1,753 research outputs found
Reset-free Trial-and-Error Learning for Robot Damage Recovery
The high probability of hardware failures prevents many advanced robots
(e.g., legged robots) from being confidently deployed in real-world situations
(e.g., post-disaster rescue). Instead of attempting to diagnose the failures,
robots could adapt by trial-and-error in order to be able to complete their
tasks. In this situation, damage recovery can be seen as a Reinforcement
Learning (RL) problem. However, the best RL algorithms for robotics require the
robot and the environment to be reset to an initial state after each episode,
that is, the robot is not learning autonomously. In addition, most of the RL
methods for robotics do not scale well with complex robots (e.g., walking
robots) and either cannot be used at all or take too long to converge to a
solution (e.g., hours of learning). In this paper, we introduce a novel
learning algorithm called "Reset-free Trial-and-Error" (RTE) that (1) breaks
the complexity by pre-generating hundreds of possible behaviors with a dynamics
simulator of the intact robot, and (2) allows complex robots to quickly recover
from damage while completing their tasks and taking the environment into
account. We evaluate our algorithm on a simulated wheeled robot, a simulated
six-legged robot, and a real six-legged walking robot that are damaged in
several ways (e.g., a missing leg, a shortened leg, faulty motor, etc.) and
whose objective is to reach a sequence of targets in an arena. Our experiments
show that the robots can recover most of their locomotion abilities in an
environment with obstacles, and without any human intervention.Comment: 18 pages, 16 figures, 3 tables, 6 pseudocodes/algorithms, video at
https://youtu.be/IqtyHFrb3BU, code at
https://github.com/resibots/chatzilygeroudis_2018_rt
Using Parameterized Black-Box Priors to Scale Up Model-Based Policy Search for Robotics
The most data-efficient algorithms for reinforcement learning in robotics are
model-based policy search algorithms, which alternate between learning a
dynamical model of the robot and optimizing a policy to maximize the expected
return given the model and its uncertainties. Among the few proposed
approaches, the recently introduced Black-DROPS algorithm exploits a black-box
optimization algorithm to achieve both high data-efficiency and good
computation times when several cores are used; nevertheless, like all
model-based policy search approaches, Black-DROPS does not scale to high
dimensional state/action spaces. In this paper, we introduce a new model
learning procedure in Black-DROPS that leverages parameterized black-box priors
to (1) scale up to high-dimensional systems, and (2) be robust to large
inaccuracies of the prior information. We demonstrate the effectiveness of our
approach with the "pendubot" swing-up task in simulation and with a physical
hexapod robot (48D state space, 18D action space) that has to walk forward as
fast as possible. The results show that our new algorithm is more
data-efficient than previous model-based policy search algorithms (with and
without priors) and that it can allow a physical 6-legged robot to learn new
gaits in only 16 to 30 seconds of interaction time.Comment: Accepted at ICRA 2018; 8 pages, 4 figures, 2 algorithms, 1 table;
Video at https://youtu.be/HFkZkhGGzTo ; Spotlight ICRA presentation at
https://youtu.be/_MZYDhfWeL
Learning to Walk Autonomously via Reset-Free Quality-Diversity
Quality-Diversity (QD) algorithms can discover large and complex behavioural
repertoires consisting of both diverse and high-performing skills. However, the
generation of behavioural repertoires has mainly been limited to simulation
environments instead of real-world learning. This is because existing QD
algorithms need large numbers of evaluations as well as episodic resets, which
require manual human supervision and interventions. This paper proposes
Reset-Free Quality-Diversity optimization (RF-QD) as a step towards autonomous
learning for robotics in open-ended environments. We build on Dynamics-Aware
Quality-Diversity (DA-QD) and introduce a behaviour selection policy that
leverages the diversity of the imagined repertoire and environmental
information to intelligently select of behaviours that can act as automatic
resets. We demonstrate this through a task of learning to walk within defined
training zones with obstacles. Our experiments show that we can learn full
repertoires of legged locomotion controllers autonomously without manual resets
with high sample efficiency in spite of harsh safety constraints. Finally,
using an ablation of different target objectives, we show that it is important
for RF-QD to have diverse types solutions available for the behaviour selection
policy over solutions optimised with a specific objective. Videos and code
available at https://sites.google.com/view/rf-qd
Bayesian Optimization with Automatic Prior Selection for Data-Efficient Direct Policy Search
One of the most interesting features of Bayesian optimization for direct
policy search is that it can leverage priors (e.g., from simulation or from
previous tasks) to accelerate learning on a robot. In this paper, we are
interested in situations for which several priors exist but we do not know in
advance which one fits best the current situation. We tackle this problem by
introducing a novel acquisition function, called Most Likely Expected
Improvement (MLEI), that combines the likelihood of the priors and the expected
improvement. We evaluate this new acquisition function on a transfer learning
task for a 5-DOF planar arm and on a possibly damaged, 6-legged robot that has
to learn to walk on flat ground and on stairs, with priors corresponding to
different stairs and different kinds of damages. Our results show that MLEI
effectively identifies and exploits the priors, even when there is no obvious
match between the current situations and the priors.Comment: Accepted at ICRA 2018; 8 pages, 4 figures, 1 algorithm; Video at
https://youtu.be/xo8mUIZTvNE ; Spotlight ICRA presentation
https://youtu.be/iiVaV-U6Kq
FastRLAP: A System for Learning High-Speed Driving via Deep RL and Autonomous Practicing
We present a system that enables an autonomous small-scale RC car to drive
aggressively from visual observations using reinforcement learning (RL). Our
system, FastRLAP (faster lap), trains autonomously in the real world, without
human interventions, and without requiring any simulation or expert
demonstrations. Our system integrates a number of important components to make
this possible: we initialize the representations for the RL policy and value
function from a large prior dataset of other robots navigating in other
environments (at low speed), which provides a navigation-relevant
representation. From here, a sample-efficient online RL method uses a single
low-speed user-provided demonstration to determine the desired driving course,
extracts a set of navigational checkpoints, and autonomously practices driving
through these checkpoints, resetting automatically on collision or failure.
Perhaps surprisingly, we find that with appropriate initialization and choice
of algorithm, our system can learn to drive over a variety of racing courses
with less than 20 minutes of online training. The resulting policies exhibit
emergent aggressive driving skills, such as timing braking and acceleration
around turns and avoiding areas which impede the robot's motion, approaching
the performance of a human driver using a similar first-person interface over
the course of training
Scaling MAP-Elites to Deep Neuroevolution
Quality-Diversity (QD) algorithms, and MAP-Elites (ME) in particular, have
proven very useful for a broad range of applications including enabling real
robots to recover quickly from joint damage, solving strongly deceptive maze
tasks or evolving robot morphologies to discover new gaits. However, present
implementations of MAP-Elites and other QD algorithms seem to be limited to
low-dimensional controllers with far fewer parameters than modern deep neural
network models. In this paper, we propose to leverage the efficiency of
Evolution Strategies (ES) to scale MAP-Elites to high-dimensional controllers
parameterized by large neural networks. We design and evaluate a new hybrid
algorithm called MAP-Elites with Evolution Strategies (ME-ES) for post-damage
recovery in a difficult high-dimensional control task where traditional ME
fails. Additionally, we show that ME-ES performs efficient exploration, on par
with state-of-the-art exploration algorithms in high-dimensional control tasks
with strongly deceptive rewards.Comment: Accepted to GECCO 202
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