Method for controlling an articulated end effector actuated by one or more actuation tendons of a surgical instrument of a surgical robotic system, and related surgical robotic system

Abstract

A method is described for controlling an articulated end effector 40 actuated by one or more actuation tendons of a surgical instrument 20 of a surgical robotic system. The method is preferably executable during an operational phase of the surgical instrument. The method is applied to a surgical instrument 20 comprising an articulated end effector 40 and at least one actuation tendon 31, 32, 33, 34, 35, 36 configured to actuate the articulated end effector 40. The method is applied to a surgical robotic system comprising, in addition to said surgical instrument 20, a control means 9 and at least one electric actuator 11, 12, 13, 14, 15, 16 operatively connectable to each of said at least one actuating tendons 31, 32, 33, 34, 35, 36, for imparting movements to each of the actuating tendons controlled by the control means 9 and for determining an unambiguous correlation between a movement of at least one of the one or more electric actuators 11, 12, 13, 14, 15, 16 and a movement of each of the articulated end effectors 40. The method first comprises detecting a force Fm exerted by at least one of said one or more electric actuators 11, 12, 13, 14, 15, 16 during said movement steps of the surgical instrument. The method then comprises estimating, based on the detected force Fm, a length change of at least one of the one or more actuating tendons 31, 32, 33, 34, 35, 36 due to elastic elongation of the actuating tendons by a predefined mathematical model, and then using the estimated length change for a position control of one or more electric actuators 11, 12, 13, 14, 15, 16. Such a position control comprises imparting a movement to said at least one electric actuator 11, 12, 13, 14, 15, 16 taking into account the estimated length change of said at least one actuating tendon 31, 32, 33, 34, 35, 36 so as to reduce or counteract an error caused by said elastic elongation between a position reached by the articulated end effector 40 and a desired nominal position of the articulated end effector 40. A surgical robotic system adapted to be controlled by and / or configured to perform the aforementioned method is further described.

Description

[Technical field]

[0001] The present invention relates to a method for controlling an articulated end effector actuated by one or more actuation tendons of a surgical instrument of a surgical robotic system, and to an associated surgical robotic system.

[0002] In particular, the present invention relates to a control method that provides compensation for position errors of joints relative to a commanded position.

[0003] The present specification therefore relates more generally to the technical field of motion control of robotic systems for teleoperated surgery. [Background technology]

[0004] Known robotic systems for medical and / or surgical applications generally comprise at least one articulated end (or "articulated end effector" or "end effector") adapted to interact with a patient's anatomy, whether to perform a surgical or microsurgical procedure such as suturing, anastomosis, incision, etc., or to obtain image or diagnostic information.

[0005] Articulated end effectors are typically actuated by actuation cables (tendons) that transmit traction to the articulated end effector.

[0006] Medical and / or surgical robotic systems can operate according to a master-slave control architecture, for example where the master is hand-held by a surgeon, or can operate in an autonomous mode, for example by executing a series of programmed actions.

[0007] Anthropomorphic robotic systems are also known in which the articulated end effector comprises anthropomorphic joints, such as the joints of the phalanges of a robotic hand, which are realized by traction applied to actuation tendons.

[0008] A robotic system motor may be located upstream of the articulated end effector, with an actuation tendon operatively connected to both the motor and the articulated end effector, the pose of the articulated end effector being determined by the motion of the robotic system motor transmitted by the actuation tendon.

[0009] The number of actuating tendons for multiple degrees of freedom movement can vary, but typically two antagonistic tendons are connected to an articulated end effector with the same degree of freedom to move the articulated end effector in both directions.

[0010] There is therefore a strong felt need to provide a solution that can ensure a correspondence between the motor motion and the pose assumed by an articulated end effector.

[0011] In fact, the tendons can slide against each other when in motion, and they can also curl up, i.e. entangle each other, or slide on the walls of the articulated end effector or on the walls of the rigid or flexible or articulated positioning shaft, which can affect the accuracy of the transmission of the motor motion to the articulated end effector, resulting in a mismatch between the motor motion and the attitude of the articulated end effector.

[0012] In other words, the motion imparted by the motor may be distorted due to the mechanical behavior of the actuating tendons such that the expected attitude is not achieved.

[0013] Furthermore, for small articulated end effectors, the size of the actuating tendons becomes critical to transfer the motor motion to the articulated end effector: indeed, as the scale decreases, the longitudinal deformation of the tendons that can be recovered in precise amounts becomes increasingly large.

[0014] To facilitate miniaturization of articulated end effectors, it is possible to use polymer actuated tendons, as shown, for example, by WO 2017-064303 and U.S. Patent Application Publication No. 2021-0106393, both of which are owned by the same applicant.

[0015] Such type of actuated tendons allow the tendon friction and diameter to be reduced, making it possible to move very small connection radii.

[0016] Additionally, small articulating end effectors are typically located at the distal end of a positioning shaft that forces the actuating tendons to extend over a relatively long extension relative to the extent of tendon extension along the articulating end effector device at only the distal end of the shaft. By providing such elongated tendons, the occurrence of tendon deformability in the longitudinal direction increases when in an actuated state.

[0017] For example, in winch transmission systems, tendons wind around a rotating spool and cross or intertwine with one another during such winding, thereby causing localized increased friction and potentially causing a tear-off transmission of the motor motion.

[0018] Similarly, when the tendons are entangled, i.e., intertwined inside the extension of the shaft of the medical and / or surgical instrument, there is a localized increase in friction that affects the transmission.

[0019] In other words, in the above cases, there is a mismatch between the action of the motor and the movement of the articulated end effector due to the sliding friction phenomenon between different tendons or between sections of the same tendon.

[0020] Another situation that can cause a mismatch between the motion of the motors and the motion of the articulated end effector can result from the inherent elasticity of the individual actuating tendons, which when stressed can lengthen and absorb some of the motion imparted by their respective motors and not effectively transmit that motion to the articulated end effector. In general, elastic recovery of deformation occurs rapidly when the perturbation ceases, and in certain cases, a tendon can immediately recover its elastic deformation when the motion imparted by the motors ceases.

[0021] However, these dynamics can impart undesired motion to the articulated end effector, for example, the revolute joint of an articulated wrist may be actuated when the motor stops working.

[0022] Miniature articulated end effectors are desirable in the medical surgical field, as well as in the field of anthropomorphic robotics, as well as in microelectronics, micromechanics, precision mechanics, watchmaking, jewellery and costume jewellery, and more generally in automation.

[0023] Particularly in the medical-surgical field, the articulated end effector is a sterile component of the system and operates within a sterile field under operating conditions, and it is often not possible or desirable to equip the articulated end effector with an active sensor system to enable the robotic system to detect in real time the pose assumed by the articulated end effector itself.

[0024] At the same time, there is a strong push in the field towards extreme miniaturization of articulated end effectors, requiring smart control over the position of, and the motions performed by, articulated end effectors to ensure safety and at the same time ease of use.

[0025] In the case of a teleoperated robotic system according to a master-slave control architecture, the movement of the motors is controlled based on movements provided by a user on a master control device, which may take the form of a joystick, i.e., a mechanical attachment that cantilevers from the master manipulation console, and may include an electromotive force feedback system that provides haptic feedback to the user that depends on information detected by a sensor system in an articulated end effector.

[0026] Non-ground bound teleoperated robotic systems are also known in which the master control device may be "ungrounded", i.e., not include a haptic feedback system.

[0027] Therefore, the need to come up with a solution to ensure correspondence between the movements imparted by the motors of a robotic system and the movements performed by the articulated end effector, while avoiding the inclusion of a sensor system in the articulated end effector itself, is highly felt in various fields.

[0028] At the same time, there is a need to reduce the size of the articulated end effector of the robotic system without reducing control of the articulated end effector itself. Summary of the Invention

[0029] The object of the present invention is to provide a method for controlling an articulated end effector actuated by an actuation tendon of a surgical instrument of a surgical robot system, making it possible to at least partially overcome the drawbacks mentioned above with reference to the background art, and to respond to the above-mentioned need, which is particularly felt in the technical field considered. Such an object is achieved by a method according to claim 1.

[0030] Further embodiments of such a method are defined in claims 2-32.

[0031] It is further an object of the present invention to provide a surgical robotic system adapted to be controlled by the above mentioned control method and / or configured to carry out the above mentioned method. Such an object is achieved by a system according to claim 33.

[0032] Further embodiments of such a system are defined by claims 34 to 51.

[0033] The above method provides a solution to the above mentioned technical problem.

[0034] In fact, the proposed solution makes it possible to use a behavioral model in the operating conditions of the actuating tendons to produce a position control method for the motors of a robot manipulator intended to actuate a small articulated end effector.

[0035] The motor position control is a feedback motion control loop based on detected information regarding the force exerted by the motor on a transmission unit comprising at least said actuating tendons.

[0036] The information about the applied force can be detected by a load cell arranged on the motor at its interface with the transmission unit. For example, the transmission unit comprises a rigid element, for example a piston, which interfaces with the motor, and an actuation tendon connected to the articulated end effector and rigidly connectable to the rigid element and for example glued to the piston. Thereby, the force detected at the interface between the motor and the rigid element of the transmission unit, rigidly connectable to the actuation tendon, is substantially equal to the traction force applied to the actuation tendon. If the connection between the motor and the actuation tendon is not rigid, the method can take into account the yielding of the connection between the motor and the tendon.

[0037] Information about the applied force is used for real-time estimation of the elastic elongation of the actuated tendon, which for example can be proportional to the force applied by the motor to the transmission unit, as detected.

[0038] The proposed solution makes it possible to avoid adding sensors to the articulated end effector, ensuring a correspondence between the motor movements and the pose assumed by the articulated end effector, while keeping the sensors as far "upstream" as possible to detect information useful for the control method, e.g. in the medical-surgical field this makes it possible to keep the sensors away from the sterile field.

