Patent Publication Number: US-6699177-B1

Title: Method and apparatus for performing minimally invasive surgical procedures

Description:
This application is a continuation of application Ser. No. 08/873,190, filed on Jun. 11, 1997, U.S. Pat. No. 6,102,850, which is a continuation-in-part of application Ser. No. 08/755,063, filed Nov. 22, 1996, U.S. Pat. No. 5,855,583, which is a continuation-in-part of application Ser. No. 08/603,543, filed on Feb. 20, 1996, U.S. Pat. No. 5,762,458. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system and method for performing minimally invasive cardiac procedures. More particularly, the present invention relates to a robotic system and surgical instruments that may be removably attached thereto, wherein said system aids in performing minimally invasive surgical procedures. 
     2. Description of Related Art 
     Blockage of a coronary artery may deprive the heart of the blood and oxygen required to sustain life. The blockage may be removed with medication or by an angioplasty. For severe blockage a coronary artery bypass graft (CABG) is performed to bypass the blocked area of the artery. CABG procedures are typically performed by splitting the sternum and pulling open the chest cavity to provide access to the heart. An incision is made in the artery adjacent to the blocked area. The internal mammary artery (IMA) is then severed and attached to the artery at the point of incision. The IMA bypasses the blocked area of the artery to again provide a full flow of blood to the heart. Splitting the sternum and opening the chest cavity, commonly referred to as ‘open surgery’, can create a tremendous trauma on the patient. Additionally, the cracked sternum prolongs the recovery period of the patient. 
     There have been attempts to perform CABG procedures without opening the chest cavity. Minimally invasive procedures are conducted by inserting surgical instruments and an endoscope through small incision in the skin of the patient. Manipulating such instruments can be awkward, particularly when suturing a graft to an artery. It has been found that a high level of dexterity is required to accurately control the instruments. Additionally, human hands typically have at least a minimal amount of tremor. The tremor further increases the difficulty of performing minimally invasive cardiac procedures. 
     To perform MIS, the surgeon uses special instruments. These instruments allow the surgeon to maneuver inside the patient. One type of instrument that is used in minimally invasive surgery is forceps, an instrument having a tip specifically configured to grasp objects, such as needles. Because forceps and other instruments designed for minimally invasive surgery are generally long and rigid, they fail to provide a surgeon the dexterity and precision necessary to effectively carry out many procedures in a minimally invasive fashion. For example, conventional MIS forceps are not well suited for manipulating a needle during a minimally invasive procedure, such as during endoscopy. Therefore, many MIS procedures that might be performed, have, as of yet, not been accomplished. 
     In essence, during open surgeries, the tips of the various instruments may be positioned with six degrees of freedom. However, by inserting an instrument through a small aperture, such as one made in a patient to effectuate a minimally invasive procedure, two degrees of freedom are lost. It is this loss of freedom of movement within the surgical site that has substantially limited the types of MIS procedures that are performed. 
     Dexterity is lacking in MIS because the instruments that are used fail to provide the additional degrees of freedom that are lost when the instrument is inserted into a patient. One problem associated with this lack of dexterity is the inability to suture when the instruments are in certain positions. As a result, surgeries that require a great deal of suturing within the surgical site are almost impossible to perform because the surgical instruments to enable much of this work are not available. 
     Another problem associated with MIS is the lack of precision within the surgical site. For procedures such as the MICABG (Minimally Invasive Coronary Artery Bypass Graft), extremely small sutures must be emplaced in various locations proximate the heart. As such, precise motion of the tool at the tip of a surgical instrument is necessary. Currently, with hand positioned instruments, the precision necessary for such suturing is lacking. 
     As such, what is needed in the art is a tool and class of surgical instruments that may be articulated within the patient such that a surgeon has additional degrees of freedom available to more dexterously and precisely position the tool at the tip of the instrument, as is needed. 
     Additionally, what is needed in the art is a method and mechanism that provides simple handle, instrument and tool changing capabilities so that various tools may be easily and readily replaced to enable faster procedures to thus minimize operating room costs to the patient and to lessen the amount of time a patient is under anesthesia. 
     It is to the solution of the aforementioned problems to which the present invention is directed. 
     SUMMARY OF THE INVENTION 
     The present invention is a system for performing minimally invasive surgical procedures, and more particularly, minimally invasive cardiac procedures. The system includes a pair or more of surgical instruments that are coupled to a pair or more of robotic arms. The system may include only a single surgical instrument and a single robotic arm as well and as is hereinbelow disclosed. The instruments have end effectors that can be manipulated to sever, grasp, cauterize, irradiate and suture tissue. Each robotic arm is coupled to a master handle by a controller. The robotic arms may be selectively connected to a specific master handle such that a surgeon may selectively control one or more of a plurality of robotic arms. The handles can be moved by the surgeon to produce a corresponding movement of the end effectors and the surgical tools attached thereto. The movement of the handles is scaled so that the end effectors have a corresponding movement that is different, typically smaller, than the movement performed by the hands of the surgeon. This helps in removing any tremor the surgeon might have in their hands. The scale factor is adjustable so that the surgeon can control the resolution of the end effector movement. The scale factor may be effectuated via a voice recognition system, control buttons or the like. The movement of the end effector can be controlled by an input button, so that the end effector only moves when the button is depressed or toggled by the surgeon. Alternatively, the movement can be activated via voice control in a manner similar to the scaling factor adjustment set out hereinbelow. The input button allows the surgeon to adjust the position of the handles without moving the end effector, so that the handles can be moved to a more comfortable position. The system may also have a robotically controlled endoscope which allows the surgeon to remotely view the surgical site. A cardiac procedure can be performed by making small incisions in the patient&#39;s skin and inserting the instruments and endoscope into the patient. The surgeon manipulates the handles and moves the end effectors to perform a cardiac procedure such as a coronary artery bypass graft or heart valve surgery. 
     The present invention is additionally directed to a surgical instrument and method of control thereof which permits the surgeon to articulate the tip of the instrument, while retaining the function of the tool at the tip of the instrument. As such, the instrument tip may be articulated with two degrees of freedom, all the while the tool disposed at the tip may be used. 
     The robotic system generally comprises: 
     a robotic arm; 
     a coupler attached to the arm; 
     a surgical instrument that is held by the coupler; 
     a controller; and 
     wherein movement at the controller produces a proportional movement of the robotic arm and surgical instrument. 
     The present invention may include a surgical instrument that has an elongated rod. The elongated rod has a longitudinal axis and generally serves as the arm of the endoscopic instrument. An articulate portion is mounted to and extends beyond the elongated rod. Alternatively, the articulate portion may be integrally formed with the elongated rod. The articulate portion has a proximal portion, a pivot linkage and a distal portion. The proximal portion may include a pair of fingers. The fingers may be orthogonal to each other and oriented radially to the longitudinal axis of the elongated rod. For use in surgical procedures, it is generally preferable that the instrument and the majority of the components therein are formed of stainless steel, plastic, or some other easily steralizable material. Each of the fingers may have at least one aperture formed therein to allow the passage of a pin which aids in the attachment of the pivot linkage to the proximal portion of the articulate portion and which allows the pivot linkage to be pivotally mounted to the proximal portion. The articulate portion provides articulation at the tip of an instrument that includes the articulate portion. More particularly, this provides additional degrees of freedom for the tool at the tip of an instrument that includes an articulate portion. 
     An instrument such as that disclosed hereinbelow, when used in conjunction with the present surgical system, provides the surgeon additional dexterity, precision, and flexibility not yet achieved in minimally invasive surgical procedures. As such, operation times may be shortened and patient trauma greatly reduced. 
     To provide increased precision in positioning the articulated tip as disclosed hereinbelow, there is provided two additional degrees of freedom to the master controller. Each of the two additional degrees of freedom are mapped to each of the degrees of freedom at the instrument tip. This is accomplished through the addition of two joints on the master and automatic means for articulating the instrument tip in response to movements made at the master. 
    
