# Inertial and Flexible Resistive Sensor Data Fusion for Wearable Breath Recognition
###### Abstract  
This paper proposes a novel data fusion technique for a wearable multi-sensory patch that integrates an accelerometer and a flexible resistive pressure sensor to accurately capture breathing patterns. It utilizes an accelerometer to detect breathing-related diaphragmatic motion and other body movements, and a flex sensor for muscle stretch detection. The proposed sensor data fusion technique combines inertial and pressure sensors to eliminate nonbreathing body motion-related artifacts, ensuring that the filtered signal exclusively conveys information pertaining to breathing. The fusion technique mitigates the limitations of relying solely on one sensor's data, providing a more robust and reliable solution for continuous breath monitoring in clinical and home environments. The sensing system was tested against gold-standard spirometry data from multiple participants for various breathing patterns. Experimental results demonstrate the effectiveness of the proposed approach in accurately monitoring breathing rates, even in the presence of nonbreathing-related body motion. The results also demonstrate that the multi-sensor patch presented in this paper can accurately distinguish between varying breathing patterns both at rest and during body movements. breath detection; respiratory monitoring; sensor data fusion; IMU sensor; flex sensor +
Footnote †: journal:monitoring changes in blood oxygenation. Wearable sensors used for breath monitoring often incorporate various electronic components. These components may be directly [8; 9] or indirectly [10; 11; 12] attached to the body. [PERSON] et al. (2020) provided an overview of recent developments in stretchable sensors and wearable technologies for real-time and portable healthcare systems [13]. This review focuses on the sensing mechanisms, design concepts, and integration of variable sensing components of these sensors for breath detection. In [14], a wearable healthcare device made with lightweight and flexible materials was introduced. The device can stick to the skin and track breathing. Different sensor types, including acoustic sensors, humidity sensors, pressure sensors, and inertial measurement units (IMUs), can be employed to monitor breathing rates, each of which has unique advantages and disadvantages [15; 16; 17; 18]. For instance, acoustic sensors may be negatively impacted by background noise. Despite their greater robustness to environmental conditions than other sensors, humidity sensors may not be ideal for prolonged use. Additionally, although accelerometers and pressure sensors are cost-effective, they are susceptible to non-breathing-related movement artifacts. Wearable pressure sensors can be used to capture diaphragmatic contractions and relaxation. When attached to the chest or abdomen using a belt, these sensors can measure the force applied during expansion [11]. Capacitive and resistive (flex) sensors are two distinct types of pressure sensors that have been used in many wearable body and muscle movement detection tasks [19]. A comparative analysis between capacitive and resistive (flex) sensors for wearable human joints and motion sensing applications revealed subtle distinctions in their performance characteristics [20]. The study demonstrated that both sensor types exhibit commendable static and dynamic capabilities, and their study showed that capacitive sensors demonstrate superiority in terms of linearity and long-term repeatability; however, capacitive sensors exhibit greater signal noise. Conversely, resistive sensors exhibit greater sensitivity and excel in terms of signal anti-interference capabilities. The optimal choice between capacitive and resistive sensors ultimately depends on the specific requirements of the application. Resistive flexible sensors used in breathing detection are commonly applied on the chest walls since they detect deformations related to respiratory movements [21]. Several studies have been conducted to explore the use of piezoresistive sensors for breath monitoring [22; 23; 24; 25; 26; 27; 28; 29].