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  • Conference paper
    Choi J, Chang HJ, Yun S, Fischer T, Demiris Y, Choi JYet al., 2017,

    Attentional correlation filter network for adaptive visual tracking

    , IEEE Conference on Computer Vision and Pattern Recognition, Publisher: IEEE, ISSN: 1063-6919

    We propose a new tracking framework with an attentional mechanism that chooses a subset of the associated correlation filters for increased robustness and computational efficiency. The subset of filters is adaptively selected by a deep attentional network according to the dynamic properties of the tracking target. Our contributions are manifold, and are summarised as follows: (i) Introducing the Attentional Correlation Filter Network which allows adaptive tracking of dynamic targets. (ii) Utilising an attentional network which shifts the attention to the best candidate modules, as well as predicting the estimated accuracy of currently inactive modules. (iii) Enlarging the variety of correlation filters which cover target drift, blurriness, occlusion, scale changes, and flexible aspect ratio. (iv) Validating the robustness and efficiency of the attentional mechanism for visual tracking through a number of experiments. Our method achieves similar performance to non real-time trackers, and state-of-the-art performance amongst real-time trackers.

  • Conference paper
    Yoo YJ, Chang H, Yun S, Demiris Y, Choi JYet al., 2017,

    Variational autoencoded regression: high dimensional regression of visual data on complex manifold

    , IEEE Conference on Computer Vision and Pattern Recognition, Publisher: IEEE, Pages: 2943-2952

    This paper proposes a new high dimensional regression method by merging Gaussian process regression into a variational autoencoder framework. In contrast to other regression methods, the proposed method focuses on the case where output responses are on a complex high dimensional manifold, such as images. Our contributions are summarized as follows: (i) A new regression method estimating high dimensional image responses, which is not handled by existing regression algorithms, is proposed. (ii) The proposed regression method introduces a strategy to learn the latent space as well as the encoder and decoder so that the result of the regressed response in the latent space coincide with the corresponding response in the data space. (iii) The proposed regression is embedded into a generative model, and the whole procedure is developed by the variational autoencoder framework. We demonstrate the robustness and effectiveness of our method through a number of experiments on various visual data regression problems.

  • Conference paper
    Rojas N, Dollar AM, 2017,

    Distance-based kinematics of the five-oblique-axis thumb model with intersecting axes at the metacarpophalangeal joint

    , 2017 IEEE RAS/EMBS International Conference on Rehabilitation Robotics, Publisher: IEEE, ISSN: 1945-7901

    This paper proposes a novel and simple methodto compute all possible solutions of the inverse kinematicsproblem of the five-oblique-axis thumb model with intersectingaxes at the metacarpophalangeal joint. This thumb model isone of the suggested results by a magnetic-resonance-imaging-based study that, in contrast to those based on cadaver fingersor on the tracking of the surface of the fingers, takes intoaccount muscle and ligament behaviors and avoids inaccuraciesresulting from the movement of the skin with respect to thebones. The proposed distance-based inverse kinematics methodeliminates the use of arbitrary reference frames as is usuallyrequired by standard approaches; this is relevant because thenumerical conditioning of the resulting system of equationswith such traditional approaches depends on the selectedreference frames. Moreover, contrary to other parametrizations(e.g., Denavit-Hartenberg parameters), the suggested distance-based parameters for the thumb have a natural, human-understandable geometric meaning that makes them easier tobe determined from any posture. These characteristics makethe proposed approach of interest for those working in, forinstance, measuring and modeling the movement of the humanhand, developing rehabilitation devices such as orthoses andprostheses, or designing anthropomorphic robotic hands.

  • Conference paper
    Bircher WG, Dollar AM, Rojas N, 2017,

    A two-fingered robot gripper with large object reorientation range

    , 2017 IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE

    It is very challenging for a robotic gripper to achieve large reorientations with grasped objects without accidental object ejection. This paper presents a simple gripper that can repeatedly achieve large reorientations over π/2 rad through the kinematics of the hand-object system alone, without the use of high fidelity contact sensors, complex control of active finger surfaces, or highly actuated fingers. This gripper is the result of two kinematic parameter search optimizations connected in cascade. Besides the large range of reorientation attained, the obtained gripper also corresponds to a novel topology since ternary joints in the palm are presented. The in-hand planar reorientation capabilities of the proposed gripper are experimentally tested with success.

