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Design• What is design?

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Design• What is design?• What is a good design?– How do you determine what a good design is?

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Design• What is design?• What is a good design?– How do you determine what a good design is?

• What is involved in design?

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Design• What is design?• What is a good design?– How do you determine what a good design is?

• What is involved in design?• Design stages?– Identify problem– Conceptual design, analysis– Preliminary design, analysis– Developing and evaluating prototypes– Detailed design, analysis– Is the design satisfactory?

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Design• What is design?• What is a good design?– How do you determine what a good design is?

• What is involved in design?• Design stages?– Identify problem– Conceptual design, analysis– Preliminary design, analysis– Developing and evaluating prototypes– Detailed design, analysis– Is the design satisfactory?

• How do you approach design?– Concurrent design– Brainstorming– Thinking about it

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Schematic Design Process

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Exercise:

• You need to develop additions to a children’s swing set that minimize injuries.–What are some constraints?–What are some design ideas?–What ideas seem to be the best?–Why?

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Objectives Tree: Convenient, Safe, Attractive Transport System 

System

Low risk of structural collapse

Efficient, cheap design

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Morphological Chart: Potato Harvester

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Selecting Designs ByEvaluating Alternatives

• List design objectives (e.g lightweight .easy to fabricate, maneuverable)• Assign each objective a relative weight (importance), with the weights 

summing to one if desired• For each alternative design, establish utility scores for each objective

– e.g. 0-10, with 0 for a useless solution and 10 for an excellent solution

• Calculate and compare the relative utility metric for each alternative by summing the product of each objective’s weight by the alternative’s utility score (inner product of the weight vector and  the utility score vector).

• This should provide a utility metric for selecting the most promising (highest-scoring) design alternatives.

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Evaluating Design Objectives

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Weighted Objectives Evaluationof Three Auto Designs

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Weighted Objectives Evaluationof Three Auto Designs

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Small City Car Alternative Design Evaluation Chart

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Example Automotive Subsystems1.4. Body and Chassis

1.4.1. Body Electrical1.4.2. Heating1.4.3. Cooling1.4.4. Body panels1.4.5. Doors1.4.6. Windows1.4.7. Seats1.4.8. Interior appointments1.4.9. Gauges1.4.10. Controls1.4.11. Fuel supply1.4.12. Finish

1.5. Suspension1.5.1. Springs1.5.2. Dampers1.5.3. Control Arms1.5.6Wheels and tires

1.6. Steering1.6.1. Rack1.6.2. Control Rods1.6.3. Power pump1.6.4. Power controls1.6.5. Ball joints 

1.1. Engine1.1.1. Engine mechanical1.1.2. Ignition1.1.2. Fuel Injection1.1.4. Engine controls1.1.5. Emission control1.1.6. Starting system1.1.3. Cooling system1.1.8. Charging system

1.2. Drive Train1.2.1. Transmission (automatic or manual) 1.2.2. Propeller shaft1.2.3. Differential1.2.4 .Half-shafts1.2.5. Hub Assemblies1.2.6. Power train control

1. 3. Braking1.3.1. Master cylinder1.3.2. Power Booster 1.3.3. Hydraulic lines 1.3.4.System sensors1.3.5. Disc and caliper assemblies1.3.6. Antiskid Braking System

Electronic Control System?

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Design Considerations

– Dynamics– Layout, weight– Stability– Sensing and Control – Heat dissipation– Power 

capacity/requirements/distribution– Thrust 

generation(wheels/tracks/propellers/jets

– Drive mechanisms

– Suspension (pneumatic tires?)– Maneuverability/quickness/

response– Speed/drag– Blocking/Blocking, falling resistance– Flag handling – Vehicle form– Esthetics– Complexity/manufacturability– Ease of repair

• Overall Contest Strategy and performance needs• System Design and Tactics• Auxiliary subsystems• Vehicles

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Physical Systems

ForceVelocityTorquePowerEnergy

ForceVelocityTorquePowerEnergy

Hardware System

Losses

Conserve: Total power, energy, linear and angular momentum, charge

Don’t Conserve: Force, Velocity, Torque, Position, EntropyAnalysis: Mechanics, thermodynamics, strength of materials,                       electromagnetic theory, etc.