System And Method for Reducing Tool Vibration At A Variable Stiffness End Effector Of A Surgical System

A variable stiffness end effector assembly for a medical robotic guidance system includes an end effector support and a tool insertion device disposed within and spaced apart from the end effector support. The assembly further includes a coupler coupling the tool insertion device within the end effector support. The coupler includes a first mode wherein the tool insertion device is rigidly coupled within the end effector support and second mode wherein the tool insertion device is compliantly coupled within the end effector support.

FIELD

The subject disclosure is related generally to a robotic surgical system, and particularly to a system for decoupling vibrations from an end effector at a robotic arm.

BACKGROUND

An instrument can be navigated relative to a subject for performing various procedures. For example, the subject can include a patient on which a surgical procedure is being performed. During a surgical procedure, an instrument can be tracked in an object or subject space. The location of the instrument that is tracked can be displayed on a display device relative to an image of the patient.

The position of the patient can be determined with a tracking system. Generally, a patient is registered to the image, via tracking an instrument relative to the patient to generate a translation map between the subject or object space (e.g., patient space) and the image space.

After registration, the position of the instrument can be appropriately displayed on the display device while tracking the instrument. The position of the instrument relative to the subject can be displayed as a graphical representation, sometimes referred to as an icon on the display device.

The instrument in guided surgery, particularly in spinal surgery, has a particular challenge for holding the position in a rigid system. A tool such as drill is used with a guide at end effector at the end of a robotic arm. Typically, a robotic arm has high rigidity relative to the patient and relative to the robot arm. The high rigidity may result in undesired system dynamics. The system dynamics may occur in natural vibrations at a high frequency due to the high stiffness in the system.

SUMMARY

The present system allows is a variable stiffness end effector that allows quick decoupling of a rigid mechanism and coupling using a compliant mechanism of the parts of the end effector support. In particular, the present disclosure allows the end effector support to be quickly decoupled from the tool insertion device located within the end effector support. This allows the natural frequency of the system to rapidly decrease and prevent natural frequency vibrations.

In one aspect of the disclosure, a variable stiffness end effector assembly for a medical robotic guidance system includes an end effector support and a tool insertion device disposed within and spaced apart from the end effector support. The assembly further includes a coupler coupling the tool insertion device within the end effector support. The coupler includes a first mode wherein the tool insertion device is rigidly coupled within the end effector support and second mode wherein the tool insertion device is compliantly coupled within the end effector support.

In another aspect of the disclosure, a system has a robotic arm with a variable stiffness end effector assembly comprising a tool insertion device disposed within the end effector support and coupled thereto with a coupler. The coupler comprises a first mode wherein the tool insertion device is rigidly coupled within the end effector support and second mode wherein the tool insertion device is compliantly coupled within the end effector support. A robotic control system is configured to control movement of the end effector support assembly. An input system is configured to receive input from a user and send a signal to the robotic control system to move the end effector support relative to a subject.

According to various embodiments, the end effector assembly may be moved relative to a subject, such as by a user and/or with a robotic system. The robotic system may include any appropriate robotic system, such as a Mazor X™ Robotic Guidance System, sold by Mazor Robotics Ltd. having a place of business in Israel and/or Medtronic, Inc. having a place of business in Minnesota, USA and/or as disclosed in U.S. Pat. No. 11,135,025, incorporated herein by reference.

The tracking or navigation system may include the end effector assembly, may also be used in various techniques and include an imaging system or following selected portions in a procedure. For example, the end effector assembly may be associated with the robotic system. The robotic system may move the end effector in a selected manner during the procedure. During the procedure, the end effector assembly may be moved based upon predetermined characteristics to follow for a selected portion during the procedure, such as during drilling for implanting certain implantable devices such as a spinal implant.

DETAILED DESCRIPTION

The subject disclosure is directed to an exemplary embodiment of a surgical procedure on a subject, such as a human patient. It is understood, however, that the system and methods described herein are merely exemplary and not intended to limit the scope of the claims included herein. In various embodiments, it is understood, that the systems and methods may be incorporated into and/or used on non-animate objects. The systems may be used to, for example, to register coordinate systems between two systems for use on manufacturing systems, maintenance systems, and the like. For example, automotive assembly may use one or more robotic systems including individual coordinate systems that may be registered together for coordinated or consorted actions. Accordingly, the exemplary illustration of a surgical procedure herein is not intended to limit the scope of the appended claims.

Discussed herein, according to various embodiments, are processes and systems for allowing the use of and navigation and registration between various coordinate systems, including robotic coordinate systems. In various embodiments, a first coordinate system may be registered to a second coordinate system, such as a robotic coordinate system to an image coordinate system or space. A navigation space or coordinate system may then be registered to the robotic or first coordinate system and, therefore, be registered to the image coordinate system without being separately or independently registered to the image space. Similarly, the navigation space or coordinate system may be registered to the image coordinate system or space directly or independently. The robotic or first coordinate system may then be registered to the navigation space and, therefore, be registered to the image coordinate system or space without being separately or independently registered to the image space.

