Dual-loop motor control for surgical stapling

Abstract

A surgical stapling instrument that includes a shaft assembly with a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally; a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly; a processor; and memory storing instructions that cause the surgical stapling instrument to perform operations that may include: controlling the motor under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile; while controlling the motor under the velocity-control loop, detecting that a firing force has reached a firing force threshold; and in response to the firing force threshold being reached, controlling the motor under a force-control loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

Description

DUAL-LOOP MOTOR CONTROL FOR SURGICAL STAPLINGCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 778,584, filed March 27, 2025, which is incorporated herein by reference in its entirety.BACKGROUND

[0001] Surgical devices for treating tissue can be utilized in a variety of treatment procedures, including for closure of tissue or organs (e.g., transection, resection, or anastomoses procedures), for occlusion of organs (e.g., thoracic or abdominal procedures), or for electrosurgically fusing or sealing of tissue (e.g., vessel sealing procedures), among others.

[0002] One type of such a surgical instrument is a surgical stapler that inserts and secures small staples into the tissue. The surgical stapler operates by placing the tissue between two jaws of the stapler. When the surgical stapler is fired, the staples are driven through the tissue. The legs of staples are initially straight when they enter the tissue. As the staples are pushed further through the tissue and contact the anvil, the legs of staples bend or crimp, causing them to form a B-shape or a rectangular shape. This bending action securely fastens the tissue together, promoting proper healing.BRIEF SUMMARY

[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0004] The technology disclosed herein relates to a dual-loop control technology that allows for controlling the motor of a surgical stapler based on both velocity and current. For instance, in one zone of the firing process where the firing force is below a force threshold, the motor of the surgical stapler is controlled based on a targeted velocity or velocity profile. In another zone, when the force reaches the force threshold, the motor is then controlled based on current or force to maintain the firing force at the force threshold. This dual-loop motor control technology allows for thesurgical stapler to respond to elasticity of the tissue but still provide an efficient surgical procedure for the surgeon.

[0005] The details of one or more aspects are set forth in the accompanying drawings and description below. Other features and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that the following detailed description is explanatory only and is not restrictive of the invention as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Various aspects of the disclosure are described herein with reference to the drawings, in which:

[0007] FIG. 1 depicts a side view of an example surgical stapling instrument.

[0008] FIG. 2 depicts an exploded view of an end effector of an example surgical stapling instrument.

[0009] FIG. 3 depicts a plot of malformed staples versus maximum firing force.

[0010] FIG. 4 depicts a plot representing an example dual-loop firing algorithm.

[0011] FIG. 5 depicts an example method for performing dual-loop motor control for a surgical stapling instrument.

[0012] FIG. 6 depicts another example method for performing dual-loop motor control for a surgical stapling instrument.DETAILED DESCRIPTION

[0013] As briefly described above, when a surgical stapler is fired, the staples are pushed through the tissue and bent or crimped to form a B-shape (or similar) shape that fastens tissue together. The formation of the staples can be important as to how well the tissue is fastened, and properly formed staples may therefore promote better healing of the tissue. The speed at which the stapling procedure is performed, however, is also important as the surgical stapler must be held in place for the total time required for firing of the staples. In addition, reducing the total length of the surgical procedure is also desirable.

[0014] The formation of the staples is based on a number of factors. One factor that has been identified is the stress and strain properties of the tissue under compression. For instance, thetissue generally displays viscoelastic properties that are dependent on the rate of compression. For instance, the higher the rate of compression, the higher the induced stress at a given strain. This property is more prominent at higher strains and stresses than at lower strains and stresses.

[0015] Some stapling devices take advantage of this property by stapling at a faster speed when the firing force required is low. When that force increases, the firing speed is reduced. Such a motor control based solely on velocity, however, limits the possibilities for overall speed of the staple firing and staple formation.

[0016] The technology disclosed herein addresses the above drawbacks, among other things, by introducing a dual-loop control technology that allows for controlling the motor of a surgical stapler based on both velocity and current. For instance, in one zone of the firing process where the firing force is below a force threshold, the motor of the surgical stapler is controlled based on a targeted velocity or velocity profile. In another zone, when the force reaches the force threshold, the motor is then controlled based on current or force to maintain the firing force at the force threshold. This dual-loop motor control technology allows for the surgical stapler to respond to elasticity of the tissue but still provide an efficient surgical procedure for the surgeon.

[0017] For example, testing and experimentation has demonstrated that there is a stapling force threshold for the occurrence of staple malformations. The dual-loop control algorithm may be developed around this force threshold. For instance, a force target may be established that is below the firing force where malformed staples may have an increased likelihood of occurring. If the force target cannot be reached (e.g., due to thin or compliant tissue), a velocity limit prevents the motor from exceeding a particular velocity. Upon reaching the force target, the surgical stapler then controls (e.g., modulates) the motor velocity to keep the force at the force target. By doing so, the stapling process adapts to the viscoelastic properties of the tissue by keeping the forces lower by lowering the rate of the firing during higher force zones of the firing process. In some examples, a lower velocity limit may also be implemented to still allow for firing in thicker tissue scenarios. For instance, if the motor velocity were to fall below the lower velocity limit, the surgical stapler would allow the current or force to increase to hold the minimum velocity at the lower velocity limit.

[0018] Referring now to FIG. 1 , an example surgical instrument 100 is depicted. In the illustrated example, the surgical instrument 100 is in the form of a handheld surgical stapling instrument ordevice configured to perform tissue closure procedures, such as anastomoses or transection procedures in some examples. It will be understood that aspects of the disclosure are not so limited and can have general applicability in other surgical instruments.

