DE102021211384A1 - Method and device for determining systematic guidance errors of movable elements of a coordinate measuring machine - Google Patents

Abstract

Method and device for determining systematic guidance errors (40, 41) of movable elements (7-1, 7-2, 7-3) of a coordinate measuring machine (2), wherein a pattern (5) with at least three pattern elements (5-1, 5 -2, 5-3) is arranged at least partially in a detection area (6) of an image detection device (3) of the coordinate measuring machine (2), the pattern (5) and / or the image detection device (3) having predetermined target movement parameters (21) are moved in such a way that different relative positions (9, 10) are set between the at least three pattern elements (5-1, 5-2, 5-3) and the image acquisition device (3), the at least three pattern elements (5-1, 5-2, 5-3) are in a first and in a further relative position (9, 10) in the detection area (6), the pattern elements (5-1, 5-2, 5-3) being identified and their position in the first and the further relative position (9, 10) are determined, with one or more systematic guidance errors (40, 4 1) as a function of the predetermined target movement parameters (21) and the positions of the pattern elements in the first and further relative positions (9, 10).

Description

The invention relates to a method and a device for determining systematic guidance errors of movable elements of a coordinate measuring machine.

Coordinate measuring machines are used to record the coordinates of points on a surface. For this purpose, a tactile and / or contactless probing of the surface is carried out by means of a mechanical and / or optical measuring system. Forms of measuring systems that use electrical distance and / or X-ray tomographic sensors are also conceivable. Typically, geometric or dimensional variables of a workpiece to be measured are determined from the coordinates recorded in this way, for example a length of an edge, a diameter of a borehole or an angle between a borehole axis and another axis, which then represent a measurement result. Such a determination can be made, for example, by means of a device for electronic data processing, which can be part of the coordinate measuring machine. Measurement results generated in this way are generally used to set and correct a manufacturing process of a workpiece and / or to check manufacturing tolerances of a workpiece. This ensures that the workpiece corresponds to the specifications of a designer.

In order to be able to measure the workpiece at different points and with different orientations, the coordinate measuring machine comprises movable elements, for example for moving the measuring system relative to the workpiece along and / or around axes of movement. The movement axes often span a Cartesian coordinate system, that is to say a movement coordinate system which can be used for the unambiguous assignment of the measured points in a measurement area. The measuring range of a coordinate measuring machine thus particularly refers to the area in which the measuring system is moved.

Moving the movable elements along the movement axes can be systematically error-prone, so that a predetermined target movement parameter, e.g. a target position, does not correspond to an actual movement parameter, e.g. an actual position, e.g. because a drive of the movable elements is due to a non-linearity has a distorted drive behavior.

There are a large number of different types of measurement errors which can adversely affect the measurement result, and the measurement errors can be of random and / or systematic origin. The aforementioned errors when moving the moving elements of a coordinate measuring machine are part of the systematic measurement errors. Such systematic management errors can be recorded and corrected with regard to a measurement result. In order to keep the measurement error in the measurement result as small as possible, it is therefore desirable to determine systematic guidance errors of the movable elements of a coordinate measuring machine and then to correct them, for example, in the measurement result.

A determination of the systematic guidance errors is repeated at regular time intervals, since the guidance behavior can change disadvantageously over time, for example if a change in the guidance behavior is triggered by environmental influences such as fluctuations in the ambient temperature or air humidity.

Special reference devices, e.g. laser interferometers, are usually used to determine systematic guidance errors. The determination of systematic guidance errors by means of a reference device is very costly and time-consuming, since the reference device must have a high degree of measurement accuracy and has to be re-aligned with the coordinate measuring device for each measurement. In addition, alignment and / or setting of the reference device can also be prone to errors. This complicates the feasibility and efficiency in determining systematic leadership errors.

From the prior art, for example, from DE 10 2009 016 858 A1 a method for calibrating a sample table of a metrology system and a metrology system with a sample table are known, several markings being arranged on a sample and individual markings being sequentially optically detected.

The technical problem arises of creating a method and a device for determining systematic guidance errors of movable elements of a coordinate measuring machine, the method being improved in terms of feasibility and efficiency.

The solution to the technical problem results from the subjects with the features of the independent claims. Further advantageous refinements of the invention emerge from the subclaims.

A basic idea of the invention is to determine systematic guidance errors of movable elements of a coordinate measuring machine using a pattern with at least three pattern elements as a reference. The pattern elements are at least partially arranged in a detection area of an image detection device of the coordinate measuring machine, in particular through a corresponding relative movement between the pattern and the coordinate measuring machine.

The image capturing device is preferably moved with at least one predetermined target movement parameter in such a way that different, in particular at least two different, relative positions are set between the pattern elements and the image capturing device. The corresponding movement can be controlled by a control device. A target movement parameter can be, for example, a target position, a target angle, a target displacement or a target rotation, in particular in relation to the axes of movement of the movable elements or in relation to a (movement) coordinate system. A target movement parameter can also describe a target position deviation, that is to say a target position change and / or a target orientation change, from a current position or enable it to be determined.

The pattern elements are then each optically imaged and identified in a first and a further relative position by the image acquisition device. Furthermore, their location, that is to say their position and / or orientation, is determined in an image coordinate system of the detection area, which is arranged in a stationary manner relative to the detection area. This can be done by an evaluation device.

