WO2015118466A1

WO2015118466A1 - Robot angular setup using current from joints

Info

Publication number: WO2015118466A1
Application number: PCT/IB2015/050853
Authority: WO
Inventors: Haytham Elhawary; Aleksandra Popovic
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2014-02-04
Filing date: 2015-02-04
Publication date: 2015-08-13
Anticipated expiration: 2016-08-04

Abstract

A method for aligning a robot includes connecting (402) a passive arm to a fixed position, and aligning (406) a remote center of motion (RCM) for a tool held by a manipulator arm with a target location. The manipulator arm is connected to the passive arm by a joint. The joint is immobilized (410) in a closed loop position control. A load on the joint is measured (411). The joint is aligned (412) with a vertical by adjusting a position of the passive arm until the load is minimized for the joint.

Description

Robot Angular Setup Using Current From Joints

BACKGROUND:

Technical Field

This disclosure relates to robotic positioning and more particularly to robot orientation using motor current feedback.

Description of the Related Art

In minimally invasive robotic surgery, a surgeon introduces laparoscopic instruments (which are long and slender) into the abdomen or thorax, while a robot manipulates an endoscope. The robot is usually designed to move the endoscope through a fulcrum point in a necessary workspace to perform the surgery. The robot may be mounted onto an operating room table above the patient and locked in place using a passive or active mechanical arm. It is common for robots with arch-based kinematics to align a first axis completely vertically to a remote center of motion. This maximizes the endoscope workspace inside of the patient's chest or abdomen. It also minimizes a torque requirement of the axis motor which, in turn, minimizes the size and weight of the system. To align the axis manually is challenging, as it is difficult to know with the naked eye exactly when the axis is vertical.

If the robot is not set-up in a correct initial position over the body of the patient, it will not be able to reach the desired workspace and assist the surgeon during the procedure, rendering it useless. In addition, setting up the robot at an angle instead of vertically aligned with the incision point can put excessive loading on a joint motor, causing it to overheat and malfunction. Equipment, such as, spirit levels, may be used to do this; however, such use may result in long setup times.

SUMMARY

In accordance with the present principles, a method for aligning a robot includes connecting a passive arm to a fixed position, and aligning a remote center of motion (RCM) for a tool held by a manipulator arm with a target location. The manipulator arm is connected to the passive arm by a joint. The joint is immobilized in a closed loop position control. A load on the joint is measured. The joint is aligned with a vertical by adjusting a position of the passive arm until the load is minimized for the joint.

Another method for aligning a robot includes connecting a passive arm to a fixed position in an operating environment; aligning a remote center of motion (RCM) for a tool held by a manipulator arm with a location on a body where an incision is made or is to be made, the manipulator arm being connected to the passive arm by a joint; moving the joint in different orientations about a substantially vertical axis; measuring a load on the joint; and aligning the joint with a vertical position corresponding with the load being minimized for the motor joint.

A system for aligning a robot includes a passive arm coupled to a fixed position, and a manipulator arm connected to the passive arm by a joint to be aligned vertically. An actuation force is provided to reposition the joint. A load measurement device is configured to monitor a loading condition in the joint while the joint is repositioned, the load

measurement device including an output configured as feedback for determining a position of the joint such that when the loading condition is minimized the joint is vertically aligned.

These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

This disclosure will present in detail the following description o] embodiments with reference to the following figures wherein:

FIG. 1 is a block/flow diagram showing a robot system for perfo vertical alignment capabilities in accordance with illustrative embodime FIG. 2A is a schematic diagram showing a vertically aligned joii torque equal to zero;

FIG. 2B is a schematic diagram showing a joint motor having an vertical alignment having a motor torque proportional to sin(a);

FIG. 3 is a diagram showing a robot system in greater detail for ] alignment in accordance with the present principles;

FIG. 4 is a flow diagram showing a method for performing verti< accordance with the present principles; and

FIG. 5 is a diagram showing a bull's eye as a display for feedbac motor joint in accordance with one illustrative embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

In accordance with the present principles, system and methods a robot can be setup with vertical alignment with respect to an incision po other target area without the use of any external equipment. In one emb current is employed as a proxy for the vertical alignment of the robot. C also be employed, e.g., torque measurement, etc. As load is reduced on indicates an improved vertical alignment. A passive mechanical arm is thus manually moved until current is small and alignment is complete. In another embodiment, an actuated mechanical arm is moved automatically to a position in which the joint motor has minimal load current, assuring vertical alignment.

