Method for controlling a slave device controlled by a master device movable by an operator near its operating limit in a robotic system for remote operation of medical or surgical operations, and related robotic system

Abstract

A method for controlling a slave device of a robotic system for medical or surgical teleoperation near the physical movement limits of the slave device is described. The robotic system comprises at least one master device adapted to be moved by an operator and at least one slave device with a surgical instrument adapted to be controlled by the master device. The method comprises the steps of determining, for each master trajectory of the master device, a respective slave target trajectory of the slave device and controlling the slave device to move along the slave trajectory. The slave target trajectory is contained within a predefined convex volume in the slave reference coordinate system for every movement of the master device. Further described is a robotic system for medical or surgical teleoperation adapted to be controlled by the aforementioned control method.

Description

[Technical Field]

[0001] The present invention relates to a method and system for controlling a robotic system for medical or surgical teleoperation.

[0002] Specifically, the present invention relates to a method for controlling a slave device controlled by a master device in a robotic system for remote operation in medical or surgical procedures, near the operating limits of the slave device. [Background technology]

[0003] In master-slave robotic systems for medical or surgical teleoperation, systems are known which have a master device that is not mechanically constrained to a "master controller" station of the robotic system, i.e. "wheel" masters (or "mechanically ungrounded", "mechanically unconstrained"), or of the type shown, for example, in patent documents WO / 2019 / 020407, WO / 2019 / 020408 and WO / 2019 / 020409 in the name of the same applicant. Summary of the Invention [Problem to be solved by the invention]

[0004] With a "wheel" master device without force feedback, and with mono-lateral teleoperation, there are problems that arise when the master device maps to a nominal target pose that the slave device cannot reach, e.g., that is outside the slave device's possible workspace.

[0005] In order to maintain high ease of use of the teleoperation and maintain intuitive operation for the operator, it is desirable to provide modified and improved control approaches and algorithms when the slave device is located near the limits of the allowed workspace and / or when the nominal target pose is outside said workspace of the slave device.

[0006] Unidirectional teleoperation is performed between a symmetric N-fold master device and a microsurgical instrument with translational degrees of freedom (typically three mutually orthogonal directions), rotational degrees of freedom (whose spatial orientation can typically be expressed by three successive rotations), and possibly additional degrees of freedom that describe the state of the microsurgical instrument, e.g., "closure" (or grasping) degree of freedom.

[0007] A symmetric N-way master is assumed to have at least as many degrees of freedom as the controlled devices. In this context, unidirectional teleoperation can be thought of as an information flow between a master device and a slave device (e.g., as shown in Figure 8).

[0008] Because the master device is unconstrained, there is no pre-fixed mapping between the master device's position and the slave device's position: such a mapping is generated at the start of teleoperation, i.e., the moment the slave device's movement "couples" to the master device's movement.

[0009] In microsurgery, it is useful for translational motion of the master device to result in scaled motion of the slave device, so that the user perceives improved positioning accuracy of the master device with respect to the translational degree of freedom. By introducing a scale factor, the user can perceive better control over the slave device, as it is easy to see the cognitive consistency between the direction and amplitude of the translational trajectory performed by the master device and the movement of the slave device.

[0010] Such consistency allows the user to close the cognitive control loop afforded by hand-eye coordination by watching the slave device rather than their own hand.

[0011] If physical limitations exist, for example those associated with translational degrees of freedom, special treatment of teleoperation near such limitations is required.

[0012] Therefore, in a master-slave robotic system with both constrained and unconstrained master devices, we feel it is necessary to define appropriate teleoperation behavior when slave devices are located near such limits, and to optimize the user experience during changes in teleoperation paradigm.

[0013] Known solutions in the considered technical field have not been able to adequately solve the problems and drawbacks mentioned above.

[0014] Therefore, there is a strong need in the considered technical field to have a way to control the subordinate operation of a slave device relative to a master device based on a control algorithm so as to solve or at least mitigate the aforementioned problems and drawbacks. [Means for solving the problem]

[0015] The object of the present invention is to provide a method for controlling a slave device controlled by a master device that is movable by an operator near the physical operating limits of the slave device, thereby making it possible to at least partially overcome the above-mentioned drawbacks of the prior art and in particular to meet the above-mentioned needs felt in the art. Such an object is achieved by a method as set forth in claim 1.

[0016] Further embodiments of such a method are defined by claims 2 to 14.

[0017] It is also an object of the present invention to provide a robotic system for medical or surgical teleoperation configured to be controlled by the aforementioned method, and such object is achieved by a system as claimed in claim 15.

[0018] A further embodiment of such a system is defined by claim 16.

