Patent Publication Number: US-2021169593-A1

Title: Surgical robotic systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage Application of PCT Application No. PCT/US2019/038871 under 35 USC § 371(a), filed Jun. 25, 2019, which claims the benefit of and priority to U.S. Provisional Application No. 62/693,488, filed Jul. 3, 2018. Each of these disclosures are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Surgical robotic systems have been used in minimally invasive medical procedures. Some surgical robotic systems included a console supporting a surgical robotic arm and a surgical instrument having at least one end effector (e.g., forceps or a grasping tool) mounted to the robotic arm. The robotic arm provided mechanical power to the surgical instrument for its operation and movement. 
     Manually-operated surgical instruments often included a handle assembly for actuating the functions of the surgical instrument. However, when using a robotic surgical system, no handle assembly was typically present to actuate the functions of the end effector. Accordingly, to use each unique surgical instrument with a robotic surgical system, an instrument drive unit was used to interface with the selected surgical instrument to drive operations of the surgical instrument. 
     The instrument drive unit was typically coupled to the robotic arm via a slide. The slide allowed the instrument drive unit and the attached surgical instrument to move along an axis of the slide, providing a means for adjusting the axial position of the end effector of the surgical instrument. 
     SUMMARY 
     In accordance with an aspect of the present disclosure, an instrument drive unit for use in a robotic surgical system is provided and includes a carriage configured to be coupled to a robotic arm, a hub rotationally coupled to the carriage and configured to be non-rotatably coupled to an electromechanical surgical instrument, a plurality of motors, a plurality of motor gears, a plurality of drive shafts, and a plurality of drive gears. Each motor gear is operably coupled to a corresponding motor, and each drive gear is fixed to a corresponding drive shafts. The drive shafts are rotationally supported in the hub and configured for interfacing with a corresponding driven member of the electromechanical surgical instrument. Each motor gear is configured to rotate a corresponding drive gear in response to an activation of a respective motor to actuate a function of the electromechanical surgical instrument. 
     In aspects, the instrument drive unit may further include a drive motor operably coupled to the hub and configured to rotate the hub about a central longitudinal axis defined by the hub. 
     In other aspects, the drive motor may have a rotatable coupling fixed to the hub to transfer torque from the drive motor to the hub. 
     In further aspects, the motors may be circumferentially spaced from one another and disposed about the hub and the drive motor. 
     The instrument drive unit may further include a sleeve rotatably coupled to a distal end portion of the carriage and non-rotatably coupled to the hub. The sleeve may be configured to non-rotatably receive the electromechanical surgical instrument, such that a rotation of the hub results in a rotation of the electromechanical surgical instrument. 
     In aspects, the instrument drive unit may further include a plurality of ring gears operably coupling a corresponding motor gear with a corresponding drive gear. 
     In other aspects, the ring gears may be vertically stacked within the hub. 
     In further aspects, a first ring gear and a first drive gear may be operably coupled to one another and aligned along a first horizontal plane, and a second ring gear and a second drive gear may be operably coupled to one another and aligned along a second horizontal plane, vertically displaced from the first horizontal plane. 
     The ring gears may be independently rotatable relative to one another. 
     In aspects, a first ring gear may have gear teeth on an inner periphery thereof and an outer periphery thereof. The gear teeth on the inner periphery may interface with a corresponding drive gear, and the gear teeth on the outer periphery may interface with a corresponding motor gear. 
     In other aspects, the drive shafts may be circumferentially spaced from one another about the hub. 
     In further aspects, the drive gears may be vertically offset from one another. 
     The motor gears may be vertically offset from one another. 
     In aspects, the instrument drive unit may further include a plurality of motor shafts extending distally from a corresponding motor. Each motor gear may be fixed to a corresponding motor shaft. 
     In other aspects, each drive shaft may have a distal end portion configured for interfacing with a corresponding driven member of the electromechanical surgical instrument. 
     In another aspect of the present disclosure, an instrument drive unit for use in a robotic surgical system is provided and includes a carriage configured to be coupled to a robotic arm, a plurality of motors supported in the carriage, a plurality of motor shafts, and a plurality of drive shafts circumferentially spaced from one another and configured for interfacing with a corresponding driven member of an electromechanical surgical instrument. Each motor shaft extends distally from a corresponding motor, and each motor shaft has a motor gear fixed thereabout. Each drive shaft has a drive gear fixed thereabout, and each drive gear is disposed at a discrete vertical location relative to one another. Each motor gear is configured to rotate a corresponding drive gear in response to an activation of a respective motor to actuate a function of the electromechanical surgical instrument. 