    
     The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and drawings wherein: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a minimally invasive surgical system in accordance with the present invention; 
     FIG. 2 is a schematic of a master of the system; 
     FIG. 3 is a schematic of a slave of the system; 
     FIG. 4 is a schematic of a control system of the system; 
     FIG. 5 is a schematic showing the instrument in a coordinate frame; 
     FIG. 6 is a schematic of the instrument moving about a pivot point; 
     FIG. 7 is an exploded view of an end effector in accordance with the system of the present invention; 
     FIG. 8 is a view of a master handle of the system in accordance with the present invention; 
     FIG. 8 a  is a side view of the master handle of the system in accordance with the present invention; 
     FIGS.  9 - 10 A-I are illustrations showing an internal mammary artery being grafted to a coronary artery; 
     FIG. 11 is a side view of a rear-loading tool driver in accordance with the system of the present invention; 
     FIG. 12 is a plan view of the motor assembly of the back loading tool driver of FIG. 11; 
     FIG. 13 is a side plan view of an articulable instrument in accordance with the present invention; 
     FIG. 14 is a side plan view of an articulable instrument, where the instrument tip is articulated; 
     FIG. 15 is an exploded view of the articulable portion of the articulable instrument in accordance with the present invention; 
     FIG. 16 is a plan view of a pivot linkage in accordance with the articulate portion of the articulable surgical instrument of the present invention; 
     FIG. 17 is a perspective view of an articulating tool driving assembly in accordance with the present invention; 
     FIG. 18 is a view of a removable tool-tip in accordance with an articulable instrument of the present invention; 
     FIG. 19 is a tool-tip receptacle in accordance with the present invention; 
     FIG. 20 is a cross-sectional view of an articulable instrument attached to the articulate-translator of the present invention; 
     FIG. 21 is a close-up cross section view of the articulate-translator in accordance with the present invention; 
     FIG. 22 is an end view of the articulate translator in accordance with the present invention; 
     FIG. 23 is a cross-sectional view of the sterile section of the articulating tool driving assembly in accordance with the system of the present invention; 
     FIG. 24 is a cross sectional view of the tool driver of the articulating tool driving assembly in accordance with the system of the present invention; 
     FIG. 25 is an schematic of a master of a system in accordance with the present invention that includes the articulating tool driving assembly; 
     FIG. 26 is a plan view of a drape for use with the robotic arm in accordance with the present invention; 
     FIG. 27 is a plan view of a surgical instrument having a stapling tool disposed at the end thereof and wherein the surgical instrument is attached to the robotic arm in accordance with the present invention; 
     FIG. 28 is a plan view of a surgical instrument having a cutting blade disposed at the end thereof wherein the instrument is attached to the robotic arm in accordance with the present invention; 
     FIG. 29 is a plan view of a surgical instrument having a coagulating/cutting device disposed at the end thereof, the instrument attached to a robotic arm in accordance with the present invention; 
     FIG. 30 is a plan view of a surgical instrument having a suturing tool disposed at the end thereof and wherein the surgical instrument is attached to the robotic arm in accordance with the present invention; 
     FIG. 31 is a plan view of an alternative master-handle console in accordance the present invention; 
     FIG. 32 is a plan view of an alternative master-handle console in accordance with the present invention; 
     FIG. 33 is a partial cut away cross-section of the master handle console in accordance with the present invention; 
     FIG. 34 is a partial cut-away plan view of a handle in accordance with the present invention; 
     FIG. 35 is a perspective view of an alternative embodiment of a handle in accordance with the present invention; 
     FIG. 36 is a top plan cross-sectional view of the handle depicted in FIG. 35; 
     FIG. 36A illustrates an interchange mechanism and biased detent latch for use with the handles depicted in FIGS. 43 and 36; 
     FIG. 37 is an alternative embodiment of a handle in accordance with the present invention; 
     FIG. 38 is an alternative embodiment of a handle in accordance with the present invention; and 
     FIG. 39 is an alternative embodiment of a handle in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings more particularly by reference numbers, FIG. 1 shows a system  10  that can be used to perform minimally invasive surgery. In a preferred embodiment, the system  10  may be used to perform a minimally invasive coronary artery bypass graft, or Endoscopic coronary artery bypass graft (E-CABG) and other anastomostic procedures. Although a MI-CABG procedure is shown and described, it is to be understood that the system may be used for other surgical procedures. For example, the system can be used to suture any pair of vessels as well as cauterizing, cutting, and radiating structures within a patient. 
     The system  10  is used to perform a procedure on a patient  12  that is typically lying on an operating table  14 . Mounted to the operating table  14  is a first articulate arm  16 , a second articulate arm  18  and a third articulate arm  20 . The articulate arms  16 - 20  are preferably mounted to the table so that the arms are in a plane proximate the patient. It is to be appreciated that the arms may be mounted to a cart or some other device that places the arms proximate the plane of the patient as well. Although three articulate arms are shown and described, it is to be understood that the system may have any number of arms, such as one or more arms. 
     The first and second articulate arms  16  and  18  each have a base housing  25  and a robotic arm assembly  26  extending from the base housing  25 . Surgical instruments  22  and  24  are preferably removably coupled at the end of each robotic arm assembly  26  of the first and second articulate arms  16 ,  18 . Each of the instruments  22 ,  24  may be coupled to a corresponding robotic arm assembly  26  in a variety of fashions which will be discussed in further detail hereinbelow. 
     The third articulate arm  20  additionally comprises a base housing  25  and a robotic arm assembly  26 , and preferably has an endoscope  28  that is attached to the robotic arm assembly  26 . The base housing  25  and robotic arm assemblies  26  of each of the articulate arms  16 ,  18 , and  20  are substantially similar. However, it is to be appreciated that the configuration of the third articulate arm  20 , may be different as the purpose of the third articulate arm is to hold and position the endoscope  28  as opposed to hold and position a surgical instrument. Additionally, a fourth arm  29  may be included in the system  10 . The fourth arm  29  may hold an additional instrument  31  for purposes set out hereinbelow. 
     The instruments  22 ,  24  and  29  and endoscope  28  are inserted through incisions cut into the skin of the patient  12 . The endoscope  28  has a camera  30  that is coupled to a monitor  32  which displays images of the internal organs of the patient  12 . 
     Each robotic arm assembly  26  has a base motor  34  which moves the arm assembly  26  in a linear fashion, relative to the base housing  25 , as indicated by arrows Q. Each robotic arm assembly  26  also includes a first rotary motor  36  and a second rotary motor  38 . Each of the robotic arm assemblies  26  also have a pair of passive joints  40  and  42 . The passive joints  40 ,  42  are preferably disposed orthogonal to each other to provide pivotal movement of the instrument  22 ,  24  or endoscope  28  that is attached to a corresponding robotic arm assembly  26 . The passive joints may be spring biased in any specific direction, however, they are not actively motor driven. The joint angle is controlled to a particular value using a feedback control loop. The robotic arm assemblies  26  also have a coupling mechanism  45  to couple the instruments  22  and  24 , or endoscope  28  thereto. Additionally, each of the robotic arm assemblies  26  has a motor driven worm gear  44  to rotate the instrument  22 ,  24  or endoscope  28  attached thereto about its longitudinal axis. More particularly, the motor driven worm gear spins the instruments or endoscope. 
     The first, second, and third articulate arms  16 ,  18 ,  20  as well as the fourth arm  29  are coupled to a controller  46  which can control the movement of the arms. The arms are coupled to the controller  46  via wiring, cabling, or via a transmitter/receiver system such that control signals may be passed form the controller  46  to each of the articulate arms  16 ,  18 , and  20 . It is preferable, to ensure error free communication between each of the articulate arms  16 ,  18 ,  20  and  29  and the controller  46  that each arm  16 ,  18 ,  20  and  29  be electrically connected to the controller, and for the purposes of example, each arm  16 ,  18 ,  20  and  29  is electrically connected to the controller  46  via electrical cabling  47 . However, it is possible to control each of the arms  16 ,  18 ,  20  and  29  remotely utilizing well-known remote control systems as opposed to direct electrical connections. As such remote control systems are well-known in the art, they will not be further discussed herein. 
     The controller  46  is connected to an input device  48  such as a foot pedal, hand controller, or voice recognition unit. For purposes of example, a foot controller and voice recognition unit are disclosed herein. The input device  48  can be operated by a surgeon to move the location of the endoscope  28  and view a different portion of the patient by depressing a corresponding button(s) disposed on the input device  48 . Alternatively, the endoscope  28  may be positioned via voice control. Essentially, a vocabulary of instructions to move the endoscope, such as up, down, back, and in may be recognized via a speech recognition system and the appropriate instructions are sent to the controller. The speech recognition system may be any well-known speech recognition software. Additionally, the controller  46  includes a vocabulary of appropriate words that may be used with the system  10 . Including such a vocabulary in the controller  46  may be accomplished through the inclusion of the aforementioned speech recognition software. To effectuate the voice recognition a microphone  37  is included in the system  10 . The microphone  37  may be part of a digital system such that integrity of the signal is ensure. 
