WO2013026012A1

WO2013026012A1 - Hybrid snake robot for minimally invasive intervention

Info

Publication number: WO2013026012A1
Application number: PCT/US2012/051396
Authority: WO
Inventors: Marco A. Zenati; Mahsen Mahvash MOHAMMADY
Original assignee: President And Fellows Of Harvard College
Priority date: 2011-08-18
Filing date: 2012-08-17
Publication date: 2013-02-21

Abstract

Described herein is a snake-like robot for use in single-port minimally invasive surgery. The snake robot is made of a highly articulated robotic probe and a concentric tube robot.

Description

HYBRID SNAKE ROBOT FOR MINIMALLY INVASIVE INTERVENTION

RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No.

61/525,108 filed on August 18, 2011, and claims priority to U.S. Provisional Application No. 61/528,441 filed August 29, 2011, the contents of each are herein incorporated by reference.

STATEMENT AS TO FEDERALLY-SPONSORED RESEARCH

[0002] This invention was made with government support under R01HL079940 awarded by National Institutes of Health. The government has certain rights in the invention.

BACKGROUND

[0003] Minimally invasive surgery, such as laparoscopic surgery or endoscopic surgery, as well as catheter based percutaneous, allows physicians to perform procedures on the body with less blood loss, less pain, fewer and smaller scars, and often a faster recovery compared to open surgery. In most minimally invasive procedures, one or several incisions, each about a half-inch long, is made to insert a tube of an laparoscopic or endoscopic device. The number of incisions depends on the device used and the type of surgery. The tube or tubes permit the doctor to insert tiny cameras or other visual tools and specially designed surgical instruments to perform the procedure. Existing robots for use in single port surgery and robotic catheters, however, exhibit many problems. The existing instruments consist of flexible surgical tools (such as endoscopes), computerized flexible instruments, and rigid and semi-rigid instruments that are either hand-held or computerized. The floppy nature of existing flexible instruments makes it impossible to perform complex tissue manipulations that require force and accuracy. Rigid and semi-rigid instruments have limited effective lengths that often are not sufficient to access the areas of interest. In general, existing robots either exhibit high stiffness and low dexterity, or high dexterity and low stiffness.

SUMMARY

[0004] The subject matter described herein represents significant improvements over earlier approaches. The subject matter described herein provides many advantages. For example, advantages of this improved device can include reducing the number of access points or incisions required and increased dexterity. The current subject matter provides a flexible instrument that provides sufficient stiffness and strength, enhanced dexterity, and steerability, which are essential for many of the tissue manipulations in confined spaces of the body. The efficacy in many tissue manipulations is strongly correlated to the stiffness and strength at the tip of the instrument. As an example, for retracting tissue, the instrument should be stiff enough to pull the tissue without being deformed. Enhanced dexterity allows the instrument to perform complex surgical maneuvers. A steerable instrument can safely access locations that were previously impossible or difficult to access, which will enable entirely new minimally invasive treatments. For example, compelling applications in surgery where there are anatomical obstacles that require the instrument to maneuver through long curved natural paths and perform complex tissue manipulation tasks.

[0005] The current subject matter can modulate tip stiffness of the instrument, thus allowing a low tip stiffness during navigation of delicate tissues and a high stiffness during high force tissue manipulation.

[0006] Accordingly, configurations of the described subject matter can feature a hybrid snake device comprising an articulated robotic probe and a concentric tube robot (also referred to as a steerable cannula). Preferably, the device is configured for single port access. The probe operates as a sheath for the steerable cannula. The tubes (e.g., tube robot portion) of the hybrid snake device preferably comprise pre-curved tubes of a superelastic material such as nickel-titanium (Ni-Ti). The probe can comprise a plurality of rigid tubular links. Thus, the hybrid snake device combines a highly- articulated robotic system and a concentric tube steerable cannula. The highly- articulated robotic system can operate as a stiff sheath while the steerable cannula can enhance the tip dexterity and allows the hybrid snake to reach tight spaces because of its small size. In some aspects, the current subject matter can include a control system including a control processor and control driver for controlling at least one of the highly articulated robotic probe and the concentric tube robot. The tube robot can include a tool at the tip of the steerable cannula to perform one or more surgical tasks of: grasping, dissecting, penetrating, cutting, and ablating tissue. A medical procedure can be performed on a subject using the current subject matter. The current subject matter can be used in an intra-vascular manner and can be introduced peripherally into the bloodstream of a patient. The current subject matter can be used to perform a natural orifice transluminal endoscopic surgery. [0007] In another aspect, a system includes a steerable sheath comprising a plurality of tubular bead chains strung on one or more cables and one or more flexible arms inserted inside the sheath. One or more of the following features can be included. A low tension on the cables can cause the sheath to be flexible and a high tension on the cables can cause the sheath to be stiff. Each of the one or more flexible arms can comprise two or more superelastic tubes nested within each other such that rotation and translation of proximal ends of the superelastic tubes can articulate the corresponding flexible arm. The system can further comprise a control system and a drive system. The drive system can include motors and sensors configured to place tension on the cables thereby articulating the steerable sheath and configured to rotate and translate proximal ends of the one or more flexible arms thereby articulating the one or more flexible arms. The control system can send instructions to the drive system to control the articulation. The control system can include a path planer.