In various embodiments, the different systems used relative to the subject may include different coordinate systems (e.g., locating systems). For example, a robotic system may be moved relative to a subject that includes a robotic coordinate system. The robot may be fixed, including removably fixed, at a position relative to the subject. Thus, movement of a portion of the robot relative to the base of the robot (i.e., the fixed portion of the robot) may be known due to various features of the robot. For example, encoders (e.g., optical encoders, potentiometer encoders, or the like) may be used to determine movement or amount of movement of various joints (e.g., pivots) of a robot. A position of an end effector assembly (e.g., a terminal end) of the robot may be known relative to the base of the robot. Given a known position of the subject relative to the base and the known position of the base relative to the subject, the position of the end effector assembly relative to the subject may be known during movement of a robot and/or during a stationary period of the end effector assembly. Thus, the robot may define a coordinate system relative to the subject.

Various other portions may also be tracked relative to the subject. For example, a tracking system may be incorporated into a navigation system that includes one or more instruments that may be tracked relative to the subject. The navigation system may include one or more tracking systems that track various portions, such as tracking devices, associated with instruments. The tracking system may include a localizer that is configured to determine the position of the tracking device in a navigation system coordinate system. Determination of the navigation system coordinate system may include those described at various references including U.S. Pat. Nos. 8,737,708; 9,737,235; 8,503,745; and 8,175,681; all incorporated herein by reference. In particular, a localizer may be able to track an object within a volume relative to the subject. The navigation volume, in which a device, may be tracked may include or be referred to as the navigation coordinate system or navigation space. A determination or correlation between the two coordinate systems may allow for or also be referred to as a registration between two coordinate systems.

In various embodiments, the first coordinate system, which may be a robotic coordinate system, may be registered to a second coordinate system, which may be a navigation coordinate system. Accordingly, coordinates in one coordinate system may then be transformed to a different or second coordinate system due to a registration. Registration may allow for the use of two coordinate systems and/or the switching between two coordinate systems. For example, during a procedure, a first coordinate system may be used for a first portion or a selected portion of a procedure and a second coordinate system may be used during a second portion of a procedure. Further, two coordinate systems may be used to perform or track a single portion of a procedure, such as for verification and/or collection of additional information.

Furthermore, images may be acquired of selected portions of a subject. The images may be displayed for viewing by a user, such as a surgeon. The images may have superimposed on a portion of the image a graphical representation of a tracked portion or member, such as an instrument. According to various embodiments, the graphical representation may be superimposed on the image at an appropriate position due to registration of an image space (also referred to as an image coordinate system) to a subject space. A method to register a subject space defined by a subject to an image space may include those disclosed in U.S. Pat. Nos. U.S. Pat. Nos. 8,737,708; 9,737,235; 8,503,745; and 8,175,681; all incorporated herein by reference.

During a selected procedure, the first coordinate system may be registered to the subject space or subject coordinate system due to a selected procedure, such as imaging of the subject. In various embodiments, the first coordinate system may be registered to the subject by imaging the subject with a fiducial portion that is fixed relative to the first member or system, such as the robotic system. The known position of the fiducial relative to the robotic system may be used to register the subject space relative to the robotic system due to the image of the subject including the fiducial portion. Thus, the position of the robotic system or a portion thereof, such as the end effector assembly, may be known or determined relative to the subject. Due to registration of a second coordinate system to the robotic coordinate system may allow for tracking of additional elements not fixed to the robot relative to a position determined or tracked by the robot.

The tracking of an instrument during a procedure, such as a surgical or operative procedure, allows for navigation of a procedure. When image data is used to define an image space it can be correlated or registered to a physical space defined by a subject, such as a patient. According to various embodiments, therefore, the patient defines a patient space in which an instrument can be tracked and navigated. The image space defined by the image data can be registered to the patient space defined by the patient. The registration can occur with the use of fiducials that can be identified in the image data and in the patient space.

FIG.1is a diagrammatic view illustrating an overview of a procedure room or arena. In various embodiments, the procedure room may include a surgical suite in which may be placed a medical robotic system20and a navigation system26that can be used for various procedures. The robotic system20may include a Mazor X™ robotic guidance system, sold by Medtronic, Inc. The robotic system20may be used to assist in guiding a selected instrument, such as drills, screws, etc. relative to a subject30. The robotic system20may include a mount34that fixes a portion, such as a robotic base38, relative to the subject30. The robotic system20may include one or more arms40that are moveable or pivotable relative to the subject30, such as including an end effector assembly44. The end effector assembly44may be any appropriate portion, such as an elongated tube, guide, or passage member. The end effector44may be moved relative to the base38with one or more motors. The position of the end effector assembly44may be known or determined relative to the base38with one or more encoders at one or more joints, such as a wrist joint48and/or an elbow joint52of the robotic system20.