The systematic guidance error or errors are then determined as a function of these positions of the pattern elements in the various relative positions and the predetermined target movement parameters, for example also by the evaluation device. This results in a determination of the systematic guidance errors in which the disadvantages indicated above do not occur or are reduced.

The systematic guidance error can have translational and / or rotational error components in a three-dimensional space. Linear or non-linear guidance errors can occur with linear motion axes. Furthermore, straightness errors, that is to say deviations from a predetermined guiding direction, are possible. A nod, as well as a roll and / or yaw, can also occur as systematic management errors. In addition, further errors can occur in the alignment of components of the coordinate measuring machine with respect to one another, such as, for example, squareness errors, with the movement axes in particular not being aligned orthogonally to one another as desired. Systematic guidance errors can also occur with the axes of rotation of the coordinate measuring machine, for example when rotating a swivel head.

The coordinate measuring machine preferably comprises a measuring table, a drive device for moving the movable elements along / around axes of movement, an incremental scale or several incremental scales that are assigned to a movement axis and enable a position to be determined, means for moving the movable elements, a measuring system, which is preferably used as a an optical image acquisition system is formed or comprises one, and / or a control and evaluation device. The movable elements of the coordinate measuring machine can in particular be the measuring table and / or elements that are moved to move the measuring system or the image acquisition system.

The pattern has several pattern elements, which are preferably arranged uniformly in the entire 2D measurement area, which is formed by two axes. In particular, the distances between the pattern elements remain unchanged. For example, the pattern can be a structure which forms or comprises the at least three pattern elements, preferably more than three pattern elements. A position can preferably include the value of a coordinate in an image and / or movement coordinate system.

A pattern element is in particular an optically detectable element of the pattern, for example a geometrical figure, i.e. a figure with a predetermined geometry that can be printed on a surface, the pattern element scattering, absorbing and / or reflecting light, so that an image capturing device the pattern element can detect and an image-based identification of the pattern element can take place. A position of the pattern element in the image coordinate system of the detection area can also be determined image-based, that is to say by evaluating the image, for example as the position of the center point of the area of the pattern element. In particular, the position of the pattern element in the image coordinate system can also be determined via a value of a depth of field of the image acquisition device or by means of a chromatic white light sensor or comparable measuring principles.

The image coordinate system of the detection area denotes a coordinate system which is arranged in a stationary manner relative to the detection area, that is to say also relative to the image sensor. The position of this image coordinate system in a movement coordinate system can change in the event of a relative movement between the image acquisition device and the pattern.

The image acquisition device can be part of the measuring system of the coordinate measuring machine or be arranged on the measuring system of the coordinate measuring machine, wherein the image acquisition device can have an image sensor, for example a CMOS or CCD sensor. The image capture device can be designed to continuously generate and / or provide image information or images of a capture area. In particular, the image acquisition device is movable and can be moved into different positions and / or orientations in the measuring area by means of the coordinate measuring device. In addition, additional sensors, such as chromatic white light sensors, can be used to record the depth of field or the topography of the pattern.

The detection area denotes the area imaged by the image detection device, in particular an at least two-dimensional area. The various, adjustable positions of the detection area in the movement coordinate system or a part of these positions define the measurement area. The explained image coordinate system can be assigned to the detection area, it being possible for this to be designed as a Cartesian coordinate system. The detection area can change in its size and / or position and / or orientation by moving the movable elements of the coordinate measuring machine. By moving the image acquisition device relative to the pattern, in particular different relative positions between the at least three pattern elements and the image acquisition device are set. In particular, the relative movement is carried out in such a way that the at least three pattern elements of the pattern are temporarily, but at least in two different relative positions, in the detection area of the image detection device.

A movement parameter describes a property of a movement of a movable element, e.g. an (angular) position to be reached by the movement or a distance / angle covered by the movement. Depending on the movement parameter, e.g. a target position can be determined in the movement coordinate system.

As a result of the movement, the movable elements are moved in such a way that, in particular, different relative positions can be set between the at least three pattern elements and the image capturing device. The target movement parameter can be specified by a user or a higher-level system. Typically, the predetermined target movement parameters are used by the control device of the coordinate measuring machine to control the drive of the movable elements of the coordinate measuring machine so that the measuring system is moved along a predetermined trajectory relative to an object to be measured, for example relative to the pattern. The predetermined target movement parameter can be defined in relation to the movement coordinate system and / or image coordinate system; the movement parameter preferably describes a target (rotational) position of the image coordinate system in the movement coordinate system, for example defined as a vector or a matrix in the movement coordinate system.

If there is a guidance error, an actual movement parameter or an actual (rotational) position dependent on the actual movement parameter can deviate from the predetermined target movement parameter or the target (rotational) position, namely by the value of the guidance error. Corresponding to the target movement parameter, the actual movement parameter can, for example, denote an actual change in position and / or angle that describes the change in a position and / or an orientation of the image coordinate system in the movement coordinate system during a relative movement from a first relative position to a further relative position, for example indicated as a vector in the motion coordinate system. An actual movement parameter can also describe an actual position deviation, that is to say an actual position change and / or an actual orientation change, from a position set before the movement was carried out or enable it to be determined.

