Method and apparatus for determining dimensional and / or geometric properties of a measured object

Abstract

Method for determining dimensional and / or geometric properties of a measurement object (14) using a measuring head (24) which is movable relative to the measurement object (14) in a measurement volume and which is configured to detect selected measurement points on the measurement object (14), comprising the steps: - Moving the measuring head (24) relative to the object being measured (14) according to a first defined measuring path (44) which runs in a first defined sectioning plane (40) of the object being measured (14), and acquiring a plurality of first sectioning plane coordinates (54) along the first defined measuring path (44) using the measuring head (24), wherein the first defined measuring path (44) defines a first direction of rotation (50) around the object being measured (14), - Moving the measuring head (24) relative to the object being measured (14) according to a defined connecting path (46) to a second defined cutting plane (42) of the object being measured (14), - Moving the measuring head (24) relative to the object being measured (14) according to a second defined measuring path (48) which runs in the second defined section plane (42) of the object being measured (14), and acquiring a plurality of second section plane coordinates (56) along the second defined measuring path (48) using the measuring head (24), wherein the second defined measuring path (48) defines a second direction of rotation (52) around the object being measured (14), and - Determining the dimensional and / or geometric properties of the measured object (14) using the first section plane coordinates (54) and the second section plane coordinates (56), characterized in that the connecting path (46) leaves the first defined section plane (40) in the first direction of rotation (50), and that the connecting path (46) enters the second defined section plane (42) in the second direction of rotation (52).

Description

[0001] The present invention relates to a method for determining dimensional and / or geometric properties of a measurement object using a measuring head that is movable relative to the measurement object in a measurement volume and that is configured to detect selected measurement points on the measurement object, comprising the steps: - Moving the measuring head relative to the object being measured according to a first defined measuring path which runs in a first defined sectioning plane of the object being measured, and acquiring a plurality of first sectioning plane coordinates along the first defined measuring path using the measuring head, wherein the first defined measuring path defines a first direction of rotation around the object being measured, - Moving the measuring head relative to the object being measured along a defined connecting path to a second defined cutting plane of the object being measured, - Moving the measuring head relative to the object being measured according to a second defined measuring path which runs in a second defined sectioning plane of the object being measured, and capturing a plurality of second sectioning plane coordinates along the second defined measuring path using the measuring head, wherein the second defined measuring path defines a second direction of rotation around the object being measured, and - Determining the dimensional and / or geometric properties of the object being measured using the first cutting plane coordinates and the second cutting plane coordinates.

[0002] The invention further relates to a device for determining dimensional and / or geometric properties of a measuring object, comprising a measuring head which is movable relative to the measuring object in a measuring volume and which is configured to detect selected measuring points on the measuring object, and comprising an evaluation and control unit which is configured to implement a method of the aforementioned type using the measuring head.

[0003] Such a method and such a device are known from EP 2 527 782 B1.

[0004] EP 2 527 782 B1 discloses a method for measuring a cross-sectional profile of a test object using a tactile measuring head. In this method, the probe tip of the measuring head is brought into contact with the surface of the test object at a selected point. The measuring head is then accelerated over a defined distance while remaining in contact with the surface until a defined starting position is reached. Once the measuring head reaches the starting position, it is moved along a defined first measuring path around the test object, keeping the probe tip in contact with the surface. Deflections of the probe tip relative to the measuring head are recorded and used to calculate measurement point coordinates along the defined first measuring path. Once the measuring head reaches the starting point of the measuring path again, it is decelerated while continuing to move a short distance along the previously traversed path.Once the measuring head has come to a standstill, it is moved along a straight path in the opposite direction to its previous movement towards a second measuring plane. In this second measuring plane, the measuring head is moved along a second defined measuring path, again first traversing a defined acceleration section. Crucially for the method according to EP 2 527 782 B1, the defined connecting path compensates for the offset caused by the acceleration and deceleration of the measuring head, ensuring that the starting points of the different measuring paths are aligned along a common axis perpendicular to the measuring planes.

[0005] DE 197 12 029 A1 discloses a method for controlling a measuring device according to target data, wherein the control data are determined based on the target positions. Optionally, the workpiece and / or the tactile measuring head can be rotated during the measurement.

[0006] WO 90 / 07 097 A1 and US 2008 / 0 021 672 A1 each disclose methods for determining dimensional properties of objects to be measured, in which a tactile measuring head is moved according to a helical measuring path relative to an object to be measured.

[0007] US 7,809,523 B2 discloses a device and a method in which a tactile measuring head is guided along the surface of a test object with changing orientations. The test object can be a turbine blade. In one embodiment, the measuring path can be wavy.

[0008] US 4 167 066 A discloses a further measuring device for determining dimensional or geometric properties of a measuring object, wherein the tip of a tactile measuring head is moved along cylindrical and axial paths.

[0009] Against this background, it is an object of the present invention to provide an alternative method and a corresponding device of the type mentioned at the outset. A method and a device that minimize the overall measurement time when measuring an object in multiple planes are desirable. In particular, it is desirable to optimize the overlap and transfer paths of the measuring head when measuring in multiple planes.

