ROBOTIC SURGICAL SYSTEM AND METHOD OF CONTROLLING ROBOTIC SURGICAL SYSTEM

A robotic surgical system according to an embodiment may include: a surgical instrument including a pair of jaw members configured to be opened and closed by an elongate element; a robotic arm which includes a motor configured to drive the elongate element and to which the surgical instrument is attached; a first storage that stores in advance a first value corresponding to a rotation angle of the motor for a predetermined current value; and a controller configured to acquire a second value corresponding to the rotation angle of the motor when the predetermined current value is reached, and perform calibration to change, based on the acquired second value and the first value stored in the first storage, a command angle for a tightening operation of the jaw members.

BACKGROUND

The disclosure may relate to a robotic surgical system and a method of controlling a robotic surgical system, and more particularly to a robotic surgical system and a method of controlling a robotic surgical system in which a drive of a pair of jaw members is controlled based on a rotation angle of a motor.

In a related art, a robotic surgical system is known that includes a surgical instrument including a pair of jaw members that are opened and closed by cables. Such a robotic surgical system is disclosed in U.S. Pat. No. 9,014,856, for example.

The above-mentioned U.S. Pat. No. 9,014,856 discloses a robotic surgical system including a surgical instrument including a pair of jaw members that are opened and closed by cables. In this robotic surgical system, as the surgical instrument is used over time, the cables that drive the pair of jaw members stretch, which may cause the pair of jaw members to be unable to exert a desired gripping force. Accordingly, the system compensates for such cable stretch. Specifically, in this robotic surgical system, a motor is torque-controlled so as to drive the jaw members within a predetermined torque range between an upper limit torque and a lower limit torque.PATENT DOCUMENT 1: U.S. Pat. No. 9,014,856

SUMMARY

In the robotic surgical system described in the above listed U.S. Pat. No. 9,014,856, the motor that drives the jaw members is controlled based on the torque; however, in some cases, it is effective to use the rotation angle to control the motor that drives the jaw members. For example, in a case in which a motor is torque-controlled, if a decelerator with a high reduction ratio is used, a behavior of a distal end side of the surgical instrument is less likely to be reflected as a change in the motor torque. In this case, it becomes difficult to detect the behavior of the distal end side of the surgical instrument by detecting changes in the torque of the motor. In order to solve this problem, it is effective to control the motor that drives the jaw members based on the rotation angle thereof. However, in a case in which the motor that drives the jaw members is controlled based on the rotation angle thereof, the method described in the above-mentioned U.S. Pat. No. 9,014,856 cannot be used. For this reason, it is desirable to suppress a decrease in the gripping force of the jaw members in a configuration in which the drive of the jaw members is controlled based on the rotation angle of the motor.

An embodiment of disclosure may provide a robotic surgical system and a method of controlling a robotic surgical system that are capable of suppressing a decrease in a gripping force of jaw members in a configuration in which a drive of the jaw members of a surgical instrument is controlled based on a rotation angle of a motor.

A robotic surgical system according to a first aspect may include a surgical instrument including a pair of jaw members configured to be opened and closed by an elongate element; a robotic arm which includes a motor configured to drive the elongate element and to which the surgical instrument is attached; a first storage that stores in advance a first value corresponding to a rotation angle of the motor when a predetermined current value is reached; and a controller that is configured to acquire a second value corresponding to the rotation angle of the motor when the predetermined current value is reached, and perform calibration to change, based on the acquired second value and the first value stored in the first storage, a command angle for a tightening operation of the jaw members.

According to the first aspect, the controller is provided that acquires the second value corresponding to the rotation angle of the motor when the predetermined current value is reached, and performs the calibration to change the command angle for the tightening operation of the jaw members based on the acquired second value and the first value stored in the first storage. Accordingly, in a configuration in which the drive of the jaw members of the surgical instrument is controlled according to the rotation angle of the motor, it is possible to perform the calibration to compensate for the stretch of the elongate element. Therefore, in the configuration in which the drive of the jaw members of the surgical instrument is controlled according to the rotation angle of the motor, the decrease in the gripping force of the jaw members can be suppressed.

A method of controlling a robotic surgical system according to a second aspect may be the method of controlling the robotic surgical system which includes: a surgical instrument including a pair of jaw members configured to be opened and closed by an elongate element; and a robotic arm which includes a motor configured to drive the elongate element and to which the surgical instrument is attached. The method may include: acquiring a second value corresponding to a rotation angle of the motor when a predetermined current value is reached; and performing calibration that changes, based on the acquired second value and a first value stored in advance that corresponding to the rotation angle of the motor when the predetermined current value is reached, a command angle for a tightening operation of the jaw members.

According to the second aspect, the method includes: acquiring the second value corresponding to the rotation angle of the motor when the predetermined current value is reached, the second value corresponding to the first value corresponding to the rotation angle of the motor when the predetermined current value is reached; and the step of performing calibration that changes, based on the acquired second value and the first value stored in advance, the command angle for the tightening operation of the jaw members. Accordingly, in a configuration in which the drive of the jaw members of the surgical instrument is controlled according to the rotation angle of the motor, it is possible to perform the calibration to compensate for the stretch of the elongate element. Therefore, it is possible to provide the method of controlling the robotic surgical system that is capable of suppressing the decrease in the gripping force of the jaw members in the configuration in which the drive of the jaw members of the surgical instrument is controlled according to the rotation angle of the motor.

Therefore, it is possible to provide a robotic surgical system and a method of controlling a robotic surgical system that are capable of suppressing a decrease in a gripping force of jaw members in a configuration in which a drive of the jaw members of a surgical instrument is controlled based on a rotation angle of a motor.

DETAILED DESCRIPTION

Descriptions are provided hereinbelow for an embodiment based on the drawings.

(Configuration of Robotic Surgical System)

A configuration of a robotic surgical system100according to an embodiment is described with reference toFIGS.1and2.

As illustrated inFIG.1, the robotic surgical system100includes a remote control apparatus10which is an operator-side device, and a patient-side apparatus20which is a surgery assist robot. The remote control apparatus10is provided to remotely control medical equipment provided to the patient-side apparatus20. When an operator, as a surgeon, inputs an action mode instruction to be executed by the patient-side apparatus20, to the remote control apparatus10, the remote control apparatus10transmits the action mode instruction to the patient-side apparatus20through a controller24. In response to the action mode instruction transmitted from the remote control apparatus10, the patient-side apparatus20operates the medical equipment, including surgical instruments40attached to robot arms21aand an endoscope50attached to a robot arm21b. This allows minimally invasive surgery. Note that the controller24is an example of a controller or a control device.

