Force sensor bias calibration method

Abstract

A computer-assisted system includes: a repositionable assembly configured to support an instrument; and a control system communicatively coupled to the repositionable assembly and a force sensor coupled to the instrument. The control system is configured to: obtain a first output from the force sensor based on a first movement of a distal end portion of the instrument within a cannula; calculate a first bias result based on the first output; obtain a second output from the force sensor based on a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; calculate a second bias result based on the second output; and determine an instrument status based on the first bias result and the second bias result.

Description

FORCE SENSOR BIAS CALIBRATION METHODCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of the filing date of U.S. Provisional Patent Application 63 / 735,498, filed on December 18, 2024, the contents of which are hereby incorporated by reference herein in their entirety.BACKGROUNDField of Invention

[0002] The present invention generally provides improved computer-assisted systems and methods.Overview

[0003] Computer-assisted systems can be used to perform a task at a work site. For example, a computer-assisted system may comprise an input system (e.g., a console, a surgeon's console), a repositionable assembly, and a control system. As an example, in a medical context, the repositionable assembly may be used to perform diagnosis, non-surgical treatment, surgical treatment (e.g, through minimally invasive apertures or natural orifices) and is guided by the user based on images or video from an imaging device. As another example, a computer-assisted system may comprise a robotic system (e.g, industrial and recreational systems), and may include one or more robotic manipulators or repositionable assemblies to manipulate instruments for performing the task.

[0004] The computer-assisted system can be automated, semi-automated, teleoperated, or any combination thereof. Furthermore, operation of the computer-assisted system may be augmented with sensor information obtained by force sensor or system of force sensors coupled to an instrument supported by the repositionable assembly (e.g., force feedback to a user control system based on forces experienced by the instrument, sensorbased control algorithms for a procedure or safety feature). However, a sensor bias value (e.g., a zero offset value) can drift or shift throughout the life of the instrument (e.g., after repeated installation, removal, transport, reprocessing), potentially resulting in non-intuitive operation of the computer-assisted system based on an erroneous sensor value. Therefore, a robust method of calibrating a force sensor is beneficial to improve system functionality and to reduce the occurrence or degree of non-intuitive operation.SUMMARY

[0005] In general, in one aspect, one or more embodiments relate to a computer- assisted system including: a repositionable assembly configured to support an instrument; and a control system communicatively coupled to the repositionable assembly and a force sensor coupled to the instrument. The control system is configured to: obtain a first output from the force sensor based on a first movement of a distal end portion of the instrument within a cannula; calculate a first bias result based on the first output; obtain a second output from the force sensor based on a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; calculate a second bias result based on the second output; and determine an instrument status based on the first bias result and the second bias result.

[0006] In general, in one aspect, one or more embodiments relate to a computer- assisted system comprising: a repositionable assembly configured to support an instrument; a control system that is communicatively coupled to the repositionable assembly and a force sensor coupled to the instrument. The control system is configured to: calculate a first bias result based on a first output from the force sensor during a first movement of a distal end portion of the instrument within a cannula; determine, based on the first bias result being valid, an instrument status based on the first bias result; determine, based on the first bias result being at least partially invalid, to perform a second bias operation that includes: calculating a second bias result based on a second output from the force sensor during a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; and determining the instrument status based on the second bias result.

[0007] Other aspects of the invention will be apparent from the following description and the appended claims.BRIEF DESCRIPTION OF DRAWINGS

[0008] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

[0009] FIG. 1 A shows an example computer-assisted system, in accordance with one or more embodiments.

[0010] FIG. IB shows an example manipulator assembly, in accordance with one or more embodiments.

[0011] FIG. 2 illustrates an example control system, in accordance with one or more embodiments.

[0012] FIG. 3 is a perspective view of a cannula, in accordance with one or more embodiments.

[0013] FIGs. 4A-4B are side views of distal end portions of example instruments, in accordance with one or more embodiments.

[0014] FIG. 5 is flowchart of a method, in accordance with one or more embodiments.

[0015] FIGs. 6A-6B are diagrams showing movement of a distal portion of an instrument, in accordance with one or more embodiments.

[0016] FIGs. 7A-7B are diagrams show a comparison of two versions of an instrument performing the first movement within a cannula, in accordance with one or more embodiments.

[0017] FIG. 8 shows an implementation examples of a method, in accordance with one or more embodiments.

[0018] FIGs. 9A-9B are diagrams of sensor outputs, in accordance with one or more embodiments.DETAILED DESCRIPTION

[0019] In the following description, specific details are set forth describing some embodiments consistent with the present disclosure. Numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that some embodiments can be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other elements that, although not specifically described here, are within the scope and the spirit of this disclosure. In addition, to avoid unnecessary repetition, one or more features shown and described in association with one embodiment may be incorporated into other embodiments unless specifically described otherwise or if the one or more features would make an embodiment non-functional.

[0020] In some instances, well known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of theembodiments. For example, devices and substitutes that provide or enable linear actuation, such as pneumatic cylinders and lead screws are well understood without detailed descriptions of aspects of such devices like gaskets, thread pitch, etc. Thus, specific descriptions regarding such devices, procedures, components, and how circuits can be integrated with, or used within, embodiments of the instant disclosure are omitted herein for concision where applicable without causing undue ambiguity or uncertainty.

[0021] Throughout the application, ordinal numbers (e.g., first, second, third, efc.) may be used as an adjective for an element ( / .< ., any noun in the application). The use of ordinal numbers is not to imply or create any particular ordering of the elements nor to limit any element to being only a single element unless expressly disclosed, such as using the terms “before,” “after,” “single,” and other such terminology. Rather, the use of ordinal numbers is to distinguish between the elements. By way of an example, a first element is distinct from a second element, and the first element can encompass more than one element and succeed (or precede) the second element in an ordering of elements.

[0022] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0023] Terms such as “approximately,” “substantially,” etc., mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0024] In the following description, any component described with regard to a figure, in various embodiments disclosed herein, may be equivalent to one or more like-named components described with regard to any other figure. For brevity, descriptions of these components are not necessarily repeated with regard to each figure. Thus, each and every embodiment of the components of each figure is incorporated by reference and assumed to be optionally present within every other figure having one or more like-named components. Additionally, in accordance with various embodiments disclosed herein, any description of the components of a figure is to be interpreted as an optional embodiment which may be implemented in addition to, in conjunction with, or in place of the embodiments described with regard to a corresponding like-named component in any other figure.

[0025] Considering the figures, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described relative to these embodiments can be used either individually and / or inany desired combination as the disclosure is not limited to only the specific embodiments described herein.

[0026] This disclosure describes various devices, elements, and portions of computer- assisted systems and elements in terms of their state in three-dimensional space. As used herein, the term “location” refers to the spatial placement of an element or a portion of an element (e.g., three degrees of translational freedom in a three-dimensional space, such as along Cartesian x-, y-, and z-coordinates). As used herein, the term “orientation” refers to the rotational placement of an element or a portion of an element (e.g., three degrees of rotational freedom in three-dimensional space, such as about roll, pitch, and yaw axes, represented in angle-axis, rotation matrix, quaternion representation, and / or the like). As used herein, and for a device with a kinematic series, such as with a repositionable structure with a plurality of links coupled by one or more joints, the term “proximal” refers to a direction toward a base of the kinematic series, and “distal” refers to a direction away from the base along the kinematic series.

[0027] As used herein, the term “pose” refers to the multi-degree of freedom (DOF) spatial placement and orientation of a coordinate system of interest attached to a rigid body. In general, a pose includes a pose variable for each of the DOFs in the pose. For example, a full 6-DOF pose for a rigid body in three-dimensional space would include 6 pose variables corresponding to the 3 locational DOFs (e.g., x, y, and z) and the 3 orientational DOFs (e.g., roll, pitch, and yaw). A 3-DOF location only pose would include only pose variables for the 3 locational DOFs. Similarly, a 3-DOF orientation only pose would include only pose variables for the 3 rotational DOFs. Further, a velocity of the pose captures the change in pose over time (e.g., a first derivative of the pose). For a full 6-DOF pose of a rigid body in three-dimensional space, the velocity would include 3 translational velocities and 3 rotational velocities. Poses with other numbers of DOFs would have a corresponding number of velocities translational and / or rotational velocities.

[0028] Aspects of this disclosure are described in reference to computer-assisted systems, which can include devices that are teleoperated, externally manipulated, autonomous, semiautonomous, and / or the like. Further, aspects of this disclosure are described in terms of an implementation using a teleoperated surgical system, such as the da Vinci® Surgical System commercialized by Intuitive Surgical, Inc. of Sunnyvale, California. Knowledgeable persons will understand, however, that inventive aspects disclosed herein may be embodied and implemented in various ways, including teleoperated and nonteleoperated, and medical and non-medical embodiments and implementations.Implementations on da Vinci® Surgical Systems are merely exemplary and are not to be considered as limiting the scope of the inventive aspects disclosed herein. For example, techniques described with reference to surgical instruments and surgical methods may be used in other contexts. Thus, the instruments, systems, and methods described herein may be used for humans, animals, portions of human or animal anatomy, industrial systems, general robotic, or teleoperated systems. As further examples, the instruments, systems, and methods described herein may be used for non-medical purposes including industrial uses, general robotic uses, sensing or manipulating non-tissue work pieces, cosmetic improvements, imaging of human or animal anatomy, gathering data from human or animal anatomy, setting up or taking down systems, training medical or non-medical personnel, and / or the like.Additional example applications include use for procedures on tissue removed from human or animal anatomies (with or without return to a human or animal anatomy) and for procedures on human or animal cadavers. Further, these techniques can also be used for medical treatment or diagnosis procedures that include, or do not include, surgical aspects.

[0029] To foster an operator’s sense of immersion, realism, and / or intuitiveness while operating a repositionable assembly, a high degree of coordination between a user input system and the repositionable assembly is required, especially while operating in a following mode (leader-follower mode of teleoperation). A force sensor (e.g., an electrical sensor element (e.g., strain sensors or strain gauges)) may be included in an instrument and / or in the repositionable assembly that supports the instrument (e.g., in a manipulator arm that supports the instrument) to provide haptic feedback information to the operator (e.g., via a force feedback module in the user input system, visual indications of force, instrument logs for procedure analytics / machine-learning).

[0030] Typically, a force sensor is calibrated during manufacture or maintenance outside of a procedure. This “factory” calibration establishes a zero offset signal of the force sensor when no force is applied. However, the force sensor bias can shift throughout the life of the instrument (e.g., positioning, transport or reprocessing), resulting in a non-zero output signal when no force is applied (i.e., in a free-space configuration). If the force sensor bias is inaccurate, the coordination of the instrument and user input system may become non- intuitive to the operator and result in unintended movements.

[0031] One or more embodiments described herein are directed to a method of calibrating a force sensor to improve functionality of a computer-assisted system and to reduce the occurrence or degree of unintended movements of an instrument of the computer- assisted system. In some embodiments, a control system is communicatively coupled to therepositionable assembly and a force sensor coupled to an instrument. Based on one or more outputs from the force sensor, the control system may determine and implement a control relationship of the computer-assisted system based on calibration results of the force sensor. The control system may be configured with a plurality of calibration processes for determining an instrument status and / or a force sensor bias.

[0032] For example, the control system may determine a first bias result based on a first output from the force sensor during a first movement of a distal end portion of the instrument within a cannula. Furthermore, the control system may determine a second bias result based on a second output from the force sensor during a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula. Based on the first bias result and the second bias result, the control system may determine an instrument status that may subsequently be used to modify the computer-assisted system (e.g., modify a force feedback module in a user input system of the computer-assisted system, modify a control mode of the computer-assisted system, modify a user interface). The control system may be configured to control one or more operational modes of the computer-assisted system based on validity of the first / second bias result.

[0033] Specific embodiments of the disclosure will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency.

[0034] FIG. 1A shows an example computer-assisted system 100 in accordance with one or more embodiments.

