Coordinate measuring instrument, and method for coupling a measuring head

Abstract

The present invention relates to a coordinate measuring instrument (10) having a control unit (44) for controlling a positioning system (18) of the coordinate measuring instrument (10), which control unit is designed to control the positioning system (18), during a coupling process in which a measuring head (20, 20') held in a measuring head receptacle (74) is coupled to the positioning system (18) and locked by means of a locking device (112), in such a way that the positioning system exerts a force onto the measuring head (20, 20'), by means of which force a movement of the measuring head (20, 20') in the z direction relative to the measuring head receptacle (74) is prevented during the entire coupling process until the locking device (112) has completely locked the measuring head (20, 20').

Description

Coordinate measuring instrument and method for coupling a measuring head

[0001] The present invention relates to a coordinate measuring machine. Furthermore, the present invention relates to a method for coupling a measuring head of a coordinate measuring machine to a positioning system of the coordinate measuring machine.

[0002] An exemplary coordinate measuring machine and a method for automatically coupling a measuring head to a positioning system of the coordinate measuring machine is known from DE 10 2013 105 753 B3.

[0003] Further exemplary coordinate measuring machines are known from DE 90 10 591 U1, EP 1 669 713 B1 and DE 30 11 002 A1.

[0004] Furthermore, DE 10 2013 113 407 B4, DE 102014 118 215 B3, DE 101 14 126 B4 and DE 10 2010 031 976 A1 disclose various interfaces for the interchangeable coupling of tactile probe elements to coordinate measuring machines.

[0005] Coordinate measuring machines are used, for example, to check the geometry of a measured object as part of quality assurance or to determine the geometry of a measured object (e.g., as part of "reverse engineering"). Furthermore, numerous other applications are conceivable, such as process control applications where dimensional metrology is directly used for online monitoring and control of manufacturing and machining processes.

[0006] The term "coordinate measuring machine" is to be interpreted broadly in the present sense, such that any measuring instrument used for the dimensional measurement and acquisition of spatial coordinates of a measured object is to be considered a coordinate measuring machine in the sense of the invention. Typically, such a coordinate measuring machine has a positioning system with at least one driven axis to which a measuring head is integrally (i.e., permanently connected) or detachably (i.e., replaceably) attached. The positioning system serves to move the measuring head relative to the measured object.

[0007] In conventional designs of such coordinate measuring machines, the positioning system is implemented, for example, in a cantilever, bridge, portal, or pedestal design. As an alternative to conventional designs of such coordinate measuring machines, the measuring head can also be attached to one end of a robot arm, such as an articulated robot. Such a robot arm can therefore also be considered a "positioning system" in the present sense.

[0008] Depending on the type of measurement required, various types of sensors can be used in the measuring heads to measure the object being measured. These sensors, referred to here as "measuring head sensors," can be broadly divided into tactile and optical measuring head sensors. Tactile measuring heads or measuring head sensors are marketed by the applicant, for example, under the product names ZEISS XDT®, ZEISS XXT®, and ZEISS VAST®. Optical measuring heads or measuring head sensors are marketed by the applicant, for example, under the product names ZEISS ViScan®, ZEISS DotScan®, ZEISS LineScan®, and ZEISS EagleEye®.

[0009] Individual measuring head components can be replaced as needed, for example, to adapt the coordinate measuring machine to different measurement requirements. Measuring head components not required for the current measurement can be detached from the positioning system and temporarily stored in a magazine. When required, the necessary measuring head component is retrieved from the corresponding magazine slot and attached to the positioning system of the coordinate measuring machine.

[0010] It is important to distinguish whether the measuring head component to be coupled is the entire measuring head including the measuring head sensor or sensor technology, or merely a tactile probe element or an optical element, i.e., a component that is coupled to the measuring head sensor.

[0011] In both cases, high demands are placed on the accuracy and reproducibility of the respective exchange interfaces in order to meet the very high precision requirements of a coordinate measuring machine. Replacing an entire measuring head (including the measuring head sensor) is generally even more difficult than replacing a single probe element or optical element on the same measuring head sensor.

[0012] These higher requirements stem, firstly, from the greater weight of the measuring head compared to a purely tactile probe or optical element. Secondly, due to the longer lever arm, tilting errors have a greater impact on dimensional inaccuracies, as the measuring head sensor is typically positioned above the tactile probe or optical element. Thirdly, the measuring head sensor, due to its function, is more prone to heating, which can negatively affect dimensional accuracy, than a tactile probe or optical element. Finally, the required tilt stiffness is higher because, for example, high accelerations result in correspondingly high forces at the interface due to the sensor's high mass.

[0013] For a reliable and reproducible change of a measuring head, it is essential that the individual magazine positions are precisely positioned and aligned. This is particularly important when the measuring head change is automated, i.e., performed by the coordinate measuring machine itself. Furthermore, it must be ensured that the exact positioning and alignment of the magazine positions are maintained over numerous changes. Otherwise, variations in reproducibility can lead to undetected measurement errors.

[0014] If the magazine slots are not precisely aligned, this can lead to inaccurate, unreliable, and error-prone measuring head changes. Furthermore, wear and tear can occur. This can occur due to increased friction. In the worst case, damage can occur to the measuring head components, the magazine and / or the positioning system of the coordinate measuring machine.

[0015] For the reasons already mentioned above, the requirements placed on an interchangeable interface for the detachable attachment and detachment of a measuring head are significantly higher than the requirements placed on an interchangeable interface for the detachable attachment and detachment of a tactile or optical probe element. This applies not only to the difference in the design of such interchangeable interfaces, but also to the requirements placed on the control of the positioning system during an attachment or detachment process.

[0016] The interchangeable interfaces disclosed in the above-mentioned prior art documents for the detachable coupling of a measuring probe to a measuring head sensor are therefore only marginally suitable, if at all, as interchangeable interfaces for coupling an entire measuring head to the positioning system of a coordinate measuring machine.

[0017] In addition to the differences already explained above, with a measuring head interchangeable interface, it is also important to ensure that the data interfaces arranged on the measuring head and on the positioning system mesh precisely to reliably guarantee the exchange of current and data between the measuring head and the control unit of the coordinate measuring machine.

[0018] To ensure high reproducibility of a measuring head exchange interface, the following additional technical requirements must also be met: The orientation of the measuring head to be exchanged must be parallel to the positioning system interface with high accuracy, which is typically located at the lower end face of a quill of the positioning system.

[0019] Furthermore, care should be taken to ensure that the connecting force between the positioning system and the measuring head to be coupled is as parallel as possible to the traversing axis. of the positioning system component, on which the positioning system interface is located, i.e. usually as parallel as possible to the pinion axis.

[0020] During the coupling process, however, lateral stress on the measuring head should be prevented so that only the bearing—and not the force-generating device—determines the lateral position. The lateral offset that the bearing must correct during the coupling process (i.e., the lateral distance between the quill and the measuring head shortly before coupling) should be as small as possible and should not become too large even with prolonged temperature fluctuations. Furthermore, care should be taken to ensure that, if the bearing has to compensate for lateral misalignments, only the friction of the bearing, and not the force-generating device, impedes this compensation process.

[0021] Furthermore, such measuring head exchange interfaces should be designed to be as compact as possible.

[0022] It is therefore an object of the present invention to provide a coordinate measuring machine with an improved measuring head exchange interface and improved control of the coupling process that meet the aforementioned requirements. It is also an object of the present invention to provide an improved method for coupling a measuring head of a coordinate measuring machine to a positioning system of the coordinate measuring machine.

[0023] This problem is solved according to a first aspect of the present invention by a coordinate measuring machine according to claim 1, which comprises the following: - a positioning system with at least one driven axis and a positioning system interface for coupling a measuring head to the positioning system, wherein the positioning system interface has a first data interface and a locking device for locking the measuring head; - a measuring head having a first measuring head interface designed to be detachably coupled to the positioning system interface and having a second data interface for data exchange with the first The data interface works together when the positioning system interface is coupled with the first measuring head interface; - a magazine with at least one measuring head receptacle for receiving and holding the measuring head, wherein the measuring head receptacle is configured to support the measuring head received therein in a vertical z-direction and to prevent, at least to a large extent, rotation about a horizontal x-direction orthogonal to the z-direction as well as rotation about a horizontal y-direction orthogonal to the z-direction and the x-direction, and to mount the measuring head received therein in a movable, in particular floating, position in an xy-horizontal plane spanned by the x-direction and the y-direction as well as rotationally about the z-direction; and - a control unit for controlling the positioning system, which is configured to control the positioning system during a coupling process in which the measuring head held in the measuring head receptacle is coupled to the positioning system and locked by means of the locking device, in such a way that it exerts a force on the measuring head by which movement of the measuring head in the z-direction relative to the measuring head receptacle is prevented during the entire coupling process until the locking device has completely locked the measuring head.

