System and method for maintaining tool attitude

Abstract

To maintain a pose of a tool in the presence of disturbances in articulated joints located proximal to the tool.SOLUTION: Provided is a system and method for maintaining a pose of a tool for a computer-assisted medical device which includes an articulated arm comprising one or more first joints and one or more second joints, a tool distal to the first joints and the second joints, and a control unit coupled to the first joints and the second joints. The control unit determines a reference coordinate frame of the tool, determines a reference conversion of the tool in the reference coordinate frame prior to movement of the first joint, determines an actual conversion of the tool in the reference coordinate frame while the first joint is moved, determines a difference between the reference conversion and the actual conversion, and drives the second joint on the basis of the difference to maintain the pose of the tool to thereby maintain the pose of the tool using the second joint at movement of the first joint.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure claims priority to U.S. Provisional Application No. 62 / 024,887, filed July 15, 2014, entitled "System and Method for Aligning with a Reference Target," and U.S. Provisional Application No. 61 / 954,261, filed March 17, 2014, entitled "System and Method for Aligning with a Reference Target," both of which are incorporated herein by reference in their entireties. This disclosure is also related to a concurrently filed U.S. provisional application having attorney docket number ISRG06930PROV2 / US / 70228.498US01 entitled "System and Method for Integrated Surgical Table," a concurrently filed U.S. provisional application having attorney docket number ISRG07010PROV / US / 70228.490US01 entitled "System and Method for Reducing Tool Disturbances," and a concurrently filed PCT application having attorney docket number ISRG06230PCT / 70228.422WO01 entitled "System and Method for Aligning with a Reference Target," all of which are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to actuation of devices with articulated arms, and more particularly to maintaining tool attitude. [Background technology]

[0003] More and more devices are being replaced with autonomous and semi-autonomous electronic devices. This is especially true in today's hospitals with many autonomous and semi-autonomous electronic devices found in operating rooms, interventional rooms, intensive care units, emergency rooms, etc. For example, glass and mercury thermometers have been replaced with electronic thermometers, intravenous lines now include electronic monitors and flow regulators, and traditional handheld surgical instruments have been replaced with computer-assisted medical devices.

[0004] These electronic devices present both benefits and challenges to those who operate them. Many of these electronic devices may enable autonomous or semi-autonomous operation of one or more articulated arms and / or end effectors. Each of these one or more articulated arms and / or end effectors includes a combination of links and articulated joints that assist in the movement of the articulated arms and / or end effectors. Often, the articulated joints are manipulated to achieve a desired position and / or orientation (collectively, a desired pose) of a corresponding tool located at the distal end of the link and articulated joint in the corresponding articulated arm and / or end effector. Each articulated joint proximal to the tool provides the corresponding articulated arm and / or end effector with at least one degree of freedom that can be used to manipulate the position and / or orientation of the corresponding tool. Often, the corresponding articulated arm and / or end effector may include at least six degrees of freedom that allow control of the x, y, and z positions of the corresponding tool, as well as the roll, pitch, and yaw orientation of the corresponding tool. To provide greater flexibility in controlling the pose of the corresponding tool, the corresponding articulated arm and / or end effector are often designed to include redundant degrees of freedom. When redundant degrees of freedom exist, multiple different combinations of positions and / or orientations at the articulated joints can be used to achieve the same pose of the corresponding tool. This creates a null space where the pose of the corresponding tool does not move even when the articulated joints are moving.

[0005] As each articulated arm and / or end effector is manipulated, it may be subject to both planned and unplanned motions that may result in movement at one or more of its articulated joints. This motion may change the position and / or orientation of one or more of its articulated joints, which may result in an undesirable change in the attitude of a tool being manipulated by the articulated arm. This change in attitude may result in injury to a patient, injury to persons near the articulated arm and / or end effector, damage to the articulated arm and / or end effector, damage to other equipment near the articulated arm and / or end effector, disruption of the sterile field, and / or other undesirable consequences. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Provisional Application No. 61 / 954,261 [Patent Document 2] U.S. Provisional Application No. 62 / 024887 [Patent Document 3] U.S. Provisional Application No. 61 / 954,120 Summary of the Invention [Problem to be solved by the invention]

[0007] It is therefore desirable to maintain the tool's attitude in the presence of disturbances at the articulated joints proximal to the tool. [Means for solving the problem]

[0008] Consistent with some embodiments, a computer-aided medical device includes an articulated arm including one or more first joints and one or more second joints, a tool distal to the one or more first joints and the one or more second joints, and a control unit coupled to the first joints and the second joints, wherein the control unit maintains the attitude of the tool during movement of the one or more first joints using the one or more second joints by determining a reference coordinate frame for the tool, determining a reference transformation of the tool in the reference coordinate frame prior to movement of the one or more first joints, determining an actual transformation of the tool in the reference coordinate frame while the one or more first joints are moved, determining a difference between the reference transformation and the actual transformation, and maintaining the attitude of the tool by driving the second joint based on the difference.

[0009] Consistent with some embodiments, a method for offsetting motion of an articulated arm of a computer-assisted medical device includes determining a pose of a tool of the medical device and maintaining the pose of the tool using one or more second joints proximal to the tool during movement of one or more first joints in the articulated arm proximal to the tool. The pose is maintained by determining a reference coordinate frame for the tool, determining a reference transformation of the tool in the reference coordinate frame prior to movement of the one or more first joints, determining an actual transformation of the tool in the reference coordinate frame while the one or more first joints are being moved, determining a difference between the reference transformation and the actual transformation, and maintaining the pose of the tool by driving the second joint based on the difference. The pose includes position and orientation.

[0010] Consistent with certain embodiments, a non-transitory machine-readable medium includes a plurality of machine-readable instructions that, when executed by one or more processors associated with a medical device, cause the one or more processors to perform a method including determining a pose of a tool of the medical device and maintaining the pose of the tool using one or more second joints proximal to the tool during movement of one or more first joints in an articulated arm proximal to the tool. The pose is maintained by determining a reference coordinate frame for the tool, determining a reference transformation of the tool in the reference coordinate frame prior to movement of the one or more first joints, determining an actual transformation of the tool in the reference coordinate frame while the one or more first joints are being moved, determining a difference between the reference transformation and the actual transformation, and maintaining the pose of the tool by driving the second joint based on the difference. The pose includes position and orientation. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a simplified diagram of a computer-assisted system according to some embodiments. [Figure 2] 1 is a simplified diagram illustrating a computer-assisted system according to some embodiments. [Figure 3] 1 is a simplified diagram of a kinematic model of a computer-assisted medical system according to some embodiments. [Figure 4] 1 is a simplified diagram of a method for maintaining the orientation of a tool during movement of one or more joints proximal to the tool, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the drawings, elements with the same designations have the same or equivalent functions. In the following description, specific details are set forth describing some embodiments according to the present disclosure. However, it will be apparent to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are intended to be illustrative and not limiting. Those skilled in the art may realize other elements not specifically described herein that are within the scope and spirit of the present disclosure. Furthermore, to avoid unnecessary repetition, one or more features illustrated and described in connection with one embodiment may be incorporated into other embodiments, unless specifically stated otherwise or unless the one or more features render the embodiment non-functional.

