Task-oriented viewpoint planning for free-form objects

A thesis submitted to the Universitat Politècnica de Catalunya to obtain the degree of Doctor of Philosophy. Doctoral programme: Automatic Control, Robotics and Computer Vision. This thesis was completed at: Institut de Robòtica i Informàtica Industrial, CSIC-UPC.[EN]: This thesis deals with active sensing and its use in real exploration tasks under both scene ambiguities and measurement uncertainties. While object modeling is the implicit objective of most of active sensing algorithms, in this work we have explored new strategies to deal with more generic and more complex tasks. Active sensing requires the ability of moving the perceptual system to gather new information. Our approach uses a robot manipulator with a 3D Time-of-Flight (ToF) camera attached to the end-effector. For a complex task, we have focused our attention on plant phenotyping. Plants are complex objects, with leaves that change their position and size along time. Valid viewpoints for a certain plant are hardly valid for a different one, even belonging to the same species. Some instruments, such as chlorophyll meters or disk sampling tools, require being precisely positioned over a particular location of the leaf. Therefore, their use requires the modeling of specific regions of interest of the plant, including also the free space needed for avoiding obstacles and approaching the leaf with tool. It is easy to observe that predefined camera trajectories are not valid here, and that usually with one single view it is very difficult to acquire all the required information. The overall objective of this thesis is to solve complex active sensing tasks by embedding their exploratory goal into a pre-estimated geometrical model, using information-gain as the fundamental guideline for the reward function. The main contributions can be divided in two groups: first, the evaluation of ToF cameras and their calibration to assess the uncertainty of the measurements (presented in Part I); and second, the proposal of a framework capable of embedding the task, modeled as free and occupied space, and that takes into account the modeled sensor's uncertainty to improve the action selection algorithm (presented in Part II). This thesishas given rise to 14 publications, including 5 indexed journals, and its results have been used in the GARNICS European project. The complete framework is based on the Next-Best-View methodology and it can be summarized in the following main steps. First, an initial view of the object (e.g., a plant) is acquired. From this initial view and given a set of candidate viewpoints, the expected gain obtained by moving the robot and acquiring the next image is computed. This computation takes into account the uncertainty from all the different pixels of the sensor, the expected information based on a predefined task model, and the possible occlusions. Once the most promising view is selected, the robot moves, takes a new image, integrates this information intothe model, and evaluates again the set of remaining views. Finally, the task terminates when enough information is gathered. In our examples, this process enables the robot to perform a measurement on top of a leaf. The key ingredient is to model the complexity of the task in a layered representation of free-occupied occupancy grid maps. This allows to naturally encode the requirements of the task, to maintain and update the belief state with the measurements performed, to simulate and compute the expected gains of all potential viewpoints, and to encode the termination condition. During this work the technology of ToF cameras has incredibly evolved. Nowadays it is very popular and ToF cameras are already embedded in some consumer devices. Although the quality of the measurements has been considerably improved, it is still not uniform in the sensor. We believe, as it has been demonstrated in various experiments in this work, that a careful modeling of the sensor's uncertainty is highly beneficial and helps to design better decision systems. In our case, it enables a more realistic computation of the information gain measure, and consequently, a better selection criterion.[CA]: Aquesta tesi aborda el tema de la percepció activa i el seu ús en tasques d'exploració en entorns reals tot considerant la ambigüitat en l'escena i la incertesa del sistema de percepció. Al contrari de la majoria d'algoritmes de percepció activa, on el modelatge d'objectes sol ser l'objectiu implícit, en aquesta tesi hem explorat noves estratègies per poder tractar tasques genèriques i de major complexitat. Tot sistema de percepció activa requereix un aparell sensorial amb la capacitat de variar els seus paràmetres de forma controlada, per poder, d'aquesta manera, recopilar nova informació per resoldre una tasca determinada. En tasques d'exploració, la posició i orientació del sensor són paràmetres claus per resoldre la tasca. En el nostre estudi hem fet ús d'un robot manipulador com a sistema de posicionament i d'una càmera de profunditat de temps de vol (ToF), adherida al seu efector final, com a sistema de percepció. Com a tasca final, ens hem concentrat en l'adquisició de mesures sobre fulles dins de l'àmbit del fenotipatge de les plantes. Les plantes son objectes molt complexos, amb fulles que canvien de textura, posició i mida al llarg del temps. Això comporta diverses dificultats. Per una banda, abans de dur a terme una mesura sobre un fulla s'ha d'explorar l'entorn i trobar una regió que ho permeti. A més a més, aquells punts de vista que han estat adequats per una determinada planta difícilment ho seran per una altra, tot i sent les dues de la mateixa espècie. Per un altra banda, en el moment de la mesura, certs instruments, tals com els mesuradors de clorofil·la o les eines d'extracció de mostres, requereixen ser posicionats amb molta precisió. És necessari, doncs, disposar d'un model detallat d'aquestes regions d'interès, i que inclogui no només l'espai ocupat sinó també el lliure. Gràcies a la modelització de l'espai lliure es pot dur a terme una bona evitació d'obstacles i un bon càlcul de la trajectòria d'aproximació de l'eina a la fulla. En aquest context, és fàcil veure que, en general, amb un sol punt de vistano n'hi haprou per adquirir tota la informació necessària per prendre una mesura, i que l'ús de trajectòries predeterminades no garanteixen l'èxit. L'objectiu general d'aquesta tesi és resoldre tasques complexes de percepció activa mitjançant la codificació del seu objectiu d'exploració en un model geomètric prèviament estimat, fent servir el guany d'informació com a guia fonamental dins de la funció de cost. Les principals contribucions d'aquesta tesi es poden dividir en dos grups: primer, l'avaluació de les càmeres ToF i el seu calibratge per poder avaluar la incertesa de les seves mesures (presentat en la Part I); i en segon lloc, la proposta d'un sistema capaç de codificar la tasca mitjançant el modelatge de l'espai lliure i ocupat, i que té en compte la incertesa del sensor per millorar la selecció de les accions (presentat en la Part II). Aquesta tesi ha donat lloc a 14 publicacions, incloent 5 en revistes indexades, i els resultats obtinguts s'han fet servir en el projecte Europeu GARNICS. La funcionalitat del sistema complet està basada en els mètodes Next-Best-View (següent-millor-vista) i es pot desglossar en els següents passos principals. En primer lloc, s'obté una vista inicial de l'objecte (p. ex., una planta). A partir d'aquesta vista inicial i d'un conjunt de vistes candidates, s'estima, per cada una d'elles, el guany d'informació resultant, tant de moure la càmera com d'obtenir una nova mesura. És rellevant dir que aquest càlcul té en compte la incertesa de cada un dels píxels del sensor, l'estimació de la informació basada en el model de la tasca preestablerta i les possibles oclusions. Un cop seleccionada la vista més prometedora, el robot es mou a la nova posició, pren una nova imatge, integra aquesta informació en el model i torna a avaluar, un altre cop, el conjunt de punts de vista restants. Per últim, la tasca acaba en el moment que es recopila suficient informació.This work has been partially supported by a JAE fellowship of the Spanish Scientific Research Council (CSIC), the Spanish Ministry of Science and Innovation, the Catalan Research Commission and the European Commission under the research projects: DPI2008-06022: PAU: Percepción y acción ante incertidumbre. DPI2011-27510: PAU+: Perception and Action in Robotics Problems with Large State Spaces. 201350E102: MANIPlus: Manipulación robotizada de objetos deformables. 2009-SGR-155: SGR ROBÒTICA: Grup de recerca consolidat - Grup de Robòtica. FP6-2004-IST-4-27657: EU PACO PLUS project. FP7-ICT-2009-4-247947: GARNICS: Gardening with a cognitive system. FP7-ICT-2009-6-269959: IntellAct: Intelligent observation and execution of Actions and manipulations.Peer Reviewe

