Name: Darryl Dave G. DitucalanCourse and Year: BS ECE 4th EE
179.1 Section: M456Laboratory Schedule: 1:00PM 4:00PM MActivity 1:
Introduction to SCILABAbstract
Objectives To introduce students to a mathematical software that
can be used to simulate control systems.List of equipment/software
vPersonal Computer Installation of SCILABSCILAB Environment and
Features OverviewScilab is a free and open-source mathematical
software. It can be used to simulate mathematical applications from
basic to advanced engineering systems. Simulations can be through
set of commands entered in the interactive command, through a
script written in the SciNotes, or through XCOS. XCOS is Scilabs
counterpart for Matlabs Simulink.For this activity, you will be
introduced to the basic command line interface as well as scripting
of a set of commands in SciNotes. Some basic features of Scilab
such as variable declarations, operations and flow control will be
examined in this activity. Some commonly used functions will also
be introduced.VariableIn Scilab, you can easily create and
instantiate variables anytime. Unlike the C language, Scilabs
variables are dynamic and dont have to be created before they are
stored with values. Open you Scilab now and try the following in
the console.--> clear--> a = 1The console should respond with
the value of a. Now, after the above command, try doing the
following:--> b = aThe console should respond with the value of
b which is just the value of a in the previous command. 1. How
about this one?--> b = aaaWhat will be the response of the
console?Since aaa has not been assigned a value yet, it still does
not exist. Another convenient feature of Scilab is that you can
assign any datatype to a variable even after you had previously
assigned a different datatype. For example:--> b = 1--> b =
Hi, this is a string--> b = [this,is, a, vector/array]These
commands will not produce an error. The datatype of the variables
in Scilab adapt to whatever value you store in it.You may have
noticed that the last command is an array. Arrays in Scilab are
values enclosed in [ and ] with values separated by spaces or
commas. You can also create a matrix by separating rows with a
semicolon. --> an_array = [1, 3, 4]--> a_matrix = [1, 2; 4,
5]2. What will you enter in the command line if you want to assign
a_matrix with ?You can easily declare an array of sequence of
numbers using :--> 1:10 // returns an array of numbers from 1 to
10 with an interval of 1--> 1:2:10 // returns an array of
numbers from 1 to 10 with an interval of 2PolynomialYou can easily
create polynomial using the poly function read the help file for
different methods of using the poly function. The simplest way is
the following:--> s= poly(0,s) //this assign polynomial s^1 to
the variable s.Now you can manipulate this variable similar to
number.
3. Write the result of (s^2+2*s+1)/(s+1) as shown in the
console.
OperatorsScilab has a lot of operators in addition to basic
arithmetic operations. Since Scilab operates on matrices by
default, basic arithmetic operations are applied on matrices.
OperatorDescription
+Matrix addition
-Matrix subtraction
*Matrix Multiplication
/Matrix division.
\Matrix back-division.
^Matrix exponential.
Transpose
If you want element-wise operation using those operators, the
operator is preceded with a .--> a = [1, 2; 3, 4]--> b = [3,
4; 5, 6]--> a + bans = 4. 6.8. 10.
4. Do a matrix multiplication and element-wise multiplication on
a and b. What are the results? Are the results equal?
5. What is the result of a?
Accessing an element in an array or matrix is by calling the
variable with a parenthesis. For example, to access the 1st element
of b:--> b(1) //this will return 3. Matrix b is treated as a
vector reading top to bottom starting from the left.
This is the same as --> b(1,1) //accessing element in column
1 row 1. First index is for the row, the second is for the
column.
You can use the $ to indicate the index of the last element.
--> b(1,$) //returns the last element of the first row.
Sub-matrices can be extracted by putting an array or matrix as
index. The content of the matrix index will be the rows/columns
that will be included in the sub-matrix. You can use : to include
all elements on that row/column.--> c = [1, 2 ,3; 4, 5, 6; 7, 8,
9]--> d = c([1,3],[1,2]) ans = 1. 2.3. 8.--> e = c(:,1)
//returns all the rows in the first column.
6. What is the result of c(1:3,$)?
Flow ControlThe flow control in Scilab can be done with if
then/else statements, select/case , return, for loop, do and while
loops. In addition, keywords such as break, continue, pause, abort
are also useable to alter the flow of a set of Scilab commands. The
syntax for this is in described in detailed in the Help menu of
Scilab. To access the Help, type help in the command line or click
the help button in the menu bar.