[0019] Further characteristics and advantages of the method according to the invention will become apparent from the following description of preferred embodiments given by way of non-limiting indication, with reference to the attached drawings, in which: [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 illustrates a master-slave robotic system for medical or surgical teleoperation according to one embodiment of the present invention. [Figure 2] FIG. 2 illustrates in more detail the master and slave devices in the robotic system of FIG. 1, in accordance with one embodiment of the present invention. [Figure 3A] FIG. 1 illustrates a convex volume that can be defined as a workspace for a slave device. [Figure 3B] FIG. 3B shows two regions defined within a convex volume such as that of FIG. 3A: an edge region and an interior region that are relevant for explaining the method of the present invention. [Figure 4] FIG. 1 shows a target trajectory S(t) of a slave device relative to a nominal target trajectory MT(t) corresponding to a mapping of the master device's trajectory in the slave device's workspace when an embodiment of the control method according to the present invention is implemented. [Figure 5] FIG. 10 shows a target trajectory S(t) of a slave device relative to a nominal target trajectory MT(t) corresponding to a mapping of the master device's trajectory in the slave device's workspace when another embodiment of the control method according to the invention is implemented. [Figure 6A]FIG. 1 illustrates the geometric relationships associated with the mapping between the aforementioned nominal target trajectory MT(t) and the target trajectory S(t), in accordance with an embodiment of the method of the present invention. [Figure 6B] FIG. 1 illustrates the geometric relationships associated with the mapping between the aforementioned nominal target trajectory MT(t) and the target trajectory S(t), in accordance with an embodiment of the method of the present invention. [Figure 7] FIG. 10 shows a target trajectory S(t) of a slave device relative to a nominal target trajectory MT(t) corresponding to a mapping of the master device's trajectory in the workspace of the slave device when yet another embodiment of the control method according to the invention is implemented. [Figure 8] FIG. 1 is a diagrammatic and simplified illustration of the flow of information between a master device and a slave device in a master-slave robotic system. [Figure 9] 1 shows an exemplary scale factor reduction function U(Pp) for different implementation options of the method according to the invention; [Figure 10] 1 shows an exemplary scale factor reduction function U(Pp) for different implementation options of the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0021] A method for controlling a slave device of a robotic system for teleoperation of a medical or surgical procedure will be described with reference to Figures 1 to 10 .

[0022] The robotic system to which this method is applied comprises at least one master device 110 adapted to be moved by an operator 150 and at least one slave device including a surgical instrument 170 adapted to be controlled by the master device.

[0023] The master device 110 is preferably a "wheel" type master device without force feedback for mono-lateral teleoperation. Thus, for example, the master device can be a master mechanically constrained to an operating console and also a "wheel" type without force feedback for mono-lateral teleoperation.

[0024] The master device 110 is preferably a type of master device that is not mechanically constrained by an operation console.

[0025] The method includes determining, for each master trajectory of the master device, a slave target trajectory for each slave device, and controlling the slave devices to move along said slave trajectories to follow.

[0026] The determining step includes, for each master trajectory of the master device, determining a respective slave target trajectory for the slave device in a slave reference coordinate system of the slave device, wherein the motion of the slave device is scaled down by a scale factor Fs relative to the motion of the master device, and the pose of the slave device has a translation offset OFF relative to the pose of the master device, which translation offset OFF can be zero or non-zero.

[0027] The aforementioned slave target trajectory is contained within a given convex volume in the slave reference coordinate system for any master device motion.

[0028] The step of determining the slave target trajectory includes defining an edge region of the convex volume near a boundary of the convex volume and an interior region of the convex volume that is interior to the edge region and therefore far from the boundary of the convex volume.

[0029] In this method, if the nominal target trajectory of the slave device corresponding to the mapped master device trajectory in the slave reference coordinate system is outside the aforementioned inner region of the convex volume, the method dynamically changes the aforementioned scale factor Fs (hereinafter also defined as "scaling factor") to obtain a dynamically variable modified scale factor Fm(t), thereby modifying the slave trajectory with respect to the nominal target trajectory obtained with the unchanged scale factor, so that the slave target trajectory remains within the aforementioned predetermined convex volume.

[0030] The method may further dynamically change said transformation offset OFF(t) if the modified scale factor Fm(t) is greater than a predetermined maximum scale factor Fmax, so that the slave device still remains within said predetermined convex volume.

[0031] The scaling factors and transformation offsets (or "offsets") are discussed in more detail below.

[0032] According to one embodiment of the method, the convex volume corresponds to a workspace of the slave device defined by three orthogonal joints contained in the slave device and having a limited stroke.

[0033] According to one embodiment, the method is applied to a slave device including at least one joint adapted to move the slave device along at least one direction X, Y, Z corresponding to one of three directions of a spatial reference system X, Y, Z associated with a slave workspace of the slave device.

[0034] Such a slave workspace has physical limitations in each of the X, Y, and Z directions of the spatial reference system described above, determined by the possible physical movement limits of the slave device in each direction.

[0035] The aforementioned edge regions of the slave workspace include points of the slave workspace that are less than predetermined thresholds Xthr, Ythr, Zthr away from the physical limits.

[0036] In this case, when said at least one joint of the slave device is in an edge region with respect to the respective direction, the method may dynamically change the scale factor as the joint approaches said physical limit so that the trajectory traced by the joint always remains within the workspace of the slave.

[0037] According to implementation options, the aforementioned physical constraints correspond to the maximum (Xmax, Ymax, Zmax) and minimum (Xmin, Ymin, Zmin) coordinates of each joint's movement or stroke in each direction.