     The controller  46  receives the input signals from the input device  48  and moves the endoscope  28  and robotic arm assembly  26  of the third articulate arm  20  in accordance with the input commands of the surgeon. Each of the robotic arm assemblies  26  may be devices that are sold by the assignee of the present invention, Computer Motion, Inc. of Goleta, Calif., under the trademark AESOP. The system is also described in U.S. Pat. No. 5,515,478, which is hereby incorporated by reference. Although a foot pedal  49  is shown and described, it is to be understood that the system may have other input means such as a hand controller, or a speech recognition interface. 
     The movement and positioning of instruments  22 ,  24  attached to the first and second articulate arms  16  and  18  is controlled by a surgeon at a pair of master handles  50  and  52 . Each of the master handles  50 ,  52  which can be manipulated by the surgeon, has a master-slave relationship with a corresponding one of the articulate arms  16 ,  18  so that movement of a handle  50  or  52  produces a corresponding movement of the surgical instrument  22 ,  24  attached to the articulate arm  16 ,  18 . Additionally, a switch  51  may be included in the system  10 . The switch  51  may be used by the surgeon to allow positioning of the fourth arm  29 . This is accomplished because the position of the switch  51  allows the surgeon to select which of the arms a specific handle  50  or  52  controls. In this way, a pair of handles  50  and  52  may be used to control a plurality of robotic arms. The switch  51  may be connected to a multiplexer to act as a selector so that output from the multiplexer is transmitted to the appropriate robotic arm. Alternatively, the switch may have several positions and may, therefore, direct its output to the appropriate input on the controller  46 . 
     The handles  50  and  52  may be mounted to a portable cabinet  54 . A second television monitor  56  may be placed onto the cabinet  54  and coupled to the endoscope  28  via well-known means so that the surgeon can readily view the internal organs of the patient  12 . The handles  50  and  52  are also coupled to the controller  46 . The controller  46  receives input signals from the handles  50  and  52 , computes a corresponding movement of the surgical instruments, and provides output signals to move the robotic arm assemblies  26  and instruments  22 ,  24 . Because the surgeon may control the movement and orientation of the instruments  22 ,  24  without actually holding the ends of the instruments, the surgeon may use the system  10  of the present invention both seated or standing. One advantage of the present system is that a surgeon may perform endoscopic surgeries in a sitting position. This helps reduce surgeon fatigue and may improve performance and outcomes in the operating room, especially during those procedures that are many hours in length. To accommodate a seated position, a chair  57  may be provided with the system. 
     Alternatively, and as depicted in FIGS. 31-33, the handles  50  and  52  may be mounted to a handle stand  900 . The handle stand  900  essentially provides for adjustment of the height and tilt of the handles  50  and  52 . The handle stand  900  includes a base  902 , a neck  904  and a handle portion  906 . The base  902  may be adjusted so that the handle stand  900  is tilted. A lever  908  connected to an elongated rod  910  may provide a means for tilting the handle stand  900 . As such, the stand  900  may be tilted such that a surgeon using the system  10  can remain comfortable standing or sitting while manipulating the handles  50  and  52 . 
     Additionally, the handle stand  900  may be heightened or shortened depending upon the position of the surgeon (i.e. standing or sitting). This is accomplished via a telescoping section  912 . The telescoping section  912  includes an upper portion  914  telescopingly housed within a lower portion  916 . A spring biased detent  918  is attached to the upper portion  914  and a plurality of apertures  920  are provided in the lower portion  916  such that the detent  918  seats in an associated aperture  920 . The upper portion  914  may be extended by depressing the detent  918  and pulling up on the stand  900 . Alternatively, the stand  900  may be lowered by depressing the detent and pushing down on the stand  900 . The telescoping section  912  and associated mechanisms serve as a means to raise and lower the stand  900 . 
     Additionally, and as depicted in FIGS. 31-33, the handles  50  and  52  may be attached to the stand  900  via a plurality of rollers  930  and an elongated rod  932 . Motion of the rod  932  is transmitted to a plurality of gears  934  disposed on the stand  900 . The gears  934  may be housed within a housing  936  to protect them from the environment and to preclude access thereto. Additionally, potentiometers  938  are utilized to measure the position of the handles  50  and  52  relative to a starting position. This will be discussed in more detail hereinbelow. It is to be appreciated that the present invention may be accomplished either utilizing a cabinet  54  or a stand  900 . As the handles  50  and  52  are connected to the controller  46  in either case. 
     Each handle has multiple degrees of freedom provided by the various joints Jm 1 -Jm 5  depicted in FIG.  2 . Joints Jm 1  and Jm 2  allow the handle to rotate about a pivot point in the cabinet  54  or on the stand  900 . Joint Jm 3  allows the surgeon to move the handle into and out of the cabinet  54  in a linear manner or in a similar manner on the stand  900 . Joint Jm 4  allows the surgeon to rotate the master handle about a longitudinal axis of the handle. The joint Jm 5  allows a surgeon to open and close a gripper. 
     Each joint Jm 1 -Jm 5  has one or more position sensors which provides feedback signals that correspond to the relative position of the handle. The position sensors may be potentiometers, or any other feedback device such as rotary optical encoders that provides an electrical signal which corresponds to a change of position. Additionally, a plurality of position sensors may be emplaced at each joint to provide redundancy in the system which can be used to alert a surgeon of malfunctions or improper positioning of a corresponding robotic arm assembly  26 . 
     In addition to position sensors, each joint may include tachometers, accelerometers, and force sensing load cells, each of which may provide electrical signals relating to velocity, acceleration and force being applied at a respective joint. Additionally, actuators may be included at each joint to reflect force feed back received at a robotic arm assembly  26 . This may be especially helpful at joint jm 5  to indicate the force encountered inside a patient by the gripper disposed at the end of one of the tools  22 , or  24 . As such, a force reflective element must be included at the gripper of the instrument  22 ,  24  to effectuate such a force reflective feedback loop. Force reflective elements, such as a piezoelectric element in combination with a whetstone bridge are well-known in the art. However, it is not heretofore know to utilize such force reflection with such a system  10 . 
     FIG. 3 shows the various degrees of freedom of each articulate arm  16  and  18 . The joints Js 1 , Js 2  and Js 3  correspond to the axes of movement of the base motor  34  and rotary motors  36 ,  38  of the robotic arm assemblies  26 , respectively. The joints Js 4  and Js 5  correspond to the passive joints  40  and  42  of the arms  26 . The joint Js 6  may be a motor which rotates the surgical instruments about the longitudinal axis of the instrument. The joint Js 7  may be a pair of fingers that can open and close. The instruments  22  and  24  move about a pivot point P located at the incision of the patient. 
     FIG. 4 shows a schematic of a control system that translates a movement of a master handle into a corresponding movement of a surgical instrument. In accordance with the control system shown in FIG. 4, the controller  46  computes output signals for the articulate arms so that the surgical instrument moves in conjunction with the movement of the handle. Each handle may have an input button  58  which enables the instrument to move with the handle. When the input button  58  is depressed the surgical instrument follows the movement of the handle. When the button  58  is released the instrument does not track the movement of the handle. In this manner the surgeon can adjust or “ratchet” the position of the handle without creating a corresponding undesirable movement of the instrument. The “ratchet” feature allows the surgeon to continuously move the handles to more desirable positions without altering the positions of the arms. Additionally, because the handles are constrained by a pivot point the ratchet feature allows the surgeon to move the instruments beyond the dimensional limitations of the handles. Although an input button  58  is shown and described, it is to be understood that the surgical instrument may be activated by other means such as voice recognition. Using the voice recognition would require a specifically vocabulary such as “AWAKE” and “SLEEP” or some other two words having opposing meanings. Voice recognition is well known in general, and it is the specific use of voice recognition in this system  10  that has substantial novelty and utility. 
     The input button may alternatively be latched so that movement of the corresponding instrument toggles between active and inactive each time the button is depressed by the surgeon. 
     When the surgeon moves a handle, the position sensors provide feedback signals M 1 -M 5  that correspond to the movement of the joints Jm 1 -Jm 5 , respectively. The controller  46  computes the difference between the new handle position and the original handle position in computation block  60  to generate incremental position values _M 1 -_M 5 . 
     The incremental position values _M 1 -_M 5  are multiplied by scale factors S 1 -S 5 , respectively in block  62 . The scale factors are typically set at less than one so that the movement of the instrument is less than the movement of the handle. In this manner the surgeon can produce very fine movements of the instruments with relatively coarse movements of the handles. The scale factors S 1 -S 5  are variable so that the surgeon can vary the resolution of instrument movement. Each scale factor is preferably individually variable so that the surgeon can more finely control the instrument in certain directions. By way of example, by setting one of the scale factors at zero the surgeon can prevent the instrument from moving in one direction. This may be advantageous if the surgeon does not want the surgical instrument to contact an organ or certain tissue located in a certain direction relative to the patient. Although scale factors smaller than a unit one are described, it is to be understood that a scale factor may be greater than one. For example, it may be desirable to spin the instrument at a greater rate than a corresponding spin of the handle. 
     The controller  46  adds the incremental values _M 1 -_M 5  to the initial joint angles Mj 1 -Mj 5  in adder element  64  to provide values Mr 1 -Mr 5 . The controller  46  then computes desired slave vector calculations in computation block  66  in accordance with the following equations. 
     
