Actively controlled steerable medical device with passive bending modes

Abstract

Apparatus, methods, and systems for a steerable medical instrument configured for use with guided tools and devices, such as endoscopes, cameras, resection tools, catheters, and the like, in robotic medical procedures. In one embodiment, the steerable instrument includes an elongated body (100), a control wire (110) disposed within a channel (104) of the elongated body and displaceable along the channel to bend the elongated body, and a controller (320) selectively controlling an actuation force applied to the control wire (110) under active and passive control modes. In the active control mode, the controller actively bends at least a portion of the elongated body. In the passive control mode, the controller (320) reduces the amount of strain or displacement of the control wire so that the control wire adapts to an external force.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 855,354, filed May 31, 2019, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates generally to robotic medical devices. More specifically, the present disclosure illustrates various embodiments of articulated, steerable medical devices with controllable stiffness that are applicable for guiding interventional tools and instruments, such as robotic endoscopes and catheters, through tortuous paths within lumens. [Background technology]

[0003] Bendable medical instruments, such as endoscopic surgical instruments and catheters, are well known and continue to gain acceptance in the medical field. Such bendable medical instruments generally include an elongated flexible tube, commonly referred to as a sleeve or sheath, having an opening extending from a proximal end to a distal end. One or more tool channels extend along (typically internally) the sheath, allowing access to an end effector located at the distal end of the sheath. Endoscopes can provide imaging, illumination and steering capabilities at the distal end of the flexible shaft, allowing navigation of non-linear lumens and tortuous paths within the human body. This type of medical instrument is meant to provide flexible access with at least one or more curves to access a target lesion area while maintaining torsional and longitudinal rigidity so that a physician can control an end effector located at the distal end by manipulating the proximal end of the instrument.

[0004] In minimally invasive surgery (MIS) and transluminal endoscopic surgery (NOTES), which primarily use steerable medical endoscopic tools to access difficult-to-reach target lesion areas, several requirements for medical device design are (1) to minimize the outer size (outer diameter) of the bendable medical device, (2) to maximize the size (inner diameter) of the tool channel opening, and (3) to provide adequate flexibility (or stiffness) to navigate tortuous paths without causing pain or discomfort to the patient. Thus, to optimize size, the bendable medical device should preferably include a sheath with a minimal wall thickness, and to minimize patient discomfort, the bendable medical device should preferably have a minimal overall outer diameter. At the same time, such thin and delicate bendable medical devices should provide sufficient stiffness and flexibility to be steerable for multiple directional movements, such as insertion and withdrawal in the direction of their longitudinal axis, rotation around the longitudinal axis (axial rotation), and radial bending in multiple directions and / or in multiple sections of the device. Recently, robotic instruments with controlled stiffness and navigation have emerged to improve the maneuverability of steerable medical instruments along tortuous paths within a lumen. In known robotic instruments, different techniques have been disclosed in patent and non-patent literature to locally bend and create curves in the distal part of the steerable instrument.

[0005] As an example, U.S. Pregrant Patent Application Publication No. 20160067450 describes a flexible device with nested conduits that provides multiple conduits to hold the shape of the proximal portion while a driving tendon bends the distal portion of the bendable medical device. The multiple conduits are dually controlled with the proximal ends of the conduits constrained and unconstrained. By selecting a constrained conduit, the bendable medical device can vary the length to which the distal segment is bent by varying the stiffness of the bendable medical device based on the area in which the conduits are deployed.

[0006] US Pre-grant Patent Publication No. 20100280449 discloses a steerable instrument with multiple independent sections that allow for decoupling of actuation forces from portions of the steerable section to allow the control section to conform to the curves of the path during insertion of the medical device. US 20100280449 discloses a steerable instrument with a "first portion" that is a steerable catheter and a "second portion" that is a steerable sheath. Each portion is independently controlled and can be decoupled from articulation or steering forces to allow each portion to conform to the path. The first portion can then be actuated again and inserted through the second portion around the curves of the second portion. This document focuses on decoupling of articulation or steering forces at selected portions during insertion of the steerable instrument through the lung airways.

[0007] US Pre-grant Patent Publication No. 20140276594 discloses a robotic surgery system in which a steerable instrument is controlled by a control wire. The control wire is actuated by a pulley, and the torque on the pulley is measured by a torque sensor. The torque on the pulley is converted to tension on the control wire. In this document, the control wire can only be pulled on the pulley, so only tension can be sensed (i.e., pushing the control wire against the pulley will cause the control wire to unwind from the pulley). US Patent No. 8,644,988 discloses a steerable medical instrument that uses force and feedback control to steer the medical instrument, such as a catheter, with non-negligible compatibility (i.e., no slack) between the distal joint positioning and the proximal actuator.

[0008] The non-patent publications “Flexible Medical Devices: Review of Controllable Stiffness Solutions” by Blanc et al. (Actuators 2017, 6, 23; doi:10.3390 / act6030023) and “Scopes Too Flexible… and Too Stiff” by Loeve et al. (Article published in IEEE Pulse, January 2011, DOI:10.1109 / MPUL.2010.939176) both describe numerous design challenges and proposed solutions for providing steerable medical devices with controllable flexibility and / or stiffness.

[0009] However, the general state of the art (particularly the exemplary documents listed above) does not address certain situations in a typical workflow or procedure where a certain level of flexibility in a steerable instrument is desired when needed. More specifically, the known prior documents do not disclose a steerable instrument with a passive bending mode of active control where there is zero tension on the control wires, which may be desirable in certain situations. Summary of the Invention

[0010] According to at least one embodiment of the present disclosure, a steerable medical instrument with a passive bending mode of active control is provided. According to one aspect of the present disclosure, the steerable medical instrument includes: an elongate body having a longitudinal axis, a proximal end, a distal end, and a plurality of channels disposed along the elongate body, the elongate body having a non-bendable section and at least one bendable section; a control wire disposed within the channel of the elongate body and extending through the non-bendable section and the at least one bendable section, the control wire being secured to a distal end of the at least one bendable section and configured to be slidable along the channel to bend the elongate body at an angle relative to the longitudinal axis; a drive unit operably connected to the control wire at its proximal end; a sensor configured to output a signal indicative of an amount of strain applied to the control wire or an amount of distance displacement of the control wire; and a controller configured to cause the drive unit to selectively apply a drive force to the control wire in one of an active control mode and a passive control mode. In an active control mode, the controller uses the command signal to cause the drive unit to apply a driving force to bend the elongated body to follow a serpentine path, and in a passive control mode, the controller uses the signal output from the sensor to cause the drive unit to reduce the amount of strain applied to the control wire or reduce the amount of distance displacement of the control wire.

[0011] According to another aspect of the present disclosure, a steerable medical device comprises: an elongate body (100) having a non-bendable section (102) and at least one bendable section (103), the elongate body including a plurality of channels (104, 105) extending from a proximal end to a distal end of the elongate body (100) along a longitudinal axis (Ax); a control wire (110) disposed within a first channel (104) of the elongate body (102), the control wire (110) extending through the non-bendable section and the at least one bendable section and attached to the at least one bendable section. 0); a sensor (221, 231) configured to measure the amount of strain or displacement of the control wire (110); an actuator (310) mechanically coupled to the control wire (110), the actuator (310) configured to actuate at least one bendable section (103) of the elongated body (100) by applying a driving force to the control wire; and a controller (320) configured to control the operation of the actuator (310) according to an active control mode and a passive control mode based on an external force other than the driving force applied to the control wire.

[0012] According to various aspects of the present disclosure, steerable medical devices are significantly improved by providing a passive bending mode of active control, whereby: (1) the force on the control wires is zero when maximum flexibility of the steerable instrument is required; (2) the force and displacement of the control wire 110 is continuously monitored regardless of the control mode employed; (3) friction in the steerable instrument is minimized even when navigating a serpentine path; and (4) the proximal ends of the control wires are allowed to translate freely while remaining actively connected to their corresponding actuators.

[0013] These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments of the present disclosure, which should be read in conjunction with the accompanying drawings and the appended claims. [Brief description of the drawings]

[0014] Further objects, features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings illustrating exemplary embodiments of the present disclosure.

[0015] [Figure 1] FIG 1A illustrates an exemplary embodiment of a continuum robotic system 1000 applicable for catheter-assisted or endoscope-assisted minimally invasive surgery (MIS) using passive bending modes of active control. FIG 1B illustrates in more detail a steerable instrument 100 having an elongated flexible shaft (elongated body) and multiple channels or openings extending from its proximal end to its distal end. [Diagram 2] Figure 2A is a perspective view of an example steerable instrument 100 with two curved sections. Figure 2B is a perspective view of an exemplary guide member with through holes for guiding control wires. Figure 2C illustrates an example of bending or steering a single curved section 106 of the steerable instrument 100. [Diagram 3] FIG. 3 illustrates an exemplary embodiment of a passive bending mode of active control, referred to herein as a "force control loop" implementation. [Figure 4] FIG. 4 illustrates an example embodiment of a passive bending mode of active control of a steerable instrument 100, referred to herein as a “frictionless direct drive” implementation. [Diagram 5] 5A and 5B show an example embodiment of a frictionless direct drive configuration implemented by an induction motor with frictionless bearings. [Figure 6] 6A, 6B and 6C are diagrams illustrating another exemplary implementation of a frictionless direct drive configuration implemented by an ultrasonic motor. [Figure 7] 7A is an example block diagram of a control system 1500 configured to implement a passive bending mode of active control of a steerable medical instrument 100 according to the present disclosure, and FIG 7B is a functional block diagram of a computer 1600 that operates or may be part of a motor controller 1504 of the control system 1500. [Figure 8] FIG. 8 is an example flow chart for implementing a passive bending mode of active control of a steerable medical device 100 with a feedback force control loop. [Figure 9] FIG. 9 is an example flow chart for implementing a passive bending mode of active control of a steerable medical device 100 with a frictionless direct drive. [Figure 10] 10A is an example flow chart for implementing an algorithm to cause the drive unit to reduce the amount of strain or compression applied to the control wire or reduce the amount of distance displacement of the control wire so that the control wire conforms to an external force by reducing the force on the control wire to zero when maximum flexibility is required for the steerable instrument. FIG. 10B illustrates an example process of a user-initiated control scenario for operating the steerable instrument 100 under active and passive control modes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The embodiments disclosed herein are described in detail with reference to the accompanying drawings. While the drawings represent several possible configurations and approaches, the drawings are not necessarily to scale, and certain features may be exaggerated, omitted, or partially cut away in order to more clearly illustrate and explain certain aspects of the present disclosure. The description set forth herein is not intended to be exhaustive or otherwise limit or restrict the scope of the claims to the exact forms and configurations shown in the drawings and disclosed in the following detailed description.