[0038] According to an embodiment, the slave device comprises three joints adapted to move the slave device along each of the three directions X, Y and Z of the aforementioned spatial reference system. The three directions X, Y and Z are mutually orthogonal and define three orthogonal translational degrees of freedom of the joint.

[0039] The X, Y, and Z physical limits of each joint comprise a three-dimensional physical limit determined by the maximum possible physical movement of the device in each of the three orthogonal directions mentioned above.

[0040] The aforementioned edge region includes the space between the first parallelepiped and the second parallelepiped.

[0041] The first parallelepiped corresponding to the aforementioned inner region is defined by distances corresponding to predetermined thresholds Xthr, Ythr, Zthr corresponding to the respective directions.

[0042] The second parallelepiped is defined by the aforementioned physical movement limits Xmax, Ymax, Zmax corresponding to the respective directions.

[0043] The scale factors include dynamic scaling factors Fsx, Fsy, Fsz for each direction.

[0044] According to the implementation options, the three dynamic scaling coefficients Fsx, Fsy, Fsz in each direction are equal to each other.

[0045] According to another implementation option, the three dynamic scaling coefficients Fsx, Fsy, Fsz in each direction are different from each other.

[0046] According to an implementation option, the aforementioned predetermined thresholds Xthr, Ythr, Zthr are equal to each other for each limit and / or each joint.

[0047] According to another implementation option, the aforementioned predetermined thresholds Xthr, Ythr, Zthr for different limits and / or different joints are different from each other.

[0048] According to an embodiment, the method further comprises the following steps: In the absence of dynamic changes in the scale factor Fs and in the absence of a transformation offset (OFF), we define a nominal target pose in the slave workspace that is controlled by the respective master device pose in the master device workspace. Check whether the nominal target pose is inside or outside the inner region of the slave workspace. When the nominal target pose is outside the interior region, dynamically varying the scale factor Fs includes scaling the scale factor Fs with a reduction function U that depends on the position of the nominal target pose.

[0049] According to an implementation option, the aforementioned shrinkage function U is a monotonic, non-decreasing function of the distance between the nominal target pose and the closest point of the interior region.

[0050] According to implementation options, the aforementioned reduction function U operates independently on each individual joint, and / or each individual joint operates according to a different reduction function U.

[0051] According to an implementation option, the reduction function U is a linearly increasing function, and at each point belonging to the boundary between the interior and edge regions, its value is 1, corresponding to the nominal scale factor Fs valid for the nominal target pose in the interior region, while for points in the edge region, the reduction function U has a value greater than 1, the value of the reduction function U increases with the distance from the boundary between the interior and edge regions, and the modified scale factor Fm applied to each point in the edge region increases linearly as a function of the distance that point is away from the boundary between the edge and interior regions.

[0052] According to another implementation option, the reduction function U is a non-linear function with a positive hyperbolic trend.

[0053] According to an embodiment, when the value of the reduction function U reaches or exceeds the aforementioned predetermined maximum scale factor Fmax, i.e., the point at which the value of the reduction function U reaches or exceeds said predetermined maximum scale factor Fmax, the method holds the target pose of the slave device stationary and stops the slave device in its translational motion, thereby causing the target pose to deviate from the nominal target pose, and determines a translation offset AOFF between the pose of the master device and the target pose of the slave device.

[0054] According to an implementation option, the aforementioned predetermined maximum scaling factor Fmax is defined in relation to the definition of the interior and edge regions of the slave workspace, whereby the controlled trajectory of the slave device lies and extends entirely within the slave workspace of the slave device.

[0055] According to an implementation option, if the nominal target pose controlled by the master device is reassociated with a value of the reduction function U that is lower than the maximum scaling factor Fmax, the method readjusts the parameters of the reduction function U to restore the accumulated translational offset OFF when the pose of the slave device re-enters the interior region of the slave workspace.

[0056] According to an embodiment, it is applicable to the slave device to provide at least one rotational degree of freedom R representing a rotation about an axis of rotation of the slave device at the control point in addition to the translational degrees of freedom corresponding to the aforementioned X, Y and Z directions, and the method comprises, in response to a movement of the master device within the workspace of the master device, controlling a movement of the slave device within the workspace of the slave device such that the slave device follows the rotation of the master device in said at least one rotational degree of freedom with a rotation scale factor Fr.

[0057] If such a joint of the slave unit is located within the aforementioned interior region, the rotation scale factor Fr is 1.

[0058] If such a joint of the slave device is located in the aforementioned edge region, the method applies a rotational scale factor greater than 1 that increases as the joint approaches the physical limit of the edge region, similar to what has already been described above for the translational degrees of freedom.

[0059] According to another embodiment, the method is applied to a slave device which, in addition to the translational degrees of freedom corresponding to the aforementioned X, Y, Z directions, also includes at least two further angular degrees of freedom P, Y, which together define the relative orientation of a control point of at least one individual joint of the slave device with respect to the orientation of the master device.

