Monitoring daily human activities, posture recognition, and gait analysis are vital for monitoring human health and routine activities, especially for the elderly. A safe and healthier living environment can be ensured using accurate and reliable information from wearable sensors monitoring and tracking human posture, activities, and gait analysis. The proposed research work is divided into two segments. The first one where the gait analysis is performed using a simple triangulation-based methodology utilizing low-cost wearable ultrasonic sensors based on ankle angle and toe clearance sensing. The second part focuses on measuring human activity and posture. The first part of the work is completed and will be presented in detail. Gait analysis study includes monitoring an individual's gait pattern using kinematic and kinetic parameters, assessing fall risks to prevent them, and evaluating surgical procedures and rehabilitation's efficacy.

Traditional methods of gait analysis are being done in an expensive motion-capture laboratory under a controlled environment. Although this provides accurate results, continuous monitoring and feedback are not feasible. The alternative is wearable systems that employ inertial measurement unit (IMU). However, IMUs suffer from drift due to the double integration to arrive at the position information. Although there are methods to overcome this drift using zero velocity updates and Kalman filtering techniques, these indirect methods of determining key gait parameters such as the ankle’s angular position require complex computation and predictive approaches. The present work highlights a simple direct measurement of the ankle angle (AA) by triangulation methods using ultrasonic sensors without any complex sensor fusion algorithms. In addition, the proposed scheme senses the minimum toe clearance (MTC) which is another critical gait measure. The gait events are determined using the AA and toe clearance data obtained in a gait cycle. The gait events and temporal parameter measurements of the gait cycle were tested and compared with an in-house made video-based reference system. The root mean square error values were found to be varying between 0.91 to 1.54 degrees for ankle angle and 0.36 to 1.26 cm for toe clearance across gait phases. Repeatability of the proposed system using the standard deviation was found to vary between 1.53 to 2.56 degrees for ankle angle and 0.27 to 1.42 cm for toe clearance across gait phases. It is found to have a good correlation with r value of 0.98 and 0.99 for p 0.001 for ankle angle and toe clearance, respectively, and matching with normative gait patterns, as expected.