The navigation system26can be used to track the location of one or more tracking devices, tracking devices may include a robot tracking device54, a subject tracking device58, an imaging system tracking device62, and/or a tool tracking device66. A tool68or moveable member may be any appropriate tool such as a drill, forceps, or other tool operated by a user72. The tool68may also include an implant, such as a spinal implant or orthopedic implant. It should further be noted that the navigation system26may be used to navigate any type of instrument, implant, or delivery system, including: guide wires, arthroscopic systems, orthopedic implants, spinal implants, deep brain stimulation (DBS) probes, etc. Moreover, the instruments may be used to navigate or map any region of the body. The navigation system26and the various instruments may be used in any appropriate procedure, such as one that is generally minimally invasive or an open procedure.

An additional or alternative, imaging system80may be used to acquire pre-, intra-, or post-operative or real-time image data of a subject, such as the subject30. It will be understood, however, that any appropriate subject can be imaged and any appropriate procedure may be performed relative to the subject. In the example shown, the imaging device80comprises an O-arm® imaging device sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colorado, USA. The imaging device80may have a generally annular gantry housing82in which an image capturing portion is moveably placed. The imaging device80can include those disclosed in U.S. Pat. Nos. 7,188,998; 7,108,421; 7,106,825; 7,001,045; and 6,940,941; all of which are incorporated herein by reference, or any appropriate portions thereof. It is further appreciated that the imaging device80may include in addition or alternatively a fluoroscopic C-arm. Other exemplary imaging devices may include fluoroscopes such as bi-plane fluoroscopic systems, ceiling mounted fluoroscopic systems, cath-lab fluoroscopic systems, fixed C-arm fluoroscopic systems, isocentric C-arm fluoroscopic systems, 3D fluoroscopic systems, etc. Other appropriate imaging devices can also include MRI, CT, ultrasound, etc.

The position of the imaging system33,80, and/or portions therein such as the image capturing portion, can be precisely known relative to any other portion of the imaging device33,80. The imaging device33,80, according to various embodiments, can know and/or recall precise coordinates relative to a fixed or selected coordinate system. For example, the robotic system20may know or determine its position and position the effector assembly44at a selected pose. Similarly, the imaging system80may also position the imaging portions at a selected pose. This can allow the imaging system80to know its position relative to the patient30or other references. In addition, as discussed herein, the precise knowledge of the position of the image capturing portion can be used in conjunction with a tracking system to determine the position of the image capturing portion and the image data relative to the tracked subject, such as the patient30.

Herein, reference to the imaging system80may refer to any appropriate imaging system, unless stated otherwise.

The imaging device80can be tracked with a tracking device62. Also, a tracking device81can be associated directly with the effector assembly44. The effector assembly44may, therefore, be directly tracked with a navigation system as discussed herein. In addition or alternatively, the effector assembly44may be positioned and tracked with the robotic system20. Regardless, image data defining an image space acquired of the patient30can, according to various embodiments, be registered (e.g., manually, inherently, or automatically) relative to an object space. The object space can be the space defined by a patient30in the navigation system26.

The patient30can also be tracked as the patient moves with a patient tracking device, DRF, or tracker58. Alternatively, or in addition thereto, the patient30may be fixed within navigation space defined by the navigation system26to allow for registration. As discussed further herein, registration of the image space to the patient space or subject space allows for navigation of the instrument68with the image data. When navigating the instrument68, a position of the instrument68can be illustrated relative to image data acquired of the patient30on a display device84. An additional and/or alternative display device84′ may also be present to display an image. Various tracking systems, such as one including an optical localizer88or an electromagnetic (EM) localizer92can be used to track the instrument68.

More than one tracking system can be used to track the instrument68in the navigation system26. According to various embodiments, these can include an electromagnetic tracking (EM) system having the EM localizer94and/or an optical tracking system having the optical localizer88. Either or both of the tracking systems can be used to track selected tracking devices, as discussed herein. It will be understood, unless discussed otherwise, that a tracking device can be a portion trackable with a selected tracking system. A tracking device need not refer to the entire member or structure to which the tracking device is affixed or associated.

The position of the patient30relative to the imaging device33can be determined by the navigation system26. The position of the imaging system33may be determined, as discussed herein. The patient30can be tracked with the dynamic reference frame58, as discussed further herein. Accordingly, the position of the patient30relative to the imaging device33can be determined.

