Variational aleatoric uncertainty calibration in neural regression

Des mesures de confiance calibrées et fiables sont un prérequis pour la plupart des systèmes de perception robotique car elles sont nécessaires aux modules de fusion de capteurs et de planification qui interviennent plus en aval. Cela est particulièrement vrai dans le cas d’applications où la sécurité est essentielle, comme les voitures à conduite autonome. Dans le contexte de l’apprentissage profond, l’incertitude prédictive est classée en incertitude épistémique et incertitude aléatoire. Il existe également une incertitude distributionnelle associée aux données hors distribution. L’incertitude aléatoire représente l’ambiguïté inhérente aux données d’entrée et est généralement irréductible par nature. Plusieurs méthodes existent pour estimer cette incertitude au moyen de structures de réseau modifiées ou de fonctions de perte. Cependant, en général, ces méthodes manquent de calibration, ce qui signifie que les incertitudes estimées ne représentent pas fidèlement l’incertitude des données empiriques. Les approches actuelles pour calibrer l’incertitude aléatoire nécessitent soit un "ensemble de données de calibration", soit de modifier les paramètres du modèle après l’apprentissage. De plus, de nombreuses approches ajoutent des opérations supplémentaires lors de l’inférence. Pour pallier à ces problèmes, nous proposons une méthode simple et efficace d’entraînement d’un régresseur neuronal calibré, conçue à partir des premiers principes de la calibration. Notre idée maîtresse est que la calibration ne peut être réalisée qu’en imposant des contraintes sur plusieurs exemples, comme ceux d’un mini-batch, contrairement aux approches existantes qui n’imposent des contraintes que sur la base d’un échantillon. En obligeant la distribution des sorties du régresseur neuronal (la distribution de la proposition) à ressembler à unedistribution cible en minimisant une divergence f , nous obtenons des modèles nettement mieuxcalibrés par rapport aux approches précédentes. Notre approche, f -Cal, est simple à mettre en œuvre ou à ajouter aux modèles existants et surpasse les méthodes de calibration existantes dansles tâches réelles à grande échelle de détection d’objets et d’estimation de la profondeur. f -Cal peut être mise en œuvre en 10-15 lignes de code PyTorch et peut être intégrée à n’importe quel régresseur neuronal probabiliste, de façon peu invasive. Nous explorons également l’estimation de l’incertitude distributionnelle pour la détection d’objets, et employons des méthodes conçues pour les systèmes de classification. Nous établissons un problème d’arrière-plan hors distribution qui entrave l’applicabilité des méthodes d’incertitude distributionnelle dans la détection d’objets.Calibrated and reliable confidence measures are a prerequisite for most robotics perception systems since they are needed by sensor fusion and planning components downstream. This is particularly true in the case of safety-critical applications such as self-driving cars. In the context of deep learning, the sources of predictive uncertainty are categorized into epistemic and aleatoric uncertainty. There is also distributional uncertainty associated with out of distribution data. Epistemic uncertainty, also known as knowledge uncertainty, arises because of noise in the model structure and parameters, and can be reduced with more labeled data. Aleatoric uncertainty represents the inherent ambiguity in the input data and is generally irreducible in nature. Several methods exist for estimating aleatoric uncertainty through modified network structures or loss functions. However, in general, these methods lack calibration, meaning that the estimated uncertainties do not represent the empirical data uncertainty accurately. Current approaches to calibrate aleatoric uncertainty either require a held out calibration dataset or to modify the model parameters post-training. Moreover, many approaches add extra computation during inference time. To alleviate these issues, this thesis proposes a simple and effective method for training a calibrated neural regressor, designed from the first principles of calibration. Our key insight is that calibration can be achieved by imposing constraints across multiple examples, such as those in a mini-batch, as opposed to existing approaches that only impose constraints on a per-sample basis. By enforcing the distribution of outputs of the neural regressor (the proposal distribution) to resemble a target distribution by minimizing an f-divergence, we obtain significantly better-calibrated models compared to prior approaches. Our approach, f-Cal, is simple to implement or add to existing models and outperforms existing calibration methods on the large-scale real-world tasks of object detection and depth estimation. f-Cal can be implemented in 10-15 lines of PyTorch code, and can be integrated with any probabilistic neural regressor in a minimally invasive way. This thesis also explores the estimation of distributional uncertainty for object detection, and employ methods designed for classification setups. In particular, we attempt to detect out of distribution (OOD) samples, examples which are not part of training data distribution. I establish a background-OOD problem which hampers applicability of distributional uncertainty methods in object detection specifically

Visual Semantic Parsing: From Images to Abstract Meaning Representation

The success of scene graphs for visual scene understanding has brought attention to the benefits of abstracting a visual input (e.g., image) into a structured representation, where entities (people and objects) are nodes connected by edges specifying their relations. Building these representations, however, requires expensive manual annotation in the form of images paired with their scene graphs or frames. These formalisms remain limited in the nature of entities and relations they can capture. In this paper, we propose to leverage a widely-used meaning representation in the field of natural language processing, the Abstract Meaning Representation (AMR), to address these shortcomings. Compared to scene graphs, which largely emphasize spatial relationships, our visual AMR graphs are more linguistically informed, with a focus on higher-level semantic concepts extrapolated from visual input. Moreover, they allow us to generate meta-AMR graphs to unify information contained in multiple image descriptions under one representation. Through extensive experimentation and analysis, we demonstrate that we can re-purpose an existing text-to-AMR parser to parse images into AMRs. Our findings point to important future research directions for improved scene understanding.Comment: published in CoNLL 202

Have i reached the intersection: A deep learning-based approach for intersection detection from monocular cameras

Long-short term memory networks(LSTM) models have shown considerable performance on variety of problems dealing with sequential data. In this paper, we propose a variant of Long-Term Recurrent Convolutional Network(LRCN) to detect road intersection. We call this network as IntersectNet. We pose road intersection detection as binary classification task over sequence of frames. The model combines deep hierarchical visual feature extractor with recurrent sequence model. The model is end to end trainable with capability of capturing the temporal dynamics of the system. We exploit this capability to identify road intersection in a sequence of temporally consistent images. The model has been rigorously trained and tested on various different datasets. We think that our findings could be useful to model behavior of autonomous agent in the real-world

MapLite: Autonomous Intersection Navigation Without a Detailed Prior Map

In this work, we present MapLite: a one-click autonomous navigation system capable of piloting a vehicle to an arbitrary desired destination point given only a sparse publicly available topometric map (from OpenStreetMap). The onboard sensors are used to segment the road region and register the topometric map in order to fuse the high-level navigation goals with a variational path planner in the vehicle frame. This enables the system to plan trajectories that correctly navigate road intersections without the use of an external localization system such as GPS or a detailed prior map. Since the topometric maps already exist for the vast majority of roads, this solution greatly increases the geographical scope for autonomous mobility solutions. We implement MapLite on a full-scale autonomous vehicle and exhaustively test it on over 15 km of road including over 100 autonomous intersection traversals. We further extend these results through simulated testing to validate the system on complex road junction topologies such as traffic circles