The Development of Projected Capacitive Array Sensing in Healthcare

• Main Authors: Wen-YingChang, 張文穎
• Other Authors: Chin-Lung Yang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/386ecm

博士 === 國立成功大學 === 電機工程學系 === 103 === The study uses two stages to develop projected capacitor for healthcare. The first stage builds up a flexible projected capacitive sensing mattress (FPCSM) that can classify the sleeping posture of an individual. The second stage is proposed using a FPCSM for personal health care and assessment. The capacitance-to-digital conversion (CDC) method was used to sensitively and accurately measure the capacitance of the projected electrodes. The required characteristics of the projected capacitor were identified to develop large-area applications for sensory mattresses. The area of the electrodes, the use of shielding, and the increased length of the transmission line were calibrated to more accurately measure the capacitance of the electrodes in large-size applications. To offer the users comfort in the prone position, a flexible substrate was selected and covered with 16 × 20 electrodes. Compared with the static charge sensitive bed (SCSB) and non-invasive respiratory monitoring system (NIRMS) of literature, our proposed system- FPCSM comes with more electrodes to increase the resolution of posture identification. As for the commercial product of body pressure system (BPS), the FPCSM has advantages such as lower cost, higher aging-resistance capability, and the ability to sense the capacitance of the covered regions without physical contact. The proposed guard ring design effectively absorbs the noise and interrupts leakage paths. The projected capacitive electrode is suitable for proximity-sensing applications and succeeds at quickly recognizing the sleeping pattern of the user. Compared with using a precision digital multi-meter, a correlation coefficient of up to 0.997 can demonstrate the feasibility of the CDC method. Unlike the interfaces of conventional measurement systems for polysomnography (PSG) and other alternative contemporary systems, the proposed FPCSM uses projected capacitive sensing capability that is not worn or attached to the body. The FPCSM is composed of a multi-electrode sensor array that can not only observe gestures and motion behaviors but also enables the FPCSM to function as a respiration monitor during sleep using the proposed approach. To improve long-term monitoring when body movement is possible, the FPCSM enables the selection of data from the sensing array, and the FPCSM methodology selects the electrodes with the optimal signals after the application of a channel reduction algorithm that counts the reversals in the capacitive sensing signals as a quality indicator. The simple algorithm is implemented in the time domain. The FPCSM system is used in experimental tests and is simultaneously compared with a commercial PSG system for verification. Multiple synchronous measurements are performed from different locations of body contact, and parallel data sets are collected. The experimental comparison yields a correlation coefficient of 0.88 between FPCSM and PSG. These results demonstrate the feasibility of the system design.