[0013] FIG. 1 is a simplified diagram of a computer-assisted system 100 according to some embodiments. As shown in FIG. 1, the computer-assisted system 100 includes an apparatus 110 having one or more movable or articulated arms 120. Each of the one or more articulated arms 120 may support one or more end effectors. In some examples, the apparatus 110 may correspond to a computer-assisted surgical apparatus. Each of the one or more articulated arms 120 may provide support for one or more tools, surgical instruments, imaging devices, and / or the like attached to a distal end of at least one of the articulated arms 120. The apparatus 110 may further be coupled to an operator workstation (not shown). The operator workstation may include one or more master controls for operating the apparatus 110, the one or more articulated arms 120, and / or the end effectors. In some embodiments, the apparatus 110 and operator workstation may correspond to the da Vinci® Surgical System commercially available from Intuitive Surgical, Inc. of Sunnyvale, California. In some embodiments, computer-assisted surgical devices having other configurations, fewer or more articulated arms, and / or the like may be used with computer-assisted system 100.

[0014] The device 110 is coupled to the control unit 130 via an interface. The interface may include one or more wireless links, cables, connectors, and / or buses, and may further include one or more networks with one or more network switching and / or routing devices. The control unit 130 includes a processor 140 coupled to a memory 150. The operation of the control unit 130 is controlled by the processor 140. While the control unit 130 is shown with only one processor 140, it should be understood that the processor 140 may be representative of one or more central processing units, multi-core processors, microprocessors, microcontrollers, digital signal processors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), and / or the like in the control unit 130. The control unit 130 may be implemented as a standalone subsystem and / or board added to a computing device or as a virtual machine. In some embodiments, the control unit may be included as part of an operator workstation and / or may operate separately from, but in cooperation with, the operator workstation.

[0015] Memory 150 may be used to store software executed by control unit 130 and / or one or more data structures used during operation of control unit 130. Memory 150 may include one or more types of machine-readable media. Some common forms of machine-readable media may include floppy disks, flexible disks, hard disks, magnetic tape, any other magnetic media, CD-ROMs, any other optical media, punch cards, paper tape, any other physical media with a pattern of holes, RAM, PROMs, EPROMs, FLASH®-EPROMs, any other memory chips or cartridges, and / or any other media configured to be read by a processor or computer.

[0016] As shown, memory 150 includes a motion control application 160 that can be used to support autonomous and / or semi-autonomous control of device 110. Motion control application 160 can include one or more application programming interfaces (APIs) for receiving position, motion, and / or other sensor information from device 110, exchanging position, motion, and / or collision avoidance information with other control units for other devices, such as a surgical table and / or imaging devices, and / or planning and / or assisting in planning movements for device 110, articulated arm 120, and / or an end effector of device 110. Also, while motion control application 160 is depicted as a software application, motion control application 160 can be implemented using hardware, software, and / or a combination of hardware and software.

[0017] In some embodiments, computer-assisted system 100 may be found in an operating room and / or interventional suite. Also, while computer-assisted system 100 includes only one device 110 having two articulated arms 120, those skilled in the art will appreciate that computer-assisted system 100 may include any number of devices having articulated arms and / or end effectors of similar and / or different designs than device 110. In some examples, each of the devices may include fewer or more articulated arms and / or end effectors.

[0018] The computer-assisted system 100 further includes a surgical table 170. Like one or more articulated arms 120, the surgical table 170 may support articulated movement of a tabletop 180 relative to a base of the surgical table 170. In some examples, the articulated movement of the tabletop 180 may include support for changing the height, tilt, slide, Trendelenburg orientation, and / or the like of the tabletop 180. Although not shown, the surgical table 170 may include one or more control inputs, such as a control pendant, for controlling the position and / or orientation of the tabletop 180. In some embodiments, the surgical table 170 may correspond to one or more control tables commercially available from Trumpf Medical Systems GmbH of Germany.

[0019] The surgical table 170 may also be coupled to the control unit 130 via a corresponding interface. The interface may include one or more wireless links, cables, connectors, and / or buses, and may further include one or more networks with one or more network switching and / or routing devices. In some embodiments, the surgical table 170 may be coupled to a control unit different from the control unit 130. In some examples, the motion control application 160 may include one or more application programming interfaces (APIs) for receiving position, motion, and / or other sensor information associated with the surgical table 170 and / or tabletop 180. In some examples, the motion control application 160 may plan and / or assist in planning the motion of the surgical table 170 and / or tabletop 180. In some examples, the motion control application 160 may prevent motion of the surgical table 170 and / or tabletop 180, such as by preventing motion of the surgical table 170 and / or tabletop 180 through the use of a control pendant. In some examples, the motion control application 160 may assist in registering the device 110 with the surgical table 170 so that a geometric relationship between the device 110 and the surgical table 170 is known. In some examples, the geometric relationship may include a translation and / or one or more rotations between a coordinate frame maintained relative to the device 110 and a coordinate frame maintained relative to the surgical table 170.

[0020] FIG. 2 is a simplified diagram illustrating a computer-assisted system 200 according to some embodiments. For example, the computer-assisted system 200 may correspond to the computer-assisted system 100. As shown in FIG. 2, the computer-assisted system 200 includes a computer-assisted device 210 having one or more articulated arms and a surgical table 280. Although not shown in FIG. 2, the computer-assisted device 210 and the surgical table 280 may be coupled together using one or more interfaces and one or more control units so that kinematic information regarding at least the surgical table 280 is made known to a motion control application being used to execute the movements of the articulated arms of the computer-assisted device 210.

[0021] The computer-assisted device 210 includes various links and joints. In the embodiment of FIG. 2, the computer-assisted device is generally divided into three different sets of links and joints. Starting at the proximal end with the mobile cart or patient side cart 215 is a setup structure 220. Coupled to the distal end of the setup structure are a series of setup joints 240. Coupled to the distal end of the setup joints 240 are manipulators 260, such as a universal surgical manipulator. In some examples, the series of setup joints 240 and manipulators 260 may correspond to one of the articulated arms 120. Also, while the computer-assisted device is shown with only one series of setup joints 240 and corresponding manipulators 260, one skilled in the articulated arms will understand that the computer-assisted device may include more than one series of setup joints 240 and corresponding manipulators 260, such that the computer-assisted device may have multiple articulated arms.

[0022] As shown, the computer-assisted device 210 is mounted on a mobile cart 215. The mobile cart 215 allows the computer-assisted device 210 to be moved from one location to another, such as between or within an operating room, to better position the computer-assisted device 210 near the operating table 180. A setup structure 220 is mounted on the mobile cart 215. As shown in FIG. 2 , the setup structure 220 includes a two-piece strut including strut links 221 and 222. Coupled to the upper or distal end of the strut link 222 is a shoulder joint 223. Coupled to the shoulder joint 223 is a two-piece boom including boom links 224 and 225. At the distal end of the boom link 225 is a wrist joint 226, and coupled to the wrist joint 226 is an orientation platform 227.