[0024] According to a second aspect of the present invention, the above-mentioned problem is solved by a method according to claim 14, which comprises the following steps: - Providing a positioning system with at least one driven axis and a positioning system interface for coupling a measuring head to the positioning system, wherein the positioning system interface has a first data interface and a locking device for locking the measuring head; - Providing a measuring head that has a first measuring head interface which is configured to be detachably coupled to the positioning system interface and which has a second data interface which cooperates with the first data interface for data exchange when the positioning system interface is coupled to the first measuring head interface; - Providing a magazine with at least one measuring head receptacle for receiving and holding the measuring head, wherein the measuring head receptacle is configured to support the measuring head received therein in a vertical z-direction and to prevent, at least to a large extent, rotation about a horizontal x-direction orthogonal to the z-direction as well as rotation about a horizontal y-direction orthogonal to the z-direction and the x-direction, and to mount the measuring head received therein in a movable, in particular floating, position in an xy-horizontal plane spanned by the x-direction and the y-direction as well as rotationally about the z-direction; and - Controlling the positioning system to perform a coupling operation in which the measuring head held in the measuring head receptacle is coupled to the positioning system and locked using the locking device, wherein the positioning system is controlled such that it exerts a force on the measuring head by which movement of the measuring head in the z-direction relative to the measuring head receptacle is prevented during the entire coupling operation until the locking device has completely locked the measuring head.

[0025] The coordinate measuring machine and the method according to the invention are characterized in particular by the following features:

[0026] First of all, the measuring head is not clamped firmly in the magazine during storage and holding, which could otherwise cause force-induced distortions and / or mechanical overdetermination.

[0027] Firstly, such a fixed clamping device would have to be manufactured with extreme precision. Secondly, this would entail limitations in reproducibility, as such systems degrade and drift thermally, which in turn would lead to mechanical stresses.

[0028] Instead, the measuring head receptacle of the magazine is designed according to the invention such that a measuring head received therein is supported only in the vertical z-direction and an rx rotation, i.e. a rotation about an axis orthogonal to the z-direction, is prevented. The x-direction and a ry-rotation (i.e., a rotation about a horizontal y-direction orthogonal to the z-direction and the x-direction) are prevented. This does not necessarily mean that an rx-rotation and a ry-rotation are completely suppressed. Rather, it means that an rx-rotation and a ry-rotation are only possible to a very limited extent, if at all. Due to tolerances, smaller rx- and ry-rotations may occur, but these are preferably less than 1 mm, more preferably less than 0.1 mm, and particularly preferably less than 10 pm. In particular, it is preferred that an rx-rotation and a ry-rotation are prevented at least to such an extent that they are smaller than the permissible rz-rotation, and particularly preferably at least five, ten, fifty, or even one hundred times smaller than the permissible rz-rotation.However, it may also be preferable that rx rotation and ry rotation are not possible at all. In the xy-horizontal plane, the measuring head is movably mounted, preferably floating, in the measuring head holder. Likewise, rz rotation, i.e., rotation around the z-direction, is enabled while the measuring head is held in the measuring head holder of the magazine.

[0029] The measuring head thus has lateral play in the xy-horizontal plane within the measuring head holder. Since it is only supported in the z-direction, the measuring head preferably also has some play in the z-direction within the measuring head holder and can move upwards against its own weight. This play allows the measuring head to be placed cleanly in the measuring head holder, which is ensured even if the measuring head holder of the magazine changes its position due to temperature fluctuations. Even then, the measuring head can still be placed reproducibly and with minimal force in the xy-horizontal plane within the measuring head holder.

[0030] The control of the positioning system during a coupling process, in which the measuring head held in the measuring head holder is coupled to the positioning system and locked by means of a locking device, is carried out in such a way that the positioning system exerts a force on the measuring head, which prevents movement of the measuring head in the z-direction (i.e. against the weight force of the measuring head) relative to the measuring head holder during the entire coupling process, until the locking device has completely locked the measuring head.

[0031] Accordingly, the measuring head can perform minor compensatory movements in the xy-horizontal plane during the coupling process without causing mechanical stress. Despite the measuring head only being supported in the measuring head holder in the vertical z-direction, i.e., despite the fundamental possibility of movement of the measuring head in the z-direction relative to the measuring head holder, the force exerted on the measuring head by the positioning system during the coupling process prevents movement of the measuring head in the z-direction, i.e., opposite to the direction in which the weight of the measuring head acts.

[0032] The latter may initially seem obvious, since the force of gravity already pushes the measuring head into the measuring head holder in the negative z-direction, counteracting the support acting in the z-direction. However, the locking mechanism, which secures the measuring head to the positioning system interface, typically counteracts this. With interchangeable interfaces that use magnets as part of the locking mechanism, locking the measuring head often causes it to be pulled upwards, i.e., in the negative z-direction, out of the measuring head holder. This occurs uncontrolled, albeit usually only for a brief moment, which can lead to measurement inaccuracies and a lack of reproducibility.

[0033] Even with interchangeable interfaces where locking anchors or locking hooks are used as parts of the locking device, the measuring head is often pulled upwards out of the measuring head mount due to the locking anchor or locking hook.

[0034] All of this is prevented by the control of the positioning system according to the invention.

[0035] In combination with the simultaneous floating bearing in the xy-horizontal plane and the rz-direction, overall optimal conditions result for an extremely accurate and precisely defined coupling of the measuring head with the positioning system of the coordinate measuring machine and an optimally reproducible coupling process of the measuring head to the positioning system.

[0036] The above-mentioned task has therefore been completely solved.

[0037] According to one design, the control unit is configured to control the positioning system- The interface is to be positioned at the beginning of the coupling process at a transfer position relative to the first measuring head interface, where the positioning system interface and the measuring head interface are opposite each other and have a predefined distance from each other or are in contact with each other, in particular at the first and the second data interface, and subsequently a control signal is to be generated by which a position control of the at least one driven axis of the positioning system is deactivated during the coupling process and the positioning system interface is moved in a negative z-direction opposite to the z-direction.

[0038] This further improves the accuracy and reproducibility of the coupling process.

[0039] Deactivating the at least one driven axis of the positioning system ensures that the position control does not interfere with the coupling process. Preferably, a control signal is generated that also deactivates the speed control of the at least one driven axis of the positioning system during the coupling process. Instead, the drive of the at least one axis is controlled, for example, with a constant current to move the positioning system interface in a defined manner in the negative z-direction.

[0040] According to a further embodiment, the control unit is designed to control the positioning system during the coupling process in such a way that the sum of a weight force of the measuring head acting in the negative z-direction and the force exerted on the measuring head by the positioning system in the negative z-direction is equal to or greater than the sum of a locking force exerted on the measuring head by the locking device in the z-direction and a coupling force acting between the first and second data interfaces.

[0041] In other words, the positioning system ensures that the resultant force acting on the measuring head is zero or acts in a negative z-direction to prevent the measuring head from lifting upwards, i.e. in the z-direction, out of the measuring head mount during the entire coupling process.

[0042] According to a further embodiment, the first data interface has a first connecting element and the second data interface has a second connecting element designed as a counterpart to the first connecting element, wherein at least one of the two connecting elements has a spring-loaded connecting element, in particular several spring-loaded pins.

[0043] For example, one of the two connecting elements can have several spring-loaded pins which, when the two data interfaces are connected, press against corresponding pads designed as counterparts, which in turn may also be spring-loaded, but do not have to be.

[0044] The spring-loaded mounting of at least one of the two connecting elements ensures compliance during the coupling process and a sufficiently good connection between the two data interfaces.

[0045] According to a further embodiment, the locking device has a locking armature that is linearly movable along the z-direction relative to the first data interface and rotatable about the z-direction. It is understood that the locking armature is preferably linearly movable by a motor in the z-direction and in the negative z-direction and rotatable about the z-direction by a motor.

[0046] Such a locking anchor has the advantage that locking forces can be generated as parallel as possible to the z-direction, and transverse forces perpendicular to the z-direction, such as those that arise during coupling with a swiveling hook device, can be largely avoided.

[0047] Compared to magnetic coupling, the locking force can be better defined and controlled using such a locking anchor. Furthermore, higher forces can be generated overall, which increases the locking mechanism's reliability.

[0048] According to a further embodiment, the locking anchor and / or an anchor counterpart cooperating with the locking anchor, which is arranged at the first measuring head interface, is coated with a sliding friction-reducing coating, which in particular comprises PTFE.