[0060] In this case, the method causes the aforementioned additional angular degrees of freedom P, Y to be controlled with an orientation scale factor of 1:1, so that wherever the slave device is placed in the slave workspace, even in an edge region, the orientation of the slave device remains constant and corresponds to the orientation of the master device.

[0061] According to one embodiment of this method, the trajectory of the joint in the slave workspace tends to follow each instantaneous direction of the master device's trajectory so as to maintain the joint position always within the allowed slave workspace.

[0062] According to one embodiment, the method further comprises the step of: controlling the movement of the slave device when the slave device is located within said interior region of the slave workspace such that the slave device replicates, in all translational directions within the slave workspace, the movement of the master device within the master workspace with a constant scale factor that is independent of the position of the slave device.

[0063] According to one embodiment of this method, when the master pose controls the slave pose along a direction, if the scaling function U in that direction is greater than a limit value U_lim (i.e., the scaling factor reaches a maximum value Fmax), the slave device remains stationary along that direction and accumulates a translation offset along that direction.

[0064] According to an implementation option of the method shown in Figure 5, a subspace (corresponding to the aforementioned "edge region") is defined in the physical space of the joint. Such a subspace is defined near the limits of the workspace, defining a region where the scale ratio between master and slave is not constant but increases until it becomes infinity at the limits of the joint itself. This solution results in less distortion of the direction of the target trajectory S relative to the nominal target trajectory MT (corresponding to the trajectory of the master device mapped into the workspace of the slave device). This allows the user to control the slave device more precisely.

[0065] The relationship between the target master pose MT and the slave device pose S in the edge region (with variable scaling) at the single joint level can be interpreted as a mapping between a straight line and a positive hyperbola, as shown in Figure 6A.

[0066] Similarly, the deformation of the trajectory S(t) relative to the trajectory MT(t) can be interpreted by introducing dynamic scaling that depends on the current position S(t), as shown in Figure 6B.

[0067] Another implementation option for the method shown in Figure 4, in addition to performing the dynamic scaling described above, allows the slave device S(t) to resume tracking according to the nominal target trajectory (target master trajectory MT(t)) as soon as the master device instantaneously moves in a direction reachable by the slave device. Assume that S(t0) is the last valid point of the slave device, MT(t1) is the previous target position, and MT(t2) is the new target position. Then, S(t2) = S(t0) + (MT(t2) - MT(t1)). If all of the trajectories S(t0) · S(t2) are valid, the slave S(t) can proceed. This solution allows for an instant return to the normal situation by introducing a translation offset that can be used by limited remote control.

[0068] 1-10, and in particular, FIGS. 1-3, a robotic system 100 for teleoperation of medical or surgical procedures included in the present invention will now be described.

[0069] Such a robotic system comprises at least one master device 110 adapted to be moved by an operator 150, at least one slave device including a surgical instrument 170 adapted to be controlled by the master device, and a control unit configured to control the slave device based on movements of the master device during teleoperation.

[0070] The control unit further comprises: determining, for each master trajectory of the master device, a respective slave target trajectory of the slave device; controlling the slave device so that the slave device moves in a tracking manner along said slave trajectory; The device is configured to perform operations including:

[0071] The aforementioned determining step includes, for each master trajectory of the master device, determining a respective slave target trajectory for the slave device in a slave reference coordinate system of the slave device, where the slave device's motion is scaled down by a scale factor Fs relative to the master device's motion and the slave device's pose has a translation offset OFF, which may be zero or non-zero, relative to the master device's pose, such that the aforementioned slave target trajectory is contained within a predefined convex volume (e.g., as shown in Figures 3A and 3B) in the slave reference coordinate system relative to the master device's motion.

[0072] The above step of determining the slave trajectory may further include: defining an edge region close to a boundary of said convex volume and an interior region of said convex volume that is interior to the edge region and therefore far from the boundary of said convex volume; when a nominal target trajectory of the slave device corresponding to a trajectory of the master device mapped to the slave reference coordinate system is outside the inner region of the convex volume, dynamically changing said scale factor Fs to obtain a dynamically variable modified scale factor Fm(t), thereby modifying the trajectory of the slave with respect to the nominal trajectory of the slave obtained with a constant scale factor, so that the target trajectory of the slave remains within said predetermined convex volume; If the modified scale factor Fm(t) is greater than a predetermined maximum scale factor Fmax, also dynamically change such a transformation offset OFF(t) so that the slave device still remains within said predetermined convex volume; Includes.

[0073] According to some possible implementation options of the robotic system, the control unit is configured to execute a method for controlling a slave device according to any of the embodiments presented herein.

[0074] A mathematical discussion of the algorithms used in the method embodiments is provided below as a non-limiting exemplary disclosure.

[0075] With reference to the aforementioned "poses" of the master and slave devices, it should be noted that for purposes of this disclosure, each "pose" is understood to be characterized by the values ​​of each degree of freedom of the slave device.

[0076] Typically, these degrees of freedom include seven degrees of freedom, including three translational degrees of freedom (X, Y, Z), three rotational degrees of freedom (e.g., roll, pitch, yaw), and an open / close degree of freedom (grasp).

