Measurement system for models

Abstract

The invention relates to a measuring system (100) comprising a frame (110) on which a plurality of reference bodies (115) are mounted; an optical detection system (125) for scanning the reference body (115); and a processing device (130). The processing device (130) is designed to determine an orientation of the frame (110) relative to the detection system (125) on the basis of a scan of the reference body (115). The reference body (115) can be removed from the frame (110) and can be repeatedly and precisely mounted on the frame (110).

Description

Technical Field

[0001] The present invention relates to a measuring system for scanning a model. In particular, the present invention relates to a measuring system for a model representing a part of a motor vehicle. Background Art

[0002] During vehicle development, models of vehicle components, assemblies, or sections need to be created to check their functionality or aesthetics. The model can consist of a flexible material, such as clay, which can be shaped to resemble the vehicle's surface. If a suitable shape is found, the model is scanned so that its shape can be documented or further processed using computer-aided methods.

[0003] Scanning can be performed using optical measuring devices or systems, which detect multiple points on the model surface. However, the shapes found in this way do not have a defined orientation in space. For example, to be able to compare model surfaces from two different revisions, the scans need to be associated with the same coordinate system.

[0004] Typically, the model is mounted on a scanning plate in a defined manner for the scanning process. Scans taken with the measuring system can then be linked to the coordinate system defined with reference to the scanning plate. By permanently linking the model's coordinate system to the measuring plate, the scans can also be linked to the model's coordinate system.

[0005] However, this method requires the model to be precisely and repeatedly mounted on the measurement plate for each scanning process. To achieve this, the model must be transported to the scanning plate and precisely oriented relative to it. Transporting and aligning the model relative to the measurement plate can be complex and time-consuming. This delays the model design process, increasing R&D costs. Summary of the Invention

[0006] The present invention is based on the object of providing an improved technique for providing model scanning. The present invention achieves this object by the technical solution of the independent claim. The dependent claims provide preferred embodiments.

[0007] The proposed measurement system comprises a frame on which a plurality of reference bodies are mounted; an optical detection system for scanning the reference bodies; and a processing device. The processing device is configured to determine the orientation of the frame relative to the detection system based on the scanning of the reference bodies. The reference bodies can be removed from the frame and accurately mounted thereon repeatedly.

[0008] The measuring system makes it easy to determine the coordinate system associated with the frame. Subsequent scans of the frame or a model connected to it can be associated with the determined coordinate system without having to orient the frame in a predetermined manner. The coordinate system fixed to the frame can be determined using only a single measurement plate.

[0009] Generally, sufficient repeatability exists if the inspection system's scans can be compared to each other within a predetermined measurement accuracy range before and after removing and reinstalling the reference body. In other words, the reference body should be able to be reinstalled onto the frame in exactly the same position after being removed from it, so that the position of a specific point associated with the frame before and after temporary removal (of the reference body) deviates by less than a predetermined value. This value can correspond to the measurement accuracy.

[0010] Thanks to the removable reference body, the design process of the model on the frame remains uninterrupted. The reference body can be attached to the frame only when scanning is to be performed. The model can be scanned more quickly overall and with fewer technical aids.

[0011] The frame is preferably configured to support the model. The detection system is configured to scan the model, and the processing device is configured to orient the scan of the model based on the determined frame orientation.

[0012] In other words, the processing device can associate points on the model surface scanned by the detection system with a coordinate system determined once relative to the frame. The model can have a variable shape. The model's material can be arbitrarily selected, and its shape can be arbitrarily complex, as long as it can be scanned by the detection system. The size of the model can be determined essentially only by the maneuverability of the frame. Another limitation may arise from the fixed-position detection system. Alternatively, a mobile or handheld detection system can also be used.

[0013] Preferably, a plurality of optical markers are mounted on the model, and the processing device is configured to orient two overlapping scans of the model relative to one another with respect to the positions of the markers detected in the two scans. The markers may also be referred to as reference points.

[0014] Markers can be attached to the model before scanning and removed again afterward. It is sufficient to distribute the markers pseudo-randomly over the model surface. The distribution of the reference points on the model can depend on the measurement volume used and / or the scanning system used. Information from the manufacturer of the scanning system can be used to distribute and attach the reference points. With the aid of the detection system, a series of scans can be created, in which two adjacent scans should partially overlap in order to be able to establish a common background between the scans. Thus, a scan chain or a series of scans can be created, the reference points of which are all located in the same coordinate system. If a sufficient number of reference bodies are identified in the scans, the entire series can be associated with the coordinate system of the framework. It is preferred to detect multiple reference bodies in just one scan.