In robotic guided minimally invasive surgery, a robot often holds an endoscope and a surgeon manually manipulates other tools. Small ports that are placed on or in a patient's body are usually the only incision points through which the instruments and an endoscope may pass to access the inside of the patient. Some robots implement a remote center of motion (RCM) at a fulcrum point, that is, they enforce that only rotation can be performed at the port and all translational forces at that location are eliminated. This can be achieved by implementing a mechanical design which has a remote center of motion at a specific location in space, and then that point in space is aligned with the port.

The robot may be designed to move the endoscope through the fulcrum point in the necessary workspace to perform the surgery. Therefore, an initial setup of the robot is an important consideration in making sure that the robot will be able to reach the entire workspace. The robot is mounted onto the operating room table or other structure above the patient and locked in place using a passive or active mechanical arm. If the robot is not setup in a correct initial position over the body of the patient, it will not be able to reach the desired workspace and assist the surgeon during the procedure. This also leads to long set-up times to ensure the robot is well-aligned at the beginning of the procedure.

Robots with arch-based kinematics align a first axis vertically (e.g., vertical relative to ground). A remote center of motion (RCM) is usually below an arched robot arm in an arch- based robot set-up, but need not be. This maximizes the endoscope workspace inside of the patient's chest or abdomen. To align this axis manually is challenging, as it is difficult to know with the naked eye exactly when the axis is vertical. In addition, setting up the robot at an angle instead of being vertically aligned with the incision point or RCM can put excessive loading on the joint motor, causing it to overheat and malfunction. Some other methods have been used before, such as in a Freehand™ robot where a spirit level is manually mounted on the robot to make sure the first axis is vertically aligned. However, this method and similar methods rely heavily on an operator's capability to position the robot.

It should be understood that the present invention will be described in terms of medical instruments; however, the teachings of the present invention are much broader and are applicable to any robotic instruments. In some embodiments, the present principles are employed in tracking, guiding, manipulating or maneuvering in complex biological or mechanical systems. In particular, the present principles are applicable to robot-controlled procedures for or on biological systems (e.g., procedures in all areas of the body such as the lungs, gastro-intestinal tract, excretory organs, blood vessels, etc.). The elements depicted in the FIGS, may be implemented in various combinations of hardware and software and provide functions which may be combined in a single element or multiple elements.

The functions of the various elements shown in the FIGS, can be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions can be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which can be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and can implicitly include, without limitation, digital signal processor ("DSP") hardware, read-only memory ("ROM") for storing software, random access memory

("RAM"), non-volatile storage, etc. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative system components and/or circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams and the like represent various processes which may be substantially represented in computer readable storage media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Furthermore, embodiments of the present invention can take the form of a computer program product accessible from a computer-usable or computer-readable storage medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable storage medium can be any apparatus that may include, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk - read only memory (CD-ROM), compact disk - read/write (CD-R/W), Blu-Ray™ and DVD. Referring now to the drawings in which like numerals represent the same or similar elements and initially to FIG. 1, a system 100 for performing a surgical procedure using a robot is illustratively shown in accordance with one embodiment. System 100 may include a workstation or console 112 from which a procedure is supervised and/or managed.

Workstation 112 preferably includes one or more processors 114 and memory 116 for storing programs and applications. Memory 116 may store a robot control module 115 configured to interpret commands from a user or from a program and control movement (e.g., translation and rotation), velocity, angular velocity, acceleration, angular acceleration, etc. for a robot system 108. Motion of the robot system 108 is provided using motion devices 130, which may include passive or active joints including but not limited to motors, actuators, servos, etc. The control module 115 may include hardware (control boards, software and/or combinations thereof).