For example, a positional deviation between the positions of the pattern elements in the image coordinate system can be determined, which arises when moving into the various relative positions. This can be transformed into the movement coordinate system by means of a predetermined transformation. Then a difference between the transformed positional deviation, which is an actual positional deviation, and the target positional deviation predetermined by the target movement parameter can be determined, the difference representing or representing the guidance error (s).

A coordinate transformation from the movement coordinate system to the image coordinate system - or vice versa - is known in advance and can be determined, for example, by calibration and / or registration methods known to the person skilled in the art.

The further relative position differs from the first relative position by a relative movement, at least partially or completely described by at least one actual movement parameter. The at least three pattern elements can be detected by the image acquisition device both in the first and in the further relative position and a position of each detected pattern element in the image coordinate system can be determined in each relative position.

The positions of the at least three pattern elements determined in the various relative positions are related to the predetermined target movement parameters by means of trigonometric or other geometric and / or mathematical relationships so that the guide error or errors of the movable elements of the coordinate measuring machine can be determined.

The method can also be used to determine systematic guidance errors of moving elements of a device or a machine, in particular a machine tool, the device / machine not being designed as a coordinate measuring device, but nevertheless comprising moving elements. If no image acquisition device is arranged on such a machine, an image acquisition device can be arranged on the machine, preferably on a movable component of the machine, in order to carry out the method. For example, the method can be used to determine guidance errors in a milling machine. To carry out the method, an image acquisition device can then be arranged on the milling machine, preferably on a milling spindle.

In a further embodiment, at least one of the at least three pattern elements is at least partially designed as a two- or three-dimensional geometric element and / or is at least partially provided by an optical projection. A geometric element denotes an element with a predetermined geometry or with predetermined geometric properties.

By forming at least one pattern element as a two- or three-dimensional geometric element, the detection of the pattern element by the image detection device is advantageously simplified. For example, the light reflection or scattering can be different from a basic structure of the pattern, for example a lattice structure or a marbling, so that the detection by the image detection device and an image-based identification is simplified. The at least one geometric element is preferably designed symmetrically and has a surface or volume center point that lies in the pattern element and can be easily determined on the basis of images. In particular, determining the position of the pattern element is advantageously simplified by means of an area or volume center point. A three-dimensional geometric element further simplifies capturing the pattern element from many possible viewing angles.

The optical projection of the pattern makes it possible in an advantageous manner to adapt the appearance of the pattern to the coordinate measuring machine or to another boundary condition, as well as a simple provision of the pattern. Furthermore, an advantageous light reflection of the pattern to the image capturing device can be set by means of an optical projection.

In a further embodiment, at least one of the at least three pattern elements is arranged on a flat measuring table, in particular on a non-curved surface of the measuring table. Arranging at least one pattern element on the flat measuring table advantageously facilitates arranging the pattern in the measuring area of the coordinate measuring machine, since the flat measuring table can be used to secure the pattern element against slipping or tilting. In particular, the pattern element can be fixed on the measuring table with a fastening means.

In a further embodiment, the pattern is formed by a plate-shaped body, the plate-shaped body having or forming the at least three pattern elements. The formation of the pattern as a plate-shaped body has the advantage that alignment of the pattern in the measuring area is advantageously simplified. For example, the plate-shaped body can be arranged on a measuring table surface plane. The pattern elements arranged in the pattern are preferably spaced from one another by the plate-shaped body in such a way that detection of the pattern elements by the image detection device is advantageously simplified in different relative positions to one another.

It is possible for various pattern elements of the pattern to be arranged along a straight line. In this case, it is possible for the pattern to be arranged in the measurement area in such a way that the orientation of the straight line is parallel or approximately parallel to an axis of the image coordinate system or an axis of linear movement of a movable element. In this context, approximately parallel means that an angle between the straight line and the linear movement axis is smaller than a predetermined angle, for example smaller than 10 °.

The plate-shaped body is preferably a plate, it being possible for the plate to be made from a glass ceramic. Such a material is sold, for example, under the name Zerodur by Schott AG, based in Jena, Germany. Zerodur has sufficient long-term stability and constant mechanical, thermal and chemical properties, which have an advantageous effect on the feasibility of the process described.

In a further embodiment, at least one target movement parameter has translational and / or rotational components. The axes of movement are usually aligned orthogonally to one another so that they can span a Cartesian coordinate system. If the target movement parameter has translational and / or rotary components, the feasibility and efficiency of the method are advantageously increased, since a change in position and / or orientation of the movable elements in the measurement area can be clearly assigned to the movement axes, for example in the form of a the corresponding axis-related length and / or angle information. An error-prone coordinate transformation can then preferably be dispensed with. Furthermore, one or more systematic guidance errors can be clearly determined with a minimum number of target movement parameters in a measurement area. Furthermore, a test plan with the target movement parameters can be processed efficiently, in particular in that different relative positions are not set multiple times.

In a further embodiment, the systematic guide error or errors are determined as translation and / or rotation errors along and / or about an axis of movement. The movement axis denotes an axis along which a movable element of the coordinate measuring machine can be moved and thus also defines a possible trajectory for the measuring system. The determination of a systematic guidance error along and / or around a movement axis advantageously increases the feasibility and efficiency of the method, since there is no need for an error-prone coordinate transformation and since the systematic guidance errors that have occurred can be assigned to this movement axis. The systematic guidance errors are thus determined during a translational movement at different positions along a movement axis of the movable elements of the coordinate measuring machine: At these positions, deviations of the actual position and orientation from the target position and orientation with respect to all six degrees of freedom can be determined. This includes the translational deviations with regard to all three axes orthogonally to one another from the setpoint position as well as the rotational deviations about all three orthogonally mutually orthogonal rotatory axes from the specified target orientation.

