Method for automated coupling and / or uncoupling of a measuring-head component to or from a positioning system of a coordinate measuring device

Abstract

The invention relates to a coordinate measuring device comprising a positioning system (18) that has: a free end (30); a positioning system interface in the region of the free end (30); and at least one drive axis (x, y, z). A measuring-head magazine (38) having at least one measuring-head receptacle for a measuring head (20) is arranged in the region of a base (12). The measuring head (20) comprises a measuring-head sensor (32) and a measuring-head interface. In order to automatedly couple the measuring head (20), the positioning system interface (48) is moved, without a measuring-head sensor (32), to a defined transfer position relative to the measuring-head receptacle. Beforehand, the free end (30) is targetedly brought into physical contact with the measuring-head magazine (38) and a contact position representing the physical contact is determined with the aid of the positioning system (18). The contact position can advantageously be determined on the basis of a contouring error. The defined transfer position is determined depending on the at least one contact position.

Description

Method for the automated coupling and / or decoupling of a measuring head component to or from a positioning system of a coordinate measuring machine

[0001] The present invention relates to methods for coupling a measuring head or measuring head component to a positioning system of a coordinate measuring machine. The invention further relates to a method for decoupling such a measuring head component from the positioning system, as well as to a coordinate measuring machine in which the methods are advantageously implemented. In particular, the present invention thus relates to methods by which measuring heads can be automatically mounted and exchanged on a 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 102013 105753 B3 or from DE 102019 122 049 B4.

[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 118215 B3, DE 101 14 126 B4 and DE 102010 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 used directly 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 generally be divided into tactile and optical measuring head sensors. Tactile measuring heads or measuring head sensors are used, for example, by the applicant. under the product names ZEISS XDT®, ZEISS XXT® and ZEISS VAST®. Optical measuring heads or measuring head sensors are sold 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 the tactile probe or optical element alone. 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. Consequently, the required tilting stiffness is higher, since high accelerations result in correspondingly high forces at the interface due to the sensor's high mass. Furthermore, in the Due to its function, a measuring head sensor is typically more prone to heating, which can negatively affect dimensional accuracy, than a tactile probe element or optical element.

[0013] For a reliable and reproducible change of a measuring head, it is essential that the individual magazine slots are precisely positioned and aligned, and that their position and orientation are known. This is particularly important when the measuring head change is automated, i.e., performed by the coordinate measuring machine itself using a pre-programmed control unit. Furthermore, it must be ensured that the precise positioning and alignment of the magazine slots are maintained over numerous changes and even under fluctuating temperatures. Otherwise, variations in reproducibility can lead to undetected measurement errors.

[0014] If the magazine positions are not precisely aligned, this can lead to messy, unreliable, and error-prone measuring head changes. Furthermore, increased friction can cause wear and tear. In the worst case, this can result in damage 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, and on a corresponding method for changing 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 aforementioned prior art documents for the detachable coupling of a measuring probe to a measuring head sensor are therefore only conditionally suitable, or not at all suitable, as interchangeable interfaces for Coupling of an entire measuring head to the positioning system of a coordinate measuring machine.

[0017] The aforementioned German patent DE 102019 122 049 B4 describes a method for mounting or changing a measuring head on the quill of a coordinate measuring machine. In this process, the quill is moved at least partially without a measuring head and, in particular, without a measuring head sensor. The centering process for coupling the measuring head to the interface is performed by acquiring and evaluating at least one actual current value from at least one drive axis of the coordinate measuring machine. The actual current value increases when the quill encounters an obstacle, and the method provides that the quill performs an evasive movement when a first target current value is exceeded by the actual current value.

[0018] The known method primarily concerns centering the quill interface when coupling it to a measuring head held in a magazine (referred to therein as a probe or sensor holder). DE 102019 122 049 B4 does not describe how the position and orientation of the magazine slot can be determined efficiently. Nor does DE 102019 122 049 B4 describe how a measuring head can be detached from a positioning system of a coordinate measuring machine and placed in a magazine in a low-wear and efficient manner.

[0019] Against this background, an object of the present invention is to provide alternative methods for the automated coupling and / or decoupling of a measuring head or measuring head component to and from a positioning system of a coordinate measuring machine. In particular, it is an object to provide methods that enable a rapid and low-wear change of a measuring head in a largely automated operating sequence. It is also an object to provide methods for automated measuring head changes that enable reliable and low-wear coupling or decoupling under changing environmental conditions, such as, in particular, changing temperatures. A further object is to provide methods for automated To provide measuring head exchanges that offer great design freedom with regard to the position and orientation of the respective measuring head mounts in an exchangeable magazine. Finally, it is a task to specify coordinate measuring machines that implement the appropriate procedures.

