• 专利附录
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    • 专利摘要:
    method for operating a coordinate positioning apparatus having a measurement probe, and a coordinate positioning apparatus. a method for operating a coordinate positioning apparatus having a measuring probe (18) is described. the method comprising a step of taking a first part (24) into a series of nominally identical parts, at least one first reference geometric property associated with one or more features of the first (24) being known. a step also of using the coordinate positioning apparatus to measure one or more characteristics of the first part (24) is also carried out and determining from it a first measured geometric property that corresponds to the first reference geometric property. a first property correction value is then determined in a way that describes a difference between the first reference geometric property and the first measured geometric property. the coordinate positioning apparatus is then used to measure the one or more characteristics of one or more additional parts in the series of nominally identical parts and, for each additional part, an additionally measured gepmetric property is determined to correspond to the first geometric property of reference. the first property correction value is then applied to each additionally measured geometric property. a corresponding coordinate positioning apparatus is also described.
    公开号:BR112012021934B1
    申请号:R112012021934
    申请日:2011-02-28
    公开日:2020-05-05
    发明作者:Barry Jonas Kevyn
    申请人:Renishaw Plc；
    IPC主号:
    专利说明:

    METHOD FOR OPERATING A COORDINATE POSITIONING DEVICE HAVING A MEASUREMENT PROBE, AND, COORDINATE POSITIONING DEVICE [001] The present invention relates to an improved apparatus and method for correcting errors in measurements taken using a positioning apparatus. coordinates comprising a measuring probe.
    [002] A coordinate positioning apparatus, such as coordinate measuring machines (CMMs) and numerically controlled machine tools, are well known and widely used in industrial inspection processes. In particular, it is known to use a coordinate positioning apparatus to measure the position of multiple points on the surface of a part (for example, a workpiece) to verify that it has been manufactured within desired tolerances. Measurements taken with any coordinate positioning device will always have a certain level of uncertainty and many different calibration techniques have been developed over the years to improve the accuracy with which the position of the points on the surface of a part can be measured.
    [003] The US5426861 patent (Shelton) describes an example of an error correction technique in which the accuracy achievable with a laboratory CMM maintained in a clean temperature controlled environment is used to improve the measurement accuracy of such a CMM. store floor. In particular, a reference part is measured by a first laboratory-based CMM, and also by a second CMM located in the production environment. The first CMM can thus acquire measurements with high accuracy, while the second CMM is subject to measurement inaccuracies due to temperature variations, etc. Comparison of surface measurements taken by the first and second CMMs allows a point-to-point error map to be constructed. The second CMM is then used to measure points on the surface of parts of production, which are nominally identical to the part of
    Petition 870190129656, of 12/06/2019, p. 7/50 / 23 reference, and the position of the measured points on the surface is corrected using the error map. Surface position measurements of production parts, which are nominally identical to that reference part, taken using the second CMM can then be corrected using the error map.
    [004] A point-to-point correction process, for example, as described in US5426861, requires the creation of a large error map that includes an entry for each measurement point. It was found that the generation of such an error map and the subsequent use of the map to provide positional corrections is typically difficult to implement. For example, the technique as described in US5426861 requires that identical or at least very similar measurement control software be installed on the first and second CMMs to allow the measured points acquired with the different machines to be compared to establish the map of point to point error. A point-to-point error correction technique is also described in US2006 / 266100.
    [005] US5257460 describes a system for measuring parts on a machine tool in which a rotating cassette is provided to hold work pieces and a pre-calibrated artifact. After each measurement of a workpiece, such pre-calibrated artifact is measured to provide a correction for measurements of the workpiece.
    [006] According to a first aspect of the present invention, a method is provided for operating the coordinate positioning apparatus having a measuring probe, the method comprising the following steps in any suitable order:
    (i) taking a first part in a series of identical parts nominally, at least one first part being known, (ii) using the coordinate positioning apparatus to measure one or more characteristics of the first part and determine from it a first measured geometric property that corresponds to that first reference geometric property, a so-called first property
    Petition 870190129656, of 12/06/2019, p. 8/50 / 23 measured geometry being established using the measured position of multiple points on the surface of each one (s) of one or more features of said first part, (iii) determining a first property correction value that describes a difference between that first reference geometric property and that first measured geometric property, (iv) use the coordinate positioning apparatus to measure one or more characteristics of a plurality of additional parts in the series of nominally identical parts and, for each additional part, determine an additional measured geometric property that corresponds to that first reference geometric property, and (v) applying the first property correction value to each additional measured geometric property.
