Compact Differential Coaxial Inductive Force Sensor

Abstract

Various applications may include devices and / or methods of providing an axial force transducer. Two coils coaxially wound relative to each other may be used with a magnet to determine a distance traveled based on applying an axial force to an instrument component. The two coils and magnet may be configured in a variety of ways relative to the instrument component. In various embodiments, the difference between the inductance associated with one of the two coils together with its relationship to the magnet and the inductance associated with the other of the two coils together with its relationship to the magnet may be used to determine an axial force on the instrument component that is associated with the distance traveled. Additional devices, systems, and methods are disclosed.

Description

[0001] Related Applications

[0002] This patent application claims the benefit of priority and filing date of U.S. Provisional Patent Application No. 62 / 901,729, filed on September 17, 2019, entitled “COMPACT, DIFFERENTIAL, COAXIAL INDUCTIVE FORCE SENSOR,” which is incorporated herein by reference in its entirety. This application is related to U.S. Provisional Patent Application No. 63 / 077,833, filed on September 14, 2020, entitled “Devices and Methods for Compact, Redundant Inductive Force Sensor,” which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments described herein relate to force sensing mechanisms, more particularly to medical devices, and further particularly to instruments for minimally invasive surgery. More particularly, embodiments described herein relate to medical devices including a force sensor unit coupled to a mechanism of the medical device and used to measure an axial force applied to an end effector of the medical device during a surgical procedure. Background Art

[0004] Minimally invasive medical technology aims to reduce the amount of tissue damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort and harmful side effects. Remotely operated surgical systems using robot-assisted technology can be used to overcome the limitations of manual laparoscopy and open surgery. The advancement of remote presentation systems provides surgeons with a field of view in the patient's body, increases the degree of motion of surgical tools, and provides the ability of long-distance surgical collaboration. In a remotely operated surgical system, the tool operator can actuate the input of the main control device to send a control signal to a mechanical control device located at the proximal portion of the elongated tool shaft to control the movement of a connector (e.g., cable) or a connector-hypotube combination extending within the length of the shaft, thereby controlling the movement of the end effector located at the distal portion of the tool shaft. The control connector or connector-hypotube combination is usually pre-tensioned so that the surgical tool at the surgical site can respond quickly and accurately to the actuation signal. Therefore, direct natural force feedback to the tool operator is largely eliminated because such a tool user does not directly manipulate the tool manually.

[0005] For example, a force sensor may be disposed at or near the tool shaft to measure clinical forces applied to patient tissue due to contact with the end effector during a medical procedure. For example, these force measurements at or near the tool shaft may be used to generate tactile feedback forces at the input of a master control device, thereby providing an indication to the user of the forces applied by the tool to the patient tissue. Enhancements to the force sensor system may result in more accurate force measurements, which in turn may produce more accurate tactile feedback. Summary of the invention

[0006] This overview introduces certain aspects of the embodiments described herein to provide a basic understanding. This overview is not an extensive review of the subject matter of the present invention, and it is not intended to identify key or important elements of the subject matter of the present invention or to describe the scope of the subject matter of the present invention. In some embodiments, a device includes a mechanical structure and a force sensor unit coupled to the mechanical structure. The force sensor unit includes a rod, a magnet coupled to the rod, a first coil coupled to the mechanical structure, and a second coil coupled to the mechanical structure and coaxial with the first coil. The rod includes a distal portion and a proximal portion, and the central axis of the rod is defined between the proximal portion and the distal portion of the rod. The magnet translates along the central axis of the rod within the first coil and the second coil.

[0007] In some embodiments, the device further comprises a shaft coupled to the mechanical structure, and the shaft is operably coupled to the rod such that translational movement of the shaft relative to the mechanical structure causes the rod to move along a central axis of the rod. In some embodiments, the shaft comprises a proximal end and a distal end, and the central axis of the shaft is defined between the proximal end and the distal end of the shaft. The shaft is coupled to the mechanical structure such that a linear displacement of the shaft along the central axis of the shaft is proportional to a force applied to the shaft in a direction along the central axis of the shaft.

[0008] In some embodiments, the central axis of the rod is in a direction parallel to the central axis of the shaft. In some embodiments, the shaft includes a proximal end and a distal end, and the central axis of the shaft is defined between the proximal end and the distal end of the shaft. The first signal generated by the first coil is associated with the position of the magnet relative to the first coil, and the second signal generated by the second coil is associated with the position of the magnet relative to the second coil. Wherein the first signal from the first coil and the second signal from the second coil are associated with the linear displacement of the shaft along the central axis of the shaft.

[0009] In some embodiments, the linear displacement of the shaft is proportional to the force applied to the shaft in the direction of the central axis of the shaft. In some embodiments, the shaft includes a proximal end and a distal end, and the central axis of the shaft is defined between the proximal end and the distal end of the shaft. In such embodiments, the device also includes a spring coupled to the shaft, and the spring is configured to displace in proportion to the force applied to the shaft in the direction of the central axis of the shaft.

[0010] In some embodiments, a first signal generated by the first coil is associated with a position of the magnet relative to the first coil, and a second signal generated by the second coil is associated with a position of the magnet relative to the second coil. The force sensor unit includes a microprocessor coupled to receive the first signal and the second signal.

[0011] In some embodiments, the first signal has a first frequency, the second signal has a second frequency different from the first frequency, and the microprocessor is configured to execute instructions to determine a linear displacement of the shaft along a central axis of the shaft based on the first frequency and the second frequency.

[0012] In some embodiments, the apparatus includes a first magnet and a second magnet. The first magnet is positioned to move within the first coil, and the second magnet is positioned to move within the second coil.

[0013] In some embodiments, a medical device includes: an instrument shaft including a proximal end and a distal end; a medical end effector coupled to the distal end of the shaft; a mechanical structure coupled to the proximal end of the shaft; and a force sensor unit coupled to the mechanical structure and the instrument shaft. The force sensor unit includes a first coil wound on a first coil axis, a second coil wound on a second coil axis and coaxial with the first coil axis, and a magnet. The instrument shaft axis is defined between the proximal end and the distal end of the instrument shaft, and the magnet is operably coupled to the instrument shaft and moves along the first coil axis as the instrument shaft moves along the instrument shaft axis.

[0014] In some embodiments, the magnet moves within the first coil as the instrument shaft moves along the instrument shaft axis. In some embodiments, the magnet moves within the first coil and within the second coil as the instrument shaft moves along the instrument shaft axis. In some embodiments, the force sensor unit includes a rod, and the rod is axially aligned with the first coil axis and couples the magnet to the instrument shaft.

[0015] In some embodiments, a first signal generated by the first coil is associated with a position of the magnet relative to the first coil, and a second signal generated by the second coil is associated with a position of the magnet relative to the second coil. The force sensor unit includes a microprocessor coupled to receive the first signal and the second signal.

[0016] In some embodiments, the first signal has a first frequency and the second signal has a second frequency.The microprocessor is configured to execute the instructions to determine a measure of force on the instrument shaft along an axis of the instrument shaft based on the first frequency and the second frequency.

[0017] In some embodiments, at a unique position of the magnet relative to the first coil and the second coil, a first signal is generated by the first coil and a second signal is generated by the second coil, and the first signal from the first coil and the second signal from the second coil are associated with a unique linear displacement of the instrument shaft along the axis of the instrument shaft.

[0018] In some embodiments, the medical device further comprises a spring coupled to the shaft and the mechanical structure, and the spring is configured to displace in proportion to a force applied to the instrument shaft in a direction along an axis of the instrument shaft.