[0035] In FIG. 1 A, the computer-assisted system 100 includes, without limitation, a manipulator structure comprising a manipulator assembly 110 and a user input system 140. In a teleoperation scenario, an operator (not shown) uses the user input system 140 to operate the manipulator assembly 110, such as in a leader-follower configuration (also often called teleoperation configuration or master-slave configuration in industry) of the computer- assisted system 100. In the leader-follower configuration, the user input system 140 is the leader, and the manipulator assembly 110 is the follower of the leader-follower configuration.

[0036] The manipulator assembly 110 can be used to introduce a set of one or more instruments to a work site through a port 130 (e.g., a gel port, a cannula, entry guide) inserted in an aperture (a cannula is shown in FIG. 1 A). In a medical scenario, the work site can be on or within a body cavity of a patient, and the aperture can be a minimally invasive incision or a natural body orifice. When used, the port 130 can be free-floating, held in place by a fixture separate from the manipulator assembly 110, or held by a drivable structure 122 (alinkage is shown in FIG. 1 A) or other part of the manipulator assembly 110. The drivable structure 122 is coupled to additional joints and links 114, 120 of the manipulator assembly 110, and these additional joints and links 114, 120 are mounted on a base 112. In some embodiments, the drivable structure 122 terminates in a manipulator-supporting link 124. In the example shown, the manipulator assembly 110 further comprises a set of manipulators 126 coupled to the manipulator-supporting link 124. Each of the manipulators 126 include a carriage (or other instrument-coupling link) configured to couple to an instrument, and each of the manipulators 126 include one or more joint(s) that can be driven to move the carriage. For example, a manipulator 126 can include a prismatic joint that, when driven, linearly moves the carriage and any instrument(s) coupled to the carriage. In some embodiments, this linear motion is along an insertion axis of the instrument. In this configuration, the elements of the manipulator assembly 110 that are proximal to the manipulators 126 may be understood as a proximal repositionable structure.

[0037] In some embodiments, the joints and links 114, 120 are used to position the port 130 at the aperture or another location. FIG. 1A illustrates a prismatic joint for vertical adjustment (as indicated by arrow “A”) and a rotary joint for horizontal adjustment (as indicated by arrow “B”). The drivable structure 122 is used to robotically pivot the port 130 (and the instruments disposed within it at the time) in yaw, pitch and roll angular rotations about a remote center of motion as indicated by arrows C, D and E, respectively. These joints may be considered part of the proximal repositionable structure.

[0038] In some embodiments, actuation of the degrees of freedom provided by joint(s) of the instrument(s) is provided by actuators disposed in, or whose motive force (e.g., linear force or rotary torque) is transmitted to, the instrument(s). Examples of actuators include rotary motors, linear motors, solenoids, and / or the like. The actuators drive transmission elements in the manipulators and / or in the instruments to control the degrees of freedom of the instrum ent(s). For example, the actuators can drive rotary discs of the manipulator that couple with rotary discs of the instrument(s), where driving the rotary discs of the instruments drives transmission elements in the instrument that couple to move the joint(s) of the instrument, or to move the end effector(s) of the instrument. Accordingly, the degrees of freedom of the instrument(s) are controlled by actuators that drive the instrument(s) in accordance with control signals determined based on inputs from the associated input devices (e.g., input devices 142 of the user input system 140). The control signals are determined in order to cause instrument motion or other actuation as indicated by movement of the input control devices or any other control signal. Furthermore, in someembodiments, appropriately positioned sensors (e.g., encoders, potentiometers, and / or the like) are provided to enable measurement of indications of the joint positions, or other data that can be used to derive joint position, such as joint velocity. The actuators and sensors are disposed in, transmit to, and / or receive signals from the manipulator(s) 126.

[0039] In many embodiments, the tool of an exemplary manipulator assembly 110 pivots about a pivot point adjacent to a minimally invasive aperture e.g., port 130). In some embodiments, the manipulator assembly 110 may utilize a hardware remote center (HRC), such as the remote center kinematics described in U.S. Patent No. 6,786,896, the entire contents of which are incorporated herein in its entirety. Such systems may utilize a double parallelogram linkage which constrains the movement of the linkages such that the shaft of the instrument supported by the manipulator pivots about a remote center point. Alternative mechanically constrained remote center linkage systems are known and / or may be developed in the future. In particular, when a surgical robotic system has a linkage that allows pivotal motion about two axes intersecting at or near a minimally invasive surgical access site, the spherical pivotal motion may encompass the full extent of a desired range of motion within the patient, but may still suffer from avoidable deficiencies (such as being poorly conditioned, being susceptible to arm-to-arm or arm-to-patient contact outside the patient, and / or the like). At first, adding one or more additional degrees of freedom that are also mechanically constrained to pivotal motion at or near the access site may appear to offer few or any improvements in the range of motion. Nonetheless, such joints can provide significant advantages by allowing the overall system to extend the range of motion.

[0040] In the embodiments shown in FIG. 1 A, the user input system 140 includes one or more input devices 142 operated by the operator (not shown). The one or more input devices 142 are contacted and manipulated by the hands of the operator, with one input device for each hand. Examples of such hand-input-devices include any type of device manually operable by human operator (e.g., joysticks, trackballs, button clusters, and / or other types of haptic devices typically equipped with multiple degrees of freedom). Additionally, in some embodiments, position, force, and / or tactile feedback devices (not shown) are employed to transmit position, force, and / or tactile sensations from the instruments back to the operator's hands through the input devices 142.

[0041] The input devices 142 are supported by the user input system 140 and are shown as mechanically grounded, and in other implementations may be mechanically ungrounded. An ergonomic support 146 is provided in some implementations. For example, FIG. 1A shows an ergonomic support 146 including forearm rests on which the operator mayrest his or her forearms while manipulating the input devices 142. In some examples, the operator performs tasks at a work site near the manipulator assembly 110 during a medical procedure by controlling the manipulator assembly 110 using the input devices 142.

[0042] In one or more embodiments, the input device is configured to provide haptic feedback to the operator. Forces and / or torques experienced by the instrument 160 may be rendered to the user when interacting with the surrounding environment (e.g., when manipulating tissue in a surgical scenario). In such a configuration, the user may rely on the force-feedback at the input device to control movement of the instrument. For example, a force feedback module of the control system 170 and / or user input system 140 may be configured to apply a force and / or torque to the input device(s) 142. In some embodiments, haptic feedback may be provided to the user by other means (e.g., quantitative / qualitative displays to the user, audio / visual indicators, etc.). In some embodiments, the haptic feedback may be used to indicate and / or track evaluate user performance (e.g., monitoring adherence to steps or requirements of a procedure).

[0043] In some embodiments, the force feedback effect is proportional to a joint tracking error in the manipulator assembly 110. A joint tracking error could be a result of a contact condition (e.g., a manipulator arm 150 cannot execute a commanded motion because it is resisted or blocked by an obstruction or another manipulator arm 150). In some embodiments, the joint tracking error may be the result of a procedure-related force or torque (in absence of a contact condition). In other words, the force feedback module may be configured to make the user aware of the presence of a contact condition.

[0044] A display unit 144 is included in the user input system 140. The display unit 144 displays images for viewing by the operator. The display unit 144 provides the operator with a view of the worksite with which the manipulator assembly 110 interacts. The view can include, for example, stereoscopic images or three-dimensional images to provide a depth perception of the worksite and the instrum ent(s) of the manipulator assembly 110 in the worksite. The display unit 144 can be moved in various degrees of freedom to accommodate the operator’s viewing position and / or to provide control functions. Where a display unit (such as the display unit 144 is also used to provide control functions, such as to command the manipulator assembly, the display unit also includes an input device (e.g., another input device 142). One or more separate displays (not shown in FIG. 1A) (e.g., in an auxiliary system 180, described below) may also be used for local and / or remote display of images, such as images of the procedure site, or other related images.

[0045] When using the user input system 140, the operator can sit in a chair or other support in front of the user input system 140, position his or her eyes to see images displayed by the display unit 144, grasp and manipulate the input devices 142, and rest his or her forearms on the ergonomic support 146 as desired. In some implementations, the operator can stand at the workstation or assume other poses, and the display unit 144 and input devices 142 may differ in construction, be adjusted in position (e.g., height, depth), etc.

[0046] FIG. IB shows an example manipulator assembly 110 in accordance with one or more embodiments.

[0047] In some embodiments, a manipulator assembly 110 (e.g., a patient-side robotic device in a medical example) may include one or more manipulator arm(s) 150, each of which may support a removably coupled instrument 160 (also called tool 160). The computer-assisted system 100 may include a drivable cart (not shown) with a primary control interface and a support column that vertically extends from a drivable cart. In some embodiments, a boom extends from the support column with at least one manipulator arm 150 connected to the distal end of the boom. In the example of FIG. IB, the manipulator assembly 110 is depicted with four manipulator arms 150, namely, a first manipulator arm 150A, a second manipulator arm 150B, a third manipulator arm 150C, and a fourth manipulator arm 150D. Where a particular manipulator arm need not be referenced, a manipulator arm may be referenced generally as manipulator arm 150.

[0048] In this example, the manipulator assembly 110 is utilized for a diagnostic or therapeutic medical procedure performed on a patient P on an operating table. The instrument 160 may enter the work site through an entry location (e.g., enter the body of the patient P through a natural orifice such as the throat or anus, or through an incision), while an operator (not shown) views the worksite e.g., a surgical site in the surgical scenario) through a user interface system (e.g., user input system 140).

[0049] In one or more embodiments, an image of the worksite may be obtained by an imaging device connected to the instrument 160 (e.g., an endoscope, an optical camera, an ultrasonic probe, etc. in a medical example). The instrument 160 may be manipulated by the manipulator assembly 110 so as to position and orient the instrument 160 to image the worksite from different perspectives.

[0050] The number of instruments 160 used at one time generally depends on the task and space constraints, among other factors. If it is appropriate to change, clean, inspect, or reload one or more of the instruments 160 being used during a procedure, an assistant (notshown) may remove the instrument 160 from the manipulator arm 150A-D, and replace it with the same instrument 160 or another instrument 160.

[0051] Various classes and types of instruments 160 can be used, or exchanged during a process or procedure, according to the needs of a procedure or process undertaken by one or more manipulator arms (e.g, 150A-D) of a computer-assisted system 100. Instruments 160 may include, but are not limited to: monopolar and bipolar instruments for dissection, coagulation, sealing, transection, and / or cutting of tissue; suction and irrigation instruments; clip appliers; and instruments for visualization of the procedure site (e.g, visual camera, infrared camera). Some instruments 160, such a monopolar and bipolar instruments, can be “energized” or apply electrical cortical stimulation in a tunable manner (e.g., “on” or “off’).

[0052] In one or more embodiments, the instrument 160 may include a transmission assembly, an instrument shaft 162, a wrist assembly, and an end effector 164 at a distal end portion of the instrument 160, as described in further detail below with respect to FIGs. 4A- 4B). In general, an instrument 160 can include a transmission assembly or backend mechanism, an instrument shaft 162 extending distally from the transmission assembly to an end effector 164 or to a wrist assembly. The instrument 160 with a wrist assembly may or may not also include an end effector 164. Non-limiting examples of the end effectors include forceps, graspers, a cutting tool, or a cauterizing tool coupled to the wrist assembly. In some instances, end effectors can be categorized as an energy-emitting end effector (e.g., used on a bipolar instrument) or a non-energy-emitting end effector. The wrist assembly may be used to move and operate the end effector when enacting a desired procedure.

[0053] In some embodiments, the transmission assembly of the instrument 160 may include transmission elements (e.g., a capstan, cables, tension member, gears, metal bands, rubber belts, metal wires, pulleys, screw drives, chains and sprockets, etc.) to connect the wrist assembly and / or elements of the end effector to the transmission assembly (e.g., extending through the instrument shaft). The transmission assembly may provide a mechanical coupling of tension members to motorized axes provided by actuators. Thus, movement and tension in the tension members as needed to position, orient, and operate wrist assembly and / or the end effector 164 can be controlled through operation of the actuators.

