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Conference paperCarrera A, Palomeras N, Hurtos N, et al., 2014,
Learning by demonstration applied to underwater intervention
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Conference paperAhmadzadeh SR, Kormushev P, Caldwell DG, 2013,
Autonomous robotic valve turning: A hierarchical learning approach
, 2013 IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE, Pages: 4629-4634, ISSN: 1050-4729Autonomous valve turning is an extremely challenging task for an Autonomous Underwater Vehicle (AUV). To resolve this challenge, this paper proposes a set of different computational techniques integrated in a three-layer hierarchical scheme. Each layer realizes specific subtasks to improve the persistent autonomy of the system. In the first layer, the robot acquires the motor skills of approaching and grasping the valve by kinesthetic teaching. A Reactive Fuzzy Decision Maker (RFDM) is devised in the second layer which reacts to the relative movement between the valve and the AUV, and alters the robot's movement accordingly. Apprenticeship learning method, implemented in the third layer, performs tuning of the RFDM based on expert knowledge. Although the long-term goal is to perform the valve turning task on a real AUV, as a first step the proposed approach is tested in a laboratory environment. © 2013 IEEE.
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Conference paperAhmadzadeh SR, Kormushev P, Caldwell DG, 2013,
Visuospatial Skill Learning for Object Reconfiguration Tasks
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Conference paperAhmadzadeh SR, Kormushev P, Caldwell DG, 2013,
Interactive Robot Learning of Visuospatial Skills
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Conference paperKormushev P, Caldwell DG, 2013,
Improving the Energy Efficiency of Autonomous Underwater Vehicles by Learning to Model Disturbances
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Conference paperKarras GC, Bechlioulis CP, Leonetti M, et al., 2013,
On-Line Identification of Autonomous Underwater Vehicles through Global Derivative-Free Optimization
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Journal articleSilk D, Filippi S, Stumpf MPH, 2013,
Optimizing threshold-schedules for sequential approximate Bayesian computation: applications to molecular systems
, Statistical Applications in Genetics and Molecular Biology, Vol: 12, Pages: 603-618, ISSN: 2194-6302The likelihood–free sequential Approximate Bayesian Computation (ABC) algorithms are increasingly popular inference tools for complex biological models. Such algorithms proceed by constructing a succession of probability distributions over the parameter space conditional upon the simulated data lying in an ε–ball around the observed data, for decreasing values of the threshold ε. While in theory, the distributions (starting from a suitably defined prior) will converge towards the unknown posterior as ε tends to zero, the exact sequence of thresholds can impact upon the computational efficiency and success of a particular application. In particular, we show here that the current preferred method of choosing thresholds as a pre-determined quantile of the distances between simulated and observed data from the previous population, can lead to the inferred posterior distribution being very different to the true posterior. Threshold selection thus remains an important challenge. Here we propose that the threshold–acceptance rate curve may be used to determine threshold schedules that avoid local optima, while balancing the need to minimise the threshold with computational efficiency. Furthermore, we provide an algorithm based upon the unscented transform, that enables the threshold–acceptance rate curve to be efficiently predicted in the case of deterministic and stochastic state space models.
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Conference paperAhmadzadeh SR, Leonetti M, Kormushev P, 2013,
Online Direct Policy Search for Thruster Failure Recovery in Autonomous Underwater Vehicles
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Conference paperKormushev P, Caldwell DG, 2013,
Comparative Evaluation of Reinforcement Learning with Scalar Rewards and Linear Regression with Multidimensional Feedback
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Conference paperJamali N, Kormushev P, Caldwell DG, 2013,
Contact State Estimation using Machine Learning
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