Method and Device for Measuring a Measurement Object

Abstract

A method for measuring a measurement object (1), in particular for determining the position and/or distance of a measurement object (1), for example for measuring the width and/or for measuring the flatness of a measurement object (1), using a measuring system (2) movable along a linear axis (7), wherein the measuring system (2) has at least one sensor (4) and wherein means (9) are arranged to detect a position of a reference point (8) of the measuring system (2), wherein at least one measured value of the measurement object (1) is detected using the sensor (4) and wherein a measurement error of the measured value caused by an inclination of the linear axis (7) by an angle of inclination ? is determined and wherein the measured value is corrected by the measurement error.

Claims

1. A method for measuring a measurement object, in particular for determining the position and/or distance of a measurement object, for example for measuring the width and/or for measuring the flatness of a measurement object, comprising: using a measuring system movable along a linear axis, wherein the measuring system has at least one sensor; wherein means are arranged to detect a position of a reference point of the measuring system; wherein at least one measured value of the measurement object is detected using the sensor; wherein a measurement error of the measured value caused by an inclination of the linear axis by an angle of inclination ? is determined; wherein the measured value is corrected by the measurement error.

2. The method according to claim 1, wherein a horizontal measured value of the measurement object is detected, which indicates a position in the extension direction of the linear axis and/or in that a vertical measured value of the measurement object is detected, which indicates a position in the direction perpendicular to the extension direction of the linear axis.

3. The method according to claim 2, wherein a horizontal measurement error p.sub.h of the horizontal measured value is determined using the formula $p_h=r.Math.\sin \left(?\right)$ wherein r is the vertical distance between the linear axis and the measurement object.

4. The method according to claim 2, wherein a horizontal measurement error p.sub.h,ges of the horizontal measured value is determined using the formulas $p_1=r.Math.\sin \left(?\right)$ $p_2=a-a.Math.\cos \left(?\right)$ $p_{h,\mathrm{ges}}=p_1-p_2$ wherein r is the vertical distance between the linear axis and the measurement object and wherein a is the horizontal distance between an edge of the measurement object and the reference point.

5. The method according to claim 2, wherein a vertical measurement error p.sub.v of the vertical measured value is determined using the formula $p_v=r-r.Math.\cos \left(?\right)$ wherein r is the vertical distance between the linear axis and the measurement object.

6. The method according to claim 2, wherein a vertical measurement error p.sub.v,ges of the vertical measured value is determined using the formulas $p_3=r-r.Math.\cos \left(?\right)$ $p_4=a.Math.\sin \left(?\right)$ $p_{v,\mathrm{ges}}=p_3+p_4$ wherein r is the vertical distance between the linear axis and the measurement object and wherein a is the horizontal distance between an edge of the measurement object and the reference point.

7. The method according to claim 1, wherein the angle of inclination ? of the linear axis is determined via an inclination sensor of the measuring system.

8. The method according to claim 1, wherein the angle of inclination ? of the linear axis is determined at defined measuring points.

9. A device for measuring a measurement object, in particular for determining the position and/or distance of a measurement object, for example for measuring the width and/or for measuring the flatness of a measurement object, comprising: a measuring system movable along a linear axis, wherein the measuring system (2) has at least one sensor; means arranged to detect a position of a reference point of the measuring system; wherein at least one measured value of the measurement object is measurable using the sensor and wherein a measurement error of the measured value caused by an inclination of the linear axis by an angle of inclination ? is determinable by a correction unit and wherein the measured value is correctable by the measurement error by the correction unit.

10. The device according to claim 9, wherein an inclination sensor for determining the angle of inclination ? of the linear axis is arranged on the measuring system.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0035] FIG. 1 shows a schematic representation of an exemplary embodiment of a device according to the present disclosure for carrying out the method according to the present disclosure,

[0036] FIGS. 2a to 2c show schematic representations of the effect of an inclination of the linear axis on the horizontal measured value,

[0037] FIG. 3 shows a schematic representation of an approximation of the horizontal measurement error when the linear axis is inclined,

[0038] FIG. 4 shows a schematic representation of the real horizontal measurement error when the linear axis is inclined,

[0039] FIG. 5 shows a schematic representation of an illustration of the angle of inclination,

[0040] FIG. 6 shows the change in the angle of inclination of a linear axis measured over several days, and

[0041] FIG. 7 shows a schematic representation of the real vertical measurement error when the linear axis is inclined.