    [007] The present invention further comprises a method for correcting measurement errors that arise when a series of parts using a coordinate positioning apparatus comprising a measurement probe. In step (i) of the method, a first part in a series of nominally identical parts is taken as one or more characteristics; for example, the first part can be a metal workpiece in which one feature or more features (for example, holes, bosses, etc.) have been machined. A first geometric reference property associated with one or more characteristics of the first part is known (for example, from design data or from a measurement of the first part using different measuring devices). The first reference geometric property can comprise, for example, a geometric property associated with a unique characteristic (for example, diameter or circularity of a cylindrical hole) or a geometric property that describes the relationship between a plurality of characteristics (for example, the angularity, parallelism or perpendicularity of two characteristics, such as surfaces).
    Petition 870190129656, of 12/06/2019, p. 9/50 / 23 [008] The first part is just one part in a series of nominally identical parts to be measured using the coordinate positioning apparatus. The first and additional parts in the series, although intended to be the same, do not need to be physically identical due to the various manufacturing tolerances involved in their production. The first and additional parts in the series can, for example, each be produced by a nominally identical process (for example, by a machine tool running the same cutting program). However, it should be noted that the term “first part” as used here does not refer only to the part that was made in the manufacturing production run; the term “first part” merely refers to one of the parts selected in the series. It should also, for example, be possible for the first part in the series of parts to differ slightly in unimportant ways from subsequent parts in the series; for example, the first part may not include non-critical features or markings that may be present elsewhere in the series.
    [009] The method of the present invention also comprises step (ii) of using the coordinate positioning apparatus to measure one or more characteristics of the first part and to determine from it a first measured geometric property that corresponds to that first geometric property of reference. Such a measurement step may conveniently include the use of the coordinate positioning apparatus to measure the position of a plurality of points on the surface of each of said one or more features of the first part. In particular, the coordinate positioning apparatus is preferably arranged to move the probe with respect to the first part to allow a plurality of points on the surface of the first part to be measured. If the probe comprises an analog probe with a deflecting needle, step (ii) includes the coordinate positioning apparatus scanning the probe tip needle along the path on the surface of the first part
    Petition 870190129656, of 12/06/2019, p. 10/50 / 23 while collecting both needle deflection data and data describing the position of the probe inside the work envelope of the coordinate positioning apparatus. The position of multiple points on the surface of the first part in the machine coordinate system can then be generated by combining the needle deflection and probe position data in a known manner.
    [0010] It should again be noted that the first measured geometric property derived in step (ii) is not merely a single data point (that is, a unique position on the surface of the first part), but a geometric property that is associated with one or more characteristics of the first part; this is described in more detail below. Such a geometric property is preferably established using the measured position of multiple points on the surface of each of the characteristics of the first part. Step (ii), therefore, advantageously comprises adjusting a plurality of points measured by the coordinate positioning apparatus for a function to establish the first measured geometric property. In other words, said first measured geometric property can be derived mathematically from multiple positional data points that are taken using said coordinate positioning apparatus. The first measured geometric property of the first part, which corresponds to the first reference property, is then preferably determined from the position of a plurality of points on the surface of the first part as measured by the coordinate positioning apparatus.
    [0011] Said method of the present invention also involves performing step (iii) of determining a first property correction value that describes a difference between the first reference geometric property and the first measured geometric property. This can include, for example, comparing the first measured geometric property with the first corresponding reference geometric property to obtain the first correction value
    Petition 870190129656, of 12/06/2019, p. 11/50 / 23 of ownership. In other words, the geometric property measured from the first part as measured using the coordinate positioning device is compared with its corresponding geometric reference property. A first property correction value is then calculated in such a way as to describe the difference between the corresponding measured and reference geometric properties. The difference determined in step (iii) can describe all, or only part, of the overall difference between the corresponding measured and reference geometric properties. This step may include, for example, comparing a hole radius as measured by said coordinate positioning apparatus for a nominal hole radius and establishing a radius correction value. Again, it should be noted that the first property correction value describes a difference in the geometric property and not the deviation in the position of individual points on the surface of the first part. [0012] The present invention also comprises performing step (iv) of using the coordinate positioning apparatus to measure one or more characteristics of one or more additional parts in a series of nominally identical parts and, for each additional part, determine geometric property additional measure that corresponds to the first reference geometric property. Step (v) of the method of this invention then comprises applying the first property correction value to each additional measured geometric property. For example, that step (v) may comprise correcting each additional measured geometric property using the first property correction value and in this way providing a first corrected error measured geometric property for each additional part. In other words, a corrected geometric property is produced for each additional part in the series from the first property correction value determined by comparing the first measured geometric property with its first corresponding reference geometric property.