[0008] Configurations of the described subject matter can also include methods for minimally-invasive robotic surgery of a living subject using the device and systems to perform delicate and complex procedures deep within bodily tissues such as the heart, lungs, brain, and abdominal organs.

[0009] Publications, U.S. patents and applications, and all other references cited herein, are herby incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is an illustration of a snake-like instrument.

[0011] Fig. 2 is a system for assisting in the control of the snake robot.

[0012] Fig. 3 is a photograph of ahighly articulated robotic probe .

[0013] Fig. 4 is a diagram of a concentric tube robot.

[0014] Fig. 5 is a photograph of a hybrid robot device.

[0015] Fig. 6 is a diagram showing concentric tubes.

[0016] Fig. 7 is a diagram showing curvature of a hybrid snake device.

[0017] Fig. 8 is a photograph of an exemplary test setup.

[0018] Fig. 9 are photographs of test results using the exemplary test setup.

[0019] Fig. 10 is a graph showing test results.

[0020] Fig. 11 is a graph showing test results. [0021] Fig. 12 is an example two-tube drive system.

DETAILED DESCRIPTION

[0022] Described herein is a snake-like robot for use in less invasive therapies such as natural orifice transluminal endoscopic surgery (NOTES) and single port access (SPA) surgery. The surgical tasks of NOTES and SPA can include two components: highly dynamic tasks such as suturing, dissection, and ablation that require the ability to control both the position and orientation of the instrument tip; and tasks such as tissue retraction that requires a high tip force and the ability to control the position of the instrument tip. These latter tasks are often performed with rigid or semi rigid instruments. The current subject matter can accomplish both groups of tasks.

[0023] FIG. 1 is an illustration of a hybrid snake-like instrument 100. The instrument includes a steerable sheath 110 and one or more flexible arms 120 that can be inserted inside the sheath. Additional tools, such as a camera, can also be inserted inside the sheath. The sheath 110 includes tubular bead chains that can be strung on cables. A tubular bead chain is a type of chain comprising of small tubular elements or links connected via lengths of cable. The links can be hollow and have two antipodal openings. The links and cable can be made of any suitable material, such as, but not limited to, steel. Multiple links can be connected to one or more cables to form a chain. Tension applied to the cable can cause the chain to change stiffness and position.

[0024] When the cables are loose, the sheath 110 is relaxed and can conform to any path. Locking the cables makes the sheath 110 stiff and stable. Each flexible arm 120 can include two or more superelastic tubes that nest within each other in a telescoping fashion, which enables control of the instrument's tip stiffness and dexterity. Additionally, small tools can be used at the tip of the arms for performing surgical tasks such as grasping, dissecting, penetrating, cutting, and ablating tissue.

[0025] FIG. 2 is a system for assisting in the control of the snake robot 100. A control system 220 can send instructions to a drive system 230, which places tension on the sheath 110 cables thereby automatically controlling articulation of the snake robot 100. Control feedback 240, such as sensors, can provide the control system 220 with information related to the state of the snake robot 100. User input 210 can be provided to the control system 220.