[0049] This reduces friction between the locking armature and the counterpart, which, for example, has an armature disc. The coating ensures, in particular, that lateral compensating movements can still be performed during the coupling process, even when the locking armature is already engaged with the counterpart. Unintentional rotations around the z-direction are further prevented by ensuring that the locking armature rotates sufficiently deep within an opening in the counterpart, into which it plunges during the coupling process. Thus, there is preferably no contact between the locking armature and the counterpart while the locking armature is rotating around the z-direction. This, in turn, improves the precision and reproducibility of the coupling process.

[0050] According to a further embodiment, the locking anchor and / or an anchor counterpart cooperating with the locking anchor, which is arranged at the first measuring head interface, is movably, in particular floatingly, mounted in the xy-horizontal plane.

[0051] Undesired lateral forces during the coupling process can also be avoided by this movable or floating mounting of the locking anchor and / or the anchor counterpart. The mounting of the locking anchor and / or the anchor counterpart should be designed so that the locking anchor and / or the The anchor counterpart is only floating in the xy-horizontal plane, but is fixed or rigidly mounted in the z-direction.

[0052] The positioning system preferably has a quill movable in the z-direction, at the free end of which the positioning system interface is arranged. Since the aforementioned locking anchor is part of the positioning interface, it is preferably arranged at the free, lower end of the quill, which is linearly movable in the z-direction.

[0053] According to a further embodiment, the positioning system interface and the first measuring head interface have a centering device which is designed to center the measuring head relative to the positioning system in the xy-horizontal plane during the coupling process before the first data interface comes into contact with the second data interface.

[0054] This centering of the first measuring head interface relative to the positioning system interface is particularly advantageous because, as mentioned above, the measuring head is mounted in the magazine's measuring head holder in the xy-horizontal plane and is rotatable around the z-direction, specifically floating. This centering therefore compensates for any unintentional slippage of the measuring head.

[0055] According to a preferred embodiment, the centering device has a centering bolt which, in the area of ​​its free, end-face end, has a first section that tapers towards the free end, in particular conical or spherical, and a second section spaced apart from or adjacent to the first section, the diameter of which is smaller compared to the first section.

[0056] During the coupling process, this centering bolt preferably dips into an opening that acts as a counterpart to the centering bolt, wherein first the first section of the centering bolt dips into the opening and then the second section of the centering bolt dips into the opening.

[0057] The different diameters of the two sections of the centering pin prevent any further lateral mechanical stress on the two interfaces (positioning system interface and first measuring head interface). The larger diameter is the first to enter the opening, thus centering the workpiece. The subsequent smaller diameter then no longer rests against the opening, preventing any lateral mechanical stress, i.e., transverse forces perpendicular to the z-direction. While the first section of the centering pin is entering the opening, the measuring head, due to its floating mounting in the magazine's measuring head receptacle, can move in the xy-horizontal plane and thus optimally align itself with the positioning system interface, which is preferably located at the lower end of the quill.

[0058] The centering bolt of the aforementioned centering device is preferably part of the positioning system interface, while the aforementioned opening is preferably part of the first measuring head interface.

[0059] According to a further embodiment, the measuring head mount has a magazine slot interface which can be detachably coupled to a second measuring head interface arranged on the measuring head, wherein the magazine slot interface has three separately spaced support surface sections, the centers of which form a triangle.

[0060] This ensures a mechanically defined, optimal support of the measuring head in the measuring head holder of the magazine.

[0061] The three spaced-apart support surface sections of the magazine space interface preferably lie in a common plane. This common plane preferably runs at least approximately orthogonal to the z-direction.

[0062] The aforementioned properties of the floating mounting of the measuring head in the measuring head holder can be optimally implemented with the help of such a three-point or three-surface support.

[0063] In a preferred embodiment, the magazine slot interface has three arms extending separately and spaced apart from a base body of the measuring head mount, with one of the three support surface sections being arranged on each of the three arms.

[0064] These three arms are designed to be inserted into corresponding openings provided at the second measuring head interface. The arms can be angled relative to each other to facilitate insertion of the measuring head into the measuring head holder.

[0065] The second measuring head interface and the magazine slot interface can further be designed such that the three arms parallel to the xy-horizontal plane have a lateral play relative to the second measuring head interface, in particular a lateral play in the range of 0.1 mm to 2 mm, when the measuring head is received and held in the measuring head receptacle.

[0066] This lateral play of the magazine arms prevents lateral constraint of the measuring head within the measuring head mount and accordingly ensures the aforementioned intended properties of the measuring head's support within the measuring head mount.

[0067] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the present invention. Furthermore, it is understood that the features of the coordinate measuring machine mentioned above and defined in the dependent claims also apply equivalently to the method according to the invention.

[0068] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description. They show: Fig. 1 shows a perspective view of an embodiment of a coordinate measuring machine according to the present invention; Fig. 2 shows a perspective view of a magazine used in the embodiment of the coordinate measuring machine according to the invention shown in Fig. 1; Fig. 3 shows a front view illustrating a coupling process in which a measuring head is coupled to a quill of the coordinate measuring machine; Fig. 4 is a schematic representation to illustrate a functional interaction of various measuring head components and magazine components of the coordinate measuring machine according to the invention; Fig. 5 is a schematic representation to illustrate a process step of a method for assembling the magazine; Fig. 6 is a schematic representation to illustrate a further step in the process for assembling the magazine; Fig. 7 shows a schematic representation of a magazine space adapter belonging to the magazine; Fig. 8 shows a perspective view of the magazine space adapter according to an embodiment of the present invention; Fig. 9 shows a perspective view of a measuring head adapter according to an embodiment of the present invention; Fig. 10 shows two sectional views of the magazine slot adapter shown in Fig. 8 and the measuring head adapter shown in Fig. 9, with Fig. 10A being a Position shown while the measuring head adapter is attached to or removed from the magazine slot adapter, and wherein Fig. 10B shows a position in which the measuring head adapter is held by the magazine slot adapter; Fig. 11 shows the magazine space adapter and the measuring head adapter in the position shown in Fig. 10B in a top view; Fig. 12 shows a sectional view of the magazine space adapter and the measuring head adapter according to section CC indicated in Fig. 11; Fig. 13 shows a top view of the measuring head adapter in a state recorded in the measuring head receptacle of the magazine space adapter, illustrating further components of the magazine or magazine space; Fig. 14 shows a sectional view to illustrate a coupling process in which the measuring head adapter is coupled to a positioning system interface of the positioning system of the coordinate measuring machine; Fig. 15 shows a sectional view to illustrate a coupled state in which the measuring head adapter is coupled to the positioning system interface; Fig. 16 shows a perspective view to illustrate a positioning system interface arranged or attachable to the positioning system according to an embodiment of the present invention; Fig. 17 shows a perspective view of the measuring head adapter, which corresponds to the representation in Fig. 9; Fig. 18 shows a top view of the positioning system interface shown in Fig. 16; Fig. 19 shows a top view of the measuring head adapter shown in Fig. 17; Fig. 20 shows a perspective partial section view to illustrate an embodiment of a locking device of the coordinate measuring machine according to the invention, wherein the locking device is in an unlocked state; Fig. 21 shows a perspective partial section view of the locking device shown in Fig. 20, in which the locking device is in a locked state; Fig. 22 shows various schematic views illustrating a measuring principle of a distance sensor, with Figs. 22A, 22B, 22C and 22D illustrating different ways of mounting the distance sensor; and Fig. 23 is a diagram illustrating a detection characteristic curve of a distance sensor according to an exemplary embodiment.

[0069] Fig. 1 shows a perspective view of an embodiment of a coordinate measuring machine according to the present invention. The coordinate measuring machine is characterized in its entirety by the reference numeral 10.

[0070] The coordinate measuring machine 10 has a base 12, which serves as the base support for the coordinate measuring machine 10 and includes a measuring table 14 on which a workpiece to be measured can be placed. The measuring table 14 preferably includes a measuring table plate 16. This measuring table plate 16 is designed as a solid granite plate. Depending on the design, the measuring table plate 16 is either horizontally movable relative to the base 12 or fixed to the base 12.

[0071] Furthermore, a positioning system 18 is attached to the base 12, which serves for the spatial positioning of a measuring head 20, with the help of which a measuring object can be dimensionally measured. The positioning system 18 is designed as a portal structure. The portal 22 serves as a movable support structure for the measuring head 20. In this case, the portal 22 has two columns 24 and a crossbeam 26 on which a carriage 28 is movably mounted. The carriage 28 carries a quill 30, at the lower, free end of which the measuring head 20 is attached.