In a particularly useful embodiment, the robot system 108 is employed for minimally invasive surgery, although the robot system 108 may be employed in other surgical procedures and non-surgical tasks. For illustrative purposes, the robot system 108 may be employed to hold an instrument 102, such as, e.g., imaging device or endoscope with a camera or other device or instrument. Other instruments 122 and 124 may also be employed for use during the surgery. The imaging device 102 and other instruments 122, 124 may include a catheter, a guidewire, a probe, an endoscope, a robot, an electrode, a filter device, a balloon device, forceps, clamps, other component or tools, etc.

In useful embodiments, the workstation 112 may include software or hardware modules for planning and controlling the robot systems 108; however, these modules are optional and presented here for as non-limiting examples of some of the functionality that may be employed in accordance with the present principles. In one embodiment, the workstation 112 may include a planning module 104 for storing and executing a surgical plan. The planning module 104 may provide instruction to the robot system 108 during the procedure. In another embodiment, the robot system 108 may be controlled using image guidance. An image guidance module 106 provides commands to the control systems in accordance with image data 134 collected by, e.g., the imaging device 102, an additional imaging system 110 (e.g., X-ray. ultrasound, etc.) and/or in accordance with image models 136 generated by scanned images (e.g., pre-operative or intra-operative image data). An image processing module 148 may be provided to convert image data into instructions for the robot system 108. It should be understood that other configurations and control systems for controlling the robot system 108 are also contemplated

Workstation 112 may include a display 118 for viewing an internal volume 131 of a subject (patient) 160. Display 118 may also permit a user to interact with the workstation 112 and its components and functions, or any other element within the system 100. This is further facilitated by an interface 120, which may include a keyboard, mouse, a joystick, a haptic device, or any other peripheral or control to permit user feedback from and interaction with the workstation 112.

In accordance with the present principles, the robot system 108 is configured to be aligned vertically using a feedback loop 126 from one or more motion devices 130. In one embodiment, the robot system (robot) 108 can be setup at a perfectly vertical alignment with respect to an incision point 128 of the patient 160 without the use of any external equipment and without relying on an operator to make sure that the orientation is correct. In one embodiment, current (or torque) of a motor (motion device) 130 is employed as a proxy for a manual vertical alignment of the robot 108. The robot system 108 is moved with the intention of minimizing the motor current as measured by a torque or current sensor 125. The sensor 125 may be part of the workstation 112 or may be a separate device. The sensor 125 may work with a visible gauge or meter for viewing its measurements by an operator.

One method for vertically aligning a robot system 108 (e.g., having an endoscope manipulator) includes attaching to a mechanical passive arm 138 that is controllable by an operator (e.g., a surgeon or a nurse). This arm 138 is then attached to an operating room table or other fixed position, and the robot 108 is positioned such that a remote center of motion (RCM) of the robot 108 is aligned with the incision point 128 (e.g., in the chest) through which the endoscope or other tool 102 will be inserted. The next step involves the surgeon, physician assistant and/or control module 115 aligning the motor joint 130 of the robot along the vertical axis to make sure that a manipulator arm 140 of the robot 108 can reach an adequate workspace (in the chest) and to ensure minimal load on the motor 130, as will be described below.

Referring to FIGS. 2A and 2B, schematic diagrams are shown for two motor configurations. In FIG. 2A, with a vertical motor axis 202, the amount of torque (T_motor) for a motor 204 to move a horizontal bar 206 is zero. The bar 206 has a length L and a mass M. The motor 204 moves the bar in the direction of arrow "A". This means that very small motors can be used to move large loads in this configuration, providing a very efficient manipulator. However, in FIG. 2B (side view), as soon as an angle (a) is introduced between the motor 204 and the vertical axis 202, then the motor load depends on the mass M of the bar 206 that is being displaced. For example, T_motor = M*g*sin(a)*L where g is the gravitational constant. In FIG. 2B, note that the bar 206 is oriented coming out of the page. In DC motors, the motor torque is directly proportional to the current, and hence the total torque (T_motor ) exerted by the motor 204 can be obtained by the motor current, which is may be measured by the control module 115 (FIG. 1) and or sensor 125 (FIG.l), which may be included, e.g., on a motor control board or boards of the control module 115.