[0010] According to one aspect of the present invention, this problem is solved by a method and a device of the type mentioned at the outset, wherein the connecting path leaves the first defined cutting plane in the first direction of rotation and wherein the connecting path enters the second defined cutting plane in the second direction of rotation.

[0011] With the new method and device, the first defined measuring path and the connecting path form a common curve segment in their transition zone, resembling the takeoff curve of an aircraft. In a tactile measuring head with a stylus whose tip touches the surface of the object being measured, the stylus tip moves along an initially shallow "takeoff curve" out of the first cutting plane. The stylus tip moves with a direction vector that forms a small angle, for example, less than or equal to 5°, with the direction vector immediately before leaving the first cutting plane. Only after leaving the first cutting plane and reaching a defined distance perpendicular to the first cutting plane ("altitude") does the stylus tip experience larger changes in direction, just as an aircraft only sets course for its actual destination after reaching a defined altitude.Similarly, the stylus tip of the tactile measuring head "lands" at the end of the connecting path with a shallow "landing approach," aligning with the direction of rotation on the second defined cutting plane. Between the "takeoff" from the first cutting plane and the "landing" in the second cutting plane, the connecting path can have one or more curves that differ significantly from the curves when leaving the first cutting plane and entering the second cutting plane, similar to the flight path of an aircraft. In particular, the connecting path can include tight turns or even a complete reversal of direction after leaving the first cutting plane and before entering the second cutting plane. In preferred embodiments, the tactile measuring head remains in contact with the object being measured throughout its entire movement along the first defined measuring path, the connecting path, and the second defined measuring path.In other embodiments, however, it is possible for the probe tip of the measuring head to "lift off" from the object being measured, for example to "jump" over a groove or other recess, or to reach the second cutting plane more quickly.

[0012] In another symbolic analogy, the movement of the measuring head corresponds to that of a motor vehicle changing lanes at a motorway interchange from the first lane of one motorway to the second lane of a second motorway. The first lane corresponds to the first defined measurement lane, and the second lane corresponds to the second defined measurement lane. Both leaving the first lane (first measurement lane) and entering the second lane (second measurement lane) involve small changes in the instantaneous direction vector. However, after leaving the first lane, the vehicle can experience larger changes in direction due to the tight curve radius of the motorway interchange.

[0013] In other words, the connecting path leaves the first defined cutting plane here without changing direction. When leaving the first cutting plane, the measuring head largely follows the same direction as the movement it made along the first defined measuring path. "Largely following the same direction" here means that the instantaneous direction vector of the movement, when leaving the first cutting plane—that is, during the transition from the first defined measuring path to the connecting path—must undergo a slight change perpendicular to the first cutting plane, since otherwise the connecting path would not leave the cutting plane. However, this change is small compared to later changes in direction that the measuring head experiences in a middle section of the connecting path.For example, the change in direction of the connecting path can be limited to 10% of the maximum change in direction along the further course of the connecting path during the first 5% of the length of the connecting path (measured from leaving the first cutting plane).

[0014] In preferred embodiments, the connecting path describes a curve that seamlessly and differently joins the respective measuring path in the region of the respective cutting plane. In other words, the common path is continuous and differentiable in the region of the transition from the first defined measuring path to the connecting path and in the region of the transition from the connecting path to the second defined measuring path in the preferred embodiments. Preferably, the common path is multiply differentiable in the aforementioned regions. In some embodiments, the common path in the aforementioned transition regions can correspond to a spline function, in particular a cubic spline function.

[0015] The new method and device enable highly efficient measurement of an object in several widely separated planes because a smooth transition from the first defined measurement path to the connecting path and from the connecting path to the second defined measurement path minimizes overlaps between these paths. In particular, the measuring head can be decelerated and accelerated along the connecting path. The measuring head can be moved along the connecting path at varying speeds without affecting its speed along the defined measurement paths. As has been demonstrated, contrary to the teaching of EP 2 527 782 B1, the respective starting points of the first and second defined measurement paths can be located at different positions (viewed in the respective direction of rotation); that is, the respective starting points do not need to be aligned with each other.The smooth transition between the measuring paths and the connecting path allows for consistently high measuring accuracy. The new method and the corresponding device can be advantageously used to measure an object in several cross-sectional planes that are not parallel to each other.

[0016] Overall, the new method and the corresponding device therefore enable a time-efficient determination of dimensional and / or geometric properties of a measurement object along multiple cross-sectional planes with high accuracy. The aforementioned problem is thus completely solved.

[0017] In a preferred embodiment of the new method and the corresponding device, the first direction of rotation and the second direction of rotation are the same.

[0018] In this configuration, the measuring head can begin the first and second defined measuring paths at starting points that are offset relative to each other in the circumferential direction, but otherwise the movement of the measuring head along the first and second defined measuring paths can be identical. Accordingly, systematic influences, for example, due to manufacturing tolerances in the machine guides or temperature influences in the device, affect the measured values ​​along the first and second defined measuring paths in a largely identical way. These systematic influences can be corrected in the same manner, and the comparability of the measurement results along the first and second defined measuring paths is increased.

