Searching and Tracking of Humans in Urban Environments with Humanoid Robots
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Searching and tracking of humans in urban environments with humanoid robots Alex Goldhoorn ADVERTIMENT La consulta d’aquesta tesi queda condicionada a l’acceptació de les següents condicions d'ús: La difusió d’aquesta tesi per mitjà del repositori institucional UPCommons (http://upcommons.upc.edu/tesis) i el repositori cooperatiu TDX ( http://www.tdx.cat/) ha estat autoritzada pels titulars dels drets de propietat intel·lectual únicament per a usos privats emmarcats en activitats d’investigació i docència. No s’autoritza la seva reproducció amb finalitats de lucre ni la seva difusió i posada a disposició des d’un lloc aliè al servei UPCommons o TDX. No s’autoritza la presentació del seu contingut en una finestra o marc aliè a UPCommons (framing). Aquesta reserva de drets afecta tant al resum de presentació de la tesi com als seus continguts. En la utilització o cita de parts de la tesi és obligat indicar el nom de la persona autora. 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Universitat Politècnica De Catalunya Doctoral Programme: Automatic Control, Robotics And Computer Vision Ph.D. Thesis Searching and Tracking of Humans in Urban Environments with Humanoid Robots Alex Goldhoorn Advisor: Prof. Alberto Sanfeliu Co-advisor: Prof. René Alquézar June, 2017 Searching and Tracking of Humans in Urban Environments with Humanoid Robots by Alex Goldhoorn Doctoral Programme: Automatic Control, Robotics and Computer Vision This thesis has been completed at: Institut de Robòtica i Informàtica Industrial, CSIC-UPC Advisor: Alberto Sanfeliu Co-advisor: René Alquézar The last version of this document and extra material will be available at http://alex.goldhoorn.net/thesis. To my wife Juliette, my parents Anneke and Klaas and my sister Brenda. ii Acknowledgements First of all, I would like to thank my supervisors Alberto Sanfeliu and René Alquézar for their support, ideas, feedback and funding. Furthermore, I would like to thank: Anaís Garrell for her support, contributions to the work and help during the experiments; Fernando Herrero and Sergi Hernández for their technical support and their patience during the experiments; all the people that helped and participated in the experiments; and all people that contributed to the research in general. Also, I want to thank my office colleagues and all the other colleagues for making the stay at IRI pleasant and fruitful. And last but not least, I want to thank my family and friends, and especially my wife Juliette for their mental support, patience and love. This work has been supported by the Institut de Robòtica i Informàtica Industrial (IRI), Universitat Politècnica de Catalunya(UPC) and the following research projects: • The Collective Experience of Empathic Systems (CEEDs) [FP7-ICT-2009-5] (funded by the European Union). • RobTaskCoop: Cooperación robots humanos en áreas urbanas [DPI2010-17112] (funded by MINECO). • Rob-In-Coop: Interacción, aprendizaje y cooperación robot-humano en áreas ur- banas [DPI2013-42458-P] (funded by MINECO). iv Abstract Searching and tracking are important behaviours for a mobile service robot to assist people, to search-and-rescue and, in general, to locate mobile objects, animals or hu- mans. Even though searching might be evident for humans, for robots it is not, since it requires exploring, handling noisy sensors, coping with dynamic obstacles, and coor- dination in the case of multiple agents. In this thesis, we present several methods to search and track a person in an urban environment. All methods were first tested extensively in simulation and then in real- life, using one or two mobile service robots, called Tibi and Dabo. The robots have laser rangefinders, which are used to navigate, to detect obstacles and to detect people’s legs. Since we focus on search-and-track methods, we use existing methods for robot navigation, for people detection and person recognition. First tests are done with the hide-and-seek problem, in which the robot learns to catch the hider. Concretely, a Mixed Observable Markov Decision Process(MOMDP) model is used, in which the seeker’s location is fully observable and the hider’s location partially observable. Since the computational complexity depends on the number of states, we propose a hierarchical on-line method that reduces the state space by group- ing them together. Although the method worked properly in simulation, in the real-life experiments the results were not satisfying and the on-line policy calculation was not fast enough to work in real-time. To handle larger environments, work in continuous state space and run in real-time, we propose to use an approach, the Continuous Real-time POMCP(CR-POMCP), that does Monte-Carlo simulations to learn a policy. The method performed correctly in simulation, but on the real robot it resulted in slow zigzag movements. Therefore, a new method is proposed, which uses the highest probable locations, according to its vi probability map (belief). Since the belief propagation of the POMCP resembles how a Particle Filter(PF) works, we also propose a method that uses aPF to maintain the belief. ThePF method has to handle lack of observations, therefore, we introduce a special weight function. Both belief update methods take into account sensor and actuator noise, false negative detections, false positive detections (for a short time) and dynamic obstacles. Finally, a cooperative distributed multi-agent method is presented, it makes use of the previous belief update functions, but it uses all the agents’ observations. Next, the search locations are assigned to explore the whole working environment, taking into account: the belief, the distance to the search location and if another agent already will search close to it. Summarizing, the main contributions of this thesis are several methods to search and track a person in an urban environment with one or more mobile service robots. All these methods have been shown to work through a set of simulations and real-life experiments. vii Resum La cerca i el seguiment de persones són comportaments importants per un robot mòbil de servei per poder assistir, trobar i ajudar als humans, i en general, per localitzar objectes, animals o vianants. Tot i que la cerca és fàcil per als humans, no ho és per a un robot, ja que requereix exploració, maneig de soroll de sensors, fer front als obstacles dinàmics, i la coordinació en el cas de múltiples agents. En aquesta tesi presentem diferents mètodes per a buscar i seguir a una persona en un entorn urbà. Tots els mètodes han estat provats extensivament en simulació i després en el món real, utilitzant dos robots mòbils de servei, la Tibi i en Dabo. Els robots utilitzen sensors làser per a navegar, detectar obstacles i detectar les cames de les persones. Atès que aquest treball es centra en mètodes de cerca i seguiment, s’han usat els mètodes existents per a la navegació del robot, la detecció i el reconeixement de persones. Primerament, s’han fet proves amb el conegut joc del fet i amagar, on el robot aprèn a trobar l’amagador. S’ha fet servir el model Mixed Observable Markov Decision Process(MOMDP), on la posició del trobador és completament visible i la posició de l’amagador és parcialment visible. Degut a que la complexitat computacional depèn del nombre d’estats, es proposa un mètode jeràrquic en línia que redueix l’espai d’estats, tot agrupant-los. Tot i que el mètode va funcionar correctament en simulació, en els experiments reals els resultats no van ser satisfactoris, i el càlcul de la política no va ser prou ràpid com per treballar en temps real. Per tal de fer front a entorns de més superfície, treballar en l’espai continu i executar en temps real, proposem un nou enfocament, el Continuous Real-time POMCP(CR- POMCP), que fa simulacions de Monte-Carlo per aprendre una política. El mètode va funcionar correctament en l’entorn simulat, però a l’entorn real el robot realitzava viii lents moviments en zig-zag. Per tant, es proposa un mètode nou, que utilitza els llocs amb més alta probabilitat, d’acord amb el seu mapa de probabilitats (belief).