The patient-side apparatus20constitutes an interface to perform a surgery for a patient P. The patient-side apparatus20is positioned beside an operation table30on which the patient P is laid. The patient-side apparatus20includes the plurality of robot arms21aand21b, an arm base22, a positioner23, the controller24, a storage25, and a temporary storage26. An endoscope50is attached to one robot arm21bamong the plural robot arms21aand21b, and the surgical instruments40are attached to the other robot arms21a. The robot arms21aand21bare commonly supported by the arm base22. Each of the plural robot arms21aand21bincludes plural joints. Each joint includes a driver including a servo-motor and a position detector such as an encoder or the like. The robot arms21aand21bare configured so that the medical equipment attached to each of the robot arms21aand21bis controlled by a driving signal given through the controller24and performs a desired movement.

The arm base22is supported by a positioner23placed on the floor of an operation room. The positioner23includes a vertical articulated robot. The positioner23is configured to move the position of the arm base22three-dimensionally. The controller24is a control circuit including an arithmetic unit such as a CPU and/or the like, and a memory such as a ROM, a RAM, and/or the like. The storage25is a data storage, and stores a threshold value θS1which will be described later and a threshold value θS2which will be described later. The temporary storage26stores a difference Δθ, which will be described later. The storage25and the temporary storage26are provided in a robot body27on which the robot arms21aand21bare provided. The temporary storage26is an example of a second storage. The threshold value θS1is an example of a second threshold value. The threshold value θS2is an example of a first threshold value.

The surgical instruments40as the medical equipment are detachably attached to the distal ends of the robot arms21a. Each surgical instrument40includes: a housing41(seeFIG.4) which is to be attached to the robot arm21a; an elongate shaft42(seeFIG.4); and an end effector43(seeFIG.4) which is provided at a tip portion (a distal end portion) of the shaft42. The end effector43may be grasping forceps, scissors, a hook, a high-frequency knife, a snare wire, a clamp, a stapler, a clip applier, an electric knife, or a needle, for example. The end effector43is not limited to those and can be various types of treatment tools. In surgeries using the patient-side apparatus20, the robot arms21aintroduce the surgical instruments40into the body of the patient P through a cannula (trocar) placed on the body surface of the patient P. The end effectors43of the surgical instruments40are then located near a surgery site.

To the distal end of the robot arm21b, the endoscope50as the medical equipment is detachably attached. The endoscope50captures an image in a body cavity of the patient P. The captured image is outputted to the remote control apparatus10. The endoscope50may be a 3D endoscope capable of capturing a three-dimensional image or a 2D endoscope. In surgeries using the patient-side apparatus20, the robot arm21bintroduces the endoscope50into the body of the patient P through a trocar placed on the body surface of the patient P. The endoscope50is then located near the surgery site.

The remote control apparatus10constitutes an interface with the operator. The remote control apparatus10is an apparatus that allows the operator to operate the medical equipment attached to the robot arms21aand21b. Specifically, the remote control apparatus10is configured to transmit action mode instructions which are inputted by the operator and are to be executed by the surgical instruments40and the endoscope50, to the patient-side apparatus20through the controller24. The remote control apparatus10is installed beside the operation table30so that the operator can see the condition of the patient P very well while operating the remote control apparatus10, for example. The remote control apparatus10may be configured to transmit the action mode instructions wirelessly and installed in a room different from the operation room where the operation table30is installed.

The action modes to be executed by the surgical instruments40include modes of actions to be taken by each surgical instrument40(a series of positions and postures) and actions to be executed by the function of each surgical instrument40. When the surgical instrument40is a pair of grasping forceps, for example, the action modes to be executed by the surgical instrument40include roll and pitch positions of the wrist of the end effector43and actions to open and close the jaws. When the surgical instrument40is a high-frequency knife, the action modes to be executed by the surgical instrument40include vibration of the high-frequency knife, specifically, supply of current to the high-frequency knife. When the surgical instrument40is a snare wire, the action modes to be executed by the surgical instrument40include a capturing action and an action to release the captured object. Further, the action modes may include an action to supply current to a bipolar or monopolar instrument to burn off the surgery site.

The action modes to be executed by the endoscope50include the position and posture of the distal end of the endoscope50and setting of the zoom magnification, for example.

As illustrated inFIGS.1and2, the remote control apparatus10includes operation handles11, an operation pedal section12, a display13, a touch panel14, and a control apparatus15.

The operation handles11are provided in order to remotely operate the medical equipment attached to the robot arms21aand21b. Specifically, the operation handles11accept operations by the operator for operating the medical equipment (the surgical instruments40and endoscope50). The operation handles11are composed of two operation handles11arranged side by side in the horizontal direction. One of the two operation handles11is operated by the right hand of the operator while the other of the two operation handle11is operated by the left hand of the operator.

The operation handles11extend from the rear side of the remote control apparatus10toward the front side. The operation handles11are configured to move in a predetermined three-dimensional operation region. Specifically, the operation handles11are configured to be movable in a vertical direction, a horizontal direction, a front-rear direction, and a rotational direction.

As illustrated inFIG.3, the operation handles11are hand controllers to be operated by the hands of the operator. The operation handle11includes a support member11a, a pair of grip members11bprovided on both sides of the support member11awith the support member11abeing interposed between the pair of grip members11b, and a finger insertion portion11cprovided in each of the pair of grip members11b. The operator inserts fingers (such as (thumb, middle finger, etc.) into the pair of finger insertion portions11cto operate the operation handle11. That is, a proximal end of each of the pair of grip members11bis rotatably connected to a support member11a. By increasing or decreasing an open angle between the pair of grip members11b(a grip open angle), an open angle between a pair of jaw members43aand43b, which will be described later, is changed. A command for opening and closing the pair of jaw members43aand43bis input to the operation handle11. The open angle between the pair of gripping members11bis detected by a sensor, for example. For example, the operation handle11is provided with a hole sensor at the support member11aand with a magnet at one or each of the pair of grip members11b, so that the open angle between the pair of grip members11bcan be detected. Alternatively, the operation handle11is provided with a hole sensor at one of the pair of grip members11band with a magnet at the other of the pair of grip members11b, so that the open angle between the pair of grip members11bcan be detected. Based on a signal relating to the detected open angle between the pair of grip members11b, the pair of jaw members43aand43bare controlled to open and close.

As illustrated inFIG.1, the remote control apparatus10and patient-side apparatus20constitute a master-slave system in terms of controlling movements of the robot arm21aand the robot arms21b. The operation handles11constitute a controlling part on the master side in the master-slave system, and the robot arms21aand21bholding the medical equipment constitute an acting part on the slave side. When the operator operates the operation handles11, the movement of one of the robot arms21aor21bis controlled so that the distal end portion (the end effector43of the surgical instrument40) of the robot arm21aor the distal end portion (the endoscope50) of the robot arm21bmoves following the movement of the operation handles11.

The patient-side apparatus20controls the movement of the robot arms21ain accordance with the set motion scaling ratio. When the motion scaling ratio is set to ½, for example, the end effectors43of the surgical instruments40move ½ of the movement distance of the operation handles11. This allows for precise fine surgery.

The operation pedal section12includes plural pedals to execute medical equipment-related functions. The plural pedals include a coagulation pedal, a cutting pedal, a camera pedal, and a clutch pedal. The plural pedals are operated by a foot of the operator.

