Patent ID: 12256911

Use of the same reference symbols in different figures indicates similar or identical items.

DETAILED DESCRIPTION

A drive system for a medical instrument can employ a single motor driven capstan on which two actuating tendons are oppositely wound for self-antagonistic drive of an actuated structure such as an end effector. In general, an antagonistic drive can actuate a degree of freedom using two drive cables or tendons respectively connected to pull in opposing directions. With one type of antagonistic drive, the two tendons connect to two independent drive motors or actuators that are respectively associated with opposing directions of a single degree of freedom. However, with self-antagonistic actuation as described herein, the two cables associated with opposite directions of a degree of freedom can connect to the same drive motor or actuator. As a result, a self-antagonistic drive system can employ one motor or actuator per degree of freedom of an actuated structure, allowing the drive system to be simpler, lower cost, and more compact than a drive system using one motor or actuator per actuating tendon. Further, a self-antagonistic drive system can be suitable for both handheld and robotic operation. One or more preload systems can maintain tension in the actuating tendons, even when drive motors or actuators are off, which also facilitates in allowing the handheld or robotic operation. In different configurations, the drive systems can be connected to proximal ends of the actuating tendons, directly or through pulley systems, or can be connected to a slide mounted motor or capstan.

FIG.2schematically illustrates a medical instrument200in accordance with an embodiment of the invention. Instrument200includes an actuated structure or steering section210at a distal end of a main tube220, which is connected to a backend mechanism230. Steering section210in the illustrated embodiment includes flexible tubing212and an actuation ring214. Steering section210may, for example, include tubular vertebrae that are interconnected by joints or alternatively a tube of an elastic material such as Nitinol having kerfs cut to create flexures. Steering section210may additionally include sheathing that covers the joints or flexures. Ring214may be a rigid structure having actuating tendons221and222coupled to opposite edges of ring214, so that pulling on tendon221or222tends to bend flexible tubing212in one direction or the opposite direction of one degree of freedom of motion of ring214. In a typical embodiment, a second pair of tendons (not shown) may be connected to actuation ring214for actuated movement in another degree of freedom for movement of ring214. Many other alternative embodiments of steering section210are possible. For example, steering section210could include multiple independently actuated joints, and tendons221and222may be employed to actuate one of those joints. Also, tendons221and222may be opposite ends of a continuous structure such as a cable that winds through ring214or around a particular joint in steering section214.

Tube220may be a rigid or flexible tube but is generally less flexible than steering section210. In particular, main tube220may be sufficiently flexible to follow the path of a natural lumen. However, for steering of main tube220, a backend mechanism230can apply different forces or tensions to tendons221and222. The desired result of the applied forces is bending of steering section210in a direction of the steering and minimal bending of tube220. To achieve this goal, main tube220may be more rigid than steering section210, or each tendon221or222may be a Bowden cable, e.g., a pull wire enclosed in a housing, which will minimize the bending of tube220. Tendons221and222can otherwise be stranded cables, wires, rods, or tubes made of metal, a polymer, or other material. In an exemplary embodiment, tendons221and222may include connected portions of different construction, e.g., stranded cable that are fused to tubes. For example, the stranded cable may be used where significant bending or flexing of the tendons221and222is expected, and the more-rigid tubes may be used elsewhere to reduce stretching of tendons221and222.

FIG.2illustrates an example instrument in which actuating tendons221and222attach to steering section210, but alternatively actuating tendons221and222could be used to operate other types of actuated structures such as a jaw as shown inFIG.1, another type of jointed structure, or any other mechanisms that permits movement of mechanical members of a medical instrument. For example, tendons221and222could drive a pivot, planar, cylindrical, or spherical rolling joint or flexure that provides clockwise and counterclockwise rotational freedom to a jaw or other structure or drive a prismatic linear joint or slide that provides linear bi-directional freedom of motion to an actuated structure.

Backend mechanism230attaches to the proximal end of tube220and acts as a transmission that converts the rotation of a drive motor250into movement of or tension in actuating tendons221and222. Backend mechanism230particularly manipulates tendons221and222to operate steering section210. In the illustrated embodiment, backend mechanism230includes a capstan235around which portions of both actuating tendons221and222are wound in opposite directions. For example, tendon221may be wound around capstan235so that counterclockwise rotation of capstan235reels in more of tendon221from the side of tendon221leading to steering section210, and tendon222may be wound around capstan235so that counterclockwise rotation of capstan235feeds out more of tendon222toward steering section210. Movement of steering section210back and forth along one degree of freedom can thus be actuated through rotation of a single capstan235.

