Determining a parameter of a force acting on a robot

Abstract

Method for determining a parameter (m, a) of a force (F) acting on a robot (10) on the basis of at least one joint moment (τ2, τ3) of the robot in at least one measuring pose of the robot, wherein the joint moment is based on a difference between a drive-side and a driven-side position (q) ab,i - q an,i ) of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one previously approached reference configuration without this force acting on the robot.

Description

[0001] The present invention relates to a method for determining a parameter of a force acting on a robot, in particular for operating the robot on the basis of the determined parameter, as well as a system or computer program product for carrying out the method.

[0002] By knowing or taking into account external forces acting on robots, the operation of the robots can be improved, in particular the robots can be controlled more precisely and / or interact (sensitively) with their environment.

[0003] In particular, when the payload is known, a more accurate robot model can be used in a model-based control system, thereby improving the control or operation of the robot.

[0004] According to DE 10 2017 130 460 A1, in an industrial robot, a correction is made for a change in the position and posture of a distal arm end due to a mechanical deflection of the robot, wherein in the robot, a moment applied to the first axis in its non-rotational direction opposite to its rotational direction is calculated from a load moment applied to the second axis in its rotational direction, a moment due to a dead weight on the side of the second axis, and a ratio of a distance between the rotational centers of the first and second axes to a distance between the rotational centers of the second axis and a tool, a deflection amount which indicates an angle of the first axis tilting in the non-rotational direction,is calculated from the moment applied to the first axis and the stiffness of the first axis in the non-rotational direction, and a control value is corrected based on the deflection amount to control the robot.

[0005] According to DE 10 2013 010 290 A1, a method for monitoring a kinematically redundant robot comprises the steps of: detecting joint forces acting in joints of the robot; determining an external effective force between a robot-fixed reference and an environment on the basis of the detected joint forces; determining a further monitoring variable, which is at least substantially independent of an external force acting on the robot-fixed reference, on the basis of the detected joint forces; and monitoring the determined external effective force and the determined further monitoring variable.

[0006] According to DE 10 2012 017 328 B4, a robot having a workpiece mass measuring function for measuring the mass of a held workpiece comprises a force measuring unit that measures the force exerted on the tip portion of the mechanical portion of the robot, and a mass calculating unit that calculates the mass of the workpiece held by the robot based on information about the force determined by the force measuring unit while the robot is moving.

[0007] DE 691 29 406 T2 relates to a turning correction method for a robot, in which the deviation between commanded and actual end point positions caused by a turning of the robot is determined and command values ​​for the individual axes are corrected on the basis of the deviation thus determined, thereby controlling the robot end point position to a desired position.

[0008] EP 2 636 491 B1 relates to a calibration method and calibration system for robots.

[0009] According to JP 2004 - 025 387 A, the load, whose weight and position of the center of gravity are known, is mounted at the head end of the arm of the articulated robot, the articulated robot is caused to move according to a movement pattern program, and a correction coefficient for correcting a detected electric drive current is calculated from the electric drive current detected at that time and from an ideal electric current calculated from the known weight of the load, the known position of the center of gravity and a mass point model.The weight of the unknown load and the unknown center of gravity position are calculated according to a corrected driving electric current by mounting the load whose weight and center of gravity position are unknown on the arm head end of the articulated robot and causing the robot to move according to the motion pattern program and eliminating the measurement error by correcting the driving electric current detected at that time with the correction coefficient.

[0010] An object of an embodiment of the present invention is to improve the determination of a parameter of a force acting on a robot, in particular an operation of the robot.

[0011] This object is achieved by a method having the features of claims 1 and 8, respectively. Claims 9 and 10 protect a system or computer program product for implementing a method described herein. The subclaims relate to advantageous developments.

[0012] According to one embodiment of the present invention, a one- or multi-dimensional parameter of a force acting on a robot is determined on the basis of one or more joint moments of the robot in one or more, in one embodiment (each) stationary, measurement poses of the robot.

[0013] In one embodiment, the robot has a robot arm with at least three, in particular at least six, in one embodiment at least seven rotary joints or axes and / or an end flange, in particular an end effector.

