An '''open-loop controller''', also called a '''non-feedback controller''', is a type of [[Controller (control theory)|controller]] that computes its input into a system using only the current [[state (controls)|state]] and its [[mathematical model|model]] of the system.
A characteristic of the open-loop controller is that it does not use [[feedback]] to determine if its output has achieved the desired goal of the input. This means that the system does not observe the output of the processes that it is controlling. Consequently, a true open-loop system can not engage in [[machine learning]] and also cannot correct any errors that it could make. It also may not compensate for disturbances in the system.
Advanced Open-Loop system based on Predefined Control methodology can be self-learning and adaptive.
'''Bold text'''== Examples ==
An open-loop controller is often used in simple processes because of its simplicity and low cost, especially in systems where feedback is not critical. A typical example would be a conventional [[washing machine]], for which the length of machine wash time is entirely dependent on the judgment and estimation of the human operator. Generally, to obtain a more accurate or more adaptive control, it is necessary to feed the output of the system back to the inputs of the controller. This type of system is called a [[Closed-loop_transfer_function|closed-loop system]].
For example, an [[irrigation sprinkler]] system, programmed to turn on at set times could be an example of an open-loop system if it does not measure [[soil]] [[moisture]] as a form of feedback. Even if rain is pouring down on the lawn, the sprinkler system would activate on schedule, wasting water.
An example of this is a conveyor system that is required to travel at a constant speed. For a constant voltage, the conveyor will move at a different speed depending on the load on the motor (represented here by the weight of objects on the conveyor). order for the conveyor to run at a constant speed, the voltage of the motor must be adjusted depending on the load. In this case, a closed-loop control system would be necessary.
==See also==
*[[Control theory]]
*[[Controller (control theory)]]
*[[Feed forward (control)|Feed-forward]]
*[[Process control]]
==References==
* Kuo, Benjamin C. (1991). ''Automatic Control Systems'' (6th ed.). New Jersey: Prentice Hall. ISBN 0-13-051046-7.