The coagulation pedal enables the surgical instrument40to coagulate a surgery site. Specifically, when the coagulation pedal is operated, voltage for coagulation is applied to the surgical instrument40to coagulate the surgery site. The cutting pedal enables the surgical instrument40to cut the surgery site. Specifically, the cutting pedal is operated to apply voltage for cutting to the surgical instrument40and cut a surgery site.

The camera pedal is used to control the position and orientation of the endoscope50that captures images within the body cavity. Specifically, the camera pedal enables operation of the endoscope50by the operation handles11. That is, the position and orientation of the endoscope50are controllable by the operation handles11while the camera pedal is being pressed. The endoscope50is controlled by using both of the right and left operation handles11, for example. Specifically, when the operator rotates the right and left operation handles11about the middle point between the right and left operation handles11, the endoscope50is rotated. When the operator presses the right and left operation handles11together, the endoscope50goes forward into the body cavity. When the operator pulls the right and left operation handles11together, the endoscope50goes back. When the operator moves the right and left operation handles11together up, down, right, or left, the endoscope50moves up, down, right, or left, respectively.

The clutch pedal is used to temporarily disconnect operation-related connection between the robot arms21aand the operation handles11to stop movement of the surgical instruments40. Specifically, when the clutch pedal is being pressed, the robot arms21aof the patient-side apparatus20do not work even if the operation handles11are operated. For example, when the operation handles11are operated and moved to the edge of the range of movement, the operator operates the clutch pedal to temporarily disconnect the operation-related connection and then returns the operation handles11to the center of the range of movement. When the operator stops operating the clutch pedal, the operation handles11are again connected to the robot arms21a. The operator restarts the operation for the operation handles11around the center thereof.

The display13is configured to display images captured by the endoscope50. The display13comprises a scope type display or a non-scope type display. (Note thatFIG.1illustrates a scope type display.) The scope type display is a display configured in such a manner that the operator looks into the display. The non-scope type display is a display like an open-type display that includes a flat screen and the operator is able to see without looking into, such as normal displays for personal computers.

When the scope type display is attached, the scope type display displays 3D images captured by the endoscope50attached to the robot arm21bof the patient-side apparatus20. When the non-scope type display is attached, the non-scope type display also displays 3D images captured by the endoscope50provided for the patient-side apparatus20. Here, when the non-scope type display is attached, 2D images captured by the endoscope50provided to the patient-side apparatus20may be displayed.

The touch panel14serves as an operation section and a display section. The touch panel14displays a screen for setting operations for the remote control apparatus10and receives setting operations for the remote control apparatus10.

As illustrated inFIG.2, the control apparatus15includes a controller151, a storage152, and an image controller153, for example. The controller151includes an arithmetic unit such as a CPU. The storage152includes a memory, such as a ROM and a RAM. The control apparatus15may be composed of a single controller performing centralized control or may be composed of plural controllers that perform decentralized control in cooperation with each other. The controller151determines whether an action mode instruction inputted by the operation handles11is to be executed by the robot arms21aor to be executed by the endoscope50, depending on the state of the operation pedal section12. When determining that the action mode instruction inputted by the operation handles11is to be executed by any one of the surgical instruments40, the controller151transmits the action mode instruction to the corresponding robot arm21athrough the controller24. The robot arm21ais thereby driven by the controller24and thus movement of the surgical instrument40attached to the robot arm21ais controlled.

When determining that the action mode instruction inputted by the operation handles11is to be executed by the endoscope50, the controller151transmits the action mode instruction to the robot arm21bthrough the controller24. The robot arm21bis thereby driven for control of movement of the endoscope50attached to the robot arm21b.

The storage152stores control programs corresponding to the types of the surgical instrument40, for example. The controller151reads the stored control programs according to the types of the attached surgical instruments40.

The action mode instructions from the operation handles11and/or the operation pedal section12of the remote control apparatus10thereby cause the respective surgical instruments40to perform proper movements.

The image controller153transmits images acquired by the endoscope50to the display13. The image controller153performs processing and modifying the images when needed.

With reference toFIGS.4to6, the configurations of the surgical instrument40, an adaptor60, a drape70, and the robot arm21aare described.

Here, the direction in which the surgical instrument40extends (the direction in which the shaft42extends) is defined as a Y direction, the distal side (the side toward the end effector43) of the surgical instrument40along the Y direction is defined as a Y1 direction, and the opposite side of the Y1 direction is defined as a Y2 direction. The direction in which the surgical instrument40and the adaptor60are adjacent to each other is defined as a Z direction, the surgical instrument40side along the Z direction is defined as a Z1 direction, and the opposite side of the Z1 direction is defined as a Z2 direction. Further, the direction orthogonal to the Y direction and the Z direction is referred to as an X direction, one side along the X direction is referred as an X1 direction, and the other side along the X direction is referred to as an X2 direction.

As illustrated inFIGS.4and5, the surgical instrument40is removably attached to the robot arm21a. Specifically, the surgical instrument40is detachably attached to the robot arm21avia the adaptor60. The adaptor60is a drape adaptor configured to sandwich a sterile drape70to cover the robot arm21a, in conjunction with the robot arm21a.

The surgical instrument40is attached to the Z1 side of the adaptor60. The adaptor60is attached to the Z1 side of the robot arm21a.

The robot arm21ais used in a clean area and is covered with the drape70. In operation rooms, clean technique is used in order to prevent surgical incision sites and medical equipment from being contaminated by pathogen, foreign matters, or the like. The clean technique defines a clean area and a contaminated area, which is outside the clean area. The surgery sites are located in the clean area. Members of the surgical team, including the operator, make sure that only sterile objects are placed in the clean area during surgery and perform sterilization for an object which is to be moved to the clean area from the contaminated area. Similarly, when an assistant, as one of the members of the surgical team including the operator, places their hands in the contaminated area, the members sterilize their hands before directly touching objects located in the clean area. Instruments used in the clean area are sterilized or are covered with the drapes70that are sterilized.

As illustrated inFIG.5, the drape70includes a body section71that covers the robot arm21aand an attachment section72sandwiched between the robot arm21aand the adaptor60. The body section71is made of a flexible film member that is formed in a film-shape. The flexible film member is made of a resin material, such as thermoplastic polyurethane and polyethylene. The body section71includes an opening so that the robot arm21ais engaged with the adaptor60. To the opening of the body section71, the attachment section72is provided. The attachment section72is made of a resin mold member. The resin mold member is made of a resin member such as polyethylene terephthalate. The attachment section72is harder (less flexible) than the body section71. The attachment section72includes an opening so that the robot arm21ais engaged with the adaptor60. The opening of the attachment section72may be provided corresponding to the section where the robot arm21ais engaged with the adaptor60. The opening of the attachment section72may include plural openings corresponding to plural sections at which the robot arm21ais engaged with the adaptor60.