[0023] The links and joints of the setup structure 220 include multiple degrees of freedom for changing the position and orientation (i.e., posture) of the orientation platform 227. For example, a two-piece support column can be used to adjust the height of the orientation platform 227 by moving the shoulder joint 223 up and down along axis 232. The orientation platform 227 can additionally be rotated about axis 232 using the shoulder joint 223, the movable cart 215, the two-piece support column, and axis 232. The horizontal position of the orientation platform 227 can also be adjusted along axis 234 using the two-piece boom. The orientation of the orientation platform 227 can also be adjusted by rotating about axis 236 using the wrist joint 226. Thus, depending on the motion limits of the links and joints in the setup structure 220, the position of the orientation platform 227 can be adjusted vertically above the movable cart 215 using the two-piece support column. The position of the orientation platform 227 can also be adjusted radially and angularly about the mobile cart 215 using the two-piece boom and shoulder joint 223, respectively. The angular orientation of the orientation platform 227 can also be changed using the wrist joint 226.

[0024] Orientation platform 227 can be used as an attachment point for one or more articulated arms. The ability to adjust the height, horizontal position, and orientation of orientation platform 227 relative to mobile cart 215 provides a flexible setup configuration for positioning and orienting one or more articulated arms around a workspace, such as a patient positioned near mobile cart 215. FIG. 2 shows a single articulated arm coupled to the orientation platform using a first setup joint, i.e., first flex joint 242. Also, while only one articulated arm is shown, one skilled in the art will understand that multiple articulated arms can be coupled to orientation platform 227 using additional first setup joints.

[0025] The first setup joint 242 forms the proximal portion of the setup joint 240, which is part of the articulated arm. The setup joint 240 may further include a series of joints and links. As shown in FIG. 2 , the setup joint 240 includes at least links 244, 246 connected via one or more joints (not explicitly shown). The joints and links of the setup joint 240 include the ability to rotate the setup joint 240 relative to the orientation platform 227 about an axis 252 using the first setup joint 242, the ability to adjust the radial or horizontal distance between the first setup joint 242 and the link 246, the ability to adjust the height of a manipulator mount 262 at the distal end of the link 246 relative to the orientation platform along an axis 254, and the ability to rotate the manipulator mount 262 about the axis 254. In some embodiments, the setup joint 240 may further include additional joints, links, and axes that provide additional degrees of freedom for changing the orientation of the manipulator mount 262 with respect to the orientation platform 227.

[0026] A manipulator 260 is coupled to the distal end of the setup joint 240 via a manipulator mount 262. The manipulator 260 includes an instrument carriage 268 mounted to the distal end of the manipulator 260, as well as additional joints 264 and links 266. An instrument, or manipulator tool 270, is mounted to the instrument carriage 268. The tool 270 includes a shaft 272 aligned along an insertion axis. The shaft 272 is typically aligned to pass through a remote center 274 associated with the manipulator 260. The position of the remote center 274 is typically maintained in a fixed translational relationship with respect to the manipulator mount 262, such that manipulation of the joints 264 in the manipulator 260 results in rotation of the shaft 272 about the remote center 274. In some embodiments, the fixed translational relationship of remote center 274 with respect to manipulator mount 262 is maintained through the use of physical constraints of joints 264 and links 266 in manipulator 260, software constraints imposed on the allowed motion of joints 264, and / or a combination of both. In some examples, remote center 274 may correspond to the location of a surgical port or incision site on patient 278 after manipulator 260 is docked to patient 278. Because remote center 274 corresponds to the surgical port, when tool 270 is used, remote center 274 remains stationary with respect to patient 278 to limit stress on the anatomy of patient 278 at remote center 274. In some examples, shaft 272 may be passed through a cannula (not shown) at the surgical port.

[0027] At the distal end of shaft 272 is a tool or tool tip 276. The degrees of freedom in manipulator 260 via joints 264 and links 266 may at least allow for control of roll, pitch, and yaw of shaft 272 and / or tool tip 276 relative to manipulator mount 262. In some examples, the degrees of freedom in manipulator 260 may further include the ability to advance and / or retract shaft 272 using instrument carriage 268 so that tool tip 276 can be advanced and / or retracted along the insertion axis and relative to remote center 274. In some examples, manipulator 260 may correspond to a universal surgical manipulator used with the da Vinci® Surgical System, commercially available from Intuitive Surgical, Inc. of Sunnyvale, California. In some examples, tool 270 may be an imaging device, such as an endoscope, a gripper, a surgical tool, such as cautery or a scalpel, and / or the like. In some examples, the tool tip 276 may include additional degrees of freedom, such as roll, pitch, yaw, grip, and / or the like, that allow for additional localized manipulation of the position of the tool tip 276 relative to the shaft 272.

[0028] During surgery or other medical procedures, a patient 278 is typically positioned on a surgical table 280. The surgical table 280 includes a table base 282 and a tabletop 284. The table base 282 is positioned near a mobile cart 215 so that instruments 270 and / or tooltips 276 can be manipulated by the computer-assisted device 210 while docked to the patient 278. The surgical table 280 further includes an articulated structure 290 including one or more joints or links between the table base 282 and the tabletop 284 so that the relative position of the tabletop 284, and therefore the patient 278, with respect to the table base 282 can be controlled. In some examples, the articulated structure 290 may be configured so that the tabletop 284 is controlled with respect to a virtually defined isocenter 286, which may be located at a point on the tabletop 284. In some examples, the isocenter 286 may be located within the patient 278. In some examples, the treatment center 286 may be positioned in the patient's body wall at or near one of multiple port sites, such as the port site corresponding to the remote center 274.

[0029] As shown in FIG. 2 , the articulated structure 290 includes a height adjustment joint 292 so that the tabletop 284 can be raised and / or lowered relative to the table base 282. The articulated structure 290 further includes joints and links for changing both the tilt 294 and Trendelenburg 296 orientation of the tabletop 284 relative to the treatment center 286. The tilt 294 allows the tabletop 284 to tilt left and right so that either the right or left side of the patient 278 can be rotated upward (i.e., about the longitudinal axis, or head-to-toe axis, of the tabletop 284) relative to the other side of the patient 278. The Trendelenburg 296 allows the tabletop 284 to rotate so that the feet of the patient 278 are raised (Trendelenburg) or the head of the patient 278 is raised (reverse Trendelenburg). In some examples, tilt 294 and / or Trendelenburg 296 rotation can be adjusted to produce rotation about the treatment center 286. The articulated structure 290 further includes additional links and joints 298 for sliding the table top 284 back and forth relative to the table base 282 in a general left and / or right motion as depicted in FIG.

[0030] FIG. 3 is a simplified diagram of a kinematic model 300 of a computer-assisted medical system according to some embodiments. As shown in FIG. 3, the kinematic model 300 may include kinematic information associated with many sources and / or devices. The kinematic information may be based on known kinematic models for the links and joints in the computer-assisted medical device and the surgical table. The kinematic information may also be based on information associated with the positions and / or orientations of the joints in the computer-assisted medical device and the surgical table. In some examples, the information associated with the positions and / or orientations of the joints may be derived from one or more sensors, such as encoders, that measure the linear position of a prismatic joint and the rotational position of a revolute joint.