[0019] In a further embodiment, the connecting track runs without reversal in the first direction of travel.

[0020] In this configuration, the measuring head is moved uniformly either clockwise or counterclockwise along the first defined measuring path, along the defined connecting path, and along the second defined measuring path. Particularly along the connecting path, the instantaneous direction of movement can vary, but this variation occurs without a reversal of direction. The maximum variation in the direction of movement is therefore between +90° and -90° (inclusive) relative to the first direction of rotation. This configuration advantageously contributes to time-efficient measurement with high measurement accuracy, as the movement of the measuring head can be very smooth. Disturbances due to inertial forces and / or vibrations are advantageously minimized.

[0021] In a further embodiment, the measuring head is moved continuously along the first defined measuring path, along the defined connecting path and along the second defined measuring path at an instantaneous velocity greater than zero.

[0022] In this configuration, the measuring head is moved continuously, without stopping, from the first defined measuring path to the second. The measuring head leaves the first defined cutting plane with a continuous movement and enters the second defined cutting plane with a similar movement. This configuration also contributes to measuring the object efficiently and with consistently high accuracy.

[0023] In a further embodiment, the measuring head is moved with an instantaneous velocity that is below a first maximum velocity along the first defined measuring path, below a second maximum velocity along the second defined measuring path, and below a third maximum velocity along the defined connecting path, wherein the third maximum velocity is higher than the first and the second maximum velocity.

[0024] In this embodiment, the instantaneous speed of the measuring head is limited to a different maximum speed depending on the path being traversed. The respective instantaneous speed can vary along the first and second defined measuring paths, but especially along the defined connecting path. In some embodiments, the measuring head can be moved along the first defined measuring path and along the second defined measuring path at a constant instantaneous speed, which may be different or the same for the first and second defined measuring paths. Advantageously, however, the measuring head can be moved at a higher instantaneous speed along the connecting path. In all these cases, the movement of the measuring head or measuring element relative to the object being measured is limited to a maximum speed, which is advantageously stored as a parameter in the device.The speed limit along the defined connecting path is higher than along the first and second measuring paths. This design advantageously facilitates the rapid transfer of the measuring head from the first defined cutting plane to the second defined cutting plane and optimizes the measurement accuracy along the measuring paths. This design is particularly advantageous in embodiments where path planning is performed in the evaluation and control unit of the device, because existing and well-known path planning algorithms can be used. By defining the parameter for the third maximum speed separately from the parameter(s) for the first and / or second maximum speed, the time-efficient implementation of the new method can be achieved in a very simple and cost-effective manner.

[0025] In particularly preferred embodiments, the measuring head is also moved with a respective instantaneous acceleration that, along the first defined measuring path, is below a first maximum acceleration; along the second defined measuring path, it is below a second maximum acceleration; and along the defined connecting path, it is below a third maximum acceleration, wherein the third maximum acceleration is higher than the first and second maximum accelerations. In other words, in these embodiments, an individual parameter for the maximum acceleration along the defined connecting path is specified, which may differ from the maximum acceleration along the first and second defined measuring paths and, in particular, may be higher. This design also advantageously contributes to the cost-effective and time-efficient implementation of the new method and the corresponding device.

[0026] In a further embodiment, the measuring head is moved continuously with a jerk limiter along the first defined measuring path, along the defined connecting path and along the second defined measuring path.

[0027] In this embodiment, jerk limitation means that the time derivative of the acceleration profile, according to which the measuring head is moved along the first defined measuring path, along the connecting path, and along the second defined measuring path, is limited to a defined maximum value. In preferred embodiments of the method and the device, the maximum value for jerk limitation is stored as a parameter in a suitable memory, and path planning and control are performed depending on this parameter. In other words, the measuring head is moved along the measuring paths and along the connecting path depending on the defined parameter for jerk limitation. This embodiment advantageously contributes to implementing a smooth and virtually vibration-free movement of the measuring head relative to the object being measured.Indirectly, the design contributes to achieving time-efficient measurement with high measurement accuracy along the first and second defined measuring paths.

[0028] In a further embodiment, the connecting path between the first defined cutting plane and the second defined cutting plane has a defined path length comprising an initial section, a middle section, and an end section, wherein the initial section and the end section each extend over ≤ 10% of the path length and bound the middle section, and wherein the tangent angles between the first cutting plane and the tangent vectors to the initial section are each less than 45°. Preferably, the tangent vectors to the initial section are each less than 30°, and more preferably, each less than 10°. These degree values ​​refer to the acute angle between the tangent vectors and the first cutting plane. Furthermore, it is preferred if the aforementioned angle values ​​also apply, alternatively or additionally, to the tangent angles between the second cutting plane and the end section.Preferably, the tangential angles on the first 5% and the last 5% of the connecting path are each less than 10°.

[0029] In this embodiment, the "take-off and landing movement" of the measuring head with respect to the first defined cutting plane and / or with respect to the second defined cutting plane is specified within an angular range that has proven advantageous in preferred embodiments. Alternatively, the new method and the corresponding device can be implemented in other embodiments with tangential angles greater than 45°, with the advantages of the new method and the corresponding device becoming more pronounced the smaller these tangential angles are.

