General method for PID controller parameter tuning - Database & Sql Blog Articles

RF cable can be customized for other specifications

Single chip microcomputer STM32L151CCU6

Photocoupler

The tuning of PID controllers is a crucial part of control system design. It involves determining the proportional, integral, and derivative parameters based on the characteristics of the process being controlled. There are two main approaches to PID tuning: theoretical calculation methods and engineering setting methods.

Theoretical methods rely on mathematical models of the system to calculate initial parameter values, but these may need further adjustment through practical testing. Engineering methods, on the other hand, are more hands-on and use experience-based formulas derived from real-world tests. These methods are widely used in industrial applications due to their simplicity and effectiveness.

Common engineering methods include the critical ratio method, reaction curve method, and the attenuation method. Each method involves conducting tests and adjusting parameters based on observed responses. No matter which approach is taken, fine-tuning during actual operation is always necessary to achieve optimal performance.

The critical ratio method is often preferred in practice. The steps typically involve:

• Choosing a short sampling period.
• Applying only proportional control until the system reaches critical oscillation, then recording the proportional gain and oscillation period.
• Calculating the PID parameters using standard formulas based on the system's response.

In terms of practical settings, the general rule is to start with small P values, gradually increase them, and adjust I and D accordingly. For example, in temperature control systems, typical P ranges from 20% to 60%, I from 180 to 600 seconds, and D from 3 to 180 seconds. Similar guidelines exist for pressure, liquid level, and flow rate control.

Experience plays a key role in PID tuning. Adjustments are made by observing the system’s response and making iterative changes. For instance, if the system oscillates too much, increasing the proportional band might help. If the response is slow, reducing the integration time could improve it.

The differential term helps reduce overshoot and improve stability, especially in systems with fast dynamics. However, it should be used carefully, as excessive D can cause instability.

In summary, PID tuning is both an art and a science. While theoretical formulas provide a starting point, real-world adjustments and experience are essential to achieving the desired control performance. Whether you're working with temperature, pressure, or flow control, understanding the role of each parameter—P, I, and D—is vital to successful automation.