[0019] In some embodiments, the medical device includes an instrument support structure, an instrument shaft, and a force sensor unit. The instrument shaft includes a proximal end and a distal end, and the instrument shaft axis is defined between the proximal end and the distal end of the instrument shaft. The force sensor unit includes a first coil wound on a first coil axis, a second coil wound on a second coil axis and coaxial with the first coil axis, and a magnet at least partially within one of the first coil and the second coil. The first coil, the second coil, and the magnet are positioned so that translation of the instrument shaft relative to the instrument support structure along the instrument shaft axis causes relative movement between the magnet and the first coil along the first coil axis and relative movement between the magnet and the second coil along the second coil axis. In some embodiments, the first coil and the second coil are fixed relative to the instrument support structure.

[0020] In some embodiments, the medical device includes a proximal mechanical structure, a distal mechanism, and a connecting member. The distal mechanism is coupled to the distal end of the instrument shaft and includes a movable component. The proximal mechanical structure includes an instrument support structure and an actuator input member mounted to move relative to the instrument support structure. The connecting member is coupled between the actuator input member and the movable component of the distal mechanism and transmits a tensile force, a compressive force, or both a tensile force and a compressive force from the actuator input member to the movable component of the distal mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] When with Figure 1 Various aspects of the present disclosure can be best understood from the following detailed description when read together. It should be emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the sizes of various features can be arbitrarily increased or reduced for clarity of discussion. In addition, the present disclosure may repeat figure numerals and / or letters in various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate the relationship between the various embodiments and / or configurations discussed.

[0022] Figure 1 is an illustrative plan view of a minimally invasive teleoperated surgical system for performing minimally invasive diagnostic or surgical procedures on a patient lying on an operating table, in accordance with various embodiments.

[0023] Figure 2 is a perspective view of a surgeon's console according to various embodiments.

[0024] Figure 3 is a perspective view of a patient side cart of a minimally invasive teleoperated surgical system according to various embodiments.

[0025] Figure 4A is an illustrative side view of a medical device including a distal portion and a proximal mechanical structure coupled to each other via an elongated shaft defining an inner bore, according to various embodiments.

[0026] Figure 4B According to various embodiments Figure 4A An illustrative bottom view of a medical device showing a control surface of an input device.

[0027] Figure 4C is a schematic illustration of a medical device including a force sensor unit according to an embodiment.

[0028] Figure 5A-5H Components of an example force sensor unit are illustrated in accordance with various embodiments.

[0029] Fig. 6A A mechanical structure according to various embodiments is shown, which can be coupled to a Figure 5A-5H The axis of the instrument in question.

[0030] Figure 6B It shows various embodiments Fig. 6A A mechanical structure in which a double coil has a rod inserted into the double coil, wherein the rod is fixed to a support base to couple to Fig. 6A The axis of the instrument.

[0031] Figure 7 is a block diagram of an example force sensor that may be implemented to measure an axial force applied to an instrument shaft in accordance with various embodiments.

[0032] Figure 8A-8C Shown are measurements of the inductance of two coils versus target position for a magnetic target according to various embodiments.

[0033] Fig. 9 is a flow chart of features of an example method of determining axial force in accordance with various embodiments. DETAILED DESCRIPTION

[0034] The following detailed description refers to the accompanying drawings, which illustrate various embodiments of the present invention by way of illustration. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice these and other embodiments. Other embodiments may be utilized, and structural, logical, mechanical and electrical changes may be made to these embodiments. Various embodiments are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments. Therefore, the following detailed description should not be construed as limiting.

[0035] The embodiments described herein can be advantageously used in a variety of force sensor applications, such as for grasping, cutting, and manipulation operations associated with minimally invasive surgery. The embodiments described herein can also be used in various non-medical applications, such as remotely operated systems for search and rescue, remotely controlled diving devices, aviation devices, and automobiles. The embodiments described herein can also be used to determine the force applied to (or by) the distal portion of an instrument during use.

[0036] The medical device described herein includes a force sensor unit that includes a compact differential inductive force sensor to measure the force applied axially to the end effector of the medical device in the z-axis direction. As described herein, two inductive coils are coaxially wound on a cylinder, and a magnet (e.g., a ferrite bead, an EMI (electromagnetic interference) suppression bead, a nickel-zinc bead, etc.; the term "magnet" is described in more detail below) held by a rod is movably positioned within the coil. When the magnet moves axially within the coil, the inductance at each coil changes. The change in inductance at each coil can be used to measure changes in the position of the instrument axis, which can be converted into a z-axis force measurement.

[0037] Figure 1 1 is an example illustrative plan view of a minimally invasive teleoperated surgical system 10 for performing minimally invasive diagnostic or surgical procedures on a patient 12 lying on an operating table 14. The system includes a surgeon's console 16 for use by a surgeon 18 during the procedure. One or more assistants 20 may also participate in the procedure. The minimally invasive teleoperated surgical system 10 also includes one or more patient side carts 22 and an electronic equipment cart 24. The patient side cart 22 can manipulate at least one medical device 26 (such as a surgical instrument) through a minimally invasive incision in the patient 12 while the surgeon 18 observes the surgical site through the surgeon's console 16. An image of the surgical site can be obtained through an endoscope 28 (such as a stereo endoscope), which can be positioned using a mechanical support arm 72 associated with the patient side cart 22 to orient the endoscope 28 to capture an image of the surgical site.

[0038] The computer processor located on the electronic equipment cart 24 can be used to process an image of the surgical site for subsequent display to the surgeon 18 via the surgeon's console 16. In addition, the computer processor at the electronic equipment cart 24 can be configured to process electrical or optical signals indicating the force applied to the medical device. For example, the computer processor can generate tactile feedback at the surgeon's console 16. In various embodiments, stereoscopic images can be captured, which allows for the perception of depth during the surgical procedure. The number of medical devices 26 used at one time generally depends on the diagnostic or surgical procedure and the space limitations within the surgical site, as well as other factors. If it is necessary to replace one or more of the medical devices 26 being used during the surgical procedure, the assistant 20 can remove the medical device 26 from the mechanical support arm 72 associated with the patient side cart 22 and replace it with another medical device 26 in the tray 30 of the operating room.

[0039] Figure 2 is a perspective view of an embodiment of an example surgeon's console 16. The surgeon's console 16 may include an observer display 31 including a left eye display 32 and a right eye display 34 for presenting a coordinated stereoscopic view of the surgical site to the surgeon 18, the view enabling depth perception. The console 16 may also include one or more hand-operated master control inputs 36, 38 to receive larger-scale manual control movements. One or more slave medical devices 26 mounted for use at one or more corresponding mechanical support arms 72 of the patient side cart 22 are capable of moving at smaller-scale distances that match the larger-scale manipulation of the one or more master control input devices 36, 38 by the surgeon 18. The master control input devices 36, 38 may provide the same mechanical degrees of freedom as their associated medical devices 26 to provide telepresence to the surgeon 18, or the master control input devices 36 are integrated with the slave medical devices 26 so that the surgeon has a keen sense of direct control of the tool 26. To this end, position, force, and / or tactile feedback sensors (not shown) may be employed to determine tool position, and measure force, and measure tactile sensation at the tool 26. The determined tool position and force may be used to generate tactile feedback on the surgeon's hand via the control input devices 36, 38. Electrical or optical signals modulated based on the force detected at the force sensor (not shown) at the tool 26 may be processed by a processor at the electronics cart 24 to generate tactile feedback at the control input devices 36, 38, which may indicate the magnitude and direction of the detected force.

[0040] Figure 32 is a perspective view of an embodiment of an example patient side cart 22 of a minimally invasive teleoperated surgical system 10. The patient side cart 22 may include four mechanical support arms 72. Each support arm 72 may include an articulated support arm segment 73 pivotally mounted end to end and a support forearm 74 pivotally mounted. A corresponding medical device carriage 75 including a motor for controlling tool movement is mounted at each support forearm 74. In addition, each of the support arms 72 may optionally include one or more assembly joints (e.g., unpowered and / or lockable) at the junction of the support arm segment 73 and at the junction with the support forearm 74, and the support forearm 74 may be used to position the attached medical device carriage 75 in relation to the patient 12 undergoing surgery. Each medical device 26 may be removably connected to the carriage 75. Although the patient side cart 22 is shown as including four support arms 72, more or fewer support arms 72 may be used. Typically, at least one of the medical devices will include a vision system, which typically includes an endoscopic camera tool (not shown) for capturing video images and one or more video displays for displaying the captured video images, and the vision system can be coupled to one of the slides 75.

