Avoidance of Concave Obstacles through Rotation of Nonlinear Dynamics

Controlling complex tasks in robotic systems, such as circular motion for cleaning or following curvy lines, can be dealt with using nonlinear vector fields. In this paper, we introduce a novel approach called rotational obstacle avoidance method (ROAM) for adapting the initial dynamics when the workspace is partially occluded by obstacles. ROAM presents a closed-form solution that effectively avoids star-shaped obstacles in spaces of arbitrary dimensions by rotating the initial dynamics towards the tangent space. The algorithm enables navigation within obstacle hulls and can be customized to actively move away from surfaces, while guaranteeing the presence of only a single saddle point on the boundary of each obstacle. We introduce a sequence of mappings to extend the approach for general nonlinear dynamics. Moreover, ROAM extends its capabilities to handle multi-obstacle environments and provides the ability to constrain dynamics within a safe tube. By utilizing weighted vector-tree summation, we successfully navigate around general concave obstacles represented as a tree-of-stars. Through experimental evaluation, ROAM demonstrates superior performance in terms of minimizing occurrences of local minima and maintaining similarity to the initial dynamics, outperforming existing approaches in multi-obstacle simulations. The proposed method is highly reactive, owing to its simplicity, and can be applied effectively in dynamic environments. This was demonstrated during the collision-free navigation of a 7 degree-of-freedom robot arm around dynamic obstaclesComment: 20 pages, 19 figure

Adaptive Robot Navigation with Collision Avoidance subject to 2nd-order Uncertain Dynamics

This paper considers the problem of robot motion planning in a workspace with obstacles for systems with uncertain 2nd-order dynamics. In particular, we combine closed form potential-based feedback controllers with adaptive control techniques to guarantee the collision-free robot navigation to a predefined goal while compensating for the dynamic model uncertainties. We base our findings on sphere world-based configuration spaces, but extend our results to arbitrary star-shaped environments by using previous results on configuration space transformations. Moreover, we propose an algorithm for extending the control scheme to decentralized multi-robot systems. Finally, extensive simulation results verify the theoretical findings

Exact Robot Navigation Using Power Diagrams

We reconsider the problem of reactive navigation in sphere worlds, i.e., the construction of a vector field over a compact, convex Euclidean subset punctured by Euclidean disks, whose flow brings a Euclidean disk robot from all but a zero measure set of initial conditions to a designated point destination, with the guarantee of no collisions along the way. We use power diagrams, generalized Voronoi diagrams with additive weights, to identify the robot’s collision free convex neighborhood, and to generate the value of our proposed candidate solution vector field at any free configuration via evaluation of an associated convex optimization problem. We prove that this scheme generates a continuous flow with the specified properties. We also propose its practical extension to the nonholonomically constrained kinematics of the standard differential drive vehicle.For more information: Kod*la

深層強化学習を用いた動的環境下における事前知識不要なロボットナビゲーションに関する研究

Tohoku University博士（工学）thesi

Autonomous Mobile Robots Controlled by Navigation Functions

This paper reviews the theory of navigation functions and the attendant use of natural control techniques with emphasis upon applications to mobile autonomous robots. Results to date will be discussed in the context of a larger program of research that seeks effective parameterizations of uncertainty in robot navigation problems. Constructive solutions to particular cases of mobile robot navigation problems with complete certainty are provided as well

Safe and Quasi-Optimal Autonomous Navigation in Environments with Convex Obstacles

We propose a continuous feedback control strategy that steers a point-mass vehicle safely to a destination, in a quasi-optimal manner, in sphere worlds. The main idea consists in avoiding each obstacle via the shortest path within the cone enclosing the obstacle and moving straight toward the target when the vehicle has a clear line of sight to the target location. In particular, almost global asymptotic stability of the target location is achieved in two-dimensional (2D) environments under a particular assumption on the obstacles configuration. We also propose a reactive (sensor-based) approach, suitable for real-time implementations in a priori unknown 2D environments with sufficiently curved convex obstacles, guaranteeing almost global asymptotic stability of the target location. Simulation results are presented to illustrate the effectiveness of the proposed approach.Comment: arXiv admin note: substantial text overlap with arXiv:2302.1230

UAV Navigation System for Prescribed Fires

Since the beginning of mankind, a lot of fires have happened and have taken millions of lives, whether they were human or animal lives. On average, there are about twenty thousand forest fires annually in the world and the burnt area is one per thousand of the total forest area on Earth. In the last years, there were a lot of big fires such as the fires in Pedrogão Grande, Portugal, the SoCal fires in the US coast, the big fire in the Amazon Forest in Brazil and the bush fires in Australia, later 2019. When fires take such dimensions, they can also cause several environmental and health problems. These problems can be damage to millions of hectares of forest resources, the evacuation of thousands of people, burning of homes and devastation of infrastructures. When a big fire starts, the priority is the rapid rescue of lives and then, the attempt to control the fire. In these scenarios, autonomous robots are a very good assistance because they can help in the rescue missions and monitoring the fire. These autonomous robots include the unmanned aerial vehicle, or commonly called the UAV. This dissertation begins with an intensive research on the work that has already been done relative to this subject. It will then continue with the testing of different simulators and see which better fits for this type of work. With this, it will be implemented a simulation that can represent fires and has physics for test purposes, in order to test without causing any material damage in the real world. After the simulation part is done, algorithm testing and bench marking are expected, in order to compare different algorithms and see which are the best for this type of applications. If everything goes according to plan, in the end, it is expected to have an autonomous navigation system for UAVs to navigate through burnt areas and wildfires to monitor the development of these.Desde o início da humanidade muitos incêndios têm acontecido e têm levado milhões de vidas, quer estas sejam humanas ou animais. Em média, no planeta, existem cerca de vinte mil incêndios florestais anualmente e a área queimada é um por mil da área total de florestas do mundo e na última década, houveram grandes incêndios. Alguns destes são os de Pedrogrão Grande, em Portugal, os incêndios no sul da Califórnia, na costa dos EUA, o incêndio que deflagrou na floresta Amazónia, no Brasil e os incêndios na Austrália, no final de 2019. Quando os incêndios assumem estas dimensões, podem vir a causar vários problemas ambientais e de saúde. Estes problemas podem ser danos a milhões de hectares de recursos florestais, a evacuação de milhares de pessoas e podem haver habitações e infraestruturas ardidas. Quando um grande incêndio começa, a primeira prioridade é o resgate rápido e de seguida a tentativa de controlar o incêndio. Nestes cenários, robôs autónomos são uma excelente assistência. Estes robôs incluem o veículo aéreo não tripulado, o UAV. Esta dissertação começa com uma intensa pesquisa sobre o trabalho já realizado em relação a este tema. De seguida, vários testes irão ser realizados para testar diferentes simuladores e ver qual melhor se adapta ao trabalho que se irá realizar. Com isto, será implementada uma simulação que consiga representar um incêndio e suporte várias fisícas do mundo real. Após a secção da simulação estar concluída, espera-se vários testes de algoritmos e comparação entre eles, para ver qual o que se adequa melhor a este tipo de situações. Se tudo correr conforme planeado, é esperado no final desta dissertação ter-se um sistema de navegação autónoma para UAVs percorrem áreas florestais e ser possível monitorizar incêndios