Method and system for controlling a flexible device in the presence of an abnormal sensor signal

Abstract

A computer-assisted medical system includes a flexible catheter configured to flex along a degree of freedom, an actuator positioned proximal to the flexible catheter, an actuator sensor, and a refractive sensor. The actuator is configured to actuate the flexible catheter along the degree of freedom, the actuator sensor is configured to provide an actuator sensor signal indicating movement of the actuator, and the refractive sensor is configured to provide a refractive sensor signal indicating refractiveness of the flexible catheter. The computer-assisted medical system further includes a controller coupled to the actuator and configured to determine a refractive estimate of the flexible catheter based on a model of the flexible catheter applied to the first actuator sensor signal, based on detecting an abnormality in the first refractive sensor signal, and to control the actuator based on the refractive estimate.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims the benefit of priority under 35 USC § 119(e) of U.S. provisional patent application No. 62 / 906,713 filed September 26, 2019, which is incorporated herein by reference as is.

[0003] Field of invention

[0004] The examples described in this specification relate to improved robot-assisted and / or medical devices, systems, and methods. Background Technology

[0005] For example, when worksites are accessible through one or more openings (e.g., one or more openings in humans, animals, machinery, etc.), a flexible device may be used to perform work at the worksite. For example, minimally invasive medical procedures may be performed through openings to reduce the amount of tissue damaged during the procedure, thereby reducing patient recovery time, discomfort, and adverse side effects. The openings may be natural openings within the patient's anatomical structures or surgical incisions. An operator (e.g., physician, physician assistant, surgeon, etc.) may insert minimally invasive medical instruments (including surgical, diagnostic, therapeutic, and / or biopsy instruments) through the openings to reach target tissue sites. Flexible and / or steerable slender devices, such as flexible catheters, may also be used to reach areas of interest within the patient's anatomical structures through anatomical passages. Control of such slender devices by an operator may involve the management of multiple degrees of freedom, including the insertion and retraction of the slender device relative to the patient's anatomical structure and the steering of the device. Various systems and methods for device control are required to address these and other challenges. Prior art literature

[0006] International Publication WO 2018 / 006046 A1

[0007] Generally, in one embodiment, one or more embodiments relate to a computer-assisted medical system comprising: a flexible catheter configured to bend along a degree of freedom; an actuator disposed proximal to the flexible catheter, wherein the actuator is configured to actuate the flexible catheter along a degree of freedom; a refractive sensor configured to provide a refractive sensor signal indicating the refractive of the flexible catheter; an actuator sensor configured to provide an actuator sensor signal indicating the movement of the actuator; and a controller coupled to the actuator and configured to determine a refractive estimate of the flexible catheter based on a model of the flexible catheter applied to the first actuator sensor signal and to control the actuator based on the refractive estimate, based on detecting an abnormality of the first refractive sensor signal.

[0008] Generally, in one embodiment, when one or more embodiments are executed by one or more processors associated with a medical system, the medical system: obtains a refraction sensor signal from a refraction sensor, wherein the refraction sensor signal represents the refraction of a flexible catheter; obtains an actuator sensor signal from an actuator sensor, wherein the actuator sensor signal represents the movement of an actuator configured to drive the refraction of a flexible catheter; and based on detecting an anomaly in the first refraction sensor signal, determines a refraction estimate based on a model of the flexible catheter applied to the first actuator sensor signal, and controls the actuator based on the refraction estimate. The invention relates to a non-transient machine-readable medium comprising machine-readable instructions.

[0009] Generally, in one embodiment, one or more embodiments relate to a method of operating a medical system comprising: a step of obtaining a refraction sensor signal from a refraction sensor, wherein the refraction sensor signal represents the refraction of a flexible slender device; a step of obtaining an actuator sensor signal from an actuator sensor, wherein the actuator sensor signal represents the movement of an actuator configured to drive the refraction of a flexible slender device; and a step of switching to an actuator feedback control mode based on detecting an abnormality in the first refraction sensor signal, wherein the switching step comprises: a step of determining a refraction estimate based on a model of a flexible slender device applied to the first actuator sensor signal; and a step of controlling an actuator based on the refraction estimate.

[0010] Other examples will be apparent from the following description and the attached claims. Brief explanation of the drawing

[0011] FIG. 1 schematically illustrates a computer-assisted medical system according to one or more embodiments. FIG. 2 illustrates an example of a computer-assisted medical system according to one or more embodiments. FIG. 3 illustrates an example of a manipulator assembly including a mechanism and a manipulator arm having the mechanism, according to one or more embodiments. FIG. 4 illustrates an example of a device manipulator including a catheter assembly according to one or more embodiments. FIGS. 5A and 5B schematically illustrate an example of a computer-assisted medical system including a flexible catheter according to one or more embodiments. FIG. 6 illustrates a medical scenario according to one or more embodiments. FIG. 7 illustrates an exemplary method for controlling a flexible catheter of a computer-assisted medical system according to one or more embodiments. FIG. 8 illustrates an exemplary method for controlling a flexible catheter of a computer-assisted medical system according to one or more embodiments. FIG. 9 illustrates an exemplary method for controlling a flexible catheter of a computer-assisted medical system according to one or more embodiments. FIG. 10 illustrates an exemplary method for performing system identification to obtain a model for controlling a flexible catheter of a computer-assisted medical system according to one or more embodiments. FIG. 11 illustrates an embodiment according to one or more embodiments. FIG. 12 provides an example for carrying out an embodiment of the present disclosure. Specific details for implementing the invention

[0012] Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same reference numerals for consistency.

[0013] In the following detailed description of the embodiments of the present disclosure, numerous specific details are described. However, it will be apparent to those skilled in the art that some embodiments may be practiced without these specific details. In other cases, known features have not been described in detail to avoid making the description unnecessarily complex.

[0014] Throughout this application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in this application). The use of ordinal numbers does not imply or create any particular order of elements or limit any element to a single element unless explicitly disclosed, as with the use of terms "before," "after," "single," and other such terms. Rather, the use of ordinal numbers is intended to distinguish elements. For example, a first element is distinguished from a second element, and the first element may include more than one element and may follow (or precede) the second element in the order of elements.

[0015] While some examples described herein refer to medical procedures and medical tools, the examples described herein may also be applicable to medical and non-medical procedures and to medical and non-medical tools. For example, the tools, systems, and methods described herein may be used for industrial applications, general robotic applications, and non-medical applications including the detection or manipulation of non-tissue workpieces. Other exemplary uses involve cosmetic enhancement, imaging of human or animal anatomical structures, data collection from human or animal anatomical structures, system setup or taking down, and training of medical or non-medical personnel. Additional exemplary uses include procedures on tissues removed from human or animal anatomical structures (without returning to the human or animal anatomical structures), and use for performing procedures on human or animal cadavers. Furthermore, these techniques may also be used in medical treatment or diagnostic procedures, with or without surgical modalities.

[0016] Generally, embodiments of the present disclosure may enable a computer-aided medical system comprising a flexible catheter to respond to one or more fault conditions. More specifically, a control method may be used to resolve a transient fault condition. A fault condition may introduce an error into a feedback signal obtained from a refraction sensor, for example, a sensor measuring the refraction (e.g., shape) of the flexible catheter. While the error is present, it may make the feedback signal less suitable or unsuitable for closed-loop control. The feedback signal may be used to control the position and / or movement of the flexible catheter under normal operating conditions, but when a fault condition is present, the control method may rely on an alternative feedback signal. The alternative feedback signal may be based on an actuator sensor signal, for example, a sensor signal indicating the movement of an actuator driving the refraction. For example, the actuator sensor signal may be processed by a simulation model of the flexible catheter to obtain an estimate of the actual refraction. The estimate may then be used as an alternative feedback signal to control the refraction.

[0017] A fault condition that may render the feedback signal obtained from the refraction sensor useless or less useful may include mechanical vibration. The fault condition(s) may be time-limited. For example, mechanical vibration may occur temporarily during the insertion or removal of a tool into or from a flexible catheter. Accordingly, an alternative feedback signal may be temporarily used for control until the appropriate feedback signal obtained from the refraction sensor returns. Thus, disturbances that would otherwise result from the deactivation of refraction control may be avoided.

[0018] Now, referring to drawings in which the same reference number indicates the same part throughout multiple drawings, FIG. 1 illustrates a simplified drawing of a computer-assisted medical system (100) according to one or more embodiments. The computer-assisted medical system (100) may be suitable for use, for example, in surgery, diagnosis, treatment, and / or biopsy procedures. While some embodiments are provided herein in relation to such procedures, any reference to medical (e.g., surgical) instruments and medical methods is non-limiting. The systems, instruments, and methods described herein may be used in animals, human cadavers, animal cadavers, parts of human or animal anatomical structures, non-surgical diagnosis, as well as industrial systems and general robotic or remotely operated systems.

[0019] As illustrated in FIG. 1, a computer-assisted medical system (100) generally includes a manipulator assembly (102) for operating a medical device (104) to perform various procedures on a patient (P) according to one or more embodiments of the present invention. The medical device (104) may include a flexible catheter and may be steered when extended into an internal part of the patient (P)'s body.

[0020] The manipulator assembly (102) and the mechanism (104) may be remote, non-remote, or hybrid remote and non-remote assemblies having selected degrees of motion freedom that may be electric and / or remotely operated and selected degrees of motion freedom that may be non-electric and / or non-remote operated. The manipulator assembly (102) may be mounted on a surgical table (T) or a main support (114) (e.g., a cart, a stand, a second table, etc.). A master assembly (106) may allow an operator (O) (e.g., a surgeon, a clinician, or a physician) to observe the site of intervention and control the manipulator assembly (102), including the mechanism (104).