[0072] The measuring head 20 can be moved along three mutually orthogonal coordinate axes by means of the positioning system 18. These coordinate axes are referred to here as the x-, y-, and z-axes. The gantry 22 can be moved in the y-direction relative to the measuring table 14 by means of a drive. The carriage 28 can be moved along the x-direction by means of another drive on the crossbeam 26. A third drive (here only schematically indicated at reference numeral 27) enables the quill 30 to be moved in the z-direction relative to the carriage 28. The positioning system 18 has position encoders along the x-, y-, and z-axes, such as linear scales (not shown here), which can be detected by an associated read head (here schematically indicated at reference numeral 29).With the help of the position sensors, the current actual position of the quill 30 along the drive axes can be determined in a manner known per se.

[0073] The measuring head 20 is detachably attached to the quill 30 of the positioning system 18 by means of an interchangeable interface, which is explained in detail below. This interchangeable interface, located at the lower end of the quill 30, makes it possible to equip the coordinate measuring machine 10 with different measuring heads 20, 20' depending on the measuring task.

[0074] In the embodiment shown in Fig. 1, a tactile measuring head 20 is coupled to the quill 30, which is shown in detail in Fig. 3. This tactile measuring head 20 comprises a measuring head sensor 32, which contains the main part of the measuring head sensor assembly. The measuring head sensor 32 is attached to the quill 30 by means of a measuring head adapter 34, which is explained in detail below. At the lower end, a tactile probe 36 is coupled to the measuring head sensor 32 (see Fig. 3).

[0075] With the aid of this measuring probe 36, various measuring points on the object being measured can be tactilely probed during a measurement. For this purpose, a stylus 37, which is often made of ruby, zirconium dioxide or silicon nitride, is located at the lower, free end of the measuring probe 36.

[0076] The tactile probes are evaluated using the measuring head sensor 32 and forwarded to a central control unit 44, which is shown here purely schematically, for further processing. The control unit 44 simultaneously receives position information from the positioning system 18 along the three drive axes from the respective position encoders 29, so that the coordinates of the probe points touched by the measuring probe 36 can be determined from the measurement signals collected in the measuring head 20 and the position information of the positioning system 18.

[0077] The control unit 44 typically serves not only to evaluate the data acquired by the measuring head 20 and to determine the spatial coordinates of the object to be measured, but also to control the positioning system 18 and thus the driven axes of the positioning system 18. In preferred embodiments, the control unit 44 implements several cascaded control loops, including a position control loop and a current control loop for each drive axis. The control loops generate a drive current for the electric drives of each drive axis.

[0078] Furthermore, it should be noted that the control unit 44 is shown schematically here as a purely external control unit. However, this is not necessarily the case. Parts of the control unit 44, or even the entire control unit 44, can also be structurally integrated directly into the coordinate measuring machine 10. Regardless, the control unit 44 is preferably designed as a computer or microcomputer on which corresponding control and evaluation logic for controlling and metrologically evaluating the coordinate measuring machine 10 is stored.

[0079] Instead of the tactile measuring head 20, an optical measuring head 20' can also be coupled to the positioning system 18. Such an optical measuring head 20', which is located in the In the present embodiment, which further features a rotary-swivel joint, the measuring head 20 is arranged in a magazine 38 as shown in Fig. 1. This magazine serves to hold and support several measuring heads and is attached to the base 12 or the measuring table 14. By moving the coordinate measuring machine 10 to this magazine 38, it can change the measuring head 20, for example by placing the tactile measuring head 20 in the magazine 38 and then removing the optical measuring head 20' from the magazine 38 and coupling it to the quill 30.

[0080] An embodiment of the magazine 38 is shown in perspective view in Fig. 2. The magazine 38 has a magazine carrier 40 and, in this case, two magazine slot adapters 42, 42' attached to the magazine carrier 40. It is understood that, of course, more than two magazine slot adapters 42 can also be arranged on the magazine carrier 40.

[0081] The magazine support 40 serves as a support structure for the magazine space adapters 42, 42'. In this case, it is essentially designed in a column-like form, although various other shapes are conceivable in principle.

[0082] The magazine carrier 40 can, for example, be attached to the measuring table 14 by means of several screws which are inserted into mounting holes which are provided in the base plate of the magazine carrier 40. The two magazine slot adapters 42, 42' can also be detachably attached to the magazine carrier 40 according to the invention, preferably by means of several screws.

[0083] Figs. 4-7 schematically illustrate a method according to the invention for assembling the magazine 38.

[0084] In a first step, the magazine carrier 40 is fixed to the base 12 (see Fig. 4). In the embodiment shown in Fig. 1, this is achieved by screwing the magazine carrier 40 to the measuring table 14 using several fastening screws.

[0085] Next, the measuring head adapter 34 is coupled to the positioning system 18. For this purpose, the measuring head adapter 34 has a first measuring head interface 46, which is designed to be detachably coupled to a positioning system interface 48, which is located at the lower end of the quill 30 and is designed as a counterpart to the first measuring head interface 46.

[0086] It goes without saying that this step of coupling the measuring head adapter 34 to the positioning system 18 can of course also be carried out before the step of fixing the magazine carrier 40 to the base 12 or simultaneously with it.

[0087] As shown schematically in Fig. 5, the measuring head adapter 34 is thus coupled to the positioning system 18 or the quill 30. The measuring head sensor 32 is preferably decoupled from the measuring head adapter 34 during the assembly of the magazine 38. This provides more freedom of movement and simplifies the process. Furthermore, it eliminates the risk of damaging the measuring head sensor 32 during assembly.

[0088] According to the embodiment shown here, the measuring head adapter 34 has an interface 50 at its lower end for connecting and disconnecting the measuring head sensor 32. This interface 50 is referred to here as the "third measuring head interface".

[0089] As can be seen in Fig. 5, the magazine slot adapter 42 is also coupled to the measuring head adapter 34. For this purpose, the magazine slot adapter 42 has a magazine slot interface 52, which is configured to correspond to an interface 54 on the measuring head adapter 34, referred to here as the "second measuring head interface".

[0090] The magazine interface 52 is designed as a male interface. The second measuring head interface 54 is designed as its counterpart, i.e., as a female interface. This is particularly advantageous because the measuring head adapter 34 can thus be designed to be as space-saving as possible. However, it is understood that it would also be possible, in principle, to design the second measuring head interface 54 as a male interface. to design the interface and the magazine space interface 52 as a correspondingly female interface without leaving the scope of the present invention.

[0091] The magazine slot adapter 42 is now also coupled to the positioning system 18 as a result of its coupling to the measuring head adapter 34. More precisely, in the situation shown schematically in Fig. 5, the magazine slot adapter 42 is coupled to the quill 30 via the measuring head adapter 34.

[0092] Preferably, in this situation, the magazine slot adapter 42 is detachably fixed to the measuring head adapter 34 to prevent it from slipping relative to the measuring head adapter 34. This can be achieved, for example, by means of a setscrew 56 located on the measuring head adapter 34 and screwed into a recess or other shaped element on the magazine slot adapter 42. This firmly clamps the magazine slot adapter 42 to the measuring head adapter 34 during the assembly of the magazine 38. Simultaneously, the setscrew 56 can also center or align the magazine slot adapter 42 relative to the measuring head adapter 34. Of course, several such setscrews 56 can also be provided, engaging in corresponding recesses 58 as counterparts.

[0093] The magazine slot adapter 42, which is indirectly coupled to the positioning system 18 via the measuring head adapter 34, is moved to the magazine carrier 40 in the next step. This is preferably done automatically, with the positioning system 18, controlled by the control unit 44, moving the measuring head adapter 34 and the associated magazine slot adapter 42 to a mounting position near the magazine carrier 40. This mounting position can be one in which the magazine slot adapter 42 is a short distance from the upper free end of the magazine carrier 40 or is in contact with this upper end of the magazine carrier 40.

[0094] In other words, a first mounting interface 60 provided on the magazine space adapter 42 is brought close to or in contact with a second mounting interface 62 acting as its counterpart on the magazine carrier 40. A first mounting surface 64 belonging to the first mounting interface 60, which is located on the The lower end of the magazine space adapter 42 has, in this situation, an not exactly defined or at least partially unknown spatial relative pose to a second mounting surface 66 belonging to the second mounting interface 62, which is located at the upper end of the magazine carrier 40.

[0095] It is quite possible that the two mounting surfaces 64, 66 are not exactly parallel to each other in this situation, but slightly misaligned. This non-parallel alignment is intentionally accepted according to the mounting method according to the invention.

[0096] For example, three lock screws 68 are screwed into the magazine slot adapter 42 from above with low torque until they are in contact with the second mounting surface 66 located on the top of the magazine carrier 40. This determines the (unknown) spatial relative orientation of the magazine slot adapter 42 relative to the magazine carrier 40, or the relative orientation of the first mounting surface 64 relative to the second mounting surface 66.

