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Abstract A wireless smart gear system has been being developed as a gear health monitoring system. This system works based on the magnetic coupling between its two major elements consisting of a monitoring antenna and a smart gear. In operation, the smart gear works as a working gear in the power transmission system while the monitoring antenna monitors this gear continuously. Specifically, since the monitoring antenna is fixed and kept connecting to a network analyzer during the gear operation, it allows the magnetic coupling to occur and remain thoroughly. As a result, the return loss signal of the monitoring antenna becomes a resonant return loss data of the smart gear system. In this paper, the authors propose a method to use this resonant return loss signal for identifying two parameters called the $$Q$$ Q value and the angular frequency of the smart gear side antenna. There are three cases of magnetic coupling that have been considered. These cases are called Open, Short, and Loaded by a 50 [Ω] resistor where the characteristics of the antenna on the smart gear side are changed via its connector by leaving Open or connecting to a Short and a 50 [Ω] resistor modules, respectively. The results indicate that the method is effective for parameter identification of the $$Q$$ Q value and the angular frequency of the smart gear side antenna for all three cases. Moreover, the analysis of the validated $$Q$$ Q value and the angular frequency also indicates the relation between these two characteristic values and the practical conditions of the smart gear. This finding consolidates the effectiveness of our developing wireless smart gear system. Article Highlights This article proposes a parameter identification method for a developing smart gear health monitoring system. By only using the resonant return loss data obtained from the monitoring antenna, there are two characteristic values of the smart gear have been achieved. This article also introduces a completed return loss equation of a magnetically coupled system. This return loss equation is helpful for the computation of characteristic parameters of the magnetically coupled system such as a wireless power transfer system or a coupled antenna system. The results figure out that the identified characteristic parameters and the physical condition of the smart gear side’s antenna circuit are related to each other. This finding affirms the effectiveness of not only the proposed parameter identification method but also the developing smart gear system.

A smart gear sensor system has been developed for the condition monitoring of gear. This system includes a smart gear—the operation gear and a monitoring antenna. The analysis of the return loss of the monitoring antenna magnetically coupled with the smart gear gives the health condition of the gear. This research considers the effects of the distance and phase fluctuations between two components on the magnetic resonant return loss. The impacts of phase fluctuations include both static and high-speed conditions. Two experimental rigs have been built for the two cases. The coupling distance and static phase fluctuation are conducted via the first experimental rig. The second experimental rig performs both the coupling distance and phase fluctuation effect simultaneously while the smart gear rotates at high speed. During each test, the monitoring antenna return loss is captured thanks to a network analyzer. Analysis of the return loss data demonstrates that both the coupling distance and the change of the phase angle at the static condition and high speed have influenced the resonant return loss of the monitoring antenna. These findings are meaningful to the authors for evaluating and improving the accuracy of this gear health monitoring technique.