As illustrated inFIGS.5and6, the surgical instrument40includes plural (four) driven members44a,44b,44c, and44d, and a storage45. The storage45is provided in the housing41. The storage45stores a serial number representing the surgical instrument40, a number of times the surgical instrument40has been used, and values θ1and θ0, which will be described later. in the embodiment, the value θ1is set to approximately half the value θ0. When the surgical instrument40is attached to the robot arm21a, the storage45is communicatively connected to the controller24. Note that the storage45is an example of a first storage. The value θ1is an example of a first value. The value θ0is an example of a third value.

The driven members44ato44dare provided within the housing41and are rotatable about the respective rotation axes extending along the Z axis. The plural driven members44ato44dare provided to operate (drive) the end effector43. The driven members44bto44dare connected to the end effector43via cables A, serving as elongate elements, passing through the inside of the shaft42. With this, rotations of the driven members44bto44ddrive the cables A, which operate (drive) the end effector43. In addition, the driven member44ais connected to the shaft42through gears42a(seeFIG.7). With this, the shaft42is rotated with rotation of the driven member44a, and the end effector43is also rotated with rotation of the shaft42.

To transmit driving forces from the robot arm21ato the end effector43, each of the driven members44ato44dincludes a projection441or442, which is engaged with a corresponding one of drive transmission members61of the adaptor60. Each of the projections441and442is projected from the Z2 side surface of the corresponding driven member44ato44dtoward the side of the adaptor60(the Z2 side). Each of the projections441and442includes plural projection portions that arranged in a straight line. The protrusions441provided to the driven members44aand44bhave different shapes from that of the protrusions442provided to the driven members44cand44d.

As illustrated inFIG.5, the adaptor60includes a plurality (four) of the drive transmission members61. The drive transmission members61are configured to transmit the driving forces from the robot arm21ato the driven members44ato44dof the surgical instrument40. That is, the drive transmission members61are provided so as to correspond to the driven members44ato44dof the surgical instrument40. The drive transmission members61are rotatable about the respective rotation axes, which extend along the Z direction.

Each of the drive transmission members61includes an engagement recess611which is engaged with the projection441or442of the corresponding driven member44ato44dof the surgical instrument40. The engagement recess611is located at the surgical instrument40side (the Z1 side) of the drive transmission member61and is recessed from the Z1 side surface of the drive transmission member61, toward the Z2 direction, opposite to the surgical instrument40. Each of the drive transmission members61includes an engagement recess, which is provided on the Z2 side surface thereof and is configured to be engaged with a corresponding engagement projection213of the robot arm21a.

The robot arm21aincludes a frame211, plural (four) drive parts212, and plural engagement projections213. The plural drive parts212are provided corresponding to the plural (four) driven members44ato44dof the surgical instrument40and corresponding to the plural (four) drive transmission members61of the adaptor60. The drive part212is configured to drive the engagement projection213to rotate about a rotation axis thereof extending in the Z direction. The engagement projection213is engaged with the engagement recess provided on the Z2 side surface of the drive transmission member61. The engagement projection213is projected from the Z1 side surface of the robot arm21atoward the Z1 side (the adaptor60side). The drive parts212are configured to drive the drive transmission members61of the adaptor60, engaged with the engagement projections213, to rotate about the rotational axes extending in the Z direction, so as to drive the driven members44ato44dof the surgical instrument40, engaged with the drive transmission members61, to rotate about the rotational axes extending in the Z direction.

(Detailed Configuration of Surgical Instrument)

Next, with reference toFIGS.7to9, the configuration of the surgical instrument40is described in detail below. Here, the case is described below in which the end effector43of the surgical instrument40is a grasping forceps including the pair of jaw members43aand43b. Note that the surgical instrument of the disclosure includes at least a pair of jaw members, and the pair of jaw members may be scissors or the like, for example.

As illustrated inFIGS.7and8, the cables A are wound around the driven members44bto44dof the surgical instrument40. That is, the cables A are connected to the driven members44bto44d.

The cable A3is wound around the driven member44b. Specifically, a first portion A3aof the cable A3is wound in the clockwise direction around an upper portion of the driven member44b, and a second portion A3bof the cable A3is wound in the counterclockwise direction around a lower portion of the driven member44b.

The cable A1is wound around the driven member44cof the surgical instrument40. Specifically, a first portion A1aof the cable A1is wound in the clockwise direction around an upper portion of the driven member44c, and a second portion A1bof the cable A1is wound in the counterclockwise direction around a lower portion of the driven member44c.

The cable A2is wound around the driven member44d. Specifically, a first portion A2aof the cable A2is wound in the clockwise direction around an upper portion of the driven member44d, and a second portion A2bof the cable A1is wound in the counterclockwise direction around a lower portion of the driven member44d.

The cables A extend respectively from the driven members44bto44dthrough the shaft42to the end effector43, are wound around the end effector43, and return through the shaft42to the driven members44bto44d. In addition, the cables A are hung on pulleys46. The pulleys46are retained by a pulley retainer461.

As illustrated inFIGS.8and9, when the driven member44crotates about the rotary axis thereof, the rotation of the driven member44coperates the jaw member43a, which is one of the jaw members43aand43bof the end effector43. Specifically, the driven member44cis rotated by the drive part212to drive the cable A1. The cable A1extends through the inside of the shaft42and connects the jaw member43aand the driven member44c. Specifically, the cable A1is wound around a pulley43dprovided at the base of the jaw member43a. When the driven member44cis rotated in the C1 direction (seeFIG.8), the first portion Ala of the cable A1is pulled and the second portion A1bof the cable A1is fed, so as to drive the jaw member43ato move in the C1 a direction (seeFIG.9), which is a direction to open the jaw member43a. When the driven member44cis rotated in the C2 direction opposite to the C1 direction (seeFIG.8), the first portion A1aof the cable A1is fed and the second portion A1bof the cable A1is pulled, so as to drive the jaw member43ato move in the C2a direction (seeFIG.9), which is a direction to close the jaw member43a.

When the driven member44drotates about the rotary axis thereof, the rotation of the driven member44doperates the jaw member43b, which is one of the jaw members43aand43bof the end effector43. Specifically, the driven member44dis rotated by the drive part212to drive the cable A2. The cable A2extends through the inside of the shaft42and connects the jaw member43band the driven member44d. Specifically, the cable A2is wound around a pulley43eprovided at the base of the jaw member43b. When the driven member44dis rotated in the C3 direction (seeFIG.8), the first portion A2aof the cable A2is pulled and the second portion A2bof the cable A2is fed, so as to drive the jaw member43bto move in the C3a direction (seeFIG.9), which is a direction to open the jaw member43b. When the driven member44dis rotated in the C4 direction opposite to the C3 direction (seeFIG.8), the first portion A2aof the cable A2is fed and the second portion A2bof the cable A2is pulled, so as to drive the jaw member43bto move in the C4a direction (seeFIG.9), which is a direction to close the jaw member43b. The jaw members43aand43bare opened and closed with respect to each other by the movements of the cables A of the driven members44band44c. Note that the cables A1and A2are examples of elongate elements.

