WO2024107655A1

WO2024107655A1 - Force sensing medical instrument

Info

Publication number: WO2024107655A1
Application number: PCT/US2023/079523
Authority: WO
Inventors: David I. MOREIRA RIDSDALE; Lizmarie COMENENCIA ORTIZ; Ashwinram Suresh; Kyle W. CLEMENTS; Alan W. PETERSEN; Cheng-Ling CHANG
Original assignee: Intuitive Surgical Operations, Inc.
Priority date: 2022-11-15
Filing date: 2023-11-13
Publication date: 2024-05-23

Abstract

Structures and methods are disclosed for preventing electromagnetic (EM) interference from affecting force indications from a force sensing medical device. The force sensing medical device includes one or more force sensor units, which generate indications of forces acting on the device. EM interference with the indications is minimized by the use of one or more ground paths, an electrically conductive shield, or both. The ground paths include one or more electrically conductive mechanical actuator structures and traces in a force sensing indication signal cable. A circuit board is configured to prevent EM interference between the circuit board and a force sensor element. The reliability of force feedback to a surgeon during an application of electrosurgical energy is enhanced while the surgeon operates the force sensing medical device in a telesurgical system.

Description

FORCE SENSING MEDICAL INSTRUMENT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the filing date benefit of U.S. Provisional Patent Application No. 63/425,524, entitled “FORCE SENSING MEDICAL INSTRUMENT,” filed November 15, 2022, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] The embodiments described herein relate to force sensing technology, and more specifically to force sensing technology adapted for use with teleoperated surgical systems. More particularly, the embodiments described herein relate to force sensing medical instruments for determining forces applied to the medical instrument in order to control a surgical system that includes a force feedback that may be provided to a system operator. Still more particularly, the embodiments described herein relate to the mitigation of electromagnetic interference when the force sensing medical instrument is exposed to an electrical field.

[0003] Known techniques for minimally invasive surgery (MIS) employ instruments to manipulate tissue that can be either manually controlled or controlled via hand-held or mechanically grounded teleoperated medical systems that operate with at least partial computer-assistance (“telesurgical systems”). Many known MIS instruments include a therapeutic or diagnostic end effector (e.g., forceps, a cutting tool, or a cauterizing tool) mounted on an optional wrist mechanism at the distal end of a shaft. During an MIS procedure, the end effector, wrist mechanism, and the distal end of the shaft are typically inserted into a small incision or a natural orifice of a patient via a cannula to position the end effector at a work site within the patient’s body. The optional wrist mechanism can be used to change the end effector’s position and orientation with reference to the shaft to perform a desired procedure at the work site. In known instruments, motion of the instrument as a whole provides mechanical degrees of freedom (DOFs) for movement of the end effector and the wrist mechanisms generally provide the desired DOFs for movement of the end effector with reference to the shaft of the instrument. For example, for forceps or other grasping tools, known wrist mechanisms are able to change the pitch and yaw of the end effector with reference to the shaft. A wrist may optionally provide a roll DOF for the end effector, or the roll DOF may be implemented by rolling the shaft. An end effector may optionally have additional mechanical DOFs, such as grip or knife blade motion. In some instances, wrist and end effector mechanical DOFs may be combined. For example, U.S. Patent No. 5,792,135 (filed May 16, 1997) discloses a mechanism in which wrist and end effector grip DOFs are combined.

[0004] Force sensing medical instruments are known and, together with associated telesurgical systems, may deliver haptic feedback during a MIS procedure to a surgeon performing the procedure. The haptic feedback may increase the surgeon’s sense of immersion, realism, and intuitiveness while performing the procedure. For effective haptics rendering and accuracy, force sensors may be placed on a medical instrument and as close to the anatomical tissue interaction as possible. One approach is to include a force sensor unit having electrical sensor elements (e.g., strain gauges) at a distal end of a medical instrument shaft to measure strain imparted to the medical instrument. The measured strain can be used to determine the force imparted to the medical instrument and as input upon which the desired haptic feedback may be generated.

[0005] In some MIS procedures an electrical current is introduced to the surgical site, such as during electrosurgery. Electrosurgery refers broadly to a class of medical procedures that rely on the application of high frequency electrical energy, usually radio frequency energy, to patient tissue to achieve a number of possible effects, such as cutting, coagulation, necrosis, and the like. For example, in some MIS procedures tissue in the patient's body must be cauterized and severed. To perform such a procedure, end effector grips configured to apply bipolar or monopolar cauterizing energy are introduced to the surgical site to engage the target tissue, and electrical energy, such as radiofrequency energy, is delivered to the grips to cauterize the engaged tissue. Alternatively, in some instances surgeons have been known to engage tissue with electrically conductive end effector grips that are not specifically configured to apply electrical energy, and then place an actively charged electrode (such as an electrically charged end effector on a second instrument) in electrically conductive contact (i.e., direct electrical coupling) with the grips in order to apply electrosurgical energy to the tissue.

[0006] Force sensing instruments may be specifically designed to apply electrosurgical energy (e.g., a bipolar forceps instrument) or not designed to apply electrosurgical energy (e.g., a Cadiere forceps instrument). Regardless of whether a force sensing medical instrument is designed to apply electrosurgical energy, during certain MIS procedures the force sensing medical instrument can be exposed to an electrical field during an electrosurgical operation. And regardless of the approach used to apply electrosurgical energy to tissue — with an instrument specifically designed to apply electrosurgical energy or with an instrument not specifically designed to apply electrosurgical energy — electrical current associated with the electrosurgical energy can be conducted via various components of the force sensing medical instrument.

[0007] The exposure of the force sensing medical instrument to the electrical field can result in the generation of electromagnetic interference within the instrument that can affect signals from the force sensing instrument’s force sensor unit. In turn, this effect on the signals can result in inaccurate indications of the forces acting on the force sensing medical instrument and the associated haptic feedback to the surgeon operating the force sensing instrument. Insofar as the haptic feedback is based on the indications of force on the instrument, it is desirable to mitigate the effects of the electromagnetic interference. Such mitigations are subject to the design and design constraints (e.g., component materials needed for strength or other mechanical properties, small component sizes required for surgery, etc.) of the force sensing instrument itself.

[0008] The magnitude and/or affect of the electromagnetic interference on the output of the force sensor unit can depend, at least in part, on the positioning of various components of the force sensing medical instrument. For example, in a force sensing medical instrument specifically designed to apply electrosurgical energy to tissue, an electrically energized end effector component can generate electrical current in one or more other electrically conductive instrument components (e.g., a metal component such as a beam, a mechanical cable, and/or a shaft) spaced apart (e.g., by insulation or an insulating gap) from the energized end effector component. Likewise, the use of a medical instrument specifically designed to apply electrosurgical energy near or in contact with a force sensing medical instrument can generate an electrical current in one or more electrically conductive components (e.g., a metal component such as a beam, a mechanical cable, and/or a shaft) of the force sensing medical instrument.

[0009] The force sensing instrument’s electrically conductive components (either those dedicated to performing the force sensing function (e.g., strain sensors, strain gauges, and/or sensor cables) or those having a structural function) can be physically separated from one another by electrical insulation or a spatial gap. However, the two electrically conductive components can become capacitively or inductively coupled (i.e., indirectly electrically coupled) when the current in a first component generates a current in the second component across the insulation or gap between the two. The magnitude of the generated current is affected, at least in part, by the positioning of the two electrically conductive components and by the dielectric quality of the insulation or gap therebetween. For example, a strain sensor can be mechanically coupled to an electrically conductive structure by an electrically insulative adhesive. In accordance with the principles of capacitive coupling, a current conducted by the structure can generate a current in the strain sensor through the electrically insulative adhesive. The magnitude of the generated current can be affected by a distance between the strain sensor and the structure as determined by the thickness of the electrically insulative adhesive and other factors. Insofar as changes in the relatively low voltage of the strain sensor can be indicative of the forces acting on the force sensing medical instrument, the presence of electromagnetic interference (in the form of the generated current) in the output of the strain sensor can distort the force indications.

[0010] In addition to problems that may occur from capacitive coupling, electromagnetic interference can also result from inductive coupling (e.g., antenna coupling or magnetic field coupling) between various components of the force sensing medical instrument. When inductively coupled, a magnetic field resulting from an electrical current in one electrially conductive component generates an electrical current in a second electrically conductive component. For example, a current can be generated via inductive coupling in a portion of the strain sensor and/or the sensor cable carrying signals from the strain sensor. The presence of the current generated by the inductive coupling is electromagnetic interference that can distort the indications of strain generated by a force sensor unit, resulting in distorted indications of force acting on the force sensing medical instrument.

[0011] In some force sensing medical devices, a distal force sensor unit is used to measure forces imparted on an end effector of the medical device in transverse (orthogonal to the instrument shaft’ s long axis; e.g., X and Y directions in a Cartesian system), and a proximal force sensor unit is used to measure a force imparted on the end effector in an axial direction (parallel to the instrument shaft’s long axis; Z direction in a Cartesian system). That is, a force sensing unit may be located at the distal end, the proximal end, or at both ends of the force sensing medical instrument. The proximal portion of the medical device can include a circuit board that includes components of the force sensing system, and to which the proximal force sensor unit is coupled. The circuit board and the proximal force sensor unit components are susceptible to current induced by inductive or capacitive coupling that can distort the the electrical signals generated by the proximal force sensor unit. Such inductive or capacitive coupling may be generated by these two components themselves, or it may be generated by other instrument components such as electrically conductive mechanical control cables, electrically conductive pulleys over which the cables are routed, or an electrically conductive mechanical structure that supports the pulleys. Thus, there is a need to protect against electromagnetic interference that can distort indications generated by the proximal force sensor unit of a force acting on the force sensing medical instrument.

