Model-Based Diagnosis of Feed Axes with Contactless Current Sensing

State of the art drive controllers, based on numerical and programmable logic controllers (NC and PLC), have not yet established standardized and easily accessible endpoints to capture status and process variables, such as motor current, torque or position values. Direct access to those data sources is limited to proprietary tools or licenses and requires modern control hardware. Besides, available data sources are limited to sample periods down to the NC or PLC cycle time, that varies between 1 and 10 ms. In this paper, we introduce a low-cost, low-tech and low-effort solution for monitoring feed axes based on contactless current sensing. We deploy split-core current transformers onto motor power cables of a variable frequency drive achieving sample rates of 50 kHz. This provides a retrofit solution for feed axes monitoring. Also, we outline the required signal processing to show the solution’s potential for further applications like anomaly detection. As a result, we enable a low-cost monitoring solution for machine tools using a physic-based model.