Continuum manipulators, inspired by nature, have drawn significant interest within the robotics community. They can facilitate motion within complex environments where traditional rigid robots may be ineffective, while maintaining a reasonable degree of precision. Soft continuum manipulators have emerged as a growing subfield of continuum robotics, with promise for applications requiring high compliance, including certain medical procedures. This has driven demand for new control schemes designed to precisely control these highly flexible manipulators, whose kinematics may be sensitive to external loads, such as gravity. This article presents one such approach, utilizing a rapidly computed kinematic model based on Cosserat rod theory, coupled with sensor feedback to facilitate closed-loop control, for a soft continuum manipulator under tip follower actuation and external loading. This approach is suited to soft manipulators undergoing quasi-static deployment, where actuators apply a follower wrench (i.e., one that is in a constant body frame direction regardless of robot configuration) anywhere along the continuum structure, as can be done in water-jet propulsion. In this article we apply the framework specifically to a tip actuated soft continuum manipulator. The proposed control scheme employs both actuator feedback and pose feedback. The actuator feedback is utilized to both regulate the follower load and to compensate for non-linearities of the actuation system that can introduce kinematic model error. Pose feedback is required to maintain accurate path following. Experimental results demonstrate successful path following with the closed-loop control scheme, with significant performance improvements gained through the use of sensor feedback when compared with the open-loop case.

In the development of telemanipulated surgical robots, a class of continuum robots known as concentric tube robots has drawn particular interest for clinical applications in which space is a major limitation. One such application is transnasal surgery, which is used to access surgical sites in the sinuses and at the skull base. Current techniques for performing these procedures require surgeons to maneuver multiple rigid tools through the narrow confines of the nasal passages, leaving them with limited dexterity at the surgical site. In this article, we present a complete robotic system for transnasal surgery featuring concentric tube manipulators. It illustrates a bagging concept for sterility, and intraoperatively interchangeable instruments that work in conjunction with it, which were developed with operating room workflow compatibility in mind. The system also includes a new modular, portable surgeon console, a variable view-angle endoscope to facilitate surgical field visualization, and custom motor control electronics. Furthermore, we demonstrate elastic instability avoidance for the first time on a physical prototype in a geometrically accurate surgical scenario, which facilitates use of higher curvature tubes than could otherwise be used safely in this application. From a surgical application perspective, this article presents the first robotic approach to removing tumors growing behind the eyes in the orbital apex region, which has not been attempted previously with a surgical robot.

Partial nephrectomy involves removing a tumor while sparing surrounding healthy kidney tissue. Compared to total kidney removal, partial nephrectomy improves outcomes for patients but is underutilized because it is challenging to accomplish minimally invasively, requiring accurate spatial awareness of unseen subsurface anatomy. Image guidance can enhance spatial awareness by displaying a 3D model of anatomical relationships derived from medical imaging information. It has been qualitatively suggested that the da Vinci robot is well suited to facilitate image guidance through touch-based registration. In this paper we validate and advance this concept toward real-world use in several important ways. First, we contribute the first quantitative accuracy evaluation of touch-based registration with the da Vinci. Next, we demonstrate real-time, touch-based registration and display of medical images for the first time. Lastly, we perform the first experiments validating use of touch-based image guidance to improve a surgeon’s ability to localize subsurface anatomical features in a geometrically realistic phantom.

Gastric cancer is the third leading cause of cancer deaths worldwide, with most new cases occurring in low and middle income countries, where access to screening programs is hindered by the high cost of conventional endoscopy. The waterjet-actuated HydroJet endoscopic platform was developed as a low-cost, disposable alternative for inspection of the gastric cavity in low-resource settings. In this work, we present a teleoperation scheme and contact detection algorithm that work together to enable intuitive teleoperation of the HydroJet within the confined space of the stomach. Using a geometrically accurate stomach model and realistic anatomical inspection targets, we demonstrate that, using these methods, a novice user can complete a gastroscopy in approximately the same amount of time with the HydroJet as with a conventional endoscope.

Continuum manipulators are flexible robots which undergo continuous deformation as they are actuated. To describe the elastic deformation of such robots, kinematic models have been developed and successfully applied to a large variety of designs and to various levels of constitutive stiffness. Independent of the design, kinematic models need to be calibrated to best describe the deformation of the manipulator. However, even after calibration, unmodeled effects such as friction, nonlinear elastic and/or spatially varying material properties as well as manufacturing imprecision reduce the accuracy of these models. In this letter, we present a method for improving the accuracy of kinematic models of continuum manipulators through the incorporation of orientation sensor feedback. We achieve this through the use of a “disturbance wrench,” which is used to compensate for these unmodeled effects, and is continuously estimated based on orientation sensor feedback as the robot moves through its workspace. The presented method is applied to the HydroJet, a waterjet-actuated soft continuum manipulator, and shows an average of 40% reduction in root mean square position and orientation error in the two most common types of kinematic models for continuum manipulators, a Cosserat rod model and a pseudo-rigid body model.

