Pid Control Basics In Detail : Part 2

The Previous article I already explain to you Why PID Control required for the Industrial application.

Now we are going to Pid Control Basics? How PID works in Industrial application.

There are many types of controllers and we’re going to touch on a lot of them as

The PID controller is a great place to start because it’s simple efficient and effective in a wide array of applications, in fact, it’s the majority of controller types and industrial applications so it’s well worth learning

let me start with the term PID Control Basics

PID is an acronym and it stands for Proportional Integral Derivative.

  • Each of these terms describes how the error term is treated prior to being summed and sent into the plant In one of its block diagram forms a PID controller can be written like this in the proportional path the error term is multiplied by a constant KP
  • in the integral path the error is multiplied by ki and then integrate it and
  • in the derivative path, it’s multiplied by KD and then differentiate it
  • the three pads are then summed together to produce the controller output
  • Now the three K terms are called gains and they can be adjusted or tuned to a particular plant with a defined set of requirements and by changing these values you’re adjusting how sensitive the system is to each of these different paths either the P I or D path let me explain what I mean

with a few plots here

let’s see the error in the system is

Proportional Plot KP :

  • changing over time like this blue line in the proportional path the output is the error scaled by the KP so you can see here that when the error is large the proportional path will produce a large output when the error is zero the output in the path is zero and when it’s negative the output is negative

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Integral Plot Ki :

  • In the integral path as the error moves over time the integral will continually sum it up and multiply it by the constant ki in this plot it’s easy to see that the integral path is the area under the curve where this blue section is the positive area in this green section here is negative area now the integral path is used to remove constant errors in a control system since no matter how small the constant error eventually the summation of that error will be significant enough to adjust the controller output

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Derivative Plot Kd :

  • Now in the derivative path, it’s the rate of change of the error that contributes to the output signal when the change in error is moving relatively slowly like it is at the beginning hair then the derivative path is small and the faster the error changes the larger the derivative path becomes now at this point you can just sum up each of these three paths and you’ve got the output of a PID controller but you don’t always need all
  • Three paths you can remove a path completely by setting its associated gain to zero when you do this you generally refer to the controller with the letters of the path that are left
  • For example, you can have a proportional integral controller or P I if you set KD to zero and just a controller if KD and ki are both zero so why would you simplify the controller like that why not just make the biggest best controller you can with all paths intact and super complicated well typically
  • when I’m designing a control law I tried to make the logic as simple as I can while still meeting all design requirements I do this for several reasons one is a simple controller is easy to implement – a simple controller is easy to tune test and troubleshoot
  • when there are problems and three a simple controller is easy for other people to understand which is important when you work on a large project and interface with other groups
  • that have to buy into the control logic, for example, a software or hardware team that has to implement it so simple controllers can save you time and money over the life of the program as long as they still meet your design requirements and this is why despite having a lot of really complicated control systems out there

Must Read : PID Control Explained In Detail : Part 1

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