[0019] In the example depicted, the surgical instrument 100 includes a handle assembly 110, a shaft assembly 120 extending from the handle assembly 110, and a tool assembly 130 coupled to the shaft assembly 120 as shown. The tool assembly 130 may also be referred to as a reload. The handle assembly 110 may also or alternatively be referred to as a controller housing, such as in examples where the surgical instrument is part of surgical robotics implementation.

[0020] The handle assembly 110 includes a handle portion 112 and a barrel portion 113. The handle portion 112 is illustrated with an activation switch or button 114 for operating the tool assembly 130. The handle portion 112 may also include a movable handle, trigger, or the like.

[0021] The shaft assembly 120 includes an elongated body 122 (e.g., a shaft) extending from a proximal end to a distal end and defines a longitudinal axis. The proximal end of the elongated body 122 may be coupled to the barrel portion 113. The tool assembly 130 is then coupled to the distal end of the elongated body 122. In the non-limiting example shown, the tool assembly 130 includes an end effector 150 and a shaft 132 extending from the end effector 150. The end effector 150 carries a staple cartridge assembly 154 and an anvil assembly 152 for closing of tissue disposed between the jaw members of the end effector 150. The end effector 150 also includes a knife 156 configured to dissect the tissue after (or during) the stapling of the tissue. The shaft 132 of the tool assembly 130 includes a connection segment 134 on the proximal end of the shaft 132. The connection segment is received in the distal end of the elongated body 122 of the shaft assembly 120.

[0022] In examples, the tool assembly 130 is configured as a single-use loading unit (SULU) or disposable loading unit (DLU). In such examples, the tool assembly 130 is releasably secured to the shaft assembly 120 for disposal upon completion of a surgical procedure (or a portion thereof). Additionally or alternatively, the tool assembly 130 may include one or more electrodes for providing electrosurgical energy, one or more cutting elements for tissue dissection, or the like.

[0023] The example surgical instrument 100 includes a drive assembly for driving operation of the end effector 150 of the tool assembly 130. The drive assembly includes a firing rod 124 extending through the shaft assembly 120 as shown. When the tool assembly 130 is connected tothe shaft assembly 120, the distal end of the firing rod 124 is received in the connection segment 134 of the tool assembly 130. The firing rod 124 then engages a drive rod or drive beam 135 that is coupled to the end effector 150 of the surgical instrument. The distal motion of the drive beam 135 causes the staples to be fired from the staple cartridge assembly 154 and the tissue to be separated by the knife 156.

[0024] The drive assembly of the surgical instrument 100 also includes at least one electric motor 119. The electric motor 119 may be a direct-current (DC) motor that is bi-directional. The electric motor 119 is coupled to the firing rod 124 such that activating the electric motor 119 in a first direction causes the firing rod 124 to move distally (e.g., forward), and activating the electric motor 119 in the opposite direction causes the firing rod 124 to move proximally (e.g., backward). Stated another way, movement of the motor 119 in the first direction pushes or drives the firing rod 124 distally, and movement of the motor 119 in a second direction retracts the firing rod 124 proximally. The movement of the firing rod 124 causes a corresponding movement of the drive beam 135. The electric motor 119 may be coupled to the firing rod 124 via one or more gears and / or linkages to translate the rotational motion of the electric motor 119 to the translational movement of the firing rod 124.

[0025] The surgical instrument 100 also includes a controller 116. The controller 116 includes at least one processor 117 and memory 118. The processor 117 may be in the form of a microcontroller, microprocessor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or the like. The memory 118 may include volatile storage (e.g., random access memory), non-volatile storage (e.g., read-only memory), flash memory, or any combination of such memories. In some examples, the memory 118 may be integrated into a common chip with the processor 117. The memory 118 stores instructions that, when executed by the processor 117, causes the surgical instrument 100 to perform the operations discussed herein. For instance, the memory 118 may store one or more programs that include instructions for performing the operations set forth in FIGs. 6-8. The controller 116 may also include one or more sensors for measuring or detecting various signals, such as the current drawn by the motor 119 and / or motor speed of the motor 119 (e.g., revolutions per minute (RPM). In some examples, the sensor(s) are integrated into the processor 117 and / or a chip package including the processor 117.

[0026] The surgical instrument 100 may also include a force sensor 121 that measures the firing force that is applied to the firing rod 124 by the motor 119. In some examples, the force sensor 121 may be a strain gauge or a piezoelectric sensor, capable of detecting minute variations in force with high precision. The firing force measurements from the force sensor 121 may be provided to the controller 116 for further analysis and processing. The controller 116 may use these measurements to adjust the operation of the motor 119 in real-time based on the dual-loop stapling algorithms discussed herein. In some examples, the firing force may be determined from the current drawn by the motor 119. For instance, the amount of current drawn by the motor 119 is directly related to the load it is driving. Essentially, the more force or torque required to move the load, the more current the motor 119 will draw. This relationship can be used to measure the force or torque by monitoring the current. By using known characteristics of the motor 119, such as its torque constant (which relates current to torque), the controller 116 can calculate the torque being produced. Similarly, where the mechanical setup (like gear ratios) is known, the firing force can be derived from the torque. In such examples where firing force is determined based on the current drawn by the motor 119, the force sensor 121 may be omitted or both the force determination from the current drawn from the motor 119 and the force sensor 121 may be used.