In a further embodiment, the systematic guidance error or errors are determined as one or more perpendicularity errors. Idealized, i.e. in a target state, axes of movement can be aligned orthogonally to one another. However, in reality, the perpendicularity between axes of motion often has an error. Thus, a perpendicularity error denotes a deviation in the angle difference between two axes of movement of 90 °. Another squareness error can denote the deviation of the angle difference between two further axes of movement from 90 °. A squareness error can affect the measurement accuracy. Determining the systematic guidance errors as squareness errors advantageously makes it possible to correct the effect of movement axes that are not exactly at right angles to one another in a measurement result.

In a further embodiment, the method is controlled by a control device, the at least one predetermined target movement parameter being specified by the control device, the pattern elements in the first and the further relative position being identified by an evaluation device and their position being determined or the systematic management errors determined. The control and evaluation device can be designed as a microcontroller or integrated circuit or comprise one (s).

The control device can thus be designed as a computer-aided device for electronic data processing and be included in the coordinate measuring machine. Other configurations, for example an analog control device, are also conceivable. Furthermore, the control device can control one or more drive devices for moving the movable elements. The control device preferably controls the setting of the various relative positions during the course of the method. The predetermined target movement parameters are set by the control device on the basis of the movement coordinate system in such a way that systematic guidance errors can be determined in the entire measuring range of the coordinate measuring machine.

The evaluation device can preferably also be designed as a computer-aided device for electronic data processing and be encompassed by the coordinate measuring device. The evaluation device can identify and record the first and each further relative position, for example between the image acquisition device and the at least three pattern elements, for example store them in a memory device. Furthermore, the evaluation device determines the position of the pattern elements and can determine at least one actual movement parameter from a change in the position of one or more pattern elements. Furthermore, one or more systematic guidance errors can then be determined as a function of the setpoint movement parameters specified by the control device, preferably by means of trigonometric and other geometric and / or mathematical relationships. The systematic guidance error (s) can be logged by the evaluation device, preferably on an electronic data carrier, for example in the form of a CSV file with values of the determined systematic guidance errors as a function of the predetermined target movement parameters. This advantageously simplifies the implementation of the method and increases the efficiency of the method. The control device and the evaluation device can be designed as a common device or as devices designed separately from one another.

In a further embodiment, the specific systematic guidance error or errors are logged for the predetermined target movement parameters. Movement control is also carried out as a function of the systematic guidance errors in such a way that no systematic guidance error occurs or this is reduced when the movable elements of a coordinate measuring machine are moved. Alternatively or cumulatively, at least one measurement result is corrected as a function of the systematic control error or errors that are determined.

The systematic guidance errors determined by means of the method are logged as a function of the predetermined target movement parameters in such a way that the control device explained above can be calibrated for these systematic guidance errors. Calibration refers to correcting an ideal target movement parameter as a function of the specific systematic guidance errors, so that when the actual movement parameters are moved, the ideal target movement parameters are set and no systematic guidance errors occur when moving the movable elements. In this way it can be checked in an advantageous manner whether a systematic guidance error has been correctly determined. This increases the practicability and efficiency of the process.

Furthermore, at least one measurement result can be corrected as a function of the systematic guidance error or errors that are determined. For example, when a workpiece is measured by means of the coordinate measuring device, a dimensional variable is determined on the basis of an actual movement parameter or an actual (rotational) position of the movable elements. Such a dimensional variable can then be corrected as a function of the determined systematic guidance error or errors, so that the dimensional variable or the resulting measurement result is free from the determined systematic guidance error or errors.

The method can be carried out by means of a device. The device is used to determine systematic guidance errors of movable elements of a coordinate measuring machine and comprises at least one coordinate measuring machine, at least one image acquisition device, at least one control device and at least one evaluation device. Furthermore, a pattern with at least three pattern elements can be arranged in a detection area of the image detection device.

The pattern and / or the image capturing device can be moved with predetermined target movement parameters by means of the device, preferably by means of the movable elements of the device, in such a way that different relative positions between the at least three pattern elements and the image capturing device can be set. This movement can be controlled by the control device.

The relative positions can be set in such a way that the at least three pattern elements are arranged in a first and in at least one further relative position in the detection area, the pattern elements being mappable by the image detection device and their position being determinable in an image coordinate system of the detection area in a first and any further relative position , in particular by means of the evaluation device of the device.

One or more systematic guidance errors can be determined by means of the device as a function of the predetermined target movement parameters and the positions of the pattern elements in the first and further relative positions.