Image data acquired from the imaging system33, or any appropriate imaging system, can be acquired at and/or forwarded from an image device controller96, that may include a processor module, to the navigation computer and/or processor system102that can be a part of a controller or workstation98having the display84and a user interface106. It will also be understood that the image data is not necessarily first retained in the controller96, but may also be directly transmitted to the workstation98. The workstation98can provide facilities for displaying the image data as an image108on the display84, saving, digitally manipulating, or printing a hard copy image of the received image data. The user interface106, which may be a keyboard, mouse, touch pen, touch screen or other suitable device, allows the user72to provide inputs to control the imaging device80, via the image device controller96, or adjust the display settings of the display84. The workstation98may also direct the image device controller96to adjust the image capturing portion of the imaging device80to obtain various two-dimensional images along different planes in order to generate representative two-dimensional and three-dimensional image data.

With continuing reference toFIG.1, the navigation system26can further include the tracking system including either or both of the electromagnetic (EM) localizer94and/or the optical localizer88. The tracking systems may include a controller and interface portion110. The controller110can be connected to the processor portion102, which can include a processor included within a computer. The controller acts as a robotic control system. The EM tracking system may include the STEALTHSTATION@ AXIEM™ Navigation System, sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colorado; or can be the EM tracking system described in U.S. patent application Ser. No. 10/941,782, filed Sep. 15, 2004, and entitled “METHOD AND APPARATUS FOR SURGICAL NAVIGATION”; U.S. Pat. No. 5,913,820, entitled “Position Location System,” issued Jun. 22, 1999; and U.S. Pat. No. 5,592,939, entitled “Method and System for Navigating a Catheter Probe,” issued Jan. 14, 1997; all of which are herein incorporated by reference. It will be understood that the navigation system26may also be or include any appropriate tracking system, including a STEALTHSTATION® TREON® or S7™ tracking systems having an optical localizer, that may be used as the optical localizer88, and sold by Medtronic Navigation, Inc. of Louisville, Colorado. Other tracking systems include an acoustic, radiation, radar, etc. The tracking systems can be used according to generally known or described techniques in the above incorporated references. Details will not be included herein except when to clarify selected operation of the subject disclosure.

Wired or physical connections can interconnect the tracking systems, imaging device80, etc. Alternatively, various portions, such as the instrument68may employ a wireless communications channel, such as that disclosed in U.S. Pat. No. 6,474,341, entitled “Surgical Communication Power System,” issued Nov. 5, 2002, herein incorporated by reference, as opposed to being coupled directly to the controller110. Also, the tracking devices62,66,54can generate a field and/or signal that is sensed by the localizer(s)88,94.

Various portions of the navigation system26, such as the instrument68, and others as will be described in detail below, can be equipped with at least one, and generally multiple, of the tracking devices66. The instrument can also include more than one type or modality of tracking device66, such as an EM tracking device and/or an optical tracking device. The instrument68can include a graspable or manipulable portion at a proximal end and the tracking devices may be fixed near the manipulable portion of the instrument68.

Additional representative or alternative localization and tracking system is set forth in U.S. Pat. No. 5,983,126, entitled “Catheter Location System and Method,” issued Nov. 9, 1999, which is hereby incorporated by reference. The navigation system26may be a hybrid system that includes components from various tracking systems.

According to various embodiments, the navigation system26can be used to track the instrument68relative to the patient30. The instrument68can be tracked with the tracking system, as discussed above. Image data of the patient30, or an appropriate subject, can be used to assist the user72in guiding the instrument68. The image data, however, is registered to the patient30. The image data defines an image space that is registered to the patient space defined by the patient30. The registration can be performed as discussed herein, automatically, manually, or combinations thereof.

Generally, registration allows a translation map to be generated of the physical location of the instrument68relative to the image space of the image data. The translation map allows the tracked position of the instrument68to be displayed on the display device84relative to the image data108. A graphical representation68i, also referred to as an icon, can be used to illustrate the location of the instrument68relative to the image data108.

With continuing reference toFIG.1, a subject registration system or method can use the tracking device58. The tracking device58may include portions or members that may be trackable, but may also act as or be operable as a fiducial assembly120. The fiducial assembly120can include a clamp or other fixation portion124and the imageable fiducial body122. It is understood, however, that the fiducial assembly120may be separate from the tracking device58. The fixation portion124can be provided to fix any appropriate portion, such as a portion of the anatomy. As illustrated in the display84ofFIG.1, the fiducial assembly120can be interconnected with a portion of a spine126such as a spinous process130. The fixation portion124can be interconnected with a spinous process130in any appropriate manner. For example, a pin or a screw can be driven into the spinous process130.