Drive motor250is connected to rotate capstan235, and in some implementations, capstan235is an extension of or is part of the shaft of motor250. In some other implementations, drive motor250has a detachable connection to capstan, so that backend mechanism230may be separated from motor250. Motor250may be under the robotic control based on human input (e.g., master control input in a master-slave servo control system) and software executed in a robotically controlled system. Additionally, a knob, lever, or other hand-operated manipulator260is coupled to capstan235or motor250, and enables a user to manually operate instrument200through manual rotation of capstan235. Instrument200may thus be used with or without motor250or knob260applying a torque to capstan235.

In various embodiments, a preload system240can be employed to maintain minimum and equal tension in tendons221and222, avoiding slack in tendons221and222as well as biased motion in steering section210even when neither motor250nor knob260applies a torque to capstan235. Preload system240can be passive such that the applied tension does not need to respond to a control or feedback system. In other embodiments, preload system240can be actively controlled (e.g., applying tensioning when a minimum tendon tension or slack is detected or maintaining a predetermined tendon tension or tension range). In the embodiment ofFIG.2, proximal ends of tendons221and222extend from capstan235to preload system240. In particular, each tendon221or222may wrap around capstan235for a set wrapping angle (that could be less than a full turn or include more than one turns) around capstan235, and the proximal ends of tendons221and222extend past capstan235to connect to preload system240. Tendons221and222are not required to be permanently attached to capstans235and thus may be able to slip relative to capstans235, for example, when motor250or knob260turns in a direction that feeds tendon221or222out toward steering section210. However, the wrap angle and the tension applied by preload system240are such that when motor250or knob260pulls in from the distal end of tendon221or222, the torque applied by motor250or knob260controls the tension in the distal portion of that tendon221or222.

Preload system240in the embodiment ofFIG.2is implemented using springs241and242that may be anchored to a case or chassis of backend mechanism230. Springs241and242may be biased, e.g., stretched, to apply non-zero and equal forces to respective tendons221and222throughout the range of motion of surgical instrument200. With this configuration, when capstan235is free to rotate, springs241and242respectively pull on tendons221and222and control the tensions in tendon221and222. Preload system240may thus prevent slack in tendons221and222by pulling in the required length of tendon221or222. Further, preload system240applies an equal amount of tension on both tendons221and222to avoid biased motion in steering section210throughout the range of motion of surgical instrument200.

Each spring241or242in preload system240more generally can be replaced with any structure or system that is able to apply a force to the free proximal end of a tendon221or222while allowing the required range of displacement of the proximal end of the tendon221or222. Springs241and242can, for example, be linear coil springs, constant force springs, or use other spring elements, such as rotary coil springs, leaf springs or compliant members, such as bending beams, cantilever beams, or elastic bands. Springs241and242can be any type of compliant members, springs, or tension-applying systems, but the tension that spring241applies may ideally be equal to that applied by spring242throughout the range of motion of the instrument. Otherwise, the preload on each tendon may be unbalanced, creating biased motion at the steering section. Further, the spring elements or compliant members can work through extension or compression to apply force directly or indirectly to the end of the attached tendons. In addition, the spring elements or compliant members may be designed so that the force applied by spring241on tendon221is equal to the force applied by spring242on tendon222throughout the range of motion of the instrument200. Other methods for applying the desired force, such as a system using weights or magnets, might alternatively be employed. In addition to the source of force, preload system240may include mechanical elements (not shown) that direct or control the magnitude of the force applied to the attached tendon, e.g., to apply a constant force throughout the range of motion of steering section210.

FIG.3illustrates an example of an instrument300including a catheter having a main tube220and a steering section210that can be controlled using tendons221and222wound around a capstan235in a backend mechanism230as described above with reference toFIG.2, but instrument300differs from instrument200by employing an alternative preload system340. Preload system340includes a biased spring342attached to a pulley344having a slide mounting that permits pulley344to move toward or away from capstan235. In preload system340, the proximal ends of tendons221and222are connected together and looped around pulley344. In operation, drive motor250or knob260can rotate capstan235to increase the tension in a distal portion of tendon221or222and cause steering section210to bend or move toward the higher tension tendon221or222. At the same time, spring342allows pulley344to shift and rotate until the proximal ends of both tendons221and222carry tensions about equal to one half of the force that spring342applies to pulley344. As described above, the tension in the distal portion of tendon221or222being pulled in will depend on the motor or manual torque applied to capstan235, and the tension in distal portion of the tendon222or221being reeled out will be about the same as the tension at the proximal end. Preload system340can thus maintain non-zero and equal tensions in the proximal ends of tendons221and222, avoiding slack in tendons221and222.

