12,473 research outputs found
Towards adaptive multi-robot systems: self-organization and self-adaptation
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The development of complex systems ensembles that operate in uncertain environments is a major challenge. The reason for this is that system designers are not able to fully specify the system during specification and development and before it is being deployed. Natural swarm systems enjoy similar characteristics, yet, being self-adaptive and being able to self-organize, these systems show beneficial emergent behaviour. Similar concepts can be extremely helpful for artificial systems, especially when it comes to multi-robot scenarios, which require such solution in order to be applicable to highly uncertain real world application. In this article, we present a comprehensive overview over state-of-the-art solutions in emergent systems, self-organization, self-adaptation, and robotics. We discuss these approaches in the light of a framework for multi-robot systems and identify similarities, differences missing links and open gaps that have to be addressed in order to make this framework possible
Applying autonomy to distributed satellite systems: Trends, challenges, and future prospects
While monolithic satellite missions still pose significant advantages in terms of accuracy and
operations, novel distributed architectures are promising improved flexibility, responsiveness,
and adaptability to structural and functional changes. Large satellite swarms, opportunistic satellite
networks or heterogeneous constellations hybridizing small-spacecraft nodes with highperformance
satellites are becoming feasible and advantageous alternatives requiring the adoption
of new operation paradigms that enhance their autonomy. While autonomy is a notion that
is gaining acceptance in monolithic satellite missions, it can also be deemed an integral characteristic
in Distributed Satellite Systems (DSS). In this context, this paper focuses on the motivations
for system-level autonomy in DSS and justifies its need as an enabler of system qualities. Autonomy
is also presented as a necessary feature to bring new distributed Earth observation functions
(which require coordination and collaboration mechanisms) and to allow for novel structural
functions (e.g., opportunistic coalitions, exchange of resources, or in-orbit data services). Mission
Planning and Scheduling (MPS) frameworks are then presented as a key component to implement
autonomous operations in satellite missions. An exhaustive knowledge classification explores the
design aspects of MPS for DSS, and conceptually groups them into: components and organizational
paradigms; problem modeling and representation; optimization techniques and metaheuristics;
execution and runtime characteristics and the notions of tasks, resources, and constraints.
This paper concludes by proposing future strands of work devoted to study the trade-offs of
autonomy in large-scale, highly dynamic and heterogeneous networks through frameworks that
consider some of the limitations of small spacecraft technologies.Postprint (author's final draft
Distributed Time-Frequency Division Multiple Access Protocol For Wireless Sensor Networks
It is well known that biology-inspired self-maintaining algorithms in
wireless sensor nodes achieve near optimum time division multiple access (TDMA)
characteristics in a decentralized manner and with very low complexity. We
extend such distributed TDMA approaches to multiple channels (frequencies).
This is achieved by extending the concept of collaborative reactive listening
in order to balance the number of nodes in all available channels. We prove the
stability of the new protocol and estimate the delay until the balanced system
state is reached. Our approach is benchmarked against single-channel
distributed TDMA and channel hopping approaches using TinyOS imote2 wireless
sensors.Comment: 4 pages, IEEE Wireless Communications Letters, to appear in 201
Real-Time Local Volt/VAR Control Under External Disturbances with High PV Penetration
Volt/var control (VVC) of smart PV inverter is becoming one of the most
popular solutions to address the voltage challenges associated with high PV
penetration. This work focuses on the local droop VVC recommended by the grid
integration standards IEEE1547, rule21 and addresses their major challenges
i.e. appropriate parameters selection under changing conditions, and the
control being vulnerable to instability (or voltage oscillations) and
significant steady state error (SSE). This is achieved by proposing a two-layer
local real-time adaptive VVC that has two major features i.e. a) it is able to
ensure both low SSE and control stability simultaneously without compromising
either, and b) it dynamically adapts its parameters to ensure good performance
in a wide range of external disturbances such as sudden cloud cover, cloud
intermittency, and substation voltage changes. A theoretical analysis and
convergence proof of the proposed control is also discussed. The proposed
control is implementation friendly as it fits well within the integration
standard framework and depends only on the local bus information. The
performance is compared with the existing droop VVC methods in several
scenarios on a large unbalanced 3-phase feeder with detailed secondary side
modeling.Comment: IEEE Transactions on Smart Grid, 201
A survey on engineering approaches for self-adaptive systems (extended version)
The complexity of information systems is increasing in recent years, leading to increased effort for maintenance and configuration. Self-adaptive systems (SASs) address this issue. Due to new computing trends, such as pervasive computing, miniaturization of IT leads to mobile devices with the emerging need for context adaptation. Therefore, it is beneficial that devices are able to adapt context. Hence, we propose to extend the definition of SASs and include
context adaptation. This paper presents a taxonomy of self-adaptation and a survey on engineering SASs. Based on the taxonomy and the survey, we motivate a new perspective on SAS including context adaptation
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