Accelerometer Integrating Electromagnetic Actuator with Negative Stiffness for Noise Reduction

This paper proposes a force balance accelerometer where a hybrid reluctance actuator (HRA) positions a flexureguided proof mass for acceleration measurement with high sensitivity and reduced noise. The HRA has a coil and a permanent magnet to generate a reluctance force, by which the proof mass can be heavy for high sensitivity. Furthermore, the HRA has an electromagnetic negative stiffness to cancel the flexures’ stiffness for noise reduction. For force balance to measure acceleration, a feedback controller is designed, achieving a closed-loop bandwidth of 305 Hz. Experimental results reveal that adjustment of the negative stiffness decreases measurement noise at a low frequency of 1 Hz from $1.3 \times 10^{-3}\left(\mathrm{~m} / \mathrm{s}^{2}\right) / \sqrt{\mathrm{Hz}}$ to $2.8 \times 10^{-4}\left(\mathrm{~m} / \mathrm{s}^{2}\right) / \sqrt{\mathrm{Hz}}$ by $77.7 \%$ without influencing the sensor’s sensitivity, which successfully demonstrates the effectiveness of the proposed accelerometer.