Effective robot navigation in real-world environments requires an understanding of terrain properties, as different terrain types impact factors such as speed, safety, and wear on the platform. Preference-based learning offers a compelling framework in which terrain costs can be inferred through simple trajectory queries to the user. However, existing query selection methods often suffer from redundant selection due to limited trajectory diversity, as well as query ambiguity, where the user must choose between trajectories with minimal distinguishable differences. These issues lead to inefficient learning and suboptimal terrain cost estimation. In this paper, we introduce a joint optimization framework that increases learning efficiency by improving both the diversity of the trajectory set and the query selection strategy. We used a variational autoencoder (VAE) to encode and group trajectories based on their terrain characteristics. Clusters were used to identify less represented terrain types so that new trajectories can be added to the corresponding cluster to ensure a balanced and representative query set. Additionally, we employ a cluster-aware query selection mechanism that prioritizes diverse trajectory pairs pulled from distinct clusters to maximize information gain. Experimental results demonstrate that our approach significantly reduces the number of queries required to converge to the ground-truth terrain cost assignment, outperforming state-of-the-art query selection techniques.

Human activity recognition is a vital area of robotics with significant real-world applications, from enhancing security and surveillance to improving healthcare and human-robot interaction. A critical challenge lies in bridging the gap between research models, which often assume ideal conditions, and the complexities of real-world environments. In practice, conditions can be far from perfect, including scenarios with poor lighting, adverse weather, or blurred views. In this paper, we present an innovative approach for robust activity recognition through learned sensor fusion, in which our recognition framework identifies a latent weighted combination of input modalities, enabling classifiers to capitalize on advantages provided by various sensors. In support of our work, we have released a dataset of human activities across multiple modalities with environmental degradation factors such as darkness, fog, and thermal blur. Our proposed approach identifies a weighted combination of modality representations derived from existing architectures. We show that our approach is able to achieve 24% higher classification performance than existing single-modality approaches. Our approach also attains comparable performance to modality fusion approaches in significantly reduced classification time. In real-world robotics applications, particularly those occurring in dangerous, degraded environments, this speed is critical.

Collaborative localization is an essential capability for a team of robots such as connected vehicles to collaboratively estimate object locations from multiple perspectives with reliant cooperation. To enable collaborative localization, four key challenges must be addressed, including modeling complex relationships between observed objects, fusing observations from an arbitrary number of collaborating robots, quantifying localization uncertainty, and addressing latency of robot communications. In this paper, we introduce a novel approach that integrates uncertainty-aware spatiotemporal graph learning and model-based state estimation for a team of robots to collaboratively localize objects. Specifically, we introduce a new uncertainty-aware graph learning model that learns spatiotemporal graphs to represent historical motions of the objects observed by each robot over time and provides uncertainties in object localization. Moreover, we propose a novel method for integrated learning and model-based state estimation, which fuses asynchronous observations obtained from an arbitrary number of robots for collaborative localization. We evaluate our approach in two collaborative object localization scenarios in simulations and on real robots. Experimental results show that our approach outperforms previous methods and achieves state-of-the-art performance on asynchronous collaborative localization.

We consider the problem of multi-robot sensor coverage, which deals with deploying a multi-robot team in an environment and optimizing the sensing quality of the overall environment. As real-world environments involve a variety of sensory information, and individual robots are limited in their available number of sensors, successful multi-robot sensor coverage requires the deployment of robots in such a way that each individual team member’s sensing quality is maximized. Additionally, because individual robots have varying complements of sensors and both robots and sensors can fail, robots must be able to adapt and adjust how they value each sensing capability in order to obtain the most complete view of the environment, even through changes in team composition. We introduce a novel formulation for sensor coverage by multi-robot teams with heterogeneous sensing capabilities that maximizes each robot's sensing quality, balancing the varying sensing capabilities of individual robots based on the overall team composition. We propose a solution based on regularized optimization that uses sparsity-inducing terms to ensure a robot team focuses on all possible event types, and which we show is proven to converge to the optimal solution. Through extensive simulation, we show that our approach is able to effectively deploy a multi-robot team to maximize the sensing quality of an environment, responding to failures in the multi-robot team more robustly than non-adaptive approaches.

Sensor coverage is the critical multi-robot problem of maximizing the detection of events in an environment through the deployment of multiple robots. Large multi-robot systems are often composed of simple robots that are typically not equipped with a complete set of sensors, so teams with comprehensive sensing abilities are required to properly cover an area. Robots also exhibit multiple forms of relationships (e.g., communication connections or spatial distribution) that need to be considered when assigning robot teams for sensor coverage. To address this problem, in this paper we introduce a novel formulation of sensor coverage by multi-robot systems with heterogeneous relationships as a graph representation learning problem. We propose a principled approach based on the mathematical framework of regularized optimization to learn a unified representation of the multi-robot system from the graphs describing the heterogeneous relationships and to identify the learned representation’s underlying structure in order to assign the robots to teams. To evaluate the proposed approach, we conduct extensive experiments on simulated multi-robot systems and a physical multi-robot system as a case study, demonstrating that our approach is able to effectively assign teams for heterogeneous multi-robot sensor coverage.

Multi-robot systems of increasing size and complexity are used to solve large-scale problems, such as area exploration and search and rescue. A key decision in human-robot teaming is dividing a multi-robot system into teams to address separate issues or to accomplish a task over a large area. In order to address the problem of selecting teams in a multi-robot system, we propose a new multimodal graph embedding method to construct a unified representation that fuses multiple information modalities to describe and divide a multi-robot system. The relationship modalities are encoded as directed graphs that can encode asymmetrical relationships, which are embedded into a unified representation for each robot. Then, the constructed multimodal representation is used to determine teams based upon unsupervised learning. We per-form experiments to evaluate our approach on expert-defined team formations, large-scale simulated multi-robot systems, and a system of physical robots. Experimental results show that our method successfully decides correct teams based on the multifaceted internal structures describing multi-robot systems, and outperforms baseline methods based upon only one mode of information, as well as other graph embedding-based division methods.

Real-time human activity recognition plays an essential role in real-world human-centered robotics applications, such as assisted living and human-robot collaboration. Although previous methods based on skeletal data to encode human poses showed promising results on real-time activity recognition, they lacked the capability to consider the context provided by objects within the scene and in use by the humans, which can provide a further discriminant between human activity categories. In this paper, we propose a novel approach to real-time human activity recognition, through simultaneously learning from observations of both human poses and objects involved in the human activity. We formulate human activity recognition as a joint optimization problem under a unified mathematical framework, which uses a regression-like loss function to integrate human pose and object cues and defines structured sparsity-inducing norms to identify discriminative body joints and object attributes. To evaluate our method, we perform extensive experiments on two benchmark datasets and a physical robot in a home assistance setting. Experimental results have shown that our method outperforms previous methods and obtains real-time performance for human activity recognition with a processing speed of 104Hz.