Detecting cable break on a cable-driven tool

Abstract

A surgical robotic tool for use with a surgical robotic system is provided that can include cables that effect movement of the surgical robotic tool. Arrest of any of these cables can be detected by checking a plurality of conditions. A method is provided that can: a) compare a tension error to a first threshold, b) compare a rate of change of a sensed tension of the cable to a second threshold, and c) compare a rate of change of a cable extension error to a third threshold. If all thresholds are exceeded, the method can disable the corresponding actuator.

Description

Technical Field

[0001] This disclosure relates generally to the field of surgical robotics, and more specifically to detecting cable breaks in cable-driven tools used in conjunction with surgical robotic systems. Background Technology

[0002] Minimally invasive surgery (MIS), such as laparoscopic surgery, involves techniques designed to minimize tissue damage during surgical procedures. For example, a laparoscopic procedure typically involves making multiple small incisions inside the patient (e.g., in the abdomen) and introducing one or more instruments and at least one endoscopic camera through these incisions. The surgical procedure is then performed using the introduced instruments, with visualization aids provided by the camera.

[0003] Generally speaking, medical instrumentation (MIS) offers multiple beneficial effects, such as reducing patient scarring, alleviating patient pain, shortening patient recovery time, and reducing medical costs associated with patient recovery. In some implementations, MIS can be performed using a surgical robotic system, which includes one or more robotic arms for manipulating surgical instruments based on commands from an operator.

[0004] In surgical robotic systems, surgical tools can be attached to the surgical robotic arm. These tools can be used to access, view, or manipulate the patient's internal anatomy. The surgical tools can be cable-driven for movement. Summary of the Invention

[0005] Typically, cable faults in mobile surgical robotic tools can be detected by checking multiple conditions. Systems or methods can check tension, the rate of change of tension, and the rate of change of cable extension error to monitor any cable. When all conditions indicate a fault (e.g., exceeding a corresponding threshold), the system can take remedial measures. For example, actuators coupled to the cable can be disabled, thereby reducing the risk of further movement if the cable is already damaged. Other aspects are described. Attached Figure Description

[0006] Figure 1 This is a drawn view of an exemplary surgical robotic system in an operating room.

[0007] Figure 2 Examples of surgical robotic arms and tools according to some implementation schemes are shown.

[0008] Figure 3 Examples of tools based on some implementation schemes are shown.

[0009] Figure 4 A method for detecting cable faults according to some implementation schemes is shown.

[0010] Figure 5A method for detecting cable faults according to some implementation schemes is shown.

[0011] Figures 6A to 6D The diagram shows the force on the cable during a cable fault.

[0012] Figures 7A to 7D The cable extension error during a cable fault is shown.

[0013] Figures 8A to 8D The rate of change of cable tension during a cable fault is shown. Detailed Implementation

[0014] Non-limiting examples of various aspects and variations of the invention are described herein and illustrated in the accompanying drawings.

[0015] See Figure 1 This is a drawing view of an exemplary surgical robotic system 1 in a surgical setting. The robotic system 1 includes a user console 2, a control tower 3, and one or more surgical robotic arms 4 at a surgical robotic platform 5 (e.g., a table, bed, etc.). The system 1 can be combined with any number of devices, tools, or accessories for performing surgery on a patient 6. For example, the system 1 may include one or more surgical tools 7 for performing surgery. The surgical tool 7 may be an end effector attached to the distal end of the surgical arm 4 for performing surgical procedures.

[0016] Each surgical tool 7 can be manually manipulated, robotically manipulated, or both during surgery. For example, a surgical tool 7 can be a tool for accessing, viewing, or manipulating the internal anatomy of a patient 6. In one embodiment, the surgical tool 7 is a gripper capable of grasping the patient's tissues. The surgical tool 7 can be manually controlled by a bedside operator 8; or it can be robotically controlled via actuated movement of its attached surgical robotic arm 4. The robotic arm 4 is shown as a tabletop system, but in other configurations, the arm 4 can be mounted on a trolley, ceiling, or sidewall, or in another suitable structural support.

