ENGINEERING DESIGN LAB I ENGR-101 FALL 2014 WEEK 5 LECTURE

Richard Primerano, Ph.D.

ENGINEERING FAILURES AND RELIABILITY WINTER TERM REGISTRATION INFORMATION

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ENGINEERING FAILURES Failure is inevitable in engineering design

When we push the boundaries of existing design (new materials, designs)

When unexpected conditions occur (environmental factors, user error)

When designs are not thoroughly tested

Failures unfortunately often result in the loss of life.

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ENGINEERING FAILURES We generally learn more from failures than successes Failures force technological improvements

Challenger space shuttle Tacoma Narrows bridge Hyatt Regency Hotel walkway collapse (Kansas City, MO)

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GM IGNITION SWITCH RECALL - 2014 Heavy key rings could produce enough torque on

the ignition key to turn the engine off while driving.

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GM IGNITION SWITCH RECALL - 2014 An insert for the key A replacement plunger

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A PARTIAL TIMELINE 2001: GM detects the defect during pre-production

testing of the Saturn Ion. 2005: A GM engineer advises the company to

redesign its key head, but the proposal is ultimately rejected.

2013: GM determines that the faulty ignition switch is to blame for at least 31 crashes and 13 deaths.

6 Timeline: A History Of GM's Ignition Switch Defect

FAILURE IN YOUR RUBE GOLDBERG MACHINE If you test an event 20 times and it works 18

times, the (estimated) reliability is 18/20 or 90%. To get a better estimate, many more trials would

be needed.

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FAILURE IN YOUR RUBE GOLDBERG MACHINE If we know the reliability of each event, the overall

reliability is just the product of these. Is the machine below reliable?

8 95% 90%

99%

95%

95%

90%

FAILURE IN YOUR RUBE GOLDBERG MACHINE

PRG = 0.95 x 0.90 x 0.99 x 0.95 x 0.95 x 0.90 = 0.688 The machine will work about 69% of the time.

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95% 90%

99%

95%

95%

90%

FAILURE IN YOUR RUBE GOLDBERG MACHINE What would you consider a reliable event?

Works 50% of the time Works 95% of the time Works 99% of the time

The estimated probability of success for each event

can be found empirically Pn=Number of successes/Number of trials

Probability that whole machine works is product of event probabilities PRG=P1P2P3P4P5P6

If each event has a 90% probability of success, a six event RG machine will have a 53% chance of success

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RELIABILITY OF THE SECTION-WIDE RUBE GOLDBERG MACHINE Each group will have 6 events minimum Many sections will have 8 groups

A typical section-level machine will have 48 events.

If each event has 95% reliability, the overall machine will only work 9% of the time

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P P^48 99% 62% 98% 38% 97% 23% 95% 9%

HOW TO REDUCE THE CHANGES OF FAILURE Thorough testing is a requirement

Determining the operating bounds, sources of uncertainty, environmental factors

Test corner cases, Test your machine in the section-level machine

platform. Vibrations, air currents, flying objects can all affect the

operation of your group’s machine

Overdesign by some safety factor (e.g. in bridges) Add redundancy (e.g. RAID array) If you see something that could cause a problem,

address it. 12

ENGR-102 ROBOTICS MODULE LECTURES: 10AM, 11AM

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NXT ROBOTICS MODULE OVERVIEW Ten weeks in duration Introduces concepts of closed loop control, algorithm

design, calibration, sensor/actuator interface.

Groups are given a Lego NXT robotics kit 3 motors 2 touch sensors 1 microphone 1 light sensor 1 ultrasonic sensor 1 color sensor 1 magnetic sensor

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ROBOT CHALLENGE A train has derailed, scattering trash and nuclear

waste in an area. A consulting firm has issued a call for companies to

submit designs and prototype robots capable of cleaning the affected area.

Your group is to submit a design and compete against other groups in receive the contract.

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NXT ROBOTICS MODULE – WEEK 1 Overview of graphical programming in the Lego

NXT environment You are provided a prebuilt robot and asked to

program it to execute simple sequences Move forward/backward defined distance Perform “zero point” and arc turns Trace shapes with robot

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NXT ROBOTICS MODULE – WEEK 2 Working with NXT sensors Using the ultrasonic and touch sensors

Program the NXT to detect objects in its path and maneuver around them

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NXT ROBOTICS MODULE – WEEK 3 Working with the NXT light sensor Characterizing the field-of-view of the light sensor Program the NXT to detect a bright light source and

move toward it.