    [0013] Unlike those previous methods and techniques that
    Petition 870190129656, of 12/06/2019, p. 12/50 / 23 implement point-to-point correction of surface position measurements taken by the coordinate positioning apparatus, the method of the present invention generates a first correction value for a first geometric property of one or more characteristics of a first part . Such first correction value can be used to subsequently correct geometric properties measured from parts nominally identical to the first part that are acquired in the coordinate positioning apparatus. The method of the present invention thus avoids the need to generate and store large point-to-point error correction maps and on the other hand creates a geometric correction value to compensate for any errors in the measured geometric property of a feature or features of a feature. part. Using such a geometric correction value also reduces some of the data point alignment difficulties that can arise when using large error maps to perform point-to-point surface corrections. Such a method of the present invention then allows a measured geometric property of a part to be precisely found using a coordinate positioning apparatus in a simpler and more convenient way than the known point-to-point correction techniques. Such an invention is particularly suitable for use with a coordinate positioning device that operates in a production environment and therefore requires frequent recalibration (for example, due to thermal changes in the environment, etc.).
    [0014] The first reference geometric property associated with one or more characteristics of the first part can comprise a nominal reference geometric property. Such a nominal reference geometric property can conveniently be derived from design data (for example, a CAD model) associated with the first part. For example, step (i) may comprise taking or processing design data associated with the first part to provide the first reference geometric property. In such an example, step (iii) can then comprise comparing
    Petition 870190129656, of 12/06/2019, p. 13/50 / 23 the geometric reference property of step (i) with the measured geometric property of step (ii) to obtain the property correction value.
    [0015] Advantageously, step (i) comprises the step of using a reference coordinate positioning device to measure the first part. The first reference geometric property can then comprise a measured reference geometric property that is obtained from measurements of the first part taken by the reference coordinate positioning apparatus. In other words, reference measurements obtained from the reference coordinate positioning apparatus are conveniently used to determine at least one measured geometric reference property associated with one or more characteristics of the first part.
    [0016] Advantageously, the reference coordinate positioning apparatus is a different machine from the coordinate positioning apparatus that implements the method of the present invention. Conveniently, the reference coordinate positioning apparatus comprises a pre-calibrated coordinate measuring machine. This CMM can be a series machine, such as a conventional bridge-type CMM, calibrated to an appropriate national or international standard. The reference coordinate positioning device can be located remotely from the coordinate positioning device in which the measurements acquired in step (ii) of the method are taken. The step of using the reference coordinate positioning apparatus to measure the first part and / or the step of determining the first geometric reference property of the first part can be carried out before or after step (ii) as necessary.
    [0017] Advantageously, the one or more characteristics of the first part comprise a first characteristic. At least one geometric reference property can then be provided in a way that describes a
    Petition 870190129656, of 12/06/2019, p. 14/50 / 23 geometric property of the first feature alone. In such an example, the first geometric reference property can conveniently describe at least one of size (e.g., radius), shape, linearity, flatness, circularity and cylindricity of the first feature. For example, the first reference geometric property can describe the radius of a first feature in the form of a hole.
    [0018] The first part can also comprise a plurality of characteristics. Conveniently, said one or more features of that first part may comprise at least one first feature and a second feature. In such an example, the first geometric reference property can describe a relationship between the first characteristic and the second characteristic. Advantageously, the first geometric reference property can comprise at least one of parallelism, perpendicularity, angularity, position, concentricity, coaxility, symmetry, circular axial displacement or total axial displacement of the first feature relative to the second feature. It should be noted that that first part may also include one or more other features or geometric properties that may or may not be measured during the method.
    [0019] The first part preferably comprises a machine part. The first part can be formed by metal cutting, molding, casting, forging, pickling, etc. the first part may comprise metal, alloy, composite material, plastic, etc. as an example, the first part may comprise an engine block. It is preferred that the first geometric reference / measurement property of the characteristics of the first part refers to a key manufacturing parameter of that part. In other words, the method of the present invention is preferably used to check whether machined parts have been manufactured to a desired tolerance. Examples of geometric properties that can be used to define a tolerance are highlighted in British Standard 308 (ISBN 0 580 33204 7), the contents
    Petition 870190129656, of 12/06/2019, p. 15/50 / 23 of which are incorporated herein by reference.
    [0020] The first property correction value determined in step (iii) can comprise a difference between a measured geometric property and the associated reference geometric property. Advantageously, the first property correction value comprises a difference vector between a measured geometric property and the associated reference geometric property. In other words, it is preferred that the first property correction value includes both a magnitude and a direction. For example, a property correction value can include the magnitude of the radius error (for example, in SI or arbitrary units) plus a direction of that radius error (for example, if the measured radius is less or greater than the radius nominal).
    [0021] The method can use only the first reference geometric property of the first part. Advantageously, at least one additional reference geometric property associated with one or more characteristics of the first part is known. Each additional geometric reference property can relate to the same, or different, characteristics of the first part. Step (ii) of the method can thus also comprise determining at least one additional measured geometric property that corresponds to an additional reference geometric property. Each additional measured geometric property can be calculated from measured points also used to determine the first measured geometric property and / or from additional measurements of the first part taken using the coordinate positioning apparatus.