[0054] In some embodiments, the instrument shaft 162 of the instrument 160 may include a proximal portion terminating at a chassis of the transmission assembly and a distal portion terminating at the wrist assembly of the instrument 160. The instrument shaft 162 may be any suitable shaft that couples the wrist assembly and the end effector 164 to thetransmission assembly. In one or more embodiments, the shaft defines at least one passageway through which one or more tensions members (e.g, cables, not shown) or other transmission members suitable for the transmission of mechanical energy such as movement, force, or torque may be routed from the transmission assembly towards the wrist assembly. In some embodiments, other components (e.g., electrical wires, push-rods, optical fibers, etc.) may also be routed through the instrument shaft 162.

[0055] In some embodiments, the wrist assembly of the instrument 160 may be configured to provide a rotational degree of freedom (e.g., a pitch rotation) of the end effector 164. The end effector 164 is configured with a yaw rotation degree of freedom that may further be used for opening and closing jaw elements of the end effector. Depending on the design, one, two, or more tension members may be used to control a degree of freedom for the instrument. In an example, two unique tension members are used to control each of a pitching, a yawing, and a jaw opening for a jawed instrument. In another example, some of the tension members are coupled to multiple degrees of freedom, including a pitching, a yawing, and a jaw opening movement for a jawed instrument. In some embodiments, the instrument 160 is configured (e.g., transmission assembly further include gears) to roll or rotate the instrument shaft 162, the wrist assembly, and / or the end effector 164 about a longitudinal axis of the instrument 160 (e.g., of the instrument shaft 162, of a distal end portion of the instrument 160).

[0056] While FIGs. 1 A-1B show the computer-assisted system 100 as a medical system, the following description is applicable to other scenarios and systems (e.g., medical scenarios or systems that are non-surgical, non-medical scenarios or systems, etc.).

[0057] Furthermore, while example configurations of a computer-assisted system 100 including manipulator assemblies 110 are shown in FIGs. 1 A-1B, those skilled in the art will appreciate that embodiments of the disclosure can be used with any design of manipulator structure. For example, a manipulator assembly 110 can have any number and any types of degrees of freedom, may or may not be configured to couple to one or more ports 130, use a port 130 other than a cannula, and / or other configuration different from what is shown in FIGs. 1A-1B.

[0058] In general, a manipulator assembly 110 of a computer-assisted system 100 may include a manipulator assembly 110 that includes a common proximal repositionable structure (i.e., proximal portion) and one or more distal repositionable structures (i.e., distal portion(s)) attached to the proximal repositionable structure. The one or more distal repositionable structures may each be configured to support one or more instruments 160.For example, in FIG. 1 A, the manipulator assembly 110 is a repositionable assembly with a proximal repositionable structure (e.g., the support column and boom) and a distal repositionable structure (e.g., the drivable structure 122 and the manipulator-supporting link 124). Alternatively, in FIG. IB, the manipulator assembly 110 is a repositionable assembly with a common proximal repositionable structure (e.g., the support column and boom) that supports a plurality of manipulator arms 150 as the distal repositionable structure.

[0059] While example configurations of repositionable assemblies are shown in FIGs. 1 A-1B, those skilled in the art will appreciate that embodiments of the disclosure can be used with any design of repositionable assemblies. For instance, each distal repositionable structure of a repositionable assembly may include a prismatic joint, that when driven, linearly moves an instrument carriage and any instrument(s) coupled to the carriage along an insertion axis. In other examples, the repositionable assembly may include a single instrument manipulator and no serial coupling of manipulators. In additional examples, the repositionable assembly may include a single instrument manipulator coupled to a single base manipulator.

[0060] Furthermore, while the present disclosure show various configurations of components, other configurations may be used without departing from the scope of the disclosure. For example, various components may be combined to create a single component. As another example, the functionality performed by a single component may be performed by two or more components. While examples of particular manipulator assemblies, particular repositionable structures, instruments, input systems, and controller portions are shown, the disclosure generalizes to any type of manipulator assemblies, repositionable structures, instruments, input systems, and controller portions with any number of degrees of freedom. Further, while components are often described in context of medical scenarios such as surgical scenarios, embodiments of the disclosure are equally applicable to other domains that involve robotic manipulation (e.g., non-surgical scenarios or systems, non-medical scenarios or systems, and / or the like).

[0061] FIG. 2 illustrates an example control system 170 in accordance with one or more embodiments.

[0062] The illustration, partitioning, organization, and interaction of the components and / or modules of the control system 170 in FIG. 2 is intended to promote clear discussion and should not be considered fixed or limiting. For example, FIG. 2 depicts a display unit 174 as an independent entity, however, it is well understood that in practice the display unit 174 may be implemented as part of, for example, an auxiliary system 180.

[0063] The control system 170 corresponds to repositionable assembly of a computer- assisted system 100 and includes one or more computing systems 172. A computing system 172 includes a processing system and is used to process input provided by the user input system 140 (e.g., from the input device(s) 142 manipulated by an operator). In some embodiments, a computing system 172 is further used to provide an output (e.g., a video, an image) to the display unit 174. Examples of display unit 174 include LCDs, LEDs, organic LED displays, projectors, etc. In some embodiments, one or more computing systems 172 are used to control the manipulator assembly 110.

[0064] In many embodiments, the repositionable assembly will often comprise a surgical tool or instrument having a shaft extending between a mounting interface and an end effector. In a first operational mode, the control system 170 may be configured to derive the desired movement of the end effector within an internal surgical space so that the shaft passes through a minimally invasive aperture site (e.g., port 130). A leader-follower controller may, for example, comprise a velocity controller using a Jacobian pseudo-inverse matrix. In a second operational mode or clutch mode, the control system 170 may employ a projection of a clutch matrix with the inverse Jacobian matrix so as to provide combinations of joint velocities that are allowed in the clutch mode. In the clutch mode, the control system 170 may float a first set of joints within a joint velocity sub-space to allow manual articulation or movement of a first portion of the repositionable assembly (e.g., a remote center of motion, an end effector), while driving a second set of joints to offset the movement of the first set of joints.

[0065] The architecture of the control methods used for controlling the repositionable assembly can be of any appropriate form. As a specific example, the control architecture can be hierarchical, and could include a high-level controller and multiple joint controllers. A commanded movement is received by the high-level controller in, for example, a Cartesiancoordinate space (referred to herein as Cartesian-space). The commanded movement could be, for example, based on a movement command (e.g., in the form of a position and / or velocity) received from the user input system 250, or any other system that provides a movement command. The commanded movement is converted into commanded joint positions or joint velocities (e.g., linear or angular joint positions, linear or angular joint velocities). In some embodiments, the conversion is performed using an inverse kinematics algorithm. Subsequently, the joint controllers convert the received commanded joint positions or velocities into commanded currents to drive the actuators producing jointmovements. The joint movements together produce a manipulator assembly movement that reflects the commanded movement.

[0066] In some embodiments, a joint controller controls a joint position. In some embodiments, the joint controller controls other variables such as joint velocity and / or joint force (linear force or angular torque). A joint controller receives a feedback signal in the form of a sensed joint state from an associated joint sensor, which it can use for closed-loop control. The sensed joint state includes, for example and without limitation, a joint position, a joint velocity (or component of velocity such as speed or direction), a joint acceleration (or component of acceleration), and / or the like, representing the joint movement. The sensed joint state is derived from the signals obtained from the joint sensor. A joint sensor can be, for example, an encoder, a potentiometer, an accelerometer, a hall effect sensor, and / or the like. In some embodiments, a state observer or estimator (not shown) is used. Each joint controller can implement any appropriate control scheme, such as a proportional integral derivative (PID), proportional derivative (PD), full state feedback, sliding mode, and / or various other control schemes, without departing from the disclosure.

[0067] A computing system 172 may include, without limitation, one or more computer processors, non-persistent storage (e.g., volatile memory, such as random access memory (RAM), cache memory), persistent storage (e.g., a hard disk, an optical drive such as a compact disk (CD) drive or digital versatile disk (DVD) drive, a flash memory, etc.), a communication interface (e.g, Bluetooth interface, infrared interface, network interface, optical interface, etc.), and / or numerous other elements and functionalities. In some embodiments, a computer processor of a computing system 172 is an integrated circuit for processing instructions. For example, the computer processor can be one or more cores or micro-cores of a processor.

[0068] In some embodiments, a communication interface of a computing system 172 includes an integrated circuit for connecting the computing system 172 to a repositionable assembly, a network (not shown) (e.g, a local area network (LAN), a wide area network (WAN) such as the Internet, mobile network, or any other type of network), and / or to another device, such as another computing system 172.

[0069] Further, in some embodiments, the computing system 172 includes one or more output devices, such as a display unit 174, a printer, a speaker, external storage, or any other output device. A display unit 174 may be a liquid crystal display (LCD), a plasma display, projector, headset device, touchscreen, organic LED display (OLED), projector, or other display device. Output devices may include, but are not limited to, a printer, a speaker,external storage, or any other output device. One or more of the output devices may be the same or different from the input device(s). Many different types of computing systems 172 exist, and the aforementioned input and output device(s) may take other forms.

[0070] Software instructions in the form of computer readable program code to perform embodiments of the disclosure may be stored, in whole or in part, temporarily or permanently, on a non-transitory computer readable medium (machine-readable medium) such as a CD, DVD, storage device, a diskette, a tape, flash memory, physical memory, or any other computer readable storage medium. Specifically, the software instructions may correspond to computer readable program code that, when executed by a processor(s), is configured to perform one or more embodiments of the disclosure.

[0071] A computing system 172 may be connected to or be a part of a network. The network may include multiple nodes. Each node may correspond to a control system, or a group of nodes. By way of an example, embodiments of the disclosure may be implemented on a node of a distributed system that is connected to other nodes. By way of another example, embodiments of the disclosure may be implemented on a distributed computing system having multiple nodes, where each portion of the disclosure may be located on a different node within the distributed computing system. Further, one or more elements of the aforementioned computing systems 172 may be located at a remote location and connected to the other elements over a network.

[0072] In some embodiments, the control system 170 includes one or more auxiliary system(s) 180. An auxiliary system 180 may be any system that operates in coordination with the repositionable assembly. For example, an auxiliary system 180 may process captured images from an imaging instrument 160 that is posed by a manipulator assembly 110. This non-limiting example of the auxiliary system 180 may include in a variety of methods for processing captured images prior to any subsequent display. For example, the auxiliary system 180 may overlay the captured images with a virtual control interface prior to displaying the combined images to the operator via the user input system 140 or other display units 174 located locally or remotely from the procedure. One or more separate displays 174 may also be coupled with a computing system 172 and / or the auxiliary system 180 for local and / or remote display of images, such as images of the procedure site, or other related images.

[0073] FIG. 3 is a perspective view of a cannula 154, in accordance with one or more embodiments.

[0074] In one or more embodiments, the manipulator assembly 110 includes a cannula 154. For example, in FIG. 1A, the port 130 may include a cannula 154. In the example manipulator assembly 110 of FIG IB, a cannula 154 may be mechanically supported by a manipulator arm 150 or may not be supported at all.

[0075] The cannula 154 may guide an instrument 160 through an orifice and / or to a surgical site in a medical scenario. For example, manipulator assembly 110 may position and orient the cannula 154 such that a distal end 156 of the cannula 154 is adjacent to the surgical site. Thus, the instrument 160 may be inserted through the cannula 154 such that a distal end portion of the instrument 160 protrudes from the distal end 156 of the cannula 154 to directly access the surgical site. As described in further detail below with respect to FIG. 5, operation of the instrument 160 (e.g., upon reaching the surgical site) may require calibration of one or more sensors coupled to the instrument.

[0076] FIGs. 4A-4B are side views of a distal end portion of example instruments 160, 160’, in accordance with one or more embodiments.

[0077] As discussed above, the instrument 160 may include an instrument shaft 162, a wrist assembly, and an end effector 164 at a distal end portion of the instrument 160. As shown in FIG. 4A, the wrist assembly may include a proximal clevis 166, a distal clevis 168, and an end effector 164. Tension members may extend along solid surfaces of guide channels in the distal clevis 168 and the proximal clevis 166 to reach the end effector 164, and from there extend back through the instrument shaft 162 to the transmission assembly of the instrument 160. The depicted end effector 164 includes two jaws, each having a grip portion attached to a hub.