Functions in ScilabYou can create a reuseable set of commands as
a function in Scilab. The basic syntax is the following:FUNCTION
[y1,, yn]= functionname(x1, , xm)//some statements or commands
hereENDFUNCTIONSome of the commonly used functions in ScilabRefer
to the Help menu for details1. plot used to plot expressions in
Scilab.2. poly function to create a polynomial.3. roots Solve the
roots of a polynomial4. coeff extract the coefficients of a
polynomial.5. evstr - evaluate a string of Scilab statements or
commands6. csim Simulation of a linear system. (time response)7.
ones Generate a matrix of ones8. zeros Generate a matrix of
zeroes9. rand generate a matrix of random values10. eye generate an
identity matrix.11. inv inverse of a matrix12. diag extract the
diagonal of matrix13. abs absolute value14. real, imag, complex for
complex numbers15. conj conjugate of a complex16. pfss partial
fraction expansion of a give transfer function17. syslin system
linear definition18. ss2tf State-space representation to transfer
function conversion19. tf2ss Transfer function to state-space
representation20. ssrand random system generator.Batch Commands or
ScriptingScilab has an integrated text editor called SciNotes for
creating and editing Scilab scripts. A set of commands or
statements can be written in a Scilab script that can be ran or
executed in a single action. SciNotes has some advance text editing
functionalities for coding like parenthesis matching and syntax
highlighting. Open Scinote by clicking the notebook icon below the
menu bar. After opening the SciNotes, do the following:
7. Write the following in the editor:a = [0:0.1:2*%pi]b = this
is executed after a=1plot(a,sin(2*a))//end
What is the result or the behavior of the above statements in
the console after executing the script?
8. Write a function called myfunct that accepts two parameters A
and B. The function will return the result of (A+B)*B. Execute the
script what is the result?
9. Call the function you created in #8 and pass as parameters
the values 3 and 9. What is the result?
10. What will your function return if the parameters are [1,2,3]
and [4; 6;7]?
11. How about [1, 2, 3 ; 3, 5, 1; 5 6 -1] and [3, -1, 4 ; -3, 5,
1; -5 6 -1]?
12. Do you have to re-execute your function from SciNotes?
Why?
Answers to Questions
1. How about this one?--> b = aaaWhat will be the response of
the console? !--error 4 Undefined variable: aaa
2. What will you enter in the command line if you want to assign
a_matrix with ?a_matrix = [ 1 2 3; 4 5 6; 7 8 9]
3. Write the result of (s^2+2*s+1)/(s+1) as shown in the
console.ans = 1 + s ----- 1
4. Do a matrix multiplication and element-wise multiplication on
a and b. What are the results? Are the results equal?
Matrix multiplication:Element-wise:Base from the results above,
They are not equal.5. What is the result of a?a:6. What is the
result of c(1:3,$)?e = 3. 6. 9.
7. Write the following in the editor:a = [0:0.1:2*%pi]b = this
is executed after a=1plot(a,sin(2*a))//end
What is the result or the behavior of the above statements in
the console after executing the script?The first line declares an
array of floating numbers representing 0 rad to 2 pi rad with
intervals of 0.1 rad. For the 2nd line, we declare a string
variable and for the 3rd line, a plot function is executed with a
as the x-axis and sin(2*a) as y-axis in a rectangular plane.
8. Write a function called myfunct that accepts two parameters A
and B. The function will return the result of (A+B)*B. Execute the
script what is the result?//start of programfunction [R]=myfunct(A,
B) R = (A+B)*Bendfunction
9. Call the function you created in #8 and pass as parameters
the values 3 and 9. What is the result?-->myfunct(3,9) ans =
108.
10. What will your function return if the parameters are [1,2,3]
and [4; 6;7]? -->myfunct([1,2,3],[4;6;7]) !--error 8
Inconsistent addition.at line 2 of function myfunct called by :
myfunct([1,2,3],[4;6;7])
11. How about [1, 2, 3 ; 3, 5, 1; 5 6 -1] and [3, -1, 4 ; -3, 5,
1; -5 6
-1]?-->myfunct([1,2,3;3,5,1;5,6,-1],[3,-1,4;-3,5,1;-5,6,1]) ans
= - 26. 43. 10. - 40. 62. 8. - 36. 60. 14.
12. Do you have to re-execute your function from SciNotes? Why?
No, as long as you dont close the SciLab session and the current
directory youre working in Scilab contains the said function file,
then we can just only execute it once and call it directly. But if
you close the SciLab session and open another session, you must
re-execute the function. Again, you only need to execute it once as
long as the SciLab session is still the same session youre working
with, with the executed function.
ConclusionAs to my experience in using MatLab, SciLab is pretty
much the same with MatLab. SciLab offers functions and variable
handling capabilities, same as MatLab does, which enables us to
perform mathematical task and numerical method techniques. SciLab
is capable in handling arrays and matrices which is vital in
numerical method, finding a solution of an equation,etc.
Furthermore, we can declare a symbolic variable (same as in MatLab)
which gives us more mathematical features like finding roots, poles
and zeros, partial fractions and more.SciLab is of great help in
simulating systems that we will use and analyze in EE 179. We can
simplify directly a frequency domain representation of using the
symbolic variable along with the arithmetic functions available in
SciLab. Frequency domain representation can then be transformed
back into time domain by hand but not if we have a complicated
frequency domain representation. In order to simplify this, we have
to do partial fraction expansion which can be readily solved by the
pfss function in SciLab. We can also convert our transfer function
to State-space representation and vice-versa like tf2ss and
ss2tf.