• 1 eine schematische Darstellung einer Ausführungsform einer Vorrichtung zum Bestimmen systematischer Führungsfehler von beweglichen Elementen eines Koordinatenmessgeräts,
• 2 eine schematische Darstellung von drei Musterelementen im Erfassungsbereich einer Bilderfassungseinrichtung,
• 3-1 eine schematische Darstellung von drei Musterelementen im Erfassungsbereich einer Bilderfassungseinrichtung in einer ersten und weiteren Relativlage bei einer Bewegung ohne Führungsfehler,
• 3-2 eine schematische Darstellung von drei Musterelementen im Erfassungsbereich einer Bilderfassungseinrichtung in einer ersten und weiteren Relativlage bei einer Bewegung mit translatorischen Führungsfehlern,
• 3-3 eine schematische Darstellung von drei Musterelementen im Erfassungsbereich einer Bilderfassungseinrichtung in einer ersten und weiteren Relativlage bei einer Bewegung mit translatorischen und rotatorischen Führungsfehlern, und
• 4 ein Flussdiagramm eines Verfahrens zum Bestimmen systematischer Führungsfehler.

The invention is explained in more detail using exemplary embodiments. The figures show:

• 1 a schematic representation of an embodiment of a device for determining systematic guidance errors of movable elements of a coordinate measuring machine,
• 2 a schematic representation of three pattern elements in the detection area of an image detection device,
• 3-1 a schematic representation of three pattern elements in the detection area of an image detection device in a first and further relative position during a movement without guidance errors,
• 3-2 a schematic representation of three pattern elements in the detection area of an image detection device in a first and further relative position during a movement with translational guidance errors,
• 3-3 a schematic representation of three pattern elements in the acquisition area of an image acquisition device in a first and further relative position during a movement with translational and rotational guidance errors, and
• 4th a flow diagram of a method for determining systematic guidance errors.

In the following, the same reference symbols designate elements with the same or similar technical features.

1 shows a schematic representation of an embodiment of a device 1 for determining systematic guidance errors of moving elements of a coordinate measuring machine 2 . The device 1 In the embodiment shown, it comprises in particular a coordinate measuring machine 2 . A pattern is also shown 5 , with the pattern 5 at least three sample elements 5-1 , 5-2 and 5-3 having. The coordinate measuring machine 2 further comprises an image acquisition device 3 with a detection area 6th , a measuring table 4th with a measuring table surface plane 4-1 , and three moving elements 7-1 , 7-2 , 7-3 on, taking the items 7-1 , 7-2 , 7-3 each along and / or around axes of motion i , j , k , are movable. Next are the moving elements 7-1 , 7-2 , 7-3 juxtaposed, with a first movable element 7-1 over a storage section 8th is stored.

The pattern 5 is designed here as a plate made of Zerodur, with the pattern 5 on the measuring table surface level 4-1 is arranged and the pattern 5 the pattern elements 5-1 , 5-2 and 5-3 having a first pattern element 5-1 as a two-dimensional square, another pattern element 5-2 as a two-dimensional triangle and a third pattern element 5-3 is designed as a two-dimensional star. The pattern elements 5-1 , 5-2 and 5-3 are in the detection area 6th the image capture device 3 .

A control device, not shown, of the device 1 controls the movement of the moving elements 7-1 , 7-2 , 7-3 the device 1 by means of drive devices, also not shown, by specifying target movement parameters. As a result, the image capturing device 3 moved into different positions and / or orientations, whereby different relative positions between the image capture device 3 and pattern 5 to adjust.

In each of the relative positions set in this way, the image capturing device 3 an image can be generated, with all the pattern elements in at least two different relative positions 5-1 , 5-2 and 5-3 in the detection area 6th and are therefore also mapped. An evaluation device (not shown) of the device can also be used 1 those in the detection area 6th lying pattern elements 5-1 , 5-2 , 5-3 and determine their positions, in particular in an image coordinate system 30th , which is an image coordinate system 30th of the detection area 6th forms. The image coordinate system 30th can in particular have two axes that are orthogonal to one another x , y have, with the axes of the image coordinate system which are orthogonal to one another 30th Spanned plane parallel to the measuring table surface plane 4-1 can be. Another, not shown, axis of the image coordinate system 30th can be oriented perpendicular to this plane. The axes of the image coordinate system can also be used 30th parallel or approximately parallel to the axes of movement i , j , k be oriented.

The target movement parameters can be specified in such a way that the image capturing device 3 parallel to one of the axes of motion i , j , k is moved or is moved with a movement, the components along several axes of movement i , j , k includes. The motion coordinate system 35 is through the axes of motion ijk stretched. The origin of the motion coordinate system 35 is defined as a reference point in the measuring range.

2 shows the detection area 6th the image capture device 3 with the image coordinate system 30th in the measuring table surface plane 4-1 in a first relative position between the image capturing device 3 and pattern 5 . The pattern elements 5-1 , 5-2 and 5-3 lie in the plane of the measuring table 4-1 and are captured by the image capture device 3 so mapped that one location A1 of the first pattern element 5-1 and a location B1 further pattern element 5-2 as well as a location C1 of the third pattern element 5-3 in the image coordinate system 30th can be determined in the first relative position. The locations A1 , B1 and C1 are preferably as vectors and / or coordinates of the surface centers of the pattern elements 5-1 , 5-2 and 5-3 shown.

3-1 , 3-2 and 3-3 show the detection area 6th the image capture device 3 with the image coordinate system 30th and a motion coordinate system 35 in the measuring table surface plane 4-1 , being a motion coordinate system 35 through the axes of motion ijk is spanned and the origin of the movement coordinate system 35 is defined as a reference point in the measuring range. The detection area 6th is in a first relative position 9 dotted and a further relative position 10 shown in dashed lines. The pattern 5 and / or the image capture device 3 are with a predetermined target movement parameter 21 moves in such a way that the pattern elements 5-1 , 5-2 in both relative positions 9 , 10 in the detection area 6th are located.

