Abstract:
A user interface device for a surgical simulation system, comprising a rigid shaft pivotably supported by a frame, and movable in the axial direction but fixed with respect to rotation around its longitudinal axis, and a handle having a sensor body rigidly attached to said rigid shaft, and a grip portion rotatable around said longitudinal axis relative said sensor body. The handle further comprises a rotator sleeve rotatable around said longitudinal axis relative said sensor body and said grip portion, a rotation sensor adapted to detect rotation of said rotator sleeve in relation to said sensor body, and a signal interface mounted on said sensor body and connected to receive a first detection signal from said rotation sensor. Through this design, all sensor elements and electronic circuitry can be provided in or adjacent to the sensor body, leading to an efficient design and manufacturing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 National Phase of PCT/EP2013/075000, filed on Nov. 28, 2013, which claims the benefit and priority of European Patent Application EP 12195067.9, filed on Nov. 30, 2012. The entire disclosures of each of the above applications are incorporated herein by reference. 
     FIELD 
     The present disclosure relates to a haptic user interface device for a surgical simulation system, and in particular a user interface device for simulating a laparoscopic procedure. 
     BACKGROUND 
     In recent years, systems for surgical simulations have become increasingly more used, in order to train physicians various surgical procedures without putting live patients at risk. In particular in the field of minimally-invasive surgery, such as laparoscopy, endoscopy, colonoscopy, etc., such simulation systems have gained significant acceptance. During minimal-invasive surgery the physician typically relies on an image on a screen rather than on an actual view of the patient, and with powerful image rendering available today, such an image can be simulated with a very high degree of realism. 
     In order to interact with the simulation software, the simulation system further requires an input device, i.e. hardware which the physician may operate and which simulates an actual surgical instrument. Such input devices should in physical appearance and function resemble an actual instrument. However, they must also provide sensor for detecting the current position of the simulated instrument, thereby enabling the simulation software to provide an appropriate image on the screen. In addition, such devices preferably include haptic feedback, i.e. provide feedback of forces that would be encountered during an actual procedure. 
     In the case of laparoscopy, an example of an input device is the Virtual Laparoscopic Interface (VLI) from Immersion Corp. This device includes a rigid shaft, corresponding to the instrument portion to be inserted into a patient, and a handle, with which the physician can move the instrument. In order to simulate the degrees of freedom of an actual instrument, which passes into a patient body through a small opening, the shaft is supported by a frame in a pivoting point with two degrees of freedom (rotation α, β). In addition, the shaft can be translated in linear motion along its longitudinal axis, i.e. in and out of a simulated body, as well as rotated around this longitudinal axis. The handle further includes a grip portion, allowing the physician to operate a simulated surgical tool at the tip of the instrument. The input device contains sensors for all degrees of freedom including rotation of the shaft. Most sensors are provided in vicinity of the pivoting point, except the sensor of grip action, which is detected in the handle and provided through a separate signal interface on the handle. This signal interface is thus movable in relation to the frame, and connected to the frame with a cord. Just as in an actual instrument, the grip portion may further be rotated in relation to the rest of the handle, corresponding to an adjustment of the grip in relation to the working position. Such adjustment is not detected by sensors, and does not result in any force feedback. 
     Another example from Immersion Corp. is the Laparoscopic Surgical Workstation, (LSW). Just as in the VLI, the shaft will rotate when the handle is rotated, requiring detection of rotation in the pivoting point. However, in this case it is the grip portion that is fixedly attached to the shaft. In order to enable adjustment of the grip position, a rotatable sleeve is arranged in front of the grip portion, and rotation of this sleeve relative the handle is detected separately. Moving the grip (and the entire handle) in relation to the sleeve will thus rotate the shaft, but the relative rotation between grip and sleeve will be detected, so that the simulation software can interpret this as a grip adjustment rather than actual instrument rotation. Grip action is detected in the grip portion similar to the VLI. The LSW is a haptic device, i.e. it has actuators arranged to provide force feedback in all degrees of freedom. In terms of force feedback, rotating only the sleeve (which does not rotate the shaft) and rotating the entire handle (including the sleeve and the shaft) will result in the same force feedback. 
     Yet another example is the Laparoscopic Impulse Engine (LIE), also from Immersion Corp. In this example, the shaft has a rotationally fixed exterior tube which does not rotate. Instead, the handle rotates in relation to the tube, and this motion is transferred by an axle extending inside the tube to the distal end of the shaft, where it is detected by a rotation encoder. Detection of grip action is done similar to the LSW mentioned above, by a sensor provided on the upper side of the grip portion. The LIE therefore also requires two signal interfaces on the moving parts of the device, one in the distal end of the shaft, and one on the grip portion. Each of these interfaces needs to be connected to the frame with a cord. 
