METHOD FOR OPERATING A ROBOT MANIPULATOR WITH INCREASED MASS OF A LOAD

Description

[0001] The invention relates to a method for operating a robot manipulator, as well as a robot system comprising a robot manipulator with an end effector and a control unit for carrying out the method.

[0002] EP 2 292 388 A1 relates to a method for stopping a manipulator, in particular a robot, comprising the steps of monitoring an area and braking the manipulator in the event of a violation of the area. The monitored area is variably specified during operation based on the braking distance of the manipulator.

[0003] DE 10 2017 102 621 B3 relates to a robot with a movable manipulator driven by actuators, with a first unit for determining external forces and / or external moments acting on the manipulator, and a second unit for controlling and regulating the actuators depending on the determined forces and / or external moments acting on the manipulator, wherein the second unit is designed to control or regulate the actuators for a predetermined subspace of a working space of the manipulator in such a way that the manipulator is moved along different projections when a determined external force and / or a determined external moment acts on the manipulator.

[0004] The following information, however, does not necessarily represent a particular state of the art, but rather arises from expert considerations of the mechanics of robot manipulators. An additional mass of a load on an end effector of a robot manipulator creates a moment that acts on the base of the robot manipulator and, in general, on the joints of the robot manipulator. If the mass of this load is very large compared to the mechanical design of the robot manipulator, the tensile or yield strength of materials in the links or at the joints, particularly a gear or torque sensor, of the robot manipulator may be reached at some point. Therefore, it is logical to define a maximum permissible mass for the load on the end effector. However, this limits the operation of the robot manipulator to handling precisely this maximum permissible mass of the load.It is therefore an object of the invention to overcome this disadvantage and also to operate loads of higher mass at the end effector of the robot manipulator.

[0005] The invention is based on the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims.

[0006] A first aspect of the invention relates to a method for operating a robot manipulator, comprising the steps: Determining a force winder or joint moment vector based on a weight force of a mass and / or based on a force of a load arranged on an end effector of the robot manipulator caused by the inertia of the mass, determining a maximum permissible working space and a maximum permissible kinematic size of the end effector or optionally of the load, each based on the force winder or joint moment vector, wherein the maximum permissible working space specifies a range for permissible positions of the end effector or optionally of the load on the end effector, such that the force winder or the joint moment vector within the working space does not exceed a predetermined metric, and controlling the robot manipulator by a control unit to execute a predetermined task taking into account the maximum permissible kinematic size and so,that the end effector or, alternatively, the load on the end effector remains within the maximum permissible working space if, at the start of the execution of the task, the end effector or, alternatively, the load on the end effector is within the maximum permissible working space.

[0007] The force winder or the joint moment vector is determined based on the weight of the mass and / or the force of the load arranged on the end effector of the robot manipulator caused by the inertia of the mass. The force winder specifies, in particular, a force, furthermore preferably additionally or alternatively, preferably only a moment, in particular relative to an earth-fixed and preferably Cartesian coordinate system. The mass itself generates a weight force in the earth's gravitational field, which generates a moment on the joints of the robot manipulator and on the base of the robot manipulator. In the static case, the mass of the load is only responsible for the weight force.In the dynamic case, however, i.e., when the robot manipulator is moving, an inertial force also acts on the end effector due to the inertia of the load's mass. This is particularly the case with a uniform circular motion of the robot manipulator, a centrifugal force; a Coriolis force when the resulting moment of inertia of the end effector's load changes; and, when the robot manipulator is moving along its path at an accelerated rate, the force resulting from the inertia of the mass counteracts the acceleration. The joint moment vector is the vector of the joint moments that correlates with the force winder.

[0008] In addition to predictive determination, the force winder can be determined very easily for all static cases as soon as the mass of the load at the end effector is known. This is because the weight of the load is then also known. The force winder or the joint moment vector based on the inertia of the mass of the load at the end effector, on the other hand, is determined predictively based on the planned task or a group of tasks. From the respective task, a trajectory and thus also the respective trajectory of the load at the end effector and the planned accelerations of the load at the end effector can be derived.

[0009] The force winder or joint moment vector that is determined does not necessarily have to be present in reality on the robot manipulator, but can also be a predictively determined hypothetical force winder or joint moment vector that would occur if the task were carried out accordingly or if the load were arranged accordingly on the end effector of the robot manipulator.