[0012] In view of the aforementioned, there is a desire to continuously seek new and improved systems and methods for control of a surgical system based on the accurate measurement of the strain imparted to the medical instrument by a force acting on the medical instrument and to convey an accurate associated haptic feedback sensation to a surgeon operating the medical instrument.

SUMMARY

[0013] This summary introduces certain aspects of the embodiments described herein to provide a basic understanding. This summary is not an extensive overview of the inventive subject matter, and it is not intended to identify key or critical elements or to delineate the scope of the inventive subject matter.

[0014] Structures and methods are described herein for preventing electromagnetic (EM) interference from affecting force indications from a force sensing medical device. The force sensing medical device includes one or more force sensor units, which generate indications of forces acting on the device. For example, a medical device as described herein can include a distal force sensor unit, a proximal force sensor unit or both a distal and proximal force sensor unit. EM interference with the indications is minimized by the use of one or more ground paths, an electrically conductive shield, or both. The ground paths include one or more electrically conductive mechanical actuator structures and traces in a force sensing indication signal cable. An electronic circuit board is configured to prevent EM interference between the electronic circuit board and a force sensor element of one or both of the force sensor units. Thus, the reliability of force feedback to a surgeon during an application of electrosurgical energy is enhanced while the surgeon operates the force sensing medical device in a telesurgical system.

[0015] In some embodiments, a medical device includes a shaft including a proximal end portion and a distal end portion. A tool is movably coupled to the distal end portion of the shaft and a distal force sensor unit is coupled to the distal end portion of the shaft and configured to sense force on the tool. A proximal mechanical structure is coupled to the proximal end portion of the shaft and an electronic circuit board is coupled to the proximal mechanical structure. A drive element is coupled between the tool and the proximal mechanical structure and actuation of the drive element causes movement of the tool. An electrical ground path is defined between the distal force sensor unit and the electronic circuit board and the electrical ground path includes the drive element.

[0016] In some embodiments, the proximal mechanical structure includes a proximal pulley and a pulley cover at least partially covering the pulley. The drive element is in electrical contact with the pulley, the pulley is in electrical contact with the pulley cover, the pulley cover is in electrical contact with the electronic circuit board, and the ground path includes the pulley and pulley cover.

[0017] In some embodiments, the medical device further includes at least one of an o-ring, a gasket, and a plating component coupled between the electronic circuit board and the proximal mechanical structure. In some embodiments, the tool includes a tool pulley and the drive element is electrically coupled to the tool pulley.

[0018] In some embodiments, the ground path is a first ground path and the medical device further includes a sensor signal cable electrically coupled between the distal force sensor unit and the electronic circuit board. A second electrical ground path is defined between the distal force sensor unit and the electronic circuit board and the second ground path includes the sensor signal cable. In some embodiments, the medical device further includes a proximal force sensor unit coupled to the electronic circuit board and the proximal force sensor unit is configured to determine a force exerted on the tool in a direction along the length of the shaft. In some embodiments, the tool is electrically insulated from the force sensor unit. In some embodiments, the tool is in electrical contact with the ground path.

[0019] In some embodiments, the electronic circuit board includes a first layer and a second layer. The first layer includes a plurality of electrically conductive traces and the second layer includes an electrically conductive material. The electrically conductive material of the second layer is electrically coupled to the electrical ground path. In some embodiments, the medical device is configured as an instrument in a telesurgical system.

[0020] In some embodiments, a medical device includes a proximal mechanical structure, an electronic circuit board coupled to the proximal mechanical structure, and the electronic circuit board includes a plurality of electrically conductive traces. An electrically grounded electrically conductive shield is positioned distally under the plurality of electrically conductive traces. A force sensor unit including a sensor element is positioned proximally over the electrically conductive traces. A physical electrical connection exists between the sensor element and one or more of the plurality of electrically conductive traces and no physical electrical connection exists between the sensor element and the electrically conductive shield.

[0021] In some embodiments, the medical device further includes a second sensor element. A physical electrical connection exists between the second sensor element and one or more of the plurality of electrically conductive traces and no physical electrical connection exists between the second sensor element and the electrically conductive shield. The sensor element and the second sensor element are each spaced from the electrically conductive shield by an equal distance. In some embodiments, the sensor element is an inductive coil sensor element.

[0022] In some embodiments, the electrically conductive shield includes a gap located to prevent an electrically inductive coupling between the electrically conductive shield and the sensor element. In some embodiments, the electronic circuit board includes a first layer and a second layer positioned distally under the first layer; the first layer includes the electrically conductive traces, the second layer includes the electrically conductive shield, and a portion of the first layer extends proximally above the gap. [0023] In some embodiments, the medical device further includes a shaft coupled to the proximal mechanical structure. The shaft is operably coupled to the force sensor unit such that translational movement of the shaft causes translational movement of a portion of the force sensor unit with reference to the electronic circuit board.

[0024] In some embodiments, the electronic circuit board includes an opening and an outer edge, and the electrically conductive shield surrounds the opening of the electronic circuit board. A gap in the electrically conductive shield is defined between the opening of the electronic circuit board and the outer edge of the electronic circuit board. In some embodiments, the medical device includes an electrical ground and the one or more of the plurality of electrically conductive traces are electrically connected to the electrical ground.

[0025] In some embodiments, the medical device further includes a shaft, a tool, and a distal force sensor unit. The shaft includes a proximal end portion and a distal end portion. The proximal end portion of the shaft is coupled to the proximal mechanical structure and the tool, and the distal force sensor are each coupled to the distal end portion of the shaft. In some embodiments, the tool is electrically insulated from the distal force sensor unit. In some embodiments, the medical device further includes a drive element operably coupled between the tool and the proximal mechanical structure such that actuation of the drive element causes movement of the tool. The drive element defines a portion of an electrical ground path between the distal force sensor unit and an electrical ground or the tool and the electrical ground, or between both the distal force sensor unit and the tool and the electrical ground.

[0026] In some embodiments, the medical device further includes a sensor signal cable electrically coupled between the distal force sensor unit and the electronic circuit board. The sensor signal cable includes an electrical ground trace, and the electrical ground trace of the sensor signal cable defines a portion of a ground path between the distal force sensor unit and the electrical ground.

[0027] In some embodiments, the electronic circuit board includes a first layer and a second layer positioned distally under the first layer. The first layer includes the electrically conductive trace, and the second layer includes the electrically conductive shield positioned distally under the electrically conductive traces. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. l is a plan view of a minimally invasive teleoperated surgery system according to an embodiment being used to perform a medical procedure such as surgery.

[0029] FIG. 2 is a perspective view of an optional auxiliary unit of the minimally invasive teleoperated surgery system shown in FIG. 1.

[0030] FIG. 3 is a perspective view of a user control console of the minimally invasive teleoperated surgery system shown in FIG. 1.

[0031] FIG. 4 is a front view of a manipulator unit, including a plurality of instruments, of the minimally invasive teleoperated surgery system shown in FIG. 1.

[0032] FIG. 5 is a diagrammatic illustration of a medical device, illustrating a ground path GP, according to an embodiment.

[0033] FIG. 6 is a diagrammatic illustration of a portion of a medical device, including an electrical circuit board coupled to a proximal mechanical structure, according to an embodiment.

[0034] FIG. 7 is a perspective view of a medical device, according to an embodiment.

[0035] FIG. 8 is an enlarged perspective view of a distal end portion of the medical device of

FIG. 7.

[0036] FIG. 9 is an enlarged view of a proximal mechanical structure of the medical device of FIG. 7 with select components removed for illustration purposes.

[0037] FIG. 10 is a side view of the proximal mechanical structure of FIG. 9.

[0038] FIG. 11 is an enlarged side view of a portion of the proximal mechanical structure of

FIG. 10 in box B of FIG. 10.

[0039] FIG. 12A is a flowchart illustrating example components included within the ground path of the medical device of FIG. 7. [0040] FG. 12B is a side view of the medical device of FIG. 7, illustrating the ground path extending between the end effector and the proximal force sensor unit.

[0041] FIG. 13 A is a perspective view of the electronic circuit board and proximal force sensor unit of the medical device of FIG. 7.

[0042] FIG. 13B is a partial exploded view of the electronic circuit board and proximal force sensor unit of FIG. 13 A.

[0043] FIG. 14A is an enlarged perspective view of a portion of the electronic circuit board and proximal force sensor unit of FIG. 13 A.

[0044] FIG. 14B is a top view of the portion of the electronic circuit board and proximal force sensor unit of FIG. 14 A.

[0045] FIG. 14C is a side view of the portion of the electronic circuit board and proximal force sensor unit of FIG. 14 A.

[0046] FIG. 15 is a top view of the electronic circuit board of the medical device of FIG. 7.

[0047] FIG. 16 is a top view of the electronic circuit board of FIG. 15 with a top layer removed.

[0048] FIG. 17 is a bottom perspective view of the electronic circuit board of FIG. 13A with a sensor signal cable attached thereto.

[0049] FIG. 18 is a diagrammatic illustration of a portion of a proximal force sensor unit, according to an embodiment.

DETAILED DESCRIPTION

[0050] The embodiments described herein can advantageously be used in a wide variety of force sensor applications, such as for grasping, cutting, and manipulating operations associated with minimally invasive surgery. The embodiments described herein can also be used in a variety of non-medical applications such as, for example, teleoperated systems for search and rescue, remotely controlled submersible devices, aerial devices, automobiles, etc. The medical instruments or devices of the present application enable motion in three or more degrees of freedom (DOFs). For example, in some embodiments, an end effector of the medical instrument can move with reference to the main body of the instrument in three mechanical DOFs, e.g., pitch, yaw, and roll (shaft roll). There may also be one or more mechanical DOFs in the end effector itself, e.g., two jaws, each rotating with reference to a clevis (2 DOFs) and a distal clevis that rotates with reference to a proximal clevis (one DOF). Thus, in some embodiments, the medical instruments or devices of the present application enable motion in six DOFs. The embodiments described herein further can be used to determine the forces exerted on (or by) a distal end portion of the instrument during use.