    [0022] In such an embodiment, step (iii) can advantageously comprise determining at least one additional property correction value describing the difference between each additional reference geometric property and the associated additional measured geometric property. Step (iv) can then include using the positioning device of
    Petition 870190129656, of 12/06/2019, p. 16/50 / 23 coordinates to also measure one or more additional parts in the series of nominally identical parts and, for each additional part, determine a measured geometric property that corresponds to each additional reference geometric property. In step (v) the appropriate additional property correction value can be applied to each measured geometric property of each of the additional parts.
    [0023] The method of the present invention can be implemented by any type of coordinate positioning apparatus. The coordinate positioning apparatus may comprise a coordinate measuring machine that is dedicated to measuring a machine tool that can be used for measurement and for machining operations. Preferably, the coordinate positioning apparatus comprises a parallel kinematic coordinate positioning apparatus. A parallel coordinate positioning apparatus may comprise a base platform connected to a mobile platform by a plurality of extensible struts. The extension of the struts in parallel produces the necessary movement of the mobile platform (for example, in the x, y, and z directions). This should be contrasted with the traditional bridge or series coordinate positioning device in which linear movements along multiple (for example, three) mutually orthogonal linear axes are achieved when applied to the parallel kinematic coordinate positioning device as measurements taken with such a device they are repeatable but the device is difficult to pinpoint the error map. The present invention thus overcomes the need for accurate initial error mapping of the instrument's measuring volume and instead uses at least one property correction value to correct the measured geometric properties of a series of parts.
    [0024] The coordinate positioning apparatus can comprise a measuring probe of any type. The measuring probe
    Petition 870190129656, of 12/06/2019, p. 17/50 / 23 can be a non-contact probe (for example, optical, inductive, capacitive, etc.). advantageously, the measuring probe of the coordinate positioning apparatus comprises a contact measuring probe having a deflecting needle. Step (ii) of the method can then conveniently comprise moving the probe so that the tip of the deflecting needle contacts multiple points on the surface of the part. The contact probe can be a touch trigger probe that emits a trigger signal when the needle is deflected. Advantageously, the contact probe is an analog probe or scanning probe that provides a needle deflection measurement in your local coordinate system. Preferably, the probe is an SP25 probe as manufactured by Reinshaw, Wottonunder-edge, Gloucestershire, United Kingdom.
    [0025] According to a second aspect of the invention, the coordinate positioning apparatus comprises a measuring probe and a controller, in which the controller is programmed to implement an error correction technique for a first part in a series of parts nominally identical having one or more characteristics, in which the controller stores at least one first reference geometric property associated with one or more characteristics of the first part, the error correction technique implemented by the controller comprises the steps of;
    use the probe to measure one or more characteristics of the first part and calculate from it a first measured geometric property of the first part, the first measured geometric property corresponding to the first reference geometric property, and compare the first geometric property of reference with the first measured geometric property and calculate a first property correction value,
    Petition 870190129656, of 12/06/2019, p. 18/50 / 23 where the controller stores the first property correction value to correct measured geometric properties of one or more additional parts that are nominally identical to the first part. [0026] Also described here is a method for determining measurement errors for a coordinate positioning apparatus comprising a measurement probe, the method comprising the steps of:
    (i) taking a first part in a series of parts, the first part having one or more features, in which at least one geometric reference property associated with one or more features is known;
    (ii) use the coordinate positioning apparatus to measure the position of a plurality of points on the surface of each of the one or more characteristics of the first part and determine from this at least one measured geometric property of the first part, in which at least at least one measured geometric property corresponds to at least one reference geometric property; and (iii) comparing at least one reference geometric property of step (i) with at least one measured geometric property of step (ii) and thus obtaining at least one property correction value.
    [0027] An error correction method for the coordinate positioning device is also presented here, the method comprises the steps of;
    (a) taking at least one property correction value that has been calculated for a first part in the manner described above, wherein the first part comprises one or more features and at least one reference geometric property of one or more features is known, (b) use a coordinate positioning device to
    Petition 870190129656, of 12/06/2019, p. 19/50 / 23 measure the position of a plurality of points on the surface of each of the characteristics of a second part that is nominally identical to the first part and determine from this at least one measured geometric property of the second part that corresponds to at least a reference geometric property, and (c) correct at least one geometric property measured in step (b) using at least one property correction value from step (a) in this way providing at least one measured geometric property corrected for the second part.
