhere in the market: If you address this last situation, then other situations are automatically addressed. http://cadvisionengineers.com/


CDEDS (Constraint Driven Engineering Design Synthesis) Methodology 2. Concept Detailing:  Concept Phrasing, have to be translated to boundary conditions or design constraints.  Once the constraints are identified, solution to the problem can be found by applying the following methodology, described broadly below: • Each specification parameter, say maximum reach, is a configuration arising from two things. • The kinematic lengths (of boom, dipper arm and bucket) and a particular orientation of the parts

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology 2. Concept Detailing: • Since different configurations arise from just changes to orientation of the parts, we recognize that lengths between pivot points should remain same between the different configurations. • We can model other specification parameters, max depth, cutting height etc., using the same variables for length between pivots. • Other design criteria, can now be brought in as either more variables or more mathematical functions. • Once we have equations for forces, section stresses can be described and consequently weight of parts can be estimated.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology 2. Concept Detailing: •

This methodology now suggest that the design synthesis problem can be solved numerically by applying multi-criteria optimization methods.

The specification targets now described as Objective functions.

Simpler problems like those of door flap or Situations 1, 2 described above, can be solved using simpler numerical optimization methods.

The seed/start/guess values for variables of lengths between pivots can always be generated from regression analysis of dimensions over weight of machine for different sizes. This is known to work.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology CDEDS Methodology Summary:  Attempt to get a variety and bulk of ideas in the Concept Phrasing stage.  More concepts can be generated by adding/removing functional requirements arising from context of application.  A tool that enables simplified modelling, should be used to distil the concepts to a handful of candidate solutions.  The software tool should have some simulation capability and should be able to handle dimensions.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology CDEDS Methodology Summary:  Once a concept is chosen, to bring engineering rigor, express all functional requirements as constraint variables.  Dimension, weight, force or some physical parameter that enables further use of software tools.  Ensure that the selected software can handle all forms of constraint expression.  A dead 2D drawing tool, 3D sketcher, spreadsheet, popular math and simulation tools

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology CDEDS Methodology Summary:  Build a math model describing various operating conditions as configurations.  The configurations are nothing but Objective functions for optimization.  Key step: Solve the math model numerically as multi-objective optimization problem.  This guarantees that that ensuing solution is a consequence of the “Simultaneous Action” of all the Design constraints.  Fine-tune the solution by defining bounding values for constraint variables.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology Conclusion: ďƒ˜ Whether such an interlinked mathematical description of geometry and constraints is possible would depend on the quality of the software tool(s) used for the purpose of Design Synthesis. And whether such a construct would result in a viable engineering solution would depend on the skill of the engineer. The ultimate measure however is the quality of the engineering solution delivered.

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CDEDS (Constraint Driven Engineering Design Synthesis) Methodology

CDEDS (Constraint Driven Engineering Design Synthesis) Methodology  

CDEDS (Constraint Driven Engineering Design Synthesis) methodology is used in conceiving new solutions to solve a problem by recognizing the...

CDEDS (Constraint Driven Engineering Design Synthesis) Methodology  

CDEDS (Constraint Driven Engineering Design Synthesis) methodology is used in conceiving new solutions to solve a problem by recognizing the...

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