     In aspects, the instrument drive unit may further include a plurality of vertically stacked ring gears operably coupling a corresponding motor gear with a corresponding drive gear, such that each motor gear is configured to rotate a corresponding drive gear in response to an activation of a respective motor to actuate a function of the electromechanical surgical instrument. 
     In other aspects, the instrument drive unit may further include a hub rotationally coupled to the carriage, and a drive motor operably coupled to the hub. The hub may be configured to be non-rotatably coupled to the electromechanical surgical instrument. The drive shafts may be rotationally supported in the hub. The drive motor may be configured to rotate the hub about a central longitudinal axis defined by the hub. 
     In further aspects, the instrument drive unit may further include a sleeve rotatably coupled to a distal end portion of the carriage and non-rotatably coupled to the hub. The sleeve may be configured to non-rotatably receive the electromechanical surgical instrument, such that a rotation of the hub results in a rotation of the electromechanical surgical instrument. 
     Further details and aspects of exemplary embodiments of the present disclosure are described in more detail below with reference to the appended figures. 
     As used herein, the terms parallel and perpendicular are understood to include relative configurations that are substantially parallel and substantially perpendicular up to about + or −10 degrees from true parallel and true perpendicular. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure are described herein with reference to the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of a surgical robotic system including an instrument drive unit coupled to a slide in accordance with the present disclosure; 
         FIG. 2  is a perspective view of the instrument drive unit of the surgical robotic system of  FIG. 1 ; 
         FIG. 3  is an enlarged, rear perspective view of the instrument drive unit of  FIG. 2 ; 
         FIG. 4  is a perspective view of a hub of the instrument drive unit of  FIG. 2 ; 
         FIG. 5  is a longitudinal cross-sectional view of the instrument drive unit of  FIG. 2 ; 
         FIG. 6  is an enlarged longitudinal cross-sectional view of the instrument drive unit of  FIG. 2 ; and 
         FIG. 7  is a side cross-sectional view of the instrument drive unit of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the presently disclosed surgical robotic system and instrument drive units thereof are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein, the term “distal” refers to that portion of the surgical robotic system or component thereof that is closest to the patient, while the term “proximal” refers to that portion of the surgical robotic system or component thereof further from the patient. 
     As will be described in detail below, provided is an instrument drive unit of a surgical robotic system configured to allow for a bottom-loading of a surgical instrument. The instrument drive unit has a plurality of drive shafts each configured to be coupled to a corresponding driven member of the surgical instrument for carrying out a discrete function of the surgical instrument. The drive shafts of the instrument drive unit are operably coupled to a discrete motor of the instrument drive unit via a discrete transmission assembly. The configuration of the transmission assemblies allows for a reduction in the overall height of the instrument drive unit (e.g., the instrument drive unit is more compact). For example, gears of the transmission assemblies are vertically and horizontally offset from the gears of the other transmission assemblies. The instrument drive unit may also include a rotatable hub that rotationally supports the drive shafts. The hub is configured to be rotated via a separate drive motor to enable rotation of the attached surgical instrument about its longitudinal axis. Other features and benefits of the disclosed instrument drive units are further detailed below. 
     Referring initially to  FIG. 1 , a surgical system, such as, for example, a surgical robotic system  1 , generally includes a plurality of surgical robotic arms  2 ,  3 ; an elongated slide  13  coupled to an end of each of the robotic arms  2 ,  3 ; an instrument drive unit  20  and an electromechanical instrument  10  removably attached to the slide  13  and configured to move along the slide  13 ; a control device  4 ; and an operating console  5  coupled with control device  4 . The operating console  5  includes a display device  6 , which is set up in particular to display three-dimensional images; and manual input devices  7 ,  8 , by means of which a person (not shown), for example a surgeon, is able to telemanipulate robotic arms  2 ,  3  in a first operating mode, as known in principle to a person skilled in the art. 
     Each of the robotic arms  2 ,  3  may be composed of a plurality of members, which are connected through joints. Robotic arms  2 ,  3  may be driven by electric drives (not shown) that are connected to control device  4 . Control device  4  (e.g., a computer) is set up to activate the drives, in particular by means of a computer program, in such a way that robotic arms  2 ,  3 , the attached instrument drive units  20 , and thus electromechanical instrument  10  execute a desired movement according to a movement defined by means of manual input devices  7 ,  8 . Control device  4  may also be set up in such a way that it regulates the movement of the instrument drive unit  20  along the slide  13 , movement of the robotic arms  2 ,  3 , and/or movement of the drives. 
