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what is pid controller

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Parth86

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hello

i want to know what is pid controller
what component is use to create pid controller circuit
why we use pid controller in control system
 
It is a control technique where you measure the output error of a system and then compensate for it by multiplying, integrating and taking a derivative of the (error) signal. The goal is to keep the output error zero. Integrating the error signal eliminates steady-state error and compensates for errors caused by parameter drifts and mechanical wear etc. Derivative compensates for fast error sources like load-changes and changes in the desired output value.

PID controller is an analog controller and can be implemented using operational-amplifiers, resistors, capacitors. etc. Modern PID controllers are usually implemented using microcontrollers or computers.

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Thank you for that, misterT.

For whatever reasons, never saw an explanation (and block diagram) as succinct as this one.
 
Perhaps one additional remark:
As mentioned by MisterT it is the GOAL to make the output error zero. Of course, this cannot be achieved by 100%.
As an example take the response to an input step. It is the goal of the PID controller to keep the system reaction (step response) within certain limits (small overshoot and small ringing) and to ensure at the same time a quick reaction of the input step. These requirements make it necessary to find a good trade-off for the three PID constants.
In this context, the classical method as described by Ziegler and Nichols can be recommended.
 
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Of course, this cannot be achieved by 100%.

True, and PID is not even near the best available controller if digital processor is used. Discrete PID can never be better than analog PID, but it is usually the easiest to implement. State-Space and Polynomial controllers are more advanced approaches than PID, but of course, those aren't 100% "accurate" either.. nothing is.
 
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For those with an interest in a PID control example in software I have one that can be downloaded here.

Years ago I had an interest in doing PID control in a software application using Visual Basic 6.0 (Yes, that many years ago). I found a program written as a demo by a Max Seim of the 3M Corporation. The link above allows download of a zip folder. If you have an interest download the folder and right click to extract the content. You will see the .vbj project source code as well as another folder in there. Open the folder PID Loop Example and run the Setup.exe to install the program. It will install and run on any Windows version XP to 7. When you are done playing around with it just use add/remove programs to remove it. There is an instructions tab in the form.

Try taking the program out of Automatic and using manual control to control the water flow. :)

The form also displays the PV (Process Variable) and SP (Set Point) graphically so things like over/under shoot can be visually seen. Keep in mind it was done over a decade ago. :)

Anyway, for anyone with an interest it is there to play around with.

Ron
 
Thanks Bob, figured I would toss it out there.

Ron
 
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