Unconstraint Knee Joint Dynamics Estimation System Using Inertial and Magnetic Composite MEMS Sensor

The estimation system of the knee joint angle that decreases the variability caused by the subjective diagnosis of the knee joint disorders has been attracting a considerable attention. This paper proposes an unconstraint knee joint angle measurement system using inertial and magnetic composite MEMS sensor. The proposed system estimated the posture difference between the thigh and shank region from the difference of the measurement vector between the compound sensors attached on the shank and the thigh, respectively, and 3-D knee joint angles can be calculated by applying Grood's definition. Through experimented results, the knee flexion angle was obtained compared with the true value due to the measurement error of 1.3 deg in average.