1,091 research outputs found
Human Motion Trajectory Prediction: A Survey
With growing numbers of intelligent autonomous systems in human environments,
the ability of such systems to perceive, understand and anticipate human
behavior becomes increasingly important. Specifically, predicting future
positions of dynamic agents and planning considering such predictions are key
tasks for self-driving vehicles, service robots and advanced surveillance
systems. This paper provides a survey of human motion trajectory prediction. We
review, analyze and structure a large selection of work from different
communities and propose a taxonomy that categorizes existing methods based on
the motion modeling approach and level of contextual information used. We
provide an overview of the existing datasets and performance metrics. We
discuss limitations of the state of the art and outline directions for further
research.Comment: Submitted to the International Journal of Robotics Research (IJRR),
37 page
Trustworthy Reinforcement Learning Against Intrinsic Vulnerabilities: Robustness, Safety, and Generalizability
A trustworthy reinforcement learning algorithm should be competent in solving
challenging real-world problems, including {robustly} handling uncertainties,
satisfying {safety} constraints to avoid catastrophic failures, and
{generalizing} to unseen scenarios during deployments. This study aims to
overview these main perspectives of trustworthy reinforcement learning
considering its intrinsic vulnerabilities on robustness, safety, and
generalizability. In particular, we give rigorous formulations, categorize
corresponding methodologies, and discuss benchmarks for each perspective.
Moreover, we provide an outlook section to spur promising future directions
with a brief discussion on extrinsic vulnerabilities considering human
feedback. We hope this survey could bring together separate threads of studies
together in a unified framework and promote the trustworthiness of
reinforcement learning.Comment: 36 pages, 5 figure
A Survey on Policy Search for Robotics
Policy search is a subfield in reinforcement learning which focuses on
finding good parameters for a given policy parametrization. It is well
suited for robotics as it can cope with high-dimensional state and action
spaces, one of the main challenges in robot learning. We review recent
successes of both model-free and model-based policy search in robot
learning.
Model-free policy search is a general approach to learn policies
based on sampled trajectories. We classify model-free methods based on
their policy evaluation strategy, policy update strategy, and exploration
strategy and present a unified view on existing algorithms. Learning a
policy is often easier than learning an accurate forward model, and,
hence, model-free methods are more frequently used in practice. However,
for each sampled trajectory, it is necessary to interact with the
* Both authors contributed equally.
robot, which can be time consuming and challenging in practice. Modelbased
policy search addresses this problem by first learning a simulator
of the robot’s dynamics from data. Subsequently, the simulator generates
trajectories that are used for policy learning. For both modelfree
and model-based policy search methods, we review their respective
properties and their applicability to robotic systems
Neuroengineering of Clustering Algorithms
Cluster analysis can be broadly divided into multivariate data visualization, clustering algorithms, and cluster validation. This dissertation contributes neural network-based techniques to perform all three unsupervised learning tasks. Particularly, the first paper provides a comprehensive review on adaptive resonance theory (ART) models for engineering applications and provides context for the four subsequent papers. These papers are devoted to enhancements of ART-based clustering algorithms from (a) a practical perspective by exploiting the visual assessment of cluster tendency (VAT) sorting algorithm as a preprocessor for ART offline training, thus mitigating ordering effects; and (b) an engineering perspective by designing a family of multi-criteria ART models: dual vigilance fuzzy ART and distributed dual vigilance fuzzy ART (both of which are capable of detecting complex cluster structures), merge ART (aggregates partitions and lessens ordering effects in online learning), and cluster validity index vigilance in fuzzy ART (features a robust vigilance parameter selection and alleviates ordering effects in offline learning). The sixth paper consists of enhancements to data visualization using self-organizing maps (SOMs) by depicting in the reduced dimension and topology-preserving SOM grid information-theoretic similarity measures between neighboring neurons. This visualization\u27s parameters are estimated using samples selected via a single-linkage procedure, thereby generating heatmaps that portray more homogeneous within-cluster similarities and crisper between-cluster boundaries. The seventh paper presents incremental cluster validity indices (iCVIs) realized by (a) incorporating existing formulations of online computations for clusters\u27 descriptors, or (b) modifying an existing ART-based model and incrementally updating local density counts between prototypes. Moreover, this last paper provides the first comprehensive comparison of iCVIs in the computational intelligence literature --Abstract, page iv
AUTONOMOUS ROBOT LEARNING MODEL BASED ON VISUAL INTERPRETATION OF SPATIAL STRUCTURES
The main concept of the presented research is an autonomous robot learning model for which a novel ARTgrid neural network architecture for the classification of spatial structures is used. The motivation scenario includes incremental unsupervised learning which is mainly based on discrete spatial structure changes recognized by the robot vision system. The learning policy problem is presented as a classification problem for which the adaptive resonance theory (ART) concept is implemented. The methodology and architecture of the autonomous robot learning model with preliminary results are presented. A computer simulation was performed with four input sets containing 22, 45, 73, and 111 random spatial structures. The ARTgrid shows a fairly high (>85%) match score when applied with already learned patterns after the first learning cycle, and a score of >95% after the second cycle. Regarding the category proliferation, the results are compared with a more predictive modified cluster centre seeking algorithm
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