To 3-1 is the first relative position 9 and the further relative situation 10 shown, the further relative position 10 by a movement corresponding to a predetermined target movement parameter 21 to the first relative position 9 is shifted. In particular, the predetermined target movement parameter 21 in the state shown, a purely translational movement along a first axis of movement i given. The predetermined target movement parameter 21 is specified by the control device.

To 3-1 it is shown that the device for such a movement does not have a systematic guide error 40 and thus the actual movement parameter 22nd the target movement parameter 21 is equivalent to.

In 3-2 is the further relative situation 10 for a scenario shown by in turn by the predetermined target movement parameters 21 a purely translational movement along a first axis of movement i is specified. Due to a mistake in leadership 40 however, is the actual motion parameter 22nd of the target movement parameter 21 different, in particular the further relative position is 10 not just by a portion parallel to the first axis of movement i , but also by a proportion parallel to the second axis of movement j postponed. The actual motion parameter 22nd is made up of the predetermined target movement parameters 21 and the systematic management error 40 together. The leadership error 40 is with the help of the pattern elements 5-1 , 5-2 or 5-3 determinable.

To 3-2 becomes the location A1 of the pattern element 5-1 in the first relative position 9 determined - represented as a vector in the image coordinate system 30th the first relative position 9 . In the further relative situation 10 will continue to be a location A2 of the pattern element 5-1 determined - represented as a vector in the image coordinate system 30th the further relative situation 10 . Then there is a positional deviation between these positions A1 , A2 determined and by means of a predetermined transformation in the movement coordinate system 35 transformed. Then there can be a difference between the transformed positional deviation, which is an actual positional deviation, and that caused by the setpoint movement parameter 21 predetermined target position deviation can be determined. Alternatively, an actual movement parameter can be derived from the actual position deviation 22nd can be determined, which depends on the locations A1 and A2 results. The systematic leadership error 40 is after 3-2 the difference between the actual motion parameter 22nd and the predetermined target movement parameter 21 , especially in the motion coordinate system 35 . An accuracy in determining the guidance errors 40 is increased when the number of determinable layers is increased by a multiplicity of pattern elements, since an averaged error when determining the positions of the pattern elements is thus reduced.

In 3-3 is the further relative situation 10 for a scenario shown by in turn by the predetermined target movement parameters 21 a purely translational movement along a first axis of movement i is specified. Due to a mistake in leadership 40 however, is the actual motion parameter 22nd of the target movement parameter 21 different. It can also be seen that the further relative position 10 relative to the first relative position 9 compared to the in 3-2 scenario also by a twisting angle α is twisted so that the actual motion parameter 22nd in addition to the leadership error 40 another mistake in leadership 41 having. The other leadership mistake 41 corresponds to the angle of rotation α and is for example with the help of the pattern elements 5-1 , 5-2 determinable. To 3-3 become the locations A1 and B1 (not shown) of the pattern elements 5-1 and 5-2 in the first relative position 9 certainly. In the further relative situation 10 become the locations A3 and B3 of the pattern elements 5-1 and 5-2 certainly. The other leadership mistake 41 results depending on the locations A1 , B1 and A3 , B3 .

As in 3-1 shown, corresponds to an error-free movement of the actual movement parameter to the target movement parameter 21 so that, for example, the y component of the pattern element 5-1 in both relative positions 9 , 10 is identical.

berechnet werden kann.To 3-2 is moving from relative position 9 in the relative position 10 flawed. So there is the target movement parameter 21 a translation along the i-axis of motion, as shown, that is, parallel to the x-axis of the image coordinate system 30th . The actual movement parameter shown 22nd however, has components along the first and second axes of motion i , j of the motion coordinate system 35 which can be referred to as x or y components. Thus, the systematic leadership error 40 as a translational guidance error parallel to the second axis of movement j or y-axis of the image coordinate system 30th shown. Such a translational discrepancy between target and actual movement parameters 21 , 22nd is considered a systematic leadership error 40 determined, where the designation FTj denotes the translational guidance error 40 in the j-direction, i.e. the direction along the second axis of movement j , designated. FTj results, for example, from a comparison of the y components of the layers of the pattern element 5-1 in the image coordinate system 30th in the relative positions 9 , 10 - here denoted by y_ (5_1) [9, 10] - so that FTj by means of the formula $$\text{FTj}=\text{y}\_\left(5-1\right)\left[9\right]\cdot \text{y}\_\left(5-1\right)\left[10\right]$$

can be calculated.

