Method and device for calibrating a robot, method for determining the 3D coordinates of a measurement object, method for determining the position and orientation of a measurement object, robot, and computer program

Abstract

The invention relates to a method for calibrating at least one robot kinematics system, wherein at least one reference object, which is attached to a first robot kinematics system and has detectable features, and at least one 3D digitiser, the 3D digitiser being attached to a further second robot kinematics system or to a further third robot kinematics system, and / or at least one camera, the camera being attached to the second robot kinematics system or to the third robot kinematics system, are brought by the first robot kinematics system and at least one of the further robot kinematics systems into different relative poses with respect to one another. In said method, in these different relative poses, data of the detectable features of the at least one reference object are recorded by the at least one 3D digitiser and / or the at least one camera, and calibration parameters are derived at least from part of the recorded data for at least one of the robot kinematics systems. The invention also relates to: one or more robot kinematics systems; a device for calibrating one or more robot kinematics systems using a coordinate measuring device or as part of a coordinate measuring device; and a method for determining the 3D coordinates of a measurement object and a method for determining the position and orientation of a measurement object. The present invention also relates to a computer program comprising instructions which, when the program is executed by at least one processor, cause said at least one processor and / or further processors to carry out the methods according to the invention.

Description

Method and device for calibrating a robot, method for determining the 3D coordinates of a measuring object, method for determining the position and orientation of a measuring object, robot and computer program

[0001] The present invention relates to one or more robots, a method and a device for calibrating one or more robots with a coordinate measuring machine or as part of a coordinate measuring machine, as well as a method for determining the 3D coordinates of a measurement object and a method for determining the position and orientation of a measurement object.

[0002] The present invention further relates to a computer program with instructions which, when the program is executed by at least one processor, cause this at least one processor and / or further processors to carry out the methods according to the invention.

[0003] Robot kinematics (hereinafter also referred to as robots) are mechanical structures in which one or more axes are coupled to one another. The goal of robot kinematics is to bring an end effector into a specific position and orientation (pose) in relation to a reference system. An axis is understood as the movable connection between two structural components of the robot kinematics, whereby this connection can be movable in up to six degrees of freedom. Examples of this are a typical robot rotary axis that only allows rotation in one rotational degree of freedom, a typical linear axis that allows translation in one translational degree of freedom, or a spherical joint (ball joint) that allows rotation in three rotational degrees of freedom. Typical robot kinematics are six-axis robots. In particular, a rotary table can also be considered a robot kinematics.The robot axes can be equipped with an actuator or operated passively. The reference system can be located on the floor, for example. Within the scope of the present invention, mobile robot kinematics traveling on corresponding mobile platforms can therefore also be calibrated individually or relative to each other. In this case, the reference system can be located on the floor of the platform that is stationary during the measurement.

[0004] Robot kinematics, whether parallel, serial, or coupled parallel and serial, such as an articulated arm on a delta robot, are inaccurate for metrology purposes in many respects. This means that the nominal forward kinematics do not correspond to the actual forward kinematics. This is caused, for example, by geometric inaccuracies, elastic deformations, thermal expansion, and inaccuracies in the determination of axis values. This is particularly problematic when the pose of the end effector or the tool mounted on the end effector (measuring device, tool, etc.) must be determined very precisely or is used for metrology. The end effector is the end interface along the link chain of the robot kinematics or the tool attached to the end interface.

[0005] In optical metrology, particularly 3D coordinate metrology, a measurement object can usually only be partially captured by an optical measuring system due to its limited measuring range. Therefore, the measuring system is positioned in various positions relative to the measurement object using a robot in order to capture the measurement object as completely as possible. The data available locally in the reference coordinate system of the measuring system is then combined in a global coordinate system. To do this, it is necessary to know the position and orientation of the measuring system in relation to the measurement object as precisely as possible. This accuracy is directly related to the positioning accuracy of the robot, or rather, the accuracy in determining the position of the end effector. The better a robot is calibrated, the more accurately the position of the measuring system can be determined and the more accurately the measurement object as a whole can be measured.

[0006] Measurement objects can be so large that even the reach of a robot is insufficient to capture the measurement object with the measuring system attached to the robot. In this case, the measurement object must be moved and realigned with the robot in order to be able to transfer the data before and after the measurement object is moved into a common global coordinate system. This is usually done using recognizable features attached to or around the measurement object, which are captured before and after the movement with the measuring system. The better the robot is calibrated, the more precise the alignment.

[0007] In 3D coordinate metrology, 3D digitizers are used to measure 3D data. These can be generated using different methods, such as triangulation with at least two cameras or one camera and a projector, time-of-flight measurement, lidar, confocal measurement, etc. The 3D data can be present, for example, in the form of individual 3D points of discrete features or as a full-surface mesh of a large number of surface points. 3D data can also be generated using a 2D camera. However, a single 2D camera that cannot generate 3D data in a single pose without further prior knowledge of the measurement object, such as a distance between features of the measurement object, is not considered a 3D digitizer within the meaning of the invention. 2D cameras are also referred to simply as cameras below.

[0008] EP 2 489 977 B1 describes a method with a measuring system for measuring the 3D Coordinates of an object with a camera and a projector and a reference camera for recording reference marks of a field of reference marks for determining the position and orientation of the measuring system from one or more images of the reference camera and an industrial robot for positioning the measuring system, whereby the measuring system and the field of reference marks are used to calibrate the robot.

[0009] Since pose determination is inaccurate due to the acquisition of data from a reference camera, and thus a 2D camera, particularly in the viewing direction of the 2D camera, EP 2 489 977 B1 further proposes using multiple reference cameras aligned in different viewing directions. However, the use of additional 2D cameras increases the cost of the system as well as the weight that must be attached to the end effector of a robot. This may mean that a robot with a correspondingly high payload must be used.

[0010] In describes a method in which the positions of a camera system of a robot relative to a reference coordinate network frame are obtained at several points in time of a scanning plan based on a comparison of three-dimensional images of a scene and the positions of the robot are obtained based on a second scanning plan, to determine the position of the reference coordinate network frame and the reference point of the camera system relative to the position of the robot. Several equations are created that are used to solve an optimization problem. It is described that the position of the reference coordinate network frame, the tool center point of the camera system, a possible time offset, and parameters of the robot model can be optimized in the optimization process. One input parameter of the optimization process is the position of the camera system, which results from a comparison of the three-dimensional images of the scene.

[0011] As mentioned in EP 3 377 948 B1, it is difficult, especially in areas with few features, to line up the three-dimensional images using visual odometry.

[0012] This is especially true for low-resolution 3D digitizers with small measurement volumes. The larger the measurement volume, the higher the probability of capturing a feature, and the higher the resolution, the higher the probability of detecting a feature or accurately capturing its location.

[0013] In "Dynamic Photogrammetry Calibration of Industrial Robots" Videometrics V, SPIE Proceedings Series Vol. 3174, SPIE's 42nd Annual Meeting, San Diego, July 27 - August 1, 1997, a method for calibrating a robot is described in which a reference object is attached to a robot and 3D coordinates of marked points of the reference object are determined by recording with three synchronized cameras. The poses of the end effector are determined based on the 3D coordinates of the marked points. The determination of the 3D coordinates and the determination of the orientation and camera model parameters of the three-camera system occur simultaneously.

[0014] The disadvantage of the method is that inexpensive cameras have a relatively low resolution and therefore the position of the points of the reference object in the camera images and thus also in space cannot be determined very precisely.

[0015] It is therefore an object of the present invention to provide a method and a device for calibrating a robot kinematics as well as a method for determining the 3D coordinates of a measurement object and a method for determining the position and orientation of a measurement object as well as a robot kinematics and a computer program for carrying out the method according to the invention, whereby the above-mentioned problems are solved.

