What is PID Controller and How it works?

What is PID Controller?

A PID controller is a device that regulates temperature, flow, pressure, speed, and other process variables in industrial control applications.

The PID controller is a feedback-based control loop that is widely used in industrial control systems for a variety of applications that require continuously modulated control.

PID controller is also called as three-term controller.

A PID controller calculates an error value continuously {\ Displays style E (T)} E (T) The difference between the required setpoint (SP) and the measured process variable (PV), applies a correction based on proportional, integral, and derivative terms P ( And D are indicated), hence the name.

How does it work?

A PID controller can be used as a way to regulate pressure, flow, temperature, and other process variables. As its name implies, a PID controller combines proportional control with additional integral and derivative settings, allowing the unit to automatically compensate for changes in the system.

Basics of PID

The purpose of a PID controller is to force feedback to match a set point, which, like a thermostat, forces the heating and cooling system to turn on or off based on a certain temperature. PID controllers are commonly used in systems with a low mass that respond quickly to changes in input power during the process. This is recommended in systems where the load changes frequently, and the controller automatically expects compensation due to frequent changes in the setpoint, the amount of available energy or the mass to be controlled.

Working Principle

The working principle behind a PID controller is that the proportional, integral, and derivative terms must be individually arranged or “tuned”. With the use of a simple on-off controller at low cost, only two control states are possible, such as fully on or off.

These two control states use it as a sufficiently limited control application for control purposes. However the oscillating nature of this control limits its use, so it can be replaced with PID controllers.

The PID controller maintains the output as having zero error between the process variable and the setpoint / desired output. PID uses the three basic control characteristics described below.

Proportional Controller

The proportional or P- controller produces an output that is proportional to the current error e. (t). It compares the desired or set point value to the actual or feedback process value. The output is obtained by multiplying the resulting error by a proportional constant. If the error value is zero, the output of this controller is also zero.

Integral Controller

Integral tuning attempts to resolve this by effectively aggregating the error result from the “P” function to increase the correction factor. Since the p-limitation controller always has an offset between the process variable and the setpoint, the i-controller is required because it has the function of eliminating static state error. It collects errors from time to time until the value of the error reaches zero. It retains the value of the last control device whose error is zero.

Derivative Controller

Attempts to reduce overshoot by slowing down the correction factor as the derivative tuning target approaches. The i-controller does not have the ability to predict the future behavior of the error. So once the setpoint is changed it will respond normally. The de-controller solves this problem by anticipating the future behavior of the error. Its output is determined by the derivative constant multiplied by the rate of error change relative to the output time. This initiates the output, which improves the response of the system.