[0041] The various medical devices 26 and cannulas 27 may be removably coupled to the carriage 75, with the tool shaft portion 410 of the medical device 26 inserted through the cannula 27. The carriage 75 may house a plurality of remotely operated actuators, such as motors (not shown), which impart motion to drive members, such as drive shafts and capstans (not shown), which in turn drive connectors coupled to end effectors, and the medical device 26 translates the motion into various movements of the end effectors on the medical device 26. In various embodiments, the remotely operated actuators in the carriage 75 may impart motion to various components of the medical device 26, such as, for example, end effector wrist movements or gripper movements.

[0042] The surgeon manipulates the master control input device 36, 38 to control the tool end effector. The input provided by the surgeon or other medical personnel to the control input device 36 or 38 ("master" command) is converted into a corresponding action ("slave" response) performed by the medical device 26 through the actuation of one or more remote motors. In some embodiments, a flexible cable-based force transfer mechanism or the like can be used to transfer the motion of each remotely located, remotely operated motor to a corresponding tool docking capstan (which acts as an actuator or actuator input) located at the carriage 75. In various embodiments, the mechanical adapter interface 76 mechanically couples the connector drive member within the tool 26 to the motor within the carriage.

[0043] The term "medical device" is used herein to describe a medical device for insertion into a patient and for performing a surgical or diagnostic procedure. A medical device typically includes an end effector associated with one or more surgical tasks, such as forceps, needle drivers, scissors, bipolar cauterizers, tissue stabilizers or retractors, clip appliers, stapling devices, imaging devices (e.g., endoscopes or ultrasound probes), and the like. In various embodiments, some medical devices may also provide articulated support for the end effector, sometimes referred to as a "wrist," so that the position and orientation of the end effector may be manipulated in one or more mechanical degrees of freedom relative to the axis 410 of the tool. In addition, many surgical end effectors may include functional mechanical degrees of freedom, such as a clamp that opens or closes, or a knife that translates along a path.

[0044] Surgical instruments suitable for use in one or more embodiments of the present disclosure may control their end effectors with one or more connectors, which may be, for example, rods and / or flexible cables. In some examples, the rod, which may be in the form of a tube, may be combined with a cable to provide a "push / pull" or "pull / pull" control of the end effector, a pull, a push, or a combination thereof, wherein the connector provides a flexible section as required. The typical elongated tool shaft 410 for medical devices is very small, for example, five to eight millimeters in diameter. The small scale of the mechanisms in surgical instruments creates unique mechanical conditions and problems associated with the construction of these mechanisms that are different from those found in similar mechanisms constructed on a larger scale, because the force and strength of the material do not scale at the same rate as the size of the mechanism. The connector must fit within the elongated tool shaft 410 and be able to control the end effector through a wrist joint. The connector may be made of a variety of metal (e.g., tungsten or stainless steel) or polymer (e.g., high molecular weight polyethylene) materials.

[0045] Figure 4A4 is an illustrative side view of a medical device 26 including a distal portion 420 and a proximal mechanical structure 422, which are coupled to each other by an elongated shaft 410 defining an inner bore. As used herein, the term "proximal" refers to a location closer to the center of the body or attachment point, while the term "distal" refers to a location farther from the center of the body or attachment point. For example, the term "proximal" refers to a location closer to a manipulator arm, while the term "distal" refers to a location farther from the manipulator arm. The mechanical structure 422 may include a support structure, which may include, for example, a housing 425 supporting an input device 429. The input device 429 may include an instrument control surface 427. In other embodiments, various support structures may be optionally used, such as a chassis, a frame, a bed, an integral surrounding outer body of the mechanical structure, and the like. The input device facilitates controlled adjustment of the end effector of the instrument via a connector extending along the inner bore of the elongated tool shaft 410 (which serves as, for example, a tension member for actuating the end effector). In some embodiments, the connector may be a cable, a strap, or the like.

[0046] The control surface 427 provides a mechanical connection to other control features of the medical device 26. During use, the instrument control surface 427 is coupled to the medical device carriage 75 (see Figure 3 ), which provides a motor-driven rotational force to a steering input device 432 at a control surface 427 to control the medical device 26. The distal portion 420 of the medical device 26 can be fixed to any of a variety of end effectors, such as the forceps 428 shown, a needle driver, a cauterization device, a cutting tool, an imaging device (e.g., an endoscope or an ultrasound probe), or a combination device including a combination of two or more different tools and imaging devices. In addition, in the illustrated embodiment, the forceps 428 are coupled to the elongated tool shaft 410 via a wrist joint 430, which allows the orientation of the forceps to be manipulated relative to the elongated tool shaft 424.

[0047] Figure 4B yes Figure 4Aillustrative bottom view of an example medical device of , showing a control surface 427 of an input device 429. For example, the control surface 427 can be placed on the top of a carriage 75, and the carriage 75 includes an actuator, such as a motor (not shown), controlled by a control signal generated in response to a user input at the control input device 36, 38. As shown, the control surface 427 includes a plurality of steering input devices 432, each steering input device controls different aspects of the movement performed by the wrist joint 430 and the forceps 428. Of course, more or less steering input devices 432 can be provided in different embodiments. When the control surface 427 is coupled to the tool carriage 75, each of the steering input devices 432 is docked with an actuator (e.g., a servo motor, not shown) driving the steering input device in the carriage 75. In this example, the steering input device 432 is configured to form a direct mechanical engagement with a corresponding rotary actuator (e.g., a servo motor) of the tool carriage 75. However, other suitable configurations for power transmission may also be used (e.g., indirect mechanical couplings, including speed converters and / or torque converters, fluid couplings, and / or electrical couplings). For example, each of the steering input devices 432 is part of a limited slip winch and drive shaft assembly that operates a drive cable that controls movement of an end effector (such as, tweezers 428). In various embodiments, the mechanical structure 422 can be configured as a rear end housing that includes a force sensor unit 440 to detect an axial force at the distal end of the elongated shaft 410. The force sensor unit 440 can be disposed in the mechanical structure 422 in many arrangements. For example, a portion of the force sensor 440 can be disposed on the elongated shaft 410.

[0048] The design of a compact axial force sensor unit with components small enough to fit on the proximal end of an instrument shaft can be achieved using a target material associated with multiple coils to generate signals that can be compared to determine axial movement of the instrument shaft in response to an axial force applied to the distal end of the instrument shaft. The design described herein is temperature stable, robust to burn disturbances, and withstands high pressure steam cleaning. The force sensor unit is frictionless and therefore does not interfere with the force being measured.

[0049] In various embodiments, a dual-coil distance displacement sensor can be used in conjunction with a spring or flexure to determine the axial force applied to the instrument shaft. Since the force is bidirectional, the spring can be constructed as a bidirectional spring. The axial direction can be taken as the z-axis direction. The z-direction force acting on the distal end of the instrument shaft causes the instrument shaft to axially displace in the proximal direction of the instrument shaft. In the case where the spring is operably coupled to the proximal portion of the instrument shaft, the distance of the spring displacement is proportional to the z-direction force applied to the distal portion of the instrument shaft. The dual-coil displacement sensor may include a proximal coil and a distal coil, which are coaxially mounted at a fixed position on the support structure of the proximal mechanical structure to measure the axial displacement of the spring based on a change in magnetic flux through the coil or inductance within the coil, as described in more detail below.