[0017] Throughout the figures, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components or portions of the illustrated embodiments. Moreover, while the present disclosure will now be described in detail with reference to the figures, it is done so in connection with the illustrated embodiments. It is intended that changes and modifications can be made to the illustrated exemplary embodiments without departing from the true scope and spirit of the present disclosure as defined by the appended claims.

[0018] In this specification, when a feature or element is referred to as being "on" another feature or element, it may be directly on the other feature or element, or intervening features and / or elements may also be present. In contrast, when a feature or element is referred to as being "directly on" another feature or element, there are no intervening features or elements present. It should also be understood that when a feature or element is referred to as being "connected," "attached," "coupled," or the like, to another feature or element, it may be directly connected, attached, or coupled to the other feature, or there may be intervening features or elements present. In contrast, when a feature or element is referred to as being "directly connected," "directly attached," or "directly coupled" to another feature or element, there are no intervening features or elements present. Although described or illustrated with respect to one embodiment, features and elements so described or illustrated in one embodiment may be applicable to other embodiments. Additionally, as will be understood by one of ordinary skill in the art, a reference to a structure or feature being located "adjacent" another feature may have portions that overlap or underlie the adjacent feature.

[0019] The present disclosure relates generally to medical devices and illustrates various embodiments of articulated, steerable medical devices with controllable stiffness that may be applied to guide interventional tools and instruments (such as endoscopes and catheters) through tortuous paths within lumens. Although embodiments of the present disclosure may be configured as part of a robotic system, those skilled in the art will appreciate that the steerable instruments disclosed herein may be utilized in similar applications that do not require a robotic system.

[0020] Embodiments of steerable medical instruments and portions thereof are described with respect to their state in three-dimensional space. As used herein, the term "position" refers to the position of an object or portion of an object in three-dimensional space (e.g., three translational degrees of freedom along Cartesian X, Y, Z coordinates), the term "orientation" refers to the rotational configuration of an object or portion of an object (three rotational degrees of freedom - e.g., roll, pitch, yaw), the term "pose" refers to the position of an object or portion of an object in at least one translational degree of freedom and the orientation of an object or portion of an object in at least one rotational degree of freedom (up to six degrees of freedom in total), and the term "shape" refers to a set of poses, positions and / or orientations measured along the elongate body of an object.

[0021] As is known in the medical device art, the terms "proximal" and "distal" are used herein in reference to the operating ends of an instrument that extend from a user to a surgical or diagnostic site. In this regard, the term "proximal" refers to the portion of the instrument closer to the user and the term "distal" refers to the portion of the instrument away from the user and closer to the surgical or diagnostic site.

[0022] <Configuration of steerable medical device> FIG. 1A illustrates an overall structure of a continuum robot system 1000 including a computer system 400 (e.g., a console), a robotic control system 300, and a steerable instrument 100 connected to the control system 300 via a handle interface 200, according to one embodiment of the present disclosure. The steerable instrument 100 has a proximal non-steerable section 102 and a steerable section 103 consisting of multiple curved sections applicable for minimally invasive medical procedures using a catheter or an endoscope. Specifically, FIG. 1A illustrates a robotically controlled steerable instrument 100 having a steerable section 103 divided into multiple curved segments or sections (1, 2, 3, ... N) arranged along a longitudinal axis Ax, and configured to bend at least one of the steerable sections at an angle β with respect to the longitudinal axis Ax.

[0023] The steerable instrument 100 is controlled by an operating system consisting of a handle interface 200 and a control system 300. The control system 300 generally includes a controller or is connected to a computer system 400 along with appropriate software, firmware and peripheral hardware (described below) operated by a processor or central processing unit (CPU) 410. Among other functions, the control system 300 and computer system 400 may provide a visual display 420 and a graphical user interface (GUI) 422 for a surgeon or other operator to interact with and operate the steerable instrument 100. The handle interface 200 provides electromechanical interconnections between the steerable instrument 100 and the control system 300. For example, the handle interface 200 may provide mechanical, electrical and / or optical connections as well as a data / digital acquisition (DAQ) system for interfacing the steerable instrument 100 with the control system 300. The handle interface 200 may also provide an access port 250 for inserting a medical tool, one or more mechanical dials or knobs 252 that an operator can use to manually control the operation of the end effector and / or steering of the instrument, and a user interface 254 having one or more control buttons and status indicators.

[0024] As part of the user interface 254, the handle 200 may include LEDs to provide the user with the operational status of the robotic steerable instrument 100. In one embodiment, the LEDs may include different light colors to indicate, for example, normal operation (green light) and abnormal operation (red light), respectively. Alternatively, the LEDs may include a flashing code, for example, to indicate some type of abnormal operation. Additionally, the user interface 254 may include an emergency on / off switch to manually deactivate the steerable instrument in the event of an emergency.

[0025] FIG. 1B shows in more detail the steerable instrument 100 having an elongated flexible shaft (elongated body) commonly referred to as a sleeve or sheath. The sheet is formed of a non-steerable section 102 and a steerable section 103 consisting of multiple curved segments. Along the longitudinal axis Ax of the steerable instrument 100, one or more channels or openings extend from the proximal end to the distal end. Among the openings or channels, the sheath may include one or more tool channels 105 that extend along (typically inwardly) the wall of the sheath and multiple wire conduits 104 that extend along (typically within) the wall of the sheath. The one or more tool channels 105 allow access to an end effector delivered and positioned at the distal end of the steerable section 103. The one or more channels 105 may also be used to deliver or retrieve liquid or gaseous substances (e.g., air or water) to or from a target area or to pass optical fibers and / or electrical wires. Additionally, one or more of the channels 105 can be used to insert a medical imaging device 180, such as an endoscopic camera or a fiber-based imaging probe. Examples of endoscopic cameras include, but are not limited to, chip-on-tip (COT) cameras, such as a camera with a miniature CMOS sensor located at the tip of the imaging device. Examples of fiber-based imaging probes include, but are not limited to, near-infrared autofluorescence (NIRAF) imaging probes, spectrally-encoded endoscopy (SEE) probes, intravascular ultrasound (IVUS) probes, or optical coherence tomography (OCT) imaging probes.

[0026] The wire conduit 104 allows for the anchoring and / or passage of control wires 110 used to steer (or bend) at least one section of the sheath. To that end, at the distal end of the sheath, the steerable section 103 is composed of multiple bendable segments. At the proximal end of the sheath, the non-steerable section 102 is connected to a handle or handle interface 200, which has one or more control wheels or knobs 252 used to bend the steerable section in one or more directions. The handle or handle also embodies an access port 250 for inserting a tool into the tool channel 105. The access port 250 can be used for the insertion of small instruments such as small forceps, needles, electrocautery instruments, etc. In some embodiments, the wire conduit 104 can be used to pass electrical wires 111 to connect, for example, an electromagnetic (EM) sensor 115 to an electrical terminal 212 located on the interface handle 200.

[0027] The steerable instrument 100 is configured to provide flexible access to an intraluminal target area with one or more curved curves to reach a desired target area near the distal end of the instrument while maintaining torsional and longitudinal rigidity, so that a physician can control an end effector or imaging device located at the distal end of the sheath by steering the control system. To provide such steerable functionality, the steerable instrument 100 is controlled by a number of control wires 110 disposed inside a wire conduit 104 along (typically within) the wall of the sheath. Some of the control wires 110 are anchored to the distal end of the sheath using wire anchors 112, while other control wires 110 can be anchored at a specific distance from the distal end using wire anchors 113. In one exemplary embodiment, in a steerable instrument 100 with six control wires, two sets of control wires 110 (i.e., four control wires) may be anchored in a central portion of the sheath (e.g., at one or more inflection points 107) by wire anchors 113, and another set of control wires 110 (two control wires) may be anchored at a distal end of the sheath by wire anchors 112. In this manner, the steerable instrument 100 may have at least two (i.e., more than two) steerable sections controlled by three sets of antagonistic control wires 110, each passing through a separate wire conduit 104.

[0028] At the proximal end of the instrument 100, a handle interface 200 is configured to provide a mechanical link and electromechanical interface between the steerable instrument 100 and a control system 300. In one embodiment, the handle interface 200 provides multiple electromechanical connections 210 (one connection for each of the control wires 110) so that an actuator system 310 can mechanically move each control wire 110. A controller 320 is used to electronically control the movement of each control wire 110 based on the tension or torsion state of each control wire, as described in more detail later in this disclosure.

[0029] 1B, the control system 300 may include multiple actuation motors (or actuators) 1 through M, where M is an integer greater than zero and equal to the number of control wires 110, as part of an actuator system 310. In this manner, each control wire 110 may be actively controlled by a feedback control loop 325 to provide proper shaft guidance for navigation through the patient's anatomy.