FIG.4illustrates another example of an instrument400including a main tube220and a steering section210that can be controlled using tendons221and222wound around a capstan235in a backend mechanism230as described above with reference toFIG.2, but instrument400includes another alternative preload system440. Preload system440includes an in-line spring442and a fixed pulley444. Fixed pulley444can be anchored to the walls, case, or chassis of backend mechanism230. The proximal end of one tendon221or222connects to one end of spring442, and the proximal end of the other tendon222or221connects to the other end of spring442after wrapping around fixed pulley444. Spring442is biased, e.g., stretched, to apply equal tension to the proximal ends of tendons221and222, and spring442has a sufficient range of motion to compensate for stretch that may occur in tendons221and222and axial compression of main tube220or steering section210. Motor250or knob260can control a higher tension at the distal end of one tendon221or222as described above, while preload system440controls the minimum tension in both tendons222and221.

FIG.5illustrates still another example of an instrument500also including a main tube220and a steering section210that can be controlled using tendons221and222wound around a capstan235in a backend mechanism230as described above with reference toFIG.2. Instrument500includes a preload system540that spring loads capstan235, instead of connecting directly to tendons221and222. InFIG.5, preload system540is coupled to drive motor250, and drive motor250has a slide mounting that permits linear movement of motor250and capstan235in a direction perpendicular to the rotation axis of capstan235. Alternatively, preload system540could couple to capstan235in another manner, e.g., to knob260, bearings (not shown) of capstan235, or to a slide mounting (not shown) of capstan235. In the embodiment ofFIG.5, the proximal ends of tendons221and222can be attached to or fixed on capstan235.

FIG.6illustrates yet another example of an instrument600also including a main tube220and a steering section210that can be controlled using tendons221and222wound in opposite directions around a capstan235in a backend mechanism230as described above with reference toFIG.2. Instrument600may also include a preload system240that is the same as preload system240ofFIG.2or an alternative preload system such as described with reference toFIG.3,4, or5. Instrument600differs from instrument200ofFIG.2in the addition of take-up spring system640that engages tendons221and222between capstan235and steering section210. Take-up system640inFIG.6includes pulleys that respectively engage tendons221and222and are spring loaded to pull on tendons in a direction perpendicular to the lengths of tendons221and222. Take-up system640thus provides another mechanism for maintaining non-zero tension and avoiding slack in tendons221and222regardless of which direction capstan235turns.

The tendon221or222being fed out may need to slip on capstan235in order for the passive preload system to maintain at least the minimum tension at all times in the distal portions of tendons221and222. In another implementation, two tendons in a self-antagonistic drive system wrap in opposite directions around two independent one-way clutches or bearings. The one-way clutches can be oriented with opposite senses, so that only one clutch engages per drive rotation direction.FIG.7A, for example, illustrates a self-antagonistic system700in which two tendons721and722respectively wrap in opposite directions around respective one-way clutches or bearing731and732. One-way clutch731is oriented so that clutch731pulls on the distal side tendon721when motor250or knob260drives a central shaft730clockwise, and clutch731slips when motor250or knob260rotates shaft730counterclockwise. One-way clutch732is oriented so that clutch732pulls on the distal side tendon722when motor250or knob260rotates shaft730counterclockwise and slips when motor250or knob260rotates shaft730clockwise. Thus, only one clutch731or732will be engaged for each drive rotation direction. A passive preload system740of system700may eliminate the chance of slack or tension build-up in tendon721or722due to the stretch of the other tendon722or721because passive preload system740can pull in slack on the free-wheeling clutch721or722.

The mechanism of the preload system740may be identical to the preload system240. As shown, proximal ends of tendons721and722connect to spring systems741and742in preload system740. Spring systems741and742maintains minimum and equal tensions in tendons721and722, avoiding slack in tendons721and722. Alternatively, any other preload system such as those described herein could be employed.FIG.7B, for example, is identical toFIG.7Aexcept that the tendons721and722connect to a preload system745including an in-line spring system743and a fixed pulley744in the same manner as preload system440ofFIG.4.

Steerable instruments as mentioned above can benefit from the ability to control the pitch and the yaw of the distal tip of the instrument.FIGS.2,3,4,5, and6shows some examples of medical instruments in a distal tip, e.g., steering section210, can be bent back and forth to control one angle, i.e., pitch or yaw, of the distal tip. More generally, a medical instrument could contain two such drive system for independent control of the pitch and yaw angles of the distal tip.FIG.8, for example, illustrates a medical instrument800employing two pairs of actuating tendons221and222and221′ and222′ having distal ends connected to a steering section210of a medical device such as a steerable instrument. For example, the distal ends of tendons221,222,221′, and222′ may all be connected to an actuation ring214at 90° separations around the perimeter of ring214. Tendons221and222wind in opposite directions around a capstan235that has a preload system240for tendons221and222. Tendons221′ and222′ similarly wind in opposite directions around a capstan235′ that has a preload system240′ for tendons221′ and222′. Pitch and yaw angles of the distal tip of instrument800can thus be controlled using two motors250or knobs260coupled to capstan235and235′.

