Surgical Robot System

Abstract

The present invention relates to a surgical robotic system comprising a robotic arm (1) holding an end effector (11) and a control unit (13) configured to controllably move the robotic arm and maintain the end effector (11) in at least one target position relative to a patient, The control unit (i) activating a hand-guided mode in which the robot arm is freely movable by a user based on a first input continuously provided to the robot arm by a user; (ii) activating a calculated trajectory mode in which the robot arm moves to a target position according to a calculated trajectory based on a second input, different from the first input, continuously provided by a user to the robot arm (1); (iii) A surgical robot system configured to, when the calculated trajectory mode is activated, detect that the end effector (11) meets at least one predetermined safety condition, and automatically switch to a servo control mode in which the robot arm (1) is automatically movable to maintain the end effector (11) at the target position relative to a tracker attached to a patient.

Description

[Technical field]

[0001] The present invention relates to a surgical robotic system comprising a robotic arm holding an end effector and a control unit configured to controllably move the robotic arm and maintain the end effector at at least one target position relative to a patient. [Background technology]

[0002] Surgical robotic arms have been used to assist a user (such as a surgeon) during surgical procedures.

[0003] For example, in a spinal surgery, a user may need to implant one or more screws into at least one vertebra. The robotic arm may assist the user by holding a drill guide and maintaining the drill guide according to a planned axis. This allows the user to use a hand-held drill through the drill guide held by the robotic arm to drill holes for inserting the screws into the vertebra along the planned axis.

[0004] However, several challenges must be addressed when using such robotic arms.

[0005] The first challenge is safety, ensuring that the robotic arm does not harm patients or medical staff.

[0006] The second challenge is to define the appropriate collaboration between the user and the robot arm: "Collaboration" means that the robot arm does not replace the human user, but complements their capabilities and helps them focus on a specific task.

[0007] Robotic arms are known that move towards a target position while continuous pressure is applied to a button or pedal. However, such displacements are slow, which has the effect of significantly increasing the operation time. Also, the trajectory of the robotic arm may not take into account all obstacles present in the patient's surroundings. For safety reasons, the robotic arm stops as soon as the user releases the button or pedal.

[0008] On the other hand, because the patient may move during a surgical procedure, for example due to breathing or mechanical responses to the use of surgical instruments to treat the patient, it is desirable for the robotic arm to be able to maintain the end effector in a target position relative to the patient.

[0009] US 2011 / 0190790 teaches a robotic system comprising a robotic arm holding an end effector and a control unit. A safe working area for the robotic arm is defined by virtual walls. The control unit is configured to stop the robotic arm or provide haptic feedback if the robotic arm leaves the working area.

[0010] US 2014 / 0350571 teaches a robotic system that includes a first robotic arm holding an end effector, a second robotic arm holding a sensor that contacts a patient's body, and a control unit configured to adjust a position of the first arm based on a displacement of the patient's body detected by the second arm. Summary of the Invention

[0011] The objective of the present invention is to design a surgical robotic system that can improve the coordination between the user and the robotic arm while ensuring safety.

[0012] To this end, the present invention provides a surgical robotic system comprising a robotic arm holding an end effector and a control unit configured to controllably move said robotic arm and maintain said end effector in at least one target position relative to a patient, said control unit comprising: (i) activating a hand-guided mode in which the robotic arm is freely movable by a user based on a first input continuously provided to the robotic arm by a user; (ii) activating a calculated trajectory mode in which the robot arm moves to a target position according to a calculated trajectory based on a second input, different from the first input, continuously provided to the robot arm by a user; (iii) providing a surgical robotic system configured to detect when the calculated trajectory mode is activated, and automatically switch to a servo-controlled mode in which the robot arm is automatically movable to maintain the end effector at the target position relative to a tracker attached to a patient, upon detecting that the end effector meets at least one predetermined safety condition.

[0013] This allows the robotic system to combine at least three usage modes, namely hand-guided mode, computed trajectory mode, and servo-controlled mode, with the combination of these modes optimizing the coordination between the robotic arm and the user. In the hand-guided mode, the user can freely and quickly move the robotic arm to move the end effector to a rough position close to the target position. In the computed trajectory mode, the robotic arm moves the end effector to the exact target position while being controlled by the user through a second input. In the servo-controlled mode, the robotic arm moves autonomously to keep the end effector at the target position once safety conditions are met. In this way, safety is guaranteed by the user and / or the control unit throughout the operation of the robotic arm.