[0030] 2A is a perspective view of an exemplary steerable instrument 100. According to one embodiment, the steerable instrument 100 may be a wire-driven continuum robot that includes a proximal non-steerable section 102 and a steerable section 103 that is divided into multiple curved segments or sections 106a and 106b by at least one inflection point 107. In the steerable instrument 100, multiple control wires 110 extend from a proximal end to a distal end through a conduit 104 along the wall of the non-steerable section 102 of the sheath and through multiple guide members 108a, 108b and anchor members 103a, 103b of the steerable section 103 of the sheath. The control wires 110 are arranged in a direction parallel to the Z-axis. Some of the control wires 110 are coupled to the first anchor member 103a at the inflection point 107, and some of the control wires 110 are coupled to the second anchor member 103b at the distal end. All the drive wires 110 are coupled at their proximal ends to individual motors or actuators (actuator system 310 as shown in FIG. 1B). The control wires 110 may be metal wires, such as piano-type wires, stainless steel wires, or nickel-titanium alloy wires. The anchor members 103a and 103b have a ring shape with its central axis extending along the Z-axis direction. Of the multiple control wires 110, some of the control wires are fixedly attached to the anchor member 103a, and some of the control wires are attached to the anchor member 103b, for example, by gluing, pinning, ultrasonic welding or heat welding, press-fitting, or screwing.

[0031] The support section or non-steerable section 102 of the sheath has a cylindrical shape with its longitudinal axis extending along the Z-axis direction and has a number of conduits or through-holes extending within the walls of the cylindrical shape. The support section is a non-steerable section and functions to transmit actuation forces from the actuators when the control wires passing through the sheath's through-holes are actuated in the Z-axis direction without buckling or sagging of the control wires.

[0032] FIG. 2B shows a perspective view of a representative guide member 108b and a representative guide member 108a. Each guide member has a circular ring shape with a central or longitudinal axis Ax extending along the Z-axis direction. The guide member 108b has wire conduits or guide holes 104a, 104b, 104c extending along the walls of the circular ring shape of the guide member. The guide holes 104a, 104b, 104c are configured to allow respective control wires 110 to pass therethrough and slide therethrough during navigational (steering) movements of the steerable instrument 100. Of the control wires 110, one control wire can be fixedly attached to a given anchor member at an inner surface of the guide hole, and the other two control wires can be slidable relative to the guide holes of the given anchor member. Since each guide member 108b contacts the control wires 110 through the guide holes 104, the guide members can include a lubricious material with a low coefficient of friction. Guide member 108a has guide holes 104a, 104b, 104c, 104d, 104e, 104f for threading control wire 110 through curved sections 106a and 106b. Similar to the design for curved section 106b, curved section 106a has multiple guide members 108a, each with guide holes 104a-104f. Guide holes 104a-104f are positioned to allow control wire 110 coupled to anchor member 103b and control wire coupled to anchor member 103a to pass through the guide holes.

[0033] The bending motion (steering) of the steerable instrument 100 will now be described as the control wires 110 are actively driven to navigate a serpentine path. For clarity, the bending of a single curved segment or section will be described. As shown in FIG. 2C, the single curved portion 106 of the steerable instrument 100 includes, from its distal end, an anchor member 109, a number of guide members 108, and a non-steerable support section 102 with a number of guide holes. The control wires 110a, 110b, 110c extend from the proximal end to the distal end of the steerable instrument along the guide holes 104a, 104b, 104c, respectively. One or all of the control wires 110 are fixedly coupled to the anchor member 109 at their distal ends. The control wires 110 coupled to the anchor member 109 at their distal ends are slidable relative to the guide member 108 by the actuation of an actuator or motor (see FIGS. 1A-1B) connected to the proximal end of each control wire. One of the three control wires 110 (e.g., control wire 110b in FIG. 2C) is fixed (or mechanically grounded) relative to all of the guide members 108, and the remaining two control wires 110 (e.g., control wires 110a and 110c in FIG. 2C) are slidable relative to the guide holes of the guide members 108.

[0034] When bending the steerable instrument 100, each control wire 110 is individually controlled by a respective actuator or motor. For example, in FIG. 2C, the control wire 110b is fixed or anchored to the anchor member 109, while the control wire 110a is pulled with a first control force F1, and the control wire 110c is pulled with a second control force F2 different from the force F1 (in this example, the control force F2 is lower than the control force F1). In this way, the bending portion 106 can be bent in a desired direction according to a combination of the driving amounts of the linear displacements of the control wires 110a and 110c. To control the attitude of the distal end of the steerable instrument 100, it is sufficient to drive two (or even one) of the three control wires. When the forces F1 and F2 are applied to the control wires 110a and 110c, respectively, the corresponding sensors detect the applied pulling forces, as will be described in more detail later. It should be noted here that forces F1 and F2 are not limited to tensile forces exerted by pulling on the control wires, but rather forces F1 and F2 may be compressive forces applied to the control wires 110 by mechanically pushing the control wires with a desired amount of compressive force.

[0035] Although the control wires anchored to the distal end of a single curved section 106 are described with reference to FIG. 2C, when the control wires of all curved sections in FIG. 2A are driven, the attitude of each curved section (1, 2, 3, ... N) can be independently and selectively controlled to bend in a snake-like motion depending on the amount of actuation of the individual control wires driven by the actuators of the actuator system 310 (drive unit). Furthermore, a mechanism may be additionally provided to twist or rotate the wire-driven steerable instrument 100 about its longitudinal axis. To impart a certain amount of rotational or twisting action to the steerable instrument 100, the curved section can be bent in a desired direction by first driving only one control wire 110, and then the entire sheath can be rotated by actuating a second control wire 110 of a different curved section. Such operation of the steerable instrument 100 can be performed based on well-known mechanical and kinematic principles, for example as described in U.S. Pat. No. 9,144,370 (incorporated herein by reference for all purposes).

[0036] According to one embodiment, the steerable instrument 100 shown in Figures 2A-2C may have an outer diameter of about 0.14 inches, with a distal steerable section 103 approximately 2.0 inches in length, and an overall length of the instrument 100 of about 24 inches. The anchor member has a conduit 104 and a tool channel 105 similar to a guide ring, and is typically constructed of a medical grade plastic or similar composite. Such materials allow for the manufacture of flexible, yet torsionally resilient, steerable instruments such as catheters and endoscopes of reduced dimensions. For example, other prototype dimensions of the steerable instrument 100 are an outer diameter (OD) of about 3.3 mm, an inner diameter (tool channel) of 2.4 mm, and a length of about 550 mm.

[0037] Typically, either during insertion or withdrawal of the steerable instrument, the centerline of the lumen (e.g., airway) is the desired trajectory to follow during active control of the curved section. Therefore, known steerable instruments, such as robotically guided catheters and endoscopes, have attempted to implement various concepts of shaft guidance, aiming to force the flexible shaft to stay on the desired trajectory. In one example, when using a shaft guidance system, the steerable instrument advances through the lumen and sensors measure the insertion depth of the shaft guide and the angulation of the user-controlled steerable tip to obtain trajectory information. The trajectory information is stored in the system's memory and is continuously updated. After a small advance in insertion depth, the shape of the steerable shaft guide is modified by adjusting (rotating or bending) the segments of the instrument so that the new shape closely matches the desired trajectory. This process is repeated until the target area is reached. The same process is applied when the steerable instrument is withdrawn from the patient. See, for example, US 2007 / 0135803, incorporated herein by reference for all purposes.

[0038] However, most steerable medical instruments still rely on support from the surrounding anatomy to follow a desired trajectory during both insertion and withdrawal. In particular, when the steerable instrument is subjected to an external disturbance (e.g., an external force due to an involuntary movement of the patient), it is difficult to keep the steerable instrument on the desired insertion (or withdrawal) trajectory, since the tip (or other part) of the steerable instrument may get caught in the patient's anatomy and prevent proper navigation (e.g., by unexpected bending or twisting of the instrument). In particular, during withdrawal of the steerable instrument, the guidance system is typically kept inactive, which places the steerable instrument in an uncontrolled (passive) state. However, the steerable instrument may still come into contact with the patient's anatomy and get caught unexpectedly. This may cause discomfort and / or pain to the patient. To avoid this situation, the above-referenced publication, US 2007 / 0135803, proposes active control of the shape of a steerable instrument using sensor-based mapping techniques that are continuously maintained as the instrument is moved within the patient.

[0039] However, when removing a steerable instrument from a path in a patient's anatomy, it may be beneficial to keep the instrument very flexible (e.g., at zero tension) while maintaining the ability to actively control its stiffness at any time. For example, keeping the instrument very flexible (compliant) during removal may result in less trauma to the patient's anatomy (e.g., airway, colon wall, etc.), less force is required to remove the instrument, and less discomfort for the patient. However, when the instrument needs to be reinserted or reoriented after partial or complete removal (e.g., due to patient breathing or movement), the position and pulling force of the instrument must be immediately controlled. Thus, there is a need for an improved steerable medical instrument that (1) has a minimum outer size (outer diameter), (2) has a maximum tool channel opening size (inner diameter), and (3) has actively controlled flexibility (or stiffness) to efficiently navigate tortuous paths without pain or discomfort to the patient. In particular, if the device needs to be reinserted or reoriented after partial or complete removal (e.g., due to patient breathing or movement), it is desirable to keep the device very flexible (e.g., near zero tension) while maintaining the ability to control its stiffness in the passive bending mode of active control.

[0040] In the present disclosure, (1) the force on the control wire 110 is zero when maximum flexibility is required for the steerable instrument, (2) the force and displacement of the control wire 110 are continuously monitored regardless of the control mode employed, (3) friction in the steerable instrument is minimized even when navigating a serpentine path during insertion or retraction, and (4) the guidance system is controlled to place the steerable instrument 100 in a passive control state (passive bending mode of active control) so that the proximal end of the control wire 110 is free to translate while remaining actively connected to the corresponding actuator.