[0016] Against this background, the invention proposes a method for calibrating robot kinematics, which comprises at least one reference object attached to a first robot kinematics, which has recognizable features, and at least one 3D digitizer, wherein the 3D digitizer is attached to a further second robot kinematics or to a further third robot kinematics, and / or at least one camera, wherein the camera is attached to the second robot kinematics or to the third robot kinematics,wherein the reference object and the 3D digitizer and / or the camera are brought into different relative poses to one another by the first robot kinematics and the second robot kinematics and / or the third robot kinematics, and wherein, in these different relative poses, data of the recognizable features of the reference object are recorded by the at least one 3D digitizer and / or the at least one camera, and calibration parameters are derived from at least part of the recorded data for at least one of the robot kinematics.

[0017] The movement of the respective robot kinematics can be conveniently carried out via a controller that controls all robot kinematics. The advantage of the present method is that at least two robot kinematics can be calibrated in one calibration process, rather than each robot kinematics having to be calibrated individually, and multiple robot kinematics then having to be calibrated one after the other. Furthermore, the method according to the invention also makes the position and orientation of the two robot kinematics known to one another. Calibration can be carried out without additional aids. It is sufficient that the reference object is attached to a first robot kinematics and a 3D digitizer or camera is attached to a second or third robot kinematics. A hand-eye calibration is therefore not necessary for the second or third robot kinematics to which the 3D digitizer or camera is attached. not necessary, since this is already included in the method according to the invention. If the reference object is replaced by a tool, the hand-eye calibration can be performed by the 3D digitizer already attached to the second or third robot kinematics or by the camera already attached to the second or third robot kinematics.

[0018] It goes without saying that the camera can be part of the 3D digitizer. This naturally also applies to the following method claims for measuring a measuring object and aligning a measuring object as well as to the corresponding device claims.

[0019] According to a further aspect of the present invention, a method for determining the 3D data of a measurement object is proposed, wherein at least one digitizer attached to a robot kinematics or several 3D digitizers attached to robot kinematics are brought into different poses for measuring the measurement object and the 3D digitizer(s) generate local 3D data in the reference coordinate systems of the 3D digitizers and wherein the local data generated for the different poses are converted into a global coordinate system on the basis of the calibration parameters of the robot kinematics derived according to the method according to the invention.

[0020] According to a further aspect of the present invention, a method is proposed for aligning a measurement object with respect to a robot kinematics on the basis of recognizable features that are distributed on or around the measurement object and are measured by at least one 3D digitizer attached to a robot kinematics and at least one camera attached to a robot kinematics, wherein the calibration parameters of the robot kinematics were derived by means of the method according to the invention.

[0021] According to a further aspect of the present invention, a device for calibrating robot kinematics is proposed, which comprises at least the following components: At least one reference object attached to a first robot kinematics, which has recognizable features, and at least one 3D digitizer, wherein the 3D digitizer is attached to a further second robot kinematics or to a further third robot kinematics, and / or at least one camera, wherein the camera is attached to the second robot kinematics or to the third robot kinematics, wherein calibration parameters are derived for at least one of the robot kinematics according to the method according to the invention.

[0022] According to a further aspect of the present invention, a robot kinematics whose calibration parameters were derived by means of the method according to the invention is proposed.

[0023] Furthermore, a computer program with instructions is proposed which, when the program is executed by at least one processor, cause this at least one processor and / or further processors to carry out the method according to the invention.

[0024] According to the invention, a method for calibrating robot kinematics is provided. This method makes it possible to calibrate one, but in particular also two or three, of the robot kinematics in a process sequence according to the invention. By calibrating two or more robot kinematics, the position and orientation of the end effectors of the respective robot kinematics relative to one another can be determined.This also means, for example, that if a reference object is replaced by a measurement object on the first robot kinematics, the position and orientation between the measurement object and the 3D digitizer are known based on the derived calibration parameters. This means that the recorded 3D data, which are present in the local reference coordinate system of the 3D digitizer, can be transferred to the correct location in the reference coordinate system of the measurement object. This way, the data from the individual recordings of the respective poses of the measurement object and the 3D digitizer result in a correctly coherent overall image of the measurement object, whereby the overall image also consists of 3D data. To move from one pose to the next, the robot kinematics can move one after the other or simultaneously. Furthermore, the 3D digitizer can also be replaced by a tool, for example. that processing of an object mounted on the first robot kinematics is carried out precisely by the tool mounted on the second robot kinematics based on the derived calibration parameters of the robot kinematics. It should be noted at this point that there are many other examples of how two or more robot kinematics calibrated according to the method according to the invention can be advantageously combined.

[0025] The data for deriving the calibration parameters are recorded by bringing a reference object, which has recognizable features and is attached to a first robot kinematics system, and at least one 3D digitizer, wherein the 3D digitizer is attached to a second robot kinematics system or to a third robot kinematics system, and / or at least one camera, wherein the camera is attached to a second robot kinematics system or to a third robot kinematics system, into different relative poses to one another, and recording data of the recognizable features of the reference object in these different relative poses. Thus, using a 3D digitizer and a camera, it is possible, for example, for the 3D digitizer and the camera to be attached to a second robot kinematics system, or for the 3D digitizer to be attached to a second robot kinematics system and the camera to be attached to a third robot kinematics system.The camera is attached to a second robot kinematics system, and the 3D digitizer is attached to a third robot kinematics system. For example, it is equally possible for only one 3D digitizer or only one camera to be attached to the second robot kinematics system.

[0026] Furthermore, the robot kinematics mentioned can be supplemented with any other robot kinematics in order to calibrate them according to the method according to the invention. For example, one robot kinematics with a reference object and three others, each with a 3D digitizer, etc.

[0027] The recorded data can be 2D data captured with one or more cameras, including one or more cameras of the 3D digitizer. It can also be 3D data generated by the 3D digitizer.

[0028] With the newly determined calibration parameters, the pose of a 3D digitizer can now be determined more precisely and thus a measurement object can be measured more accurately.

[0029] Furthermore, the newly determined calibration parameters also enable a more precise alignment of a measuring object to the calibrated robot kinematics.

[0030] The above-mentioned task is thus completely solved.

[0031] According to a further embodiment, the 3D digitizer is a triangulation sensor, in particular one with stripe light projection.

[0032] The advantage of triangulation sensors is that they can determine 3D data very precisely and can also be implemented relatively easily, for example by combining two cameras or a camera and a projector.

[0033] According to a further embodiment, the reference object is measured or re-measured within the method according to the invention and thus the recognizable features of the reference object are related to one another in a coordinate system or the reference object is measured beforehand or subsequently outside the method according to the invention.

[0034] In order to calibrate robot kinematics using a reference object, the reference object must be calibrated with high precision. This can be achieved, for example, by calibrating the reference object in advance in a calibration laboratory, i.e., outside the method according to the invention. If the reference object does not remain calibrated with long-term stability, regular calibration is necessary to ensure lasting accuracy. This can be done within the method according to the invention, so that the reference object is calibrated with high precision during the method according to the invention by generating calibration data that relate the recorded features of the reference object to one another in a coordinate system, thus eliminating the complexity of prior calibration and long-term stability.

[0035] Since the requirement for long-term stability of the reference object is reduced in this case, a lightweight reference object can be used that is mounted on a robot kinematics, thereby reducing the load on the robot kinematics.

[0036] Influencing factors such as the gravitational orientation of the reference object or the ambient temperature can also be taken into account. It is therefore possible, for example, to generate calibration data at different ambient temperatures and to generate the calibration data or the references of the recorded recognizable features of the at least one reference object in a coordinate system in a temperature-dependent manner. It must be ensured that sufficient recordings of the recognizable features of the at least one reference object are generated at the different ambient temperatures. Due to the existing temperature dependence of the references of the recorded recognizable features of the at least one reference object, this can lead to improved ambient temperature-dependent calibration of the robot kinematics.