     Surgical robotic system  1  is configured for use on a patient “P” lying on a surgical table “ST” to be treated in a minimally invasive manner by means of a surgical instrument, e.g., electromechanical instrument  10 . Surgical robotic system  1  may also include more than two robotic arms  2 ,  3 , the additional robotic arms likewise being connected to control device  4  and being telemanipulatable by means of operating console  5 . A surgical instrument, for example, an electromechanical surgical instrument  10  (including an electromechanical end effector), may also be attached to the additional robotic arm. 
     Control device  4  may control a plurality of motors, e.g., motors (Motor  1  . . . n), with each motor configured to drive movement of robotic arms  2 ,  3  in a plurality of directions. Further, control device  4  may control a plurality of drive motors  22  ( FIGS. 2 and 3 ) of the instrument drive unit  20  to drive various operations of the surgical instrument  10 . The instrument drive unit  20  transfers power and actuation forces from its motors to driven members (not shown) of the electromechanical instrument  10  to ultimately drive movement of components of the end effector of the electromechanical instrument  10 , for example, a movement of a knife blade (not shown) and/or a closing and opening of jaw members of the end effector. 
     For a detailed description of the construction and operation of a robotic surgical system, reference may be made to U.S. Pat. No. 8,828,023, entitled “Medical Workstation,” the entire contents of which are incorporated by reference herein. 
     With reference to  FIGS. 2-7 , the instrument drive unit  20  will now be described in detail. The instrument drive unit  20  includes a carriage  26  and a coupling or sleeve  28  rotatably coupled to a distal end portion  26   b  of the carriage  26  for connecting a surgical instrument  10  ( FIG. 1 ) to the instrument drive unit  20 . The carriage  26  of the instrument drive unit  20  is configured to be slidably coupled to a linear track (not shown) defined longitudinally along the slide  13  ( FIG. 1 ). A proximal end portion  26   a  of the carriage  26  houses a plurality of drive motors  22   a ,  22   b ,  22   c ,  22   d ,  22   d ,  22   e  (collectively referred herein as “ 22 ”) for carrying out various functions of an attached surgical instrument. The distal end portion  26   b  of the carriage  26  defines a longitudinally-extending channel  30  therethrough dimensioned for receipt of a hub  46  of the instrument drive unit  20 . The distal end portion  26   b  has an annular ledge  32  ( FIGS. 5 and 6 ) that extends radially inward from an inner peripheral surface of the carriage  26 . The annular ledge  32  is configured to support internal components of the instrument drive unit  20 . 
     In embodiments, the distal end portion  26   b  of the carriage  26  may have a slip ring  33  received therein for transferring electrical signals or power between fixed structures (e.g., the drive motors  22 ) and rotating structures (e.g., the electromechanical surgical instrument  10 ). The electrical signals transferred by the slip ring  33  may be feedback signals from the electromechanical surgical instrument  10  relating to the status and location of the surgical instrument  10  and/or the status and location of adjacent tissue structures. For example, the feedback may include the temperature of the surgical instrument  10 , forces experienced by the surgical instrument  10 , and/or the position of certain structures of the surgical instrument  10  relative to one another or relative to the adjacent tissue structures. 
     With reference to  FIG. 2 , the coupling or sleeve  28  of the instrument drive unit  20  is rotatably coupled to the distal end portion  26   b  of the carriage  26 . The sleeve  28  has a proximal end portion  28   a  received within the channel  30  of the carriage  26  and fixed to the hub  46 , such that the sleeve  28  rotates with the hub  46 . The sleeve  28  has a plurality of annular members  29  ( FIG. 5 ) fixed therein having a respective drive shaft  66  extending therethrough. Rotation of the hub  46  causes the drive shafts  66  to rotate therewith, which, in turn, drives a rotation of the sleeve  28 , as will be described. The sleeve  28  has a distal end portion  28   b  configured to non-rotationally fix the main body portion of the surgical instrument  10  therein. The sleeve  28  may have a pair of latch members  31   a ,  31   b  configured to releasably retain the main body portion of the electromechanical surgical instrument  10 . Accordingly, when the surgical instrument  10  is coupled to the instrument drive unit  20 , a rotation of the sleeve  28  results in a rotation of the attached surgical instrument  28 . 