Referring now toFIG.2A, one process that the end effector assembly44may be used for is a drilling process for pedicle screw implantation into a vertebra. However, the teachings also apply to other types of tools. The end effector assembly44is a variable stiffness end effector used to guide the tool at a desired position. Previous systems used rigid coupling of the end effector or compliant coupling but do not provide a system capable of providing variable stiffness by switching between compliant coupling and rigid coupling. That is, during a procedure it may be advantageous to be rigid for a portion of the procedure and compliant during other portions such as when vibrations are sensed.

The desired position for the procedure of the effector assembly44is located by movement of the robotic arm40. The variable stiffness end effector44is rigidly coupled to the robotic arm40during a portion of the procedure. When a drill is used as the tool, it may rotate at a high speed such as over 70000 rpms. Both the robotic arm40and the end effector assembly44have a resonant or natural frequency. The motion of the tool may cause the end effector assembly44to vibrate at a frequency that corresponds to a resonant or natural frequency of the end effector assembly44, which may be deemed undesirable because it can be felt by the surgeon. Further, the harmonics of the vibration at the robot arm40may align with the vibration frequency at the end effector assembly44which may cause the rigidly coupled robotic arm to vibrate as well, which may be undesired. The variable stiffness end effector refers to an assembly allowing a tool holder of the end effector44(as described below) that absorbs vibration.

A representation of the robotic arm40and elbow joint50of the effector assembly44are illustrated. The effector assembly44has the coupling to the arm40represented by a spring210though which vibration may be coupled. The natural or resonant frequency of the system is the square root of the quotient of the stiffness and mass of the robotic arm. One example of a suitable robotic system is found in U.S. Pat. No. 11,135,035, the disclosure of which is incorporated by reference herein.

Referring now toFIG.2B, the robot arm40is illustrated with the effector assembly44thereon. In this example, a vertebra212is illustrated. The vertebra is the pivot point214of the instrument68and the effector assembly44. Lateral forces are illustrated by the arrow216. Longitudinal forces are illustrated by the arrow218inFIG.2C. The lateral force216is due to the surgeon and the tool to patient reactive force. The forces and deflection are relative to the robotic arm and the patient. The robotic arm motion causes a deviation which may be undesirable but monitored. The patient motion may be monitored or unmonitored. Arm motion and patient motion based on the energy balances at the end of the arm40at the effector44are described below.Drill Longitudinal Work=F*dInternal Energy=AUHeat=ΔQRotational Energy=½ [I ω]2Drill Rotation Work=T*θ=T*w*tLinear Spring Energy=½ [k(Δx)]2Rotational Spring Energy=½ [G (Δθ)]2

The work of the rotation by the drill is the product of T, the drill torque, ω, the rotation speed of the drill, and t, the time over which the work is done. The drill longitudinal work is the product of the force, F, of the drill and the distance, d. The rotational spring work uses the spring constant G and the angular distance θ through which the drill travels. The linear spring energy uses the spring constant, k, and the distance in the X direction to determine the spring work. The work also manifests in the energy U and heat Q at the vertebra.

The work may be balanced in an equation summing the work being done at different components. The energy balance at the vertebra212of the spine is simplified to be:

where the work of the rotation by the drill is the product of T, the drill torque, w, the rotation speed of the drill, and t, the time over which the work is done. The drill work Z is the product of the force, F, of the drill and the distance, d, and the angular distance Θ through which the drill travels. The work also manifests in the energy U and heat Q at the vertebra.

Because patient rotation and Shanz arm force resistance is zero. The formula for energy balance is simplified above. The lateral forces are due to the surgeon and surgeon tool lateral forces at216. In this example, the tool slides freely in the arm axially relative to the longitudinal axis314of the end effector assembly44. There are no vertical forces to the arm40and there is no rotational torque to the tool insertion device described below.

Referring now toFIGS.2D and2E, the reactive force222and longitudinal force224are illustrated. In this example, there is right lateral force and a Shanz force that is parallel with the spine as illustrated in 224. Therefore, the Shanz arm force does not resist lateral forces. In this example, the work balance formula is:

All of the elements are described above except the patient translation which is half of the product of the stiffness spring constant due to the patient's anatomy's deflection under load, kptn, and the square of the lateral distance moved by the patient.

Referring now toFIGS.2F and2G, a lateral force226is illustrated while a reaction force228is illustrated inFIG.2G. In this example, cranial tilt, a Shanz parallel force is provided relative to the spine and does not resist a compressive force. In this example, the work force equation is the same as that directly above.