     A relevant patent documents in this context are U.S. Pat. No. 6,323,837 and U.S. Pat. No. 6,902,405. 
     Despite the many user interfaces that are already available, these solutions are mechanically and electrically complex, typically with electric circuitry distributed between several locations. Also, they fail to correctly mimic an actual surgical instrument, such as a laparoscope, due to multiple cables connected to the device, and in some cases cables connected to the grip portion. 
     SUMMARY 
     It is an object of the present disclosure to address the shortcomings of the prior art, and to provide an improved user interface device which is robust in function and cost effective to manufacture. Another object is to provide a user interface device which in use provides the user with an experience more closely resembling that of an actual surgical instrument. 
     According to the disclosure, these and other objects are achieved with a device comprising a rigid shaft having a primary extension along a longitudinal axis, the rigid shaft being pivotably supported by a frame, and movable in relation to the frame in the axial direction, but being fixed in relation to the frame with respect to rotation around the longitudinal axis, and a handle having a sensor body rigidly attached to the rigid shaft, and a grip portion rotatable around the longitudinal axis relative the sensor body, the grip portion being adapted to transform a gripping motion of a user into a linear displacement. The handle further comprises a rotator sleeve rotatable around the longitudinal axis relative the sensor body and the grip portion, a rotation sensor adapted to detect rotation of the rotator sleeve in relation to the sensor body, and a signal interface mounted on the sensor body and connected to receive a first detection signal from the rotation sensor. 
     Features of this design are 1) a shaft which is fixed with respect to rotation around its longitudinal axis, and 2) a handle which has a sensor body which is fixedly attached to the shaft, and a rotator sleeve which is rotatable relative to the sensor body. The combination of these features has not been previously disclosed, and provides several advantages compared to prior art user interface devices. 
     To begin with, all sensor elements and electronic circuitry can be provided in or adjacent to the sensor body, leading to an efficient design and manufacturing. Further, the signal interface, which also is provided on the sensor body, will be subject to translational movement, but not to any rotational movement around the longitudinal axis of the shaft. This reduces the amount of shear stress and wear on any cables or wiring connected to the signal interface, improving lifetime of the user interface device. 
     According to an embodiment, the handle further comprises a linear sensor mounted in the sensor body, and a displacement transfer arrangement for transferring any linear displacement generated in the grip portion to the linear sensor, wherein the signal interface is connected to receive a second detection signal from the linear sensor. 
     According to this embodiment, also grip action can be detected in the sensor body, so that no sensor circuitry is required in the grip portion. The grip portion can thus be a purely mechanical device, facilitating manufacture of the handle. 
     Further, as only one single signal interface is required (from the sensor body), only one cable or wire is required. In particular, the grip portion is completely free from cables or wiring. 
     In embodiments, the user interface device is arranged to provide haptic feedback to a user. For this purpose, a plurality of actuators may be mounted on the frame to provide force feedback when the shaft and handle are rotated or translated relative the frame. Typically, force feedback is provided in at least one linear and two rotational degrees of freedom. 
     Further, an actuator arranged to provide force feedback around a first axis (B) can advantageously be mounted on a part of the frame that rotates with said handle around a second axis (A). This means that a force transfer means, such as a drive belt or wire, extending between the actuator and the first axis will run in a fixed path, i.e. will not be subject to torsion or twist. This arrangement of force feedback actuators on the frame of a user interface device for a surgical simulation is considered to be novel and inventive per se, also without limitation to the features of the first teaching of the present disclosure. 
     The rigid shaft may have a rack on one side, which rack engages a gear wheel on said frame, thereby transforming a linear motion of the shaft into a rotation of the gear wheel. This design can be an effective way to enable detection of the shaft position, as well as force feedback by an actuator connected to the gear wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be described in more detail with reference to the appended drawings, showing current embodiments of the disclosure. 
         FIG. 1  is a schematic view of a surgical simulation system with a user interface device according to an embodiment of the disclosure. 
         FIG. 2  is a schematic view of a surgical simulation system with a user interface device according to a further embodiment of the disclosure. 
         FIG. 3  is a side view of the handle in  FIG. 1 . 
         FIG. 4  is a side view of a handle in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a user interface device  1  according to an embodiment of the present disclosure, schematically connected as part of a simulation system  2 . 
