Answer / arulnainar

1.P(Proportional): to calculate the error signal (Error
signal means the difference between Process variable(PV)and
Setpoint.(E=SP-PV)-- Present(Howmuch)

2.I(Integral): to remove the offset error. It will decide
howlong the error exist in the cycle.(Iitegral time in RPM
or MPR)--Past(HowLong)

3.D(derivative): It will decide how fast the control action
to remove the error without any overshooting or
undershooting in the process for future cycle.

For practically we can say Howmuch(present), Howlong(Past),
Howfast(Future) respectively P,I,& D.

Answer / abdus sattar mollah

lets us dscribe the role of indivitual |P,|I,|D in |PID
controller....
|P(proportonal)==to give one to one correspondense between
the error signal and manipulated signal.This give linearity
between the above two signal and thus bring output varialbe
to controlled value or set point.
|I(integral)==to remove the offset error.
|D(derivative)==to fasten the control action.

Answer / lenin kumar

P(proptional):To control the present difference between sp
and pv
I(integral): To control the past
D(derivative) :To control the futcher

Answer / arpan singhania

PID controller.....
P is to attain the set point..
I is to remove the offset error..
D is to make the action fast and controllable..

Answer / www.islamqa.com

Actually we can make it simple:

# P:
it's a controller gain which modify the controller o/p
proportional to the error.

# I:
it's a controller gain which modify the controller o/p
proportional to the integral of the error.

# D:
it's a controller gain which modify the controller o/p
proportional to error rate of change.



We have 4 parameters in our control loop to focus on:
1 - the rise time: the period of time during which the pv
get 90% of the desired sp value
2 - max overshoot
3 - settling time: the period of time during which the pv
get the desired sp value and saturate.
4 - error/offset

we can get it clear from this pic:
http://controls.ame.nd.edu/ame437/S2003/hw1/specifications.j
pg

Now we will take a look about the effect of each controller
gain on these parameters:

# P gain:
decrease rise time
increase max.overshoot
increase settling time
decrease error (but not eliminate)


# I gain:

decrease rise time
increase max.overshoot
increase settling time
eliminate error.


# D gain:

no effect on rise time
decrease max.overshoot
decrease settling time
decrease error.

the previous is guidelines to be in background while
dealing with PID,but they are not sharp limits.

Regards,

Ahmed Sabry
Control and Instrumentation Engineer
GPC - General Petroleum Company
ahmedsabry.online@gmail.com
CELL.: 00 2 0121367310

Answer / panchal c.a.

Proportional- to control the offset between the process
variable and the set-point.
Integral- to control the time duration of the offset error.
Derivative- to control the rate of change of error.

Answer / praveen kumar

P- means Offset remains
I- means removes the offset
D- means fast action,

Answer / chandra mohan

in PID controller
P controller used for reducing the over shoot,
I-controller used for reducing the offset,
D-controller used for reducing the ossilations

Answer / praveen kumar

p--> directly proportional to the process variable and give final element to fast action
i--> responds the error between process variable and setpoint
d-->rate of change of error with respective time.

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