A low-cost diagnostic tool for stepping motors

This paper presents a low-cost diagnostic tool to point out if an anomalous no-motion condition occurs when stepping motors are used in machine-tool industrial applications. The method is based on current sensing. By evaluating the second derivative of the current in the switched on windings, it is possible to determine if motion takes place. The proposed method has been implemented using a 16-b microcontroller. Since this diagnostic tool is based mainly on the internal resources of the microcontroller and takes about 10 μs every 26 μs, it could be integrated into the digital motor drive. Experimental results show that under heavy-load working conditions about 90% of the anomalous waveforms are detected, while spurious alarms are negligible (0.001% measured with respect to over half a million analyzed waveforms)