[0030] In a further embodiment, the middle section has at least one curved track section and / or at least one straight track section.

[0031] In some embodiments, the central section of the connecting path can have a path segment that runs perpendicular to the first and / or second defined cutting plane. This design makes it possible to minimize the time required to transfer the measuring head from the first defined measuring path to a distant second measuring path.

[0032] In a further embodiment, the measuring head is moved along the first defined measuring path and along the second defined measuring path at a defined distance to the selected measuring points, whereby the defined distance is set using a closed control loop.

[0033] In this configuration, the measuring head is moved along the measuring paths in so-called distance control mode or scanning mode. In some embodiments, the measuring head has a stylus with a probe tip that is brought into contact with the measuring points. The measuring head detects deflections of the stylus relative to the base of the measuring head, and the section plane coordinates along the measuring paths are determined using the detected stylus deflections. In distance control mode or scanning mode, the measuring head in these embodiments is often moved such that the stylus is held in its rest position; that is, the stylus deflections are minimized by means of the closed control loop. The defined distance to the selected measuring points is advantageously set in these embodiments by minimizing the stylus deflections during the movement of the measuring head along the respective measuring path.Similarly, movement of the measuring head in a distance control or scanning mode is also possible with a non-contact measuring head by moving the measuring head, for example, using optical and / or capacitive distance measurement and a closed control loop. This design enables very rapid acquisition of a large number of measurement points along the defined measurement paths and is therefore highly advantageous for time-efficient measurement with a high level of detail.

[0034] In a further embodiment, the measuring head is moved along the connecting path with a defined transfer distance to the object being measured, whereby the defined transfer distance is set using a closed control loop.

[0035] In this embodiment, the measuring head is also moved along the connecting path in a distance control or scanning mode. Preferably, the transition distance is equal to the aforementioned measuring distance. This embodiment contributes to a particularly smooth transition from the movement of the measuring head along the first defined measuring path to the movement along the connecting path and further to the second defined measuring path, because the measuring head is moved continuously in the same mode. Furthermore, measured values ​​along the connecting path can be used to determine the dimensional and / or geometric properties of the object being measured.

[0036] In a further embodiment, the measuring head is moved along the connecting path using defined target positions.

[0037] In this embodiment, the measuring head is advantageously moved along the connecting path using a position controller or in a position controller mode. With position control, the measuring head moves along predefined target positions, which are approached using the position controller. In this case, it is irrelevant whether the relative distance between the measuring head and the object being measured changes. An advantage of this embodiment is that the measuring head can be moved along the connecting path at a higher speed. Accordingly, this embodiment can advantageously contribute to minimizing the overall measurement time.

[0038] In a further embodiment, the connecting path is determined depending on the first defined measuring path and the second defined measuring path using a route planning algorithm that minimizes the total measurement time.

[0039] In this configuration, the total measurement time is calculated as the sum of the times for the movement of the measuring head along the first defined measuring path, along the second defined measuring path, and along the connecting path. In this configuration, the total measurement time is used as the primary optimization criterion, with this prioritization being limited to the determination of the connecting path in preferred embodiments. Accordingly, in some embodiments, the path planning for the first defined measuring path and the second defined measuring path can be prioritized for measurement accuracy, whereas the path planning for the movement of the measuring head along the connecting path uses minimizing the total measurement time as the primary optimization criterion.In preferred embodiments, the respective instantaneous velocities and angles at which the measuring head undergoes changes in direction are used as variables whose current values ​​are determined using the route planning algorithm and the optimization criterion "minimizing total measurement time". Any route planning algorithm available to those skilled in the art in this field can be used for the route planning itself, provided it allows for minimizing the total measurement time as an optimization criterion.

[0040] In a further embodiment, the measuring object has a front and a back in the first direction of rotation, wherein the connecting path leaves the first defined cutting plane on the front and merges into the second defined cutting plane on the back.

[0041] In this configuration, the starting points of the first and second defined measurement paths are located on opposite sides of the object being measured. This configuration is particularly advantageous when the object is flat, and especially cuboid in shape, as is the case, for example, with smartphones or turbine blades. Placing the respective starting points of the first and second measurement paths on different sides of the object enables a particularly time-efficient measurement with high precision, because the measuring head can be moved very quickly to a defined starting point of the second measurement path. Furthermore, this configuration easily prevents the starting points of the defined measurement paths from lying on largely flat surfaces of the object, thus increasing measurement accuracy.

[0042] In a further embodiment, the first defined measuring path has a first starting point and the second defined measuring path has a second starting point, wherein the first starting point and the second starting point are offset from each other in the first circumferential direction.

[0043] Even in this configuration, the new method and the corresponding device benefit from the advantage that an offset placement of the starting points of the respective measuring paths makes it easy to minimize the total measuring time.

[0044] In a further embodiment, the measuring head has a light source that generates a light pattern on the object being measured, in particular a line of light.