[0039] When a teleoperated master-slave robotic system is provided, the proposed solution helps to ensure correspondence between the motions of the master device and the poses assumed by the articulated end effector of the slave device, minimizing master-slave tracking delays.

[0040] The proposed solution makes it possible to compensate for the elastic component of said mismatch between the motor's motion and the pose assumed by the articulated end effector.

[0041] The proposed solution allows the use in a precise and controlled manner of actuated tendons that are long, thin and undergo high elastic deformations based on the force applied by the motor.

[0042] The proposed solution makes it possible to accurately estimate the current pose of the articulated end effector by means of a model of the transmission movement performed by the transmission unit based on the forces applied to it, as detected.

[0043] The methods of the present invention are particularly adapted, but not necessarily intended uniquely, to control surgical robotic systems, particularly in a master-slave fashion.

[0044] The method according to the present invention is adapted to control anthropomorphic robotic systems that do not necessarily comprise robotic phalanges actuated by actuation tendons.

[0045] Further features and advantages of the method according to the invention will become apparent from the following description of preferred exemplary embodiments, given by way of non-limiting indication, in connection with the attached drawings, in which: [Brief description of the drawings]

[0046] [Figure 1] FIG. 1 illustrates an axonometric view of a telesurgical robotic system according to one embodiment. [Diagram 2] FIG. 2 illustrates a portion of the telerobotic system of FIG. 1 in an axonometric view. [Diagram 3] FIG. 2 illustrates an axonometric view of a distal portion of a robotic manipulator according to one embodiment. [Figure 4] FIG. 1 illustrates an axonometric view of a surgical instrument according to one embodiment, with tendons shown diagrammatically in dashed lines. [Diagram 5] 13A-13C illustrate schematic diagrams of actuation of degrees of freedom of an articulated end effector of a surgical instrument according to possible modes of operation. [Figure 6] 3 illustrates an operation mode of an embodiment of a control method according to the present invention. [Figure 7-1] 3 illustrates an operation mode of an embodiment of a control method according to the present invention. [Figure 7-2] 3 illustrates an operation mode of an embodiment of a control method according to the present invention. [Figure 7-3] 3 illustrates an operation mode of an embodiment of a control method according to the present invention. [Figure 8] FIG. 4 is a flow diagram showing the steps of the adjustment method according to possible modes of operation. [Figure 9] 1 illustrates a schematic diagram of a powered actuator, a transmission element, and a tendon of a surgical instrument according to one embodiment. [Figure 10] 1A-1C are schematic cross-sectional views of a portion of a surgical instrument and a portion of a robotic manipulator illustrating actuation of degrees of freedom of the surgical instrument according to possible modes of operation. [Figure 11] FIG. 1 is a partial cross-sectional axonometric view for clarity showing an articulating end effector of a surgical instrument, according to one embodiment. [Figure 12-1]FIG. 2 shows a time domain block diagram of a control / compensation method according to an embodiment of the present invention. [Figure 12-2] 1 shows a block diagram of a control / compensation method according to an embodiment of the present invention in two different conditions in the Z-transform domain. [Figure 12-3] 1 shows a block diagram of a control / compensation method according to an embodiment of the present invention in two different conditions in the Z-transform domain. [Figure 13] 1 illustrates some operating conditions and / or states of a surgical instrument in which the implementation of the control / compensation method according to the present invention may be applied or inhibited, according to various possible operating modes. [Figure 14] 1 illustrates some operating conditions and / or states of a surgical instrument in which the implementation of the control / compensation method according to the present invention may be applied or inhibited, according to various possible operating modes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] 1-14, a method of controlling an articulated end effector 40 actuated by one or more actuation tendons of a surgical instrument 20 of a surgical robotic system is described.

[0048] The articulated end effector is hereinafter also referred to as an "articulated end device" or "end effector" (the commonly used English term).

[0049] The method is preferably executable during an operational phase of a surgical instrument.

[0050] The method is applied to a surgical instrument 20 comprising an articulated end effector 40 and at least one actuation tendon 31 , 32 , 33 , 34 , 35 , 36 configured to actuate the articulated end effector 40 .

[0051] The method is applied to a surgical robotic system comprising, in addition to the surgical instrument 20, a control means 9 and at least one electric actuator 11, 12, 13, 14, 15, 16 operably connectable to each of the at least one actuating tendon 31, 32, 33, 34, 35, 36, for imparting movements to each actuating tendon controlled by the control means 9 and for determining a unique correlation between a movement of at least one of the one or more electric actuators 11, 12, 13, 14, 15, 16 and a movement of each of the articulated end effectors 40.

[0052] The method first comprises the step of detecting a force Fm exerted by at least one of said one or more powered actuators 11, 12, 13, 14, 15, 16 during said phase of operation of the surgical instrument.

[0053] The method then includes a step of estimating a length change of at least one of the one or more actuating tendons 31, 32, 33, 34, 35, 36 due to elastic elongation of the actuating tendons by a predetermined mathematical model based on the detected force Fm, and then using the estimated length change for position control of one or more electric actuators 11, 12, 13, 14, 15, 16.

[0054] Such position control includes imparting movement to said at least one electric actuator 11, 12, 13, 14, 15, 16 taking into account the estimated change in length of said at least one actuating tendon 31, 32, 33, 34, 35, 36 so as to reduce or offset the error caused by said elastic stretching between the position reached by the articulated end effector 40 and the desired nominal position of the articulated end effector 40.

[0055] Such a desired nominal position may be, for example, the position that would be obtained in the absence of elastic stretch.

[0056] It should be noted that the aforementioned technical effect of reducing or offsetting errors caused by elastic stretching may include or correspond to "compensating" for such errors and / or "minimizing" such errors.

[0057] According to an embodiment in which the robotic system is a master-slave system and the surgical instrument is a slave device that is commanded by the master device of the robotic system according to a control mode, the method makes it possible to achieve a predetermined kinematic correspondence between the pose commanded by the master device and the pose reached by the articulated end effector 40 of the slave device (i.e. in the absence of external forces, this makes it possible to minimize in a finite time the error between the pose commanded by the master device and the pose reached by the articulated end effector 40 of the slave device).

[0058] According to one embodiment of the method, in which the robotic system is a master-slave system and the surgical instrument is a slave device controlled by the master device of the robotic system according to a control mode, the imparting step takes into account command actions performed by a user.

[0059] According to an alternative embodiment, the method is applied to an autonomous robotic system without a master device or where the master device has been temporarily or permanently deactivated.

[0060] According to one implementation option, the method is applied to an untethered master device (i.e., "in flight" or "grounded").

[0061] According to one implementation option, the method is applied to a master device without a force feedback system, whereby the user does not receive information from the master device.

[0062] According to one embodiment of the method, in which the surgical instrument 20 comprises a plurality of actuating tendons 31, 32, 33, 34, 35, 36 and the surgical robotic system comprises a respective plurality of electric actuators 11, 12, 13, 14, 15, 16, the aforementioned step of detecting forces is performed for a plurality or all of the electric actuators 11, 12, 13, 14, 15, 16, the aforementioned step of estimating is performed with reference to a plurality or all of the actuating tendons 31, 32, 33, 34, 35, 36, and the step of applying is performed for a plurality or all of the electric actuators 11, 12, 13, 14, 15, 16.

[0063] According to one embodiment, the method further comprises a step of verifying information regarding the state of the robotic system and then deciding, by the control means 9, based on one or more conditions related to the state of the robotic system, whether or not to execute the aforementioned step of imparting movements to the electric actuators in order to reduce and / or counteract and / or compensate for errors caused by elastic stretching, and executing the imparting step only if said one or more conditions are fulfilled.

[0064] According to one embodiment, the method is applied to a robotic system having a handheld, untethered master device adapted to be moved and manipulated by an operator according to degrees of freedom related to closure and / or grasping of a microsurgical slave instrument.

[0065] In one implementation option of such an embodiment, it is provided that during remote operation, when the surgical instrument is in a grasped state, the aforementioned step of imparting movement to the electric actuators to reduce and / or counteract and / or compensate for errors caused by elastic elongation is inhibited for at least one of the electric actuators connected to at least one actuating tendon of each of the grasp degrees of freedom.

[0066] Another implementation option of such an embodiment provides that, during remote operation, when the surgical instrument is in a grasped state, the aforementioned step of imparting movement to the powered actuators is reduced according to a scaling factor between 0 and 1 for at least one of the powered actuators connected to at least one actuating tendon of each of the grasp degrees of freedom.

[0067] In another implementation option of such an embodiment, it is provided that the aforementioned step of imparting movement to the electric actuators is constrained with respect to two electric actuators connected to two antagonistically actuated tendons in each of the grip closing degree of freedom, or four electric actuators connected to four actuated tendons of a pair of antagonistically actuated tendons in the grip closing degree of freedom and the grip opening degree of freedom.

[0068] In another implementation option of such an embodiment, it is provided that the aforementioned step of imparting movement to the motorized actuators is reduced according to a scaling factor between 0 and 1 for two motorized actuators connected to two antagonistically actuated tendons in each of the grip closing degree of freedom, or for four motorized actuators connected to four actuated tendons of a pair of antagonistically actuated tendons in the grip closing and grip opening degrees of freedom.

[0069] In another implementation option of such an embodiment, it is provided that the aforementioned step of imparting movement to the electric actuators is suppressed for all electric actuators.

[0070] Another implementation option of such an embodiment provides that the aforementioned step of imparting movement to the electric actuators is reduced according to a scaling factor between 0 and 1 for all electric actuators.

