The effects of movement speeds and magnetic disturbance on inertial measurement unit accuracy: the implications of sensor fusion algorithms in occupational ergonomics applications

Musculoskeletal disorders of the upper extremity are among the most common and expensive of all occupational injuries and illnesses. Understanding and measuring the risk factors associated with these conditions is important for improving worker health and well-being. The measurement systems available for this purpose, however, are quite limited. Inertial measurement units (IMUs), a relatively new technology available for measuring important aspects of worker motion in the field, offer improved data collection prospects for ergonomists. However, the accuracy of IMUs can vary beyond clinically- acceptable levels. The overall goals of this thesis were to (i) provide knowledge about the capabilities and limitations of IMUs in order to explain the inconsistencies observed in previous studies that have assessed IMU accuracy, and (ii) provide guidance for the ergonomics community to leverage this technology within its current capabilities. The studies in this dissertation systematically examined factors known to adversely affect IMU accuracy. Results suggested that the advertised capabilities of IMUs (full-body motion capture in workplace settings) may not be achievable using current sensor technologies. However, these sensors are still substantially more accurate than the devices commonly used by ergonomists to measure upper extremity postures and movements in field settings.