Referring now toFIGS.2H and21, in this example, there is the force228in a lateral direction and force230illustrated inFIG.21having an upward or direction away from the vertebra. In this example, a caudal tilt force, a Shanz force is parallel to the spine and resists a tensile force. The work equation is simplified to:

Referring now toFIGS.2J and2K, forces232and234are illustrated. In this example, the forces232and234correspond to caudal tilt and a broken Shanz arm parallel with the spine. The forces set forth herein simplify to:

Referring now toFIGS.2L and2M, forces236and238are illustrated and correspond to a right lateral tilt and a Shanz force perpendicular to the spine. The Shanz force does not resist compressive force. The work equation simplifies to:

Referring now toFIGS.2N and20, forces240and242are illustrated. In this example, a left lateral tilt in Shanz force perpendicular to the spine are illustrated. The Shanz arm resists a tensile force. The simplified work equation is set forth as:

Referring now toFIGS.2P and2Q, forces244and246are illustrated. In this example, a right lateral tilt force and a Shanz force parallel with the spine are illustrated. The Shanz force does not resist lateral force. In this example, the drill grips the surface but does not drive into the vertebra212. The work equation simplifies in this case to:

Referring now toFIG.3A, the end effector assembly44is illustrated in a simplified view. The effector assembly44is an elongated guide tube as illustrated above inFIGS.2A-2Q. The end effector assembly44has an end effector support310and a tool insertion device312disposed therein. In this example, the tool insertion device312is concentric or coaxial with the end effector support310about the longitudinal axis314when in rigid mode. In this example, the end effector support310and the tool insertion device312are tubular and circular in shape and define an annular space315therebetween. InFIG.3A, the end effector support310is held rigid to the tool insertion device312. That is, the tool insertion device312is held rigidly inside the end effector support310.

A rigid coupling mechanism such as a plurality of radially extending pins316A,316B and316C are disposed axially and hold the tool insertion device312fixed relative to the end effector support310. As mentioned above, the forces of a tool being inserted into the tool insertion312may have a plurality of forces that are transmitted to the end effector support310. The end effector support310may then transmit the forces or vibrations to the robotic arm40illustrated above. The end effector support310is affixed rigidly to the robotic arm40and therefore the vibrations travel from the effector support310to the robotic arm40. The pins316A,316B and316C are retractably coupled to the end effector support310so as to allow compliant coupling.

Referring now toFIGS.3A and3B, a compliant mechanism such as springs318A,318B and318C are illustrated between the inner wall of the end effector support310and the outer wall of the tool insertion device312. The springs318A,318B and318C are illustrated as coil springs. However, other types of spring or compliant mechanisms may be used. For example, the compliant mechanisms may include but are not limited to coil springs, leaf springs, torsional springs, compression springs, rounds springs, foam, foam rubber and other compressible material. InFIG.3A, the springs318A-318C do not act to rigidly hold the tool insertion device312within the end effector support310. However, when vibrations are sensed at the effector assembly44, the pins316A-316C may be retracted or removed so that the end effector support310has the tool insertion device312rigidly decoupled therefrom. That is, the springs318A-318C act as the compliant mechanism to allow compliance in the movement of the tool insertion device312and to hold the tool insertion device312in place. Therefore, the vibrations and forces provided by the tool on the tool insertion device312are reduced so as not to be undesirable at the end effector support310.

In this manner, the amount of forces or vibration from the effector assembly44is reduced or eliminated relative to the robot arm40. In a compliant mode, the tool insertion device312moves within and relative to the end effector support310. The movement may be caused by the vibration of the tool and thus the vibration at the tool insert device312. The compliant mechanism locally expands and contracts to absorb he vibrations and prevents or reduced the vibration at the end effector support310. In compliant mode, the tool insertion device312may not be concentric relative to the end effector support310. The tool insertion device312is held within the end effector support310with the complaint mechanism.

Referring now toFIGS.3C and3D, a cutaway view of the effector assembly44is illustrated. In this example, three sets or levels or rows of axially place support pins316A-316C are illustrated. That is, a plurality of pins may be required depending upon the length of the effector. The outboard most pins316A and316A″ be used together with pins316B-316B″. Pins316C and316C″ are not illustrated in this cutaway view as they are out of view but present behind the tool insertion device312. In some examples, only pins located near the center of the length of the effector assembly44may be used. In this example, pins316A′-316B′ are set forth in the center of the length. The pins316A-316C′″ are illustrated in a rigid mode. However, the dotted lines illustrate where the pins316A-316C″ may be in a compliant mode or retracted mode. The pins inFIGS.3A-3Ctogether with the actuator such as a solenoid, motor, (now shown inFIGS.3A-3C) may be referred to as a coupler320.

InFIG.3C, two sets of springs318A-318C and318A′-318B′ are illustrated. Various numbers of sets of springs may be implemented. For example, only one set of springs may be provided or a spaced apart set of springs may be provided depending upon the system requires and the forces required to be overcome. Of course, if foam or foam rubber is used the foam or foam rubber may continuously surround the inner device may be pieces spaced apart within the annular space315.