[0014] In some embodiments, the predetermined safety condition is that a tracker attached to the patient is within a controlled volume relative to a base of the robotic arm, the dimension of the controlled volume being greater in the direction of expected movement of the tracker than in the direction of unexpected movement of the tracker.

[0015] In some embodiments, the target position is selected from among the drilling axis, the drilling axis and depth, the cutting plane, and the optimal working position of an active surgical instrument.

[0016] In some embodiments, the control unit is configured to adjust the calculated trajectory based on a pose of the robot arm imposed by a user in the hand-guided mode.

[0017] In some embodiments, the system comprises a user interface coupled to the control unit and configured to provide information regarding the current mode.

[0018] The user interface may comprise a display monitor disposed on the robotic arm and configured to display graphical items that change depending on the current mode.

[0019] The user interface may include a ring containing a number of LEDs configured to have a predetermined color and / or blinking state depending on the current mode.

[0020] In some embodiments, the control unit is further configured to initiate a safety mode that inhibits movement of the robotic arm based on detection of movement of the robotic arm exceeding a predetermined amplitude, direction, acceleration, and / or velocity in the servo control mode.

[0021] In some embodiments, the control unit is configured to continuously maintain the end effector at a plurality of target positions.

[0022] In some embodiments, the robotic arm comprises a first switch configured for application of the first input by a user and a second switch, distinct from the first switch, configured for application of the second input by a user.

[0023] The control unit may be configured to transition between two successive targets when a user double-clicks the second switch during a surgical procedure.

[0024] In some embodiments, the control unit is configured to place the robotic arm in an idle mode when tracking of the robotic arm is not enabled and the surgical robotic system is in either the hand guided mode or the calculated trajectory mode.

[0025] In some embodiments, the control unit is configured to, when the surgical robotic system is in the servo control mode and tracking of the robotic arm is lost, place the robotic arm in a special standby mode, which can switch back to the servo control mode when tracking is regained.

[0026] Another object is to provide a method for positioning an end effector held by a robotic arm relative to a patient, comprising: (i) activating a hand-guided mode in which the robotic arm is freely movable by a user based on a first input continuously provided by a user to the robotic arm; (ii) activating a calculated trajectory mode in which the robot arm moves to a target position according to a calculated trajectory based on a second input, different from the first input, continuously provided to the robot arm by a user; (iii) if the calculated trajectory mode is activated, detecting that the end effector is within a controlled volume about the target position and automatically switching to a servo control mode in which the robotic arm is automatically movable within the controlled volume to maintain the end effector at the target position relative to a patient.

[0027] In some applications, the target position is planned relative to the patient's spine.

[0028] In some applications, the target position is planned relative to a bone of the patient. [Brief description of the drawings]

[0029] Further features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0030] [Figure 1] A general overview of the robot system is given. [Diagram 2] FIG. 1 is a perspective view of one embodiment of a robotic arm. [Diagram 3] FIG. 3 is a perspective view of an end effector of the robot arm of FIG. 2. [Figure 4A] FIG. 2 is a state machine diagram illustrating the operation of the robotic system in different modes. [Figure 4B] FIG. 2 is a state machine diagram illustrating the operation of the robotic system in different modes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present invention may be practiced in connection with surgical procedures performed on a patient's bones, such as, but not limited to, the implantation of orthopedic implants such as pedicle screws in the spine, the implantation of various orthopedic implants in bones, the reduction and fixation of fractures during trauma procedures, or simply the placement of a guide or cannula in a desired location relative to a pre-determined target.

[0032] More specifically, the present invention can be used to maintain targets for pedicle screw placement determined during pre-operative or intra-operative image-based planning steps.

[0033] In this regard, the robotic system may be connected to other surgical systems, for example imaging devices such as a motorized C-arm imaging unit (as described in EP 2 868 277 A1) or a CT scanning unit such as the MobiusAiro.

[0034] These systems provide 2D and 3D image capture capabilities and, if connected to a location system such as that described in EP 3361977, navigation capabilities.