     The simulation system  2  comprises a processing unit  3  running simulation software for simulating a surgical procedure, and a display  4  for displaying a visualization of the simulated procedure to a user. The interface device  1  is connected to the simulation system, and allows a user to provide input to the system  2 , thereby interacting with the simulation visualized in the display device. The interface illustrated here is a haptic rig, i.e. it is adapted to provide a user with force feedback from the simulation in at least some of the degrees of freedom of the interface. It is noted that the disclosure is not limited to a haptic interface, but is also applicable to a non-haptic interface. 
     The user interface device  1 , comprises a movable instrument  10  pivotably suspended by a frame  11 . The frame  11  allows rotation of the instrument  10  around a first axis A and a second axis B, typically orthogonal to the first axis A. 
       FIG. 2  very schematically shows some parts of the user interface device  1  in  FIG. 1 , in order to illustrate the various degrees of freedom in the frame  11 . Note that the handle  120  in  FIG. 2  is different from the handle  20  in  FIG. 1 . 
     In the illustrated embodiments, rotation around the first axis A is provided close to the stationary base  12  of the frame, by a disc  13  rotatably mounted to the base  12 . A first actuator, such as a electric motor  14 , is also mounted to the base  12 , and arranged to transfer a torque to the disc  13 . As illustrated schematically in  FIG. 2 , this can be accomplished by a driving belt  7  arranged around the disc  13  and the motor axle. By operation of the motor  14 , force feedback can be provided in movement around the axis A. A rotation sensor (not shown) is provided to detect the position of the disc  13  in relation to the base  12 . The sensor may advantageously be a rotational encoder integrated in the motor  14 , and arranged to detect rotation of the motor axis. 
     Rotation around the second axis B is provided in a distal end  15   a  of the neck  15  of the frame  11 . The neck  15  and its distal end  15   a  are fixedly mounted on the disc  13 , and will thus rotate with the disc when the frame is rotated around the axis A. A suspension portion  16  is mounted on the distal end  15   a  so as to be rotatable around axis B. The suspension portion  16  is arranged to suspend the handle  10 , and the details of this suspension will be discussed below. A second electric motor  17  is mounted on the neck  15 , and is arranged to transfer a torque to the suspension portion  16 . As illustrated schematically in  FIG. 2 , this can be accomplished by a driving belt  8  arranged around the portion  16  and the motor axle. By operation of the motor  17 , force feedback can be provided in movement around the axis B. A rotation sensor (not shown) is provided to detect the position of the suspension portion  16  in relation to the distal end  15   a  of the neck  15 . The sensor may advantageously be a rotational encoder integrated in the motor  17 , and arranged to detect rotation of the motor axis. 
     Primarily with reference to  FIG. 2 , it is noted that the motor  17  is mounted on the neck  15 , and thus will rotate together with the neck  15  and the suspension portion  16  around the axis A. The path of the drive belt  8  or drive wire loop extending between the axle of the motor  17  and the suspension portion  16  will thus be fixed in space, and will not be subject to any twist or torsion. This extends the life time of the belt  8  or wire. 
     It is noted that in the case of a non-haptic interface, in which case there are no actuators, sensors for detection of rotation around axis A and B is probably better provided directly on the axis A, B, e.g. on the disc  13  and the distal end  15   a.    
     Turning now to the instrument  10 , it comprises a handle  20  attached to the end of a rigid shaft  21 . The handle  20  has a sensor body  22 , fixedly connected to the shaft  21 , and a rotator sleeve  23  and a grip portion  24  which are both rotatable around the longitudinal axis C of the shaft  21 . 
     Just as in an actual instrument, rotation of the sleeve  23  represents rotation of the instrument. Any rotation of the rotator sleeve  23  in relation to the sensor body will thus be detected by a sensor in the sensor body  22 . The grip  24  and rotator sleeve  23  are coupled by a certain friction so that they are normally rotated together. However, a user may overcome the friction, to rotate the sleeve  23  and the grip  24  in relation to each other. Rotation of the grip  24  while the sleeve  23  is held fix merely represents an adjustment of the grip in relation to the instrument, and will not influence the simulated procedure. Rotation of the sleeve  23  in relation to the sensor body while the grip  24  is held fix, will however represent rotation of the instrument and will accordingly be detected by the sensor body. 
     The grip portion  24  allows the user to perform a gripping action using a scissor-like grip  25 , and this action will also be detected by a sensor in the sensor body  22 . A signal line  26  connects the sensor body  22  with the frame  11 , in the illustrated example with the distal end  15   a  of the neck  15 . The signal line  26  enables communication of sensor signals from the sensor body  22 . The signal line is flexible, so as to allow movement of the instrument  10  in relation to the frame  11 . 
