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Continuum robots (CRs) have been recently shown capable of micron-scale motion resolutions. Such motions are achieved through equilibrium modulation using indirect actuation for altering either internal preload forces or changing the cross-sectional stiffness along the length of a CR. Previously reported, but unexplained, turning point behavior is modeled using two approaches. An energy minimization approach is first used to explain the source of this behavior. Subsequently, a kinematic model using internal constraints in multibackbone CRs is used to replicate this turning point behavior. An approach for modeling the micromotion differential kinematics is presented using experimental data based on the solution of a system of linear matrix equations. This approach provides a closed-form approximation of the empirical micromotion kinematics and could be easily used for real-time control. A motivating application of image-based biopsy using 3-D optical coherence tomography (OCT) is envisioned and demonstrated in this article. A system integration for generating OCT volumes by sweeping a custom B-mode OCT probe is presented. Results showing high accuracy in obtaining 3-D OCT measurements are shown using a commercial OCT probe. Qualitative results using a miniature probe integrated within the robot are also shown. Finally, closed-loop visual servoing using OCT data are demonstrated for guiding a needle into an agar channel. Results of this article present what we believe is the first embodiment of a CR capable of micro and macromotion control for 3-D OCT imaging. This approach can support the development of new technologies for CRs capable of surgical intervention and micromotion for ultraprecision tasks. [ABSTRACT FROM AUTHOR]

Currently, surgical continuum robots (CRs) are predominantly used as telemanipulators where modeling errors are overcome by the user. Such errors preclude their use for autonomous tasks. In this paper, we investigate the calibration of CRs with specific focus on capturing joint space errors due to homing offsets, assembly errors causing twist about the robot's backbone, and uncertainty in the equilibrium bending shapes of segments of these robots. A kinematic framework focusing on multibackbone CR is presented with emphasis on deriving calibration identification Jacobians. This framework captures the coupling between twist and the equilibrium shapes of a continuum segment as a function of its bending angle. To capture equilibrium shape variations as a function of bending, a homotopy of curves is defined and represented by respective modal coefficients. The estimation of the calibration parameters is cast as a nonlinear least-squares problem. The framework is validated by simulations and experimentally using a single-port access surgery robot. We believe this calibration framework will facilitate semiautomation of surgical tasks carried out by CRs. [ABSTRACT FROM AUTHOR]

The prevalence of wire-actuated mechanisms and continuum robots (CRs) for surgical applications stems from several advantages due to the remote location of actuators from the end-effectors (e.g., improved down scalability and sterilization). These advantages, however, come at the expense of inherent uncertainties due to backlash effects, compliance, and friction in the actuation lines, which in turn, limit their precision. In addition, multisegment CRs suffer from actuation coupling, diminishing the accuracy of their kinematic model. This paper aims to address these two gaps by presenting a model-based estimation and actuation compensation framework enabling the online estimation of modeling uncertainties and friction, despite possible temporal changes in these parameters and cross coupling between segments. A capstan friction model accounting for friction-induced actuation line extensions in both fixed and variable geometry conduits is presented. A modified statics model for multisegment robots is presented to account for cross-coupling effects between subsequent CR segments. A sequential estimation approach using the robot inverse kinematics, statics, and measurements of actuated joint positions and forces is then presented. These approaches are then validated experimentally on a two-segment single port access surgery CR. [ABSTRACT FROM PUBLISHER]

Cochlear implant surgery is a procedure that requires delicate insertion of an electrode array into the inner ear. This paper reports the clinical motivation, design considerations, analysis, and design optimization of a new robot for electrode arrays insertion. This paper describes a new approach for coordinated insertion of perimodiolar electrode arrays in order to minimize shape discrepancy between the shape of the electrode array and the shape of the inner ear anatomy. A new design of a 3-degrees-of-freedom (DoF) parallel robot with wire-actuated prismatic legs is presented. The dimensional synthesis of the robot design was based on satisfying the accuracy, speed, system size, and workspace requirements. The robot prototype is validated experimentally to execute electrode insertions in plastic models of temporal bones. [ABSTRACT FROM PUBLISHER]