[0014] In one embodiment, the end flange or end effector can advantageously move to any position using at least three rotary joints; any pose using at least six rotary joints; and the same pose with different (joint or robot) positions using at least seven rotary joints. In one embodiment, a pose has a one-, two-, or preferably three-dimensional position and / or a one-, two-, or preferably three-dimensional orientation.

[0015] In one design, the force acting on the robot acts on or at the end flange or end effector. This allows a payload or machining force to be taken into account in one design, thereby improving the operation of the robot.

[0016] In one embodiment, the robot remains in the measurement pose(s) (respectively). This allows for more precise and / or more meaningful values ​​to be determined. In one embodiment, the robot moves through the measurement pose(s), with a further development limiting the (maximum) speed of its end effector to a maximum of 250 mm / s. This allows for more rapid measurement values ​​and / or reduced loads on a robot-guided payload, particularly a patient.

[0017] In one embodiment, an end effector of the robot has the same orientation in two or more of the measurement poses, particularly stationary ones. This allows a parameter of a robot-guided payload with a patient to be determined more advantageously.

[0018] According to one embodiment of the present invention, the joint torque(s) on the basis of which the parameter is determined are determined on the basis of a difference between a drive-side and an output-side position, in particular an angular position, in a drive train(s) (for adjusting) the (respective) robot joint in which the joint torque (respectively) acts or for which the joint torque (respectively) is determined.

[0019] The underlying idea is that forces and moments acting on the output side of a drive train to adjust a joint lead to a difference compared to a drive-side position of this drive train due to elasticity, play, and the like. Conversely, forces and / or moments acting on the output side in the drive train or joint can be determined based on such a difference. In one embodiment, a drive-side position of a drive train is a position, in particular an angular position, (within or at a point) of the drive train that is closer to a drive, in particular the engine, of the drive train than (in) an output-side position.

[0020] In this way, joint moments or forces acting on the robot can be determined advantageously, in particular more precisely and / or with less equipment effort, in particular in comparison to a (pure) determination based on electrical drive variables, which can be inadequate due to friction, especially in stationary poses.

[0021] In one embodiment, a or the drive-side position of the (respective) drive train is a position of a drive and / or before or at a transmission input and / or is detected by a (first) angle sensor. Additionally or alternatively, a or the output-side position of the (respective) drive train in one embodiment is a position of a robot link or joint and / or at or after a transmission output and / or is detected by a (second) angle sensor.

[0022] According to one embodiment of the present invention, the joint torque(s) on the basis of which the parameter is determined are determined on the basis of a difference between a measurement configuration in which the force whose parameter is to be determined acts on the robot and one or more reference configurations previously approached (if necessary again) in an embodiment for determining the parameter, in which this force does not (in each case) act on the robot, in one embodiment on the basis of a difference between the measurement configuration and a reference configuration in which the robot is load-free or not subjected to an external force, and / or on the basis of at least one difference between the measurement configuration and a reference configuration in which the robot is (only) subjected to a known external force in the same way as the force whose parameter is to be determined.

[0023] This is based on the knowledge that the robot's own weight and the like also cause joint moment components which are added to the joint moment components which result from an external force acting on the robot, in particular from the force acting on the robot whose parameters are to be determined, and the idea based on this of determining these joint moment components which result from the robot's own weight and the like or which are independent of the force acting on the robot whose parameters are to be determined, using one or more reference configurations and then deducting them from the determined total joint moments, so that this parameter can be determined on the basis of the remaining joint moments.

[0024] In this way, the parameter of the force acting on the robot can be determined in an (even) more advantageous manner, in particular more precisely and / or with less effort, in particular in terms of equipment.

[0025] The present invention can be used with particular advantage for identifying a robot-guided payload, with even more advantage for identifying a robot-guided payload with a patient (transported and / or positioned by the robot).

[0026] In one embodiment, the parameter depends accordingly on a mass and / or center of gravity of a robot-guided payload, in particular a robot-guided payload with a patient (transported and / or positioned by the robot).