Referring now toFIGS.4A and4B, a second example of a coupler320′ is illustrated. In this example, the coupler320′ is a rigid coupling mechanism illustrated as a plurality of cams330A,330B and330C. The cams330A-330C have motors that are used to rotate the cams into and out of the positions illustrated inFIGS.4A and4B. The cams330A,330B and330C are actuators that are used to change modes. In the mode illustrated inFIG.4A, the tool insertion device312is compliant and therefore can move relative to the end effector support310as resisted by the springs. InFIG.4B, the cams330A-330C are rotated into engagement with the tool insertion device312by the motors332A-332C. The motors332A and cams330A may be referred to later as an actuator.

As illustrated inFIG.3C, sets of cams330A-330C and springs318A-318C may be disposed in different positions within the longitudinal length of the effector44.

Referring now toFIG.5, another example of a coupler320″ that acts as the rigid coupling mechanism is illustrated. In this example, the coupler320″ comprises a plurality of fasteners such as screws340A-340C. The screws340A-340C extend through the wall of the end effector support310. The coupler320″ also includes a plurality of motors342A,342B and342C that are coupled to respective screws340A-340C The motors may be a stepper motor or a solenoid. It should be that the screw340A is illustrated in a retracted position so that effector44is in a compliant mode. The screws340B and340C are illustrated in the rigid mode. When desired, the screws340A-340B are rotated from one mode to another mode. As mentioned above, the screws340A-340C may be retracted to reduce transmission of vibration and therefore enter a compliant mode. Although screw340A is shown retracted, all three screws340A-340C may be moved simultaneously during a procedure.

Referring now toFIG.6, another example of a coupler320″ is illustrated. The coupler320′″ acts as a rigid coupling mechanism that has a plurality of retractable pneumatic cylinders350A-350C. In a similar manner to that illustrated inFIG.5, the pneumatic cylinders350A-350C may operate simultaneously. However, in this example, the cylinder350A is shown in a retracted or compliant position. The cylinders350B and350C are illustrated in a rigid position. The cylinders350A-350B have a pump that provide pressure or air to the pneumatic cylinders350A-350C. An accumulator354provides a reservoir for air to be provided or within from the cylinders350A-350C. It should be noted that the pneumatic cylinders may also be replaced by hydraulic cylinders with hydraulic fluid therein. In this example, passages356A,356B and356C are provided through the wall forming the end effector support310. The pump352and the pneumatic cylinders350A-350C form the actuator for switching between a compliant mode and a rigid mode as described above.

The example ofFIG.6may be configured with many groups of compliant mechanisms such as the springs318A-318C and groups of rigid mechanisms such as the pneumatic cylinders350A-350C at different positions along the length of the effector assembly similar to that set forth inFIG.3C.

Referring now toFIG.7A-7C, an effector44in a fourth example of a rigid coupling mechanism, a coupler320IV, is set forth. In this example, a first set of stops360A,360B and360C extend axially from the end effector support310. A second plurality of stops362A,362B and362C extend axially from the tool insertion device312. In a rigid position as illustrated inFIG.7A, the stops360A-360C line up respectively with respect to the stops362A-362C. The stops form a similar configuration to the pins illustrated in FIG.3A. However, inFIG.7B, the stops360A-360C are misaligned with the stops362A-362C. That is, inFIG.7B, a compliant mode is entered wherein the springs318A-318C hold the tool insertion device312within the end effector support310.

InFIG.7C, the tool insertion device312is illustrated relative to the end effector support310. In this example, the stops360A are engaged with stop362A and stop360B is engaged with stop362B. In this example, two sets of springs318A,318B and318A′ and318B′ are illustrated. In this example, a motor364is used as part of the actuator. The motor364rotates the relative position of the tool insertion device312and the end effector support310. A small rotation may be provided by the motor364to the tool insertion device312or the end effector support310so that the sets of stops are misaligned when needed. Of course, the motor364may realign the stops when the rigid mode is to be entered. The mode acts as part of the coupler320IV.

As illustrated best inFIG.7B, the springs318A-318C flex but are compliant enough to allow the position of the tool insertion device to move and prevent the transmission of vibration or movement to the end effector support310.