[0045] In this configuration, the measuring head is preferably a laser scanner. The new method offers significant advantages not only with a tactile measuring head but also when using such an optical measuring head. In particular, with a laser scanner that generates a line of light on the object being measured, the new method allows for very fast and highly accurate scanning of the object. In this way, a so-called 3D scan of the entire object can be obtained very quickly.

[0046] In a further embodiment, the object being measured is held on a rotary table, whereby the measuring head is moved relative to the object being measured using the rotary table.

[0047] The new method and the corresponding device are particularly advantageous in conjunction with a rotary table, as the measuring head can be moved around the object being measured very quickly (relatively speaking). The advantages mentioned above are particularly noticeable in this context.

[0048] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0049] An embodiment of the invention is shown in the drawings and is explained in more detail in the following description. The drawings show: Fig. 1 a simplified representation of an embodiment of the new device, Fig. 2 a simplified representation to illustrate an exemplary embodiment of the new method, Fig. 3 an enlarged representation of the transition from the first defined measuring path to the defined connecting path in the embodiment according to Fig. 2, and Fig. 4 a detail of the device Fig. 1.

[0050] In Fig. Figure 1 is an embodiment of the new device in its entirety, designated by reference numeral 10. The device 10 is a gantry-type coordinate measuring machine with a table 12 on which a measuring object 14 can be placed. A gantry 16 carries a carriage 18. The carriage 18 carries a quill 20. At the lower free end of the quill 20, a rotary-swivel joint 22 is arranged, which here carries a tactile measuring head 24. The gantry 16 can be moved relative to the table 12 along an axis by means of suitable drives (not shown separately here). Fig. The Y-axis is the first axis. The carriage 18 can be moved relative to the portal along another axis, which is here referred to as the X-axis. The quill 20 can be moved relative to the carriage 18 along a third axis, which is here referred to as the Z-axis. The X, Y, and Z axes of movement define a measuring volume 25 in which the measuring head 24 can be moved.

[0051] Furthermore, in this embodiment, the measuring head 24 can be moved about one or more axes of rotation or pivoting by means of the rotary-swivel joint 22. The respective positions of the portal 16, the slide 18, the quill 20, and the rotary-swivel joint 22 can be determined in a manner known per se using encoders. Examples are shown in Fig. Figure 1 shows three scales 26x, 26y, and 26z. These scales can be, for example, glass scales that are detected by an optical sensor (not shown here) to determine the current position of the measuring head 24 along the three axes X, Y, and Z. An evaluation and control unit 28 can control the movements of the measuring head 24 along the X, Y, and Z axes and along the rotation axes of the swivel joint 22 and determine the respective spatial position using the scales 26 and encoders.

[0052] In contrast to the embodiment shown here, the device 10 can, in further embodiments, have a measuring head 24 that is movable relative to a measuring object 14 in a different manner. For example, the gantry 16 can be stationary and the table 12 can be moved along the Y-axis. Furthermore, the measuring head 24 can be arranged on a coordinate measuring machine in a bridge-type, column-type, or horizontal-arm configuration. In further embodiments, the measuring head 24 can also be arranged on a robot arm or a parallel kinematic system. The measuring object 14 can also be mounted on a rotary table and / or clamped in another movable fixture.

[0053] In the embodiment according to Fig. In 1, the measuring head 24 has a stylus 30 with a free end, which serves to touch selected measuring points on the object 14. In other embodiments, the measuring head can detect selected measuring points on an object 14 without contact, in particular optically, capacitively, or inductively. In some preferred embodiments, the measuring head includes a light source, in particular a laser light source, which generates a light point, a light line, or an area light pattern on the object, as well as an optical detector that detects the light point, light line, or light pattern on the object. For example, the measuring head can be a laser line scanner, such as the one offered by the applicant under the product name LineScan.

[0054] In all preferred embodiments, the device 10 is able to move the measuring head 24 relative to the object 14 along defined measuring paths in order to acquire measuring points along these paths. The evaluation and control unit determines the spatial coordinates of the acquired measuring points as a function of the respective position of the measuring head 24 relative to the object 14. In further steps, dimensional and / or geometric properties of the object can then be determined based on these spatial coordinates, such as the diameter of a bore or the distance between two edges of the object 14.

[0055] The evaluation and control unit 28 can, in preferred embodiments, include one or more computers on which one or more software modules are executed. For example, in Fig. Figure 1 shows a software module 32 that controls the movement of the measuring head 24 relative to the object 14. In some embodiments, the control of these movements can be implemented using a programmable logic controller (PLC). Reference numeral 34 denotes another software module used to determine the spatial coordinates of the acquired measurement points and the dimensional and / or geometric properties of the object. In some preferred embodiments, software module 34 is a software package such as the one offered commercially by the applicant under the name Calypso. Reference numeral 36 denotes a memory in which various parameters can be stored that are required for the movement of the measuring head 24 relative to the object 14 and for determining the spatial coordinates and properties of the object (detailed below).