[0035] From the perspective of performing navigation, the end effectors and / or instruments used during the surgical procedure are equipped with a tracker, e.g., an optical, electromagnetic, ultrasonic, or inertial tracker, and are measured by at least one localization system. A separate tracker is attached to the patient's bone to be operated on (or to another bone that is considered to be fixed to the bone to be operated on), detected by the localization system, and designated as a reference tracker attached to the patient.

[0036] The robotic system includes a robotic arm having a proximal end extending from a base, such as a movable cart or an imaging device, or a base attached to a surgical table, an end effector attached to a distal end of the robotic arm, and a control unit configured to controllably move the robotic arm and maintain the end effector at at least one target position relative to a patient.

[0037] A robot arm has multiple degrees of freedom in translation and / or rotation. Typically, a robot arm has six or seven motorized degrees of freedom. Therefore, the robot arm has multiple articulated segments that are driven by motors. The robot arm is, for example, a LBRMed from KUKA. TM It's a robot.

[0038] The end effector includes a hand grip configured to be held by a user's hand to manipulate the robotic arm, particularly in the hand-guided mode described below.

[0039] In some embodiments, the hand grip comprises first and second switches configured to be actuated by a user, respectively, to trigger a motion mode of the robotic arm. These switches may include push buttons, resistive switches, piezoelectric switches, etc. The above switches may be located on other parts of the robotic arm, but are preferably located on the hand grip such that a user can actuate one of the switches with one hand and simultaneously manipulate the end effector to move the robotic arm (in hand guided mode) or follow the movement of the robotic arm (in calculated trajectory mode).

[0040] In some embodiments, the handgrip comprises at least one user interface configured to provide information regarding the current mode. Said user interface may be located in other parts of the robotic system, but is advantageously located on or near the handgrip so that the user can focus on the end effector when manipulating the robotic arm. According to one embodiment, the user interface comprises a display with graphic items (e.g., text, variable color marks, etc.) that change depending on the current mode. According to another embodiment, the user interface may comprise a number of LEDs. The LEDs may be configured to have a predefined color and / or blinking state depending on the current mode. This LED ring may be arranged as a ring around the handgrip or around the robotic arm near the handgrip.

[0041] The end effector also comprises a passive or active tool holder. The passive tool holder is configured to hold a guide on which slides a surgical instrument, which may be a drill guide, cutting guide, drill or any active tool. The active tool holder is configured to hold a surgical instrument, which may be a drill, ultrasonic cutter, burr or any active tool. The active tool holder may also hold an actuator with several motorized degrees of freedom to move and actuate the active surgical instrument. In a preferred embodiment, the tool holder holds a linear actuator capable of moving the drill or burr along its axis. The tool holder also comprises a tracker detectable by the localization system.

[0042] The hand grip and / or tool holder may be reusable and sterilizable or may be used as a disposable item.

[0043] The control unit includes a processor, a data storage device, and a communication device. The control unit may advantageously be embedded in the base of the robot arm, which also has switches such as a power switch, an emergency button, etc.

[0044] The robotic system can be operated as follows.

[0045] Intraoperative 3D and / or 2D images are acquired by an imaging system such as a C-arm.

[0046] The planning can be performed by the surgeon defining at least one surgical target for these images to be processed by the robotic system, these targets being defined in the coordinate system of the imaging system.

[0047] The robotic system may be mobile on wheels of a cart that forms the base of the robotic arms and is wheeled near the operating table.

[0048] The patient is provided with at least one reference tracker that can be detected by the localization system. Also attached to the end effector, in particular to the tool holder, is another tracker. Based on the localization data of both trackers, the control unit can determine the relative position of the end effector with respect to the patient. Using various registration methods, the transformation between the coordinate system of the patient reference tracker and the imaging system can be determined. Thus, the target is known in a coordinate system attached to the patient reference tracker. Providing the robot with a tracker makes it possible to calculate the transformation between the current end effector position and the target position and to assign the robot to a target-aligned position.

[0049] As an alternative to image-based planning, targets can be defined directly in the coordinate system of a reference tracker attached to the patient, for example a navigation pointer can be used to define a target, which can then be removed and the end effector axes of the robot aligned to this target location.

[0050] The robot system start-up procedure, including security tests, is initiated.

[0051] Once ready, the robot arm goes into idle mode, in which it cannot move on its own.