[0010] The maximum permissible kinematic value of the end effector, or alternatively, the load on the end effector, is, in particular, a speed or acceleration of the end effector, or alternatively, the load on the end effector. Whether the end effector or the load on the end effector is considered plays only a minor or even no role in the concept of the invention.

[0011] The workspace is preferably a spherical space with the sphere's center within or in the area of ​​the base of the robot manipulator, or alternatively, preferably a cuboid space. Ellipsoids or parts thereof are also possible. Other shapes are possible, depending on the calculation method and the accuracy with which the workspace is determined. Thus, the workspace can also be determined only approximately, and a predefined finite number of cuboid-shaped, spherical, or other areas with different volumes can be provided in order to select the closest suitable approximation from this finite number.

[0012] At least if the end effector, or optionally the load on the end effector, is within the maximum permissible working envelope at the start of task execution, the control unit connected to the robot manipulator determines the specified task in such a way that the determined maximum permissible working envelope and the maximum permissible kinematic size are maintained. To this end, the task can be limited beyond these maximum permissible geometric and kinematic ranges, modified, or at least the user can be given an indication of how the task should be modified so that these geometric or kinematic ranges are not exceeded.

[0013] If the end effector or, alternatively, the load on the end effector is not within the maximum permissible working space at the start of the execution of the task, the task is preferably not executed at all, or alternatively, preferably in response to the signals from the control unit, the robot manipulator and in particular the end effector or, alternatively, the load on the end effector is moved back into the geometrically maximum permissible working space at a speed and / or acceleration that lies within the respective permissible kinematic size, and in particular the execution of the task is then started by the control unit.

[0014] The specified metric is, in particular, a limit value for a moment exerted on the base, i.e., in particular, the base, of the robot manipulator by the weight of the load. The specified metric can be specified as the radius from a vertical axis passing through the base of the robot manipulator to the load multiplied by the mass of the load. If the mass of the load is, in particular, constant and known, the metric can also simply consist of a limit value that is compared with this radius.

[0015] It is an advantageous effect of the invention that a robot manipulator which is limited to a maximum permissible mass for a load on the end effector for general operation can also be operated with higher masses on the end effector.

[0016] According to an advantageous embodiment, the maximum permissible working space and the maximum permissible kinematic size of the end effector, or optionally the load of the end effector, are determined based on a mass distribution of the robot manipulator and / or a center of gravity of the robot manipulator and / or a mass of the end effector of the robot manipulator and / or a center of gravity of the end effector. To determine the total moment acting on the base or on the links or joints of the robot manipulator, the total mass distribution of the robot manipulator, together with the end effector and the mass of the load, is required.Whether an explicit mass distribution is determined or the mass distribution is summarized in individual centers of gravity of the robot manipulator's elements or in the entire center of gravity of the robot manipulator and considered with a corresponding inertia tensor plays only a minor role. This embodiment advantageously makes it possible to determine the maximum permissible working space and / or the maximum permissible kinematic size as a function of a maximum specified torque on a corresponding element of the robot manipulator (base, gear, joint, torque sensor, link, etc.).

[0017] According to a further advantageous embodiment, the weight of the mass of the load is determined by static or dynamic system identification. In static system identification, the robot manipulator is left in a rest position, and a respective joint moment is preferably detected by torque sensors, particularly in the joints of the robot manipulator, from which the weight and, in turn, the mass of the load are determined. Other force and / or torque sensors known in the prior art can be used to detect the weight of the load and, from this, determine the mass of the load.In dynamic system identification, a sinusoidal signal with a frequency that increases over time is specified as the input signal for at least one actuator of the robot manipulator, and the response of the robot manipulator or the manipulated variable generated by the controller of the robot manipulator, in particular a current of an electrical actuator, is recorded. In the case of the recorded kinematic response of the robot manipulator, a spectrum of the input signal and a spectrum of the output signal are obtained. With appropriate signal conditioning and division of the spectra, these produce a frequency response from which the mass of the load of the end effector can be read.can be approximated to a mass model using optimization methods by approximating parameters of the mass model, in particular of the robot manipulator, including the mass of the load, to minimize the error between the mass model and the frequency response. Advantageously, this embodiment eliminates the need to specify the mass of the load and communicate it to the control unit of the robot manipulator. Instead, the control unit of the robot manipulator is able to determine the exact mass of the load at the end effector of the robot manipulator using appropriate sensors on the robot manipulator itself.