[0071] According to one implementation option, the method is performed in an operation phase (here defined as "not squeezing", shown in FIG. 13 ) where teleoperation is active and the operator moves the degree of freedom of the master device related to the closure and / or grasping of the microsurgical slave instrument (closure angle greater than a certain threshold) within the interval of the master movement that is transferred in the corresponding movement of the end effector and not the grasping force.

[0072] In contrast, the compensation method is inhibited in the phase (defined here as “freeze”) where the teleoperation is active and the operator keeps the master above the grasping threshold (with a closure angle smaller than a certain threshold—the “squeezing” state shown in FIG. 13 ) while maintaining the compensation value at the same level as when the “freeze” step was entered.

[0073] According to an embodiment in which the master device is a handheld, untethered master device adapted to be moved and manipulated by the operator according to degrees of freedom related to the closure and / or grasping of the microsurgical slave instrument, it is provided that, at the end of the teleoperation, if the surgical instrument is in a grasping state and it is desired to maintain the grasping state (here defined as "holding compression"), the aforementioned step of imparting movement to the powered actuators is inhibited for all powered actuators connected to the respective actuation tendons.

[0074] According to one embodiment, the method provides that when terminating telemetry in a non-gripped state, the estimated length changes of each of the one or more actuated tendons during the previous telemetry are removed before re-entering a new telemetry.

[0075] According to one implementation option, in such a condition, the elastic compensation action is removed, thereby returning the surgical instrument to a known initial zero position.

[0076] According to one embodiment, each of the one or more actuating tendons 31, 32, 33, 34, 35, 36 is operably connected to both a respective electric actuator of the robotic surgical system and to the articulated end effector 40 to actuate a respective one of the one or more degrees of freedom (P, Y, G) of the articulated end effector 40.

[0077] According to one implementation option, the degrees of freedom of the articulated end effector 40 include a pitch degree of freedom, and / or a yaw degree of freedom, and / or a grip degree of freedom.

[0078] According to one implementation option, at least one of the one or more actuating tendons 31 , 32 , 33 , 34 , 35 , 36 actuates a rotational degree of freedom of the articulated end effector 40 .

[0079] According to one embodiment, the aforementioned steps of detecting the forces exerted by the electric actuators 11, 12, 13, 14, 15, 16 are performed by respective force or torque sensors operatively connected to the respective electric actuators.

[0080] According to one implementation option, such a sensor is a force sensor arranged at the contact interface of each motor (eg, on the sterile side).

[0081] According to one implementation option, such a sensor is a torque sensor.

[0082] According to one embodiment, the step of detecting the force Fm is performed continuously at a detection frequency Fr and the aforementioned position control of the one or more electric actuators is performed continuously at a position control frequency Fcp.

[0083] The aforementioned detection frequency Fr and position control frequency Fcp are set to ensure compensation of elastic stretching substantially in real time relative to the actuation time of the remote control, i.e. in real time with dynamics that are not perceptible to the user.

[0084] According to one implementation option, said detection frequency Fr and position control frequency Fcp are coincident and are comprised in the interval between 100 Hz and 1000 Hz.

[0085] In such a case, the compensation method is therefore carried out at each period T comprised in an interval between 1 and 10 ms, based on the force Fm detected at the same period.

[0086] According to one embodiment, the estimating step includes estimating the length change of the actuated tendon as a ratio of the elastic modulus Fm of the force detected in the actuated tendon to an effective elastic constant value K, which may be experimentally determined or calculated or predetermined to ensure system response stability.

[0087] According to one embodiment, the steps of using the estimated length change for position control and imparting motion to the respective motorized actuators are performed based on the following equation: TIFF2024535362000002.tif9150 Such a formula is specific to each electric actuator and therefore determines the specific control of each electric actuator.

[0088] In the above equation, u is the commanded position of the electric actuator, Kel is the elastic constant of the actuating tendon (hereinafter such elastic constant will also be denoted K_exp when experimentally determined), and Ω is a multiplication parameter.

[0089] According to the implementation option, since the multiplication parameter Ω is greater than 1, the effective elastic constant value K=ΩKel used in the calculation is greater than the tendon elastic constant value by a factor equal to the aforementioned multiplication parameter Ω, thus ensuring that the effective tendon elastic constant value K is overestimated and therefore larger than the elastic constant Kel of the same actuated tendon.

[0090] In the aforementioned embodiment, an important aspect concerns the ratio between the experimentally determined elastic constant (Kel, or K_exp) and the elastic constant K used in the model, also defined as the "effective elastic constant value K".

[0091] In particular, in such embodiments, as discussed above, the value K used in the algorithm must be greater than the experimentally determined value k_exp due to the need for convergence of the algorithm.

[0092] The aforementioned parameter Ω defines a ratio between K and K_exp comprised in the interval 100% to 150%, preferably +10% to +50%.

[0093] According to one implementation option, such multiplication parameter is between 0.7 and 1.5.

[0094] According to an implementation option of the aforementioned embodiment, the aforementioned effective elastic constant value K and therefore also the multiplication parameter Ω are variably determined depending on the state of the robot system, and / or the spatial conditions of the master device and / or the slave device, and / or the teleoperation endurance time.

[0095] In other words, K can change depending on the teleoperation endurance time, or depending on the point in the workspace where it is located (master or slave), or changing the compromise between system consistency and stability. The value of K can be re-estimated during teleoperation, e.g., if the force spikes are large, the value of K can be changed / adjusted as needed for stability.

[0096] The value of K can be adjusted empirically without regard to the actual elastic stiffness value of the tendon. For example, the value of K can be chosen experimentally to account for dispersions in the tendon-instrument system (e.g., due to local sliding friction in the extension of the tendon) and therefore the value of K does not necessarily relate to the actual elastic constant of the tendon when considered alone.

[0097] According to one implementation option, the value of K, if considered alone, is an underestimate of the tendon elastic constant value.

[0098] According to one implementation option, the value of K is chosen experimentally in an arbitrary manner to experimentally ensure system stability.

[0099] According to one embodiment, the compensation method is performed in the presence of force values ​​below 40N.

[0100] It should be noted that according to some possible implementations related to the successively detected force intervals Fm, the algorithm can work over the entire spectrum. In an implementation option where the method is applied to a robotic system for microsurgery, it is carried out in the presence of low forces present in such situations, i.e. forces below 40 N, for example of the order of 10 N.

[0101] The advantage of such an implementation option is that it ensures compensation during operation.

[0102] According to one embodiment, the method is applied to a surgical instrument 20 further comprising at least one transmission element 21, 22, 23, 24, 25, 26 operably connected to at least one actuating tendon 31, 32, 33, 34, 35, 36, respectively, and operably connectable to respective electric actuators 11, 12, 13, 14, 15, 16.

[0103] Thus, in such a case, the surgical instrument comprises a number of "transmitting units", each comprising an actuating tendon and a piston, preferably with the tendon fixed to the piston, and each electric actuator acting by imparting a displacement to the piston of the transmission unit.

[0104] According to one implementation option, the surgical instrument comprises six transmission units, i.e. six tendons, six electric actuators and six pistons.

[0105] According to an implementation option, each sending unit (i.e. each motor-piston-tendon chain) is managed individually.

[0106] According to another implementation option, the antagonistic transmission units (and therefore the antagonistic tendons) are managed in pairs.

[0107] According to one implementation option, the step of imparting movement and / or exerting force includes controlling movement of each electric actuator such that movement of the transmission element includes compensation due to elongation or relaxation of each actuating tendon based on both the estimated length change of each actuating tendon and the elastic modulus and stiffness of the actuating tendon.

[0108] According to an implementation option, a reference kinematic zero state is defined in the robotic system by relating a virtual zero point to which the movements imparted by the control means to the electric actuators are referenced to stored reference positions. In such a case, the step of imparting movements and / or exerting forces to each of said transmission elements comprises calculating a corrective kinematic zero taking into account the compensation performed.

[0109] According to one implementation option, the step of imparting motion and / or exerting a force on each transmission element includes exerting a force on the transmission elements by a dual feedback operating loop, in which an elastic compensation correction is inserted in parallel with the displacement of the electric actuator by the kinematic mechanism.

[0110] According to one embodiment, when the motorized actuator is a stepper motor actuator, the position control is performed via a velocity control, known as the work time unit, which determines the position control.

[0111] In an implementation option of such an embodiment, velocity and position control is performed by a feedback motion control loop, with the gain parameter (Kp) sized to ensure convergence of the compensation with a time constant lower than the maximum convergence time.

[0112] According to one embodiment, such maximum convergence time is less than 1 second and is preferably comprised in the interval 100ms to 200ms.

[0113] According to one implementation option, the speed control comprises a kinematic component and a dynamic component.

[0114] The dynamic compensation component receives the detected forces Fm as input, calculates the estimated displacement lost due to the elasticity of the actuated tendons according to the aforementioned equations, and generates a velocity compensation contribution that is added to said velocity kinematic component by a proportional controller tuned to have dynamics that comply with the stability requirements.

[0115] The sum of the aforementioned kinematic and dynamic velocity contributions is provided as an input to the electromotive actuator to be controlled.

[0116] The controllers for the kinematic and dynamic components are preferably parallel.

[0117] According to one embodiment, position and / or velocity control is performed in a common manner for multiple powered actuators, for example by performing joint control for each pair of antagonist tendons based on common effective elastic constant values, depending on conditions such as the position of the master or slave device and / or the aging or state of the robotic system.

[0118] According to one embodiment, position and / or velocity control is performed only if the detected force Fm is lower than a maximum operating force value Fmax, and execution of the method is inhibited when only one of the electric actuators detects a force greater than such maximum operating force Fmax.

[0119] Indeed, in such cases, the maximum force available for the safety margin is required to prevent the algorithm from diverging, i.e., to ensure convergence.