Referring now toFIG.8, the system may be automatically controlled by a controller810or manually controlled by the surgeon. The system may be stand-alone or incorporated into a controller such as the controller110described above. The controller810may be microprocessor-based and is programmed to perform various steps including controlling an actuator812in response to a vibration from an effector vibration sensor814A or a robotic arm vibration sensor814B. The controller810may be one of the controllers described above such as the controller110which acts as the robotic control system. That is, the vibration sensor814A may be positioned on the outside, inside or end of the effector assembly44or the tool insertion device. The vibration sensor814B may be fixed to one of the segments of the robot arm40. Upon sensing a natural frequency vibration at one of the vibration sensors814A,814B (with an amplitude above a predetermined threshold), the controller810may automatically control one of the actuators812illustrated inFIGS.3-7should the vibrations reach a threshold level. The actuator812may move the mechanical coupling mechanism relative to the effector assembly so that the end effector support310is rigidly disengaged with the tool insertion device312to cease the rigid mode and enter a compliant mode. The compliant device allows the tool insertion device312to maintain a position within the end effector support310. The vibration sensors814A,814B provide vibration signals to the controller810. When the vibration ceases after the compliant mode is entered (amplitude below a predetermined threshold), the vibration sensor814may allow the controller810to control re-engagement of the rigid coupling mechanism in the rigid mode. That is, the actuator812may hold the tool insertion device relative to the end effector support310.

The system may also be used in a manual mode. A user interface820may be located external to the effector assembly44to initiate manually decoupling of the end effector support310from the tool insertion device312. A foot pedal, button, dial or the like, may be used by the surgeon as the user interface820. Upon sensing vibration, the effector assembly44is switched from the tool insertion device312being coupled in the rigid mode to a compliant mode. The surgeon may do this by feel or in response to a warning indicator822such as a buzzer or a light. That is, when a vibration in the natural frequency greater than a predetermined amplitude is sensed at the robotic arm or the effector assembly, a warning signal (light and/or sound), may be generated. The warning signal may be generated at the display84of the workstation98. After the vibration or movement ceases, the user interface820may be used to re-engage the actuator812to re-enter a rigid mode. Of course, the controller810may be part of the surgery system and integrated in the controller110.

With reference toFIG.9, a process430is illustrated. The process430is used to switch modes from a rigid mode to a compliant mode at the effector44and may be included in a guided surgery procedure.

The process430may start in start Block440.

In Block442. the patient position is registered into the system. The robotic arm in Block444is also registered and located into the robotic surgery system.

In Block450, the robotic system20may then move the effector assembly44in a manner based on known anatomy. As illustrated above, inFIGS.2A-2Q, the effector assembly44may be moved into various positions relative to the patient. The robot arm40is used to move the variable stiffness effector assembly44to the desired position that can be tracked by the navigation system. In one example, the end effector support310and the tool insertion device2312are in a rigid mode.

In Block452, the tool is inserted into the tool insertion device. In Block454, the tool, such as a drill, is activated or operated.

In Block456, the vibration sensors are monitors to determine whether unwanted drill vibration or skiving is detected. As mentioned above, the detection of vibration or the vibration associated with skiving may be detected at a vibration sensor that detects a certain frequency or a vibration that is above a certain amplitude threshold. The surgeon may also detect the unwanted vibration through visual, audible or a tactile feeling of the effector assembly44, the robotic arm or the tool.

In response to the vibrations from the vibration sensor814A or814B, or the user interface820, Block462may generate a warning signal and the tool insertion device312is automatically rigidly decoupled from the effector support310. That is, the tool insertion device is placed into a compliant mode in Block464. The surgeon may then continue operating the tool within the tool insertion device in block466.

In Block468, if the vibration is not present, the tool insertion device remains decoupled from the effector in Block464. In Block468, if the vibration has ended, Block454continues the process of operating the tool.

The apparatuses and methods described in this application may be partially or fully implemented by a processor (also referred to as a processor module) that may include a special purpose computer (i.e., created by configuring a processor) and/or a general purpose computer to execute one or more particular functions embodied in computer programs. The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may include a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services and applications, etc.

The computer programs may include: (i) assembly code; (ii) object code generated from source code by a compiler; (iii) source code for execution by an interpreter; (iv) source code for compilation and execution by a just-in-time compiler, (v) descriptive text for parsing, such as HTML (hypertext markup language) or XML (extensible markup language), etc. As examples only, source code may be written in C, C++, C#, Objective-C, Haskell, Go, SQL, Lisp, Java®, ASP, Perl, Javascript®, HTML5, Ada, ASP (active server pages), Perl, Scala, Erlang, Ruby, Flash®, Visual Basic®, Lua, or Python®.

Communications may include wireless communications described in the present disclosure can be conducted in full or partial compliance with IEEE standard 802.11-2012, IEEE standard 802.16-2009, and/or IEEE standard 802.20-2008. In various implementations, IEEE 802.11-2012 may be supplemented by draft IEEE standard 802.11ac, draft IEEE standard 802.11ad, and/or draft IEEE standard 802.11ah.

A processor, processor module, module or ‘controller’ may be used interchangeably herein (unless specifically noted otherwise) and each may be replaced with the term ‘circuit.’ Any of these terms may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.