[0027] In a further development, the parameter depends only on the mass and / or center of gravity of this payload. In one embodiment, a center of gravity position comprises a one- or two-dimensional distance from an axis, in particular a distal joint axis.

[0028] The idea behind this is that, in contrast to inertial sensors, mass and center of gravity can be determined (more precisely) using slower robot movements and, in particular, stationary or slowly moving measurement poses, and, on the other hand, they are sufficient, in particular, for transporting and / or positioning patients who, in turn, should not be moved quickly.

[0029] Likewise, the present invention can also be used with particular advantage for determining a contact force, in particular its direction, its magnitude and / or point of application, in an environmental contact of the robot, in particular its end effector, or the parameter depends, in particular only, on this contact force, in particular its direction, its magnitude and / or point of application.

[0030] In one embodiment, the parameter is determined on the basis of the joint moments of a number of robot joints in the same, in particular stationary, measuring pose of the robot, wherein the number in one embodiment is at least two.

[0031] The idea behind this is that by means of at least two joint moments, both a mass and a center of gravity position or both an amount and a point of application, in particular a distance from an axis, in particular a distal(est) joint axis, can be determined.

[0032] Additionally or alternatively, the number is equal to the total number of joints of the robot and / or equal to six. This allows the parameter to be determined more precisely in one embodiment and / or to have more components or dimensions.

[0033] In an alternative embodiment, the number is smaller than the total number of joints of the robot and / or smaller than six. This allows the parameter of the force acting on the robot to be determined more advantageously, particularly with less equipment required, using the idea explained above that just two joint moments can be used to determine both a mass and a center of gravity position, or both a magnitude and a point of application, in particular a distance from an axis, in particular a distal joint axis.

[0034] In one embodiment, the parameter is determined on the basis of the joint moments of the same robot joint(s) in two or more, in particular stationary, measuring poses of the robot, wherein the robot or these robot joints have different positions in these measuring poses in one embodiment.

[0035] The idea behind this is that the same force acting on the robot, in particular the same robot-guided payload, causes different joint moments in the individual robot joints in different measuring poses or robot positions, so that on the basis of joint moments determined in or for several measuring poses or robot positions, the parameter can be determined (even) more advantageously, in particular more precisely and / or with less effort, in particular in terms of equipment.

[0036] In one embodiment, the parameter is determined using a balancing problem-solving method. For this purpose, in one embodiment, more joint moments are determined than the dimension of the parameter, i.e., in particular, joint moments of more robot joints in one position and / or joint moments in more positions or along a path. For example, if the mass and the one-, two-, or three-dimensional center of gravity of a robot-guided payload are to be determined (dimension of the parameter = 2, 3, or 4, respectively), then in one embodiment, more joint moments are used, for example, at least 3, 4, or5, in one embodiment, for example, for the mass and the one-dimensional center of gravity distance of a robot-guided payload to an axis, the joint moments of at least two joints in at least two measuring poses or the joint moments of one joint in at least three measuring poses or the joint moments of at least three joints in at least one measuring pose.

[0037] Additionally or alternatively, in one embodiment, the parameter is determined based on mean values, in particular of one or more of the joint moments and / or the differences between the drive train positions and / or measurement and reference configurations. In one embodiment, the measurement pose(s), measurement configuration(s), and / or reference configuration(s) are each approached multiple times, and in the process or for this purpose, the joint moment(s), in particular the difference(s), is determined, and the joint moment(s) is determined based on mean values ​​of the differences determined thereby, or the parameters are determined based on mean values ​​of the joint moments, in particular determined in this way.

[0038] This allows the parameter to be determined in an even more advantageous, particularly more reliable, manner in one embodiment.

[0039] In one embodiment, the measurement configuration and the reference configuration(s) are approached in the same way, in particular by adjusting at least the joints whose joint moments are used in determining the parameter (each or joint by joint) from or in the same direction.

[0040] The idea behind this is that play and / or friction effects can be advantageously compensated for.

[0041] In one embodiment, the (respective) joint torque is determined on the basis of a difference between a drive-side and an output-side position of the drive train of the (respective) joint and a stiffness of this drive train (between this drive-side and output-side position).