[0052] By continuously activating the first switch, the user can activate the hand guided mode, which allows the user to freely move the robot arm by manipulating the hand grip. This mode is available for the KUKA LBR iiwa TMIt can be implemented using a conventional cooperative mode of a robotic device such as a robot arm. This allows the user to easily approach the end effector to the first surgical target defined in the plan. The robot arm is continuously handled and controlled by the user, so its displacement speed can be relatively increased while avoiding obstacles. The hand guide mode is maintained as long as the first switch is activated. As soon as the user stops activating the first switch, the control unit stops the motor, preventing the user from moving the robot arm and preventing the robot arm from moving independently (idle mode). In a preferred embodiment, the first switch is located at the proximal end side of the end effector, at the robot base side.

[0053] When a tracker attached to a tool holder of an end effector on a robot arm enters the measurement field of the localization system and is accurately located by the localization system, the operator can stop the hand guide mode and enable the calculated trajectory mode by successively activating the second switch instead of the first switch. The transition between the hand guide mode and the calculated trajectory mode can be visualized via a user interface, for example, by changing the color and / or blinking condition of an LED when the tracker becomes detectable by the localization system. In a preferred embodiment, the second switch is located at the distal end of the end effector, opposite the base.

[0054] In this calculated trajectory mode, the user only has to follow the robot arm, which moves autonomously according to a pre-calculated trajectory relative to the surgical object. Safety is guaranteed by the user's continuous activation of the second switch. As soon as the user stops activating the second switch, the control unit stops the motor and the robot arm does not move. The calculated trajectory mode can therefore be considered as a collaborative mode of the robot system. When the robot reaches the target position, a signal is displayed on the user interface; in the preferred embodiment, the LED turns green; i.e. the user can now perform the surgery and insert the instruments in the tool holders.

[0055] If the tracker on the end effector can no longer be detected by the localization unit, e.g., in optical localization, if the tracker is obscured by another item in the field of view of the optical localization system, the control unit will exit the current mode and stop the robot arm. Such a situation may be indicated by the user interface, e.g., using a particular LED color and / or blinking state. In a preferred embodiment, the LED blinks white if the current mode is the hand guided mode or the calculated trajectory mode, and blinks orange if the current mode is the servo controlled mode.

[0056] After the target is reached and the user interface lights up green, if the user applies too much force to the robot's end effector, causing the end effector's tracker to deviate from the target within a certain range, the control unit will first attempt to move the robot back to the target and the user interface will display, for example, an orange light, but if the robot is unsuccessful, the control unit will exit servo control mode and stop the robot arm. Such a situation may be indicated by the user interface, for example, using a particular LED color and / or blinking state. In a preferred embodiment, the LED will be orange.

[0057] In a preferred embodiment, the user can impose a specific pose of the tool holder during the hand-guiding mode, after which this overall pose or the tool holder is held in its essential components to reach the target. This pose can be determined to preposition the robot arm in a position favorable for the surgical procedure, for example to avoid collisions with other surgical instruments. If the user notices that a collision may occur when pressing the second switch, he can stop and return to the hand-guiding mode using the first switch, change the tool holder pose in this mode, and then press the second switch to proceed to the target. In this mode, a final target calculation is performed to move the robot arm as close as possible to the initial robot arm position. In this mode, the redundancy of a 6- or 7-axis robot can be exploited to adjust a linear trajectory to the final target position, which requires only 5 degrees of freedom. Among the infinite number of possible poses of the robot around the tool holder axis, the one closest to the initial position of the robot is selected.

[0058] Next, we will focus on passive tool holders that slide various surgical instruments (drills, drivers, etc.).

[0059] Once the robotic arm reaches the planned surgical target, the user can release the second switch. This situation can be detected based on a comparison between the position of the end effector's tracker and the desired target position. If neither the first nor the second switch is actuated, the control unit triggers an autonomous mode that is servo-controlled for small patient movements (e.g., breathing) by monitoring the relative positions of the end effector and the patient, enabled by the tracking system. The transition between the computed trajectory mode and the servo-controlled mode can be visualized via the user interface, for example, by different LED colors and / or different blinking conditions.

[0060] In this servo-controlled mode, the user can execute the planned manipulation with the assistance provided by the robotic system holding the guide or tool itself, thus freeing the user from the need to activate switches and allowing them to focus on the instruments that will be used to perform the procedure.

