May 22, 2023

What is a PID controller?

What is a PID controller?

In the world of engineering and automation, a PID controller is a ubiquitous tool used for controlling a wide range of mechanical and electrical systems. PID stands for Proportional-Integral-Derivative, which are the three control modes used by a PID controller to adjust the input of a system. Essentially, a PID controller adjusts the system's output to maintain a desired setpoint, making it a critical component in maintaining precise control over a variety of systems. In this article, we will provide a comprehensive overview of PID controllers and their applications, as well as discuss the various types and tuning methods.

Understanding PID Controllers

The Components of a PID Controller

Before we dive into how a PID controller works, let's first examine its three components: the proportional, integral, and derivative terms.

The proportional term is essentially a gain factor that adjusts the output of a system in proportion to the difference between the setpoint and the current state of the system. This means that the larger the error signal, the larger the proportional term will be, resulting in a faster response to changes in the system.

The integral term, on the other hand, calculates the accumulated error over time and adjusts the control input accordingly. This is important because it ensures that even small errors over a long period of time will be corrected, preventing the system from drifting too far from the setpoint.

Finally, the derivative term takes the rate of change of the error into account and adjusts the input to prevent overshooting or undershooting of the setpoint. By anticipating changes in the error signal, the derivative term can help to stabilize the system and prevent oscillation.

How PID Controllers Work

At its core, a PID controller continuously monitors the input and output of a system and adjusts the output to maintain the desired setpoint. This means that the controller is constantly making small adjustments to the control input in response to changes in the system.

The proportional term responds to changes in the error signal in real-time, while the integral and derivative terms provide long-term adjustment to the control input, preventing oscillation or instability. By combining these three terms, the PID controller is able to provide precise control over a wide range of systems.

One important aspect of PID controllers is the tuning process. Because the behavior of each system is unique, the controller must be tuned to ensure optimal performance. This involves adjusting the gain factors of each term to achieve the desired response.

The History of PID Controllers

PID controllers have been around for decades, with their origin dating back to the early 20th century. The first mathematical treatment of a closed-loop control system, which forms the basis of modern PID controllers, was published by Nicholas Minorsky in 1922.

However, it wasn't until the late 1930s that the first practical application of a PID controller was implemented in an experimental furnace by Elmer Sperry. This early controller used a mechanical amplifier to adjust the control input, but it paved the way for more advanced electronic controllers in the decades to come.

Today, PID controllers are an essential tool in countless industries, from manufacturing to aerospace. They are used to control everything from temperature and pressure to speed and position, and their versatility and precision make them an invaluable asset in the modern world.

Types of PID Controllers

A PID (Proportional-Integral-Derivative) controller is a feedback control loop mechanism used in industrial control systems to regulate process variables. PID controllers are used in a wide variety of applications, from temperature control in ovens and refrigerators to speed control in motors and pumps.

Analog PID Controllers

Traditionally, PID controllers were implemented in analog form, using electrical components such as resistors, capacitors, and op-amps to adjust the control input. Analog PID controllers are still widely used today, particularly in industrial automation systems where precise control is crucial.

One advantage of analog PID controllers is their simplicity. They are relatively easy to design and implement, and can be very reliable when properly calibrated. Analog PID controllers are also able to respond quickly to changes in the process variable, making them ideal for applications where fast response times are required.

However, analog PID controllers have some limitations. They are not as flexible as digital controllers, and cannot easily be reconfigured or updated. They are also susceptible to noise and drift, which can cause inaccuracies in the control output.

Digital PID Controllers

In recent years, digital PID controllers have become increasingly popular due to the proliferation of low-cost microcontrollers and digital signal processors. Digital PID controllers offer greater flexibility and functionality than their analog counterparts, allowing for advanced algorithms and complex control strategies to be implemented.

One advantage of digital PID controllers is their ability to store and analyze data. They can monitor process variables over time, and use this data to optimize control parameters and improve performance. Digital controllers are also able to compensate for non-linearities and other process disturbances, making them more accurate than analog controllers.

However, digital PID controllers can be more complex to design and implement than analog controllers. They require specialized software and hardware, and may be more expensive than analog controllers. They also require a higher level of expertise to operate and maintain.

Hybrid PID Controllers

Hybrid PID controllers combine both analog and digital components, providing the best of both worlds. They offer the precision and reliability of analog systems, combined with the advanced functionality of digital systems, making them ideal for complex control applications.

One advantage of hybrid PID controllers is their flexibility. They can be configured to meet the specific needs of a particular application, and can be updated or reconfigured as needed. They are also able to compensate for noise and drift, while still providing fast response times.

