5,894 research outputs found
Model-Based Iterative Learning Control Applied to an Industrial Robot with Elasticity
In this paper model-based Iterative Learning Control (ILC) is applied to improve the tracking accuracy of an industrial robot with elasticity. The ILC algorithm iteratively updates the reference trajectory for the robot such that the predicted tracking error in the next iteration is minimised. The tracking error is predicted by a model of the closed-loop dynamics of the robot. The model includes the servo resonance frequency, the first resonance frequency caused by elasticity in the mechanism and the variation of both frequencies along the trajectory. Experimental results show that the tracking error of the robot can be reduced, even at frequencies beyond the first elastic resonance frequency
Multi-Task Generative Adversarial Nets with Shared Memory for Cross-Domain Coordination Control
Generating sequential decision process from huge amounts of measured process
data is a future research direction for collaborative factory automation,
making full use of those online or offline process data to directly design
flexible make decisions policy, and evaluate performance. The key challenges
for the sequential decision process is to online generate sequential
decision-making policy directly, and transferring knowledge across tasks
domain. Most multi-task policy generating algorithms often suffer from
insufficient generating cross-task sharing structure at discrete-time nonlinear
systems with applications. This paper proposes the multi-task generative
adversarial nets with shared memory for cross-domain coordination control,
which can generate sequential decision policy directly from raw sensory input
of all of tasks, and online evaluate performance of system actions in
discrete-time nonlinear systems. Experiments have been undertaken using a
professional flexible manufacturing testbed deployed within a smart factory of
Weichai Power in China. Results on three groups of discrete-time nonlinear
control tasks show that our proposed model can availably improve the
performance of task with the help of other related tasks
A constrained control-planning strategy for redundant manipulators
This paper presents an interconnected control-planning strategy for redundant
manipulators, subject to system and environmental constraints. The method
incorporates low-level control characteristics and high-level planning
components into a robust strategy for manipulators acting in complex
environments, subject to joint limits. This strategy is formulated using an
adaptive control rule, the estimated dynamic model of the robotic system and
the nullspace of the linearized constraints. A path is generated that takes
into account the capabilities of the platform. The proposed method is
computationally efficient, enabling its implementation on a real multi-body
robotic system. Through experimental results with a 7 DOF manipulator, we
demonstrate the performance of the method in real-world scenarios
Iterative Machine Learning for Precision Trajectory Tracking with Series Elastic Actuators
When robots operate in unknown environments small errors in postions can lead
to large variations in the contact forces, especially with typical
high-impedance designs. This can potentially damage the surroundings and/or the
robot. Series elastic actuators (SEAs) are a popular way to reduce the output
impedance of a robotic arm to improve control authority over the force exerted
on the environment. However this increased control over forces with lower
impedance comes at the cost of lower positioning precision and bandwidth. This
article examines the use of an iteratively-learned feedforward command to
improve position tracking when using SEAs. Over each iteration, the output
responses of the system to the quantized inputs are used to estimate a
linearized local system models. These estimated models are obtained using a
complex-valued Gaussian Process Regression (cGPR) technique and then, used to
generate a new feedforward input command based on the previous iteration's
error. This article illustrates this iterative machine learning (IML) technique
for a two degree of freedom (2-DOF) robotic arm, and demonstrates successful
convergence of the IML approach to reduce the tracking error.Comment: 9 pages, 16 figure. Submitted to AMC Worksho
Special issue on smart interactions in cyber-physical systems: Humans, agents, robots, machines, and sensors
In recent years, there has been increasing interaction between humans and non‐human systems as we move further beyond the industrial age, the information age, and as we move into the fourth‐generation society. The ability to distinguish between human and non‐human capabilities has become more difficult to discern. Given this, it is common that cyber‐physical systems (CPSs) are rapidly integrated with human functionality, and humans have become increasingly dependent on CPSs to perform their daily routines.The constant indicators of a future where human and non‐human CPSs relationships consistently interact and where they allow each other to navigate through a set of non‐trivial goals is an interesting and rich area of research, discovery, and practical work area. The evidence of con- vergence has rapidly gained clarity, demonstrating that we can use complex combinations of sensors, artificial intelli- gence, and data to augment human life and knowledge. To expand the knowledge in this area, we should explain how to model, design, validate, implement, and experiment with these complex systems of interaction, communication, and networking, which will be developed and explored in this special issue. This special issue will include ideas of the future that are relevant for understanding, discerning, and developing the relationship between humans and non‐ human CPSs as well as the practical nature of systems that facilitate the integration between humans, agents, robots, machines, and sensors (HARMS).Fil: Kim, Donghan. Kyung Hee University;Fil: Rodriguez, Sebastian Alberto. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Matson, Eric T.. Purdue University; Estados UnidosFil: Kim, Gerard Jounghyun. Korea University
Learning to Adapt in Dynamic, Real-World Environments Through Meta-Reinforcement Learning
Although reinforcement learning methods can achieve impressive results in
simulation, the real world presents two major challenges: generating samples is
exceedingly expensive, and unexpected perturbations or unseen situations cause
proficient but specialized policies to fail at test time. Given that it is
impractical to train separate policies to accommodate all situations the agent