[0078] A first pin 166a in the proximal clevis 166 attaches the distal clevis 168 to the proximal clevis 166 and allows the distal clevis 168 to rotate about a pivot axis defined by the first pin 166a. A second pin 168a in the distal clevis 168 is perpendicular to the first pin 166a and defines a pivot axis for the end effector 164 as a whole or for individual jaws. In the illustrated example, the working tips of jaws have a surface for gripping and may be used, for example, in forceps or cautery applications. Alternatively, “gripping,” which closes the jaws can be a cutting action when the tips of the jaws are blades that cooperatively cut as scissors. Thus, gripping can perform different functions depending on the end effector 164 attached to or otherwise employed on - or as part of - the instrument 160.

[0079] It is noted that the example wrist assembly and end effector 164 depicted use a small number of parts. A low number of tension members are configured to actuate the wrist assembly and the end effector 164 and facilitate implementation of a small diameter forthe wrist assembly and the instrument shaft. For example, in FIG. 4 A, a diameter of the proximal clevis 166 is substantially similar to the instrument shaft 162 to allow for insertion of the instrument 160 through a port 130, a cannula 154, and / or a small orifice.

[0080] In one or more embodiments, a diameter of the proximal clevis 166 is smaller than the instrument shaft 162, as shown in FIG. 4B. In some embodiments, a diameter of the distal clevis 168 is smaller than the instrument shaft 162. As discussed in further detail below with respect to FIGs. 7A-7B, a reduced diameter of one or more of the proximal clevis 166, the distal clevis 168, or any portion of the wrist assembly and / or end effector 164 may allow for a more accurate calibration of the instrument 160.

[0081] As shown in FIGs. 4A-4B, the instrument 160 may be connected to or may include a sensor system 169 that provides information to the control system 170. In one or more embodiments, the sensor system 169 may include one or more force sensors (e.g., an electrical sensor elements (e.g., strain sensors or strain gauges)) configured to detect forces acting on a portion of the instrument 160 (e.g., a distal end of the instrument 160). For example, a set of force sensors may be configured to detect longitudinal forces acting along a longitudinal axis of the instrument 160 (i.e., + / - z-axis forces) and / or transverse forces acting perpendicularly to the longitudinal axis of the instrument 160 (i.e., + / - x-axis forces, + / - y- axis forces). In some embodiments, multiple sets of force sensors may measure one or more portions of the instrument 160 (e.g., three redundant sensor sets). As described in further detail below with respect to FIG. 5, operation of the instrument 160 (e.g., upon reaching the surgical site) may require calibration of one or more force sensors of the sensor system 169.

[0082] While the above description relates to an instrument 160 with an actuating grip at the distal end, it will be appreciated that other instrument configurations may be used. For example, an instrument 160 may include a single end effector 164 instead of a pair of end effectors 164. In some embodiments, the instrument 160 may include zero, one, two, or any number of joints (e.g., any type of wrist clevis configuration). In some embodiments, the instrument 160 may include a surgical instrument (e.g., a cutting tool, a cauterizing tool, a suction / irrigation tool) at the distal end and / or integrated into an end effector 164.

[0083] FIG. 5 is flowchart of a method 500, in accordance with one or more embodiments.

[0084] As described above, information from the sensor system 169 may be used to provide feedback information to the control system 170 and / or operator. The sensor system 169 may measure forces upon the instrument 160 in the work site (e.g., a surgical site) to provide an indication of contact with an object or obstruction. For example, the output fromthe sensor system 169 may be used to provide haptic feedback via a force feedback module in the user input system 140 (e.g., controlling motors to manipulate the input devices 142). The output of the sensor system 169 may be used to obtain data during execution that may be used for analytics / machine-learning purposes (e.g., instrument health monitoring, process optimization). It will be appreciated that the sensor system 169 and information produced may be utilized for any appropriate application.

[0085] To acquire accurate information from the sensor system 169, a force sensor bias must be determined prior to execution of any algorithms that are based on the output of the force sensors. A force sensor bias for any given sensor in the sensor system 169 includes a zero offset signal that is produced by the sensor in a zero-load configuration (e.g., satisfying a free space condition in which the sensor is not affected by contact with another object). If the force sensor bias of any number of sensors in the sensor system 169 is inaccurate, the coordination of the instrument 160 and user input system 140 may become non-intuitive to the operator and result in unintended movements, especially while operating in a following mode of the control system 170 (leader-follower mode of teleoperation).

[0086] In view of the above, the following describes a method of calibrating the sensor system, in accordance with one or more embodiments of the invention. In particular, one or more embodiments of the invention provide improvements to calibration method of a force sensor coupled to an instrument, as the instrument is introduced to a work site via a cannula.

[0087] At 505, the control system obtains a first output from the force sensor based on a first movement of a distal end portion of the instrument within a cannula.

[0088] The first output from the force sensor may be an electrical signal (e.g., voltage, current resistance, pulse width modulated any appropriate signal) or a processed value (e.g., a quantitative force measurement). In some embodiments, the first output includes multiple first outputs (e.g., multiple outputs from a single multi-axis force sensor, multiple outputs from multiple multi-axis force sensors, multiple outputs from a number of single-axis sensors in different orientations, multiple outputs from redundant single-axis sensors in a same orientations, and appropriate combination of outputs based on the configuration of the sensor system).

[0089] As shown in FIG. 6 A, the first movement of the instrument includes: (1) an insertion motion AZ along the longitudinal axis of the instrument (i.e., moving through thecannula along a z-axis); and (2) a roll motion ARz about the longitudinal axis of the instrument (i.e., rotating within the cannula about the z-axis).

[0090] In one or more embodiments, the first movement of the distal end portion of the instrument is partially or completely driven by manual movement of an operator of the computer-assisted system. For example, the operator may install the instrument into the manipulator assembly (including connecting the sensor system to the control system) and guide the instrument through a cannula that is positioned relative to a surgical work site. As the instrument is inserted through the cannula, the sensor system communicates the first output of a force sensor (i.e., the first output corresponding forces detected during the first movement) to the control system.

[0091] In one or more embodiments, the first movement of the distal end portion of the instrument is partially or completely driven by a commanded movement of the control system. For example, the operator may install the instrument into the computer-assisted system and the control system may execute a commanded movement to guide the instrument through the cannula toward the work site by actuating a portion of the repositionable assembly (e.g., an prismatic joint and / or a revolute joint aligned with the longitudinal axis of the cannula). As the instrument is driven through the cannula, the sensor system communicates the first output of the force sensor (i.e., the first output corresponding forces detected during the first movement) to the control system.

[0092] As described in further detail below with respect to FIGs. 7A-7B, obtaining the first output from the force sensor may be further improved by modifying the geometry of the instrument. For example, reducing a diameter of the distal end portion of the instrument (e.g., a diameter of the proximal clevis of the wrist portion of the instrument) may prevent the instrument from contacting the interior surface of the cannula. Accordingly, the first output will not contain spurious components from the instrument rubbing or scraping against the cannula, as described in further detail below with respect to FIG. 7A.

[0093] At 510, the control system calculates a first bias result based on the first output.

[0094] The control system may process the first output to obtain the first bias result. The processing may include any appropriate processing (e.g., signal filtering, transformation, data processing, calculations) that outputs a quantitative measurement of force based on the first output. For example, filtering of the first output may include selecting a portion of the first output that satisfies one or more conditions.

[0095] In one or more embodiments, a filtering condition may include identifying a free-space portion of the first output that corresponds to when the instrument is not affected by contact with another object (e.g., the cannula, an obstruction) while the distal end portion of the instrument is within the cannula. As described in further detail below with respect to FIG. 9B, a free-space condition may require a time window (e.g., a continuous span of the first movement) or a movement window (e.g., a continuous portion of the insertion motion AZ of the first movement, a continuous portion of a roll motion of the first movement, a continuous portion of movement in any degree of freedom of the instrument) of the force sensor output that has an output range AF less than a maximum amplitude threshold. The maximum amplitude threshold may be a predetermined value based on the instrument, system, or operator.

[0096] In some embodiments, the first bias result is based on a portion of the first output that satisfies the free-space condition (i.e., the free-space portion of the first output). After identifying the free-space portion of the first output from the force sensor, the control system calculates the first bias result based on an amplitude of the free-space portion of the first output while the distal end portion of the instrument is inside the cannula. It will be appreciated that other conditions may be used in determining the first bias result without departing from the scope of the disclosure.

[0097] The first bias result may be one or more force measurements (e.g., corresponding to one or more force sensors in the sensor system) that may be used as an offset value for the force sensor(s) of the sensor system. In other words, the first bias result is a zero offset result for an In-Cannula (IC) portion of the calibration method 500.

[0098] At 515, the control system obtains a second output from the force sensor based on a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula.

[0099] The second output from the force sensor may be an electrical signal (e.g., voltage, current resistance, pulse width modulated any appropriate signal) or a processed value (e.g., a quantitative force measurement). In some embodiments, the second output includes multiple second outputs (e.g., multiple outputs from a single multi-axis force sensor, multiple outputs from multiple multi-axis force sensors, multiple outputs from a number of single-axis sensors in different orientations, multiple outputs from redundant single-axis sensors in a same orientations, and appropriate combination of outputs based on the configuration of the sensor system).

[0100] As shown in FIG. 6B, the second movement of the instrument includes an insertion motion AZ of the distal end portion of the instrument, parallel to a longitudinal axis of the instrument, beyond the distal end of the cannula. In some embodiments, the second movement further includes a roll motion of the distal end portion of the instrument, about a longitudinal axis of the instrument, beyond the distal end of the cannula. In some embodiments, the second movement further includes a flex motion of the distal end portion of the instrument beyond the distal end of the cannula. It will be appreciated that the second movement may include any movement of the distal end portion of the instrument beyond the distal end of the cannula. Furthermore, movement of the distal end portion of the instrument may include any motion of the manipulator assembly (e.g., yaw and / or pitch rotation of a manipulator arm about a rotational center of motion, that causes the distal end portion of the instrument to move relative to the rotational center of motion).

[0101] In one or more embodiments, the second movement of the distal end portion of the instrument is partially or completely driven by manual movement of an operator of the computer-assisted system. For example, the operator may install the instrument into the manipulator assembly (including connecting the sensor system to the control system) and guide the instrument beyond the cannula to a surgical work site. After the distal end portion of the instrument extends beyond the distal end of the cannula, the sensor system communicates the second output of the force sensor (i.e., the second output corresponding forces detected during the second movement) to the control system.

[0102] In one or more embodiments, the second movement of the distal end portion of the instrument is partially or completely driven by a commanded movement of the control system. For example, the operator may install the instrument into the computer-assisted system and the control system may execute a commanded movement to guide the instrument beyond the cannula to the work site by actuating a portion of the repositionable assembly (e.g., an prismatic joint and / or a revolute joint aligned with the longitudinal axis of the cannula). As the instrument is driven through the cannula, the sensor system communicates the second output of the force sensor (i.e., the second output corresponding forces detected during the second movement) to the control system.

[0103] In some embodiments, the control system may be configured to obtain the second output after a predetermined time interval or after a predetermined insertion distance interval based on when the distal end portion of the instrument extends beyond the distal end of the cannula. When the distal end portion of the instrument extends beyond the distal endof the cannula, may be determined in any manner (e.g., an encoder of the manipulator assembly that supports the instrument, reverse kinematic calculations based on the dimensions of the instrument and cannula, physical sensor, optical sensor, user input).

[0104] In some embodiments, obtaining the second output from the force sensor may depend on a result of the IC portion (e.g., the first bias result) of the calibration method 500. For example, the control system may be configured to display a user interface element (e.g., a prompt, a button) in response to the first bias result not satisfying a calibration condition (e.g., a portion of the first bias result exceeds a threshold value, includes an invalid measurement). In response to receiving an input via the user interface element, the control system may obtain the second output from the force sensor. In other words, the appearance of the user interface element may be used to notify the operator of an unsuccessful calibration within the cannula and prompt the operator to proceed with a secondary calibration process outside of the cannula (OOC). If the first bias result is deemed satisfactory by the operator (regardless of the prompt), obtaining the second output may be eliminated by ignoring the user interface element (or dismissing / closing the user interface element) and proceeding directly to operation of the instrument.