Introduction: Concentric tube robots are flexible, needle-diameter robots which have shown great promise for surgical application requiring dexterous tools to be passed into an anatomical space through a natural orifice or small incision.

We propose a new kind of continuum robot based on crossed elastic strips. The actuator-specified location of the crossover point controls the lengths of the sections, enabling a wider range of configurations than would be possible with traditional fixed-section-length robots. Push-pull actuation of the crossed strips controls the curvature of the sections. We provide a model that describes the resulting configurations in terms of tangent circular arcs of varying lengths. Experiments with a prototype yield tip positions that agree with model predictions with an average error of 4.6% of the robots length.

Many applications in medicine require flexible surgical manipulators and endoscopes capable of reaching tight curvatures. The maximum curvature these devices can achieve is often restricted either by a strain limit, or by a maximum actuation force that the device's components can tolerate without risking mechanical failure. In this paper we propose the use of precurvature to "bias" the workspace of the device in one direction. Combined with axial shaft rotation, biasing increases the size of the device's workspace, enabling it to reach tighter curvatures than a comparable device without biasing can achieve, while still being able to fully straighten. To illustrate this effect, we describe several example prototype devices which use flexible nitinol strips that can be pushed and pulled to generate bending. We provide a statics model that relates the manipulator curvature to actuation force, and validate it experimentally.

Lung cancer is the most deadly form of cancer in part because of the challenges associated with accessing nodules for diagnosis and therapy. Transoral access is preferred to percutaneous access since it has a lower risk of lung collapse, yet many sites are currently unreachable transorally due to limitations with current bronchoscopic instruments. Toward this end, we present a new robotic system for image-guided trans-bronchoscopic lung access. The system uses a bronchoscope to navigate in the airway and bronchial tubes to a site near the desired target, a concentric tube robot to move through the bronchial wall and aim at the target, and a bevel-tip steerable needle with magnetic tracking to maneuver through lung tissue to the target under closed-loop control. In this work, we illustrate the workflow of our system and show accurate targeting in phantom experiments. Ex vivo porcine lung experiments show that our steerable needle can be tuned to achieve appreciable curvature in lung tissue. Lastly, we present targeting results with our system using two scenarios based on patient cases. In these experiments, phantoms were created from patient-specific computed tomography information and our system was used to target the locations of suspicious nodules, illustrating the ability of our system to reach sites that are traditionally inaccessible transorally.

Lung cancer is the most deadly form of cancer, and survival depends on early-stage diagnosis and treatment. Transoral access is preferable to traditional between-the-ribs needle insertion because it is less invasive and reduces risk of lung collapse. Yet many sites in the peripheral zones of the lung or distant from the bronchi cannot currently be accessed transorally, due to the relatively large diameter and lack of sufficient steerablity of current instrumentation. To remedy this, we propose a new robotic system that uses a tendon-actuated device (bronchoscope) as a first stage for deploying a concentric tube robot, which itself is a vehicle through which a bevel steered needle can be introduced into the soft tissue of the lung outside the bronchi. In this paper we present the various components of the system and the workflow we envision for deploying the robot to a target using image guidance. We describe initial validation experiments in which we puncture ex vivo bronchial wall tissue and also target a nodule in a phantom with an average final tip error of 0.72 mm.

Several robotic systems have been proposed for removing blood from the brain in patients who have undergone a hemorrhagic stroke. In this paper we explore the use of imagebased feedback to address tissue deformation when aspirating a hemorrhage in a phantom model. This is the first time intraoperative image feedback has been used with a concentric tube robot in this application. We describe a layer by layer approach to motion planning. Computed tomography (CT) images are collected periodically during hemorrhage removal. After each CT scan, the robot's tip path is re-planned to account for the tissue deformation that has occurred since the previous scan. We compare open loop hemorrhage removal to our sequential imaging-replanning approach, illustrating that the latter has the potential to enhance the safety and efficacy of the procedure.