[0020] According to a first aspect of the invention, a method for the automated coupling of a measuring head component to a positioning system of a coordinate measuring machine is therefore proposed, wherein the positioning system has a free end, a positioning system interface in the region of the free end and at least one drive axis, wherein the measuring head component comprises a measuring head sensor, wherein the positioning system interface has a locking anchor for releasably locking the measuring head component to the positioning system interface, and wherein the at least one drive axis is configured to move the free end together with the positioning system interface relative to a base of the coordinate measuring machine, with the steps - Providing a measuring head magazine with at least one measuring head receptacle in the base area, - Placing the measuring head component in the measuring head holder, - (preferably automated) moving of the positioning system interface without a measuring head sensor to a defined transfer position relative to the measuring head mount using the positioning system, - Locking the measuring head component at the positioning system interface using the locking anchor at the defined transfer position, and - Moving the positioning system interface with the measuring head component locked to it to a working position away from the measuring head mount using the positioning system, wherein the free end is deliberately moved into the defined transfer position using at least one drive axis before moving the positioning system interface to the defined transfer position. physical contact is brought into contact with the measuring head magazine, wherein at least one contact position representing the physical contact of the free end with the measuring head magazine is determined by means of the positioning system, and wherein the defined take-up position is determined as a function of the at least one contact position.

[0021] According to a further aspect of the invention, a method for the automated coupling or uncoupling of a measuring head component to or from a positioning system of a coordinate measuring machine is proposed, wherein the positioning system has a positioning system interface and at least one drive axis, wherein the measuring head component has a measuring head interface and a measuring head sensor, wherein the positioning system interface has a locking anchor for releasably locking the measuring head interface, and wherein the at least one drive axis is configured to move the positioning system interface relative to a base of the coordinate measuring machine, with the steps - Providing a measuring head magazine with at least one measuring head receptacle in the base area, - Providing the measuring head component, - Moving the positioning system interface to a defined transfer position relative to the measuring head mount using the positioning system, - Locking the measuring head interface to the positioning system interface using the locking anchor at the defined transfer position in the case of coupling, or unlocking the measuring head interface from the positioning system interface using the locking anchor at the defined transfer position in the case of decoupling, and - Moving the positioning system interface with the measuring head component locked to it to a working position using the positioning system. the measuring head receptacle is removed, in the case of coupling, or the positioning system interface is moved without the measuring head component to a working position that is removed from the measuring head receptacle, in the case of decoupling, wherein the positioning system has at least one position encoder that provides a position signal which represents an actual position of the positioning system interface along the at least one drive axis, wherein the positioning system interface is moved at a defined speed along the at least one drive axis to the defined transfer position and there, in the case of coupling, comes into physical contact with the measuring head interface or, in the case of decoupling, causes physical contact of the measuring head component with the measuring head receptacle, and wherein the respective physical contact is determined on the basis of the defined speed and on the basis of the position signal.

[0022] According to yet another aspect of the invention, a coordinate measuring machine is proposed, comprising a base, a measuring head magazine with at least one measuring head receptacle in the region of the base, at least one measuring head component comprising a measuring head sensor and a measuring head interface, wherein the measuring head component can be stored in the measuring head receptacle, a positioning system comprising a free end, a positioning system interface in the region of the free end, and at least one drive axis configured to move the free end relative to the base, wherein the positioning system interface further comprises a locking anchor for releasably locking the measuring head component to the positioning system interface, and a control unit configured to perform methods of the type described herein.to couple the measuring head component to the positioning system interface using the positioning system and remove it from the measuring head holder, or to place the measuring head component in the measuring head holder using the positioning system and disconnect it from the positioning system interface.

[0023] The new methods and the corresponding coordinate measuring machine have in common that an outer contour, such as a protruding surface, tip and / or edge, which is relative to the positioning system along at least one drive axis, is used. When a device is moved towards the measuring head magazine, it is deliberately and intentionally brought into physical contact with it. Physical contact with the measuring head magazine in this case means that the magazine absorbs a force that is introduced into it via the outer contour at the beginning of physical contact. Due to Newton's third law (action = reaction), the measuring head magazine generates a corresponding counterforce. The physical contact of the outer contour with the measuring head magazine can be direct or indirect. Direct contact means that the outer contour touches one or more surfaces that are permanently an integral part of the measuring head magazine. Indirect contact means that the force exerted by the outer contour is introduced into the measuring head magazine via a component that is mechanically and, in particular, rigidly connected to the measuring head magazine at the time of contact.The latter is the case in some preferred embodiments, in which the outer contour deliberately contacts a measuring head adapter described below, thus transmitting a force into the measuring head magazine via the measuring head adapter. The measuring head magazine, or a component mechanically connected to it at the time of contact, is therefore physically probed, as is well known in the field of coordinate measuring technology when measuring an object with a tactile measuring head.