[0050] The proximal end of the instrument shaft or a component coupled to the proximal end of the instrument shaft may include a magnet disposed thereon. Any magnet described herein may be, for example, a ferrite bead, an EMI suppression bead, a nickel-zinc bead, or any other suitable material. Therefore, in one aspect, it should be understood that the term "magnet" as used herein may refer to any component or material coupled to the instrument shaft that may be used to provide a signal indicating the position of the shaft within the coil when the magnet moves within the coil. The magnet may be in the form of a bead, but other forms may also be used. The magnet may be disposed or connected to the instrument shaft in a variety of ways. In the case where the magnet is connected to the instrument shaft, movement of the instrument shaft results in movement of the magnet. The proximal end of the instrument shaft (or an extension of the instrument, a rod, or the like) with the magnet thereon extends through the dual windings so that there is an air gap between the instrument shaft (or rod) with the magnet thereon and the dual coils. When "stationary", in the absence of a z-direction force applied to the instrument shaft, the instrument shaft may be axially positioned so that the magnet is partially disposed within each coil. In some embodiments, an equal portion of the magnets can be disposed within each coil in the absence of a z-directed force applied to the instrument axis. Each coil is coupled to a separate LC circuit in which the coil acts as an inductor (L) and the inductance varies with the amount of magnets contained in the coil. The resonant frequency of each circuit varies with the change in the inductance of the circuit. Materials other than magnetic materials may be used, where these other materials contribute to or affect the inductance associated with the coils used in the LC circuits. For example, these other materials may be used with respect to Figure 5A-Figure 9 in the configuration under discussion.

[0051] The inductance of each coil and therefore the resonant frequency of each circuit varies with the z-direction force on the distal portion of the instrument shaft. Where the spring is operably coupled to the proximal portion of the instrument shaft, the displacement of the spring in response to the z-direction force on the distal portion of the instrument shaft corresponds to the amount of axial displacement of the instrument shaft and the amount of axial displacement of the magnet thereon. The amount of axial displacement of the magnet determines the portion of the magnet that extends into each coil. For example, a greater z-direction force results in more magnets being disposed in the proximal coil than in the distal coil.

[0052] A frequency detection circuit can be used to detect the resonant frequency of a circuit including a proximal coil and a circuit including a distal coil. Each of the two circuits will have a resonant frequency defined by its coil and magnet, wherein the contribution of the magnet is based on the distance of the magnet in the z-direction within the respective coil. When the magnet is disposed more within the proximal coil than within the distal coil, the resonant frequency of the circuit using the proximal coil will be different from the resonant frequency of the circuit using the distal coil. The resonant frequency can be used to determine the axial displacement of the shaft, and therefore determine the amount of displacement of the spring, from which a measure of the z-direction force on the distal portion of the shaft can be determined accordingly.

[0053] Figure 4C 326 is a schematic illustration of a medical device 326 according to an embodiment. In some embodiments, the medical device 326 or any component thereof is optionally part of a surgical system for performing a surgical procedure, and the surgical system may include the above referenced Figure 1-4B The manipulator unit, a series of kinematic linkages, a series of cannulas, or the like. The medical device 326 and the medical devices described herein may include a mechanical structure 322 and a force sensor unit 340 coupled to the mechanical structure 322 or included in the mechanical structure 322, a shaft 310 coupled to the mechanical structure 322, and an end effector 328 coupled to the distal end of the shaft 310. The end effector 328 may include, for example, an articulated clamp or other suitable surgical tool coupled to the link 330. In some embodiments, the link 330 may be included in a wrist assembly having a plurality of articulated links. In some embodiments, the shaft 310 is also movably coupled to the mechanical structure 322 at a proximal portion. The mechanical structure 322 may include a component configured to move one or more components of the medical device, such as, for example, the end effector 328. The mechanical structure 322 may be similar to the mechanical structure 422 described herein.

[0054] Typically, during a medical procedure, the end effector 328 contacts anatomical tissue, which may cause forces in the X, Y, or Z directions to be exerted on the end effector 328 and may cause moments, such as Figure 4C The moment M about the y-axis is shown YIn some embodiments, one or more strain sensors (not shown), which may be strain gauges, may be included in the medical device 326 to measure strains that can be used to determine forces applied to the end effector 328 along the X and Y axis directions. These X and Y axis forces are transverse (e.g., perpendicular) to the Z axis (which is parallel or co-linear with the central axis of the shaft).

[0055] The force sensor unit 340 (and any force sensor unit described herein) can be used to measure the axial force(s) applied to the end effector 328 (i.e., in the Z-axis direction parallel to the central axis of the shaft). For example, an axial force applied to the end effector 328 in the Z-axis direction can cause the shaft 310 to be axially displaced in a direction along the central axis CA of the shaft 310. The axial force can be in the proximal direction (e.g., a reaction force generated by pushing tissue with the end effector), or it can be in the distal direction (e.g., a reaction force generated by pulling grasped tissue with the end effector). As described herein, the shaft 310 can be coupled to the mechanical structure 322 via a biasing mechanism (e.g., a spring member) so that the amount of travel of the shaft 310 relative to the mechanical structure 322 can be correlated to the magnitude of the axial force applied to the end effector 328. In this way, measuring the distance that the shaft 310 moves relative to the mechanical structure 322 can be used to determine the axial force.

[0056] In some embodiments, the force sensor unit described herein may include any suitable components to isolate axial movement of the shaft (i.e., to constrain the shaft so that the measured movement is caused only by axial forces and not by lateral forces along the X-axis and Y-axis) and to limit friction forces opposing the movement of the shaft (which friction forces may cause errors in determining the axial force). In some embodiments, the force sensor unit may include a coil assembly and a microprocessor.

[0057] As described herein, the coil assembly of the force sensor unit measures the displacement of the shaft along the z-axis and then converts the displacement into a force measurement. The coil assembly may include two induction coils, each of which is wound on a cylinder formed by a non-conductive material (e.g., PEEK). The two coils may be coaxially positioned relative to each other and coupled to or within a mechanical structure. In some embodiments, the rod is movable inside the coil and coupled to the instrument shaft of the medical device. In alternative embodiments, the medical device may not include a rod, but the proximal portion of the instrument shaft is movable within the coil. The rod may include, for example, a core having a magnet, the magnet is coupled to the core, and the core moves with the rod within the coaxial coil. The core may be, for example, a glass core, a stainless steel core, or a core formed by another suitable material. The magnet and any magnet described herein may be, for example, a ferrite bead, an EMI suppression bead, a nickel-zinc bead, or any other suitable material. Therefore, on the other hand, it should be understood that the term "magnet" used herein may refer to any component or material coupled to the core, which may be used to provide a signal indicating the position of the core within the coil when the rod and the core move within the coil. The rod is operably coupled to the shaft so that when the shaft moves axially due to a force applied to the distal end of the medical device, the rod moves with the shaft and within the coil. As the rod moves within the inductive coil, the inductance of each coil changes, which can be used to measure changes in the position of the instrument shaft. As described above, the change in the position of the shaft can be converted into a z-axis force measurement.

[0058] During use of the medical device, when a force is applied to the shaft in the z-direction, the shaft will travel along the z-axis, which in turn causes the rod to move along the z-axis. As the rod moves within the coil, each coil generates a signal associated with the position of the magnet on the rod within the coil. The microprocessor receives the signals from the coils. For example, in some embodiments, each coil generates a signal associated with the linear displacement of the shaft along the central axis of the shaft (e.g., along the z-axis). In some embodiments, the signals from the coils may include a first signal having a first frequency from the first coil and a second signal having a second frequency from the second coil. The microprocessor is configured to execute instructions to determine a measure of force on the shaft along the central axis of the shaft based on the first frequency and the second frequency. Reference is made below to Figure 7 Further details regarding the operation and interaction of the microprocessor are described.

