Subject Spotlight: Control Systems

Welcome to a series covering the variety of electrical engineering subjects available at Melbourne Uni. This series hopes to give those who have not done the subjects a more overall outlook of what the subject entails, tips and more interesting information that is only known by those who have done the subject.

Disclaimer: These articles are written from past experiences and may not reflect what the subject is currently like or will be like in the future. The opinions expressed are purely the authors’ and not representative of the Melbourne Uni Electrical Engineers Club or the University of Melbourne. In no way is anything here presented as fact. Do not come complaining to us if after reading something you think the subject is easy and then you fail or if something crucial has changed in the subject.

 

Year this subject was taken: 2016 Semester 1 (It is available both semesters with different lecturers and different curriculum).

Feedback loops are when you use the output of a system to adjust the input of a system. Feedback control is used in a wide variety of applications such at in aircraft aerodynamics, robotics, motors and is a key part in nature. Control systems engineering is based on turning scenarios into a model called the system, and then designing a feedback loop for the system to meet some specifications.

There are two types of control theory, Classical and Modern. Classical control theory models systems as time domain equations and then use mathematical concepts to determine the properties of the systems and design the feedback loop. Modern control theory models the systems as state space equations, matrices and uses linear algebra to manipulate these and design the feedback loop, usually with computers.

Control Systems the subject focuses on classical control theory, whereas the subject Advanced Control Systems focuses on modern control theory. This subject is a core for the Master of Engineering Electrical but also for Mechanical and Mechatronics.

Topics:

  • Introduction (What is a system, names of parts of a control system, why a control system is good)

    There is a function that will plot the sensitivity TF for you in Matlab.

  • Systems specifications, modelling and responses.
  • Convolution, Fourier Transform and Laplace Transform.
  • Poles and Zeros, stability and responses of 1st and 2nd Order Systems.
  • Sensitivity Transfer Functions.
  • Bode Plots, Nyquist Plots, Routh-Hurwitz Criteron, Root Locus. (These are all analysis techniques)
  • Compensation. (Designing controllers such as lead, lag, lead-lag)

Lectures: (Semester 1)

The lecturer for Semester 1 is Dr Simon Illingworth, and 2016 is the first time he has taken this subject. He once stayed back late in a day after all the lectures were done to get back into the lecture theatre and learn all the functions with the lecture projector.

Lectures are mostly handwritten on the lecture projector, they are then scanned and uploaded on the LMS later.

Due to being a core subject for 3 different disciplines the lectures can be really crowded if there is only one stream.

Prior Knowledge:

This subject follows on from Signals and Systems, the key part being the properties of systems and transfer functions. Initially in Control Systems expect to go through properties and analysis of systems again.

Electrical Network Analysis and Design while not a prerequisite shares Bode Plots, 1st and 2nd order system responses and transfer functions with Control Systems as well.

Workload:

There is one workshop every week, based mostly on Matlab and Simulink. Altogether the workshops are divided into 4 parts. The first 2 workshops are not accessed, and go through several examples on paper and on Matlab.

Lego Mindstorms

The motor on these robots is much faster than you think. Don't start them on the table.

The 3rd and 4th workshop applies the knowledge from the first two workshops into building a feedback system for a robot. The 3rd workshop designs the system for making the robot move forward, and the 4th workshop designs the system for the pendulum on the robot to stay up.

When you finish your design you have to show the demonstrator it working and they will ask each member of the group individually questions to ensure that everyone understands how to do the work. Afterwards a report about the workshop is written and submitted online.

The Control Systems mid-semester test is a timed online test. Because of this it is multiple choice and matching graphs to responses. Questions are from a pool and so it is not possible to get the same test as someone else.

Tips:

A lot of the examples in this subject are not going to be electrical because of its multidisciplinary status. The subject accounts for this by ensuring that the equations for the systems are given to you so you don't have to derive them. However you still have to be able to manipulate the equations using Fourier and Laplace transforms.

The robots in the 3rd and 4th workshop are really fiddly sometimes, they have to be connected and detected by Matlab but also they have to connect to the Bluetooth dongle which has to be detected by the computer. Try using an older version of Matlab (on the lab computers), and if the Bluetooth dongle cannot be detected by the computer it might already have been connected.

Because the lecturers have recently changed, the exams are quite a bit different than before, unfortunately that means only the most recent exam would be similar to what you might get.

Brian Douglas Lectures (look it up on YouTube) is a very good study guide as he gives a good introduction to all the new analysis techniques taught in this subject.

 


BY Dennis Nguyen

Melbourne University Electrical Engineering Club

2016

One Response to “Subject Spotlight: Control Systems

  • Thank you for posting this series, it is really helpful as there isn't much information regarding students' perspective of Masters of Engineering (particularly electrical) at the University of Melbourne.

    Could you continue doing more Masters subjects please?

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