CVT-based 2D motion planning with maximal clearance

Maximal clearance is an important property that is highly desirable in multi-agent motion planning. However, it is also inherently difficult to attain. We propose a novel approach to achieve maximal clearance by exploiting the ability of evenly distributing a set of points by a centroidal Voronoi tessellation (CVT). We adapt the CVT framework to multi-agent motion planning by adding an extra time dimension and optimize the trajectories of the agents in the augmented domain. As an optimization framework, our method can work naturally on complex regions. We demonstrate the effectiveness of our algorithm in achieving maximal clearance in motion planning with some examples.published_or_final_versionThe 2011 IEEE International Conference on Robotics and Automation (ICRA), Shanghai, China, 9-13 May 2011. In Proceedings of the IEEE-ICRA, 2011, p. 2281-228

Control-law for Oil Spill Mitigation with a team of Heterogeneous Autonomous Vehicles

Oil spill incidents in the sea or harbours occur with some regularity during exploration, production, and transport of petroleum products. In order to mitigate the impact of the oil spill in the marine life, immediate, safety, effective and eco-friendly actions must be taken. Autonomous vehicles can assume an important contribution by establishing a cooperative and coordinated intervention. This dissertation presents the development of two path planning control-laws, the first one an autonomous surface vehicle (ASV) being able to contour the oil spill while s deploying microorganisms and nutrients (bioremediation) capable of mitigate and contain the oil spill spread, and the second one for a unmanned aerial vehicle (UAV) in order to perform the coverage of the entire spillage area with the same microorganisms and nutrients deployment capabilities. In order to validate both methods, a simulation environment was developed in Gazebo with a oil spill scenario, an ASV and an UAV. Field tests have been conducted in the Leixões Harbour in Porto, Portugal.Incidentes relacionados com derrames de petróleo no oceano ou em portos ocorrem com alguma regularidade, durante a exploração, produção e transporte de petróleo e seus derivados. Para mitigar o impacto desses derramamentos na fauna e flora marinha de uma forma imediata, segura, efectiva e amiga do ambiente novas ações são necessárias. Veículos autónomos podem providenciar uma importante contribuição estabelecendo uma intervenção cooperativa e coordenada. Esta dissertação apresenta o desenvolvimento de dois algoritmos de controlo para o planeamento de trajectórias, a primeira para um veículo de superfície autónomo (ASV) ser capaz de contornar o perímetro do derrame enquanto distribui microorganismos e nutrientes (bio-remediação), capazes de mitigar e conter a propagação do derramamento de petróleo e a segunda para um veículo aéreo não-tripulado (UAV) ser capaz de cobrir todo a área de derrame enquanto distribui os mesmos microorganismos e nutrientes. De forma a validar ambos os métodos, um ambiente de simulação foi desenvolvido em Gazebo com cenário do derrame de petróleo, um ASV e um UAV. Testes de campo foram realizados no porto de Leixões, no Porto, Portugal

Real path planning based on genetic algorithm and Voronoi diagrams

PostprintIn the context of Mobile Robotics, the efficient resolution of the Path Planning problem is a key task. The model of the environment and the search algorithm are basic issues in the resolution of the problem. This paper highlights the main features of Path Planning proposal for mobile robots in static environments. In our proposal, the path planning is based on Voronoi diagrams, where obstacles in the environment are considered as the generating points of the diagram, and a genetic algorithm is used to find a path without collisions from the robot initial to target position. This work combines some ideas presented by Roque and Doering, who use Voronoi diagrams for modelling the environment, and other ideas presented by Zhang et al. who adopt a genetic algorithm for computing paths on a regular grid based environment, considering certain quality attributes. The main results were probed both in simulated and real environments

