Quick Primer On Open Loop Control

Quick Primer On Open Loop Control


The definition of an open loop control system is one where there is no information about ‘controlled’ variable, which in this example is the temperature of the liquid out.



The easiest way to explain open loop control is to take a blank sheet of paper and put a dot in the middle of the page….now close your eyes and put your finger on the dot…chances are that you missed the dot in the middle since you don’t have any visual feedback or guide, but this is open loop! The goal is defined but there is no feedback information to let you know how well the goal is being achieved.

In the example shown below, the position of steam valve is the control of the process and since there is no measurement of the temperature of the outgoing liquid, any process control is based on the familiarity and experience of the operator adjusting the steam valve.


Mathematical model

Since there is no measurement or feedback, the control portion is entirely subjective and consequently there can be no mathematical model for this type of control.