Design of wireless inertial trackers for human joint motion analysis

Body motion analyzing has always been a useful tool to evaluate patients' joint kinematics. Optical tracking is one of the most accurate dynamic tracking systems, and is commonly used as diagnosis devices for joint motion analysis. However, these systems are usually located in gait analysis laboratory and not readily available in clinic or hospital for day to day diagnostic use. In order to provide an alternative means for joint kinematics assessment, the following method is examined. An inertial sensing node composes of a set of inertial micro-electromechanical system (MEMS) sensors (accelerometers, gyroscopes and magneto-meters) were used to track two adjacent joint segments. This paper presents a preliminary study of motion tracking of the upper and lower extremities of the leg during dynamic activities. Each node communicates wirelessly to the base station with Bluetooth. A quaternion based Extended Kalman Filter (EKF) was implemented to process the data for orientation estimation. Anatomy constraint is applied to the relative orientation of the estimation. The focus of this paper is to introduce the framework of easy to use, high mobility, low cost motion analysis and diagnostic system that can be used in doctor's office.