I. Introduction
Motion capture system is a new information acquirement system, which is considered to be one of the cutting-edge technologies that would have great impact on human development in the era of century [1]. Motion capture technology extends human's visual sense, provides precious and accurate motion data for scientific research and application in many fields such as interactive digital media (games, virtual reality, interactive learning, animation and film special effects), medical care as well as rehabilitation, athletic training, and navigation system. It has attracted lots of research interests in last two decades, and a number of motion capture system have been developed for virtual reality and biomedical applications, including optical system, mechanical system, hybrid magnetic/inertial system, and hybrid ultrasonic/inertial system. Most of them are susceptible to interference and noise.