Answer / karthika

Tunning is a process in which we adjust the controller parameters(Kp,Ki,Kd) so as to obtain desired performance of the controller.

different tyes of tunning:-
1. Zigler-Nicholes method
2. Cohen Choon
3. 1/4 decay ratio

Answer / chhote lal

by the help of P we calculate the error signal
Error signal=SP-PV (How Much)in the timming of pid tunning.
By the help of I we Remove the offset error-it will decide
how long the error exit in the cycle inthe timming of pid
tunning.
And by the help od D we fasten the control action-it will
decide how fast the control action to remove the error
without any overshoot for failure cycle.
at last
P=How Much(present)
I=How Long(past)
D=How Fast(future)

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 / sumit sharma

pid is proportional integrative derivative
pid is a closed loop system which is used for error checking of analog devices only, it cant used on digital devices.
pid consistes of
kp proportional
ki integrative
kd derivative
in pid tuning first kp,ki,kd is taken as any integer and then error is checked by the pid formulae
if there is error then the values of kp ki kd can be changed to give the error 0

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