[0027] The surgical instrument 100 may be configured for longitudinal, rotational, and / or articulating motion of the tool assembly 130. In such examples, an articulation mechanism 115 is provided for pivoting or articulating motion of the tool assembly 130 with respect to the longitudinal axis.

[0028] The end effector 150 includes an anvil 152 and a cartridge assembly 154. The cartridge assembly 154 may be pivotably supported in relation to the anvil 152 to facilitate movement of the end effector 150 between an unclamped position and a clamped position. In some examples, the end effector 150 includes a mounting assembly that supports the anvil 152 and the cartridge assembly 154 for movement between the unclamped position and the clamped position. In some examples, the anvil 152 and the cartridge assembly 154 are coupled to the mounting assembly by screws or pins.

[0029] FIG. 2 depicts an exploded view of an end effector 150 of the example surgical stapling instrument 100. The cartridge assembly 154 which includes a staple cartridge 201 and a channel member 214. The channel member 214 includes side walls and a bottom channel wall that definea cavity. In some examples, the staple cartridge 201 may be removably received within the cavity of the channel member 214 such that the staple cartridge 201 is replaceable to facilitate reuse of the surgical stapling instrument 100 after each firing of the surgical stapling instrument 100. In other examples, the entire end effector 150 and / or tool assembly 130 is removably attached to the shaft, and the tool assembly may be replaced rather than just the staple cartridge 201 itself.

[0030] The example staple cartridge 201 includes a cartridge body 202, an actuation sled 216, staples 208, pushers 210, and a staple guard 212. The cartridge body 202 defines a knife slot 204 and staple receiving pockets 206 that are positioned on each side of the knife slot 204. The staple receiving pockets 206 may be aligned in two or more rows on opposite sides of the knife slot 204. The knife slot 204 is longitudinally aligned with the elongate slot in the channel member 214.

[0031] The staples 208 and the pushers 210 are received within the staple receiving pockets 206 of the cartridge body 202, and the staple guard 212 is secured to the bottom of the cartridge body 202 to retain the staples 208 and pushers 210 within the cartridge body 202. The staple guard 212 also includes a bottom wall that defines an elongate slot that is aligned with the elongate slot and knife slot 204 defined in the channel member 214 and the cartridge body 202, respectively.

[0032] The actuation sled 216 is received within and is movable through the cartridge body 202. The actuation sled 216 includes angled inner and outer fins that have angled fin surfaces that are positioned to sequentially engage the pushers 210 as the actuation sled 216 moves through the cartridge body 202 from the sled retracted position towards the sled advanced position to lift the pushers 210 within the staple receiving pockets 206 and eject the staples 208 from the cartridge body 202.

[0033] A working member 218 (e.g., an I-Beam) is advanced distally by the drive beam 135. As the working member 218 advanced distally, the working member 218 engages (e.g., contacts) the actuation sled 216 and moves the actuation sled 216 forward, which causes the pushers 210 to push the staples 208 through the staple receiving pockets 206. The legs of the staples 208 extend through the tissue and then contact the anvil assembly 152, which causes the legs of each staple 208 to bend and turn back towards the backspan of the staple 208. For instance, the legs of the staples 208 may generally bend such that the formed staple is in a “B” shape. If the staples 208 do not bend far enough, bend too far, or are otherwise bent or shaped by the tissue, the staples may be considered to be malformed.

[0034] As the staples 208 are pushed through the tissue, or after the staples 208 are pushed through the tissue, the tissue is separated by advancement of the knife 156 through the knife slot 204. For instance, the tissue is cut and separated in between the lines of staples 208 on either side of the knife slot 204. In the example depicted, the knife 156 is integrated with the working member 218. In other examples, the knife 156 may be a separated element that may also be advanced by the working member 218.

[0035] The working member 218 may also control the clamping of the tissue between the jaws (e.g., the anvil assembly 152 and the staple cartridge assembly 154). For instance, the working member 218 may have flanges on opposing ends of the beam or strut of the working member 218. One flange engages the anvil assembly 152 and the other flange engages of the staple cartridge assembly 154. Thus, as the working member 218 advances distally, the jaws are brought closer to one another, thus clamping the tissue therebetween.

[0036] This process of advancing the working member 218 to cause the clamping of the jaws and ejection and formation of the staples 208 (along with the cutting process where applicable), may be referred to herein as “firing” of the surgical stapler. The resistive forces of clamping the tissue, pushing the staples 208 and / or driving the knife 156 through the tissue require the motor 119 to exert additional torque (e.g., draw additional current) to continue advancing the working member 218. As discussed herein, this firing force used to fire the staples has a relationship as to how well the staples are formed.

[0037] FIG. 3 depicts a plot 300 of malformed staples versus maximum firing force. The plot 300 shows different experimental examples for example staple firings at different firing speeds. For instance, example results are displayed for firing speeds of 2.0 millimeters per second (mm / s), 4.0 mm / s, 7.5 mm / s, and 12.0 mm / s. For each result, a maximum firing force, in pounds (lbs), was recorded and percentage of malformed staples were also recorded. Those results were then plotted in plot 300.

[0038] As can be seen from the plot 300, as the maximum firing force increases, the likelihood of having higher percentage of malformed staples increases. In addition, with higher firing forces, the speed at which the firing is performed also impacts the likelihood of malformed staples. For instance, at higher maximum firing forces, higher firing speeds increase the likelihood for malformed staples. This occurs due to the viscoelastic properties of the tissue, which effectivelymakes the tissue response speed dependent. Higher speeds result in higher stresses. Because the staple formation is dependent on the tissue stress, a higher tissue stress increases the likelihood of staple malformations.