[0017] Generally, a remote operator 9 (such as a surgeon or other operator) can use the user console 2 to remotely manipulate the arm 4 or attached surgical instruments 7, for example, through remote operation. The user console 2 may be located in the same operating room as the rest of the system 1, such as... Figure 1As shown. However, in other environments, the user console 2 may be located in an adjacent or nearby room, or it may be located in a remote location, such as in different buildings, cities, or countries. The user console 2 may include a seat 10, foot controls 13, one or more handheld user input devices (UIDs) 14, and at least one user display 15 configured to display a view, for example, of a surgical site within a patient 6. In the exemplary user console 2, a remote operator 9 sits in the seat 10 and views the user display 15 while manipulating the foot controls 13 and the handheld UID 14 to remotely control the arm 4 and the surgical instrument 7 (which is mounted on the distal end of the arm 4).

[0018] In some variations, the bedside operator 8 can also operate the system 1 in a "bedside" mode, where the bedside operator 8 (the user) is now positioned to one side of the patient 6 and simultaneously manipulates robot-driven tools (end-effectors attached to arm 4), for example, holding a handheld UID 14 and a manual laparoscopic tool with one hand. For instance, the bedside operator's left hand can manipulate the handheld UID to control the robotic components, while the bedside operator's right hand can manipulate the manual laparoscopic tool. Therefore, in these variations, the bedside operator 8 can perform both robot-assisted minimally invasive surgery and manual laparoscopic surgery on the patient 6.

[0019] During the exemplary procedure (surgical operation), patient 6 is prepared for surgery and aseptically covered with a sterile drape to administer anesthesia. Initial access to the surgical site can be manually performed (to facilitate access to the surgical site) while the arms of robotic system 1 are in a retracted or withdrawn configuration. Once access is complete, initial positioning or preparation of robotic system 1, including its arms 4, can be performed. The surgery then continues, with remote operator 9 at user console 2 using foot controls 13 and UID 14 to manipulate various end effectors and, possibly, imaging systems to perform the surgery. Artificial assistance can also be provided at the operating table or surgical table by a bedside person (e.g., bedside operator 8) wearing sterile surgical gowns, who can perform tasks on one or more arms of robotic arms 4, such as tissue retraction, manual repositioning, and tool changes. Non-sterilized personnel may also be present to assist remote operator 9 at user console 2. When a procedure or surgical operation is completed, System 1 and User Console 2 can be configured or set to a certain state to facilitate the completion of postoperative procedures, such as cleaning or disinfection, and the input or printing of health records via User Console 2.

[0020] In one embodiment, the remote operator 9 holds and moves UID 14 to provide input commands, thereby moving the robotic arm actuator 17 in the robotic system 1. UID 14 may be communicatively coupled to the rest of the robotic system 1, for example, via a console computer system 16. UID 14 may generate spatial state signals corresponding to the movement of UID 14, such as the position and orientation of the UID's handheld housing, and the spatial state signals may be input signals for controlling the movement of the robotic arm actuator 17. The robotic system 1 may use control signals derived from the spatial state signals to control the proportional movement of the actuator 17. In one embodiment, a console processor of the console computer system 16 receives the spatial state signals and generates corresponding control signals. Based on these control signals controlling how the actuator 17 is energized to move a segment or connector of the arm 4, the movement of a corresponding surgical tool attached to the arm may simulate the movement of UID 14. Similarly, the interaction between the remote operator 9 and UID 14 may generate, for example, a clamping control signal that causes the jaws of the gripper of the surgical tool 7 to close and clamp the tissue of the patient 6.

[0021] The surgical robot system 1 may include a plurality of UIDs 14, wherein a corresponding control signal is generated for each UID that controls the actuators and surgical instruments (end-effectors) of a respective arm 4. For example, a remote operator 9 may move a first UID 14 to control the movement of an actuator 17 located in the left robotic arm, wherein the actuator responds by moving links, gears, etc. in the arm 4. Similarly, movement of a second UID 14 by the remote operator 9 controls the movement of another actuator 17, which in turn moves other links, gears, etc. of the robot system 1. The robot system 1 may include a right arm 4 fixed to a bed or table on the right side of the patient, and a left arm 4 located on the left side of the patient. The actuators 17 may include one or more motors, which are controlled such that they drive the joints of the arm 4 to rotate, for example, to change the orientation of the endoscope or gripper of the surgical instrument 7 attached to the arm relative to the patient. The movement of a plurality of actuators 17 in the same arm 4 may be controlled by spatial state signals generated from a particular UID 14. The UID 14 may also control the movement of the corresponding surgical instrument gripper. For example, each UID 14 can generate a corresponding clamping signal to control the movement of an actuator (e.g., a linear actuator) that opens or closes the jaws of the gripper at the distal end of the surgical tool 7 to clamp tissue in the patient 6.