  • Conference paper
    Kanner O, Rojas N, Dollar AM, 2017,

    Between-leg coupling schemes for passively-adaptive non-redundant legged robots

    , 2017 IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE

    This paper studies the synthesis of between-leg coupling schemes for passively-adaptive non-redundant legged robots. Highly actuated legged robots can arbitrarily locate their feet relative to their bodies through active control, but often wind up kinematically over-constrained following ground contact, requiring complex redundant control for stable locomotion. The use of passive sprung joints can provide some minimal passive adaptability to terrain, but it is limited to relatively low terrain variability due to practical travel limits. In this paper, using a 4-RR platform as case study, we show that implementing parallel adaptive couplings between legs of a stance platform can yield substantial passive adaptability to rough terrain while still ensuring that the body is fully constrained in stance. This study uses screw theory-based mobility analysis methods to determine the number of constraints required to control the stance platform. Several coupling schemes are then considered and evaluated through a simulation of their stance capabilities over arbitrary terrain. An experimental validation of these simulation results is presented; it demonstrates the viability of the proposed scheme for passive adaptability.

  • Conference paper
    Rojas N, Thomas F, 2017,

    Forward kinematics of the general triple-arm robot using a distance-based formulation

    , 7th IFToMM International Workshop on Computational Kinematics, Publisher: Springer

    Distance-based formulations have successfully been used to obtain closure polynomialsfor planar mechanisms without relying, in most cases, on variable eliminations. The methods re-sulting from previous attempts to generalize these techniques to spatial mechanisms exhibit somelimitations such as the impossibility of incorporating orientation constraints. For the first time, thispaper presents a complete satisfactory generalization. As an example, it is applied to obtain a clo-sure polynomial for the the general triple-arm parallel robot (that is, the 3-RPS 3-DOF robot). Thispolynomial, not linked to any particular reference frame, is obtained without variable eliminationsor tangent-half-angle substitutions.

  • Journal article
    Ward-Cherrier B, Rojas N, Lepora NF, 2017,

    Model-free precise in-hand manipulation with a 3D-printed tactile gripper

    , IEEE Robotics and Automation Letters, Vol: 2, Pages: 2056-2063, ISSN: 2377-3766

    The use of tactile feedback for precision manipulation in robotics still lags far behind human capabilities. This study has two principal aims: 1) to demonstrate in-hand reorientation of grasped objects through active tactile manipulation; and 2) to present the development of a novel TacTip sensor and a GR2 gripper platform for tactile manipulation. Through the use of Bayesian active perception algorithms, the system successfully achieved inhand reorientation of cylinders of different diameters (20, 25, 30, and 35 mm) using tactile feedback. Average orientation errors along manipulation trajectories were below 5° for all cylinders with reorientation ranges varying from 42° to 67°. We also demonstrated an improvement in active tactile manipulation accuracy when using additional training data. Our methods for active tactile manipulation with the GR2 TacTip gripper are model free, can be used to investigate principles of dexterous manipulation, and could lead to essential advances in the areas of robotic tactile manipulation and teleoperated robots.

  • Journal article
    Kanner OY, Rojas N, Odhner LU, Dollar AMet al., 2017,

    Adaptive legged robots through exactly-constrained and non-redundant design

    , IEEE Access, Vol: 5, Pages: 11131-11141, ISSN: 2169-3536

    This paper presents a novel strategy for designing passively adaptive, statically stable walking robots with full body mobility that are exactly constrained and non-redundantly actuated during stance. In general, fully mobile legged robots include a large number of actuated joints, giving them a wide range of controllable foot placements but resulting in overconstraint during stance, requiring kinematic redundancy and redundant control for effective locomotion. The proposed design strategy allows for the elimination of actuation redundancy, thus greatly reducing the weight and complexity of the legged robots obtained and allowing for simpler control schemes. Moreover, the underconstrained nature of the resulting robots during swing allows for passive adaptability to rough terrain without large contact forces. The strategy uses kinematic mobility analysis tools to synthesize leg topologies, underactuated robotics design approaches to effectively distribute actuation constraints, and elastic elements to influence nominal leg behavior. Several examples of legged robot designs using the suggested approach are thoroughly discussed and a proof-of-concept of a non-redundant walking robot is presented.