[0024] Unlike the conventional tactile measurement of a workpiece, the probing in this case is "sensorless" in the sense that the time and / or location of physical contact is determined without the need for a measuring head, i.e., a dedicated contact sensor. Instead, the new methods and the corresponding coordinate measuring machine use information provided by the positioning system independently of physical contact, and they determine the location and / or time of physical contact based on, i.e., using, this information. In other words, physical contact is detected based on signals inherent in the positioning system of the coordinate measuring machine. These signals are, in particular, position signals originating from the position encoders of the drive axes, which, during normal operation, provide the current actual positions for the drive control loops of the coordinate measuring machine.For example, the position signals used for contact detection can be captured using linear scales and / or encoders, which provide input signals for. The drive control loops of the coordinate measuring machine provide the necessary information. In some preferred embodiments, the time and / or location of physical contact is determined based on the so-called following error of the drive control loops. The following error is the difference between the target position and the actual position of the moving contour along the at least one drive axis. The following error increases significantly upon physical contact during movement. Advantageously, the target position can be determined based on the control data used to move the outer contour along the at least one drive axis, while the actual position is determined based on the position signals from the position encoders. Alternatively or additionally, the time and / or location of physical contact can also be determined based on at least one drive current used to control an electric drive of the positioning system to move the outer contour.Such a drive current is also a controlled variable that is inherently present in the positioning system of the coordinate measuring machine.

[0025] The new methods and the corresponding coordinate measuring machine also share the characteristic that the coupling process, and in particular the coupling movement of the positioning system interface and / or the actuation of the locking anchor, is executed depending on the previously detected physical contact. The physical contact of the outer contour with the measuring head magazine and the information obtained thereby, which represents a position of the measuring head magazine relative to the outer contour, are advantageously used in subsequent movements of the positioning system interface to couple and / or decouple a measuring head component at the positioning system interface.The control unit can therefore execute the coupling movement and / or the actuation of the locking anchor in a targeted, safe, and low-wear manner based on position information determined by a movement that precedes the coupling or uncoupling process and is preferably completed before the coupling or uncoupling takes place. In particular, the position information obtained through physical contact between the outer contour and the measuring head magazine can thus be used for multiple subsequent coupling and / or uncoupling operations.

[0026] According to one aspect of the invention, the outer contour can be an externally accessible contour at a movable free end of the positioning system, for example. An outer edge or surface on the quill or horizontal arm of a coordinate measuring machine. In some embodiments, the outer contour may be a housing exterior, a projecting edge of the quill or horizontal arm, and / or an end face of an end effector. Furthermore, the outer contour may be a pin or a projecting surface at the positioning system interface. In some preferred embodiments, the outer contour that comes into physical contact with the measuring head magazine is rigidly mounted on the positioning system; that is, the outer contour is neither flexible nor pivotable with respect to the positioning system.

[0027] In contrast to the method described in the aforementioned DE 102019 122 049 B4, the first aspect of the invention determines at least one contact position representing the physical contact of the free end with the measuring head magazine. Subsequently, depending on the individually obtained contact position, the defined transfer position is determined at which the measuring head component is locked to the positioning system interface using the locking anchor. This means that the new method and coordinate measuring machine can actuate the locking anchor reliably and with minimal wear, regardless of temperature fluctuations and the resulting positional changes. Furthermore, attaching and detaching a measuring head can be done quickly and efficiently because the defined transfer position is determined by the prior physical contact.This measurement is advantageously automated using the new methods and the corresponding coordinate measuring machine.

[0028] Furthermore, calibrating the measuring head magazine with the positioning system without a measuring head attached to it offers the advantage that the measuring head magazine can extend deeper into the positioning system's range of motion than in other cases where a measuring head is used to calibrate the magazine to the positioning system. The installation space occupied by the measuring head is thus eliminated. For example, in a gantry or bridge-type coordinate measuring machine, the measuring head magazine can be positioned higher than previously possible. Conversely, a new coordinate measuring machine with an interchangeable magazine can be designed more compactly. The new methods therefore enable greater [application / application / etc.]. Design freedom regarding the position and orientation of the measuring head mounts of an interchangeable magazine.

[0029] Furthermore, the method described in the second aspect offers the advantage that the actuation of the locking armature at the defined transfer position can occur in continuous contact between the positioning system interface and the measuring head interface, controlled by the positioning system. In particular, a defined probing force can be generated during the coupling process for at least one drive axis using the drive control. This contributes advantageously to a reliable and reproducible coupling or placement of the measuring head in the measuring head holder.

[0030] The tasks mentioned above have therefore been completely solved.

[0031] In a preferred embodiment of the above-mentioned methods and the coordinate measuring machine, the free end is brought into physical contact with the measuring head magazine without the positioning system interface carrying a measuring head sensor.

