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  • Journal article
    Petersen J, Bowyer S, Rodriguez y Baena F, 2016,

    Mass and friction optimization for natural motion in hands-on robotic surgery

    , IEEE Transactions on Robotics, Vol: 32, Pages: 201-213, ISSN: 1552-3098

    In hands-on robotic surgery, the surgical tool is mounted on the end-effector of a robot and is directly manipulated by the surgeon. This simultaneously exploits the strengths of both humans and robots, such that the surgeon directly feels tool-tissue interactions and remains in control of the procedure, while taking advantage of the robot's higher precision and accuracy. A crucial challenge in hands-on robotics for delicate manipulation tasks, such as surgery, is that the user must interact with the dynamics of the robot at the end-effector, which can reduce dexterity and increase fatigue. This paper presents a null-space-based optimization technique for simultaneously minimizing the mass and friction of the robot that is experienced by the surgeon. By defining a novel optimization technique for minimizing the projection of the joint friction onto the end-effector, and integrating this with our previous techniques for minimizing the belted mass/inertia as perceived by the hand, a significant reduction in dynamics felt by the user is achieved. Experimental analyses in both simulation and human user trials demonstrate that the presented method can reduce the user-experienced dynamic mass and friction by, on average, 44% and 41%, respectively. The results presented robustly demonstrate that optimizing a robots pose can result in a more natural tool motion, potentially allowing future surgical robots to operate with increased usability, improved surgical outcomes, and wider clinical uptake.

  • Journal article
    Leibinger A, Forte AE, Tan Z, Oldfield MJ, Beyrau F, Dini D, Rodriguez Y Baena Fet al., 2015,

    Soft tissue phantoms for realistic needle insertion: a comparative study

    , Annals of Biomedical Engineering, Vol: 44, Pages: 2442-2452, ISSN: 1573-9686

    Phantoms are common substitutes for soft tissues in biomechanical research and are usually tuned to match tissue properties using standard testing protocols at small strains. However, the response due to complex tool-tissue interactions can differ depending on the phantom and no comprehensive comparative study has been published to date, which could aid researchers to select suitable materials. In this work, gelatin, a common phantom in literature, and a composite hydrogel developed at Imperial College, were matched for mechanical stiffness to porcine brain, and the interactions during needle insertions within them were analyzed. Specifically, we examined insertion forces for brain and the phantoms; we also measured displacements and strains within the phantoms via a laser-based image correlation technique in combination with fluorescent beads. It is shown that the insertion forces for gelatin and brain agree closely, but that the composite hydrogel better mimics the viscous nature of soft tissue. Both materials match different characteristics of brain, but neither of them is a perfect substitute. Thus, when selecting a phantom material, both the soft tissue properties and the complex tool-tissue interactions arising during tissue manipulation should be taken into consideration. These conclusions are presented in tabular form to aid future selection.

  • Journal article
    Bowyer SA, Rodriguez y Baena F, 2015,

    Dissipative control for physical human-robot interaction

    , IEEE Transactions on Robotics, Vol: 31, Pages: 1281-1293, ISSN: 1552-3098

    Physical human-robot interaction is fundamental to exploiting the capabilities of robots in tasks and environments where robots have limited cognition or comprehension and is virtually ubiquitous for robotic manipulation in highly unstructured environments, as are found in surgery. A critical aspect of physical human-robot interaction in these cases is controlling the robot so that the individual human and robot competencies are maximized, while guaranteeing user, task, and environment safety. Dissipative control precludes dangerous forcing of a shared tool by the robot, ensuring safety; however, it typically suffers from poor control fidelity, resulting in reduced task accuracy. In this study, a novel, rigorously formalized, n-dimensional dissipative control strategy is proposed that employs a new technique called “energy redirection” to generate control forces with increased fidelity while remaining dissipative and safe. Experimental validation of the method, for complete pose control, shows that it achieves a 90% reduction in task error compared with the current state of the art in dissipative control for the tested applications. The findings clearly demonstrate that the method significantly increases the fidelity and efficacy of dissipative control during physical human-robot interaction. This advancement expands the number of tasks and environments into which safe physical human-robot interaction can be employed effectively.

  • Journal article
    Beretta E, De Momi E, Rodriguez y Baena F, Ferrigno Get al., 2015,

    Adaptive hands-on control for reaching and targeting tasks in surgery

    , International Journal of Advanced Robotic Systems, Vol: 12, ISSN: 1729-8814

    Cooperatively controlled robotic assistants can be used in surgery for the repetitive execution of targeting/reaching tasks, which require smooth motions and accurate placement of a tool inside a working area. A variable damping controller, based on a priori knowledge of the location of the surgical site, is proposed to enhance the physical human-robot interaction experience. The performance of this and of typical constant damping controllers is comparatively assessed using a redundant light-weight robot. Results show that it combines the positive features of both null (acceleration capabilities > 0.8m/s2) and optimal (mean pointing error < 1.5mm) constant damping controllers, coupled with smooth and intuitive convergence to the target (direction changes reduced by 30%), which ensures that assisted tool trajectories feel natural to the user. An application scenario is proposed for brain cortex stimulation procedures, where the surgeon’s intentions of motion are explicitly defined intra-operatively through an image-guided navigational system.