[0026] The snake robot 100 can be made of a highly articulated robotic probe

("HARP") and a concentric tube robot. The HARP operates as a stiff shield for the concentric tube robot. The snake robot can provide simultaneously high tip stiffness and dexterity that cannot be obtained by the single use of any of two robots. Elements of the design permit a variety of curves of the device such as a small radius of curvature for the hybrid snake robot 100. For various applications and embodiments, the minimum achievable radius of curvature can be computed. Snake-like robots with high tip dexterity and stiffness can assist surgeons to operate in confined spaces in a similar way that dexterous rigid robots assist them to perform multi-port surgery. Other configurations are possible.

[0027] In some embodiments, the control system 220 can control all cables of the sheath 110 along with translation and rotations of the tubes 120. The control system 220 can be, for example, a computer system. User input 210 can be provided for a surgeon to control/guide the snake robot 100, for example, a joystick or other interface can be used. The drive system 230 can include motors and sensors that enable translation and rotation of the tubes 120 as well as locking/relaxing and translation of the bead chains of the sheath 110. Additionally, control and planner algorithms can provide commands for the drive system 230.

[0028] In some embodiments, the drive system 230 can assemble and reassemble to drive any combination of sheath 110 and tubes 120. As an example, a concept sketch for a two- tube drive system suitable for the prototypes shown in FIG. 12. Each tube 120 can be mounted on a metal stand that holds the motor that rotates the tube 120. The metal stand can mount on a rail a motor can control its linear motion. For each bead chain of the sheath 110, a similar metal stand can be used for linear motion. A motor can be used to control the tension of the bead chain cables.

[0029] In some embodiments, the motors can be sized based on the force and torque required. A computer can be programmed to control tube 120 displacements and rotations. The computer can output commands and read motor encoders via a multifunction data acquisition board.

[0030] In some embodiments, there can be a "two state" control for the hybrid snake robot 100. The control system 230, at its "first state," can bring the sheath 110 to the targeted position. At the second state, it can control the position of the tip of the tube 120 (e.g., steerable cannula). A phantom haptic device (Sensible Inc. MA) can operate the sheath 110, using the "follow-the-leader" approach (described, for example, in Degani A., Choset H., A. Wolf, and M. Zenati, Highly Articulated robotic probe for Minimally Invasive Surgery, Proc. 2006 IEEE International Conference on Robotics & Automation, Orlando, USA, May 2006). After the sheath 110 reaches the intended configuration, the sheath 110 can lock at a position and then the phantom device can control the position of the tube 120 tip (e.g., steerable cannula tip). Tip position controllers can also be provided to control tip configuration of the arms of the hybrid snake robot 100.

[0031] In some embodiments, a path planner can coordinate the internal degrees of freedom of the hybrid snake robot 100 to produce desired motions. The path planer removes any requirements on the physician to control each joint in the hybrid snake robot 100. Path planners can be developed from the kinematic models described herein (implemented, for example, in control system 220 using software). The path planer can allow the physician to specify high-level directives that a computer can computationally perform thereby allowing the physician to focus on important high-level decisions.

[0032] The device can be suitable for single-port access, e.g., through natural orifices and/or lumens or by subxiphoid access. Single port access surgery can be beneficial for many reasons. In single port surgery, the targeted surgical sites are typically accessed through only one port of entry such as natural orifices or subxiphoid. Single port surgery usually leaves little or no scarring and can reduce complications that occur after traditional open and even traditional endoscopic multi-port surgery. The snake robot preferably comprises multiple internal degrees of freedom that allow the device to thread through tightly packed volumes and access anatomical targets that conventional tools cannot.

[0033] In addition, the robotic devices and systems described herein can preferably be used to perform complex single port procedures on target areas located deep inside the body. For example, the articulated robot can be suitable for epicardial intervention, and can be capable of accessing internal recesses and complex tissue manipulation such as in and around a beating heart. The hybrid snake robot 100 does not require a large body cavity in which to operate and can be deployed inside "virtual" spaces (e.g. normal "dry" pericardial sac) without adversely affecting hemodynamic or causing collateral damage to surrounding mediastinal structures. Additionally, there are several complex tissue manipulation tasks (e.g. deforming, dissecting, and retracting) that can be performed with the robotic instruments described herein that include enhanced tip dexterity and tip stiffness. Configurations of the devices described herein are also suitable for manipulations in and around other challenging anatomical structures (e.g. hilum of the lung, mediastinum, abdominal mesentery, etc.) where serous membranes (epicardium, pleura or peritoneum) fold over neurovascular and airway structures.

