| A battery-less wireless sensing technology to monitor the cage temperature in bearings was developed. Non-contact measurements are necessary because the bearing cage performs a sliding motion with respect to inner and outer races, and its rotation excludes direct wiring and the use of slip rings. Four wireless sensing circuit prototypes were implemented. Three circuits are based on a Colpitts oscillator, a Voltage Controlled Oscillator (VCO) and a Meissner oscillator, respectively, and a fourth sensor is based on Radio Frequency Identification (RFID) principles. Radio-frequency (RF) signals are used to supply the energy to the sensor electronics, so no direct contacts to the sensor circuits are required. Experimental results on a bearing while it is operating are presented. The techniques developed provide a feasible solution for the measurement of the bearing cage temperature, which can be adapted to monitor the condition of other mechanical components for which wired circuits are difficult to use. |
