In our lab, we are developing and applying wearable, unobtrusive sensors for various studies to record and analyze features like human motion, cardiovascular function and stress.
Inertial Measurement Units
Inertial measurement units (IMUs) are sensors which are able to measure movement in terms of acceleration (accelerometers) and angular velocities (gyroscopes). The application areas of IMUs are widespread and range from aerial and nautic navigation, over robotics, gaming, or image stabilization. Wearables are another rapidly growing application area for IMUs.
Due to advancements in processing technologies, IMUs are nowadays manufactured as microelectromechanical systems (MEMS-IMUs) which result in extremely small package sizes and ultra-low power consumption. This enables the integration of such sensors in smartwatches, smartphones, activity trackers or even smart clothing like fitness shirts or insoles which can be used for the assessment of various motion related parameters in health and sport applications.
However, as IMU sensors in wearable applications are mostly optimized for small size, low-power consumption and low price point, these sensors suffer from certain imperfections which need to be considered for later data analysis. These are – amongst other influences – noise, offset, temperature drift, scaling errors, misalignments. To a certain extent, some of these errors can be counteracted by proper calibration procedures of the IMU sensors. Other factors which cannot be easily compensated but one needs to be aware of are e.g. sampling rate inaccuracies / time-drifts or the phenomenon called gimbal lock. Still, there are also various algorithmic approaches available to improve the measurement accuracy of IMU sensors, such as sensor fusion, which helps to combine the best worlds of accelerometers and gyroscope for optimized spatial orientation.
Monitoring of Cardiovascular Function
Cardiovascular function is usually assessed by recording electrocardiogram (ECG), photoplethysmogram (PPG) or blood pressure (BP). In the past, these signals were typically acquired by stationary systems in a clinical environment. However, recent technology developments also made wearable sensors to monitor cardiovascular function possible. While clinical systems might provide higher data quality and a more controlled environment, these clinical examinations are typically limited to one-time snapshot assessments. Additionally, especially the monitoring of cardiovascular functions is very susceptible to the white-coat syndrome, a phenomenon in which people experience elevated blood pressure and heart rate in a clinical setting.
This issue can be solved by unobtrusive wearable sensors that can measure the human physiology in a familiar home environment and without creating the feeling of actually being monitored.