During exploration through tortuous unstructured passages by continuum robots, methods are required to minimize the force interaction between the environment and the robot along its length. This paper presents and evaluates an algorithm for compliant motion control of continuum robots subjected to multiple unknown contacts with the environment. A mapping of external wrenches to a generalized force in the configuration space of a multisegment continuum robot is presented and related to measured joint-level actuation forces. These measurements are applied as inputs to a low-level compliant motion controller. Friction and modeling uncertainties, presenting an unknown nonlinear deviation from the nominal system model, are corrected via a feed-forward estimate provided by a support vector machine. The controller is evaluated on Ø9 and Ø5 mm multisegment continuum robots. We quantify the minimal interaction forces needed to generate compliant motion and demonstrate the ability of the controller to minimize interaction forces during insertion through tortuous passages. [ABSTRACT FROM PUBLISHER]

Single port access surgery (SPAS) presents surgeons with added challenges that require new surgical tools and surgical assistance systems with unique capabilities. To address these challenges, we designed and constructed a new insertable robotic end-effectors platform (IREP) for SPAS. The IREP can be inserted through a Ø15 mm trocar into the abdomen and it uses 21 actuated joints for controlling two dexterous arms and a stereo-vision module. Each dexterous arm has a hybrid mechanical architecture comprised of a two-segment continuum robot, a parallelogram mechanism for improved dual-arm triangulation, and a distal wrist for improved dexterity during suturing. The IREP is unique because of the combination of continuum arms with active and passive segments with rigid parallel kinematics mechanisms. This paper presents the clinical motivation, design considerations, kinematics, statics, and mechanical design of the IREP. The kinematics of coordination between the parallelogram mechanisms and the continuum arms is presented using the pseudo-rigid-body model of the beam representing the passive segment of each snake arm. Kinematic and static simulations and preliminary experiment results are presented in support of our design choices. [ABSTRACT FROM PUBLISHER]

In this paper, we present a novel kinematic-based framework for collision detection and estimation of contact location along multisegment continuum robots. Screw theory is used to define a screw motion deviation (SMD) as the distance between the expected and the actual instantaneous screw axis (ISA) of motion. The expected ISA is computed based on the unconstrained kinematics model of the robot, while the actual ISA is computed based on sensory information. Collisions with rigid environments at any point along the robot are detected by monitoring the SMD. Contact locations are estimated by the minimization of the SMD between the ISA that is obtained from a constrained kinematic model of the continuum robot and the one that is obtained from sensor data. The proposed contact detection and localization methods only require the relative motion of each continuum segment with respect to its own base. This strategy allows the straightforward generalization of these algorithms for an n -segment continuum robot. The framework is evaluated via simulations and experimentally on a three-segment multibackbone continuum robot. Results show that the collision-detection algorithm is capable of detecting a single collision at any segment, multiple collisions occurring at multiple segments, and total-arm constraint. It is also shown that the estimation of contact location is possible at any location along the continuum robot with an accuracy better than 20% of the segment nominal length. We believe this study will enhance manipulation safety in unstructured environments and confined spaces. [ABSTRACT FROM PUBLISHER]

In this paper we present the clinical motivation, design specifications, kinematics, statics, and actuation compensation for a newly constructed telerobotic system for Minimally Invasive Surgery (MIS) of the throat. A hybrid dual-arm telesurgical slave, with 20 joint-space Degrees-of-Freedom (DoFs), is used in this telerobotic system to provide the necessary dexterity in deep surgical fields such as the throat. The telerobotic slave uses novel continuum robots that use multiple super-elastic backbones for actuation and structural integrity. We present the kinematics of the telesurgical slave and methods for actuation compensation to cancel the effects of backlash, friction, and flexibility of the actuation lines. A method for actuation compensation is presented in order to overcome uncertainties of modeling, friction, and backlash. This method uses a tiered hierarchy of two novel approaches of actuation compensation for remotely actuated snake-like robots. The tiered approach for actuation compensation uses compensation in both joint space and configuration space of the continuum robots. These hybrid actuation compensation schemes use intrinsic model information and external data through a recursive linear estimation algorithm and involve compensation using configuration space and joint space variables. Experimental results validate the ability of our integrated telemanipulation system through experiments of suturing and knot tying in confined spaces. [ABSTRACT FROM AUTHOR]