[0018] According to a further advantageous embodiment, the control of the robot manipulator to carry out the specified task takes place taking into account the maximum permissible working space by specifying virtual walls at the boundaries of the maximum permissible working space, wherein to generate the virtual walls the robot manipulator is controlled in such a way that it exerts a force directed away from the virtual walls on the robot manipulator when the robot manipulator is manually guided.The force directed away from the virtual walls can either increase gradually, so that the user, when manually guiding the robot manipulator, experiences a smooth transition toward the respective virtual wall via increasing resistance from the robot manipulator against guiding the robot manipulator toward the virtual wall. Alternatively, the virtual wall is preferably a hard boundary, so that a sudden counterforce from the robot manipulator occurs on the virtual wall, as if the user were actually driving against a physical wall when manually guiding the robot manipulator. Advantageously, this embodiment allows for intuitive support of the user's manual guidance, so that the user intuitively receives feedback about which geometric boundaries of the workspace have already been defined.The virtual walls can be realized not only in the Cartesian earth-fixed coordinate system, but also as artificial stops at a respective joint, so that in the latter case the angular ranges of a respective joint are artificially limited.

[0019] According to a further advantageous embodiment, controlling the robot manipulator to perform the specified task, taking into account the maximum permissible working space and the maximum permissible kinematic size, comprises controlling the brakes of the robot manipulator. The brakes of the robot manipulator are released from a closed state only if the end effector or, optionally, the load on the end effector is within the permissible working space at the start of the task execution. If, for example, the user places a load with a nominally impermissible mass on the end effector, the brakes can remain closed, particularly to protect gears on the joints of the robot manipulator, if the mass of the load would, for example, cause impermissible damage to the gears of the robot manipulator through its weight alone.This advantageously increases the service life of the robot manipulator and in particular of the gears of the robot manipulator, or advantageously prevents the premature shortening of the service life of the robot manipulator.

[0020] According to a further advantageous embodiment, the maximum permissible working space and the maximum permissible kinematic size are determined on the basis of a trajectory of the robot manipulator predefined by the specified task and on the basis of the inertia tensor of the robot manipulator and / or the end effector and / or the load occurring over the trajectory, by determining a time-dependent acceleration of the robot manipulator and / or the end effector and / or the load from the predefined trajectory and by determining the time-dependent inertia tensor of the robot manipulator and / or the end effector and / or the load from the time-dependent pose of the robot manipulator dependent on the predefined trajectory.The trajectory of the robot manipulator comprises, in particular, the information of a trajectory curve and, furthermore, preferably additionally, time information associated with the trajectory curve, so that the term "trajectory of the robot manipulator" preferably includes not only the geometric path of the end effector or the load, but also the respective velocities and / or accelerations occurring when traversing the trajectory curve. Thus, sufficient kinematic information is available to determine a dynamic moment caused by the inertia of the mass of the load. When operating the robot manipulator and, in particular, when executing the specified output, to consider not only the weight of the mass of the load, but also the dynamic forces that lead to a moment on the limbs, joints, and the base of the robot manipulator.

[0021] According to a further advantageous embodiment, the method further comprises the steps: Checking the specified task to see whether the end effector or, optionally, the load has left the maximum permissible working space and / or whether the maximum permissible kinematic size of the end effector or, optionally, the load has been exceeded, and issuing a note to a user at an output unit on how the task can be changed so that when the task is carried out, the maximum permissible working space is not left by the end effector or, optionally, the load and / or the maximum permissible kinematic size of the end effector or, optionally, the load is not exceeded.

[0022] The output unit is preferably a screen on which the user is shown, preferably via arrows, how the task could be modified so that the maximum permissible workspace and the maximum permissible kinematic dimensions are not exceeded when executing the task. This advantageously provides the user with intuitive feedback on how the task should be modified, so that, in particular, the service life of the robot manipulator is not unnecessarily reduced when executing the task with a load exceeding the nominal permissible mass, and the safe operation of the robot manipulator is still ensured.