  • Journal article
    Ma RR, Rojas N, Dollar AM, 2016,

    Spherical hands: toward underactuated, in-hand manipulation invariant to object size and grasp location

    , Journal of Mechanisms and Robotics, Vol: 8, Pages: 061021-061021-12, ISSN: 1942-4302

    Minimalist, underactuated hand designs can be modified to produce useful, dexterous, in-hand capabilities without sacrificing their passive adaptability in power grasping. Incorporating insight from studies in parallel mechanisms, we implement and investigate the “spherical hand” morphologies: novel, hand topologies with two fingers configured such that the instantaneous screw axes, describing the displacement of the grasped object, always intersect at the same point relative to the palm. This produces the same instantaneous motion about a common point for any object geometry in a stable grasp. Various rotary fingertip designs are also implemented to help maintain stable contact conditions and minimize slip, in order to prove the feasibility of this design in physical hand implementations. The achievable precision manipulation workspaces of the proposed morphologies are evaluated and compared to prior human manipulation data as well as manipulation results with traditional three-finger hand topologies. Experiments suggest that the spherical hands' design modifications can make the system's passive reconfiguration more easily predictable, providing insight into the expected object workspace while minimizing the dependence on accurate object and contact modeling. We believe that this design can significantly reduce the complexity of planning and executing dexterous manipulation movements in unstructured environments with underactuated hands.

  • Journal article
    Palomeras N, Carrera A, Hurtós N, Karras GC, Bechlioulis CP, Cashmore M, Magazzeni D, Long D, Fox M, Kyriakopoulos KJ, Kormushev P, Salvi J, Carreras Met al., 2016,

    Toward persistent autonomous intervention in a subsea panel

    , Autonomous Robots, Vol: 40, Pages: 1279-1306
  • Journal article
    Rojas N, Dollar AM, 2016,

    Classification and kinematic equivalents of contact types for fingertip-based robot hand manipulation

    , Journal of Mechanisms and Robotics, Vol: 8, Pages: 041014-1-041014-9, ISSN: 1942-4302

    In the context of robot manipulation, Salisbury's taxonomy is the common standard used to define the types of contact interactions that can occur between the robot and a contacted object; the basic concept behind such classification is the modeling of contacts as kinematic pairs. In this paper, we extend this notion by modeling the effects of a robot contacting a body as kinematic chains. The introduced kinematic-chain-based contact model is based on an extension of the Bruyninckx–Hunt approach of surface–surface contact. A general classification of nonfrictional and frictional contact types suitable for both manipulation analyses and robot hand design is then proposed, showing that all standard contact categories used in robotic manipulation are special cases of the suggested generalization. New contact models, such as ball, tubular, planar translation, and frictional adaptive finger contacts, are defined and characterized. An example of manipulation analysis that lays out the relevance and practicality of the proposed classification is detailed.

  • Journal article
    Rojas N, Dollar AM, 2016,

    Gross motion analysis of fingertip-based within-hand manipulation

    , IEEE Transactions on Robotics, Vol: 32, Pages: 1009-1016, ISSN: 1552-3098

    Fingertip-based within-hand manipulation, also called precision manipulation, refers to the repositioning of a grasped object within the workspace of a multifingered robot hand without breaking or changing the contact type between each fingertip and the object. Given a robot hand architecture and a set of assumed contact models, this paper presents a method to perform a gross motion analysis of its precision manipulation capabilities, regardless of the particularities of the object being manipulated. In particular, the technique allows the composition of the displacement manifold of the grasped object relative to the palm of the robot hand to be determined as well as the displacements that can be controlled-useful for high-level design and classification of hand function. The effects of a fingertip contacting a body in this analysis are modeled as kinematic chains composed of passive and resistant revolute joints; what permits the introduction of a general framework for the definition and classification of nonfrictional and frictional contact types. Examples of the application of the proposed method in several architectures of multifingered hands with different contact assumptions are discussed; they illustrate how inappropriate contact conditions may lead to uncontrollable displacements of the grasped object.