       
           Rdx=Mr   3 ·sin( Mr   2 )·cos( Mr   1 )+ Px   
       
     
     
       
           Rdy=Mr   3 ·sin( Mr   2 )·sin( Mr   1 )+ Py   
       
     
     
       
           Rdz=Mr   3 ·cos( Mr   2 )+ Pz   
       
     
     
       
         Sdr=Mr 4   
       
     
     
       
         Sdg=Mr 5   
       
     
     where; 
     Rdx,y,z=the new desired position of the end effector of the instrument. 
     Sdr=the angular rotation of the instrument about the instrument longitudinal axis. 
     Sdg=the amount of movement of the instrument fingers. Px,y,z=the position of the pivot point P. 
     The controller  46  then computes the movement of the robotic arm  26  in computational block  68  in accordance with the following equations.        Jsd1   =   Rdz           Jsd3   =     π   -       cos     -   1            [         Rdx   2     +     Rdy   2     -     L1   2     -     L2   2         2        L1   ·   L2         ]                 Jsd2   =           tan     -   1            (     Rdy   /   Rdx     )       +     Δ                 for                 Jsd3       ≤   0             Jsd2   =           tan     -   1            (     Rdy   /   Rdx     )       -     Δ                 for                 Jsd3       &gt;   0             Δ   =       cos     -   1            [         Rdx   2     +     Rdy   2     +     L1   2     -     L2   2           2   ·   L1              Rdx   2     +     Rdy   2             ]               Jsd6   =   Mr4           Jsd7   =   Mr5                   
     where; 
     Jsd 1 =the movement of the linear motor. 
     Jsd 2 =the movement of the first rotary motor. 
     Jsd 3 =the movement of the second rotary motor. 
     Jsd 6 =the movement of the rotational motor. 
     Jsd 7 =the movement of the gripper. 
     L1=the length of the linkage arm between the first rotary motor and the second rotary motor. 
     L2=the length of the linkage arm between the second rotary motor and the passive joints. 
     The controller provides output signals to the motors to move the arm and instrument in the desired location in block  70 . This process is repeated for each movement of the handle. 
     The master handle will have a different spatial position relative to the surgical instrument if the surgeon releases, or toggles, the input button and moves the handle. When the input button  58  is initially depressed, the controller  46  computes initial joint angles Mj 1 -Mj 5  in computational block  72  with the following equations.        Mj1   =       tan     -   1            (     ty   /   tx     )               Mj2   =       tan     -   1            (     d   /   tz     )               Mj3   =   D           Mj4   =   Js6           Mj5   =   Js7           d   =         tx   2     +     ty   2                 tx   =           Rsx   -   Px     D                   ty     =           Rsy   -   Py     D                   tz     =       Rsz   -   Pz     D                 D   =           (     Rsx   -   Px     )     2     +       (     Rsy   -   Py     )     2     +       (     Rsz   -   Pz     )     2                         
     The forward kinematic values are computed in block  74  with the following equations. 
       Rsx=L 1·cos( Js 2)+ L 2·cos( Js 2 +Js 3) 
     
       
           Rsy=L 1·sin( Js 2)+ L 2·sin( Js 2 +Js 3) 
       
     
     
       
           Rsz=J 1 
       
     
     The joint angles Mj are provided to adder  64 . The pivot points Px, Py and Pz are computed in computational block  76  as follows. The pivot point is calculated by initially determining the original position of the intersection of the end effector and the instrument PO, and the unit vector Uo which has the same orientation as the instrument. The position P(x, y, z) values can be derived from various position sensors of the robotic arm. Referring to FIG. 5 the instrument is within a first coordinate frame (x, y, z) which has the angles θ4 and θ5. The unit vector Uo is computed by the transformation matrix:        Uo   =       [           cos                   Θ   5           0             -   sin                     Θ   5                                -   sin                     Θ   4        sin                   Θ   5             cos                   Θ   4               -   sin                     Θ   4        cos                   Θ   5                 cos                   Θ   4        sin                   Θ   5             sin                   Θ   4             cos                   Θ   4             ]          [         0           0             -   1           ]                       
     After each movement of the end effector an angular movement of the instrument ΔΘ is computed by taking the arcsin of the cross-product of the first and second unit vectors Uo and U 1  of the instrument in accordance with the following line equations Lo and L 1 . 
      Δθ=arcsin(| T |) 
     
       
         T= U   0 × U   1   
       
     
     where; 
     T=a vector which is a cross-product of unit vectors Uo and U 1 . The unit vector of the new instrument position U 1  is again determined using the position sensors and the transformation matrix described above. If the angle Δθ is greater than a threshold value, then a new pivot point is calculated and Uo is set to U 1 . As shown in FIG. 6, the first and second instrument orientations can be defined by the line equations L 0  and L 1 : 
     
       
           x   0 = M   x   0 · Z   0 + Cx   0   
       
     
     
       
           y   0 = M   y   0 · Z   0 + Cy   0   L0 
       
     
     
       
           x   1 = Mx   1 · Z   1 + Cx   1   
       
     
     
       
           y   1 = My   1 · Z   1 + Cy   1   L1 
       
     
     where; 
     Zo=a Z coordinate along the line Lo relative to the z axis of the first coordinate system. 
     Z 1 =a Z coordinate along the line L 1  relative to the z axis of the first coordinate system. 
     Mxo=a slope of the line Lo as a function of Zo. 
     Myo=a slope of the line Lo as a function of Zo. 
     Mx 1 =a slope of the line L 1  as a function of Z 1 . 
     My 1 =a slope of the line L 1  as a function of Z 1 . 
     Cxo=a constant which represents the intersection of the line Lo and the x axis of the first coordinate system. 
     Cyo=a constant which represents the intersection of the line Lo and the y axis of the first coordinate system. 
     Cx 1 =a constant which represents the intersection of the L 1  and the x axis of the first coordinate system. 
     Cy 1 =a constant which represents the intersection of the line L 1  and the y axis of the first coordinate system. 
     The slopes are computed using the following algorithms: 
     
       
         
           Mxo=Uxo/Uzo 
         
       
     
     
       
         
           Myo=Uyo/Uzo 
         
       
     
     
       
           Mx   1 = Ux   1 / Uz   1   
       
     
     
       
           My   1 = Uy   1 / Uz   1   
       
     
       Cx   0 = Pox−Mx   1 · Poz   
     
       
           Cy   0 = Poy−My   1 · Poz   
       
     
     
       
           Cx   1 = P   1   x−Mx   1 · P   1   z   
       
     
     
       
           Cy   1 = P   1   y−My   1 · P   1   z   
       
     
     where; 
     Uo(x, y and z)=the unit vectors of the instrument in the first position within the first coordinate system. 
     U 1 (x, y and z)=the unit vectors of the instrument in the second position within the first coordinate system. 
     Po(x, y and z)=the coordinates of the intersection of the end effector and the instrument in the first position within the first coordinate system. 
     P 1 (x, y and z)=the coordinates of the intersection of the end effector and the instrument in the second position within the first coordinate system. 
     To find an approximate pivot point location, the pivot points of the instrument in the first orientation Lo (pivot point Ro) and in the second orientation L 1  (pivot point R 1 ) are determined, and the distance half way between the two points Ro and R 1  is computed and stored as the pivot point R ave  of the instrument. The pivot point R ave  is determined by using the cross-product vector T. 
     To find the points Ro and R 1  the following equalities are set to define a line with the same orientation as the vector T that passes through both Lo and L 1 . 
     
