361 research outputs found
Hybrid system identification using switching density networks
Behaviour cloning is a commonly used strategy for imitation learning and can
be extremely effective in constrained domains. However, in cases where the
dynamics of an environment may be state dependent and varying, behaviour
cloning places a burden on model capacity and the number of demonstrations
required. This paper introduces switching density networks, which rely on a
categorical reparametrisation for hybrid system identification. This results in
a network comprising a classification layer that is followed by a regression
layer. We use switching density networks to predict the parameters of hybrid
control laws, which are toggled by a switching layer to produce different
controller outputs, when conditioned on an input state. This work shows how
switching density networks can be used for hybrid system identification in a
variety of tasks, successfully identifying the key joint angle goals that make
up manipulation tasks, while simultaneously learning image-based goal
classifiers and regression networks that predict joint angles from images. We
also show that they can cluster the phase space of an inverted pendulum,
identifying the balance, spin and pump controllers required to solve this task.
Switching density networks can be difficult to train, but we introduce a cross
entropy regularisation loss that stabilises training
Learning Latent Space Dynamics for Tactile Servoing
To achieve a dexterous robotic manipulation, we need to endow our robot with
tactile feedback capability, i.e. the ability to drive action based on tactile
sensing. In this paper, we specifically address the challenge of tactile
servoing, i.e. given the current tactile sensing and a target/goal tactile
sensing --memorized from a successful task execution in the past-- what is the
action that will bring the current tactile sensing to move closer towards the
target tactile sensing at the next time step. We develop a data-driven approach
to acquire a dynamics model for tactile servoing by learning from
demonstration. Moreover, our method represents the tactile sensing information
as to lie on a surface --or a 2D manifold-- and perform a manifold learning,
making it applicable to any tactile skin geometry. We evaluate our method on a
contact point tracking task using a robot equipped with a tactile finger. A
video demonstrating our approach can be seen in https://youtu.be/0QK0-Vx7WkIComment: Accepted to be published at the International Conference on Robotics
and Automation (ICRA) 2019. The final version for publication at ICRA 2019 is
7 pages (i.e. 6 pages of technical content (including text, figures, tables,
acknowledgement, etc.) and 1 page of the Bibliography/References), while this
arXiv version is 8 pages (added Appendix and some extra details
Stabilize to Act: Learning to Coordinate for Bimanual Manipulation
Key to rich, dexterous manipulation in the real world is the ability to
coordinate control across two hands. However, while the promise afforded by
bimanual robotic systems is immense, constructing control policies for dual arm
autonomous systems brings inherent difficulties. One such difficulty is the
high-dimensionality of the bimanual action space, which adds complexity to both
model-based and data-driven methods. We counteract this challenge by drawing
inspiration from humans to propose a novel role assignment framework: a
stabilizing arm holds an object in place to simplify the environment while an
acting arm executes the task. We instantiate this framework with BimanUal
Dexterity from Stabilization (BUDS), which uses a learned restabilizing
classifier to alternate between updating a learned stabilization position to
keep the environment unchanged, and accomplishing the task with an acting
policy learned from demonstrations. We evaluate BUDS on four bimanual tasks of
varying complexities on real-world robots, such as zipping jackets and cutting
vegetables. Given only 20 demonstrations, BUDS achieves 76.9% task success
across our task suite, and generalizes to out-of-distribution objects within a
class with a 52.7% success rate. BUDS is 56.0% more successful than an
unstructured baseline that instead learns a BC stabilizing policy due to the
precision required of these complex tasks. Supplementary material and videos
can be found at https://sites.google.com/view/stabilizetoact .Comment: Conference on Robot Learning, 202
Robot learning from demonstration of force-based manipulation tasks
One of the main challenges in Robotics is to develop robots that can interact with humans in a natural way, sharing the same dynamic and unstructured environments. Such an interaction may be aimed at assisting, helping or collaborating with a human user. To achieve this, the robot must be endowed with a cognitive system that allows it not only to learn new skills from its human partner, but also to refine or improve those already learned.