[0042] To improve clarity, not all elements in the figures are always provided with a reference numeral, wherein the same elements are identified by the same reference numerals in the figures.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0043] With FIG. 1, the measurement errors to be compensated for by the present disclosure are explained using a measurement of width. For a measurement of flatness, a sensor system for distance measurement would have to be outlined in FIG. 1. Instead of the horizontal measuring direction, the vertical measuring direction would have to be considered instead.

[0044] FIG. 1 shows an exemplary embodiment of a device for measuring the width of a measurement object 1. The device has a measuring system 2 having a C-frame 3 and a sensor 4, which in this exemplary embodiment is designed as an optical micrometer. The sensor 4 detects the relative edges 5, 6 of the measurement object 1 to the C-frame 3 in a horizontal measuring direction, i.e., along the extension direction of the linear axis 7. In order to determine the position of the sensor 4, a reference point 8 is provided, the position of which on the linear axis 7 is determinable using suitable means 9 for detecting the position. In this exemplary embodiment, the position of the reference point 8 can be determined absolutely using an incremental magnetic tape 9, which is thus used as a means 9 for detecting the position. Other embodiments of the means 9 are conceivable, for example a sensor, in particular an optical sensor or a cable pull sensor. If both position values are detected synchronously during the measurement run, the absolute edge position of the measurement object can be determined by simply adding the two values.

[0045] The difference between the measured values of the sensor 4, i.e., the measured positions of the two edges 5, 6 of the measurement object 1, corresponds to the width of the measurement object 1, wherein the latter must not be moved during the width measurement.

[0046] Furthermore, a correction unit 10 is shown in FIG. 1, which can be, for example, a computer having appropriate software. The correction unit 10 is used to correct measurement errors caused by an inclination of the linear axis 7 by an angle of inclination ?. In order to detect the angle of inclination ?, the measuring system 2 can have an inclination sensor 11, wherein this does not necessarily have to be the case. To simplify the illustration, the correction unit 10 and the inclination sensor 11 are not shown in the other figures, but can nevertheless be provided therein.

[0047] The horizontal measurement error is illustrated in FIGS. 2a to 2c, wherein three situations are shown on the linear axis 7: [0048] Ideal alignment (FIG. 2a): the actual position of the edge 6 of the measurement object 1 and the detected position of the edge 6 of the measurement object 1 on the linear axis 7 correspond. [0049] Inclination forward (FIG. 2b): the detected position of the edge 6 of the measurement object 1 is trailing behind the actual position of the edge 6 of the measurement object 1. [0050] Inclination backward (FIG. 2c): the detected position of the edge 6 of the measurement object 1 is leading in front of the actual position of the edge 6 of the measurement object 1.

[0051] If the angle of inclination ? and the geometric position of the measurement object 1 are known, the position deviation can be determined in the manner according to the present disclosure.

[0052] FIG. 3 shows the basic error in simplified form. The edge 6 of the measurement object 1 was chosen as the pivot point 12 for the inclination. The expected horizontal measurement error p.sub.h is plotted in the direction of the linear axis 7. The representation is simplified in that the detected measured value of the edge 6 of the sensor 4 and the detection of the reference point 8 (for example sensor of the magnetic tape on the slide of the linear axis 7) lie geometrically one above another. If this is not the case, the result is a slightly different calculation, which is shown in FIG. 4. Only the horizontal position changes are shown in FIG. 4.

[0053] According to FIG. 3, the corresponding inclination of the measuring system 2 caused by the angle of inclination ? of the linear axis 7 can be split into two movements: [0054] The rotational movement causes a vertical height change (difference measurement object 1?linear axis 7), which can be ignored for a width measurement. It comes into play when measuring flatness, as the measuring distance is then distorted due to the inclination. [0055] The rotational movement causes a horizontal distance change between the measured value of the edge 6 detected by the sensor 4 and the reference point 8 of the linear axis 7.