[0077] Thus, a "pose" is defined by the values ​​of each of the aforementioned degrees of freedom, and the velocity associated with the pose refers to the rate of change of each degree of freedom over time. A translational trajectory refers to a translational trajectory in a coordinate system of translational degrees of freedom X, Y, and Z.

[0078] With respect to poses, the following conventions are used herein: "master pose", "slave pose", "nominal target pose", and "corrected target pose".

[0079] The "master pose" is the current pose of the master device in the reference coordinate system of the master device's workspace (e.g., the space defined by a tracking mechanism included in the robotic system).

[0080] "Slave Pose" is the current pose of the slave device in the reference coordinate system of the slave device's workspace.

[0081] The "nominal target pose" (sometimes referred to below as the "proxy pose") is the pose of the master device mapped into the workspace of the slave device, so called because it is the pose that would be tracked by the slave device under "nominal" conditions, i.e., in the absence of any further control mechanisms or processing.

[0082] It should be noted that the determination of the "nominal target pose" depends solely on the translation offset between the centers of the master and slave reference coordinate systems and the application of a scale factor to the translation. The translation offset can be, for example, specified in the alignment step, or specified by explicit operator intervention, or specified according to the operation of an available algorithm.

[0083] The "corrected target pose" (hereinafter sometimes referred to as "target pose") is the reference pose of the slave device, i.e., the required pose to which the slave device will follow and converge in response to movements controlled by the control system. This pose will in principle coincide with the nominal target pose, but may differ from the nominal target pose if there is a reason for it to change due to predetermined additional control actions and associated algorithms.

[0084] In this specification, the modification of the nominal target pose (proxy pose) to obtain a modified target pose (target pose) is performed, for example, based on information about the current position of the slave device, thereby reducing the delay perceived by the operator between the movement of the slave device and the movement communicated to the master device.

[0085] Such a correction can be achieved, for example, by inserting an additional transformation offset between the proxy pose and the target pose (as explained further below).

[0086] A pose Pm of the master device is given, expressed relative to the master device's reference frame OM, and a pose Ps of the slave device is given, expressed relative to the slave device's reference frame OS.

[0087] In this part of the description, the term "pose of the slave device" is used to refer to the "target pose Ps of the slave device", i.e., the upstream pose of the joint control system, which may depend on other factors, e.g., actuation dynamics, etc., and does not refer to the actual position of the slave device at time t.

[0088] Without loss of generality, we assume that OM and OS are both Cartesian coordinate systems, and that no transformation between the two reference systems is required in master-slave teleoperation, or (extending such thinking to all axes) a movement of the master device along the X axis of the reference system OM is transformed into a controlled movement of the slave device along the X axis of the reference system OS.

[0089] Under these conditions, a transformation mapping function is defined from the master pose Pm expressed in OM to the slave target pose Ps expressed in OS. Such a function can be expressed in differential form (discrete time) by the following equation (EQ1):

[0090]

number

[0091] where Ps(t) and Pm(t) are two column vectors containing the coordinates x, y, z in the respective reference systems at time t. Fs is a diagonal matrix whose elements are the scale factors along the directions x, y, and z. OFF(0) is a column vector containing the translation offset coefficients between the reference systems defined at the start of the teleoperation itself in order to minimize the movement of the slave device during the alignment step.

[0092] During the remote control process, it is possible to change the differential relationship between the master device motion and the slave device motion, as expressed in the above equation (EQ1), by inserting an additional differential offset coefficient as in the following equation (EQ2):

[0093]

number

[0094] where OFF(t) is the instantaneous deviation coefficient (i.e., instantaneous offset) between the master pose and the slave pose introduced instantaneously at time t as a result of direct operator intervention or other algorithms adapted to improve the teleoperation experience.

[0095] At time t, the total offset TOT_OFF can be defined as the sum of all instantaneous offsets OFF(t) from time 0 to time t.

[0096] In the embodiment described here, the method involves dynamically (i.e., at each instant t) varying the scale factor Fs and the offset TOT_OFF so that each point of the translational trajectory Ps of the slave device controlled by the master device always lies within the workspace of the slave device's own joints.

[0097] In implementation, the method involves providing permanence of the slave device's trajectory Ps within any predefined convex volume within R3.

[0098] The slave workspace (or volume) is if the slave workspace is defined by an orthogonal joint of finite stroke, then the aforementioned interior region encompassing points of the slave workspace that are at least predetermined thresholds Xthr, Ythr, Zthr away from the aforementioned physical limits; The aforementioned edge region, which is a region that does not belong to the interior region of the workspace; an area outside the workspace; Includes.

[0099] When at least one joint of the slave device is located in the aforementioned edge region, in each direction, the method gradually increases the aforementioned scale factor as the joint approaches its relative physical limit, so that the trajectory traced by the joint always remains within the slave workspace.

[0100] Ignoring for now the behavior of other algorithms that can insert an instantaneous offset OFF(t) without loss of generality, equation (EQ2) is modified to the following (EQ3):

[0101]

number

[0102] That is, a "proxy pose" Pp (or nominal target pose) is calculated in slave device space taking into account the scale factor Fs, which is unaffected by the methods presented herein.