By being rotated about the rotation axis thereof, the driven member44boperates a wrist portion43cof the end effector43. Specifically, the driven member44bis rotated by the drive part212to drive the cable A3. The cable A3extends through the inside of the shaft42and connects the wrist portion43cand the driven member44b. When the driven member44bis rotated in the C5 direction (seeFIG.8), the first portion A3aof the cable A3is pulled and the second portion A3bof the cable A3is advanced, so as to drive the wrist portion43cto move in the C5a direction (seeFIG.9). When the driven member44bis rotated in the C6 direction opposite to the C5 direction (seeFIG.8), the second portion A3bof the cable A3is pulled and the first portion A3aof the cable A3is fed, so as to drive the wrist portion43cto move in the C6a direction, which is opposite to the C5a direction (seeFIG.9).

When the drive part212rotates the driven member44aabout the rotation axis thereof with the gear portion443of the driven member44abeing engaged with a gear portion42aconnected to the proximal end of the shaft42, the shaft42is driven to operate the end effector43. Specifically, when the driven member44arotates in the C7 direction (seeFIG.8), the shaft42is driven to rotate in the C7a direction (seeFIG.9) and thus the end effector43is driven to rotate in the C7a. When the driven member44arotates in the C8 direction (seeFIG.8), the shaft42is driven to rotate in the C8a direction, which is opposite to the C7a direction (seeFIG.9), and thus the end effector43is driven to rotate in the C8a direction.

(Configuration Relating to Opening and Closing Jaw Members)

Next, a configuration relating to opening and closing of the jaw members43aand43bwill be described with reference toFIGS.10and11.

As illustrated inFIG.10, each drive part212includes a motor212a, a decelerator212b, and a position detector212c. The motor212ais composed of a servo motor, and is a drive source that drives the cable A1(A2) and the jaw member43a(43b). The decelerator212breduces a rotation speed of the motor212aand outputs the reduced rotation. The position detector212cis composed of an absolute encoder and detects a rotation angle of the motor212a. Further, a current detector214is provided for the motor212a. The current detector214detects a current value of the motor212a.

The controller24drives the motors212abased on a signal from the operation handles11. With this, the decelerator212b, the engagement protrusion213, the drive transmission member61, and the driven members44c,44dare rotated, so as to drive the cables A1, A2. As a result, the jaw members43aand43bare opened and closed. The controller24drives the motor212asuch that the open angle between the jaw members43aand43bbecomes an open angle that corresponds to a signal from the operation handles11(a target open angle). The controller24controls, based on the detection result of the rotation angle of the motor212adetected by the position detector212c, the rotation angle of the motor212asuch that the rotation angle corresponds to the target open angle. That is, the controller24controls the driving of the jaw members43aand43bby the rotation angle of the motor212a.

For example, in the following cases, it is more effective to control the motor212athat drives the jaw members43aand43baccording to the rotation angle of the motor212arather than controlling the motor212athat drives the jaw members43aand43baccording to the torque. That is, in order to reduce the size of the robot arm21aaround the surgical field so as to ensure a working area, it is effective to reduce the size of the motor212a. In order to reduce the size of the motor212a, it is effective to use the decelerator212bhaving a high reduction ratio. However, if the decelerator212bhaving the high reduction ratio is used in a case in which the motor212ais torque-controlled, the behavior of the distal end side of the surgical instrument40is less likely to be reflected as a change in the torque of the motor212a. This makes it difficult to detect the behavior of the distal end side of the surgical instrument40by detecting the change in the torque of the motor212a. In order to solve this problem, it is effective to control the rotation angle of the motor212athat drives the jaw members43aand43b.

In addition, by further rotating the motor212ain the closing direction of the jaw members43aand43bfrom a state in which the jaw members43aand43bare closed (i.e., a state in which the open angle is zero), a tightening force (gripping force) can be generated by the jaw members43aand43b. Hereinafter, a command angle by which the jaw members43aand43bare further closed from the state in which the open angle between the jaw members43aand43bis zero is referred to as a tightening angle. in the embodiment, the tightening angle is a negative value, but is not limited thereto. The tightening angle is an example of a value corresponding to the rotation angle of the motor212a, and is calculated by the following formula (1).

Here, θ, Rp, Rm and θm are as follows:θ: Tightening angleRp: Reduction ratio between the driven members44cand44dand the pulleys43dand43eof the jaw members43aand43bRm: Reduction ratio of the decelerator212bθm: Rotation angle of the motor212a

Here, the surgical instrument40is washed and sterilized after each surgery and is used multiple times. Therefore, as the surgical instrument40is used over time, lengths of the cables A1and A2that drive the jaw members43aand43bmay become elongated. When the lengths of the cables A1, A2become elongated, even if the motor212ais controlled to a predetermined rotation angle, the jaw members43aand43bcannot be sufficiently tightened, and the gripping force of the jaw members43aand43bdecreases.

Therefore, in the embodiment, as illustrated inFIG.11, the controller24performs calibration to compensate for the elongation of the cables A1and A2. Specifically, the storage45stores in advance a tightening angle θ1when the current value reaches a predetermined value I1. The controller24acquires a tightening angle62when the current value reaches the predetermined current value I1, and performs calibration to change the command angle for the tightening operation of the jaw members43aand43bbased on the acquired value θ2and the value θ1stored in the storage45. Specifically, the controller24corrects a maximum tightening angle θ0based on the tightening angle θ1and the tightening angle θ2. The maximum tightening angle is the tightening angle an absolute value of which is the largest. With this, it possible to perform the calibration to compensate for the elongation of the cables A1and A2in a configuration in which the drive of jaw members43aand43bof surgical instrument40is controlled by the rotation angle of the motor212a. Accordingly, the decrease in the gripping force of the jaw members43aand43bcaused by the elongation of the cables A1and A2can be suppressed in the configuration in which the drive of the jaw members43aand43bof surgical instrument40is controlled by the rotation angle of the motor212a. In the graph ofFIG.11, the right side is the negative side.

In the embodiment, the storage45stores the maximum tightening angle θ0in advance. The maximum tightening angle θ0is an example of a value corresponding to a maximum rotation angle of the motor212ain the closing direction of the jaw members43aand43b. The controller24corrects the value θ0based on the values θ2and θ1. With this, it possible to correct the maximum tightening angle θ0between the jaw members43aand43b, and therefore to increase the maximum rotation angle of the motor212awhich can rotate in the closing direction of the jaw members43aand43b. As a result, it is possible to reliably prevent the decrease in the gripping force of the jaw members43aand43bcaused by the elongation of the cables A1and A2.

