Motion tracking for virtual reality using inertial motion sensors

Abstract: Human motion capture has until recently been dominated by camera-based solutions. With advancements within Micro Electro-Mechanical Systems (MEMS) technology new Inertial Measurement Unit (IMU) based solutions are being explored. This thesis explores the possibility of using IMUs for augmenting motion tracking for Virtual Reality (VR). More specifically it aims to explore one existing tracking method, developed for medical rehabilitation, and evaluate its suitability for tracking the angle of an elbow in real time. The method was first implemented and explored in simulation with ideal sensor outputs. Disturbances were then introduced to explore its feasibility for VR. The magnitude and types of disturbances were chosen based on the performance of Commercial Off-The-Shelf (COTS) IMUs as well as the VR application. A range of motions was simulated to explore the methods stated reliance on gravity being a dominant part of the acceleration measured by the IMUs, and also the stated sensitivity to measurement errors when an acceleration vector used in the calculation of the angle is almost collinear with the joint axes. Additionally the computation speed was explored by implementing the same algorithm in a low-level programming language, evaluation was then done on relevant computer hardware. It is found that COTS IMUs performance is sufficient for the application and the algorithm runs more than fast enough on any computer that is able to run VR. The major causes of delay between sampling the sensors and having a calculated joint angle is data transfer and numerical derivation. However it was found that the method produces significant errors in the acceleration based part of the angle calculation whenever the acceleration vector used strays to far from being perpendicular to the joint axes. It is concluded that the method is not suitable for tracking the angle of an elbow since the very free movement of the arm often puts the joint axes much too close to being parallel with gravity