  • Journal article
    Jamisola RS, Kormushev P, Roberts RG, Caldwell DGet al., 2016,

    Task-Space Modular Dynamics for Dual-Arms Expressed through a Relative Jacobian

    , Journal of Intelligent & Robotic Systems, Pages: 1-14, ISSN: 1573-0409
  • Journal article
    Rojas N, Ma RR, Dollar AM, 2016,

    The GR2 gripper: an underactuated hand for open-loop in-hand planar manipulation

    , IEEE Transactions on Robotics, Vol: 32, Pages: 763-770, ISSN: 1552-3098

    Performing dexterous manipulation of unknown objects with robot grippers without using high-fidelity contact sensors, active/sliding surfaces, or a priori workspace exploration is still an open problem in robot manipulation and a necessity for many robotics applications. In this paper we present a two-fingered gripper topology that enables an enhanced predefined in-hand manipulation primitive controlled without knowing the size, shape, or other particulars of the grasped object. The in-hand manipulation behavior, namely, the planar manipulation of the grasped body, is predefined thanks to a simple hybrid low-level control scheme and has an increased range of motion due to the introduction of an elastic pivot joint between the two fingers. Experimental results with a prototype clearly show the advantages and benefits of the proposed concept. Given the generality of the topology and in-hand manipulation principle, researchers and designers working on multiple areas of robotics can benefit from the findings.

  • Book chapter
    Kormushev P, Ahmadzadeh SR, 2016,

    Robot Learning for Persistent Autonomy

    , Handling Uncertainty and Networked Structure in Robot Control, Editors: Busoniu, Tamás, Publisher: Springer International Publishing, Pages: 3-28, ISBN: 978-3-319-26327-4
  • Book chapter
    Ahmadzadeh SR, Kormushev P, 2016,

    Visuospatial Skill Learning

    , Handling Uncertainty and Networked Structure in Robot Control, Editors: Busoniu, Tamás, Publisher: Springer International Publishing, Pages: 75-99, ISBN: 978-3-319-26327-4
  • Conference paper
    Maurelli F, Lane D, Kormushev P, Caldwell D, Carreras M, Salvi J, Fox M, Long D, Kyriakopoulos K, Karras Get al., 2016,

    The PANDORA project: a success story in AUV autonomy

    , OCEANS Conference 2016, Publisher: IEEE, ISSN: 0197-7385

    This paper presents some of the results of the EU-funded project PANDORA - Persistent Autonomy Through Learning Adaptation Observation and Re-planning. The project was three and a half years long and involved several organisations across Europe. The application domain is underwater inspection and intervention, a topic particularly interesting for the oil and gas sector, whose representatives constituted the Industrial Advisory Board. Field trials were performed at The Underwater Centre, in Loch Linnhe, Scotland, and in harbour conditions close to Girona, Spain.

  • Book chapter
    Ma RR, Rojas N, Dollar AM, 2016,

    Towards predictable precision manipulation of unknown objects with underactuated fingers

    , Advances in Reconfigurable Mechanisms and Robots II, Editors: Ding, Kong, Dai, Cham, Publisher: Springer International Publishing, Pages: 927-937, ISBN: 978-3-319-23327-7

    This paper describes a new concept in underactuated hand design, motivated by a study of parallel mechanisms. Inspired by the end-effector motion and system reconfiguration in parallel wrists, we propose a morphology of fingers such that during fingertip precision manipulation the instantaneous screw axes, which describe the displacement of the grasped object respect to the palm of the hand, always intersect at the same known fixed point regardless of the object’s particularities. A physical hand was built to evaluate the feasibility of the design concept in improving precision manipulation capabilities while preserving power-grasping functionality. The tendon-driven hand is underactuated, with one actuator for each of the two-degree-of-freedom fingers, and passive rotary fingertips are used to minimize slip at contact points during manipulation. Experimental results with the hand demonstrate the effectiveness of the concept, thus encouraging further research in the area.

  • Conference paper
    Kryczka P, Kormushev P, Tsagarakis N, Caldwell DGet al., 2015,

    Online Regeneration of Bipedal Walking Gait Optimizing Footstep Placement and Timing

  • Conference paper
    Kormushev P, Demiris Y, Caldwell DG, 2015,

    Kinematic-free Position Control of a 2-DOF Planar Robot Arm

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