[0061] When placing pedicle screws, the surgeon can manipulate the drill. Drilling can be accomplished with a manual drill bit or an ultrasonic tool that slides into a tool holder.

[0062] In another embodiment, the drilling instrument can be an active end effector such as a small compact active robot for burring bone.

[0063] For safety reasons, servo control mode allows moving and servoing the end effector to a target only if certain safety conditions are met. To allow activation of servo control mode, several safety conditions can be implemented, including one or more of the conditions in the following list: (a) In a first embodiment, the safety condition is met if the position of the end effector remains within a limited volume around the target position. For example, if the target moves more than 5 mm in the coordinate system of the base of the robot arm compared to its initial position, the safety condition is not met, the robot arm stops, a signal is displayed on the user interface, and the user must press one of the switches again to activate the robot arm again in either hand guided mode or calculated trajectory mode. Advantageously, said volume is updated in real time based on patient movements, such as breathing or mechanical responses to the application of the instrument on the patient. (b) In another preferred embodiment, which is a more advanced feature, the safety condition is met if the detected movement of the reference bone tracker relative to the robot base corresponds to an expected movement of the bone within a given range, for example 8 mm, and the safety condition is not met if the detected movement exceeds 3 mm in the direction of the unexpected movement. The expected movement can be the result of respiratory modeling or a modeled interaction of the bone with a surgical instrument that applies pressure to the bone. In other words, the safety condition corresponds to a volume within which the bone tracker may move, which has a larger dimension in a first direction, which is the direction of the expected movement of the bone tracker, than in a second direction, which is the direction of the unexpected movement of the bone tracker. (c) In another preferred embodiment, if the detected movement of the reference bone tracker relative to the robot base has a velocity that exceeds a given threshold, the safety condition is not met. (d) In another preferred embodiment, the safety condition is not met if the detected movement of the reference bone tracker relative to the robot arm base has an acceleration above a given threshold. Such a situation can occur, for example, if a tracker attached to a patient by magnetic fixation is unintentionally displaced during a surgical procedure. Indeed, an impact can cause the patient tracker to fall or be displaced, and since the robot arm is servo-controlled to the position of the patient tracker, the robot arm can move quickly and with large amplitude to follow the fallen or displaced tracker, potentially injuring the patient or medical staff.

[0064] The various safety conditions can be used individually or partially together.

[0065] The above safety conditions are in addition to, not a replacement for, the standard safety conditions for surgical robots. For example, if the position of the robot arm relative to the target calculated by the bone reference tracker exceeds a 1mm threshold, an alarm will be triggered and the robot will be stopped. Similarly, standard safety conditions that simply measure excessive forces on the robot and the integrity of redundant measurements of the robot position sensor and robot force sensor will also trigger an alarm or safety stop and remain in effect.

[0066] If the user activates either the first or second switch, the control unit may exit the safety mode.

[0067] As soon as the manipulation step is performed at the target position, the servo control mode may be stopped by the user.

[0068] For example, once a user has drilled a hole in a vertebra according to a first target, the user can move the robotic arm to a next target and drill a different vertebra.

[0069] In a preferred embodiment, the user can double-click the second switch to cause the robot arm to switch to the next planned target at any time.

[0070] In some situations, the user may want to remove the robot arm from the surgical site. For example, the user may drill a hole in a vertebra and immediately want to place a pedicle screw in this hole. For this purpose, the user may continuously activate the first switch to trigger the hand guided mode and quickly move the robot arm away from the surgical site to allow enough space to perform the pedicle screw implantation. Furthermore, the user may continuously activate the second switch to return the robot arm to the target position and perform the action with the robot guidance in the servo controlled mode.

[0071] If a new screw is then implanted, the user can perform the same sequence as above, starting from the hand guide mode, to select the next target with a double click as described in the embodiment above and quickly move the end effector close to the next target.

[0072] In a preferred embodiment, the held tool is an active tool, e.g. holding a drill. When the end effector reaches the target, the control unit moves the high speed rotary drill in a linear motion along its axis along the planned trajectory. As long as the trajectory satisfies the safety constraints, the safety condition is met. This is an extension of the previously mentioned case where safety-conscious positioning is required. For example, the trajectory of an active tool satisfies the safety condition if the tool itself remains aligned with the target line calculated in the robot base coordinate system.