[0051] Generally, the present disclosure is directed to systems and methods for controlling a surgical system (system) such as a minimally invasive teleoperated surgery system. In particular, the present disclosure includes a force sensing system that can include proximal and distal force sensor units configured to mitigate electromagnetic interference. The force sensor units can be employed with a force sensing medical instrument (instrument) to provide an indication of force affecting the instrument. This indication of the force(s) can be used by the system to deliver haptic feedback to a user control unit of the system.

[0052] The distal force sensor unit can include a strain sensor coupled to a resiliently deformable beam. The beam is configured to deform in response to a load affecting at a distal end portion of the instrument. The strain sensor includes strain gauges that measure the resultant strain in the beam due to the deflection. In some embodiments, a sensor signal cable can be coupled to the distal force sensor unit, extend proximally, and be coupled to an electronic circuit board of the medical device. The sensor signal cable carries the strain signal to the electronic circuit board. Further details regarding the sensor signal cable are provided in U.S. Provisional Patent Application No. 63/425,520, filed November 15, 2022, the disclosure of which is incorporated herein by reference. The strain sensor indicates the strain magnitude in the form of relatively small voltage differentials. In some embodiments, the strain gauges are arranged in a split-bridge configuration with one half of the split-bridge configured to carry a signal from one location on the beam (“positive”) and the other half configured to carry a signal from a different location on the beam (“negative”). The voltage differential, as opposed to an absolute voltage, between the signal carried by the positive trace and the signal carried by the negative trace is indicative of the measured strain magnitude in the absence of electromagnetic interference. [0053] During certain procedures, the distal force sensor unit can be exposed to an electrical field. This exposure can result in the development of electromagnetic interference that can affect the signals in the positive and/or negative traces. For example, a current conducted through a portion of the distal force sensor unit, such as the beam, can induce an unintended current in another portion of the distal force sensor unit. The induced current can result from capacitive coupling and/or inductive coupling between the various conductive components of the distal force sensor unit. The magnitude of the induced current, and thus the magnitude of the electromagnetic interference, can be affected by the positions and/or orientations of the various conductive components of the distal force sensor unit relative to one another. When the magnitude of the electromagnetic interference (i.e., the generated current(s)) in one of the traces is greater than the magnitude of the electromagnetic interference in other trace, then the voltage differential, and thus the measured strain magnitude, is distorted. However, when a difference between the magnitude of the electromagnetic interference in each of the traces is minimized, the effect of electromagnetic interference in one trace is substantially cancelled out by the electromagnetic interference in the other trace, and vice versa. Accordingly, it is desirable to mitigate the effects of the electromagnetic interference by minimizing a differential between the induced current in the positive trace coupled to one half of the split-bridge and the induced current in the corresponding negative trace coupled to the other half of the split-bridge. Further details regarding such embodiments are described in U.S. Provisional Application No. 63/425,518, filed November 15, 2022, the disclosure of which is incorporated herein by reference.

[0054] In some operations, exposure to the electrical field can result in an electric current being conducted by the beam. This current can induce, via capacitive coupling, a current in the strain sensor components that are mechanically coupled to the beam by an insulator. However, the distance between each of the components of the strain sensor and the beam can vary based, for example, on variability in the thickness of the adhesive employed to couple the components to the beam. This variability in the distance between the components in the beam results in capacitively induced currents of varying magnitudes within the strain sensor. Accordingly, in some embodiments the distal force sensor unit described herein is configured to reduce or eliminate the variability in the magnitudes of the induced currents. The distal force sensor unit utilizes an electrically conductive layer positioned between the beam and the strain sensor, with an electrically insulative layer positioned between the electrically conductive layer and the strain sensor. As such, the insulative layer can have a uniform thickness and the electrically conductive layer can have a flatness that is within a specified flatness tolerance. The uniform thickness and/or the flatness can establish the strain sensor at a uniform separation distance from the electrically conductive layer. The electrically conductive layer is electrically coupled to the beam such that a current conducted by the beam is likewise conducted by the electrically conductive layer. As a result, the magnitude of the capacitively induced current in the various components (e.g., the strain gauges) of the strain sensor is determined by the uniform distance between the strain sensor and the electrically conductive element rather than by the variable distances between the strain sensor components and the beam. As the strain sensor has a uniform separation distance with the electrically conductive layer, the induced current introduced to the positive trace is substantially equal to the induced current introduced to the corresponding negative trace, resulting in the canceling out of the electromagnetic interference effects.

[0055] In some operations, exposure to the electrical field can result in electromagnetic interference (EMI) resulting from inductive coupling between various components of the strain sensor. In order to mitigate the effects of the inductive coupling, the strain sensor can be configured to maximize longitudinal symmetry and lateral symmetry. The symmetry of the strain sensor facilitates the canceling out of the various inductively induced currents, and thus the canceling out of the effects of electromagnetic interference. For example, as described herein, the strain sensor can include a first region that is adjacent to a first strain gauge and a second region that is adjacent to a second strain gauge.

[0056] The medical instruments described herein include a proximal force sensor unit that includes a compact inductive force sensor to measure forces applied to the end effector of the medical instrument in an axial direction (parallel to the instrument shaft’s long axis; Z direction in a Cartesian system). As described herein, two inductive coils are each wound around a polymeric cylinder and a magnet (e g., a ferrite bead, EMI suppression bead, nickel-zinc bead, etc.; the term “magnet” as used herein is described in more detail below) held by a rod is movably positioned within each of the coils. As the magnets are moved axially within their respective coil, a change in inductance at each coil results. The change in inductance at each of the coils can be used to measure changes in position of the instrument shaft, which can be used to determine z-axis force measurements. The inductive force sensors described herein provide for redundancy of force measurements by using two inductive coils positioned side-by-side. This arrangement also reduces the overall height of the force sensor, thereby conserving space within the proximal mechanical structure. Such an embodiment is described in more detail in International PCT Application No. PCT/US2021/049792, filed September 10, 2021, the disclosure of which is incorporated herein by reference.

[0057] As described above, when the medical device is an electrosurgical type device that provides electrical energy (e.g., a cautery device), there is typically an insulator between the cable drive pulley on the instrument tools (e.g., grips) and the portion of tools that are exposed to the electrical energy. The presence of the insulator causes the components between the end effector, distal force sensor unit and cables to generally be at a lower voltage. In a situation where the medical device is a non-cautery type instrument and there is no insulator between the end effector and the cable drive pulleys on the instrument tools, but the end effector is nevertheless energized by electrical energy, the cable drive pulley, distal force sensor unit, and a circuit board ground plane of the instrument may all be at a higher voltage. For example, the tools may be energized through contact with another electrical source or medical instrument. Thus, a ground path GP is provided between the tool of the end effector and the electronic circuit board to accommodate for this higher voltage. The drive element is electrically connected to the electronic circuit board through a proximal pulley (which can function as an idler pulley) and a grounding screw to maintain the drive element, drive pulley, and distal force sensor unit all on the same ground voltage. In some embodiments, the ground plane of the electronic circuit board can include an electrically conductive layer that functions as an electrically grounded electrically conductive shield. In alternative embodiments, the electrically conductive shield can be a separate electrically conductive component positioned to function as an electrically grounded electrically conductive shield. The force-sensing signals from the distal force sensor unit can then be isolated from the energy caused by cautery or other electrical energy applied to the end effector.

[0058] As described herein, in some embodiments, the electrically conductive layer of the electronic circuit board is extended underneath or distal to the inductive coil force sensors. The inductive coil force sensors are positioned relative to the electrically conductive layer such that a close distance and spatial uniformity of the capacitive coupling between the sensors and the electrically conductive layer in the electronic circuit board is maintained, which limits the likelihood of an eddy current from the sensors from producing spatial non-uniformity in electric potential of the electronic circuit board, which couples the sensors capacitively to the ground plane, and ensures both sensors are equally affected. Thus, a uniform separation distance in multiple directions between the inductive force sensors and the electrically conductive layer of the electronic circuit board is established. In some embodiments, a gap defined in the electrically conductive layer of the electronic circuit board is provided to limit the likelihood of eddy current in the inductive coil sensors from producing spatial non-uniformity in electric potential of the electronic circuit board. In such an embodiment, the electrically conductive layer (i.e., ground plane) spans the entire circuit board and divides around the inductive coil sensors to protect the ground path defined between the distal force sensor beam and the electronic circuit board from magnetic fields caused by the inductive coil sensors.

[0059] As used herein, the term “about” when used in connection with a referenced numeric indication means the referenced numeric indication plus or minus up to 10 percent of that referenced numeric indication. For example, the language “about 50” covers the range of 45 to 55. Similarly, the language “about 5” covers the range of 4.5 to 5.5.

[0060] The term “flexible” in association with a part, such as a mechanical structure, component, or component assembly, should be broadly construed. In essence, the term means the part can be repeatedly bent and restored to an original shape without harm to the part. Certain flexible components can also be resilient. For example, a component (e.g., a flexure) is said to be resilient if possesses the ability to absorb energy when it is deformed elastically, and then release the stored energy upon unloading (i.e., returning to its original state). Many “rigid” objects have a slight inherent resilient “bendiness” due to material properties, although such objects are not considered “flexible” as the term is used herein.