[0021] The master assembly (106) may be located on an operator console, which may generally be located within the same room as the operating table (T), such as on the side of the operating table where the patient (P) is positioned. However, it should be understood that the operator (O) may be located in a different room or in a completely different building from the patient (P). The master assembly (106) may include one or more control devices for controlling the operator assembly (102). The control devices may include any number of various input devices, such as a joystick, trackball, data glove, trigger gun, manual operation controller, voice recognition device, body motion or presence sensor, etc. To provide the operator (O) with a strong sense of directly controlling the device (104), the control devices may be provided with the same degrees of freedom as the associated medical device (104). In this way, the control devices provide the operator (O) with telepresence or perception that the control devices are one with the medical device (104).

[0022] In one or more embodiments, the manipulator assembly (102) including a flexible catheter supports the medical device (104) and may include a kinematic structure of one or more non-servo-controlled links (e.g., one or more links that may be manually positioned in place and locked, generally referred to as setup structures) and / or one or more servo-controlled links (e.g., one or more motorized links that may be controlled in response to a command from a control system) and a manipulator. The manipulator assembly (102) may include a plurality of actuators (e.g., motors) that drive the medical device (104) in response to a command from a control system (e.g., control system (112)).

[0023] The actuator may include a drive system capable of advancing the medical device (104) into a naturally or surgically created anatomical opening when coupled to the medical device (104). Another drive system may move the distal end of the medical device (104) with one or more degrees of freedom, which may include at least a linear insertion / retraction motion and one or more bending motions for orienting the device, as described in detail below. Additionally, the actuator may be used to actuate a bending end effector of the medical device (104) for purposes such as grasping tissue within the jaws of a biopsy device. An actuator sensor (e.g., a resolver, encoder, potentiometer, and other mechanism) may provide sensor data describing the position, rotation, and / or orientation of the motor shaft to the medical system (100). This actuator sensor data may be used to determine the motion of an object manipulated by the actuator. The actuator sensor may include a proximal sensor positioned along the medical device or on the proximal side of another sensor used to measure the distal part of the medical device.

[0024] A computer-assisted medical system (100) may include a sensor system (108) having one or more subsystems for receiving information about an instrument (including a flexible catheter) of a manipulator assembly (102). Such subsystems may include a position / location sensor system (e.g., an electromagnetic (EM) sensor system); a shape sensor system for determining the position, orientation, speed, velocity, posture, and / or shape of one or more segments and / or distal portions along a flexible body that may constitute a flexible catheter that accommodates a medical instrument (104); and / or a visualization system for capturing images from the distal end of the instrument (104). One or more sensors of the sensor system (108) may include a distal sensor used to measure at the distal portion of the flexible catheter that accommodates the instrument and / or along the flexible catheter.

[0025] In one or more embodiments, the computer-assisted medical system (100) also includes a display system (110) for displaying an image or representation of a medical device (104) including a surgical site and a flexible catheter, which is generated by a subsystem of the sensor system (108) and recorded before or during surgery using image data and / or real-time images from imaging technologies such as computed tomography (CT), magnetic resonance imaging (MRI), fluoroscopy, thermography, ultrasound, optical coherence tomography (OCT), thermal imaging, impedance imaging, laser imaging, nanotube X-ray imaging, endoscopic imaging, etc. The pre-operative or intra-operative image data may be presented as a two-dimensional, three-dimensional, or four-dimensional image (e.g., including time-based or velocity-based information) and / or as an image from a model generated from a pre-operative or intra-operative image data set. The display system (110) and the master assembly (106) may be oriented so that the surgeon (O) can control the medical device (104) and the master assembly (106) through the perception of telepresence.

[0026] Referring again to FIG. 1, the computer-assisted medical system (100) may also include a control system (112). The control system (112) includes at least one memory and at least one computer processor (not shown) for executing control between the medical device (104), the master assembly (106), the sensor system (108), and the display system (110). The control system (112) also includes programmed instructions (e.g., a non-transient machine-readable medium storing instructions) for implementing some or all of the methods described below, including instructions for operating in the presence of unreliable or less reliable sensor signals as described with reference to the flowcharts of FIG. 7, FIG. 8, FIG. 9 and FIG. 10. Although the control system (112) is depicted as a single block in the simplified schematic diagram of FIG. 1, the system may include multiple data processing circuits having one part of processing performed optionally on or adjacent to the manipulator assembly (102), another part of processing performed on the master assembly (106), etc. Any wide range of centralized or distributed data processing architectures may be employed. Similarly, programmed instructions may be implemented as a number of individual programs or subroutines, or may be integrated into a number of other aspects of the system described herein.

[0027] In one or more embodiments, the control system (112) may receive force and / or torque feedback from the medical device (104). In response to the feedback, the control system (112) may transmit a signal to the master assembly (106). In some examples, the control system (112) may transmit a signal to one or more actuators of the manipulator assembly (102) commanding the medical device (104) to move (e.g., to move a flexible catheter).

[0028] Any suitable conventional and / or specialized actuator may be used to actuate a link or segment of the actuator assembly (102) and / or mechanism (104). One or more actuators may be separated from or integrated with the actuator assembly (102).

[0029] In one or more embodiments, the control system (112) may include a hierarchical control architecture. The hierarchical control architecture may include a supervisor state machine, a mid-level controller, and a servo controller (feedback controller) for each actuator. The supervisor state machine may be event-driven. Based on an event, the supervisor state machine may transmit a behavioral primitive to the mid-level controller. The behavioral primitive may be a high-level command specifying an overall goal, such as the target configuration of the manipulator assembly (102). In response, the mid-level controller may issue a servo command to the servo controller to move the actuator. More specifically, the mid-level controller may perform numerical calculations to configure, initialize, and reset the servo controller based on the behavioral primitive. For example, the mid-level controller may transmit parameters specifying a position and / or trajectory to the servo controller. The servo controller may then drive the actuator based on a command received from the intermediate-level controller. The servo controller may report back to the supervisor state machine, for example, to indicate whether the movement was successfully executed according to the servo command. Additional aspects of the control system (112) are described below with reference to FIGS. 7, 8, 9 and 10. In one or more embodiments, the supervisor state machine and the intermediate-level controller have low latency. For example, a response to an event may be provided within 50 ms. Each servo controller may operate a closed loop using Proportional-Integral-Derivative (PID), Proportional-Derivative (PD), full-state feedback, sliding mode and / or various other control schemes. Feedback signals to the servo controller may be obtained, for example, from an encoder or resolver of the actuator controlled by the servo controller.Alternatively, as further described below, the servo controller may also rely on other sensors for feedback. More specifically, a servo controller for controlling the bending (e.g., flexion) of a flexible catheter may use signals from a bending sensor, e.g., a flexion or shape sensor, to control the bending or flexion of the flexible catheter. A more detailed description of various aspects of the control system (112) is provided below with reference to FIGS. 7, 8, 9, and 10.

[0030] Referring again to FIG. 1, the control system (112) may operate in various modes in addition to the aforementioned servo control mode. For example, the control system (112) may control one or more of the joints of the actuator assembly described below to float. The floating joint may be driven in reverse by an externally applied force or a braking force reacting to a sufficient externally applied force without a control algorithm. For example, a user may cause the floating joint to be driven in reverse by applying a force that meets one or more criteria (e.g., magnitude, direction, duration, frequency, etc.) to a link on the distal side of the floating joint. The floating joint may also be gravity-compensated, particularly when floating in degrees of freedom affected by gravity (e.g., a vertical joint or a non-horizontal direction). Furthermore, friction compensation may facilitate the driving in reverse. Additionally or alternatively, the floating joint may also be controlled to impart other characteristics, such as a specific level of damping.

[0031] In one or more embodiments, the floating joint may be particularly advantageous during the setup phase, so that during the setup phase, when preparing to perform a procedure using the device (104), the assistant can manually position and / or orient the manipulator assembly (102) by reversing the floating joint. Multiple control modes may be combined during the operation of the manipulator assembly, for example, some joints may be position-controlled to resist or rebound external bending of these joints, while other joints may be floating to facilitate external bending of these other joints.

[0032] The control system (112) may optionally include a virtual visualization system to provide navigation assistance to the operator (O) when controlling the medical instrument (104) during an image-guided surgical procedure. Virtual navigation using the virtual visualization system may be based on a reference to an acquired preoperative or intraoperative data set of anatomical passages.

[0033] During a virtual navigation procedure, a sensor system (108) may be used to calculate the approximate location of a medical device (104) relative to the anatomical structure of the patient (P). The location may be used to generate both a macroscopic (external) tracking image of the anatomical structure of the patient (P) and a virtual internal image of the anatomical structure of the patient (P). The system may include one or more electromagnetic (EM) sensors, fiber optic sensors, and / or other sensors for aligning and displaying the medical device together with preoperative surgical images, such as those from a virtual visualization system. For example, PCT publication WO 2016 / 191298 (published December 1, 2016), incorporated herein by reference as is (disclosing "Systems and Methods of Registration for Image Guided Surgery") discloses an exemplary system.

[0034] The computer-assisted medical system (100) may further include optional motion and support systems (not shown), such as a lighting system, a steering control system, a perfusion system, and / or a suction system. In some embodiments, the computer-assisted medical system (100) may include more than one manipulator assembly and / or more than one master assembly. The exact number of remote manipulator assemblies may depend, among other factors, on the surgical procedure and spatial constraints within the operating room.

[0035] In some embodiments, the manipulator assembly (102), control system (112), sensor system (108), and display system (110) may all be supported by a support structure (114) or integrated within the support structure (114). Alternatively, one or more components (e.g., manipulator assembly (102), control system (112), sensor system (108), and / or display system (110)) may be mounted on the operating table (T) or integrated into the master assembly (106).

[0036] FIG. 2 illustrates an example of a computer-assisted medical system (200) according to one or more embodiments. The computer-assisted medical system (200) may include a master control (220) and a system cart (214) that supports a manipulator assembly (202) and a display system (216). The manipulator assembly (202) may be configured to support and position an elongated device, such as a flexible catheter (222). Various elongated devices are described in PCT / US18 / 43041 (filed July 20, 2018) (disclosing "Flexible elongate device systems and methods"), to which various elongated devices are incorporated herein by reference. The system cart (214) supports a display system (216) comprising a monitor support arm (210) and a display monitor (216a, 216b).