    [0028] The coordinate positioning apparatus is also described in such a way that it comprises a measuring probe and a controller provided, in which the controller is programmed to implement an error correction technique for a part in a series of nominally identical parts having one or more characteristics, in which the controller stores at least one geometric reference property associated with one or more characteristics of the part, the error correction technique implemented by the controller comprising the steps of; use the probe to measure the position of a plurality of points on the surface of each of the one or more characteristics of the part and calculate from it at least one measured geometric property of the part, at least one measured geometric property corresponding to reference geometric property, and compare at least one reference geometric property with at least one measured geometric property and calculate at least one property correction value. Advantageously, the controller stores at least one correction value owned by one or more additional parts that are nominally identical to the first part.
    [0029] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which;
    Petition 870190129656, of 12/06/2019, p. 20/50 / 23
    Figure 1 illustrates a modality of the coordinate positioning apparatus of the present invention,
    Figure 2 shows the parallel positioning mechanism of the device in Figure 1 in greater detail,
    Figures 3a and 3b show an example of a part to be measured that comprises a plurality of features and illustrates geometric properties of these features,
    Figure 4 illustrates a coordinate measuring machine (reference) in series, and
    Figures 5a to 5c illustrate how various geometric properties can be represented in drawings according to BS308. [0030] Referring to Figure 1, a device for positioning parallel coordinates is shown in such a way that it is operable according to the present invention. The apparatus comprises a bed 2 attached to a base platform or higher 4 by a plurality of support struts 6. The support struts 6 are sufficiently rigid to ensure that the base platform 4 is secured in a fixed position with respect to the bed 2. The base platform 4 is also attached to a mobile platform 8 by a restricted parallel positioning mechanism 10. For clarity, details regarding the parallel positioning mechanism 10 are omitted from Figure 1 and the mechanism is shown in detail in Figure 2. The base platform 4, the mobile platform 8 and the parallel positioning mechanism 10 thus form a restricted parallel positioning machine that controls the translational movement of the mobile platform 8 along three axes (X, Y, Z).
    [0031] The mobile platform 8 carries a measuring probe 18 having a deflecting needle 20. A part 24 to be measured by the measuring probe 18 is also shown located on the bed 2 of the apparatus. A computer controller 22 is provided for controlling operations of the apparatus, in particular for controlling movement of the mobile platform 8 and for receiving data from
    Petition 870190129656, of 12/06/2019, p. 21/50 / 23 measurement from measurement probe 18.
    [0032] Measurement probe 18 may be an SP25 probe as sold by Renishaw plc, Wotton-under-edge, Gloucestershire, United Kingdom. The SP25 measuring probe is a so-called scanning probe or similar probe that emits needle tip deflection measurements in its local coordinate system. the probe 18 is moved (that is, by the movement of the mobile platform 8) so that the needle tip traces a path on the surface of part 24. Controller 22 receives the needle tip deflection from the measurement probe 18 and Parallel coordinate positioning device data referring to the position of the probe. These are combined to allow said positions of multiple points on the surface of the part to be found in the machine coordinate system (that is, with respect to a fixed point or the origin of the machine).
    [0033] Although the present example shows an analog measuring probe, it would also be possible to take measurements using a so-called touch trigger probe that emits a signal when the needle is deflected. If such a touch trigger probe was used, the needle would be triggered in contact with a plurality of different measurement points on the surface of the part. Data referring to the position of the probe when the trigger signal is issued can then be used to establish the position of the surface contact points. It should also be noted that although the probe 18 is a contact probe, on the other hand it would also be possible to use a non-contact probe (for example, optical, inductive, capacitive, etc.).
    [0034] Referring to Figure 2, the parallel positioning mechanism used in the Figure 1 apparatus will now be described in greater detail, note that the illustration of the restricted parallel positioning mechanism given in Figure 2 is inverted (that is, upside down) below) compared to the view in Figure 1.
    Petition 870190129656, of 12/06/2019, p. 22/50 / 23 [0035] The restricted parallel positioning mechanism comprises a base platform 4 which is mounted on a mobile platform or stage 8 by a plurality of struts. In particular, the base platform 4 and the mobile platform 8 are connected by three energized telescopic struts 40, the ends of which are connected to the respective platforms by the pivot joints. Each energized telescopic strut 40 has a motor 42 to increase or decrease its length and a position encoder (restricted within the motor housing and therefore not visible in Figure 2) to measure its length. Three anti-rotational devices 44 are also provided to restrict the three degrees of rotation between the base platform 4 and the mobile platform 8; it should be noted that the anti-rotation devices are passive and do not comprise an engine or any other type of actuator. The extension of the energized telescopic struts 40 of the machine then provides only translational (non-rotational) movement between the base platform 4 and the mobile platforms 8. In other words, the mobile platform 8 can be translated into space with respect to the base platform 4 fixed and such a translation can be described in terms of movement along the X, Y and Z axes. the controller 22 as shown in Figure 1 then activates the various motors that extend and retract the energized telescopic struts 40 to move the probe 18 and also receive feedback from the position encoders referring to the strut extension from which the positions of the mobile platform and the probe can be determined.