[0041] More specifically, the present disclosure proposes a passive bending mode that can be easily transferred to active shape control (and vice versa) without losing important feedback information such as the position of the control wires and the tension or compression force on the control wires. The main principle of this passive to active mode conversion is that the drive wires (control wires 110) are actively controlled, making the applied forces negligible, and thus creating a very soft bending behavior of the steerable instrument 100. This effect or mode is referred to herein as the passive bending mode of active control of the steerable medical device. Although the passive bending mode of active control of the steerable medical device can be achieved in various configurations, it is important that the drive wires are directly driven by hardware so as not to add friction or excessive slack. To that end, it is preferable to drive the control wires 110 by hardware that can maintain a stable and precise relationship between the controller and the end effector so that the position of the actuated element is precisely controlled. The passive bending mode of active control is particularly advantageous in controlling smooth and precise bending of steerable medical instruments during insertion and pullback through tortuous paths in a patient's anatomy.

[0042] In any of the embodiments, there are motors or actuators actuating the control wires. There may be a separate motor or actuator for each control wire, or there may be a single motor or actuator capable of individually controlling the various control wires. The control wires move longitudinally along the length of the instrument in conjunction with other control wires to generate bending moments at the distal portion of the instrument. The instrument may be constructed to actuate one or more of such curved sections individually. In this disclosure, one important point is that regardless of the type of actuator used (DC motor, linear induction motor, ultrasonic motor, etc.), linear forces are generated to move the control wires individually in active bending mode, and a control loop is used to keep each control wire completely passive (compliant and capable of being moved by an external force as if the wire was decoupled from the drive actuator) while maintaining encoder position feedback and force feedback for the drive wires. In one embodiment, to keep each control wire completely passive, the controller performs force balancing by reducing the strain force to substantially zero. In another embodiment, the controller performs active operation of the actuators connected to the control wires. This differs from force balance feedback because in this example the actuators can be passively moved by control wires.

[0043] For direct current (DC) motors, conversion from rotary to linear motion is required. Typically, a lead screw or ball screw mechanism is used for this. However, other alternatives such as ultrasonic or direct drive actuators may be more advantageous. The advantage of ultrasonic motors and linear induction motors is that they are both linear actuators and do not require mechanical conversion. Ultrasonic or linear induction motors can drive the control wires directly, without mechanical gears or intermediate mechanisms. One advantage of directly driving the control wires with such linear actuators is that friction and other nonlinearities (e.g., mechanical slop in lead screw mechanisms) are reduced.

[0044] In active control mode, each control wire in a given curved section is assigned a specific position. Any error in position is measured and corrective action is taken to reduce this error. This occurs many times per second, quickly reducing the position error to a negligible amount. As a result, the commanded shape of the instrument is under closed-loop control based on the control wire positions.

[0045] However, sometimes it is necessary to adapt the shape of the instrument to external forces applied to the instrument from outside, such as forces from the walls of the tortuous path or unexpected changes in the navigation path due to, for example, the patient's breathing motion. To apply force feedback, the present disclosure includes a force sensor on each of the control wires. If tension or compression is sensed on the control wire, the controller can measure the tension or compression or displacement of the control wire based on the signal from the sensor. An algorithm is then provided to take corrective action to reduce the measured force towards zero. This will reduce the overall force acting between the walls of the tortuous path and the instrument. This process can occur many times per second, quickly reducing the force to a negligible amount.

[0046] In the present disclosure, another aspect of reducing the external forces on the instrument due to contact between the instrument and the serpentine path is achieved by a unique control wire configuration and actuation method. Most known steerable instruments use only tension mode for their control wires, with at least two control wires in an antagonistic configuration for each set of actuation positions. This means that if only tension is used, two control wires are required for one curved section that can bend in one plane. This conventional method also requires that the instrument have a stiff backbone that prevents the instrument from deforming longitudinally under tension. However, in the present disclosure, both tension and compression can be used for the control wires, and the steerable instrument does not have a backbone. Instead, the present disclosure uses multiple control wires in a symmetrical configuration with couple forces to create a pure bending moment in the curved section. A pure bending moment creates zero longitudinal forces along the instrument. This not only allows precise control of tension and compression forces, but also allows the size of the instrument to be reduced by not incorporating a backbone. Typically, with tension-only control wires, a small but non-zero amount of tension is always maintained on the control wire to preload the mechanism and avoid slack or non-linearities that can interfere with the control system. The steerable instrument of the present disclosure has no such problems. The control wire has no mechanical slop or slack (especially when connected directly to the actuator), and the actuator is a linear actuator. This allows all axial forces on the control wire to be reduced to zero while the control forces are continuously monitored and adjusted. This action, combined with the lack of a stiff backbone, results in a very compliant instrument on demand. Furthermore, the programmed algorithm seamlessly changes from an active control bending mode to a passive control bending mode and vice versa.

[0047] <First implementation: Force control loop> FIG. 3 illustrates an exemplary embodiment of a passive bending mode of active control (referred to herein as a "force control loop" implementation). As shown in FIG. 3, each control wire 110 of the steerable instrument 100 is connected at its proximal end to a corresponding motor and motor control system. For simplicity of illustration, FIG. 3 shows a first control wire 110a connected to a first linear motor 311 controlled by a first motor control system 321 (motor controller). Similarly, a second control wire 110b is connected to a second linear motor 312 controlled by a second motor control system 322. To ensure accurate positioning (to avoid sagging), the linear motor 311 is fixed to a structural foundation 311a, and the linear motor 312 is fixed to a similar foundation 312a. The foundation 311a / 312a may be, for example, a housing or chassis of a patient interface unit (PIU) that encloses the interface 200 and at least a portion of the control system 300. If a steerable instrument 100 has control wires i through M 110, corresponding control motors or actuators i through M are expected. However, it is not expected or necessary to provide a corresponding number of motor controllers. A single controller can be programmed to individually drive each of all the motors or actuators described herein, so long as each motor M is individually controlled to actuate its corresponding control wire 110.

[0048] In the embodiment of Fig. 3, to implement the principle of passive-active mode conversion, each control wire 110 is also connected to a strain sensor and a position sensor. In Fig. 3, the first control wire 110a is connected to a strain sensor 221 and a position sensor 231 (displacement sensor). Similarly, the second control wire 110b is connected to a strain sensor 222 and a position sensor 232. The strain sensor may be a strain gauge-based, optical-based, or encoder-based sensor, and the position sensor may be an encoder-based, electromagnetic-based, or Hall effect-based sensor. Encoder-based sensors include optical encoders, magnetic encoders, potentiometers, etc.

[0049] The strain sensors detect and / or measure the compressive or tensile force F on the actuated control wires 110 and output a signal (Fi) corresponding to (indicative of) the amount of compressive or tensile force (amount of strain) being applied to the control wires at a given time. Similarly, the position sensors detect the longitudinal position (or distance moved) of the control wires 110 and output a signal (Xi) corresponding to (indicative of) the current position of the control wires. The signals from the strain and position sensors of each control wire 110 are sent to a motor control system. The motor control system generates a control signal (Ci) that is sent back to the motor or actuator to move the corresponding control wire 110 in a direction with less force. That is, the control signal (Ci) generated by the motor control system is used in a feedback loop of the corresponding actuator or motor to move the corresponding control wire 110 in a direction opposite to the direction of the force F so as to reduce the amount of strain being applied to the control wire. This allows the force remaining on the control wires to be negligible after a short time t, as will be described in more detail below with respect to Figures 7A-10. In this manner, by actively driving the control wires 110, it is possible to apply substantially negligible forces to the steerable instrument 100, resulting in a very soft bending behavior of the distal end of the instrument.

[0050] <Second implementation: frictionless direct drive> FIG. 4 illustrates another exemplary embodiment of a passive bending mode of active control of the steerable instrument 100, which is referred to herein as a “frictionless direct drive” implementation. In FIG. 4, the first control wire 110a of the steerable instrument 100 is directly connected at its proximal end to a corresponding first motor 311 via a moving carriage 341, and the second control wire 110b is directly connected at its proximal end to a second motor 312 via a moving carriage 342. The moving carriages 341, 342 are mechanically connected to the corresponding motors 311, 312 by threaded linear shafts configured to displace the control wire 110 linearly, for example along paths L1, L2. Such threaded linear actuators may be based on well-known lead screw, ball screw, or roller screw principles. The first and second control motors 311, 312 are both operatively connected to a motor controller 320. Additionally, the first support wire 121a is connected at its proximal end to a first strain sensor 211, and the second support wire 121b is connected at its proximal end to a second strain sensor 222. Each strain sensor outputs a signal corresponding to the amount of strain applied to its nearest control wire 110 (or a signal corresponding to the average of the strain forces applied to at least the two nearest control wires 110). The first strain sensor 221 outputs a first strain signal (F i ), and the second strain sensor 222 outputs a second strain signal (F i+1 ) The output signals corresponding to the amount of strain detected by all of the strain sensors are fed back to the controller 320 as a feedback loop 325. In some embodiments, the controller 320 can be implemented using a standard scheme such as proportional-integral-derivative control (PID).

[0051] In the previous embodiment of FIG. 3, the linear motors are connected to the control wires 110 with the strain sensor disposed therebetween. In contrast, according to the embodiment of FIG. 4, the linear motors 311 / 312 are directly connected to the corresponding control wires 110a / 110b from the moving carriages 341 / 342. A first strain sensor is provided at the distal end of the first supporting wire 121a and a second strain sensor 222 is provided at the proximal end of the second supporting wire 121b to monitor the strain being applied to the control wires. Such a direct connection configuration minimizes friction between the moving carriages 341 / 342 and the foundation (or housing) of the actuators or motors 311 / 312. In this way, when the linear motor mode is commanded to have zero force, the force from the drive wires will displace the moving carriage 341 / 341 of the corresponding motor, thus eliminating residual force or tension on the control wires.

