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Symmetry Signatures for Image-Based Applications in Robotics

The robots that are to find their way in our future households and everyday lives necessarily have to be mobile and self-dependent. For such autonomous systems it becomes more and more important to efficiently process the incoming data and to thereby eradiate what we might call "intelligent behaviour". While intelligence in terms of plans and goals are abstract metaphors of each robot's decision process, the perception of the local environment has to be a central issue. Dealing with this demand in the context of intelligent systems shows plainly what sophisticated human visual perception is like. The creators and developers of artificial systems therefore build up a construction kit with construction blocks that try to represent the reproduction of cognitive perception mechanisms by machine algorithms. In this chapter, we will show how a construction block for symmetry perception can be added to this set. The main issues discuss three layers that describe this block from its origin of biological motivation up to its application for intelligent systems: 1. Symmetry as a Feature: The first layer addresses the basic motivation of symmetry as a feature. Therefore, symmetry references to diverse domains are given and new methods developed that provide description and application of symmetry as an image feature. These include two main symmetry measures that offer a variety of symmetry properties for higher-level image processing tasks. 2. Regional Symmetry Features: The second layer proceeds to application in relation to modern regional image features. The three steps of detection, description and robust matching of regional symmetry features form the necessary links between the basic motivation and the practical application of symmetry. Symmetry features are evaluated and compared to stateof-the-art features considering their robustness w.r.t. common image transformations. 3. Integration and Application: A practical example from the area of mobile robot navigation is proposed in the third layer to demonstrate the capability of the developed symmetry features in applications. For this purpose, the mobile service robot TASeR from the working group of Technical Aspects of Multimodal Systems (University of Hamburg, Germany) is used. The application provides the links to higher-level construction blocks from the set of visual object analysis and robot navigation.