A translational guidance error along the first axis of movement i FTi can be determined analogously to the procedure explained. The x-value is the target parameter 21 (x_21) must also be taken into account $$\text{FTi}=\text{x}\_\left(5-1\right)\left[9\right]-\text{x}\_\left(5-1\right)\left[10\right]-\text{x}\_21$$

With a suitable depth of field measuring device, the translational guidance error in the third axis FTk can also be calculated: $$\text{FTk}=\text{z}\_\left(5-1\right)\left[9\right]-\text{z}\_\left(5-1\right)\left[10\right]$$

Of course, the leadership mistake 40 also by comparing the positions of the pattern element 5-2 or 5-3 to be determined.

berechnet werden kann.The after 3-3 shown, error-related rotation by the angle of rotation α with respect to the third axis of movement k can by means of the layers of two pattern elements, e.g. 5-1 and 5-3 to be determined. Another such mistake in leadership 41 is an angle FRk, where FRk is the angle of rotation α corresponds to and by means of the trigonometric relationship $$\text{tan}\left(\text{FRk}\right)=\left(\left(\text{y}\_\left(5-3\right)\left[10\right]-\text{y}\_\left(5-1\right)\left[10\right]\right)-\left(\text{y}\_\left(5-3\right)\left[9\right]-\text{y}\_\left(5-1\right)\left[9\right])\right)\text{/ x}\_\left(5-3\right)\left[9\right]-\text{x}\_\left(5-1\right)\left[9\right]\right)$$

can be calculated.

A rotational guidance error about the first or second axis of movement i , j , FRi and / or FRj, can be determined analogously to the explained formula 4, if a depth of field of the image capturing device 3 sufficient or another suitable device, such as a chromatic white light sensor, is used to detect a corresponding guidance error by means of the in 3-2 illustrated pattern elements 5-1 , 5-2 and 5-3 to identify. The j and k position parameters of the pattern elements are particularly important for determining the rotational guidance errors about the first axis FRi 5-1 and 5-2 to consider. The i and k position parameters of the pattern elements are particularly important for determining the rotational guidance errors of the second axis FRj 5-1 and 5-3 to consider.

The preceding explanations relate, for example, to the fact that the target movement parameter 21 translational changes in the first axis i provides. To guide errors along the other axes j and k to record, the explanations or formulas and also the target movement parameters must be 21 be adjusted accordingly.

4th FIG. 3 shows a flow diagram of a method for determining systematic guidance errors 40 , 41 of moving elements 7-1 , 7-2 , 7-3 a coordinate measuring machine 2 . In a first step S1 becomes a pattern 5 - Having at least three, preferably more than three, pattern elements 5-1 , 5-2 , 5-3 - in the measuring range of a coordinate measuring machine 2 arranged so that the at least three pattern elements 5-1 , 5-2 and 5-3 in the detection area 6th the image capture device 3 are located. The pattern 5 with the at least three pattern elements 5-1 , 5-2 and 5-3 is still in a first relative position 9 relative to the image capture device 3 .

In a second step S2 will be the at least three sample elements 5-1 , 5-2 and 5-3 in the first relative position 9 optically through the image capture device 3 recorded and their location A1 , B1 , C1 in the image coordinate system 30th certainly.

In a third step S3 become the moving elements 7-1 , 7-2 , 7-3 such as the image capture device 3 , corresponding to a predetermined target movement parameter 21 moves so that it moves between image capture device 3 and the at least three pattern elements 5-1 , 5-2 and 5-3 another relative position 10 adjusts. The pattern elements 5-1 , 5-2 and 5-3 lie in the further relative position 10 still in the detection area 6th the image capture device 3 . The target movement parameter 21 is saved.

In a fourth step S4 will be the at least three sample elements 5-1 , 5-2 and 5-3 in the further relative situation 10 optically through the image capture device 3 mapped and their positions in the image coordinate system 30th certainly.

In a fifth step S5 becomes from the shift in position of the pattern elements resulting from the movement 5-1 , 5-2 and 5-3 in the image coordinate system 30th an actual movement parameter in the movement coordinate system 35 and a deviation between the target movement parameter 21 and the actual movement parameter 22nd determines what a previously known transformation rule for a coordinate transformation from the image coordinate system 30th into the motion coordinate system 35 is being used. The actual motion parameter 22nd can have a translational component.

In a sixth step S6 becomes the actual motion parameter 22nd with the predetermined target movement parameter 21 related to one or more systematic leadership errors 40 , 41 to determine. For example, a Deviation between actual movement parameters 22nd and target movement parameters 21 or a deviation of the movement parameters caused by these 22nd , 21 described situations as leadership errors 40 , 41 to be determined.

A test plan (not shown) can be generated in suitable measuring software, with the sample 5 by means of the image capture device 3 , for example a camera, in a desired number of relative positions 9 , 10 is mapped. For each recording by means of the image acquisition device 3 is the current position of the image capture device 3 in the motion coordinate system 35 save. For each recording of the image capture device 3 are the positions of all pattern elements 5-1 , 5-2 and 5-3 to calculate and store. Preferably at each position of the image capturing device 3 Several recordings were made to identify inaccuracies when calculating the positions of the pattern elements 5-1 , 5-2 and 5-3 to reduce.

The test plan can be automated and preferably run unattended, for example overnight. The results generated by means of the test plan can be imported into software such as that sold under the name Lasercal by Carl Zeiss AG, based in Oberkochen, Germany. All imported results can be transformed into the software coordinate system. The software can then use the imported results to calculate simulated measuring lines which, for example, correspond to those obtained using a laser interferometer. For the simulated measuring lines, the systematic guide errors are calculated using a suitable mean value calculation 40 , 41 calculated. In Lasercal, the bandwidth minimization must be deactivated when calculating the mean value. In this way, best-fit straight lines are retained in the measuring lines, the slope of the best-fit straight lines being able to correspond to a squareness error between two axes, ie the squareness error does not have to be recorded separately. By means of certain systematic management errors 40 , 41 A so-called CAA file can then be created that can be used to correct the systematic guidance errors of a coordinate measuring machine and thus ultimately also for measurement results.

