Temporal landmark graphs for solving overconstrained planning problems

This paper presents TempLM, a novel approach for handling temporal planning problems with deadlines. The proposal revolves around the concept of temporal landmark, a proposition that must be necessarily true in all solution plans to achieve the problem goals within their deadlines. The temporal landmarks extracted from the problem form a landmarks graph where nodes are landmarks and edges represent temporal as well as causal relationships between landmarks. The graph comprises information about which propositions and when these propositions must be achieved in a solution plan, information that is later used to guide the search process as well as reduce the search space. Thus, the partial plans of the search tree that are not compliant with the information comprised in this graph are pruned. We present an exhaustive experimentation evaluation in overconstrained and unsolvable problems and we compare the performance of TempLM with other state-of-the-art planners. The results will show the efficiency of TempLM in the detection of unsolvable problems. (C) 2016 Elsevier B.V. All rights reserved:We thank Derek Long for solving our doubts about the modal operators in PDDL3 and Erez Karpas for supplying the compiled domain and problem files with their temporal landmarks. This work has been partially supported by Spanish Government Project MINECO TIN2014-55637-C2-2-R.Marzal Calatayud, EJ.; Sebastiá Tarín, L.; Onaindia De La Rivaherrera, E. (2016). Temporal landmark graphs for solving overconstrained planning problems. Knowledge-Based Systems. 106:14-25. https://doi.org/10.1016/j.knosys.2016.05.029S142510

Planning for execution monitoring on a planetary rover

A planetary rover will be traversing largely unknown and often unknowable terrain. In addition to geometric obstacles such as cliffs, rocks, and holes, it may also have to deal with non-geometric hazards such as soft soil and surface breakthroughs which often cannot be detected until rover is in imminent danger. Therefore, the rover must monitor its progress throughout a traverse, making sure to stay on course and to detect and act on any previously unseen hazards. Its onboard planning system must decide what sensors to monitor, what landmarks to take position readings from, and what actions to take if something should go wrong. The planning systems being developed for the Pathfinder Planetary Rover to perform these execution monitoring tasks are discussed. This system includes a network of planners to perform path planning, expectation generation, path analysis, sensor and reaction selection, and resource allocation

DocuDrama

This paper presents an approach combining concepts of virtual storytelling with cooperative processes. We will describe why storytelling is relevant in cooperation support applications. We will outline how storytelling concepts provide a new quality for groupware applications. Different prototypes illustrate a combination of a groupware application with various storytelling components in a Theatre of Work

Artificial Intelligence and Systems Theory: Applied to Cooperative Robots

This paper describes an approach to the design of a population of cooperative robots based on concepts borrowed from Systems Theory and Artificial Intelligence. The research has been developed under the SocRob project, carried out by the Intelligent Systems Laboratory at the Institute for Systems and Robotics - Instituto Superior Tecnico (ISR/IST) in Lisbon. The acronym of the project stands both for "Society of Robots" and "Soccer Robots", the case study where we are testing our population of robots. Designing soccer robots is a very challenging problem, where the robots must act not only to shoot a ball towards the goal, but also to detect and avoid static (walls, stopped robots) and dynamic (moving robots) obstacles. Furthermore, they must cooperate to defeat an opposing team. Our past and current research in soccer robotics includes cooperative sensor fusion for world modeling, object recognition and tracking, robot navigation, multi-robot distributed task planning and coordination, including cooperative reinforcement learning in cooperative and adversarial environments, and behavior-based architectures for real time task execution of cooperating robot teams

Modelo de landmarks temporales para problemas de planificación temporal altamente restringidos