[0034] Additionally, the devices and instruments described herein can also be used in an intra-vascular manner (i.e., not just limited to natural spaces). For example, the hybrid snake robot 100 can be configured as a very sophisticated catheter that can be introduced peripherally into the bloodstream to reach hard-to-access branches of the vasculature (e.g., the mesenterial artery branch of the aorta) during complex stent-grafting or during complex intra-cardiac interventions.

[0035] Figure 3 shows an example of the highly articulated robotic probe (HARP). The robotic probe is preferably made of two mechanisms: an inner mechanism and an outer mechanism. Though, configurations of a HARP used in the hybrid snake robot 100 can include only the inner mechanism, or the outer mechanism (both mechanisms are not required). Each mechanism is preferably composed of several rigid tubular links connected with cables (e.g., cables of braided stainless steel or Aramid cables). When the cables of the mechanisms are tightened, the mechanisms become stiff. The HARP can follow a tortuous path in three dimensions with making one mechanism stiff and extending the other mechanism, which is limp, along the stiff one, and then alternating the process (e.g., a follow-the-leader configuration). The HARP also preferably includes one or more motors attached to the cables that are configured to tighten the cables of the mechanisms to control the stiffness. Preferably, the motors of the HARP and its cables are designed such that they can provide required tension. Details about the HARP can be found in U.S. Patent Pub. No. 2009/0171151, which is incorporated by reference herein in its entirety.

[0036] Figure 4 shows an embodiment of a concentric tube robot or flexible arm 120 (also called a steerable cannula) which is constructed from telescopically extending

concentrically combined precurved superelastic tubes. The robot's shape and tip location can be controlled by rotating and translating the tubes at their proximal ends. The HARP can typically take any shape but it has a limited tip dexterity. The concentric tube robot is flexible by design but can provide tip dexterity. Details about the concentric tube robot can be found in U.S. Patent Pub. No. 2009/0171271, and U.S. Pat. No. 7,883,475, both of which are incorporated by reference herein in their entirety. [0037] Preferably the HARP operates as a stiff sheath for the concentric tube robot so it significantly increases the tip stiffness of the concentric tube robot. The hybrid snake robot 100 preferably provides the ability to follow a preplanned arbitrary three dimensional curve and also preferably provides the ability to perform dexterous contact tasks inside complex surgical environments. Surgical instruments (e.g., a camera, forceps, probes, etc.) can be provided alongside the concentric tube within the HARP, or within the concentric tube itself.

Additionally, the tip of the concentric tube itself can be configured as a surgical instrument.

[0038] Referring to Figures 5-6, the hybrid snake robot 100 preferably includes a robotic probe and a set of pre-curved Ni-Ti tubes. The tubes are preferably mounted in the space between the inner mechanism and the outer mechanism of the probe inside a narrow channel (in an embodiment where both mechanisms are used). In one exemplary configuration, two pre- curved tubes of the same length, initial curve, and bending stiffness are used for the hybrid snake robot 100. The tubes are preferably composed of two segments: 1) a long straight segment that is longer than the length of the HARP, and 2) a short curved section (preferably having a constant curve) that is long enough to provide sufficient tip displacement for the intended task. The outer and inner diameters of both tubes are preferably selected such that they can be inserted inside each other and the combination can be inserted inside of a port of the HARP. The combination of the two tubes is referred to herein as a combined tube. The tubes can be curved to a desired shape by fixing the tube to a desired shape, heating the tubes in a high-temperature oven, and water quenching the tubes.

[0039] By rotating two tubes with respect to each other, the curvature of the curved segment of the combined tube can vary from zero (e.g., a straight configuration) to a maximum curvature. When the combined tube is inserted into the HARP, the straight portion preferably takes the shape of the robotic probe. The combined tube can also extend and rotate inside the robotic probe and the orientation of its distal portion can preferably be changed by the last link of the HARP. Two or three concentric tubes can generally provide tip dexterity required for many intended surgical tasks. A hybrid snake robot 100 can use less tubes than a concentric tube robot for reaching the same curved confined spaces and providing the same level of tip dexterity. Preferably the hybrid snake robot 100, using the combined tube, is strong enough to achieve the desired radius of the curvature. [0040] In some configurations, the tubes of steerable cannula twist when they are rotated inside each other; for long tubes, this may cause unstable motions, such as jerking of the tubes. This behavior can be mitigated by avoiding tube rotation. In such a case, the tubes can glide forwards and backwards within themselves. In order to have a 3D workspace, the sheath 110 can change the orientation of the entire proximal end of the flexible arm 120. The change in the orientation of the plane of the flexible arm 120 by the sheath 110 can enable the tip to maneuver in 3D.

