Revisiting the Minimum Constraint Removal Problem in Mobile Robotics

The minimum constraint removal problem seeks to find the minimum number of constraints, i.e., obstacles, that need to be removed to connect a start to a goal location with a collision-free path. This problem is NP-hard and has been studied in robotics, wireless sensing, and computational geometry. This work contributes to the existing literature by presenting and discussing two results. The first result shows that the minimum constraint removal is NP-hard for simply connected obstacles where each obstacle intersects a constant number of other obstacles. The second result demonstrates that for $n$ simply connected obstacles in the plane, instances of the minimum constraint removal problem with minimum removable obstacles lower than $(n+1)/3$ can be solved in polynomial time. This result is also empirically validated using several instances of randomly sampled axis-parallel rectangles.Comment: Accepted for presentation at the 18th international conference on Intelligent Autonomous System 202

Computational Tradeoff in Minimum Obstacle Displacement Planning for Robot Navigation

In this paper, we look into the minimum obstacle displacement (MOD) planning problem from a mobile robot motion planning perspective. This problem finds an optimal path to goal by displacing movable obstacles when no path exists due to collision with obstacles. However this problem is computationally expensive and grows exponentially in the size of number of movable obstacles. This work looks into approximate solutions that are computationally less intensive and differ from the optimal solution by a factor of the optimal cost.Comment: Accepted for presentation at the 2023 IEEE International Conference on Robotics and Automation (ICRA

Planejamento para missões autônomas persistentes cooperativas de longo prazo

Orientador: Andre Ricardo FioravantiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: Uma metodologia para abordar missões autônomas persistentes a longo prazo é apresentada juntamente com uma formalização geral do problema em hipóteses simples. É derivada uma realização dessa metodologia que reduz o problema geral para subproblemas de construção de caminho e de otimização combinatória, que são tratados com heurísticas para a computação de solução viável. Quatro estudos de caso são propostos e resolvidos com esta metodologia, mostrando que é possível obter caminhos contínuos ótimos ou subótimos aceitáveis a partir de ma representação discreta e elucidando algumas propriedades de solução nesses diferentes cenários, construindo bases para futuras escolhas educadas entre o uso de métodos exatos ou heurísticosAbstract: A Methodology for tackling Persistent Long Term Autonomous Missions is presented along with a general formalization of the problem upon simple assumptions. A realization of this methodology is derived which reduces the overall problem to a path construction and a combinatorial optimization subproblems, which are treated themselves with heuristics for feasible solution computation. Four case studies are proposed and solved with this methodology, showing that it is possible to obtain optimal or acceptable suboptimal continuous paths from a discrete representation, and elucidating some solution properties in these different scenarios, building bases for future educated choices between use of exact methods over heuristicsMestradoMecanica dos Sólidos e Projeto MecanicoMestre em Engenharia Mecânica1687532CAPE

Combining task and motion planning for mobile manipulators

Aplicat embargament des de la data de defensa fins el dia 31/12/2019Premi Extraordinari de Doctorat, promoció 2018-2019. Àmbit d’Enginyeria IndustrialThis thesis addresses the combination of task and motion planning which deals with different types of robotic manipulation problems. Manipulation problems are referred to as mobile manipulation, collaborative multiple mobile robots tasks, and even higher dimensional tasks (like bi-manual robots or mobile manipulators). Task and motion planning problems needs to obtain a geometrically feasible manipulation plan through symbolic and geometric search space. The combination of task and motion planning levels has emerged as a challenging issue as the failure leads robots to dead-end tasks due to geometric constraints. In addition, task planning is combined with physics-based motion planning and information to cope with manipulation tasks in which interactions between robots and objects are required, or also a low-cost feasible plan in terms of power is looked for. Moreover, combining task and motion planning frameworks is enriched by introducing manipulation knowledge. It facilitates the planning process and aids to provide the way of executing symbolic actions. Combining task and motion planning can be considered under uncertain information and with human-interaction. Uncertainty can be viewed in the initial state of the robot world or the result of symbolic actions. To deal with such issues, contingent-based task and motion planning is proposed using a perception system and human knowledge. Also, robots can ask human for those tasks which are difficult or infeasible for the purpose of collaboration. An implementation framework to combine different types of task and motion planning is presented. All the required modules and tools are also illustrated. As some task planning algorithms are implemented in Prolog or C++ languages and our geometric reasoner is developed in C++, the flow of information between different languages is explained.Aquesta tesis es centra en les eines de planificació combinada a nivell de tasca i a nivell de moviments per abordar diferents problemes de manipulació robòtica. Els problemes considerats són de navegació de robots mòbil enmig de obstacles no fixes, tasques de manipulació cooperativa entre varis robots mòbils, i tasques de manipulació de dimensió més elevada com les portades a terme amb robots bi-braç o manipuladors mòbils. La planificació combinada de tasques i de moviments ha de cercar un pla de manipulació que sigui geomètricament realitzable, a través de d'un espai de cerca simbòlic i geomètric. La combinació dels nivells de planificació de tasca i de moviments ha sorgit com un repte ja que les fallades degudes a les restriccions geomètriques poden portar a tasques sense solució. Addicionalment, la planificació a nivell de tasca es combina amb informació de la física de l'entorn i amb mètodes de planificació basats en la física, per abordar tasques de manipulació en les que la interacció entre el robot i els objectes és necessària, o també si es busca un pla realitzable i amb un baix cost en termes de potència. A més, el marc proposat per al combinació de la planificació a nivell de tasca i a nivell de moviments es millora mitjançant l'ús de coneixement, que facilita el procés de planificació i ajuda a trobar la forma d'executar accions simbòliques. La combinació de nivells de planificació també es pot considerar en casos d'informació incompleta i en la interacció humà-robot. La incertesa es considera en l'estat inicial i en el resultat de les accions simbòliques. Per abordar aquest problema, es proposa la planificació basada en contingències usant un sistema de percepció i el coneixement de l'operari humà. Igualment, els robots poden demanar col·laboració a l'operari humà per a que realitzi aquelles accions que són difícils o no realitzables pel robot. Es presenta també un marc d'implementació per a la combinació de nivells de planificació usant diferents mètodes, incloent tots els mòduls i eines necessàries. Com que alguns algorismes estan implementats en Prolog i d'altres en C++, i el mòdul de raonament geomètric proposat està desenvolupat en C++, es detalla el flux d'informació entre diferents llenguatges.Award-winningPostprint (published version

Modeling Network Interdiction Tasks

Mission planners seek to target nodes and/or arcs in networks that have the greatest benefit for an operational plan. In joint interdiction doctrine, a top priority is to assess and target the enemy\u27s vulnerabilities resulting in a significant effect on its forces. An interdiction task is an event that targets the nodes and/or arcs of a network resulting in its capabilities being destroyed, diverted, disrupted, or delayed. Lessons learned from studying network interdiction model outcomes help to inform attack and/or defense strategies. A suite of network interdiction models and measures is developed to assist decision makers in identifying critical nodes and/or arcs to support deliberate and rapid planning and analysis. The interdiction benefit of a node or arc is a measure of the impact an interdiction task against it has on the residual network. The research objective is achieved with a two-fold approach. The measures approach begins with a network and uses node and/or arc measures to assess the benefit of each for interdiction. Concurrently, the models approach employs optimization models to explicitly determine the nodes and/or arcs that are most important to the planned interdiction task