Referring to FIG. 3, a diagram shows a robot system 302 in accordance with one illustrative embodiment. Robot system 302 includes a manipulator arm 304 configured to hold and move a tool 305 (e.g., an endoscope). The manipulator arm 304 is coupled to a passive arm 306 that is controllable by an operator (e.g., a surgeon or a nurse) to move in one or more directions 308 using an actuator 309 or the like or manually. The passive arm 306 is attachable to an operating room table or other fixed position 310. The robot system 302 is positioned such that a remote center of motion (RCM) 312 is aligned with an incision point 314 (e.g., in the chest) through which the endoscope or other tool 305 will be inserted. A joint 316 couples the passive arm 306 to the manipulator arm 304. The joint 316 may be motorized or may be moved using an external motor, actuator, linkage, etc.

In one embodiment, a surgeon, physician assistant and/or control module 115 may align the joint 316 of the robot 302 along a vertical axis 318 to make sure that the robot 302 can reach an adequate workspace (in the chest) and to ensure minimal load on the joint 316. A current meter 320 is employed to monitor the current drawn by the joint 316 and is employed as feedback for determining whether the joint has achieved vertical alignment (e.g., current is zero or substantially zero). It should be understood that additional linkages, joints, motors, etc. may be employed. In addition, each joint or a subset thereof may be aligned in accordance with the present principles. The robot system 302 may include arch-based kinematics (e.g., arch-shapes arms), although other configurations are also contemplated.

In another embodiment, an actuated mechanical arm 324 may optionally be configured to move one of the manipulator arm 304 or the passive arm 306 automatically to a position in which the joint 316, e.g., motor joint, has virtually no load/current. This assures vertical alignment. The actuated mechanical arm 324 may be manually controlled or computer controlled or a combination of both.

Referring to FIG. 4, a method for vertically aligning robotic elements is illustratively shown in accordance with exemplary embodiments. In block 402, a passive arm is connected to an operating room table or other stable surface. In block 404, a manipulator is rotatably connected to the passive arm using a joint, such as a motorized joint, which rotates about an upright axis. Other joints or couplings are also contemplated. The passive arm may be controlled by an operator (e.g. a surgeon or a nurse) or by a computer. In block 406, the robot is positioned such that a remote center of motion of the robot is aligned with the incision point or other target region through which an endoscope or other tool held by the manipulator arm will be inserted.

In block 408, the surgeon or physician assistant aligns a motor joint of the robot along the vertical axis to make sure that the robot can reach an adequate workspace in the chest and to ensure minimal load on the motor. In block 410, the joint motor is rendered immobile in a closed loop control, which means that the joint motor will try and hold the robot completely still. The amount of torque needed to do so will depend on the angle at which the motor is aligned with respect to the vertical.

In block 412, the operator of the robot can move the passive mechanical arm until the motor joint is exerting a very small torque (e.g., drawing a very small amount or zero current) which is indicative of vertical alignment. The current value can be measured in block 411 and indicated or shown, in block 413, to the operator in a graphical interface or readout that is easy to understand even if the operator is not skilled in technical components of the system, such as, e.g., showing a bull' s eye (FIG. 5), alignment dial, meter, digital readout or indicator, as feedback. In another embodiment, in block 414, an actuated or controlled arm may be employed to hold the manipulator arm. The separate actuator arm can be moved using actuation such that the manipulator arm is moved until the current drawn by the joint motor is drastically reduced or zero to indicate of vertical alignment.

Referring to FIG. 5, an illustrative display 502 of a bull's eye 506 is shown in accordance with one embodiment. The display 502 may be rendered on the display device 118 (FIG. 1) or as a meter to indicate the load (e.g., torque, current, etc.) being measured as a result of an actuating force or motion imparted to a motor joint during alignment in accordance with the present principles. As the load is reduced, a cursor or indicator 504 will get closer to a center of the bull's eye to indicate alignment has been achieved. It should be understood that other symbols, displays, meters, etc. may be employed for feedback to users and/or control systems instead of or in addition to those described herein.