[0037] The computer-assisted medical system (200) of FIG. 2 also includes a master control (220) according to one or more embodiments, some of which are described with respect to the master assembly (106). The master control (220) may include various input controls for an operator (e.g., operator (O), FIG. 1) to use for interactively controlling the operation of the actuator assembly (202), for example, a function performed by the mechanical actuator (206). In one or more embodiments, the master control (220) includes a scroll wheel and a trackball on a surface that enable the operator to control an aspect of the computer-assisted medical system (200). In an exemplary embodiment, the scroll wheel may be rolled forward or backward to control the advancement / insertion or retraction of a medical device (e.g., a flexible catheter (222)) relative to the patient's anatomical structure, and the trackball may be rolled in various directions by an operator to steer the position of the distal end and / or distal tip of the flexible catheter (222), for example, to control bending or flexion. Various systems and methods related to motion control consoles are described in PCT / US18 / 44419 (filed July 30, 2018) ("Systems and methods for safe operation of a device") and U.S. Patent Application No. 16 / 049,640 (filed July 30, 2018) ("Systems and methods for steerable elongate device"), which are incorporated herein by reference as is.

[0038] FIG. 3 illustrates a manipulator assembly (202) comprising a mechanism manipulator (206) coupled to a support structure (204) according to one or more embodiments of the present invention. The links of the support structure (204) may include one or more non-servo-controlled links (e.g., manually positioned and locked in place) and / or one or more servo-controlled links (e.g., motorized links that may be controlled in response to commands from a control system). The support structure (204) provides adjustments for positioning the mechanism manipulator (206) to an optimal position and orientation and / or positioning the flexible catheter (222) to optimally position the flexible catheter (222) relative to a patient anatomical structure or other medical device. For example, the support structure (204) may provide rotation (E1) about an axis (E), extension / contraction (E2) along the axis (E), rotation (D1) about an axis (D), rotation (C1) about an axis (C), and rotation (B1) about an axis (B) to position the instrument manipulator (206) at a desired position for a table (T), a medical device, and / or a patient (P).

[0039] In some embodiments, the optimal location and orientation may include the alignment of the instrument manipulator (206) with respect to the patient's anatomical structure to minimize friction of the flexible catheter (222) positioned within the patient's anatomical structure (e.g., anatomical opening, patient vascular structure, patient endovascular passage, etc.) or within a medical device coupled to the patient's anatomical structure (e.g., cannula, trocar, endotracheal tube (ETT), laryngeal esophageal mask (LMA), etc.). In other embodiments, the optimal location and orientation of the instrument manipulator (206) may additionally or alternatively include optimizing the operator (O) ergonomics by providing sufficient operator workspace and / or ergonomic access to the flexible catheter (222) when using various medical tools such as needles, grippers, scalpels, grippers, ablation probes, visualization probes, etc., together with the flexible catheter (222).

[0040] The instrument manipulator (206) may also be configured to provide remote manipulation, robotic control, or other forms of controlled translation or manual translation (A1) along an axis (A) to provide insertion and retraction of the flexible catheter (222) into the patient's anatomical structure.

[0041] Each adjustment (e.g., A1, B1, C1, D1, E1, and E2) may be operated by robot control or by manual intervention of an operator. For example, in one embodiment, each rotational or linear adjustment may be held in a fixed configuration using a brake, so that pressing one or more buttons and switches releases one or more corresponding brakes, allowing the operator to manually position the mechanism manipulator. Additionally or alternatively, one or more adjustments may be controlled by one or more actuators (e.g., motors), so that the operator may use a button or switch to operate the motor to change the support structure (204) and / or the mechanism manipulator (206) to position the manipulator assembly (202) in a desired configuration, typically to provide the optimal position and orientation of the mechanism manipulator (206).

[0042] Referring again to FIG. 3, the manipulator assembly (202) may be equipped with various control buttons (324, 326, 328, 330) that may be used for various purposes, such as adjusting the coupled links and unlocking the support structure (204) for free movement, to allow adjustment (C1, D1, E1 and / or E2) and / or linear adjustment (A1) for manual translational movement by an operator rather than by robot control to insert / retract a medical device (e.g., flexible catheter (222)). In one or more embodiments, for safety purposes, the device manipulator (206) may be manually movable only in one direction along a linear axis (A), such as retraction, to prevent the operator from inadvertently or undesirably advancing the medical device against the patient's anatomical structure, which could cause injury to the patient, and may not be manually movable in a direction along the linear axis (A) corresponding to the insertion of the medical device. In another example, robotic or manual control of rotational motion (B1) about axis (B) may be enabled by pressing a switch. Additionally, one or more buttons may be used to control visual indicators, markers, and / or images displayed on a touchscreen on a monitor (216a, 216b) and / or a master control (220).

[0043] FIG. 4 illustrates an example of a device manipulator (406) that may be substantially similar to the device manipulator (206). The device manipulator (406) may include a base (404), an insertion stage (402), and a device carriage (408) to which a catheter assembly (410) is coupled. In one or more embodiments, the device manipulator (406) provides insertion and retraction of the catheter assembly (410) into the patient's anatomical structure by moving the device carriage (408) and the insertion stage (402) in an extendable manner relative to the base (404) and along a linear axis (A), as also illustrated in FIG. 6. Thus, the device manipulator (406) provides an insertion degree of freedom for the insertion and retraction of the flexible catheter (410a) along the linear axis (A). In a medical scenario, insertion may advance the flexible catheter (410a) into the patient's anatomical structure, while retraction may withdraw the flexible catheter (410a) from the patient's anatomical structure.

[0044] The base (404) includes a shaft portion (404a) and a main portion (404b). As described in detail below, the shaft portion (404a) is removablely coupled to a device connector or pivot connector (418) that accommodates a flexible catheter (410a). An insertion stage (402) is coupled to the main portion (404b) of the base (404) and translates along the main portion (404b). An instrument carriage (408) is coupled to the insertion stage (402) and translates along it. The catheter assembly (410) may include a flexible catheter (410a) and a control assembly (410b). The instrument carriage (408) is coupled to the control assembly (410b) at the instrument interface (414) of the instrument carriage (408). The instrument manipulator (406) is also coupled to a probe assembly (416) comprising a probe (416b) and a probe connector (416a). The probe assembly (416) may be inserted into the operating lumen of the flexible catheter (410a) via a connector (412) on the control assembly (410b) or may extend through the flexible catheter (410a). The probe (416b) may include, for example, a viewing scope assembly that provides an image of the surgical site. The instrument carriage (408) may include electronic and optical components that provide endoscopic functions to the probe (416b). In some embodiments, the probe assembly (416) may be detached from the instrument manipulator (406) and the flexible catheter control assembly (410b) and removed from the catheter assembly (410). Alternative instruments, such as biopsy needles, excision tools, and other flexible instruments, may be coupled to the instrument manipulator (406) and / or the catheter assembly (410) through the operating lumen of the flexible catheter (410a).

[0045] Referring further to FIG. 4, the device connector or pivot connector (418) may include a manipulator interface that may be removablely coupled to the base (404), a distal end that may be removablely coupled to a patient medical device (420), for example, an endotracheal tube, and a proximal end that may receive a flexible catheter (410a). The patient medical device (420) (e.g., an endotracheal tube, a laryngeal mask airway, a cannula, etc.) may be fixed to the patient anatomical structure to facilitate the insertion of various medical devices into the patient anatomical structure. For example, the patient medical device (420) may be an endotracheal tube inserted into the mouth and trachea of ​​the patient (P) to provide a conduit for a flexible catheter (410a) to be navigated within the lungs of the patient (P) to facilitate imaging, biopsy, and / or treatment. Various systems and methods related to device connectors are described in PCT / US2018 / 017085 (filed February 6, 2018) (disclosing "Systems and methods for coupling components of a medical system"), which is incorporated herein by reference as is. In some embodiments, the flexible catheter (410a) is extended via a catheter guide (422), which is an optionally foldable and extendable device that supports the length of the flexible catheter (410a) during movement of the instrument carriage (408). The flexible catheter (410a) without the guide may be buckled in an area that does not have lateral support, for example, in the space between the instrument interface (414) and the device connector (418). To avoid buckling, the catheter guide (422) may function as a buckling prevention guide by providing lateral support to the flexible catheter (410a).Various systems and methods related to catheter guides are described in PCT / US2017 / 041160 (filed July 7, 2017) (disclosing "Guide apparatus for delivery of an elongate device and methods of use"), which is incorporated herein by reference as is.

[0046] FIG. 5a is a simplified drawing of a computer-assisted medical system (500) according to one or more embodiments. While the aforementioned drawings primarily illustrate aspects of the entire computer-assisted medical system (100) and instrument manipulator (206), FIG. 5a and FIG. 5b primarily illustrate aspects related to a flexible catheter (502). The computer-assisted medical system (500) may be similar to the computer-assisted medical system (100) previously introduced with reference to FIG. 1. The computer-assisted medical system (500) may include a flexible catheter (502) (or more generally, an elongated flexible device) on an instrument interface (504). The instrument interface may be a physical interface that enables the coupling of the flexible catheter to other components of the computer-assisted medical system (500). In the example of FIG. 4, the instrument interface may be part of an instrument carriage (408).

[0047] In one or more embodiments, the flexible catheter (502) comprises a flexible body (516) having a proximal portion (517) and a distal portion (518) (e.g., a tip portion). The flexible body (516) may have an outer diameter of approximately 3 mm. Other flexible body outer diameters may be larger or smaller.