[0039] Interestingly, however, at lower maximum firing forces, an increase in firing speed does not significantly increase the likelihood for malformed staples. Indeed, there is an apparent maximum-firing-force threshold around 65 lbs. Below that threshold, the firing speed has little impact on the likelihood of malformed staples. Thus, as long as the maximum firing force remains below that maximum-firing-force threshold, the firing speed can be higher without risking increased staple malformation. The dual-loop stapling algorithms discussed herein take advantage of that discovery by increasing the firing speed when the firing force is below a force threshold (e.g., the maximum-firing-force threshold), and controlling the motor to maintain the firing force at the force threshold by targeting the particular firing force threshold (e.g., current level).

[0040] FIG. 4 depicts a plot 400 representing an example dual loop firing algorithm. The plot 400 represents the firing speed (mm / s) for a staple firing on the Y-axis and the firing force (Newtons (N)) on the X-axis. The firing speed is the speed that firing rod 124 and / or the working member 218 advances distally during the staple firing. The example dual loop firing algorithm has multiple different phases or zones, including a first zone 402, a second zone 404, and third zone 406. The example dual loop firing algorithm may also have a motor-stop zone 408.

[0041] The first zone 402 is a zone where the firing force is below a firing force target or threshold, which is this example is about 314 N. In other examples, the firing force threshold may be between about 200-400 N, 250-400 N, 250-350 N, or 300-350 N, among other ranges. In the example depicted, the firing speed is controlled to target the velocity profile shown in the first zone 402 (e.g., the downward sloping line segment between 0 N and 314 N). For instance, the velocity profile has a descending velocity between a firing force of zero and the firing force threshold. Thus, the motor is controlled with a velocity target. As an example, at 0 N, the motor is operated to generate a firing speed of about 16 mm. At 100 N, the motor is operated to generate a firing speed of about 14.5 mm / s. Accordingly, the firing force is continuously determined or measured (e.g., at a sampling rate of the corresponding sensor) and that firing force may be used as an input to dual-loop stapling algorithm to set a target speed when in the first zone 402. The firing forcemay be measured from a force sensor (e.g., force sensor 121) and / or determined from the current drawn by the motor 119.

[0042] The second zone 404 is a zone where the firing force is at the firing force target or threshold. For instance, as the firing progresses during the first zone 402, the firing force may reach the firing force target (e.g., 314 N in this example). When the firing force target is reached, the dual-loop stapling algorithm enters the second zone 404, where the force (e.g., current) is held constant and the velocity is allowed to change. For instance, the current to the motor 119 is modulated such that the force or current drawn stays remains substantially constant at the firing force target. As a result, the velocity likely drops during this second zone 404 in order to keep the force constant. But, rather than targeting particular velocities as in the first zone 402, the control algorithm targets a constant current or force.

[0043] The third zone 406 is a zone where velocity is kept constant and the force or current is allowed to increase. As such, similar to the first zone 402, the third zone is also a velocity-controlled zone where a particular velocity is targeted. The third zone 406 exists as a low-velocity limit. For instance, in the second zone 404, while the firing force target is attempted to be maintained, the speed of the motor 119 may drop significantly and potentially drop to zero, effectively causing the firing process to stall or stop. To prevent this stalling, a low- velocity limit is implemented where, if during the second zone 404, the velocity drops to the low-velocity limit, the dual loop stapling algorithm enters the third zone 406 where the velocity is held constant at the low- velocity limit (e.g., 3.5 mm / s in this example). In other examples, the low- velocity limit may be between 2-5 mm / s.

[0044] The motor-stop zone 408 is a zone where the motor is stopped. The motor-stop zone 408 exists as a safety precaution to prevent an overly large force from being applied by the surgical stapler. For instance, if a high-force threshold (e.g., 605 N in this example) is reached, the motor is stopped and the firing process is paused or ended. As an example, the motor operates at the low-speed while in the third zone 406, and if the high-force threshold is reached, the motor is stopped and the velocity of the motor is therefore reduced to zero. In some examples, the high-force threshold may be between 500-700 N.

[0045] FIG. 5 depicts an example method 500 for performing dual loop motor control for a surgical stapling instrument. The method 500 is performed by the surgical stapling instrument100. For instance, the memory 118 may store instructions for method 500 that are executed by processor 117 to cause the surgical stapling instrument 100 to perform the operations of method 500.

[0046] The method 500 is depicted in three different zones that are similar to the zones discussed above. For instance, the method 500 operates in a first zone 551, a second zone 552, and a third zone 553. The first zone 551 is a velocity-controlled zone or loop that is intended to operate at a relatively high speed. Because the first zone is velocity-controlled, a particular target velocity or velocity profile based on the firing force is used to control the motor and the current is allowed to vary to reach that target velocity. The second zone 552 is a current-controlled (e.g., force controlled) zone or loop where the current of the motor is held constant to maintain the force or current at a particular level while the velocity is allowed to vary. The third zone 553 is another velocity-controlled zone or loop where a minimum velocity limit is targeted and the motor is controlled to maintain that minimum velocity limit while the current (e.g., force) is allowed to increase or otherwise vary.

