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Abstract
Autonomous mobile robots in general and service robots in particular consist of many actuators and
sensors, which allow the robot to perceive and to interact with the world. Each of these actuators
and sensors define an own coordinate frame. An actuator can change the transformation between
two frames, whereas the data captured by a sensor is always relative to the sensor frame. If now,
applications like collision avoidance or manipulation of objects should be done, sensor data has to be
transformed from the sensor frame to another frame. To do this, a transformation tree, which describes
the relation of frames to each other is needed. The tree allows to determine the single transformations
which must be applied to get from one frame to another.
In a component-based robot system the information of the current transformations between the
frames has to be transfered to all interested components. Therefor the robotic middleware (resp.
framework), has to provide methods to do this. Further the quality of a transformation is not always
the same. For example, it depends on the position uncertainty of the actuator and on the frequency at
which the current position is captured.
The focus of this work is laid on the quality measurement for transformation chains and on the
description of the data flow in component-based robotic systems. This description allows to understand
the system, to compare it with other systems and to find bottlenecks in it. Further the quality
measurement allows the system integrator, who builds a robotic system out of components, to see if
his desired configuration gives the quality needed for a specific application. The quality is defined
as the position uncertainty of a frame in 3D space modeled as a multidimensional Gaussian normal
distribution. This thesis also presents methods to increase the quality of a transformation by adjusting
parameters like the frequency at which the position of an actuator is captured.
Examples and a simulation of a system verify that the proposed methods are usable and general
enough to describe all elements of the system relevant for managing transformations in a componentbased
robotic system.
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