[0056] In Fig. Figure 2 shows a measuring object 14 as a cylinder, the outer circumference of which is to be measured in several offset section planes 40, 42. For this purpose, the stylus 30 is moved along a first defined measuring path 44 in contact with the measuring object 14. Subsequently, the stylus 30 is transferred along a defined connecting path 46 to a second defined measuring path 48. The measuring path 48 lies in the second section plane 42. In the embodiment according to Fig. 2. The first measuring track 44 and the second measuring track 48 lie in parallel, offset cutting planes 40, 42. In other embodiments, the first measuring track 44 and the second measuring track 48 may lie in obliquely offset cutting planes (not shown here).

[0057] As in Fig. As shown in Figure 2, the first measuring track 44 defines a first direction of rotation 50 around the object being measured 14. The second measuring track 48 defines a second direction of rotation 52. In some embodiments, the first direction of rotation 50 and the second direction of rotation 52 can be the same or largely the same. In other embodiments, the first direction of rotation 50 and the second direction of rotation 52 can be different from each other, in particular opposite to each other. In some embodiments, a reversal of direction from the first direction of rotation 50 to an opposite second direction of rotation 52 can occur along the connecting track 46. In contrast, Figure 2 shows... Fig. 2 An embodiment in which the measuring head 24 is moved around the object 14 without reversal along the first defined measuring path 44, along the defined connecting path 46 and along the second defined measuring path 48. For example, in this embodiment, the measuring head 24 can be moved uniformly clockwise (not shown here) or counterclockwise (as shown here).

[0058] As already indicated above, measuring points along the defined measuring paths 44, 48 are recorded using the measuring head 24 and the spatial coordinates of the recorded measuring points are determined. Examples are shown in Fig. 2. Several measuring points are designated with the reference symbols 54 and 56. Corresponding spatial coordinates are determined for each recorded measuring point 54, 56. The spatial coordinates along the first measuring path 44 lie in the first sectioning plane 40 and are subsequently referred to as the first sectioning plane coordinates. The spatial coordinates of the measuring points 56 along the second measuring path 48 lie in the second sectioning plane 42 and are subsequently referred to as the second sectioning plane coordinates.

[0059] As in Fig. As indicated in Figure 2, the first defined measuring path 44 has a first starting point 60, which in this embodiment also forms the endpoint of the first defined measuring path 44. In other words, the first measuring path 44 is non-overlapping here. In other embodiments, the first measuring path 44 may include an overlap, i.e., the stylus 30 is moved over a circumferential angle of more than 360° on the first measuring path 44.

[0060] In any case, the connecting path 46 joins the first defined measuring path 44 in the area of ​​the endpoint. The stylus 30 begins the first measuring path 44 here at the starting point 60 and is moved in the direction of rotation 50 until it reaches point 60 again after completing a 360° circumferential angle. Here, the stylus 30 leaves the first measuring path 44 while maintaining movement in the first direction of rotation 50 and with a very shallow "starting angle" towards the second cutting plane 42. The stylus 30 is transferred along the connecting path 46 to the second cutting plane 42 and "lands" with a shallow "landing angle" at the starting point 62 of the second defined measuring path 48.

[0061] The connecting path 46 has a defined path length between the first cutting plane 40 and the second cutting plane 42. The path length can be divided into an initial section 66, a middle section 68, and an end section 70. As in Fig. As indicated in Figure 3, a tangent 72, 74 can be conceptually drawn to each point of the connecting path 46, each defining a corresponding tangent vector 72', 74'. In preferred embodiments, the tangent angles 76, 78 between the tangents 72, 74 or the corresponding tangent vectors 72', 74' and the first cutting plane 40 are acute angles in the first circumferential direction 50. In some embodiments, the initial section 66 extends over approximately 5% of the path length of the connecting path 46, and the tangent angles 76, 78 in this initial section are each acute angles less than or equal to 45°, preferably less than or equal to 15°, and more preferably less than or equal to 5°. In some embodiments, the tangent angles on the first 5% of the connecting path 46 can be less than or equal to 3°.

[0062] Similarly, the tangential angles between tangents to the end section 70 of the connecting path 46 and the second cutting plane 42 can be acute angles less than or equal to 45°, preferably less than or equal to 30°, and more preferably less than or equal to 10° (not shown separately here). Accordingly, the connecting path 46 leaves the first defined cutting plane 40 in the first direction of rotation 50 at tangential angles of a few degrees, and the connecting path 46 enters the second defined cutting plane 42 at tangential angles of a few degrees in the second direction of rotation 52.

[0063] In the central section 68, the connecting track 46 can include one or more curved track sections 80 and / or one or more straight track sections 82. In some embodiments, the connecting track 46 in the central section 68 can have a path that forms an angle greater than 45° up to 90° with the first cutting plane 40 and / or the second cutting plane 42. In the latter case, the connecting track 46 can accordingly have a track section that runs largely perpendicular to the first cutting plane 40 and / or the second cutting plane 42 (not shown here).

[0064] As in Fig. As shown in Figure 2, the first starting point 60 and the second starting point 62 can be offset from each other in the first direction of rotation 50 and / or the second direction of rotation 52. In some embodiments, the object being measured 14 can be a cuboid body with a flat front and a flat back, with the first starting point 60 located on the flat front and the second starting point 62 on the flat back. Likewise, the first starting point 60 and the second starting point 62 can be located on different sides of an object being measured 14, the surface normals of which (not shown here) point in different directions, as shown in Figure 2. Fig. Figure 2 shows the new method. Advantageously, it can be used to measure smartphone housings or turbine blades (not shown here) in a time-efficient manner, with the connecting path 46 leaving the first cutting plane 40 on the front of the object being measured and entering the second defined cutting plane 42 on the back of the object being measured.

