What is control Systems?

[lord loh.]

What does the subject "Control Systems" deal with. This is a subject taught only to engineers in my country and I have absolutely no idea about what it is.

Please enlighten me. :idea:

Thank You.

 

[checkmate]

Are you referring to Control Theory or Control Engineering?
If so, then it's the process of designing a control system that gives the desired outputs given the inputs, in simple words, control :lol:

 

[samcheetah]

control systems is a very vast field. it deals with single-input-single-output (SISO) systems and multiple-input-multiple-output (MIMO) systems. it deals with linear systems as well as discrete systems. it deals with time-invariant systems as well as time-variant systems. it deals with deterministic as well as stochastic processes. the components of a control system could be lumped or distributed. and the list goes on.

so basically control systems is a study of systems in general and their design, modelling and simulation.

the control systems course usually taught at the undergraduate level starts with laplace transforms, transfer functions, poles and zeros, mathematical modelling of systems, transient analysis, root locus, bode analysis, nyquist analysis etc.

it is really fun!!!!

 

[lord loh.]

So is it just designing systems that control other systems ???

I think not, if so then a transistor that ascts as a switch should be a control system.

Can anyone give me a few examples of control systems that one sees everyday? and a few example of uncommon control systems?

Thanks in advance.

 

[niga]

hmm...okay,how abt this,

u have a tank of water with an inlet and outlet but the tank shud always maintain say,2litre.Now how do u control that?The inlet is conntd to a huge reservoir of water.U can do it maunally or automatically.
Manaully-then u need an perator to check the level of water and open the inlet valve to maintain the water tank at 2litres.
to do it automatically u need to design a system embedded to the whole thing which can sense the decrease in the water level in the tank and regulate the inflow...

hope this helps atleast in ateeny weenyway.I am new to control systems so i also hope this interpretation is right.

 

[checkmate]

I think not, if so then a transistor that ascts as a switch should be a control system.

You are right. Such a control system can be classified as a feedforward control system. But something as simple as a switch, or a transistor, is a non-linear device and would prove pretty messy in control calculations.

Strange that there is so much interest in control theory all of a sudden. :lol:

 

[samcheetah]

yes indeed its really strange to see all of this control systems related talk going on today on electro tech. i mean first it was control systems then state transition matrix and then characteristic equation.

i think i should call today as "Control systems day at Electro-Tech-Online"

just kidding :lol:

there are numerous applications of control system in our daily life. the air conditioning unit is a simple On-Off control system. an aeroplane is a huge control system. servo drives, stepper motor applications, you name it and there will be some sort of application of control systems in it.

 

[lord loh.]

The control system day.

I saw a lot of my engineer friends study books on control systems. At that time I did not have enough know-how to understand the contenrts of the book. And this morning I saw nigga's post on some control system and wondered what actually it might be.

From all the talk so far on electroTech and EDA Board (I posted the same question there too), I gather that control systems is not exclusive to electrical /Electronics. It could be mechanical as well (governers). But mostly control system is developed using electronics to cordinate several parameters like in aircrafts or simply keep the input and output of a system in harmony.

Tell me if I have got anything wrong?

So can I call a feedback circuit of an amplifier as a control system?

 

[niga]

I hope someone will suggest some good books on control systems which can help us out.

niga the newbie

 

[Optikon]

Re: The control system day.

I saw a lot of my engineer friends study books on control systems. At that time I did not have enough know-how to understand the contenrts of the book. And this morning I saw nigga's post on some control system and wondered what actually it might be.

From all the talk so far on electroTech and EDA Board (I posted the same question there too), I gather that control systems is not exclusive to electrical /Electronics. It could be mechanical as well (governers). But mostly control system is developed using electronics to cordinate several parameters like in aircrafts or simply keep the input and output of a system in harmony.

Tell me if I have got anything wrong?

So can I call a feedback circuit of an amplifier as a control system?

You are correct in your assertion that "control systems" are not exclusive to electric circuits. Your body trying to regulate your internal temperature is a closed loop control system.

You can think about (and analyze) a feedback circuit in an amplifier as part of a control system. But control systems are not restricted to feedback loops. You can have something called open-loop control.

And then there are the types that are somewhere in between like "bang-bang" temperature controllers that just look for over or under temp and fuzzy control systems where fuzzy logic is applied.

 

[fsahmed]

I hope someone will suggest some good books on control systems which can help us out.

Modern Control Systems (Prentice Hall), Bishop/Dorf.
Modern Control Engineering (Prentice Hall), Ogata.

 

[samcheetah]

yeah, lord loh, i saw your post on EDABoard and the replies you got.

you are right, control systems is not just limited to electronics. it also deals with mechanical systems, thermal systems, hydraulics, pneumatics, spring-mass-dashpot systems etc.

and ofcourse the human body is also an excellent application of control systems. you know our control systems instructor also told us about the PQRS complex (the waveform you get in an ECG). so control systems apply to a great number of fields.

the two books suggested by fsahmed are the best you can get. these are a must have if you have some interest in control systems. and in addition to these, try to get the book

"Control Systems Engineering" by Norman Nise.

have fun!

 

[Agent 009]

Control Systems can be mechanically built, though I find it hard to beleive that they would consist of mechanical stuff only: u need electronics, ie, transistors, op-amps...

 

[niga]

thanx fs and sam for the names of the books

niga the newbie.

 

[fsahmed]

Control Systems can be mechanically built, though I find it hard to beleive that they would consist of mechanical stuff only: u need electronics, ie, transistors, op-amps...

Certainly not. Bear in mind that a control system need not be something external, measuring a system's response & taking required actions, in electronics even a simple two resistor voltage divider can be modelled as a control system.

Simply put, a system is something that generates an output to a given input, a control system is something that gives a controlled or a defined output in response to the input.

As for mechanical systems, electronic feedback is not necessary, the simplest example of an electronic independent mechanical control system is a common spring mass damper system used in shock absorbers of cars.