[0048] The flexible body (516) may include a lumen or channel (521) that is sized and molded to accommodate a medical device (526), ​​as illustrated in FIG. 5b. FIG. 5b is a simplified drawing of the flexible body (516) having an extended medical device (526) according to one or more embodiments. The medical device (526) may be used for procedures including, but not limited to, surgery, biopsy, resection, illumination, perfusion, and / or aspiration. For example, the medical device (526) may be a flexible bronchial device, such as a bronchoscope or bronchial catheter, for use in the examination, diagnosis, biopsy, or treatment of the lungs. The medical device (526) may also be suitable for navigation and treatment of other tissues through naturally or surgically created and connected passages within any various anatomical system, including the large intestine, small intestine, kidneys and renal calyces, brain, heart, circulatory system including vascular structures, etc.

[0049] The medical device (526) may be deployed through the lumen (521) of the flexible body (516) and may be used at a target site within an anatomical structure. The medical device (526) may include, for example, an image capture probe, a biopsy device, a laser ablation fiber, and / or other surgical, diagnostic, or therapeutic tools. The medical tool may include an end effector having a single operating member, such as a scalpel, a blunt blade, an optical fiber, an electrode, etc. Other end effectors may include, for example, forceps, a gripper, scissors, clip appliers, etc. Other end effectors may further include an electro-activated end effector, such as an electrosurgical electrode, a transducer, a sensor, etc. In one or more embodiments, the medical device (526) is a biopsy device that may be used to remove a sample of tissue or cells from a target anatomical site. The medical device (526) may also be used in conjunction with an image capture probe within the flexible body (516).

[0050] Returning to FIG. 5a, the medical device (526) may be an image capture probe comprising a distal portion having a stereoscopic or monoscopic camera at or near the distal portion (218) of the flexible body (516) to capture an image (including video images) that is processed by a visualization system (531) for display and / or provided to a tracking unit (530) to support tracking of one or more of the distal portion (518) and / or segments (524). The image capture probe may include a cable coupled to the camera to transmit the captured image data. In some examples, the image capture device may be a bundle of optical fibers, such as a fiber optic cable, coupled to the visualization system (531). Alternatively, the medical device (526) itself may be the image capture probe. The medical device (526) may be advanced from the opening of the lumen (521) to perform a procedure and then retracted back into the lumen when the procedure is completed. The medical device (526) may be removed from the proximal portion (517) of the flexible body (516) or from another optional device port (not shown) along the flexible body (516).

[0051] In one or more embodiments, one or more actuators (506) may be used to drive the flexible catheter (502). For example, one actuator may be used to drive the catheter along the insertion degree of freedom of the flexible catheter. Additional actuators may also be used to drive the catheter along one or more degrees of freedom of bending, as also described below. In one or more embodiments, the flexible body (516) accommodates a traction wire, link device, or other steering control (540) extending between the actuator (506) and the distal part (518) to controllably bend the distal part (518), for example, as illustrated by the dashed line illustration (519) of the distal part (518). In one or more embodiments, at least four traction wires (540) actuated by at least four actuators (506) are used to provide independent up-and-down steering to control the pitch of the distal portion (518) and left-and-right steering to control the yaw of the distal portion (518). A steerable elongated device is described in detail in U.S. Patent Application No. 13 / 274,208 (filed October 14, 2011), which is incorporated herein by reference as is (disclosing "Catheter with Removable Vision Probe"). Further details regarding a control mechanism for a control system for controlling a flexible catheter are provided in U.S. Patent Application No. 62 / 671,758, which is incorporated herein by reference as is (disclosing "Control Mechanism of a Catheter Control System"). In one or more embodiments, the actuator (506) may be removablely coupled to the flexible catheter (502) through the mechanism interface (504). The actuator (506) may be, for example, a servo motor, a hydraulic and / or pneumatic actuator, etc.Referring to FIG. 4, the actuator (506) may be housed, for example, within the control assembly (410b) of the mechanism carriage (408).

[0052] Referring further to FIG. 5a, when the actuator applies torque, a capstan (not shown) attached to the actuator's drive shaft may be rotated. Rotation may cause additional winding or unwinding of the traction wire (540) around the capstan, thereby acting the traction wire to steer the distal end (518) of the flexible catheter (502). Each traction wire (540) may be driven by an individual actuator. Accordingly, the tension on each traction wire (540) may be controlled individually.

[0053] Monitoring the rotational position (e.g., angle) and / or rotational speed of the capstan or actuator may be used to provide an indication of how far the traction wire (540) is released or pulled. Thus, the rotational angle and / or rotational speed of the capstan and / or the torque applied by the actuator to drive the capstan may provide useful feedback for steering to be applied to the distal end (518). In which way the distal end (518) bends may depend on the arrangement of the traction wire (540) relative to other traction wires that also contribute to steering. Actuator sensors (508), such as resolvers, encoders, potentiometers, and other mechanisms, may be used to track the rotation and / or orientation of the capstan and / or actuator. The motor current of the actuator may also be used to calculate the force and / or torque applied to the traction wire (540).

[0054] When configured to act as a resistor, a pair of actuators (506) (e.g., a pair of actuators for pitch control of the distal portion (518) and a pair of actuators for yaw control of the distal portion (518)) may be used to bend the distal portion (518) and control the rigidity of the flexible body (516). Additionally, by maintaining a minimum level of tension on the traction wire (540), looseness of the traction wire (540) may be avoided. Releasing or reducing the force on the traction wire (540) of the flexible catheter (502) may cause a corresponding reduction in rigidity or stiffness of the flexible catheter (502). Similarly, applying or increasing the traction force on the traction wire (540) of the flexible body (516) may cause an increase in rigidity or stiffness of the flexible catheter (502). For example, the material of the flexible body (516) may become more rigid when a plurality of steering traction wires are pulled simultaneously. The rigidity or stiffness of the flexible catheter (502) may be a closed-loop rigidity or stiffness controlled by a control system. Examples of a closed-loop catheter control system and method are described, for example, in U.S. Patent Application No. 13 / 274,198 (filed October 14, 2011), which is incorporated herein by reference as is (disclosing "Catheters with Control Modes for Interchangeable Probes").

[0055] In one or more embodiments, the computer-assisted medical system (500) may further include a tracking unit (530) for determining the position, orientation, speed, velocity, attitude, and / or shape of a distal portion (518) and / or one or more segments (524) along a flexible body (516) using one or more sensors and / or imaging devices as described in more detail below. The tracking unit (530) may be implemented as hardware, firmware, software, or a combination thereof. One or more aspects of the tracking unit may be performed by processor(s) of the control system (112) of FIG. 1.

[0056] The tracking unit (530) may track the distal portion (518) and / or one or more segments (524) using a refraction sensor such as the shape sensor (522). The shape sensor (522) may include an optical fiber aligned with the flexible body (516) (e.g., provided within an internal channel (not shown) of the flexible body (516) or mounted externally). In one embodiment, the optical fiber has a diameter of approximately 200 μm. The diameter of the fiber may be larger or smaller without departing from the present disclosure. The optical fiber of the shape sensor (522) forms an optical fiber bending sensor for determining the shape of the flexible body (516). An optical fiber including a fiber Bragg grating (FBG) may be used to provide strain measurements within the structure in one or more dimensions. Various systems and methods for monitoring the shape and relative position of an optical fiber in three dimensions are all described in U.S. Patent Application No. 11 / 180,389 (filed July 13, 2005) ("Fiber optic position and shape sensing device and method relating thereto"), which is incorporated herein by reference; U.S. Patent Application No. 12 / 047,056 (filed July 16, 2004) ("Fiber-optic shape and relative position sensing"); and U.S. Patent No. 6,389,187 (filed June 17, 1998) ("Optical Fibre Bend Sensor"). Other suitable strain sensing techniques, such as Rayleigh scattering, Raman scattering, Brillouin scattering, and fluorescence scattering, may be employed without departing from the present disclosure. Alternatively, the shape of the elongated device may be determined using other techniques.For example, the history of the distal end position of the flexible body (516) may be used to reconstruct the shape of the flexible body (516) over a given time interval.

[0057] Referring further to FIG. 5a, the tracking unit (530) may receive a raw signal from the shape sensor (522). In one or more embodiments, the tracking unit (530) processes the raw signal to obtain information about the shape of the flexible body (516). The information obtained may be about the shape of the distal portion (518) and / or one or more segments (524) along the flexible body (516). The tracking unit (530) may, for example, provide feedback about the bending of the flexible catheter (502) in combination with the shape sensor (522). The tracking unit may also be configured to detect abnormalities in the shape sensor (522) and / or the tracking unit itself. For example, the tracking unit (530) may detect noise (such as vibration) within the raw signal. The tracking unit (530) may also detect a defective raw signal associated with a contaminated or poorly fitted fiber optic connector to the shape sensor (522).

[0058] In some embodiments, the tracking unit (530) uses a position sensor system (520) to optionally and / or additionally track the distal part (518). The position sensor system (520) may use, for example, any suitable sensing technology or a combination of sensing technologies such as electromagnetic technology. The electromagnetic (EM) sensor system may include one or more conductive coils that may receive an externally generated electromagnetic field. Each coil of such EM sensor system used to implement the position sensor system (520) subsequently generates an induced electrical signal having characteristics that depend on the position and orientation of the coil with respect to the externally generated electromagnetic field. In some embodiments, the position sensor system (520) may be configured and positioned to measure six degrees of freedom, for example, three position coordinates (X, Y, Z) of a base point and three orientation angles indicating pitch, yaw, and roll, or five degrees of freedom, for example, three position coordinates (X, Y, Z) of a base point and two orientation angles indicating pitch and yaw. Further description of a position sensor system is provided in U.S. Patent No. 6,380,732 (filed August 11, 1999), which is incorporated herein by reference as is (disclosing "Six-Degree of Freedom Tracking System Having a Passive Transponder on the Object Being Tracked"). The position sensor system (520) may also be used as a refraction sensor. For example, a plurality of sensors (520), such as EM sensors, may be positioned along the flexible catheter (502) (e.g., on a plurality of segments (524)), and the refraction (e.g., shape) of the flexible catheter (502) may be determined based on the detected position of the sensors (520).