[0061] As used in this specification and the appended claims, the word “distal” refers to direction towards a work site, and the word “proximal” refers to a direction away from the work site. Thus, for example, the end of a tool that is closest to the target tissue would be the distal end of the tool, and the end opposite the distal end (i.e., the end manipulated by the user or coupled to the actuation shaft) would be the proximal end of the tool. [0062] Further, specific words chosen to describe one or more embodiments and optional elements or features are not intended to limit the invention. For example, spatially relative terms — such as “beneath”, “below”, “lower”, “above”, “upper”, “proximal”, “distal”, and the like — may be used to describe the relationship of one element or feature to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions (i.e., translational placements) and orientations (i.e., rotational placements) of a device in use or operation in addition to the position and orientation shown in the figures. For example, if a device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be “above” or “over” the other elements or features. Thus, the term “below” can encompass both positions and orientations of above and below. A device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along (translation) and around (rotation) various axes include various spatial device positions and orientations. The combination of a body’s position and orientation defines the body’s pose.

[0063] Similarly, geometric terms, such as “parallel”, “perpendicular”, “round”, or “square”, are not intended to require absolute mathematical precision, unless the context indicates otherwise. Instead, such geometric terms allow for variations due to manufacturing or equivalent functions. For example, if an element is described as “round” or “generally round,” a component that is not precisely circular (e.g., one that is slightly oblong or is a many-sided polygon) is still encompassed by this description.

[0064] In addition, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. The terms “comprises”, “includes”, “has”, and the like specify the presence of stated features, steps, operations, elements, components, etc. but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, or groups.

[0065] Unless indicated otherwise, the terms apparatus, medical device, instrument, and variants thereof, can be interchangeably used.

[0066] Inventive aspects are described with reference to a teleoperated surgical system. An example architecture of such a teleoperated surgical system is the da Vinci® surgical system commercialized by Intuitive Surgical, Inc., Sunnyvale, California. Knowledgeable persons will understand, however, that inventive aspects disclosed herein may be embodied and implemented in various ways, including computer-assisted, non-computer-assisted, and hybrid combinations of manual and computer-assisted embodiments and implementations. Implementations are merely presented as examples, and they are not to be considered as limiting the scope of the inventive aspects disclosed herein. As applicable, inventive aspects may be embodied and implemented in both relatively smaller, hand-held, hand-operated devices and relatively larger systems that have additional mechanical support.

[0067] FIG. l is a plan view illustration of a teleoperated surgical system (“system”) 1000 that operates with at least partial computer assistance (a “telesurgical system”). Both telesurgical system 1000 and its components are considered medical devices. Telesurgical system 1000 is a Minimally Invasive Robotic Surgical (MIRS) system used for performing a minimally invasive diagnostic or surgical procedure on a Patient P who is lying on an Operating table 1010. The system can have any number of components, such as a user control unit 1100 for use by an operator of the system, such as a surgeon or other skilled clinician S, during the procedure. The MIRS system 1000 can further include a manipulator unit 1200 (popularly referred to as a surgical robot) and an optional auxiliary equipment unit 1150. The manipulator unit 1200 can include an arm assembly 1300 and a surgical instrument tool assembly removably coupled to the arm assembly. The manipulator unit 1200 can manipulate at least one removably coupled medical instrument (instrument) 1400 (e.g., a force sensing medical instrument) through a minimally invasive incision in the body or natural orifice of the patient P while the surgeon S views the surgical site and controls movement of the instrument 1400 through control unit 1100. An image of the surgical site is obtained by an endoscope (not shown), such as a stereoscopic endoscope, which can be manipulated by the manipulator unit 1200 to orient the endoscope. The auxiliary equipment unit 1150 can be used to process the images of the surgical site for subsequent display to the Surgeon S through the user control unit 1100. The number of instruments 1400 used at one time will generally depend on the diagnostic or surgical procedure and the space constraints within the operating room, among other factors. If it is necessary to change one or more of the instruments 1400 being used during a procedure, an assistant removes the instrument 1400 from the manipulator unit 1200 and replaces it with another instrument 1400 from a tray 1020 in the operating room. Although shown as being used with the instruments 1400, any of the instruments described herein can be used with the system 1000.

[0068] FIG. 2 is a perspective view of the user control unit 1100. The user control unit 1100 includes a left eye display 1112 and a right eye display 1114 for presenting the surgeon S with a coordinated stereoscopic view of the surgical site that enables depth perception. The user control unit 1100 further includes one or more input control devices 1116 (input device), which in turn causes the manipulator unit 1200 (shown in FIG. 1) to manipulate one or more tools. The input devices 1116 provide at least the same degrees of freedom as instruments 1400 with which they are associated to provide the surgeon S with telepresence, or the perception that the input devices 1116 are integral with (or are directly connected to) the instruments 1400. In this manner, the user control unit 1100 provides the surgeon S with a strong sense of directly controlling the instruments 1400. To this end, position, force, strain, or tactile feedback sensors (not shown) or any combination of such sensations, from the instruments 1400 back to the surgeon's hand or hands through the one or more input devices 1116.

[0069] The user control unit 1100 is shown in FIG. 1 as being in the same room as the patient so that the surgeon S can directly monitor the procedure, be physically present if necessary, and speak to an assistant directly rather than over the telephone or other communication medium. In other embodiments, however, the user control unit 1100 and the surgeon S can be in a different room, a completely different building, or other location remote from the patient, allowing for remote surgical procedures.

[0070] FIG. 3 is a perspective view of the auxiliary equipment unit 1150. The auxiliary equipment unit 1150 can be coupled with the endoscope (not shown) and can include one or more processors to process captured images for subsequent display, such as via the user control unit 1100, or on another suitable display located locally (e.g., on the unit 1150 itself as shown, on a wall-mounted display) and/or remotely. For example, where a stereoscopic endoscope is used, the auxiliary equipment unit 1150 can process the captured images to present the surgeon S with coordinated stereo images of the surgical site via the left eye display 1112 and the right eye display 1114. Such coordination can include alignment between the opposing images and can include adjusting the stereo working distance of the stereoscopic endoscope. As another example, image processing can include the use of previously determined camera calibration parameters to compensate for imaging errors of the image capture device, such as optical aberrations.

[0071] FIG. 4 shows a front perspective view of the manipulator unit 1200. The manipulator unit 1200 includes the components (e.g., arms, linkages, motors, sensors, and the like) to provide for the manipulation of the instruments 1400 and an imaging device (not shown), such as a stereoscopic endoscope, used for the capture of images of the site of the procedure. Specifically, the instruments 1400 and the imaging device can be manipulated by teleoperated mechanisms having one or more mechanical joints. Moreover, the instruments 1400 and the imaging device are positioned and manipulated through incisions or natural orifices in the patient P in a manner such that a center of motion remote from the manipulator and typically located at a position along the instrument shaft is maintained at the incision or orifice by either kinematic mechanical or software constraints. In this manner, the incision size can be minimized.

[0072] FIG. 5 is a schematic illustration of a medical device 2400 (e.g., an instrument), according to an embodiment. In some embodiments, the medical device 2400 or any of the components therein are optionally parts of a surgical system that performs surgical procedures. The surgical system can include a manipulator unit, a series of kinematic linkages, a series of cannulas, or the like. The medical device 2400 (and any of the instruments described herein) can be used in any suitable surgical system, such as the MIRS system 1000 shown and described above. The medical device 2400 includes a proximal mechanical structure 2700, a shaft 2410 coupled to the proximal mechanical structure 2700, a force sensor system that includes a distal force sensor unit 2800, a tool 2462 coupled to the distal force sensor unit 2800, a drive element 2420 coupled between the tool 2462 and the proximal mechanical structure, and an electronic circuit board 2920 coupled within or to the proximal mechanical structure 2700. The distal force sensor unit 2800 includes a beam 2810 coupled to the shaft 2410. The tool 2462 can include, for example, articulatable jaws or another suitable surgical tool that is coupled to a link (not shown). In some embodiments, the link can be included within a wrist assembly having multiple articulating links. The shaft 2410 includes a distal end portion 2412 that is coupled to a proximal end portion of the beam 2810 and a proximal end portion 2411 coupled to the proximal mechanical structure 2700. The drive element 2420 can be, for example, a cable, band, rod or the like. The proximal mechanical structure 2700 can include components configured to actuate the drive element 2420, which causes one or more components of the surgical instrument to move, such as, for example, the tool 2460. The proximal mechanical structure 2700 can be similar to the proximal mechanical structure 4700 described in more detail below with reference to medical device 4400. As shown in FIG. 5, an electrical ground path GP is defined between the tool 2462 and/or distal force sensor unit 2800 and the electronic circuit board 2920 as described in more detail below.

[0073] Generally, during a medical procedure, the tool 2462 contacts anatomical tissue, which may result in x and y direction forces, which can be radial, transverse, or perpendicular to the shaft’s long axis or z direction forces, which are axial or parallel to the shaft’s long axis (see, e.g., x, y, and z axes directions shown in FIG. 8) being imparted on the tool 2462. In some embodiments, one or more strain sensors (not shown), which can include one or more strain gauges, can be coupled to a beam 2810 of the distal fore sensor unit 2800 to measure strain in the beam during operation of the medical device. The measured beam strain can be used to determine forces imparted on the tool 2462 in 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 collinear with a center axis Cb of the beam).

