Design of a dual-coil type electromagnetic actuator for implantable bone conduction hearing devices

This paper describes the design and implementation of a dual-coil type electromagnetic actuator for implantable bone conduction hearing devices.

The structure of the proposed actuator was designed to generate maximum Lorentz force via the dual-coil method with a closed magnetic circuit. To satisfy the indications required by implantable bone conduction hearing devices, high output was generated within a specific frequency range using a vibrational membrane with a cantilever.

The structure of the membrane consists of a fixed ring, a circular plate, and two cantilevers connected symmetrically. Variable elements of the vibrational membrane affecting the actuator frequency characteristics were analyzed through mathematical modeling and finite element analysis, based on the analysis used to derive the optimum structure of the vibrational membrane. The components of the actuator were fabricated through chemical etching and computer numerical control process, and the bone conduction actuator was fabricated through the precision assembly process.

The output characteristics of the implemented actuator were measured using a laser Doppler vibrometer. As a result of measurement, the proposed actuator generated mechanical resonance at 1.2 kHz.

By comparing the measured results with the finite element analysis results, we confirmed the validity of the proposed actuator design.