Mechanism Feasibility Design Task Dr. James Gopsill Design & - - PowerPoint PPT Presentation

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Mechanism Feasibility Design Task Dr. James Gopsill Design & - - PowerPoint PPT Presentation

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2017 Mechanism Feasibility Design Task Dr. James Gopsill Design & Manufacture 2 Mechanism Feasibility Design 1 Lecture 3 2017 Contents 1. Last Week 2. The Convertible Roof System 3. Boundary Calculations 4. Modelling the

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Mechanism Feasibility Design Task

  • Dr. James Gopsill

1 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Contents

1. Last Week 2. The Convertible Roof System 3. Boundary Calculations 4. Modelling the Deployment using Simulink

  • Pendulum
  • Fix it in position
  • Deploy the pendulum

5. Stage-Gate Reminder 6. This Week

2 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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But First! Points of Clarification

  • Soft-top roof – lecture 2
  • No sliding pins (time constraints)

– lecture 2

  • Unable to get Linkage on the

University PCs this year

  • Your criteria is your PDS

3 2017 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 2

YOUR PDS!!

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SLIDE 4

Last Week

We looked at:

  • Product Design Specifications Techniques
  • Concept Generation Techniques
  • Concept Selection Techniques

Where we should be:

  • Formed Product Design Specification
  • Generated Concept Designs
  • Started to Select a Concept to Carry Forward
  • Ready for the Stage-Gate Submission

4

Product Design Specification Concept Design Concept Selection Deployment Modelling Stage-Gate

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Systems Modelling

5 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Systems Modelling The development of models that simulate complex engineering systems that often span multiple engineering disciplines

6 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Systems Modelling (illustration)

7 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3

Compressor S1 S2 Sn Combustion Turbine S1 S2 Sn Control system Engine bleeds Air breathing Operating Conditions Pilot Prop Gearbox Wing anti-icing

2017

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Systems Modelling

8 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3

Not forgetting!

  • Fuel system
  • Cooling system
  • Lubrication system
  • Engine start system

Other Jet Engines

  • Varying intake
  • Reheat

2017

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Systems Modelling (Why?)

9 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3

  • Global optimisation of the

products design

  • Performance analysis
  • Sensitivity analysis
  • Product health monitoring
  • Diagnosis of product issues
  • Pass-off tests

2017

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Convertible Roof as a System

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1 2 3

Electro-mechanical system 1. Electric Motor 2. Worm Gear 3. Multi-Stage Gearbox 4. Connecting Rod 5. Multi-Bar Mechanism

4 4 5

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3

(Illustration)

2017

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SLIDE 11

Convertible Roof as a System

Energy transfer through the system

  • Power to the motor

provides initial torque

  • Torque travels through the

gear box where the gear ratio will change the amount of torque delivered

  • Which then drives the

mechanism against gravity (initially)

11 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Convertible Roof as a System

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https://www.youtube.com/watch?v=UqcKYFU6VIg

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Boundary Calculations

13 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Boundary Calculations (Why?)

  • Help us determine initial conditions for our models
  • Provide a sanity check for our models
  • Provides evidence for our initial component selection

14 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Boundary Calculations

What are our boundary conditions and what do we need to know?

15 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Boundary Calculations

  • What torque do you require to get

the mechanism moving?

  • Assume a single mass
  • Think centre of mass

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𝑛𝑕 𝑚 ∝

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Boundary Calculations

  • What torque do you require to get

the mechanism moving?

  • Assume a single mass
  • Think centre of mass
  • What motor and gear ratio is

required to achieve this?

  • Select a motor from Bosch
  • Refer to your PDS when selecting the

motor

  • Determine the gear ratio required
  • Note: you will need a gear ratio!
  • Record your rationale for your choice

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𝑛𝑕 𝑚 ∝

http://www.bosch-ibusiness.com/boaaelmoocs/category/D.C.%20motors%20without%20transmission/114?locale=en_GB Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Boundary Calculations

18 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3

Design Report

  • Deployment Modelling (Boundary Calculations)
  • How did you calculate the torque required?
  • What were your assumptions?
  • From this information and your PDS, how did you determine the initial

gear ratio & motor

2017

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Modelling the System

19 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Modelling the System

What do we want to know?

  • Energy required to deploy

the roof

  • Time to deploy the roof
  • To help us determine the

final Motor, Gear Ratio and Damping values

20 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Modelling the System

What is changing over time?

  • Torque provided by the motor
  • Force due to gravity
  • Inertia of the mechanism
  • Mechanism
  • Acceleration
  • Velocity
  • Displacement

What remains constant?

  • Gear ratio
  • Mass of mechanism

21 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Modelling the System

What assumptions are we making?

  • Friction
  • Air Resistance
  • ?

If included, what effect would they have? This is important to know so we can be analyse the results in the appropriate

  • context. (Put this in your report)

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 22 2017

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How are we going to model this?

  • Simulink
  • A block modelling language that is

great for modelling systems.

  • Blocks represent calculations that

need to be performed.

  • Handles the iterations and time

domain for us

  • We are going to use it to help us

model the dynamics of a multi-bar mechanism

23 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Demo - Pendulum

24 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Co-ordinate System

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Fixing It Into Position

26

𝑛𝑕 𝑚 ∝

Calculate the torque required to oppose the motion

+𝑈

𝑝𝑞𝑞𝑝𝑡𝑓

−𝑈

𝑝𝑞𝑞𝑝𝑡𝑓

−𝑈

𝑝𝑞𝑞𝑝𝑡𝑓

𝑈

𝑨 +

+𝑈

𝑝𝑞𝑞𝑝𝑡𝑓

𝑦 𝑧

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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SLIDE 27

Fixing It Into Position

27 Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Deploying the Single Mass

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𝑛𝑕 𝑚 ∝ 𝑦 𝑧 𝑈 Start Finish 𝛾

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Deploying the Single Mass using a Motor

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This will need to change!

  • Motor Torque is a Function of

Angular Velocity

  • Motor Curves from Bosch
  • Use Angular Velocity as the

feedback

  • The gear ratio will change the

speed and motor

  • The motor will be running at a

different speed to the mechanism

  • Note: Next week we will look at

damping so that we can keep the motor in its operating window!

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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Stage-gate: Submission

  • Product Design

Specification (Current Progress, A4 page)

  • Chosen Concept Model
  • Images
  • Paragraph discussing

main features

  • Online Submission

Blackboard

  • 5% Pass/Fail Criteria

30 No . Requirement Must/Wish Method of Assessment Success Criteria Will be assessed during the feasibility stage 1 2 3 … Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017

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This Week

  • Boundary Condition Calculation
  • What torque is required to get your mechanism moving?
  • Assume a single mass
  • Generate the Demo Models
  • Pendulum
  • Fixed Pendulum
  • Deployment Pendulum
  • Templates on the website
  • Model your single mass (from your boundary calculation!) moving

from start to finish using the motor and gear ratio selected

  • Next Week
  • Demo: Four-Bar Mechanism with Damping

31

𝑛𝑕 𝑚 ∝

Design & Manufacture 2 – Mechanism Feasibility Design Lecture 3 2017