[0052] Frictionless direct drive by induction linear motor and air bearing stage Another implementation of the frictionless direct drive configuration could be the use of linear induction actuators where the friction between the moving carriage and the actuator or motor foundation is very low. One example of this implementation is the use of high-precision linear motors with air bearings. High-precision linear motors (PLMs) with air bearings are widely used in the optical lithography manufacturing of wafers to achieve near-zero friction and achieve sub-micron positional accuracy when it comes to stage movements. The mover of the PLM is suspended on the stator by three air bearings in the normal direction and two air bearings in the lateral direction (one on each side). A PLM with air bearings is expected to move along a straight line and can reach sub-micron positioning accuracy during operation. The advantages of air bearings are near-zero friction, less heat generation, and less noise. A PLM with air bearings also significantly reduces nonlinearities and disturbances caused by backlash and friction. These advantages enable PLM with air bearings to be applied in advanced manufacturing fields such as semiconductor manufacturing, but can also be implemented in frictionless direct drive configurations of the control wires 110 of novel steerable medical devices 100 using microelectromechanical systems to operate the control wires.

[0053] 5A and 5B show an example embodiment of a frictionless direct drive configuration implemented by an induction motor with frictionless bearings. In FIG. 5A, the steerable medical instrument 100 is similar to the structure described above with reference to FIG. 1A, FIG. 1B, FIG. 3 and / or FIG. 4. In FIG. 5A, the actuator or motor is implemented as a drive unit 1300 consisting of a mover or motor carriage 1330 and a stator, which consists of a magnetic base plate 1360 and a top plate or guide 1310. The drive unit 1300 is labeled M1, representing the motor 1 in FIG. 1A. Of course, in FIG. 5A, there are multiple drive units 1300 (e.g., one per control wire). FIG. 5B shows a more detailed view of an induction linear motor (drive unit 1300) combined with an air bearing stage. In FIG. 5B, the top plate or guide 1310 includes multiple pressure zones (P) 1312 and multiple vacuum zones (V) 1314. These zones balance each other to maintain the guide 1310 at a predetermined distance from the motor carriage 1330. The pressure and vacuum zones are preloaded by the manufacturer and are represented herein as springs to account for the "floating" effect of the air bearing section 1320. The mover or motor carriage 1330 is free to move in a linear direction 1302 when the inductive force 1340 applied to the motor carriage 1330 is zero (no inductive force). The position sensor 1331 monitors the linear motion of the motor carriage 1330 and outputs a signal Xi indicative of the amount of displacement of the motor carriage 1330 (moving carriage). Here, the signal Xi is used as a feedback signal 1325 to control the actuation of the motor 1300 of the control wire 110. The inductive force 1340 is applied to the motor windings 1332 of the motor carriage 1330. An air gap 1350 is provided between the motor windings 1332 and the permanent magnets (N, S) of a magnetic base plate 1360 (which is a permanent magnet).

[0054] In this arrangement, the motor carriage 1330 floats freely on an air bearing due to the air gap 1350. Because of the air gap, there is no longitudinal friction, and no forces are applied to the motor carriage 1330 when no current is passing through the linear induction motor. Thus, the motion and forces applied to the motor carriage 1330 by the control wires 110 will cause the motor carriage to move freely in the linear direction 1302. The movement of the carriage can be continuously measured by the position sensor 1331. When active control of the position of the control wires 110 and motor carriage 1330 is desired, the control system simply needs to drive current through the linear induction motor and use the position data as feedback in the control loop, as in the previous embodiment.

[0055] FIG. 5B shows a simplified diagram of an induction linear motor 1300 combined with a frictionless air bearing. The implementation of this embodiment requires both bearing and induction drive elements. Here, it is necessary to have a mode in which the motor carriage 1330 (attached to the drive control wires 110) is free to move. Then, as needed, current can be applied to the motor windings 1332, which generates a force 1340 to move the carriage 1330 in a desired direction (preferably the direction of less force). Another component of this implementation here is that the motor carriage 1330 can be allowed to move freely while maintaining position sensor feedback. And, since position sensor data is constantly being acquired, the mode can be changed back from the free move mode to the active control mode at any time.

[0056] One more detailed explanation of the air bearing. In the diagrams of Figures 5A and 5B, the inventors have shown a spring to represent the air mass located between the motor dolly 1330 and the top guide surface of the top plate 1310. This particular diagram shows the pressure (P) and vacuum (V) zones of a so-called vacuum preloaded air bearing. The pressure and vacuum zones "fight" each other. The pressure pushes the motor dolly away and the vacuum pulls it closer. The motor dolly settles at a distance from the top guide surface where these two opposing forces are in balance. If the distance from the motor dolly 1330 to the top guide surface of the top plate 1310 changes, the balance between the vacuum and pressure forces is disturbed and a net corrective force naturally occurs, returning the motor dolly 1330 to its original flying height (where the forces are in balance). This causes the control wire 110 to continuously maintain a substantially zero force unless an external force is applied.

[0057] Frictionless direct drive by ultrasonic motors Another implementation of a frictionless direct drive configuration may be the use of a linear ultrasonic motor, which can function in a mode where contact between the carriage and the stator is very low friction by applying a control signal. Figures 6A, 6B and 6C show an example embodiment of an ultrasonic motor actuated on a control wire 110. In Figure 6A, the steerable medical instrument 100 is similar to the structure previously described with reference to Figures 1A, 1B, 3 and / or 4, and the bending control is similar to that described with respect to Figures 2A-2C.

[0058] In FIG. 6A, the motor or actuator is implemented as an ultrasonic piezoelectric drive unit 1400 consisting of a slider or mover 1430 and a stator, which consists of a coupling plate 1420 and a vibrating piezoelectric element 1410. The drive unit 1400 is labeled M1, representing the motor 1 of FIG. 1A. Of course, in FIG. 6A, there are multiple drive units 1400 (e.g., one per control wire). Piezoelectric actuators are transducers that convert electrical energy into mechanical displacement based on the piezoelectric effect. Such actuators can be advantageously used as high-precision positioning mechanisms, since they can generate relatively large forces while controlling small mechanical displacements at high speed. As an example, the PILine® ultrasonic piezo motor can achieve a speed of 500 mm / s with a resolution of 2 nm, with a holding force of up to 15 N and a torque of up to 0.3 Nm.

[0059] 6B and 6C show the application of the ultrasonic drive unit 1400 to the steerable medical device 100 in more detail. In a linear ultrasonic piezoelectric motor, a high frequency oscillating voltage waveform is applied to the piezoelectric element 1410 under programmed control from the controller system 300. The waveform signal induces modal vibrations in the coupling plate 1420, causing the contact points 1421, 1422 ('feet') to alternately contact the movable body 1430 at high speed. There is a preload normal force between the movable body 1430 and the foot points 1421, 1422, which creates momentary stiction between one foot at a time and the movable body 1430 (movable plate) during contact. The path followed by the contact points during this oscillatory oscillation has both vertical and planar or horizontal components. Vertical motion causes one foot at a time to contact the plate, and horizontal motion pushes the movable body 1430 in one direction, preferably along the length of the control wires. As in the previous embodiment, the strain and / or position sensor 1431 outputs a signal Xi indicative of the amount of strain or amount of displacement (distance) actuated by the moveable body 1430 or transmitted to the control wire 110. The feedback signal 1425 is used to control the actuation of the steerable instrument 100.

[0060] For example, Figure 6B shows an initial position where the first foot 1421 contacts the moveable body 1430, causing it to slide or move to the right. Figure 6C shows a second or final position where the second foot 1422 contacts the moveable body 1430, causing it to continue to slide or move to the right. The resulting effect is that the strain sensor 1431 continuously monitors the position of the moveable body 1430 while the moveable body 1430 undergoes linear motion of the distance 1450. In this manner, the moveable body 1430 can be linearly translated (moved) from a first position Z0 to a second position Z1 when at least one segment of the steerable section 103 of the steerable instrument 100 is bent (e.g., by bending of a catheter or endoscope).

[0061] Depending on the voltage waveform applied to the ultrasonic motor, various movements and behaviors can be realized. The movable body 1430 is attached to the control wire 110 so that it can be driven in either direction of linear motion 1402 at a controllable speed. Position feedback is also constantly monitored by the strain sensor 1431 so that at any time, the control system can use information from the strain sensor 1431 for positioning purposes. The piezoelectric actuator also has the property that there is static friction between the foot and the movable body when no power is applied to the piezoelectric actuator 1410. This acts as a passive braking force for the drive control wire and is also useful in avoiding involuntary movements of the end effector in clinical settings. Another behavior of the ultrasonic drive unit 1400 is that it has a low friction mode. By applying a specific oscillating voltage signal to the piezoelectric element 1410, it can be ensured that the foot (contact points 1421, 1422) produces little horizontal force on the movable body 1430 and spends little time in contact with the surface of the movable body 1430. The resulting effect is that the ultrasonic actuator behaves more like a low friction bearing than a friction drive actuator.

[0062] Similar to the inductive actuator design, the movable mass 1430 of the linear ultrasonic motor is free to move in response to position changes in the control wires caused by bending of the catheter. The position of the movable mass 1430 is continuously monitored by strain sensors 1431, and the control system can return to active mode at any time to apply a force to the movable mass.

[0063] In either case, the linear motor is directly connected to the control wires 110 and can be moved by small forces from the control wires. The forces on and displacements of the control wires can be measured independently of each other and regardless of the control mode of the motor, and because the strain and position sensors are continuously active even when the drive forces are negligible, these forces are not disturbed by mode changes.