[0041] Preferably the HARP is rigid enough to accept a concentric tube robot, which may include increasing the stiffness of the HARP. The strength of the HARP should be high enough to be able to sustain the bending moment M caused by the concentric tube robot. The bending moment caused by a straight concentric tube robot when it is deformed to the radius of curvature R is M = 0.26E(D I R)T where E is the Young's modulus of the tubes of the concentric tube robot, D is the nominal diameter of the steerable cannula, and T is the thickness of cannula. The maximum moment that the HARP can withstand is M = γμΈ_ε where F_c is the cable tension, μ is the friction coefficient of the joint of the HARP and r is the radius of the HARP joint. As a result, the HARP can sustain the cannula moment if r/ _c > 0.26E(D I R)T. If desired, the stiffness of the HARP can be increased by increasing the size of the motors in the HARP such that more tension can be applied to the cables, by fabricating the links using materials having an appropriate coefficient of friction (e.g., Aluminum), and/or increasing the diameter of the links.

[0042] A kinematic model can preferably be used in order to precisely control the position and/or the stiffness of the tip of the hybrid snake robot 100. The kinematic model can be use to calculate the mapping between the tip configuration of the snake and the rotational angles of the motors of the snake. Using the kinematic model, software can be used to allow a physician to specify high-level directives and have a computer perform the necessary

computations to carry out these objectives.

[0043] A kinematic model of the hybrid snake robot 100 can be described as the product of kinematic models of the probe and the concentric tube robot. The configuration of the tip of hybrid snake robot 100 relative to a reference frame, can be written as the product of two transformations:

§h— SpShp (1) [0044] where gh is a rigid body transformation of the tip of the hybrid snake robot 100, g_p is the transformation of the tip of the probe, and gh_p is the transformation of the tip of the concentric tubes in respect to the tip of the probe. g_p depends on all joint angles of the probe. gh_p depends on rotational angles and insertion length of the tubes. The kinematic model of the hybrid snake robot 100 can be obtained by combining available kinematics models for concentric tube robots and the articulated probe as given in (1).

[0045] A superelastic composition, e.g., a Ni-Ti material (such as that produced by Ni-Ti Tubes Inc, of Freemont, California) can be used to create concentric tubes having a small radius of curvature. Ni-Ti tubes can have recoverable strains of more than 8%. With this recoverable strain, a Ni-Ti tube of 2 mm diameter can typically take a minimum radius of curvature of 1.25cm. This radius is small enough for many intended surgical applications, although other minimum radiuses are possible. Other materials with superelastic properties including metal alloys such as copper-zinc-aluminum (Cu-Zn-Al), copper-zinc-aluminum-nickel (Cu-Zn-Al-Ni), and ferrous superelastic alloys such as iron-nickel-cobalt-titanium (Cu-Ni-Co-Ti) and iron-nickel-cobalt-aluminum-tantalum (Fe-Ni-Co-Al-Ta) can be useful for the tubing material. An example of the latter alloy is Fe-28Ni-1711.5Al-2.5Ta-0.05B [atomic percent (at.%); known as "NCATB" and described in Tanaka et al., 2010, Science 327: 1488-1490]. Non-metal compositions with superelastic properties (Philips Inc.) are also useful. While the foregoing has been described with respect to superelastic materials, other materials that are not superelastic can also be used in certain configurations.

[0046] The maximum achievable curvature of the hybrid snake robot 100 can be modeled by a mechanic model that relates the maximum achievable curvature to the tension of its cables. When concentric tubes are mounted into the robotic probe, each mechanism of the robotic probe is preferably strong enough to curve the tubes. The total cable tension of a mechanism used to keep a tube or tubes on a small radius of curvature can be calculated. First, the following assumptions are made: 1) the weight of the Ni-Ti tubes and the mechanism are ignorable, 2) the concentric tubes pass along the center line of each mechanism, and 3) there is no clearance between the tubes and the channel of the mechanism that houses the tubes. Each probe mechanism can sustain a limited torque at its joints. The maximum torque that a joint of the mechanism can sustain is: (2) where μ is the friction constant between joint surfaces, F_c is the cable tension, and r is the radius of the joint.