[0059] Information from the tracking unit (530) may be transmitted to the navigation system (532), which may be combined with information from the visualization system (531) and / or a model obtained prior to surgery to provide real-time location information to a doctor or other operator. Real-time location information may be displayed on the display system (110) of FIG. 1 for use in controlling the computer-assisted medical system (500). In some examples, the control system (112) of FIG. 1 may use the location information as feedback for positioning the computer-assisted medical system (500). Various systems for using fiber optic sensors to align surgical instruments with surgical images and display them are provided in U.S. Patent Application No. 13 / 107,562, filed May 13, 2011, which discloses “Medical System Providing Dynamic Registration of a Model of an Anatomic Structure for Image-Guided Surgery,” incorporated herein by reference as is.

[0060] FIG. 6 schematically illustrates a medical scenario including a side view of the patient coordinate space according to one or more embodiments. The surgical scenario (600) may include a patient (P) positioned on a platform (602). An instrument carriage (606) is mounted on an insertion stage (608) as also illustrated in FIG. 4. The instrument carriage (606) may be used to control the insertion / retraction (e.g., motion along the insertion axis (A)) of a flexible catheter (610) into and out of the anatomical structure of the patient (P), thereby establishing the insertion degrees of freedom for the flexible catheter (610). The instrument carriage (606) may also be used to control the motion (e.g., bending) of the distal end (618) of the flexible catheter in a number of directions including yaw and pitch. The mechanism carriage (606) or the insertion stage (608) may include an actuator, such as a servo motor (not shown), that controls the motion of the mechanism carriage (606) along the insertion stage (608). Additionally, the mechanism carriage (606) may include an actuator that controls the bending of the distal portion (618) of the flexible catheter.

[0061] The flexible catheter (610) may be coupled to the mechanism interface (612) described for FIGS. 4 and 5. The mechanism interface (612) may be coupled to and fixed to the mechanism carriage (606). In one or more embodiments, the optical fiber shape sensor (614) provides information about the configuration of the flexible catheter (610), for example, including the position and / or orientation of the distal portion (618) of the catheter (610). The position measuring device (620) may provide information about the position of the mechanism interface (612) when moving along the retraction and / or insertion axis (A) (such as the direction along the longitudinal central axis of the mechanism body) to set the insertion freedom of the flexible catheter (610). The position measuring device (620) may include a resolver, encoder, potentiometer, and / or other sensor that determines the rotation and orientation of a drive shaft that controls the motion of the mechanism carriage (606) and consequently the motion of the mechanism interface (612). The insertion stage (608) may be linear, curved, or a combination thereof.

[0062] FIGS. 1, 2, 3, 4, 5a, 5b, and 6 illustrate various configurations of components, but other configurations may be used without departing from the scope of the present disclosure. For example, various components may be combined to form a single component. As another example, a function performed by a single component may be performed by two or more components. Additionally, while components are described in the context of medical scenarios, embodiments of the present disclosure may be equally applicable to other domains involving robotic manipulation, e.g., non-medical scenarios or systems. Embodiments of the present disclosure may be suitable for use, e.g., in surgical, diagnostic, therapeutic, and / or biopsy procedures. While some embodiments are provided herein in relation to such procedures, any reference to medical or surgical instruments and medical or surgical methods is non-limiting. The systems, instruments, and methods described herein may be used in animals, human cadavers, animal cadavers, parts of human or animal anatomical structures, non-surgical diagnostics, as well as industrial systems and general robotic or remotely operated systems. Rather than interacting with the anatomical structure of a patient or subject, systems, instruments, and methods may operate or interact at any type of work site.

[0063] FIGS. 7, 8, 9, and 10 illustrate flowcharts according to one or more embodiments. One or more of the operations of FIGS. 7, 8, 9, and 10 may be performed by various components of the system described above with reference to FIGS. 1, 2, 3, 4, 5a, 5b, and 6. These figures describe a specific manipulator assembly and a specific flexible catheter, wherein the manipulator assembly and the flexible catheter have specific degrees of freedom. However, the method described below is not limited to a specific configuration of the manipulator assembly, the flexible catheter, and / or degrees of freedom. Instead, the method is applicable to any type of flexible catheter supported by a manipulator assembly used in any type of scenario.

[0064] Although the various operations of these flowcharts are presented and described sequentially, a person skilled in the art will understand that some or all of the operations may be executed in a different order, may be combined or omitted, or may some or all of the operations be executed in parallel. Additional operations not illustrated in the flowcharts may also be performed. Furthermore, operations may be performed actively or passively. For example, some operations may be performed using polling or interrupt-driven according to one or more embodiments of the present disclosure. For example, a decision operation may not require the processor to process an instruction if an interrupt is not received to indicate that a state exists according to one or more embodiments of the present disclosure. As another example, a decision operation may be performed by performing a test, such as checking a data value to test whether the value matches a tested condition according to one or more embodiments of the present disclosure. Accordingly, the scope of the present disclosure should not be considered limited to a specific arrangement of operations illustrated in FIGS. 7, FIGS. 8, FIGS. 9, and FIGS. 10.

[0065] The flowcharts of FIGS. 7, 8, 9, and 10 illustrate a method for handling an anomaly (e.g., a transient fault condition) according to one or more embodiments. The fault condition may introduce an error into a feedback signal obtained from a sensor measuring the deflection of a flexible catheter. For example, the sensor signal of a shape sensor measuring the shape of a flexible catheter may become unavailable in the presence of mechanical vibration. Mechanical vibration may be generated, for example, by the insertion or removal of a tool (e.g., a vision probe, tool, needle, forceps, etc.). These tools may be more rigid than the flexible catheter and may excite some vibration during insertion / retraction. The fault condition may be transient. For example, the fault condition may disappear once the insertion or retraction of the tool is completed or immediately thereafter. While the error in the sensor signal is present, it may make the sensor signal unsuitable or less suitable for use as a feedback signal for closed-loop control. Accordingly, in the presence of the anomaly, the control method may rely on an alternative feedback signal. In one or more embodiments, the alternative feedback signal is an estimate of the actual refraction. The estimate of the actual refraction may be generated by a model of the flexible catheter based on a sensor signal indicating the movement of an actuator driving the refraction of the flexible catheter.

[0066] The flowchart of FIG. 7 illustrates an exemplary method (700) for controlling a flexible catheter according to one or more embodiments. The method may be used to control the bending of the flexible catheter. The bending may follow one or more degrees of freedom (e.g., pitch and / or yaw). A single segment (e.g., end segment), multiple segments, or the entire flexible catheter may be bent. For example, the distal portion (518) of the flexible catheter (502) shown in FIG. 5a may be bent. The method (700) may be executed repeatedly to control the flexible catheter over time, for example, based on the cycle time of a control loop implemented to control the bending of the flexible catheter.

[0067] In operation 702, a refraction sensor signal is obtained from a refraction sensor. The refraction sensor signal may indicate the refraction (e.g., shape) of at least a portion of the flexible catheter. As previously described, the refraction sensor may be any type of sensor suitable for measuring the refraction of the catheter. The refraction sensor may detect along a single or multiple degrees of freedom of refraction. The refraction sensor may detect the refraction of a single segment, multiple segments, or the entire flexible catheter. The sensor may be a shape sensor, for example, as previously described. The refraction sensor signal may provide a value for the refraction, and the value may indicate the angle, position, orientation, speed, velocity, posture, and / or shape of one or more portions of the flexible catheter. The refraction sensor signal may be accompanied by one or more flags for labeling the refraction sensor signal. For example, the refractive sensor signal may be labeled as unreliable when the tracking unit (e.g., as described with reference to FIG. 5a) concludes that the raw sensor signal obtained from the refractive sensor is unreliable (e.g., based on a buffer that holds only old raw refractive sensor signal values). The refractive sensor signal may not provide a value when the raw sensor signal is considered unreliable.

[0068] In operation 704, an actuator sensor signal is obtained from the actuator sensor. The actuator sensor signal may indicate the movement (e.g., position or rotation) of the actuator used to drive the bending of the flexible catheter (e.g., by pulling the traction wire or releasing tension). As previously described, the actuator sensor may be any type of sensor suitable for measuring the movement of the actuator driving the bending. The actuator sensor may be, for example, an encoder on the motor shaft of a servo motor (e.g., an incremental encoder). If multiple actuators are used for bending along one or more degrees of freedom, the bending sensor signal may include signals obtained from multiple encoders. A configuration for driving bending using one or more actuators has been described with reference to FIG. 5a. The actuator sensor signal may provide one or more values ​​indicating the state of the actuator, for example, the angle of the motor shaft. The actuator sensor signal may include position and / or velocity information.

[0069] A person skilled in the art will understand that refraction sensor signals and actuator sensor signals may contain position and / or velocity information. A velocity signal may be obtained from a position signal through numerical differentiation. Similarly, a position signal may be obtained from a velocity signal through numerical integration.

[0070] In operation 706, a test may be performed to determine whether an abnormality exists in the refractive sensor signal. An abnormality may be any change in the refractive sensor signal that prevents or interferes with the use of the refractive sensor signal as a feedback signal to control the refractive of the flexible catheter. For example, an abnormality may be a degradation of the refractive sensor signal caused by mechanical vibration (e.g., noise). As previously mentioned, mechanical vibration may occur during the insertion or removal of a tool into or from the flexible catheter. The test may be performed by evaluating a flag associated with the refractive sensor signal. The flag may be set when used to indicate mechanical vibration, for example, after analyzing the refractive sensor signal for the frequency indicating mechanical vibration. In the exemplary flowchart of FIG. 7, an abnormality is present in the refractive sensor, and the process may proceed to operation 708.

[0071] Operations 708 and 710 may also be performed in actuator feedback control mode. In actuator feedback control mode, the actuator sensor signal may be used as a feedback signal to control the bending of the flexible catheter.

