how can i select P, PI, PD, PID controllers for different process(flow,pressure,temperature,level)?

Question

the above question related to instrumentation technology.

Answer 1

The basic criteria for selecting the type of control that you require is dependent on the application. There is no particular recommended selection to control different parameters like flow, pressure, temperature etc vis-a-vis the type of control. If you application can't tolerate any amount of overshoot, then you have to go in for PI, if you need faster response, go for PD or PD and so on. (another thing to be taken care is to decided on the type of response, first order, second order or third order). To summarize, the type of controller is not dependent on the parameter to be controlled, but on the responses demanded by an application

Answer 2

Actually There are no controllers like P , PI , PD and PID ,
What you mentioned here are the Calculation methods to achieve the Desired values of some Process Variables

This can be clearly explained by below

There are controllers like

Pneumatic , Electronic and Etc..

The calculation methods to what response and to what speed and to what range this controllers will work are depend on the P, D and I values.

The P, D and I values can be tuned for it's best operating range

Literatures are available for this tuning methods


One controller can be worked with any of the calculation from P,PD,PI,PID.

Answer 3

Extremely complicated, the rest of the people have the basics and definitions down right. Its all depending on what you're doing. If its homework then its a little harder to know which to pick, but its all on how much you care about which values. Take a pump for example and a temp probe. The P (proportional) controller just slows it down any time it warms up....and that makes it go slower and faster all the time (waste of time). You can add an I to it (makes a PI) and that will look for trends, it will see if the temperature is too high for a longer period of time and can notice if there is going to be bearing damage from long term high temp. The D (derivative) will see spikes. If the temp spikes, the design of the pump might be able to handle it or it might let you in that there might be a sudden blockage in the line and you need to fix it fast. I know that's a lot, and only for a pump, but they are very complicated but extremely good controllers

Answer 4

for temp u select PD controller.for other process u may selet PID controller

Answer 5

see:
http://en.wikipedia.org/wiki/PID_control for discussion of the different parts of the PID and why they're important.