[0032] As mentioned above, the new methods, by their very nature, do not require a dedicated sensor to detect physical contact between the outer contour of the positioning system and the measuring head magazine. Nevertheless, it is still possible, in principle, to perform the calibration using a measuring head sensor located at the positioning system interface. In this case, too, the contact position can be additionally determined using the inherent signals of the positioning system. The preferred design requires less space within the movement range of the positioning system and therefore offers greater design flexibility in positioning the measuring head mounts.

[0033] In a further embodiment of the above-mentioned methods and the coordinate measuring machine, the positioning system has at least one position encoder that provides a position signal which indicates the actual position of the positioning system. Interface along at least one drive axis, where the at least one contact position is determined based on the position signal.

[0034] This design enables a cost-effective and very precise implementation, since suitable position encoders are typically available in a coordinate measuring machine and provide very precise position information along the drive axes.

[0035] In a further embodiment of the above-mentioned methods and the coordinate measuring machine, the free end is moved along the at least one drive axis at a defined first velocity to effect physical contact with the measuring head magazine, wherein the at least one contact position is further determined on the basis of the defined first velocity.

[0036] In this configuration, the contact position can be determined very precisely based on the following error of at least one drive axle. As mentioned above, the following error can be determined as the difference between the target and actual positions. The target position can be determined very simply and efficiently based on the defined initial velocity. Therefore, this configuration contributes to a cost-effective and efficient implementation.

[0037] In a further embodiment of the aforementioned methods and the coordinate measuring machine, the free end is first accelerated to the defined first velocity to determine the at least one contact position, and then the free end is moved at the defined first velocity until physical contact is reached. After reaching the contact position, the free end is preferably moved in the opposite direction to terminate the physical contact.

[0038] In this embodiment, the positioning system brings the free end into physical contact with the measuring head magazine from a constant-speed movement. Preferably, the constant speed is a maximum of 1 mm / s, particularly preferably in the range of 0.5 mm / s. The constant speed facilitates The determination of the target position, and thus the determination of the contact position, enables a very efficient and cost-effective implementation. The movement in the opposite direction terminates the physical contact and helps to minimize the forces exerted on the measuring head magazine and the positioning system overall.

[0039] In a further embodiment of the above-mentioned methods and the coordinate measuring machine, the at least one drive axis has an electric drive which is supplied with a drive current, wherein at least one actual value of the drive current is determined while the free end is brought into physical contact with the measuring head magazine, and wherein the at least one contact position is determined using the actual value of the current.

[0040] This configuration can be used as an alternative or supplement to determine physical contact with the measuring head magazine using inherent signals from the positioning system. The configuration is simple and cost-effective to implement, as actual values ​​of the drive current are already available in the drive control loops of the positioning system.

[0041] In a further embodiment, the measuring head magazine has a multitude of potential contact points, wherein the free end is brought into physical contact with the measuring head magazine at at least three different contact points from the multitude of potential contact points by means of the positioning system.

[0042] In preferred embodiments, the free end is brought into physical contact with the measuring head magazine at three different locations and / or from three different approach directions. Preferably, the three different approach directions are orthogonal to each other. Furthermore, it is preferred if the free end is brought into physical contact with the measuring head magazine at least once from top to bottom, i.e., in a largely vertical direction. These configurations enable the unambiguous determination of a reference position that is representative for the placement of the measuring head magazine relative to the positioning system. The pick-up and drop-off position for receiving and placing a measuring head The position of the component in the measuring head magazine can be determined with high accuracy and reliability by knowing this reference position. In some embodiments, the free end can be brought into physical contact with the measuring head magazine at six different points. This allows for an unambiguous determination of the position and orientation (pose) of the measuring head magazine relative to the positioning system. In some preferred embodiments, the points to be probed on the measuring head magazine are predefined and provided with optically detectable markings. In some preferred embodiments, the measuring head magazine can have an outer corner with a largely horizontal outer surface and two largely vertical and mutually perpendicular side surfaces, wherein the outer corner is probed vertically from above and also horizontally along the two other side surfaces with the free end.These features can be implemented in a coordinate measuring machine in a simple and efficient manner.

[0043] In a further embodiment, the multitude of potential contact points includes a self-centering receptacle for the free end.

[0044] Preferably, the positioning system of this embodiment has three drive axes extending orthogonally to one another, wherein only one of these three drive axes is electrically driven to effect the physical contact of the free end in the self-centering receptacle, while the two drive axes operating transversely to it are de-energized. This embodiment enables very rapid calibration of the measuring head magazine with a single probing movement. The free end can advantageously slide into the self-centering receptacle in the direction of the non-driven (de-energized) drive axes. The actual positions of the free end along each of the three drive axes can advantageously be determined based on the position information from the position sensors along the three drive axes. For example, a self-centering receptacle can be implemented with a spherical triplet and / or a pyramid-shaped inner corner.