[0072] In operation 708, a refraction estimate is determined by applying a model of the flexible catheter to the actuator sensor signal. The model may be based on known characteristics of the flexible catheter (e.g., kinematics and / or dynamics) that enable the refraction estimate to be determined based on the actuator sensor signal by simulation when actual measurement of refraction by the refraction sensor is not available. The model used in operation 708 may be predetermined, as described below with reference to FIG. 8. An exemplary implementation of the model will be described below with reference to FIG. 11.

[0073] In operation 710, the actuator(s) used to bend the flexible catheter may be controlled based on a bending estimate. A feedback controller used to control the actuator(s) may use the bending estimate as a feedback signal and may also accept a command input. The feedback controller may be configured to minimize the error between the command input and the feedback signal (here, the bending estimate) to drive the actuator(s). When the actuator(s) are driven, the bending of the flexible catheter (driven by the actuator(s)) may follow the command input.

[0074] Operations 708 and 710 may be executed repeatedly, for example, when the above exists. For each execution, an updated refraction estimate is determined (when executing operation 708).

[0075] The flowchart of FIG. 8 illustrates an exemplary method (800) for controlling a flexible catheter according to one or more embodiments. For example, the method may be used to control the deflection of the flexible catheter. The deflection may follow one or more degrees of refractive freedom. A single segment of the flexible catheter (e.g., end segment), multiple segments, or the entire flexible catheter may be deflected. For example, the distal end of the flexible catheter may be deflected.

[0076] In operation 802, a refraction sensor signal is obtained from the refraction sensor. The refraction sensor signal may indicate the refraction (e.g., shape) of at least a portion of the flexible catheter. As previously described, the refraction sensor may be any type of sensor suitable for measuring the refraction of the catheter. The refraction sensor may detect along a single or multiple degrees of freedom of refraction. The refraction sensor may detect the refraction of a single segment, multiple segments, or the entire flexible catheter. The sensor may be a shape sensor, for example, as previously described. The refraction sensor signal may provide a value for the refraction, and the value may indicate the angle, position, orientation, speed, velocity, posture, and / or shape of one or more portions of the flexible catheter. In some embodiments, the refraction sensor signal may be low-pass filtered for smoothing the refraction sensor signal. The low-pass filter may be a moving average filter. In addition to performing filtering, the moving average filter may also serve as a buffer to store the history of the refraction sensor values. When a raw refractive sensor signal value is defective, it may not be input into the buffer. Instead, the last known good raw refractive sensor signal value may be retained. Accordingly, the moving average filter may provide the refractive sensor signal even when one or several raw refractive sensor signal values ​​are defective. Once the buffer no longer holds valid raw refractive sensor signal values, the buffer may be considered depleted, and a flag may be set to indicate that the refractive sensor signal is no longer valid. Therefore, the refractive sensor signal may be accompanied by one or more flags for labeling the refractive sensor signal.For example, the refractive sensor signal may be labeled as unreliable when the tracking unit (e.g., as described with reference to FIG. 5a) concludes that the raw sensor signal obtained from the refractive sensor is unreliable (e.g., based only on a buffer holding old raw refractive sensor signal values). The refractive sensor signal may not provide a value when the raw sensor signal is considered unreliable.

[0077] In operation 804, an actuator sensor signal is obtained from the actuator sensor. The actuator sensor signal may indicate the movement (e.g., position or rotation) of the actuator used to drive the bending of the flexible catheter (e.g., by pulling the traction wire or releasing tension). As previously described, the actuator sensor may be any type of sensor suitable for measuring the movement of the actuator driving the bending. The actuator sensor may be, for example, an encoder on the motor shaft of a servo motor (e.g., an incremental encoder). If multiple actuators are used for bending along one or more degrees of freedom, the bending sensor signal may include signals obtained from multiple encoders. A configuration for driving bending using one or more actuators has been described with reference to FIG. 5a. The actuator sensor signal may provide one or more values ​​indicating the state of the actuator, for example, the angle of the motor shaft. The actuator sensor signal may include position and / or velocity information.

[0078] A person skilled in the art will understand that refraction sensor signals and actuator sensor signals may contain position and / or velocity information. A velocity signal may be obtained from a position signal through numerical differentiation. Similarly, a position signal may be obtained from a velocity signal through numerical integration.

[0079] In operation 806, a test may be performed to determine whether there is an abnormality in the refractive sensor signal. An abnormality may be any change in the refractive sensor signal that prevents or interferes with the use of the refractive sensor signal as a feedback signal to control the refractive of the flexible catheter. For example, an abnormality may be a degradation of the refractive sensor signal caused by mechanical vibration (e.g., noise). As previously mentioned, mechanical vibration may occur during the insertion or removal of a tool into or from the flexible catheter. The test may be performed by evaluating a flag associated with the refractive sensor signal. If the flag indicates that the refractive sensor signal is normal (e.g., undamaged), the method may proceed to operation 808. If the flag indicates that the refractive sensor signal is abnormal (e.g., damaged by mechanical vibration), the method may proceed to operation 816.

[0080] In operation 808, a test may be performed to determine whether the system returns from the actuator feedback control mode to the flexion feedback control mode. The actuator feedback control mode may be used when the flexion sensor signal is not available as a feedback signal to control the flexion of the flexible catheter. The flexion feedback control mode may be used when the flexion sensor signal is available as a feedback signal to control the flexion of the flexible catheter. According to one or more embodiments, operation 808 may be performed to enable a controlled transition to the normal operation of the system when the flexion sensor signal returns. The determination in operation 808 may be made, for example, by checking a flag indicating whether the system was previously operating in the actuator feedback control mode. If the flag indicates that the system is returning from the actuator feedback control mode (808: Y), one or more of the operations shown in the exemplary method of FIG. 9 may be executed. If the flag indicates that the system does not return from actuator feedback (e.g., indicates that it continues operation in bending feedback control mode), the method may proceed to operation 810.

[0081] Operations 810 and 812 may also be performed in a refractive feedback control mode. In a refractive feedback control mode, the refractive sensor signal may be used as a feedback signal to control the refractive of the flexible catheter.

[0082] In operation 810, the refraction estimate may be determined based on a model of the flexible catheter. For example, under normal operating conditions (e.g., while no abnormalities are detected), the refraction estimate may be calculated at regular time intervals based, for example, on the cycle time of a control loop implemented to control the refraction of the flexible catheter. The refraction estimate may also be generated by a model operating on the actuator sensor signal. The model (e.g., a simulation model) may establish a mathematical relationship between the state of the actuator (e.g., rotational position and / or velocity) and the state of the flexible catheter in one or more degrees of refraction freedom (e.g., refraction expressed as an angle and / or the rate of change of refraction expressed as angular velocity). Accordingly, the model may be used to predict the current state of the flexible catheter in one or more degrees of refraction freedom based on the current state of the actuator as indicated by the actuator sensor signal. The state processed by the model may include position, velocity, and / or acceleration.

[0083] In operation 812, an error correction for the refraction estimate may be determined and / or the error correction may be applied to the refraction estimate. The error-corrected refraction estimate may correspond (e.g., match) to the actual refraction of the flexible catheter as measured by the refraction sensor. In some scenarios, the refraction estimate determined in operation 810 may be inaccurate because the simulation model may not always accurately reflect the mechanical configuration of the flexible catheter. The error correction may be determined based on a comparison of the refraction estimate and the actual refraction (e.g., shape) of the flexible catheter as indicated by the refraction sensor signal. For example, the error correction may be determined by subtracting the refraction estimate from the actual refraction indicated by the refraction sensor signal. To compensate for possible inaccuracies in the refraction estimate, the error correction may subsequently be applied to the refraction estimate to achieve a result that is more closely similar to the refraction sensor signal. Before applying the error correction to the refraction estimate, the error correction may be low-pass filtered. Low-pass filtering may facilitate smoother transitions between different control modes of the system, as exemplified in the performance data of FIG. 12 below. After error correction, the refraction estimate (e.g., determined in operation 810) may correspond (e.g., match) to the actual refraction as indicated by the refraction sensor signal. Since operation 810 may be executed repeatedly when no abnormalities exist, the error-corrected refraction estimate may track the actual refraction over time.

[0084] An exemplary implementation of a simulation model and error correction is provided below with reference to FIG. 11. Additionally, the identification and configuration of the simulation model are described below with reference to FIG. 10.

[0085] In operation 814, the actuator(s) used to flex the flexible catheter may be controlled based on a flexion sensor signal. In one or more embodiments, a feedback controller (e.g., a servo controller) initially described with reference to FIG. 1 may be used to control the flexion. The feedback controller may rely on feedback from the flexion sensor and may accept command input. Command input may be provided by a user commanding the flexion and / or by an algorithm involved in controlling the flexion of the flexible catheter. Command input may include a commanded flexion position and / or a commanded flexion velocity.

[0086] Returning to operation 806, if an abnormality is present in the refraction sensor signal (806: Y), the method may optionally proceed to operation 816. In operation 816, as described below, a test may be performed to determine whether additional requirements are met to allow the system to operate in actuator feedback control mode. Additional requirements may be, for example, that the flexible catheter is in position holding mode. In position holding mode, the refraction may be maintained constant. During position holding mode, user commands may prevent the flexible catheter from refraction. For example, the system may reject user commands during position holding mode. The absence of movement in the refraction degrees of freedom may make it more possible to maintain the mapping from actuator motion to refraction movement constant, and thus to maintain the simulation model validly. Alternatively, the system may allow movement commands of limited amplitude and / or speed during position holding mode. If additional requirements(s) are satisfied (816: Y), the method may proceed by entering actuator feedback control mode. If additional requirements(s) are not satisfied (816: N), the method may proceed to operation 824 to switch the system to lymph catheter control mode, as described in more detail below.

[0087] One or more of operations 818, 820, or 822 may be performed in actuator feedback control mode. In actuator feedback control mode, the refraction sensor signal may not be available as a feedback signal to control the refraction of the flexible catheter. A refraction estimate generated based on a model of the flexible catheter may be used instead.