More people die from lung cancer each year than any other form of cancer. Over 150,000 lives are lost to the disease each year in the U.S. alone [1]. Early detection is critical in reducing the mortality rate, and despite advances in imaging, biopsy remains the only definitive diagnostic tool. The most common lung biopsy approaches are percutaneous and transoral. Percutaneous biopsy punctures the pleura (the membrane surrounding the lung) in order to reach the suspicious nodule and risks pneumothorax (lung collapse), which is a serious complication and can be deadly for patients with poor baseline lung function. Transoral lung biopsy is preferable due to the fact that the biopsy device never traverses the pleura. However, current bronchoscopes cannot access the majority of the peripheral lung, due to their large diameter in relation to bronchi diameter. While smaller diameter endoscopes and endoscopelike devices are under development, there will always remain locations where a path that exits the bronchi and travels through the parenchyma is desirable, either because it is shorter or because the nodule lies away from a usable bronchial access path. To facilitate the biopsy tool exiting the bronchi to reach such targets, we have developed the puncture mechanism described in this paper. In addition to biopsy with a straight-line biopsy needle, our device may enable the use of steerable needles in the lung parenchyma. Recent advances in robotics such as concentric tube robots (CTRs) [2] and bevel-tip steerable needles [3] (among other new needle steering technologies) may be useful in reaching targets through controllable curved paths. But these technologies require the means of exiting the bronchi that we provide in this paper. Inspired by the prior work showing that fast needle insertion can controllably transit tissue with minimal deformation [4–6], in this paper we develop a bronchoscope-deployed system that can drive the needle tip through the bronchial wall and surrounding cartilage and connective tissue, providing a port for subsequent deployment of biopsy needles and/or steerable needles into the lung parenchyma.

This paper discusses a new class of robots known as concentric tube robots and their application to transnasal skull base surgery. The endonasal approach has clear benefits for patients, but the surgery presents challenges that strongly motivate the use of robotic tools. In this paper, the concentric tube robot concept is described, and preliminary experimental results for transnasal skull base surgery are reviewed. Just as the da Vinci robot has revolutionized many laparoscopic surgeries, we expect concentric tube robots will enable the advancement of skull base surgery and the development of other minimally invasive procedures that require access through constrained paths.