     With reference to  FIGS. 2 and 3 , the motors  22  of the instrument drive unit  20  are concealed within the proximal end portion  26   a  of the carriage  26 . The drive motors  22   a ,  22   b ,  22   c ,  22   d  are circumferentially spaced from one another and are independently actuatable via the control device  4  ( FIG. 1 ). One of the drive motors, such as, for example, drive motor  22   e , is configured to effectuate a rotation of the surgical instrument  10  when the surgical instrument  10  is coupled to the instrument drive unit  20 , and the remaining drive motors  22   a ,  22   b ,  22   c ,  22   d  are configured to actuate functions of the surgical instrument  10 . The drive motors  22   a ,  22   b ,  22   c ,  22   d  are disposed about the fifth drive motor  22   e . The drive motors  22  may be cylindrical or pancake motors. Other types of motors are also contemplated. 
     While the instrument drive unit  20  is illustrated as having five drive motors, it is contemplated that the instrument drive unit  20  may have more or less than five drive motors. 
     The first four drive motors  22   a ,  22   b ,  22   c ,  22   d  each have a rotatable motor shaft  40   a ,  40   b ,  40   c ,  40   d  (collectively referred to herein as “ 40 ”) extending distally therefrom and through the distal end portion  26   b  of the carriage  26 . The motor shafts  40  are circumferentially spaced from one another about the channel  30  of the distal end portion  26   b  of the carriage  26  and the hub  46 . The motor shafts  40  each have a motor gear  42   a ,  42   b ,  42   c ,  42   d  (collectively referred to herein as “ 42 ”), such as, for example, a spur gear, rotationally fixed thereabout. Each of the motor gears  42  are positioned at a discrete vertical location on their respective motor shaft  40 , such that the motor gears  42  are vertically offset a selected distance from one another. Since the motor gears  42 , in addition to be vertically offset from one another, are also circumferentially spaced from one another, the motor gears  42  are offset from one another in all three dimensions. 
     With reference to  FIGS. 2, 3, 5, and 6 , the instrument drive unit  20  further includes an outer housing assembly  44  received in the channel  30  of the distal end portion  26   b  of the carriage  26 . The outer housing assembly  44  may be non-rotatably fixed to the distal end portion  26   b  of the carriage  26  and supported on the ledge  32 . As best shown in  FIGS. 5 and 6 , the outer housing assembly  44  includes a plurality of bearings  48   a ,  48   b ,  48   c ,  48   d  (collectively referred to herein as “ 48 ”), or the like, and a plurality of ring supports  50   a ,  50   b ,  50   c ,  50   d  (collectively referred to herein as “ 50 ”) interposed between and fixed with adjacent bearings  48 . The ring supports  50  and the bearings  48  are vertically stacked within the channel  30  of the carriage  26  in an alternating arrangement. The ring supports  50  interconnect adjacent bearings  48 , such that the entire outer housing assembly  44  is configured as a unitary structure. Each of the ring supports  50  has an opening  52  having a corresponding motor gear  42  extending therethrough to allow the motor gears  42  to interface with a corresponding ring gear  62 , as will be described. 
     With reference to  FIGS. 4-6 , the hub  46  of the instrument drive unit  20  is supported in the outer housing assembly  44  and is configured to rotate relative to and within the outer housing assembly  44 . The hub  46  has a pair of proximal and distal radial extensions  58   a ,  58   b  disposed adjacent respective proximal and distal ends thereof. The radial extensions  58   a ,  58   b  axially support the hub  46  in the channel  30  of the distal end portion  26   b  of the carriage  26 . The hub  46  has a plurality of support struts  47  extending vertically between the radial extensions  58   a ,  58   b , thereby connecting the radial extensions  58   a ,  58   b  and providing integrity to the overall hub  46 . 
     The hub  46  further includes a protuberance  49  extending proximally from a central location of the proximal radial extension  58   a . The protuberance  49  of the hub  46  is non-rotatably fixed to a coupling, such as, for example, a sleeve coupling  23 , of the fifth drive motor  22   e  to receive torque from the fifth drive motor  22   e . As such, a rotation of the sleeve coupling  23  of the fifth motor  22   e  drives a rotation of the hub  46  relative to the carriage  26  about a central longitudinal axis “X” defined by the hub  46 . 