[EN] Automated temporal planning deals with the construction of plans for problems specified with durative actions of possibly different duration. The goal of temporal planning is to select and schedule the actions so as to achieve the problem goals, and the optimality criteria is the plan makespan. However, many real-word application define goals with time constraints which may not be satisfied with the plan of optimal makespan. The 2006 International Planning Competition introduced the PDDL3.0 language and organized the first and only track in planning with state trajectory constraints, including time restrictions, soft constraints and preferences. Particularly, four domains that feature deadline constraints were tested at the IPC and two planners participated in such competition although no one exhibited a good performance or fully-correction in the fulfillment of deadlines. An early detection of unsolvability in temporal planning problems, specifically those with strict deadlines, is crucial for avoiding an unfruitful exploration of the search space. And this is precisely the objective of this PhD dissertation. This work contributes with a temporal landmark-based model embedded into a temporal planner that allows for a rapid and eficient identification of unsolvable problems with deadline constraints. Our model incorporates the basic model operators of PDDL3.0 for defining temporal constraints and extends the STRIPS landmark concept to a temporal context. A temporal landmark is associated to three intervals that denote the time frame of the generation, validity and necessity of the landmark in the plan, respectively. The set of temporal landmarks of a problem along with their ordering relations and temporal restrictions define a temporal landmark graph which comprises the relationships that must exist between the literals of a solution plan and, therefore, between the corresponding actions. As long as new data is incorporated in the graph, the landmarks intervals are updated and propagated accordingly, thus reflecting a more accurate picture of a solution plan. The temporal landmark model is integrated in a domain-independent temporal planner named TempLM. During the search process, TempLM uses the temporal landmark graph to prune those partial plans of the search tree that are not compliant with the information of the graph. Additionally, we present a further improvement by which a feedback routine between the landmarks graph and the plan of a node tree is established. This process is used to refine the information of the graph and likewise narrow the search. In the experimental evaluation, we show the effectiveness of the proposed approach for detecting unsolvability and solving temporal planning problems with tight deadline constraints.[ES] El objetivo de la planificación temporal automática es la construcción de planes con acciones de diferente duración que necesitan ser programadas adecuadamente con el fin de conseguir los objetivos del problema. En planificación temporal, la optimalidad se mide como la duración del plan más corto. Sin embargo, en muchos problemas del mundo real es necesario gestionar restricciones temporales asociadas a los objetivos del problema que pueden no satisfacerse con el plan de menor duración. En la Competición Internacional de Planificación del año 2006 se presentó el lenguaje PDDL3.0 y se realizó la primera y única competición de planificadores con gestión de restricciones de trayectorias de estado y preferencias. Concretamente, en esta IPC se probaron cuatro dominios con restricciones temporales donde los objetivos deben satisfacerse dentro de un límite de tiempo establecido o deadline. Dos planificadores participaron en esta competición aunque ninguno presentó un buen comportamiento respecto al cumplimiento de los deadlines. En este tipo de problemas, especialmente cuando se trata de problemas altamente restringidos, es crucial detectar la irresolubilidad de los mismos lo antes posible, y en este punto es donde se establece nuestro objetivo. Este trabajo de tesis presenta un modelo de landmarks temporales que permite identificar rápida y eficientemente la irresolubilidad de problemas de planificación con restricciones. Nuestro modelo incorpora las restricciones temporales del lenguaje PDDL3.0 y extiende el concepto de landmark STRIPS al contexto temporal. A cada landmark temporal se le asocian tres tipos de intervalos que se actualizan y propagan de acuerdo a las relaciones de orden y restricciones temporales entre ellos. Los landmarks temporales junto con sus relaciones de orden y restricciones temporales forman un grafo de landmarks temporales donde se sintetiza las relaciones que existen entre los literales de un plan solución y, consecuentemente, entre sus correspondientes acciones. Cuando se añade nueva información al grafo, se actualizan y propagan los intervalos de los landmarks, reflejando una imagen más precisa del plan solución. Posteriormente, el modelo de landmarks temporales se integra en un planificador temporal heurístico independiente del dominio denominado TempLM. TempLM utiliza toda la información extraída del problema para podar los planes parciales en el árbol de búsqueda que no son compatibles con la información del grafo de landmarks temporales. Además, se dispone de un proceso de retroalimentación entre el grafo de landmarks temporales y el proceso de búsqueda de un plan solución que permite enriquecer el grafo y, asimismo, acotar el espacio de búsqueda. Los resultados experimentales muestran que esta aproximación detecta rápidamente problemas irresolubles y también es muy efectiva para resolver problemas con restricciones muy ajustadas.[CA] L'objectiu de la planificació temporal automàtica és la construcció de plans amb accions de diferent durada que necessiten ser programades adequadament amb la finalitat d'aconseguir els objectius del problema. En planificació temporal, l'optimitat es mesura com la durada del pla més curt. No obstant açò, en molts problemas del món real és necessari gestionar restriccions temporals associades als objectius del problema que poden no satisfer-se amb el pla de menor durada. En la Competició Internacional de Planificació de l'any 2006 es va presentar el llenguatge PDDL3.0 i es va realitzar la primera i única competició de planificadors amb gestió de restriccions de trajectòries d'estat i preferències. Concretament, en aquesta IPC es van provar quatre dominis amb restriccions temporals on els objectius han de satisfer-se dins d'un límit de temps establit o deadline. Dos planificadors van participar en aquesta competició encara que cap va presentar un bon comportament respecte al compliment dels deadlines. En aquest tipus de problemes, especialment quan es tracta de problemes altament restringits, és crucial detectar la irresolubilitat dels mateixos el més prompte possible, i en aquest punt és on s'estableix el nostre objectiu. Aquest treball de tesi presenta un model de landmarks temporals que permet identificar ràpida i eficientment la irresolubilitat de problemes de planificació amb restriccions. El nostre model incorpora les restriccions temporals del llenguatge PDDL3.0 i estén el concepte de landmark STRIPS al context temporal. A cada landmark temporal se li associen tres tipus d'intervals que s'actualitzen i propaguen d'acord a les relacions d'ordre i restriccions temporals entre ells. Els landmarks temporals juntament amb les seues relacions d'ordre i restriccions temporals formen un graf de landmarks temporals on se sintetitza les relacions que existeixen entre els literals d'un pla solució i, conseqüentment, entre les seues corresponents accions. Quan s'afig nova informació al graf, s'actualitzen i propaguen els intervals dels landmarks, reflectint una imatge més precisa del pla solució. Posteriorment, el model de landmarks temporals s'integra en un planificador temporal heurístic independent del domini denominat TempLM. TempLM utilitza tota la informació extreta del problema per a podar els plans parcials en l'arbre de cerca que no són compatibles amb la informació del graf de landmarks temporals. A més, es disposa d'un procés de retroalimentació entre el graf de landmarks temporals i el procés de cerca d'un pla solució que permet enriquir el graf i, així mateix, limitar l'espai de cerca. Els resultats experimentals mostren que aquesta aproximació detecta ràpidament problemes irresolubles i també és molt efectiva per a resoldre problemes amb restriccions molt ajustades.Marzal Calatayud, EJ. (2016). Modelo de landmarks temporales para problemas de planificación temporal altamente restringidos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61460TESI

Methodology and themes of human-robot interaction: a growing research field

Original article can be found at: http://www.intechweb.org/journal.php?id=3 Distributed under the Creative Commons Attribution License. Users are free to read, print, download and use the content or part of it so long as the original author(s) and source are correctly credited.This article discusses challenges of Human-Robot Interaction, which is a highly inter- and multidisciplinary area. Themes that are important in current research in this lively and growing field are identified and selected work relevant to these themes is discussed.Peer reviewe