       
         
           tx=Tx/Tz 
         
       
     
     
       
         
           ty=Ty/Tz 
         
       
     
     where; 
     tx=the slope of a line defined by vector T relative to the Z-x plane of the first coordinate system. 
     ty=the slope of a line defined by vector T relative to the Z-y plane of the first coordinate system. 
     Tx=the x component of the vector T. 
     Ty=the y component of the vector T. 
     Tz=the z component of the vector T. 
     Picking two points to determine the slopes Tx, Ty and Tz (e.g. Tx=x 1 −xo, Ty=y 1 −yo and Tz=z 1 −z 0 ) and substituting the line equations Lo and L 1 , provides a solution for the point coordinates for Ro (xo, yo, zo) and R 1  (x 1 , y 1 , z 1 ) as follows. 
       z   0 =(( Mx   1 − tx ) z   1 + Cx   1 − Cx   0 )/( Mx   0 − tx ) 
     
       
           z   1 =(( Cy 1− Cy   0 )( Mx   0 − tx )−( CX   1 − Cx   0 )( My   0 − ty ))/(( My   0 − ty )( Mx   1 − tx )−( My   1 − ty )( Mx   0 − tx )) 
       
     
     
       
           y   0 = My   0 · z   0 + Cy   0   
       
     
     
       
           y   1 = My   1 · z   1 + Cy   1   
       
     
     
       
           x   0 = Mx   0 · z   0 + Cx   0   
       
     
     
       
           x   1 = Mx   1 · z   1 + Cx   1   
       
     
     The average distance between the pivot points R0 and R1 is computed with the following equation and stored as the pivot point of the instrument. 
     
