what is linear control system?

What is linear control system and what is the difference among linear control systems and traditional control systems?

I think that linear is the classical way. It is different from sampled control systems.

flatulent said:

I think that linear is the classical way. It is different from sampled control systems.

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Could you explain what sampled control system is?

A sampled system is when the output variable is only available at periodic intervals. One early example was from RADAR for automatically pointing the antenna at the target. Another example is a shaft encoder that puts out pulses every certain angle revolution.

hi,

likely the LINEAR control system is referred to a controller that perform its action on a linear (or linearized) system.
For example LQ (Linear Quadratic) control is LINEAR because the systems considered are linear and QUADRATIC because of the use of a performance measure that involve the square of an error signal.

This is a modern control technique which involve the feedback of the state of a system, a classical control which feedback the output could be the pole placement technique or some frequency based technique.

hope this little brief can help,
Ciao

A linear control system is based on the aproximation opf a physical system to be controlled by a linear one.

A linear system roughly speaking has two properties:
1. The output of a sum of inputs is sum of the output due to single input.
2. The output of a constant A multiplied for an input is the same output scaled by the A factor.

Please read the chapter one, two of the book "structure and intepretation of signals and systems" present in this forum, for best understanding of these topics

Finally I tell you that a linear control system can be continous or discrete (as Flatulent says "sampled"), but their proper feature is that the controller can be described for linear diferential equations (continuous case) or diference equations (discrete case).

The linear controller can be described by constant matrices and linear algebra properties apply to these control systems

Hope this helps

neb,,,,,

As opposed to this a Non Linear system is one that has nonlinear transfer functions in it block description.

For example in the analysis of a speed control of a DC motor we assume that the transfer function of the DC motor is linear but infact there is no linear relation between the Voltage applied and the speed if we speak in exact terms.

As neb says most of the time we approximate the physical system - with all its nonlinearities to a linear system by operating over the linear region alone just as we operate a transistor in the linear region for amplification. If the transistor gets into the nonlinear region, clipping occurs and harmonics are produced which is undesirable which is the case even in other physical systems.

the question was about linear systems or linear controls?

The linear control is a type of linear system actuating over other linear system (the system to be controlled).

Other diference is that transfer function approach for modeling linear systems can not be applied for nonlinear systems. This is a great difference.


nebisman,...

Nonlinear systems don't have a transfer function because the output can't simply be expressed as the sum of scaled-shifted impulses.

If you remember we are able to express the output of a linear system as a sum of shifted-scaled impulses because of SUPERPOSITION & SCALING properties (that neb explained in a previous post).

It is this property that enabled us to write the output vector as the product of a matrix and the input vector. Now this matrix is the transfer function matrix. (discrete case only)

This same representation can't be extended to Nonlinear systems because of the lack of the abovesaid properties.

You can write a transfer function for linear sys. because an 1V impulse and a 4V impulse have the same impulse response except for the scaling which is not the case with non-linear systems.

Hope all that blah!blah! is right. Please check the logic.

the question was about linear systems or linear controls?

Click to expand...

it was abt controls but they are inter-related ,aint they? I mean the study of linear control systems is preceded by the study of linear systems.

ash said:

What is linear control system and what is the difference among linear control systems and traditional control systems?

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Linear control systems dont interest by nonlinear systems.

Linear control system may be analog (opamp circuits) or digital (dsp, microprocessor).

Traditional control and analog control are same.

can any one give the inforamtion on PID CONTROL SYSTEM

when u have defined output for a defined input, the system is said to be linear in behavoir.
such systems r also refered as BIBO (bounded input bounded output) systems.

regards