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Description
Flat 2-D alignment sensors are required by the printing industry for precise mounting of the plate on the drum to avoid position misalignment in the overlapped patterns. Another application is for the coil alignment for contactless charging. High linearity is not required as the sensor serves as a null indicator in the automatic alignment process. The sensor should be very thin and the moving part should be passive target. Existing X-Y optical position systems such as [1] achieve high accuracy, but they are sensitive to dirt. Capacitive sensors such as [2] are sensitive to tilt, which cannot be avoided in industrial applications.
Our novel sensor consists of flat coil system on the stationary part and flat magnetically soft cross-shaped armature on the moving part as shown in Fig. 1a. One excitation and four 20-turns PCB pickup coils are used. The output voltage is measured by synchronous detector to suppress the interference from external fields and indicate the displacement direction. The temperature dependence and the influence of liftoff will be suppressed by using ratiometric output. The sensor simulated output for 0.5 mm thick FeSi armature is shown in Fig. 1b). The performance was confirmed experimentally. In the full paper we will compare simulations to experimental results for both FeSi and nanocrystalline armatures for frequencies up to 1 MHz. We will also demonstrate the influence of the eddy currents in the armature as well as possibilities of using non-magnetic armature. The sensor geometry will be further optimized for sensitivity and linearity for arbitrary movement direction.
Fig. 1 a) Magnetic x-y position sensor b) sensor output for FeSi armature movement in x direction - FEM simulation.
Acknowledgements
This work was supported by GACR project 24-12705S Novel Magnetic Position Sensor.
References
[1] J.-A. Kim, J. W. Kim, C.-S. Kang, and J. Jin, “Note: An absolute X-Y-$\Theta$ position sensor using a two-dimensional phase-encoded binary scale,” Review of Scientific Instruments, vol. 89, no. 4. AIP Publishing, Apr. 01, 2018. doi: 10.1063/1.5022717.
[2] S. B. Field and J. Barentine, “Capacitive position sensor with simultaneous, linear X–Y readout,” Review of Scientific Instruments, vol. 71, no. 6. AIP Publishing, pp. 2603–2607, Jun. 01, 2000. doi: 10.1063/1.1150656.