[0074] As described above, when the medical device is a cautery type device that provides electrical energy, there is typically an insulator between drive pulleys of the tool 2462 in which the drive element 2420 engages and the tool (e.g., jaws”) itself which is exposed to the electrical energy. The presence of the insulator causes the components between the tool 2462, distal force sensor unit 2800 and the drive element 2420 to generally be at a lower voltage. In a situation where the medical device is a non-cautery type instrument and there is no insulator between the tool 2462 and the drive pulley on the tool 2420, but the tool 2462 is nevertheless energized by electrical energy, the drive pulley, distal force sensor unit 2800, and a ground plane of the electronic circuit board 2920 may all be at a high voltage. For example, the tool may be energized through contact with another electrical source or medical instrument. Thus, the ground path GP is provided between the tool 2462 and the electronic circuit board 2920 to accommodate for this higher voltage and create a “floating ground” at the electronic circuit board 2920 referenced to the voltage at the distal end of the medical device 2400. In other words, the floating ground maintains the electronic circuit board 2920 at a voltage the same as the voltage at the distal end of the medical device 2400. To establish the ground path GP, the drive element 2420 is electrically connected to the electronic circuit board 2920 through a grounding screw (not shown in FIG. 5) to maintain the drive element 2420, drive pulley, and distal force sensor unit 2800 all on the same ground voltage. In some embodiments, the ground plane of the electronic circuit board 2920 can include an electrically conductive layer that functions as an electrically grounded electrically conductive shield. In alternative embodiments, the electrically conductive shield can be a separate electrically conductive component positioned to function as an electrically grounded electrically conductive shield.

[0075] As described above, and as shown in FIG. 5, the ground path GP is defined from the tool 2462 to electronic circuit board 2920. In some embodiments, the ground path GP is defined from the distal force sensor unit 2800 to the electrically conductive layer of the electronic circuit board 2920. This maintains a ground from, for example, the beam of the distal force sensor unit 2800 to the electrically conductive layer. As described previously, the force-sensing signals from the distal force sensor unit 2800 need to be immune from or not substantially impacted by the energy caused by cautery or other electrical energy applied to the tool 2462. Thus, when the distal force sensor unit 2800 and drive element 2420 are energized, the electronic circuit board 2920 is electrically connected to the drive element 2420 such that the distal force sensor unit 2800 and drive element 2420 are on the same ground voltage. Thus, the ground path GP provides a low impedance ground connection between the tool 2462 and/or distal force sensor unit 2800 and the circuit board 2920. This arrangement minimizes or eliminates any voltage difference between these components at the distal end of the medical device 2400 and the circuit board 2920 that could result from voltage losses due to higher impedance. In some embodiments, the impedance of the ground path GP is less than about 1 ohm. In other embodiments, the impedance of the ground path GP is less than about 2 ohms.

[0076] As described herein, in some embodiments, the electrically conductive layer of the electronic circuit board 2920 is extended underneath or distal to the inductive coil force sensors. The inductive coil force sensors are positioned relative to the electrically conductive layer such that a close separation and spatial uniformity of the capacitive coupling between the sensors and the electrically conductive layer in the electronic circuit board 2920 is maintained. This positioning limits the likelihood of an eddy current from the sensors producing spatial nonuniformity in electric potential of the electronic circuit board 2920. Thus, a uniform separation distance in multiple directions between the inductive force sensors and the electrically conductive layer of the electronic circuit board 2920 is established. In some embodiments, a gap (not shown in FIG. 5) is defined in the electrically conductive layer of the electronic circuit board 2920 which limits the likelihood of eddy current in the inductive coil sensors from producing spatial nonuniformity in electric potential of the electronic circuit board 2920. In such an embodiment, the electrically conductive layer (i.e., ground plane) spans the entire surface area of the electronic circuit board 2920 and divides around an area where the inductive coil sensors are positioned to protect the ground path GP defined between the distal force sensor beam and the electronic circuit board 2920 from magnetic fields caused by the inductive coil sensors.

[0077] FIG. 6 is a schematic illustration of portion of a medical device 3400, according to another embodiment. In some embodiments, the medical device 3400 or any of the components therein are optionally parts of a surgical system that performs surgical procedures, and which can include a manipulator unit, a series of kinematic linkages, a series of cannulas, or the like. The medical device 3400 (and any of the instruments described herein) can be used in any suitable surgical system, such as the MIRS system 1000 shown and described above. The medical device 3400 includes a proximal mechanical structure 3700, an electronic circuit board 3920 coupled to or within the proximal mechanical structure 3700, multiple electrically conductive traces 3925, an electrically grounded electrically conductive shield 3922 positioned distally under the electrically conductive traces 3925, and a force sensor system that includes a proximal force sensor unit 3900. The proximal force sensor unit 3900 includes a sensor element 3912 positioned proximally over the electrically conductive traces 3925. As shown in FIG. 6, a physical electrical connection exists between the sensor element 3912 and one or more of the electrically conductive traces 3925 and no physical electrical connection exists between the sensor element 3912 and the electrically conductive shield 3922.

[0078] In some embodiments, the electrically conductive traces 3925 can optionally be electrically coupled to a ground (as shown in FIG. 6), which can be, for example, a local ground, or an earth ground. In some embodiments, the medical device 3400 further includes a distal force sensor unit (not shown in FIG. 6) as described above for medical device 2400, and a sensor signal cable (not shown) electrically coupled between the distal force sensor unit and the electronic circuit board 3920. The sensor signal cable can include an electrical ground trace and the electrical ground trace of the sensor signal cable can define a portion of a second ground path between the distal force sensor unit and the electrical ground. In this manner, the force sensor system includes a primary ground path (GP as described above) and a secondary ground path. This arrangement produces a low impedance ground connection between the tool 2462 and/or distal force sensor unit 2800 and the circuit board 2920.

[0079] Although not shown in FIG. 6, the medical device 3400 can also include a shaft coupled to the proximal mechanical structure 3700, a distal force sensor unit including a beam coupled to the shaft, an end effector including a tool coupled at a distal end portion of the beam, and a drive element coupled between the tool and the proximal mechanical structure 3700 as described above for medical device 2400. The tool can include, for example, articulatable jaws or another suitable surgical tool that is coupled to a link (not shown). In some embodiments, the link can be included within a wrist assembly having multiple articulating links. The shaft can include a distal end portion that is coupled to a proximal end portion of the beam and a proximal end portion coupled to the proximal mechanical structure 3700. The drive element can be, for example, a cable, band, rod or the like. The proximal mechanical structure 3700 can include components configured to actuate the drive element, which causes one or more components of the surgical instrument to move, such as, for example, the tool. The proximal mechanical structure 3700 can be similar to the proximal mechanical structure 4700 described in more detail below with reference to medical device 4400. An electrical ground path can also be defined between the tool and the electronic circuit board 3920. In some embodiments, the drive element defines a portion of the electrical ground path between the distal force sensor unit and an electrical ground or the tool and the electrical ground, or between both the distal force sensor unit and tool and the electrical ground.

[0080] The proximal force sensor unit 3900 (and any of the proximal force sensor units described herein) can be used to measure the axial force(s) (i.e., in the direction of the z-axis parallel to a center axis of a beam of a distal force sensor unit) (see e.g., x, y, and z axes directions in FIG. 8) imparted on the end effector. For example, an axial force imparted to the end effector in a direction of the z-axis can cause axial displacement of the shaft in a direction along a center axis of the shaft (substantially parallel to the beam center axis Cb). An axial force in the z-direction may be in the proximal direction (e.g., a reactive force resulting from pushing against tissue with the end effector) or it may be in the distal direction (e.g., a reactive force resulting from pulling tissue grasped with the end effector). In some embodiments, the shaft can be coupled to the proximal mechanical structure 3700 via a biasing mechanism (e.g., a linkage or a spring-loaded coupling, not shown) such that the amount of travel of the shaft relative to the proximal mechanical structure 3700 can be correlated to the magnitude of the axial force in the z direction imparted to the end effector. In this manner, measuring the distance through which the shaft moves relative to the proximal mechanical structure 3700 can be used to determine the axial force in the z direction. Further details regarding such an embodiment are described in International PCT Application No. PCT/US2021/049792, incorporated by reference above.

[0081] In some embodiments, the sensor element 3912 of the proximal force sensor unit 3900 is an inductive coil sensor that includes a coil assembly, a linkage, and a microprocessor (each not shown in FIG. 6) similar to or the same as described in International PCT Application No. PCT/US2021/049792, incorporated by reference above. The proximal force sensor unit 3900 can optionally include two sensor elements 3912, which can each be an inductive coil sensor. In such an embodiment, a physical electrical connection exists between the second sensor element and one or more of the plurality of electrically conductive traces 3925, and no physical electrical connection exist between the second sensor element and the electrically conductive shield 3922.

[0082] As described above, the electrically conductive shield 3922 extends underneath or distal to the sensor element 3912 and in an embodiment having two sensor elements, the electrically conductive shield 3922 is also extended underneath or distal to the second sensor element. The sensor elements 3912 and second sensor element are positioned relative to the electrically conductive shield 3922 such that a spatial uniformity of the capacitive coupling between the sensor elements and the electrically conductive shield 3922 is maintained. As described above, this limits the likelihood of an eddy current from the sensor elements from producing spatial non-uniformity in electric potential of the electronic circuit board 3920. Thus, a uniform separation distance in multiple directions between the sensor elements and the electrically conductive shield 3922 of the electronic circuit board 3920 is established. More details regarding such an embodiment are described below with reference to medical device 4400.

[0083] In some embodiments, a gap is defined in the electrically conductive shield 3922 to further limit the likelihood of eddy current in the sensor elements from producing spatial non- uniformity in electric potential of the electronic circuit board 3920. In such an embodiment, the electrically conductive shield 3922 spans the entire circuit board surface area and divides around the sensor elements to protect the ground path (as described above for FIG. 5) defined between the distal force sensor unit and the electronic circuit board 3920 from an electrically inductive coupling between the sensor elements and the electrically conductive shield 3922.

[0084] In some embodiments, the electronic circuit board includes a first layer and a second layer positioned distally under the first layer. In some such embodiments, the first layer includes the electrically conductive traces 3925, the second layer includes the electrically conductive shield 3922 and a portion of the first layer extends proximally above the gap.