     With reference to  FIGS. 4-7 , the instrument drive unit  20  further includes a plurality of transmission assemblies  60   a ,  60   b ,  60   c ,  60   d  (collectively referred to herein as “ 60 ”) that function independently from one another to transfer torque from a corresponding drive motor  22  to a corresponding driven member of the attached surgical instrument  10 . Each transmission assembly  60   a ,  60   b ,  60   c ,  60   d  may include a respective motor gear  42 , a ring gear  62   a ,  62   b ,  62   c ,  62   d  (collectively referred to herein as “ 62 ”), a drive gear  64   a ,  64   b ,  64   c ,  64   d  (collectively referred to herein as “ 64 ”), and a drive shaft  66   a ,  66   b ,  66   c ,  66   d  (collectively referred to herein as “ 66 ”) operably coupled to one another. 
     Components of the transmission assemblies  60  are vertically offset from one another along the central longitudinal axis “X” defined by the hub  46 , and certain components of each transmission assembly  60  are aligned along a horizontal plane. For example, as best shown in  FIGS. 5 and 6 , the first motor gear  42   a , the first ring gear  62   a , and the first drive gear  64   a  of the first transmission assembly  60   a  (e.g., the proximal-most transmission assembly) are operably coupled to one another and substantially aligned along a first horizontal plane “P 1 ,” and the second motor gear  42   b , the second ring gear  62   b , and the second drive gear  64   b  of the second transmission assembly  60   b  are operably coupled to one another and substantially aligned along a second horizontal plane “P 2 ,” which is vertically displaced (e.g., disposed distally) from the first horizontal plane “P 1 ” along the longitudinal axis “X.” The remaining transmission assemblies  60   c  and  60   d  are also disposed in a discrete horizontal plane. While only four transmission assemblies are shown, it is contemplated that the instrument drive unit  20  may have more or less than four transmission assemblies. 
     The ring gears  62  of the transmission assemblies  60  are vertically stacked within the hub  46 . In particular, the ring gears  62  are coaxial along the central longitudinal axis “X” defined by the hub  46 . The ring gears  62  are rotationally supported by a respective bearing  48  of the outer housing assembly  44 . The ring gears  62  are disposed about the support struts  47  of the housing  46  and are interposed between the proximal and distal radial extensions  58   a ,  58   b.    
     Each of the ring gears  62  has gear teeth  68  extending from both an inner periphery  70  thereof and an outer periphery  72  thereof. The gear teeth  68  on the outer periphery  72  of each of the ring gears  62  interfaces with a corresponding motor gear  42 , and the gear teeth  68  on the inner periphery  70  of each of the ring gears  62  interfaces with a corresponding drive gear  64 , as will be described. In embodiments, each of the rings gears  62  may be constructed from inner and outer ring gears integrally formed with one another. 
     The drive shafts  66   a ,  66   b ,  66   c ,  66   d  of the transmission assemblies  60   a ,  60   b ,  60   c ,  60   d  extend longitudinally through the hub  46  and distally therefrom. In particular, each of the drive shafts  66  has proximal end portions  67   a  rotatably coupled to the proximal radial extension  58   a  of the hub  46 , intermediate portions  67   c  extending between the proximal and distal radial extensions  58   a ,  58   b  of the hub  46 , and distal end portions  67   b  extending distally from the distal radial extension  58   b  of the hub  46 . The drive shafts  66  are circumferentially spaced from one another about the central longitudinal axis “X” of the hub  46 . The drive shafts  66  are free to rotate about their respective longitudinal axes in relation to the hub  46 . 
     The distal end portion  67   b  of each of the drive shafts  66  is configured to operably couple to a driven member (not explicitly shown) of the surgical instrument  10 . For example, the distal end portion  67   b  of each of the drive shafts  66  may have a coupler (e.g., a gear) for coupling with a corresponding coupler of a driven member of the surgical instrument  10 . Accordingly, upon bottom-loading of the electromechanical instrument  10  into the instrument drive unit  20 , the distal end portions  67   b  of the drive shafts  66  of the instrument drive unit  20  operably couple to the gears/couplers in a distal end of the main body portion (not shown) of the electromechanical instrument  10 , such that a rotation of each drive shaft  66  rotates a correspondingly coupled driven member of the surgical instrument  10  to effectuate a discrete function of the surgical instrument (e.g., opening/closing of the end effector, articulation of the end effector, etc.) 