It should also be understood that the present principles may be employed in a plurality of different applications including minimally invasive surgery, other robotic surgeries, robotic application such as in manufacturing or processing; etc. Applications where the present principles are particularly useful include cardiac surgery, such as minimally invasive coronary artery bypass grafting, atrial septal defect closure, valve repair/replacement, etc.; laparoscopic surgery, such as hysterectomy, prostactomy, gall bladder surgery, etc.; or other surgeries. The other surgeries may include, e.g., natural orifice transluminal surgery

(NOTES), single incision laparoscopic surgery (SILS), pulmonary/bronchoscopic surgery, minimally invasive diagnostic interventions, such as, arthroscopy, etc.

In interpreting the appended claims, it should be understood that:

a) the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim;

b) the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; c) any reference signs in the claims do not limit their scope; d) several "means" may be represented by the same item or hardware or software implemented structure or function; and

e) no specific sequence of acts is intended to be required unless specifically indicated.

Having described preferred embodiments for robot angular setup using current from joints (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the disclosure disclosed which are within the scope of the embodiments disclosed herein as outlined by the appended claims. Having thus described the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.

Claims

CLAIMS:

1. A method for aligning a robot, comprising:

connecting (402) a passive arm to a fixed position;

aligning (406) a remote center of motion (RCM) for a tool held by a manipulator arm with a target location, the manipulator arm being connected to the passive arm by a joint; immobilizing (410) the joint in a closed loop position control;

measuring (411) a load on the joint; and

aligning (412) the joint with a vertical by adjusting a position of the passive arm until the load is minimized for the joint.

2. The method as recited in claim 1, wherein the manipulator arm is configured to hold a tool and the target location includes a location where the tool is inserted.

3. The method as recited in claim 1, further comprising indicating (413) the load to a user to provide feedback for aligning the motor joint.

4. The method as recited in claim 1, further comprising:

connecting (414) an actuation arm to the manipulator arm; and

moving (412) the manipulator arm using the actuation arm until the load is minimized for the motor joint.

5. The method as recited in claim 1, wherein the robot is employed during surgery and the fixed position includes an operating table and the target location includes an incision point.

6. The method as recited in claim 1, wherein load includes a current load.

7. The method as recited in claim 1, wherein the joint includes a motorized joint controlled by a control module.

8. A method for aligning a robot, comprising:

connecting (402) a passive arm to a fixed position in an operating environment; aligning (406) a remote center of motion (RCM) for a tool held by a manipulator arm with a location on a body where an incision is made or is to be made, the manipulator arm being connected to the passive arm by a joint;

moving (412) the joint in different orientations about a substantially vertical axis; measuring (411) a load on the joint; and

aligning (412) the joint with a vertical position corresponding with the load being minimized for the motor joint.

9. The method as recited in claim 8, wherein the manipulator arm is configured to hold an endoscope at an area of the incision.

10. The method as recited in claim 8, further comprising indicating (413) the load to a user to provide feedback for aligning the joint.

11. The method as recited in claim 7, further comprising:

connecting (414) an actuation arm to the manipulator arm; and moving (412) the manipulator arm using the actuation arm until the load is minimized for the joint.

12. The method as recited in claim 8, wherein load includes a current load or torque.

13. The method as recited in claim 8, wherein the joint includes a motorized joint controlled by a control module.

14. A system for aligning a robot, comprising:

a passive arm (306) coupled to a fixed position;

a manipulator arm (304) connected to the passive arm by a joint (316) to be aligned vertically;

an actuation force (308, 324) provided to reposition the joint; and

a load measurement device (320) configured to monitor a loading condition in the joint while the joint is repositioned, the load measurement device including an output configured as feedback for determining a position of the joint such that when the loading condition is minimized the joint is vertically aligned.

15. The system as recited in claim 14, wherein the manipulator arm (304) is configured to hold a tool (305) to be used during surgery.

16. The system as recited in claim 14, wherein the load measurement device (320) includes a torque sensor or a current meter.

17. The system as recited in claim 14, further comprising an actuation arm (324) connectable to one of the manipulator arm or to the passive arm and configured to provide the actuation force to move one of the manipulator arm or the passive arm.

18. The system as recited in claim 14, wherein the robot is employed during surgery and the fixed position (310) includes an operating table.

19. The system as recited in claim 14, wherein the joint (316) includes a motorized joint controlled by a control module (115).

20. The system as recited in claim 14, wherein the actuation force (308) is manually provided by a user to reposition the joint.