Fuzzy controller

[varunmahendran91]

Can i use fuzzy controller for the controller purpose in programing?
if yes how? any suggestion?

 

[shooter]

A fuzzy controller can be used as a 1 in / 1 out controller, (standard PID), however the big force of fuzzy is the use of multiple inputs to get better grip on an process.

you will have to enlighten more to get better answers.

 

[varunmahendran91]

how can i use it in AB5000?

 

[JordanCClark]

What shooter means is that the more details you can give on what you are trying to do, the quality of our answers will get better.

What PLC are you trying to use?
What hardware are you attaching to it?

There are likely many more, but as I said, if you can a detailed explanation, we may be able to help you better.

 

[varunmahendran91]

Alright.. using allenbradley 5000... i have a system to be controlled... which should satisfy the following conditions...
1- 3 pumps are there to pump water(lead, lag, standby)
2- maintain system pressure at a setpoint
3- system pressure varies according to downstream pressure
(a flow transmitter is there to take measurement)
4- when pressure decreases..means the downstream demand is high...
to maintain it, make use of speed controling of motor(ie speed increases)
5- when lead pump reaches 98% of its max speed, lag should start.
6- lead deacreases its speed and lag increases speed... when both come in a line(same speed)..now only it start to maintain the system pressure...
7- when both lead and lag are not able to control pressure... standby start...
8- when lead pump is not able to control high system pressure ie less downstream demand(require below min speed of lead pump) bypass valve open to maintain system pressure.....

I think i need to use a PID speed of motor....

 

[keithkyll]

Use PID. Fuzzy would be worse in this application.

 

[shooter]

hey hey i am fuzzy, it is not worse, however due to lack of experience by users, a faster result is done with PID.

I think it is for learning the unit so yes PID is easier.

 

[Peter Nachtwey]

There are three problems here.
1. A PID should be used to compute the % of max pump capacity to use. There is no point in using a fuzzy controller for this.
2. Pressure control systems are not linear. Pressure goes up with the flow squared.
3. There needs to be a away of dividing the load between the different pumps.
This part could be done with fuzzy logic because there are multiple outputs but I think it would be easier to simply write some equations or use a look up table that specifies which pump combination is required to get a specific flow. There may need to be two tables. One for increasing flow and another for decreasing flow to avoid pumps rapidly cycling on and off at some flows. Fuzzy logic would not help here unless it got complicated by remembering state.