     In the illustrated embodiment, the interface device  1  is not adapted to provide any force feedback associated with rotation of the instrument around axis C. It is noted that there are typically very limited forces acting on an actual instrument in this degree of freedom when operated inside a body. However, if such feedback is nevertheless desired, it may be accomplished by coupling a force to the rotation of the sleeve  23  relative the sensor body. As a simple example, a passive variable brake can be provided to the sleeve  23 . Such a brake would introduce a resistance to turning the sleeve, and this resistance can be variable depending on the simulation. Of course, also active force feedback can be envisaged with a suitable actuator, such as an electric motor. It is however important that such actuator, if mounted on the handle, is not too heavy or bulky, as it could otherwise impact negatively on the user experience. 
     The rigid shaft  21  is mounted to the suspension portion  16  of the frame  11  so as to be movable along the longitudinal axis C. A third electric motor  27  is mounted to the suspension portion  16  to transfer a force along the axis C to the shaft  21 . By operation of the motor  27 , force feedback can thus be provided along the axis C. A sensor (not shown) is provided in the suspension portion  16  to detect linear motion of the shaft in relation to the portion  16 . In the illustrated example, the shaft  21  is provided on one side with a rack  28  which engages a gearwheel  29  on the end of a motor shaft. Any linear motion of the shaft  21  will thus effectively be converted into rotational motion, to which a torque can be applied by the motor  27 . Detection of the linear motion is also facilitated, and the sensor may be a rotational encoder integrated in the motor  17 , and arranged to detect rotation of the motor axis 
     The base  12  of the frame  11  is mounted to a control unit  30 , which includes drive circuitry  31  and communication interface  32 , typically mounted on a printed circuit board  33 . The control unit  30  can be incorporated in a working table (not shown). The interface  32  is connected to receive sensor signals from the various sensors in handle  10  and frame  11 , and to communicate these signals to the simulation system  2 . The interface  32  is further connected to receive force feedback signals from the simulation system  2 , i.e. forces acting on the simulated instrument as a result of user actions. The drive circuitry  31  is connected to the interface  32 , and arranged to drive the motors  14 ,  17  and  27  based on the force feedback signals from the simulation system. The interface  32  is here connected to the simulation system via a signal line  34  connecting a terminal  35  of the control unit  30  with the processing unit  3  of the simulation system. The connection may alternatively be wireless, e.g. Bluetooth or WiFi. 
     Details of the operation of the various parts of the handle, and in particular the sensor body, will now be discussed with reference to  FIGS. 3 and 4  showing two different handles according to embodiments of the present disclosure. 
       FIG. 3  shows the handle in  FIG. 1  in more detail. Reference numeral  40  denotes a rotation encoder, such as an optic or magnetic encoder mounted in the sensor body  22 . The encoder  40  has a house  41 , and a central pin  43  extending out of the house. Rotation of the pin  43  in relation to the house  41  can be detected, and results in a sensor signal indicative of the rotation. The encoder  40  is here in electric contact with circuitry on a printed circuit board  44 , from which the sensor signal can be outputted via a terminal  45 . The pin  43  of the encoder  40  is rotationally coupled to the rotator sleeve  23 , which is rotatably connected to the sensor body  22 . Rotation of the sleeve  23  will thus rotate the pin  43 , and generate a sensor signal available at the terminal  45 . 
     The grip portion  24  comprises a mechanical arrangement to generate a linear motion in response to action of the scissors-like grip  25 . In the illustrated example, the rear part of the grip  25   a  is pivotable and connected to displace an elongate member  48  along the axis C. This linear motion is transferred by a motion transfer arrangement to a linear sensor  46  in the sensor body  22  in electric contact with circuitry on the circuit board  44 . The linear sensor here includes a sliding potentiometer  47 , the resistance of which is converted into a sensor signal indicative of a displacement of the potentiometer. Activation of the grip  25  will thus generate a sensor signal available at the terminal  45 . 
     The motion transfer arrangement will be described in the following. The member  48  extends into the rotator sleeve  23 , where it is mechanically connected to a disc  49  which is slidable inside the rotator sleeve  23  along the C-axis (see  FIG. 1 ). The front end  48   a  of the member  48  is connected to the disc  49  in such a way that forces along the C-axis are transferred between the member  48  and the disc  49 , while rotational forces around the C-axis are not transferred between the member  48  and the disc  49 . As an example of such a coupling, the member  48  is illustrated as having a magnet  50  in its front end  48   a , which magnet  50  is attracted to the central part of the disc  49 . A second elongate member  51  has one end  51   a  mechanically connected to the slidable potentiometer  47 , and another end  51   b  connected to the disc  49 . Similar to the end  48   a  of the elongate member  48 , the end  51   b  is connected to the disc  49  in such a way that forces along the C-axis are transferred between the member  51  and the disc  49 , while other forces are not transferred between the member  48  and the disc  49 . As an example of such a coupling, the member  51  is illustrated as having a magnet  52  in its end  51   b , which magnet  52  is attracted to the peripheral part of the disc  49 . 