[0120] Alternatively, as explained above, the controller may act on many tendons and take into account the state of the entire control system.

[0121] In one embodiment, the algorithm is stopped when only one of the motors is above a certain threshold.

[0122] According to one embodiment, the stretch compensation parameter is controlled and variably determined as a function of the pose of the articulated end effector 40 to take into account different frictions associated with different poses.

[0123] For example, the wrap angle of the tendons on the end effector links can be different between one tendon and the other antagonistic tendon, e.g., near the stroke end of the yaw degree of freedom. In such an embodiment, each tendon slides on the convex curved surface of the link that defines a contact path, and the sum of all the contact paths of the tendons on the convex curved surfaces of all links (excluding the fixed links) at a given time defines the wrap angle.

[0124] Therefore, the link tendon friction forces between the two antagonistic tendons of a pair are not always the same, but change based on the wrist posture. The algorithm recognizes the wrist posture and therefore compensates for the elasticity of one tendon differently than the other.

[0125] In this embodiment, the algorithm can associate the determination of the variable K and / or the suppression or operation of compensation and / or the use of a compensation method to one tendon rather than another, based on the known or calculated kinematic position of the wrist (end effector).

[0126] In implementation options, experimental data is stored and / or the expected forces on each tendon are mathematically computer modeled as a function of wrist posture due to sliding friction.

[0127] If an object is struck or moved (causing an increase in the external force acting on the end effector), the detected force associated with at least one tendon of the pair increases without activating a degree of freedom. In such a case, according to an embodiment, the method can modify K and / or inhibit the operation of the compensation and / or use the compensation method on one tendon but not on the other tendon.

[0128] More generally, in one embodiment, it is determined whether an increase in force read by a sensor on the powered actuator is due to wrist movement or an external force, and compensation is adapted accordingly.

[0129] According to one embodiment, the method is applied to a polymer actuated tendon, preferably formed from entangled polymer fibers.

[0130] According to one embodiment, the robotic system is a micro-telesurgery robotic system and the surgical instrument is a micro-surgical instrument.

[0131] Referring again to Figures 1-14, further details are provided below, by way of non-limiting examples, with reference to some specific embodiments of the method.

[0132] First, it should be noted that during remote operation, the user can control the instrument through a kinematic relationship that relates the displacement of the master device to the displacement of electric actuators (e.g., six linear electric actuators housed within a motor box).

[0133] The controllability of the instrument is also ensured by a mechanical connection between the aforementioned electric actuators and corresponding pistons present in the back end of the instrument itself.

[0134] Therefore, a procedure is foreseen that ensures the correct success of such a coupling, called "engagement" of the instrument. The engagement procedure is a necessary condition for each control action of the instrument itself.

[0135] In this embodiment, the linear actuator present in the motor box can control the three degrees of freedom (the aforementioned "yaw", "pitch" and "grip") present in the wrist of the surgical instrument (i.e., the end effector, or articulated end device) via an appropriate transmission system consisting of a tendon system.

[0136] In particular, the controllable part of a microsurgical instrument consists of two tips with a shared degree of freedom (Pitch) and a degree of freedom (Yaw) specific to each tip. Therefore, in this expression, a degree of freedom grip can be defined as the difference between the commanded Yaw values ​​of the two tips of the microsurgical instrument.

[0137] In such a mechanism, the coupling between the instrument piston and the wrist is performed by two antagonistic tendons for each of the aforementioned degrees of freedom, i.e., two antagonistic tendons (shared by the two tips) for control of the "pitch" degree of freedom, and two antagonistic tendons for control of the "yaw" degree of freedom of each of the two tips.

[0138] Approximately, the kinematic law coupling the six pistons of the instrument to the tip of the instrument considers the pistons of the motor box connected to the two tips of the microsurgical instrument via inelastic tendons. As already observed in the previous description, the model accuracy required for a robust and efficient control of the instrument must take into account that the tendons undergo reversible and irreversible deformations every time they are stressed.

[0139] In particular, the actuation model used here provides that the instrument pistons are actuated by six motors via dedicated mechanical linkages that directly convert the motor displacements into displacements of the relative pistons. Due to the slight internal friction of the instrument, the motor displacements result in the application of forces to the relative pistons. This command is converted into a cyclic extension of the associated tendons.

[0140] From the sole analysis of the system in static equilibrium, while ignoring the dynamic components of the motion and the presence of external forces, it is clear that a control system intended to control the degrees of freedom of the instrument must take into account the following components added together: - displacement of the piston such that the wrist can reach the desired configuration; the presence of a displacement of said piston adapted to compensate for the elongation of the cable.

[0141] In this embodiment, by way of example, an algorithm is described having the objective of ensuring the kinematic coincidence between the master and slave devices and compensating for the elastic elongation of the tendons while taking into account internal and external steady states.

[0142] In this connection, it is assumed that the plastic components can be neglected or are in any case compensated for by other appropriately designed components of the control system.

[0143] The algorithm is based on observability of the forces applied by the actuators, an open loop and real-time compensation of elastic losses calculated according to Hooke's law. According to one implementation option, the algorithm operates during the robot teleoperation phase.

[0144] According to the assumptions made in the previous paragraph, each of the motor-piston-tendon systems can be considered as a decoupled system and can be modeled graphically as shown after Fig. 7-3 (Fig. 7ter). As a first approximation, external forces on the tip or caused by antagonistic tendons are not taken into account.

[0145] In particular, the motor is suitably dimensioned and controlled with a much faster dynamics than the model in question, so that the motor dynamics can be modeled by a pure displacement of position. In this context, the controlled displacement u of the motor corresponds to a force Fp applied to the piston. The reaction force Fm=-Fp experienced by the motor during the movement is acquired by a suitable force sensor placed at the contact surface between the motor and the piston. The motor-piston coupling is assumed to be secured at all times.

[0146] Thus, the piston transmits a force Fp to the tendon which acts during traction to transmit motion to the tip of the microsurgical instrument, and the force Fp (acting on the outer surface of a non-zero radius revolute joint integral with the tip of the instrument) is balanced by a torque Ma which sums up the friction forces present in the final revolute joint.

[0147] Referring to FIG. 5, the friction provided by the ball bearings (shown as circles in the figure) can be neglected with respect to Fp, so the force in the cable section between the bearings can be considered to be the same as the force of the cable section towards the wrist.

[0148] The cable ends (provided between the wrist pitch joint and the end node) are typically two orders of magnitude smaller than the total length of the cable, so the extension of such ends can be neglected. Thus, the tendon elastic constant Kel and constant force Fm along the entire cable can be considered, and the elongation is calculated as |Fm| / Kel. r=u-|Fm| / Kel(1) where Kel is the tendon elastic constant, calculated in this case as Kel=EAL (where E=Young's modulus, A=cable cross section, L=cable length), and r is the actual tip movement.

[0149] In one embodiment, Kel can be considered constant despite the cycles the polymer tendons undergo for a particular actuation method, and thus governed by the variable Kel. This is again due to the fact that for a particular type of actuation, each degree of freedom is controlled by two antagonistic tendons, where it can be stated that only the tendons associated with the pushing motors contribute to the actual displacement in the desired direction, while the antagonistic muscles are placed with negligible force to avoid force components opposing the movement. It is therefore possible to approximate the value Kel to a constant value that reflects the rising front of the hysteresis cycle characteristic of the polymer fiber in question.

[0150] |Fm| is the modulus of force exerted by the piston and measured by an appropriate force sensor, u is the position controlled by the motor, r is the displacement of a point on the outer surface of the non-zero joint related to the angular rotation of the tip y from the ratio y = r / R, and R is the radius of the revolute joint.

[0151] Starting from equation (1), we get: y=(u-|Fm| / Kel) / R (2)

[0152] In this context, the objective of the control algorithm is to provide the motor with an appropriate control position u such that: 1. It is necessary to minimize the error between the desired position x and the final position r, and further ensure the asymptotic stability of the final position r, as well as its reachability in finite time. 2. Ensure the internal stability of the system (finite u and Fm) in the borderline case of no end effector motion at the desired target position change for arbitrarily long time intervals, e.g. due to the presence of external forces or the prevalence of static friction.

[0153] Without loss of generality, we assume that the actuator is controlled by a discrete velocity control. The control dynamics of the actuator can be considered to be much faster than the dynamics of the system in question, and therefore, at any instant t (a multiple of the discrete execution time of the algorithm), the position u can be considered to be equal to the time integral of the velocity v delivered to the motor up to that instant.

[0154] In Figure 12-1 (Figure 12), the control algorithm is shown for the case where Delta_r ≠ 0 (the system is moving). Similarly, for Delta_r = 0, the equations present in the physical system block are of the type Fm = Ke lu.

[0155] Thus, the proposed algorithm, modeled discretely in the space of Z-transforms, looks as shown in Figure 12-2 (Figure 12bis) when Delta_r ≠ 0 and as shown in Figure 12-3 (Figure 12ter) when Delta_r = 0.

[0156] It should be noted that in the embodiment described herein, the algorithm does not assume knowledge of whether the end effector is stationary or moving, but proceeds according to the steps shown below: Figures 12-1, 12-2 (Figure 12bis) and 12-3 (Figure 12ter) should therefore be understood as merely exemplary modelings written in the space of the Z-transformation.

[0157] In this embodiment, the proposed algorithm is intended to be executed on each of the motor-piston-transmission tendon systems independently of each other.

[0158] Therefore, the algorithm consists of the following steps:

[0159] A) The force modulus |Fm| exerted by the motor on the piston is obtained in real time, for example by a load cell placed at the contact surface between the motor and the piston.