[0031] The kinematic model 300 includes multiple coordinate frames or systems and transformations, such as homogeneous transforms, for converting position and / or orientation from one of the multiple coordinate frames to another of the multiple coordinate frames. In some examples, the kinematic model 300 can be used to enable forward and / or reverse mapping of position and / or orientation in one of the multiple coordinate frames to any other coordinate frame by composing forward and / or reverse (opposite) transformations as illustrated by the transform linkages included in FIG. 3. In some examples, if the transformations are modeled as homogeneous transformations in matrix form, the composition can be achieved using matrix multiplication. In some embodiments, the kinematic model 300 can be used to model the kinematic relationship between the computer-assisted device 210 and the surgical table 280 of FIG. 2.

[0032] Kinematic model 300 includes a table base coordinate frame 305 that may be used to model the position and / or orientation of a surgical table, such as surgical table 170 and / or surgical table 280. In some examples, table base coordinate frame 305 may be used to model other points on the surgical table relative to a reference point and / or reference direction associated with the surgical table. In some examples, the reference point and / or reference direction may be associated with a table base of the surgical table, such as table base 282. In some examples, table base coordinate frame 305 may be suitable for use as a world coordinate frame for a computer-aided system.

[0033] The kinematic model 300 further includes a tabletop coordinate frame 310 that can be used to model positions and / or orientations in a coordinate frame representing a tabletop of a surgical table, such as tabletop 284. In some examples, the tabletop coordinate frame 310 can be centered about the tabletop's center of rotation or treatment center, such as treatment center 286. In some examples, the z-axis of the tabletop coordinate frame 310 can be oriented vertically with respect to the floor or surface on which the surgical table rests and / or perpendicular to the surface of the tabletop. In some examples, the x- and y-axes of the tabletop coordinate frame 310 can be oriented to occupy the major longitudinal (from head to toe) and lateral (from one side to the other) axes of the tabletop. In some examples, a tablebase / tabletop coordinate transformation 315 can be used to map positions and / or orientations between the tabletop coordinate frame 310 and the tablebase coordinate frame 305. In some examples, one or more kinematic models of the articulated structures in a surgical table, such as articulated structure 290, along with past and / or current joint sensor measurements, may be used to determine table base / table top coordinate transformation 315. In some examples consistent with the embodiment of FIG. 2, table base / table top coordinate transformation 315 may model the combined effects of height, Trendelenburg, and / or slide settings associated with the surgical table.

[0034] Kinematic model 300 further includes a device-based coordinate frame that may be used to model the position and / or orientation of a computer-assisted device, such as computer-assisted device 110 and / or computer-assisted device 210. In some examples, device-based coordinate frame 320 may be used to model other points on the computer-assisted device relative to a reference point and / or a reference direction associated with the computer-assisted device. In some examples, the reference point and / or the reference direction may be associated with a device base of the computer-assisted device, such as mobile cart 215. In some examples, device-based coordinate frame 320 may be suitable for use as a world coordinate frame for a computer-assisted system.

[0035] To track the positional and / or orientational relationship between the surgical table and the computer-assisted device, it may be desirable to establish registration between the surgical table and the computer-assisted device. As shown in FIG. 3 , the registration may be used to determine a registration transformation 325 between the tabletop coordinate frame 310 and the device base coordinate frame 320. In some embodiments, the registration transformation 325 may be a partial or complete transformation between the tabletop coordinate frame 310 and the device base coordinate frame 320. In some examples, the table base and the device base are typically placed on the same floor surface at the same height, so the registration transformation 325 may only model the rotational relationship of the device base relative to the table base about the z-axis of the table base coordinate frame 305 (e.g., θz registration). In some examples, the registration transformation 325 may model the horizontal offset (e.g., XY registration) between the table base coordinate frame 305 and the device base coordinate frame 320. This is possible because both the computer-assisted device and the surgical table are placed on the same horizontal surface (floor) and operated in an upright position. In this operational relationship, height adjustments in the table base / table top transform 315 are analogous to vertical adjustments in the machine base coordinate frame 320. The vertical axis of the table base coordinate frame 305 and the vertical axis of the machine base coordinate frame 320 are the same or nearly the same so that the height difference between the table base coordinate frame 305 and the machine base coordinate frame 320 is within a reasonable tolerance of each other. In some examples, tilt and Trendelenburg adjustments in the table base / table top transform 315 can be mapped to the machine base coordinate frame 320 by knowing the height and θz and / or XY alignment of the table top (or its treatment center). In some examples, the alignment transform 325 and the table base / table top transform 315 can be used to model a computer-assisted surgery device as if it were attached to a table top.

[0036] Kinematic model 300 further includes arm gantry coordinate frame 330, which may be used as an appropriate model of a shared coordinate frame associated with the most proximal point on the articulated arm of the computer-assisted apparatus. In some embodiments, arm gantry coordinate frame 330 may be associated with and oriented relative to a convenient point on the arm gantry, such as orientation platform 227. In some examples, the center point of arm gantry coordinate frame 330 may be located on axis 236, and its z-axis may be aligned with axis 236. In some examples, machine base / arm gantry coordinate transform 335 may be used to map positions and / or orientations between machine base coordinate frame 320 and arm gantry coordinate frame 330. In some examples, one or more kinematic models of the links and joints in the computer-assisted apparatus between the machine base and an arm gantry, such as setup structure 220, along with past and / or current joint sensor measurements, may be used to determine machine base / arm gantry coordinate transform 335. In some examples consistent with the embodiment of FIG. 2, the machine base / arm gantry coordinate transform 335 may model the combined effects of a two-piece column, shoulder joint, two-piece boom, and wrist joint in a computer-assisted machine.

[0037] The kinematic model 300 further includes a set of coordinate frames and transformations associated with each of the articulated arms in the computer-aided device. As shown in Figure 3, the kinematic model 300 includes coordinate frames and transformations for three articulated arms, although one skilled in the art will understand that another computer-aided device may include fewer and / or more articulated arms. Consistent with the link and joint configuration in the computer-aided device 210 of Figure 2, each of the articulated arms may be modeled using a manipulator mount coordinate frame, a remote center coordinate frame, and a tool / camera coordinate frame, depending on the type of instrument mounted at the distal end of the articulated arm.

[0038] In kinematic model 300, the kinematic relationships of a first one of the articulated arms are captured using manipulator mount coordinate frame 341, remote center coordinate frame 342, tool coordinate frame 343, gantry-to-mount transform 344, mount-to-remote center transform 345, and remote center-to-tool transform 346. Manipulator mount coordinate frame 341 represents a model suitable for representing positions and / or orientations associated with a manipulator, such as manipulator 260. Manipulator mount coordinate frame 341 is typically associated with a manipulator mount, such as manipulator mount 262, of the corresponding articulated arm. And, gantry-to-mount transform 344 is based on one or more kinematic models of links and joints in a computer-aided system between the corresponding manipulator mount, such as corresponding setup joint 240, and the arm gantry, as well as past and / or current measurements of joint sensors at the corresponding setup joint 240.