[0103] The scaling factor Fs'(Pp) is then defined according to the position of the proxy pose Pp in the reference system OS.

[0104] Specifically, if the proxy pose Pp is outside the interior region of the workspace, the scale factor is gradually increased so that the slave target pose Ps is no longer outside the slave device's workspace when the master pose Pm is changed. It should be noted that the space deformation effect occurs both when Pp is in an edge region (i.e., Pp is at a point that can be moved by the robot device's joints) and when Pp is outside the slave device's own workspace.

[0105] According to an embodiment of this method, the dynamic scaling factor Fs' is defined as follows:

[0106]

number

[0107] Here we express the dependence of the dynamic scaling factor on a further reduction function U that depends on the position of the proxy pose Pp. In particular, by expressing the joint dynamic scaling factor Fs' relative to the orthogonal X, Y, and Z directions of the robot system, we obtain:

[0108]

number

number

number

[0109] According to one embodiment of this method, the formulation of the scalar reduction function u is independent of the axis to which it is applied. The scalar reduction function u, by its formulation, is inherently non-decreasing; that is, the scale factor increases without bound as the proxy pose Pp moves away from the interior region of the slave device's workspace. The overall effect is a decrease in the velocity of the slave device (pose Ps) as it approaches the limits of the workspace.

[0110] Here, a reduction value U_lim is defined, beyond which the movement of the slave device following that of the master device cannot be sensed. In other words, the limit scale factor Fs'_lim is defined (in vector form for simplicity) as follows:

[0111]

number

[0112] The motion dPs=Ps(t)-Ps(t-1) obtained by the slave device following the displacement dPm=Pm(t)-Pm(t-1) of the master device is given by This would then be invisible to the user in remote control and / or would cause unacceptable degradation of remote control along such axis.

[0113] An implementation option for this method is that the choice of value U_lim depends on the relative axis scaling factor Fs, which allows direct control over the maximum scale factor represented by Fs' that the user will experience.

[0114] In the implementation option, by this method, when the scale factor related to the axis reaches the value Fs’_lim, the movement of the slave device is no longer instructed by the movement of the master device in which the target pose moves away from the internal area of the work space, that is, an instantaneous offset OFF(t) is introduced with respect to the expected movement described by the formula (EQ3).

[0115] In other words, in such an embodiment, the formulas (EQ2) and (EQ3) are modified as shown by the following algorithm. The following formulas refer to the case of a single axis that is processed independently as represented by an embodiment of the method (ALG1).

[0116] TIFF2025511056000011.tif81170

[0117] It should be noted that due to the dynamic change of the offset, a drift occurs between the position of the master device and the position of the slave device, thereby improving the responsiveness of the robot system.

[0118] Also, it should be noted that by inserting the conversion offset upstream of the pose Pp, the movement of the pose is restricted by the amount Pp_lim defined as the inverse function of U applied to U_lim.

[0119] In the implementation of this method, there is a relationship between U_lim (and Fs’_lim) and the size of the edge area. Specifically, it is necessary to define Xthr, Ythr, and Zthr so that the movement of the slave pose Ps is always included within the work space of the slave device. Here, the amounts of Xthr, Ythr, and Zthr (which contribute to the definition of Pp_lim) are defined individually for each joint as follows.

[0120] As shown in FIG. 9, when Pp < Pp_lim and Pp > -Pp_lim, U(Pp) is a non-decreasing active general function greater than 1. Without loss of generality, only the positive half-axis of Pp is considered.

[0121] Note that the area under the 1 / U(Pp) curve (between Pp_thr and Pp_lim) when Pp is active corresponds to the space that the slave device Ps moves into as Pp changes, as shown in Figure 10. Therefore, having Ps in the workspace is equivalent to requiring (Equation 9).

[0122]

number

[0123] where Joint_Max is a parameter representing the maximum possible movement by an individual joint.

[0124] In an implementation option, when the master device controls the proxy pose on a trajectory that approaches an interior region of the workspace, if the slave pose becomes saturated because the scale factor is greater than a limit value, the shape of the reduction function U is readjusted so that the accumulated offset can be recovered when the slave device returns to the interior region.

[0125] Specifically, the function LT is dynamically defined with the following characteristics: It is a monotonic and non-decreasing function. The outer limit of the inner region of the workspace is equal to "1". The current point of the proxy pose (Pp_lim) at the time of return has the value "lim". The following relationships will be observed:

[0126]

number

[0127] where Σ(OFF(t)) is the sum of all instantaneous offsets accumulated since the system entered the saturation step of the slave pause.

[0128] According to one embodiment, for the case already considered above where the slave device includes three joints X, Y, Z, the maximum and minimum physical limits of each joint comprise three-dimensional physical limits determined by the maximum possible physical movement of the device in each of three orthogonal directions.

[0129] The aforementioned edge region then comprises the space between a first parallelepiped, called the inner region, defined by distances corresponding to the aforementioned predetermined thresholds Xthr, Ythr, Zthr in each direction, and a second parallelepiped defined by the aforementioned physical movement limits Xmax, Xmin, Ymax, Ymin, Zmax, Zmin in each direction.

