Unobtrusive Wearable System for Load Vertical Location Estimation.

Low back pain (LBP) is a leading musculoskeletal disorder, and manual material lifting is proven to be a major cause of LBP. However, current solutions for monitoring a major LBP risk factor - load vertical location (LVL), are not user-friendly or accurate, which makes them impractical for real-world applications. To address these problems, a user-friendly wearable system was proposed in this study to realize an accurate measurement of LVL over time. The wearable system consists of a pair of smart insoles, each integrated with an insole-shaped pressure sensor array and an Inertial Measurement Unit (IMU), and a smart wristband integrated with one IMU and one barometer. To ensure an accurate LVL measurement with the barometer in the wristband over time, a novel Known Vertical Location Update (KVLU) method was proposed to calibrate the barometer drifting errors continuously. The method proposed in this study achieved a Mean Absolute Error (MAE) of 5.84 cm, which significantly outperforms the state-of-the-art methods.