[0160] B) Assuming that the elongation experienced by the tendon is only of elastic type, it is calculated as Δ_stretch=(|Fm|) / K, where the tendon elastic constant K has been previously estimated experimentally (in the preferred form, K=φk_exp, where 0.7>Ω>1.5, thus entailing an underestimation or overestimation of the experimentally obtained elastic constant).

[0161] C) The obtained Δ_stretch value is used as a reference for a proportional controller that returns the velocity Vstr(z) component in the feedforward that is added to the commanded kinematic trajectory to compensate for the tendon extension in each control cycle. It can be demonstrated that a properly calibrated proportional controller is a sufficient condition to obtain stability of the system modeled in this way.

[0162] Finally, in this embodiment, the management of the activation and deactivation of the algorithms is based on a state machine, which is described in the following paragraphs.

[0163] The following parameters are involved:

[0164] K-Estimated Tendon Elastic Constants (also defined above as "effective elastic constant values") According to the proposed model, the elastic constant is an important parameter since its value is much larger than the actual one (experimentally obtained) k_exp to ensure that the control variable u(z) is bounded.

[0165] In particular, consider the case where the torque Me compensates for or exceeds the torque caused by the force Fm (e.g., the presence of strong static friction or the active presence of antagonistic tendons, or the absence of movement of the end effector due to external forces acting on the end effector). In this condition, the force Fm depends on the elongation of the cable and therefore: Fm = -K u Here, K=Ωk_exp. The force measured by the sensor is therefore Fm=Ωk_exp u, where Ω>1, and hence the command to the motor is u=Fm / (Ωk_exp).

[0166] According to the model shown in Figure 12-3 (Figure 12ter), the control variable u(z) can be expressed as a function of the input xkine(z). The transfer function in the space of the Z-transform of the system formed by the controller, the actuation and the physical system is: TIFF2024535362000003.tif9150 has a single pole TIFF2024535362000004.tif11150

[0167] According to discrete system analysis studies, such a criterion function is stable if its poles are completely contained within the unit circle, i.e., the following relationship holds: For K_p>0, values ​​of K>k_exp are considered. As K increases, the stability margin of the system also increases. The physical meaning of having K larger than the real k_exp is equivalent to compensating for smaller stretches than exist in the physical system.

[0168] The evaluation of the error introduced by the difference K-k_exp can be performed by analyzing the trend of the error when Delta_r≠0 (considering FIG. 12-2 (FIG. 12bis)). e=ru

[0169] In this regard, it is possible to express the error. TIFF2024535362000006.tif6150 MISO system functions of position Xkine(z) and force Fm(z) as: TIFF2024535362000007.tif6150 in this case TIFF2024535362000008.tif6150 TIFF2024535362000009.tif11150 i.e. TIFF2024535362000010.tif11150

[0170] F m For discrete variants of (z), the degree of error can be evaluated using the final value theorem, i.e., TIFF2024535362000011.tif10150This shows that perfect error compensation is obtained only for K=k_exp. In this scenario, according to the proposed algorithm, the choice of K depends on a compromise between the amount of compensated tendon elongation and the robustness of the algorithm itself.

[0171] The fine tuning of such parameters therefore depends on empirical considerations given the variations in the actual physical system relative to the model used, as well as the occurrence of relevant forces that oppose the movement of the tip of the microsurgical instrument.

[0172] It should be noted that the dynamics of the system, to a first approximation, reflects the dynamics of the first-order system, i.e., appropriate selection of the control parameters ensures monotonic convergence of the position at the desired target.

[0173] Finally, it should be noted that due to the nature of the system being controlled, it is not possible to know the final force Fm to which the algorithm will converge in advance. Thus, such a value Fm will converge to a force value that is based on the dynamics of the applied trajectory, the physical plastic elastic stretch characteristics, the external disturbances of the system, and the friction within the system.

[0174] Alternatively or additionally, as mentioned above, the constant K can be selected empirically regardless of the value of the actual tendon elastic constants. Thus, the value of the multiplication parameter Ω can be less than 1, for example between 0.7 and 1. In one embodiment, the value of the multiplication parameter Ω belongs to the interval 0.7-1.5.

[0175] K_p: The algorithm convergence speed. Referring to the equations in the previous paragraph, it is clear that when static friction is exceeded, the transfer function SYS2(z) has a single pole located at the location 1-K_p. In this regard, By setting \(0 < K_p < 2\), the control system becomes stable.

[0176] The convergence speed increases as \(K_p\to1\). However, as the convergence speed increases, the phase margin of the system decreases.

[0177] When not exceeding static friction, the transfer function SYS1(z) has a single pole existing at the position. TIFF2024535362000012.tif9150

[0178] In this regard, when \(K_p\to1\), the dynamics are dominated by the ratio \((k_{exp}) / K\) (an increase in the value of K corresponds to a higher convergence speed obtained at the expense of the accuracy of the algorithm itself). When \(K_p\) is small, the dynamics of the algorithm are mainly dominated by \(K_p\).

[0179] Therefore, considering the nature of the algorithm from the considerations in the previous paragraph, it is clear that it is impossible to compensate for 100% of the elastic elongation when a given force converges in a finite time. The selection of the gain \(K_p\) and the accuracy of the estimated value K satisfy both the stability criterion and the ensuring of the convergence time reflecting the time - usefulness requirements of the master - slave remote operation.

[0180] An algorithm that is overly slow will impair the intuitiveness of the response of the microsurgical instrument to the commands given by the operator. It should be noted that the controllable parameters \(v(z)\) and \(u(z)\) (instantaneous actuator speed and position) are subject to the physical amplitude and bandwidth constraints of the operating system under consideration. Similarly, the observability of the variable \(F_m\) (the force provided by the actuator at time t) is subject to the physical limitations of the selected measuring instrument. Finally, the magnitude of the force \(F_m\) must be small enough so as not to affect the dynamics of the operating system as a first approximation commanded based on pure position. In this regard, the selection of the parameters K and \(K_p\) must also take into account the above - mentioned constraints.

[0181] To increase the robustness of the algorithm with unmodeled dynamics, a parameter Max Force is also provided that defines the interval of the variable F_max within which the algorithm can operate.

[0182] Such unmodeled dynamics are classified into the following families: - Tendon friction along the entire gearbox of the instrument, but not completely applied at the end points; - application of a direct force to the tendon as a result of a torque applied to the tip of the instrument; -Reversible and irreversible elongation of tendons that do not conform to Hooke's law. The effect of such components can be mitigated by introducing additional compensation components into the open loop and studying the stability of the overall control system as before.

[0183] Possible configuration settings are given as examples. Such settings, in addition to being dependent on the parameters reported in the previous paragraph, are uniquely associated with a type / class of microsurgical instrument. Identification of such settings is performed experimentally, taking into account the criteria stated in the previous paragraph. Kp=0.02 K=25N / mm Maximum force = 14N

[0184] Algorithm Launch Management One of the features of the instrument in question is its ability to grasp surgical sutures. The grasping concept is achieved by the simultaneous closure of two tips belonging to microsurgical instruments.

[0185] In this context, the grasping force is generated by controlling the gripping degree of freedom of the instrument, which is nothing more than a mirror control of the yaw degree of freedom of each of the two tips of the microsurgical system towards an objective that cannot be reached by the kinematics of the instrument itself (as it would require interpenetration of the tips themselves and thus the breaking of the kinematic constraints).The system therefore behaves as an open-loop force control that uses the mechanical impedances of the two tendons to determine the grasping force as a function of the control variable u(z).

[0186] In this context, the need to compensate for cable elongation becomes moot since such elongation contributes to the forces present at the end effector.

[0187] According to the above considerations, it is important to ensure that the algorithm does not aversively interfere with the quality of the grasp. To this end, the steps of instrument usability where the algorithm can be used are analyzed below.

[0188] The steps (or states) of instrument operability can be summarized as follows:

[0189] Holding: A state in which the instrument is engaged or in which there is kinematic continuity between the actuation system present in the motor box and the piston housed in the instrument. In such a state, the user has no direct control over the instrument. The motor exerts and maintains a force F_0 on the piston. Thus, the kinematic position of the end effector is maintained at the expense of external forces acting on the tip.

[0190] Operation: A state in which an operator can directly control a slave device using a special master device, i.e., the operator can freely move the tip of the microsurgical instrument. In particular, as shown in FIG. 13, the user has the ability to adjust the gripping force by bringing the opening of the master device within the gripping interval of the "squeezing" region. Such a "squeezing" state is: - No squeeze behavior: teleoperation is active and the operator keeps the master device above the grasp threshold; - Squeezing action: Teleoperation is active and the operator keeps the master device within the grasp threshold; can be divided into two substates called

[0191] The elastic compensation algorithm is active in a state called "non-compressive operation." In the "compressive operation" state, the feedforward component provided by the algorithm is frozen, i.e., it is not possible to change the position offset provided by the algorithm until returning to the "non-compressive operation" step.

[0192] In the embodiment where the two specific motors involved in the corresponding tips close towards the inside of the instrument, the offset fix is ​​necessary because, as mentioned before, this would prevent the algorithm from converging on an arbitrary force value and thus reaching the force required for grasping.

[0193] The "acting" state can be ended by direct command of the operator who wishes to discontinue direct control of the slave device. Abandoning the "acting" state means transitioning to the "holding" state, going through the "release" state (in the case of the "acting without squeezing" substate) or the "freeze" state (in the case of the "acting with squeezing" substate).

[0194] Release: A transitional state from decompression to retention. In this state, the motor kinematic position components are preserved by instead removing the elastic compensation components from each motor, so that teleoperation can resume in repeatable dynamic conditions.

[0195] Freeze: A state during the transition from a squeeze to a hold. In this state, the motors are frozen in their current positions to maintain the gripping force during the next hold step. In another implementation option, the freeze step involves a transition to purely prescriptive control over the tendons kinematically involved in the grip.