[0065] In some embodiments, the stylus 30 can be moved along the first defined measuring path 44 and the second defined measuring path 48 as well as along the connecting path 46 in a distance control mode or scanning mode. In this mode, the measuring head 24 is moved at a defined distance 84 to the surface of the object being measured, the defined distance 84 being set in a closed control loop using a scanning controller 86. Fig. 4) The scanning controller 86 regulates the movement of the measuring head 24 relative to the surface of the object being measured such that the stylus 30 is held in its rest position relative to the measuring head 24. Accordingly, in some embodiments, the measuring head 24 is held in contact with the surface of the object being measured not only along the measuring track 44, 48, but also along the connecting track 46.

[0066] In other embodiments, the measuring head 24 is moved only along the measuring paths 44, 48 in scanning mode or distance control mode. Along the connecting path 46, the measuring head 24 is then moved in a position control mode or with the aid of a position controller 88. The position controller 88 receives a plurality of target positions 90 (see Fig. 1) as input variables and moves the measuring head 24 from one target position 90 to the next. The target positions can be stored in a memory 92, which is contained, for example, in the evaluation and control unit 28. The evaluation and control unit 28 moves the measuring head 24 along the defined target positions 90 regardless of whether the distance between the measuring head 24 and the surface of the object being measured changes. Accordingly, the drives 94 of the device 10 can be selectively controlled either by means of the scanning controller 86 or by means of the position controller 88, as shown in Fig.As indicated in Figure 4. Preferably, both the scanning controller 86 and the position controller 88 are closed-loop control systems, as is known to those skilled in the art in coordinate measuring technology for devices of this type. For example, the movement of the measuring head 24 along the measuring tracks 44, 48 and along the connecting track 46 can be carried out according to a method as described in DE 197 12 029 A1, which is incorporated herein by reference.

[0067] In some advantageous embodiments, the connecting path 46 can be determined using a route planning algorithm 96, which can be implemented as a software module in the evaluation and control unit 28. The route planning algorithm 96 can, for example, obtain position 60 as the starting position for the connecting path 46 and position 62 as the end position for the connecting path 46 and calculate a connecting path 46 based on these positions by iteratively varying the motion parameters of the measuring head 24, including motion speed and direction, along several possible connecting paths until the time for moving the measuring head 24 from position 60 to position 62, and thus the total measurement time, is minimized.Minimizing the time can result in the measuring head 24 being moved along the connecting path 46 at a constant or varying instantaneous velocity that is higher than the instantaneous velocity of the measuring head 24 along the first defined measuring path 44 and / or along the second defined measuring path 48.

[0068] In some preferred embodiments, parameter values ​​representing a first maximum speed 98 along the first defined measuring path 44, a second maximum speed 100 along the second defined measuring path 48, and a third maximum speed 102 along the connecting path 46 are stored in a memory of the evaluation and control unit 28. In these embodiments, the route planning algorithm 96 determines the connecting path 46 based on parameters 98 to 102. Advantageously, the third maximum speed 102 is higher than the first and / or second maximum speeds 98 and 100, so that the measuring head 24 can be moved at a higher speed along the connecting path 46 than along the measuring paths 44 and 48.Furthermore, another parameter in the memory can define a maximum jerk (= time derivative of the acceleration) and the route planning algorithm 96 can determine the connecting path 46 depending on the maximum jerk.

[0069] In preferred embodiments, the measuring head 24 is moved continuously along the defined measuring paths 44, 48 and along the defined connecting path 46 at an instantaneous velocity greater than zero. Accordingly, in the preferred embodiments, the measuring head 24 is moved from the first measuring path 44 to the second measuring path 48 without stopping.