[0105] In some embodiments, the control system is configured to always display a user interface element that causes the control system to obtain the second output from the force sensor and calculate the second bias result. The control system is configured to: disable the user interface element while the distal end portion of the instrument is inside the cannula (i.e., disable the OOC portion of the calibration method during the IC portion of the calibration method), and enable the user interface element after the distal end portion of the instrument extends beyond the distal end of the cannula.

[0106] At 520, the control system calculates a second bias result based on the second output.

[0107] The control system may process the second output to obtain the second bias result. The processing may include any appropriate processing (e.g., signal filtering, transformation, data processing, calculations) that outputs a quantitative measurement of force based on the second output. For example, filtering of the second output may include selecting a portion of the first output that satisfies one or more conditions.

[0108] In one or more embodiments, a filtering condition may include identifying a free-space portion of the second output that corresponds to when the instrument is not affected by contact with another object (e.g., an obstruction outside of the cannula) while at least a portion of the distal end portion of the instrument extends beyond the distal end of thecannula. As described above and shown below in FIG. 9B, a free-space condition may require a time window (e.g., a continuous span of time during the first movement) or a movement window (e.g., a continuous portion of the insertion motion AZ of the first movement, a continuous portion of a roll motion of the first movement, a continuous portion of movement in any degree of freedom of the instrument) of the force sensor output that has an output range AF less than a maximum amplitude threshold. The maximum amplitude threshold may be a predetermined value based on the instrument, system, or operator.

[0109] In some embodiments, the second bias result is based on a portion of the second output that satisfies the free-space condition (i.e., the free-space portion of the second output). After identifying the free-space portion of the second output from the force sensor, the control system calculates the second bias result based on an amplitude of the free-space portion of the second output while at least a portion of the distal end portion of the instrument extends beyond the distal end of the cannula. It will be appreciated that other conditions may be used in determining the second bias result without departing from the scope of the disclosure.

[0110] The second bias result may be one or more force measurements (e.g., corresponding to one or more force sensors in the sensor system) that may be used as another offset value for the force sensor(s) of the sensor system. In other words, the second bias result is a zero offset result for an OOC portion of the calibration method 500.

[0111] At 525, the control system determines an instrument status based on the first bias result and the second bias result.

[0112] In some embodiments, the instrument status is based on whether or not the first output and the second output are obtained, and the first bias result and the second bias result are successfully calculated. The instrument status may be determined based on the first bias results and second bias results satisfying one or more calibration conditions (e.g., for all directions, results are within an acceptable range, results are less than an absolute threshold value, difference in the first and second bias results is less than an error margin).

[0113] In some embodiments, the control system may be configured to determine that the instrument status is not valid (e.g., calibration failed) when a difference between an insertion bias value of the second bias result and an insertion bias value of the first bias result is greater than a threshold. In other words, in a case where a detectable difference in insertion force is detected between the IC portion and the OOC portion of the calibration(e.g., tissue obstruction in OOC portion), the control system may determine that the instrument status is not valid (even if a force sensor bias is determined).

[0114] Determining the instrument status may include determining a force sensor bias for the force sensor (i.e., set of one or more zero offset values) based on the IC portion and / or the OOC portion of calibration method. The force sensor bias may include: an insertion bias value (i.e., a zero offset for force measured along the insertion axis of the instrument); and an orthogonal bias value (i.e., one or more zero offsets for force(s) perpendicular to the insertion axis of the instrument).

[0115] In some embodiments, the control system may be configured to determine the force sensor bias based on one of the first bias result or the second bias result. The force sensor bias may be based on the first bias result when the output range of the free-space portion of the first output is smaller than the output range of the free-space portion of the second output. Alternatively, the force sensor bias may be based on the second bias result when the output range of the free-space portion of the second output is smaller than the output range of the free-space portion of the first output.

[0116] In some embodiments, the force sensor bias may be based on the first bias result, the second bias result, or both. For example, the force sensor bias may include: an insertion bias value, for a force along an insertion axis of the instrument, based on one or more of the first bias result and the second bias result; and an orthogonal bias value, for a force perpendicular to the insertion axis of the instrument, based on one or more of the first bias result and the second bias result.

[0117] In some embodiments, the force sensor bias may include: an insertion bias value, for a force along an insertion axis of the instrument, based on the first bias result (alternate case: the second bias result); and an orthogonal bias value, for a force perpendicular to the insertion axis of the instrument, based on the second bias result (alternate case, the first bias result). For example, an invalid portion of the first bias result be replaced with and / or supplemented by a valid portion of the second bias result. By determining the force sensor bias based on the IC portion and the OOC portion of the calibration (i.e., in different environments), the occurrence of failed instrument calibration may be reduced, improving operator workflows. In other examples, the force sensor bias may be based on an average of the first bias result and the second bias result.

[0118] Optionally, at 530, the control system implements a control action (e.g., based on the instrument status).

[0119] In some embodiments, the control action is a user-facing action that improves operator workflows. For example, the control system may provide a calibration indication to an operator based on the instrument status. The calibration indication may be visual, audible, and / or tactile feedback provided by any portion of the computer-assisted system. For example, a calibration indication may be a user interface element or prompt on a display that provides additional instructions to resolve a failed calibration attempt or that indicates an active force feedback module after a successful calibration attempt.

[0120] In some embodiments, the control system is configured to modify a function of the instrument based on whether or not the instrument status is valid. For example, the control system may reject the instrument when the instrument status is not valid. Rejecting the instrument may include locking one or more functions (e.g., actuation of the end effector), prompting the operator to remove the instrument (e.g., to reattempt installation and calibration), changing user interface elements related to the instrument (e.g., disabling control options, providing indicators of not valid status), any appropriate command action, or any combination thereof.

[0121] In some embodiments, the control system is configured to modify control of one or more joints of the repositionable assembly based on whether or not the instrument status is valid. For example, the control system may lock, limit, or otherwise change permissions for a portion of the repositionable assembly (e.g., lock a prismatic joint to prevent further insertion of the instrument) when the instrument status is not valid. In another example, the control system may prevent a leader-follower control mode of teleoperation based on the instrument status, the first and second bias results, a force sensor bias, or any combination thereof.

[0122] In some embodiments, the control mode is a haptic feedback mode implemented by a force feedback module of a user input system. Haptic feedback provided to the operator may be based on a load value of the force sensor during operation of the instrument. The load value obtained by the force sensor during operation may be modified by a gain value or an offset value. Each of the gain value and the offset value may be determined based on a portion of the force sensor bias (or the first and / or second bias results). For example, haptic feedback provided in different directions may be adjusted independently based on the calibration results.

[0123] In one or more embodiments, in response to determining the instrument status as valid, the control system may be configured to: determine a force sensor bias based on the first bias result or the second bias result (if not already determined); enable the forcefeedback module of the user input system; and control the force feedback module by modifying, based at least in part on the force sensor bias, a haptic feedback provided to the user input system. In response to determining the instrument status as not valid, the control system may be configured to disable the force feedback module, enable the force feedback module with a default parameter (e.g., previous valid force sensor bias), request that the instrument be removed from the repositionable assembly, any appropriate command action, or any combination thereof.

[0124] In one or more embodiments, in response to determining the instrument status as valid, the control system may be configured to determine a force sensor bias based on the first bias result or the second bias result (if not previously determined). Based on the force sensor bias satisfying a force feedback condition (e.g., force sensor bias falls within acceptable range of values), the control system may be configured to enable the force feedback module of the user input system. Based on the force sensor bias not satisfying the force feedback condition, the control system may be configured to disable the force feedback module and prevent enablement of the force feedback module until the force sensor bias satisfies the force feedback condition (e.g., reattempt calibration).

[0125] One or more of the individual processes shown in the flowchart of FIG. 5 may be omitted, repeated (e.g., performed in parallel for multiple force sensors in the sensor system), combined, and / or performed in a different order than the order shown in this disclosure. Each process may be implemented by hardware (e.g., circuitry, physical components), software (e.g. , machine code, programming on non-transitory computer readable media), or any combination thereof. The processes may be performed actively or passively. For example, some steps may be performed using at intervals, based on polling, and / or may be event / interrupt driven in accordance with one or more embodiments of the invention. Additional processes may be performed. Accordingly, the scope of the invention should not be limited by the specific arrangement as depicted in FIG. 5.

[0126] FIGs. 6A-6B are diagrams showing movement of a distal portion of an instrument, in accordance with one or more embodiments.

[0127] As described above with respect to step 505 in FIG. 5, FIG. 6A shows a first movement of the instrument 160. The first movement of the instrument 160 includes: (1) an insertion motion AZ along the longitudinal axis of the instrument 160 (i.e., moving through the cannula along a z-axis); and (2) a roll motion ARz about the longitudinal axis of the instrument 160 (i.e., rotating within the cannula about the z-axis). The wrist portion of theinstrument 160 may implement the roll motion ARz directly to the end effector 164 (i.e., rolling the wrist portion), or the roll motion ARz may be implemented by rolling the shaft 162 of the instrument 160 (i.e., rolling the wrist portion and end effector 164 together). In some embodiments, the roll motion ARz may be implemented by a combination of rolling the wrist portion and rolling the shaft 162 of the instrument 160.

[0128] As described above with respect to step 515 in FIG. 5, FIG. 6B shows a second movement of the instrument 160. The second movement of the instrument 160 includes an insertion motion AZ of the distal end portion of the instrument 160, parallel to a longitudinal axis of the instrument 160, beyond the distal end 156 of the cannula 154.

[0129] In some embodiments, the second movement further includes a roll motion ARz of the distal end portion of the instrument 160, about the longitudinal axis of the instrument 160, beyond the distal end 156 of the cannula 154. For example, the roll motion ARz may be implemented by rolling the wrist portion of the instrument 160 (e.g., directly rolling the end effector 164), or by rolling the shaft 162 of the instrument 160 (i.e., rolling the wrist portion and end effector 164 together). In some embodiments, the roll motion ARz may be implemented by a combination of rolling the wrist portion and rolling the shaft 162 of the instrument 160.

[0130] In some embodiments, the second movement further includes a flex motion FLEXX / Y of the distal end portion of the instrument 160 beyond the distal end 165 of the cannula 154. For example, a portion of the instrument 160 may flex in a direction perpendicular to the longitudinal axis of the instrument 160 (e.g., the distal clevis 168 about the pin 166a, the end effector 164 about the pin 168a).

[0131] In some embodiments, the second movement includes a movement of the distal end portion of the instrument caused by a movement of the manipulator assembly (e.g., yaw and / or pitch rotation of a manipulator arm about a rotational center of motion, that causes the distal end portion of the instrument to move relative to the rotational center of motion).

[0132] While various examples of the second movement are shown in FIG. 6B, it will be appreciated that the second movement may include any movement of the distal end portion of the instrument 160 beyond the distal end 156 of the cannula 154.

[0133] FIGs. 7A-7B are diagrams showing a comparison of two versions of the instrument 160, 160’ performing the first movement within the cannula 154, in accordance with one or more embodiments.

[0134] In FIG. 7A, instrument 160 includes a distal end portion that is substantially the same diameter as the shaft 162 of the instrument. More specifically, the proximal clevis166 has approximately the same diameter as the shaft 162. In contrast, instrument 160’ includes a distal end portion that has a diameter that is smaller than the shaft 162. For example, the proximal clevis 167 may have a reduced diameter. In some embodiments, any or all portions of the distal end portion of the instrument 160’ may have an outermost diameter that is less than the shaft 162.

[0135] As shown in FIG. 7A, it is possible that an angular offset between the longitudinal axis of the instrument 160 and a longitudinal axis of the cannula 154 may cause the insertion motion AZ of the first movement to drive the distal end portion of the instrument 160 (e.g., the proximal clevis 166 in this non-limiting example) into contact the interior surface of the cannula 154. Regardless of the cause of the angular offset (e.g., insertion angle deviation, unintended curvature of instrument 160 or cannula 154), this contact may cause one or more artifacts in the first output of the force sensor that may directly or indirectly impact the quality and / or accuracy of the first bias result or force sensor bias.