[0015] In one embodiment, the reference body carries an individualized optical marking that can be detected by means of a detection system.

[0016] This allows the processing device to eliminate confusion about reference bodies during evaluation. It also eliminates ambiguity when associating the scan with a coordinate system fixed to the frame. Furthermore, the reference bodies are preferably assigned to predetermined locations on the frame. This allows for a more precise and unambiguous association of the positions of scanned points on the model surface with the coordinate system fixed to the frame.

[0017] The positions are preferably selected so that the series of reference bodies on the frame produce a favorable geometry. For example, the surface formed by the reference bodies or the volume formed by the reference bodies can be maximized. To correctly orient the frame in space, three rotational degrees of freedom and three translational degrees of freedom are typically determined. It is sufficient to use at least three reference bodies. However, it is preferred to use at least six reference bodies in order to provide sufficient reference points for the association of the coordinate system fixed to the frame.

[0018] Furthermore, a predetermined mechanical interface is preferably provided between the reference body and the frame for tool-free separation and connection.

[0019] Configuring the frame with a reference body requires minimal time. The interface is designed to hold the reference body on the frame with sufficient repeatability.

[0020] The reference body is preferably mounted on the frame only for scanning purposes and during the scan. Therefore, the interfaces do not have to be robust enough to withstand accidental contact during model processing. By connecting and disconnecting the reference body from the frame without tools, the assembly effort before and after scanning can be reduced.

[0021] If the reference body is individually assigned to a certain position on the frame, the interface can include a mechanical coding that prevents another reference body from being mounted at this position. However, the interfaces of several reference bodies can also be interchangeable.

[0022] Typically, the section of the interface that is fixed to the frame is preferably mounted so that the reference body can be connected to it without contacting the model. For example, the frame can be arranged so that the model is located on the top side of the frame and the interface is located on the bottom side. In another embodiment, the interface can be located in an area where the model has a recess or cavity.

[0023] The interface preferably comprises two surfaces for abutting one another, on which corresponding sections for form-locking engagement are constructed. The surfaces are assigned to different sections of the interface and can move away from one another when the interface is open. The reference body can be reproducibly and accurately placed in a predetermined position relative to the frame via the surfaces. The form-locking sections can prevent the surfaces from moving relative to one another. The surfaces can comprise flat or curved surfaces. The corresponding concave or convex sections can comprise, for example, hemispheres, prisms, cylinders, elongated holes, or cones. A plurality of sections for form-locking engagement can be distributed on the surfaces in a predetermined manner. The position of the reference body relative to the frame can be determined or overdetermined.

[0024] In another preferred embodiment, the interface includes a magnetic fastening device between the reference body and the frame. The fastening device is preferably configured to bring the reference body closer to the frame. This allows for the establishment or maintenance of a positive connection via the mutually corresponding sections. The magnetic fastening device can be quickly established or released. In the event of an overload, the fastening device can be opened, allowing the reference body to be separated from the frame.

[0025] It is further preferred that a cantilever is provided between the reference body and the frame so that the reference body can protrude beyond the outline of the model, and when the reference body is removed, the interface portion fixed to the frame will not hinder the impression or operation of the model.

[0026] In one embodiment, an auxiliary frame is movably mounted on the frame. At least one additional reference body can be mounted on the auxiliary frame. Depending on the number of degrees of freedom of the auxiliary frame relative to the frame, multiple reference bodies can also be provided. To fully determine the orientation of the auxiliary frame relative to the coordinate system fixed to the frame, at least three reference bodies are preferably used.

[0027] A movable auxiliary frame can support the functionality of the model. For example, the auxiliary frame can represent a vehicle door, which moves relative to the vehicle in the same way as the auxiliary frame moves relative to the frame. This allows, for example, to check whether the independently determined shapes of the vehicle and the door are compatible with each other in terms of the predetermined movability. The auxiliary frame can be designed to be detachable from the frame. The interface between the frame and the auxiliary frame ensures that they can be reassembled precisely and repeatedly after detachment. In an extension of this concept, multiple auxiliary frames can also be movably mounted on the frame. This concept can also be cascaded by movably mounting another auxiliary frame on an auxiliary frame.