[0059] Figure 5A-5H The components of an example axial force sensor unit embodiment that can be included in a medical device are shown. Since the components in the illustrated configuration can use some of the same materials, Figure 5A and Figure 5B The part numbers in Figure 5C-5H middle. Figure 5AA dual coil 545 is shown having a first coil 546 displaced from a second coil 548, wherein the first coil 546 and the second coil 548 are fixed to a tube 547. Each of the first coil 546 and the second coil 548 is made of a conductive material such as the same as the antenna coil. The two conductive coils, the first coil 546 and the second coil 548, can be coaxially wound on the tube 547. The tube 547 can be a plastic tube, such as but not limited to a polyetheretherketone (PEEK) plastic tube for low dimensional variation with temperature. The first coil 546 and the second coil 548 can be coated with silicone. Using a silicone coating on the coil allows the coil to remain substantially unaffected by high pressure steam cleaning (withstands high pressure steam cleaning).

[0060] The tube 547 can be coupled to a proximal mechanical structure to which the axial force sensor unit is coupled or incorporated. Since the tube 547 is coupled to the mechanical structure, the first coil 546 is further away from the distal end of the instrument shaft to which the axial force applied is to be measured than the second coil 548. Therefore, in the dual coil arrangement, the first coil 546 is the proximal coil and the second coil 548 is the distal coil. The proximal coil 546 has leads 546-1 and 546-2, which can be coupled to a capacitor to form a portion of an LC circuit, which can be coupled to a precision dual inductance sensor that measures the inductance of the LC circuit. The distal coil 548 has a lead 548-1 and another lead (not shown), which can be coupled to another capacitor to form a portion of another LC circuit, which can be coupled to a precision dual inductance sensor that can effectively measure the inductance of this other LC circuit.

[0061] Figure 5B An arrangement 550 is shown having a rod 554 and a magnet 552 on the rod 554, which can be used with Figure 5A The rod 554 may also be referred to as a rod. Since the magnet 552 is a relatively small structure, the configuration 550 may be referred to as a magnet on a rod or a bead on a rod. The rod 554 has a proximal portion, a distal portion, and a central axis, wherein the central axis extends between the proximal portion and the distal portion. The rod 554 may be, for example, a fiberglass rod or a stainless steel rod, although other embodiments may be used. For example, the rod 554 may include materials such as, but not limited to, quartz, glass, silica, ceramic, and alumina. For example, these other materials for the rod 554 may be used with respect to Figure 5A-Figure 9 In the configuration discussed, magnet 552 can be disposed on a distal portion of rod 554. Magnet 552 can be a ferrite structure, which can be implemented as a ferrite bead. The ferrite bead on the rod can be connected to the proximal end of the instrument shaft whose axial force is to be sensed.

[0062] Figure 5C An example embodiment of a magnet and rod implemented with a double coil is shown. Figure 5B The configuration of 550 can be used Figure 5A The magnet 552 on the rod 554 can be inserted into the tube 547, and the proximal coil 546 and the axial coil 548 are coaxially wound on the tube 547. The magnet 552 can be a ferrite structure. The two conductive coils, the proximal coil 546 and the distal coil 548, can be coaxially wound on the tube 547. The tube 547 can be a plastic tube, such as but not limited to a polyetheretherketone (PEEK) plastic tube. The proximal coil 546 and the distal coil 548 can be coated with silicone.

[0063] The rod 554 can move in the proximal coil 546 and the distal coil 548; wherein the magnet 552 is disposed on the proximal portion of the rod 554. The magnet 552 can have such a dimension along the central axis of the rod 554 that the dimension is sized so that the magnet 552 can extend within a portion of the proximal coil 546 and a portion of the distal coil 548 at the same time. The magnet 552 can be disposed at an initial position centered between the distal coil 546 and the proximal coil 548 along the z-axis. The initial position can be a position where no axial force is applied to the instrument shaft to which the rod is attached. The initial position can provide a zero reference that can be used to determine the distance that the instrument shaft moves in response to a force applied to the distal end of the instrument shaft. The initial position can be a position corresponding to the center of the magnet 552 centered between the distal coil 546 and the proximal coil 548, wherein the magnet 552 extends within a portion of the proximal coil 546 and within a portion of the distal coil 548. In various embodiments, the initial position as a zero reference may be different than the magnet 552 centered between the distal coil 546 and the proximal coil 548. For example, the initial position may depend on the characteristics of the distal coil 546 and the proximal coil 548 along with the respective capacitors to which the distal coil 546 and the proximal coil 548 are coupled relative to the measurement arrangement.

[0064] The instrument shaft to which the rod 554 is attached can be connected by a spring member ( Figure 5A-Figure 5C When the central axis of the instrument shaft is moved in the z direction (see, e.g. Figure 5C ) When a force is applied to the distal end of the instrument shaft, the spring member is displaced in proportion to the force applied to the distal end of the instrument shaft. Where the distal coil 546 and the proximal coil 548 are coupled to a precision dual inductance sensor, the movement of the magnet 552 on the rod 554 within the tube 547 relative to the distal coil 546 and the proximal coil 548 can be detected. The detection can be based on the movement of the magnet 552 relative to the initial position.

[0065] The dual coils in the axial force sensor unit can be configured in a variety of ways about the instrument axis to measure the axial force on the instrument axis. For example, Figure 5D An embodiment of a magnet example implemented with a dual coil is shown, where magnet 552 is disposed on the proximal end of instrument shaft 510 instead of a rod (e.g., rod 554). Instrument shaft 510 can be coupled to a proximal mechanical structure via spring member 560 such that the displacement of spring member 560 is proportional to the force applied to instrument shaft 510 in a direction along the central axis. Figure 5D The use of the double coil can be similar to Figure 5C The spring member 560 may also be configured with Figure 5C-5G Different arrangements are shown.

[0066] The proximal end of the instrument shaft 510 can be used as Figure 5C 54. The proximal end of the instrument shaft 510 with the magnet 552 thereon can extend in the tube 547 through a double winding consisting of a proximal coil 546 and a distal coil 548, such that an air gap exists between the instrument shaft 510 with the magnet 552 thereon and the tube 547 with the double coil wound thereon. When "at rest", in the absence of an axial (z-direction) force applied to the instrument shaft 510, the instrument shaft 510 can be axially positioned so that the magnet 552 is partially disposed within each coil. In some embodiments, in the absence of a z-direction force applied to the instrument shaft 510, an equal portion of the magnet 552 can be disposed within each coil. Each coil 546 and 548 can be coupled to a separate LC circuit in which the coil acts as an inductor (L) and the inductance varies with the amount of magnetic material contained within the respective coil. The resonant frequency of each circuit varies with the variation in the inductance of the respective circuit.

[0067] Figure 5E An embodiment of a magnet example implemented with a double coil is shown, wherein a magnet 552 is disposed on the proximal end of a rod 554. The rod 554 can be attached to an instrument shaft 510, which can be coupled to a mechanical structure via a spring member 560 such that the displacement of the spring member 560 is proportional to the force applied to the instrument shaft 510 in a direction along the central axis. The rod 554 can be configured to be attached to the instrument shaft 510, wherein the rod 554 is inserted into the instrument shaft 510. Figure 5E The use of the double coil can be similar to Figure 5C The use of double coils.

[0068] The proximal end of the rod 554 with the magnet 552 thereon can extend in the tube 547 through the double windings of the proximal coil 546 and the distal coil 548 so that there is an air gap between the rod 554 with the magnet 552 thereon and the tube 547 with the double coils wound thereon. As the instrument shaft 510 moves, the rod 554 moves axially. When "stationary", in the absence of an axial (z-direction) force applied to the instrument shaft 510, the rod 554 attached to the instrument shaft 510 can be axially positioned so that the magnet 552 is partially disposed within each coil. In some embodiments, in the absence of a z-direction force applied to the instrument shaft, an equal portion of the magnet 552 can be disposed within each coil. Each coil can be coupled to a separate LC circuit in which the coil acts as an inductor (L) and the inductance varies with the amount of magnetic material contained in the respective coil. The resonant frequency of each circuit varies with the variation in the inductance of the respective circuit.