[0047] Each zone may include a plurality of operations that are performed while the method 500 is within each respective zone. As discussed herein, the method 500 may proceed in and out of each zone as the firing process progresses. For example, the method may begin in the first zone 551, then enter the second zone 552, and then return to the first zone 551 or proceed to the third zone 553.

[0048] At operation 502, a firing command is received. The firing command may include the depression of a button on the surgical stapler or a command received from or input into a robotic system controlling the surgical stapler.

[0049] At operation 504, a Zone 1 velocity setpoint is set. This velocity setpoint may be a single velocity target or based on a velocity profile. For instance, where a velocity profile is used, the Zone 1 velocity setpoint may be based on a present firing force. The setting of the setpoints discussed herein may be performed automatically by the surgical stapler. The velocity setpoint may include one or more velocities between 12-20 mm / s.

[0050] At operation 506, a Zone 2 current limit is set. The Zone 2 current limit may be the current threshold or target, similar to the firing force threshold or targets discussed above.

[0051] At operation 508, the motor is started or activated. At operation 510, the velocity may be profiled based on the load force (e.g., the firing force). At operation 512, the velocity is regulated to target the profiled velocity and / or the velocity setpoint.

[0052] At operation 514, the current being drawn by the motor is monitored. Then, at decision 516, a determination is made as to where the the current being drawn by the motor is greater than (or greater than or equal to) the Zone 2 current limit. If the current being drawn by the motor is not greater than the Zone 2 current limit, the method 500 flows back to operation 504 where the velocity-controlled loop of the first zone 551 is repeated. If the current being drawn by the motor is greater than the Zone 2 current limit, the method 500 flows into the second zone 552 where operation 518 is performed.

[0053] At operation 518, a minimum velocity is set. This minimum velocity may be the low-velocity limit discussed above. At operation 520, a current trip level is set. The current trip level is the level of current that causes the method 500 to flow back to the first zone 551 as discussed further herein. In some examples, the current trip level may be about 90-98% or at least 90% of the Zone 2 current limit.

[0054] At operation 522, the velocity is monitored. At operation 524, the current setpoint is limited to the Zone 2 current limited. At operation 526, the current is regulated to target the Zone 2 current limit which is the current setpoint.

[0055] At decision 528, a determination is made as to whether the present current (e.g., the most recently measured current) is less than the current trip level set in operation 520. If the present current is less than the current trip level, the method 500 flows back to operation 504 in the first zone 551 where the velocity-control loop resumes. If the present current is not less than the current trip level, the method 500 flows to decision 530.

[0056] At decision 530, the present velocity (e.g., the most recent measured velocity) is compared to the minimum velocity. If the present velocity is not less than the minimum velocity, then the method 500 flows back to operation 520 and remains in the current-controlled loop of the second zone 552. If the present velocity is less than the minimum velocity, then the method 500 flows to operation 532 in the third zone 553.

[0057] At operation 532, a safety current limit is set. The safety current limit is a maximum current limit that will be allowed for the method 500. The safety current limit is similar to the high-force threshold discussed above.

[0058] At operation 534, a Zone 3 velocity setpoint is set. The Zone 3 velocity setpoint may be the same or similar to the low- velocity limit discussed above. For instance, the Zone 3 velocity setpoint is a minimum velocity that allows for the firing process to continue without stalling or stopping.

[0059] At operation 536, the velocity is regulated to maintain a velocity at or above the Zone 3 velocity setpoint. At operation 538, the current is monitored to determine or measure the present current.

[0060] At decision 540, a determination is made as to whether the present current is greater than the safety current limit set in operation 532. If the present current is greater than the safety current limit, the method 500 flows to operation 544 where the motor is stopped, which causes the firing process to pause or stop. If the present current is not greater than the safety current limit, the method 500 flows to decision 542.

[0061] At decision 542, a determination is made as to whether the present current is less than the current trip level. If the present current is not less than the current trip level, the method 500 remains in the third zone 553 and flows back to operation 536 where operations of the velocity-controlled loop of the third zone 553 repeat. If the present current is less than the current trip level, then the method 500 returns to the second zone 552 and flows to operation 518, where operations the operations of current-controlled loop of the second zone 552 are performed.

[0062] FIG. 6 depicts an example method 600 for performing dual loop motor control for a surgical stapling instrument. The method 600 is performed by the surgical instrument 100. For instance, the memory 118 may store instructions for method 600 that are executed by processor 117 to cause the surgical stapling instrument 100 to perform the operations of method 600.

[0063] At operation 602, the motor of the surgical stapling instrument is controlled under a highspeed velocity-control loop. In some examples, the velocities targeted in the high-speed velocity loop are greater than 10 mm / s and may be between 12-20 mm / s.

[0064] Controlling the motor under the velocity- control loop causes the motor to operate at a target velocity or along a velocity profile. For instance, the power provided to the motor is adjustedor modulated (e.g., via pulse width modulation (PWM)) to maintain the velocity of the motor at the target velocity or along the velocity profile. Thus, during the velocity-control loop, the current drawn by the motor and the resultant firing force is allowed to increase or change to achieve the targeted velocity.

[0065] At operation 604, while the motor is controlled under the velocity-control loop, a determination is made as to whether a present firing force (e.g., based on the most recent measurements or calculations) is greater than or equal to a firing force threshold. If the present firing force is not greater than the firing force threshold, the method 600 flows back to operation 602 where the motor continues to be controlled under the velocity-controlled loop. Operations 602 and 604 may continue to repeat as long as the firing process is continuing and the firing force threshold is not reached. If the present firing force is greater than or equal to the firing force threshold, the method 600 flows to operation 606.