The separation of tendons221and222and the separation of tendons221′ and222′ at ring214may be perpendicular to each other for pitch and yaw actuations. As a result, associated drive systems, particularly capstans235and235′, may also be perpendicular to each other. The perpendicular orientations may not be the best configuration for a compact drive system for convenient handheld use of instrument800. However, the orientation and position of drive system components such as capstans235and drive motors250can be rearranged using a pulley system852or a drive transfer systems854. In particular, pulley systems852can be used to redirect tendons221,222,221′ and222′ so that capstans235and235′ do not need to be perpendicular. Drive transfer system854, e.g., a belt or gear system, can similarly be used to change the position or orientation of either motor250relative to the capstan235or235′.

Motor250as shown inFIG.8does not need to directly attach to capstan235. More generally, a motor pack, which may include multiple drive motors, e.g., motors250and250′ in system800, can connect to capstans, e.g., capstans235and235′, through an engagement mechanism that allows the motor pack to engage or disengage the backend mechanism including capstans of a self-antagonistic drive system. Each manual knob260may remain attached to the corresponding capstan235and apply higher tension on one of the tendon221or222to steer the instrument manually. Removal of the motor pack from the backend mechanism has advantages. In particular, the removable motor pack may be outside a sterile barrier that encloses a sterile area in which a medical procedure is performed. The motor pack may then be spared from the standard but intrusive cleaning procedures such as high pressure autoclave sterilization that may be required for the backend mechanism and the rest of the instrument. If the backend mechanism is part of a single-use instrument, the instrument can be easily replaced and recycled while the motor pack can be used again and again. The motor pack can also remain or be permanently attached to a robotically controlled arm, making the instrument smaller and lighter during manual use. For example, once a physician is done with the handheld operation of the instrument, the physician can attach the backend mechanism of the instrument onto the motor pack and robotic arm. An input device (e.g., a joystick) can then be used to control the instrument robotically.

One compact or small radius configuration of a drive system for an instrument steerable in pitch and yaw directions orients rotation axes of drive motors250and250′ and capstans235and235′ along the direction of main tube220.FIG.9illustrates an instrument900in which drive motors250and capstans235are oriented along the axis of main tube220. Pulley systems910and910′ in instrument900can connect to respective passive preload systems440and440′ and change the directions of tendons221and222and tendons221′ and222′ that run along that axis through main tube220, so that the proximal ends of tendons221and222and tendons221′ and222′ are perpendicular to the axis of main tube220. Tendons221and222and tendons221′ and222′ can thus be wound around respective capstans235and235′ as described above.

One specific embodiment of instrument900, which can provide pitch-yaw drive, can be light weight, e.g., around one pound and compact, e.g., have a maximum outside diameter less than about 60 mm. Main shaft220can include four tendons or pull wires, two for pitch and two for yaw, terminated at the tip of the steering section210at the cardinal points. Each tendon may be a pull wire in a Bowden cable with the pull wire being distally terminated on a ring in the distal steering section and proximally terminated on a preload system that allows controlled sliding. Each pull wire may include a section of a polymer cable (e.g. Kevlar) that may be routed by idlers to the motor shaft or capstan. The polymer cable portion may also wrap or wind around on motor shaft, where two sections that wind around the same motor shaft are wound in opposite directions. The preload mechanism can keep minimum tension in the pull wires at all times.

The drive systems described above can provide significant benefits for manual and computer assisted operation of an instrument. In particular, for a biopsy, a surgeon or other medical personnel may want to manually insert an instrument through a patient natural orifice such as the mouth or anus and the backend mechanisms, as described above, may be made small enough for handheld use during the insertion. One or two mechanical knobs can be provided for manual operation, allowing 2-way or 4-way, bending of a tip section of the instrument. For example, the knobs can be oriented as in a standard bronchoscope or colonoscope. The motor axis of the actuation motors can be parallel with the instrument shaft, which may leave more room near the patient's anatomy for easier manipulation. The relatively light weight and small visual mass of at least some of the drive systems described above may also be appealing or less frightening to patients undergoing a procedure such as a biopsy under conscious sedation, where the patient may be moving and aware. For computer assisted operation, drive systems can use one motor or actuator per degree of freedom, which may reduce cost and system complexity when compared to a drive system using one motor per cable.

Although particular implementations have been disclosed, these implementations are only examples and should not be taken as limitations. Various adaptations and combinations of features of the implementations disclosed are within the scope of the following claims.