       
         R ave =(( x   1 + x   0 )/2,( y   1 + y   0 )/2,( z   1 + z   0 )/2 
       
     
     The pivot point can be continually updated with the above described algorithm routine. Any movement of the pivot point can be compared to a threshold value and a warning signal can be issued or the robotic system can become disengaged if the pivot point moves beyond a set limit. The comparison with a set limit may be useful in determining whether the patient is being moved, or the instrument is being manipulated outside of the patient, situations which may result in injury to the patient or the occupants of the operating room. 
     While substantial real time movement of the robotic arms is provided, it may be appreciated that pre-planned movements may be incorporated into the present system  10 . This is most advantageous with regard to movement of the endoscope. Any type of movement may be stored in am associated memory of the controller so that a surgeon may define his own favorite movements and then actuate such movement by pressing a button or via voice control. Because the movement is taught in the present application as well as those patents incorporated herein by reference, no further disclosure of this concept is required. 
     To provide feedback to the surgeon, the system  10  may include a voice feedback unit. As such, it the robotic arms suffer any malfunction, the voice feedback may supply a message that such error has occurred. Additionally, messages regarding instrument location, time-in-use, as well as a host of other data may be supplied to the surgeon through the voice feedback unit. If such a condition occurs that requires a message, the system has a set of messages stored in an associated memory, such message may be encoded and saved in the memory. A speech synthesis unit  89 , as depicted in FIG. 1 can then vocalize the message to the surgeon. In this fashion, a surgeon can maintain sight of the operative environment as opposed to looking for messages displayed on a video screen or the like. Speech synthesis is well known, although its inclusion in a master-slave robotic system for minimally invasive surgery is heretofore unknown and present novel and unobvious advantages. 
     To provide feedback to the surgeon the fingers of the instruments may have pressure sensors that sense the reacting force provided by the object being grasped by the end effector. Referring to FIG. 4, the controller  46  receives the pressure sensor signals Fs and generates corresponding signals Cm in block  78  that are provided to an actuator located within the handle. The actuator provides a corresponding pressure on the handle which is transmitted to the surgeon&#39;s hand. The pressure feedback allows the surgeon to sense the pressure being applied by the instrument. As an alternate embodiment, the handle may be coupled to the end effector fingers by a mechanical cable that directly transfers the grasping force of the fingers to the hands of the surgeon. 
     FIG. 7 shows a preferred embodiment of an end effector  80  that may be used in the present invention. The end effector  80  includes a surgical instrument  82 , such as those disclosed hereinabove  22 ,  24 , that is coupled to a front loading tool driver  84 . The end effector  80  is mounted to one of the robotic arm assemblies  26  by coupling mechanism  45 . The coupling mechanism  45  includes a collar  85  that removably attaches to a holder  86 . The holder  86  includes a worm gear  87  that is driven by a motor in the robotic arm assembly  26  to rotate the collar  85  and in turn rotate the instrument  82  about its longitudinal axis. The holder  86  includes a shaft  88  that seats into a slot in the robotic arm assembly  26 . The shaft  88  may be turned by the motor in the arm assembly, which then rotates the worm gear  87  thus rotating the collar  86  and the instrument  82 . A tightening tool  89  may be employed to tighten and loosen the collar about the instrument  82 . Such a tool operates like a chuck key, to tighten and loosen the collar  86 . 
     The surgical instrument  82  has a first finger  90  that is pivotally connected to a second finger  91 . The fingers  90 ,  91  can be manipulated to hold objects such as tissue or a suturing needle. The inner surface of the fingers may have a texture to increase the friction and grasping ability of the instrument  82 . The first finger  90  is coupled to a rod  92  that extends through a center channel  94  of the instrument  82 . The instrument  82  may have an outer sleeve  96  which cooperates with a spring biased ball quick disconnect fastener  98 . The quick disconnect  98  allows instruments other than the finger grasper to be coupled to front loading tool driver  84 . For example, the instrument  82  may be decoupled from the quick disconnect  98  and replaced by a cutting tool, a suturing tool, a stapling tool adapted for use in this system, such as the stapling apparatus disclosed in U.S. Pat. No. 5,499,990 or 5,389,103 assigned to Karlsruhe, a cutting blade, or other surgical tools used in minimally invasive surgery. The quick disconnect  98  allows the surgical instruments to be interchanged without having to re-sterilize the front loading tool driver  84  each time an instrument is plugged into the tool driver  84 . The operation of the front loading tool driver  84  shall be discussed in further detail hereinbelow. 
     The quick disconnect  98  has a slot  100  that receives a pin  102  of the front loading tool driver  84 . The pin  102  locks the quick disconnect  98  to the front loading tool driver  100 . The pin  102  can be released by depressing a spring biased lever  104 . The quick disconnect  98  has a piston  106  that is attached to the tool rod  92  and in abutment with an output piston  108  of a load cell  110  located within the front loading tool driver  84 . 
     The load cell  110  is mounted to a lead screw nut  112 . The lead screw nut  112  is coupled to a lead screw  114  that extends from a gear box  116 . The gear box  116  is driven by a reversible motor  118  that is coupled to an encoder  120 . The entire end effector  80  is rotated by the motor driven worm gear  87 . 
     In operation, the motor  118  of the front loading tool driver  84  receives input commands from the controller  46  via electrical wiring, or a transmitter/receiver system and activates, accordingly. The motor  118  rotates the lead screw  114  which moves the lead screw nut  112  and load cell  110  in a linear manner. Movement of the load cell  110  drives the coupler piston  106  and tool rod  92 , which rotate the first finger  88 . The load cell  110  senses the counteractive force being applied to the fingers and provides a corresponding feedback signal to the controller  46 . 
     The front loading tool driver  84  may be covered with a sterile drape  124  so that the tool driver  84  does not have to be sterilized after each surgical procedure. Additionally, the robotic arm assembly  26  is preferably covered with a sterile drape  125  so that it does not have to be sterilized either. The drapes  124 ,  125  serve substantially as a means for enclosing the front loading tool driver  84  and robotic arm assembly  26 . The drape  125  used to enclose the robotic arm assembly  26  is depicted in further detail in FIG.  26 . The drape  125  has a substantially open end  300  wherein the robotic arm assembly  26  may be emplaced into the drape  125 . The drape  125  additionally includes a substantially tapered enclosed end  302  that effectively separates the arm assembly  26  from the operating room environment. A washer  304  having a small aperture  306  formed therethrough allows an instrument to be coupled to the arm assembly  26  via the coupling mechanism  45 . The washer  304  reinforces the drape  125  to ensure that the drape  125  does not tear as the arm assembly  26  moves about. Essentially, the instrument cannot be enclosed in the drape  125  because it is to be inserted into the patient  12 . The drape  125  also includes a plurality of tape  308  having adhesive  310  disposed thereon. At least one piece of tape  308  is opposedly arranged the other pieces of tape  308  to effectuate the closing of the drape  125  about the arm assembly  26 . 
     FIGS. 8 and 8 a  show a preferred embodiment of a master handle assembly  130 . The master handle assembly  130  includes a master handle  132  that is coupled to an arm  134 . The master handle  132  may be coupled to the arm  134  by a pin  136  that is inserted into a corresponding slot  138  in the handle  132 . The handle  132  has a control button  140  that can be depressed by the surgeon. The control button  140  is coupled to a switch  142  by a shaft  144 . The control button  140  corresponds to the input button  58  shown in FIG. 4, and activates the movement of the end effector. 
     The master handle  132  has a first gripper  146  that is pivotally connected to a second stationary gripper  148 . Rotation of the first gripper  146  creates a corresponding linear movement of a handle shaft  150 . The handle shaft  150  moves a gripper shaft  152  that is coupled a load cell  154  by a bearing  156 . The load cell  154  senses the amount of pressure being applied thereto and provides an input signal to the controller  46 . The controller  46  then provides an output signal to move the fingers of the end effector. 
     The load cell  154  is mounted to a lead screw nut  158  that is coupled to a lead screw  160 . The lead screw  160  extends from a reduction box  162  that is coupled to a motor  164  which has an encoder  166 . The controller  46  of the system receives the feedback signal of the load cell  110  in the end effector and provides a corresponding command signal to the motor to move the lead screw  160  and apply a pressure on the gripper so that the surgeon receives feedback relating to the force being applied by the end effector. In this manner the surgeon has a “feel” for operating the end effector. 
     The handle is attached to a swivel housing  168  that rotates about bearing  170 . The swivel housing  168  is coupled to a position sensor  172  by a gear assembly  174 . The position sensor  172  may be a potentiometer which provides feedback signals to the controller  46  that correspond to the relative position of the handle. Additionally, an optical encoder may be employed for this purpose. Alternatively, both a potentiometer and an optical encoder may be used to provide redundancy in the system. The swivel movement is translated to a corresponding spin of the end effector by the controller and robotic arm assembly. This same type of assembly is employed in the stand  900 . 
     The arm  134  may be coupled to a linear bearing  176  and corresponding position sensor  178  which allow and sense linear movement of the handle. The linear movement of the handle is translated into a corresponding linear movement of the end effector by the controller and robotic arm assembly. The arm can pivot about bearings  180 , and be sensed by position sensor  182  located in a stand  184 . The stand  184  can rotate about bearing  186  which has a corresponding position sensor  188 . The arm rotation is translated into corresponding pivot movement of the end effector by the controller and robotic arm assembly. 
     A human hand will have a natural tremor typically resonating between 6-12 hertz. To eliminate tracking movement of the surgical instruments with the hand tremor, the system may have a filter that filters out any movement of the handles that occurs within the tremor frequency bandwidth. Referring to FIG. 4, the filter  184  may filter analog signals provided by the potentiometers in a frequency range between 6-12 hertz. Alternatively, an optical encoder and digital filter may be used for this purpose. 
     As shown in FIGS.  9  and  10 A-J, the system is preferably used to perform a cardiac procedure such as a coronary artery bypass graft (CABG). The procedure is performed by initially cutting three incisions in the patient and inserting the surgical instruments  22  and  24 , and the endoscope  26  through the incisions. One of the surgical instruments  22  holds a suturing needle and accompanying thread when inserted into the chest cavity of the patient. If the artery is to be grafted with a secondary vessel, such as a saphenous vein, the other surgical instrument  24  may hold the vein while the end effector of the instrument is inserted into the patient. 
     The internal mammary artery (IMA) may be severed and moved by one of the instruments to a graft location of the coronary artery. The coronary artery is severed to create an opening in the artery wall of a size that corresponds to the diameter of the IMA. The incision(s) may be performed by a cutting tool that is coupled to one of the end effectors and remotely manipulated through a master handle. The arteries are clamped to prevent a blood flow from the severed mammary and coronary arteries. The surgeon manipulates the handle to move the IMA adjacent to the opening of the coronary artery. Although grafting of the IMA is shown and described, it is to be understood that another vessel such as a severed saphaneous vein may be grafted to bypass a blockage in the coronary artery. 