    [0036] Now referring to Figures 3a and 3b, the part 24 positioned in bed 2 of the above described coordinate positioning apparatus is shown in greater detail. In particular, Figure 3a shows a side sectional view of part 24 and Figure 3b shows a top view of part 24.
    [0037] Part 24 can be viewed to comprise a substantially cylindrical bore 50 having a central axis 52 which is angled by
    Petition 870190129656, of 12/06/2019, p. 23/50 / 23 an angle θ in the x - z plane with respect to a reference surface 54. Part 24 can thus be considered to comprise a first feature (hole 50) and the second feature (reference surface 54) . Part 24 also has certain geometric properties associated with the first and second characteristics. For example, one or more geometric properties of part 24 may include the radius r of the hole, the angle θ by which the center axis of the hole is inclined with respect to the reference surface or the spacing “a” between the center of the hole a from the reference surface. It can then be observed in such a way that a geometric property associated with the first and second features can comprise a geometric property of a single feature or a plurality of features: it should be noted that the position of a single point on the surface of the measured part in the machine coordinate system is not a geometric property of that part.
    [0038] In a first step of a method of the present invention, part 24 is positioned on bed 2 of the parallel coordinate positioning apparatus which is described above with reference to Figures 1 and 2. In this example, one or more geometric properties The reference radius comprises the nominal radius r of the cylindrical hole and the nominal inclination angle θ of the central axis of the hole relative to the reference surface. These reference geometric properties may have been measured previously (for example, using a calibrated CMM as described in more detail below) or can be derived from the design data (for example, CAD / CAM data) for part 24.
    [0039] Once part 24 is positioned on the parallel coordinate positioning apparatus, the probe 18 is moved along a path in which it allows the surface of part 24 to be scanned. The scanner path allows the position of multiple points on the surface of part 24, particularly in the region of the first and second
    Petition 870190129656, of 12/06/2019, p. 24/50 / 23 features 50 and 54, to be collected from which the one or more geometric properties measured in part 24 can be found. For example, multiple measurement points can be collected on the inner surface of the hole and thus allowing the radius r of the hole to be determined using a numerical adjustment process (for example, sum of least squares). The central axis of the hole can also be determined in the machine coordinate system using this adjustment process. Multiple measurements acquired on the reference surface can then also be used to find that location of the reference surface in machine coordinates. The inclination angle θ of the center hole axis with respect to the reference surface can then be determined.
    [0040] Once the measured geometric properties have been discovered, they are compared to the associated reference geometric properties and a property correction value is determined. For example, a reference hole radius can be compared to the measured hole radius and a determined hole reaction correction value. Similarly, the measured and reference values of the tilt angle θ (ie, the angularity between the central axis and the reference surface) can be compared to establish a tilt angle correction value. The property correction values that are determined using this method can then be observed to allow geometric properties measured using the parallel coordinate positioning device to be mapped or corrected to match the associated reference geometric properties. This avoids the need for the parallel coordinate positioning device's error map, which is practically difficult to reach, but still allows precise geometric properties to be determined using the device.
    [0041] The method described above for determining the property correction values realized in a first part of a series of
    Petition 870190129656, of 12/06/2019, p. 25/50 / 23 nominally identical parts. The property correction values can then be used to correct the measured geometric properties that are determined from measurements taken using the coordinate positioning apparatus on additional parts that are nominally identical to the first part. In other words, property correction values can be determined for a first part in a series of identical parts to be measured using the coordinate positioning apparatus and such property correction values used to correct the subsequent measured geometric properties of other parts in series. The measurement of additional parts in the series preferably takes place in a similar region of the parallel coordinate positioning machine, but the present invention removes the need to perform a point-to-point correction of the measurements acquired by the parallel coordinate positioning apparatus. Instead, the measured geometric properties (for example, the radius r and the slope angle θ in the present invention) that are found from multiple points measured on the surface of the part are corrected. This process has been found to be simpler to implement than point-to-point corrections while also providing measurements that are corrected to the required precision.
    [0042] Referring to Figure 4, illustrates a coordinate measuring machine in series 102 to measure the reference geometric properties of a part is shown. CMM 102 comprises a base or table 104 on which an object (for example, a part such as a part 24 described above) can be positioned and a gantry 106 which is movable in the x and y directions with respect to the base 104. The gantry 106 includes a hollow axis 108 that is movable along a z direction with respect to frame 106. Position encoders are provided on each axis of the CMM 102 to measure the position of the hollow axis in the x, y and z directions. it can be seen that the three axes (x, y, z) of the CMM movement are built in a series way.