[0047] Considering a section of the mechanism that extends from s = a to s = L (e.g., Figure 7), when the mechanism deforms the tubes from the initial curvature u(s) to a new curvature u(s), a bending moment, m(s), is generated. Assuming linear e/astic be/zavior for the tubes, the bending moment at point a along the tubes is given as: m(a) = K(a)(u(a) - u(a)) (3) where K(a) is the frame-invariant stiffness tensor. For the tubes, K(a) is given by

where E_x(a), E_y(a) are moduli of elasticity, I_x(a) and I_y(a) are area moments of inertia, J_p(a) is the polar moment of inertia and G(a) is the shear modulus.

[0048] As shown in Figure 7, the concentric tubes apply a combination of distributed forces η(*) and moments <P(s) along their length to the mechanism. The bending moment m(a) at point a of the tubes is defined as: m t) - / η($) x r(s) ~r ${$))d$ (5) where r(s) is a vector that defines the point s of the tubes in a local frame at point a. This bending moment is equal to the torque applied to the mechanism at point a due to the

forces η(*) and moments <P(s). [0049] Now considering a tube (or tubes) with a constant curvature 1/R and curvature vector u(s) = [1/R 0 0]. The bending moment for the tube is calculated by (3) and (4) as: m(a) = [EI/R 0 0] (6)

Where a is the center of a spherical joint of the mechanism then this joint can hold the tubes at the radius of curvature R if

¾at > ®n {e ⁾ -— (?)

A

The minimum radius of curvature that the mechanism can create is then obtained as:

This shows a linear relation between the maximum curvature of the mechanism and the applied cable tension.

[0050] A series of experiments were performed to validate the models (2) and (8). Seven tubular links of the inner mechanism of the robotic probe were used to perform the experiments as shown in Figure 8. The tubular links were connected with a cable that goes through the center of the links. The mechanism was mounted on a piece of wood and gravity loading is used to create cable tension F_c. The total length of the mechanism was 4cm.

[0051] First Experiment: The first experiment was to validate the linear relation between the maximum joint torque and the cable tension (2). No Ni-Ti Tube was used during this test. The mechanism was set to a straight configuration and gravity loading was used. For each load, a force was applied to the tip of the mechanism perpendicular to straight configuration of the mechanism until the first proximal joint of the mechanism started to move. The applied force was measured by a 22-N tension/compression load cell (Sensotec model 31). The applied torque to the joint is the product of measured normal force and the length of the mechanism. Figure 9 includes several pictures of measured curvatures. Three top pictures are for tube 1 and tensions of 9.16 N, 18.32N, and 36.64 N, respectively. Three bottom pictures are for the combination of tubes 1 and 2 and tensions of 18.32 N, 45.8N, and 73.28 N, respectively. Figure 10 compares the measurement results and the outputs of the model (2) obtained for r = 3mm and μ = 0.42.

[0052] Second Experiment: The second experiment is to validate the relation between the minimum radius of curvature and the cable tension (8). Each link of the mechanism had three grooves. The tubes were located inside one of the grooves. Then, these grooves were covered with a piece of tape such that the Ni-Ti Tubes would not slip out of the grooves. During these experiments, two Ni-Ti tubes were used with these stiffness tube(l): 0.00137 N.m and tube(2): 0.00116 N.m . During each test, the mechanism was first set to a straight configuration and gravity loading was used. For each load, then, the mechanism was bent manually to a maximum curvature allowable by the applied cable tension. For each load, the final shape of the mechanism was captured by a camera (Figure 9). A circle was fitted to the picture of the mechanism in each test and the angle of the portion of the circle in contact with the mechanism was measured. The radius of the curvature of each mechanism is the length of the mechanism divided by the measured angle. Figure 8 compares the measurement results and the outputs of the model (8) obtained for r = 3mm and m = 0.42 both tube 1 and the combination of tube 1 and 2. Figure 11 shows additional results.

[0053] Additionally advanced path planners and tip controllers can be used to exploit the unique abilities of the hybrid snake robot 100. Preferably the path planners and tip controllers will allow safe navigation of the robot inside pericardium space while the robot tip can be in contact. The novelty of this approach can be a function of the controller's ability to modulate tip stiffness of the robot so low tip stiffness can be obtained while navigating near delicate tissues and a high stiffness during blunt dissection. Preferably these capabilities are exploited to coordinate both mechanisms, the HARP and the steerable cannula, as if they are one.