[0136] For example, a constant dragging motion along the wall may introduce an artificial constant or time varying force in the -Z-direction (i.e., drag force that offsets the insertion portion of the first bias result or force sensor bias). In another example, the roll motion ARz of the first movement may cause the proximal clevis 166 and the distal clevis 168 to repeatedly contact the interior wall of the cannula 154 and create spurious intermittent peaks in the first output (e.g., artificial spikes that may invalid the first output by failing to provide a window that satisfies a free space condition).

[0137] In one or more embodiments, the instrument 160’ includes a proximal clevis167 with an outermost diameter that is smaller than a diameter of a shaft 162 of the instrument 160. As shown in FIG. 7B, under the same conditions as FIG. 7A (i.e., same angular offset between instrument 160 and cannula 154), the reduced geometry of the wrist portion of the distal end portion of the instrument 160 causes the contact with the interior surface of the cannula 154 to occur at the shaft 162 of the instrument. Even when the first movement includes an insertion movement and a roll movement of the proximal clevis 167, in this configuration, the distal end portion of the instrument 160 does not contact the interior surface of the cannula 154 and may preventing spurious artifacts from appearing in the first output of the force sensor. For example, in some embodiments, the sensor system 169 may be configured to measure forces on the components of the instrument 160’ that extendthrough the shaft 162 while minimizing contributions from the shaft 162 itself. In some embodiments, the distal end portion of the shaft 162 may be configured to reduce impact forces by deflecting or absorbing any impacts.

[0138] In general, a reduction in the outermost diameter of any portion of the wrist portion of the instrument 160’ may improve the calibration method 500 by preventing spurious artifacts from appearing in the first output of the force sensor and increasing the reliability of the IC portion of the calibration method 500.

[0139] FIG. 8 shows an implementation example of method 500, in accordance with one or more embodiments.

[0140] The workflow for installing an instrument for use by a repositionable assembly includes various pathways that result in the instrument being accepted (i.e., use of one or more features of the instrument is allowed by the control system) or rejected (i.e., use of one or more features of the instrument is prevented by the control system). Rejecting the instrument may require that the instrument be reinstalled (e.g., removed or at least partially disconnected from the system) before calibration can be reattempted. Such reinstallation procedures may be time consuming and frustrating to the operator.

[0141] As shown in FIG. 8, the OOC portion of the calibration method creates an alternative pathway for the instrument to be accepted by the control system when instrument fails the IC portion of the calibration method. In other words, instead of immediately rejecting the instrument when the instrument status is determined to be invalid while in the cannula, a second attempt to validate the instrument (e.g., determine a valid force sensor bias) may be performed outside of the cannula before the operator is required to initiate reinstallation procedures. Therefore, the OOC portion of the calibration method improves the overall instrument installation workflow by reducing the occurrence of multiple installation attempts.

[0142] At the start of the workflow, the instrument is physically installed into a repositionable assembly that is configured to support the instrument. As discussed above with respect to FIGs. 1 A-1B, the instrument may be supported by a manipulator assembly, a manipulator arm, a combination of reconfigurable joints and links, or any appropriate manipulator system. Installation further includes connecting a sensor system (e.g., a sensor that is included in or coupled to the instrument) to a control system that controls the instrument and the repositionable assembly. Once the instrument is installed, the process continues to the IC portion of the calibration method.

[0143] The IC portion of the calibration method (i.e., a first bias operation) is performed to calculate a first bias result based on a first output from the force sensor during a first movement of a distal end portion of the instrument within a cannula. Based on the first bias result, the control system determines an instrument status. For example, the instrument status may be based on whether or not the first bias result is valid and satisfies a calibration condition (e.g., the zero offset determined for each axis of the force sensor is valid). The IC portion of the calibration method results in: pathway (1) - the first bias result is valid, and the instrument status is determined to be valid (i.e., instrument is accepted); or pathway (2) - the first bias result is invalid, and the instrument status is determined to be invalid.

[0144] In pathway (1), the control system may allow use of the instrument and reinstallation of the instrument is not required.

[0145] In pathway (2), the control system determines whether or not to immediately reject the instrument. In some embodiments, the determination in pathway (2) may be based on the first bias result from the IC portion of the calibration method. The determination on pathway (2) results in: pathway (3) - the instrument is immediately rejected (i.e., OOC portion of the calibration method is not performed); or pathway (4) - the calibration method continues to the OOC portion.

[0146] In some embodiments, the first bias result from the IC portion of the calibration method includes an insertion bias value (i.e., z-axis component aligned with the longitudinal axis of the instrument and / or the insertion vector in the cannula) and an orthogonal bias value (i.e., the x-axis or y-axis components that are orthogonal to the z-axis component). The insertion bias value may be used as an indicator of whether or not it is safe to proceed with the OOC portion of the calibration method. For example, an obstruction in the cannula may be identified based on the insertion bias value of the first bias result exceeding a predetermined threshold. Based on the invalid insertion bias value, the control system may immediately reject the instrument as a safety measure (pathway (3)). In one or more embodiments, the control system may reject the instrument for an alternative reason (e.g., failing a sensor-health check, failing any appropriate validation check). However, when the insertion bias value of the first bias result is valid (i.e., the first bias result of the IC portion of the calibration method is invalid due to an invalid orthogonal bias value), the OOC portion of the calibration method may be used to replace or supplement the invalid first bias result (pathway (4)). In other words, based on the first bias result being at least partially invalid, the control system may determine to perform the OOC portion of the calibration method (i.e., a second bias operation)

[0147] The OOC portion of the calibration method is performed to calculate a second bias result based on a second output from the force sensor during a second movement while at least a portion of the instrument extends beyond a distal end of the cannula. Based on the second bias result, the control system determines an instrument status. For example, the instrument status may be based on whether or not the second bias result is valid and satisfies a calibration condition (e.g., the zero offset determined for each axis of the force sensor is valid). The OOC portion of the calibration method results in: pathway (5) - the second bias result is invalid (i.e., the instrument is rejected); or pathway (6) - the second bias result is valid, and the instrument status is determined to be valid (i.e., instrument is accepted).

[0148] In some embodiments, the OOC portion of the calibration method may be executed with different actions based on an operational mode of the control system. In particular, while at least a portion of the instrument extends beyond the distal end of the cannula, the second movement may be executed in different ways based on the current operational mode of the control system. In some embodiments, the control system includes a clutch operational mode and a guided tool change (GTC) operational mode that affect the second movement during the OOC portion of the calibration method.

[0149] In some embodiments, a clutch operational mode (also known as a clutch mode or an instrument clutch mode) corresponds to the control system fixing a first group of joints of the repositionable assembly (e.g., active or passive braking methods) to maintain a given configuration while floating a second group of joints that control an insertion motion of the instrument (i.e., active or passive compensation of the joints that allows freely driving the instrument forward or backward along the insertion axis). For example, when an operator activates the clutch operation (e.g., holding an activation button on the repositionable assembly), the instrument may be freely moved along the insertion axis (and only the insertion axis) based on the manual manipulation by the operator.

[0150] In some embodiments, a guided tool change (GTC) operational mode corresponds to a limited clutch operational mode. The GTC mode may be an instrument clutch mode in which the insertion motion of the instrument is limited to a maximum insertion distance. For example, when preparing to switch a first instrument with a second instrument, the control system may record the position and / or orientation of the first instrument before it is removed. Based on the configuration of the repositionable assembly (e.g., dimensions and joint configuration) and the configurations of the instruments (e.g., dimensions, end effector configurations), the control system may actively or passively manipulate the repositionable assembly during insertion of the second instrument such thatthe second instrument follows the same insertion path as the first instrument (e.g., avoiding anatomy or obstructions) to reach and stop at the record position and / or orientation.

[0151] As shown in FIG. 8, to perform the OOC portion of the calibration method, the control system may switch between different operational modes to execute the second movement of the instrument while at least a portion of the instrument extends beyond the distal end of the cannula.

[0152] For example, if the clutch operational mode is active at the start of the OOC portion of the calibration method and the clutch movement concludes before the instrument extends beyond the distal end of the cannula, the control system may switch back to the clutch operational mode (e.g., prompt the operator to repeat activation of the instrument clutch mode) to allow for more movement along the insertion axis. Once the operator inserts the instrument such that at least a portion of the instrument extends beyond the distal end of the cannula, a portion of the movement, where at least a portion of the instrument extends beyond the distal end of the cannula, constitutes the second movement during which the second output from the force sensor is obtained. In other words, the second output is obtained from the force sensor while operating in an instrument clutch mode and the second movement is a manual insertion by an operator.

[0153] Alternatively, if the GTC operational mode is active at the start of the OOC portion of the calibration method, the insertion motion is limited by a reference position of a previous instrument. If the reference position is located beyond the distal end of the cannula, the second movement is a limited manual insertion movement by the operator and the second output from the force sensor is obtained after at least a portion of the instrument extends beyond the distal end of the cannula. If the reference position is located within the cannula (i.e., the GTC mode concludes by stopping insertion of the instrument before the instrument extends beyond the distal end of the cannula), the control system may switch to the clutch operational mode to allow for more movement along the insertion axis. After switching to the clutch operational mode, the operator manually inserts the instrument such that at least a portion of the instrument extends beyond the distal end of the cannula. After the clutch operation mode concludes, a portion of the movement, where at least a portion of the instrument extends beyond the distal end of the cannula, is identified as the second movement.

[0154] In some embodiments, the control system is configured to obtain the second output after a predetermined time interval or after a predetermined insertion distance interval based on when the distal end portion of the instrument extends beyond the distal end of thecannula. For example, the control system may estimate when the distal end portion of the instrument extends beyond the distal end of the cannula based on the dimensions of the cannula and the instrument, and the configuration of the repositionable assembly (e.g., dimensions and joint configuration). To ensure the second output corresponding to when the distal end portion of the instrument extends beyond the distal end of the cannula, the control system may wait for some number of milliseconds after the estimated position is reached. Alternatively, or in combination, the control system may wait for the instrument to be inserted some additional distance after the estimated position is reached.

[0155] While the above description is limited to a clutch operational mode and a GTC operational mode, it will be appreciated that other operational modes may be used to execute the second movement required for the OOC portion of the calibration method. For example, an operational mode that includes insertion movement that is at least partially executed by the control system (i.e., not manual movement by the operator) may be used for the OOC portion of the calibration method.

[0156] Regardless of the operational mode used to execute the second movement, a second bias result is calculated based on a second output from the force sensor during the second movement of a distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula. Based on the second bias result, the control system determines the instrument status (e.g., reevaluates the instrument status based on the first bias result and / or the second bias result). For example, the instrument status may be based on whether or not the second bias result is valid and satisfies the calibration condition. The OOC portion of the calibration method results in: pathway (5) - the second bias result is invalid and the instrument status is determined to be invalid (i.e., instrument is rejected); or pathway (6) the first bias result is valid and the instrument status is determined to be valid (i.e., instrument is accepted).

[0157] One or more of the individual processes shown in FIG. 8 may be omitted, repeated (e.g., performed in parallel for multiple force sensors in the sensor system), combined, and / or performed in a different order than the order shown in this disclosure. Each process may be implemented by hardware (e.g., circuitry, physical components), software (e.g., machine code, programming on non-transitory computer readable media), or any combination thereof. The processes may be performed actively or passively. For example, some steps may be performed using at intervals, based on polling, and / or may be event / interrupt driven in accordance with one or more embodiments of the invention.Additional processes may be performed. Accordingly, the scope of the invention should not be limited by the specific arrangement as depicted in FIG. 8.

[0158] FIGs. 9A-9B are diagrams of sensor outputs, in accordance with one or more embodiments.

[0159] As discussed above, the control system calculates first and second bias results based on the first and second outputs of the force sensor, respectively. FIGs. 9A-9B describe one or more embodiments of algorithms that may be utilized to determine a bias result based on the sensor output. In some embodiments, the sensor output during a portion or the entirety of the movement may be processed. The algorithms may include quantitative algorithms that operate on the sensor output (e.g., cleaning data (filtering, smoothing removing artifacts), calculations and statistical analysis (averaging, confidence intervals)). Furthermore, the algorithms may include methods of determining whether or not the sensor output and / or calculated bias result are valid and / or suitable for use in determining instrument status. For example, an invalid sensor output and / or bias result may be used to determine that the instrument status is invalid (e.g., rejected).