List of reference symbols

1

contraption

2

Coordinate measuring machine

3

Image capture device

4th

Measuring table

4-1

Measuring table surface plane

5

template

5-1

first pattern element

5-2

second pattern element

5-3

third pattern element

6th

Detection area

7-1

first movable element

7-2

second movable element

7-3

third movable element

8th

storage

9

first relative position

10

further relative situation

21

Target movement parameters

22nd

Actual motion parameters

30th

Image coordinate system

35

Motion coordinate system

40

systematic leadership error

41

further leadership error

A1

Position of the first pattern element in the first relative position

A2

Position of the first pattern element in the further relative position

A3

Position of the first pattern element in the further relative position with rotation

B1

Position of the second pattern element in the first relative position

B3

Position of the second pattern element in the further relative position with rotation

C1

Position of the third pattern element in the first relative position

x

x-axis of the image coordinate system

y

y-axis of the image coordinate system

i

first axis of movement

j

second axis of motion

k

third axis of motion

S1

first procedural step

S2

second procedural step

S3

third process step

S4

fourth procedural step

S5

fifth procedural step

S6

sixth procedural step

α

Twist or twist angle

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102009016858 A1 [0008]

Claims (10)

Method for determining systematic guidance errors (40, 41) of movable elements (7-1, 7-2, 7-3) of a coordinate measuring machine (2), wherein a pattern (5) with at least three pattern elements (5-1, 5-2 , 5-3) is arranged at least partially in a detection area (6) of an image detection device (3) of the coordinate measuring machine (2), the pattern (5) and / or the image detection device (3) moving with predetermined target movement parameters (21) in this way be that different relative positions (9, 10) between the at least three pattern elements (5-1, 5-2, 5-3) and the image capture device (3) are set, characterized in that the at least three pattern elements (5-1 , 5-2, 5-3) are in a first and at least one further relative position (9, 10) in the detection area (6), the pattern elements (5-1, 5-2, 5-3) in the first and each further relative position (9, 10) identified and their position determined, with one or more systematic Guiding errors (40, 41) can be determined as a function of the predetermined target movement parameters (21) and the positions of the pattern elements in the first and further relative positions (9, 10). Procedure according to Claim 1 , characterized in that at least one of the at least three pattern elements (5-1, 5-2, 5-3) is at least partially designed as a two- or three-dimensional geometric element and / or is at least partially provided by an optical projection. Method according to one of the preceding claims, characterized in that at least one of the at least three pattern elements (5-1, 5-2, 5-3) is arranged on a flat measuring table (4), in particular on a non-curved surface of the measuring table (4) will. Method according to one of the preceding claims, characterized in that the pattern (5) is formed by a plate-shaped body, the plate-shaped body having or forming the at least three pattern elements (5-1, 5-2, 5-3). Method according to one of the preceding claims, characterized in that at least one setpoint movement parameter (21) has translational and / or rotational components. Method according to one of the preceding claims, characterized in that the systematic guide error or errors (40, 41) are determined as translation and / or rotation errors along and / or around an axis of movement (i, j, k). Method according to one of the preceding claims, characterized in that the systematic guide error or errors (40, 41) are determined as one or more perpendicularity errors. Method according to one of the preceding claims, characterized in that the method is controlled by a control device, the at least one predetermined target movement parameter (21) being specified by the control device, the pattern elements (5-1, 5-2) in the the first and the further relative position (9, 10) is identified by an evaluation device and the position thereof is determined, the evaluation device determining the systematic guide error (s) (40, 41). Method according to one of the preceding claims, characterized in that the determined systematic guidance error or errors (40, 41) are logged for the predetermined target movement parameters (21), movement control being carried out as a function of the systematic guidance errors (40, 41) that when moving the movable elements (7-1, 7-2, 7-3) of a coordinate measuring machine (2) no or a reduced systematic guidance error (40, 41) occurs and / or at least one measurement result as a function of the certain systematic management error (s) (40, 41) is corrected. Device (1) for determining systematic guidance errors (40, 41) of movable elements (7-1, 7-2, 7-3) of a coordinate measuring machine (2), comprising at least one coordinate measuring machine (2), at least one image acquisition device (3), at least one control device and at least one evaluation device, wherein a pattern (5) with at least three pattern elements (5-1, 5-2, 5-3) can be arranged at least partially in a detection area (6) of the image detection device (3), the pattern (5) and / or the image acquisition device (3) can be moved with predetermined target movement parameters (21) in such a way that different relative positions (9, 10) between the at least three pattern elements (5-1, 5-2, 5-3) and the image acquisition device (3) are adjustable, characterized in that the at least three pattern elements (5-1, 5-2, 5-3) can be arranged in a first and in a further relative position (9, 10) in the acquisition area (6), where in the first and the next row relative position (9, 10) the pattern elements (5-1, 5-2, 5-3) and their position can be determined, with one or more systematic guidance errors (40, 41) can be determined as a function of the predetermined target movement parameters (21) and the positions of the pattern elements (5-1, 5-2, 5-3) in the first and further relative positions (9, 10).

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