[0045] In a further embodiment of the above-mentioned methods and the coordinate measuring machine, the measuring head component has a measuring head interface, wherein the measuring head interface and / or the positioning system interface at least having a spring pin that defines a spring force with a spring direction, and wherein the positioning system interface is moved against the spring force to the defined takeover position.

[0046] This design is particularly advantageous for picking up and dropping a measuring head from and into the measuring head receptacle of the magazine. The movement of the positioning system interface against the spring force contributes to high stability and reproducibility when coupling the measuring head component. The coupling movement takes place under controlled conditions, and the risk of uncontrolled tilting movements is reduced. Preferably, the positioning system interface is moved vertically from top to bottom against the spring force to apply a defined force to the measuring head interface.This design enables low-wear coupling under controlled conditions, even when the transfer position is not determined based on the defined speed and / or position signals from at least one position sensor, but rather on other inherent signals from the positioning system, such as at least one drive current and, in particular, on the current increase of that drive current. For example, the physical contact between the measuring head interface and the positioning system interface can be determined via the at least one spring pin based on the inherent signals of the positioning system. Subsequently, the positioning system interface is moved against the spring force to the defined transfer position and / or held there by current control.Once the defined takeover position has been detected based on the position signals from at least one position sensor and / or based on at least one drive current, the locking armature can be actuated for coupling under controlled conditions.

[0047] In a further embodiment of the above-mentioned methods and the coordinate measuring machine, the positioning system interface is moved to the defined transfer position at a defined second velocity against the spring force, whereby the defined transfer position is detected on the basis of the defined second velocity.

[0048] In some embodiments, the defined second speed can be the same as the defined first speed described above. However, in other embodiments, it can differ from the defined first speed and, in particular, be determined using a scaling factor other than 1 based on the defined first speed. Moving the positioning system interface at a defined speed enables a simple and efficient determination of the respective target position of the positioning system interface during movement along at least one drive axis, and consequently, a simple and efficient determination of when the optimal transfer position has been reached. Movement against the spring force prevents uncontrolled tilting or evasive movements. Therefore, this design advantageously contributes to a safe and low-wear measuring head change.

[0049] In a further embodiment of the above-mentioned methods and the coordinate measuring machine, the positioning system interface is pressed against the measuring head interface with a current control after the defined transfer position has been detected, while the locking anchor is actuated to lock the measuring head interface with the positioning system interface.

[0050] In this configuration, the positioning system interface is pressed against the measuring head interface in a controlled manner by a defined target current generated by the current control. This configuration has the advantage that the positioning system interface actively moves towards the measuring head interface when locked. During a general coupling movement from top to bottom, the positioning system interface continues to move downwards, while the measuring head interface remains in its current position within the measuring head receptacle. The measuring head interface is not pulled upwards out of the measuring head receptacle by actuating the locking mechanism, or at most only to a reduced extent. This advantageously helps to prevent uncontrolled tilting of the measuring head component before and during actuation of the locking mechanism.The design promotes a secure and low-wear coupling and prevents a tilted measuring head component from being pulled into the positioning system interface at an angle and therefore inaccurately or undefined.

[0051] 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 on their own, without leaving the scope of the present invention.

[0052] 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 showing a position while the measuring head adapter is being attached to or removed from the magazine slot adapter, and with Fig. 10B showing 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 slot adapter, illustrating further components of the magazine or magazine slot; 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.

[0053] 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.

[0054] 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.

[0055] A positioning system 18 is also attached to the base 12. This system serves to spatially position a measuring head 20, which is used to dimensionally measure an object. 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.

[0056] 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.

[0057] 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 The coordinate measuring machine 10 can be equipped with different measuring heads 20, 20' depending on the measuring task.

[0058] 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. A tactile probe 36 is coupled to the measuring head sensor 32 at its lower end (see Fig. 3).

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 in the present embodiment also has a rotary-swivel joint, is arranged in a magazine 38 in Fig. 1. This magazine 38 serves to hold and support several measuring heads and is attached to the base 12 or the measuring table 14. By moving to this magazine 38, the coordinate measuring machine 10 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.

[0064] 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.

[0065] The magazine carrier 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.

[0066] 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 provided in the base plate of the magazine carrier 40. The two magazine slot adapters 42 and 42' are also attached. According to the invention, they can in turn be detachably attached to the magazine carrier 40, preferably with the aid of several screws.

[0067] Figs. 4-7 schematically illustrate a method according to the invention for assembling the magazine 38.

[0068] 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 done by screwing the magazine carrier 40 to the measuring table 14 using several fastening screws.

[0069] 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 arranged at the lower end of the quill 30 and is designed as a counterpart to the first measuring head interface 46.

[0070] 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.

[0071] 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 disconnected from the measuring head adapter 34 during the assembly of the magazine 38. This provides greater freedom of movement and simplifies the process. Furthermore, it eliminates the risk of damaging the measuring head sensor 32 during assembly.