[0037] The generation of calibration data and the derivation of calibration parameters can occur simultaneously in a single step, for example, in an optimization process. However, it can also occur in multiple steps, so that, for example, the calibration data is generated first and then, in a separate step, the calibration parameters are determined based on the previously generated calibration data.

[0038] According to a further embodiment, the data for generating the measurement data and for deriving the calibration parameters can be different, identical or partially identical.

[0039] The use of a camera, especially a high-resolution one, is advantageous for measuring the recognizable features of the reference object. The use of a 3D digitizer is advantageous for determining the pose of the end effector, since depth data is particularly relevant for the pose. Nevertheless, a camera can also be used to determine the pose of the end effector. or a 3D digitizer to measure the recognizable features of the reference object, or both can be combined.

[0040] For example, it can be helpful to only use data recorded with a high-resolution camera to generate calibration data, and to only use data recorded with a 3D digitizer to derive the calibration parameters, so that these are completely different. However, it can also be helpful to select poses in such a way that the recorded data is suitable for both generating calibration data and deriving calibration parameters. The data sets are therefore suitable for generating calibration data and deriving calibration parameters, and these can therefore be completely or at least partially identical. This can advantageously reduce the time required to acquire the data.

[0041] According to a further embodiment, a scale-defining element is present on the reference object and / or a robot link itself is a scale-defining element.

[0042] A scale-defining element is advantageous in order to be able to specify the distances between the recognizable features absolutely and not just relatively. In particular, when only 2D data is available, the distances between the recognizable features of the reference object are scalable if there is no fixed reference to a scale-defining element. The scale-defining element is, for example, a stable precision body. This is measured with high precision, usually using a tactile coordinate measuring machine, and consists of a material that hardly expands, ideally not at all, when the temperature changes. The precision bodies are usually simple forms of length scales, such as a ball rod. The advantage is that by generating the calibration data, the accuracy of the precision body is transferred to the rather complex reference object without the reference object itself having to be measured with high precision (e.g. tactilely).However, a scale-defining element can also be an exactly measured distance between two recognizable features of the reference object.

[0043] According to a further embodiment, the recognizable features of the reference object are absolutely related to one another by at least one absolute measurement with the 3D digitizer, whereby the 3D digitizer itself is the scale-determining element.

[0044] A calibrated 3D digitizer measures 3D data absolutely. A measurement of the recognizable features of the reference object with the 3D digitizer can therefore be used to determine the absolute distances between the recognizable features of the reference object, which may only be available in relative terms. This advantageously eliminates the need for a scale-defining element on the reference object.

[0045] According to a further embodiment, at least part of the local data of the recognizable features of the reference object present in the local reference coordinate system of the 3D digitizer and / or the local data of the recognizable features of the reference object present locally in the reference coordinate system of the camera are converted into a global reference coordinate system.

[0046] For the transfer or transformation of the local data of the recognizable features of the reference object (actual observations) into a global coordinate system, it is helpful to know the pose of the 3D digitizer attached to the end effector and / or the camera attached to the end effector or the reference object attached to the end effector. This results from the forward kinematics of the robot kinematics and the relationship between the 3D digitizer and / or camera or reference object and the end effector. The forward kinematics, or forward transformation, is the function that describes the position and orientation of the end effector, as well as individual robot links, in a given coordinate system, depending on the robot configuration given in the axis space (for example, angular positions of rotary joints or linear positions of linear axes).To do this, the coordinate transformations of, for example, the individual robot limbs must be known. These coordinate transformations for a given robot are nominally known from data sheets, technical drawings, CAD data, given Denavit-Hartenberg parameters, etc. The local data available in the local reference coordinate system of the 3D digitizer or camera relate, for example, to the position and orientation of the camera sensors. In the case of a triangulation sensor, this is This is provided, for example, by the calibration of the igulationsens. The lengths and angles required for the transformation between the local reference coordinate system of the camera sensor and the coordinate system of the end effector can therefore nominally be read, for example, from the CAD data of the 3D digitizer and / or the camera and any necessary adapters between the 3D digitizer and the end effector. Similarly, CAD data of the reference object can also be used, for example, to establish a relationship between the end effector and the recognizable features of a reference object attached to the end effector.

[0047] In the following, the calculation of the forward kinematics from these nominally known values ​​(i.e., values ​​not calibrated to reality by any kind of calibration) is referred to as "nominal forward kinematics." However, due to factors such as geometric inaccuracies, elastic or thermal deformations, or inaccuracies in determining the axis angles or lengths of the robot limbs, the accuracy of determining the position of the 3D digitizer and / or the camera or reference object on the robot kinematics is usually insufficient. The nominal forward kinematics therefore differs from the actual kinematics.

[0048] The data available after the transformation in the global coordinate system are then used as starting values ​​for subsequent optimization procedures. By transforming the data into a global coordinate system, the application of forward kinematics increases the likelihood of finding a better extremum for the optimization procedure.

[0049] According to a further embodiment, the calibration parameters of the at least one robot kinematics are derived and, optionally, before the calibration parameters are derived or during the calibration parameters are derived, the reference object is measured and, optionally, the calibration parameters of the at least one 3D digitizer or the at least one camera are adjusted in such a way that the deviations between the coordinates of the recorded recognizable features of the reference object and the coordinates of the recognizable features of the reference object calculated from a mathematical model are minimized.

[0050] A deviation can, for example, be a deviation in the position and / or a deviation in the orientation of the recognizable features of the reference object.

[0051] The reference object is measured by generating measurement data from at least part of the recorded data, which relate the recorded features of the reference object to one another in a coordinate system.

[0052] If the reference object has not been calibrated or needs to be calibrated again, this can be achieved using an optimization process to generate the calibration data using the data provided for this purpose, for example, according to a mathematical model using bundle block adjustment according to Luhmann Robson, Kyle, Boehm, Close Range Photogrammetry and 3D Imaging, Second Edition, Chapter 4, ISBN 978-3-1110-2986-3. The calibration parameters can be derived in a further optimization process by minimizing the deviations between the recorded recognizable features of the reference object and the recognizable features of the reference object related to one another from the calibration data.This can be done, for example, using a mathematical model containing the calibration parameters of the robot kinematics, with methods for solving a nonlinear optimization problem according to Nocedal, Wright, Numerical Optimization, Second Edition, ISBN 978-1-4939-3711-0. However, both optimization methods can also be combined into one optimization method. If necessary, the calibration parameters of the 3D digitizer and / or the camera can also be adjusted within a separate or combined optimization method, provided that a scale-defining element is captured by the 3D digitizer and / or the camera (see Luhmann, Robson, Kyle, Boehm, Close Range Photogrammetry and 3D Imaging, Second Edition, ISBN 978-3-1110-2986-3).If necessary, the calibration parameters of the 3D digitizer and / or the camera can also be adjusted without a scale-defining element being detected by the 3D digitizer and / or the camera, provided that one of the robot limbs and thus a part of the robot kinematics itself is the scale-defining element. Likewise, if necessary, scale-independent calibration parameters of the 3D digitizer and / or the camera can also be adjusted without a scale-defining element being detected, provided that the scale-dependent parameters of the Calibration of the 3D digitizer and / or camera was previously recorded using a scale-setting element.

[0053] The method according to the invention can therefore be used to calibrate a robot kinematics, to measure the reference object if necessary, and to calibrate the 3D digitizer or camera if necessary.

[0054] By minimizing, an ideal solution to the optimization problems is advantageously found.

