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  • JOURNAL ARTICLE
    Cully A, Demiris Y, 2019,

    Online knowledge level tracking with data-driven student models and collaborative filtering

    , IEEE Transactions on Knowledge and Data Engineering, ISSN: 1041-4347

    Intelligent Tutoring Systems are promising tools for delivering optimal and personalised learning experiences to students. A key component for their personalisation is the student model, which infers the knowledge level of the students to balance the difficulty of the exercises. While important advances have been achieved, several challenges remain. In particular, the models should be able to track in real-time the evolution of the students' knowledge levels. These evolutions are likely to follow different profiles for each student, while measuring the exact knowledge level remains difficult given the limited and noisy information provided by the interactions. This paper introduces a novel model that addresses these challenges with three contributions: 1) the model relies on Gaussian Processes to track online the evolution of the student's knowledge level over time, 2) it uses collaborative filtering to rapidly provide long-term predictions by leveraging the information from previous users, and 3) it automatically generates abstract representations of knowledge components via automatic relevance determination of covariance matrices. The model is evaluated on three datasets, including real users. The results demonstrate that the model converges to accurate predictions in average 4 times faster than the compared methods.

  • JOURNAL ARTICLE
    Zhang F, Cully A, Demiris Y, 2019,

    Probabilistic real-time user posture tracking for personalized robot-assisted dressing

    , IEEE Transactions on Robotics, ISSN: 1552-3098

    Robotic solutions to dressing assistance have the potential to provide tremendous support for elderly and disabled people. However, unexpected user movements may lead to dressing failures or even pose a risk to the user. Tracking such user movements with vision sensors is challenging due to severe visual occlusions created by the robot and clothes. In this paper, we propose a probabilistic tracking method using Bayesian networks in latent spaces, which fuses robot end-effector positions and force information to enable cameraless and real-time estimation of the user postures during dressing. The latent spaces are created before dressing by modeling the user movements with a Gaussian process latent variable model, taking the user’s movement limitations into account. We introduce a robot-assisted dressing system that combines our tracking method with hierarchical multitask control to minimize the force between the user and the robot. The experimental results demonstrate the robustness and accuracy of our tracking method. The proposed method enables the Baxter robot to provide personalized dressing assistance in putting on a sleeveless jacket for users with (simulated) upper-body impairments.

  • CONFERENCE PAPER
    Cully A,

    Autonomous skill discovery with Quality-Diversity and Unsupervised Descriptors

    Quality-Diversity optimization is a new family of optimization algorithmsthat, instead of searching for a single optimal solution to solving a task,searches for a large collection of solutions that all solve the task in adifferent way. This approach is particularly promising for learning behavioralrepertoires in robotics, as such a diversity of behaviors enables robots to bemore versatile and resilient. However, these algorithms require the user tomanually define behavioral descriptors, which is used to determine whether twosolutions are different or similar. The choice of a behavioral descriptor iscrucial, as it completely changes the solution types that the algorithmderives. In this paper, we introduce a new method to automatically define thisdescriptor by combining Quality-Diversity algorithms with unsuperviseddimensionality reduction algorithms. This approach enables robots toautonomously discover the range of their capabilities while interacting withtheir environment. The results from two experimental scenarios demonstrate thatrobot can autonomously discover a large range of possible behaviors, withoutany prior knowledge about their morphology and environment. Furthermore, thesebehaviors are deemed to be similar to handcrafted solutions that uses domainknowledge and significantly more diverse than when using existing unsupervisedmethods.

  • SOFTWARE
    Cully A, Chatzilygeroudis K, Allocati F, Mouret J-B, Rama R, Papaspyros Vet al., 2018,

    Limbo: A Flexible High-performance Library for Gaussian Processes modeling and Data-Efficient Optimization

    Limbo (LIbrary for Model-Based Optimization) is an open-source C++11 library for Gaussian Processes and data-efficient optimization (e.g., Bayesian optimization) that is designed to be both highly flexible and very fast. It can be used as a state-of-the-art optimization library or to experiment with novel algorithms with “plugin” components. Limbo is currently mostly used for data-efficient policy search in robot learning and online adaptation because computation time matters when using the low-power embedded computers of robots. For example, Limbo was the key library to develop a new algorithm that allows a legged robot to learn a new gait after a mechanical damage in about 10-15 trials (2 minutes), and a 4-DOF manipulator to learn neural networks policies for goal reaching in about 5 trials.The implementation of Limbo follows a policy-based design that leverages C++ templates: this allows it to be highly flexible without the cost induced by classic object-oriented designs (cost of virtual functions). The regression benchmarks show that the query time of Limbo’s Gaussian processes is several orders of magnitude better than the one of GPy (a state-of-the-art Python library for Gaussian processes) for a similar accuracy (the learning time highly depends on the optimization algorithm chosen to optimize the hyper-parameters). The black-box optimization benchmarks demonstrate that Limbo is about 2 times faster than BayesOpt (a C++ library for data-efficient optimization) for a similar accuracy and data-efficiency. In practice, changing one of the components of the algorithms in Limbo (e.g., changing the acquisition function) usually requires changing only a template definition in the source code. This design allows users to rapidly experiment and test new ideas while keeping the software as fast as specialized code.Limbo takes advantage of multi-core architectures to parallelize the internal optimization processes (optimization of the acquisition funct

  • CONFERENCE PAPER
    Cully A, Demiris Y, 2018,

    Hierarchical behavioral repertoires with unsupervised descriptors

    , the Genetic and Evolutionary Computation Conference, Publisher: ACM Press
  • CONFERENCE PAPER
    Zhang F, Cully A, Demiris YIANNIS, 2017,