[0039] Remote center coordinate frame 342 is typically associated with a remote center of a manipulator mounted on an articulated arm, such as corresponding remote center 274 of corresponding manipulator 260. Mount-to-remote center transform 345 is then based on one or more kinematic models of links and joints in a computer-aided system between the corresponding remote center and the corresponding manipulator mount, such as corresponding joint 264, corresponding link 266, and corresponding carriage 268 in corresponding manipulator 260, as well as past and / or current joint sensor measurements at the corresponding joint 264. If the corresponding remote center is maintained in a fixed position relative to the corresponding manipulator mount, as in the embodiment of FIG. 2, mount-to-remote center transform 345 may include an essentially static translational component and a dynamic rotational component.

[0040] The tool coordinate frame 343 is typically associated with a tool and / or tool tip in an articulated arm-mounted instrument, such as the corresponding tool 270 and / or tool tip 276. The remote center / tool ​​transform 346 is then based on past and / or current joint sensor measurements as well as one or more kinematic models of the links and joints in a computer-aided system that move and / or orient the corresponding tool and corresponding remote center. In some examples, the remote center / tool ​​transform 346 describes the direction in which a shaft, such as the corresponding shaft 272, passes through the remote center and the distance the shaft is advanced and / or retracted relative to the remote center. In some examples, the remote center / tool ​​transform 346 may be constrained to reflect that the insertion axis of the tool's shaft passes through the remote center and describe the rotation of the shaft and tool tip about an axis defined by the shaft.

[0041] In kinematic model 300, the kinematic relationships of the second one of the articulated arms are captured using manipulator mount coordinate frame 351, remote center coordinate frame 352, tool coordinate frame 353, gantry-to-mount transform 354, mount-to-remote center transform 355, and remote center-to-tool transform 356. Manipulator mount coordinate frame 351 represents a model suitable for representing positions and / or orientations associated with a manipulator, such as manipulator 260. Manipulator mount coordinate frame 351 is typically associated with a manipulator mount, such as manipulator mount 262, of the corresponding articulated arm. And, gantry-to-mount transform 354 is based on one or more kinematic models of links and joints in a computer-aided system between the corresponding manipulator mount, such as corresponding setup joint 240, and the arm gantry, as well as past and / or current measurements of joint sensors at the corresponding setup joint 240.

[0042] Remote center coordinate frame 352 is typically associated with a remote center of a manipulator mounted on an articulated arm, such as corresponding remote center 274 of corresponding manipulator 260. Mount-to-remote center transform 355 is then based on one or more kinematic models of links and joints in a computer-aided system between the corresponding remote center and the corresponding manipulator mount, such as corresponding joint 264, corresponding link 266, and corresponding carriage 268 of corresponding manipulator 260, as well as past and / or current joint sensor measurements at the corresponding joint 264. If the corresponding remote center is maintained in a fixed position relative to the corresponding manipulator mount, as in the embodiment of FIG. 2, mount-to-remote center transform 355 may include an essentially static translational component and a dynamic rotational component.

[0043] Tool coordinate frame 353 is typically associated with a tool and / or tool tip in an articulated arm-mounted instrument, such as corresponding tool 270 and / or tool tip 276. Remote center / tool ​​transform 356 is then based on past and / or current joint sensor measurements as well as one or more kinematic models of the links and joints in a computer-aided system that move and / or orient the corresponding tool and corresponding remote center. In some examples, remote center / tool ​​transform 356 describes the direction in which a shaft, such as corresponding shaft 272, passes through the remote center and the distance the shaft is advanced and / or retracted relative to the remote center. In some examples, remote center / tool ​​transform 356 may be constrained to reflect that the insertion axis of the tool's shaft passes through the remote center and may describe the rotation of the shaft and tool tip about the insertion axis defined by the shaft.

[0044] In kinematic model 300, the kinematic relationships of the third one of the articulated arms are captured using manipulator mount coordinate frame 361, remote center coordinate frame 362, camera coordinate frame 363, gantry-to-mount transform 364, mount-to-remote center transform 365, and remote center-to-camera transform 366. Manipulator mount coordinate frame 361 represents a model suitable for representing positions and / or orientations associated with a manipulator, such as manipulator 260. Manipulator mount coordinate frame 361 is typically associated with a manipulator mount, such as manipulator mount 262, of the corresponding articulated arm. And, gantry-to-mount transform 364 is based on one or more kinematic models of links and joints in a computer-aided system between the corresponding manipulator mount, such as corresponding setup joint 240, and the arm gantry, as well as past and / or current measurements of joint sensors at the corresponding setup joint 240.

[0045] Remote center coordinate frame 362 is typically associated with a remote center of a manipulator mounted on an articulated arm, such as corresponding remote center 274 of corresponding manipulator 260. Mount-to-remote center transform 365 is then based on one or more kinematic models of links and joints in a computer-aided system between the corresponding remote center and the corresponding manipulator mount, such as corresponding joint 264, corresponding link 266, and corresponding carriage 268 in corresponding manipulator 260, as well as past and / or current joint sensor measurements at the corresponding joint 264. If the corresponding remote center is maintained in a fixed position relative to the corresponding manipulator mount, as in the embodiment of FIG. 2, mount-to-remote center transform 365 may include an essentially static translational component and a dynamic rotational component.

[0046] The camera coordinate frame 363 is typically associated with an imaging device, such as an endoscope mounted on an articulated arm. The remote center / camera transform 366 is then based on one or more kinematic models of the links and joints in a computer-aided system that move and / or orient the imaging device and corresponding remote center, as well as past and / or current joint sensor measurements. In some examples, the remote center / camera transform 366 describes the direction in which a corresponding shaft, such as shaft 272, passes through the remote center and the distance the shaft is advanced and / or retracted relative to the remote center. In some examples, the remote center / camera transform 366 may be constrained to reflect that the insertion axis of the imaging device's shaft passes through the remote center and describe the rotation of the imaging device about the axis defined by that shaft.

[0047] As discussed above and further emphasized herein, FIG. 3 is merely an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, alternatives, and modifications. According to some embodiments, the alignment between the surgical table and the computer-assisted device may be determined between the tabletop coordinate frame 310 and the device base coordinate frame 320 using a different alignment transformation. If a different alignment transformation is used, the alignment transformation 325 may be determined by combining the different alignment transformation with the inverse / opposite of the table base / tabletop transformation 315. According to some embodiments, the coordinate frame and / or transformation used to model the computer-assisted device may be prepared differently depending on the unique configuration of links and joints in the computer-assisted device, its articulated arm, its end effector, its manipulator, and / or its instrument. According to some embodiments, the coordinate frame and transformation of the kinematic model 300 may be used to model the coordinate frame and transformation associated with one or more virtual tools and / or virtual cameras. In some examples, the virtual tool and / or virtual camera may be associated with pre-stored and / or pre-latched tool positions, projections of the tool and / or camera with motion, reference points defined by a physician and / or other interested party, and / or the like.