[0130] The scale factors include, for each direction, respective dynamic scaling factors Fs_x'(Pp_x), Fs_y'(Pp_y), Fs_z'(Pp_z) that depend on the proxy pose Pp, i.e., the pose that would control the master device in slave space if this method were not adopted.

[0131] According to an implementation option, the dynamic scaling factor associated with each axis has a minimum limit (maximum scale factor) equal to Fs_lim'. According to an implementation option, the scale limit factor is the same for all axes. According to another implementation option, the scale limit factor depends on the scale factor before applying the method.

[0132] According to one embodiment of this method, each of said dynamic scaling factors Fs' takes the form Fs'=Fs*U(Pp), where Fs is the scale factor before applying this method and U(Pp) is a reduction function expressed as a non-increasing function of the distance between said proxy pose and the nearest point belonging to the interior region of the slave device's workspace as defined above.

[0133] By providing such a control method, it is possible to avoid escaping from master-slave teleoperation when the pose controlled by the master device is outside the limits of the slave's workspace, improving usability.

[0134] As can be seen, the above-mentioned objects of the present invention are fully achieved by the method described above, thanks to the features disclosed in detail above.

[0135] To meet unexpected needs, those skilled in the art can make changes and adaptations to the above method embodiments or substitute other functionally equivalent elements without departing from the scope of the following claims. Each feature described above as belonging to one possible embodiment can be implemented regardless of the other embodiments described.

Claims

1. A method for controlling a slave device of a robotic system for remote operation of medical or surgical procedures, wherein the robotic system comprises at least one master device (110) adapted to be operated by an operator (150), and at least one slave device including a surgical instrument (170) adapted to be controlled by the master device, and the method is A step of determining, for each master trajectory of the master device, the respective slave target trajectory of the slave device in the slave reference coordinate system of the slave device, wherein the movement of the slave device is reduced by a scale factor (Fs) relative to the movement of the master device, the pose of the slave device has a transformation offset (OFF) which may be zero or non-zero relative to the pose of the master device, and the slave target trajectory is contained within a predetermined convex volume in the slave reference coordinate system for all movements of the master device, The steps include controlling the slave device so that it moves along the slave trajectory, Includes, The step of determining the slave target trajectory is, The edge region of the convex volume near the boundary of the convex volume and the internal region of the convex volume that is inside the edge region and therefore far from the boundary of the convex volume are defined. When the nominal target trajectory of the slave device, which corresponds to the trajectory of the master device mapped to the slave reference coordinate system, is outside the internal region of the convex volume, the scale factor (Fs) is dynamically changed to obtain a dynamically variable modified scale factor (Fm(t)), and the slave trajectory is modified with respect to the nominal slave trajectory obtained with the invariant scale factor so that the slave target trajectory remains within the predetermined convex volume. When the modified scale factor (Fm(t)) is greater than a predetermined maximum scale factor (Fmax), the conversion offset (OFF(t)) is also dynamically changed so that the slave device remains within the predetermined convex volume. including, method.

2. The convex volume corresponds to the slave working space of the slave device, defined by three orthogonal joints having a limited stroke. The method according to claim 1.

3. At least one of the slave devices comprises at least one joint adapted to move the slave device along at least one distinct direction (X, Y, Z) corresponding to one of three directions of the spatial reference coordinate system (X, Y, Z) associated with the slave workspace of the slave device, The slave workspace has physical limitations determined by the limits of the possible physical movement of the slave device in each direction (X, Y, Z) of the spatial reference coordinate system. The edge region of the slave workspace includes a point in the slave workspace that is less than a predetermined threshold (Xthr, Ythr, Zthr) from the physical limit. When at least one of the joints of the slave device is within the edge region, the method, with reference to the respective direction, dynamically changes the scale factor as the joint approaches the physical limit so that the trajectory traced by the joint always remains within the slave workspace. The method according to claim 1 or 2.

4. The slave device comprises three joints adapted to move the slave device along one of the three directions (X, Y, Z) of the spatial reference coordinate system. The three directions (X, Y, Z) are mutually orthogonal, defining the three orthogonal translational degrees of freedom of the joint. For each joint associated with the aforementioned directions (X, Y, Z), the physical constraint includes a three-dimensional physical constraint determined by the maximum possible physical movement of the device in each of the three orthogonal directions, and the edge region includes the space between a first parallelepiped corresponding to the internal region defined by distances corresponding to predetermined thresholds (Xthr, Ythr, Zthr) corresponding to each of the aforementioned directions, and a second parallelepiped defined by the limits of the physical movement corresponding to each of the aforementioned directions. The scaling factor includes, for each direction, the respective dynamic scaling factors (Fsx, Fsy, Fsz), where the three dynamic scaling factors (Fsx, Fsy, Fsz) for each direction are either the same or different from each other, and the predetermined thresholds (Xthr, Ythr, Zthr) are either the same or different from each other for each limit and / or joint. The method according to claim 3.