[0055] While the optimization procedures and the identification of the calibration parameters can be formulated using forward kinematics, it is equally possible to set up an equivalent optimization problem using inverse kinematics.

[0056] According to a further embodiment, the calibration parameters of the robot kinematics are geometric and / or elastic and / or thermal and / or calibration parameters of the robot kinematics that take the configuration of the robot kinematics into account, and / or calibration parameters that take the direction of travel into account, and / or calibration parameters of the characteristics of the or calibration parameters for determining the error curves of the length or angle measurement technology of the robot kinematics and / or calibration parameters that characterize the play of individual or all axes of the robot kinematics, and / or calibration parameters that describe the dependence of the robot kinematics on other variables that can be recorded, for example, with sensors or can be calculated based on the available data.

[0057] Depending on the type of robot kinematics and the environmental conditions of the robot kinematics, as well as the type of 3D digitizer or camera and the reference object, it is useful to use different combinations of calibration parameters for optimization.

[0058] However, the method according to the invention is not limited to these calibration parameters and can be supplemented and combined with other parameters.

[0059] According to a further embodiment, the calibration parameters are used to determine the pose of the end effector of the robot kinematics and / or to align the end effector based on the parameters.

[0060] The adjusted calibration parameters resulting from the optimization process can be used to position the end effector of the robot kinematics more precisely. This is useful when the measurement of a measurement object takes place after the robot kinematics have been calibrated. The calibration parameters can also be used to precisely determine the pose of the end effector. This makes it possible, for example, to use cost-effective robot kinematics whose approach accuracy to a certain pose is low due to mechanical reasons, but the pose can still be precisely determined using the adjusted calibration parameters. Furthermore, it is also possible to subsequently correct the poses of a measurement.

[0061] If a 3D digitizer or camera is attached to the robot kinematics and is also used as a measurement sensor, the forward kinematics already includes the transformation from the global reference coordinate system to the local reference coordinate system of the 3D digitizer or camera. Thus, no additional hand-eye calibration is necessary. If the reference object attached to the first robot kinematics is replaced by a tool, hand-eye calibration between a local reference coordinate system of the tool and a reference coordinate system of the first robot kinematics can be performed by the camera or 3D digitizer attached to the second or third robot kinematics. Therefore, no additional system is required to perform hand-eye calibration.

[0062] According to a further embodiment, 3D digitizers and / or cameras and / or reference objects are mounted on several robot kinematics and at least one of the robot kinematics is calibrated according to the method according to the invention.

[0063] For example, a combination is possible in which the reference object is mounted on one robot kinematic system and a 3D digitizer is mounted on two or more other robot kinematic systems. It is also conceivable that a reference object is mounted on two or more robot kinematic systems and the 3D digitizer and / or camera are mounted on one robot kinematic system.

[0064] A configuration of multiple robot kinematics is also possible, in which one, several, or all robot kinematics are equipped with a 3D digitizer and / or a camera as well as a reference object. The reference object can be attached anywhere on the robot kinematics.

[0065] In principle, it is possible to realize various combinations of robot kinematics with 3D digitizers, cameras and reference objects according to the method according to the invention,

[0066] According to a further embodiment, at least one of the robot kinematics is a turntable.

[0067] A rotary table is particularly advantageous when 3D data is to be determined not only on the front of a measuring object, but also on the sides or back, and another robot kinematics to which the 3D digitizer is attached cannot reach the sides or back of the measuring object, which is made possible by the rotary table.

[0068] The turntable can be calibrated individually or with another robot kinematics, for example a six-axis robot.

[0069] According to a further embodiment, the robot kinematics are measured relative to each other.

[0070] If, for example, two or more 3D digitizers, each mounted on a robot kinematic, measure the reference object, this has the advantage that, for example, all Coordinate systems of the end effectors of the respective robot kinematics can be converted into a common global reference coordinate system. This also works for combinations with two or more reference objects, each attached to a robot kinematic.

[0071] This means, for example, with regard to the measurement of a measuring object, that two or more robot kinematics, each with 3D digitizers attached to it, can be used and the data from the respective 3D digitizers can be represented in a common global reference coordinate system.

[0072] Furthermore, it is possible to calibrate entire streets to robot kinematics and to transfer them into a common reference coordinate system.

[0073] According to a further embodiment, in addition to the 3D digitizer and / or camera and / or reference object, one or more further tools are attached to the robot kinematics and / or the 3D digitizer and / or the camera and / or the reference object on the robot kinematics are replaced by one or more tools.

[0074] This makes it possible for the method according to the invention to be used not only for 3D coordinate measurement technology, but also for other robot kinematics tasks.

[0075] According to a further embodiment, the reference object is designed such that the recognizable features are located on an independent body and / or on one or more arbitrary members of a robot kinematics and / or on a 3D digitizer or a camera and / or on a tool and / or on a measurement object and / or around a measurement object.

[0076] Depending on the application, structure and environmental conditions of a robot kinematics, it is advantageous to create a reference object with a specific arrangement of the recognizable features for the method according to the invention.

[0077] The reference object can be an independent body that is attached to a de-effector. The reference object can be attached to any robot link or extend over one or more links of the robot kinematics. It can be located on the end effector of the robot kinematics or on a tool attached to the end effector. The reference object can consist of multiple reference objects. Reference objects can be constructed spatially separated from one another. The reference object can also be part of the 3D digitizer. This means, for example, that two robot kinematics can be mutually calibrated if each robot kinematics carries a 3D digitizer to which recognizable features are attached, and the respective derived calibration parameters are mutually checked or linked. The reference object is normally a separate object from the measurement object. However, a combination of the two objects is also possible.

[0078] According to a further embodiment, the recognizable features are optical markers which themselves actively illuminate and / or are passively illuminated, and / or features recognizable in two dimensions with a unique 2D geometry and features recognizable in three dimensions with a unique geometry.

[0079] Depending on the type and application of a 3D digitizer or camera, it is advantageous to use corresponding recognizable features.

[0080] Features recognizable in two dimensions can be, for example, patterns, circles, holes, spheres, canes or corners; features recognizable in three dimensions can be, for example, spheres, cylinders, cones, etc.

[0081] According to a further embodiment, the camera is removed from the robot kinematics when it is not in use.

[0082] This has the advantage of increasing the accessibility of the 3D digitizer to the reference object and to a measurement object. This makes it much easier to work in the car body, for example, if the measurement object is a car body. measure when the camera for the measurement process has been removed from the robot kinematics to which the 3D digitizer is also attached.

[0083] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also alone or in other combinations without departing from the scope of the present invention.

[0084] In addition, it is understood that the features defined in the dependent claims for the method for calibrating the robot kinematics can also be used in the same or equivalent manner as device features for the method according to the invention, without these being listed again separately here as device features.

[0085] The indefinite term "a", "an", "an" etc. is not to be understood as a number in the sense of the present invention, but as an indefinite term in the sense of "at least one", "at least one", "at least one" etc. Thus, the features designated by "an element" also include several such elements, such as several robot kinematics or a robot kinematics with one or more 3D digitizers, cameras or reference objects. Furthermore, other elements are not excluded.

[0086] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. They show: Fig. 1 is a schematic representation of a device of the method according to the invention for calibrating robot kinematics with two robot kinematics; Fig. 2 is a schematic representation of a device of the method according to the invention for measuring a measurement object; Fig. 3 shows a further schematic representation of a device of the method according to the invention for measuring a measurement object; and Fig. 4 shows a further schematic representation of a device of the method according to the invention with a turntable and a six-axis robot.

