Presentation Information
[C-12-42]Development of a Trans-nail PPG Sensor with a Dual-Stage Offset Compensation Function
◎△Akihiro Suzuki1, Aoi Kataura1, Yuqi Duan1, Ryotaro Kawashima1, Kotaro Torazawa1, Pattaramon Thianmontri1, Yukino Sakurai1, Koji Kiyoyama2, Tetsu Tanaka1 (1. Tohoku University, 2. Nagasaki Institute of Applied Science)
Keywords:
Trans-nail,PPG,HMI,offset compensation
This paper proposes a trans-nail PPG sensor circuit for robust finger gesture classification. The proposed circuit incorporates a two-stage offset compensation scheme. Reattachment of the device causes significant variations in the DC baseline, which can be misinterpreted as features of finger gestures, resulting in degraded classification accuracy. To address this issue, the proposed circuit combines a coarse current-mode DAC and a fine voltage-mode DAC. This combination enables the PPG signal to be rapidly and accurately stabilized to a target voltage. A debounce mechanism with temporal redundancy is introduced to suppress erroneous compensation caused by motion artifacts and chattering. The proposed PPG sensor circuit was fabricated using a 0.18 µm CMOS process. Experimental results using the fabricated chip and an machine learning model demonstrate that extremely high classification accuracy is maintained regardless of offset variations due to device attachment and detachment. The proposed system provides a seamless HMI environment without requiring user recalibration or model retraining, indicating strong potential for practical applications.