[0064] When no force is present on the drive control wires 110, the control wires are free to translate, allowing the shape of the instrument 100 to be easily changed. For example, external contact with the distal end of the steerable instrument 100 by some obstacle (such as the patient's airway wall) may cause bending of the steerable instrument, thereby causing displacement of the control wires. Upon movement of the control wire, the strain sensor 1431 provides an output signal to the controller, which triggers the actuator to apply a drive force to the control wire in the opposite direction (the direction of the lesser force).

[0065] The sensing principle of the "strain sensor" in all embodiments may be strain gauge based. A known strain gauge is a circuit using a force-sensing resistor that is used to measure the compressive or tensile forces (strain) applied to an object. When an object is deformed within its elastic limits, it becomes thinner and longer or shorter and wider. As a result, there is a change in resistance. The force-sensing resistor contains a conductive polymer film whose resistance changes in a predictable way when a force is applied to its surface. The amount of change in resistance allows the amount of applied force to be measured. Strain gauges are available in various forms, such as linear strain gauges and shear strain gauges. There are also semiconductor strain gauges called piezoresistive elements, nanoparticle strain gauges made of gold or carbon-based resistors, and microscale strain gauges that are widely used in microelectromechanical systems (MEMS). Other implementations can use fiber optic sensors such as fiber Bragg gratings and Fabry-Perot interferometers. See, e.g., publication US2018 / 0193100, which is incorporated by reference herein for all purposes.

[0066] Of the two modes of implementation, the embodiment using ultrasonic motors may be more advantageous. Specifically, with the continuing advances in ultrasonic motor technology, it is possible to implement the steerable instrument 100 with lightweight ultrasonic motors, capable of handling large forces without slowing down with micron-sized movements, and capable of functioning independently of force or position sensing. Furthermore, ultrasonic motors are very small, so they can be assembled in very compact spaces. Greater speeds can be achieved without affecting the amount of force transmission.

[0067] <Control system and feedback control implementation> 7A shows an example block diagram of a control system 1500 configured to implement a passive bending mode of active control of a steerable medical instrument 100 according to the present disclosure. In the passive bending mode of active control, the control system 1500 controls the steerable instrument 100 such that (1) the force on the control wire 110 is zero when maximum flexibility of the steerable instrument is required, (2) the force and displacement of the control wire 110 are continuously monitored regardless of the control mode employed, (3) friction on the steerable instrument is minimized even when navigating a tortuous path during insertion or pullback through the path, and (4) the proximal end of the control wire 110 is free to translate while remaining connected to its corresponding actuator.

[0068] In FIG. 7A, the control system 1500 includes a "desired wire position" block 1502, a "motor controller" block 1504, a motor or actuator block 1506, an "actual wire position" block 1508, a strain and / or position sensor block 1510, and a comparator block 1512. This control system 1500 is a highly simplified version of a feedback control loop that generates an error signal (at the comparator block 1512) from the difference between the desired position and the actual position (provided by the force / position sensor block 1510). The error signal may also be generated from a comparison of a desired or previously measured force on the control wire with a sudden change in force (e.g. an external force) detected by a strain sensor. The error signal is converted by the motor controller 1504 into a control input signal that is then sent to the motor or actuator. This is a closed loop control of one of the control wires. Each control wire 110 will have its own feedback loop (this is called single input single output "SISO"). In this case, multiple input / output systems are also possible if it is desired to control multiple motors with a single feedback loop, but their implementation is not described in this patent application.

[0069] Those skilled in the art will appreciate that the control system 1500 may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be referred to herein as a "circuit," "module," or "system." Additionally, some aspects of the control system 1500 may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code stored thereon. For example, some aspects of the control system 1500 described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products may be implemented by computer program instructions. The computer program instructions may be stored on a computer readable medium capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored on the computer readable medium constitute an article of manufacture that includes instructions and processes that implement the functions / acts / steps specified in the flowcharts and / or block diagrams.

[0070] FIG. 7B illustrates functional blocks of a computer 1600 that may operate or be part of the motor controller 1504 or computer system 400. As shown in FIG. 7B, the computer 1600 may include, among other things, a central processing unit (CPU) 1601, a storage memory 1602 including volatile random access memory (RAM) and non-volatile read-only memory (ROM), a user input / output (I / O) interface 1603, and a system interface 1604, which are operatively interconnected via a data bus 1605. The computer 1600 may be programmed to issue commands that may be sent to various parts of the control system 1600 upon receiving user input, for example, via the user interface 1603. Part of the user interface 1603 may include a touch screen, a keyboard, a mouse, a joystick, a ball controller, and / or foot pedals. Using the user interface 1603, a user may issue commands that cause the control system 1500 to actively manipulate the steerable instrument 100. For example, when a user inputs a command via the user interface 1603, the command is sent to the central processing unit CPU 1601 for execution of a given program routine, which in turn causes the CPU 1601 to send the command via the system interface 1604 to one or more of the control wires 110 or to prepare output signals from one or more strain sensors 221 or 222.

[0071] The CPU 1601 may include one or more microprocessors (processors) configured to read and execute computer-executable instructions stored in the storage memory 1602. The computer-executable instructions may include program code for the execution of the novel processes, methods and / or calculations disclosed herein. In particular, the computer-executable instructions may include program code for the execution of the processes illustrated in Figures 8, 9, 10A and 10B to implement a passive bending mode of active control of the steerable medical device 100.

[0072] The storage memory 1602 may include one or more computer readable and / or computer writeable media, such as, for example, magnetic disks (e.g., hard disks), optical disks (e.g., DVDs, Blu-ray), magneto-optical disks, semiconductor memories (e.g., non-volatile memory cards, flash memory, solid state drives, SRAM, DRAM), EPROM, EEPROM, etc. The storage memory 1602 may store computer readable data and / or computer executable instructions.

[0073] The system interface 1604 provides an electronic communication interface for input and output devices. In particular, the system interface 1604 may include one or more circuits (such as a field programmable gate array (FPGA)) for interfacing the computer 1600 to motors or actuators that operate the control wires 110. The system interface 1604 may also include a keyboard, a display, a mouse, a printing device, a touch screen, a light pen, an optical storage device, a scanner, a microphone, a camera, drives, communication cables and networks (either wired or wireless).

[0074] 8 shows an example flow chart for implementing a passive bending mode of active control of the steerable medical device 100 with a feedback force control loop. The process of FIG. 8 includes the following steps: (a) determining if the catheter has been bent by an external force; (b) reading the tensile / compressive forces sensed by a strain or position sensor at the proximal end of the catheter; (c) executing a control algorithm to determine how to move the drive wire actuator to reduce the bending force; and (d) determining if a residual bending force on the drive wire continues to exist.

[0075] More specifically, the flow of FIG. 8 assumes that the steerable instrument 100 is in active shaft guidance mode, and in step 1702, the control system 1500 performs ongoing steerable instrument guidance. That is, in step 1702, the system monitors the navigation of the steerable instrument either during catheter insertion or removal (withdrawal). In step 1704, the system 1500 reads signals from sensors, that is, from either strain sensors 221 / 222, position sensors 231 / 232, or one or more strain sensors and one or more position sensors located at the proximal end of the device. In some embodiments, strain, position and / or orientation sensors (e.g., EM sensor 115) may be provided at the distal end of the steerable instrument 100. In step 1706, the system 1500 continuously monitors signals from the sensors until it determines whether the steerable instrument has been actuated (bent) by an external force other than the active driving force. If the instrument is bent by an external force (YES at step 1706), flow proceeds to step 1708. At step 1708, the system 1500 temporarily stops navigation of the steerable instrument 100. At step 1710, the system 1500 initiates an algorithm to determine how to move motors or actuators to reduce the distortion of the forces being applied to the steerable device. At step 1712, the system 1500 determines whether the bending force is negligible. If the force exerted by the external bending force is not negligible (NO at step 1712), the system 1500 continuously adjusts the force applied to the control wire 110 until the external force is negligible. If the bending force is negligible (approximately equal to zero), flow proceeds to step 1714 and the control system continues normal navigation of the steerable instrument 100.

[0076] According to one embodiment, in the process of FIG. 8, in step 1706, the system transitions from active shape control (active control mode: steps 1702-1704) to passive bending mode (passive control mode: 1708-1712) without losing important feedback information such as control wire position and control wire force (tension or compression). To do so, the system may employ a sensor-based mapping technique in which trajectory information is stored in the system's memory and continuously updated as the instrument moves within the patient's anatomy, in a manner similar to that described in US 2007 / 0135803. However, in the present disclosure, in step 1706, once the system determines that the instrument has been bent by an external force, the system enters passive bending mode and can easily transition to active shape control (or vice versa) without losing important feedback information such as control wire position and control wire force (tension or compression). The decision at step 1706 may be based on a comparison made by the system controller between the desired or recorded wire position (or the desired or recorded drive force on the control wire) and the actual force or position measured by the sensor. The decision at step 1706 may include a threshold. Specifically, the user may set a threshold in the software for the amount of linear displacement, twist, or rotation (or amount of strain force) to prevent twisting of the steerable instrument and ensure patient comfort and safety. For example, if the user sets a threshold difference between the desired value and the measured value of 5% or 10% or 15%, the system controller software will trigger a change between active and passive control modes only if the error exceeds the threshold. The active transition from "active" to "passive" control of the steering wires reduces system response time without losing important feedback information such as control wire position and control wire force.

[0077] Figure 9 shows an example flow chart for implementing a passive bending mode of active control of a steerable medical device with frictionless direct drive 100. The process of Figure 9 includes the following steps: (a) determining if the catheter has been bent by an external force; (b) reading the tensile / compressive forces sensed by a strain or position sensor at the proximal end of the catheter; (c) executing a control algorithm to place the actuator in a passive mode such that the actuator itself moves in response to the forces on the wires; (d) determining if the bending forces on the drive control wires are negligible; and (e) returning the actuator to its active mode (engaged with the control wires).