[0066] At operation 606, the motor is controlled under a force-control loop (e.g., a constant current loop). For instance, instead of targeting a particular velocity or velocity profile, the motor is controlled to target a particular force or current level. The particular force or current level may be the firing force threshold. Thus, under the force-control loop the force (or current) remains substantially constant while the velocity is allowed to decrease or change to maintain the constant force.

[0067] At decision 608, while controlling the motor under the force-control loop, a determination is made as to whether the present velocity is at or below a low-velocity limit. If the present velocity is not at or below the low-velocity limit, the method 600 flows back to operation 606 where the motor continues to be controlled under the force-controlled loop. Operations 604 and 606 may continue to repeat as long as the firing process is continuing and the low-velocity limit is not reached. If the present velocity is less than or equal to the low-velocity limit, then the method 600 flows to operation 610.

[0068] At operation 610, the motor is controlled under a low-speed velocity-control loop where the velocity of the motor is maintained at the low- velocity limit and the force is allowed to increase or change. The low-speed velocity-control loop controls the motor at a lower velocity than the high-velocity loop of operation 602.

[0069] At decision 612, while the motor is being controlled under the low-speed velocity-control loop, the present firing force is compared to a maximum force threshold to determine if the firing force is greater than or equal to the maximum force threshold. If the firing force is below the maximum force threshold, the method 600 flows back to operation 610 where the motor continues to be controlled under the low-speed velocity-control loop.

[0070] If the firing force is at or above the maximum force threshold, the method 600 flow to operation 614. At operation 614, the motor is stopped which pauses or stops the firing process.

[0071] As will be appreciated from the foregoing, the technology disclosed herein provides for at least the examples in the following numbered paragraphs.

[0072] 1 : A surgical stapling instrument that may include: a shaft assembly that may include a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally; a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly; a processor; and memory storing instructions that, when executed by the processor, causes the surgical stapling instrument to perform operations that may include: controlling the motor under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile; while controlling the motor under the velocity- control loop, detecting that a firing force has reached a firing force threshold; and in response to the firing force threshold being reached, controlling the motor under a force-control loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

[0073] 2: The surgical stapling instrument as paragraph 1 describes, where the operations further may include: while controlling the motor under the force-control loop, detecting a velocity at a low-velocity limit; and in response to detecting the velocity at the low-velocity limit, controlling the motor to maintain the low-velocity limit and allowing the force to increase.

[0074] 3 : The surgical stapling instrument as either of paragraphs 1 or 2 describe, where the operations further may include: while controlling the motor to maintain the low-velocity limit, detecting a maximum-force threshold being reached; and based on the maximum-force threshold being reached, stopping the motor.

[0075] 4: The surgical stapling instrument as any of paragraphs 1-3 describe, further may include a force sensor configured to measure the firing force.

[0076] 5 : The surgical stapling instrument as any of paragraphs 1-4 describe, where the firing force is determined based on current drawn by the motor.

[0077] 6: The surgical stapling instrument as any of paragraphs 1-5 describe, where controlling the motor under the velocity-control loop causes the motor to operate at the velocity profile.

[0078] 7: The surgical stapling instrument as any of paragraphs 1-6 describe, where the velocity profile has a descending velocity between a firing force of zero and the firing force threshold.

[0079] 8 : The surgical stapling instrument as any of paragraphs 1-7 describe, where the velocity profile includes at least one velocity between 12-20 millimeters per second.

[0080] 9: The surgical stapling instrument as any of paragraphs 1-8 describe, where the velocity profile is a profile of velocity versus firing force.

[0081] 10: The surgical stapling instrument as any of paragraphs 1-9 describe, where the firing force threshold is between 250-400 Newtons.

[0082] 11 : A surgical stapling instrument that may include: a shaft assembly that may include a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally; a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly; a processor; and memory storing instructions that, when executed by the processor, cause the surgical stapling instrument to perform operations that may include: setting a first zone velocity setpoint; setting a second zone current limit; regulating velocity of the motor to target the first zone velocity setpoint; monitoring current of the motor; detecting that the current of the motor exceeds the second zone current limit; and based on detecting that the current of the motor exceeds the second zone current limit, limiting the current of the motor to the second zone current limit.

[0083] 12: The surgical stapling instrument as paragraph 11 describes, where the operations further may include: detecting that the velocity of the motor has reached a minimum velocity threshold; and based on detecting that the velocity of the motor has reached the minimum velocity threshold, regulating the velocity to maintain the velocity at the minimum velocity threshold.

[0084] 13: The surgical stapling instrument as either of paragraphs 11 or 12 describe, where the operations further may include: detecting that the current of the motor has reached a safety current limit; and based on detecting that the current of the motor has reached the safety current limit, stopping the motor.

[0085] 14: A method, implemented by a surgical stapling instrument, for dual loop motor control of the surgical stapling instrument, the method may include: controlling a motor of the surgical stapling instrument under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile; while controlling the motor under the velocity-control loop, detecting that a firing force has reached a firing force threshold; and in response to the firing force threshold being reached, controlling the motor under a force-control loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

[0086] 15: The method as paragraph 14 describes, further may include: while controlling the motor under the force-control loop, detecting a velocity at a low-velocity limit; and in response to detecting the velocity at the low-velocity limit, controlling the motor to maintain the low-velocity limit and allowing the force to increase.