[0022] In some respects, communication between platform 5 and user console 2 can be achieved via control tower 3, which translates user commands received from user console 2 (and more specifically from console computer system 16) into robot control commands transmitted to arm 4 on robot platform 5. Control tower 3 can also transmit status and feedback from platform 5 back to user console 2. Communication connections between robot platform 5, user console 2, and control tower 3 can be established via wired or wireless links using any suitable data communication protocol from a variety of data communication protocols. Any wired connection may optionally be embedded in the floor, walls, or ceiling of the operating room. Robot system 1 may provide video output to one or more displays, including displays within the operating room, or remote displays accessible via the Internet or other networks (e.g., robot system 1 may include one or more endoscopic cameras that provide video output or other suitable image data to the displays). Video output or feeds may also be encrypted to ensure privacy, and all or part of the video output may be stored on a server or electronic healthcare record system.

[0023] refer to Figure 2 A surgical robotic arm with an attached surgical tool is shown according to some embodiments. The surgical robotic arm 4 may be attached to the surgical tool 7 at its distal end. An actuator 17 may include an actuator for the surgical robotic arm that achieves movement of the joint of the surgical robotic arm. The actuator 17 also includes a surgical tool actuator, which... Figure 2 As shown in the image.

[0024] The actuator of the surgical tool may be housed in the tool actuator 34. The actuator is controlled by a controller 42. In some embodiments, the controller 42 may be integrated as part of a surgical robot system control tower or console computing system. In other embodiments, the controller may be a standalone controller with one or more processors. The controller may generate commands received by the actuator to achieve movement of the actuator. Each command may specify the amount and direction of movement to coordinate the desired movement of the surgical robot tool.

[0025] Surgical tools may include multiple cables 42. The cables may be housed in a tool shaft 36, which may be an elongated member having one or more channels for receiving the cables. Each cable is coupled to i) a corresponding tool actuator at the proximal end of the tool, and ii) an end effector 40 of the tool at the distal end of the tool, such that the corresponding actuator enables movement of the end effector via the cable.

[0026] For example, the actuator can transmit force in the cable in a coordinated manner to produce pitch or yaw movement at the tool wrist 38, thereby providing angular manipulation of the tool during surgery. The actuator can also cause jaw movement (e.g., opening and closing) of an end effector, which may include a gripper or cutter. Thus, cable-actuated tools can grip or cut within the surgical site at various angles. The number of cables can vary depending on the application. In some embodiments, four or more cables are present. In some embodiments, three cables may be dedicated to tool wrist movement. In some embodiments, one cable may be dedicated to jaw movement, such that when used in combination with a spring, opening and closing jaw movement can be produced.

[0027] The controller may have a condition checker 43 that receives and processes cable information from the tool to detect cable breaks. The cable information is compared to various conditions, and if all conditions are met, the condition checker can determine that the cable has failed. The controller can sense the moment exactly before and / or when the cable breaks and take immediate remedial action to reduce the risk of injury to the patient.

[0028] Figure 3 An actuator in one embodiment is shown. The illustration shows a general representation of the actuator and components. The actuator can represent Figure 1 and Figure 2 One or more actuators are shown. Still referencing... Figure 3 The actuator may include a motor 48 that rotates by an angle θ in the direction and / or amount specified in the controller command.

[0029] The tension of each cable can be sensed by any of the sensors in sensor 50, which may include a tension sensor coupled to the corresponding cable or a torque sensor that measures the torque of the corresponding motor coupled to the cable. The measured torque (rotational force) can be converted into tension (linear force). Each cable may have an initial tension (pretension) at the tool's initial "relaxed" position. In some embodiments, the pretension Tp is 10 N. The tension error can be determined as the difference between the pretension and the currently sensed tension, which can be expressed as ΔT = Tp – Ts. This tension error can represent the tension drop in the cable.

