Annual Report 2010 - Fachgruppe Informatik an der RWTH Aachen ...

implementation of the algorithm on the mobile robot Carl has been completed with promising
results. Localization of broadband sound sources could be achieved with excellent precision.
Localization of low frequency, narrowband signals is less than satisfactory. This was initially
ascribed to the acoustical characteristics of the microphone mount. With the help of acoustic
room simulations conducted in 2006, we could show that the inferior performance for lowfrequency,
narrowband signals is not caused by the microphone mount and neither by the
algorithm, but by room reverberations. We integrated a sound localizer based on inter-aural
level differences as well as an attention module with the current system. Furthermore, a
beamformer module was developed which allows spatial filtering, i.e., sounds coming from a
given direction can be enhanced while all other directions are attenuated. A first attempt was
made at combining laser-based object recognition and sound localization on one of the
RoboCup robots. We are currently working on more sophisticated methods for exploiting
these two sensor modalities. Specifically, a Markov Chain Monte Carlo-based tracking
algorithm is in the process of being implemented, which will make it possible for the robot to
track dynamic objects emitting sounds (e.g. humans) over time. In combination with the
beamformer, this system can act as a front end for speech recognition, by enhancing speech
signals from the direction of a human, on which the robot’s attention is focused.
PLATAS – Planning Techniques and Action Languages
Jens Claßen, Gerhard Lakemeyer
Bernhard Nebel, Gabriele Roeger (University of Freiburg)
Although there is a common origin, research on automated planning on the one hand and
action logics on the other hand developed rather independently over the last three decades.
This is mainly due to the fact that work on action languages was concerned with formalisms of
high expressiveness, whereas for planning methods, the focus had to lie on computational
efficiency, yielding input languages with less expressive possibilities. However, one can
observe that during the last few years, the two separate fields began to converge again.
Exemplary for this trend is the development of the planning domain definition language
PDDL, which extends simple STRIPS-based planning by features such as conditional effects,
time, concurrency, axioms, and plan constraints and preferences, and which virtually
constitutes a standard in the field of planning.
This soon to be completed, DFG-funded project started in 2005 and has been conducted in
cooperation with the Research Group on the Foundations of Artificial Intelligence lead by
Bernhard Nebel at the University of Freiburg. It aims at integrating latest results in the areas of
both action languages (in particular, GOLOG) and planning techniques (in particular, PDDLbased
planners like Hoffmann and Nebel’s FF) to acquire systems that are both expressive and
efficient. In the first project phase we have worked on establishing a common semantic basis
for both GOLOG and PDDL within the situation calculus. This has been achieved first for the
ADL fragment of PDDL, and was subsequently extended by the language’s further features.
The situation calculus semantics for PDDL now covers roughly the full scope of PDDL, thus
providing the foundation for embedding state-of-the-art planning systems like FF in Golog.
Expressiveness was further studied formally by means of compilation schemes between
corresponding fragments of both formalisms, and experimental evaluations have shown that
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