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Homework answers / question archive / This assignment tests the following skills Implement classes in Matlab Writing robust code including creation of unit tests Create a Matlab app for a specific purpose
This assignment tests the following skills Implement classes in Matlab Writing robust code including creation of unit tests Create a Matlab app for a specific purpose. Only complete tasks 1 and 5.
ES2D7 – Assignment Briefing Sheet – Sept FFA/Resit
Assignment overview
This assignment tests the following skills:
• Implement classes in Matlab
• Writing robust code, including creation of unit tests
• Create a Matlab app for a specific purpose
Important notes
1) The work that you submit must be your own work. Do not copy from online sources or share your solution with other students. Plagiarism detection software will be used to identify solutions with a high similarity.
2) It is very important that you use the specified filenames, class names, variable names and method names. These are case sensitive. Some example mistakes would be:
• Using calculatearea or Calculatearea or Calculate_Area as a method name instead of
CalculateArea
• Implementing a method called GetA or geta instead of getA
3) Please carefully check that you have submitted the correct files to tabula and do NOT change the filenames from those given in the template (you will score zero for that task).
4) Several example scripts are given in this briefing sheet to show how the classes might be used. It is highly recommended to test your solutions with these test scripts as it will highlight whether the methods have been properly set-up.
Assignment Task 1 (20%) – Gasket Class
Using the template on moodle, write matlab code for a class called Gasket, which calculates the area of a ring gasket (the blue area in the figure below). A ring gasket has an inner diameter d_hole and an outer diameter d_gasket (both in centimetres). A template class file has been provided for you with the following properties (with public access): d_gasket
and d_hole.
d_gasket
d_hole
The class Gasket shall have the following methods:
• SetSize(d_gasket, d_hole) which has two input arguments: d_gasket and d_hole.
Upon calling this method, the two dimensions shall be stored (in cm). If d_gasket OR d_hole are negative, the following error message shall be given: ‘ERR_NEG’.
2
• CalculateArea() which calculates and returns the area of the gasket in cm . If this
method is called when d_gasket OR d_hole is empty, then the follow error message
shall be given: ‘ERR_EMPTY’.
• CalculateRatio() which calculates and returns the ratio of d_hole to d_gasket. If this method is called when d_gasket OR d_hole is empty, then the following error message shall be given: ‘ERR_EMPTY’.
The example below shows how this class might be used.
g = Gasket;
g.SetSize(2,1);
a = g.CalculateArea() % returns the ratio in variable a
r = g.CalculateRatio() % returns the ratio in variable r
In order to help you with this task, a test script has been provided with a few tests implemented (testGasket.m). Note – you will need more tests to properly test this class.
Assignment Task 2 (20%) – MSD_sim Class
Using the template on moodle, create a class MSD_sim for simulating a mass-spring-damper
system, following the requirements below. You might find it useful to consult your
notes/resources from the ES197 module and Chapter 9 of the Engineering Databook.
Implement requirements 4, 5, 6, 7 using the formulas given in Sections 9.3 and 9.4 of the
databook. Do not use the TF or step functions for this task.
1. The class shall have a method SetMass(mass) which sets the value of the mass. The
method has one input argument mass which is in Kg.
2. The class shall have a method for setting the damper value in N m s-1:
SetDamper(damper_coefficient).
3. The class shall have a method for setting the spring constant
SetSpring(spring_constant).
4. The class shall have a method CalcNaturalFreq() which calculates and returns the
undamped natural frequency in rad s-1.
5. The class shall have a method CalcDampingFactor() which calculates and returns the
damping factor (has no units).
6. The class shall have a method isUnderDamped() which calculates whether the
system is underdamped or not. If the system is underdamped then the method shall
return 1, otherwise the method shall return a zero.
7. The class shall have a method CalcUnitStepResponse(t) which returns the output of
the system at time t, given unit step input at t=0. Use section 9.4 of the Engineering
Databook to calculate this.
The code below contains an example script for how the class MSD_sim can be used. Make
sure that your class works with the script below and produces the correct answers.
msd = MSD_sim;
msd.SetMass(1); % the class stores the mass = 1Kg
msd.SetDamper(1); % the class stores the damper coefficient = 1 Nm/s
msd.SetSpring(10); % the class stores the spring constant = 10 N/m
wn = msd.CalcNaturalFreq() % the class returns the undamped natural frequency in wn
zeta = msd.CalcDampingFactor() % the class returns the damping factor in zeta
under = msd.isUnderDamped() % the class returns whether the systems is underdamped in variable under
% these lines of code generate a step response from t=0 to t=12
tvals = 0:0.1:12;
y = [];
for t = tvals
newy = msd.CalcUnitStepResponse(t);
y = [y newy];
end
figure;
plot(tvals,y); % this should plot the step response
Assignment Task 3 (20%) – Test script for MSD_sim class
Create a test script to test your MSD_sim class for assignment task 2. The name of your test
script shall be: testMSD_sim.m. Ensure that your test script can be run using:
Runtests(‘testMSD_sim.m’);
Your test script should be done in the format shown in the labs, with each test starting with
a double %% symbol (see TestSqrt.m).
Marks will be awarded for:
• Does a perfectly written class pass all your tests?
• Does the test script find basic errors in a class?
• Does the test script find subtle errors in a class?
The test script should work with any implementation that meets the requirements and not
just your specific solution to Task 2.
Assignment Task 4 (20%) – Data Analysis Class
Using the template on moodle, create a class DataAnalysis that stores and performs some
analysis on a dataset. You may wish to consult your notes/resources from ES2C7 for fitting
the linear model.
1. The class shall have a method LoadData(x,y) which stores the data given in x and y.
Both x and y shall contain vectors of data points and it is expected that x and y both
have the same size. The method shall accept vectors which are provided in column
format (e.g. 5x1) or row format (e.g. 1x5).
2. For the method LoadData(x,y), an error will be given for any of the following cases:
• x and y have different sizes (e.g. x is a 1x6 and y is a 5x1 matrix).
• x and/or y is empty
• x does not contain a column vector or row vector (e.g. a 5x2 matrix has been
provided)
• y does not contain a column vector or row vector (e.g. a 5x2 matrix has been
provided)
3. The class shall have a method Max_x() which returns the maximum value in the
vector x .
4. The class shall have a method Max_y() which returns the maximum value in the
vector y.
5. The class shall have a method Mean_x () which returns the mean value of the
elements in vector x .
6. The class shall have a method Mean_y() which returns the mean value of the
elements in vector y.
7. The class shall have a method FitLinearModel() which fits a linear model y = mx+c to
the data stored. This method will calculate and return the coefficients m and c as
shown in this example:
da = DataAnalysis;
x = [0; 1; 2; 3];
y = [3; 5; 7; 9];
da.LoadData(x,y);
[m,c] = da.FitLinearModel() % returns the coefficients of the
model y=mx+c in the variables m and c
The example below shows how the class may be used:
da = DataAnalysis;
x = -3:3;
y = [-1.4 -0.7 1.8 4.8 6.6 8.9 10.3];
figure; plot(x,y,'r+');
da.LoadData(x',y');
[m,c] = da.FitLinearModel();