[0196] FIG. 14 shows a diagram illustrating the above mentioned states and the transitions from one state to another.

[0197] As can be seen from such a diagram, the elasticity compensation algorithm is only active during the teleoperation step (operation). When the user controls the instrument using a master in the "non-compression operation" range, the algorithm is active in each motor, whereas if the user is teleoperating using a master in the "compression operation" range, the position contribution of the elasticity compensation of the two motors that contribute to the closure of the tip is frozen on entering the state and the algorithm is deactivated in those motors. On the next input to the "non-compression operation", the algorithm is restarted in all motors.

[0198] The surgical robot system according to the present invention will be described below with reference again to FIGS.

[0199] Such a surgical robot system comprises a surgical instrument 20, a control means 9, at least one electric actuator 11, 12, 13, 14, 15, 16, and a force detection means.

[0200] The surgical instrument 20 comprises an articulating end effector 40 and at least one actuation tendon 31 , 32 , 33 , 34 , 35 , 36 configured to actuate the articulating end effector 40 .

[0201] At least one electric actuator 11, 12, 13, 14, 15, 16 is operatively connectable to each of said at least one actuating tendons 31, 32, 33, 34, 35, 36 and imparts motion to each of the actuating tendons controlled by the control means 9 to determine a unique correlation between at least one movement of the one or more electric actuators 11, 12, 13, 14, 15, 16 and at least one movement of each of the articulated end effectors 40.

[0202] The force detection means is configured to detect a force Fm exerted by at least one of said one or more electric actuators 11, 12, 13, 14, 15, 16 during an operation step of the surgical instrument.

[0203] The control means 9 is adapted to carry out the following operations, namely: - estimating, based on the detected force Fm, by means of a predetermined mathematical model, the change in length of at least one of said one or more actuated tendons 31, 32, 33, 34, 35, 36 due to the elastic elongation of said actuated tendons; - using the estimated length change for position control of one or more electric actuators 11, 12, 13, 14, 15, 16, It is configured as follows: The position control includes imparting movement to at least one of the one or more electric actuators 11, 12, 13, 14, 15, 16 taking into account an estimated length change of at least one of the one or more actuating tendons 31, 32, 33, 34, 35, 36 to reduce or offset the error caused by the elastic stretch between the position reached by the articulated end effector 40 and the desired nominal position of the articulated end effector 40.

[0204] According to one embodiment, the robotic system is a master-slave system in which the surgical instrument is a slave device controlled according to a control mode by a master device of the robotic system, the robotic system being configured to enable minimizing in a finite time the error between the pose commanded by the master device and the pose reached by the articulated end effector 40 of the slave device in the absence of external forces.

[0205] According to one embodiment of the robotic system, the surgical instrument 20 comprises a plurality of actuating tendons 31, 32, 33, 34, 35, 36 and the surgical robotic system comprises a respective plurality of powered actuators 11, 12, 13, 14, 15, 16.

[0206] According to implementation options of this embodiment, the aforementioned operation of detecting forces is performed for multiple or all of the electric actuators 11, 12, 13, 14, 15, 16, the aforementioned operation of estimating is performed with reference to multiple or all of the actuating tendons 31, 32, 33, 34, 35, 36, and the aforementioned operation of applying is performed for multiple or all of the electric actuators 11, 12, 13, 14, 15, 16.

[0207] According to one embodiment of the robotic system, the control means 9 are further configured to verify information regarding the state of the robotic system and to decide based on one or more conditions related to the state of said robotic system whether or not to perform a step of imparting a movement to the electric actuator in order to reduce and / or counteract and / or compensate for errors introduced by elastic stretching, and to perform said imparting action only if said one or more conditions are fulfilled.

[0208] According to one implementation option, the master device is a handheld, untethered master device adapted to be moved and manipulated by an operator according to degrees of freedom associated with closing and / or grasping of the microsurgical slave instruments.

[0209] In such a case, during remote operation, when the surgical instrument is in a grasped state, the aforementioned action of imparting movement to the electric actuators to reduce and / or counteract and / or compensate for errors caused by elastic stretching is suppressed or reduced according to a scaling factor between 0 and 1 for at least one of the electric actuators connected to a respective at least one actuating tendon for actuation of the grasp degree of freedom.

[0210] According to one embodiment of the system, said means for detecting the forces exerted by the electric actuators 11, 12, 13, 14, 15, 16 comprise respective force or torque sensors operatively connected to the respective electric actuators.

[0211] According to one embodiment, the robot system is configured such that the operation of detecting the force Fm is performed continuously at a detection frequency Fr, and the aforementioned position control of the one or more electric actuators is performed continuously at a position control frequency Fcp.

[0212] The detection frequency Fr and the position control frequency Fcp are set to ensure compensation of elastic stretching in real time, at dynamics that are not perceptible to the end user in real time, at dynamics that are not perceptible to the user.

[0213] According to one implementation option, the aforementioned detection frequency Fr and position control frequency Fcp are coincident and are comprised in the interval between 100 Hz and 1000 Hz, and therefore the compensation method is performed in each period T comprised in the interval between 1 and 10 ms based on the force Fm detected in the same period.

[0214] According to one embodiment, the estimation operation includes estimating the change in length of the actuated tendon as a ratio of the elastic modulus Fm of the force detected on the actuated tendon to an effective elastic constant value K determined experimentally or calculated or predetermined to ensure system response stability.

[0215] Further exemplary details regarding the formulas and parameters employed in the above calculations have already been given in the description of the method according to the invention.

[0216] According to one embodiment of the robotic system, the aforementioned surgical instrument 20 further comprises at least one transmission element 21, 22, 23, 24, 25, 26 operably connected to at least one respective actuating tendon 31, 32, 33, 34, 35, 36 and operably connectable to a respective electric actuator 11, 12, 13, 14, 15, 16.

[0217] In such cases, the act of imparting movement and / or exerting force includes controlling the movement of each electric actuator such that the movement of the transmission element includes compensation by stretching or relaxing each actuated tendon based on both the estimated length change of each actuated tendon and the elastic modulus and stiffness of the actuated tendon.

[0218] According to one implementation option, a reference kinematic zero condition is defined for the robotic system, which associates a virtual zero point where the movements imparted by the control means to the electric actuators are referenced to a stored reference position. In such a case, the act of imparting a movement and / or exerting a force to each transmission element includes calculating a corrective kinematic zero that takes into account the compensation performed.

[0219] According to one implementation option, the act of imparting motion and / or exerting force on each transmission element includes applying a force to the transmission element by a dual feedback operating loop, in which an elastic compensation correction is inserted in parallel with the displacement of the electric actuator due to the kinematic mechanism.

[0220] According to one embodiment of the robotic system, the motorized actuator is a stepper motorized actuator and the position control is performed by a velocity control with a known work time unit determining the position control. In particular, the velocity and position control is performed by a feedback motion control loop with a gain parameter Kp dimensioned to ensure convergence of the compensation with a time constant lower than the maximum convergence time.

[0221] According to one implementation option, the speed control comprises a kinematic component and a dynamic component.

[0222] The dynamic compensation component receives the detected forces Fm as input, calculates the estimated displacements lost due to the elasticity of the actuated tendons according to the formula reported in claim 16, and generates a velocity compensation contribution that is added to said velocity kinematic component by a proportional controller tuned to have dynamics that comply with the stability requirements.

[0223] The sum of the kinematic and dynamic velocity contributions is provided as an input to the controlled electric actuator. The controllers for the kinematic and dynamic components are preferably in parallel.

[0224] According to one embodiment, position and / or velocity control is only performed if the detected force Fm is lower than a maximum operating force value Fmax, and compensation is also inhibited if only one of the electric actuators detects a force higher than said maximum operating force Fmax.

[0225] According to various possible embodiments, the robotic system is configured to carry out the method according to any one of the aforementioned embodiments of the method (in particular under the control of a control means of the robotic system).

[0226] As can be seen, the above-mentioned objects of the present invention are fully accomplished by the method and system described above, by the features detailed above, and as broadly described in the preceding "Summary of the Invention" section.

[0227] Those skilled in the art can make modifications and adaptations to the embodiments of the above-described methods and systems, or can replace functionally equivalent elements with other elements to meet conditional needs, without departing from the scope of protection of the appended claims. Each of the features described as belonging to a possible embodiment can be achieved independently of the other embodiments described. [Explanation of symbols]

[0228] 1. Remote surgical robot system 2. Slave Assembly of the Robot System 3 Master Console 9. Controller 10 Robot System Manipulator 11, 12, 13, 14, 15, 16 Electric manipulator actuator or motor 17,18 Force sensor or load cell 19 Sterile Barrier 20 Surgical instruments 21, 22, 23, 24, 25, 26 Surgical instrument transmission elements 27 Shaft 28 Pockets 29 Surgical instrument back end or surgical instrument transmission interface 31, 32, 33, 34, 35, 36 Tendon 40 End devices, or articulating tips or end effectors of surgical instruments 41, 42, 43, 44 Links of Articulated End Effector xx linear direction rr center line P, Y, G hinged tip, pitch, yaw and grip degrees of freedom k_exp Experimentally obtained elastic constant Elastic constants used by the K algorithm Ω Ratio parameter of K and k_exp Fm Power u Controlled movement of the motor of the electric actuator