[0072] 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".

[0073] 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 congruent with an interface 54 on the measuring head adapter 34, which is referred to here as the "second measuring head interface".

[0074] The magazine slot interface 52 is configured as a male interface. The second measuring head interface 54 is configured as a corresponding 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 configure the second measuring head interface 54 as a male interface and the magazine slot interface 52 as a corresponding female interface, without departing from the scope of the present invention.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] In other words, a first mounting interface 60 provided on the magazine slot adapter 42 is brought close to or into contact with a second mounting interface 62 acting as its counterpart on the magazine carrier 40. In this situation, a first mounting surface 64 belonging to the first mounting interface 60, which is located at the lower end of the magazine slot adapter 42, has a spatial relative position 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, that is not precisely defined or at least partially unknown.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] It is also understood that other fastening elements 70 can be used instead of the fastening screws to detachably connect the magazine slot adapter 42 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.

[0084] 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.

[0085] In summary, the magazine slot adapter 42 is not attached to the magazine carrier 40 as a loose component in the usual way and then aligned relative to the positioning system 18. Rather, the magazine slot adapter 42 is attached to the Magazine carrier 40 is attached, while the magazine space adapter 42 is coupled to the positioning system 18 via the measuring head adapter 34.

[0086] 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.

[0087] 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 to design the first measuring head interface 46 as well as the second measuring head interface 54 directly, i.e. integrally, on the measuring head 20 or the measuring head sensor 32.

[0088] 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.

[0089] 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.

[0090] Fig. 8 shows a perspective view of an embodiment of a magazine slot component 72 belonging to the magazine slot adapter 42. In this Magazine space component 72 is the component of the magazine space adapter 42, on which the magazine space interface 52, which functions as a counterpart to the second measuring head interface 54, is designed.

[0091] 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.

[0092] 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 bearing surface sections 80, 80', 80" lie in a common plane, which is preferably parallel to the xy-horizontal plane.

[0093] 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.

[0094] 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 spacers 68. Fastening elements 70. To ensure optimal three-point support between the magazine- To reach component 72 and the magazine carrier 40, the first openings 82 as well as the second openings 84 are arranged relative to each other in a regular triangle.

[0095] Fig. 9 shows a perspective view of an embodiment of the measuring head adapter 34. Here, the third measuring head interface for coupling a measuring head sensor 32, which is dovetail-shaped and integrated into the underside of the measuring head component, 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.

[0096] Fig. 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 component 72. A further opening or recess 90, which serves to receive the third arm 78", is not visible or is obscured in Fig. 9. This recess or opening 90 is, however, visible in Fig. 10A.

[0097] 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 Fig. 10A could also be a position during the withdrawal of the measuring head component from the magazine space component 72.

[0098] 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 can also be fully inserted into the measuring head receptacle 74. The condition has a certain amount of play on the arms 78, 78', 78". The measuring head adapter 34 can be moved, particularly in the xy-horizontal plane, relative to the magazine slot component 72. This is therefore a floating mounting of the measuring head adapter 34 in the measuring head receptacle 74 of the magazine slot component 72.

[0099] 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 immersed in the openings 86, 88, 90.

[0100] The measuring head receptacle 74, defined by the magazine slot interface 52, is further designed such that it supports the measuring head component 34, 20 received therein in the z-direction. 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 space component 72 in the z-direction, at least to a limited extent, provided that the latter's weight force is overcome.

[0101] 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.

[0102] Fig. 13 shows a top view of the magazine slot adapter 42 with the measuring head adapter 34 inserted 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 inserted 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.

[0103] 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.

[0104] The following section explains the structure of the positioning system interface 48 and the first measuring head interface 46 interacting with the positioning system interface 48, with reference to Figures 14-21. Furthermore, 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.

[0105] 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.

[0106] 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 preferably takes place between the data interfaces 100 and 104. the measuring head 20 and the control unit 44 as well as a power supply for the measuring head 20.

[0107] 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.

[0108] 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.

[0109] 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. Furthermore, the locking anchor 114 is rotatable about the z-axis by a motor. During locking, the locking anchor 114 thus engages the anchor plate 116, as shown in Fig. 20, by moving linearly in the negative z-direction. This is indicated in Fig. 20 by arrow 118. Subsequently, the locking anchor 114 is rotated about the z-axis, as indicated in Fig. 21 by arrow 120, and then 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.

[0110] To minimize unwanted shear 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 shear forces is to coat the locking anchor 114 and / or the The anchor plate 116 is to be mounted so that it floats 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] Thus, the first section 134, with its larger diameter, is used to initially center the bolt. 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.

[0115] 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.

[0116] A coupling process in which the measuring head 20 is removed from the magazine 38 during a measuring head change and coupled to the positioning system interface 48 of the positioning system 18 proceeds in particular as follows.