[0048] As previously mentioned, when a computer-assisted system, such as computer-assisted systems 110 and / or 210, is activated, it may be desirable to allow continued control of the tool and / or tool tip while allowing movement of a surgical table, such as surgical table 170 and / or 280. In some instances, this may allow for a faster procedure, as the surgical table movement may occur without the need to disengage the manipulator from the patient. In some instances, this may allow a physician and / or other medical personnel to monitor organ movement while the surgical table movement is occurring to obtain a more appropriate position for the surgical table. In some instances, this may even allow for active continuation of the surgical procedure during the surgical table movement.

[0049] When a computer-assisted system such as computer-assisted systems 110 and / or 200 is operated, one of the goals is to maintain the proper orientation of the tool and / or tool tip, respectively. In one mode of operation of the computer-assisted system, the joints of the operating table and the proximal joints of the manipulator are locked and / or held in the proper position through the use of servo controls and / or brakes so that joint movement is limited and / or completely prohibited. This allows the joints in the manipulator to control the orientation of the tool to perform the desired procedure without interference from the motion of other joints. In some examples, the manipulator may be docked to the patient during the procedure. In some examples, the orientation of the tool and / or tool tip may be controlled via remote operation by a physician at an operator console. However, it may be desirable to support other modes of operation of the computer-assisted system that allow movement of the articulated arm while the tool remains docked to the patient. These other modes of operation may introduce risks that are not present in modes of operation when the tool is not docked to the patient. In some examples, these risks may include patient injury if the tool and / or tool tip is allowed to move relative to the patient, disruption of the sterile field, collision between articulated arms, and / or the like.

[0050] In the general case, these other aspects of operation may be characterized by the goal of maintaining the orientation of a tool attached to a docked manipulator relative to a patient when one or more joints proximal to the tool are subjected to a disturbance that results in a change in the position and / or orientation (i.e., movement) of the one or more joints. Because a disturbance at one or more first joints proximal to the tool, i.e., disturbed joints, results in a change in the orientation of the tool and its tool tip, it may be desirable to introduce movement of one or more second joints, i.e., compensating joints, that offset the change in tool orientation caused by movement of the disturbed joints. The determination of the magnitude of the disturbance and the amount of compensation depends on the type and nature of the disturbance, such as whether the disturbance is associated with movement of the operating table or patient, or whether the disturbance is limited to the articulated arm used to manipulate the tool.

[0051] Disturbances associated with these other aspects of motion that maintain tool pose can be divided into two broad categories. In the first category, the patient to which the manipulator is docked is not moving, so that the pose of the tool and / or tool tip is monitored and maintained in any appropriate world coordinate frame. The first category can include disturbances associated with controlled movement of the articulated arm. In some examples, that controlled movement of the articulated arm can include movement of one or more joints used to set up the articulated arm and / or manipulator before performing a procedure. One example of this includes movement of one or more joints in a setup configuration of a computer-assisted device consistent with the embodiment of FIG. 2, in which the orientation platform 227 is translated and adjusted to allow the setup joint 240 to be moved to provide a good range of motion for the manipulator 260 during a procedure. Examples of this type of movement are described in more detail in U.S. Provisional Application No. 62 / 024,887, filed July 15, 2014, entitled "System and Method for Aligning with a Reference Target," and U.S. Provisional Application No. 61 / 954,261, filed March 17, 2014, entitled "System and Method for Aligning with a Reference Target," both of which are incorporated herein by reference. Another example of this includes movement of one or more joints to provide collision prevention with another articulated arm and / or a known obstacle in the vicinity of the articulated arm. The first category may also include disturbances associated with releasing brakes and / or locks on other joints before initiating other movements. In some examples, external forces and / or torques on the shaft of the tool, such as those due to forces and torques applied to the remote center of the manipulator by the patient's body wall, may result in undesired movement of the tool and / or tool tip when the brakes and / or locks are released and the force and / or torque is absorbed by the released joint.The first category may further include disturbances caused by operation of the articulated arm in a clutched or floating state, such as may occur during manual repositioning of the articulated arm by an operator and / or due to a collision between the articulated arm and an obstacle. Examples of this type of movement are described in more detail in U.S. Provisional Application No. 61 / 954,120, filed March 17, 2014, entitled "System and Method for Breakaway Clutching in an Articulated Arm," which is incorporated herein by reference.

[0052] In the second category, the patient to which the manipulator is docked is moving, allowing the pose of the tool and / or tool tip to be monitored in a local coordinate frame. This category may include disturbances caused by movement of the articulated structure in the surgical table (i.e., table motion) or by allowing movement of the patient relative to the surgical table. In the second category, it is generally desirable to move the articulated arm and tool with the patient so that the pose of the tool relative to the patient does not change. In some instances, this may be achieved by utilizing port dragging, which may involve releasing and / or unlocking one or more joints in the articulated arm and allowing the patient's body wall at the port to pull on the remote center and tool as the patient moves. In some instances, as the remote center moves, the orientation of the tool relative to the remote center begins to change, resulting in a change in the pose of the tool relative to the patient.

[0053] 4 is a simplified diagram of a method 400 for maintaining tool attitude during movement of one or more joints proximal to the tool, according to some embodiments. One or more processes 410-460 in method 400 may be implemented, at least in part, in the form of executable code stored on a non-transitory, tangible, machine-readable medium that, when executed by one or more processors (e.g., processor 140 in control unit 130), can cause the one or more processors to perform one or more processes 410-460. In some embodiments, method 400 may be used to offset changes in tool attitude due to movement at one or more disturbance joints by introducing compensating movement at one or more compensating joints. In some examples, method 400 may be used when movement at a disturbance joint is due to controlled movement, clutch operation, brake or lock release, patient movement, and / or the like. 2 , the one or more disturbance joints and / or the one or more compensation joints may include any of the joints in setup structure 220, setup joint 240, and / or any joint in manipulator 260 proximal to the tool. In some examples, use of method 400 may be limited to operations when an instrument, cannula, and / or the like is coupled to the distal end of a corresponding articulated arm, end effector, and / or manipulator such that a telecenter is defined for the articulated arm, end effector, and / or manipulator. In some examples, method 400 may include maintaining the tool attitude at least in part using resistance from a patient port and / or by an operator of a computer-assisted device.

[0054] According to some embodiments, method 400 may facilitate one or more useful improvements over methods that do not maintain tool orientation during movement of one or more disturbance joints. In some examples, method 400 may reduce the likelihood of collision between the tool and / or other links and joints in the articulated arm on which the tool is mounted and other articulated arms, end effectors, and / or tools whose positions and orientations are known to a computer-assisted device. In some examples, method 400 may reduce movement of one or more sterile drapes attached to the articulated arm on which the tool is mounted to better prevent the one or more sterile drapes from being pushed and / or moved into contact with one or more non-sterile obstacles, such as one or more exposed areas of the operator (e.g., the operator's face), resulting in a disruption of the sterile field. In some examples, method 400 may reduce the likelihood of moving and / or pushing the tool and / or tool tip within the patient's body to reduce the likelihood of injury to the patient by the tool and / or tool tip.