[0097] Subsequently, the defined spatial relative orientation of the two mounting surfaces 64, 66 is fixed by, for example, screwing several fastening screws 70 through the magazine space adapter 42 into the magazine carrier 40 in order to attach the magazine space adapter 42 to the magazine carrier 40.

[0098] It is understood that, instead of lock screws, other adjustable spacer elements 68 can also be used to fix the two mounting interfaces 60, 62 in the relative orientation specified by the positioning system 18. For example, one or more wedges could also be used as spacer elements 68. However, it is preferred that adjustable spacer elements 68 be used which can be adjusted to the required distance between the two mounting surfaces 64, 66.

[0099] It is also understood that other fastening elements 70 can be used instead of the fastening screws to attach the magazine slot adapter 42 with to be detachably connected to the magazine carrier 40. It is also conceivable, in principle, to attach the magazine slot adapter 42 to the magazine carrier 40 by gluing.

[0100] During the attachment of the magazine slot adapter 42 to the magazine carrier 40, the position control of the quill 30, initiated by the control unit 44, is preferably deactivated. Otherwise, the movements transmitted to the quill 30 by screwing in the fasteners 70 would lead to a corresponding position adjustment by which the control unit 44 attempts to hold the quill 30 in the predetermined position. This would result in forces that could cause stress in the mounting interfaces 60, 62. Accordingly, it is advantageous to de-energize the drives of the coordinate measuring machine 10, in particular the drive of the quill 30, during the fastening process.

[0101] In summary, the magazine slot adapter 42 is not attached to the magazine carrier 40 as a loose component and then aligned relative to the positioning system 18, as is usually the case. Instead, the magazine slot adapter 42 is attached to the magazine carrier 40, while the magazine slot adapter 42 is coupled to the positioning system 18 via the measuring head adapter 34.

[0102] It should be noted that a measuring head adapter 34, as shown, for example, in Fig. 5, does not necessarily have to be coupled to the positioning system interface 48, which is located on the underside of the quill 30, during the assembly procedure described above. Such a measuring head adapter 34 does have the advantage that a measuring head sensor 32 can be detachably coupled using the third measuring head interface 50. For example, the measuring head sensor 32 can be inserted into a type of dovetail guide, as shown in Fig. 3 for the realization of the third measuring head interface 50. In this way, almost any measuring head sensor can be subsequently attached to the measuring head adapter 34.

[0103] However, for the method according to the invention it would also generally be conceivable to design the measuring head 20 without such a measuring head adapter 34 and the first The measuring head interface 46 as well as the second measuring head interface 54 are to be designed directly, i.e. integrally, on the measuring head 20 or the measuring head sensor 32.

[0104] It would also be conceivable, in principle, to use an extra mounting adapter instead of the measuring head adapter 34, to which the measuring head sensor 32 can be detachably coupled, which has the two measuring head interfaces 46, 54 and is used only for the mounting method according to the invention, but is subsequently replaced by a measuring head adapter 34 with a measuring head sensor 32 coupled to it or a measuring head 20 integrally designed with the measuring head interfaces 46, 54.

[0105] Because of these different possibilities, the term "measuring head component" is generally used here for the component to be coupled to the positioning system 18 or to the positioning system interface 48, be it the measuring head adapter 34, the measuring head 20 itself or a mounting adapter.

[0106] Fig. 8 shows a perspective view of an embodiment of a magazine slot component 72 belonging to the magazine slot adapter 42. This magazine slot component 72 is the component of the magazine slot adapter 42 on which the magazine slot interface 52, functioning as a counterpart to the second measuring head interface 54, is designed.

[0107] The magazine slot interface 52 defines a measuring head receptacle 74 for receiving and holding the measuring head component, in particular the measuring head adapter 34. In this case, the magazine slot interface 52 has three arms 78, 78', 78" projecting separately and at intervals from a plate-shaped base body 76. The arms 78, 78', 78" together with the base body 76 form a kind of fork onto which the measuring head component, in particular the measuring head adapter 34, can be slid.

[0108] A corresponding bearing surface section 80, 80', 80" is arranged on the upper surface of each arm 78, 78', 78". Preferably, each of these three bearing surface sections 80, 80', 80" is a planar surface section. Particularly preferably All three support surface sections 80, 80', 80" lie in a common plane, which is preferably parallel to the xy-horizontal plane.

[0109] The three arms 78, 78', 78" are advantageously aligned parallel to each other and, in this case, have different sizes and shapes. In this embodiment, they are positioned at an angle, i.e., at an angle other than 90°, in the measuring head receptacle 74. The centers of the three support surface sections 80, 80', 80" arranged on the arms 78, 78', 78" preferably form a triangle, the center of gravity of which is located inside the measuring head component to be coupled when this component is connected to the magazine adapter 42.

[0110] Figure 8 further shows that the base body 76 of the magazine compartment component 72 has three first openings 82 and three second openings 84. Both the first openings 82 and the second openings 84 are preferably designed as stepped bores. The first openings 82 serve to receive the aforementioned counter screws or spacer elements 68. The second openings 84 serve to receive the aforementioned fastening screws or fastening elements 70. To achieve optimal three-point support between the magazine component 72 and the magazine carrier 40, the first openings 82 and the second openings 84 are arranged relative to each other in a regular triangle.

[0111] Fig. 9 shows a perspective view of an embodiment of the measuring head adapter 34. Here, the third measuring head interface, dovetail-shaped and integrated into the underside of the measuring head component, for coupling a measuring head sensor 32 is again visible. On the top side of the measuring head adapter 34, the first measuring head interface 46 for coupling the measuring head adapter 34 to the positioning system interface 48 is visible. Details of this first measuring head interface 46 are explained below with reference to Figs. 16-19.

[0112] Figure 9 also shows two openings 86, 88 laterally incorporated into the measuring head adapter 34, which serve to receive the arms 78 and 78' of the magazine compartment component 72. A further opening or recess 90, which receives the third arm, is also shown. The purpose of the recess or opening 90, which is 78", is not visible or is obscured in Fig. 9. However, this recess or opening 90 is visible in Fig. 10A.

[0113] Figures 10A and 10B show the two positions during the sliding of the measuring head adapter 34 onto the magazine slot component 72. Figure 10A shows a state in which the measuring head adapter 34 is only partially slid onto the magazine slot component 72. Figure 10B, on the other hand, shows the measuring head adapter 34 in a state in which it is fully slid onto the magazine slot component 72 or fully received in the measuring head receptacle 74 of the magazine slot component 72. Of course, the situation shown in Figure 10A could also be a position during the withdrawal of the measuring head component from the magazine slot component 72.

[0114] As can be seen particularly from the combined view of Figures 10A and 10B, the measuring head adapter 34 is pushed onto or pulled out of the arms or fingers 78, 78', 78" at an angle. Furthermore, it can be seen from Figure 10B that the measuring head adapter 34 has a certain amount of play on the arms 78, 78', 78" even when fully inserted into the measuring head receptacle 74. The measuring head adapter 34 can be moved, in particular, in the xy-horizontal plane relative to the magazine component 72. The measuring head adapter 34 is therefore mounted in a floating manner within the measuring head receptacle 74 of the magazine component 72.

[0115] The openings 86, 88, 90 belonging to the second measuring head interface 54 and the arms 78, 78', 78" belonging to the magazine slot interface 52 are preferably designed such that the three arms 78, 78', 78" have lateral play relative to the second measuring head interface 54 parallel to the xy-horizontal plane, which is in the range of 0.1 mm to 2 mm when the measuring head component (the measuring head adapter 34 or the entire measuring head 20) is received and held in the measuring head receptacle 74. This enables self-centering or self-alignment of the measuring head adapter 34 when the arms 78, 78', 78" are inserted into the openings 86, 88, 90.

[0116] The measuring head receptacle 74 defined by the magazine space interface 52 is further designed such that it holds the measuring head component 34, 20 in z- The direction is supported. This is particularly evident from the sectional view shown in Fig. 12, the section line CC of which is indicated by a dashed line in Fig. 11. The measuring head adapter 34 rests flat against the support surface sections 80, 80', 80" arranged on the upper side of the arms 78, 78', 78" from above. Below the arms 78, 78', 78" there are clearances 92 in the openings 86, 88, 90, so that the measuring head adapter 34 is only supported, but not rigidly clamped, in the z-direction. The measuring head adapter 34 can therefore be moved relative to the magazine component 72 in the z-direction, at least to a limited extent, provided that the latter's weight force is overcome.

[0117] As can be further seen from the combined view of Figures 10-12, the measuring head mount 74 is designed such that the measuring head adapter 34 held therein is held in the xy-plane. Rotation about the z-axis is possible to a defined extent due to the lateral play.