[0028] A method for scanning a model carried by a frame, the method comprising the steps of: mounting a plurality of reference bodies on the frame; optically scanning the reference bodies; determining a coordinate system fixed to the frame based on the scans of a predetermined number of the reference bodies; temporarily removing the reference bodies; and repeating the scan.

[0029] This method can be performed, in particular, with the aid of the measuring system described herein. Temporarily removing the reference body allows the model to be processed in any desired range. Compared to conventional methods, only an external device for determining the coordinate system is required once. Any number of subsequent scans can then be oriented relative to the determined coordinate system.

[0030] According to this method, different revisions of the same model can be scanned on a single frame with reduced effort. This makes it easier to correlate different scans of a model. Therefore, in one development of this method, different scans of a model can be compared with one another. This allows for better identification and quantification of differences between two revisions or versions of a model. Unchanged parts of the model can also be identified. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will now be described in more detail with reference to the accompanying drawings.

[0032] Figure 1 A measurement system is shown;

[0033] Figure 2 A flow chart illustrating a method;

[0034] Figure 3 A frame with an interior model is shown;

[0035] Figure 4 A reference body on the frame is shown;

[0036] Figure 5 An exemplary reference body having a mechanical interface is shown;

[0037] Figure 6 A reference body is shown in another embodiment. DETAILED DESCRIPTION

[0038] Figure 1 Measuring system 100 is shown. Measuring system 100 is configured to scan a model 105, which is preferably used in the development of a motor vehicle. Although smaller components can also be processed using measuring system 100, model 105 is shown as an example of a complete vehicle.

[0039] The measurement system 100 includes a frame 110, which is configured to support a model 105 and on which a plurality of reference bodies 115 may be mounted. The reference bodies may extend from the frame 110 via cantilevers 118. A mechanical interface 120 is preferably provided between the frame 110 and the reference bodies 115. The measurement system 100 also includes an optical detection system 125 and a processing device 130. A data storage device 135 is optionally provided.

[0040] The dimensions of frame 110 are designed so that it can support model 105 without excessive deformation (which would affect the measurement results). For larger models 105, frame 110 is typically designed as a steel tube structure. Model 105 can be made of a flexible or hardenable material such as clay or plastic. For weight reasons, a filler material, such as a hardening plastic foam, can be placed between model 105 and frame 110.

[0041] The frame-side interface 120 is preferably mounted on the frame 110 such that it is located outside the area where the model 105 is located. Furthermore, the interface 120 is preferably designed such that it cannot or cannot be accidentally repositioned on the frame 110. A non-repositionable interface 120 can, for example, be fixed to the frame 110 by a material fit. A repositionable interface 120 may require the use of a key, a predetermined tool, or the breaking of a seal to change its position relative to the frame 110.

[0042] The frame 110 can be arranged to be mechanically oriented relative to a base plate (not shown). For this purpose, an adapter can be used on the base plate, which can be positively embedded in a corresponding structure on the frame 110. This adapter can also be called a top sleeve.

[0043] Detection system 125 is configured to contactlessly and, in particular, optically determine the position of at least one point on the surface of an object. Detection system 125 can typically detect hundreds or thousands of points on a surface in just one recording or measurement process. When both frame 110 and detection system 125 are positioned relative to the measuring plate, the position of detection system 125 relative to frame 110 can be determined at least initially. For this purpose, a coordinate system fixed to the frame, i.e., associated with frame 110, can be determined.

[0044] exist Figure 1 , a Cartesian coordinate system defined relative to frame 110 is shown as an example. The x-axis extends horizontally and rearward, opposite the vehicle's normal direction of travel. The y-axis extends horizontally from left to right. The z-axis extends vertically and upward. The origin of the coordinate system is located on the axis about which the vehicle's two front wheels can rotate, i.e., at the midpoint between the left and right wheels. Alternatively, the origin may be determined in other ways. Alternatively, a non-Cartesian coordinate system or a non-Cartesian coordinate system may be used.

[0045] Before starting the scan, the processing unit 130 may generate a coordinate system in the detection area of the detection system 125, which is also called a sensor coordinate system. After the detection is completed, the coordinate system may be converted into another coordinate system. Figure 1 The sensor coordinate system is not shown in the diagram and without loss of generality it is assumed that all measurements are transformed into the shown x / y / z coordinate system before their further processing.

[0046] The specific points can be stored in the data storage 135. Optionally, the processing device 130 can also process these points, such as smoothing, converting to other data formats, or creating a model based on other geometric structures such as NURBs (Non-Uniform Rational B-Splines). These points or processing results can be output externally.

