Ultra-Low-Power, Temperature Field-Based Condition Monitoring of Particle Contamination and Overheating in Plain Bearings

Hydrodynamic plain bearings are widely used in heavy-duty applications, e.g., wind turbine drivetrains or ship propulsion systems. However, abnormal events such as mechanical overload causing overheating or particle contamination can lead to rapid bearing damage and the failure of the entire drivetrain. Most existing condition monitoring systems (CMS) cannot detect particle contamination and mechanical overloading in a timely manner or are associated with high costs and installation effort that limit their practical applicability. In this paper, temperature field measurement (TFM) is investigated as a promising approach to address this gap via the development of a sensor-integrating plain bearing (SiPB) prototype. The approach is characterized by its low cost and low energy demand, with the potential for autarkic operation through the thermoelectric harvesting of the frictional waste heat within the bearing. In both overheating tests, characteristic signal discontinuities in the temperature field occurred at least 10 min before the friction torque limit was reached, which served as the criterion for terminating the experiment. Particle contamination resulted in a pronounced increase in the scattering in the temperature field over the entire duration of the experiment compared to regular operation. The interquartile range ($IQR$) of the mean temperature was identified as a promising characteristic; in the single-contamination test, the $IQR$ was increased by a factor of 2.6 compared with regular operation. These characteristics were derived descriptively from one test per abnormal event; repeated tests are required to validate them. The energy demand of the SiPB prototype is determined as a function of the sampling rate (1.3 mW at a sampling rate of 0.2 Hz). The temperature differences required for cold start and the supply mode of the DC-DC converter necessary for supplying the required operating voltage of the SiPB prototype via thermoelectric energy harvesting are determined (approximately 2 and 5 K, respectively). Based on simulation data, this corresponds to the magnitude of temperature differences expected in the plain bearing during normal operation, meaning that the autarkic operation of the SiPB can be enabled in the future.