     Referring to FIGS. 10A-J, the surgeon moves the handle to manipulate the instrument into driving the needle through the IMA and the coronary artery. The surgeon then moves the surgical instrument to grab and pull the needle through the coronary and graft artery as shown in FIG.  10 B. As shown in FIG. 10C, the surgical instruments are then manipulated to tie a suture at the heel of the graft artery. The needle can then be removed from the chest cavity. As shown in FIGS. 10D-F, a new needle and thread can be inserted into the chest cavity to suture the toe of the graft artery to the coronary artery. As shown in FIGS. 10H-J, new needles can be inserted and the surgeon manipulates the handles to create running sutures from the heel to the toe, and from the toe to the heel. The scaled motion of the surgical instrument allows the surgeon to accurately move the sutures about the chest cavity. Although a specific graft sequence has been shown and described, it is to be understood that the arteries can be grafted with other techniques. In general the system of the present invention may be used to perform any minimally invasive anastomostic procedure. 
     Additionally, it may be advantageous to utilize a fourth robotic arm to hold a stabilizer  75 . The stabilizer may be a tube or wire or some other medical device that may be emplaced within an artery, vein or similar structure to stabilize such structure. Using the switch  51  to interengage the fourth robotic arm, with a handle  50  or  52  a surgeon may position the stabilizer  75  into the vessel. This eases the task of placing a stitch through the vessel as the stabilizer  75  maintains the position of the vessel. Once the stabilizer  75  has been placed, the surgeon then flips the switch or like mechanism to activate the robotic arm that had been disconnected to allow for movement of the fourth robotic arm. The stabilizer  75  should be substantially rigid and hold its shape. Additionally, the stabilizer should be formed form a material that is steralizable. Such material are well known in the medical arts. However, this application and configuration is heretofore unknown. 
     As disclosed hereinabove, the system may include a front loading tool driver  84  which receives control signals from the controller  46  in response to movement of a master handle  50  or  52  and drives the tool disposed at the end of a surgical instrument. Alternatively, a back loading tool driver  200  may be incorporated into the system  10  of the present invention, as depicted in FIGS. 11 and 11 a . The back loading tool driver  200  cooperates with a back loadable surgical instrument  202 . The incorporation of such a back loading tool driver  200  and instrument  202  expedites tool changing during procedures, as tools may be withdrawn from the tool driver  200  and replaced with other tools in a very simple fashion. 
     The back loading tool driver  200  is attached to a robotic arm assembly  26  via a collar and holder as disclosed hereinabove. The back loading tool driver includes a sheath  204  having a proximal end  206  and a distal end  208 . The sheath  204  may be formed of plastic or some other well-known material that is used in the construction of surgical instruments. The sheath  204  is essentially a hollow tube that fits through the collar  85  and is tightened in place by the tightening tool that is described in more detail hereinabove. 
     The back loadable surgical instrument  202  has a tool end  210  and a connecting end  212 . A surgical tool  214 , such as a grasper or some other tool that may be driven by a push/pull rod or cable system, or a surgical tool that does not require such a rod or cable, such as a coagulator, or harmonic scalpel is disposed at the tool end  210  of the instrument  202 . 
     A housing  216  is disposed at the connecting end  212  of the instrument  202 . The housing has a lever  218  disposed interiorly the housing  216 . The lever  218  has a pivot point  220  that is established by utilizing a pin passing through an associated aperture  222  in the lever. The pin may be attached to the interior wall  224  of the housing. A push/pull cable or rod  226 , that extends the length of the instrument  202  is attached to the lever  218 , such that movement of the lever  218  about the pivot point  220  results in a linear movement of the cable or rod  226 . Essentially the cable or rod  226  servers as a means  227  for actuating the tool  214  at the tool end  210  of the instrument  202 . The cable or rod  226  may be attached to the lever via a connection pin as well. The lever  218  has a C-shape, wherein the ends of the lever  218  protrude through two apertures  228 ,  230  in the housing  216 . The apertures  228 ,  230  are preferably surrounded by O-rings  232  the purpose of which shall be described in more detail hereinbelow. 
     The tool end  210  of the back loadable surgical instrument  202  is emplaced in the hollow tube of the back loading tool driver  200 . The tool  202  may be pushed through the tool driver until the tool end  210  extends beyond the sheath  204 . The O-rings  232  seat in associated apertures  234 ,  236  in a housing  238  of the tool driver  200 . The housing additionally has an aperture  240  centrally formed therethrough, the aperture being coaxial with the interior of the hollow tube. In this fashion, the surgical instrument  202  may be inserted into and through the tool driver  200 . Each of the O-rings  232  snugly seats in its associated aperture in the housing  238  of the tool driver  200 . 
     The housing  238  additionally includes a motor assembly  242  which is depicted in FIG. 11 a . The motor assembly  242  is attached to the housing  238  and is held firmly in place therein. The motor assembly generally includes a motor  244  attached to a reducer  246 . The motor drives a leaf  248  attached at the end thereof. The leaf  248  engages the ends of the lever  218  such that rotational movement of the motor results in the movement of the lever  218  about the pivot point  220 . This in turn results in the lateral movement of the means  227  for actuating the tool  214  at the tool end  210  of the instrument  202 . The motor moves in response to movements at a control handle. Additionally, force sensors  248 ,  250  may be attached at the ends of the leaf  248 . As such, a force feedback system may be incorporated to sense the amount of force necessary to actuate the tool  214  at the tool end  210  of the instrument  202 . Alternatively, the motor  244  may have a force feedback device  252  attached thereto, which can be used in a similar fashion. 
     One advantage of utilizing the back loading tool driver  200  is that the sheath  204  always remains in the patient  12 . As such, the tools do not have to be realigned, nor does the robotic arm assembly  26  when replacing or exchanging tools. The sheath  204  retains its position relative to the patient  12  whether or not a toll is placed therethrough. 
     The system  10  of the present invention may additionally be supplied with one or two additional degrees of freedom at the tip of an instrument. For the purposes of example, two additional degrees of freedom will be disclosed; however it is to be appreciated that only one degree of freedom may be included as well. To provide the additional degrees of freedom, and as depicted in FIGS. 13-16, an articulable surgical instrument  300  may be incorporated into the present. The instrument  300  may be coupled to the arm assembly  26  via a collar and holder as disclosed hereinabove. In order to articulate the tip of the articulable instrument  300  an articulating tool driver  500  must be employed. The articulating tool driver  500  shall be described in more detail hereinbelow. The master must have an additional two degrees of freedom added thereto to proved the controls for the articulation at the tip of the instrument  300 . FIG. 25 depicts an alternative master schematic that includes the two additional degrees of freedom. As disclosed hereinbelow, the two additional degrees of freedom are mapped to the articulable portion of the instrument  300 . The two additional axes at the master are referred to as Jm 6  and Jm 7 . 
     By incorporating the articulable instrument  300  and the articulating tool driver  500  and the additional degrees of freedom at the master, difficult maneuvers may be carried out in an easier fashion. 
     With reference to FIGS. 13-16, the articulable instrument  300  generally includes an elongated rod  302 , a sheath  304 , and a tool  306 . The tool can be a grasper, a cutting blade, a retractor, a stitching device, or some other well-known tool used in minimally invasive surgical procedures. FIGS. 27-30 show various tools that may be emplaced at the distal end of the articulable surgical instrument  300 . 
     The instrument  300  includes an articulable portion  301  having a proximal portion  308 , a pivot linkage  310  and a distal portion  212  each of which will be discussed in more detail hereinbelow. Additionally, the instrument  300  includes means  311  for articulating the articulable portion  301  of the instrument  300  with respect to the elongated rod  302 . The inclusion of the articulable portion  301  provides two additional degrees of freedom at the instrument tip. It must also be appreciated that although the articulable portion  301  is described as including a proximal portion, a pivot linkage and a distal portion, there may be provided a plurality of intermediate portions each mounted to each other via a corresponding pivot linkage. 
     Disposed between and mounted to each of the respective proximal portion and distal portion and any intervening intermediate portions are pivot linkages  310 . The pivot linkage  310  interengages with the proximal and distal portions of the articulable portion to provide articulation at the instrument tip. Essentially, the cooperation of the proximal portion, pivot linkage and distal portion serves as a universal joint. 
     The elongated rod  302  is preferably hollow and formed of stainless steel or plastic or some other well-know material that is steralizable. Because the rod  302  is hollow, it encompasses and defines an interior  314 . The elongated rod  302  additionally has a proximal end  316  and a distal end  318 . The distal end  318  of the elongated rod  302  should not be confused with the distal portion  312  of the articulable portion  301  of the instrument  300 . 
     The proximal portion  308  of the articulable portion  301  may be integrally formed with the elongated rod  302  or it may be attached thereto vie welding, glue or some other means well-known to the skilled artisan. It is preferable that the proximal portion  308  be integrally formed with the elongated rod  302  to ensure sufficient stability and durability of the instrument  300 . The proximal portion  308  of the articulable portion  301  comprises two fingers  320 ,  322  each of which have an aperture  324 ,  326  formed therethrough. 
     A pivot linkage  310  is mounted to the proximal portion  308  via a plurality of pins  328  that each pass through an associated aperture in an adjoining finger. The pivot linkage  310  is a generally flat disk  330  having a central aperture  332  passing therethrough and four apertures  334 ,  336 ,  338 ,  340  evenly spaced at the periphery of the disk  330 . Additionally pins  328  are attached to and extend from the edge  342 . The pins  328  seat in the apertures of the associated fingers to provide the articulability of the instrument  300 . Five leads  350 ,  352 ,  354 ,  356 ,  358  extend interiorly the hollow shaft. On lead  350  extends down the center and passes through the center aperture  332  in the pivot linkage  310 . Two  352 ,  354  of the five leads extend down the hollow interior of the instrument and are attached to the pivot linkage such that linear tension on one of the leads results in rotational movement of the pivot portion  301 . These two leads  352 ,  354  attach to the pivot linkage at two of the apertures formed therethrough. Additionally, they attach at those apertures that are adjacent to the pins that pass through the fingers of the proximal portion  308  of the articulable portion  301  of the instrument  300 . The other two leads  356 ,  358  pass through the two other apertures in the pivot linkage and attach at the distal end of the articulable portion  301 . Movement of these two leads results in movement of the articulable portion  301  that is orthogonal to the movement when the two other leads  352 ,  354  are moved. 
     To articulate the instrument as a part of the present system, and as depicted in FIGS. 17-24, there is provided an articulating mechanism  400 . The articulating mechanism  400  generally comprises the articulating tool driver  500 , a sterile coupler  600 , a translator  700  and the articulable tool  300 . 
     The translator is attached to the proximal end  316  of the instrument  300 . The instrument  300  may additionally have a removable tool  420  as shown in FIGS. 18-19. The removable tool  420  may be any tool, such as a cutter  422  that is attached to an elongated rod or cable  424 . At the end of the rod  246  there is disposed a flat section  428  with an aperture  430  formed therethrough. The flat section  428  seats into a channel  432  disposed at the end of a second cable or rod  434  that travels down the elongated shaft of the instrument  300 . The second cable  434  has a channel  432  formed in the end thereof such that the flat section  428  seats in the channel  432 . At least one spring biased detent  436  seats in the aperture  430  disposed through the flat section  428 . This connects the tool  420  to the rest of the instrument  300 . As such, tools may be exchanged at the tip of the instrument without having to remove the instrument from the system  10  every time a new tool is required. 
