Das Video kommt von YouTube: erst beim Abspielen verbindet sich die Seite mit YouTube (Google).
PID Controller Explained
Das Wichtigste aus dem Video
Tipp auf eine Zeit – das Video springt genau dorthin.
Transkriptautomatisch erstellt · 71 Zeilen
- This video is brought to you by us, RealPars!
- Join the top 1% of PLC programmers. Learn from the world's best so you can join their rank.
- Head on over to realpars.com and start learning now In this video, we're going to talk about the PID Controller
- and its transformation from a single station device to what it has evolved into today.
- We’re going to explain why PID Controllers are used in industrial processes instead of simple ON/OFF Controllers.
- 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
- as it’s familiar to lots of people. 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 the furnace turns ON and OFF.
- As you can see, the temperature is not exactly held at the setpoint of seventy degrees Fahrenheit,
- but cycles above and below the setpoint. ON/OFF control may be ok for your house,
- 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.
- In most industrial applications, 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. Each block contributes a unique signal
- 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, or PV signal, and the Setpoint.
- Based on that comparison, the controller produces an output signal to operate the Final Control Element.
- This PID Controller output is capable of operating the Final Control Element over its entire 100% range.
- Most modern PID Controllers are part of a PLC or DCS and are created in the program control logic using block commands.
- Before PLCs came along, 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 mounted on a panel.
- There are still many stand-alone PID controllers being manufactured and used today.
- OK, let’s get back and talk about 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
- and the Setpoint as the Error signal. *The proportional block* creates an output signal proportional
- to the magnitude of the Error Signal. Unfortunately, the closer you get to the setpoint, the less it pushes.
- Eventually, the process just runs continuously close to the setpoint, but not quite there.
- That’s when Integral jumps in. 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 for specific process requirements.
- 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
- produces a quarter-wave damped response. 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.
- One method involves increasing the amount of setpoint change and repeating the procedure
- until the process enters a state of steady-state oscillation. This method of tuning produces adequate results
- but is often impractical in many applications. For example, how practical is it to force the fluid level in a large tank
- to reach a steady-state oscillation? Most process controllers, PLC, and DCS loop controllers sold today
- have Autotuning capability. The PID controller learns how the process responds to a change in setpoint,
- and suggested PID settings. Regardless of whether the initial PID parameters are derived
- from manual or auto-tuning methods, additional tweaking is often required by seasoned automation professionals
- to get the response desired. That should do it for this video.
- If you want to learn more about PID control you might want to watch our other two videos called
- *“What are PID Tuning Parameters?”* and *“How to Tune a PID Controller.”*
- You can find the links to these videos in the description. Ok,… let's review:
- An ON/OFF or Bang-Bang controller has only two output conditions and switches abruptly between these two conditions.
- In a PID Controller, P stands for Proportional, I stands for Integral, and D stands for Derivative.
- The PID Controller is responsible for ensuring that the Process remains as close to the desired value as possible regardless of various disruptions.
- The PID controller determines how much and how quickly correction is applied by using varying amounts of P, I, and D action.
- *The proportional block* creates an output signal proportional to the magnitude of the Error Signal.
- The *integral block* creates an output proportional to the duration and magnitude of the Error Signal.
- The *derivative block* creates an output signal proportional to the rate of change of the error signal.
- Controller Tuning involves correctly setting the controller P, I, and D values for specific process requirements either manually or automatically.
- Want to learn PLC programming in an easy-to-understand format? and take your career to the next level?
- Head on over to realpars.com