[0117] The positioning system interface 48 is moved to a predefined initial position relative to the first measuring head interface 46 by the control unit 44 using 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 the positioning system 18, thus moving it towards the first measuring head interface 46. This can advantageously be achieved by driving the drive axis of the quill 30 with a constant current. Preferably, the instantaneous actual velocity of the positioning system interface 48 along the drive axis is repeatedly recorded, and the resulting velocity profile 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 ended and the control unit 44 takes over (preferably after a defined waiting time or (During the settling phase) the current drive current value as the target current value for a current-controlled movement of the positioning system interface 48. The positioning system- Interface 48 is thus moved in a 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.

[0118] 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.

[0119] 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. 1), remains in place.12) is not moved upwards in the z-direction and thus is not lifted upwards out of the measuring head receptacle 74 during the coupling process, especially 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.

[0120] In some embodiments, the control unit 44 uses the position encoders 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, the control unit 44 determines the speed, which is preferably measured at the end of the Once the acceleration phase is reached, a current target position of the positioning system interface 48 along the drive axis is determined. 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.

[0121] 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 at three different points and / or from three different directions in this way to calibrate the measuring head magazine 38 with respect to the three spatial axes x, y, z. Preferably, the control unit 44 reduces the drive current 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.

[0122] In some embodiments, the measuring head magazine 38 can have a plurality of predefined contact points 137, which enable self-centering. Form or include a receptacle for the free end of the positioning system 18 (see Fig. 2)

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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, the distance sensors 138, 140, 142 to read out the generated sensor signals using the control unit 44 and to compare them with the reference value stored in the storage unit 144.

[0127] 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.

[0128] 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 detected difference exceeds a predefined threshold.

[0129] 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.

[0130] 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.

[0131] 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 assist in ensuring that the locking anchor 114 does not engage with the anchor plate 116. This is possible 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, functioning 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.

[0132] 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.

[0133] 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.

[0134] Preferably, identical 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 The effect is the same for all sensors 138, 140, and 142. As long as a temperature-dependent drift occurs similarly in all sensors 138, 140, and 142, it is virtually averaged out by the described relative evaluation of the sensors.

[0135] 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.

[0136] 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 moving 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.

[0137] 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 has been 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. 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 circular milled counter surfaces, i.e. counter surfaces that are surrounded by a depression and opposite this depression. are raised. Such a structure as a counter-surface makes it possible in a suitable manner to utilize the near and far range that such distance sensors 138, 140, 142 typically have for the present measurement.

[0138] 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 can be seen 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.

[0139] 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.

[0140] 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 including at least one directional component in the positive z-direction. z-direction. In principle, it could even be oriented in such a way that it measures exactly in the positive z-direction. However, it is sufficient if its measurement direction has at least a small directional component in the positive z-direction.

[0141] 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. Method for automatically coupling a measuring head component (20) to a positioning system (18) of a coordinate measuring machine (10), wherein the positioning system (18) has a free end (30), a positioning system interface (48) in the region of the free end (30) and at least one drive axis (x, y, z), wherein the measuring head component (20) comprises a measuring head sensor (32), wherein the positioning system interface (48) has a locking anchor (114) for releasably locking the measuring head component (20) to the positioning system interface (48), and wherein the at least one drive axis is configured to move the free end (30) together with the positioning system interface (48) relative to a base (12) of the coordinate measuring machine (10), comprising the steps: - Providing a measuring head magazine (38) with at least one measuring head receptacle (74) in the area of ​​the base (12), - Providing the measuring head component (20) in the measuring head receptacle (74), - Moving the positioning system interface (48) without measuring head sensor (32) to a defined transfer position relative to the measuring head mount (74) using the positioning system (18), - Locking the measuring head component (20) at the positioning system interface (48) using the locking anchor (114) at the defined transfer position, and - Moving the positioning system interface (48) with the measuring head component (20) locked to it to a working position away from the measuring head mount (74) using the positioning system (18), wherein the free end (30) is brought into physical contact with the measuring head magazine (38) at the defined transfer position by means of at least one drive axis before the positioning system interface (48) is moved, wherein at least one contact position, which represents the physical contact of the free end (30) with the measuring head magazine (38), is determined by means of the positioning system (18), and wherein the defined transfer position is determined as a function of the at least one contact position.

2. Method according to claim 1, wherein the free end (30) is brought into physical contact with the measuring head magazine (38) without the positioning system interface (48) carrying a measuring head sensor (32).

3. Method according to claim 1 or 2, wherein the positioning system (18) has at least one position sensor (29) which provides a position signal which represents an actual position of the positioning system interface (48) along the at least one drive axis (x, y, z), and wherein the at least one contact position is determined on the basis of the position signal.

4. Method according to claim 3, wherein the free end (30) is moved at a defined first speed along the at least one drive axis (x, y, z) to effect physical contact with the measuring head magazine (38), and wherein the at least one contact position is further determined on the basis of the defined first speed.