  • Journal article
    Oldfield MJ, Leibinger A, Seah TE, Rodriguez Y Baena Fet al., 2015,

    Method to Reduce Target Motion Through Needle-Tissue Interactions.

    , Annals of Biomedical Engineering, Vol: 43, Pages: 2794-2803, ISSN: 1573-9686

    During minimally invasive surgical procedures, it is often important to deliver needles to particular tissue volumes. Needles, when interacting with a substrate, cause deformation and target motion. To reduce reliance on compensatory intra-operative imaging, a needle design and novel delivery mechanism is proposed. Three-dimensional finite element simulations of a multi-segment needle inserted into a pre-existing crack are presented. The motion profiles of the needle segments are varied to identify methods that reduce target motion. Experiments are then performed by inserting a needle into a gelatine tissue phantom and measuring the internal target motion using digital image correlation. Simulations indicate that target motion is reduced when needle segments are stroked cyclically and utilise a small amount of retraction instead of being held stationary. Results are confirmed experimentally by statistically significant target motion reductions of more than 8% during cyclic strokes and 29% when also incorporating retraction, with the same net insertion speed. By using a multi-segment needle and taking advantage of frictional interactions on the needle surface, it is demonstrated that target motion ahead of an advancing needle can be substantially reduced.

  • Journal article
    Secoli R, Robinson M, Brugnoli M, Rodriguez y Baena Fet al., 2015,

    A low-cost, high-field-strength magnetic resonance imaging-compatible actuator

  • Conference paper
    Leibinger A, Burrows C, Oldfield MJ, Rodriguez y Baena Fet al., 2015,

    Tissue Motion Due to Needle Deflection

    , 37th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 1873-1876, ISSN: 1557-170X
  • Conference paper
    Petersen JG, Rodriguez y Baena F, 2014,

    Mass and inertia optimization for natural motion in hands-on robotic surgery

    , Pages: 4284-4289
  • Journal article
    Bowyer SA, Rodriguez y Baena F, 2014,

    Deformation invariant bounding spheres for dynamic active constraints in surgery

  • Journal article
    Merican AM, Ghosh KM, Baena FRY, Deehan DJ, Amis AAet al., 2014,

    Patellar thickness and lateral retinacular release affects patellofemoral kinematics in total knee arthroplasty

    , KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 22, Pages: 526-533, ISSN: 0942-2056
  • Journal article
    Oldfield MJ, Burrows C, Kerl J, Frasson L, Parittotokkaporn T, Beyrau F, Rodriguez y Baena Fet al., 2014,

    Highly resolved strain imaging during needle insertion: results with a novel biologically inspired device

    , Journal of The Mechanical Behavior of Biomedical Materials, Vol: 30, Pages: 50-60, ISSN: 1751-6161

    Percutaneous needle insertions are a common part of minimally invasive surgery. However, the insertion process is necessarily disruptive to the substrate. Negative side effects are migration of deep-seated targets and trauma to the surrounding material. Mitigation of these effects is highly desirable, but relies on a detailed understanding of the needle–tissue interactions, which are difficult to capture at a sufficiently high resolution.Here, an adapted Digital Image Correlation (DIC) technique is used to quantify mechanical behaviour at the sliding interface, with resolution of measurement points which is better than 0.5 mm, representing a marked improvement over the state of the art. A method for converting the Eulerian description of DIC output to Lagrangian displacements and strains is presented and the method is validated during the simple insertion of a symmetrical needle into a gelatine tissue phantom. The needle is comprised of four axially interlocked quadrants, each with a bevel tip. Tests are performed where the segments are inserted into the phantom simultaneously, or in a cyclic sequence taking inspiration from the unique insertion strategy associated to the ovipositor of certain wasps. Data from around the needle–tissue interface includes local strain variations, material dragged along the needle surface and relaxation of the phantom, which show that the cyclic actuation of individual needle segments is potentially able to mitigate tissue strain and could be used to reduce target migration.

  • Journal article
    Bowyer SA, Davies BL, Rodriguez y Baena F, 2014,

    Active Constraints/Virtual Fixtures: A Survey

    , IEEE TRANSACTIONS ON ROBOTICS, Vol: 30, Pages: 138-157, ISSN: 1552-3098
  • Conference paper
    Bowyer SA, Rodriguez y Baena F, 2014,

    Dynamic Frictional Constraints in Translation and Rotation

    , IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE, Pages: 2685-2692, ISSN: 1050-4729
  • Conference paper
    Leibinger A, Oldfield M, Rodriguez y Baena F, 2014,

    Multi-objective design optimization for a steerable needle for soft tissue surgery