[0118] Fig. 13 shows a top view of the magazine slot adapter 42 while the measuring head adapter 34 is held in the measuring head receptacle 74. In addition to the essentially fork-shaped magazine component 72, which defines the measuring head receptacle 74, the magazine slot adapter 42 has a mechanical locking device 94 that holds the measuring head adapter 34 to the magazine slot adapter 42 as long as it is held in the measuring head receptacle 74. The locking device 94 prevents the measuring head adapter 34 or the measuring head 20 from unintentionally falling out of the magazine 38.

[0119] Furthermore, two rails 96 are visible in Fig. 13, on which a cover (not shown) is guided longitudinally. This cover serves to cover the first measuring head interface 46, while the measuring head adapter 34 or the measuring head 20 is held in the magazine 38. This cover 98, which is shown in particular in Fig. 2, prevents, in particular, contamination or damage to the first measuring head interface 46 during storage in the magazine 38.

[0120] The following describes, with reference to Fig. 14-21, the structure of the positioning system interface 48 and the first components interacting with the positioning system interface 48. The measuring head interface 46 is explained. In addition, a method for coupling the measuring head adapter 34 or the measuring head 20 to the positioning system 18 is explained, particularly with reference to Figures 14 and 15.

[0121] The positioning system interface 48 has a data interface 100 which in the present embodiment comprises several spring-loaded pins 102, which are grouped together in three pads spaced apart from each other.

[0122] The first data interface 100, located at the positioning system interface 48, interacts with a second data interface 104, located at the first measuring head interface 46, when coupled. The second data interface 104 has several recesses 106 into which the pins 102 engage when the two data interfaces 100 and 104 are connected. Data exchange between the measuring head 20 and the control unit 44, as well as power supply to the measuring head 20, preferably takes place via the data interfaces 100 and 104.

[0123] For the clearly defined mounting of the first measuring head interface 46 at the positioning system interface 48, three pairs of balls 108 are arranged at the positioning system interface 48, which interact with three rollers 110 arranged at the first measuring head interface 46. The pairs of balls 108 as well as the cylindrical rollers 110 are each arranged at an angular distance of 60° to each other. They thus each form an equilateral triangle.

[0124] The first measuring head interface 46 and the positioning system interface 48 each have a locking device 112, which is shown in detail in Figures 20 and 21. This locking device 112 has a locking anchor 114 arranged at the positioning system interface and an anchor plate 116 designed as an anchor counterpart, which is part of the first measuring head interface 46.

[0125] The locking anchor 114 is linearly movable along the z-axis relative to the other parts of the positioning system interface 48 by a motor. In addition, the locking anchor 114 is rotatable around the z-axis by a motor. When locking, the The locking anchor 114 is inserted into the anchor plate 116 as shown in Fig. 20 by moving it linearly in the negative z-direction. This is indicated by arrow 118 in Fig. 20. The locking anchor 114 is then rotated about the z-axis, as indicated by arrow 120 in Fig. 21, and subsequently retracted in the z-direction. Fig. 20 shows the unlocked state of the locking device 112. Fig. 21 shows the locked state of the locking device 112.

[0126] To minimize unwanted transverse forces between the locking anchor 114 and the anchor plate 116, the locking anchor 114 and / or the anchor plate 116 can be coated with a sliding friction-reducing coating, in particular made of PTFE. Another way to avoid unwanted transverse forces is to mount the locking anchor 114 and / or the anchor plate 116 so that it is floating in the xy direction. In this way, the locking anchor 114 and / or the anchor plate 116 can perform lateral compensating movements during the coupling process of the measuring head adapter 34 or the measuring head 20 to the positioning system interface 48. However, it should be ensured that both the locking anchor 114 and the anchor plate 116 are immobile in the z direction, in particular axially, during this coupling process.

[0127] The positioning system interface 48 and the first measuring head interface 46 also have a centering device 122, which is configured to center the measuring head adapter 34 or measuring head 20 relative to the positioning system 18 in the xy-horizontal plane during the coupling process. This centering takes place before the two data interfaces 100, 104 come into contact with each other.

[0128] The centering device 122 includes two centering bolts 124, 126, which are inserted into two fitting sleeves 128, 130 during the coupling process. In the present embodiment, the two centering bolts 124, 126 are part of the positioning system interface 48. The two fitting sleeves 128, 130, on the other hand, are part of the first measuring head interface 46 in the present embodiment. It is understood, however, that the reverse arrangement can also be chosen.

[0129] As can be seen particularly in Figures 14 and 15, each of the two centering pins 124, 126 is conically shaped in the region of its lower, free end to allow for the easiest possible, collision-free insertion into the respective fitting sleeve 128, 130. Adjacent to this conical section 132, in the case of the first centering pin 124, is a section 134 of increased diameter, and adjacent to this, in turn, is a section 136 with a comparatively small diameter. Both sections 134, 136 are cylindrical in this case. The diameter of the first section 134 is preferably adapted to the diameter of the fitting sleeve 128.

[0130] Thus, the first section 134, with its larger diameter, is used to initially center the component. As the centering bolt 124 is inserted further, the reduced diameter of the second section 136 results in a small (but greater compared to section 134) lateral play in the fitting sleeve 128. This allows for free lateral movement of the centering bolt 124 in the xy-horizontal plane within the fitting sleeve 128.

[0131] The same principle is preferably applied to the second centering pin 126, which interacts with the second fitting sleeve 130. However, the second centering pin 126 is intentionally chosen to be somewhat shorter than the first centering pin 124, so that during the coupling process it comes into contact with its associated fitting sleeve 130 after the first centering pin 124.

[0132] A coupling process in which the measuring head 20 is removed from the magazine 38 during a measuring head change and is coupled to the positioning system interface 48 of the positioning system 18 proceeds in particular as follows.

[0133] The positioning system interface 48 is controlled by the control unit 44 and moved to a predefined initial position relative to the first measuring head interface 46 by means of the positioning system 18. Subsequently, the position control of the positioning system 18 is deactivated, and the positioning system interface 48 is accelerated in the negative z-direction by means of the positioning system 18 and thus to the first The measuring head interface 46 is moved. This can advantageously be achieved by driving the drive axis of the quill 30 with a constant current. Preferably, the instantaneous actual speed of the positioning system interface 48 along the drive axis is repeatedly recorded, and the speed profile thus obtained is filtered with a low-pass filter. As soon as the positioning system interface 48 has reached a defined target speed, the acceleration phase is terminated, and the control unit 44 adopts (preferably after a defined waiting period or settling phase) the current drive current value as the target current value for current-controlled movement of the positioning system interface 48. The positioning system interface 48 is thus moved in current-controlled operation with a defined drive current, which preferably results from the previously achieved defined speed.The latter has the advantage that the defined drive current automatically adapts to individual environmental conditions such as temperature, wear, axle stiffness, etc. Individual calibration is therefore unnecessary. Preferably, superimposed speed and / or position controllers are deactivated during this phase of the probing or coupling process.

[0134] As mentioned, during coupling, the two centering pins 124, 126 first come into contact with the respective fitting sleeves 128, 130 and ensure that the positioning system interface 48 is centered relative to the first measuring head interface 46. This type of positioning is possible in particular due to the floating bearing of the measuring head adapter 34 in the measuring head receptacle 74.

[0135] The two data interfaces 100 and 104 then come into contact with each other. Due to the spring-loaded pins 102, this generates a spring force opposing the feed of the positioning system interface 48. The current-controlled feed movement of the positioning system interface 48 exerts a force on the measuring head adapter 34 or the measuring head 20, which prevents upward movement of the measuring head adapter 34 or the measuring head 20 in the z-direction relative to the measuring head receptacle 74 during the entire coupling process. This ensures that the measuring head adapter 34 or the measuring head 20, despite its fundamental ability to move in the z-direction (see clearances 92 in Fig. 12), does not move upward in the z-direction and thus does not lift out of the measuring head receptacle 74 during the coupling process. This occurs, in particular, when the locking anchor 114 plunges into the anchor plate 116 and the anchor plate 116 is locked by a rotational movement and a subsequent axial movement.

[0136] In some embodiments, the control unit 44 uses the position sensors 29 to detect the current actual position of the positioning system interface 48 in the direction of movement, in this case along the z-axis. Furthermore, based on the speed, which is preferably reached at the end of the acceleration phase, the control unit 44 determines a current target position of the positioning system interface 48 along the drive axis. The difference between the target position and the actual position represents the so-called following error. In some embodiments, the control unit 44 monitors the following error. As soon as the following error exceeds a predefined threshold, this is detected as physical contact between the positioning system interface 48 and the measuring head interface 46.In some advantageous embodiments, the transfer position is determined in this way, at which the locking armature 114 is rotated against the armature plate 116 to lock the positioning system interface 48 and the measuring head interface 46 against each other. Alternatively or additionally, the control unit can detect the transfer position based on an increase in the drive current.

