Determining whether a control system is open-loop or closed-loop depends on observing its feedback mechanism and whether it functions during the current control process. Open-loop control is a control activity completed in a short period, while closed-loop control requires a certain duration and can be used to verify the effectiveness of the feedback loop.

Open-loop control system: In such systems, there is only a forward action relationship between the control device and the controlled object, with no backward connection. Therefore, the output of an open-loop control system does not affect the control effect of the system. For example, automatic vending machines, automatic washing machines, automatic production lines, and automatic lathes typically use open-loop control systems.

Closed-loop control system: A closed-loop control system is a control method that adjusts based on feedback from the controlled object's output. When there is a deviation between actual measurement results and preset values, the system corrects according to predefined standards. In a closed-loop control system, a control signal is extracted from changes in the output and fed back to the input to adjust the input. Typically, the extracted signal is in opposite phase to the input signal, hence termed as negative feedback control.

In summary, the difference between open-loop and closed-loop stepper motor control lies in whether the motor can provide feedback on its current operating status. Open-loop stepper motors do not have feedback signals; they only execute actions sequentially without detecting output results or correcting outputs. In contrast, closed-loop stepper motors have feedback signals. They take corresponding action measures based on the driver or feedback the signal to the PLC, which then determines the next step in program processing. This means closed-loop stepper motors can detect output results and adjust based on differences between actual output and theoretical requirements. Therefore, compared to open-loop stepper motors, closed-loop stepper motors have higher precision.