[0047] In various embodiments, detection system 125 can be stationary, mobile, or handheld. Stationary detection systems 125 are equipped with a device that mechanically controls or limits the position of the detection system. This ensures that the orientation of the detection system relative to the surroundings, and in particular the measuring plate, is always known. Mobile detection systems 125 can be mounted on an autonomous platform that can be moved, for example, around model 105.

[0048] Figure 2 A flow chart of a method 200 for scanning a model 105 is shown. The method 200 can be carried out, in particular, by means of the measuring system 100 .

[0049] In step 205, a frame 110 may be provided for the model 105. Preferably, the model 105 is not yet mounted on the frame 110 at this point.

[0050] In step 210, reference bodies 115 can be mounted on frame 110. The positions of reference bodies 115 on frame 110 can be determined. Preferably, at least six reference bodies 115 are used. Reference bodies 115 can be positioned relative to one another in a plane or in any other geometric configuration. Furthermore, reference bodies 115 are preferably positioned on frame 110 so that they can be observed from as wide an angular range as possible. The angular range can be determined horizontally and / or vertically.

[0051] In step 215, the frame 110 can be calibrated. A frame-fixed coordinate system can be determined. Subsequently determined positions on the surface of the model 105 can be associated with this frame-fixed coordinate system. The frame-fixed coordinate system is a prerequisite for the comparability of different scans of the model 105 in potentially different states or shapes.

[0052] For calibration purposes, the relative positions of the reference bodies 115 can be determined. For example, the coordinate system can be determined manually. Preferably, a Cartesian coordinate system is used. Figure 1 In the embodiment shown in FIG, the coordinate system can be defined such that the first axis corresponds to the longitudinal axis of the vehicle represented by model 105, the second axis corresponds to the transverse axis of the vehicle, and the third axis corresponds to the vertical axis of the vehicle. The directions of the axes and the zero point can be freely determined or determined according to existing conventions. In one embodiment, a 3-2-1 orientation is achieved using geometric elements of the measurement board. The zero point of the coordinate system can then be shifted to a predetermined position, for example, to the center of the front axle as shown in the figure.

[0053] In one embodiment, the coordinate system is determined automatically by utilizing a predetermined geometric relationship between the reference bodies 115. For example, two reference bodies can define an axis. The axes can intersect at a point, which can be determined as the origin of the coordinate system.

[0054] In another embodiment, the coordinate values of the reference body are detected and, after optional orientation correction, are input as target coordinate values into the software running on the processing device 130. The data scanned by the detection system 135 can then be stored in the form of coordinate values of the pattern of detected reference points and the position and orientation of the origin of the coordinate system.

[0055] In step 220, the reference bodies 115 may be removed from the frame 110. These reference bodies 115 may be stored in a safe location so that they may be used later with the current frame 110 or the model 105 supported thereby.

[0056] In step 225, the model 105 may be mounted on the frame 110 or processed. Processing may include changing the surface of the model 105. The degree or scope of the change is not limited in principle.

[0057] In step 230, reference body 115 can be reinstalled on frame 110. Reference body 115 can be individually marked. A first marking can be read by a person, and a second marking can be scanned by detection system 125 and recognized by processing device 130. During installation, it is preferably ensured that reference bodies 115 each occupy the position on frame 110 that they had in step 215.

[0058] In step 235, the model 105 can be measured. To this end, the surface of the model 105 can be scanned using the detection system 125. Simultaneously, one or more reference bodies 115 can be scanned. Typically, the scan includes multiple points within a predetermined measurement range. Multiple partially overlapping scans can be combined into a single, expanded scan.

[0059] Each point of the scan can be associated with a coordinate system fixed to the frame by determining the position of the point relative to the position of a reference body 115 that is identifiable during the scan and considering the position of the point relative to the coordinate system fixed to the frame. The association of the scan with the coordinate system fixed to the frame can be achieved in a known manner by means of a transposition of the corresponding matrix.

[0060] When the reference point pattern obtained by scanning includes three or more reference bodies, it is possible to determine whether all actual data is converted to previously stored target data. All data in the project can be converted. This allows the scan data (i.e., the positions of the detected reference points) to be stored in the vehicle coordinate system without having to reinstall the physical model 105 on the top sleeve on the base plate.