[0087] Figure 1 shows an exemplary embodiment of one of several possible devices for the method according to the invention. This device comprises a reference object 7, which is attached to a first robot kinematic system 1a and has recognizable features 8, and a 3D digitizer 2, wherein the 3D digitizer 2 is attached to a second robot kinematic system 1b, and a camera 4, wherein the camera 4 is also attached to the second robot kinematic system 1b. The robot kinematic system 1a and the robot kinematic systems 1b bring the reference object, the 3D digitizer 2, and the camera 4 into different relative poses to one another. In these different relative poses, data of the recognizable features 8 of the reference object 7 are recorded by the 3D digitizer 2 and / or by the camera 4, and calibration parameters for at least one of the robot kinematic systems 1a, 1b are derived from at least part of the recorded data.In this exemplary embodiment, the robot kinematics 1a, 1b are six-axis robots. The axes are each marked with hatching. The device, as well as the exemplary embodiments mentioned below, can be controlled, for example, via a computer 5. This computer contains a computer program with commands which, when executed by at least one processor, cause this at least one processor and / or other processors to execute the method according to the invention.

[0088] Another possible device can be provided in that the reference object 7 is attached to a first robot kinematics 1a, the 3D digitizer 2 to a second robot kinematics 1b and the camera 4 to a third robot kinematics 1c (not shown).

[0089] In order to calibrate a robot kinematics 1a, 1b, 1c using the reference object 7, the reference object 7 must be measured with high precision. This can be done, for example, by It must be ensured that the reference object 7 has been calibrated in advance in a calibration laboratory, i.e., outside the method according to the invention. If the reference object 7 does not remain calibrated with long-term stability, regular calibration is necessary to ensure lasting accuracy. This can be done within the method according to the invention, so that the reference object 7 is calibrated with high precision during the method according to the invention by generating calibration data that relate the recorded features of the reference object 7 to one another in a coordinate system, thus eliminating the complexity of a preliminary calibration and long-term stability.

[0090] The generation of calibration data can be carried out by data which consist at least partly of the recorded data which were recorded in the different relative sen of the method according to the invention.

[0091] The reference object 7 can be designed such that the recognizable features 8 are located on an independent body and / or on one or more arbitrary members of a robot kinematics / or on a 3D digitizer 2 or a camera 4 and / or on a 'I un*' on a measurement object 9 and / or around a measurement object 9.

[0092] The recognizable features 8 can be optical markers that themselves actively illuminate and / or are passively illuminated, and / or features 8 that are recognizable in two dimensions with a unique 2D geometry and / or features 8 that are recognizable in three dimensions with a unique 3D geometry.

[0093] A scale-defining element 6 can optionally be attached to the reference object 7 in order to be able to define the distances of the recognizable features absolutely and not just relatively. The scale-defining element 6 is, for example, a stable precision body. This is measured with high precision, usually with a tactile coordinate measuring machine, and consists of a material that hardly expands, ideally not at all, when the temperature changes. > < - expansion bodies are usually . - times Shapes of length scales, such as a ball rod. The advantage is that the By generating the calibration data, the accuracy of the precision body is transferred to the rather complex reference object 7, without the reference object 7 itself having to be calibrated with high precision (e.g. tactile).

[0094] A scale-defining element 6 can also be provided by the digitizer 2 or one of the digitizers 2, in that the digitizer 2 provides at least one recording of 3D data. An additional scale-defining element 6, as shown in Figure 1, is therefore not absolutely necessary. The 3D digitizer 2 can be the scale-defining element 6, since it absolutely measures the distances between the recognizable features 8 of the reference object based on the calibration of the digitizer by at least one 3D data recording. The recognizable features 8 of the reference object 7, which are possibly related to one another only from 2D data, can therefore be absolutely related to one another by combining them with at least one recording of 3D data from the 3D digitizer 2. It is also conceivable that one of the robot limbs itself is the scale-determining element.In this case, no further scale-determining element would be required for the method according to the invention.

[0095] The data recorded to generate the calibration data can come from the 3D digitizer of camera 4.

[0096] Preferably, a high-resolution digital camera is used to generate the calibration data, whereby this camera is placed in many different poses relative to the reference object 7 to record images. From the images recorded in these poses, the recognizable features can be determined using bundle block adjustment (according to Luhmann, Robson, ahm, Close Range Photogrammetry and 3D Imaging, Second Edition, Chapter 4). Features of the reference object 7 can be related to each other in a coordinate system.

[0097] Typically, 2D data is used in bundle block adjustment. However, it is also possible to use 3D data from a 3D digitizer.

[0098] To derive the calibration parameters of the robot kinematics 1a, 1b, 1c, 2D data can be used, which can be recorded, for example, with a camera. 3D data can be used, which can be recorded by a 3D digitizer 2, in particular an angulation sensor, which can determine 3D data very precisely and can also be implemented relatively easily, for example by combining two cameras or a camera and a vector.

[0099] / For example, a fringe projection system can be used for the angulation sensor. This consists of two cameras and a projector for projecting fringe images. Homologous image points, i.e. points that depict the same object point on a surface in both cameras, are triangulated, thus determining the object point in space, i.e., a 3D coordinate in the local reference coordinate system > > S of the fringe projection system for the object point is generated. Since a large number of homologous pixels are recorded in a stripe projection system, it is an area sensor. This allows 3D data of multiple recognizable features 8 of a reference object 7 to be generated in a pose of the stripe projection system. Due to the high resolution of the 3D data of the stripe projection system in all three spatial dimensions, the pose of the stripe projection system in relation to the reference object 7 can be determined very precisely, and thus the calibration of the robot kinematics 1a, 1b, 1c can be carried out very precisely. (See also Luhmann, Robson, Kyle, Boehm, Close Range Photogrammetry and 3D Imaging, Second Edition, Chapter 6, ISBN 975-3).

[0100] In this case, it may be useful to move to the poses suitable for calibrating the robot kinematics in order to record the recognizable features 8 of the reference object 7 with the 3D digitizer 2 and the camera 4. For example, poses are used that cover as many axis angles as possible or poses that generate different gravitational effects on the robot limbs or axes of the robot kinematics 1. While for generating calibration data, it may be useful to move to poses so that the recognizable features of the reference object 7 must be measured precisely.

[0101] However, it is also possible to use poses that are suitable for both generating calibration data and deriving calibration parameters for the robot kinematics 1a, 1b, 1c. The data recorded in this case can then be identical for generating the calibration data and for deriving the calibration parameters.

[0102] In general, the data used to generate the measurement data and to derive the calibration parameters can be different, identical, or partially identical. Furthermore, the chronological order in which the data are recorded is irrelevant.

[0103] A portion of the data of the recognizable features 8 of the reference object 7 present in the local reference coordinate system DOS of the 3D digitizer 2 or in the local reference coordinate system CCS of the camera 4 can be transformed into a global reference coordinate system, for example, RCS1 or RCS2, although other reference coordinate systems, including non-global reference coordinate systems, are also conceivable. This particularly applies to the portion of the data used to derive the calibration parameters.

[0104] For the transformation of local data (actual observations) into a global coordinate system, for example, RCS1 or RCS2, it is helpful to know the pose of the 3D digitizer 2 and / or the camera 4 attached to the end effector, or the reference object 7 attached to the end effector. This results from the forward kinematics of the robot kinematics 1a, 1b, 1c and the relationship between the 3D digitizer 2 and / or camera 4 and / or reference object 7 and the end effector. The forward kinematics or forward transformation is the function that describes the position and orientation of the end effector or its coordinate system ECS1, ECS2 as well as individual robot links in a given coordinate system, for example RCS1 or RCS2, depending on the robot configuration given in the axis space (e.g. angular positions of rotary joints or linear positions of linear axes).To do this, the coordinate transformations of the individual robot elements must be known. These coordinate transformations are nominally known for a given robot, for example, from data sheets, technical drawings, CAD data, given Denavit-Hartenberg parameters, or similar. The coordinate transformations in the local The data available in the reference coordinate system of the 3D digitizer 2 or the camera 4 relate, for example, to the position and orientation of their camera sensors. In the case of a triangulation sensor, this is specified by the calibration of the triangulation sensor. The lengths and angles required for the transformation between the local reference coordinate system (DCS, CCS) of the camera sensor and the coordinate system of the end effector (ECS1, ECS2) can therefore nominally be read out, for example, from the CAD data of the 3D digitizer 2 and / or the camera 4 and any necessary adapters between the 3D digitizer 2 and / or the camera 4 and the end effector. CAD data of the reference object 7 can also be used to establish a relationship between the end effector and the recognizable features 8 of a reference object 7 attached to the end effector.The relationship between RCS1 and RCS2 can, for example, also be derived from CAD data or measured.