[0073] FIG. 1 illustrates an embodiment of a surgical robotic system as described above in an operating room for spinal surgery.

[0074] The operating room includes an operating table 14. For spinal surgery, the patient may be in a prone position on the operating table, although for other surgical procedures the patient may be in another position. Although not shown, at least one tracker is securely attached to the patient, particularly to a vertebra in the case of spinal surgery. Multiple reference trackers may be used, one for each vertebra being operated on.

[0075] The operating table may also include an imaging system, such as a C-arm 15. The imaging system allows intraoperative images of the patient to be acquired.

[0076] The robotic system comprises a robotic arm 1 including a base 10 and an end effector 11, which will be described in more detail with reference to Figures 2 and 3. The base is fixed to a mobile cart and is fixed relative to an operating table during a surgical procedure.

[0077] The control unit that controls the robotic arm may be embedded in the cart and is indicated by the reference numeral 13 .

[0078] An enlarged view of the robot arm is shown in Figure 2.

[0079] The robot arm 1 comprises a number of articulated segments. An end effector 11 is provided at the distal segment opposite the base 10.

[0080] The end effector 11 includes a handgrip configured to be held by a user's hand, and as such may have an ergonomic shape, such as a cylinder, having a diameter adapted to allow the handgrip to be at least partially covered by the user's hand.

[0081] The hand grip comprises two switches 4, 5, different from each other. The first switch is configured to trigger the hand guide mode and the second switch is configured to trigger the calculation trajectory mode. To implement each of the above modes, the user must successively activate the respective switch. If the user releases the first or second switch when the robot arm has not reached the target, the robot arm will stop immediately. Advantageously, the switches are located on the outer surface of the hand grip so that the user can handle the end effector and activate the switches with one hand.

[0082] The end effector further comprises an LED ring 3 including multiple LEDs configured to emit light in different colors and / or with different blinking conditions. For example, the LEDs emit the following light signals: -Blinks white when the Robot Arm is in idle mode. Illuminates white when the robot arm is in either hand-guided or computed trajectory mode and the tracker is detectable by the localization system. -Lights green when the robot arm is in servo control mode and has reached its target. -In servo control mode, turns orange when the positioning system cannot detect the tracker.

[0083] Such an LED ring is convenient in that it is visible to the user regardless of the orientation of the end effector, but the user interface may take other forms, such as a small display, say an inch or two diagonal, that can be rotated anywhere around the robot's end effector.

[0084] The end effector holds a tool holder 2, e.g. a linear and cylindrical guide for an active tool held by the user, e.g. a drill, which allows to keep the active tool in a defined pose and at a defined distance from the patient.

[0085] The tracker 12 is attached to the end effector and is used to determine the position and orientation of the end effector relative to the tracker attached to the patient. This measurement is acquired using a high speed 3D camera with low latency of less than 10 milliseconds and frame rates in the range of 100 Hz or higher.

[0086] A close-up of the end effector is shown in Figure 3.

[0087] Figure 4 shows an embodiment of a state machine describing the operation of the robot arm by the control unit: the right side of the figure shows the different states of an LED ring forming the user interface.

[0088] When the system is powered on, it goes through an initialization (init) process.

[0089] In the first step, the next goal to be achieved is selected. This selection can be made by the user during the planning step, or it can be selected by double-clicking on the second switch, as described above.

[0090] The robot arm then goes into idle mode, waiting for input from the user, and the LED flashes white.

[0091] When the user activates the first switch (presses the primary input), the robotic arm enters hand guidance mode. This mode remains as long as the first switch is activated. When the user releases the first switch (releases the primary input), the robotic arm returns to idle mode.

[0092] When the user activates the second switch (presses the secondary input), the robot arm enters the calculated trajectory mode and moves to the selected target. This mode can only be activated if the tracker attached to the end effector is detectable by the localization system (evt_tracker_visible). The calculated trajectory target is maintained as long as the target has not been reached and the second switch is activated. In this state, the LED is illuminated white.

[0093] If the user releases the second switch and the goal has not yet been reached (secondary input released), the robotic arm returns to idle mode.

[0094] When the target is reached (a situation detected by the control unit comparing the position of the target with that of a tracker attached to the end effector), the LED turns green.

