What is PID control?

Temperature control in process cooling typically involves the use of a temperature control system.

Applied Thermal Control use Proportional-Integral-Derivative (PID) control in the design of our recirculating chillers (aside from the ecoMini). PID is a more advanced form of feedback control that uses a mathematical algorithm to optimise temperature control. The algorithm takes into account the current temperature, the rate of change in temperature, and the accumulated error over time to determine the optimal cooling rate.

PID control is a closed-loop system that uses feedback from the process being controlled to make adjustments to the control system. It works by calculating the difference between the desired output (setpoint) and the actual output and using this error information to make corrections to the control system.

The correction is made up of three components, as shown below. These components are combined and applied to the control system to produce a correction that optimises the control of the process.

Proportional (P) Control

This component of the correction is proportional to the size of the error. If the error is large, the correction is also large. If the error is small, so is the correction. The proportional control component helps to bring the process variable towards the setpoint quickly.

Integral (I) Control

This component of the correction is based on the accumulated error over time. It helps to eliminate any persistent error that may remain after the proportional control component has been applied.

Derivative (D) Control

This component of the correction is based on the rate of change of the process variable. It helps to anticipate and prevent overshoots in the process variable.

The benefits of using PID include:

Accurate control – PID control is highly accurate and can maintain a precise setpoint, even in the presence of disturbances or changes in the process. This makes it ideal for applications where precise control is required.
Fast response time – PID control can respond quickly to changes in the process, which is important in applications where fast response times are required.
Robustness – PID control is highly robust, and can handle a wide range of process conditions, including changes in load, process gain, and dead time. This makes it a good choice for applications where the process conditions are subject to change.
Ease of use – PID control is relatively simple to implement and can be easily tuned to achieve the desired performance. This ease of use makes it a popular choice for process control.
Cost-effective – PID control is a cost-effective solution for process control, especially when compared with more complex control systems.