5. Method according to claim 4, wherein the free end (30) is first accelerated to the defined first velocity to determine the at least one contact position, wherein the free end (30) is moved at the defined first velocity until physical contact with the measuring head magazine (38), and wherein the positioning system (18) moves the free end (30) in a opposite direction after reaching the contact position in order to terminate the physical contact.

6. Method according to any one of claims 1 to 5, wherein the at least one drive axis (x, y, z) has an electric drive (27) which is supplied with a drive current, wherein at least one actual current value of the drive current is determined while the free end (30) is brought into physical contact with the measuring head magazine (38), and wherein the at least one contact position is determined using the actual current value.

7. Method according to any one of claims 1 to 6, wherein the measuring head magazine (38) has a plurality of potential contact points (137), and wherein the free end (30) is brought into physical contact with the measuring head magazine (38) at at least three different contact points from the plurality of potential contact points (137) by means of the positioning system (18).

8. Method according to claim 7, wherein the plurality of potential contact points (137) include a self-centering receptacle (137) for the free end (30).

9. Method according to any one of claims 1 to 8, wherein the measuring head component (20) has a measuring head interface (46), wherein the measuring head interface (46) and / or the positioning system interface (48) have at least one spring pin (102) which (in the relaxed state) defines a spring force with a spring direction, and wherein the positioning system interface (48) is moved against the spring force to the defined transfer position.

10. Method according to claim 9, wherein the positioning system interface (48) is moved to the defined transfer position at a defined second velocity against the spring force, and wherein the defined transfer position is detected on the basis of the defined second velocity.

11. Method according to claim 10, wherein the positioning system interface (48) is pressed against the measuring head interface (46) by means of a current control after the defined transfer position has been detected, while the The locking anchor (114) is actuated to lock the measuring head interface (46) with the positioning system interface (48).

12. Method for automatically attaching or detaching a measuring head component (20) to or from a positioning system (18) of a coordinate measuring machine (10), wherein the positioning system (18) has a positioning system interface (48) and at least one drive axis (x, y, z), wherein the measuring head component (20) has a measuring head interface (46) and a measuring head sensor (32), wherein the positioning system interface (48) has a locking anchor (114) for releasably locking the measuring head interface (46), and wherein the at least one drive axis is configured to move the positioning system interface (48) relative to a base (12) of the coordinate measuring machine (10), comprising the steps: - Providing a measuring head magazine (38) with at least one measuring head receptacle (74) in the area of ​​the base (12), - Providing the measuring head component (20), - Moving the positioning system interface (48) with the aid of the positioning system (18) to a defined transfer position relative to the measuring head mount (74), - Locking the measuring head interface (46) to the positioning system interface (48) using the locking anchor (114) at the defined transfer position in the case of coupling, or unlocking the measuring head interface (46) from the positioning system interface (48) using the locking anchor (114) at the defined transfer position in the case of decoupling, and - Moving the positioning system interface (48) with the measuring head component (20) locked to it using the positioning system (18) a working position that is remote from the measuring head receptacle (74) in the case of coupling, or moving the positioning system interface (48) without the measuring head component (20) with the aid of the positioning system (18) to a working position that is remote from the measuring head receptacle (74) in the case of decoupling, wherein the positioning system (18) has at least one position encoder (29) that provides a position signal which represents an actual position of the positioning system interface (48) along the at least one drive axis (x, y, z), wherein the positioning system interface (48) is moved at a defined speed along the at least one drive axis (x, y, z) to the defined transfer position and there, in the case of coupling, comes into physical contact with the measuring head interface (46) or, in the case of decoupling, causes physical contact of the measuring head component (20) with the measuring head receptacle (74),and whereby the respective physical contact is determined based on the defined speed and on the basis of the position signal.

13. Coordinate measuring machine (10) comprising: - a base (12), - a measuring head magazine (38) with at least one measuring head receptacle (74) in the area of ​​the base (12), - at least one measuring head component (20) comprising a measuring head sensor (32) and a measuring head interface (46), wherein the measuring head component (20) can be placed in the measuring head receptacle (74), A positioning system (18) comprising a free end (30), a positioning system interface (48) in the region of the free end (30), and at least one drive axis (x, y, z) configured to move the positioning system (18) relative to the base (12), wherein the positioning system interface (48) further comprises a locking anchor (114) for releasably locking the measuring head component (20) to the positioning system interface (48), and a control unit (44) configured to execute a method comprising the method steps according to one of claims 1 to 12 in order to couple the measuring head component (20) to the positioning system interface (48) using the positioning system (18) and to remove it from the measuring head receptacle (74), or to place the measuring head component (20) in the measuring head receptacle (74) using the positioning system (18) and to remove it from the Disconnect the positioning system interface (48).

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