4 research outputs found
Active Localization of Gas Leaks using Fluid Simulation
Sensors are routinely mounted on robots to acquire various forms of
measurements in spatio-temporal fields. Locating features within these fields
and reconstruction (mapping) of the dense fields can be challenging in
resource-constrained situations, such as when trying to locate the source of a
gas leak from a small number of measurements. In such cases, a model of the
underlying complex dynamics can be exploited to discover informative paths
within the field. We use a fluid simulator as a model, to guide inference for
the location of a gas leak. We perform localization via minimization of the
discrepancy between observed measurements and gas concentrations predicted by
the simulator. Our method is able to account for dynamically varying parameters
of wind flow (e.g., direction and strength), and its effects on the observed
distribution of gas. We develop algorithms for off-line inference as well as
for on-line path discovery via active sensing. We demonstrate the efficiency,
accuracy and versatility of our algorithm using experiments with a physical
robot conducted in outdoor environments. We deploy an unmanned air vehicle
(UAV) mounted with a CO2 sensor to automatically seek out a gas cylinder
emitting CO2 via a nozzle. We evaluate the accuracy of our algorithm by
measuring the error in the inferred location of the nozzle, based on which we
show that our proposed approach is competitive with respect to state of the art
baselines.Comment: Accepted as a journal paper at IEEE Robotics and Automation Letters
(RA-L
GadenTools: a toolkit for testing and simulating robotic olfaction tasks with Jupyter Notebook support
This work presents GadenTools, a toolkit designed to ease the development and integration of mobile robotic olfaction applications by enabling a convenient and user-friendly access to Gaden’s realistic gas dispersion simulations. It is based on an easy-to-use Python API, and includes an extensive tutorial developed with Jupyter Notebook and Google Colab technologies. A detailed set of examples illustrates aspects ranging from basic access to sensory data or the generation of ground truth images, to the more advanced implementation of plume tracking algorithms, all in an online web-editor with no installation requirements. All the resources, including the source code, are made available in an online open repository.Universidad de Málaga. Campus de Excelencia Internacional AndalucÃa Tech
Architectures for online simulation-based inference applied to robot motion planning
Robotic systems have enjoyed significant adoption in industrial and field applications
in structured environments, where clear specifications of the task and observations are
available. Deploying robots in unstructured and dynamic environments remains a
challenge, being addressed through emerging advances in machine learning. The key
open issues in this area include the difficulty of achieving coverage of all factors of
variation in the domain of interest, satisfying safety constraints, etc. One tool that has
played a crucial role in addressing these issues is simulation - which is used to generate
data, and sometimes as a world representation within the decision-making loop.
When physical simulation modules are used in this way, a number of computational
problems arise. Firstly, a suitable simulation representation and fidelity is required
for the specific task of interest. Secondly, we need to perform parameter inference of
physical variables being used in the simulation models. Thirdly, there is the need for
data assimilation, which must be achieved in real-time if the resulting model is to be
used within the online decision-making loop. These are the motivating problems for
this thesis.
In the first section of the thesis, we tackle the inference problem with respect to
a fluid simulation model, where a sensorised UAV performs path planning with the
objective of acquiring data including gas concentration/identity and IMU-based wind
estimation readings. The task for the UAV is to localise the source of a gas leak, while
accommodating the subsequent dispersion of the gas in windy conditions. We present
a formulation of this problem that allows us to perform online and real-time active
inference efficiently through problem-specific simplifications.
In the second section of the thesis, we explore the problem of robot motion planning
when the true state is not fully observable, and actions influence how much of the
state is subsequently observed. This is motivated by the practical problem of a robot
performing suction in the surgical automation setting. The objective is the efficient
removal of liquid while respecting a safety constraint - to not touch the underlying
tissue if possible. If the problem were represented in full generality, as one of planning
under uncertainty and hidden state, it could be hard to find computationally efficient
solutions. Once again, we make problem-specific simplifications. Crucially, instead of
reasoning in general about fluid flows and arbitrary surfaces, we exploit the observations
that the decision can be informed by the contour tree skeleton of the volume, and the
configurations in which the fluid would come to rest if unperturbed. This allows us
to address the problem as one of iterative shortest path computation, whose costs are
informed by a model estimating the shape of the underlying surface.
In the third and final section of the thesis, we propose a model for real-time parameter
estimation directly from raw pixel observations. Through the use of a Variational
Recurrent Neural Network model, where the latent space is further structured by
penalising for fit to data from a physical simulation, we devise an efficient online
inference scheme. This is first shown in the context of a representative dynamic
manipulation task for a robot. This task involves reasoning about a bouncing ball that it
must catch – using as input the raw video from an environment-mounted camera and
accommodating noise and variations in the object and environmental conditions. We
then show that the same architecture lends itself to solving inference problems involving
more complex dynamics, by applying this to measurement inversion of ultrafast X-Ray
scattering data to infer molecular geometry