A Novel Sensorless Position Sensing for Free-Piston Engine Generation Using Observation Coil

The accurate observation of mover is crucial for the effective operation and control of free-piston engine generator (FPEG). The conventional position sensors have drawbacks such as high cost, limiting the development of FPEG. This study introduces a novel sensorless position observation technique based on the structural characteristics of FPEG. The proposed approach employs an observation coil to establish the relationship between the flux and the displacement for observing the position of the mover in real time. This paper presents the establishment of an equivalent magnetic network model and a finite element model for the analysis of flux. A series of displacement observation experiments were conducted on a test bench. It is found that the calculated flux value has a linear connection with the actual position. The difference between the model results and the linear model results obtained from the testing is less than 3%. This approach can acquire instantaneous the observed position of the mover in real time during the test within a ±5mm range. The sensorless position observation approach can achieve a position detection error of less than 5%. This novel sensorless approach provides essential guidance for optimizing the performance and improving the commercial viability of FPEG.