Claims

1. 1. A method for controlling an articulated end effector (40) actuated by one or more actuation tendons of a surgical instrument (20) of a surgical robotic system, the method being executable during an operating phase of the surgical instrument, comprising: The surgical instrument (20) comprises an articulated end effector (40) and at least one actuation tendon (31, 32, 33, 34, 35, 36) configured to actuate the articulated end effector (40); In addition to the surgical instrument (20), the surgical robotic system comprises a control means (9) and at least one electric actuator (11, 12, 13, 14, 15, 16) operably connectable to each of the at least one actuation tendon (31, 32, 33, 34, 35, 36) to impart a movement to the respective actuation tendon controlled by the control means (9), and determines a unique correlation between a movement of at least one of the one or more electric actuators (11, 12, 13, 14, 15, 16) and at least one movement of each of the articulated end effectors (40); The method comprises: - detecting the force (Fm) exerted by at least one of said one or more electric actuators (11, 12, 13, 14, 15, 16) during said operating phase; - estimating, based on said detected forces (Fm), by means of a predetermined mathematical model, the change in length of at least one of said one or more actuated tendons (31, 32, 33, 34, 35, 36) due to elastic elongation of said actuated tendons; - using said estimated length change for position control of said one or more electric actuators (11, 12, 13, 14, 15, 16); The position control includes: - imparting a movement to the at least one of the one or more electrically operated actuators (11, 12, 13, 14, 15, 16) taking into account the estimated change in length of the at least one of the one or more actuating tendons (31, 32, 33, 34, 35, 36) so as to reduce or offset an error caused by the elastic elongation between a position reached by the articulated end effector (40) and a desired nominal position of the articulated end effector (40); A method comprising:

2. the robotic system is a master-slave system, and the surgical instrument is a slave device controlled by a master device of the robotic system according to a control mode; the method allows minimizing in a finite time the error between a pose commanded by the master device and a pose reached by the articulated end effector (40) of the slave device in the absence of external forces; and / or the step of providing takes into account the command actions performed by a user. The method of claim 1.

3. The surgical instrument (20) comprises a plurality of actuating tendons (31, 32, 33, 34, 35, 36), and the surgical robot system comprises a plurality of respective electric actuators (11, 12, 13, 14, 15, 16); the step of detecting a force is performed for a plurality or all of the electric actuators (11, 12, 13, 14, 15, 16); the step of estimating is performed in relation to a plurality or all of the actuated tendons (31, 32, 33, 34, 35, 36); The applying step is performed for a plurality or all of the electric actuators (11, 12, 13, 14, 15, 16). The method of claim 1.

4. - verifying information related to the state of the robotic system; - deciding by said control means (9) whether or not to perform said step of imparting movements to electric actuators in order to reduce and / or counteract and / or compensate for errors introduced by said elastic extensions, based on one or more conditions related to the state of said robot system; - performing said step of granting only if said one or more conditions are met; The method of claim 1 further comprising:

5. the master device is a handheld, untethered master device adapted to be moved and manipulated by an operator according to degrees of freedom associated with closing and / or grasping the microsurgical slave instrument; and during remote manipulation, when the surgical instrument is in a grasped state, the step of imparting movement to electric actuators is suppressed or reduced according to a scaling factor between 0 and 1 for at least one of the electric actuators connected to a respective at least one actuation tendon for actuation of a grasp degree of freedom, in order to reduce and / or counteract and / or compensate for the error caused by the elastic extension. The method of claim 4.

6. 6. The method of claim 5, wherein the step of imparting movement to the electric actuators is suppressed or reduced according to a scaling factor between 0 and 1 for two electric actuators connected to two antagonistically actuated tendons in each of the gripping closing degrees of freedom, or for four electric actuators connected to four actuated tendons of a pair of antagonistically actuated tendons in the gripping closing and gripping opening degrees of freedom, in order to reduce and / or counteract and / or compensate for the error caused by the elastic stretching.

7. 6. The method of claim 5, wherein the step of imparting movement to electric actuators is suppressed or reduced according to a scaling factor between 0 and 1 for all electric actuators to reduce and / or counteract and / or compensate for the error introduced by the elastic extension.

8. the master device is a handheld, untethered master device adapted to be moved and manipulated by an operator according to degrees of freedom associated with closing and / or grasping the microsurgical slave instrument; At the end of the remote operation, when the surgical instrument is in a gripping state and the gripping state is to be maintained, the step of imparting movement to electric actuators is inhibited for all the electric actuators connected to the respective actuation tendons in order to reduce and / or cancel and / or compensate for the error caused by the elastic elongation. The method of claim 4.

9. 9. The method of claim 1, wherein when the teleoperation is terminated in a non-grasping state, the estimated length change in each of the one or more actuated tendons is reset to that during a previous teleoperation before re-entering a new teleoperation.

10. 9. The method of claim 1, wherein each of the one or more actuating tendons (31, 32, 33, 34, 35, 36) is operatively connected to both a respective electric actuator of the surgical robot system and the articulated end effector (40) to actuate a respective degree of freedom of the one or more degrees of freedom (P, Y, G) of the articulated end effector (40).

11. The method of claim 10, wherein at least one of the one or more actuating tendons (31, 32, 33, 34, 35, 36) actuates a rotational degree of freedom of the articulated end effector (40).

12. 9. The method according to any one of claims 1 to 8, wherein the step of detecting the forces exerted by the electric actuators (11, 12, 13, 14, 15, 16) is performed by a respective force or torque sensor operatively connected to each said electric actuator.

13. the step of detecting a force (Fm) is continuously performed at a detection frequency (Fr), and the position control of the one or more electric actuators is continuously performed at a position control frequency (Fcp); The detection frequency (Fr) and the position control frequency (Fcp) are set to ensure compensation of the elastic stretch in real time, with dynamics that are imperceptible to an end user in real time, with dynamics that are imperceptible to a user; 9. The method according to any one of claims 1 to 8.

14. the detection frequency (Fr) and the position control frequency (Fcp) are coincident and are included in the interval between 100 Hz and 1000 Hz; The compensation method is therefore carried out at each period T comprised in an interval between 1 and 10 ms, based on the force (Fm) detected at the same period; The method of claim 13.

15. 2. The method of claim 1, wherein the estimating step includes estimating the length change of the actuated tendon as a ratio between a modulus of elasticity (Fm) of the force detected at the actuated tendon and an effective elastic constant value (K), wherein the effective elastic constant value (K) is experimentally determined, calculated, or pre-established to ensure system response stability.

16. The steps of using the estimated length change for position control and imparting motion to the respective electric actuators are performed based on the following equation: said formula being unique for each electric actuator and therefore determining the specific control for each electric actuator; where u is the position controlled by the electric actuator, K is the elastic constant of the actuating tendon, and Ω is a multiplication parameter.

16. The method of claim 15.

17. 17. The method of claim 16, wherein the multiplication parameter Ω is greater than 1, whereby the effective elastic constant value K=ΩKel used in the calculation is greater than the tendon elastic constant value by a factor equal to the multiplication parameter Ω, and therefore the effective tendon elastic constant value (K) is overestimated and therefore greater than the elastic constant (Kel) of the same actuated tendon.

18. 17. The method of claim 16, wherein the multiplication parameter is between 0.7 and 1.

5.

19. 19. The method according to claim 15, wherein the effective elastic constant value K, and therefore the multiplication parameter Ω, is also variably determined depending on a state of the robot system, and / or a spatial condition of the master device and / or the slave device, and / or the teleoperation endurance time.

20. The method according to claim 1 , wherein the compensation method is carried out in the presence of a force value of less than 40 N.

21. 2. The method of claim 1, wherein the surgical instrument (20) further comprises at least one transmission element (21, 22, 23, 24, 25, 26) operably connected to a respective at least one actuating tendon (31, 32, 33, 34, 35, 36) and operably connectable to a respective electric actuator (11, 12, 13, 14, 15, 16).

22. 22. The method of claim 21, wherein the step of imparting movement and / or exerting a force comprises controlling movement of each of the electric actuators such that movement of the transfer element includes compensation due to elongation or relaxation of the respective actuating tendon based on both the estimated change in length of each actuating tendon and the elastic modulus and stiffness of the actuating tendon.

23. a reference kinematic zero condition is defined in the robot system, which associates a virtual zero point where a movement imparted to the electric actuator by the control means is referenced to a stored reference position; the step of imparting a movement and / or exerting a force on each of the transmission elements comprises a step of calculating a corrected kinematic zero taking into account the compensation performed; 23. The method of claim 21 or 22.

24. 22. The method of claim 21, wherein the step of imparting a movement and / or exerting a force on each transfer element comprises applying a force to the transfer element by means of a dual feedback operating loop, wherein an elastic compensation correction is inserted in parallel with the displacement of the electric actuator due to a kinematic mechanism.

25. 2. The method of claim 1, wherein the electric actuator is a stepper electric actuator, and the position control is performed by a speed control known as a work time unit, the speed control determining the position control.

26. 26. The method of claim 25, wherein the velocity and position control is performed by a feedback motion control loop, and a gain parameter (Kp) is dimensioned to ensure convergence of the compensation with a time constant lower than a maximum convergence time.

27. 27. The method according to claim 26, wherein the maximum convergence time is less than 1 second and is preferably comprised in the interval between 100 ms and 200 ms.

28. the velocity control includes a kinematic component and a dynamic compensation component; The dynamic compensation component receives the detected force (Fm) as an input, calculates the estimated displacement lost due to the elasticity of the actuated tendons according to the formula of claim 16, and generates a velocity compensation contribution to be added to the velocity kinematic component by a proportional controller tuned to have dynamics that meet stability requirements; the sum of the kinematic and dynamic velocity contributions is provided as an input to the electric actuator to be controlled; The controllers of the kinematic components and the dynamic components are preferably parallel.

26. The method of claims 24 and 25.

29. 9. The method according to any one of claims 1 to 8, wherein the position control and / or velocity control is performed in a common manner for a plurality of electrically powered actuators, for example by performing joint control for each pair of antagonistic tendons based on common effective elastic constant values, depending on conditions such as the position of the master or slave device and / or the ageing or state of the robotic system.

