Open-loop controller: Difference between revisions

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{{more footnotes|date=January 2015}}

In [[control theory]], an '''open-loop controller''', also called a '''non-feedback controller''', is a [[control loop]] part of a [[control system]] in which the control action ("input" to the system<ref>{{Cite journal |lastlast1=Escudier |firstfirst1=Marcel |last2=Atkins |first2=Tony |date=2019 |title=A Dictionary of Mechanical Engineering |url=http://dx.doi.org/10.1093/acref/9780198832102.001.0001 |doi=10.1093/acref/9780198832102.001.0001|isbn=978-0-19-883210-2 |url-access=subscription }}</ref>) is independent of the "process output", which is the [[process variable]] that is being controlled.<ref name="auto">"Feedback and control systems" - JJ Di Steffano, AR Stubberud, IJ Williams. Schaums outline series, McGraw-Hill 1967</ref> It does not use [[feedback]] to determine if its output has achieved the desired goal of the input command or process [[Setpoint (control system)|setpoint]].

There are many open-[[Control loop|loop]] controls, such as on/off switching of valves, machinery, lights, motors or heaters, where the control result is known to be approximately sufficient under normal conditions without the need for feedback. The advantage of using open-loop control in these cases is the reduction in component count and complexity. However, an open-loop system cannot correct any errors that it makes or correct for outside disturbances, and cannot engage in [[machine learning]], unlike a [[closed-loop control system]].

== Open-loop and closed-loop ==