Ambulatory assessment of human body kinematics and kinetics

Traditional human movement analysis systems consist of an optical position measurement system with one or more 6D force plates mounted in a laboratory. Although clinically accepted as `the golden standard' for the assessment of human movement, the restriction to a laboratory environment with its limited measurement volume prevents these systems to be used in an ambulatory environment. To overcome this limitation, this thesis proposes two measurement systems. First, an instrumented shoe is proposed that is used to assess the 3D ground reaction force, the center of pressure trajectory, the center of mass trajectory, and the movement of the foot. The instrumented shoe consists of an orthopedic sandal with two 6D force/moment sensors beneath the heel and the forefoot, and two inertial sensors rigidly attached to the force/moment sensors. Second, a measurement system is proposed which fuses inertial and magnetic sensing to estimate relative positions and orientations on the human body. Fusion is achieved using a realtime Extended Kalman Filter (EKF) with a tightly coupled structure. Change of position and orientation is predicted by integration of acceleration and angular velocity measured by an inertial sensor. Magnetic updates are used to reduce the inherent integration drift due to noise and a fluctuating offset. To minimize energy consumption, the magnetic system only actuates if the uncertainty associated with the position and orientation exceeds a predefined threshold. Moreover, only the coil delivering most information for the reduction of the uncertainty is actuated.