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NXT ROBOTICS MODULE – WEEK 4 Design a gripper capable of picking up objects in the

arena. 2.5” PVC end caps

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NXT ROBOTICS MODULE – WEEK 5-8 Design a robot to complete the challenge

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PROGRAMMING ALTERNATIVES THE LEGO NXT-G ENVIRONMENT Uses graphical programming Blocks are placed and wired together to make program Requires no prior programming knowledge Can be limiting for those with prior programming knowledge This is the ‘official’ programming alternative supported through our

course. Additional/Advanced NXT-G Tutorials: http://www.stemcentric.com/nxt-

tutorial/

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PROGRAMMING ALTERNATIVES NXC WITH BRICX COMMAND CENTER

C-like syntax, more appropriate when writing complex code. Some prior programming knowledge is recommended Software is provided on lab computes and is free to install

We offer this as an ‘unofficial’ option this year. No formal support is offered through the course but we will help when we can.

Tutorial - http://bricxcc.sourceforge.net/nbc/nxcdoc/NXC_tutorial.pdf

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ENGR-102 BRIDGE DESIGN MODULE LECTURES: 1PM, 2PM

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BRIDGE DESIGN MODULE OVERVIEW Ten weeks in duration Introduces concepts of stress and strain, structures,

computer analysis/simulation, laboratory testing.

You will work in groups of 3 students Groups are given a k’NEX erector sets and asked to

construct bridges to meet certain given constraints Bridges are tested to failure and the winning team is

decided based on bridge strength-to-weight and cost.

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THE TACONY-PALMYRA BRIDGE A combined steel arch, double-leaf bascule bridge

that connects Tacony (PA) with Palmyra (NJ). Completed in August 1929 The total length is 3,659 feet

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THE TACONY-PALMYRA BRIDGE Operation of the TPB is managed by the the

Burlington County Bridge Commission (BCBC) The bascule is the portion of the bridge that

opens to allow large ships to pass.

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BRIDGE REDESIGN CHALLENGE Engineering firms have been contacted to develop

prototype bridge designs to replace the existing Tacony-Palmyra Bridge

Your bridge will need to meet dimensional, load carrying, and cost constraints.

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BRIDGE DESIGN MODULE WEEK 1 INTRODUCTION TO TRUSS ANALYSIS

We introduce several fundamental structural engineering concepts Tension and compression Trusses The method of joints (for calculating forces within a truss)

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BRIDGE DESIGN MODULE WEEK 2 SOFTWARE TOOLS FOR BRIDGE DESIGN

We introduce one of the three design tools (West Point Bridge Designer) that will be used in this module for bridge design and analysis. AutoCAD and Visual Analysis are the others

WPBD is an educational package developed and

distributed by the United States Military Academy.

It allows you to quickly design and simulate bridges using a variety of common construction materials.

Using this, you can visualize the forces in a truss for given loads. 29

BRIDGE DESIGN MODULE WEEK 3 ANALYZING SENSOR DATA FROM A REAL BRIDGE The Tacony-Palmyra Bridge has been outfitted with

numerous sensors Strain gauges Vibration sensors (accelerometers) Tilt sensors Cameras

By analyzing sensor data, we can determine how the bridge is loaded and monitor for structural problems.

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BRIDGE DESIGN MODULE WEEK 4 INTRODUCTION TO AUTOCAD AND VISUAL ANALYSIS

Software tools are an integral part of most engineering projects.

This week, we use a combination of AutoCAD and Visual Analysis to perform structural analysis of our bridge design.

AutoCAD is used for design of the structure. Visual Analysis provides the simulation tools for

analysis of the structure.

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BRIDGE DESIGN MODULE WEEK 5 DESIGN ITERATION WITH SOFTWARE AND LAB TESTING

Often, engineers rely on a combination of (pen and paper) calculation, simulation, and testing to arrive at final designs.

In this lab, we use simulation to predict failure conditions of a bridge.

Through lab testing, we verify our simulation results.

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BRIDGE DESIGN MODULE WEEK 6-10 During the remainder of the module, groups,

analyze, and test bridges to operate within a set of given constraints

The module culminates in an in-lab competition.

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IN SUMMARY If you are interested in the Robotics Module

Register for the 9am, 10am, or 11am lecture Labs run Tuesday through Friday

If you are interested in the Bridge Design Module Register for the 1pm or 2pm lecture Labs run Thursday and Friday

Both are designed to cover the same basic

concepts and have the same deliverables.

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