    , Pages: 420-423, ISSN: 1680-0737

    A novel steerable probe is being developed to access deep seated targets within soft tissue, with the aim of improving the accuracy of minimally invasive percutaneous needle insertions. Consisting of multiple axially interlocked segments that independently slide along each other, miniaturization of the design is required in order for the needle to be used in surgery. Within this study, a set of parameters which minimizes the risk of both buckling and separation is identified and a design optimization procedure based on finite element models is developed for the needle geometry. Four significant design variables are defined for a genetic multi-objective optimization algorithm. Loads and interactions between the four parts due to curved paths taken inside the soft tissue are modeled using generalized plane strain elements. The optimized set of non-dominated solutions is analyzed. By applying a decision- making process based on the value path method, the nondominated solutions are compared across the four objectives. It is found that smaller and less pronounced interlock features reduce contact forces and improve the sliding performance between needle segments. This results in a trade-off relationship between sliding performance and interlock strength and the most feasible design showing the best performance across all objectives is selected. The outcome is a new optimized design for the needle, which will be manufactured and tested with a suitable controller both in vitro and ex vivo.

  • Conference paper
    Oldfield M, Leibinger A, Kaufmann P-A, Bertucchi M, Beyrau F, Rodriguez y Baena Fet al., 2014,

    Needle Geometry, Target Migration and Substrate Interactions in High Resolution

    , 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 852-855, ISSN: 1557-170X

    Recent investigations considering flexible, steerableneedles for minimally invasive surgery have shown thesignificance of needle shape in determining the needle-tissueinteractions leading to the access of targets. Digital ImageCorrelation has enabled internal deformation and strain causedby needle insertions to be seen in a soft tissue phantom at highresolution for the first time. Here, the impact of tip designon strains and displacements of material around the insertionaxis is presented using Digital Image Correlation in a stable,plane-strain configuration. Insight into the shape of needles tominimise tissue trauma and generate interactions that wouldenable optimal steering conditions is provided. Needle tipswith an included bevel angle up to 40‚ó¶result in asymmetricdisplacement of the surrounding tissue phantom. Increasingthe included tip angle to 60‚ó¶results in more predictabledisplacement and strains that may enhance steering forces withlittle negative impact on the phantom.

  • Conference paper
    Blyth WA, Barr DRW, Hankinson N, Baena FRYet al., 2014,

    An assessment of mecanum wheels for non-destructive testing (NDT) applications

    We present a study into the suitability of mecanum wheels for obtaining holonomic motion on complex geometries, such as those encountered within NDT. There are a number of industrial inspections with challenging requirements for sensors positioning, such as ultrasonic inspection of nozzle welds in pressure vessels. These challenging trajectories necessitate additional degrees of control over conventional two-axis approaches, for example crawlers or X-Y frame systems, which are restrictive. Mecanum wheels in principle offer an excellent advantage for NDT crawlers, enabling unlimited motion within the plane, however the accurate and controllable behaviour of these wheels on non-planar and non-horizontal surfaces is not well understood. In this paper we illustrate the interactions between a mecanum wheel based crawler and complex geometries and construct a model to assess the performance of the mecanum wheels with respect to the requirements of NDT, to smoothly and precisely follow complex trajectories. The potential of mecanum wheel systems is then contrasted against other wheeled systems in terms of NDT demands, and we conclude that the applicability of mecanum wheels to some tasks offers potential gains yet presents additional challenges in others.

  • Conference paper
    Secoli R, Rodriguez y Baena F, 2014,

    Rate Dependency during Needle Insertions with a Biologically Inspired Steering System: an Experimental Study

    , 36th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 856-859, ISSN: 1557-170X
  • Journal article
    Rodriguez Y Baena F, Hawke T, Jakopec M, 2013,

    A bounded iterative closest point method for minimally invasive registration of the femur.

    , Proc Inst Mech Eng H, Vol: 227, Pages: 1135-1144

    This article describes a novel method for image-based, minimally invasive registration of the femur, for application to computer-assisted unicompartmental knee arthroplasty. The method is adapted from the well-known iterative closest point algorithm. By utilising an estimate of the hip centre on both the preoperative model and intraoperative patient anatomy, the proposed 'bounded' iterative closest point algorithm robustly produces accurate varus-valgus and anterior-posterior femoral alignment with minimal distal access requirements. Similar to the original iterative closest point implementation, the bounded iterative closest point algorithm converges monotonically to the closest minimum, and the presented case includes a common method for global minimum identification. The bounded iterative closest point method has shown to have exceptional resistance to noise during feature acquisition through simulations and in vitro plastic bone trials, where its performance is compared to a standard form of the iterative closest point algorithm.

  • Conference paper
    Oldfield MJ, Dini D, Jaiswal T, Rodriguez y Baena Fet al., 2013,

    The significance of rate dependency in blade insertions into a gelatin soft tissue phantom

    , 1st International Conference on Biotribology (ICoBT), Publisher: ELSEVIER SCI LTD, Pages: 226-234, ISSN: 0301-679X
  • Conference paper
    Secoli R, Rodriguez Y Baena F, 2013,

    Closed-loop 3D Motion Modeling and Control of a Steerable Needle for Soft Tissue Surgery

    , 2013 IEEE International Conference on Robotics and Automation (ICRA 2013)

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