1

Quiz Preparation

Quiz 4 sheet provided. Fill in your Name, etc. Date is 9/11/12 Answer questions

during lecture.

Lab Day/Time Section Number

Mon. 1:00 8Mon. 3:00 9Wed. 1:00 10Wed. 3:00 11Fri. 1:00 12

Lab Day/Time Section Number

Mon. 1:00 8Mon. 3:00 9Wed. 1:00 10Wed. 3:00 11Thu. 2:00 29Fri. 1:00 12

Lab Day/Time Section Number

Mon. 1:00 8Mon. 3:00 9Tue. 2:00 36Wed. 1:00 10Wed. 3:00 11Thu. 2:00 35Fri. 1:00 12

2

Lego Car Project

Wirelessly driven Lego car Left and right channels/motors for steering Goal is to navigate and finish course as

quickly as possible Penalty of 1 second for each 0.5 V over

10V in voltage regulator output

3

Lego Car Overview

Receiver

R1, R2

PPM

PWM

PWM

START/FINISH

BLOCK

Required Gates

Optional Gates

(+5 sec. penalty if missed)

Push block across finish line or incur a +30 sec.

penalty

Each floor tile is 1 foot × 1 foot square

5

Penalties

Penalties are a way to introduce “cost” into the design and cause the team to make tradeoff decisions.» Incurring a penalty should not be considered unethical or “wrong” in any

sense. 5 second penalty for missing an optional gate 30 second penalty if the block is not pushed across the finish line Penalty of 1 second for each 0.5 V over 10V in voltage regulator

output (Vo). Voltages rounded to nearest 0.1 V.» Vo ≤10.0V = no penalty» 10.0V < Vo ≤10.5V = 1 second penalty» 10.5V < Vo ≤11.0V = 2 second penalty» etc.

6

Competition Grading

Fastest time = 100 points » Fastest time ever (Spring 11) was 7 sec. =“World Record”

30 seconds = 75 points

Other times linearly interpolated between fastest time and 30 sec.

Maximum time is 60 seconds

7

Preliminary Design Report Due week of Lab 10, in lab. Describe design decisions

» Output voltage» Power supply» Wheel size/gears, etc.

Justify your decisions. Explain any disadvantages, and why you’ll

tolerate them. Include supporting drawings, figures, and

tables if needed.

8

Lego Car Design Output voltage

» Higher output voltage increases speed» Penalties apply above 10V

Power supply (batteries)» One 9V battery (light, but less than 10V)» Two 9V batteries (≥10V, but heavy)» Watch batteries (very light, but drain quickly)

Wheel size and gears» Torque vs. speed tradeoff

Drive strategy» Front wheel vs. rear wheel drive

Course path» Passing through all gates vs. missing gates» Pushing block vs. not pushing block

Body» Light vs. heavy

9

Today’s Topics

Introduction to MATLAB

MATLAB graphics

Image processing

10

MATLAB MATLAB® allows us to work with large

amounts of data easily.» The basic data structure in MATLAB is a

vector.» A vector is a convenient way to store a

sequence or array of numbers, such as sensor readings.

We can also manipulate sounds and images from within MATLAB.

11

MATLAB Basics

Assign a value to a variable>> a=3

a =

3

>> a=3;>> a

a =

3>>

Semicolon suppresses echo

Typing a variable name displays the value

Be careful!!

12

MATLAB Basics Vectors

>> v=[1,3]v = 1 3

>> v=[1;3]v = 1 3

>> v'ans = 1 3

>> v=1:0.5:3v = 1.0000 1.5000 2.0000 2.5000 3.0000

Comma delimits columns

Semicolon delimits rows

Apostrophe means transpose(turn rows into columns andvice versa)

start value : increment : end value

13

Sine wave:

is the frequency of the sine wave. Sample the waveform every T seconds.

» Let » We get a sequence » Let n=0,…,N to get sequence corresponding to

a duration of NT seconds.

Generating Sine Waves

tftx 02sin)( 0f

nTt Tnfnx 02sin)(

14

MATLAB

>> f0=100;>> T=.0008;>> n=0:62;>> x=sin(2*pi*f0*T*n);>> stem(n,x)

Tnfnx 02sin)(

start value : end value (assumes increment of 1)

10 20 30 40 50 60-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

stem(n,x) plot(n,x)

15

MATLAB vs. C C code to create a sine wave:#include <stdio.h>#include <math.h>

main(argc,argv)int argc;char *argv[];{ int i,n; double *sv, f0;

n=5000; f0=100;

sv = (char *) calloc(n, double);

for (i = 0; i < 50000; i++) { sv(i) = sin(2*3.1415927*f0*I/44100); }}

16

Other MATLAB Abilities

Many built-in functions Can easily add your own functions Immediate results without compiling Can solve systems of equations easily All kinds of plotting methods Simulink Maple Symbolic Math Toolbox

17

Example – Large Array

M file “multiplies.m” creates a 1000 x 1000 array, and then computes inverse.

Performs order of one billion FLOPS in a few seconds.

18

Example – 3D Plots

M-file “surfaces.m” creates a 3D “landscape” using the function

z=cos(.05*x).*sin(.1*y)

This can be rotated in 3D with the mouse.

19

Example – Image Processing

Start with photo “office.jpg”

Convert to grayscale image

Detect edges

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Image processing commands

i=imread('office.jpg'); % convert to MATLAB format igray=i(:,:,1); % keep only one color channel bw=edge(igray,'canny'); % perform Canny edge detection

21

Playing Sounds in MATLAB

Can play sounds directly from MATLAB:» sound(x,44100)

– x is the sequence of values in a vector– 44100 is the output sampling rate

» soundsc(x,44100)– Same as sound() but auto-levels before playing– Each sound played at the same level

22

Playing Sounds in MATLAB

Can read or write WAV files:» y = wavread(‘fast.wav’);

– y is the sound sequence read in as a vector– fast.wav is the name of the file to be read.

» wavwrite(y,44100,’fast.wav’)

23

Stereo in MATLAB

If x is an Nx2 vector, the left column will be played as the left channel, and the right column will be played as the right channel.» fl=200;» fr=300;» t=[0:1/44100:8];» xl = sin(2*pi*fl*t);» xr = sin(2*pi*fr*t);

sound([xl’ xr’],44100)