5 research outputs found
Decentralized Vision-Based Byzantine Agent Detection in Multi-Robot Systems with IOTA Smart Contracts
Multiple opportunities lie at the intersection of multi-robot systems and
distributed ledger technologies (DLTs). In this work, we investigate the
potential of new DLT solutions such as IOTA, for detecting anomalies and
byzantine agents in multi-robot systems in a decentralized manner. Traditional
blockchain approaches are not applicable to real-world networked and
decentralized robotic systems where connectivity conditions are not ideal. To
address this, we leverage recent advances in partition-tolerant and
byzantine-tolerant collaborative decision-making processes with IOTA smart
contracts. We show how our work in vision-based anomaly and change detection
can be applied to detecting byzantine agents within multiple robots operating
in the same environment. We show that IOTA smart contracts add a low
computational overhead while allowing to build trust within the multi-robot
system. The proposed approach effectively enables byzantine robot detection
based on the comparison of images submitted by the different robots and
detection of anomalies and changes between them
Loosely Coupled Odometry, UWB Ranging, and Cooperative Spatial Detection for Relative Monte-Carlo Multi-Robot Localization
As mobile robots become more ubiquitous, their deployments grow across use
cases where GNSS positioning is either unavailable or unreliable. This has led
to increased interest in multi-modal relative localization methods.
Complementing onboard odometry, ranging allows for relative state estimation,
with ultra-wideband (UWB) ranging having gained widespread recognition due to
its low cost and centimeter-level out-of-box accuracy. Infrastructure-free
localization methods allow for more dynamic, ad-hoc, and flexible deployments,
yet they have received less attention from the research community. In this
work, we propose a cooperative relative multi-robot localization where we
leverage inter-robot ranging and simultaneous spatial detections of objects in
the environment. To achieve this, we equip robots with a single UWB transceiver
and a stereo camera. We propose a novel Monte-Carlo approach to estimate
relative states by either employing only UWB ranges or dynamically integrating
simultaneous spatial detections from the stereo cameras. We also address the
challenges for UWB ranging error mitigation, especially in non-line-of-sight,
with a study on different LSTM networks to estimate the ranging error. The
proposed approach has multiple benefits. First, we show that a single range is
enough to estimate the accurate relative states of two robots when fusing
odometry measurements. Second, our experiments also demonstrate that our
approach surpasses traditional methods such as multilateration in terms of
accuracy. Third, to increase accuracy even further, we allow for the
integration of cooperative spatial detections. Finally, we show how ROS 2 and
Zenoh can be integrated to build a scalable wireless communication solution for
multi-robot systems. The experimental validation includes real-time deployment
and autonomous navigation based on the relative positioning method
Exploiting Redundancy for UWB Anomaly Detection in Infrastructure-Free Multi-Robot Relative Localization
Ultra-wideband (UWB) localization methods have emerged as a cost-effective
and accurate solution for GNSS-denied environments. There is a significant
amount of previous research in terms of resilience of UWB ranging, with
non-line-of-sight and multipath detection methods. However, little attention
has been paid to resilience against disturbances in relative localization
systems involving multiple nodes. This paper presents an approach to detecting
range anomalies in UWB ranging measurements from the perspective of multi-robot
cooperative localization. We introduce an approach to exploiting redundancy for
relative localization in multi-robot systems, where the position of each node
is calculated using different subsets of available data. This enables us to
effectively identify nodes that present ranging anomalies and eliminate their
effect within the cooperative localization scheme. We analyze anomalies created
by timing errors in the ranging process, e.g., owing to malfunctioning
hardware. However, our method is generic and can be extended to other types of
ranging anomalies. Our approach results in a more resilient cooperative
localization framework with a negligible impact in terms of the computational
workload
Multiscale modeling of tumor growth and angiogenesis: Evaluation of tumor-targeted therapy
The dynamics of tumor growth and associated events cover multiple time and spatial scales, generally including extracellular, cellular and intracellular modifications. The main goal of this study is to model the biological and physical behavior of tumor evolution in presence of normal healthy tissue, considering a variety of events involved in the process. These include hyper and hypoactivation of signaling pathways during tumor growth, vessels' growth, intratumoral vascularization and competition of cancer cells with healthy host tissue. The work addresses two distinctive phases in tumor development-the avascular and vascular phases-and in each stage two cases are considered-with and without normal healthy cells. The tumor growth rate increases considerably as closed vessel loops (anastomoses) form around the tumor cells resulting from tumor induced vascularization. When taking into account the host tissue around the tumor, the results show that competition between normal cells and cancer cells leads to the formation of a hypoxic tumor core within a relatively short period of time. Moreover, a dense intratumoral vascular network is formed throughout the entire lesion as a sign of a high malignancy grade, which is consistent with reported experimental data for several types of solid carcinomas. In comparison with other mathematical models of tumor development, in this work we introduce a multiscale simulation that models the cellular interactions and cell behavior as a consequence of the activation of oncogenes and deactivation of gene signaling pathways within each cell. Simulating a therapy that blocks relevant signaling pathways results in the prevention of further tumor growth and leads to an expressive decrease in its size (82% in the simulation)
A multiscale cell-based model of tumor growth for chemotherapy assessment and tumor-targeted therapy through a 3D computational approach
Objectives: Computational modeling of biological systems is a powerful tool to clarify
diverse processes contributing to cancer. The aim is to clarify the complex biochemical
and mechanical interactions between cells, the relevance of intracellular signaling
pathways in tumor progression and related events to the cancer treatments, which
are largely ignored in previous studies.
Materials and Methods: A three-dimensional
multiscale cell-based
model is developed,
covering multiple time and spatial scales, including intracellular, cellular, and extracellular
processes. The model generates a realistic representation of the processes
involved from an implementation of the signaling transduction network.
Results: Considering a benign tumor development, results are in good agreement
with the experimental ones, which identify three different phases in tumor growth.
Simulating tumor vascular growth, results predict a highly vascularized tumor morphology
in a lobulated form, a consequence of cells' motile behavior. A novel systematic
study of chemotherapy intervention, in combination with targeted therapy, is
presented to address the capability of the model to evaluate typical clinical protocols.
The model also performs a dose comparison study in order to optimize treatment efficacy
and surveys the effect of chemotherapy initiation delays and different regimens.
Conclusions: Results not only provide detailed insights into tumor progression, but
also support suggestions for clinical implementation. This is a major step toward the
goal of predicting the effects of not only traditional chemotherapy but also tumor-targeted
therapies