    Petition 870190129656, of 12/06/2019, p. 26/50 / 23 [0043] The hollow shaft 108 carries the indexing probe head 110, as does a motorized probe head Renishaw PH10. The CMM 102 can be considered a reference measuring machine. The indexing probe head 110 comprises a base attachment portion that is attached to the hollow shaft 108 and a probe attachment portion that carries a scanning probe 112 having a deflecting needle 114. The scanning probe 112, which can comprising a Renishaw SP25 probe, includes internal transducers that measure any deflection of needle 114 away from a so-called neutral or resting position. Any deflection of the needle 114 is thus measured by the scanning probe 112 in its local (a, b, c) coordinate system (probe). To improve the ability to scan complex objects, the indexing probe head 110 allows the scanning probe 112 to be rotated, with respect to the hollow axis, around the orthogonal axes A1 and A2 and locked in any of the multiple indexed positions . In the case of the Renishaw PH10 probe head, the probe can be indexed in any of 720 different indexed positions. A controller 116 controls the operation of the CMM.
    [0044] The 102 series CMM is calibrated in a known manner, for example, using a traceable calibration standard. The CMM is also preferably located in a clean, temperature-controlled environment to maximize measurement accuracy. This allows points on the object's surface to be measured in the machine coordinate system with a high level of measurement accuracy.
    [0045] The present invention can thus include a step of using CMM in series 102 to measure multiple points on the surface of a part, such as part 24 described above with reference to Figures 1 to 3. The one or more geometric reference properties of the part (for example, the radius r and the inclination angle θ) can be extracted. These measured geometric reference values are taken as reverence values (real) and the
    Petition 870190129656, of 12/06/2019, p. 27/50 / 23 same geometric properties are measured using the parallel CMM described above.
    [0046] The examples of geometric properties shown in Figures 3a and 3b are merely illustrative. Figures 5a to 5c (which are drawn according to BS308: Part 3: 1990) illustrate additional examples of parts that can comprise a plurality of features and in which at least one geometric property can be defined in a way that describes a relationship between the plurality of characteristics.
    [0047] Figure 5 shows angularity as an example of a geometric property. The oblique surface shown in the diagram is defined as having an angle of 60 ° in relation to the reference surface A. The diagram also specifies how this angularity is to be achieved within the tolerance of 0.1 °.
    [0048] Figure 5b shows the relative position as an example of a geometric property. The diagram shows how the center of the identified hole is located 30 mm from the reference surface A and 60 mm from the reference surface B. The diagram also specifies how accurate these distances should be in the 0.1 mm range.
    [0049] Figure 5c shows parallelism as an example of a geometric property. The diagram shows how the hole wall should be parallel to reference surface A within a range of 0.1 °.
    [0050] Figures 5a to 5c are merely a few examples of how geometric properties and tolerances are typically represented graphically in design documents and the like. Many other additional examples of such geometric properties are described in section one of part three of document BS308 referenced above and such examples are hereby incorporated by reference.
    [0051] It should also be remembered that the above modalities are merely examples of the present invention. In particular, it is important to note
    Petition 870190129656, of 12/06/2019, p. 28/50 / 23 that the method of the present invention could be used to correct a serial coordinate positioning apparatus, and not just a parallel coordinate positioning apparatus as described above. In addition, the reference geometric properties of a part can be determined in a number of different ways. While using a reference CMM (for example, calibrated) to obtain measured reference geometric properties of a part is advantageous, it is by no means the only way in which the necessary reference geometric properties of a part can be found to a high level of accuracy. The nominal reference geometric properties of one or more characteristics of the part can also, for example, be derived from the design data.
    [0052] It would also be possible to derive property correction values between a plurality of different derived geometric properties. For example, in addition to obtaining property correction values that describe the difference between geometric properties as measured by a serial (reference) positioning device and a parallel coordinate positioning device, it would also be possible to obtain correction values. of property describing the difference between geometric properties as measured by the serial coordinate positioning device (reference) and the associated nominal geometric properties. In this way, geometric properties measured by the parallel coordinate positioning device can be corrected to allow comparison with the measured reference geometric properties acquired using a serial (reference) positioning device and additionally corrected for comparison with the geometric reference properties. nominal values derived from design data.
    权利要求:
    Claims (15)
    [1]
    1. Method for operating a coordinate positioning apparatus having a measuring probe (18), a method characterized by the fact that it comprises the following steps in any suitable order:
    (i) taking a first part (24) in a series of identical parts nominally, at least one first geometric reference property associated with one or more characteristics of the first part (24) being known, (ii) using such a coordinate positioning apparatus to measure said (s) one or more characteristics of the first part (24) and determine from it a first measured geometric property that corresponds to the first reference geometric property, such a first measured geometric property being established using the measured position of multiples points on the surface of each of those (s) one or more characteristics of said first part (24), (iii) determining a first property correction value that describes a difference between the first reference geometric property and the first measured geometric property , (iv) use such a coordinate positioning device to measure said (s) one or more characteristics of a plurality of additional parts in the series of identical parts nominally and, for each additional part, determine an additional measured geometric property that corresponds to that first reference geometric property, and (v) apply the first property correction value to each additional measured geometric property .
