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we use an Ontology for the model. With the help of the
model, the tool can derive the dependencies which need to
be met to fulfill a task.
To derive which configuration fulfills the dependencies
a separate reasoning process is performed. This separate
reasoning process uses the data contained in the model to
yield a minimal configuration. Through this separation, the
model can be capped simply by avoiding the âcomplexâ
reasoning for a minimal configuration.
Using the information fromtheontologyand the reasoning
to derive a minimal configuration the tool can present a
possible configuration to the user through a graphical user
interface. The interface allows selecting tasks to perform,
which components are used as well as which configuration
would be minimal. In the remainder of the section, we will
discuss each part in more detail.
A. Ontology
To model the relationships between tasks and necessary
components, an ontology describing this relationship is
needed. The ontology we use for the implementation is an
open-source knowledge base and can be found at [3]. In this
ontology, tasks are referred as capabilities. Each capability
can be comprised of other basic capabilities. The ontology
also describes the relationship of capabilities to hard- and
software components that are needed for their implementa-
tion. Some of these components may be compulsory and do
not include alternatives while others may be chosen from a
pool of similar components that may all be used to fulfill the
same task.
The information, stored in the ontology can be loaded
and queried with an appropriate tool. We use the framework
Jena [4] to load the ontology into a model. The model can
be queried using the SPARQL query language. The Jena
framework allows multiple ontologies to be loaded into a
single model. The base ontology we use already contains
references to the sub-ontologies, including descriptions of
robot components. Therefore, it is enough to load the base
ontology as all sub-ontologies will be loaded into the model
automatically by the framework.
B. Calculation of Configuration
With the help of the ontology mentioned above, we can
define the dependencies which need to be met to perform
a task. The above calculate gives as a set of capabilities
Cap, which can be requested to be fulfilled directly or
indirectly. We use the variablesX and Y in the remaining
subsections for variables with the domain of capabilities
dom(X) = dom(Y) = Cap. Besides the capabilities, we
have additionally the set of componentsComp. These com-
ponents describe a software component, e.g. a laser-based
localization or a hardware component, e.g. a laser scanner.
We use the variableZ in the remainder of the subsection for
variables with the domain of componentsdom(Z)=Comp.
As the description of the components is rather abstract
one needs a concrete implementation/realization of such a
component, e.g. a Sick LMS100 for a laser scanner. To describe this implementation/realization of components the
ontologyaboveyields theset ImplComp. In the remainderof
the subsection, we use the variableW for variables with the
domain of the implementations of components dom(W)=
ImplComp.
Beside the sets of possible capabilities, components and
their implementation we additionally have four different
functions describing the dependencies which need to be
fulfilled for a capability, component and its implemen-
tation. The function capReqCap : Cap â 2Cap de-
scribes which set of capabilities needs to be fulfilled by
the robot to implement a certain capability. For example,
the capability liftObject depends on two other capabili-
ties moveArm,graspObject which is described as follows
capReqCap(liftObject) â {moveArm,graspObject}. To
describe the dependencies between capabilities and com-
ponents the function capReqComp : Cap â 2Comp is
used. For example, the capability liftObject depends on
two components arm,gripper which is described as fol-
lows capReqComp(liftObject) â {arm,gripper}. Each
requested component can be implemented differently to link
a component and an implementation we use the predicate
implComp : Comp Ă ImplComp â {>,â„}. Like a
capability a component can depend on capabilities, we use
the function compReqCap :Compâ2Cap to describe this
dependency. Additionally, a component can depend on other
components which define through the following function
compReqComp : Compâ 2Comp . Using this functions
and the predicate we can define the dependencies which need
to be met to implement a certain capability.
As we are interested in a configuration of the system
which is minimal we need a specific reasoning to derive
such a configuration. This is done by first extracting all
dependenciesofa task togetherwitheverypossibility tomeet
this dependency. The model does not store all dependencies
in a single level. Instead, some dependencies may result
from other dependencies. Therefore, a recursive extraction
of dependencies must be performed.
Once all these dependencies are extracted, a constraint
problem can be defined to find (all) minimal configurations
which fulfill the dependencies. This is done as follows. For
each capabilityY which is required the predicate reqCap(Y)
isused todescribe thecapabilities andcomponentswhichare
needed by the robot.
reqCap(Y)â â§
XâcapReqCap(Y) reqCap(X)â§
â§
ZâcapReqComp(Y) reqComp(Z)
Through this equation, one can simply resolve the recursive
dependencies on the capabilities. Some of these capabili-
ties might need components. As several hard- or software
instances can implement a specific component we use an
equation for the required capabilities to resolve components.
If a componentW implements a required componentZwe
33
Proceedings of the OAGM&ARW Joint Workshop
Vision, Automation and Robotics
- Titel
- Proceedings of the OAGM&ARW Joint Workshop
- Untertitel
- Vision, Automation and Robotics
- Autoren
- Peter M. Roth
- Markus Vincze
- Wilfried Kubinger
- Andreas MĂŒller
- Bernhard Blaschitz
- Svorad Stolc
- Verlag
- Verlag der Technischen UniversitÀt Graz
- Ort
- Wien
- Datum
- 2017
- Sprache
- englisch
- Lizenz
- CC BY 4.0
- ISBN
- 978-3-85125-524-9
- Abmessungen
- 21.0 x 29.7 cm
- Seiten
- 188
- Schlagwörter
- Tagungsband
- Kategorien
- International
- TagungsbÀnde