     The drive shafts  66  each have a drive gear  64  such as, for example, a spur gear, rotationally fixed thereabout. Each of the drive gears  64  are positioned at a discrete vertical location on their respective drive shaft  66 , such that the drive gears  64  are vertically offset a selected distance from one another. Since the drive gears  64 , in addition to being vertically offset, are also circumferentially spaced from one another, the drive gears  64  are offset from one another in all three dimensions. As mentioned above, the drive gears  64  each interface or intermesh with the gear teeth  68  on the inner periphery  70  of a corresponding ring gear  62  and receive torque therefrom originating from the respective motor  22 . 
     In operation, the electromechanical instrument  10  is coupled to the instrument drive unit  20  by passing the main body portion of the electromechanical instrument  10  through the sleeve  28  of the instrument drive unit  20  in a proximal direction. The latch members  31   a ,  31   b  may engage opposing lateral sides of the main body portion of the surgical instrument  10  ( FIG. 1 ) to selectively retain the surgical instrument  10  within the sleeve  28 . With the main body portion of the electromechanical instrument  10  attached to the sleeve  28  of the instrument drive unit  28 , the distal end portion  67   b  of each of the drive shafts  66  interfaces with corresponding gears/couplers (not shown) in the proximal end of the main body portion of the electromechanical instrument  10 . 
     To actuate a particular function of the surgical instrument  10 , such as, for example, an opening or closing of an end effector of the surgical instrument  10 , one of the drive motors  22  of the instrument drive unit  20 , such as the first drive motor  22   a , is activated via the control device  4  ( FIG. 1 ). An activation of the first drive motor  22   a  rotates the first motor shaft  40   a . Rotation of the first motor shaft  40   a  actuates the first transmission assembly  60   a  to transfer torque from the first motor shaft  40   a  to a first driven member of the electromechanical instrument  10 . 
     In particular, with reference to  FIG. 7 , the first motor gear  42   a  of the first transmission assembly  60   a  rotates with the first motor shaft  40   a , which, in turn, rotates the first ring gear  62   a  and the first drive gear  64   a  of the first transmission assembly  60   a . Since the first drive gear  64   a  is rotationally fixed about the first drive shaft  66   a , and the distal end portion  67   b  ( FIG. 5 ) of the first drive shaft  66   a  is operably coupled to the proximal end of the first driven member of the surgical instrument  10  ( FIG. 1 ), a rotation of the first drive gear  64   a  causes the first drive shaft  66   a  to rotate, thereby rotating the first driven member of the electromechanical instrument  10  to actuate an associated function of the surgical instrument  10 . The drive motor  22   e  may be configured to resist rotation of the motor shaft  40   e  thereof during actuation of any of the transmission assemblies  60   a ,  60   b ,  60   c ,  60   d  so that actuation of one of the transmission assemblies  60   a ,  60   b ,  60   c ,  60   d  does not inadvertently result in a rotation of the hub  46 . 
     To rotate the electromechanical instrument  10  about its longitudinal axis, the fifth drive motor  22   e  of the instrument drive unit  20  is activated by the control device  4  ( FIG. 1 ). As noted above, an activation of the fifth drive motor  22   e  rotates the hub  46  about the central longitudinal axis “X.” Due to the drive shafts  66  extending through the distal radial extension  58   b  of the hub  46  and the annular members  29  ( FIG. 5 ) of the sleeve  28 , the sleeve  28  rotates with the hub  46 . Given that the electromechanical instrument  10  is non-rotationally supported in the sleeve  28 , the electromechanical instrument  10  rotates with the sleeve  28  relative to the carriage  26  to change a rotational orientation of the electromechanical instrument  10 . The drive motors  22   a ,  22   b ,  22   c ,  22   d  may be configured to concurrently rotate the motor shafts  40   a ,  40   b ,  40   c ,  40   d , and in turn the drive gears  64   a ,  64   b ,  64   c ,  64   d , with the hub  46  rotation. This would prevent rotation of the drive shafts  66   a ,  66   b ,  66   c ,  66   d  about their respective longitudinal axes during rotation of the hub  46 , which may otherwise occur if the drive gears  64   a ,  64   b ,  64   c ,  64   d  were held stationary during rotation of the hub  46 . 
     As can be appreciated, the instrument drive unit  20  described above improves usability of the surgical robotic system  1 , reduces a foot-print of the overall system  1 , improves safety architecture, reduces the time required to remove surgical instruments in case of an emergency, and simplifies the electronics used in the instrument drive unit  20 . 
     It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended thereto.