System and method for monitoring step motor

A step motor monitoring system, for monitoring a step motor, wherein the step motor is driven by a driving unit, and the driving unit outputs a command signal and drives the step motor to rotate from a start position to an end position and then back to the start position repeatedly, the step motor monitoring system comprising:

• an encoder, mechanically coupled to the step motor, the encoder detecting a status of the step motor and outputting a status signal;
• a judgment unit, for real time receiving the command signal from the driving unit and the status signal from the encoder, recording a variation of a difference between the command signal and the status signal vs. time as an error data, and determining whether the step motor is starting from the start position, in action, reaching the end position, or returning to the start position according to the command signal and the status signal, wherein if the judgment unit determines that the step motor is in action, the judgment unit records the error data as a tracking error and determines whether an alarm is to be issued according to the tracking error;
• a notification unit, coupled to the judgment unit, the notification unit performing a notification function when the judgment unit determines that the alarm is to be issued.