[0023] According to a further advantageous embodiment, the maximum permissible working space and the maximum permissible kinematic size are determined using a nonlinear optimization search algorithm. If an analytical solution for determining the maximum permissible working space and / or the maximum permissible kinematic size is possible, nonlinear optimization methods are advantageous for finding a corresponding restriction. The nonlinear optimization methods are, in particular, systematic search algorithms, such as gradient-based methods, quadratic optimization methods, genetic and evolutionary algorithms, as well as hybrids of the aforementioned. Restrictions of nonlinear optimization are then determined, in particular, by compliance with the specified metric and compliance with the permissible kinematic size.

[0024] According to a further advantageous embodiment, a starting point of the search algorithm is the angular position of the second joint, counted from the distal link of the robot manipulator, at which the influence of gravity on the moment at the second joint is maximum. In particular, this angular position can be determined off the cuff by a person skilled in the art based on knowledge of the mechanical situation at the robot manipulator. In particular, while holding the third joint, counted from the distal link of the robot manipulator, the second joint is then preferably perturbed, preferably within a cone with a vertical axis of rotational symmetry, in order to achieve a reduction in the load on the second joint.

[0025] A further aspect of the invention relates to a robot system comprising a robot manipulator with an end effector and a control unit, wherein the control unit is designed to determine a force winder or joint moment vector based on a weight force of a mass and / or based on a force caused by the inertia of the mass of a load arranged on an end effector of the robot manipulator, and is designed to determine a maximum permissible working space and / or a maximum permissible kinematic size of the end effector or optionally of the load, each based on the force winder or joint moment vector, wherein the maximum permissible working space specifies a range for permissible positions of the load on the end effector or the end effector, such that the force winder or the joint moment vector does not exceed a predetermined metric within the working space,and for controlling the robot manipulator by a control unit to perform a specified task taking into account the maximum permissible kinematic size and to perform the specified task in such a way that the end effector or optionally the load on the end effector remains within the maximum permissible working space if, at the start of the execution of the task, the end effector or optionally the load on the end effector is within the maximum permissible working space.

[0026] Advantages and preferred developments of the proposed robot system result from an analogous and analogous transfer of the statements made above in connection with the proposed method.

[0027] Further advantages, features, and details will become apparent from the following description, which – where appropriate with reference to the drawings – describes at least one embodiment in detail. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.

[0028] They show: Fig. 1 shows a method according to an embodiment of the invention, and Fig. 2 shows a robot system according to a further embodiment of the invention.

[0029] The representations in the figures are schematic and not to scale.

[0030] Fig. 1 shows a method for operating a robot manipulator 1. The method of Fig. 1 is carried out on a robot system 100 as shown in Fig. 2 described, executed.