However, hybrid PID controllers can be more complex to design and implement than either analog or digital controllers alone. They require specialized knowledge and expertise, and may be more expensive than either analog or digital controllers. They also require regular maintenance and calibration to ensure optimal performance.

Applications of PID Controllers

Industrial Process Control

PID controllers are widely used in industrial settings to control a broad range of processes, such as temperature, pressure, and flow rate. In manufacturing, for example, PID controllers are used to regulate the temperature of ovens and furnaces, ensuring consistent product quality. In addition, PID controllers are also used in the production of semiconductors, where precise temperature control is critical for the manufacturing process.

PID controllers are also used in the chemical industry to regulate the flow rate of chemical processes, ensuring that the correct amount of materials is used in the production of chemicals. This helps to improve efficiency and reduce waste, ultimately leading to cost savings for the company.

Robotics and Automation

In robotics and automation, PID controllers are used to control the movement and positioning of robotic arms and other automated systems. By maintaining precise control over these systems, PID controllers help to improve efficiency and reduce errors. This is particularly important in industries such as automotive manufacturing, where robotic arms are used to assemble cars and other vehicles.

PID controllers are also used in the field of agriculture, where they are used to control the movement of automated farming equipment. This helps to improve crop yields and reduce labor costs, making farming more efficient and sustainable.

Temperature Control Systems

Temperature control systems, such as those used in HVAC (heating, ventilation, and air conditioning) systems, rely heavily on PID controllers to maintain precise temperature regulation. This is particularly important in settings such as hospitals and laboratories, where temperature control is critical for patient care and research.

PID controllers are also used in the food industry to regulate the temperature of cooking and storage equipment. This helps to ensure that food is cooked and stored at the correct temperature, reducing the risk of foodborne illness.

Motor Speed Control

In motor control applications, PID controllers are used to regulate the speed and position of motors, ensuring smooth, precise movement. This is vital in industries such as aerospace, where precise motor control is necessary for maintaining stable flight. PID controllers are also used in the automotive industry to control the speed of engines and other motorized components, improving fuel efficiency and reducing emissions.

PID controllers are also used in the field of robotics to control the movement of robotic limbs and other motorized components. This helps to improve the precision and accuracy of robotic movements, making them more effective in a wide range of applications.

Tuning a PID Controller

A proportional-integral-derivative (PID) controller is an essential component of many control systems. It is used to regulate the output of a system based on feedback from sensors. The PID controller uses three control parameters: proportional, integral, and derivative. These parameters are adjusted to achieve optimal performance.

Manual Tuning Methods

Manual tuning involves adjusting the control parameters by trial and error. The proportional, integral, and derivative terms are adjusted until the system's response is optimal. To measure the system's response, a step response test is used. This method can be effective but can also be time-consuming and difficult to achieve optimal results.

Manual tuning is often used when the system's behavior is well understood, and the control parameters can be adjusted based on experience. However, it may not be suitable for complex systems or applications with nonlinear behavior.

Auto-Tuning Techniques

Auto-tuning techniques employ algorithms to automatically adjust the control parameters based on the system's response. There are various auto-tuning methods available, including relay tuning, Zeigler-Nichols method, and model-based tuning.

Relay tuning involves applying a small input signal to the system and observing the output. The control parameters are adjusted based on the system's response to the input signal. Zeigler-Nichols method involves applying a step input to the system and adjusting the control parameters based on the system's response. Model-based tuning involves using a mathematical model of the system to predict the system's response to different control parameters.

Auto-tuning techniques can be highly effective in achieving optimal control performance quickly and with minimal effort. They are particularly useful in complex systems or applications with nonlinear behavior.

Common Tuning Challenges

Tuning a PID controller can be challenging, particularly when dealing with complex applications or systems with nonlinear behavior. Common tuning challenges include removing oscillations, preventing overshot or undershot, and reducing steady-state error.

Oscillations can occur when the control parameters are too high, causing the system to overshoot and undershoot its setpoint. Overshoot and undershoot can be prevented by adjusting the control parameters to reduce the system's response time. Steady-state error can be reduced by adjusting the integral term to compensate for any steady-state error.

However, with the right approach and tools, these challenges can be overcome, resulting in high-performing, precise control systems.


PID controllers are a critical component in the world of engineering and automation, providing precise control over a wide range of mechanical and electrical systems. By understanding the components and operation of a PID controller, as well as the various types and tuning methods available, engineers can design and implement effective control systems for a wide range of applications. With the ongoing advancements in technology and automation, the role of PID controllers is only set to become more prominent in the years to come.

Learn more about how Collimator’s controller development capabilities can help you fast-track your development. Schedule a demo with one of our engineers today.

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