[0095] Therefore, the user must release the second switch and enter servo control (servo) mode.

[0096] During servo control mode, the control unit continuously monitors whether the tracker attached to the end effector is within the area of ​​the localization system (is_tracker_visible loop). When said tracker becomes invisible to the localization system (evt_tracker_invisible), the servo control mode is interrupted and the LED turns orange. The robot arm goes into tracker wait mode until the tracker becomes visible again (evt_tracker_visible). This causes the robot arm to return to servo control mode and the LED turns green again.

[0097] When the control unit detects an unmet safety condition, such as the robot arm movement exceeding a given amplitude, direction, acceleration or speed in servo control mode, it activates a safety mode that inhibits the robot arm movements (evt_safety_mode_activated) and the robot arm returns to idle mode. [Prior art documents] [Patent documents]

[0098] [Patent Document 1] US Patent Application Publication No. 2011 / 0190790 [Patent Document 2] US Patent Application Publication No. 2014 / 0350571 [Patent Document 3] European Patent Application Publication No. 2868277 [Patent Document 4] European Patent Application Publication No. 3361977

Claims

1. 1. A surgical robotic system comprising a robotic arm (1) holding an end effector (11) and a control unit (13) configured to controllably move said robotic arm and maintain said end effector (11) at at least one target relative to a patient, The control unit (i) activating a hand-guided mode in which the robot arm is freely movable by a user based on a first input continuously provided to the robot arm (1) by a user; (ii) activating a calculated trajectory mode in which the robot arm moves to a target according to a calculated trajectory based on a second input, different from the first input, continuously provided by a user to the robot arm (1); (iii) the surgical robot system is configured to detect when the calculated trajectory mode is activated, and to automatically switch to a servo-controlled mode in which the robot arm is automatically movable to maintain the end effector (11) on the target relative to a tracker attached to a patient, upon detecting that the end effector (11) meets at least one predetermined safety condition.

2. The goal is to Drilling shaft, Drilling axis and drilling depth, cut surface, A working position of an active surgical instrument held by said end effector (11).

2. The surgical robot system of claim 1, wherein the surgical robot system is selected from the group consisting of:

3. 3. The surgical robotic system of claim 1, wherein the predetermined safety condition is that the tracker attached to the patient remains within a controlled volume relative to a base of the robotic arm, the controlled volume having a dimension greater in a direction of expected movement of the tracker than in a direction of unexpected movement of the tracker.

4. The surgical robot system according to any one of claims 1 to 3, wherein the control unit is configured to adjust the calculated trajectory based on a pose of the robot arm (1) imposed by a user in the hand-guided mode.

5. The surgical robot system of any one of claims 1 to 4, further comprising a user interface coupled to the control unit and configured to provide information regarding a current mode.

6. The surgical robot system of claim 5 , wherein the user interface comprises a display monitor disposed on the robot arm and configured to display graphical items that change depending on a current mode.

7. 6. The surgical robot system of claim 5, wherein the user interface comprises a ring (3) including a plurality of LEDs configured to have a predetermined color and / or blinking state depending on a current mode.

8. 8. The surgical robot system of claim 1, wherein the control unit is further configured to activate a safety mode that inhibits movement of the robot arm upon detection of movement of the robot arm (1) exceeding a predetermined amplitude, direction, acceleration, and / or velocity in the servo control mode.

9. The surgical robot system of any one of claims 1 to 8, wherein the control unit is configured to continuously maintain the end effector (2) on multiple targets.

10. 10. The surgical robot system of claim 1, further comprising a first switch (4) configured for application of the first input by a user, and a second switch (5), different from the first switch, configured for application of the second input by a user.

11. The surgical robot system of claim 10 , wherein the control unit is configured to transition between two successive goals when a user double-clicks the second switch during a surgical procedure.

12. 12. The surgical robot system of claim 1, wherein the control unit is configured to put the robot arm (1) into an idle mode in which the robot arm cannot move independently when tracking of the robot arm is not enabled and the surgical robot system is in either the hand guided mode or the calculated trajectory mode.

13. 12. The surgical robot system of claim 1, wherein the control unit is configured to place the robot arm in a special standby mode when the surgical robot system is in the servo control mode and tracking of the robot arm is lost, the special standby mode being capable of switching back to the servo control mode when tracking is regained.

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