With the advent of endoscopic sinus surgery in the late 1980's [1], a completely new surgical field was born. The endoscope, passed through the natural orifice of the nose, allowed for much more precise visualization of the operative field and enabled a new understanding of the function of the sinuses. Today, functional endoscopic sinus surgery (FESS) is commonly used to improve the sinuses' natural drainage pathways in patients with chronic sinusitis, to remove pathologies such as nasal polyps and tumors, and even to access the skull base to remove brain tumors.Commonly used angled endoscopes allow for visualization of nearly every portion of the sinus cavities and skull base. However, traditional tools have not enabled adequate surgical access to all of these areas. This is because the current surgical method requires a nearly direct line of access from the opening of the nose to the surgical target. Due to anatomical obstacles, not all areas visible to the endoscope can be directly accessed in this way. As a result, procedures have been developed to remove anatomical structures in order to clear a direct line of access to hard-to-reach targets. However, removal of these structures comes at a cost, with complications including vascular, nerve and soft tissue damage that can result in pain or numbness in the mouth and face.Current technique requires one hand to hold the surgical instrument, while the other hand is typically occupied holding the endoscope, as shown in Fig. 1. Generally, these tools are supported entirely by the surgeon's hands, in contrast with other types of laparoscopic surgery in which a trocar provides additional support. As a result, tools must be lightweight and comfortable to hold. These tools have traditionally been designed to be rigid (so as to be easily controlled with one hand), though not necessarily straight. In an attempt to reach around corners and avoid obstacles in the anatomy, some devices incorporate curved tool shafts. However, these are limited in their maneuverability, since the curved shape is fixed during surgery. These rigid tools have been adequate for the majority of surgeries, but as techniques have advanced, surgeons have reached the limits of what they can accomplish with these tools. In order to avoid the need to remove tissue in order to access hard-to-reach sites, new tools must be developed which are capable of navigating through angled pathways in the nasal cavities. A new approach to this problem involving a stiff yet elastic steerable tool tip is presented in this paper. This approach uses a continuum structure. For a review of prior uses of continuum structures in robotic tools, see Ref. [2].Our objective was to develop a stiff, yet bendable manual grasper with controllable curvature, allowing the surgeon to easily steer the tip of the tool within the sinuses. The device was required to be relatively stiff to effectively accomplish surgical tasks such as grasping and cutting; yet we also required the tool shaft to have the ability to bend locally near tool tip. The goal was to access a larger set of potential targets in the sinus cavities, without the need for a clear line of access between the opening of the nostril and the target site.User control represented an additional design challenge. We sought a design in which a single hand could comfortably and intuitively control gross tool manipulation, bending of the tool shaft, and gripper opening and closing. We targeted a shaft diameter of 4 mm or less, such that the device could fit through a nostril, and a shaft length and handle width comparable to those of currently available sinus surgery tools (approximately 80 mm and 5 mm, respectively). The CAD model and physical prototype we developed are shown in Fig. 2.To allow for tool shaft bending, we implemented a “multibackbone” continuum mechanism [3] at the distal end of the shaft, shown in detail in Fig. 3. It consists of a set of 4 superelastic nitinol wires passed through a series of small plastic support disks, which hold them in a desired configuration. These wires are stiff enough to create a structure that can apply reasonable forces to the anatomy during surgery (an open research question is optimizing wire diameters based on exact surgical force requirements), yet are capable of bending significantly without experiencing plastic deformation. The spacing between the support disks was maintained by placing flexible PTFE tube sections around the wire segments between disks, to serve as spacers. A thumb-activated joystick at the rear of the handle enables the surgeon to control tool shaft bending. As the joystick is deflected, the nitinol wires on one side are pushed forward, while those on the other side are pulled back. As a result, these wires bend, causing the tool shaft to deflect in the direction opposite joystick motion. This deflection is achievable in any direction. This design was inspired by the continuously flexible manipulators featured in some surgical robots [2], and to our knowledge, this tool represents the first time such a multi-backbone mechanism has been used in a manual surgical tool.A grasper is attached to the tip of the tool. It is actuated by a flexible push-pull wire, which is fed through the center of the hollow tool shaft and into the handle. There, it is affixed to a trigger mechanism, which the user actuates with his or her index finger at the front of the handle. The ergonomics of the device were designed to be similar to those of current endoscopic sinus surgery tools, with the addition of the joystick to control shaft bending. It is hoped that this will facilitate rapid adoption of the new instrument, since surgeons are expected to feel comfortable using it, due to its similarity to devices they already use.Our goal in constructing the prototype described above was to determine the feasibility of constructing the proposed device and to obtain qualitative feedback from surgeons. The intent was to determine whether any modifications or improvements were necessary. In our initial qualitative tests of the tool, we found that surgeons were able to easily use the joystick to deflect the flexible tool shaft in any direction, as shown in Fig. 4, as well as to effectively open and close the grasper tool using the trigger on the front of the handle.The results described in this paper are early stage prototyping and design efforts. There remains much research to be done before this tool becomes a commercial product, and even before the merits of our new tool concept can be fully evaluated. First, to provide a clear and obvious advantage with respect to existing tools, we must find ways to increase the achievable curvature. Currently, we are exploring adding mechanisms to the thumb control to amplify the distance the rods are pushed and pulled in response to a given handle deflection. This would permit higher tip curvatures for the same joystick curvature.Next, we must choose a specific set of sinus surgeries and evaluate their requirements in detail. In particular, the force application requirements and workspace requirements must be determined. This will enable us to size the push-pull rods appropriately to satisfy the force requirements, and also to choose the length and maximum curvature of the bending section appropriately based on the areas it must reach.Lastly, we will pursue substantial user testing on the benchtop and then in cadaveric specimens. These experiments will be designed to ensure that surgeons are able to effectively use the device to perform the intended surgical procedures.In this paper, we have presented a new tool design for endonasal sinus and skull-base surgery. The tool features a multi-backbone continuously bending mechanism that enables the surgeon to change the curvature of the tool tip. This enables the surgeon to actively steer the grasper within the surgical field during the procedure. The grasper itself is opened and closed by a trigger on the handle.While this design concept appears promising, much work remains to be done before one can conclusively say that this device will provide valuable benefits to the surgeon. However, it does appear to hold the potential to enhance surgical dexterity in endonasal procedures. In so doing, it is our hope that working in concert with angled endoscopes, it may eliminate the need to remove anatomical features in order to clear a straight line of access to the target in some procedures. If it is effective in doing so, this will make sinus surgeries less invasive and may lead to reductions in complication rates.

In this contribution we present a new, objective-based controller which works on the basis of a Pareto set, that is the solution of a multiobjective optimization problem. The controller can be used for self-optimizing systems to adapt the system behavior in terms of the desired objectives in spite of unknown disturbances over time. New system configurations are computed, that fit best to the current situation. The objective-based control is realized by means of a discrete controller which operates in a large sample time due to objective evaluation. Parametric reduced models are used to shorten the simulation time during controller design. An active suspension system of a railbound vehicle serves as an application example. The controller is tested with different linear models of the suspension system and is finally applied to a Hardware-in-the-Loop test rig.