[0085] In some embodiments, the electronic circuit board 3920 includes an opening and an outer edge (not shown in FIG. 6) and the electrically conductive shield 3922 surrounds the opening. In some such embodiments, a gap in the electrically conductive shield is defined between the opening of the electronic circuit board 3920 and the outer edge of the electronic circuit board 3920.

[0086] FIGS. 7-17 illustrate another medical device that includes a proximal force sensor unit configured and positioned to mitigate electromagnetic interference. In some embodiments, the medical device 4400 or any of the components therein are optionally parts of a surgical system that performs surgical procedures, and which can include a manipulator unit 4200, a series of kinematic linkages, a series of cannulas, or the like, and a control unit 4100. The manipulator 4200 and control unit 4100 can be configured the same as or similar to and function the same as or similar to the manipulator 1200 and control unit 1100 described above for surgical system 1000. The medical device 4400 (and any of the instruments described herein) can be used in any suitable surgical system, such as the MIRS system 1000 shown and described above. The medical device 4400 includes a proximal mechanical structure 4700, a force sensor system that includes a proximal force sensor unit 4900 and a distal force sensor unit 4800, a shaft 4410 coupled to the proximal mechanical structure 4700 and to the proximal force sensor unit 4900, and an end effector 4460 coupled to a wrist assembly 4500 at a distal end portion of the medical device 4400. The proximal mechanical structure 4700 is couplable to the manipulator unit 4200 which is couplable to the control unit 4100 either directly or indirectly. As shown, for example, in FIG. 8, medical device 4400 also includes one or more drive elements 4420 that couple the proximal mechanical structure 4700 to the wrist assembly 4500 and end effector 4460. The drive elements 4420 can be, for example, a cable, a band or the like. The medical device 4400 is configured such that select movements of the drive elements 4420 produce rotation of the wrist assembly 4500 (i.e., pitch rotation) about a first axis of rotation Ai (see FIG. 8) (which functions as a pitch axis; the term pitch is arbitrary), yaw rotation of the end effector 4460 about a second axis of rotation A2 (see FIG. 8) (which functions as the yaw axis; the term yaw is arbitrary), a cutting or gripping rotation of the tool members of the end effector 4460 about the second axis of rotation A2, or any combination of these movements. Changing the pitch or yaw of the instrument 4400 can be performed by manipulating the drive elements 4420 in a similar manner as described, for example, in U.S. Patent No. US 8,821,480 B2 (filed Jul. 16, 2008), entitled “Four-Cable Wrist with Solid Surface Cable Channels,” which is incorporated herein by reference in its entirety. Thus, the specific movement of each of the drive elements to accomplish the desired motion is not described below.

[0087] The shaft 4410 includes a proximal end portion 4411 that is coupled to the proximal mechanical structure 4700, and a distal end portion 4412 that is coupled to a beam 4810 of the distal force sensor unit 4800. The beam 4810 can include or have coupled thereto one or more strain sensors 4830 to measure forces imparted on the surgical instrument in the x and y directions during a surgical procedure. Although abeam 4810 with strain sensor 4830 is shown and described in this embodiment, in other embodiments, a beam 4810 and strain sensor 4830 may not be included. As shown in FIG. 8, a sensor signal cable 4840 is electrically coupled between the distal force sensor unit 4800 and the electronic circuit board 4920. The sensor signal cable 4840 includes one or more electrical ground traces 4890. The sensor signal cable 4840 extends proximally through the shaft 4410 and is coupled to a bottom or distal side of the electronic circuit board 4920 as shown in FIG. 17 and carries strain signals to the electronic circuit board 4920 as described above for medical device 3400. Further details regarding the sensor signal cable are provided in U.S. Provisional Patent Application No. 63/425,520, filed November 15, 2022, the disclosure of which is incorporated herein by reference.

[0088] The proximal end portion 4411 of the shaft 4410 is coupled to the proximal mechanical structure 4700 in a manner that allows translational movement of the shaft 4410 along a z-axis direction relative to the proximal mechanical structure 4700. Allowing the shaft 4410 to translate with reference to the proximal mechanical structure 4700 in the z direction facilitates measurement of forces along the z-axis, as described herein and as described in more detail in International PCT Application No. PCT/US2021/049792, incorporated by reference above. The shaft 4410 also defines a lumen (not shown) and/or multiple passageways through which the drive elements and other components (e.g., electrical wires, ground wires, or the like) can be routed from the proximal mechanical structure 4700 to the wrist assembly 4500.

[0089] The end effector 4460 included a first tool 4462 and a second tool 4482 each having a contact portion configured to engage or manipulate a target tissue during a surgical procedure. For example, in some embodiments, the contact portion can include an engagement surface that functions as a gripper, cutter, tissue manipulator, or the like. In other embodiments, the contact portion can be an energized tool member that is used for cauterization or electrosurgical procedures. The end effector 4460 is operatively coupled to the proximal mechanical structure 4700 such that the tools 4462 and 4464 rotate relative to shaft 4410 about the first axis of rotation Ai.

[0090] As described previously, during a medical procedure, the tools 4462, 4482 of the end effector 4460 contact anatomical tissue, which may result in x, y, or z direction forces (see, e.g., x, y, and z axes directions shown in FIG. 8) being imparted on the tools 4462, 4482. The strain sensors 4830 can measure strain in the beam 4810 during operation of the medical device 4400. The measured beam strain can be used to determine forces imparted on the tools 4462, 4482 in 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 collinear with a center axis of the beam).

[0091] The proximal mechanical structure 4700 includes a chassis that supports or contains components configured to actuate the drive elements 4420, which causes one or more components of the surgical instrument to move, such as, for example, the wrist assembly 4500 or the tools 4462, 4482. The drive elements 4420 extend from the proximal mechanical structure 4700 to drive pulleys 4467 and 4487 of the end effector 4460 for the tools 4462 and 4482, respectively (see FIG. 9). As shown in FIGS. 9 and 10, the proximal mechanical structure 4700 also includes an instrument support structure that includes a base 4770, an electronic circuit board 4920, the proximal force sensor unit 4900, and a common-mode choke 4763. The common-mode choke 4763 can be used to reduce interference with the electronic circuit board 4920. For example, because the ground path GP can be a floating ground (i.e., is not an earth ground), in certain situations the ground path GP can be at higher voltage due to energizing of the instrument as described herein. In such situations, the common-mode choke 4763 can impede the current flow that would otherwise flow towards the chassis of the proximal mechanical structure 4700. In other embodiments, various support structures optionally may be used, such as a chassis, a frame, a bed, a unitized surrounding outer body of the proximal mechanical structure, and the like.

[0092] The proximal mechanical structure 4700 surrounds (or is coupled to) the proximal force sensor unit 4900, which includes a coil assembly 4915, a linkage assembly 4950, which functions as a movable four-bar linkage, and a microprocessor (see example microprocessor in FIG. 20). The coil assembly 4915 includes a first inductive coil sensor element 4912 (also referred to as first sensor element), a second inductive coil sensor element 4914 (also referred to as second sensor element), a first rod (not shown), a second rod (not shown) a first magnet (not shown) coupled to the first rod, a second magnet (not shown) coupled to the second rod, and a mounting bracket 4937. The mounting bracket 4937 is secured within the proximal mechanical structure 4700 and is electrically coupled to the electronic circuit board 4920 via wiring 4935 (shown in FIGS. 12A- 13C). The first sensor element 4912 and the second sensor element 4914 are each mounted within the mounting bracket 4937 and positioned side-by-side to each other and are electrically coupled to the electronic circuit board 4920. The first sensor element 4912 and the second sensor element 4914 are each inductive coils and are each wound around a cylinder of an electrically nonconductive material, such as, for example, PEEK. The first sensor element 4912 and the second sensor 4914 can be made with identical characteristics, such as coil length, coil width, and thickness of the coil wire. The rods are coupled to the linkage assembly 4950, which is coupled to the shaft 4410 such that translational movement of the shaft 4410 in the z-axis direction causes the rods, and magnets coupled thereto, to translate in the z-axis direction within the first and second sensor elements 4912 and 4914. This movement causes a change in inductance at the coils, which can be used to measure changes in position of the shaft 4410, which can be converted to z-axis force measurements. Further details regarding the components and function of the proximal mechanical structure are described in International PCT Application No. PCT/US2021/049792, incorporated by reference above. [0093] As shown in FIG. 11, the proximal mechanical structure 4700 also includes one or more idler pulleys 4930, one or more pulley shafts 4932, and a pulley cover 4934. The drive elements 4420 are routed about the idler pulleys 4930 and are thus electrically coupled to the pulley shafts 4932. The pulley cover 4934 is positioned proximally over and electrically coupled to the idler pulley shafts 4932 (e.g., via a bushing or bearing). The pulley cover 4934 is also electrically coupled to the electronic circuit board 4920 with a grounding screw 4936 and gasket 4938. An o- ring 4940 is positioned between the electronic circuit board 4920 and the pulley cover 4934 to prevent corrosion at the electronic circuit board 4920. A plating component (not shown) is also provided inside the pulley cover 4930 near or at the attachment to the electronic circuit board 4920. The plating component can improve the electrical coupling (i.e., reduce the electrical resistance) between the pulley cover 4930 and the electronic circuit board 4920 (and the ground plane therein). By this arrangement, the drive elements 4420 provide a low resistance ground path GP from the distal end of the medical device to the electronic circuit board 4920.