[0078] More specifically, the flow of FIG. 9 is similar to FIG. 8 in that it assumes that the steerable instrument 100 is in active shaft guidance mode, and in step 1802, the control system 1500 is performing ongoing steerable instrument guidance. That is, in FIG. 9, steps 1802, 1804, 1806, and 1808 are similar to steps 1702, 1704, 1706, and 1708, respectively. In particular, in step 1806, the system controller determines whether the steerable instrument has been bent by an external force other than the normal navigation forces applied by the actuators. In step 1810, the system 1500 initiates an algorithm to put the motors or actuators into a passive mode (where the actuators stop exerting any force on the control wires). In this state, when an external force acts on the control wires, the actuators will displace (move) linearly with minimal friction until the external force on the control wires 110 is negligible (e.g., substantially zero). In step 1812, the system 1500 determines whether the bending force is negligible. If the bending force is negligible (equals zero tenons), flow proceeds to step 1814 where the control system 1500 places the actuator in active mode (motors engaged with control wires) and resumes normal navigation of the steerable instrument 100.

[0079] In another scenario, the algorithm for releasing (disconnecting) the control wires can be based on user input. Specifically, in step 1806, the user can determine a specific abnormal event in the instrument navigation and manually input a signal to switch from active to passive control mode. For example, during navigation, pushing and / or tracking issues may occur as the catheter is driven through a tortuous path. When such issues occur, the system can prompt the user to manually stop active navigation and enter passive control. Pushing issues occur when the proximal portion of the catheter is pushed into the luminal access point, but the distal end of the catheter does not move a corresponding distance. Tracking issues occur when a torque is applied to the proximal portion and the distal end does not rotate proportionally as expected. Pushing and tracking control are very important aspects of the catheter as it navigates around difficult curves and / or obstacles in the patient's anatomy. To address such issues, the system may be equipped with a warning system, such as haptic feedback, or an audible or visual indicator, for example in the handle 200, to alert the user to a pushing and / or tracking issue if the instrument becomes stuck.

[0080] An example algorithm for reducing tension on the control wires in a passive bending mode of active control of the steerable medical device 100 may include processes similar to those described above with respect to Figures 8 and 9. Figure 10A shows an example algorithm that may be equally useful in reducing tension (or displacement) in step 1710 of Figure 8 and releasing the control wires in step 1810 of Figure 9.

[0081] In FIG. 10A, the flow begins when normal navigation of the steerable instrument 100 is temporarily stopped (interrupted) due to detection of an external force exerting a pulling force on one or more control wires 110. That is, in step 1710 of FIG. 8 or step 1810 of FIG. 9, the control system 1500 receives a signal from a strain or position sensor (step 1902 of FIG. 10A). In the algorithm of FIG. 10A, in step 1904, the system controller reduces the strain force measured in step 1902 by reversing the drive direction of the actuator or motor (in FIG. 8: step 1710) or by releasing the control wire (in FIG. 9: step 1810). Next, in step 1906 of FIG. 10A, the system 1500 determines whether the pulling signal represents a near-zero (or negligible) value of strain force. If the signal from the sensor indicates a value other than approximately zero (NO at 1906), the system continues reducing the strain force according to either the flow process of Figure 8 or Figure 9, depending on whether the steerable instrument is controlled under a force control loop or a frictionless direct drive. Once the external force pull is reduced to approximately zero (YES at 1906), active control of the pull force is terminated.

[0082] FIG. 10B illustrates an exemplary algorithm that may similarly reduce the tension force by releasing the actuation (or adjusting the displacement) of one or more control wires 110 in step 1710 of FIG. 8 or step 1810 of FIG. 9 based on user input. More specifically, according to the previous description, the automatic change from active control mode to passive control mode (and vice versa) occurs based on external forces (e.g., patient movement) monitored by strain and / or position sensors and certain thresholds thereof. However, in alternative embodiments, the switching between passive / active modes may also be implemented by the operator of the steerable instrument 100. In particular, the passive control mode may be useful for getting out of a catheter "blocked" situation during navigation through a tortuous anatomy of a patient (e.g., airway). In this case, if the physician operator determines that the catheter is stuck, the user may switch from active to passive mode, for example by pressing a button on the controller to stop the active control mode and enter the passive control mode. In passive mode, the system controller "relaxes" the catheter and allows it to get out of the "stuck" condition, after which the operator can change the mode back to active mode and continue using the robotic control.

[0083] 10B illustrates an example process of a user-initiated control scenario for operating the steerable instrument 100 under active and passive control modes. In FIG. 10B, the controller 320 receives an input signal from the user in step 1912, for example, when the user determines that the steerable instrument 100 is blocked or stuck in the intraluminal pathway and presses a control button on the user interface 254 of the handle 200 or manually inputs a command via the GUI 422 of the computer system 400. As soon as the user inputs such an input signal, in step 1914, the system controller 320 disconnects and releases the actuator 310 from the control wire 110. In step 1915, the strain sensor measures the tension remaining in the control wire. Then, in step 1916, the system controller determines whether the tension signal on the control wire is approximately zero (or negligible). If the signal from the sensor indicates a value other than approximately zero (NO at 1916), the system determines that the steerable instrument is stuck and proceeds to step 1918. In step 1918, the system actively reduces the strain force by actuating the control wire 110 in the direction of less force. This process of steps 1915, 1916 and 1918 continues until the catheter is released (in passive mode). Once the tension on the control wire is reduced to approximately zero (YES at 1906), the passive control mode is ended and the user can return the system to active control mode.

[0084] In the passive bending mode of active control, there is no active force applied to the control wire 110. When there is no force on the control wire 110, the control wire is free to translate, allowing the shape of the steerable instrument 100 to be easily changed. For example, if an external contact against the distal end of the steerable device 100 occurs due to something such as an airway wall, this disturbance may cause an unexpected bending of the sheath, which may cause a displacement of the control wire, reducing possible discomfort or pain to the patient. In contrast, if the control wire 110 is actively bent with a pulling force applied to it, the external contact may not be detected and therefore may not be able to be corrected.

[0085] If the steerable instrument may be accidentally blocked or stuck within the patient's anatomy, the user can manually stop the actuation force and put the steerable instrument into a passive association state. Furthermore, under manual operation, if the catheter is passive but still stuck, the system or user can control the actuator to drive the control wire in the direction of less force until the catheter is no longer stuck. The operator then changes the mode back to active mode and continues to use robotic control. Passive mode under user manual operation is a very simple decision for the system to perform (as the operator makes the decision to switch modes).

[0086] The passive bending mode of active control provides various advantages over known shaft-guided control systems. First, for both embodiments, one advantage is that the control wires can be completely passive (i.e., can be moved by external forces as if they were decoupled from the drive actuator) while still maintaining encoder position feedback and force feedback. Furthermore, the control wires 110 are driven directly by the linear actuators without gears, belts or pulleys, which avoids adding friction and prevents excessive slack in the control wires. The control wires 110 can be actively controlled in pull and push modes (tension and compression). Thus, the passive bending mode of active control can be implemented during insertion and removal (withdrawal) of the steerable instrument 100.

[0087] A particular advantage of the second embodiment is that in this case the actuator is passively moved by the drive wires, unlike force balancing using feedback, which is not subject to sensor noise or speed issues. Furthermore, friction is minimized (using unique frequencies and waveforms in the case of ultrasonic motor drive systems, or low friction surfaces such as air bearing stages in the case of linear induction motors), allowing the motor moving mass to move passively.

[0088] While all of the embodiments described herein are believed to provide significant advantages over the prior art of active bending modes, the second embodiment is believed to be even more advantageous, especially when using ultrasonic motors. That is, implementing the passive bending mode of active control with ultrasonic motors allows for steerable instruments with small moving weights and the ability to measure large forces without slowing down. Furthermore, the steerable instrument can operate in either active or passive control modes, independent of force and position sensing. The ultrasonic motor technology allows for high precision control with small actuators, allowing the steerable instrument to be very compact. Furthermore, the absence of mechanical slop allows for a seamless transition between active shape control and passive bending control, allowing for higher speed control without affecting force transfer.

[0089] Modifications, Definitions, and Other Embodiments The embodiments of the present invention may be implemented by a computer of a system or device that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may be more fully referred to as a "non-transitory computer-readable storage medium") to perform one or more functions of the aforementioned embodiments and / or includes one or more circuits (e.g., application specific integrated circuits (ASICs)) for performing one or more functions of the aforementioned embodiments, or may be implemented by a method performed by a computer of a system or device that reads and executes computer-executable instructions from a storage medium to perform one or more functions of the aforementioned embodiments and / or controls one or more circuits to perform one or more functions of the aforementioned embodiments. The computer may include one or more processors (e.g., central processing unit (CPU), microprocessing unit (MPU)) and may include a separate computer or a network of separate processors for reading and executing the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, one or more of a hard disk, a random access memory (RAM), a read-only memory (ROM), storage of a distributed computing system, an optical disk (such as a compact disk (CD), a digital versatile disk (DVD) or a Blu-ray Disc (BD)™), a flash memory device, a memory card, etc. The I / O interface may be used to provide a communication interface for input / output devices, including keyboards, displays, mice, touch screens, touchless interfaces (e.g., gesture recognition devices), printing devices, light pens, optical storage devices, scanners, microphones, cameras, drives, communication cables and networks (wired or wireless).

[0090] When referring to the description, specific details are set forth to provide a thorough understanding of the disclosed examples. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily lengthen the present disclosure. Unless otherwise defined herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. The breadth of the present invention is not limited by this specification, but rather only by the plain meaning of the claim terms employed.

[0091] It will be understood that when an element or component is referred to as "on," "to," "connected to," or "coupled to" another element or component, it may be directly on, connected to, or coupled to the other element or component, or there may be intervening elements or components present. In contrast, when an element is referred to as "directly on," "directly connected to," or "directly coupled to" another element or component, there are no intervening elements or components present. When used, the term "and / or" may be abbreviated as " / " and, when so provided, includes any and all combinations of one or more of the associated listed items.