    Personalized Robot-assisted Dressing using User Modeling in Latent Spaces

    , 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Publisher: IEEE, ISSN: 2153-0866

    Robots have the potential to provide tremendous support to disabled and elderly people in their everyday tasks, such as dressing. Many recent studies on robotic dressing assistance usually view dressing as a trajectory planning problem. However, the user movements during the dressing process are rarely taken into account, which often leads to the failures of the planned trajectory and may put the user at risk. The main difficulty of taking user movements into account is caused by severe occlusions created by the robot, the user, and the clothes during the dressing process, which prevent vision sensors from accurately detecting the postures of the user in real time. In this paper, we address this problem by introducing an approach that allows the robot to automatically adapt its motion according to the force applied on the robot's gripper caused by user movements. There are two main contributions introduced in this paper: 1) the use of a hierarchical multi-task control strategy to automatically adapt the robot motion and minimize the force applied between the user and the robot caused by user movements; 2) the online update of the dressing trajectory based on the user movement limitations modeled with the Gaussian Process Latent Variable Model in a latent space, and the density information extracted from such latent space. The combination of these two contributions leads to a personalized dressing assistance that can cope with unpredicted user movements during the dressing while constantly minimizing the force that the robot may apply on the user. The experimental results demonstrate that the proposed method allows the Baxter humanoid robot to provide personalized dressing assistance for human users with simulated upper-body impairments.

  • JOURNAL ARTICLE
    Cully AHR, Demiris Y, 2017,

    Quality and diversity optimization: a unifying modular framework

    , IEEE Transactions on Evolutionary Computation, Vol: 22, Pages: 245-259, ISSN: 1941-0026

    The optimization of functions to find the best solution according to one or several objectives has a central role in many engineering and research fields. Recently, a new family of optimization algorithms, named Quality-Diversity optimization, has been introduced, and contrasts with classic algorithms. Instead of searching for a single solution, Quality-Diversity algorithms are searching for a large collection of both diverse and high-performing solutions. The role of this collection is to cover the range of possible solution types as much as possible, and to contain the best solution for each type. The contribution of this paper is threefold. Firstly, we present a unifying framework of Quality-Diversity optimization algorithms that covers the two main algorithms of this family (Multi-dimensional Archive of Phenotypic Elites and the Novelty Search with Local Competition), and that highlights the large variety of variants that can be investigated within this family. Secondly, we propose algorithms with a new selection mechanism for Quality-Diversity algorithms that outperforms all the algorithms tested in this paper. Lastly, we present a new collection management that overcomes the erosion issues observed when using unstructured collections. These three contributions are supported by extensive experimental comparisons of Quality-Diversity algorithms on three different experimental scenarios.

  • CONFERENCE PAPER
    Zambelli M, Fischer T, Petit M, Chang HJ, Cully A, Demiris Yet al., 2016,

    Towards Anchoring Self-Learned Representations to Those of Other Agents

    , Workshop on Bio-inspired Social Robot Learning in Home Scenarios IEEE/RSJ International Conference on Intelligent Robots and Systems, Publisher: Institute of Electrical and Electronics Engineers (IEEE)

    In the future, robots will support humans in their every day activities. One particular challenge that robots will face is understanding and reasoning about the actions of other agents in order to cooperate effectively with humans. We propose to tackle this using a developmental framework, where the robot incrementally acquires knowledge, and in particular 1) self-learns a mapping between motor commands and sensory consequences, 2) rapidly acquires primitives and complex actions by verbal descriptions and instructions from a human partner, 3) discoverscorrespondences between the robots body and other articulated objects and agents, and 4) employs these correspondences to transfer the knowledge acquired from the robots point of view to the viewpoint of the other agent. We show that our approach requires very little a-priori knowledge to achieve imitation learning, to find correspondent body parts of humans, and allows taking the perspective of another agent. This represents a step towards the emergence of a mirror neuron like system based on self-learned representations.

  • JOURNAL ARTICLE
    Cully A, Mouret J-B, 2016,

    Evolving a Behavioral Repertoire for a Walking Robot

    , Evolutionary Computation, Vol: 24, Pages: 59-88, ISSN: 1063-6560
  • CONFERENCE PAPER
    Tarapore D, Clune J, Cully A, Mouret J-Bet al., 2016,

    How do Different Encodings Influence the Performance of the MAP-Elites Algorithm?

    , the 2016, Publisher: ACM Press
  • CONFERENCE PAPER
    Maestre C, Cully A, Gonzales C, Doncieux Set al., 2015,

    Bootstrapping interactions with objects from raw sensorimotor data: A novelty search based approach

    , 2015 Joint IEEE International Conference on Development and Learning and Epigenetic Robotics (ICDL-EpiRob), Publisher: IEEE
  • JOURNAL ARTICLE
    Cully A, Clune J, Tarapore D, Mouret J-Bet al., 2015,

    Robots that can adapt like animals

    , Nature, Vol: 521, Pages: 503-507, ISSN: 0028-0836
  • JOURNAL ARTICLE
    Koos S, Cully A, Mouret J-B, 2013,

    Fast damage recovery in robotics with the T-resilience algorithm

    , The International Journal of Robotics Research, Vol: 32, Pages: 1700-1723, ISSN: 0278-3649
  • CONFERENCE PAPER
    Cully A, Mouret J-B, 2013,

    Behavioral repertoire learning in robotics

    , Proceeding of the fifteenth annual conference, Publisher: ACM Press

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