[0055] In process 410, a coordinate frame of reference for the tool is determined. The determination of the coordinate frame of reference for the tool depends on the mode of operation. In some examples, the determination of the reference frame may further depend on the type of disturbance expected for the articulated arm to which the tool is mounted and / or one or more joints (i.e., disturbance joints) that may move as a result of the disturbance. If the source of the disturbance is associated with controlled movement of the articulated arm, manual repositioning of the articulated arm, movement caused by a collision of the articulated arm, and / or the like, where the patient is not moving and the remote center for the manipulator attached to the articulated arm is not subject to translational motion, any coordinate frame that is fixed with respect to the world coordinate frame may be used. Consistent with the embodiments of FIGS. 2 and 3 , the machine base coordinate frame 320, the arm gantry coordinate frame 330, and / or any of the remote center coordinate frames 342, 352, and 362 may be used as the coordinate frame of reference. If the source of the disturbance is associated with the release of brakes and / or locks on one or more disturbance joints that cause the remote center to move, any coordinate frame that is fixed with respect to the world coordinate frame may be used. Consistent with the embodiments of Figures 2 and 3, either the machine base coordinate frame 320 and / or the arm gantry coordinate frame 330 may be used as the reference coordinate frame, rather than one of the remote center coordinate frames 342, 352, and 362. If the source of the disturbance is associated with patient movement and / or movement of the operating table, a local coordinate frame that moves with the patient may be used. Consistent with the embodiments of Figures 2 and 3, either the remote center coordinate frame 342, 352, or 362 associated with the articulated arm and / or the tabletop coordinate frame 310 may be used as the reference coordinate frame.

[0056] In process 420, a reference transformation of the tool in the reference coordinate frame is determined. Prior to the initiation of movement of one or more disturbance joints, one or more kinematic models of the computer-aided device are used to determine a reference transformation for the tool in the reference coordinate frame determined during process 410. In some examples, the one or more kinematic models may include one or more kinematic models for links and joints in an articulated arm, manipulator, tool, setup structure, and / or the like. Using the embodiment of FIGS. 2 and 3 as an example, if the reference coordinate frame is the remote center coordinate frame 342, 352, or 362, then the remote center-to-tool transformation 346, 356, or remote center-to-camera transformation 366, respectively, latched or recorded before the disturbance began becomes the reference transformation of the tool. If the reference coordinate frame is the arm gantry coordinate frame 330, the composition of the corresponding gantry-to-mount transformation 344, 354, or 364, the corresponding mount-to-remote center transformation 345, 355, or 365, and the corresponding remote center-to-tool transformation 346, 356, or the corresponding remote center-to-camera transformation 366, latched or recorded before the disturbance began, becomes the reference transformation for the tool. In some examples, if the tool is not mounted on an articulated arm, end effector, and / or manipulator, the cannula and / or virtual tool may be used to determine the reference transformation based on the insertion direction of the cannula and / or the virtual shaft of the instrument.

[0057] In process 430, the actual translation of the tool in the reference coordinate frame is determined. When a disturbance causes one or more disturbance joints to begin moving, the tool's pose begins to change because the tool is distal to the one or more disturbance joints. The movement of the one or more disturbance joints is monitored, and the same kinematic model(s) used during process 420 are again applied using the current joint positions and / or orientations to determine the actual translation of the tool in the reference coordinate frame. The actual translation describes how the movement of the one or more disturbance joints tends to move the tool away from its intended pose.

[0058] In process 440, the difference between the actual transformation and the reference transformation is determined. The difference between the actual transformation and the reference transformation represents the error introduced into the tool pose by the disturbance. If the error in the tool pose is not offset by movement using one or more compensating joints in the articulated arm, the tool pose will change undesirably. In some examples, the difference may be determined by subtracting corresponding matrix and / or vector representations of the actual transformation and the reference transformation. In some examples, the difference may be expressed as an error transformation determined by combining the inverse / reverse transformation of the reference transformation with the actual transformation.

[0059] In process 450, compensating joint changes are determined based on the difference. The difference between the actual transformation and the reference transformation determined during process 440 is used to determine changes in one or more compensating joints. The difference between the actual transformation and the reference transformation is mapped from the reference coordinate system of the actual transformation and the reference transformation to one or more local coordinate systems associated with each of the compensating joints. In effect, this converts the error in the tool pose from the reference coordinate system to an error in pose relative to the compensating joint. In some examples, one or more kinematic models may be used to convert the difference to the local coordinate system. In some examples, the compensating joint may include any of the joints in the articulated arm and / or manipulator that is not one of the disturbance joints. Once the relative errors in pose are determined, they may be used to determine motions for each of the compensating joints. In some examples, an inverse Jacobian may be used to map the relative errors to compensating motions of the compensating joints. In some examples, the motions at the compensating joints may be applied as joint velocities applied to the compensating joints.

[0060] In process 460, the compensating joint is actuated. One or more commands are sent to one or more actuators in the compensating joint based on the movement of the compensating joint determined during process 450. The commands sent to the compensating joint correct for errors in the tool attitude caused by the movement of one or more disturbance joints so that the tool attitude in the reference coordinate system is maintained with minimal error. As long as the one or more compensating joints continue to perform corrective changes to the tool attitude, processes 430-460 are repeated to offset any errors introduced into the tool attitude.

[0061] According to some embodiments, process 460 may be subject to practical limitations. In some examples, the ability of one or more compensating joints to offset errors in tool attitude may be limited by the Range of Motion (ROM) limits of one or more compensating joints. In some examples, method 400 and / or process 460 may be stopped when a ROM limit for one or more compensating joints is reached and / or is about to be reached, and the error may be indicated to the operator using one or more visual and / or audible error cues. In some examples, rather than stopping operation of method 400 and / or process 460, process 460 may operate in a variant that partially offsets errors in tool attitude to minimize controllable errors while providing feedback to the operator that not all of the motion caused by the disturbance has been offset. In some examples, the feedback may include one or more visual and / or audible cues indicating that compensation is limited and / or the application of resistance to one or more compensating joints. In some examples, the resistance may include partially applying one or more brakes associated with one or more compensating joints and / or applying a motion resistance voltage and / or signal to one or more actuators associated with one or more compensating joints.

[0062] As noted above and further emphasized herein, FIG. 4 is merely an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, alternatives, and modifications. According to some embodiments, method 400 may be applied independently to each of the tools being manipulated by the computer-assisted device. In some examples, the tools may include any of the tools docked to the patient. In some examples, a compensation joint may be located distal to the arm gantry, such as the orientation platform 227 in the computer-assisted device, so that compensation for maintaining the orientation of each of the tools may be applied separately to each of the tools.

[0063] According to some embodiments, the disturbance joint and the compensation joint may not include every joint in the articulated arm and / or manipulator. In some examples, the compensation joint may include only the roll joint, pitch joint, and yaw joint of the manipulator. In some examples, other joints in the articulated arm and / or manipulator may be locked to prevent their relative movement during method 400. In some examples, one or more non-actuated joints in the articulated arm and / or manipulator may be unlocked and / or placed in a clutched and / or floating state during method 400 so that errors in the tool pose are reduced, at least in part, by changes in the unlocked joints. In some examples, changes in the unlocked joints may reduce the amount the compensation joint must be driven. In some examples, the tool pose may be maintained, at least in part, using resistance from the patient port and / or by an operator of a computer-assisted device.

