EGR 115 Introduction to Computing for Engineers Introduction to Computer Programming Wednesday 27...

EGR 115 Introduction to Computing for Engineers

Introduction to Computer Programming

Wednesday 27 Aug 2014 EGR 115 Introduction to Computing for Engineers

http://www.erau.edu/

Lecture Outline


• Introduction to Programming Why learn programming? A first example How to access MATLAB

Slide 2 of 12


Introduction to Computer ProgrammingWhy Learn Programming?


• As engineers it is often more cost effective for us to “simulate” complex systems before implementation Simulate = computer programming!!! Testing on a simulated system is cheaper than building

hardware A system failure on a simulated system is less catastrophic

than failure of hardware!! The fidelity of the simulation determines the accuracy of the

results Most complex systems involve significant software (i.e.,

programming!!) Analyzing the results of a test often involves programming!!

Slide 3 of 12


Introduction to Computer ProgrammingWhy Learn Programming?


• It is often faster to write a program to automate a tedious/repetitive task (10x faster!!)

• Embedded computers are everywhere Modern automobiles contain up to 50 microprocessors

o They all require programming!!

• The software that runs the Boeing 787 has approximately 7 million lines of code

• Programming is a critical skill for engineers today and even more so tomorrow The Chevrolet Volt has more lines of code than a Boeing

787!!! Future version will have up to 100 M lines of code!!

Slide 4 of 12


Introduction to Computer ProgrammingA First Example:


• A First Example Problem: Design the suspension for an small car.

o Select the shock absorber and spring so that the oscillations “diminish” after about 4 seconds.

Consider just one corner (i.e. 1 wheel)o Viscous damping of shock is “c”o Spring constant is “k”o Displacement is “X”o External force is “F”

Mathematical dynamic model

( ) ( ) ( ) ( )F t m X t c X t k X t

F

X

Slide 5 of 12




• Solution to the differential equation can be written as: Response to a step-force of magnitude ‘F”

where: , , , and

• If we assume: a mass of 20 kg (i.e., m = 20) spring constant of 1,000 (k = 1,000)

• Select a suitable shock absorber (i.e., damping const. c)

1( ) 1 nt

n

FX t e Sin t

k

Slide 6 of 12




• Develop a “simple” MATLAB program to simulate the displacement vs time (i.e., system’s response)

Defi

ne

cons

tant

s

Com

pute

pa

ram

eter

s

Calc

ulat

e re

spon

se

Plot

re

sults

Slide 7 of 12




• Results:

C = 10C = 100C = 50

Looks like a shock with damping of 50 N / (m/s) will do the job!!!

0 1 2 3 4 5 6 7 8 9 100

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02Step Response of Car Suspension: F=10, m=20, k=1000, & c=10

Time in Sec

X in

met

ers

0 1 2 3 4 5 6 7 8 9 100

0.002

0.004

0.006

0.008

0.01

0.012


Time in Sec

X in

met

ers

0 1 2 3 4 5 6 7 8 9 100

0.002

0.004

0.006

0.008

0.01

0.012

0.014


Time in Sec

X in

met

ers

Slide 8 of 12


Introduction to Computer ProgrammingHow to Access MATLAB:


1. MATLAB can be found on ERAU computers at: All Programs College of Engineering MATLAB We are currently using version 2013b

2. MATLAB can also be accessed via ERNIE: For home use (slow)

3. Can be purchasedfrom the bookstorefor ~$99

Slide 9 of 12

http://ernie.erau.edu/


Introduction to Computer ProgrammingThe Advantages & Disadvantages of MATLAB:


Advantages Disadvantages

Ease of use• Interpreted, allows interactive prototyping,

and debugging

Speed• The interpreted nature of MATLAB

makes it inherently slower to execute than some other languages

• Tools exist to speed up MATLAB code above interpreted speed

• Speed is frequently not important in experimental code

Platform Independence• Same MATLAB code can be executed on a

broad range of machines and will provide identical results

Predefined Functions• Library of common operations (e.g., sin, …)• Toolboxes for specific applications

Cost• Typically 10X more expensive• MATLAB is not an open standard and

is a single-source vendor (i.e. MathWorks Inc.)

Device-Independent Plotting• Allows visualization of results across many

platforms (e.g., MAC, Linux, …)

Graphical User Interface• Can develop GUI for programs

Memory• MATLAB typically uses more memory

than comparable programming languages

MATLAB Compiler• Stand-alone & Java-like p-code

Slide 10 of 12


Introduction to Computer ProgrammingHistory of MATLAB:


• MATLAB is an acronym for MATrix LABoratory Simplifies programming with arrays (i.e., matrices and

vectors)

• Development of MATLAB was begun by Dr. Cleve Moler, a CS professor from UNM, in the late 70’s. For teaching programming to engineers

• MathWorks was founded in 1984 In 2004 MATLAB had over 1 million users

Slide 11 of 12


Next Lecture


• Introduction to MATLAB The Environment Using MATLAB as a Calculator

Slide 12 of 12


EGR 115 Introduction to Computing for Engineers Introduction to Computer Programming Wednesday 27...

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