In open loop operation, the controller determines the actuator command from the input or a programmed sequence, not from the actual output. The command therefore follows a planned relationship between input and action. This arrangement keeps the control path straightforward and avoids the measurement and comparison stage that a feedback-based system requires, which helps explain its simplicity and low cost.
Because no output comparison occurs, disturbances, load changes, and measurement errors do not trigger an automatic correction. The resulting output can depart from the intended value even when the command itself is unchanged. This sensitivity is a central performance consideration: open loop operation is most appropriate when operating conditions are predictable or when exact output regulation is not essential.
Compared with closed-loop operation, open loop operation trades adaptability for simpler implementation. A closed-loop arrangement can use output information to correct deviations, whereas an open-loop arrangement continues according to its predetermined command. The choice therefore depends on whether the application prioritizes rapid, uncomplicated control or improved accuracy and responsiveness to changing conditions.
An engineering workflow begins by specifying the desired input or sequence, relating that command to the required actuator action, and programming or setting the controller accordingly. The system then applies the command to the actuator while the process runs. Evaluation focuses on whether the resulting output is acceptable under expected conditions, since automatic correction is unavailable.
An open-loop setup requires a controller that can issue a predetermined command, an actuator that converts the command into system action, and the controlled process itself. Depending on the application, the command may be time-based, input-based, or sequential. The arrangement does not require an output measurement to drive correction, supporting relatively simple and low-cost implementations.
Timers, traffic signals, washing machines, and basic motor drives illustrate where this strategy can be useful. These systems can follow programmed timing, sequencing, or drive commands without continuously regulating the final output. In engineering, such examples show how open loop operation provides rapid control when predictable behavior is sufficient, while also highlighting situations where feedback may later become necessary.