Specifically, in the embodiment, the controller24corrects the value θ0by adding the difference Δθ between the value θ2and the value θ1to the value θ0. This allows the value θ0to be corrected simply by adding the difference Δθ between the values θ2and θ1to the value θ0, so that the calibration correction process can be performed by a simple process. The controller24performs the calibration that changes the value θ0of the command angle to a value θ0+Ae.

More specifically, in the embodiment, the controller24corrects the value θ0so that the jaw members43aand43bcan close up to the tightening angle of (θ0+Δθ) obtained by adding the difference Δθ between the tightening angle values θ2and θ1to the tightening angle value θ0. This enables the jaw members43aand43bto be closed up to a tightening angle obtained by adding the difference Δθ between the tightening angle values θ2and θ1to the tightening angle value θ0(i.e., the maximum tightening angle θ0+A8taking into account the elongation of the cables A1, A2). Therefore, it is possible to more reliably suppress a decrease in the gripping force of the jaw members43aand43bcaused by the elongation of the cables A1, A2over time.

Here, the principle of calibration for compensating for the elongation of the cables A1and A2in the embodiment will be described. The storage45stores in advance, as initial values, the tightening angle value θ1when the current value reaches the predetermined value I1, and a maximum tightening angle θ0. The values θ1and θ0are stored in advance in the storage45by an operator at the manufacturer before the surgical instrument40is shipped from the manufacturer. At the manufacturer, the values θ1and θ0are obtained taking into account the initial slack of the cables A1and A2. The value θ0is set to a value that enables the jaw members43aand43bto exert a predetermined gripping force. The absolute value of the value θ0is greater than the absolute value of the value θ1.

The controller24starts the calibration from a state in which the jaw members43aand43bare closed (a state in which the open angle between the jaw members43aand43bis zero). The controller24drives the motor212ato rotate to make the tightening angle the maximum tightening angle θ0. In addition, in the course of rotating the motor212ato close the jaw members43aand43bto a point where the value corresponding to the rotation angle of the motor212abecomes the value θ0(as the target value), the controller24acquires the value θ2. As the jaw members43aand43bare further closed from the state the jaw members43aand43bare closed, the current value of the motor212aincreases. The current value of the motor212ais detected (monitored) by the current detector214. in the case in which the cables A1, A2are stretched, even when the tightening angle of the jaw members43aand43breaches the value θ1, the current value of the motor212areaches a value smaller than the predetermined current value I1. The controller24obtains the tightening angle value θ2when the current value of the motor212areaches the predetermined current value I1based on the detection result of the current detector214. In addition, the controller24calculates the difference Δθ between the value θ2and the value θ1. The difference Δθ between the value θ2and the value θ1corresponds to the elongation of the cables A1and A2due to use. Further, the controller24corrects the value θ0so that the jaw members43aand43bare able to be closed up to a tightening angle θ0+A8obtained by adding the difference Δθ between the values θ2and θ1to the initial maximum tightening angle value θ0. This can make the current response of the motor212ain the state in which the cables A1and A2are elongated equivalent to the initial current response of the motor212a, thereby suppressing a decrease in the gripping force of the jaw members43aand43bcaused by the elongation of the cables A1and A2. Note that the absolute value of the value θ0is greater than the absolute value of the value θ2.

Further, in the embodiment, the controller24determines, based on the threshold value θS1, whether or not the value θ2is within a predetermined range with respect to the value θ1. when it is determined that the value θ2is within the predetermined range with respect to the value θ1, the controller24does not correct the value θ0. To the contrary, when it is determined that the value θ2is out of the predetermined range with respect to the value θ1, the controller24corrects the value θ0. This makes it possible to avoid unnecessarily correcting the value θ0when it is determined that the value θ2is within the predetermined range relative to the value θ1(that is, when the elongation of the cables A1and A2is small and thus the correction is not necessary). Further, when it is determined that the value θ2is out of the predetermined range relative to the value θ1(that is, when the extension of the cables A1and A2is large and thus the correction is necessary), the value θ0is appropriately corrected.

Specifically, the controller24determines whether the value θ2is within the range θ1±θS1. The threshold value θS1is not particularly limited, and may be a value obtained by converting a value (such as Y Newtons) that determines the upper and lower limits of the range (such as X±Y Newtons) of the set gripping force of the jaw members43aand43binto a tightening angle using a conversion coefficient. Note that when the range of the set gripping force differs depending on the type of the jaw members43aand43b(i.e., the type of the end effector43), the threshold value θS1may be different for each type of the end effector43. The threshold value θS1is a positive value in the embodiment, and is stored in the storage25provided in the robot body27.

Further, in the embodiment, the controller24determines whether the difference Δθ between the value θ2and the value θ1is within the normal range based on the threshold value θS2. When it is determined that the difference Δθ between the value θ2and the value θ1is within the normal range, the controller24corrects the value θ0. To the contrary, when it is determined that the difference Δθ between the value θ2and the value θ1is outside the normal range, the controller24reacquires the value θ2. As a result, when it is determined that the difference Δθ between the value θ2and the value θ1is within the normal range, the value θ0is corrected so that the calibration can be performed appropriately. Further, when it is determined that the difference Δθ between the value θ2and the value θ1is outside the normal range, the value θ2is acquired again, thereby making it possible to avoid acquiring an excessively large value θ2(and difference Δθ). As a result, it is possible to prevent the value θ0from being corrected to an excessively large value based on an excessively large θ2(and the difference Δθ). With this, it possible to prevent the cables A1and A2from being damaged due to an excessive load being applied to the cables A1and A2caused by the value θ0being corrected to an excessively large value.

Specifically, the controller24determines whether the difference Δθ between the value θ2and the value θ1is within the range of θ32<Δθ<0. The threshold value θS2is not particularly limited, and may be a common value regardless of the type of the end effector43. In the embodiment, the threshold value θS2is a negative value and is obtained in advance by experiment or the like and stored in the storage25provided in the robot body27.

In the embodiment, the storage45that stores the value θ1is provided in the surgical instrument40. This allows a different value θ1for each surgical instrument40to be stored in advance in the storage45provided in the surgical instrument40, so that an appropriate value θ1for each surgical instrument40can be easily used when using the surgical instrument40. In the embodiment, the storage45also stores the value θ0. As in the value θ1, this allows a different value θ0for each surgical instrument40to be stored in advance in the storage45provided in the surgical instrument40, so that an appropriate value θ0for each surgical instrument40can be easily used when using the surgical instrument40.

Further, in the embodiment, the temporary storage26that stores a correction value (Δθ) based on the value θ1and the value θ2is provided in the robot body27. As a result, even when the surgical instrument40is removed from the robot arm21aduring surgery and then reattached to the robot arm21a, there is no need to re-acquire the correction value (Δθ) since the correction value (Δθ) is stored in the temporary storage26provided in the robot body27. As a result, it is possible to eliminate the need to re-acquire the correction value (Δθ) each time the surgical instrument40is attached to the robot arm21a. The correction value (Δθ) stored in the temporary storage26is reset (deleted) for each surgery (for example, each time the power to the robot body27is turned off or restarted). Therefore, it is possible to obtain an appropriate value Δθ for each surgery.