Deep Learning-Based Robotic Perception for Adaptive Facility Disinfection

Hospitals, schools, airports, and other environments built for mass gatherings can become hot spots for microbial pathogen colonization, transmission, and exposure, greatly accelerating the spread of infectious diseases across communities, cities, nations, and the world. Outbreaks of infectious diseases impose huge burdens on our society. Mitigating the spread of infectious pathogens within mass-gathering facilities requires routine cleaning and disinfection, which are primarily performed by cleaning staff under current practice. However, manual disinfection is limited in terms of both effectiveness and efficiency, as it is labor-intensive, time-consuming, and health-undermining. While existing studies have developed a variety of robotic systems for disinfecting contaminated surfaces, those systems are not adequate for intelligent, precise, and environmentally adaptive disinfection. They are also difficult to deploy in mass-gathering infrastructure facilities, given the high volume of occupants. Therefore, there is a critical need to develop an adaptive robot system capable of complete and efficient indoor disinfection. The overarching goal of this research is to develop an artificial intelligence (AI)-enabled robotic system that adapts to ambient environments and social contexts for precise and efficient disinfection. This would maintain environmental hygiene and health, reduce unnecessary labor costs for cleaning, and mitigate opportunity costs incurred from infections. To these ends, this dissertation first develops a multi-classifier decision fusion method, which integrates scene graph and visual information, in order to recognize patterns in human activity in infrastructure facilities. Next, a deep-learning-based method is proposed for detecting and classifying indoor objects, and a new mechanism is developed to map detected objects in 3D maps. A novel framework is then developed to detect and segment object affordance and to project them into a 3D semantic map for precise disinfection. Subsequently, a novel deep-learning network, which integrates multi-scale features and multi-level features, and an encoder network are developed to recognize the materials of surfaces requiring disinfection. Finally, a novel computational method is developed to link the recognition of object surface information to robot disinfection actions with optimal disinfection parameters

