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P, PI, PD and PID Compensation

Proportional Controller and Integral Controller.

PID Controllers

Proportional controllers

– pure gain or attenuation

Integral controllers

– integrate error

Derivative controllers

– differentiate error

Proportional Controller

U = Kp e

o   Controller input is error (reference output)

o   Controller output is control signal

o   P controller involves only a proportional gain (or attenuation)

Integral Controller

o   Integral of error with a constant gain

o   Increase system type by 1

o   Eliminate steady-state error for a unit step input

Derivative Control

o   Differentiation of error with a constant gain

o   Reduce overshoot and oscillation

o   Do not affect steady-state response

o   Sensitive to noise

Controller Structure

o   Single controller

o   P controller, I controller, D controller

o   Combination of controllers

o   PI controller, PD controller

o   PID controller

Controller Performance

o   P controller

o   PI controller

o   PD Controller

o   PID Controller

Design of PID Controllers

o   Based on the knowledge of P, I and D

trial and error

manual tuning

simulation

Design of PID Controllers

o   Time response measurements are particularly simple.

o   A step input to a system is simply a suddenly applied input - often just a constant voltage applied through a switch.

o   The system output is usually a voltage, or a voltage output from a transducer measuring the output.

o   A voltage output can usually be captured in a file using a C program or a Visual Basic program.

o   You can use responses in the time domain to help you determine the transfer function of a system.

o   First we will examine a simple situation. Here is the step response of a system. This is an example of really "clean" data, better than you might have from measurements. The input to the system is a step of height 0.4. The goal is to determine the transfer function of the system.

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Control Systems : Time Response Analysis : P, PI, PD and PID Compensation |