[0031] Therefore, the following description also contains explanations for Fig. 2 The procedure involves the following steps: Determining S1 of a force winder or joint moment vector based on a weight of a mass and a force of a load 5 arranged on an end effector 3 of the robot manipulator 1, caused by the inertia of the mass. The weight of the mass of the load 5 is determined by static system identification. This means that after a user has arranged the load 5 on the end effector 3, the torque sensors arranged in the joints of the robot manipulator 1 detect a moment, and from the known mass distribution of the robot manipulator 1 and the end effector 3, the mass of the load 5 is obtained via the current joint angles of the robot manipulator 1. The force of the load 5 arranged on the end effector 3 of the robot manipulator 1, caused by the inertia of the mass, is, in contrast, determined predictively by analyzing the specified task and determining a trajectory for the end effector 3 or for the load 5.Determination S2 of a maximum permissible working space and a maximum permissible kinematic size of the end effector 3, each based on the force winder or joint moment vector, whereby the maximum permissible working space specifies a range for permissible positions of the end effector 3 such that the force winder or the joint moment vector does not exceed a predetermined limit within the working space. The determination of the maximum permissible working space and the maximum permissible kinematic size of the end effector 3 is carried out based on a mass distribution of the robot manipulator 1 and a mass distribution of the end effector 3 and based on a mass and an inertia tensor of the load 5. Due to the completely known mass distribution of all elements of the robot manipulator 1, including the load 5, a moment on the basis of the robot manipulator 1 is known through the integral of all mass elements over the radii.A gradient-based search procedure is then used to generate the maximum permissible working space and the maximum permissible speed and acceleration of end effector 3. In the gradient-based procedure, further search points are determined in the objective function around a starting point at a certain distance to maintain the specified metric, namely the current limit value based on robot manipulator 1. A gradient is determined from these search points and multiplied by a specified length to obtain the next step. This procedure is repeated iteratively until the algorithm converges and the gradient magnitude falls below a certain threshold. This calculation results in a cylindrical region to limit the maximum permissible working space.Furthermore, the maximum permissible speed and acceleration of end effector 3 are determined based on a trajectory of robot manipulator 1 predefined by the given task and based on the inertia tensor of robot manipulator 1, end effector 3, and load 5 occurring over the trajectory. This is done taking into account the previously determined maximum permissible workspace. The predefined trajectory provides a time-dependent acceleration of robot manipulator 1, end effector 3, and load 5. All moments of inertia and accelerations are then known from the time-dependent pose of robot manipulator 1, the time-dependent inertia tensor of robot manipulator 1, end effector 3, and load 5, which is dependent on the predefined trajectory.Checking S3 of the specified task to see whether the end effector 3 has left the maximum permissible working space and whether the maximum permissible kinematic size of the end effector 3 has been exceeded. Outputting S4 of a visual indication in the form of an arrow to a user on a screen 11 of a user computer connected to the control unit 7, indicating how the task can be changed by the user so that when the task is carried out the maximum permissible working space is not left by the end effector 3 and / or the maximum permissible kinematic size of the end effector 3 is not exceeded.Controlling S5 of the robot manipulator 1 by a control unit 7 to carry out a specified task taking into account the maximum permissible kinematic size and in such a way that the end effector 3 or optionally the load 5 on the end effector 3 remains within the maximum permissible working space if, at the start of the execution of the task, the end effector 3 or optionally the load 5 on the end effector 3 is within the maximum permissible working space. The determined cylindrical working space serves as the basis for generating virtual walls on the outer surface of the cylinder. The control of the robot manipulator 1 to carry out the specified task is carried out in such a way that, in order to generate the virtual walls, the robot manipulator 1 exerts a force directed away from the virtual wall on the robot manipulator 1 when the robot manipulator 1 is manually guided.If, at the start of the task execution, load 5 is located outside the outer surface of the cylindrical workspace, the brakes 9 of the robot manipulator are not released at all. Instead, a message is displayed on screen 11 to the user that load 5 is outside the permissible workspace.

[0032] Fig. 2 shows a robot system 100. The robot system 100 is designed in particular to carry out the method of Fig. 1to be carried out and comprises a robot manipulator 1 with an end effector 3 and a control unit 7, wherein the control unit 7 is designed to determine a force winder or joint moment vector based on a weight force of a mass and / or a force caused by the inertia of the mass of a load 5 arranged on an end effector 3 of the robot manipulator 1, and to determine a maximum permissible working space and / or a maximum permissible kinematic size of the end effector 3 or optionally of the load 5, each based on the force winder or joint moment vector, wherein the maximum permissible working space specifies a range for permissible positions of the load 5 on the end effector 3 or of the end effector 3, such that the force winder or the joint moment vector within the working space does not exceed a predetermined metric,and for controlling the robot manipulator 1 by a control unit 7 to carry out a predetermined task taking into account the maximum permissible kinematic size and for carrying out the predetermined task in such a way that the end effector 3 or optionally the load 5 on the end effector 3 remains within the maximum permissible working space if, at the start of the execution of the task, the end effector 3 or optionally the load 5 on the end effector 3 is within the maximum permissible working space.

