Name: PID Controller Explained
Uploaded: 2024-03-26T21:55:12.000Z
Duration: 9 min 25 s
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In this video, we're going to talk about the PID Controller

and its transformation from a single station device

We’re going to explain why PID Controllers are used in industrial processes

We’ll illustrate how Controller settings called Proportional, Integral and Derivative

affect different processes under control.

We’ll also provide an overview of the very important activity called Controller Tuning.

Let’s start with a discussion about home temperature control

This house has a furnace that distributes heat throughout,

and a wall-mounted  controller called a thermostat.

The thermostat has a sensor that measures the house temperature

and compares that measurement to an adjustable setpoint.

If the room temperature is below the setpoint, the furnace is turned ON.

When the room temperature increases above the setpoint, the furnace turns OFF.

This type of control is referred to as ON/OFF or Bang-Bang Control.

Here’s a plot of what the room temperature does over a period of time

As you can see, the  temperature is not exactly held

at the setpoint of seventy degrees Fahrenheit,

but it is not ok for industrial processes or motion control.

Let’s look at an example of tank level control to explain why.

The Valve fills the tank as the pump drains it.

If the valve is operated with ON/OFF control,

the water will fluctuate around the 50% setpoint.

For our purpose, let’s say the fluctuation  is plus or minus ten percent.

this fluctuation around the setpoint is not acceptable.

OK, well, what if it’s possible to throttle the valve

and place it in any position between ON and OFF?

Now we can move on to talking about a PID Controller.

P stands for Proportional, I stands for Integral, and D stands for Derivative.

Because every process responds differently,

the PID controller determines how much and how quickly correction is applied

by using varying amounts of *Proportional, Integral, and Derivative* action.

that is added together to create the controller output signal.

Let’s look at how a PID Controller fits into a feedback control loop.

The Controller is responsible for ensuring that the Process

remains as close to the desired value as possible regardless of various disruptions.

The controller ****compares the Transmitter Process Variable,

the controller produces an output signal to operate the Final Control Element.

This PID Controller output is capable of operating the Final Control Element

Most modern PID Controllers are part of a PLC or DCS

and are created in the program control logic using block commands.

a PID controller was a stand-alone device responsible for controlling one loop.

A control room would have dozens or hundreds of stand-alone controllers

There are still many  stand-alone PID controllers

what each of the P, I, and D components of the PID controller does.

Remember earlier we  said that the PID Controller

is responsible for ensuring that the Process remains

as close to the setpoint as possible regardless of various disruptions.

Let’s refer to the difference between the Process Variable

*The proportional block* creates an output signal proportional

Unfortunately, the closer you get to the setpoint, the less it pushes.

Eventually, the process just runs continuously close to the setpoint,

The *integral block*  creates an output proportional

to the duration and magnitude of the Error Signal.

The longer the error and the greater the amount, the larger the integral output.

As long as an Error exists,  Integral action will continue.

The *derivative block* creates an output signal proportional

to the rate of change of the error signal.

The faster the error changes, the larger the derivative output.

Derivative control looks ahead to see what the error will be in the future

and contributes to the controller output accordingly.

That brings us to a term called Controller Tuning.

We said earlier that every process responds differently

and that the PID controller determines how much and how quickly correction is applied

by adjusting *Proportional, Integral, and Derivative* action.

Controller Tuning involves correctly setting the controller P, I, and D values

Interestingly, the correct settings achieved by Controller Tuning

can differ vastly between processes because of specific requirements.

For example,  after the controller has been tuned,

a setpoint bump of one percent in a tank level control

This type of response may be suitable in a tank-level process

but could be disastrous in a motion control process.

There are many different manual methods for tuning a controller

that involves observing the process response

after inflicting controller  setpoint changes.

Subtitles ListPlay Video

PID Controller Explained

specific

process

determine

force