[0069] Fig. 5F An embodiment of an example of a magnet 552 implemented with a double coil is shown, wherein the magnet 552 is disposed on the proximal end of a rod 554. The rod 554 can be attached to the instrument shaft 510, wherein the instrument shaft 510 can be coupled to the component 523 of the mechanical structure by a spring member 560 so that the displacement of the spring member 560 is proportional to the force applied to the instrument shaft 510 in the direction along the central axis. The rod 554 can be configured to be attached to the instrument shaft 510 using a support base 555 to fix the rod 554 to the instrument shaft 510. The central axis of the rod 554 can be aligned in a direction parallel to the central axis of the instrument. In the case where the rod 554 is attached to the instrument shaft 510 by the support base 555, as the instrument shaft 510 moves in its axial direction, the rod 554 moves in an axial direction parallel to the central axis of the instrument shaft 510. Fig. 5F The use of the double coil can be similar to Figure 5C The use of double coils.

[0070] The proximal end of the rod 554 with the magnet 552 thereon can extend in the tube 547 through the double windings of the proximal coil 546 and the distal coil 548 so that there is an air gap between the rod 554 with the magnet 552 thereon and the tube 547 with the double coils wound thereon. When "at rest", in the absence of an axial (z-direction) force applied to the instrument shaft 510, the rod 554 attached to the instrument shaft 510 can be axially positioned so that the magnet 552 is partially disposed within each coil. In some embodiments, in the absence of a z-direction force applied to the instrument shaft, an equal portion of the magnet 552 can be disposed within each coil. Each coil can be coupled to a separate LC circuit in which the coil acts as an inductor (L) and the inductance varies with the amount of magnetic material contained in the respective coil. The resonant frequency of each circuit varies with the variation in the inductance of the respective circuit.

[0071] The dual coils and magnets may be arranged in other configurations with the instrument shaft. For example, the proximal coil 546 and the distal coil 548 may be fixed to the movable instrument shaft 510, wherein the magnet 552 is coupled to the stationary rear end member 523 of the proximal mechanical structure to which the instrument shaft is coupled via the spring 560, as shown in FIG. Figure 5G In another example, the coils 546 and 548 of the dual coil configuration may be arranged on the tube 547 more Figure 5C-5F The coils used in the configuration are relatively further apart, with two magnets 552-1 and 552-2 on rod 547, such as Figure 5H As shown, one of the magnets 552-1 is proximal to the proximal coil 546 and the other magnet 552-2 is proximal to the distal coil 548. In addition, any of the dual coil / magnet arrangements described herein can be coupled to the instrument shaft and / or within the proximal mechanical structure using any suitable linkage, such as shown and described in U.S. Provisional Patent Application No. 63 / 077,833, entitled “Devices and Methods for Compact, Redundant Inductive Force Sensor,” which is incorporated by reference as described above.

[0072] Fig. 6A A proximal mechanical structure 622 is shown, which may be as described with respect to Figure 5A-5H The mechanical structure 622 includes a dual coil 645 for measuring the axial force applied to the distal end of the instrument shaft 610. Figure 6B Shows Fig. 6A The mechanical structure 622, wherein the double coil 645 has a rod 647 inserted into the double coil 645, wherein the rod 647 is fixed to the support base 655 to couple to Fig. 6A The instrument axis 610.

[0073] Figure 7 7 is a block diagram of an embodiment of an example force sensor 700 that can be implemented to measure an axial force applied to an instrument shaft. The force sensor 700 can be arranged as a sensing z-axis force sensor. An axial force on the instrument shaft causes an axial movement of the instrument shaft, which can be detected by the force sensor 700. The force sensor 700 can include an antenna coil 746 and an antenna coil 748, wherein a magnet such as a magnetic bead 752 is on a rod 754. Figure 5A-5H and Figure 6A-6BAny of one or more associated teachings in the teachings of, antenna coil 746 and antenna coil 748 can be configured as a proximal coil and a distal coil coaxially positioned relative to each other, wherein the magnet is on the rod. In some embodiments, as described herein, the magnet is coupled to the instrument shaft instead of the rod.

[0074] The antenna coil 746 can be coupled to the multi-channel frequency detection 765 through a capacitor C, which can form an LC circuit with the antenna coil 746, wherein the inductance contribution is based on the distance that the magnetic bead 752 moves within the antenna coil 746. The antenna coil 748 can be coupled to the multi-channel frequency detection 765 through a capacitor C, which can form an LC circuit with the antenna coil 748, wherein the inductance contribution is based on the distance that the magnetic bead 752 moves within the antenna coil 746. The LC circuits associated with the antenna coil 746 and the antenna coil 748 can be implemented with different capacitances, wherein such differences are taken into account. Since the magnetic bead 752 is closer to the antenna coil 746 than the antenna coil 748, the inductance contribution to the LC circuit associated with the antenna coil 746 is greater than the inductance contribution to the LC circuit associated with the antenna coil 748. That is, since the magnetic bead 752 is centered inside the antenna coils 746 and 748, when the magnetic bead 752 moves axially with the instrument shaft, the inductance of one coil increases and the inductance of the other coil decreases. The difference in the inductor values ​​indicates the change in force on the shaft. Temperature changes, long term aging and burn-in interference pickup of the inductor are the same for both coils. Taking the difference cancels out these effects.

[0075] The multi-channel frequency detection 765 can be implemented as a precision dual inductance sensor for measuring inductance. Since the capacitor C forms an LC circuit together with the antenna coil 746 input to the multi-channel frequency detection 765, the multi-channel frequency detection 765 can output a first signal associated with the frequency of the circuit, such as the ratio of the frequency to a known reference frequency. Since the capacitor C forms an LC circuit together with the antenna coil 748 input to the multi-channel frequency detection 765, the multi-channel frequency detection 765 can output a second signal associated with the frequency of the circuit, such as the ratio of the frequency to a known reference frequency. The multi-channel frequency detection 765 can output N digital signals to the microprocessor 770. For two LC circuits, the multi-channel frequency detection 765 can output two digital signals to the microprocessor 770.

[0076] The microprocessor 770 may include or have access to an EEPROM 772 or other storage device that may include calibration values ​​for implementing the magnetic bead 752 using the antenna coil 746 and the antenna coil 748. When determining the axial force on the instrument shaft, the calibration values ​​may be accessed to determine the distance moved based on the frequency received from the multi-channel frequency detection 765. The frequency difference may be stored in the EEPROM 772 as an inductance difference as a function of the distance. This distance difference may be correlated with a reference position and the inductance difference. Using the distance selected from the measured inductance difference, the distance may be used with a spring constant stored in the EEPROM 772, where the spring constant is a property of the spring by which the instrument shaft is coupled to the proximal mechanical structure on which the force sensor 700 may be deployed.

[0077] The force sensor 700 may include other components. For example, the microprocessor 770 may include a universal asynchronous receiver / transmitter (UART) interface 774 or other communication interface to send (TX) digital outputs and receive (RX) digital signals. The received signal can be used to update the calibration value in the EEPROM 772 of the microprocessor 770. The common mode choke 780 can be used to reduce interference with other boards of the mechanical structure on which the force sensor 700 is deployed. Optionally, the force sensor 700 may include a magnet 762 located between the common mode choke 780 and the microprocessor 770. The magnet 762 can be inserted to help reduce electromagnetic interference (EMI) radiation. The magnet 762 can be implemented as a ferrite bead. For the magnet 762, other magnetic material formats can be implemented.

[0078] Figure 8A-8C The measured values ​​of the inductance of the magnet target and the two coils compared to the target position are shown, and the value of the axial force on the instrument shaft is shown, which causes a small displacement of the shaft relative to the mechanical structure (± 0.025 inches). The target for shaft displacement (also called target position) is ± 0.025 inches. Fig. 8A is a graph of the difference of two inductors labeled L3 and L2 versus the position of a ferrite bead attached to a micrometer. Curve 862 is the measured difference of the two inductors L3 and L2. Curve 861 is the ideal difference of the two inductors L3 and L2. The two vertical lines 863 and 864 represent -0.025 inches and +0.025 inches distances from the center of the bead, respectively.