30. 9. The method according to claim 1, wherein the position control and / or velocity control is performed only if the detected force (Fm) is lower than a maximum operating force value (Fmax), and the method is also inhibited if only one of the electric actuators detects a force greater than the maximum operating force (Fmax).

31. 9. The method of claim 1, wherein an extension compensation parameter is determined in a controlled and variable manner depending on the pose of the articulated end effector (40) to take into account different frictions associated with different poses.

32. 9. The method according to any one of claims 1 to 8, wherein the actuated tendon is a polymer tendon, preferably formed by intertwined polymer fibers.

33. a surgical instrument (20) comprising an articulated end effector (40) and at least one actuation tendon (31, 32, 33, 34, 35, 36) configured to actuate said articulated end effector (40); - control means (9), at least one electric actuator (11, 12, 13, 14, 15, 16) operatively connectable to each of said at least one actuating tendon (31, 32, 33, 34, 35, 36) for imparting to said respective said at least one actuating tendon a movement controlled by said control means (9) so as to determine an unambiguous correlation between at least one movement of one or more electric actuators (11, 12, 13, 14, 15, 16) and at least one movement of each of said articulated end effectors (40); - force detection means configured to detect a force (Fm) exerted by at least one of said one or more electric actuators (11, 12, 13, 14, 15, 16) during an operating phase of said surgical instrument; Equipped with The control means (9) is adapted to perform the following operations: - estimating, based on said detected forces (Fm), by means of a predetermined mathematical model, the change in length of at least one of said one or more actuated tendons (31, 32, 33, 34, 35, 36) due to elastic elongation of said actuated tendons; - using the estimated length change for position control of the one or more electric actuators (11, 12, 13, 14, 15, 16); and the position control includes imparting movement to the at least one of the one or more electric actuators (11, 12, 13, 14, 15, 16) taking into account the estimated change in length of the at least one of the one or more actuating tendons (31, 32, 33, 34, 35, 36) so as to reduce or offset an error caused by the elastic elongation between a position reached by the articulated end effector (40) and a desired nominal position of the articulated end effector (40). Surgical robot system.

34. the robotic system is a master-slave system, and the surgical instrument is a slave device controlled by a master device of the robotic system according to a control mode; the robotic system is configured to minimize, in a finite time, an error between a pose commanded by the master device and a pose reached by the articulated end effector (40) of the slave device in the absence of external forces; and / or the action of imparting movement to the one or more electric actuators takes into account the command action performed by a user.

34. The robotic system of claim 33.

35. The surgical instrument (20) comprises a plurality of actuating tendons (31, 32, 33, 34, 35, 36), and the surgical robot system comprises a plurality of respective electric actuators (11, 12, 13, 14, 15, 16); The operation of detecting a force is performed on a plurality of or all of the electric actuators (11, 12, 13, 14, 15, 16), the operation of estimating is performed in relation to a plurality or all of the actuated tendons (31, 32, 33, 34, 35, 36); The action of applying is performed on a plurality or all of the electric actuators (11, 12, 13, 14, 15, 16).

34. The robotic system of claim 33.

36. The control means (9) - verifying information relating to the state of the robotic system; - determining whether to perform the step of imparting a movement to an electric actuator to reduce and / or counteract and / or compensate for errors introduced by the elastic extension based on one or more conditions related to the state of the robotic system; - performing the action to be granted only if the one or more conditions are met; 36. The robotic system of any one of claims 33 to 35, further configured to:

37. the master device is a handheld, untethered master device adapted to be moved and manipulated by an operator according to degrees of freedom associated with closing and / or grasping the microsurgical slave instrument; During remote manipulation, when the surgical instrument is in a grasped state, the action of imparting movement to electric actuators is suppressed or reduced according to a scaling factor between 0 and 1 for at least one of the electric actuators connected to a respective at least one actuation tendon for actuation of a grasp degree of freedom, in order to reduce and / or counteract and / or compensate for the error caused by the elastic extension.

37. The robotic system of claim 36.

38. In order to reduce and / or counteract and / or compensate for the error caused by the elastic stretching, the actuation of the electric actuators to impart movements is suppressed or reduced according to a scaling factor between 0 and 1 for two electric actuators connected to two respective antagonistic tendons associated with actuation of the grip closing degree of freedom or for four electric actuators connected to four actuating tendons of a pair of antagonistic tendons associated with actuation of the grip closing and grip opening degrees of freedom, or said actuation of imparting movement to the electric actuators is suppressed or reduced according to a scaling factor between 0 and 1 for all electric actuators in order to reduce and / or counteract and / or compensate for said error caused by elastic stretching.

38. The robotic system of claim 37.

39. the master device is a handheld, untethered master device adapted to be moved and manipulated by an operator according to degrees of freedom associated with closing and / or grasping the microsurgical slave instrument; At the end of remote operation, when the surgical instrument is in a gripping state and the gripping state is to be maintained, the action of imparting movement to the electric actuators is suppressed for all the electric actuators connected to the respective actuation tendons in order to reduce and / or cancel and / or compensate for the error caused by the elastic elongation.

37. The robotic system of claim 36.

40. 36. The robotic system according to any one of claims 33 to 35, wherein the means for detecting the forces exerted by the electric actuators (11, 12, 13, 14, 15, 16) comprise respective force or torque sensors operatively connected to the respective electric actuators.

41. The operation of detecting a force (Fm) is continuously performed at a detection frequency (Fr), and the position control of the one or more electric actuators is continuously performed at a position control frequency (Fcp), The detection frequency (Fr) and the position control frequency (Fcp) are set to ensure compensation of the elastic stretch in real time, with dynamics that are imperceptible to an end user in real time, with dynamics that are imperceptible to a user; 36. The robotic system of any one of claims 33 to 35.

42. 42. The robotic system of claim 41, wherein the detection frequency (Fr) and the position control frequency (Fcp) are coincident and are comprised in an interval between 100 Hz and 1000 Hz, and therefore the compensation method is performed in each period T comprised in an interval between 1 and 10 ms based on the force (Fm) detected in the same period.

43. 36. The robotic system of any one of claims 33 to 35, wherein the operation of estimating includes estimating the length change of the actuated tendon as a ratio between a modulus of elasticity (Fm) of the force detected at the actuated tendon and an effective elastic constant value (K), wherein the effective elastic constant value (K) is experimentally determined or calculated or pre-established to ensure system response stability.

44. The steps of using the estimated length change for position control and imparting movement to each of the electric actuators are performed based on the following equations: said formula being specific to each electric actuator and therefore determining the specific control for each electric actuator; where u is the position controlled by the electric actuator, K is the elastic constant of the actuating tendon, and Ω is a multiplication parameter. and / or the multiplication parameter Ω is greater than 1, so that the effective elastic constant value K=ΩKel used in the calculation is greater than the tendon elastic constant value by a factor equal to the multiplication parameter Ω, and therefore the effective tendon elastic constant value (K) is overestimated and therefore greater than the elastic constant (Kel) of the same working tendon, and / or the multiplication parameter is between 0.7 and 1.5; and / or the effective elastic constant value K, and therefore the multiplication parameter Ω, is variably determined depending on the state of the robot system, and / or the spatial conditions of the master device and / or the slave device, and / or the endurance time of teleoperation.

44. The robotic system of claim 43.

45. the surgical instrument (20) further comprises at least one transmission element (21, 22, 23, 24, 25, 26) operably connected to a respective at least one actuating tendon (31, 32, 33, 34, 35, 36) and operably connectable to a respective electric actuator (11, 12, 13, 14, 15, 16); the act of imparting movement and / or exerting force includes controlling movement of each electric actuator based on both the estimated length change of each actuating tendon and the elastic modulus and stiffness of the actuating tendon such that movement of the transfer element includes compensation due to elongation or relaxation of the respective actuating tendon; 34. The robotic system of claim 33.

46. a reference kinematic zero condition is defined that associates a virtual zero point where the movement imparted to the electric actuator by the control means is referenced to a stored reference position; the act of imparting a movement and / or exerting a force on each of the transmission elements includes calculating a corrected kinematic zero taking into account the compensation performed; 46. ​​The robotic system of claim 45.

47. 46. ​​The robotic system of claim 45, wherein the act of imparting motion and / or exerting force on each transfer element comprises applying forces to the transfer elements by a dual feedback actuation loop, wherein an elastic compensation correction is inserted in parallel with the displacement of the electric actuator due to a kinematic mechanism.

48. the electric actuator is a stepper electric actuator, and the position control is performed by a speed control known as a work time unit, and the speed control determines the position control; the velocity and position control is performed by a feedback motion control loop with a gain parameter (Kp) sized to ensure convergence of the compensation with a time constant lower than the maximum convergence time; 34. The robotic system of claim 33.

49. the velocity control includes a kinematic component and a dynamic compensation component; The dynamic compensation component receives the detected force (Fm) as an input, calculates the estimated displacement lost due to the elasticity of the actuated tendons according to the formula of claim 16, and generates a velocity compensation contribution to be added to the velocity kinematic component by a proportional controller tuned to have dynamics that meet stability requirements; the sum of the kinematic and dynamic velocity contributions is provided as an input to the electric actuator to be controlled; The controllers of the kinematic components and the dynamic components are preferably parallel.

49. A robotic system according to claims 47 and 48.

50. 36. The robot system of claim 33, wherein the position control and / or velocity control is performed only if the detected force (Fm) is lower than a maximum operating force value (Fmax), and the compensation is also inhibited if only one of the electric actuators detects a force greater than the maximum operating force (Fmax).

51. 34. The robotic system of claim 33 configured to perform the method of claim 1.

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