[0105] For information on how to perform coordinate transformations, see Luhmann, Robson, Kyle, Boehm, Close Range Photogrammetry and 3D Imaging, Second Edition, Chapter 2, ISBN 978-3-1110-2986-3.

[0106] In the following, the calculation of the forward kinematics from these nominally known values ​​(i.e., values ​​not calibrated to reality by any kind of calibration) is referred to as "nominal forward kinematics." However, due to, for example, geometric inaccuracies, elastic or thermal deformations, or inaccuracies in determining the axis angles or lengths of the robot links, the accuracy of the position determination of the 3D digitizer 2 and / or the camera 4 or the reference object 7 on the robot kinematics 1a, 1b, 1c is usually insufficient. The nominal forward kinematics therefore differs from the real ones.

[0107] The data available after transformation into the global coordinate system, for example, RCS1 or RCS2, are then used as starting values ​​for a subsequent optimization procedure. By transforming into a global coordinate system, RCS1 or RCS2, using forward kinematics, it is more likely that a better extremum of the optimization procedure will be found.

[0108] In the optimization process, the calibration parameters of the at least one robot kinematics 1a, 1b, 1c can be derived and, optionally before the calibration parameters are derived or during the calibration parameters are derived, the reference object 7 can be measured and, optionally, the calibration parameters of the at least one 3D digitizer 2 or the at least one camera 4 can be adjusted in such a way that the deviations between the coordinates of the recorded recognizable features 8 of the reference object 7 and the coordinates of the recognizable features 8 of the reference object 7 calculated from a mathematical model are minimized.

[0109] A deviation can be, for example, a deviation in the position and / or a deviation in the orientation of the recognizable features 8 of the reference object 7.

[0110] The measurement of the reference object 7 is carried out by generating measurement data from at least part of the recorded data, which relate the recorded features 8 of the reference object 7 to one another in a coordinate system.

[0111] If the reference object 7 has not been calibrated or needs to be calibrated again, this can be done using an optimization process to generate the calibration data with the data provided for generating the calibration data, for example, according to a mathematical model using bundle block adjustment according to Luhmann Robson, Kyle, Boehm, Close Range Photogrammetry and 3D Imaging, Second Edition, Chapter 4, ISBN 978-3-1110-2986-3. The calibration parameters can be derived in a further optimization process by minimizing the deviations between the recorded recognizable features 8 of the reference object 7 and the recognizable features of the reference object 7 related to one another from the calibration data.This can be done, for example, according to a mathematical model containing the calibration parameters of the robot kinematics 1a, 1b, 1c, using methods for solving a nonlinear optimization problem according to Nocedal, Wright, Numerical Optimization, Second Edition, ISBN 978-1-4939-3711-0. However, both optimization methods can also be combined into one optimization method. If necessary, the calibration parameters of the 3D digitizer 2 and / or the camera 4 can also be adjusted within a separate or combined optimization method, provided that a scale-defining element is captured by the 3D digitizer 2 and / or the camera 4. (see Luhmann, Robson, Kyle, Boehm, Close Range Photogrammetry and 3D Imaging, Second Edition, ISBN 978-3-1110-2986-3) or, if necessary, the calibration parameters of the 3D digitizer 2 and / or the camera 4 can also be adjusted without a scale-defining element 6 being detected by the 3D digitizer 2 and / or the camera 4, provided that one of the robot links and thus a part of the robot kinematics 1a, 1b, 1c itself is the scale-defining element 6. Likewise, if necessary, scale-independent calibration parameters of the 3D digitizer 2 and / or the camera 4 can also be adjusted without a scale-defining element 6 being detected, provided that the scale-dependent parameters of the calibration of the 3D digitizer 2 and / or the camera 4 were previously detected using a scale-defining element 6.

[0112] With the method according to the invention, the robot kinematics 1a, 1b, 1c can be calibrated, the reference object 7 can be measured if necessary and the 3D digitizer 2 or the camera 4 can be calibrated if necessary.

[0113] By minimizing, an ideal solution to the optimization problem is advantageously found.

[0114] As an example, an optimization problem to be solved is explained for the case of calibrating two robot kinematics. Here, PLCS,i,j contains the coordinates of the i-th recognizable feature 8 of the reference object 7 for the j-th pose between the robot kinematics 1a and 1b in the local reference coordinate system DCS of the 3D digitizer 2 or CCS of the camera 4, and QLCS.i contains the coordinates of the i-th recognizable feature 8 of the reference object 7 in the local reference coordinate system of the reference object 7. The forward kinematics of the first robot kinematics 1a is described by the axis values ​​belonging to the j-th pose. The forward kinematics of the second robot kinematics 1b is described by the axis values ​​J belonging to the j-th pose. 2j. Axis values ​​can, for example, be an angle or a displacement between structural components of the robot kinematics 1a. The coordinates Qccs.ij transformed into a global reference coordinate system, for example RCS1 , dependence of the calibration parameters q for robot kinematics 1a are obtained by applying a transformation function F 1,q , which for example by sequentially executing several transformations for the individual robot elements of robot kinematics 1a. The coordinates PGCS.i, j transformed into a global reference coordinate system RCS1 as a function of the calibration parameters p for robot kinematics 1b are obtained by applying a transformation function F2, p This includes, for example, the transformation from RCS2 to RCS1.

[0115] Thus, an optimization problem (3) to solve. If the reference object is also to be measured, the optimization problem can be expanded with the parameters r, where QGCS, i, j(q ,r) are the coordinates of the i-th recognizable feature of the recognizable features 8 of the reference object 7 to the pose j and these can also be adjusted using the parameters r.

[0116] This makes it possible to correct errors when measuring the recognizable features 8 of the reference object 7, which are detected by deriving the calibration parameters. If the recognizable features 8 of the reference object 7 were first measured and the calibration parameters of the robot kinematics 1a, 1b were derived in a further optimization process, then the errors that were generated during the measurement would also be included in the further optimization process for deriving the Calibration parameters may be included as follow-up errors. The parameters r can, for example, contain the coordinates of the features 8 of the reference object 7.

[0117] The optimization procedures and the identification of calibration parameters can be formulated using forward kinematics. However, it is also possible to formulate an equivalent optimization problem using inverse kinematics.

[0118] The calibration parameters of the robot kinematics 1a, 1b, 1c can be, for example, geometric and / or elastic and / or thermal and / or calibration parameters of the robot kinematics 1a, 1b, 1c that take the configuration of the robot kinematics 1a, 1b, 1c into account, and / or calibration parameters that take the direction of travel into account, and / or calibration parameters of the characteristics of or calibration parameters for determining the error curve of the length or angle measurement technology of the robot kinematics 1a, 1b, 1c and / or calibration parameters that characterize the play of individual or all axes of the robot kinematics 1a, 1b, 1c and / or calibration parameters that describe the dependence of the robot kinematics 1a, 1b, 1c on other quantities that can be recorded, for example, with sensors or calculated based on the available data.