[0137] With such a movement, the control unit 44 can also measure the measuring head magazine 38 sensorlessly before a coupling process by probing the measuring head magazine 38 and / or a measuring head adapter 34 held on the measuring head magazine 38 with a (preferably rigid) free end of the positioning system 18, for example with an edge of the quill 30 or with one of the centering pins 124, 126. The physical contact can be detected based on the tracking error and / or the drive current in the manner described above. Advantageously, in these embodiments, the control unit 44 determines a position measurement value with the aid of the position encoders 29, which represents the location of the physical contact, i.e., the contact position along the direction of movement from which the probing was carried out.In preferred embodiments, the measuring head magazine 38 is probed in this way at three different points and / or from three different directions in order to calibrate the measuring head magazine 38 with respect to the three spatial axes x, y, z. Preferably, the control unit 44 reduces the... The drive current drops to zero as soon as physical contact is detected, thus stopping the feed movement. Preferably, the control unit 44 then moves the free end of the positioning system in the opposite direction to terminate the physical contact.

[0138] In some embodiments, the measuring head magazine 38 can have a plurality of predefined contact points 137 which form or include a self-centering receptacle for the free end of the positioning system 18 (see Fig. 2)

[0139] In some embodiments, the positioning system interface 48 can have three distance sensors, which are referred to here as the first distance sensor 138, the second distance sensor 140, and the third distance sensor 142. These distance sensors 138, 140, and 142 are preferably optical sensors. They serve to measure the distance between the positioning system interface 48 and the measuring head component to be coupled, in this case, the measuring head adapter 34.

[0140] Each of these three distance sensors 138, 140, 142 generates a corresponding sensor signal, which is processed in the control unit 44. The control unit 44 is configured to determine a calculated value from the three sensor signals, which depends on the relative orientation of the first measuring head interface 46 relative to the positioning system interface 48. Instead of an absolute measurement, the control unit 44 determines, for example, a relative difference between the three sensor signals as the calculated value. In particular, the control unit 44 determines a vectorial calculated value, e.g., a normal vector, which describes the relative orientation of the first measuring head interface 46 relative to the positioning system interface 48.

[0141] Furthermore, the control unit 44 is configured to compare the calculated value with a reference value stored in a storage unit 144. The storage unit 144 is shown schematically in Fig. 1. It can, for example, be a hard drive, an SSD, or a cloud server. The reference value is, for example, measurement data generated during a calibration process on a reference sphere.

[0142] Thus, for example, it is possible during each changeover process in which a measuring head 20, 20' is placed in the magazine 38 and another measuring head 20, 20' is removed from the magazine 38, to read out the sensor signals generated by the distance sensors 138, 140, 142 using the control unit 44 and to compare them with the reference quantity stored in the storage unit 144.

[0143] The control unit's reaction to possible detected measurement deviations of the distance sensors 138, 140, 142 relative to the reference measurement can be varied.

[0144] For example, if a measurement deviation is detected in the coupled state, i.e., a detected difference between the calculated quantity determined from the sensor signals relative to the reference quantity, the control unit 44 can generate a control signal that generates visual, haptic and / or auditory feedback if the determined difference exceeds a predefined threshold.

[0145] It is also possible for the control unit 44 to generate a control signal based on a comparison of the calculated value derived from the sensor signals with the reference value, and based on this signal, a pose and / or movement of the positioning system 18 is corrected. For example, the determined probe data can be adjusted accordingly. In this way, errors that are constant over a measurement sequence are computationally compensated.

[0146] Furthermore, the control unit 44 can be configured to correct detected rotations and / or tilts of the first measuring head interface 46 relative to the positioning system interface 48 in real time, so that even with non-constant movement of the two interfaces 46, 48 relative to each other, the measured values ​​of the object measured by the control unit remain correct.

[0147] In some embodiments, the distance sensors 138, 140, 142 can be used by the control unit 44 during the coupling process of the measuring head adapter 34 to the positioning system 18, as shown in Figures 14 and 15. For example, the distance sensors 138, 140, 142 can help prevent the immersion of the The locking anchor 114 can be inserted into the anchor plate 116 before the interfaces 46, 48 are connected to each other. The distance sensors 138, 140, 142 are preferably aligned in the z-direction for this purpose. Three structures 146, 148, 150, which function as counterparts to the distance sensors 138, 140, 142, are arranged at the first measuring head interface 46 (see Figs. 17 and 19). These structures can, for example, be pyramid-shaped or conical, so that corresponding preferred positions are formed in the center of these structures 146, 148, 150, at which the distance sensors 138, 140, 142 measure. In other words, the distance between these structures 146, 148, 150 and the distance sensors 138, 140, 142 will be minimal when the optimal lateral alignment in the xy-horizontal plane between the two interfaces 46, 48 is achieved.

[0148] To determine the optimal lateral position, the control unit 44 can, in some embodiments, perform a gradient method in which the positioning system interface 48 is moved in an arbitrary direction, e.g., in the x-direction. Depending on the magnitude of the change in the signal from the distance sensors 138, 140, 142, the factor (positive and negative) is determined. The same process is then repeated orthogonally, e.g., in the y-direction. This process can be repeated multiple times if necessary.

[0149] A second possibility is that the control unit 44 controls the positioning system 18 such that the positioning system interface 48 performs a movement along an X or a meandering movement in the x,y horizontal plane, whereby the expected shape of the signal is fitted using the data points, e.g., a Gaussian curve for Hall sensors or the shape of the counterpart for optical sensors. The center position of this shape then corresponds to the optimal lateral relative position of the measuring head interface 46 relative to the positioning system interface 48.

[0150] Preferably, the same types of distance sensors 138, 140, 142 are used. Due to the described relative evaluation of the sensor signals, comparatively inexpensive sensor systems can be used that have low linearity and constant drift. The sensors 138, 140, 142 are preferably evaluated with identical circuitry (amplifiers) so that temperature changes are reflected equally. All sensors 138, 140, 142 are affected. As long as a temperature-dependent drift occurs similarly in all sensors 138, 140, 142, this is virtually averaged out by the described relative evaluation of the sensors.

[0151] To detect rotations about the z-axis, in some embodiments additional sensors, for example a fourth distance sensor, can be mounted transversely to the z-direction, as shown schematically in Fig. 22A. Advantageously, three such transversely arranged distance sensors 146 are mounted at the positioning system interface 48.

[0152] The number of distance sensors is preferably greater than the degrees of freedom to be detected. When detecting a tilt (rx and ry), at least three distance sensors are necessary to distinguish between measurement system drift and changes in distance. Furthermore, it is advantageous to detect both the positive and negative movements of a given degree of freedom. For example, when detecting movement in the x-direction, it is advantageous to detect both the positive and negative x-directions. Therefore, preferably, n + 1 sensors are used for n degrees of freedom to be detected. Ideally, 2n sensors are used.

[0153] Figures 22A-22D show various possible sensor orientations in schematic representation. Figure 22A shows, as already mentioned, an arrangement of a fourth distance sensor 145, which is oriented transversely, preferably orthogonally, to the three first distance sensors 138, 140, 142. Figure 22B schematically shows the situation that was explained with reference to the embodiment shown in Figures 16-19, in which the three distance sensors 138, 140, 142 each measure vertically along the z-axis against a raised counter surface 146, 148, 150. Figure 22C shows a modification of the embodiment shown in Figure 22B. With the same arrangement of the distance sensors 138, 140, 142, the counter surfaces 146', 148', 150' are slightly modified here. In particular, the opposite surfaces 146', 148', 150' are smaller compared to the opposite surfaces 146, 148, 150.In particular, the counter surfaces 146', 148', 150' are circularly milled counter surfaces, i.e., counter surfaces surrounded by a depression and raised above this depression. Such a structure as a counter surface makes it possible in a suitable manner to define the near and far range, which is the case for such surfaces. Distance sensors 138, 140, 142 typically have to be used for the present measurement.

[0154] Figure 23 shows a diagram illustrating the collector current as a relative value of its maximum over the measured distance for a distance sensor. It shows that, particularly in the near range (< 0.4 mm), the collector current behaves approximately linearly with respect to the measured distance and exhibits a high slope. This high slope provides high sensitivity in the near range, resulting in high position resolution. Linearity is achieved due to the relative measurement. The distance sensors themselves may be non-linear and drift, as long as the three distance sensors exhibit the same behavior. In the far range (> 1.5 mm), this behavior is only approximately linear, although this linearity is sufficient for the present measurement.

