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Bluetrack

A Scalable Wireless 6 DOF Motion Tracking System

Our group is developing a wireless six degrees of freedom tracking system within a joint research project ('mqube', consortium management: FhG-FIT) funded by the bmbf (Federal Ministry of Education and Research).

The project's goal is the development of an augmented reality (AR) environment enabling several users to participate in collaborative processes. A user in an AR environment wears a semitransparent head-mounted displays (HMD) which projects virtual objects into his view (Fig.3). In order to display these virtual objects correctly it is crucial to determine the user's position and orientation with high precision and minimal latency. A major demand of the mqube project is the scaleability and mobility of its components. Therefore we decided to develop our own tracking system to meet these specs.

 

Principle of Operation

The BlueTrak motion tracking system is composed of two different types of modules: The 'user modules' which include inertial sensors and an ultrasonic transponder and the 'reference modules' which use the ultrasonic transponder only.
The modules are connected to a computer either using a wireless Bluetooth interface or an USB-interface.

Bluetrack_Principle

Fig.1 - Reference and user module

The orientation of a user module is derived from three different goups of sensors measuring acceleration, angular velocity and earth magnetic field. This common setup does not require any external sources.
The ultrasonic transponders measure the distances between a user module and the reference modules. This data is used to determine its spatial position.

Bluetrack_CompleteSystem

Fig.2 - Complete BlueTrak tracking system with four references and one user module

The number of BlueTrak reference modules is variable and allows an easy adjustment to the desired tracking volume and geometry.
The number of tracked users is not limited and has no impact on the update rate or the tracking accuracy. Users can be added and removed dynamically.

Bluetrack_Stage

Fig.3 - 'Mixed-Reality-Stage' for the mqube-project

 

Technical Data

Degrees of Freedom: 

6 (Yaw, Pitch, Roll, X, Y, Z)

Update Rate: 

100 Hz (Bluetooth), 500 Hz (USB)

Interfaces: 

USB, Bluetooth

Operating System: 

Windows 2000/XP

Size(mm) and Weight: 

30 x 38 x 38, 43g (user)

 

22 x 38 x 64, 36g (reference)

 

  9 x 35 x 64, 36g (battery pack)

Battery Runtime: 

8 hours (approx.)

The system performance in terms of accuracy, resolution and latency is subject of ongoing development.

 

Applications

  • A Mobile Multiuser Mixed Reality Environment
  • Augmented/Virtual Reality
  • Motion tracking for movement analysis

 

Events

  • Demonstration of the prototype at ISAR'01, NewYork ('The Second IEEE and ACM International Symposium on Augmented Reality')

  • Demonstration of the mqube 'Mixed-Reality-Stage' at the bmbf International VR/AR Statustagung, Leipzig '02

  • Demonstration of the wireless 6DOF tracking system at CeBIT'03, Hannover

  • Demonstration of the wireless 6DOF tracking system at ISMAR'03, Tokio ('The Second IEEE and ACM International Symposium on Mixed and Augmented Reality')

  • Demonstration of the mqube 'Mixed-Reality-Stage' at the bmbf International VR/AR Statustagung, Leipzig '04
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