[0042] This stiffness can be specified in a design, in particular it can be taken from a machine data set.

[0043] In one embodiment, the (respective) stiffness is determined on the basis of a difference between one or more first reference configurations, in which (in each case) a (different, in each case) known, in particular predetermined or measured, first force acts on the robot, in one embodiment (in each case) a (different) known payload is attached to its end effector, and one or more second reference configurations, in which (in each case) a (different, possibly different) known, in particular predetermined or measured, second force or payload or no (external) force acts on the robot or the robot is load-free, in one embodiment no payload is attached to its end effector.In one embodiment, the stiffness can thus be determined or specified in regions on the basis of one, two or more different known forces acting successively on the robot, in particular one, two or more different known payloads attached successively to its end effector, in particular on the basis of two different known forces acting successively on the robot, in particular payloads attached to its end effector. In one embodiment, linear, interpolation and / or extrapolation is carried out on the basis of the determined or specified stiffness values. In one embodiment, the robot has the same (joint) position in the first and second reference configuration(s) (in each case).

[0044] In one embodiment, the (respective) stiffness of the drive train is determined or specified for a specific position of the robot or its joints, in particular the position of the robot or its joints in the first and second reference configuration(s). In one embodiment, the measurement pose(s) are determined based on several position-specific stiffnesses, in one embodiment linearly, interpolated, and / or extrapolated.

[0045] In one embodiment, this allows the drivetrain's stiffness between the input and output positions to be determined more accurately and / or more precisely. Based on this stiffness and the determined difference between the input and output positions in the (respective) measurement pose, the current joint torque can then be determined, in particular interpolated or extrapolated. In another embodiment, this stiffness can also be determined in a different way.

[0046] In one embodiment, the joint torque(s) on the basis of which the parameter is determined are (each also) determined on the basis of an electrical drive variable of a drive, in particular an electric motor, of the corresponding drive train, in one embodiment a motor current and / or a motor voltage, or this drive variable is taken into account when determining the joint torque(s), in particular by averaging or comparing them with one another in another way.

[0047] This allows the parameter to be determined in an embodiment in an (even) more advantageous manner, in particular more precisely and / or reliably.

[0048] In one embodiment, the robot is operated on the basis of the determined parameter, in one embodiment it is controlled, in particular regulated, and / or monitored and / or a path of the robot is planned.

[0049] This can improve the operation of the robot, allow the robot to be controlled more precisely and / or interact (sensitively) with its environment.

[0050] According to one embodiment of the present invention, a system for determining a parameter of a force acting on a robot on the basis of at least one joint torque of the robot in at least one, in particular stationary, measurement pose of the robot is set up, in particular in terms of hardware and / or software, in particular in terms of programming, to carry out a method described here and / or comprises: means for determining the joint torque on the basis of a difference between a drive-side and an output-side position of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one previously approached reference configuration without this force acting on the robot.

[0051] In one embodiment, the system or its means comprises: - means for determining the parameter based on the joint moments of a number of robot joints in the same, in particular stationary, measurement pose of the robot, wherein the number is at least two and / or less than or equal to the total number of joints of the robot and / or less than or equal to six; and / or - means for determining the parameter based on the joint moments of the same robot joint in at least two, in particular stationary, measuring poses of the robot; and / or - means for determining the parameter using a balancing problem-solving method and / or on the basis of mean values; and / or - Means for similarly approaching the measurement configuration and at least one reference configuration; and / or - Means for determining the joint torque based on a stiffness of the drive train, in particular for determining the stiffness based on a difference between at least one first reference configuration with a first force acting on the robot and at least one second reference configuration with no force or a second force acting on the robot; and / or - means for determining the joint torque based on an electrical drive variable; and / or - Means for operating the robot on the basis of a parameter of a force acting on the robot, wherein the parameter is determined by means of a method or system or means thereof described here.

