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A Prototype Optical Tracking System Investigation and Development - page 17 / 170

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1.1 Review of tracking systems

3

pose of the scanner can be estimated.

This work combines tracking theory, embedded software design, PC software design, and hardware design to produce a prototype that can be developed into a fully-fledged tracking system in the future.

While the aim is to build a prototype system, the emphasis has been on producing the “Black Spot” prototype camera modules that form the rigid group of cameras. Due to this focus, the thesis concentrates on reporting the design and performance of the camera modules rather than the entire system. In Section 1.1 existing tracking technologies are discussed. This is followed by an overview of available optical tracking systems in Section 1.2. Finally, a summary of the structure of this thesis is given in Section 1.3.

1.1

Review of tracking systems

Many methods exist for determining the pose of an object.

lthough the focus of this

project

is

on

an

optical

system,

it

is

worth

noting

other

tracking

methods.

Mechanical,

acoustic, inertial, magnetic, and radio frequency trackers have all been implemented in the past, however, just like optical tracking, each method has its advantages and disad- vantages [12]. Mechanical trackers typically have a mechanical linkage between the object being tracked and a fixed point. s the object moves, its position can be determined using measurements of transducers attached to the mechanical links. This method has the disad- vantage that the pose of the object is limited by the physical constraints of the mechanical

links. gies [13].

commercial example of a mechanical tracker is the Faro

rm by Faro Technolo-

Inertial trackers use gyroscopes and accelerometers as building blocks. These are available as microelectronic mechanical systems (MEMS) in integrated circuits. Inertial trackers have several advantages. They do not rely on any line of sight measurements as do optical track- ers. They are not affected by magnetic fields or acoustic noise. They have a low latency and a high pose output rate. The big disadvantage with these systems is that the sensing components drift from their initial calibration. Given the small size of MEMS devices, in- ertial systems could be integrated into a super tracker that relies on optical, magnetic, and inertial tracking.

coustic tracking uses sound to determine the position of an object. Commercial systems are based on the time of flight of an ultrasonic sound wave. The performances of these systems are affected by temperature, humidity, and airflow. Typically, they, have slower

update rates than inertial trackers. system is the InterSense IS-900 [14].

n example of a hybrid acoustic and inertial tracking That 6 DOF system uses ultrasonic range sensors to

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