[0030] In some implementations, the pretension can be zero if the tool does not require cable pretension. Therefore, in this case, Δtension can be the sensed tension.

[0031] The controller can determine the measured cable extension q based on the measured cable position x, the sensed cable tension T, and the known cable stiffness constant Ke. In some implementations, the measured cable extension q can be determined by the following equation: q = x – T / Ke.

[0032] The measured cable position x can be based on the actuator position P. A and the radius r of the driving wheel c The radius of the drive wheel is the radius of drive wheel 51. When the drive wheel rotates, the corresponding cable is fixed to and wound around it. The rotation of the drive wheel can be achieved by one or more gears 54, which convert the rotational motion of the motor 48 into the rotational motion of the drive wheel. When the drive wheel rotates, the cable position and cable tension change accordingly, depending on the amount and direction of rotation. In some embodiments, the measured cable position x is determined by the following equation: x = P A* r c .

[0033] Actuator position P A The position P can be determined based on the position P encoded by the position encoder 52, the known gear ratio (Gr) of the actuator, and the offset (e.g., determined through calibration). The position encoder can be a rotary position encoder that monitors the motor shaft position and, for example, encodes the current motor shaft position as a value representing the angular position. In some embodiments, the actuator position P... A It can be determined by the following equation: P A =P / Gr + offset.

[0034] The controller can generate joint commands (Jcmd), such as "close jaws by X degrees" and "roll wrist by X degrees." Joint commands are commands in the "joint space" that can be transformed into physical space using a kinematic model (inverse kinematic matrix B'). The modeled cable extension q... cmd It can be determined by the following equation: q cmd =(B'*Jcmd)*r c The cable extension modeled represents the desired cable extension. It should be understood that cable extension describes the degree of cable stretching, while the measured cable position describes how much displacement the actuator has placed on the cable.

[0035] Robot kinematics relates the dimensions and connectivity of kinematic chains to the position, velocity, and acceleration of each link in a robotic system. This allows for planned and controlled movement of the robot. Kinematic equations can be nonlinear equations that map joint parameters to the configuration of the robot system. Forward kinematics uses the robot's kinematic equations to calculate the position of the end effector from specified values ​​of the joint parameters. The reverse process of calculating the joint parameters that achieve a specified position of the end effector is called inverse kinematics. The robot's dimensions and its kinematic equations define the spatial volume that the robot can achieve, known as its workspace.

[0036] The cable extension error Δq can be determined, which represents the difference between the measured cable extension q and the modeled cable extension q.cmd The difference between them. In some implementations, Δq can be expressed as Δq = abs(qq) cmd ).

[0037] The controller can monitor tension error ΔT, cable extension error Δq, and their derivatives to determine if a cable breakage has occurred. These conditions can be monitored over a time period that can be formed through continuous sampling. If, within a predefined number of samples, these conditions (tension error ΔT, cable extension error Δq, and their derivatives) exceed corresponding thresholds, the controller can flag a cable fault and disable the corresponding actuator. This method... Figure 4 and Figure 5 Further details are provided below.

[0038] exist Figure 4 The diagram illustrates a method for detecting cable braking in a cable-driven surgical robotic tool by performing a series of operations. For each cable, a cable condition check can be performed. The order in which operations 71, 72, and 73 are performed relative to each other can vary. For example, operation 71 does not need to be performed first, and operation 73 does not need to be performed last.

[0039] Operation 71 includes comparing the tension error ΔT relative to a first threshold, where the tension error is the difference between the cable's pre-tension and the sensed tension. As discussed, the sensed tension can be detected by a torque or tension sensor. Assume the initial tension of the cable when it is, for example, at the tool's default position.

[0040] Operation 72 includes comparing the rate of change of the sensed tension in the cable with a second threshold. This rate of change can be the time derivative of the sensed cable tension and can be expressed as dTs / dt, where Ts is the sensed tension of the corresponding cable, as previously described. The second threshold can be expressed as dT / dt, where T is a measure of force, typically in Newtons. When the rate of change of the sensed tension exceeds the second threshold, this indicates a fault in the corresponding cable if other conditions used for fault detection also indicate the same result.