     The tool  300  is attached to the translator  700  and essentially is integrally formed therewith. The articulating mechanism  400  is attached to the robotic arm assembly  26  via the collar  85  as is disclosed hereinabove. The collar  85  fits about the shaft  302  of the instrument  300 . 
     The translator  700  has a proximal end  702  and a distal end  704 . The distal end  704  of the translator  700  has a cross sectional shape that is substantially similar to the cross sectional shape of the elongated rod  302  of the instrument  300 . Additionally, the translator  700  has a hollow interior  706 . The center rod  350  extends through the hollow interior  706  of the translator  700  and emerges at the proximal end  702  thereof. Two of the leads  352 ,  354  terminate interiorly the translator at two shoulders  708 ,  710  that are attached to a first hollow tube  712  through which the center lead  350  extends. The first hollow tube  712  may be formed of some strong durable material such as stainless steel, steel, hard plastic or the like. 
     The first hollow tube  712  is mounted to a bearing  714  such that it may be rotated. Rotation of the first hollow tube  712  results in the linear motion of the leads  352 ,  254  and the articulation of the articulable portion  301  of the instrument  300  in one plane of motion. 
     A second hollow tube  716  has a pair of shoulders  718 ,  719  extending therefrom. Two leads  356 ,  358  attach to one each of the shoulders  718 ,  719 . The hollow tube  716  is disposed within a bearing assembly  720  such that it may be rotated. Again, rotation of the second hollow tube  716  results in linear movement of the leads  356 ,  358  which articulates the articulable portion  301  of the instrument  300  in a plane orthogonal the plane of motion established through the rotation of the first hollow tube. It is to be appreciated that the second hollow tube  714  radially surrounds the first hollow tube  712 . The translator  700  additionally includes a quick disconnect  722  comprising a pin  724  disposed at the end of a spring biased lever  726  which provides removable attachment of the translator  700  to the sterile coupler  600 . Both of the hollow tubes  712  and  716  may have notches  750  formed therein at their ends. The notches serve as a means  752  for interconnecting each of the tubes to the sterile coupler  600  which will be discussed in further detail hereinbelow. 
     The translator  700  is removably attached to the sterile coupler  600  via the quick disconnect  722 . Because the articulable tool driver  500  is not easily sterilized, it is advantageous to include a sterile coupler  600  so that instruments may be exchanged without having to sterilize the articulable tool driver  500 . Additionally, the coupler  600  provides a means by which the translator  700  may be attached to the tool driver  500  while the tool driver is enclosed in a drape  125  such as that depicted in FIG.  26 . The translator  600  has a housing  610 . Preferably the housing and the components of the coupler  600  are formed of some easily steralizable mater such as stainless steel, plastics or other well-known sterilizable materials. The housing  610  has a substantially hollow interior  612  and open ends  614  and  616 . Two hollow tubes  618  and  620  are rotatively disposed within the housing  610 . To effectuate the rotation of each of the tubes  618  and  620 , bearings  622  and  624  are disposed about each of the tubes. Each of the tubes has notches  626  formed in the ends thereof so effectuate the attachment of the translator  700  to the coupler  600  at one end. And to effectuate the attachment of the coupler  600  to the articulable tool driver  500  at the other end thereof. 
     The pin  724  on the translator may seat in a notch  628  to attach the translator  700  to the coupler  600 . Additionally, the coupler  600  may include a pin  630  attached to a spring biased pivot  632  to effectuate attachment of the coupler to the driver  500 . The coupler  600  additionally includes a center section  634  that slidably receives the end  351  of the center cable or rod  350 . The end  351  may include a tip with a circumferential groove  353  disposed thereabout. The tip seats in a recess  636  formed in the center section  634  and is removably locked in place by at least one spring biased detent  638 . A tip  640 , which is substantially similar to the tip containing the circumferential groove  353  is disposed adjacent the recess  636  and serves to attach the cable center cable  350  to the articulable tool driver  500 , which will be discussed in further detail hereinbelow. 
     The center section  634  is intended to laterally slide within the innermost tube  618 . To effectuate such a sliding motion, a linear bearing may be disposed about the center section interiorly of the innermost tube. Alternatively, the center section  634  may be formed of a bearing material that provides smooth sliding within the innermost tube  618 . 
     The coupler  600  is removably attached to the articulable tool driver  500 . It is intended that the articulable tool driver be enclosed by a drape  125 . The articulable tool driver  500  includes a substantially hollow housing  502  having a closed first end  504  and a substantially open second end  504 . Securely disposed interiorly the housing  502  is a gripper motor  506 , and a pair of wrist motors  508  and  510 . Each of the motors are in electrical connection with the controller  46 . Alternatively, the motors may receive signals from the controller via a transmitter/receiver system where such systems are well known. It is the application of such a transmitter/receiver system to the present invention that is new. The gripper motor  506  is attached to a load nut  510  that surrounds a load screw  512 . The motor  506  receives the control signals and turns in response thereto. The load nut  510  turns which laterally moves the load screw  512 . The load screw  512  is attached to a load cell  514  which may be employed to measure the force required to laterally move the cable  350  which is attached vie the coupler  600  to the gripper motor  506 . This may be used in a force feedback system that may be incorporated in the system  10  of the present invention. A rod  516  having a channel  518  formed at the end thereof is attached to the load cell  514 . As such, the rod  516  moves in a linear fashion. The tip  640  of the coupler  600  seats in the channel  518  and is removably held in place by at least one spring biased detent or some other similar attachment mechanism  520 . Therefore, if a surgeon at a master handle actuates the grippers, the gripper motor  506  turns, thus laterally moving the rod  516 , and in turn the center cable  350  which opens and closes the grippers at the tool accordingly. Of course, the action at the tool will depend upon the type of tool disposed thereat. For example, if a stapling tool is disposed at the end of the surgical instrument  300  then a stapling action would take place. 
     If a master handle  50  or  52  is turned about axes J 6  or J 7  then one of the two wrist motors  510 ,  508  corresponding to the required motion turns. Each of the motors  508 ,  510  are attached to a corresponding gear  522 ,  524 . Each of the gears  522 ,  524  engage a corresponding slotted section  530 ,  532  of an associated hollow tube  526 ,  528  to turn the associated tube radially about its longitudinal axis. Each of the tubes  526 ,  528  include notched ends  534 ,  536  to engage the notched ends of corresponding hollow tubes of the coupler  600 . It is to be appreciated that each of the hollow tubes  526 ,  528 ,  618  and  620  are all coaxial. Additionally, bearings may be emplaced intermediate each of the tubes  526  and  528  to provide easy independent rotatability of the individual tubes. 
     When the tubes  526 ,  528  are rotated, they rotate the tubes in the coupler which rotates the tubes in the translator. This results in the articulation at the tip of the surgical instrument  300 . More particularly, this results in the articulation of the articulable portion of the surgical instrument  300 . Additionally, whether the front loading tool driver, the back loading tool driver, or the articulable tool driver are employed, surgical instruments may be easily exchanged. 
     As such, a cutting blade  800  may be exchanged for a grasper, and a grasper may be exchanged for a stapler  810 . Essentially, such a system simplifies the performance of minimally invasive surgical procedures where the procedures include the step of changing one tool for another. And because the system allows articulation at the tip of certain instruments, the articulation mechanism may be used to articulate such stapling, or cutting instruments that incorporate the articulable portion as disclosed hereinabove. 
     Additionally, the instrument may not be an articulable instrument, but the articulating mechanism can be used to control other functions, such as stapling. FIG. 27 depicts a stapling instrument  810  attached to the robotic arm assembly via the collar  85  and holder  86 . The lead that is generally use for the grasping tool, may be used to effectuate the stapling mechanism. Endoscopic staplers are generally well known in the art, however, it is heretofore to known to use a stapler that is attached to a robotic arm as is disclosed herein. 
     Additionally, a cutting blade, such as that depicted in FIG. 28 may be employed in the system of the present invention. The cutting blade  800  is attached to the robotic arm assembly  26  via the collar  85  and holder  86 . The cutting blade does not require a lead such as that required by the grasper or the stapler; however, the cutting tool, may be articulated via the articulating mechanism that has been disclosed hereinabove. 
     A cauterizer or coagulator may additionally be attached to the robotic arm assembly  26  via the collar  85  and holder. Cauterizers and coagulators are well known and the cauterizing tool may be attached at the end of an articulable instrument as disclosed hereinabove. By using a variety of tools in predetermined sequences, various procedures may be carried out. It is generally preferable to be able to change instruments because many procedures require such. 
     As disclosed hereinabove, the handles  50  and  52  allow a surgeon to control the movement of the tools attached to the robotic arms. As such, the configuration of the handles  50  and  52  should provide great ease of use for a surgeon. FIGS. 34-39 depict various handle configurations. Additionally, the handles  50  and  52  may be selected by a surgeon from a plurality of handles  960  that are available for use by the surgeon. 
     A proximally open handle  962  has a proximal end  963  and a distal end  965 . The handle  962  has first finger portion  964  and a second finger portion  966  pivotally attached at the distal end  965  of the handle  962 . A joint  968  disposed intermediate the finger portion  964  and  966  provides linear motion of an elongated rod  970  which is used to actuate the tool tip of an instrument attached to the robotic arm. This handle may serve as one or both of the two handles  50  and  52  of the system. 
     A distally open handle  972  has a proximal end  973  and a distal end  975 . The handle  972  has first finger portion  974  and a second finger portion  976  pivotally attached at the proximal end  973  of the handle  972 . A joint  978  disposed intermediate the finger portion  964  and  966  provides linear motion of an elongated rod  980  which is used to actuate the tool tip of an instrument attached to the robotic arm. This handle may serve as one or both of the two handles  50  and  52  of the system. 
     Such handles  962  and  972  may be interchanged through the inclusion of an interchange mechanism  984 . The interchange mechanism  984  includes a biased detent latch  986  that engages an aperture in the elongated rod  932  such that the handle may be attached or removed from the rod  932 . 
     Other handle configurations are depicted in FIGS. 37-39. And more particularly, each of the handles  1000 ,  1100 , and  1200  have a pair of fingerseats  1020 . The major difference between each of the handles  1000 ,  1100 , and  1200  is the orientation of the fingerseats to a pivot point on the handle. The fingerseats may be parallel, or perpendicular to the axis S of the pivot point of the handle. Each of these configurations may be included as an attachable handle. As such, a surgeon may exchange handles throughout a procedure depending upon the task to be accomplished. A surgeon may prefer one handle for a set of tasks and another handle for a different set of tasks. As such, the surgeon may exchange handles during the performance of a surgical procedure to enable such tasks. 
     While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.