[0087] 16: The method as either of paragraphs 14 or 15 describe, further may include: while controlling the motor to maintain the low-velocity limit, detecting a maximum-force threshold being reached; and based on the maximum-force threshold being reached, stopping the motor.

[0088] 17: The method as any of paragraphs 14-16 describe, where the firing force is determined based on current drawn by the motor.

[0089] 18: The method as any of paragraphs 14-17 describe, where the firing force is based on measurements from a force sensor of the surgical stapling instrument.

[0090] 19: The method as any of paragraphs 14-18 describe, where the target velocity is at least 10 mm / s.

[0091] 20: The method as any of paragraphs 14-19 describe, where the firing force threshold is between 250-400 Newtons.

[0092] Those skilled in the art will recognize that the methods and systems of the present disclosure may be implemented in many manners and as such are not to be limited by the foregoing aspects and examples. In other words, functional elements being performed by a single or multiple components, in various combinations of hardware and software or firmware, and individual functions, can be distributed among software applications at either the client or server level or both. In this regard, any number of the features of the different aspects described herein may be combined into single or multiple aspects, and alternate aspects having fewer than or more than all of the features herein described are possible.

[0093] Functionality may also be, in whole or in part, distributed among multiple components, in manners now known or to become known. Thus, a myriad of software / hardware / firmware combinations are possible in achieving the functions, features, interfaces and preferences described herein. In addition, the operations of the methods described herein may be performed in different orders than depicted and / or one or more operations may be performed concurrently.

[0094] Although the disclosure provides specific examples, various modifications and changes can be made without departing from the scope of the disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Any benefits, advantages, or solutions to problems that are described herein with regard to a specific example are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.

[0095] As used herein, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. In addition, “a set” of elements as used herein can refer to any number of elements, including only one element.

[0096] Further, as used herein, the phrase “at least one of element A, element B, or element C” is intended to convey any of: element A, element B, element C, elements A and B, elements A and C, elements B and C, and elements A, B, and C. In addition, one having skill in the art will understand the degree to which terms such as “about” or “substantially” convey in light of the measurement techniques utilized herein. To the extent such terms may not be clearly defined or understood by one having skill in the art, the term “about” shall mean plus or minus ten percent.

[0097] Unless stated otherwise, terms such as "first" and "second" are used to arbitrarily distinguish between the components such terms describe, and are not intended to indicate relative, temporal, or other prioritization of such components.

[0098] All directional references as may be used herein, e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, etc., are only used for identification purposes to aid the reader's understanding of the present disclosure and do not create limitations, particularly as to the position, orientation, or use of the disclosure. Connection references as may be used herein (e.g., attached, coupled, connected, or joined) are to be construed broadly and can include intermediate members between a collection of elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected or in fixed relation to one another. Additionally, the drawings of the present disclosure are for purposes of illustration only, and the dimensions, positions, order, or relative sizes of components reflected in the drawings can vary.

[0099] The following examples are illustrative of the techniques described herein.

[0100] Example 1. A surgical stapling instrument, comprising: a shaft assembly comprising a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally; a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly; a processor; and memory storing instructions that, when executed by the processor, causes the surgical stapling instrument to perform operations comprising: controlling the motor under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile; while controlling the motor under the velocity-control loop, detecting that a firing force has reached a firing force threshold; and in response to the firing force threshold being reached, controlling the motor under a forcecontrol loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

[0101] Example 2. The surgical stapling instrument of example 1, wherein the operations further comprise: while controlling the motor under the force-control loop, detecting a velocity at a low-velocity limit; and in response to detecting the velocity at the low-velocity limit, controlling the motor to maintain the low- velocity limit and allowing the force to increase.

[0102] Example 3. The surgical stapling instrument of example 2, wherein the operations further comprise: while controlling the motor to maintain the low-velocity limit, detecting a maximum-force threshold being reached; andbased on the maximum-force threshold being reached, stopping the motor.

[0103] Example 4. The surgical stapling instrument of example 1, further comprising a force sensor configured to measure the firing force.

[0104] Example 5. The surgical stapling instrument of example 1, wherein the firing force is determined based on current drawn by the motor.

[0105] Example 6. The surgical stapling instrument of example 1, wherein controlling the motor under the velocity-control loop causes the motor to operate at the velocity profile.

[0106] Example 7. The surgical stapling instrument of example 6, wherein the velocity profile has a descending velocity between a firing force of zero and the firing force threshold.

[0107] Example 8. The surgical stapling instrument of example 6, wherein the velocity profile includes at least one velocity between 12-20 millimeters per second.

[0108] Example 9. The surgical stapling instrument of example 6, wherein the velocity profile is a profile of velocity versus firing force.

[0109] Example 10. The surgical stapling instrument of example 1, wherein the firing force threshold is between 250-400 Newtons.

[0110] Example 11. A surgical stapling instrument, comprising: a shaft assembly comprising a firing rod; a motor coupled to the firing rod and configured to drive the firing rod distally; a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly;a processor; and memory storing instructions that, when executed by the processor, causes the surgical stapling instrument to perform operations comprising: setting a first zone velocity setpoint; setting a second zone current limit; regulating velocity of the motor to target the first zone velocity setpoint; monitoring current of the motor; detecting that the current of the motor exceeds the second zone current limit; and based on detecting that the current of the motor exceeds the second zone current limit, limiting the current of the motor to the second zone current limit.