Lifelong topological visual navigation

La possibilité pour un robot de naviguer en utilisant uniquement la vision est attrayante en raison de sa simplicité. Les approches de navigation traditionnelles basées sur la vision nécessitent une étape préalable de construction de carte qui est ardue et sujette à l'échec, ou ne peuvent que suivre exactement des trajectoires précédemment exécutées. Les nouvelles techniques de navigation visuelle basées sur l'apprentissage réduisent la dépendance à l'égard d'une carte et apprennent plutôt directement des politiques de navigation à partir des images. Il existe actuellement deux paradigmes dominants : les approches de bout en bout qui renoncent entièrement à la représentation explicite de la carte, et les approches topologiques qui préservent toujours une certaine connectivité de l'espace. Cependant, alors que les méthodes de bout en bout ont tendance à éprouver des difficultés dans les tâches de navigation sur de longues distances, les solutions basées sur les cartes topologiques sont sujettes à des défaillances dues à des arêtes erronées dans le graphe. Dans ce document, nous proposons une méthode de navigation visuelle topologique basée sur l'apprentissage, avec des stratégies de mise à jour du graphe, qui améliore les performances de navigation sur toute la durée de vie du robot. Nous nous inspirons des algorithmes de planification basés sur l'échantillonnage pour construire des graphes topologiques basés sur l'image, ce qui permet d'obtenir des graphes plus épars et d'améliorer les performances de navigation par rapport aux méthodes de base. En outre, contrairement aux contrôleurs qui apprennent à partir d'environnements d'entraînement fixes, nous montrons que notre modèle peut être affiné à l'aide d'un ensemble de données relativement petit provenant de l'environnement réel où le robot est déployé. Enfin, nous démontrons la forte performance du système dans des expériences de navigation de robots dans le monde réel.The ability for a robot to navigate using vision only is appealing due to its simplicity. Traditional vision-based navigation approaches require a prior map-building step that was arduous and prone to failure, or could only exactly follow previously executed trajectories. Newer learning-based visual navigation techniques reduce the reliance on a map and instead directly learn policies from image inputs for navigation. There are currently two prevalent paradigms: end-to-end approaches forego the explicit map representation entirely, and topological approaches which still preserve some loose connectivity of the space. However, while end-to-end methods tend to struggle in long-distance navigation tasks, topological map-based solutions are prone to failure due to spurious edges in the graph. In this work, we propose a learning-based topological visual navigation method with graph update strategies that improves lifelong navigation performance over time. We take inspiration from sampling-based planning algorithms to build image-based topological graphs, resulting in sparser graphs with higher navigation performance compared to baseline methods. Also, unlike controllers that learn from fixed training environments, we show that our model can be finetuned using a relatively small dataset from the real-world environment where the robot is deployed. Finally, we demonstrate strong system performance in real world robot navigation experiments

Enhanced online programming for industrial robots

The use of robots and automation levels in the industrial sector is expected to grow, and is driven by the on-going need for lower costs and enhanced productivity. The manufacturing industry continues to seek ways of realizing enhanced production, and the programming of articulated production robots has been identified as a major area for improvement. However, realizing this automation level increase requires capable programming and control technologies. Many industries employ offline-programming which operates within a manually controlled and specific work environment. This is especially true within the high-volume automotive industry, particularly in high-speed assembly and component handling. For small-batch manufacturing and small to medium-sized enterprises, online programming continues to play an important role, but the complexity of programming remains a major obstacle for automation using industrial robots. Scenarios that rely on manual data input based on real world obstructions require that entire production systems cease for significant time periods while data is being manipulated, leading to financial losses. The application of simulation tools generate discrete portions of the total robot trajectories, while requiring manual inputs to link paths associated with different activities. Human input is also required to correct inaccuracies and errors resulting from unknowns and falsehoods in the environment. This study developed a new supported online robot programming approach, which is implemented as a robot control program. By applying online and offline programming in addition to appropriate manual robot control techniques, disadvantages such as manual pre-processing times and production downtimes have been either reduced or completely eliminated. The industrial requirements were evaluated considering modern manufacturing aspects. A cell-based Voronoi generation algorithm within a probabilistic world model has been introduced, together with a trajectory planner and an appropriate human machine interface. The robot programs so achieved are comparable to manually programmed robot programs and the results for a Mitsubishi RV-2AJ five-axis industrial robot are presented. Automated workspace analysis techniques and trajectory smoothing are used to accomplish this. The new robot control program considers the working production environment as a single and complete workspace. Non-productive time is required, but unlike previously reported approaches, this is achieved automatically and in a timely manner. As such, the actual cell-learning time is minimal