[0094] As previously described herein, when the medical device is a cautery type device that provides electrical energy, there is an insulator (not shown) between the drive pulleys 4467, 4487 of the tools 4462, 4482 in which the drive elements 4420 engage and the tools 4462, 4482 (e.g., jaws”) which are exposed to the electrical energy. The presence of the insulator causes the components between the tools 4462, 4482, the distal force sensor unit 4800 and the drive elements 4420 to generally be at a lower voltage. In a situation where the medical device is a non-cautery type instrument, and there is no insulator between the tools 4462, 4482 and the drive pulleys 4467, 4487, but the tools 4462, 4482 are nevertheless energized by electrical energy, the drive pulleys 4467, 4487, the distal force sensor unit 4800, and a ground plane of the electronic circuit board 4920 may all be at a high voltage. For example, the tools 4462, 4482 may be energized through contact with another electrical source or medical instrument. Thus, a ground path GP is provided between the tools 4462, 4482 and the electronic circuit board 4920 to accommodate for this higher voltage (see FIGS. 12A and 12B) and to maintain the components at the same ground voltage. More specifically, the drive elements 4420 are electrically connected to the electronic circuit board 4920 through the grounding screw 4936 to maintain the drive elements 4420, pulleys 4467, 4487, and distal force sensor unit 4800 all on the same ground voltage. As described above, a floating ground is created at the electronic circuit board 4920 and maintains the electronic circuit board 4920 at the same voltage as the voltage at the distal end of the medical device 4400. In some applications (e.g., with an energized instrument), the potential of the floating ground can be above zero.

[0095] As shown in FIGS. 12A and 12B, the ground path GP is defined from the tools 4462, 4482, to the drive elements 4420, to the idler pulley 4930, pulley shaft 4932, pulley cover 4934, to the grounding screw 4936, to the electronic circuit board 4920, to the common-mode choke 4763 in the proximal mechanical structure 4700 and to the control unit 4100. More specifically, in this embodiment, the electronic circuit board 4920 includes a first layer 4921 that includes one or more electrically conductive traces 4925 (see FIG. 15), and a second layer 4922 (see FIG. 16) that includes an electrically conductive material that functions as an electrically grounded electrically conductive shield. The first layer 4921 is positioned above or proximally to the second layer 4922. The ground path GP is defined from the tools 4462, 4482, to the drive elements 4420, to the idler pulley 4930, pulley shaft 4932, pulley cover 4934, to the grounding screw 4936, to the electrically grounded electrically conductive second layer 4921 of the electronic circuit board 4920, to the common-mode choke 4763 in the proximal mechanical structure 4700 and to a control unit 4100. As described above, the common-mode choke 4763 can be used to reduce interference with the electronic circuit board 4920. For example, because the ground plane of the electronic circuit board 4920 is a floating ground with reference to the voltage of the distal end of the medical device 4400, the electronic circuit board 4920 could in some instances be at a high cautery potential, in which case the current would tend to flow to the support structure of the proximal mechanical structure 4700. In such cases, the common-mode choke 4763 impedes this current if it is flowing in the same direction down the different wires of the medical device 4400, such as for example, a ground wire, power wire, and drive cables.

[0096] In some embodiments, the ground path GP is defined from the distal force sensor unit 4800 to the electrically conductive second layer 4922 of the electronic circuit board 4920. This maintains a ground from, for example, the beam 4810 of the distal force sensor unit 4800 to the electrically conductive second layer 4922. As described previously, with this grounding configuration, the force-sensing signals from the distal force sensor unit 4800 can be isolated from the energy caused by cautery or other electrical energy applied to the tools 4462, 4482. Thus, when the distal force sensor unit 4800 and drive elements 4420 are energized, the electronic circuit board 4920 is electrically connected to the drive elements 4420 such that the distal force sensor unit 4800 and drive elements 4420 are on the same ground voltage.

[0097] As described herein, the electronic circuit board 4920 is extended underneath or distal to the sensor elements 4912, 4914. The sensor elements are positioned relative to the electrically conductive second layer 4921 of the electronic circuit board 4920 such that a spatial uniformity of the capacitive coupling between the sensor elements 4912, 4914 and the electrically conductive second layer 4922 is maintained. This limits the likelihood of an eddy current from the sensor elements 4912, 4914 from producing spatial non-uniformity in electric potential of the electronic circuit board 4920. Thus, a uniform separation distance in multiple directions between the inductive force sensor elements 4912, 4914 and the electrically conductive second layer 4921 of the electronic circuit board 4920 is established.

[0098] More specifically, as shown, for example, in FIGS. 13A-14C, the electronic circuit board 4920 defines an opening 4923 and an outer peripheral edge 4924. The electronic circuit board 4920 and the electrically conductive second layer 4922 of the electronic circuit board 4920 is extended at least partially underneath or distal to the sensor elements 4912, 4914 such that the rods and magnets (not shown) of the sensor elements 4912, 4924 can extend through the opening 4923 and are connected to the linkage 4950 and shaft 4410 as described above. A physical electrical connection exists between the sensor elements 4912, 4914 and one or more of the plurality of electrically conductive traces 4925 (see FIG. 15) of the first layer 4921 via the wiring connection 4935 and pogo pins 4941 (see FIG. 14C). However, no physical electrical connection exists between the sensor elements 4912, 4914 and the electrically conductive second layer 4922. As shown, for example, in FIGS. 14A-14C, the sensor elements 4912, 4914 are positioned relative to the electrically conductive second layer 4922 such that a spatial uniformity of the capacitive coupling between the sensor elements 4912, 4914 and the electrically conductive second layer shield 4922 is maintained. By extending the outer peripheral edge 4924 past the sensor element 4912, the capacitive coupling between the electrically conductive second layer 4922 and the sensor element 4912 is substantially the same as the capacitive coupling between the electrically conductive second layer 4922 and the sensor element 4914. As described above, this limits the likelihood of an eddy current from the sensor elements 4912, 4914 from producing spatial nonuniformity in electric potential of the electronic circuit board 4920. For example, as shown in the top view of FIG. 14B, the sensor element 4912 and the sensor element 4914 are each positioned above the electronic circuit board 4920 and the opening 4923 equidistance in both the X and Y directions. As shown in FIG. 14C, the first sensor element 4912 is spaced in the z-direction a distance dl from the electronic circuit board 4920, and the second sensor element 4914 is spaced in the z-direction a distance d2 from the electronic circuit board 4920, where dl is equal to d2. Thus, a uniform separation distance in multiple directions (x- y- and z- directions) between the sensor elements 4912, 4914 and the electrically conductive second layer 4922 of the electronic circuit board 4920 is established.

[0099] Further, as shown in FIG. 16, the electrically conductive second layer 4922 includes a gap 4926 that is defined between the opening 4923 and the outer peripheral edge 4924 of the electronic circuit board 4920. The gap 4926 is provided to further limit the likelihood of eddy current in the inductive coil sensor elements 4912, 4914 from producing spatial non-uniformity in electric potential of the electronic circuit board 4920. In such an embodiment, the electrically conductive material of the second layer 4922 spans across the entire surface area of the second layer 4922 of the electronic circuit board 4920, and divides around the inductive coil sensor elements 4912, 4914 to protect the ground path GP from magnetic fields caused by the inductive coil sensor elements 4912, 4914.

[0100] FIG. 18 is a block diagram of a portion of an embodiment of a proximal force sensor unit 5900 that can be implemented to measure axial force applied to an instrument shaft 5410. The proximal force sensor unit 5900 can be implemented as an inductive z-axis force sensor unit as described above for any of the previous embodiments (including the proximal force sensor unit 5900). As described above, an axial force on the instrument shaft 5410 results in an axial movement of the instrument shaft 5410, which can be detected by the proximal force sensor unit 5900. The proximal force sensor unit 5900 can include a coil assembly 5915 as described herein that includes a pair of coils 5912 and 5914 with a rod 5916 and rod 5918 movably positioned within the coils 5912 and 5914, respectively. The rod 5916 can have a magnet 5931 coupled thereto and the rod 5918 can have a magnet 5933 coupled thereto.

[0101] The coil 5912 can be coupled to a multi-channel frequency detection block 5965 by a capacitor C that can form an inductor/capacitor (LC) circuit with the coil 5912 with an inductance contribution based on the distance the rod 5916 and magnet 5931 move within the coil 5912. The coil 5914 can be coupled to the multi-channel frequency detection block 5965 by a capacitor C that can form an LC circuit with the coil 5914 with an inductance contribution based on the distance the rod 5918 and magnet 5933 move within the coil 5914. The LC circuits associated with the coils 5912 and 5914 can be implemented with different capacitances in implementations where such differences are taken into account.

[0102] The multi-channel frequency detection block 5965 can be implemented as a precision, dual inductance sensor that measures the inductance. With the capacitor C forming an LC circuit with the coil 5912 input to the multi-channel frequency detection block 5965, the multi-channel frequency detection block 5965 can output a first signal associated with a frequency of this circuit, for example a ratio of the frequency with a known reference frequency. With the capacitor C forming an LC circuit with the coil 5914 input to the multi-channel frequency detection 5965, the multi-channel frequency detection block 5965 can output a second signal associated with a frequency of this circuit, for example a ratio of the frequency with a known reference frequency. The multi-channel frequency detection block 5965 can output N digital signals to a microprocessor 5952. For two LC circuits, the multi-channel frequency detection block 5965 can output two digital signals to the microprocessor 5970.