[0119] The distance and angular position of the two coordinate systems RCS1 and RCS2 to each other can also be regarded as a parameter of the robot kinematics 1a, 1b, 1c.

[0120] Depending on the type of robot kinematics 1a, 1b, 1c and the environmental conditions of the robot kinematics 1a, 1b, 1c as well as the type of 3D digitizer 2 or camera 4 and reference object 7, it is useful to use different combinations of calibration parameters for optimization.

[0121] However, the method according to the invention is not limited to these calibration parameters and can be supplemented and combined with other parameters.

[0122] The calibration parameters resulting from the optimization procedure can be used to determine the pose of the end effector of the respective robot kinematics 1a, 1b, 1c and / or to align the end effector based on the calibration parameters.

[0123] The adjusted calibration parameters resulting from the optimization process can be used to position the end effector of the respective robot kinematics 1a, 1b, 1c more precisely. This is useful if the measurement of a measurement object 9 takes place after the calibration of the robot kinematics 1a, 1b, 1c. However, the calibration parameters can also be used to precisely determine a pose of the end effector. This makes it possible, for example, to use a cost-effective robot kinematics 1a, 1b, 1c whose approach accuracy to a specific pose is low due to mechanical reasons, but the pose can still be precisely determined using the adjusted calibration parameters. Furthermore, it is also possible to subsequently correct the poses of a measurement.Accordingly, data of the measurement object 9 can first be recorded with the 3D digitizer 2 in different poses of the 3D digitizer 2, then the calibration parameters of the robot kinematics 1a, 1b, 1c can be derived using the method according to the invention and, using the subsequently derived calibration parameters, the recorded data of the measurement object 9 can be transferred into a global coordinate system, for example RCS1 or RCS2.

[0124] As shown in Figure 2, a measurement object 9 attached to a robot kinematics 1a and a 3D digitizer 2 attached to a robot kinematics 1b can be brought into different poses for measuring the measurement object 9 and the 3D digitizer 2 can generate local 3D data in the reference coordinate system DCS of the 3D digitizer 2 and the local 3D data generated for the different poses can be transferred into a global coordinate system, for example RCS1 or RCS2, on the basis of the robot kinematics 1a, 1b calibrated according to the method according to the invention.

[0125] As shown in Figure 3, however, only one 3D digitizer 2 attached to a robot kinematics 1b can be brought into different poses for measuring an initially stationary measuring object 9 and the 3D digitizer 2 can generate local 3D data in the reference coordinate system DCS of the 3D digitizer 2 and the local 3D data generated for the different poses can be stored on the basis of the data stored in the reference coordinate system DCS according to the method according to the invention. calibrated robot kinematics 1a, 1b are converted into a global coordinate system, for example RCS2.

[0126] Thus, during the measurement, the 3D data of a measurement object 9, in which a 3D digitizer 2 can only capture partial areas 10 of the measurement object 9 with its measurement volume 3, can be determined more accurately overall by precisely transferring the local 3D data into a global coordinate system RCS2.

[0127] Furthermore, a measurement object 9 can be aligned with the robot kinematics 1b based on recognizable features 8', which are distributed on or around the measurement object 9 and are captured by a 3D digitizer 2 and / or camera 4 attached to a robot kinematics 1b, wherein the robot kinematics 1b has been calibrated according to the method according to the invention. This is useful, for example, if the measurement object 9 cannot be completely captured due to its size and the limited arm length of the robot kinematics 1b. As shown in Figure 3, the measurement object 9 can, for example, be located on a mobile platform 11 that has recognizable features 8', wherein the recognizable features 8* can differ from the recognizable features 8. A measurement sequence can, for example, proceed as follows: Providing a measurement object 9 attached to a mobile platform 11; First measuring the 3D data of the recognizable features 8' with the 3D digitizer 2 in the local reference coordinate system DCS of the 3D digitizer 2 and transforming the 3D data into a global reference coordinate system RCS2; First measurement of the measurement object 9 with the 3D digitizer 2 attached to the robot kinematics 1b in different poses and for each measurement in the corresponding pose. Carrying out a transformation of the 3D data measured in the local reference coordinate system DCS of the 3D digitizer 2 into the global reference coordinate system RCS2; Moving the measuring object 9 with the mobile platform 11 in order to be able to measure the previously inaccessible areas of the measuring object 9; Second measurement of the 3D data of the recognizable features 8' with the 3D digitizer 2 in the local reference coordinate system DCS of the 3D digitizer 2 and transformation of the 3D data into a global reference coordinate system RCS2; Determining the displacement and rotation of the mobile platform 11 in the global reference coordinate system RCS2 based on the 3D data of the recognizable features 8' recorded during the first and second measurements; Second measurement of the measurement object 9 with the 3D digitizer 2 attached to the robot kinematics 1b in different poses and for each measurement in the corresponding pose. Carrying out a transformation of the 3D data measured in the local reference coordinate system DCS of the 3D digitizer 2 into the global reference coordinate system RCS2 and shifting and rotating the 3D data based on the determined shift and rotation of the mobile platform 11.

[0128] As an alternative to moving the measuring object 9 on the mobile platform 11, the robot kinematics 1b or only the robot kinematics 1b can also be moved.

[0129] An analogous procedure can also be applied to a robot kinematics 1c not shown in the figures or to a robot kinematics 1a if the reference object 7 is replaced by a 3D digitizer 2 and / or a camera 4.

[0130] However, a mobile platform 11 can also itself be a robot kinematics 1a, 1b, 1c, provided that, for example, position data of the mobile platform 11 can be read out via the control of the mobile platform 11, and these can be calibrated according to the method according to the invention, so that the measured 3D data of the measurement object 9 are thereby transferred into a global reference coordinate system.

[0131] In general, the setups shown in the application examples are not limited to one, two or three robot kinematics 1a, 1b, 1c. It is also possible to calibrate entire streets on robot kinematics 1a, 1b, 1c and to transfer them into a common reference coordinate system.

[0132] However, this also means that a measurement object 9 can be measured with several 3D digitizers 2 on robot kinematics Ta, 1b, 1c, and the measurement data can be transferred into a common reference coordinate system RCS1 or RCS2 or RCS3 etc.

[0133] Another device example is shown in Figure 4. This shows a rotary table as the first robot kinematics 1a and a six-axis robot as the second robot kinematics 1b. The robot kinematics 1a, 1b can be controlled separately or by a controller located, for example, on a computer 5. If one of the robot kinematics 1a, 1b is already sufficiently well calibrated, it may be sufficient to calibrate the other robot kinematics 1b, 1a according to the present method in order to determine the position and orientation between the end effectors ECS1 and ECS2 or the position and orientation between CCS or DCS and ECS1.However, both robot kinematics 1a, 1b can also be calibrated simultaneously according to the present method and measured relative to one another, so that all calibration parameters of the robot kinematics 1a, 1b are determined at once and from this the position and orientation of the two end effectors ECS1, ECS2 relative to one another or the position and orientation of CCS, DCS relative to ECS1 are determined. To carry out the method according to the invention, in this example the camera 4 is part of the 3D digitizer 2. In its dual function, it firstly supplies 2D data, in particular for measuring the reference object 7, which here is represented by two partial reference objects 7' located on the rotary plate 12, and secondly it generates data for the 3D digitizer for calculating 3D data, which is used in particular for deriving calibration parameters. The coordinate systems CCS and DCS can also be identical.

[0134] It should be noted at this point that the method according to the invention can be applied not only to 3D measurements. Thus, in addition to the 3D digitizer 2 and / or camera 4 and / or reference object 7, one or more other tools can be connected to the Robot kinematics 1a, 1b, 1c can be attached and / or 3D digitizer 2 and / or camera 4 and / or reference object 7 can be replaced on the robot kinematics 1a, 1b, 1c by one or more tools, so that other tasks can also be performed with the robot kinematics 1a, 1b, 1c.