[0088] In operation 818, a refraction estimate is determined by applying a model of the flexible catheter to the actuator sensor signal. The model used in operation 818 may be the model determined when operating in the refraction feedback control mode, as previously described. In some examples, the model may include error correction. For example, the error correction used in operation 818 may be the most recent error correction determined before the abnormality occurred (e.g., by performing operation 812). An example of operation 818 will be described below with reference to FIG. 11.

[0089] In operation 820, the actuator(s) used to bend the flexible catheter may be controlled based on a bending estimate. A feedback controller used to control the actuator(s) may use the bending estimate as a feedback signal and may also accept a command input. The feedback controller may be configured to minimize the error between the command input and the feedback signal (here, the bending estimate) to drive the actuator(s). When the actuator(s) are driven, the bending of the flexible catheter (driven by the actuator(s)) may follow the command input.

[0090] Operations 818 and 820 may be executed repeatedly, for example, when the above exists. For each execution, an updated refraction estimate is determined (when executing operation 818).

[0091] In operation 822, a test is performed to determine whether the time limit has been exceeded. The time limit may govern how long the system operates in actuator feedback control mode. Over time, when actual feedback from the refraction sensor is not available to error-correct the refraction estimate, the refraction estimate may become increasingly inaccurate. The time limit may be specified so that the system continues to operate in actuator feedback control mode only for a limited time. The time limit may include a predetermined time limit. The time limit may be set based on the mechanical characteristics of the flexible catheter, such as the control algorithm being used. These factors may affect how quickly the flexible catheter branches off from the estimated refraction. Additionally, operating conditions may also influence the selection of the time limit. In a completely stationary environment, there may be no possibility of the flexible catheter branching off from the estimated refraction, whereas in an environment involving motion, branching may occur relatively quickly. The time limit may be selected to minimize the possibility of unstable and / or unwanted motion. For example, the time limit may be set so that errors that may occur during the limited time are considered acceptable. If the time limit is not exceeded (822:N), the method may proceed to operation 802 as described above. If the time limit is exceeded (822:Y), the method may proceed to operation 824.

[0092] In operation 824, the system may be switched to operate in lymph catheter control mode. In lymph catheter control mode, the flexible catheter may be relaxed along the degrees of freedom of flexion. When entering lymph catheter control mode, the actuator(s) may be controlled to gradually reduce the tension of the traction wire used to actuate the catheter along the degrees of freedom of flexion. A specified minimum tension may be maintained. In lymph catheter control mode, the flexible catheter may be reverse-actuated along the degrees of freedom of flexion. When the flexible catheter is reverse-actuated, an external force acting on the flexible catheter may cause flexion. A relatively small force may be sufficient to cause reverse actuation.

[0093] In method (800), the system may temporarily operate in actuator feedback control mode when vibrations caused by, for example, the insertion of the instrument into a flexible catheter temporarily impair the refractive sensor signal. Operation in actuator feedback control mode may be time-limited, but the available time may be sufficient to bridge the time period between when the refractive sensor signal is unavailable and when the refractive sensor signal is available. After the refractive sensor signal becomes available (e.g., no longer impairing it), the system may return to operating in refractive feedback control mode. Additional aspects of the transition between the refractive feedback control mode and the actuator feedback control mode are described below with reference to the exemplary embodiment shown in FIG. 10.

[0094] The flowchart of FIG. 9 illustrates an exemplary method (900) for controlling a flexible catheter according to one or more embodiments. The method may be used to control the deflection of the flexible catheter during a transition from an actuator feedback control mode to a deflection feedback control mode. As previously described, one or more of the operations illustrated in FIG. 9 may be performed after the system decides to return from the actuator feedback control mode to the deflection feedback control mode (e.g., as determined in operation 808 of FIG. 8). The exemplary method (900) may be used for a smooth transition between modes and may be used when the deflection estimate deviates from the actual deflection reflected by the deflection sensor signal. A hard switch may cause undesirable sudden movement of the flexible catheter, which may be avoided by a smooth transition.

[0095] In operation 902, a gradual transition from the actuator feedback control mode to the refraction feedback control mode is performed. In this hybrid operation mode, both the refraction feedback control mode and the actuator feedback control mode are active. To control the actuator, stepwise interpolation may be performed between controlling the actuator based on the refraction sensor signal (e.g., as described in operation 814) and controlling the actuator based on the refraction estimate (e.g., as described in operation 820). Initially, the control may be substantially based on the refraction estimate (e.g., entirely based on the refraction estimate). Over multiple iterations of operation 902 resulting from iterative executions of method (900), the control may become increasingly based on the refraction sensor signal, for example, until the control is substantially based on the refraction sensor signal (e.g., entirely based on the refraction sensor signal). The rate at which the transition occurs may be configurable.

[0096] Execution of operation 902 is optional. Even without executing operation 902, the system can perform a gradual transition from actuator feedback control mode to refraction feedback control mode. As previously stated, it is assumed that error correction (e.g., as determined in operation 812) is low-pass filtered. When updating the refraction estimate, the refraction estimate, which is gradually governed by the time constant of the low-pass filter, may gradually approach the refraction sensor signal. Accordingly, the refraction estimate may be used to control the actuator until the refraction estimate converges to the refraction sensor signal. Until then, control may switch to using the refraction sensor signal directly while achieving a smooth transition.

[0097] When using a transition scheme as described in operation 902, additional control for the transition from the actuator feedback control mode to the refraction feedback control mode may be available, for example, the progression of the transition may no longer be governed by the time constant of the low-pass filter. Other methods for the transition between prediction-based and sensor-based signals, such as Kalman filters, may also be used, as briefly described below.

[0098] In operation 904, a test is performed to determine whether convergence of the refraction estimate to the refraction sensor signal has been reached. If convergence has not been reached, operation 902 may be repeated with the next execution of method (900). If convergence has been reached, the method may proceed to operation 906.

[0099] In operation 906, after the refraction estimate converges to the refraction sensor signal, error correction may be set so that the refraction estimate corresponds to (e.g., matches) the refraction sensor signal. Operation 906 may be advantageous when the transition performed in operation 902 proceeds at a faster rate than the time constant of the low-pass filter would allow. In this case, to ensure that the error correction is accurate and to allow for an immediate return to the actuator feedback control mode if necessary, the error correction may be set using operation 904 rather than waiting for the gradual convergence.

[0100] In operation 908, the gradual transition may be terminated. Accordingly, once operation 908 is reached, during the next execution of operation 808 of method (800), the system may switch to operation in reflex feedback control mode (808: N).

[0101] The flowchart of FIG. 10 illustrates an exemplary method for performing system identification to set up a simulation model. The method may be executed before the execution of the methods of FIG. 7, FIG. 8, and FIG. 9. The method may also be executed as part of system and / or flexible catheter initialization, calibration, or recalibration.

[0102] In operation 1002, system identification is performed. System identification may involve determining the relationship between the movement by the actuator(s) as measured by the actuator sensor(s) and the resulting flexion movement by the flexible catheter as measured by the flexion sensor. System identification may be performed under known motion conditions. For example, a pattern of specific calibration movement may be commanded to the actuator. System identification may be part of a catheter test sequence that may be performed during or after the manufacture or assembly of the system and / or flexible catheter, at system startup, after installation of the flexible catheter on the system, and / or before insertion of the flexible catheter into the patient, etc. Examples of catheter calibration and test sequences are provided in PCT patent application number PCT / US2019 / 053928 (published as WO2020 / 072398, U.S. patent application number 62 / 741,242 priority (filed October 4, 2018, “Systems and Methods for Device Verification and Sensor Calibration”)), which is incorporated herein by reference as is.

[0103] The simulation model described herein may include a matrix (e.g., a coupling matrix) that establishes the relationship between the actuator angle and the refraction angle. The gains of the coupling matrix may also establish how a specific actuator angle affects a specific refraction angle. For example, consider a flexible catheter having pitch and yaw degrees of freedom. Additionally, assume that two pairs of opposing actuators drive the flexible catheter with pitch and yaw degrees of freedom. Accordingly, the coupling matrix may include a total of eight gains to couple the actuator movement to the refraction movement. The magnitude of the gains may depend on the mechanical design of the flexible catheter. For example, the gains for pitch and yaw degrees may be orthogonal. As another example, the gains may be isotropic with respect to the pitch and yaw degrees of freedom. Alternatively, the gains may be anisotropic, for example, if the pitch and yaw degrees of freedom are not mechanically symmetric. Additionally, cross-coupling may exist between the pitch and yaw degrees of freedom. These factors will be represented by a coupling matrix, as obtained during system identification. The coupling matrix may be static; for example, the gain may remain constant after the completion of system identification.

[0104] Other simulation models that may be more complex may be used without departing from the present disclosure. For example, a model that considers system dynamics including compliance and friction may be used.

[0105] FIG. 11 illustrates an embodiment according to one or more embodiments. In the example, the position of a flexible catheter along the degree of flexion freedom ( )(1102) and the position of the driving actuator ( )(1104) is displayed as input. (1102) may be obtained from a refractive sensor (e.g., a fiber shape sensor) and may be low-pass filtered (e.g., using a moving average filter). (1104) may be obtained from a position sensor (e.g., an encoder) of an actuator that drives a flexible catheter along the degrees of freedom of bending. (1102) and (1104) so ​​that it can be directly compared Assume that (1104) is processed through a simulation model (e.g., multiplication by appropriate gain). Error ( )(1106) is From (1102) It can also be obtained by subtracting (1104). The low-pass filter (LPF) operation (1112) It may also be performed for (1106). When no abnormalities are detected (e.g., (1102) Good), the system may be in the refraction feedback control mode described in FIG. 8. Refraction estimate ( )(1108) is (1104) It may also be obtained by adding (which may be low-pass filtered and pass through the switch (1112) and switch (1114)). Also, (1102) is an output for feedback control of refraction ( It may also be used as )(1110). In the presence of the above (e.g., (1102) fault), the system may be in the actuator feedback control mode described in FIG. 8. Refraction estimate ( )(1108) is (1104) was last successfully obtained (Finally, successfully obtained It may also be obtained by adding the switch (1114) in the open position to maintain it. (1108) is the output for feedback control of the refraction ( It may also be used as )(1110). The transition from the refraction feedback control mode to the actuator feedback control mode (e.g., when an abnormality in the refraction sensor is detected) may be instantaneous in some examples. In contrast, the transition from the actuator feedback control mode to the refraction feedback control mode (e.g., after recovery from an abnormality) may be incremental in some examples, as described in FIG. 9. Accordingly, when transitioning from the actuator feedback control mode to the refraction feedback control mode, (1110) is (1108) and It may also be temporarily controlled by a combination of (1102). This behavior is illustrated in FIG. 12.