[0160] While a limited number of algorithms are described herein, it will be appreciated that other algorithms may be used in calculating the first and / or second bias results may be used without departing from the gist of the present invention.

[0161] In FIG. 9A, an output of a force sensor oriented along the longitudinal axis of the instrument (i.e., the z-axis) is plotted in units of force (e.g., Newtons) against a metric that quantifies the movement of the instrument. The metric may be a movement distance (e.g., measured by an encoder, determined based on the configuration and / or position of joints of the manipulator assembly and / or instrument). The movement may be in any degree of freedom of the instrument (e.g., insertion movement, roll movement). Alternatively, the metric may be an elapsed insertion time (e.g., relative to a reference point or timestamp of an insertion movement (e.g., reaching a point in the cannula, reaching the distal end of the cannula, reaching a point beyond the distal end of the cannula)).

[0162] As shown in FIG. 9A, the sensor output during the first half of the insertion movement (e.g., the first movement or the second movement) has low variability and a low amplitude. This output profile may be an indication of a free-space condition of the instrument (discussed in further detail below with respect to FIG. 9B) during the first half of the insertion movement. However, in the second half of the insertion movement, the force along the z-axis increases. This output profile may be an indication of an obstruction thatresists the movement of the instrument (e.g., foreign matter or defect in the interior surface of the cannula, tissue obstructing the path to the surgical site).

[0163] In some embodiments, when a sensor output (or portion of the sensor output) exceeds a maximum amplitude threshold (Fthresh in FIG. 9A), a bias result that is based on that sensor output is invalid. For example, an excessive force experienced at any point in the insertion movement may indicate that the instrument is not suitable to use (e.g., potentially unsafe for the instrument and / or patient). Therefore, any bias result based on the sensor output shown in FIG. 9A would be flagged invalid. In one or more embodiments, even if the control system calculates a bias result (e.g., from the first half of insertion movement), the bias value would be flagged as invalid. In some embodiments, the bias value could be determined to be valid if other conditions are satisfied (e.g., a free-space condition described in further detail below with respect to FIG. 9B). In other words, the control system may be configured to determine whether or not a bias result is valid based on a condition that an output (e.g., some or all of the sensor output during the movement, a free-space portion of the sensor output) is less than a maximum amplitude threshold. The maximum amplitude threshold may be defined for each force sensor of the sensor system (e.g., individual thresholds, common thresholds, any combination thereof). The maximum amplitude threshold may be defined for each axis of a force sensor (e.g., independent thresholds, common thresholds, any combination thereof). In some embodiments, the maximum amplitude threshold is based on the instrument, the manipulator assembly, the operator, or any combination thereof.

[0164] In some embodiments, the control system is configured to determine a bias result (e.g., the first bias result, the second bias result) and / or a force sensor bias (e.g., a selection / fusion of the first and / or second bias results) based on identifying a free-space portion of the sensor output, as described below with respect to FIG. 9B.

[0165] Similar to FIG. 9A, in FIG. 9B, the output of a force sensor (any axis or orientation) is plotted in units of force (e.g., Newtons) against a metric that quantifies the movement of the instrument. A portion of the sensor output that satisfies a free-space condition is considered a free-space portion of the sensor output. The free-space portion of the sensor output may be identified based on a sliding inspection window of fixed width (e.g., time window corresponding to a continuous portion of the movement, a displacement window corresponding to a continuous portion of the movement) that is swept across the sensor output.

[0166] In some embodiments, the free-space condition may require that the sensor output within the inspection window is less than the maximum amplitude threshold. The maximum amplitude threshold may be a predetermined value based on the instrument, system, or operator. In other words, an entirety of the free-space portion must be less than the maximum amplitude threshold. As shown in FIG. 9A, exceeding the maximum amplitude threshold may indicate the instrument is obstructed or has collided with an object.

[0167] In some embodiments, the free-space condition may require that the sensor output within the inspection window has an output range (AF in FIG. 9B) that is less than maximum variability range. In other words, a difference between the maximum and the minimum output values across the entirety of the free-space portion must be less than the maximum variability range. The maximum variability range may be a predetermined value based on the instrument, system, or operator. As shown in FIG. 9B, exceeding the maximum variability range may indicate the instrument is obstructed or has collided with an object.

[0168] In one or more embodiments, a free-space condition for the first output (e.g., based on a first movement of a distal end portion of the instrument within a cannula) may be the same as or different from a free-space condition for the second output (e.g., based on a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula). For example, parameters of the free- space condition (e.g., inspection window size, range limits, threshold values) may differ based on the type of output from the force sensor.

[0169] After the free-space portion of the sensor output is identified, the bias result may be calculated based on the free-space portion. In some embodiments, the bias result is an average of the sensor output in the free-space portion. After the first bias result and / or the second bias result are calculated, a force sensor bias for the force sensor (i.e., set of one or more zero offset values) may be determined based on the first bias result (i.e., the IC portion of the calibration method) and / or the second bias result (i.e., the OOC portion of calibration method). The force sensor bias may include an insertion bias value (i.e., a zero offset for force measured along the insertion axis of the instrument) and one or more orthogonal bias values (i.e., zero offset for a force perpendicular to the insertion axis of the instrument) that are selected or calculated (e.g., averaged, weighted average, minimum, maximum, etc.) based on the first and / or second bias result.

[0170] In some embodiments, the control system is configured to determine whether or not a bias result is valid based on one or more aspects of the free-space condition. Forexample, the control system is configured to determine whether or not a bias result is valid based on: a first condition that the free-space portion (e.g., a portion of, an entirety of) is less than a maximum amplitude threshold; and / or a second condition that the entire output range of the free-space portion falls within a maximum variability range assigned to the respective bias result.

[0171] In some embodiments, the control system may be configured to calculate a confidence score for the bias result and / or the free-space portion of the sensor output. For example, when the sensor system include a plurality of force sensors (e.g., redundant sensors) that measure a given force, the confidence score may be based on a statistical measure (e.g., range, variance, etc.) of the plurality of bias results from the plurality of force sensor.

[0172] In some embodiments, the control system may be configured to determine whether or not a bias result is valid based on the confidence score. The confidence score may be an indication of a correlation between the free-space portion of the sensor output and a condition of the instrument in which the movement corresponding to the sensor output is not affected by contact with another object. Contact with another object during the calibration process may invalidate one or more bias results determined during the calibration process, and result in the instrument status being determined as invalid.

[0173] In some embodiments, in response to the confidence score not satisfying a confidence threshold, the control system may be configured to: obtain a replacement sensor output from the force sensor. The confidence threshold may be based on the instrument, the manipulator assembly, the operator, or any combination thereof. For example, when a second movement produces a second output from the force sensor that fails to satisfy the confidence threshold, the control system may execute (or prompt) a new movement (e.g., insertion motion of the distal end portion of the instrument) while at least a portion of the instrument extends beyond the distal end of the cannula. The sensor output during the new movement (i.e., the replacement second output) may be analyzed to identify a replacement free space portion of the replacement second output and calculate a replacement second bias result based at least in part on the replacement free space portion.

[0174] In some embodiments, in response to the confidence score not satisfying a confidence threshold, the control system may be configured to indicate an error to a user input system. For example, a confidence score that reflects a large variability in performance of redundant sensors may indicate that the sensor system and / or the whole instrument may require maintenance / refurbishment / replacement.

[0175] In some embodiments, in response to the confidence score not satisfying a confidence threshold, the control system may be configured to generate a maintenance alert indicative of a failed or failing force sensor. For example, a confidence score that reflects a large variability in performance of redundant sensors may indicate that the sensor system and / or the whole instrument may require maintenance / refurbishment / replacement.

[0176] In some embodiments, in response to the confidence score not satisfying a confidence threshold, the control system may be configured to modify, based at least in part on the confidence score, a force feedback module of a user input system. For example, a parameter (e.g., gain value or offset value) used by the force feedback module may be modified based on the confidence score. In some embodiments, different parameter values may be associated with different ranges of the confidence score (e.g., a first range that satisfies the confidence threshold corresponds to a first parameter value, a second range that satisfies the confidence threshold corresponds to a second parameter value, a third range that does not satisfy the confidence threshold results in a third parameter value). In some embodiments, the force feedback module may be disabled based on the confidence score.

[0177] While FIGs. 9A-9B are described with respect to a sensor output that corresponds to an insertion movement, it will be appreciated that the same techniques and algorithms may be applied to any sensor output. For example, in one or more embodiments, the sensor output may correspond to a flexing motion or a roll motion of the instrument (i.e., the movement of the instrument may not include an insertion movement) and the analysis of the sensor output may be used to identify a free-space condition of the instrument in a direction other than the insertion direction. In some embodiments, the sensor output may correspond to a movement of the manipulator assembly (e.g., yaw and / or pitch rotation of a manipulator arm about a rotational center of motion, that causes the distal end portion of the instrument to move relative to the rotational center of motion).

[0178] Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

[0179] Although a limited number of example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention.Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A computer-assisted system comprising: a repositionable assembly configured to support an instrument; and a control system communicatively coupled to the repositionable assembly and a force sensor coupled to the instrument, wherein the control system is configured to: obtain a first output from the force sensor based on a first movement of a distal end portion of the instrument within a cannula; calculate a first bias result based on the first output; obtain a second output from the force sensor based on a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; calculate a second bias result based on the second output; and determine an instrument status based on the first bias result and the second bias result.

2. The computer-assisted system of claim 1, wherein the first bias result is based on a free-space portion of the first output that satisfies a free-space condition for the first output, and the second bias result is based on a free-space portion of the second output that satisfies a free-space condition for the second output.

3. The computer-assisted system of claim 2, wherein the control system calculates the first bias result based on an amplitude of the free-space portion of the first output while distal end portion of the instrument is inside the cannula, and the control system calculates the second bias result based on an amplitude of the free- space portion of the second output after the distal end portion of the instrument extends beyond the distal end of the cannula.

4. The computer-assisted system of any of claims 1-3, wherein the control system is configured to control a force feedback module of a user input system based on the instrument status.

5. The computer-assisted system of claim 4, wherein the control system is configured to determine a force sensor bias based on: the first bias result when an output range of the free-space portion of the first output is smaller than an output range of the free-space portion of the second output; and the second bias result when the output range of the free-space portion of the second output is smaller than the output range of the free-space portion of the first output, and6. The computer-assisted system of any of claims 1-3, wherein the control system is configured to determine a force sensor bias is determined based on the first bias result and the second bias result.

7. The computer-assisted system of claim 6, wherein the force sensor bias includes: an insertion bias value, for a force along an insertion axis of the instrument, based on one or more of the first bias result and the second bias result; and an orthogonal bias value, for a force perpendicular to the insertion axis of the instrument, based on one or more of the first bias result and the second bias result.

8. The computer-assisted system of any of claims 2-3, wherein the control system is configured to determine whether or not each bias result is valid based on: a first condition that the free-space portion is less than a maximum amplitude threshold; and a second condition that an entire output range of the free-space portion falls within a maximum variability range.

9. The computer-assisted system of any of claims 1-3, wherein the control system is configured to determine the instrument status as not valid when a difference between an insertion bias value of the second bias result and an insertion bias value of the first bias result is greater than a threshold.

10. The computer-assisted system of any of claims 2-3, wherein the control system is configured to calculate a confidence score for the free-space portion of the second output based on a plurality of force sensors coupled to the instrument, and the confidence score indicates a correlation between the free-space portion of the second output and a condition of the instrument in which the second movement is not affected by contact with another object.

11. The computer-assisted system of claim 10, wherein in response to the confidence score not satisfying a confidence threshold, the control system is configured to: obtain a replacement second output from the force sensor based on a new movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond the distal end of the cannula; identify a replacement free-space portion of the replacement second output; and calculate a replacement second bias result based at least in part on the replacement free-space portion.

12. The computer-assisted system of claim 10, wherein in response to the confidence score not satisfying a confidence threshold, the control system is configured to indicate an error to a user input system.

