EGB345 Control and Dynamic Systems JJF/18
COMPUTER LAB 1 – MATLAB BASICS
This computer lab involves 3 tasks centred on: 1) Data manipulation, 2) loading csv files
and data comparison, and 3) loading practical lab csv files, smoothing noisy data,
creating data structures and saving data. (You will need to demonstrate these skills
in the pre-lab submission and other assessment pieces).
Task 1: MATLAB has a number of script programming and plotting tools. In the first
task you will familiarise yourself with creation of signals and plot vectors to help you
with the practical lab that occurs in middle of semester. Please consider two sinusoidal
waveforms, with frequency 0.1 radian / time instant (zero phase) and 0.5 radian / time
instant (zero phase). Hint: at time instant k, y1(k)=sin (0.1*k).
(a) Please develop MATLAB commands that produce a vectors y1 and y2 that represent
100 time instants of each of the signals. Plot both signals on the same graph (but the
second waveform should be plotted with a red line).
(b) Using MATLAB, determine the time instant, k, that each waveform signal crosses
from above zero to below zero (after k=0). Then separately shift to the left the elements
each vector so that this time instant becomes the first element in the vector (discarding
the elements before this time instant). Then admen or add to each vector new elements
equal to 0 so that vectors remain 100 elements long. Create a second figure, and plot
both of the vectors on the same figure (but the second waveform should be plotted in
red).
Task 2: In this 2nd task you will load in some data from a CSV file (representing a noisy
measured waveform), and then compare this data with the two sinusoidal waveforms
described in the first task on the basis of RMS error (smaller RMS means closer). There
is a MATLAB function called rms(.). Create an error vector that is the difference between
various vectors.
(a) Load the data from the CSV file sinedata.csv as the vector yn and then plot. Hint:
csvread.
(b) Compare the vector yn with above waveforms on the basis of RMS value. Which
vector is closer? What does that mean. Hint: recall that you concatenated these vectors
with 0, and you shouldn’t use these parts of the vectors in the comparison (maybe use
only first 25 elements).
Learning Objectives
• To practice using MATLAB data analysis tools for manipulation of data.
Where Learning Outcomes Assessed:
• In Pre-lab report, Prac lab report, mid-semester and final exam.
PTO… Task 3 and hints on next page
Task 3: In this 3rd task, you will load an example of servo motor position data that was
captured in last year’s practical lab.
(a) Open the csv file openloop_1.csv in excel to inspect the structure of the file, and use
this information to load the csv data into MATLAB and plot the two represented signals
(one signal is the response, the other is a time vector). You may need to type “help
csvread” in MATLAB to work out how to skip the initial unnecessary information
present in the csv file.
(b) Use MATLAB’s smooth(.) (or smoothdata(.), depending on the version of MATLAB
you are using) function to smooth that response data and plot both the raw and
smoothed response data on the same figure. You may need to type “help smooth” to
learn the syntax of MATLAB’s smooth command. NOTE: in latest versions of MATLAB
the smooth(.) command has changed name to smoothdata(.).
(c) Use MATLAB structures to store both the raw and smoothed vector in one variable.
For example, perhaps data.raw and data.smoothed. Then save this structure variable
(and only this variable) into a matlab data file with the filename “smootheddata.mat”.
You may need to type “help save” to learn the syntax of matlab’s save command.
Congratulations you have just learned the basics of create data vectors, manipulating
data, using RMS to understand noisy data, loading data from csv files, smoothing data,
saving data, and using data structures in matlab (the above steps will be required when
working with data captured in the practical lab.)
MATLAB HINTS: You might find it helpful to use the following MATLAB commands:
help, clc, clear, for, end, find (y1>0), hold on, hold off, plot(y1), figure(2), kv=1:1:100,
y1(25:end), ones, csvread, smooth, save and rms. You should use script files and
structures
See all the MATLAB hints pdf.
Learning Objectives