Claims

[1] Method for determining dimensional and / or geometric properties of a measurement object (14) using a measuring head (24) which is movable relative to the measurement object (14) in a measurement volume and which is configured to detect selected measurement points on the measurement object (14), comprising the steps: - Moving the measuring head (24) relative to the object being measured (14) according to a first defined measuring path (44) which runs in a first defined sectioning plane (40) of the object being measured (14), and acquiring a plurality of first sectioning plane coordinates (54) along the first defined measuring path (44) using the measuring head (24), wherein the first defined measuring path (44) defines a first direction of rotation (50) around the object being measured (14), - Moving the measuring head (24) relative to the object being measured (14) according to a defined connecting path (46) to a second defined cutting plane (42) of the object being measured (14), - Moving the measuring head (24) relative to the object being measured (14) according to a second defined measuring path (48) which runs in the second defined section plane (42) of the object being measured (14), and acquiring a plurality of second section plane coordinates (56) along the second defined measuring path (48) using the measuring head (24), wherein the second defined measuring path (48) defines a second direction of rotation (52) around the object being measured (14), and - Determining the dimensional and / or geometric properties of the object being measured (14) using the first section plane coordinates (54) and the second section plane coordinates (56), characterized by , that the connecting path (46) leaves the first defined cutting plane (40) in the first direction of rotation (50), and that the connecting path (46) merges into the second defined cutting plane (42) in the second direction of rotation (52). [2] Method according to claim 1, characterized by, that the first direction of rotation (50) and the second direction of rotation (52) are the same. [3] Method according to claim 1 or 2, characterized by , that the connecting path (46) runs without reversal in the first direction of travel (50). [4] Method according to any one of claims 1 to 3, characterized by , that the measuring head (24) is moved continuously along the first defined measuring path (44), along the defined connecting path (46) and along the second defined measuring path (48) at an instantaneous velocity greater than zero. [5] Method according to any one of claims 1 to 4, characterized by, that the measuring head (24) is moved with an instantaneous velocity which is below a first maximum velocity (98) along the first defined measuring path (44), which is below a second maximum velocity (100) along the second defined measuring path, and which is below a third maximum velocity (102) along the defined connecting path, wherein the third maximum velocity (102) is higher than the first and the second maximum velocities. [6] Method according to any one of claims 1 to 5, characterized by , that the measuring head (24) is moved continuously with a jerk limit along the first defined measuring path (44), along the defined connecting path (46) and along the second defined measuring path (48). [7] Method according to any one of claims 1 to 6, characterized by, that the connecting path (46) between the first defined cutting plane (40) and the second defined cutting plane (42) has a defined path length comprising an initial section (66), a middle section (68) and an end section (70), wherein the initial section (66) and the end section (70) each extend over ≤ 10% of the path length, and wherein the tangent angles (76, 78) between the first cutting plane (40) and the tangent vectors (72', 74') to the initial section (66) are each less than or equal to 45°, preferably less than or equal to 30° and further preferably less than or equal to 10°. [8] Method according to claim 7, characterized by that the middle section (68) has at least one curved track section (80) and / or at least one straight track section (82). [9] Method according to any one of claims 1 to 8, characterized by, that the measuring head (24) is moved along the first defined measuring path (44) and along the second defined measuring path (48) at a defined distance (84) to the selected measuring points, the defined distance (84) being set by means of a closed control loop (86). [10] Method according to any one of claims 1 to 9, characterized by , that the measuring head (24) is moved along the connecting path (46) with a defined transfer distance to the object being measured (14), the defined transfer distance being set by means of a closed control loop (86). [11] Method according to any one of claims 1 to 9, characterized by , that the measuring head (24) is moved along the connecting path (46) using defined target positions (90) in the measuring volume. [12] Method according to any one of claims 1 to 11, characterized by, that the connecting path (46) is determined depending on the first defined measuring path (44) and the second defined measuring path (48) using a route planning algorithm (96) which minimizes a total measurement time. [13] Method according to any one of claims 1 to 12, characterized by , that the object being measured has a front and a back side in the first direction of rotation (50), wherein the connecting path (46) leaves the first defined cutting plane (40) on the front side and enters the second defined cutting plane (42) on the back side. [14] Method according to any one of claims 1 to 13, characterized by , that the first defined measuring path (44) has a first starting point (60) and that the second defined measuring path (48) has a second starting point (62), wherein the first starting point (60) and the second starting point (62) are offset from each other in the first circumferential direction (50). [15] Method according to any one of claims 1 to 14, characterized by that the measuring head has a light source that produces a light pattern on the object being measured, in particular a line of light. [16] Method according to any one of claims 1 to 15, characterized by , that the object being measured (14) is held on a rotary table, wherein the measuring head (24) is moved relative to the object being measured (14) with the aid of the rotary table. [17] Device for determining dimensional and / or geometric properties of a measurement object (14), comprising a measuring head (24) which is movable relative to the measurement object (14) in a measurement volume and which is configured to detect selected measurement points on the measurement object (14), and comprising an evaluation and control unit (28) which is configured to - to move the measuring head (24) relative to the object being measured (14) according to a first defined measuring path (44) which runs in a first defined section plane (40) of the object being measured (14) and to acquire a plurality of first section plane coordinates (54) along the first defined measuring path (44) using the measuring head (24), wherein the first defined measuring path (40) defines a first direction of rotation (50) around the object being measured (14), - to move the measuring head (24) relative to the object being measured (14) according to a defined connecting path (46) to a second defined cutting plane (42) of the object being measured (14), - to move the measuring head (24) relative to the object being measured (14) according to a second defined measuring path (48) which runs in the second defined section plane (42) of the object being measured (14), and to acquire a plurality of second section plane coordinates (56) along the second defined measuring path (48) using the measuring head (24), wherein the second defined measuring path (48) defines a second direction of rotation (52) around the object being measured (14), and - to determine the dimensional and / or geometric properties of the object being measured (14) using the first section plane coordinates (54) and the second section plane coordinates (56), characterized by , that the connecting path (46) leaves the first defined cutting plane (40) in the first direction of rotation (50), and that the connecting path (46) merges into the second defined cutting plane (42) in the second direction of rotation (52).

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