[0041] Operation 73 involves comparing the rate of change of the cable extension error Δq with a third threshold. The cable extension error Δq can be a modeled cable extension q. cmd The difference between the measured cable extension q and the actual cable extension error. In some implementations, the cable extension error is determined based on the absolute value of this difference. This error can be expressed in terms of length (e.g., mm).

[0042] As discussed elsewhere, the measured cable extension q can be determined based on the measured cable position (derived from the actuator position), the sensed tension in the cable, and the cable stiffness. The actuator position can be determined by the actuator's position encoder. The cable stiffness can be a known constant, and the tension can be sensed by a sensor.

[0043] The modeled cable extension is determined based on the joint command and the kinematic transformation that converts the joint command into physically measurable parameters (e.g., rotation or distance). In some embodiments, the joint command is the angular position of the motor. As described, physical parameters can be applied to the drive wheel radius to produce the modeled cable extension.

[0044] The rate of change of the cable extension error can be the time derivative of Δq, which can be expressed as dΔq / dt. Therefore, the third threshold can be expressed as the time derivative of the length, or ds / dt, where s is the length (e.g., in mm). Given the command of the surgical instrument and known kinematics, this indicates the sensed rate of cable stretching relative to the rate at which the cable should be stretched.

[0045] Box 75 illustrates a condition check (for all conditions and corresponding thresholds) that can be repeatedly performed within a time window, which can also be defined as the number of consecutive samples N. For example, such a check for all thresholds can be performed within 30, 35, or 40 consecutive samples. The number of consecutive samples can vary depending on the application, such as based on the tool or the sampling frequency per sample. If all N consecutive samples exceed all thresholds, the system proceeds to operation 76.

[0046] Operation 76 includes marking a cable fault detected at the corresponding cable where all thresholds are exceeded in consecutive samples. Remedial measures are taken, including disabling at least the corresponding actuator. This can be performed immediately to reduce the risk of unwanted movement during surgery and to minimize additional damage to surgical instruments. By requiring all these conditions to fail in consecutive frames, the method reduces false positives that may arise from normal use of surgical instruments. It should be understood that the method is performed within consecutive samples for each cable. Thus, a cable may be marked as faulty within N samples, while another cable is not faulty within the same time period. The corresponding actuator connected to the faulty cable may be disabled. In some embodiments, other actuators (besides those connected to the faulty cable) may be disabled to prevent less predictable movement of the tool at the end effector that may occur due to a broken cable.

[0047] Figure 5 A method 80 for detecting cable breaks is shown, similar to... Figure 4The method shown in the figure. This method includes checking additional conditions at operation 82. At operation 82, the method includes comparing the cable extension error relative to a fourth threshold, which can be determined as the difference between the modeled cable extension and the measured cable extension. Therefore, in addition to its rate of change, the method also considers the difference between the modeled cable extension and the measured cable extension, which can further reduce false positives. When all conditions are indicated as faults, the system can take remedial measures, such as those described in the reference... Figure 4 As mentioned above.

[0048] Figures 6A to 6D The diagram illustrates the force on the cable when it breaks. The red dashed line represents the threshold, and the y-axis represents the cable tension error. These examples illustrate why both tension error and its time derivative are needed to avoid false positives. In some cases, the threshold may be exceeded without a break. In other cases, the rate of change may be high without a cable break.

[0049] Figures 7A to 7D The cable extension error is shown; it is the difference between the modeled cable extension and the measured cable extension in the event of a cable fault. Note that this should be considered when the cable is near an open circuit (e.g., Figure 7A and Figure 7C (As shown) The sharp increase in cable extension error can be limited by the time derivative of the cable extension error.

[0050] Figures 8A to 8D The rate of change of cable tension for different cables during a fault is shown. Here, cable tension is the sensed tension of the cable. As shown in the figure, the rate of change of cable tension with respect to time increases sharply just before the cable breaks.