[0052] A means within the meaning of the present invention can be designed in hardware and / or software, in particular a processing unit, in particular a microprocessor unit (CPU), graphics card (GPU) or the like, which is preferably connected to a memory and / or bus system in terms of data or signals, and / or can have one or more programs or program modules. The processing unit can be designed to execute instructions implemented as a program stored in a memory system, to detect input signals from a data bus, and / or to output signals to a data bus. A memory system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state, and / or other non-volatile media. The program can be designed in such a way that it embodies the methods described here oris capable of executing, so that the processing unit can execute the steps of such methods and thus, in particular, determine the parameter or operate the robot. In one embodiment, a computer program product can have, in particular be, a storage medium, in particular a non-volatile one, for storing a program or with a program stored thereon, wherein executing this program causes a system or a controller, in particular a computer, to execute a method described here or one or more of its steps.

[0053] In one embodiment, one or more, in particular all, steps of the method are carried out fully or partially automatically, in particular by the system or its means.

[0054] In one embodiment, the system comprises the robot.

[0055] Further advantages and features emerge from the subclaims and the exemplary embodiments. The following shows, partly schematically: Fig. 1: a system for determining a parameter of a force acting on a robot according to an embodiment of the present invention; Fig. 2: a drive train of the robot; and Fig. 3: a method for determining the parameter according to an embodiment of the present invention.

[0056] Fig. 1 shows a robot 10 with six rotary joints in a first measuring pose (solid in Fig. 1; α=0°) and a second measurement pose (dashed in Fig. 1; α≠0°) and a robot controller 20 which carries out the method explained below or is set up to do so.

[0057] Each of the six swivel joints has a Fig. 2 shown drive train with an electric motor 11 and a gear output 12, which is connected on the one hand to the electric motor or its (output) shaft and on the other hand (rotationally) fixedly to a member of the robot which is actuated or to be adjusted by the drive train.

[0058] A first angle sensor 1 detects the (position of the electric motor shaft as) drive-side position q an,i of the i-th drive train, a second angle sensor 2 the (position of the gearbox output or relative position of the robot link to the previous robot link as) output-side position q ab,i of the drive train i.

[0059] A force F acts on an end flange 13 of the robot, which is offset by a distance a from the axis of rotation of the end flange (vertical in Fig. 1). In particular, it can be the weight force m g of a robot-guided payload whose center of gravity is at a distance a from the rotational axis of the end flange 13.

[0060] In a first step S10 (cf. Fig. 3) the Fig. 1 without any external force acting on the end flange 13.

[0061] In these measuring positions, the angle sensors 1, 2 each detect the input and output side positions of the drive trains of at least the third joint, in particular the second and third joint, and in one embodiment also of further joints.

[0062] In one version, the measuring poses are approached several times, the drive train positions are recorded and from this or from the differences Δ i = (q ab,i - q an,i ) of the input and output side positions, average values ​​are calculated and used for further processing. Repeated approaching serves primarily to compensate for any measurement errors, but is not mandatory.

[0063] In a second step S20, the Fig. 1 are approached again in the same way, in particular from the same direction, with a known external force now acting on the end flange 13, in particular a payload with a known mass and center of gravity being attached to the end flange 13. In one embodiment, the measuring poses are approached one after the other with different known external forces, in particular different payloads with different, respectively known masses and / or center of gravity positions.

[0064] Again, the angle sensors 1, 2 each record the input and output side positions, whereby in one embodiment the measuring poses (with the respective known external forces, in particular different payloads) are each approached several times, the drive train positions are recorded and from this or from the differences between the input and output side positions average values ​​are formed and these are further used.

[0065] Then, in a third step S30 stiffnesses c i of the individual joints based on these differences or averages, in a design according to JT⋅h=τ=K⋅(ΔL1−ΔL0) with the transposed Jacobian matrix J T , the winder h the known external force and the torque caused by it, the vector Δ L1 the drive train position differences for the known external force from step S20, the vector Δ L0 the drive train position differences from step S10 without external force and the stiffness matrix K with the joint stiffnesses c i Additionally or alternatively, the stiffnesses can also be determined in an analogous manner based on the different known payloads.