[0061] After measuring model 105, method 200 can continue in step 225 to modify model 105 and determine the results. In step 240, model 105 can be evaluated based on the scan of the model. This evaluation can be performed in any manner. For example, model 105 can be simulated in a wind tunnel based on the scan. In another embodiment, a computer graphic can be created based on the scan, which can be rendered, animated, or otherwise further developed in subsequent processing steps. In step 240, different revisions of model 105 can also be compared with one another. To this end, portions of model 105 that have changed between two predetermined revisions can be identified.

[0062] Figure 3 A frame 110 is shown with a model 105 of a motor vehicle interior. The frame 110 is shown from the outside, with the model 105 positioned on the side of the frame 110 facing away from the viewer. An auxiliary frame 310 is mounted on the frame 110 and is movable relative to the frame 110 in a predetermined manner. In the illustrated embodiment, the auxiliary frame 310 is pivotally mounted relative to the frame 110 about a predetermined axis 305. Alternatively, the auxiliary frame 310 can be removed from the frame 110. In the illustrated embodiment, the mobility of the auxiliary frame 310 relative to the frame 110 represents the mobility of the motor vehicle door simulated by the model 105.

[0063] A plurality of reference bodies 115 are preferably mounted on the auxiliary frame 310. The reference bodies 115 can be detected from the outside, which is not important for the model 105. Thus, the position of the modeled door relative to the rest of the motor vehicle can be determined.

[0064] Figure 4 An exemplary reference body 115 is shown on the frame 110. The model 105 can be located on the upper side of the frame 110, facing away from the viewer. A mechanical interface 400 is provided between the reference body 115 and the frame 110, comprising a section 405 fixed to the frame and a section 410 fixed relative to the reference body 115. The cantilever 118 is located between the reference body 115 and the second section 410 and is shaped so that it does not extend into the area of the model 105 and can be easily detected by the detection system 125 at the model 105.

[0065] In the illustrated embodiment, an adjustment mechanism 415 is provided, by means of which the position of the first section 405 of the mechanical interface 400 can be adjusted. This mechanism 415 is preferably used only once to initially determine the position of the reference body 115. For subsequent measurements or machining of the model 105, this mechanism 415 can be removed or locked. Optionally, the height of the reference body 115 on the frame 110 can be adjusted by installing spacers. It is also provided that the relative position does not change after the initial determination.

[0066] Figure 5 An exemplary reference body 115 is shown with a mechanical interface 400 for fastening to a frame 110. A first section 405 is implemented as a plate that can be attached to the frame 110. Fastening holes 502 or other structures can be provided for fastening. A second section 410 is formed directly on the reference body 115, which has, for example, a cuboid shape.

[0067] Exemplary optical markings 505 are shown on the surface of reference body 115 . Markings 505 can be provided on five surfaces of cuboid-shaped reference body 115 that are not covered by second section 410 of mechanical interface 400 .

[0068] The segments 405 and 410 may each have a surface 510 configured to abut against one another. A magnetic securing device 515 may be provided to secure the segments 405 and 410 to one another. The magnetic securing device may include a combination of two permanent magnets or a permanent magnet and a matching metal component. The securing device 515 is preferably configured to press the surfaces 510 against one another.

[0069] In order to uniquely position the second section 410 on the first section 405 , structures can be formed on both sides, which are provided for positively engaging with one another.

[0070] The first exemplary structure 520 comprises a spherical segment and a socket. In the present case, the socket 520 is formed on the first section 405 and the spherical segment 520 is formed on the second section 410. When the spherical segment is embedded in the socket, the sections 405, 410 are prevented from moving laterally along the surface 510.

[0071] The second exemplary structure 525 comprises a prism and an oblong hole. In the present example, the oblong hole is formed on the first section 405 and the prism is formed on the second section 410. The second structure 525 also defines the rotational position of the sections 405, 410 about a rotation axis extending perpendicular to the surface 510.

[0072] The third exemplary structure 530 includes a cylinder and a corresponding hollow cylinder. In the illustrated embodiment, the cylinder is configured on the first section 405 and the hollow cylinder is configured on the second section 410.

[0073] Mechanical interface 400 preferably includes a plurality of structures 520 to 530 in order to reproducibly and unambiguously set the orientation of reference body 115 relative to first section 405 or frame 110 with respect to the existing degrees of freedom.