[0051] For purposes of explanation, the foregoing description uses specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that specific details are not required to practice the invention. The foregoing description of specific embodiments of the invention has been provided for illustrative and descriptive purposes. These are not intended to be exhaustive or to limit the invention to the specific forms disclosed; various modifications and alterations can be made to this disclosure in light of the foregoing teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to best utilize the invention and its various embodiments with various modifications suitable for the contemplated particular uses.

Claims

1. A surgical robotic system, comprising: a surgical robotic tool comprising a plurality of cables, each cable coupled to i) a respective actuator at a proximal end, and ii) an end effector at a distal end of the tool, such that the respective actuator effects movement of the end effector; and one or more processors configured to: for each cable of the plurality of cables, a) compare a tension error to a first threshold, wherein the tension error is a difference between a pre-tension of the cable and a sensed tension, b) compare a rate of change of the sensed tension of the cable to a second threshold, and c) compare a rate of change of a cable extension error to a third threshold, wherein the cable extension error is a difference between a modeled cable extension and a measured cable extension, and for the cable, disable at least the respective actuator when all of the first, second, and third thresholds are exceeded. the measured cable extension is determined based on a sensed cable position, the sensed tension of the cable, and a cable stiffness.

2. The surgical robotic system of claim 1, wherein, the modeled cable extension is determined based at least on a command to the respective actuator and a kinematic translation that translates the command to the modeled cable extension.

3. The surgical robotic system of claim 2, wherein, the one or more processors are further configured to compare the cable extension error to a fourth threshold for each cable, and disable the respective actuator only when all of the first, second, third, and fourth thresholds are exceeded.

4. The surgical robotic system of claim 1, wherein, each cable of the plurality of cables is loaded with the pre-tension of 10 N.

5. The surgical robotic system of claim 1, wherein, the surgical robotic tool comprises at least one of a gripper, a hook, or a cutter.

6. The surgical robotic system of claim 1, wherein, the movement of the surgical robotic tool is a jaw movement of the gripper, the hook, or the cutter of the surgical robotic tool.

7. The surgical robotic system of claim 6, wherein, the movement of the surgical robotic tool is a pitch or yaw movement at a wrist of the surgical robotic tool.

8. The surgical robotic system of claim 1, wherein, the plurality of cables comprises four or more cables.

9. The surgical robotic system of claim 1, wherein, 10. A method performed for detecting a fault of a surgical robotic tool having a plurality of cables, each cable coupled to i) a respective actuator at a proximal end, and ii) an end effector at a distal end of the surgical robotic tool, such that the respective actuator effects movement of the end effector, the method comprising: for each cable of the plurality of cables, a) comparing a tension error to a first threshold, wherein the tension error is a difference between a pre-tension of the cable and a sensed tension, b) comparing a rate of change of the sensed tension of the cable to a second threshold, and c) comparing a rate of change of a cable extension error to a third threshold, wherein the cable extension error is a difference between a modeled cable extension and a measured cable extension; and ​ for the cable, disabling at least the respective actuator when all thresholds including the first threshold, the second threshold, and the third threshold are exceeded within a continuous number of samples; wherein the method is performed prior to a surgical procedure.

11. The method of claim 10, wherein, The measured cable extension is determined based on a sensed cable position, the sensed tension of the cable, and a cable stiffness.

12. The method of claim 11, wherein, The modeled cable extension is determined based at least on an angular position of a motor of the respective actuator and a kinematic transformation that converts the angular position to the modeled cable extension.

13. The method of claim 10, wherein, The method further includes comparing, for each cable, the cable extension error relative to a fourth threshold, and disabling the respective actuator when all of the first threshold, the second threshold, the third threshold, and the fourth threshold are exceeded.

14. The method of claim 10, wherein, The pretension of each cable is 10 N, and the first threshold is 8 N.

15. The method of claim 10, wherein, The surgical robotic tool includes at least one of a gripper, a hook, or a cutter.

16. The method of claim 15, wherein, The movement of the surgical robotic tool is a jaw movement of the gripper, the hook, or the cutter of the surgical robotic tool.

17. The method of claim 10, wherein, The movement of the surgical robotic tool is a pitch or yaw movement at a wrist of the surgical robotic tool.

18. The method of claim 10, wherein, The plurality of cables includes four or more cables.

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