[0079] Figure 8BIt is shown that the difference L3-L2 is almost a straight line for the inductance difference compared to the micrometer (bead) position. This measurement can be used to define the operating range from the sensor to a linear signal because the subtraction only works in the linear region. However, the dual coil method can also work when the drift of the two coils is equal and independent of temperature, which can eliminate the use of subtraction of one from the other. Curve 872 is the measured difference of the two inductors L3 and L2. Curve 871 is the ideal difference of the two inductors L3 and L2. The two vertical lines 873 and 874 represent the distance of -0.025 inches and +0.025 inches from the center position of the bead, respectively.

[0080] Figure 8C A graph of inductances L3 and L2 versus micrometer (bead) position is shown. Curve 876 is the measured inductance L3. Curve 878 is the measured inductance L2.

[0081] Fig. 9 Flowchart of features of an embodiment of an example method 900 for determining axial force. At 910, a first signal having a first frequency is received at an electronic signal frequency detector from a proximal coil fixed to a proximal mechanical structure. At 920, a second signal having a second frequency is received at the electronic signal frequency detector from a distal coil fixed to the proximal mechanical structure and coaxial with the proximal coil. A rod movable in the proximal coil and the distal coil is used to provide the first frequency and the second frequency, wherein the rod has a magnet disposed on a proximal portion of the rod. The rod has a proximal portion, a distal portion, and a central axis, wherein the central axis extends between the proximal portion and the distal portion.

[0082] At 930, a first frequency and a second frequency are determined. At 940, the first frequency and the second frequency are used to determine a measure of an axial force on an instrument shaft to which the rod is connected. Using the first frequency and the second frequency to determine a measure of the axial force on the instrument shaft may include using the first frequency and the second frequency to determine an axial displacement of a spring member by which the instrument shaft is coupled to the proximal mechanical structure.

[0083] Variations of method 900 or methods similar to method 900 may include multiple different embodiments that may be combined depending on the application of the methods and / or the architecture of the system in which the methods are implemented. Such a method may include converting a first frequency and a second frequency into a first inductance and a second inductance; and using the difference between the first inductance and the second inductance to generate an identification of a change in force on the instrument shaft. Such measurements can be used in the operating range from the sensor to a linear signal because the subtraction only works in the linear region. However, the dual coil method can also work when the two coil drifts are equal and independent of temperature, which can eliminate the use of subtraction of subtracting one from the other. The change in force is a measure of the axial force on the distal portion of the instrument shaft to which the rod is connected. Since the force is bidirectional, the measure of the axial force on the distal portion of the instrument shaft is bidirectional.

[0084] Variations of method 900 or methods similar to method 900 may include: converting a first frequency and a second frequency into a first inductance and a second inductance; using the first inductance and the second inductance for a proximal coil and a distal coil to generate identification of changes in force on the instrument shaft, wherein the proximal coil and the distal coil are constructed as temperature-independent coils with equal drift.

[0085] A machine-readable storage device may include any non-transitory mechanism for storing information in a machine-readable form, such as a computer or microprocessor, whose task is to perform a specific function. For example, a machine-readable storage device may include a read-only memory (ROM), a random access memory (RAM), a disk storage medium, an optical storage medium, a flash memory device, and other storage devices and media. In various embodiments, the non-transitory machine-readable medium may include instructions that, when executed by a set of processors, may cause the system to perform operations including: receiving a first signal having a first frequency from a proximal coil fixed to a mechanical structure at an electronic signal frequency detector; receiving a second signal having a second frequency from a distal coil fixed to the mechanical structure and coaxial with the proximal coil at the electronic signal frequency detector, wherein a rod is movable in the proximal coil and the distal coil, the rod having a proximal portion, a distal portion, and a central axis, the central axis extending between the proximal portion and the distal portion, and the rod having a magnet disposed on the proximal portion of the rod; determining a first frequency and a second frequency; and using the first frequency and the second frequency to determine a measure of an axial force on an instrument shaft to which the rod is connected. In various embodiments, a non-transitory machine-readable medium may include instructions that, when executed by a set of processors, cause a system to perform operations including features of method 900 or similar methods, and may include executing and communicating with Figure 1-8C Associated features are associated with functions.

[0086] In various embodiments, a system may include: an axial force transducer, wherein the axial force transducer includes a mechanical structure; a proximal coil fixed to the mechanical structure; a distal coil fixed to the mechanical structure, the distal coil being coaxial with the proximal coil; a rod having a proximal portion, a distal portion, and a central axis, the central axis extending between the proximal portion and the distal portion, the rod being movable in the proximal coil and the distal coil; a magnet disposed on the proximal portion of the rod; and an electronic signal detector for detecting a first signal from the proximal coil and a second signal from the distal coil. The electronic signal detector may be implemented as an electronic signal frequency detector to detect a first frequency of the first signal from the proximal coil and a second frequency of the second signal from the distal coil. The axial force transducer may be implemented as a system.

[0087] Variations of such a system may include a number of different embodiments that may be combined depending on the implementation of the design of such a system. Such a system may include a magnet having a dimension along a central axis that is sized such that the magnet may extend within a portion of the proximal coil and within a portion of the distal coil simultaneously. Such a system may include a magnet disposed in an initial position centered between the distal coil and the proximal coil.

[0088] Such a system may include a rod attachable to an instrument shaft, wherein the instrument shaft is coupled to a mechanical structure by a spring member for displacement in proportion to a force applied to the instrument shaft in a direction along the central axis. The central axis of the rod may be configured in a direction parallel to the central axis of the instrument shaft. Such a system may include a rod that is a fiberglass rod, although other materials for the rod may be used. Such a system may include an axial force transducer according to claim 1, wherein the magnet disposed on the proximal portion of the rod is a ferrite structure.

[0089] Such a system may include a proximal coil and a distal coil coaxially wound on a plastic tube, although other materials may be used. The plastic tube may be a polyetheretherketone tube.

[0090] Such a system may include an axial force sensor having a microprocessor coupled to receive a first frequency of a first signal and a second frequency of a second signal, wherein the microprocessor is configured to determine a measure of axial force on a distal portion of an instrument shaft to which the rod is connected based on the first frequency and the second frequency.

[0091] In various embodiments, an axial force transducer may include: a mechanical structure; an axis having a proximal portion, a distal portion and a central axis extending between the proximal portion and the distal portion; a spring member operably coupled to the mechanical structure for displacement in proportion to a force applied to the axis in a direction along the central axis; a proximal coil fixed to the mechanical structure; a distal coil fixed to the mechanical structure and coaxial with the proximal coil; a magnet disposed on the proximal portion of the axis, wherein the magnet has a dimension along the central axis that is sized so that the magnet can extend simultaneously within a portion of the proximal coil and within a portion of the distal coil; wherein the axis extends within the proximal coil and the distal coil so that at least a portion of the magnet extends within at least one of the proximal coil and the distal coil; and an electronic signal frequency detector for detecting the frequency of an electrical signal within at least one of the proximal coil and the distal coil in which the magnet extends.

[0092] In various embodiments, an instrument having an axial force transducer may include: an instrument shaft; a mechanical structure; a spring member for coupling the instrument shaft to the mechanical structure for displacement in proportion to a force applied to the instrument shaft in a direction along a central axis; a proximal coil fixed to the mechanical structure; a distal coil fixed to the mechanical structure and coaxial with the proximal coil; a rod having a proximal portion, a distal portion, and a central axis, the central axis extending between the proximal portion and the distal portion, the rod being movable in the proximal coil and the distal coil; a magnet disposed on the proximal portion of the rod; and an electronic signal detector for detecting a first signal from the proximal coil and a second signal from the distal coil. The electronic signal detector may be implemented as an electronic signal frequency detector to detect a first frequency of the first signal from the proximal coil and a second frequency of the second signal from the distal coil.

