Continuous Calibration and Narrow Compensation Algorithm to Estimate a Joint Axis under the Various Conditions with Unit Sensor

Wearable robots have been developed to aid or substitute the gait locomotion of humans. To assist gait locomotion based on the intention of a wearer, a gait pattern analysis is required with a wearable sensor by measuring body information, i.e., a joint angular velocity. However, measuring a precise joint angular velocity is difficult because the attachment position of a sensor has a curvature and an anatomical joint axis which is invisible. Therefore, a sensor calibration algorithm, which aligns a sensor axis into an anatomical joint axis, is required to provide an optimal assist for a wearer. Hence, in this paper, a new and simple sensor calibration algorithm is proposed with a unit sensor. Since a wearer shakes the body or collides with the ground when walking, the attachment position of a sensor may be changed. Thus, a continuous sensor compensation algorithm is also proposed. Additionally, the effectiveness of this new algorithm is demonstrated by gait locomotion experiments on various paths.