IMU-based Characterization of the Leg for the Implementation of Biomechanical Models

Abstract

The main limitation of using inertial measurement units (IMUs) for inertial navigation systems (INS) is the accumulated error in the heading angle estimation. Different approaches have been proposed to reduce the position error caused by the heading drift, but accurate biomechanical models have not been explored in INS. A precise leg characterization method is needed to develop INS-oriented biomechanical models. The main goal of this work is to evaluate an IMU-based method to locate the leg joint centers and axes, and to estimate the leg segment lengths. These leg parameters are required for the implementation of lower-limb biomechanical models. Four different versions of the method are implemented and compared using a stereo- photogrammetric system as gold standard. The method validation is conducted in four volunteers by doing five exercises. The calibration exercises involve five different leg movements. The proposed method shows an average accuracy of 2 cm and 3 cm over 21cm and 54 cm in joint centers and axes determination, respectively. In the estimation of the leg segment lengths, the average accuracy of the proposed method is 2 cm over 39 cm. The proposed method brings promising results improving the estimations of the state-of-the-art methods.