[0054] There are several challenges associated with the development of the hybrid snake robot 100 and its controllers. One concern with is the potential complexity due to the length of its steerable cannula. As the length of the steerable cannula increases, the torsional twist of the concentric tubes can increase and other potential phenomena can affect the kinematic mapping of the steerable cannula. A second concern is the desired strength for the HARP to bend the combined tube. To address these concerns, optional multi-segment pre-curved tubes where each segment has different material properties. Additionally, materials can be used that have a low bending stiffness and high torsional stiffness for portions of the tubes which are inside the articulated probe and use a material with a high bending stiffness for the portion which is outside of the HARP. Functional approximation for building kinematics mapping that allows computationally expensive model to be implemented can be used. A third concern is the instability and oscillation that can be caused due to the use of tip sensors in closed loop controllers. In order to reduce and even prevent possible instability and oscillations, aggressive analytical methods based on passivity theory and absolute stability theory can be used to ensure the stability of hybrid snake robot 100 in worst case scenarios.

[0055] Other embodiments are within the scope and spirit of the invention. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

[0056] What is claimed is:

Claims

1. A device comprising:

a highly articulated robotic probe comprising one or more tubular bead chains, each bead chain comprising a plurality of links connected by at least one cable; and

a concentric tube robot comprising a set of pre-curved concentric tubes disposed within at least one of the tubular bead chains, wherein the concentric tube robot and the highly articulated robotic probe are motorized.

2. The device of claim 1, wherein the device is configured for use in a single port access.

3. The device of claim 1, wherein one tubular bead chain is used as a sheath for the concentric tube robot.

4. The device of claim 1, wherein the highly articulated robotic probe comprises two tubular bead chains, the two tubular bead chains being an inner tubular bead chain mechanism and an outer tubular bead chain mechanism.

5. The device of claim 1, wherein the concentric tube robot is used to articulate the one or more tubular bead chains.

6. The device of claim 1, wherein one of the tubular bead chains is strung with three cables such that applying tensions to the cables causes an articulation of the bead chain.

7. The device of claim 1 wherein the concentric tube robot includes a telescopically extending set of precurved elastic tubes.

8. The device of claim 7 wherein each of the elastic tubes include a substantially straight section and a curved section.

9. The device of claim 1 wherein a tip of the concentric tube robot can be controlled by rotating the tubes at their proximal ends.

10. The device of claim 1 wherein a stiffness of the highly articulated robotic probe is greater than the concentric tube robot.

11. The device of claim 1 , further comprising:

a control system including a control processor and control driver for controlling at least one of the highly articulated robotic probe and the concentric tube robot.

12. The device of claim 1, wherein the tube robot comprises a steerable cannula, the device further comprising:

a tool at the tip of the steerable cannula to perform one or more surgical tasks of:

grasping, dissecting, penetrating, cutting, and ablating tissue.

13. A method for minimally- invasive robotic surgery of a living subject, comprising performing a medical procedure on said subject using the device of claim 1.

14. The method of claim 13 wherein the device of claim 1 is used in an intra-vascular manner.

15. The method of claim 13 wherein the device of claim 1 is introduced peripherally into the bloodstream of a patient.

16. The method of claim 13 wherein the device of claim 1 is used to perform a natural orifice transluminal endoscopic surgery.

17. A system comprising:

a steerable sheath comprising a plurality of tubular bead chains strung on one or more cables; and

one or more flexible arms inserted inside the sheath.

18. The system of claim 15, wherein a low tension on the cables causes the sheath to be flexible and a high tension on the cables causes the sheath to be stiff.

19. The system of claim 15, wherein each of the one or more flexible arms comprise two or more tubes nested within each other such that rotation and translation of proximal ends of the tubes articulates the corresponding flexible arm.

20. The system of claim 15, further comprising:

a control system; and

a drive system including motors and sensors configured to place tension on the cables thereby articulating the steerable sheath and configured to rotate and translate proximal ends of the one or more flexible arms thereby articulating the one or more flexible arms;

wherein the control system sends instructions to the drive system to control the articulation.

21. The system of claim 18, wherein the control system includes a path planer.