[0066] This is based on the idea of ​​determining joint moments on the basis of drive train position differences (τ = K Δ), and on the other hand, determining those joint moments that result from a force acting on the robot, the parameters of which are to be determined, on the basis of the difference between a measurement configuration with this force acting on the robot and a previously approached reference configuration without this force acting on the robot, in particular a load-free reference configuration, in particular deducting the joint moment components from the total joint moments determined on the basis of drive train position differences that do not result from this force acting on the robot (τ L0 = K·Δ L0), whereby the stiffness of the respective drive train taken into account for this purpose is determined on the basis of the difference between the first reference configuration approached in step S20 with the known external (first) force and the second reference configuration approached in step S10 without a force acting on the robot or a load-free reference configuration.

[0067] In a fourth step S40, the Fig. The measurement poses shown in Figure 1 are approached again in the same way, in particular from the same direction, with the (unknown) payload now attached to the end flange 13, whose mass m and center of gravity distance a are to be determined. Again, the angle sensors 1, 2 each detect the input and output-side positions. In one embodiment, the measurement poses are approached several times, the drive train positions are detected, and average values ​​are calculated from these values ​​or from the differences between the input and output-side positions, which are then used for further processing.

[0068] Then, in step S50, the winder h of the weight of the payload and the torque caused by it is calculated based on the drive train position differences Δ L0 with the robot unloaded from step S10 and the drive train position differences Δ N determined for the payload from step S40, in an embodiment according to h=(JT)−1⋅τ=(JT)−1⋅K⋅(ΔN−ΔL0)

[0069] The difference (Δ N - Δ L0 ) between the measurement configuration of step S40, in which the unknown force acts on the robot, and the previously approached reference configuration of step S10, in which this force does not act on the unloaded robot. This allows the robot's own weight to be masked out, so to speak.

[0070] In addition, the difference between the input and output side drive train positions Δ = [Δ1,...,Δ6] T , Δ i = (q ab,i - q an,i ) and using the stiffness(ies) c previously determined in step S30 ior K, the joint torques τ (resulting from the payload) are determined. In one embodiment, motor currents of the drives of the drive trains can also be used for this purpose, in particular in an analogous manner by determining the motor currents when the robot is unloaded (see step S10) and with a payload (see step S40), whereby the joint torques determined based on the drive train position differences and the joint torques determined based on the motor currents can be averaged or otherwise compared with one another.

[0071] In one embodiment in step S50, if there is a sufficient number of measurement data, a balancing problem min‖JT⋅h−τ‖ be solved, in an embodiment with the constraint C h = b, by which the known direction of the weight force and the resulting disappearance of at least one force and at least one torque component of the winder can be taken into account, for example in a coordinate system with the direction of gravity parallel or in Fig. 1 vertical z-axis and on the drawing plane of the Fig. 1 vertical x-axis: h = [0, 0, -m·g, -m·g·a,0, 0] T .

[0072] In a step S60, the robot is then operated on the basis of the mass and center of gravity of the currently guided payload determined in step S50, for example, a path is planned, the robot is monitored and / or controlled, in particular regulated, preferably on the basis of a model of the payload-guiding robot.

[0073] Steps S10 - S30 represent a calibration, which can be performed before steps S40 - S60 are carried out, but does not have to be performed.

[0074] In particular, if only the mass m of the payload and its distance a to the axis of rotation of the end flange 13 are to be determined, one joint and two measuring poses or one measuring pose and two joints may be sufficient or taken into account, as shown below using the Fig. 1 and the two measurement poses shown in Fig. 1 left joints with on the drawing plane of the Fig. 1 vertical axes of rotation should be explained.

[0075] It is assumed that the stiffness c3 and, if applicable, c2 as well as the difference Δ 3,L0 = (q ab,3 - q an,3 ) L0 and if necessary Δ 2,L0 = (q ab,2 - q an,2 ) L0between a drive-side and an output-side position of the drive train of these two joints when the robot is unloaded, as determined above with reference to steps S10 to S40.

