Difference between Open-loop and Closed-loop Control Systems

A control system is a system in which a differential equation governs the behavior of the computer system. Control loops are mainly utilized to handle systems and devices. There are mainly two types of control systems: open-loop and closed-loop. The open-loop control system is that type of control system where the control action is independent of the output generated by the physical system. It indicates that the control action is not changed by the open-loop control system's output.

On the other hand, the closed-loop control system is a form of system in which the control action relies on the output that is offered by the physical system. It signifies that the closed-loop control system's output changes the control action. The user's experience defines the accuracy of the open-loop control system. In contrast, the closed-loop system is highly accurate and precise even in the presence of nonlinearity.

In this article, you will learn about the difference between Open-loop and Closed-loop Control Systems. But before discussing the differences, you must know about Open-loop and Closed-loop Control Systems with their advantages and disadvantages.

What is Open-loop Control System?

An "open-loop control system" is a type of control system in which the system's output relies on the input whereas the input or controller of the system relies on the system's output. These open-loop systems lack a feedback loop, and they are sometimes known as non-feedback systems.

The control system receives input in the system. After that, the system processes the input and produces output. The open-loop control system is made up of two physical components: a controller and a plant. The controller is responsible for controlling the input value, which is then transmitted to the plant.

The controlled input is processed by the plant component, which produces the associated output. In this control system, the controlled amount of input that offers to the plant is freed of the produced output.

Advantages and Disadvantages of Open-loop Control System

There are various advantages and disadvantages of the open-loop control system. Some main advantages and disadvantages of the open-loop control system are as follows:

Advantages

1. These systems are designed to be simple to build and maintain.
2. The open-loop control systems respond more quickly because there are fewer physical components to process input.
3. The system's output demonstrates stability.
4. These systems are less costly.
5. The operation of open-loop control system is quite convenient.

Disadvantages

1. The changes in output caused by external disturbances are not automatically adjusted.
2. These systems must be calibrated on a regular basis.
3. The systems are more vulnerable to malfunction.

What is a Closed-loop Control System?

A "closed-loop control system" is a kind of system in which the system's output signal is fed-back to the system's input. As a result, the associate output signal defined the control action in a closed-loop control system.

A controller, plant, feedback or a sensor, and an error detection component are the main physical components of a closed-loop system. Initially, the controller receives the input, i.e., reference input. The controller controls the amount of input and sends it to the plant. After that, the plant processes the controlled input and produces the output.

When the initial output is generated, the feedback component selects it and converts it to a signal of the same kind as the reference signal. The feedback signal is routed to the error detector. The error detector detects the difference between the reference and feedback signals, creates the error signal, and sends it to the controller.

The controller alters the error signal to produce the control action. The control action is subsequently processed by the plant in order to rectify its output. Closed-loop control signals are less impacted by external disturbances and thus more accurate.

Advantages and Disadvantages of Closed-loop Control System

There are various advantages and disadvantages of the closed-loop control system. Some main advantages and disadvantages of the closed-loop control system are as follows:

Advantages

1. These systems are more precise even in the presence of non-linearities.
2. They have a simpler layout and so these systems are more affordable and stable as a result.
3. It is equipped to deal with external disturbances.
4. These systems are less affected by noise.
5. The feedback system corrects the output automatically.

Disadvantages

1. These systems are more expensive and sophisticated.
2. The feedback decreases the system's overall gain.
3. The main issue with the closed-loop system is stability; therefore extra effort is required to create a stable closed-loop system.
4. Feedback in a closed-loop system may result in an oscillating response.

Key differences between Open-loop and Closed-loop Control Systems

There are various key differences between open-loop and closed-loop control systems. Some of the key differences between open-loop and closed-loop control systems are as follows:

1. In an open-loop system, control actions are not dependent on the output generated. On the other hand, a closed-loop system is a kind of system in which the control action relies on the output produced.
2. A controller and a plant are the physical components of an open-loop system. On the other hand, closed-loop control systems utilize a controller, feedback element, plant, and error detector as physical components.
3. The open-loop system generated output doesn't change or modify the control actions. In contrast, the closed-loop system generated output change and modifies the control action.
4. In terms of cost, closed-loop system is more costly than the open-loop system.
5. In terms of reliability, closed-loop control system is more reliable than open control loop system.
6. An open-loop control system is incapable of dealing with external disturbances. In contrast, the closed-loop control system is prepared to deal with external disturbances.
7. The physical components of the open-loop control system are fairly simple to configure. In contrast, the setup of the main components of the closed-loop system is quite complicated.
8. Open-loop systems are sometimes known as manual or non-feedback control system. In contrast, closed-loop control systems are frequently referred to as automatic control systems or feedback control systems.
9. Open-loop control systems are inaccurate because there is no automated correcting mechanism. In contrast, there is an automatic corrective mechanism that ensures the closed-loop control system's accuracy.
10. Open-loop systems need less maintenance than the closed-loop control system. In contrast, closed-loop systems need more maintenance.
11. Open-loop control systems respond to input faster because it contains several physical components to process the information. In contrast, closed-loop control system responds more slowly because it has more components than the open-loop control system.
12. Open-loop control systems are commonly utilized in practical applications such as automatic washing machines, immersion heaters, automatic traffic signal systems, and so on. In contrast, closed-loop control systems are commonly utilized in several applications, including toasters, rocket launching systems, air conditioners, refrigerators, radar tracking systems, and so on.

Head-to-head comparison between Open-loop and Closed-loop Control Systems

Here, you will learn the head-to-head comparisons between open-loop and closed-loop control systems. The main differences between open-loop and closed-loop control systems are as follows:

Conclusion:

Open-loop and closed-loop control systems are two types of control systems that are mainly utilized to manage the behavior of systems. Both systems have their own benefits and cons. Closed-loop control systems are often more reliable and consistent because they offer feedback. Many automatic processes utilize both open-loop and closed-loop control systems, such as temperature control systems in refrigerators, automatic washing machines, traffic lights, air conditioners, etc.