G0210104 Knee Joint Center of Rotation Estimation using Inertial Sensor

Abstract

This paper proposes a novel method for estimating the knee joint center of rotation (CoR) using inertial sensors. The inertial sensors used in this work contain tri-axial accelerometers and gyroscopes. The inertial sensors are attached to the femur and tibia segments of the leg and are capable of measuring the acceleration and angular in all 3 axes simultaneously. The angular velocity data was used to calculate the rotation angle around the CoR and the centrifugal acceleration was used to calculate the distance from the inertial sensor to the CoR. Experiments were carried out in two stages: preliminary pendulum experiment and measuring the flexion-extension motion of the human knee. In both experiments the accuracy of the sensor's distance to the CoR was evaluated. The preliminary pendulum experiment showed correlation coefficient (CC) of over 0.99 whereas the human flexion-extension motion showed lower CC and the average absolute error was about 5.1 cm. Improvements such as a countermeasure for attachment errors/skin motion and consideration for other rotational motions such as internal-external rotation and varus-valgus rotation should be considered to further increase the accuracy of the proposed method.