Development and Validation of Mechatronic Systems for Image-Guided Needle Interventions and Point-of-Care Breast Cancer Screening with Ultrasound (2D and 3D) and Positron Emission Mammography

The successful intervention of breast cancer relies on effective early detection and definitive diagnosis. While conventional screening mammography has substantially reduced breast cancer-related mortalities, substantial challenges persist in women with dense breasts. Additionally, complex interrelated risk factors and healthcare disparities contribute to breast cancer-related inequities, which restrict accessibility, impose cost constraints, and reduce inclusivity to high-quality healthcare. These limitations predominantly stem from the inadequate sensitivity and clinical utility of currently available approaches in increased-risk populations, including those with dense breasts, underserved and vulnerable populations. This PhD dissertation aims to describe the development and validation of alternative, cost-effective, robust, and high-resolution systems for point-of-care (POC) breast cancer screening and image-guided needle interventions. Specifically, 2D and 3D ultrasound (US) and positron emission mammography (PEM) were employed to improve detection, independent of breast density, in conjunction with mechatronic and automated approaches for accurate image acquisition and precise interventional workflow. First, a mechatronic guidance system for US-guided biopsy under high-resolution PEM localization was developed to improve spatial sampling of early-stage breast cancers. Validation and phantom studies showed accurate needle positioning and 3D spatial sampling under simulated PEM localization. Subsequently, a whole-breast spatially-tracked 3DUS system for point-of-care screening was developed, optimized, and validated within a clinically-relevant workspace and healthy volunteer studies. To improve robust image acquisition and adaptability to diverse patient populations, an alternative, cost-effective, portable, and patient-dedicated 3D automated breast (AB) US system for point-of-care screening was developed. Validation showed accurate geometric reconstruction, feasible clinical workflow, and proof-of-concept utility across healthy volunteers and acquisition conditions. Lastly, an orthogonal acquisition and 3D complementary breast (CB) US generation approach were described and experimentally validated to improve spatial resolution uniformity by recovering poor out-of-plane resolution. These systems developed and described throughout this dissertation show promise as alternative, cost-effective, robust, and high-resolution approaches for improving early detection and definitive diagnosis. Consequently, these contributions may advance breast cancer-related equities and improve outcomes in increased-risk populations and limited-resource settings

A real-time low-cost vision sensor for robotic bin picking

This thesis presents an integrated approach of a vision sensor for bin picking. The vision system that has been devised consists of three major components. The first addresses the implementation of a bifocal range sensor which estimates the depth by measuring the relative blurring between two images captured with different focal settings. A key element in the success of this approach is that it overcomes some of the limitations that were associated with other related implementations and the experimental results indicate that the precision offered by the sensor discussed in this thesis is precise enough for a large variety of industrial applications. The second component deals with the implementation of an edge-based segmentation technique which is applied in order to detect the boundaries of the objects that define the scene. An important issue related to this segmentation technique consists of minimising the errors in the edge detected output, an operation that is carried out by analysing the information associated with the singular edge points. The last component addresses the object recognition and pose estimation using the information resulting from the application of the segmentation algorithm. The recognition stage consists of matching the primitives derived from the scene regions, while the pose estimation is addressed using an appearance-based approach augmented with a range data analysis. The developed system is suitable for real-time operation and in order to demonstrate the validity of the proposed approach it has been examined under varying real-world scenes

Modelling, synthesis and model-based motion planning for hyper-redundant, binary actuated manipulators