In this context, learning from demonstration appears as a natural and userfriendly way to transfer knowledge from humans to robots. This dissertation addresses such a topic and its application to an unexplored field, namely force-based manipulation tasks learning. In this kind of scenarios, force signals can convey data about the stiffness of a given object, the inertial components acting on a tool, a desired force profile to be reached, etc. Therefore, if the user wants the robot to learn a manipulation skill successfully, it is essential that its cognitive system is able to deal with force perceptions.
The first issue this thesis tackles is to extract the input information that is relevant for learning the task at hand, which is also known as the what to imitate? problem. Here, the proposed solution takes into consideration that the robot actions are a function of sensory signals, in other words the importance of each perception is assessed through its correlation with the robot movements. A Mutual Information analysis is used for selecting the most relevant inputs according to their influence on the output space. In this way, the robot can gather all the information coming from its sensory system, and the perception selection module proposed here automatically chooses the data the robot needs to learn a given task. Having selected the relevant input information for the task, it is necessary to represent the human demonstrations in a compact way, encoding the relevant characteristics of the data, for instance, sequential information, uncertainty, constraints, etc. This issue is the next problem addressed in this thesis. Here, a probabilistic learning framework based on hidden Markov models and Gaussian mixture regression is proposed for learning force-based manipulation skills. The outstanding features of such a framework are: (i) it is able to deal with the noise and uncertainty of force signals because of its probabilistic formulation, (ii) it exploits the sequential information embedded in the model for managing perceptual aliasing and time discrepancies, and (iii) it takes advantage of task variables to encode those force-based skills where the robot actions are modulated by an external parameter. Therefore, the resulting learning structure is able to robustly encode and reproduce different manipulation tasks.
After, this thesis goes a step forward by proposing a novel whole framework for learning impedance-based behaviors from demonstrations. The key aspects here are that this new structure merges vision and force information for encoding the data compactly, and it allows the robot to have different behaviors by shaping its compliance level over the course of the task. This is achieved by a parametric probabilistic model, whose Gaussian components are the basis of a statistical dynamical system that governs the robot motion.
From the force perceptions, the stiffness of the springs composing such a system are estimated, allowing the robot to shape its compliance. This approach permits to extend the learning paradigm to other fields different from the common trajectory following. The proposed frameworks are tested in three scenarios, namely, (a) the ball-in-box task, (b) drink pouring, and (c) a collaborative assembly, where the experimental results evidence the importance of using force perceptions as well as the usefulness and strengths of the methods
Habitat 3.0: A Co-Habitat for Humans, Avatars and Robots
We present Habitat 3.0: a simulation platform for studying collaborative
human-robot tasks in home environments. Habitat 3.0 offers contributions across
three dimensions: (1) Accurate humanoid simulation: addressing challenges in
modeling complex deformable bodies and diversity in appearance and motion, all
while ensuring high simulation speed. (2) Human-in-the-loop infrastructure:
enabling real human interaction with simulated robots via mouse/keyboard or a
VR interface, facilitating evaluation of robot policies with human input. (3)
Collaborative tasks: studying two collaborative tasks, Social Navigation and
Social Rearrangement. Social Navigation investigates a robot's ability to
locate and follow humanoid avatars in unseen environments, whereas Social
Rearrangement addresses collaboration between a humanoid and robot while
rearranging a scene. These contributions allow us to study end-to-end learned
and heuristic baselines for human-robot collaboration in-depth, as well as
evaluate them with humans in the loop. Our experiments demonstrate that learned
robot policies lead to efficient task completion when collaborating with unseen
humanoid agents and human partners that might exhibit behaviors that the robot
has not seen before. Additionally, we observe emergent behaviors during
collaborative task execution, such as the robot yielding space when obstructing
a humanoid agent, thereby allowing the effective completion of the task by the
humanoid agent. Furthermore, our experiments using the human-in-the-loop tool
demonstrate that our automated evaluation with humanoids can provide an
indication of the relative ordering of different policies when evaluated with
real human collaborators. Habitat 3.0 unlocks interesting new features in
simulators for Embodied AI, and we hope it paves the way for a new frontier of
embodied human-AI interaction capabilities.Comment: Project page: http://aihabitat.org/habitat
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