[0093] Variations of this instrument may include many different embodiments that may be combined depending on the implementation in which the instrument is designed. Such an instrument may include a magnet having a dimension along a central axis that is sized such that the magnet may extend within a portion of the proximal coil and within a portion of the distal coil simultaneously.

[0094] Such an instrument may include a rod connected to the instrument shaft. The central axis of the rod may be in a direction parallel to the central axis of the instrument shaft.

[0095] Such an instrument may include a microprocessor coupled to receive a first frequency of a first signal and a second frequency of a second signal, wherein the microprocessor is configured to use the first frequency and the second frequency to determine a measure of an axial force on a distal portion of an instrument shaft to which the rod is connected. The instrument may include a common mode choke coupled to the microprocessor to reduce interference with determining the measure of the axial force. Such an instrument may include an additional magnet, wherein the additional magnet is disposed between the common mode choke and the microprocessor to help reduce electromagnetic interference radiation. The additional magnet may include a ferrite bead.

[0096] Although specific embodiments have been illustrated and described herein, it will be understood by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose may replace the specific embodiments shown. Various embodiments use permutations and / or combinations of the embodiments described herein. It should be understood that the above description is intended to be illustrative rather than restrictive, and that the wording or terminology used herein is for descriptive purposes. Combinations of the above embodiments and other embodiments will be clear to those skilled in the art after studying the above description.

Claims

1. A device comprising: A medical device comprising a mechanical structure and a force sensor unit coupled to the mechanical structure; as well as a shaft coupled to the mechanical structure; wherein the force sensor unit comprises a rod, a magnet coupled to the rod, a first coil coupled to the mechanical structure, and a second coil coupled to the mechanical structure and coaxial with the first coil; wherein the rod comprises a distal portion and a proximal portion, and a central axis of the rod is defined between the proximal portion and the distal portion of the rod; wherein the shaft is operably coupled to the rod such that translational movement of the shaft relative to the mechanical structure moves the rod along the central axis of the rod; wherein the magnet translates within the first coil and the second coil along the central axis of the rod; and In the initial position, the magnet can extend simultaneously in a portion of the first coil and a portion of the second coil.

2. The apparatus according to claim 1, wherein: The shaft includes a proximal end and a distal end; A central axis of the shaft is defined between the proximal end and the distal end of the shaft; and The shaft is coupled to the mechanical structure such that a linear displacement of the shaft along the central axis of the shaft is proportional to a force applied to the shaft in the direction of the central axis of the shaft.

3. The apparatus according to claim 2, wherein: The central axis of the rod is in a direction parallel to the central axis of the shaft.

4. The apparatus according to claim 1, wherein: The shaft includes a proximal end and a distal end; a central axis of the shaft being defined between the proximal end and the distal end of the shaft; a first signal generated by the first coil being associated with a position of the magnet relative to the first coil; a second signal generated by the second coil is associated with a position of the magnet relative to the second coil; and The first signal from the first coil and the second signal from the second coil are associated with a linear displacement of the shaft along the central axis of the shaft.

5. The apparatus according to claim 4, wherein: The linear displacement of the shaft is proportional to a force applied to the shaft in the direction of the central axis of the shaft.

6. The apparatus of claim 1, wherein: The shaft includes a proximal end and a distal end; a central axis of the shaft being defined between the proximal end and the distal end of the shaft; The apparatus further includes a spring coupled to the shaft; and The spring is configured to displace in proportion to a force applied to the shaft in a direction of the central axis of the shaft.

7. The apparatus of claim 1, wherein: a first signal generated by the first coil being associated with a position of the magnet relative to the first coil; a second signal generated by the second coil is associated with a position of the magnet relative to the second coil; and The force sensor unit includes a microprocessor coupled to receive the first signal and the second signal.

8. The apparatus of claim 7, wherein: The first signal has a first frequency; The second signal has a second frequency different from the first frequency; and The microprocessor is configured to execute instructions to determine a linear displacement of the shaft along the central axis of the shaft based on the first frequency and the second frequency.

9. The apparatus according to any one of claims 1 to 8, wherein: The first coil is a proximal coil; The second coil is a distal coil; The magnet comprises a first magnet and a second magnet; The first magnet is positioned to move within the first coil; and The second magnet is positioned to move within the second coil.

10. A medical device comprising: an instrument shaft comprising a proximal end and a distal end; a medical end effector coupled to the distal end of the instrument shaft; a mechanical structure disposed at a proximal portion of the medical device, the mechanical structure coupled to the proximal end of the instrument shaft; as well as a force sensor unit coupled to the mechanical structure at the proximal portion of the medical device; wherein the force sensor unit comprises a first coil wound on a first coil axis, a second coil wound on a second coil axis coaxial with the first coil axis, and a magnet; wherein an instrument shaft axis is defined between said proximal end and said distal end of said instrument shaft; and Wherein the magnet is operably coupled to the instrument shaft and moves along the first coil axis as the instrument shaft moves along the instrument shaft axis.

11. The medical device according to claim 10, wherein: As the instrument shaft moves along the instrument shaft axis, the magnet moves within the first coil.

12. The medical device of claim 10, wherein: As the instrument shaft moves along the instrument shaft axis, the magnet moves within the first coil and within the second coil.

13. The medical device of claim 10, wherein: The force sensor unit comprises a rod; and The rod is axially aligned with the first coil axis and couples the magnet to the instrument shaft.

14. The medical device of claim 10, wherein: a first signal generated by the first coil being associated with a position of the magnet relative to the first coil; a second signal generated by the second coil is associated with a position of the magnet relative to the second coil; and The force sensor unit includes a microprocessor coupled to receive the first signal and the second signal.

15. The medical device of claim 14, wherein: The first signal has a first frequency; The second signal has a second frequency; and The microprocessor is configured to execute instructions to determine a measure of force on the instrument shaft along an axis of the instrument shaft based on the first frequency and the second frequency.

16. The medical device of claim 10, wherein: At a unique position of the magnet relative to the first coil and the second coil, a first signal is generated by the first coil and a second signal is generated by the second coil; and The first signal from the first coil and the second signal from the second coil are associated with a unique linear displacement of the instrument shaft along the instrument shaft axis.

17. The medical device according to any one of claims 10 to 16, wherein: The medical device further comprises a spring coupled to the instrument shaft and the mechanical structure; and The spring is configured to displace in proportion to a force applied to the instrument shaft in a direction along an axis of the instrument shaft.

18. A medical device comprising: an instrument support structure, an instrument shaft, and a force sensor unit; The instrument support structure is disposed at a proximal portion of the medical device, and the force sensor unit is coupled to the instrument support structure at the proximal portion of the medical device; wherein the instrument shaft comprises a proximal end and a distal end, and an instrument shaft axis is defined between the proximal end and the distal end of the instrument shaft; wherein the force sensor unit comprises a first coil wound on a first coil axis, a second coil wound on a second coil axis coaxial with the first coil axis, and a magnet at least partially within at least one of the first coil and the second coil; and Wherein the first coil, the second coil and the magnet are positioned such that translation of the instrument axis relative to the instrument support structure along the instrument axis axis causes relative movement between the magnet and the first coil along the first coil axis and relative movement between the magnet and the second coil along the second coil axis.

19. The medical device of claim 18, wherein: The first coil and the second coil are fixed relative to the instrument support structure.

20. The medical device according to claim 18 or 19, wherein: The medical device comprises a proximal mechanical structure, a distal mechanism and a connecting member; The distal mechanism is coupled to the distal end of the instrument shaft and includes a movable member; The proximal mechanical structure includes the instrument support structure and an actuator input mounted for movement relative to the instrument support structure; and The connecting member is coupled between the actuator input and the movable component of the distal mechanism, and transmits tension, compression, or both tension and compression from the actuator input to the movable component of the distal mechanism.

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