Die Untersuchung von schwer zu erreichenden Hohlräumen durch schmale Zugänge wird im technischen Umfeld als Boroskopie und in der Medizin als Endoskopie bezeichnet. Wenn neben der reinen Inspektion auch eine Manipulation erfolgen soll, wird ergänzend zu einer guten Anpassbarkeit an gekrümmte Pfade auch eine stabile Arbeitsplattform zur Aufnahme von Manipulationskräften benötigt. Einen Ansatz, die daraus resultierenden Anforderungen an die verwendeten Systeme zu adressieren, stellen schlangenartige Roboter dar. Ihre hyperredundante Struktur aus einzelnen Stellgliedern bietet eine vielseitige Positionierbarkeit. Die Verwendung von binären, kippstabilen Aktoren beschränkt zwar den Arbeitsraum auf wenige diskrete Punkte, bietet aber – in Abhängigkeit vom Antriebsmechanismus – besonders hohe Haltemomente und ermöglicht damit eine gezielte Systemversteifung. Eine Kombination beider Ansätze zur Klasse der binär aktuierten, hyperredundanten Manipulatoren ist in der Lage, diese Anforderungen zu erfüllen, jedoch existiert deutlicher Forschungsbedarf hinsichtlich Methoden zur optimalen Auslegung sowie zur gezielten Verfolgung von Referenzpfaden, sodass Kern der vorliegenden Arbeit die Erforschung der modellbasierten Bewegungsplanung dieser Roboterklasse ist. Voraussetzung für eine hohe Pfadfolgegenauigkeit ist, dass der Manipulator sich grundsätzlich gut an einen vorgegebenen Referenzpfad anschmiegen kann. Der Einschränkungsgrad durch die diskrete Positionierbarkeit des Manipulators ist dabei abhängig von den geometrischen Parametern der einzelnen Segmente. Die Untersuchungen in dieser Arbeit zeigen, dass durch die Analyse kinematischer Leistungsmerkmale, wie Arbeitsraum(-dichte) oder erzielbarer Krümmungsradius, kein allgemeingültiges optimales Design gefunden werden kann. Daher wird eine Maßsynthese unter Berücksichtigung von Randbedingungen entworfen, in der optimale geometrische Parameter eines einzelnen binären Aktors synthetisiert werden. Darauf aufbauend wird eine Pfadverfolgung gemäß dem „Follow-the-Leader“-Prinzip erarbeitet. Grundidee ist, dass das Endeffektorsegment den Referenzpfad exploriert, während alle weiteren Aktoren dem führenden Segment automatisch folgen. Da binäre Aktoren einen nicht-kontinuierlichen Schaltprozess aufweisen, wird ein modellbasierter Ansatz für die Bestimmung optimaler Schaltsequenzen vorgeschlagen, die zu jedem Zeitpunkt eine hohe Pfadtreue garantieren. Die anschließende experimentelle Evaluation erfolgt nach der Modellierung und Identifikation relevanter Parameter für den Prototyp einer elektromagnetischen Kippaktorkette. Grundsätzlich kann die Funktionsfähigkeit der in dieser Arbeit erforschten Methoden zur Bewegungsplanung sowohl in der Simulation als auch experimentell nachgewiesen werden.The investigation of difficult to reach cavities through narrow accesses is called borescopy in the technical environment and endoscopy in medicine. If manipulation is to be performed in addition to pure inspection, a stable working platform is required to withstand manipulation forces in combination with good adaptability to curved paths. One approach to address the resulting requirements for the systems used are snake-like robots. Their hyper-redundant structure of individual actuators allows for versatile positioning. Although the use of binary, tilt-stable actuators limits the working space to a few discrete points, they offer - depending on the drive mechanism - particularly high holding torques and thus enable a targeted system stiffening. A combination of both approaches to the class of binary actuated, hyper-redundant manipulators is able to meet the required requirements, however, there is a clear need for research into methods for optimal design and the targeted pursuit of reference paths, so that the core of the present work consists the investigation of model-based motion planning of this robot class. A prerequisite for a high path following accuracy is that the manipulator is able to adapt well to a given reference path. The degree of limitation due to discrete positionability of the manipulator depends on the geometric parameters of the individual segments. The studies in this thesis show that the analysis of kinematic performance characteristics, such as work space (density) or achievable radius of curvature, does not lead to a generally valid optimal design. Therefore, a dimensional synthesis is developed under consideration of boundary conditions, in which optimal geometric parameters of a single binary actuator are synthesized. Based on this, a path following according to the "Follow-the-Leader"principle is elaborated. The basic idea is that the end effector segment explores the reference path, while all other actuators automatically follow the leading segment. Since binary actuators have a discontinuous switching process, a model-based approach is proposed for determining optimal switching sequences that guarantee high path accuracy at all times. The subsequent experimental evaluation is performed after modelling and identification of relevant parameters for the prototype of an electromagnetic tilting actuator chain. In principle, the functionality of the motion planning methods investigated in this thesis are proven both in simulation and experimentally