[0064] According to some embodiments, one or more of processes 430-460 may be performed simultaneously. According to some embodiments, additional conditions may result in early termination of method 400, such as by returning control of the computer-assisted device to the operator and / or by ceasing operation of the computer-assisted device. In some examples, the additional conditions may include an inability to complete a compensation operation, manual operator intervention and / or override using one or more controls on the operator workstation and / or articulated arm, detection of an operator disengagement from the operator workstation due to one or more safety interlocks, a position tracking error in the computer-assisted device, a system failure, and / or the like. In some examples, a desired movement may not be possible due to detection of an impending collision between links and / or joints in the computer-assisted device, limitations on the range of motion of one or more joints in the computer-assisted device, an inability to maintain tool orientation due to patient movement, and / or the like. In some examples, early termination of method 400 may result in an error notification being sent to the operator. In some examples, the error notification may include any visible and / or audible indication, such as a text message, a flashing light, an audible sound, a spoken phrase, and / or the like.

[0065] Some examples of control units, such as control unit 130, may include non-transitory tangible machine-readable media containing executable code that, when executed by one or more processors (e.g., processor 140), causes the one or more processors to perform the processes of method 400. Some common forms of machine-readable media that may contain the processes of method 400 may include, for example, a floppy disk, a flexible disk, a hard disk, magnetic tape, any other magnetic medium, a CD-ROM, any other optical medium, a punch card, paper tape, any other physical medium with a pattern of holes, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge, and / or any other medium configured to be read by a processor or computer.

[0066] While exemplary embodiments have been shown and described, a wide range of modifications, variations, and substitutions are contemplated in the foregoing disclosure and in some examples, and some features of the embodiments may be employed without the corresponding use of other features. Those skilled in the art will recognize many variations, alternatives, and modifications. Thus, the scope of the present invention is to be limited only by the following claims, which claims are appropriate to be construed broadly and in a manner consistent with the scope of the embodiments disclosed herein.

Claims

1. 1. A computer-aided apparatus, comprising: an articulated structure including a plurality of joints between a proximal end of the articulated structure and a distal end of the articulated structure, the articulated structure being configured to support an instrument; a control unit coupled to the articulated structure; The control unit determining a change in position and orientation of the instrument due to movement of a first joint of the plurality of joints; In response to determining that (i) the movement of the first joint has changed the position and the orientation of the instrument, and (ii) that a second joint of the plurality of joints is at or about to reach a limit of its range of motion, actuating one or more of the plurality of joints to partially compensate for the change in the position or orientation of the instrument, but not to eliminate all of the change in the position and orientation of the instrument due to the movement of the first joint; and providing feedback to an operator that not all of the changes in the position and orientation of the instrument have been eliminated; Computer-aided devices.

2. In response to determining that the second joint is at a limit of the range of motion or is about to reach a limit of the range of motion, the control unit: partially braking the second joint; or The computer-aided apparatus of claim 1 , further configured to: apply a motion resistance signal to an actuator associated with the second joint.

3. 3. The computer-assisted device of claim 1, wherein the control unit is further configured to unlock an inactive third joint of the plurality of joints to allow movement of the unlocked third joint, the movement of the unlocked third joint reducing the amount that the second joint needs to be actuated to minimize changes in the position and orientation of the instrument.

4. 3. The computer-aided apparatus of claim 1, wherein the control unit is further configured to lock a third joint of the plurality of joints to prevent relative movement of the third joint while driving the one or more joints.

5. To determine the change in the position and orientation of the instrument, the control unit determining a coordinate frame of reference for the instrument; determining a reference transformation of the instrument in the reference coordinate frame prior to the movement of the first joint; determining an actual translation of the instrument in the reference coordinate frame while moving the first joint; 5. A computer-aided apparatus according to claim 1, configured to determine the change in the position and orientation of the instrument based on a difference between the actual transformation of the instrument and the reference transformation of the instrument.

6. The computer-aided device of claim 5 , wherein the control unit determines the reference coordinate frame of the instrument based on a cause of the movement of the first joint based on an operating mode of the computer-aided device.

7. 7. The computer-assisted device of claim 6, wherein the reference coordinate frame is associated with a remote center of the articulated structure when the movement of the first joint is due to movement of a patient coupled to the articulated structure, and the movement of the patient is due to movement of a table supporting the patient.

8. 7. The computer-aided device of claim 6, wherein the reference coordinate frame is fixed relative to a world coordinate frame associated with the computer-aided device when the movement of the first joint is due to controlled movement of the articulated structure, such as due to manual repositioning of the articulated structure, due to movement caused by a collision, or due to release of a brake or lock on the first joint.

9. 9. The computer-aided device of claim 5, wherein the control unit determines the reference transformation and the actual transformation based on positions of joints of the plurality of joints and one or more kinematic models of the computer-aided device.

10. 10. A computer-aided apparatus according to claim 5, wherein, to determine the difference between the actual transform and the reference transform, the control unit is configured to construct an inverse transform of the reference transform using the actual transform.

11. 1. A non-transitory machine-readable medium comprising a plurality of machine-readable instructions, the machine-readable instructions, when executed by one or more processors associated with a computer-aided device, causing the one or more processors to: determining a change in position and orientation of an instrument supported by an articulated structure of the computer-assisted device, the change being due to movement of a first joint of a plurality of joints of the articulated structure; In response to determining that (i) the movement of the first joint has changed the position and the orientation of the instrument, and (ii) that a second joint of the plurality of joints is at a limit of range of motion or is about to reach the limit of range of motion, using one or more actuators to actuate one or more of the joints to partially compensate for, but not eliminate, the change in the position or orientation of the instrument due to the movement of the first joint; and providing feedback to an operator that not all of the changes in the position and orientation of the instrument have been eliminated; Non-transitory machine-readable media.

12. In response to determining that the second joint is at or about to reach a limit of its range of motion, the step partially braking the second joint; or The non-transitory machine-readable medium of claim 11 , further comprising applying a motion resistance signal to an actuator associated with the second joint.

13. 13. The non-transitory machine-readable medium of claim 11 or 12, wherein the step further comprises unlocking a third joint of the plurality of joints to allow movement of the unlocked third joint, wherein movement of the unlocked third joint reduces the amount the second joint needs to be actuated to minimize the change in the position and orientation of the instrument.

14. 13. The non-transitory machine-readable medium of claim 11 or 12, wherein the step further comprises locking a third joint of the plurality of joints to prevent relative movement of the third joint while driving the one or more joints.

15. Determining the change in the position and orientation of the instrument comprises: determining a coordinate frame of reference for the instrument; determining a reference transformation of the instrument in the reference coordinate frame prior to the movement of the first joint; determining an actual translation of the instrument in the reference coordinate frame while moving the first joint; 15. The non-transitory machine-readable medium of claim 11, comprising determining the change in the position and orientation of the instrument based on a difference between the actual transformation of the instrument and the reference transformation of the instrument.

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