     The motion transfer arrangement  48 ,  49 ,  50 ,  51 ,  52  operates in the following way. When the grip  25  is activated, the elongate member  48  is displaced along the C-axis. This displacement is transferred to the disc  49 , so that the disc  49  is displaced along the C-axis inside the rotator sleeve  23 . The displacement of the disc  49  is further transferred to the member  51 , which displaces the slide potentiometer  47  of the sensor  46 . When the linear displacement is towards the shaft  21 , the member  48  will simply abut against and push the disc  49 , which will abut against and push the member  51 , so that motion will be transferred by direct contact. When the linear displacement is away from the shaft  21 , the magnet  50  will attract the disc  49 , which will attract the magnet  52 , so that motion will be transferred by magnetic contact. When the grip portion  24  is rotated in relation to the sleeve  23 , the elongate member  48  will also rotate, but this rotation will not cause any (substantial) forces on the disc  49 . In the illustrated example, the magnet  50  will simply slip against the surface of the disc  49 . In a similar way, when the rotator sleeve  23  is rotated in relation to the sensor body  22 , the disc  49  will slide against the elongate member  51 , without transferring any (substantial) force. 
       FIG. 4  shows a handle  120  according to a further embodiment of the disclosure. Similar to the handle  20  in  FIG. 3 , the handle  120  comprises a sensor body  122  fixedly connected to the shaft  121 , and a rotator sleeve  123  and a grip portion  124 , both rotatable around the longitudinal axis C of the shaft  121 . Compared to the embodiment in  FIG. 3 , the rotator sleeve  123  is more elongated, and extends outside the sensor body  122  so as to cover most of the sensor body. 
     Also in this embodiment, the sensor body  122  houses a rotation encoder  140  to detect rotation of the rotator sleeve  123  relative the sensor body. The encoder is here an optical encoder, and the sensor optics of the encoder  140  includes a light transceiver  141  arranged on the sensor body side, and a reflector disc  143  arranged on the sleeve side. Rotation of the reflector disc  143  can be detected and results in a sensor signal indicative of the rotation. The encoder  140  is here in electric contact with circuitry on a printed circuit board  144 , from which the sensor signal can be outputted via a terminal  145 . The disc  143  is fixed to the sleeve  123 , so that rotation of the sleeve  123  will generate a sensor signal which is available at the terminal  145 . 
     The grip portion  124  is similar to the grip portion  24  in  FIG. 3 , and has a scissor-like grip  125  which can be operated by a user to generate a linear motion. Also here, the rear part of the grip  125   a  is pivotable and connected to displace an elongate member  148  along the axis C. This linear motion is transferred by a motion transfer arrangement to a linear sensor  146  in the sensor body  122  in electric contact with circuitry on the circuit board  144 . Also in this case the linear sensor includes a sliding potentiometer  147 , the resistance of which is converted into a sensor signal indicative of a displacement of the potentiometer. Activation of the grip  125  will thus generate a sensor signal available at the terminal  145 . 
     The motion transfer arrangement in the embodiment in  FIG. 4  is different from the arrangement in  FIG. 3 . In addition to the elongate member  148 , the arrangement here comprises a second elongate member  149 , aligned with the first elongate member  148  along the central axis C of the handle. The second elongate member  149  is coupled to the slide potentiometer  147 , and extends through a hole in the center of optical encoder (i.e. the transceiver  141  and the reflector disc  143 ). The members  148  and  149  are mechanically connected such that forces along the C-axis are transferred between the members, while rotational torque is not transferred (to any significant degree). In the illustrated example, a magnet  150  is arranged on the end of member  148 , and is attracted to member  149 . The magnet  150  will connect the members  148 ,  149  in the axial direction, while it will slip against the member  149  when the members  148 ,  149  are rotated relative each other. 
     The person skilled in the art realizes that the present disclosure by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, other types of sensors and encoders may be used, for detection of rotation as well as translation. For example, hall effect sensors or piezoelectric sensors. Further, the torque transmission from motors  14  and  17  may comprise suitable gear transmission instead of belt drive.