Open Loop Control System

An open loop control system is a type of control system in which the system’s output does not have any effect on its input and, therefore, does not have any feedback.

Open loop system is also known as non feedback control system because it does not depend on the any previous output or any continuous output of the system. In this type of system input is provided to the system and the output is generated without taking any feedback from the output.

Open-loop Drying System

For example, let us consider an electric clothes dryer .On the basis of amount of clothes on their wetness a user sets a timer(Controller) for the 30 mins. The machine will work for 30 mins and will automatically stop and turn off even if the cloths are still wet or damp. This examples shows that clothes dryer operates as an open-loop system as it doesn’t monitors the dryness of the clothes(the output signal).The Block Diagram can be given as

The Disadvantages of the Open loop system in that it does not have knowledge of the outputs so it does not correct errors when the output has any deviation. The open loop control system poorly handles disturbances or changes in conditions. For example in the Drying System ,if the door remain open of the Dryer then the heat will be lost but still the timing controller continues to run for the full 30 minutes which can lead to the incomplete drying of the clothes.

To Solve this error Feed forward Control is used which is a type of a manual system which will act before the error. So in this example if the user closes the door the dryer very quickly then the system error will be minimized But however the feed forward control is not always the correct approach as the system changes.

Block Diagram of Open Loop Control System

In the Open loop control system the output of the System is fixed accordingly to the input Provided. It does not get influenced by the System’s Feedback. The basic of the Block diagram is given below

In this Block Diagram,

• The Input represents the Desired setpoint that the System should achieve.
• The Controller is like Processing block which Process the input and generates the Control signal based on the Algorithms and Commands provided to it.
• The Controlled Process Represents the Physical System that is controlled by the Controller Block. It could Mechanical, Electrical or any other system based on the Requirements.
• The Output is the response of the system to the control signal generated by the controller.

Control systems are of wide use which can be understood in a better way by the following real-life examples which we use every now and then some of the examples are Regulating the speed of a fan with regulator, Oven temperature control, Washing machine cycle selection based on the type of clothes, Remote control for TV and other electronic devices.

In this article we will be going through an open loop system, We will begin our Article with what is Control System, Then we will Proceed to the definition of the control system and go through its block diagram. Then we will go through the gain of the open loop system and explore its components. At last, we will conclude our Article with Advantages, Disadvantages, Characteristics, and Some FAQs.