may see in the real world, this work proposes to learn how to quickly and
effectively adapt online to new tasks. To enable sample-efficient learning, we
consider learning online adaptation in the context of model-based reinforcement
learning. Our approach uses meta-learning to train a dynamics model prior such
that, when combined with recent data, this prior can be rapidly adapted to the
local context. Our experiments demonstrate online adaptation for continuous
control tasks on both simulated and real-world agents. We first show simulated
agents adapting their behavior online to novel terrains, crippled body parts,
and highly-dynamic environments. We also illustrate the importance of
incorporating online adaptation into autonomous agents that operate in the real
world by applying our method to a real dynamic legged millirobot. We
demonstrate the agent's learned ability to quickly adapt online to a missing
leg, adjust to novel terrains and slopes, account for miscalibration or errors
in pose estimation, and compensate for pulling payloads.Comment: First 2 authors contributed equally. Website:
https://sites.google.com/berkeley.edu/metaadaptivecontro
Trajectory-Optimized Sensing for Active Search of Tissue Abnormalities in Robotic Surgery
In this work, we develop an approach for guiding robots to automatically
localize and find the shapes of tumors and other stiff inclusions present in
the anatomy. Our approach uses Gaussian processes to model the stiffness
distribution and active learning to direct the palpation path of the robot. The
palpation paths are chosen such that they maximize an acquisition function
provided by an active learning algorithm. Our approach provides the flexibility
to avoid obstacles in the robot's path, incorporate uncertainties in robot
position and sensor measurements, include prior information about location of
stiff inclusions while respecting the robot-kinematics. To the best of our
knowledge this is the first work in literature that considers all the above
conditions while localizing tumors. The proposed framework is evaluated via
simulation and experimentation on three different robot platforms: 6-DoF
industrial arm, da Vinci Research Kit (dVRK), and the Insertable Robotic
Effector Platform (IREP). Results show that our approach can accurately
estimate the locations and boundaries of the stiff inclusions while reducing
exploration time.Comment: 8 pages, ICRA 201
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Towards Informed Exploration for Deep Reinforcement Learning
In this thesis, we discuss various techniques for improving exploration for deep reinforcement learning. We begin with a brief review of reinforcement learning (RL) and the fundamental v.s. exploitation trade-off. Then we review how deep RL has improved upon classical and summarize six categories of the latest exploration methods for deep RL, in the order increasing usage of prior information. We then explore representative works in three categories discuss their strengths and weaknesses. The first category, represented by Soft Q-learning, uses regularization to encourage exploration. The second category, represented by count-based via hashing, maps states to hash codes for counting and assigns higher exploration to less-encountered states. The third category utilizes hierarchy and is represented by modular architecture for RL agents to play StarCraft II. Finally, we conclude that exploration by prior knowledge is a promising research direction and suggest topics of potentially impact
Data Management in Industry 4.0: State of the Art and Open Challenges
Information and communication technologies are permeating all aspects of
industrial and manufacturing systems, expediting the generation of large
volumes of industrial data. This article surveys the recent literature on data
management as it applies to networked industrial environments and identifies
several open research challenges for the future. As a first step, we extract
important data properties (volume, variety, traffic, criticality) and identify
the corresponding data enabling technologies of diverse fundamental industrial
use cases, based on practical applications. Secondly, we provide a detailed
outline of recent industrial architectural designs with respect to their data
management philosophy (data presence, data coordination, data computation) and
the extent of their distributiveness. Then, we conduct a holistic survey of the
recent literature from which we derive a taxonomy of the latest advances on
industrial data enabling technologies and data centric services, spanning all
the way from the field level deep in the physical deployments, up to the cloud
and applications level. Finally, motivated by the rich conclusions of this
critical analysis, we identify interesting open challenges for future research.
The concepts presented in this article thematically cover the largest part of
the industrial automation pyramid layers. Our approach is multidisciplinary, as
the selected publications were drawn from two fields; the communications,
networking and computation field as well as the industrial, manufacturing and
automation field. The article can help the readers to deeply understand how
data management is currently applied in networked industrial environments, and
select interesting open research opportunities to pursue
Iterative Learning Control with Application to Robotics
Many machines and robots working today in factories are programmed to perform the same task repeatedly. By observing the tracking error in each iteration of the same task it becomes clear that it is actually repetitive, even though disturbances from noise and possibly sligthly changing friction dynamics affect the response. The idea of Iterative learning Control D ILC E is to use the knowledge from the previous iterations of the same task to reduce the tracking error the next time the task is performed. ILC utilizes the tracking error knowledge from the previous iteration to change the input signal to the system. In the thesis ILC is applied to an ABB Irb-2000 industrial robot. Using ILC the tracking error on the motor side has been reduced without changing the internal structure or any parameter in the robot controller. Three different ILC algorithms are considered in the thesis. Also some important theorems about ILC stability are taken into account. Two of these three ILC algorithms have been applied to the robot to improve the tracking of desired trajectories. ILC has also been used in order to improve the robot motion of an open container with liquid. The purpose was to shorten the motion time of the package transfer with control of the slosh inside
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