[0074] Figure 6 A reference body 15 is shown in another embodiment. The reference body 115 shown is essentially plate-shaped and has a base area that is, for example, pentagonal. The second section 410 is connected to the reference body 115 via a cantilever 118. The second section 410 is also designed in the form of a plate and, in the embodiment shown, includes a surface 510 for contact with the corresponding first section 405 and three structures 605 formed on the surface 510 of the second section 410.

[0075] Structure 605 is constructed as three spaced-apart truncated cones extending upward from surface 510. A corresponding concave receiving portion can be constructed in the corresponding first section 405 of mechanical interface 400. Truncated cones 605 are spaced apart from each other substantially in the form of equilateral triangles. Optionally, magnetic securing devices 515 can be constructed between the truncated cones and the receiving portions. In another embodiment, securing devices 515 can also be constructed between structures 605.

[0076] Reference Signs List

[0077] 100 measurement systems

[0078] 105 model

[0079] 110 framework

[0080] 115 reference body

[0081] 118 cantilever

[0082] 120 interface

[0083] 125 detection system

[0084] 130 processing device

[0085] 135 data storage

[0086] 200 Methods

[0087] 205 provides framework

[0088] 210 installation reference body

[0089] 215 calibration frame, determine the coordinate system fixed on the frame

[0090] 220 Remove reference body

[0091] 225Build / Process Model

[0092] 230 installation reference body

[0093] 235 measurement model

[0094] 240 Evaluation Model

[0095] 305 axis

[0096] 310 auxiliary frame

[0097] 400 mechanical interface

[0098] 405 The first section fixed on the frame

[0099] 410 The second section fixed to the frame

[0100] 415 adjustment mechanism

[0101] 502 fixing hole

[0102] 505 optical marking

[0103] 510 faces

[0104] 515 magnetic fixing device

[0105] 520 First Structure, Ball Segment and Ball Socket

[0106] 525 Second Structure, Prism and Long Hole

[0107] 530 Third Structure, Cylinder and Hollow Cylinder

[0108] 605 Fourth Structure, Truncated Cone and Accommodation

Claims

1. A measurement system (100), comprising: - a frame (110) on which a plurality of reference bodies (115) are mounted; - an optical detection system (125) for scanning the reference body (115); and - a processing device (130) configured to determine the orientation of the frame (110) relative to the detection system (125) based on a scan of the reference body (115); characterized in that The reference body (115) can be removed from the frame (110) and can be mounted on the frame (110) with repeatable accuracy.

2. The measuring system (100) according to claim 1, wherein The frame (110) is configured to carry a model (105); the detection system (125) is configured to scan the model (105); and the processing device (130) is configured to orient the scan of the model (105) based on the determined orientation of the frame (110).

3. The measurement system (100) according to claim 2, wherein: A plurality of optical markers are mounted on the model (105); the processing device (130) is configured to orient two overlapping scans of the model (105) relative to one another with respect to the positions of the markers detected in the two scans.

4. The measuring system (100) according to any one of the preceding claims, wherein The reference body (115) carries an individualized optical marking (505) that can be detected by means of a detection system (125).

5. The measuring system (100) according to any one of the preceding claims, wherein The reference body (115) is assigned to a predetermined position on the frame (110).

6. The measuring system (100) according to any one of the preceding claims, wherein A predetermined mechanical interface (400) is provided between the reference body (115) and the frame (110) for tool-free separation and connection.

7. The measurement system (100) according to claim 6, wherein: The interface (400) comprises two surfaces (510) for contact with each other, on which corresponding sections (520-530, 605) are formed for positive engagement with each other.

8. The measuring system (100) according to claim 6 or 7, wherein: The interface includes a magnetic fixing device (515) between the reference body (115) and the frame (110).

9. The measuring system (100) according to any one of the preceding claims, wherein A cantilever (118) is provided between the reference body (115) and the frame (110).

10. The measuring system (100) according to any one of the preceding claims, wherein An auxiliary frame (310) is movably mounted on the frame (110); at least one additional reference body (115) is mounted on the auxiliary frame (310).

11. A method (200) for scanning a model (105) carried by a frame (110), the method (200) comprising the following steps: - mounting (210) a plurality of reference bodies (115) on the frame (110); - optically scanning (215) the reference body (115); - determining (215) a coordinate system fixed to the frame based on scanning of a predetermined number of reference bodies (115); - temporarily removing (220, 230) the reference body (115); and - Repeat (235) scan.

12. The method (200) of claim 11, further comprising comparing (240) the scans.

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