Latency and Distortion of Electromagnetic Trackers for Augmented Reality Systems (Paperback)

Augmented reality (AR) systems are often used to superimpose virtual objects or information on a scene to improve situational awareness. Delays in the display system or inaccurate registration of objects destroy the sense of immersion a user experiences when using AR systems. AC electromagnetic trackers are ideal for these applications when combined with head orientation prediction to compensate for display system delays. Unfortunately, these trackers do not perform well in environments that contain conductive or ferrous materials due to magnetic field distortion without expensive calibration techniques. In our work we focus on both the prediction and distortion compensation aspects of this application, developing a "small footprint" predictive filter for display lag compensation and a simplified calibration system for AC magnetic trackers.

In the first phase of our study we presented a novel method of tracking angular head velocity from quaternion orientation using an Extended Kalman Filter in both single model (DQEKF) and multiple model (MMDQ) implementations. In the second phase of our work we have developed a new method of mapping the magnetic field generated by the tracker without high precision measurement equipment. This method uses simple fixtures with multiple sensors in a rigid geometry to collect magnetic field data in the tracking volume. We have developed a new algorithm to process the collected data and generate a map of the magnetic field distortion that can be used to compensate distorted measurement data.

Table of Contents: List of Tables / Preface / Acknowledgments / Delta Quaternion Extended Kalman Filter / Multiple Model Delta Quaternion Filter / Interpolation Volume Calibration / Conclusion / References / Authors' Biographies

擴增實境（AR）系統通常用於在場景上疊加虛擬物體或信息，以提高情境感知能力。當AR系統的顯示系統延遲或物體配準不準確時，會破壞使用者在使用AR系統時所體驗到的沉浸感。交流電磁跟踪器在與頭部方向預測相結合以補償顯示系統延遲時，非常適合這些應用。不幸的是，這些跟踪器在包含導電或鐵質材料的環境中表現不佳，因為會產生磁場失真，而需要昂貴的校準技術。在我們的工作中，我們專注於該應用的預測和失真補償方面，開發了一種“小尺寸”預測濾波器，用於補償顯示延遲，以及一種簡化的AC磁跟踪器校準系統。

在我們研究的第一階段，我們提出了一種新的方法，使用擴展卡爾曼濾波器（Extended Kalman Filter）在單模型（DQEKF）和多模型（MMDQ）實現中，從四元數方向中跟踪角速度。在我們工作的第二階段，我們開發了一種新的方法，用於在沒有高精度測量設備的情況下對跟踪器產生的磁場進行映射。該方法使用具有多個傳感器的簡單固定裝置在跟踪區域內收集磁場數據。我們開發了一種新的算法來處理收集到的數據並生成磁場失真的地圖，以用於補償失真的測量數據。

目錄：表格列表 / 前言 / 致謝 / Delta Quaternion Extended Kalman Filter / Multiple Model Delta Quaternion Filter / 插值區域校準 / 結論 / 參考文獻 / 作者簡介