[0092] For ease of description to describe the relationship of one element or feature to another as shown in the various figures, spatially relative terms such as "below," "below," "lower," "upper," "top," "proximal," "distal," and the like may be used herein. However, it should be understood that the spatially relative terms are intended to encompass various orientations of the device during use or operation in addition to the orientation depicted in the figures. For example, an element described as being "below" or "below" another element or feature would be oriented "above" that other element or feature if the device in the figures were flipped over. Thus, a relative spatial term such as "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein should be interpreted accordingly. Similarly, the relative spatial terms "proximal" and "distal" may be interchangeable, where applicable.

[0093] The term "about" or "approximately" as used herein means, for example, within 10%, within 5% or less. In some embodiments, the term "about" may mean within measurement error. In this regard, when described or claimed, all numerical values ​​may be read as if they were preceded by the word "about" or "approximately", even if the term is not explicitly indicated. The phrase "about" or "approximately" may be used when describing a size and / or location to indicate that the stated value and / or location is within a reasonable expected range of value and / or location. For example, a numerical value may include values ​​that are ±0.1% of the stated value (or range of values), ±1% of the stated value (or range of values), ±2% of the stated value (or range of values), ±5% of the stated value (or range of values), ±10% of the stated value (or range of values), etc. Any numerical range, when described herein, is intended to include all subranges subsumed therein.

[0094] In this specification, terms such as first, second, third, etc. may be used to describe various elements, components, regions, parts, and / or portions. It should be understood that these elements, components, regions, parts, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, region, part, or portion from another region, part, or portion. Thus, a first element, component, region, part, or section described below can be referred to as a second element, component, region, part, or section without departing from the disclosure of this specification.

[0095] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "comprising," as used herein, specifies the presence of recited features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof that are not expressly recited. It should also be noted that some claims may be drafted to exclude any element, and such claims may use exclusive terms such as "solely," "only," and the like in connection with the recitation of the claim elements, or may use a "negative" limitation.

[0096] In describing the exemplary embodiments illustrated in the drawings, specific terminology is used for clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is understood that each specific element includes all technical equivalents that function in a similar manner.

[0097] Although the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments, and the scope of the following claims should be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A steerable medical instrument, comprising: an elongated catheter body having a non-bendable section and at least one bendable section, the elongated catheter body including a plurality of channels extending longitudinally from a proximal end to a distal end of the elongated catheter body; a control wire disposed in a first channel along a wall of the elongated catheter body, the control wire extending through the non-bendable section and into the at least one bendable section such that a distal end of the control wire is attached to the at least one bendable section; a sensor configured to measure an amount of strain and an amount of displacement of the control wire; an actuator mechanically coupled to a proximal end of the control wire, the actuator configured to actuate the elongate catheter body by applying a driving force to the control wire to push or pull the at least one bendable section; a controller configured to: (a) monitor forces and displacements of the control wires based on measurements of the sensor; (b) control operation of the steerable medical instrument in an active mode; (c) control compliance of the steerable medical instrument in a passive mode of active control; and (d) alternate between the active mode and the passive mode of active control based on the monitored forces and displacements of the control wires; Equipped with the controller, in the active mode, controls actuation of the steerable medical instrument based on the driving force applied to the control wire by the actuator; the controller determines whether an external force other than the driving force acts on the control wire based on the monitored force and displacement of the control wire, and transitions to a passive mode of the active control based on a determination that the external force acts on the control wire, and the controller controls the control wire to conform to the external force by reducing the driving force applied to the control wire by the actuator to allow the control wire to be operated by the external force as if the control wire were disconnected from the actuator. Steerable medical instruments.

2. In a passive mode of active control, the controller controls the actuator to move the control wire in a direction opposite to the drive force applied to the control wire, such that the control wire is completely passive, as if the control wire were disconnected from the actuator. The steerable medical instrument of claim 1 .

3. In the active mode, the controller controls the actuator to apply the actuation force to the control wire to actively bend the elongate catheter body by displacing the control wire in a first direction, and the sensor outputs a first signal indicative of the amount of the strain applied to the control wire or the amount of the displacement of the control wire exerted by the actuation force. The steerable medical instrument of claim 1 .

4. In the passive mode of active control, the controller controls the actuator to stop applying the drive force to the control wire, such that the control wire is completely passive and can be moved by the external force as if the control wire was disconnected from the actuator. The steerable medical instrument of claim 3.

5. In a passive mode of the active control, the sensor is configured to output a second signal indicative of the external force on the control wire; the controller uses the second signal output from the sensor to cause the actuator to reduce the amount of the strain applied to the control wire or reduce the amount of the displacement of the control wire. The steerable medical instrument of claim 3.

6. In the passive mode of active control, the controller causes the actuator to reduce the driving force applied to the control wire to adjust the amount of strain applied to the control wire or the amount of displacement of the control wire.

6. The steerable medical instrument of claim 5.

7. In a passive mode of active control, the controller controls the actuator to move the control wire in a second direction opposite to the first direction such that the control wire is completely passive, as if the control wire were disconnected from the actuator. The steerable medical instrument of claim 3.

8. the sensor includes a strain gauge that measures the amount of strain on the control wire, and an encoder that measures the amount of displacement of the control wire regardless of the active mode and the passive mode of active control. The steerable medical instrument of claim 1 .

9. In the active mode, the sensor is configured to measure an amount of strain applied to the control wire by the actuation force and an amount of strain applied by the external force; the controller terminates the active mode and enters a passive mode of active control based on the amount of strain applied by the external force. The steerable medical instrument of claim 1 .

10. In the active mode, the controller is configured to receive an input signal from a user indicating an abnormality in the steerable medical instrument; the controller deactivating the active mode and entering a passive mode of active control based on the signal input by the user. The steerable medical instrument of claim 1 .

11. the actuator includes a direct drive motor directly coupled to the control wire; The steerable medical instrument of claim 1 .

12. the direct drive motor is a linear motor directly connected to the control wires; the controller controls the linear motor to exert a negligible force on the control wire using a command signal based on the external force.

12. The steerable medical instrument of claim 11.

13. the actuator includes a linear ultrasonic motor having a movable carriage and a stator; The controller controls the linear ultrasonic motor using a signal output from the sensor or a signal input by a user, and displaces the movable carriage by a force from the control wire. The steerable medical instrument of claim 1 .

14. In the passive mode of active control, while the sensor continues to output a position feedback signal and / or a force feedback signal based on the measured amount of strain or the measured amount of displacement of the control wire, the controller causes the actuator to drive the control wire such that the control wire is completely passive and is moved by the external force as if the control wire were decoupled from the actuator. The steerable medical instrument of claim 1 .

15. In the active mode, the at least one bendable section is configured to be driven in insertion and withdrawal directions through a tortuous path within a lumen; In a passive mode of the active control, the controller causes the actuator to drive the control wire to adjust the strain in the insertion direction and / or the withdrawal direction. The steerable medical instrument of claim 1 .

16. In the passive mode of active control, the controller causes the actuator to freely translate the control wire along the first channel without actuating the elongated catheter body while the control wire remains connected to the actuator. The steerable medical instrument of claim 1 .

17. the sensor continuously measures the amount of strain and the amount of displacement of the control wire in both the active mode and the passive mode of active control; the controller switches between the active mode and the passive mode of active control based on a difference between a desired amount and a measured amount of strain and displacement of the control wire. The steerable medical instrument of claim 1 .

18. the controller automatically switches between the active mode and the passive mode of active control without disconnecting the control wires from the actuators. The steerable medical instrument of claim 1 .

19. the controller automatically switches from the active mode to the passive mode of active control by actively controlling the actuator to move the control wire in a direction opposite to the direction of the external force until the external force becomes negligible; and / or the controller automatically switches from the passive mode of active control to the active mode by actively controlling the actuator to push or pull the control wire using the driving force after the external force becomes negligible; The steerable medical instrument of claim 1 .

20. The controller is further configured to switch between the active mode and the passive mode of active control based on a command input by a user. The steerable medical instrument of claim 1 .

21. Upon receiving the command input by the user, the controller switches from the active mode to the passive mode of active control by releasing or stopping the driving force or by actively controlling the actuator to move the control wire in a direction opposite to a direction of the external force until the amount of the strain measured by the sensor becomes negligible; the controller switches from the passive mode of active control to the active mode upon receiving a second command input by the user when the amount of strain measured by the sensor becomes negligible.

21. The steerable medical instrument of claim 20.

22. the actuator includes a direct drive unit coupled directly to the proximal end of the control wire; the controller controls the direct drive unit to move freely in a linear direction without friction and switches between the active mode and the passive mode of active control by at least temporarily stopping the direct drive unit in the passive mode of active control. The steerable medical instrument of claim 1 .

23. The actuator includes a rotary motor and a mechanism for converting rotary motion into linear motion; the rotary to linear motion conversion mechanism is coupled directly to the proximal end of the control wire such that the control wire can be controlled by applying the driving force in a first direction in the active mode. The steerable medical instrument of claim 1 .

24. In the passive mode of active control, the rotary motor drives the control wire in a second direction opposite to the first direction via the rotary-to-linear motion conversion mechanism so as to reduce the amount of strain in the control wire while the sensor continuously measures the amount of strain and the amount of displacement of the control wire.

24. The steerable medical instrument of claim 23.

25. the actuator includes a linear ultrasonic actuator directly coupled to the proximal end of the control wire; the controller switches from the active mode to the passive mode of active control by controlling the linear ultrasonic actuator to move the control wire in a linear direction without the driving force while the sensor continuously measures the amount of strain and the amount of displacement. The steerable medical instrument of claim 1 .

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