5. When there is no dynamic change in the scale coefficient (Fs) and there is no conversion offset (OFF), the nominal target pose in the slave workspace is defined, which is controlled by the pose of each master device in the master device's workspace. Verifying whether the nominal target pose lies inside or outside the internal region of the convex volume in the slave workspace, When the nominal target pose is outside the internal region, the step of dynamically changing the scale factor (Fs) includes scaling the scale factor (Fs) by a reduction function (U) that depends on the position of the nominal target pose. The method according to claim 2.

6. The reduction function (U) is a monotonic and non-decreasing function as a function of the distance between the nominal target pose and the nearest point in the internal region. The method according to claim 5.

7. The reduction function (U) acts independently on each individual joint and / or, Each individual joint operates according to a different reduction function (U). The method according to claim 5 or 6.

8. The reduction function (U) is a linearly increasing function, having a value of 1 at each point belonging to the boundary between the internal region and the edge region, corresponding to the nominal scale coefficient (Fs) effective for the nominal target pose within the internal region, and increasing with respect to the points in the edge region as they move away from the boundary between the internal region and the edge region, and having a value greater than 1, wherein the modified scale coefficient (Fm) applied to each point in the edge region increases linearly as a function of the distance the point moves away from the boundary between the edge region and the internal region. The method according to claim 6.

9. The reduction function (U) is a nonlinear function that exhibits a tendency toward a regular hyperbola. The method according to claim 6.

10. When the value of the reduction function (U) reaches or exceeds the predetermined maximum scale coefficient (Fmax), that is, at the point where the value of the reduction function (U) reaches or exceeds the predetermined maximum scale coefficient (Fmax), The method keeps the target pose of the slave device stationary, and stops the slave device translationally, thereby causing the target pose to deviate from the nominal target pose and determining the conversion offset (AOF) between the pose of the master device and the target pose of the slave device. The method according to claim 5 or 6.

11. The predetermined maximum scale factor (Fmax) is defined in relation to the definition of the internal region and the edge region of the slave workspace, thereby ensuring that the controlled trajectory of the slave device is located within the slave workspace of the slave device and extends entirely within it. The method according to claim 10.

12. When the nominal target pose controlled by the master device is reassigned to a reduction function (U) lower than the maximum scale factor (Fmax), the method provides readjusting the parameters of the reduction function (U) so as to recover the accumulated transformation offset (OFF) when the pose of the slave device re-enters the internal region of the slave workspace. The method according to claim 6.

13. The slave device provides, in addition to translational degrees of freedom corresponding to directions (X, Y, Z), at least one rotational degree of freedom (R) representing rotation about the axis of the slave device at the control point. The method controls the movement of the slave device in the workspace of the slave device in accordance with the movement of the master device in the workspace of the master device, so that the slave device follows the rotation of the master device in at least one rotational degree of freedom with a rotational scale factor (Fr). The method is such that when the joint of the slave device is within the internal region, the rotational scale factor (Fr) is equal to 1, and when the joint of the slave device is within the edge region, the method applies a rotational scale factor that is greater than 1 and increases as the joint approaches the physical limit of the edge region. The method according to claim 1 or 2.

14. The master device is an ungrounded master device, preferably one without force return. and / or, The master device is a type of master device that is not mechanically constrained by the operating console. The method according to claim 1 or 2.

15. A robotic system (100) for remote control of medical or surgical procedures, At least one master device (110) adapted to be operated by an operator (150), A slave device comprising at least one surgical instrument (170) adapted to be controlled by the master device, A control unit configured to control the slave device based on the movement of the master device during remote operation, Equipped with, The control unit is For each master trajectory of the master device, the determination of each slave target trajectory of the slave device in the slave reference coordinate system of the slave device, wherein the movement of the slave device is reduced by a scale factor (Fs) relative to the movement of the master device, and the pose of the slave device has a transformation offset (OFF) which may be zero or non-zero relative to the pose of the master device, and the slave target trajectory is contained within a predetermined convex volume in the slave reference coordinate system for all movements of the master device, and for each master trajectory of the master device, the determination of each slave target trajectory of the slave device in the slave reference coordinate system of the slave device, Controlling the slave device so that it moves along the slave trajectory, It is configured to do so, Determining the slave target trajectory is, The edge region of the convex volume near the boundary of the convex volume and the internal region of the convex volume that is inside the edge region and therefore far from the boundary of the convex volume are defined. When the nominal target trajectory of the slave device, which corresponds to the trajectory of the master device mapped to the slave reference coordinate system, is outside the internal region of the convex volume, the scale factor (Fs) is dynamically changed to obtain a dynamically variable modified scale factor (Fm(t)), and the slave trajectory is modified with respect to the nominal slave trajectory obtained with the invariant scale factor so that the slave target trajectory remains within the predetermined convex volume. When the modified scale factor (Fm(t)) is greater than a predetermined maximum scale factor (Fmax), the conversion offset (OFF(t)) is also dynamically changed so that the slave device remains within the predetermined convex volume. including, Robot system (100).

16. The control unit is configured to perform the method for controlling the slave device according to claim 1 or 2. The robot system (100) according to claim 15.

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