[0033] Although the invention has been illustrated and explained in detail by means of preferred embodiments, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that the embodiments mentioned by way of example are truly only examples and should not be construed as limiting the scope, possible applications, or configuration of the invention in any way.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description. List of reference symbols

[0034] 1Robot manipulator 3End effector 5Load 7Control unit 9Brakes 11Output unit 100Robot system S1Determine S2Determine S3Check S4Output S5Control

Claims

1. A method for operating a robot manipulator (1), having the following steps: - ascertaining (S1) a wrench or joint torque vector on the basis of a weight force of a mass and / or on the basis of a force induced by the inertia of the mass of a load (5) on an end effector (3) of the robot manipulator (1), - ascertaining (S2) a maximum permissible workspace and a maximum permissible kinematic variable of the end effector (3) or optionally the load (5), in each case on the basis of the wrench or joint torque vector, wherein the maximum permissible workspace specifies a range for permissible positions of the end effector (3) or optionally the load (5), such that the wrench or the joint torque vector does not exceed a predetermined metric within the workspace, and - controlling (S5) the robot manipulator (1) by way of a control unit (7) for executing a predetermined task in consideration of the maximum permissible kinematic variable and such that the end effector (3) or optionally the load (5) on the end effector (3) remains within the maximum permissible workspace if, at the beginning of the execution of the task, the end effector (3) or optionally the load (5) on the end effector (3) is located within the maximum permissible workspace.

2. The method as claimed in claim 1, wherein the ascertaining of the maximum permissible workspace and the maximum permissible kinematic variable of the end effector (3) or optionally the load (5) of the end effector (3) is implemented on the basis of a mass distribution of the robot manipulator (1) and / or a center of gravity of the robot manipulator (1) and / or a mass of the end effector (3) of the robot manipulator (1) and / or a center of gravity of the end effector (3), respectively.

3. The method as claimed in any one of the preceding claims, wherein the weight force of the mass of the load (5) is ascertained by static or dynamic system identification.

4. The method as claimed in any one of the preceding claims, wherein the controlling of the robot manipulator (1) is implemented for executing the predetermined task in consideration of the maximum permissible work by predetermining virtual walls at the limits of the maximum permissible workspace, wherein for generating the virtual walls, the robot manipulator (1) is controlled such that it exerts a force directed away from the virtual walls on the robot manipulator (1) during the manual guiding of the robot manipulator (1).

5. The method as claimed in any one of the preceding claims, wherein the controlling of the robot manipulator (1) for executing the predetermined task in consideration of the maximum permissible workspace and the maximum permissible kinematic variable comprises the controlling of brakes (9) of the robot manipulator (1), wherein the brakes (9) of the robot manipulator (1) are only opened starting from a closed state when the end effector (3) or optionally the load (5) on the end effector (3) is located within the permissible workspace at the beginning of the execution of the task.

6. The method as claimed in any one of the preceding claims, wherein the ascertaining of the maximum permissible workspace and the maximum permissible kinematic variable is implemented on the basis of a trajectory of the robot manipulator (1) predefined by the predetermined task and on the basis of the inertial tensor of the robot manipulator (1) and / or the end effector (3) and / or the load (5) occurring over the trajectory, in that a time-dependent acceleration of the robot manipulator (1) and / or the end effector (3) and / or the load (5) is ascertained from the predefined trajectory and in that the time-dependent inertial tensor of the robot manipulator (1) and / or the end effector (3) and / or the load (5) is ascertained from the time-dependent pose of the robot manipulator (1) dependent on the predefined trajectory.

7. The method as claimed in any one of the preceding claims, furthermore having the following steps: - checking (S3) the predetermined task for leaving the maximum permissible workspace by the end effector (3) or optionally by the load (5) and / or for exceeding the maximum permissible kinematic variable of the end effector (3) or optionally the load (5), and - outputting (S4) an instruction to a user at an output unit (11) of how the task can be changed so that during the executing of the task the maximum permissible workspace is not left by the end effector (3) or optionally by the load (5) and / or the maximum permissible kinematic variable of the end effector (3) or optionally the load (5) is not exceeded.

8. The method as claimed in any one of the preceding claims, wherein the ascertaining of the maximum permissible workspace and the maximum permissible kinematic variable is implemented by a search algorithm of nonlinear optimization.

9. The method as claimed in claim 8, wherein a starting point of the search algorithm is that angle position of the second joint counted from the distal limb of the robot manipulator (1) at which the influence of gravity on the torque at the second joint is maximal.

10. A robot system (100) having a robot manipulator (1) having an end effector (3) and a control unit (7), wherein the robot system (100) is configured to execute the method according to claim 1.