17,042 research outputs found
Methods for Learning Control Policies from Variable Constraint Demonstrations
Many everyday human skills can be framed in terms of performing some task subject to constraints imposed by the task or the environment. Constraints are usually not observable and frequently change between contexts. In this chapter, we explore the problem of learning control policies from data containing variable, dynamic and non-linear constraints on motion. We discuss how an effective approach for doing this is to learn the unconstrained policy in a way that is consistent with the constraints. We then go on to discuss several recent algorithms for extracting policies from movement data, where observations are recorded under variable, unknown constraints. We review a number of experiments testing the performance of these algorithms and demonstrating how the resultant policy models generalise over constraints allowing prediction of behaviour under unseen settings where new constraints apply
Human-Machine Collaborative Optimization via Apprenticeship Scheduling
Coordinating agents to complete a set of tasks with intercoupled temporal and
resource constraints is computationally challenging, yet human domain experts
can solve these difficult scheduling problems using paradigms learned through
years of apprenticeship. A process for manually codifying this domain knowledge
within a computational framework is necessary to scale beyond the
``single-expert, single-trainee" apprenticeship model. However, human domain
experts often have difficulty describing their decision-making processes,
causing the codification of this knowledge to become laborious. We propose a
new approach for capturing domain-expert heuristics through a pairwise ranking
formulation. Our approach is model-free and does not require enumerating or
iterating through a large state space. We empirically demonstrate that this
approach accurately learns multifaceted heuristics on a synthetic data set
incorporating job-shop scheduling and vehicle routing problems, as well as on
two real-world data sets consisting of demonstrations of experts solving a
weapon-to-target assignment problem and a hospital resource allocation problem.
We also demonstrate that policies learned from human scheduling demonstration
via apprenticeship learning can substantially improve the efficiency of a
branch-and-bound search for an optimal schedule. We employ this human-machine
collaborative optimization technique on a variant of the weapon-to-target
assignment problem. We demonstrate that this technique generates solutions
substantially superior to those produced by human domain experts at a rate up
to 9.5 times faster than an optimization approach and can be applied to
optimally solve problems twice as complex as those solved by a human
demonstrator.Comment: Portions of this paper were published in the Proceedings of the
International Joint Conference on Artificial Intelligence (IJCAI) in 2016 and
in the Proceedings of Robotics: Science and Systems (RSS) in 2016. The paper
consists of 50 pages with 11 figures and 4 table
Learning Task Constraints from Demonstration for Hybrid Force/Position Control
We present a novel method for learning hybrid force/position control from
demonstration. We learn a dynamic constraint frame aligned to the direction of
desired force using Cartesian Dynamic Movement Primitives. In contrast to
approaches that utilize a fixed constraint frame, our approach easily
accommodates tasks with rapidly changing task constraints over time. We
activate only one degree of freedom for force control at any given time,
ensuring motion is always possible orthogonal to the direction of desired
force. Since we utilize demonstrated forces to learn the constraint frame, we
are able to compensate for forces not detected by methods that learn only from
the demonstrated kinematic motion, such as frictional forces between the
end-effector and the contact surface. We additionally propose novel extensions
to the Dynamic Movement Primitive (DMP) framework that encourage robust
transition from free-space motion to in-contact motion in spite of environment
uncertainty. We incorporate force feedback and a dynamically shifting goal to
reduce forces applied to the environment and retain stable contact while
enabling force control. Our methods exhibit low impact forces on contact and
low steady-state tracking error.Comment: Under revie
Neural Task Programming: Learning to Generalize Across Hierarchical Tasks
In this work, we propose a novel robot learning framework called Neural Task
Programming (NTP), which bridges the idea of few-shot learning from
demonstration and neural program induction. NTP takes as input a task
specification (e.g., video demonstration of a task) and recursively decomposes
it into finer sub-task specifications. These specifications are fed to a
hierarchical neural program, where bottom-level programs are callable
subroutines that interact with the environment. We validate our method in three
robot manipulation tasks. NTP achieves strong generalization across sequential
tasks that exhibit hierarchal and compositional structures. The experimental
results show that NTP learns to generalize well to- wards unseen tasks with
increasing lengths, variable topologies, and changing objectives.Comment: ICRA 201
Batch Policy Learning under Constraints
When learning policies for real-world domains, two important questions arise:
(i) how to efficiently use pre-collected off-policy, non-optimal behavior data;
and (ii) how to mediate among different competing objectives and constraints.
We thus study the problem of batch policy learning under multiple constraints,
and offer a systematic solution. We first propose a flexible meta-algorithm
that admits any batch reinforcement learning and online learning procedure as
subroutines. We then present a specific algorithmic instantiation and provide
performance guarantees for the main objective and all constraints. To certify
constraint satisfaction, we propose a new and simple method for off-policy
policy evaluation (OPE) and derive PAC-style bounds. Our algorithm achieves
strong empirical results in different domains, including in a challenging
problem of simulated car driving subject to multiple constraints such as lane
keeping and smooth driving. We also show experimentally that our OPE method
outperforms other popular OPE techniques on a standalone basis, especially in a
high-dimensional setting
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