Further, in the embodiment, the controller24starts the calibration at least one of the following times: when the surgical instrument40is attached to the robot arm21a; and when a user interface (such as the operation handle11or the touch panel14) that accepts an operation to execute the calibration is operated. As a result, in the case in which the calibration is started at the time when the surgical instrument40is attached to the robot arm21a, the calibration is executed simply by attaching the surgical instrument40to the robot arm21a, thereby saving the user effort. In the case in which the calibration is started at the timing when the user interface that accepts the operation to execute the calibration is operated, the calibration is executed at a timing desired by the user. The operation handle11or the touch panel14is an example of a user interface.

Further, in the case where the calibration is started at the timing when the surgical instrument40is attached to the robot arm21a, the controller24determines whether or not the surgical instrument40is attached to the robot arm21afor the first time during the surgery. When it is determined that the attachment of the surgical instrument40to the robot arm21ais for the first time during the surgery, the controller24starts the calibration, and when it is determined that the attachment of the surgical instrument40to the robot arm21ais not for the first time during the surgery, the controller24does not start the calibration. This allows the calibration to be started appropriately when it is determined that the surgical instrument40is attached to the robot arm21afor the first time during the surgery (i.e., when the calibration has not been performed). Further, when it is determined that the attachment of the surgical instrument40to the robot arm21ais not the first time during the surgery (i.e., when the calibration has already been performed), the calibration is not started, thereby preventing unnecessary calibration from being performed.

When the surgical instrument40is attached to the robot arm21a, the controller24obtains the serial number of the surgical instrument40from the storage45, and determines based on the obtained serial number of the surgical instrument40whether or not this is the first time that the surgical instrument40has been attached to the robot arm21aduring the surgery. Specifically, when the obtained serial number of the surgical instrument40is not stored in the storage25or the temporary storage26, the controller24determines that this is the first time that the surgical instrument40has been attached to the robot arm21aduring the surgery. In addition, the controller24stores the obtained serial number of the surgical instrument40in the storage25or the temporary storage26. When the obtained serial number of the surgical instrument40is stored in the storage25or the temporary storage26, the controller24determines that this is not the first time that the surgical instrument40has been attached to the robot arm21aduring the surgery (that is, this is the second or subsequent time). When the controller24determines that it is not the first time that the surgical instrument40is attached to the robot arm21aduring the surgery, the controller24does not start calibration and corrects θ0using the correction value (Δθ) at the time of the initial attachment.

Further, in the embodiment, the controller24corrects the value θ0based on the value θ2, the value θ1, and the value θacorresponding to the rotation angle of the motor212athat is determined in advance according to the number of times the surgical instrument40is used. This allows the value θ0to be corrected not only based on the values θ2and θ1but also on the tightening angle θathat is determined in advance according to the number of times the surgical instrument40is used, thereby more reliably suppressing the decrease in the gripping force of the jaw members43aand43bcaused by the elongation of the cables A1and A2. The value θais a fixed value determined according to the number of times the surgical instrument40is used, and is obtained in advance by experiment or the like. The value θais an example of a fourth value.

(Control Process when Attaching Surgical Instrument)

Next, with reference toFIG.12, a control process performed when the surgical instrument40is attached to the robot arm21awill be described based on a flowchart. Note that here, the case will be described in which the calibration is started at the time when the surgical instrument40is attached to the robot arm21a.

As illustrated inFIG.12, first, in step S101, the surgical instrument40is attached to the robot arm21avia the adapter60. Then, in step S102, a matting operation mode is started. In the mating operation mode, the engagement projections213of the robot arm21aare mated with the engagement recesses of the drive transmission members61of the adapter60, and the engagement recesses611of the drive transmission members61of the adapter60are mated with the projections441and442of the driven members44ato44d.

Then, in step S103, it is determined whether or not the surgical instrument40is attached to the robot arm21afor the first time during surgery. When it is determined that the attachment of the surgical instrument40to the robot arm21ais the first time during the surgery, the process proceeds to step S104. Then, in step S104, a calibration mode in which calibration is performed is started. When the process of step S104is completed, the process proceeds to step S106. The calibration mode process will be described in detail later.

To the contrary, when it is determined in step S103that the attachment of the surgical instrument40to the robot arm21ais not the first time during the surgery, the process proceeds to step S105. Then, in step S105, a correction of the tightening angle is executed. That is, in step S105, in the calibration mode at the first time attachment, which will be described later, the tightening angle is corrected in accordance with the formula: θ0c=θ0+θa+Δθ (where θ0cis the maximum tightening angle after correction). Then, the process proceeds to step S106.

In step S106, a gripping force check mode is started. In the gripping force check mode, it is determined whether or not the predetermined gripping force can be output as the gripping force by the jaw members43aand43b. Then, when it is determined that the predetermined gripping force can be output as the gripping force by the jaw members43aand43b, the control process is terminated.

(Control Process of Calibration Mode)

Next, a control process of the calibration mode will be described with reference to a flowchart illustrated inFIG.13

As illustrated inFIG.13, in step S201, a tightening operation of the jaw members43aand43bis performed. In the tightening operation, the jaw members43aand43bare driven to close to the tightening angle of θ0+θa+Δθ (where Δθ=0).

Then, in step S202, the rotation angle of the motor212awhen the current value reaches the predetermined value I1is obtained. At this time, the current value of the motor212ais obtained taking into consideration the friction and inertia of the motor212a. Further, the rotation angle of the motor212athat is detected by the position detector212cwhen the current value reaches the predetermined value I1is converted into the tightening angle of the jaw members43aand43bby the above described formula (1), thereby obtaining the tightening angle value θ2.

Then, in step S203for the first time, it is determined, based on the threshold value θS1, whether or not the value θ2is within the predetermined range with respect to the value θ1. Specifically, it is determined whether the value θ2is within the range of θ1−θS1≤θ2−Δθ≤θ1+θS1(where Δθ=0). When it is determined that the value θ2is within the predetermined range with respect to the value θ1, it means that it is determined that the elongation of the cables A1and A2is small and no correction is necessary, so that no correction is performed and the control process is terminated. In this case, θ0stored in advance in the storage45is used as the maximum tightening angle.

Further, when it is determined in step S203for the first time that the value θ2is not within the predetermined range with respect to the value θ1, it means that it is determined that the elongation of the cables A1and A2is large and the correction is necessary, and the process proceeds to step S204.

Then, in step S204, the difference Δθ between the value θ2and the value θ1is obtained as the correction value.

Then, in step S205, it is determined based on the threshold value θS2whether or not the difference Δθ is within the normal range. Specifically, it is determined whether the difference Δθ is within the range of θS2<Δθ<0. When it is determined that the difference Δθ is within the normal range, the process proceeds to step S207.