[0103] The microprocessor 5952 can include or have access to an EEPROM 5972 or other storage device that can include calibration values for implementation of the magnet 5931 within the coil 5912 and the magnet 5933 within the coil 5914. In a measurement of axial force on the instrument shaft, the calibration values can be accessed to determine a distance moved for each magnet 5931 and 5933 based on the frequencies received from the multi-channel frequency detection block 5965. The difference in frequencies can be stored in the EEPROM 5972 as a difference of inductance as a function of distances. This difference of distances can be correlated with a reference position and the difference in inductances. With a distance selected from a measured difference in inductances, the distance can be used with a spring constant stored in the EEPROM 5972, where the spring constant is a property of a spring (e.g., spring 5829 described above) by which the instrument shaft 5410 is coupled to a support structure on which the proximal force sensor unit 5900 can be deployed. [0104] The proximal force sensor unit 5900 can include other optional components. For example, the microprocessor 5952 can include a Universal Asynchronous Receiver/Transmitter (UART) interface 5974 or other communication interface to transmit (TX) a digital output and receive (RX) a digital signal. The received signal can be used to update calibration values in the EEPROM 5972 of the microprocessor 5952. A common-mode choke 5763 (such as commonmode choke 5863) can be used to reduce interference with other electronic circuit boards of the support structure on which the proximal force sensor unit 5900 is deployed. Optionally, the proximal force sensor unit 5900 can include a magnetic structure 5962 between the common-mode choke 5763 and the microprocessor 5952. The magnetic structure 5962 can be inserted to help with electromagnetic interference (EMI) radiation reduction. The magnetic structure 5962 can be realized as a ferrite bead. Other magnetic material formats can be implemented for the magnetic structure 5962, as described above.

[0105] A machine-readable storage device may include any non-transitory mechanism for storing information in a form readable by a machine, for example, a computer or a microprocessor tasked to perform specific functions. For example, a machine-readable storage device may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. In various embodiments of a medical device with a proximal force sensor unit described herein, a non- transitory machine-readable medium can comprise instructions, which when executed by one or more processors, can cause a system to perform operations that include without limitation: (i) receiving a first signal generated by a first coil associated with a position of a first magnet with reference to the first coil, (ii) receiving a second signal generated by a second coil associated with a position of a second magnet with reference to a second coil, and where 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 center axis of the shaft. The force sensor unit can comprise a microprocessor coupled to receive the first and second signals. In various embodiments, a non-transitory machine- readable medium can comprise instructions, which when executed by one or more processors cause a system to perform operations comprising methods of performing functions associated with the various embodiments described herein. [0106] While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Where methods and/or schematics described above indicate certain events and/or flow patterns occurring in certain order, the ordering of certain events and/or operations may be modified. While the embodiments have been particularly shown and described, it will be understood that various changes in form and details may be made.

[0107] For example, any of the instruments described herein (and the components therein) are optionally parts of a telesurgical system that performs minimally invasive surgical procedures, and which can include a manipulator unit, a series of kinematic linkages, a series of cannulas, or the like. Thus, any of the instruments described herein can be used in any suitable surgical system, such as the MIRS system 1000 shown and described above. Moreover, any of the instruments shown and described herein can be used to manipulate target tissue during a surgical procedure. Such target tissue can be cancer cells, tumor cells, lesions, vascular occlusions, thrombosis, calculi, uterine fibroids, bone metastases, adenomyosis, or any other bodily tissue. The presented examples of target tissue are not an exhaustive list. Moreover, a target structure can also include an artificial substance (or non-tissue) within or associated with a body, such as for example, a stent, a portion of an artificial tube, a fastener within the body or the like.

[0108] For example, any of the components of a surgical instrument as described herein can be constructed from any material, such as medical grade stainless steel, nickel alloys, titanium alloys or the like. Further, any of the links, tool members, beams, shafts, connectors, cables, or other components described herein can be constructed from multiple pieces that are later joined together. For example, in some embodiments, a link can be constructed by joining together separately constructed components. In other embodiments however, any of the links, tool members, beams, shafts, connectors, cables, or components described herein can be monolithically constructed.

[0109] Although the instruments are generally shown as having an axis of rotation of the tool members (e.g., axis A2) that is normal to an axis of rotation of the wrist member (e.g., axis Ai), in other embodiments any of the instruments described herein can include a tool member axis of rotation that is offset from the axis of rotation of the wrist assembly by any suitable angle. Although various embodiments have been described as having particular features and/or combinations of components, other embodiments are possible having a combination of any features and/or components from any of embodiments as discussed above. Aspects have been described in the general context of medical devices, and more specifically surgical instruments, but inventive aspects are not necessarily limited to use in medical devices.

Claims

What is claimed is:

1. A medical device comprising: a shaft including a proximal end portion and a distal end portion; a tool movably coupled to the distal end portion of the shaft; a distal force sensor unit coupled to the distal end portion of the shaft; a proximal mechanical structure coupled to the proximal end portion of the shaft; an electronic circuit board coupled to the proximal mechanical structure; and a drive element coupled between the tool and the proximal mechanical structure; wherein actuation of the drive element causes movement of the tool; wherein an electrical ground path is defined between the distal force sensor unit and the electronic circuit board; and wherein the electrical ground path includes the drive element.

2. The medical device of claim 1, wherein: the proximal mechanical structure includes a proximal pulley and a pulley cover at least partially covering the proximal pulley; the drive element is in electrical contact with the pulley; the proximal pulley is in electrical contact with the pulley cover; the pulley cover is in electrical contact with the electronic circuit board; and the ground path includes the proximal pulley and pulley cover.

3. The medical device of claim 1, wherein: the medical device further includes at least one of an o-ring, a gasket, and a component coupled between the electronic circuit board and the proximal mechanical structure.

4. The medical device of claim 1, wherein: the tool includes a tool pulley; and the drive element is electrically coupled to the tool pulley.

5. The medical device of claim 1, wherein: the ground path is a first ground path; the medical device further includes a sensor signal cable electrically coupled between the distal force sensor unit and the electronic circuit board; a second electrical ground path is defined between the distal force sensor unit and the electronic circuit board; and the second ground path includes the sensor signal cable.

6. The medical device of claim 1, wherein: the medical device further includes a proximal force sensor unit coupled to the electronic circuit board.

7. The medical device of claim 6, wherein: the proximal force sensor unit is configured to measure a force exerted on the tool in a direction along the length of the shaft.

8. The medical device of claim 1, wherein: the electronic circuit board includes a first layer and a second layer; the first layer includes a plurality of electrically conductive traces; the second layer includes an electrically conductive material; and the electrically conductive material of the second layer is electrically coupled to the electrical ground path.

9. The medical device of claim 1, wherein: the tool is electrically insulated from the force sensor unit.

10. The medical device of claim 1, wherein: the tool is in electrical contact with the ground path.

11. The medical device of claim 1, wherein: the distal force sensor unit is configured to sense force on the tool.

12. The medical device of any of claims 1-11, wherein: the medical device is configured as an instrument in a telesurgical system. The medical device of any of claims 1-11, further comprising: a common-mode choke coupled to the proximal mechanical structure, the common-mode choke configured to attenuate a current flowing towards a chassis of the proximal mechanical structure. A medical device comprising: a proximal mechanical structure; an electronic circuit board coupled to the proximal mechanical structure and including a plurality of electrically conductive traces; an electrically grounded electrically conductive shield positioned distally under the plurality of electrically conductive traces; and a force sensor unit positioned proximally over the electrically conductive traces and including a sensor element; wherein a physical electrical connection exists between the sensor element and one or more of the plurality of electrically conductive traces; and wherein no physical electrical connection exists between the sensor element and the electrically conductive shield. The medical device of claim 14, wherein: the medical device further includes a second sensor element; a physical electrical connection exists between the second sensor element and one or more of the plurality of electrically conductive traces; no physical electrical connection exists between the second sensor element and the electrically conductive shield; and the sensor element and the second sensor element are each spaced from the electrically conductive shield by an equal distance. The medical device of claim 14, wherein: the sensor element is an inductive coil sensor element. The medical device of claim 14, wherein: the electrically conductive shield includes a gap located to prevent an electrically inductive coupling between the electrically conductive shield and the sensor element. The medical device of claim 17, wherein: a portion of the first layer extends proximally above the gap. The medical device of claim 14, wherein: the medical device further includes a shaft coupled to the proximal mechanical structure; and the shaft is operably coupled to the force sensor unit such that translational movement of the shaft causes translational movement of a portion of the force sensor unit with reference to the electronic circuit board. The medical device of claim 14, wherein: the electronic circuit board includes an opening and an outer edge; the electrically conductive shield surrounds the opening of the electronic circuit board; and a gap in the electrically conductive shield is defined between the opening of the electronic circuit board and the outer edge of the electronic circuit board. The medical device of claim 14, wherein: the medical device further includes an electrical ground; and one or more of the plurality of electrically conductive traces are electrically connected to the electrical ground. The medical device of claim 14, wherein: the medical device further includes a shaft, a tool, and a distal force sensor unit; the shaft includes a proximal end portion and a distal end portion; the proximal end portion of the shaft is coupled to the proximal mechanical structure; the tool is coupled to the distal end portion of the shaft; and the distal force sensor unit is coupled to the distal end portion of the shaft. The medical device of claim 22, wherein: the tool is electrically insulated from the distal force sensor unit. The medical device of claim 21, wherein: the medical device further includes a drive element operably coupled between the tool and the proximal mechanical structure such that actuation of the drive cable causes movement of the tool; and the drive element defines a portion of an electrical ground path between the distal force sensor unit and the electrical ground, between the tool and the electrical ground, or between both the distal force sensor unit and the tool and the electrical ground. The medical device of claim 21, wherein: the medical device further includes a sensor signal cable electrically coupled between the distal force sensor unit and the electronic circuit board; the sensor signal cable includes an electrical ground trace; and the electrical ground trace of the sensor signal cable defines a portion of a ground path between the distal force sensor unit and the electrical ground. The medical device of any of claims 14 to 25, wherein: the electronic circuit board includes a first layer and a second layer positioned distally under the first layer; the first layer includes the electrically conductive traces; and the second layer includes the electrically conductive shield positioned distally under the electrically conductive traces.