[0056] If the angle of inclination ? and the height difference r between the linear axis 7 and the measurement object 1 are known, the position changes in the horizontal direction, i.e., the horizontal measurement error p.sub.h, and the position change in the vertical direction, i.e., the vertical measurement error p.sub.v, can be calculated as follows:

[00005]$p_h=r.Math.\sin \left(?\right)$$p_v=r-r.Math.\cos \left(?\right)$

[0057] If the distance between the edge 6 of the measurement object 1 and the reference point 8 on the measuring system 2 is also taken into consideration when determining the inclination, then FIG. 4 shows the situation schematically.

[0058] The horizontal measurement error p.sub.h,ges can be determined by two movements. As shown in FIG. 3, the height difference r causes the majority of the position change p.sub.1. The distance a between the edge 6 of the measurement object 1 and the reference point 8 causes a second horizontal position change p.sub.2. The difference between the two position changes results in the total horizontal measurement error p.sub.ges:

[00006]$p_1=r.Math.\sin \left(?\right)$$p_2=a-a.Math.\cos \left(?\right)$$p_{h,\mathrm{ges}}=p_1-p_2$

[0059] From the formula for p.sub.2 it can be seen that this distance value can be neglected for small angles of inclination ?.

[0060] FIG. 6 shows the measured inclination change of a linear axis 7 of 2.2 m length. The inclination of the linear axis 7 was measured over several days. Typically, inclination values are given in degrees [?]. Since the expected values of an inclination change on a linear axis 7 are relatively small and in order to get a better idea of the expected error, [?m/m] was chosen as the unit, i.e., the inclination change in [?m] per meter and reference distance are selected to be plotted against one another. If the height difference between the edge 5, 6 of the measurement object 1 and the linear axis is to be 1 m, the expected inclination error is shown in [?m]. FIG. 5 illustrates the relationship. An inclination of 600 ?m/m corresponds to an angle of approximately 0.057?.

[0061] Depending on where the edges 5, 6 lie, the angle of inclination ? of the linear axis 7 influences the result of a width measurement to a greater or lesser extent. The method according to the present disclosure and the device according to the present disclosure can be used to correct the measured values of the positions of the edges 5, 6 and thus minimize the expected measurement uncertainty.

[0062] The vertical measurement error p.sub.v, caused by the angle of inclination ? of a linear axis, is already shown in FIG. 3. The largest part of the measurement uncertainty is caused by the horizontal distance a between the measuring position on the measurement object 1 and reference point 8 on the linear axis. The relationship is shown in FIG. 7. The edge 6 on the measurement object 1 has again been selected as the measurement position as the virtual pivot point 12.

[0063] The vertical measurement error p.sub.v is shown in FIG. 3, which can be determined as follows:

[00007]$p_v=r-r.Math.\cos \left(?\right)=p_3$

[0064] In addition, the horizontal distance a between the edge 6 of the measurement object 1 and the reference point 8 causes a further vertical position change p.sub.4. This can be calculated by the following formula:

[00008]$p_4=a.Math.\sin \left(?\right)$

[0065] The total vertical position change p.sub.v,ges, caused by the axis inclination, can be determined by adding the two values p.sub.3 and p.sub.4:

[00009]$p_{v,\mathrm{ges}}=p_3+p_4$

[0066] With known angle of inclination ? of the linear axis 7 and known geometric dimensions of the measuring system in relation to the measuring position, the resulting vertical measuring error p.sub.v,ges can thus be calculated and corrected.

[0067] To avoid repetitions with regard to further advantageous embodiments of the device according to the present disclosure and the method according to the present disclosure, reference is made to the general part of the description and to the appended claims.

[0068] Finally, it should be expressly noted that the above-described exemplary embodiments of the device according to the present disclosure and of the method according to the present disclosure are used solely to explain the claimed teaching, but do not restrict it to the exemplary embodiments.

LIST OF REFERENCE NUMERALS

[0069] 1 measurement object [0070] 2 measuring system [0071] 3 frame [0072] 4 sensor [0073] 5 edge (measurement object) [0074] 6 edge (measurement object) [0075] 7 linear axis [0076] 8 reference point [0077] 9 means for position detection [0078] 10 correction unit [0079] 11 inclination sensor [0080] 12 pivot point [0081] ? angle of inclination [0082] r distance (linear axis?measurement object) [0083] a distance (measuring point?reference point)