1,721,111 research outputs found
ReCon: An Online Task ReConfiguration Approach for Robust Plan Execution
No full textThe paper presents an approach for the robust plan execution in presence of consumable and continuous resources. Plan execution is a critical activity since a number of unexpected situations could prevent the feasibility of tasks to be accomplished; however, many robotic scenarios (e.g. in space exploration) disallow robotic systems to perform significant deviations from the original plan formulation. In order to both (i) preserve the “stability” of the current plan and (ii) provide the system with a reasonable level of autonomy in handling unexpected situations, an innovative approach based on task reconfiguration is presented. Exploiting an enriched action formulation grounding on the notion of execution modalities, ReCon replaces the replanning mechanism with a novel reconfiguration mechanism, handled by means of a CSP solver. The paper studies the system for a typical planetary rover mission and provides a rich experimental analysis showing that, when the anomalies refer to unexpected resources consumption, the reconfiguration is not only more efficient but also more effective than a plan adaptation mechanism. The experiments are performed by evaluating the recovery performances depending on constraints on computational costs
Proactive and Reactive Reconfiguration for the Robust Execution of Multi Modality Plans
Full text linkThe paper addresses the problem of executing a plan in a dynamic environment for tasks involving constraints on consumable resources modeled as numeric fluents. In particular, the paper proposes a novel monitoring and adaptation strategy joining reactivity and proactivity in a unified framework. By exploiting the flexibility of a multi modality plan (where each action can be executed in different modalities), reactivity and proactivity are guaranteed by means of a reconfiguration step. The reconfiguration is performed (i) when the plan is no more valid to recovery from the impasse (reactively), or (ii) under the lead of a kernel based strategy to enforce the tolerance to unexpected situations (proactivity). Both mechanisms have been integrated into a continual planning system and experimentally evaluated over three numeric domains, extensions of planning competition domains. Results show that the approach is able to increase the percentage of cases successfully solved while preserving efficiency in most situations
Developing Co-operating Legal Knowledge Based Systems
No full textIn attempting to build intelligent litigation support tools, we have moved beyond first generation, production rule legal expert systems. Our work supplements rule-based reasoning with case based reasoning and intelligent information retrieval. This research, specifies an approach to the case based retrieval problem which relies heavily on an extended object-oriented / rule-based system architecture that is supplemented with causal background information. Machine learning techniques and a distributed agent architecture are used to help simulate the reasoning process of lawyers. In this paper, we outline our implementation of the hybrid IKBALS II Rule Based Reasoning / Case Based Reasoning system. It makes extensive use of an automated case representation editor and background information
Knowledge Representation and Reasoning for Fault Identification in a Space Robot Arm
No full textThe constrnction of diagnostic systems able
to manage tasks like fault detection, fault
localization or fault identificat.ion in autonomous
\pacecraft is currently considered
a txg c-hallenge for Artific~al Intell~gence
technique:, I11 the present paper we report
on thc work done inside a project sponsored
11y AS1 (the Italian Space Agency) aimed
at h~~ildinagn intelliger~t multi-agent syste~
n for the control and superv~sion of thc
Sl'IDF:I< Manipulation Systerri with some
for111 of int,eract,ion with the human operat.
os. III part,icular, we will discuss knowledge
represe~lt.at,iona nd reasoning issues related
to t hc cmlst,ruct,ion of a modcl-based diagnost
ic c~omponent which has t,o co-operate
\vit,ll ot8her modules of the ~yst~emA.1 1 indrpt,
h analysis of FMECA docunlent~s has
~ItdIed t he inodeling of the domain knowledge
on the faulty behavior of SPIDER. I11
th~sp aper, prohlcnls related to the choice
of the st~ltatm~ol~de l~ngfo rrnal~sniln volving
abstrac-t~oi~asn d ~nteractiona mong compoticnts
arc formally addressed, as well as the
definrt~ono f Innovat~ved ~agnost~sctr atrgleb
ablf. to deal w~thth e huge riunlber of possi-
111~ diagnos(>sthat mag arise during t,he diagr~
ostic act,ivit,y. The paper report,s some
prelilninar); result,s of t,he prot,ot,ypical version
of the diagnostic module on simulated
dat
Intelligent Supervision for Robust Plan Execution
Full text linkThe paper addresses the problem of supervising the execution
of a plan with durative actions in a just partially known world, where discrepancies
between the expected conditions and the ones actually found
may arise. The paper advocates a control architecture which exploits additional
knowledge to prevent (when possible) action failures by changing
the execution modality of actions while these are still in progress. Preliminary
experimental results, obtained in a simulated space exploration
scenario, are reported
Adapting Planetary Rover Plans via Action Modality Reconfiguration
No full textRobust execution of exploration mission plans has to
deal with limited computational power on-board a planetary
rover, and with limited rover’s autonomy. Typically,
these limitations prevent the rover to synthesize a
new mission plan when contingencies arise.
The paper shows that when contingencies are deviations
on the consumption of resources, robust execution can
be achieved efficiently through action reconfiguration
rather than replanning from scratch. The paper therefore
introduces a novel representation of actions with modalities,
and proposes an action reconfiguration module -
ReCon - that detects the violation of mission resource
constraints, and finds (if any) a new configuration of action
modalities to resolve these violations
Robust plan execution via reconfiguration and replanning
Full text linkActing in the real world may be a difficult task for an agent, either software or robotic, because unexpected contingencies
may arise at any step of the execution. Previous approaches to robust plan execution consider propositional goals to
be achieved and time constraints to be satisfied. However, realistic plans must obey to constraints on continuous/consumable
resources, too.
To face the complexity in handling these resources, the paper proposes the notion of Multi Modality Action (MMA). The
model allows to explicitly express the multiple execution modalities in which a given action can be executed; each execution
modality models requirements/consequences on the involved consumable resources when that modality is selected. Relying on
the MMA notion, the paper presents how the repair problem can be seen as a problem of reconfiguring actions modalities, and
how it can be solved by exploiting a CSP encoding.
The MMAs are employed by a new continual planner, FLEX-RR, which, exploiting the synergy from the reconfiguration and a
numeric planning mechanism, can efficiently repair on the fly the plan keeping it rather stable. An empirical analysis, performed
on three numeric planning domains, confirms the large benefits of FLEX-RR in terms of competence, efficiency and stability of
the repaired plan
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