Then, in step S207, the tightening angle correction is performed to correct the value θ0based on the values θ1and θ2. Specifically, the value θ0is corrected by adding the difference Δθ between the value θ1and the value θ2to the value θ0. More specifically, the maximum tightening angle is corrected as expressed by the formula: θ0c=θ0+θa+Δθ (where θ0cis the corrected maximum tightening angle).

Then, in step S208, a re-tightening operation is performed that closes the jaw members43aand43bagain. In the re-tightening operation, the jaw members43aand43bare driven to close up to the corrected maximum tightening angle θ0c. Then, the process proceeds to step S202. Then, in step S202, the tightening angle θ2at which the current value becomes the predetermined value I1is obtained again.

Then, in step S203for the second time after step S208, it is determined whether θ2−Δθ (where Δθ=θ2−θ1) is within the range of θ1−θS1≤θ2−Δθ≤θ1+θS1. Here, (θ2−Δθ) is (θ2−θ2+θ1), which is θ1. Therefore, in step S203, it is determined that θ2−Δθ is within the range of θ1−θS1≤θ2−Δθ≤θ1+θS1, and the control process is terminated with the correction being performed.

When it is determined in step S205that the difference Δθ is not within the normal range, the process proceeds to step S209.

Then, in step S209, it is determined whether the difference Δθ is determined to be outside the normal range for two consecutive times. When it is not determined that the difference Δθ is determined to be outside the normal range for two consecutive times, the process proceeds to step S201. Then, the processes of step S201to step S205are repeated. To the contrary, when it is determined that the difference Δθ is determined to be outside the normal range for two consecutive times, the process proceeds to step S210. Then, in step S210, an error message is displayed and the control process is terminated.

Modifications

It should be understood that one or more embodiments described above are illustrated by way of example in every respect and do not limit the disclosure. The scope of the invention is indicated by claims, not by the explanation of the one or more embodiments described above, and includes equivalents to the claims and all alterations (modifications) within the same.

For example, in the embodiment described above, the case has been described in which the values corresponding to the rotation angles of the motor (θ1, θ2, θ0, etc.) are values that represent the tightening angles between the jaw members, but the invention is not limited to this. In the invention, the value corresponding to the rotation angle of the motor may represent a value other than the tightening angle between the jaw members. For example, the value corresponding to the rotation angle of the motor may be the rotation angle of the motor.

Further, in the embodiment described above, the case has been described in which the third value (θ0) is a value that corresponds to the maximum rotation angle of the motor in the closing direction of the jaw members, but the invention is not limited to this. In the invention, the third value may be a value having an absolute value greater than the value θ1and corresponding to a rotation angle other than the maximum rotation angle of the motor in the closing direction of the jaw members.

In the embodiment described above, the case has been described in which it is determined whether or not the difference (Δθ) between the second value (θ2) and the first value (θ1) is within the normal range, but the invention is not limited to this. In the invention, it is not necessary to determine whether the difference between the second value and the first value is within the normal range.

In the embodiment described above, the case has been described in which it is determined whether the second value (θ2) is within the predetermined range with respective to the first value (θ1), but the invention is not limited to this. In the invention, it is not necessary to determine whether the second value is within the predetermined range with respective to the first value.

In the embodiment described above, the case has been described in which the first storage (45) that stores the first value (θ1) and the third value (θ0) is provided in the surgical instrument, and the second storage (26) that stores the correction value (Δθ) based on the first value and the second value (θ2) is provided in the robot body, but the invention is not limited to this. In the invention, the first storage may be provided in the robot body, and the second storage may be provided in the surgical instrument. Further, the second storage does not have to be a temporary storage.

In the embodiment described above, the case has been described in which it is determined whether or not the attachment of the surgical instrument to the robot arm is the first time during the surgery, but the invention is not limited to this. In the invention, the calibration may be started every time the surgical instrument is attached to the robot arm.

Further, in the embodiment described above, the case has been described in which the third value (θ0) is corrected based on the second value (θ2), the first value (θ1), and the fourth value (θa), but the invention is not limited to this. In the invention, the fourth value (θa) may not be used to correct the third value (θ0).

Further, in the embodiment described above, the case has been described in which the decrease in the gripping force of the jaw members caused by the elongation of the cables is suppressed in the configuration in which the drive of the jaw members of the surgical instrument is controlled according to the rotation angle of the motor. However, the invention is not limited to this. In the invention, a rod may be used as an elongate element, and a gear, a pulley, or a bearing may be used as a driven member, and the decrease in the gripping force of the jaw members caused by wear, seizure, galling, chipping, rust, etc., of the gear, pulley, bearing, and rod of the surgical instrument may be corrected.

Further, in the invention, the decrease in the gripping force due to wear of the jaw members may be corrected.

The functions of each of the elements disclosed herein may be carried out by a circuitry or a processing circuitry including a general purpose processor, a dedicated processor, an integrated circuit, an ASIC (application specific integrated circuit), a conventional circuit, or a combination of two or more of them, that is configured or programmed to perform the functions. A processor is considered as a processing circuitry or a circuitry because it contains transistors and other circuit elements. In the disclosure, a circuit, a unit, or a means may be either a hardware that is configured to perform the recited function(s) or a hardware that is programmed to perform the recited function(s). The hardware may be the hardware disclosed herein, or may be other known hardware that is programmed or configured to perform the recited function(s). If the hardware is a processor which is considered as a type of a circuit, a circuit, a means, or a unit is a combination of hardware and software, and the software is used to configure the hardware and/or the processor.

Further, in the embodiment described above, the case has been described in which the third value (θ0) as the command angle is corrected based on the second value (θ2) and the first value (θ1). However, a modified example illustrated inFIG.14may be used. In the modified example illustrated inFIG.14, the controller24performs the calibration based on the value θ2and a difference Δθ2between the values θ1and θ0, to change the command angle for closing the jaw members43aand43bwithout correcting the value θ0. In a modified example illustrated inFIG.14, the value θ1and the difference Δθ2between the value θ1and the value θ0are stored in advance in the storage45. During the calibration, the controller24acquires the value θ2in the course of rotating the motor212ato close the jaw members43aand43bso that the value corresponding to the rotation angle of the motor212abecomes the value θ1+Δθ2(the value θ1+Δθ2as the target value). The controller24adds the difference Δθ2to the value θ2. As a result, the controller24performs the calibration to change the command angle value θ1+Δθ2to a value θ2+Δθ2. This allows the jaw members43aand43bto close up to the tightening angle equal to the sum of the value θ2and the difference Δθ2.

FIG.15illustrates another modified example using the difference Δθ2. In this example, the value θ0and the difference Δθ2between the values θ1and θ0are stored in advance in the storage45. In the calibration, the controller24acquires the value θ2in the course of rotating the motor212ato close the jaw members43aand43bto the point where the value corresponding to the rotation angle of the motor212abecomes the value θ0(the value θ0is the target value). The controller24adds the difference Δθ2to the value θ2. As a result, the controller24performs the calibration that changes the command angle value θ0to the value θ2+Δθ2.