[0111] Example 12. The surgical stapling instrument of claim 11, wherein the operations further comprise: detecting that the velocity of the motor has reached a minimum velocity threshold; and based on detecting that the velocity of the motor has reached the minimum velocity threshold, regulating the velocity to maintain the velocity at the minimum velocity threshold.

[0112] Example 13. The surgical stapling instrument of claim 12, wherein the operations further comprise: detecting that the current of the motor has reached a safety current limit; andbased on detecting that the current of the motor has reached the safety current limit, stopping the motor.

[0113] Example 14. A method, implemented by a surgical stapling instrument, for dual loop motor control of the surgical stapling instrument, the method comprising: controlling a motor of the surgical stapling instrument under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile; while controlling the motor under the velocity-control loop, detecting that a firing force has reached a firing force threshold; and in response to the firing force threshold being reached, controlling the motor under a force-control loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

[0114] Example 15. The method of example 14, further comprising: while controlling the motor under the force-control loop, detecting a velocity at a low-velocity limit; and in response to detecting the velocity at the low-velocity limit, controlling the motor to maintain the low-velocity limit and allowing the force to increase.

[0115] Example 16. The method of example 15, further comprising: while controlling the motor to maintain the low-velocity limit, detecting a maximum-force threshold being reached; and based on the maximum-force threshold being reached, stopping the motor.

[0116] Example 17. The method of example 14, wherein the firing force is determined based on current drawn by the motor.

[0117] Example 18. The method of example 14, wherein the firing force is based on measurements from a force sensor of the surgical stapling instrument.

[0118] Example 19. The method of example 14, wherein the target velocity is at least 10 mm / s.

[0119] Example 20. The method of example 14, wherein the firing force threshold is between 250-400 Newtons.

Claims

WHAT IS CLAIMED IS:

1. A surgical stapling instrument, comprising:a shaft assembly comprising a firing rod;a motor coupled to the firing rod and configured to drive the firing rod distally;a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly;a processor; andmemory storing instructions that, when executed by the processor, causes the surgical stapling instrument to perform operations comprising:controlling the motor under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile;while controlling the motor under the velocity-control loop, detecting that a firing force has reached a firing force threshold; andin response to the firing force threshold being reached, controlling the motor under a force-control loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

2. The surgical stapling instrument of claim 1, wherein the operations further comprise: while controlling the motor under the force-control loop, detecting a velocity at a low-velocity limit; andin response to detecting the velocity at the low-velocity limit, controlling the motor to maintain the low-velocity limit and allowing the force to increase.

3. The surgical stapling instrument of claim 2, wherein the operations further comprise: while controlling the motor to maintain the low-velocity limit, detecting a maximumforce threshold being reached; andbased on the maximum-force threshold being reached, stopping the motor.

4. The surgical stapling instrument of any one of claims 1-3, further comprising a force sensor configured to measure the firing force.

5. The surgical stapling instrument of any one of claims 1-4, wherein the firing force is determined based on current drawn by the motor.

6. The surgical stapling instrument any one of claims 1-5, wherein controlling the motor under the velocity-control loop causes the motor to operate at the velocity profile.

7. The surgical stapling instrument of claim 6, wherein the velocity profile has a descending velocity between a firing force of zero and the firing force threshold.

8. The surgical stapling instrument of claim 6, wherein the velocity profile includes at least one velocity between 12-20 millimeters per second.

9. The surgical stapling instrument of claim 6, wherein the velocity profile is a profile of velocity versus firing force.

10. The surgical stapling instrument of any one of claims 1-9, wherein the firing force threshold is between 250-400 Newtons.

11. A surgical stapling instrument, comprising:a shaft assembly comprising a firing rod;a motor coupled to the firing rod and configured to drive the firing rod distally;a tool assembly including an end effector coupled to the firing rod such that distal advancement of the firing rod causes firing of staples in the tool assembly;a processor; andmemory storing instructions that, when executed by the processor, causes the surgical stapling instrument to perform operations comprising:setting a first zone velocity setpoint;setting a second zone current limit;regulating velocity of the motor to target the first zone velocity setpoint; monitoring current of the motor;detecting that the current of the motor exceeds the second zone current limit; and based on detecting that the current of the motor exceeds the second zone current limit, limiting the current of the motor to the second zone current limit.

12. The surgical stapling instrument of claim 11, wherein the operations further comprise:detecting that the velocity of the motor has reached a minimum velocity threshold; and based on detecting that the velocity of the motor has reached the minimum velocity threshold, regulating the velocity to maintain the velocity at the minimum velocity threshold.

13. The surgical stapling instrument of claim 12, wherein the operations further comprise:detecting that the current of the motor has reached a safety current limit; andbased on detecting that the current of the motor has reached the safety current limit, stopping the motor.

14. A method, implemented by a surgical stapling instrument, for dual loop motor control of the surgical stapling instrument, the method comprising:controlling a motor of the surgical stapling instrument under a velocity-control loop to cause the motor to operate at a target velocity or a velocity profile;while controlling the motor under the velocity-control loop, detecting that a firing force has reached a firing force threshold; andin response to the firing force threshold being reached, controlling the motor under a force-control loop to cause the motor to operate at a substantially constant firing force at the firing force threshold.

15. The method of claim 14, further comprising:while controlling the motor under the force-control loop, detecting a velocity at a low-velocity limit; andin response to detecting the velocity at the low-velocity limit, controlling the motor to maintain the low-velocity limit and allowing the force to increase.

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