13. The computer-assisted system of claim 10, wherein in response to the confidence score not satisfying a confidence threshold, the control system is configured to generate a maintenance alert indicative of a failed or failing force sensor.

14. The computer-assisted system of claim 10, wherein in response to the confidence score not satisfying a confidence threshold, the control system is configured to modify, based at least in part on the confidence score, a force feedback module of a user input system.

15. The computer-assisted system of any of claims 1-3, wherein in response to determining the instrument status as not valid, the control system is configured to request that the instrument be removed from the repositionable assembly.

16. The computer-assisted system of any of claims 1-3, wherein in response to determining the instrument status as valid, the control system is configured to: determine a force sensor bias based on one or more of the first bias result or the second bias result; enable a force feedback module of a user input system; and control the force feedback module by modifying, based at least in part on the force sensor bias, a haptic feedback provided to the user input system.

17. The computer-assisted system of claim 16, wherein the control system is configured to modify a function of the instrument based on whether or not the instrument status is valid.

18. The computer-assisted system of any of claims 1-3, wherein in response to determining the instrument status as valid, the control system is configured to determine a force sensor bias based on the first bias result or the second bias result, based on the force sensor bias satisfying a force feedback condition, the control system is configured to enable a force feedback module of a user input system, based on the force sensor bias not satisfying the force feedback condition, the control system is configured to disable the force feedback module and prevent enablement of the force feedback module until the force sensor bias satisfies the force feedback condition.

19. The computer-assisted system of any of claims 1-3, wherein the control system is configured to modify control of one or more joints of the repositionable assembly based on whether or not the instrument status is valid.

20. The computer-assisted system of any of claims 1-3, wherein the control system is configured to provide a calibration indication to an operator based on the instrument status.

21. The computer-assisted system of claim 1, wherein the control system is configured to display a user interface element in response to the first bias result not satisfying a calibration condition, andthe control system is further configured to, in response to receiving an input via the user interface element, obtain the second output from the force sensor and calculate the second bias result.

22. The computer-assisted system of claim 1, wherein the control system is configured to always display a user interface element that causes the control system to obtain the second output from the force sensor and calculate the second bias result.

23. The computer-assisted system of any of claims 21-22, wherein the control system is configured to: disable the user interface element while the distal end portion of the instrument is inside the cannula, and enable the user interface element after the distal end portion of the instrument extends beyond the distal end of the cannula.

24. The computer-assisted system of any of claims 1-3 and 21-22, wherein the second movement includes a roll motion of the distal end portion of the instrument, about a longitudinal axis of the instrument, beyond the distal end of the cannula.

25. The computer-assisted system of any of claims 1-3 and 21-22, wherein the second movement includes an insertion motion of the distal end portion of the instrument, parallel to a longitudinal axis of the instrument, beyond the distal end of the cannula.

26. The computer-assisted system of any of claims 1-3 and 21-22, wherein the second movement includes a flex motion of the distal end portion of the instrument beyond the distal end of the cannula throughout the flex motion.

27. The computer-assisted system of any of claims 1-3 and 21-22, wherein the instrument includes a proximal clevis with an outermost diameter that is smaller than a diameter of a shaft of the instrument, and the first movement includes an insertion movement and a roll movement of the proximal clevis within the cannula.

28. A method of operating a computer-assisted system including a repositionable assembly configured to support an instrument, and a control system communicatively coupled to the repositionable assembly and a force sensor couple to the instrument, the method comprising: obtaining a first output from the force sensor based on a first movement of a distal end portion of the instrument within a cannula; calculating a first bias result based on the first output; obtaining a second output from the force sensor based on a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; calculating a second bias result based on the second output; and determining an instrument status based on the first bias result and the second bias result.

29. The method of claim 28, wherein the first bias result is based on a free-space portion of the first output that satisfies a free-space condition for the first output, and the second bias result is based on a free-space portion of the second output that satisfies a free-space condition for the second output.

30. The method of claim 29, wherein the first bias result is calculated based on an amplitude of the free-space portion of the first output while distal end portion of the instrument is inside the cannula, and the second bias result is calculated based on an amplitude of the free-space portion of the second output after the distal end portion of the instrument extends beyond the distal end of the cannula.

31. The method of any of claims 28-30, further comprising: controlling a force feedback module of a user input system based on the instrument status.

32. The method of claim 31, further comprising: determining a force sensor bias based on: the first bias result when an output range of the free-space portion of the first output is smaller than an output range of the free-space portion of the second output; andthe second bias result when the output range of the free-space portion of the second output is smaller than the output range of the free-space portion of the first output, and33. The method of any of claims 28-30, further comprising: determining a force sensor bias based on the first bias result and the second bias result.

34. The method of claim 33, wherein the force sensor bias includes: an insertion bias value, for a force along an insertion axis of the instrument, based on one or more of the first bias result and the second bias result; and an orthogonal bias value, for a force perpendicular to the insertion axis of the instrument, based on one or more of the first bias result and the second bias result.

35. The method of any of claims 29-30, further comprising: determining whether or not each bias result is valid based on: a first condition that the free-space portion is less than a maximum amplitude threshold; and a second condition that an entire output range of the free-space portion falls within a maximum variability range.

36. The method of any of claims 28-30, further comprising: determining the instrument status as not valid when a difference between an insertion bias value of the second bias result and an insertion bias value of the first bias result is greater than a threshold.

37. The method of any of claims 29-30, further comprising: calculating a confidence score for the free-space portion of the second output based on a plurality of force sensors coupled to the instrument, wherein the confidence score indicates a correlation between the free-space portion of the second output and a condition of the instrument in which the second movement is not affected by contact with another object.

38. The method of claim 37, further comprising: in response to the confidence score not satisfying a confidence threshold, obtaining a replacement second output from the force sensor based on a new movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond the distal end of the cannula; identifying a replacement free-space portion of the replacement second output; and calculating a replacement second bias result based at least in part on the replacement free-space portion.

39. The method of claim 37, further comprising: in response to the confidence score not satisfying a confidence threshold, indicating an error to a user input system.

40. The method of claim 37, further comprising: in response to the confidence score not satisfying a confidence threshold, generating a maintenance alert indicative of a failed or failing force sensor.

41. The method of claim 37, further comprising: in response to the confidence score not satisfying a confidence threshold, modifying, based at least in part on the confidence score, a force feedback module of a user input system.

42. The method of any of claims 28-30, further comprising: in response to determining the instrument status as not valid, requesting that the instrument be removed from the repositionable assembly.

43. The method of any of claims 28-30, further comprising: in response to determining the instrument status as valid, determining a force sensor bias based on one or more of the first bias result or the second bias result; enabling a force feedback module of a user input system; and controlling the force feedback module by modifying, based at least in part on the force sensor bias, a haptic feedback provided to the user input system.

44. The method of any of claims 28-30, further comprising: modifying a function of the instrument based on whether or not the instrument status is valid.

45. The method of any of claims 28-30, further comprising: in response to determining the instrument status as valid, determining a force sensor bias based on the first bias result or the second bias result, based on the force sensor bias satisfying a force feedback condition, enabling a force feedback module of a user input system, based on the force sensor bias not satisfying the force feedback condition, disabling the force feedback module and preventing enablement of the force feedback module until the force sensor bias satisfies the force feedback condition.

46. The method of any of claims 28-30, further comprising: modifying control of one or more joints of the repositionable assembly based on whether or not the instrument status is valid.

47. The method of any of claims 28-30, further comprising: providing a calibration indication to an operator based on the instrument status.

48. The method of claim 28, further comprising: displaying a user interface element in response to the first bias result not satisfying a calibration condition, and in response to receiving an input via the user interface element, obtaining the second output from the force sensor and calculate the second bias result.

49. The method of claim 28, further comprising: always displaying a user interface element that causes the control system to obtain the second output from the force sensor and calculate the second bias result.

50. The method of any of claims 48-49, further comprising: disabling the user interface element while the distal end portion of the instrument is inside the cannula, and enabling the user interface element after the distal end portion of the instrument extends beyond the distal end of the cannula.

51. The method of any of claims 28-30 and 48-49, wherein the second movement includes a roll motion of the distal end portion of the instrument, about a longitudinal axis of the instrument, beyond the distal end of the cannula.

52. The method of any of claims 28-30 and 48-49, wherein the second movement includes an insertion motion of the distal end portion of the instrument, parallel to a longitudinal axis of the instrument, beyond the distal end of the cannula.

53. The method of any of claims 28-30 and 48-49, wherein the second movement includes a flex motion of the distal end portion of the instrument beyond the distal end of the cannula throughout the flex motion.

54. The method of any of claims 28-30 and 48-49, wherein the instrument includes a proximal clevis with an outermost diameter that is smaller than a diameter of a shaft of the instrument, and the first movement includes an insertion movement and a roll movement of the proximal clevis within the cannula.

55. A non-transitory machine-readable medium comprising a plurality of machine-readable instructions executed by one or more processors associated with a computer-assisted system, the plurality of machine-readable instructions causing the one or more processors to perform the method of any of claims 28-30 and 48-49.

56. A computer-assisted system comprising: a repositionable assembly configured to support an instrument; and a control system communicatively coupled to the repositionable assembly and a force sensor coupled to the instrument; and wherein the control system is configured to: calculate a first bias result based on a first output from the force sensor during a first movement of a distal end portion of the instrument within a cannula; determine, based on the first bias result being valid, an instrument status based on the first bias result;determine, based on the first bias result being at least partially invalid, to perform a second bias operation that includes: calculating a second bias result based on a second output from the force sensor during a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; and determining the instrument status based on the second bias result.

57. The computer-assisted system of claim 56, wherein the first bias result includes an insertion bias value and an orthogonal bias value, the control system determines to perform the second bias operation when the insertion bias value is valid and the orthogonal bias value is invalid, and the control system determines to reject the instrument when the insertion bias value is invalid.

58. The computer-assisted system of any of claims 56-57, wherein the control system is configured to obtain the second output after a predetermined time interval or after a predetermined insertion distance interval based on when the distal end portion of the instrument extends beyond the distal end of the cannula.

59. The computer-assisted system of any of claims 56-57, wherein the second output is obtained from the force sensor while operating in an instrument clutch mode and the second movement is a manual insertion by an operator, or the second output is obtained while in a guided tool change mode and the second movement is a limited manual insertion movement by the operator, and calculating of the second bias result and determining of the instrument status occur after conclusion of the instrument clutch mode or guided tool change mode, while at least the portion of the instrument extends beyond the distal end of the cannula.

60. A method of operating a computer-assisted system including a repositionable assembly configured to support an instrument, and a control system communicatively coupled to the repositionable assembly and a force sensor, the method comprising: calculating a first bias result based on a first output from the force sensor during a first movement of a distal end portion of the instrument within a cannula;determining, based on the first bias result being valid, an instrument status based on the first bias result; determining, based on the first bias result being at least partially invalid, to perform a second bias operation that includes: calculating a second bias result based on a second output from the force sensor during a second movement of the distal end portion of the instrument while at least a portion of the instrument extends beyond a distal end of the cannula; and determining the instrument status based on the second bias result.

61. The method of claim 60, wherein the first bias result includes an insertion bias value and an orthogonal bias value, and the method further comprises: determining to perform the second bias operation when the insertion bias value is valid and the orthogonal bias value is invalid, and determining to reject the instrument when the insertion bias value is invalid.

62. The method of any of claims 60-61, further comprises: obtaining the second output after a predetermined time interval or after a predetermined insertion distance interval based on when the distal end portion of the instrument extends beyond the distal end of the cannula.

63. The method of any of claims 60-61, wherein the second output is obtained from the force sensor while operating in an instrument clutch mode and the second movement is a manual insertion by an operator, or the second output is obtained while in a guided tool change mode and the second movement is a limited manual insertion movement by the operator, and calculating of the second bias result and determining of the instrument status occur after conclusion of the instrument clutch mode or guided tool change mode, while at least the portion of the instrument extends beyond the distal end of the cannula.

64. A non-transitory machine-readable medium comprising a plurality of machine-readable instructions executed by one or more processors associated with a computer-assistedsystem, the plurality of machine-readable instructions causing the one or more processors to perform the method of any of claims 60 to 61.

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