[0106] In the embodiment of FIG. 11, similar operations may be performed in the velocity domain. The operations in the velocity domain may be performed in addition to the operations in the position domain when a control algorithm, for example, a proportional derivative (PD) controller for driving an actuator, uses both position and velocity information. (1122) and (1124) is by numerical differentiation (1140) (1102) and They can also be obtained from (1104) respectively. Error( )(1126) is From (1122) It can also be obtained by subtracting (1124). The low-pass filter (LPF) operation (1132) It may also be performed for (1126). When no abnormalities are detected (e.g., (1102) Good), the system may be in the refraction feedback control mode described in FIG. 8. Refraction estimate ( )(1128) is (1124) It may also be obtained by adding (which may be low-pass filtered and pass through the switch (1132) and switch (1134). Also, (1122) is the output for feedback control of the refraction ( It may also be used as )(1130). In the presence of the above (e.g., (1122) fault), the system may be in the actuator feedback control mode described in FIG. 8. Refraction estimate ( )(1128) is It can also be obtained by setting it to 0 (switch (1134) connected to the 0 input). (1108) is the output for feedback control of the refraction ( It can also be used as )(1110).

[0107] In the embodiment of FIG. 11, It may be calculated continuously when in the bending feedback control mode, or a smooth transition from / to the actuator feedback control mode may be possible. For example, and When the relationship between them changes, silver and Despite changes in the relationship between them go You can also capture changes in the relationship to track it accurately. and The relationship between them may change, for example, when a segment of a flexible catheter located proximal to the flexion site changes its configuration (e.g., due to the bending of the catheter). In this case, the length of the traction wire from various actuators is changed, thereby and It changes the relationship between them. Changes in catheter stiffness may also change the relationship as a result of slight changes in catheter length associated with changes in stiffness.

[0108] As an alternative to the embodiment illustrated in FIG. 11, a nonlinear state estimator may be used to estimate catheter refraction. For example, a Kalman filter (e.g., an extended Kalman filter) that takes into account the overall system dynamics (e.g., friction, inertia, and / or compliance) and sensor noise characteristics, as well as nonlinearities due to quantization and sampling effects, may be used to provide a more accurate estimate of the refraction state, including the tension of individual traction wires and the actual angle of refraction. An extended Kalman filter embodiment may replace the embodiment illustrated in FIG. 11, and the Kalman filter gain may coordinate a smooth transition between using the refraction sensor signal and using the refraction estimate without requiring a dedicated switching instance.

[0109] FIG. 12 illustrates plots (1200, 1250) illustrating the performance of an embodiment as described in FIG. 11 when a flexible catheter is operated under realistic conditions. The upper panel plot (1200) illustrates various variables associated with catheter movement, while the lower panel plot (1250) illustrates the cycle count of an invalid refractive sensor signal following an effective refractive sensor signal. Plots (1200, 1250) are time-aligned. Referring to the lower panel plot (1250), two extended time intervals with invalid refractive sensor signals (1252, 1254) are illustrated. The two time intervals are illustrated as being interrupted by a very short moment (1256) with effective refractive sensor data. An additional time interval with effective refractive sensor signals (1258, 1260) is illustrated before and after the time intervals (1252, 1254). As previously mentioned, the invalid sensor signal may be the result of vibration. Referring to the upper panel plot (1200), the refraction sensor signal ( ( ) is plotted using a black dashed line. Points when a valid refractive sensor signal is not collected are indicated using the symbols "x" or "o". A combination of the "x" and "o" symbols represents a cycle with a void refractive sensor signal, as plotted in the lower panel plot (1250). There is a distinction between the void refractive sensor signal plotted using the "x" symbol and the void refractive sensor signal plotted using the "o" symbol. Specifically, although a valid sample was not obtained at the point indicated using the "o" symbol, a buffer configured to store the history of refractive sensor signal values ​​may be used to provide a value for the refractive sensor signal. Accordingly, at any point where the "o" symbol indicates a missing sample, the controller may continue to operate normally based on the buffered refractive sensor signal. Once the buffer is depleted (e.g., indicated using the "x" symbol), the controller may switch to operating in actuator feedback control mode.

[0110] In the example shown in the upper panel plot (1200), the command input may be a commanded position maintained constant at 80° (gray dashed line, 1202). The black solid line (1204) is the output of the algorithm used for feedback control of refraction ( ) represents. The black dashed line (1206) is the refraction estimate ( ...represents ). The black dashed line (1208) represents the refraction sensor signal. When the refraction sensor signal is not available (e.g., the "x" symbol), the system may be in actuator feedback control mode. Accordingly, the signal used for feedback to the controller ( ) is the refraction estimate( It may also follow ). In addition, when the refraction sensor signal is available, the signal used for feedback to the controller ( ) is the refraction sensor signal( It may also follow ). As previously mentioned, the transition from actuator feedback control mode to bend feedback control mode may occur during the transition period. During the transition period, the signal used for feedback to the controller ( ) is the refraction sensor signal( It may also converge smoothly toward ). After convergence is reached, the refraction estimate ( As described above with reference to FIG. 9, the refraction sensor signal ( It may also be set to match ) (for example, in one step).

[0111] Although the present invention has been described with respect to a limited number of embodiments, a person skilled in the art having the benefit of the present disclosure will understand that other embodiments may be devised without departing from the scope of the invention as disclosed herein. Accordingly, the scope of the present invention should be limited only by the claims.

Claims

Claim 1 A computer-assisted medical system (200), comprising: a flexible catheter (222) configured to bend along a degree of freedom; an actuator (506) positioned proximal to the flexible catheter (222), wherein the actuator (506) is configured to actuate the flexible catheter (222) along a degree of freedom; a refractive sensor (522) configured to provide a refractive sensor signal indicating the bending of the flexible catheter (222); and an actuator sensor (508) configured to provide an actuator sensor signal indicating the movement of the actuator (506). A computer-assisted medical system (200) comprising a controller (112) coupled to an actuator (506), determining a refraction estimate of a flexible catheter (222) based on a model of a flexible catheter (222) applied to a first actuator sensor signal based on determining whether the state of the first refraction sensor signal prevents or interferes with the first refraction signal being used as a feedback signal to control the actuator; and a controller configured to control the actuator (506) based on the refraction estimate. Claim 2 A computer-assisted medical system (200), wherein determining the state includes detecting an abnormality, and the controller (112) determines a second refraction estimate of the flexible catheter (222) based on a model of the flexible catheter (222) applied to the second actuator sensor signal based on not detecting an abnormality; determines an error correction based on the difference between the second refraction estimate and the actual refraction of the flexible catheter (222), wherein the actual refraction is based on the second refraction sensor signal; and is also configured to control the actuator (506) based on the second refraction sensor signal. Claim 3 In paragraph 2, a computer-assisted medical system (200) that determines the second refraction estimate, which includes adjusting the second refraction estimate based on error correction. Claim 4 In paragraph 2, the controller (112) is also configured to apply a low-pass filter to error correction, in a computer-assisted medical system (200). Claim 5 In paragraph 1, the controller (112) is also configured to determine whether a requirement is met before determining the refraction estimate, in a computer-assisted medical system (200). Claim 6 In paragraph 5, determining whether the requirements are met includes determining that the computer-assisted medical system (200) is in a position-keeping mode, the computer-assisted medical system (200). Claim 7 In paragraph 5, the controller (112) is also configured to relax the flexible catheter (222) along the degrees of freedom when the requirements are not met, in a computer-assisted medical system (200). Claim 8 A computer-assisted medical system (200) in which, in paragraph 1, the controller (112) is also configured to control the actuator (506) based on the second refraction sensor signal based on detecting the extinction of the state. Claim 9 In paragraph 8, the controller (112) is also configured to perform a gradual transition from controlling the actuator (506) based on a refraction estimate based on one or more of stepwise interpolation; or based on one or more Kalman filters, to controlling the actuator (506) based on a second refraction sensor signal, computer-assisted medical system (200). Claim 10 In claim 9, the controller (112) is configured to determine a second refraction estimate corresponding to the actual refraction of the flexible catheter (222) after the completion of a gradual transition, in a computer-assisted medical system (200). Claim 11 In any one of claims 1 to 10, the model indicates the relationship between the movement of the actuator (506) and the bending of the flexible catheter (222) caused by the movement of the actuator (506), a computer-assisted medical system (200). Claim 12 delete Claim 13 delete Claim 14 In any one of claims 1 to 10, the controller (112) is also configured to process the refractive sensor signal in a buffer configured to store the history of the refractive sensor signal value, and the state is detected when the buffer is depleted, computer-assisted medical system (200). Claim 15 delete Claim 16 In paragraph 14, a computer-assisted medical system (200) is configured such that a buffer is maintained to maintain the last known good refractive sensor signal value, and the buffer is depleted when the last known good refractive sensor signal value becomes old. Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 delete Claim 21 delete Claim 22 delete Claim 23 delete Claim 24 delete Claim 25 delete Claim 26 delete Claim 27 delete Claim 28 delete Claim 29 delete Claim 30 delete

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