Review of Linear Control Systems, In Brief.

Good day! 

Today, I'm going to rant 

a brief on a favourite 

(read: "favourite") 

subject of mine for this semester. 

ENT220/4 Linear Control Systems. 

I've posted on Instagram 

about how cool the lecturer is. 

I've posted on Facebook 

about the syllabus. 

Now, allow me to elaborate about the subject 

a lil bit more. 

Beware! 

It's only suitable for people 

with mild engineering knowledge.

So before we go further 

This subject, simply put 

is all about 

CONTROL. 

lol, yeah. 

Exactly what the lecturer said 

at the first lecture 

as in 

"If you want to be queen/king of control, 

you must learn this subject" impression. 

Next, he came with this. 

"If you put your grandma into the input, 

you'll get your grandma from the output." 

That is, by having control of a particular system 

(or plant, as specified by throughout the course) 

You shall get the output 

exactly as it is desired 

(or in this case, as it is inserted at the input). 

It's clear anyway 

that the control we speak of here 

is the control in the context of engineering field. 

The first chapter's all about the basic terms

systems, sub-systems, plant, control, open & closed loop.  

and some revisions on Laplace Transforms (LTs)

so it's nothing much in particular. 

Boleh google sendiri kot istilah kat atas tu ea? Hihi

Afterwards, using the reaffirmed knowledge of LTs 

we learnt to deduce transfer functions 

from block diagrams 

and signal flow graphs 

also, by using the above 
we model a few systems 
deducing transfer functions outta them 

be it mechanical, electrial & biomedical 

Simple electrical system => RLC circuit 

Mechanical system consisting of
mass, spring, gears & damper

Biomedical system => ECG machine

Going forward 

we're being familiarized to analyze a system 

in time domain & frequency domain. 

A pinch of terms 101, 

system is something that produces output 

upon an input is fed into it 

while time domain & frequency domains 

are just like s-domain in LTs.  

might as well say it's similar to currencies used in banking 

so time & frequency domains be like American & Australian Dollar 

s-domain's like Britain Pound Sterling. Lol. 

In usual practices, it is just fine to do analysis 

in these two domains. 

Time domain analysis (TDA) 

is practical for most types of inputs 

(step, ramp, parabolic) 

while frequency domain analysis (FDA) 

is practical when the input is sinusoidal. 

We learnt a few more new terms & specifications 

unique to TDA & FDA respectively. 

For TDA 
we were taught to perform it in two situations:  
when the system is giving usual response (transient) 
and when it is stable (steady-state) 
also, new terms 
rise & settling time, time delay, maximum time, maximum overshoot 
and how damping factor affects a system response 
again, we compute the system response 
using LTs 
in cases of simple, multiple & complex poles 
(partial fraction thingy, if anyone recalls) 
also, we consider the steady-state error 
that difference between the output 
and reference input at steady-state 
considering the system isn't producing the exact result. 

As for FDA 
those new terms be like 
resonant peak & frequency, bandwidth & cut-off rate. 
Else, the focus is more on doing Bode plot & Nyquist plot 

Bode plot in MATLAB environment. 

An example of Nyquist plot

so as to estimate better the frequency response 
as well as determining system stability 
and converting it later for estimation in time response. 
Kalau dah datang US kenalah pakai US$ kan, 
takkan nak guna MYR pulak. Hew 

Last but not least 
what's the point of having the control 
if you're clueless about the system's stability? 
Realizing that (kononnya), 
we were exposed to a few techniques 
to examine the stability. 
namely Routh's Table 

and root locus 

one of those examples of root locus techniques

As a side note, 
Routh-Hurwitz's criterion 
is always the major consideration here. 
After knowing all these, 
we are acquired 
to design controllers 
be it PID or lead-lag. 
while PID or Proportional Integral Derivative type 
is a combination of PI & PD types, 
one features a good steady-state error & cut-off rate improvement  
while another features higher stability & bandwidth improvement 
thus PID is a compensation for both types 
as lead-lag 
is merely another name for PI-PD combo. 
In addition, Ziegler-Nichols First & Second Tuning Method 
are also applied 
in order to find parameters for said controller types 
Kp, Ti, Td 
assuming the plant's on transient response.

Well, that sums up the subject that consumes 
partly the past 14 weeks of four-hour lectures. 
Sorry for the extremely brief story, I guess. 
I'm in the attempt of 
lessening the gravity of the matter 
while keeping the interest intact in between 
nanti ada yang pening. Siapa tau 
Kepada sesiapa yang belajar benda ni untuk sem ni 
terutamanya geng satu kelas 
semoga berjaya! 
untuk subjek ni dan subjek-subjek yang sewaktu dengannya. 
Best wishes to everyone else whom taking finals too. 
Assalamualaikum!

P/S: Using sources from Wiki since I can't link sources from my varsity portal.