[0135] It is understood that the exemplary embodiments shown here serve merely to schematically illustrate the principle and embodiment of the present invention. Various functional and structural modifications are possible without departing from the scope of the present invention.

Claims

Patent claims 1. A method for calibrating at least one robot kinematics (1a; 1b; 1c), characterized in that at least one reference object (7) which is attached to a first robot kinematics (1a) and has recognizable features (8), and at least one 3D digitizer (2), wherein the 3D digitizer (2) is attached to a further second robot kinematics (1b) or to a further third robot kinematics (1c), and / or at least one camera (4), wherein the camera (4) is attached to the second robot kinematics (1b) or to the third robot kinematics (1c), through the first robot kinematics (1a) and at least one of the further robot kinematics (1b;1c) are brought into different relative poses to one another and in which, in these different relative poses, data of the recognizable features (8) of the at least one reference object (7) are recorded by the at least one 3D digitizer (2) and / or the at least one camera (4) and calibration parameters are derived from at least part of the recorded data for at least one of the robot kinematics (1a; 1b; 1c); 2. The method according to claim 1, wherein the at least one 3D digitizer (2) is a triangulation sensor, in particular one with stripe light projection.

3. Method according to claim 1 or 2, wherein the reference object (7) is measured or re-measured within the inventive method according to claims 1-2 and thus the recognizable features (8) of the reference object (7) are related to one another in a coordinate system or the reference object (7) was or is measured previously or subsequently outside the inventive method according to one of claims 1-2.

4. Method according to one of claims 1-3, wherein a scale-defining element (6) is present on the at least one reference object (7) and / or a robot member itself is a skate-defining element.

5. Method according to one of claims 1-3, wherein the recognizable features (8) of the reference object (7) are absolutely related to one another by at least one absolute measurement with the 3D digitizer and thus the 3D digitizer itself is the scale-determining element.

6. The method according to any one of claims 1-5, wherein at least a portion of the data of the recognizable features (8) of the at least one reference object (7) present in the local reference coordinate system (DCS) of the at least one 3D digitizer (2) and / or the data of the recognizable features (8) of the at least one reference object (7) present locally in the reference coordinate system (CCS) of the at least one camera (4) are converted into a global reference coordinate system (RCS1; RCS2).

7. The method according to any one of claims 1-6, wherein the derivation of the calibration parameters of the at least one robot kinematics (1a; 1b; 1c) and optionally before deriving the calibration parameters or during deriving the calibration parameters, a measurement of the reference object (7) and optionally an adjustment of the calibration parameters of the at least one 3D digitizer (2) or the at least one camera (4) are carried out in such a way that the deviations between the coordinates of the recorded recognizable features (8) of the reference object (7) and the coordinates of the recognizable features (8) of the reference object (7) calculated from a mathematical model are minimized, 8. The method according to claim 7, wherein the calibration parameters of the robot kinematics (1a; 1b; 1c) are geometric and / or elastic and / or thermal and / or calibration parameters of the at least one robot kinematics (1a; 1b; 1c) that take the configuration of the at least one robot kinematics (1a; 1b; 1c) into account, and / or calibration parameters that take the direction of travel into account, and / or calibration parameters of the characteristics of the calibration parameters for determining the error curves of the length or angle measurement technology of the at least one robot kinematics (1a; 1b; 1c) and / or calibration parameters that characterize the play of individual or all axes of the at least one robot kinematics (1a; 1b; 1c) and / or calibration parameters that determine the dependence of the robot kinematics (1a; 1b; 1c) on other Describe quantities that can be recorded using sensors or calculated using existing data.

9. The method according to any one of claims 7-8, wherein the calibration parameters are used to determine the pose of the at least one end effector of the at least one robot kinematics (1a; 1b; 1c) and / or to align the at least one end effector of the at least one robot kinematics (1a; 1b; 1c) based on the calibration parameters.

10. A method for calibrating a plurality of robot kinematics (1a; 1b; 1c), wherein at least one 3D digitizer (2) and / or at least one camera (4) and / or at least one reference object (7) are mounted on each of the plurality of robot kinematics (1a; 1b; 1c), and wherein at least one of the robot kinematics (1a; 1b; 1c) is calibrated according to one of claims 1-9.

11. The method according to claim 10, wherein the plurality of robot kinematics (1a; 1b; 1c) are calibrated relative to one another.

12. Method according to one of claims 1-11, wherein at least one of the robot kinematics (1a, 1b, 1c) is a turntable 13. The method according to any one of claims 1-12, wherein in addition to the at least one 3D digitizer (2) and / or the at least one camera (4) and / or the at least one reference object (7), one or more further tools are attached to at least one robot kinematics (1a; 1b; 1c) and / or wherein the at least one 3D digitizer (2) and / or the at least one camera (4) and / or the at least one reference object (7) are replaced by one or more tools on at least one robot kinematics (1a; 1b; 1c).

14. Method according to one of claims 1-13, wherein the at least one reference object (7) is designed such that the recognizable features (8) are located on an independent body and / or on one or more arbitrary members a robot kinematics (1a; 1b; 1c) and / or on a 3D digitizer (2) or a camera (4) and / or on a tool and / or on a measuring object (9) and / or around a measuring object (9).

15. The method according to any one of claims 1-14, wherein the recognizable features (8, 8') are optical markers which themselves actively illuminate and / or are passively illuminated, and / or features (8, 8') which are recognizable in two dimensions and have a unique 2D geometry, and / or features (8, 8') which are recognizable in three dimensions and have a unique 3D geometry.

16. A method for determining the 3D data of a measurement object (9), wherein at least one 3D digitizer (2) attached to a robot kinematics (1a; 1b; 1c) or several 3D digitizers (2) attached to robot kinematics (1a; 1b; 1c) are brought into different poses for measuring the measurement object (9) and the 3D digitizer(s) (2) generate(s) local 3D data in the reference coordinate systems (DOS) of the 3D digitizers (2), and wherein the local 3D data generated for the different poses are transferred into a global coordinate system (RCS1; RCS2) on the basis of the calibration parameters of at least one robot kinematics (1a; 1b; 1c) derived according to one of the method claims 1-15.

17. Method for the relative alignment of a measurement object (9) in relation to a robot kinematics system (1a; 1b; 1c) using recognizable features (8') that are distributed on or around the measurement object (9) and are detected by at least one 3D digitizer (2) attached to a robot kinematics system (1a; 1b; 1c) and / or by at least one camera (4) attached to a robot kinematics system (1a; 1b; 1c), wherein the calibration parameters of the at least one robot kinematics system (1a; 1b; 1c) were derived by means of a method according to one of claims 1-15.

18. Device for calibrating at least one robot kinematics (1a; 1b; 1c) comprising at least one reference object (7) fixed to a first robot kinematics, which reference object has recognizable features (8), and at least one 3D digitizer (2), wherein the 3D digitizer (2) is fixed to a further second Robot kinematics (1b) or is attached to a further third robot kinematics (1c), and / or at least one camera (4), wherein the camera (4) is attached to the second robot kinematics (1b) or to the third robot kinematics (1c), wherein for at least one of the robot kinematics (1a; 1b; 1c) calibration parameters for this robot kinematics (1a; 1b; 1c) are derived by means of a method according to one of claims 1-15.

19. Device according to claim 18 comprising at least one scale-defining element (6).

20. Robot kinematics (1a; 1b; 1c), the calibration parameters of which were derived by means of a method according to one of claims 1-15.

21. A computer program comprising instructions which, when the program is executed by at least one processor, cause said at least one processor and / or further processors to execute the method according to any one of claims 1-17.

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