[0076] Should only the Fig. 1 solid measurement pose is used (if necessary with multiple approaches and averaging), the result is τ2=c2⋅(Δ2,N−Δ2,L0)=(l2+a)⋅m⋅g τ3=c3⋅(Δ3,N−Δ3,L0)=(l3+a)⋅m⋅g with the gravitational constant g and the drive train position differences Δ determined with the payload in the measuring pose 2,N , Δ 3,N : a=(l2⋅τ3−l3⋅τ2) / (τ2−τ3) m=τ3 / [(l3+a)⋅g]

[0077] If, on the other hand, only one joint is to be used (possibly with multiple approaches and averaging), the two joints shown in Fig. 1 shown measuring poses τ3,α=0°=c3⋅(Δ3,N−Δ3,L0)α=0°=(l3+a)⋅m⋅g τ3,α≠0°=c3⋅(Δ3,N−Δ3,L0)α≠0°=(cosα⋅l3+a)⋅m⋅g with the values ​​α=0° for the Fig. 1 solid measurement pose and α≠0° for the Fig. 1 dashed measurement pose: m=(τ3,α=0°−τ3,α≠0°) / [g⋅l3⋅(1−cosα)] a=τ3,α=0° / (m⋅g)−l3

[0078] Although exemplary embodiments have been explained in the preceding description, it should be noted that a large number of modifications are possible.

[0079] In the exemplary embodiment, the mass and center of gravity of a robot-guided payload were determined, which is particularly advantageous for robot-assisted patient positioning or similar applications due to the limited adjustment options for parameter identification. However, parameters of contact forces acting on the robot can also be determined instead. List of reference symbols 1 drive-side angle sensor 2 output-side angle sensor 10 robots 11 Electric motor 12 Gearbox output 13 End flange 20 Robot control q an,i drive-side position of the i. joint q ab,i Output-side position of the i. joint τ i Joint moment of the i. joint (i=1,2,...,6) I2, I3 distances (known from robot kinematics) a Distance F to axis 6 (center of gravity payload) F force acting on the robot (end flange) (m g) m mass of the payload

Claims

[1] Method for determining a parameter (m, a) of a force (F) acting on a robot (10) on the basis of at least one joint moment (τ2, τ3) of the robot in at least one measuring pose of the robot, wherein the joint moment is determined on the basis of a difference between a drive-side and an output-side position (q ab,i - q an,i ) of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one previously approached reference configuration without this force acting on the robot. [2] Method according to claim 1, characterized by that the parameter depends on a mass (m) and / or center of gravity position (a) of a robot-guided payload or a contact force in an environmental contact of the robot. [3] Method according to one of the preceding claims, characterized bythat the parameter is determined on the basis of the joint moments (τ2, τ3) of a number of robot joints in the same measuring pose of the robot, wherein the number is at least two and / or less than or equal to the total number of joints of the robot and / or less than or equal to six. [4] Method according to one of the preceding claims, characterized by that the parameter is determined on the basis of the joint moments (τ3) of the same robot joint in at least two measuring poses of the robot and / or that the parameter is determined using a balancing problem solving method and / or on the basis of mean values. [5] Method according to one of the preceding claims, characterized by that the joint torque is determined based on the stiffness of the drive train and / or on the basis of an electrical drive variable. [6] Method according to the preceding claim, characterized bythat the stiffness is determined on the basis of a difference between at least one first reference configuration with a first force acting on the robot and at least one second reference configuration with no force or a second force acting on the robot. [7] Method according to one of the preceding claims, characterized by that the measurement configuration and at least one reference configuration are approached in the same way. [8] Method for operating (S60) a robot (10) based on a parameter of a force acting on the robot, characterized by that the parameter is determined by means of a method according to one of the preceding claims (S10 - S50). [9] System for determining a parameter (m, a) of a force (F) acting on a robot (10) on the basis of at least one joint moment (τ2, τ3) of the robot in at least one measuring pose of the robot, wherein the system is designed to carry out a method according to one of the preceding claims and / or comprises: means for determining the joint moment on the basis of a difference between a drive-side and an output-side position (q ab,i - q an,i ) of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one previously approached reference configuration without this force acting on the robot. [10] Computer program product comprising a program code stored on a computer-readable medium for carrying out a method according to any one of the preceding claims.

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