[0155] With a counter surface 146', 148', 150' as shown in Fig. 22C, which is surrounded by a recess and raised relative to it, the aforementioned sensor properties can be utilized as follows: The distance sensors 138, 140, 142 measure against this counter surface 146', 148', 150' during a coupling process of the measuring head component 34, 20. The depth of the recess surrounding the counter surface 146', 148', 150' is distinguishable at a distance of the distance sensors 138, 140, 142, e.g., 1 mm. Thus, during the coupling process, it can be checked from a certain distance whether the measurement is being taken against the desired measuring points on the counter surfaces 146', 148', 150' or into the surrounding recess. For this purpose, the approximate linearity in the far range of the distance sensors 138, 140, 142 is sufficient.When the interfaces 46, 48 are fully coupled together, the desired measuring point of the distance sensors 138, 140, 142 is then in the immediate vicinity, so that measurements can be taken with high accuracy against the corresponding points.

[0156] Fig. 22D further shows one possible way of mounting the fourth distance sensor 145'. Here, the fourth distance sensor 145' is oriented such that it enables measurement in the negative z-direction. It is, so to speak, oriented upside down, with its measuring direction having at least one directional component in the positive z-direction. In principle, it could even be oriented in this case so that it measures exactly in the positive z-direction. It measures the z-direction. However, it is sufficient if its measurement direction has at least a small directional component in the positive z-direction.

[0157] Various other alignment options for the distance sensors 138, 140, 142, 145 are of course conceivable without leaving the scope of the present invention.

Claims

Patent claims 1. Coordinate measuring machine (10), comprising: a positioning system (18) with at least one driven axis (x, y, z) and a positioning system interface (48) for coupling a measuring head (20, 20') to the positioning system (18), wherein the positioning system interface (18) has a first data interface (100) and a locking device (112) for locking the measuring head (20, 20'); a measuring head (20, 20') having a first measuring head interface (46) which is configured to be detachably coupled to the positioning system interface (48) and which has a second data interface (104) which cooperates with the first data interface (100) for data exchange when the positioning system interface (48) is coupled to the first measuring head interface (46);a magazine (38) with at least one measuring head receptacle (74) for receiving and holding the measuring head (20, 20'), wherein the measuring head receptacle (74) is configured to support the measuring head (20, 20') received therein in a vertical z-direction and to prevent rotation about a horizontal x-direction orthogonal to the z-direction as well as rotation about a horizontal y-direction orthogonal to the z-direction and the x-direction, and to mount the measuring head received therein in a movable, in particular floating, position in an xy-horizontal plane spanned by the x-direction and the y-direction and rotationally about the z-direction;and a control unit (44) for controlling the positioning system (18), which is configured to control the positioning system (18) during a coupling process in which the measuring head (20, 20') held in the measuring head receptacle (74) is coupled to the positioning system (18) and locked by means of the locking device (112), such that the positioning system (18) exerts a force on the measuring head (20, 20') by which a movement of the measuring head (20, 20') in the z-direction relative to the measuring head receptacle (74) during the entire coupling process; is prevented until the locking device (112) has fully locked the measuring head (20, 20').

2. Coordinate measuring machine according to claim 1, wherein the control unit (44) is configured to (i) to position the positioning system interface (48) at the beginning of the coupling process at a transfer position relative to the first measuring head interface (46), where the positioning system interface (48) and the first measuring head interface (46) are opposite each other and have a predefined distance from each other or are in contact with each other, in particular at the first and the second data interface (100, 104), and subsequently (ii) to generate a control signal by which the position control of the at least one driven axis (x, y, z) of the positioning system (18) is deactivated during the coupling process and the positioning system interface (48) is moved in a negative z-direction opposite to the z-direction.

3. Coordinate measuring machine according to claim 1 or 2, wherein the control unit (44) is configured to control the positioning system (18) during the coupling process such that the sum of a weight force of the measuring head (20, 20') acting in the negative z-direction and the force acting in the negative z-direction which the positioning system (18) exerts on the measuring head (20, 20') is equal to or greater than the sum of a locking force exerted in the z-direction by the locking device (112) on the measuring head (20, 20') and a coupling force acting between the first and second data interface (100, 104).

4. Coordinate measuring machine according to one of claims 1-3, wherein the first data interface (100) has a first connecting element (102) and the second data interface (104) has a second connecting element (106) designed as a counterpart to the first connecting element (102), and wherein at least one of the two connecting elements (102, 106) has a spring-loaded connecting element, in particular several spring-loaded pins.

5. Coordinate measuring device according to one of claims 1-4, wherein the locking device (112) has a locking anchor (114) which is linearly movable along the z-direction relative to the first data interface (100) and rotatable about the z-direction.

6. Coordinate measuring instrument according to claim 5, wherein the locking anchor (114) and / or an anchor counterpart (116) cooperating with the locking anchor (114), which is arranged at the first measuring head interface (46), is coated with a sliding friction reducing coating, which in particular comprises PTFE.

7. Coordinate measuring instrument according to claim 5, wherein the locking anchor (114) and / or an anchor counterpart (116) cooperating with the locking anchor (114), which is arranged at the first measuring head interface (46), is movably, in particular floatingly, mounted in the xy-horizontal plane.

8. Coordinate measuring machine according to one of claims 1-7, wherein the positioning system (18) has a quill (30) movable in the z-direction, at the free end of which the positioning system interface (48) is arranged.

9. Coordinate measuring machine according to one of claims 1-8, wherein the positioning system interface (48) and the first measuring head interface (46) have a centering device (122) which is configured to center the measuring head (20, 20') in the xy-horizontal plane relative to the positioning system (18) during the coupling process before the first data interface (100) comes into contact with the second data interface (104).

10. Coordinate measuring device according to claim 9, wherein the centering device (122) has a centering pin (124) which in the area of ​​its free, end face The end has a tapered, in particular conical or spherical, first section (134) and a second section (136) spaced apart from or adjacent to the first section (134), the diameter of which is smaller than that of the first section (134).

11. Coordinate measuring machine according to one of claims 1-10, wherein the measuring head mount (74) has a magazine slot interface (52) which can be detachably coupled to a second measuring head interface (54) arranged on the measuring head (20, 20'), wherein the magazine slot interface (52) has three support surface sections (80, 80', 80") spaced apart from each other, the centers of which form a triangle.

12. Coordinate measuring device according to claim 11, wherein the magazine slot interface (52) has three arms (78, 78', 78") projecting separately and spaced apart from a base body (76) of the measuring head receptacle (74), wherein one of the support surface sections (80, 80', 80") is arranged on each of the three arms (78, 78', 78").

13. Coordinate measuring machine according to claim 11 or 12, wherein the second measuring head interface (54) and the magazine slot interface (52) are designed such that the three arms (78, 78', 78") parallel to the xy-horizontal plane have lateral play relative to the second measuring head interface (54), in particular lateral play in the range of 0.1 mm to 2 mm, when the measuring head (20, 20') is received and held in the measuring head receptacle (74).

14. Method for coupling a measuring head (20, 20') of a coordinate measuring machine (10) to a positioning system (18) of the coordinate measuring machine (10), comprising: Providing a positioning system (18) with at least one driven axis (x, y, z) and a positioning system interface (48) for coupling a measuring head (20, 20') to the positioning system (18), wherein the positioning system- interface (48) has a first data interface (100) and a locking device (112) for locking the measuring head (20, 20'); Providing a measuring head (20, 20') which has a first measuring head interface (46) which is configured to be detachably coupled to the positioning system interface (48) and which has a second data interface (104) which cooperates with the first data interface (100) for data exchange when the positioning system interface (48) is coupled to the first measuring head interface (46); Providing a magazine (38) with at least one measuring head receptacle (74) for receiving and holding the measuring head (20, 20'), wherein the measuring head receptacle (74) is configured to support the measuring head (20, 20') received therein in a vertical z-direction and to prevent rotation about a horizontal x-direction orthogonal to the z-direction as well as rotation about a horizontal y-direction orthogonal to the z-direction and the x-direction, and to mount the measuring head (20, 20') received therein in a movable, in particular floating, position in an xy-horizontal plane spanned by the x-direction and the y-direction and rotationally about the z-direction; and Controlling the positioning system (18) to perform a coupling process in which the measuring head (20, 20') held in the measuring head receptacle (74) is coupled to the positioning system (18) and locked by means of the locking device (112), wherein the positioning system (18) is controlled such that it exerts a force on the measuring head (20, 20') which prevents movement of the measuring head (20, 20') in the z-direction relative to the measuring head receptacle (74) during the entire coupling process until the locking device (112) has completely locked the measuring head (20, 20').

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