    [2]
    2. Method according to claim 1, characterized in that said (s) one or more characteristics of the first part comprise at least a first characteristic (50) and a second characteristic (54), in which the first geometric property of reference describes a relationship between the first characteristic (50) and the second characteristic (54).
    Petition 870190129656, of 12/06/2019, p. 30/50
    2/4
    [3]
    3. Method according to claim 2, characterized by the fact that that first reference geometric property comprises at least one among parallelism, perpendicularity, angularity, position, concentricity, coaxility, symmetry, circular or total axial displacement of the first characteristic (50 ) in relation to the second characteristic (54).
    [4]
    Method according to claim 1, characterized in that said (s) one or more characteristics of the first part comprise first characteristic (50), and the first reference geometric property describes a geometric property of the first characteristic (50) alone.
    [5]
    5. Method according to claim 4, characterized by the fact that that first reference geometric property describes at least one among the size, shape, linearity, flatness, circularity and cylindricity of the first characteristic (50).
    [6]
    Method according to any one of claims 1 to 5, characterized in that the first reference geometric property comprises a nominal geometric property derived from design data associated with the first part (24).
    [7]
    Method according to any one of claims 1 to 5, characterized in that step (i) comprises the step of using a reference coordinate positioning apparatus (102) to measure the first part (24), in that such a first reference geometric property comprises a measured reference geometric property obtained from the measurements of the first part taken using a reference coordinate positioning apparatus.
    [8]
    Method according to claim 7, characterized by the fact that said reference coordinate positioning apparatus (102) comprises a pre-calibrated coordinate measuring machine, bridge type.
    [9]
    Method according to any one of claims 1 to 8, characterized in that step (ii) comprises using that coordinate positioning apparatus to measure the position of a plurality of
    Petition 870190129656, of 12/06/2019, p. 31/50
    3/4 points on the surface of each of those one or more characteristics of said first part (24).
    [10]
    10. Method according to claim 9, characterized by the fact that step (ii) comprises adjusting the plurality of points measured by the coordinate positioning apparatus in a function to establish the first measured geometric property.
    [11]
    A method according to any one of claims 1 to
    10, characterized by the fact that the first property correction value determined in step (iii) comprises a vector difference between the first measured geometric property and the first reference geometric property.
    [12]
    12. Method according to any one of claims 1 to
    11, characterized by the fact that the coordinate positioning device comprises a device for positioning parallel kinematic coordinates.
    [13]
    13. Method according to any one of claims 1 to
    12, characterized by the fact that at least one additional reference geometric property associated with one or more characteristics of said first part (24) is known.
    [14]
    14. Method according to any one of claims 1 to
    13, characterized by the fact that that measuring probe (18) of the coordinate positioning apparatus comprises a contact measuring probe having a deflecting needle (20).
    [15]
    15. Coordinate positioning device, this device comprising a measuring probe (18) and a controller (22), characterized by the fact that the controller (22) is programmed to implement an error correction technique for a first part ( 24) in a series of identical parts nominally having one or more characteristics, wherein said controller (22) stores at least one first reference geometric property that is associated with said one or more characteristics of the first part (24), the error correction technique implemented by the controller (22) including the steps of:
    Petition 870190129656, of 12/06/2019, p. 32/50
    4/4 use the measurement probe (18) to measure said (s) one or more characteristics of the first part (24) and calculate from it a first measured geometric property of the first part (24), the first measured geometric property corresponding to that first reference geometric property, with that first measured geometric property being established using the measured position of multiple points on the surface of each of said (s) one or more characteristics of the first part (24), and comparing the first geometric property reference with that first measured geometric property and calculate a first property correction value, where the controller (22) stores the first property correction value and uses the first property correction value to correct the measured geometric properties of a plurality of additional parts that are nominally identical to that first part (24).
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    法律状态:
    2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2019-09-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-03-17| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2020-05-05| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 28/02/2011, OBSERVADAS AS CONDICOES LEGAIS. |
    2021-12-21| B21F| Lapse acc. art. 78, item iv - on non-payment of the annual fees in time|Free format text: REFERENTE A 11A ANUIDADE. |
    优先权:
    申请号 | 申请日 | 专利标题
    GBGB1003363.7A|GB201003363D0|2010-03-01|2010-03-01|Measurement method and apparatus|
    PCT/GB2011/000274|WO2011107729A1|2010-03-01|2011-02-28|Correcting errors in measurements taken using a coordinate positioning apparatus|
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