DE3241074A1 - Method for error compensation in three-dimensional measuring and/or marking-out instruments - Google Patents

Abstract

A method for computerised error compensation of three-D measuring instruments is proposed, in which the deflection of the columns in two vertical, mutually perpendicular planes is measured by means of electronic spirit-levels and fed to a computer. The errors are determined from this in terms of angular tangent functions as a function of the transverse arm overhang length and the vertical distance thereof from the plane surface of the table per coordinate to a measurement point, and are logically combined by computer with the measured value for the purpose of correction. All errors are thereby taken into consideration, including temperature influences, errors in the drive system and other external effects on the instrument.

Description

Procedure for error compensation in three-dimensional

sionalen measuring and / or scribing devices The invention relates to a method for error compensation in three-dimensional measuring and / or scribing devices of the type mentioned in the preamble of claim 1.

Due to the stand construction of such devices, the result is Area of the cross arm and the vertical column deflections.

The deflection of the outer arm can be compensated in a known manner by that the Ouerarm inside with special, parallel as well as oblique to it extending clamping rods is braced. There are bending deformations in the area of the vertical column to be recorded, which are conditioned by the moment, which of the transverse arm accordingly the respective overhang. The bend in the column also hangs from the respective vertical distance of the cross arm with cross slide from the device base or the table surface. It is known to have a compensation device in these devices to be built in, the effects of the cantilevered cross arm on the column with foot at least partially compensated. These compensation devices include, for example Balance weight from which in a guide in the direction parallel to the cross arm so movable at the upper end of the column or on the cross slide or on the cross arm itself is stored that the exerted by the cross arm on the column, of the Cantilever dependent moment should be compensated.

This is intended to falsify the measurement due to the bending deformation of the perpendicular Pillar can be counteracted. The effort for such compensation devices is substantial.

This makes the device much more expensive and heavier.

In addition, there is almost complete error compensation in such devices not possible because this, for example, does not relate to other errors that also cause errors Can adapt to influences, e.g. external influences where the device is located, such as Influences of temperature, signs of wear and tear that have an increasing effect in the course of the operating time, e.g. in the area of guides, undetected damage to the device, etc. like

The invention is based on the object of a method for error compensation to create the type described in the preamble of claim 1, the constructive Design of the device not at all or only slightly impaired, therefore that is, it can be used with existing devices and retrospectively as well as in the case of newly created and delivered devices, especially no constructive ones Requires effort and weight and costs of the device practically not increased and nevertheless makes error compensation possible, which is quite precise within limits.

In the case of a method, the task is that described in the preamble of the claim 1 mentioned type according to the invention by the features in the characterizing part of the claim 1 solved. Advantageous further developments in this regard result from claims 2 - 7th

In principle, according to the method according to the invention, the error compensated arithmetically. The error deviations are only shown once each Coordinate is conveyed, so it is a record of the errors in different measuring positions The entire error deviation image of the device is drawn and stored in the computer. If the dismissal processing a measuring task a measured value in has taken over the computer, the computer looks for the correction value for the position and corrects the read-in measured value based on the stored error deviation image.

With this computational method, no changes at all are necessary on the device so that this procedure can also be used retrospectively for devices that have already been used can be used for error compensation. Even more precise because it is the error situation The mathematical error compensation method is always taken into account again at the respective measuring point, according to which the device-dependent error deviations for each individual measuring point the actual measurement. Here the invention proceeds from knowledge from that the vertical column in the one vertical plane, which is essentially is spanned by the transverse arm and the column, a turn in the direction of the transverse arm out, whereby one arithmetically this bending profile approximately through an angle can detect, according to the tangent function of the vertical distance of the transverse arm over the Table on the one hand and the projection length of the cross arm on the other hand is determined. Likewise can be a second bending angle within a perpendicular, perpendicular to the first plane standing level for the column also according to the tangent function and as a function of the sizes mentioned can be calculated. In this error compensation method in a simple way with the help of two transducers aligned at right angles to each other, each of which runs horizontally and lies in one of the said planes, the Turning angle detected. The advantage here is that this is independent of the projection length of the cross arm happens.

The error deviation is then calculated for each measuring point.

This is done either separately or in the computer. The resulting Error deviation is then compensated for in the computer by the fact that it uses the actual value by linking, namely adding or subtracting, to correct the error deviation and then calculates the measurement task entered for him. This also includes errors with not compensated for that caused by the turn, e.g. such errors that are caused by external influences, e.g. temperature influences, Influences from the management system or the like. Again, this procedure can be done without much difficulty used with existing devices. For this purpose, these devices only have to e.g. in the area of the cross slide with the aforementioned two transducers, preferably electronic spirit levels. This can easily be done afterwards happen.

The low structural effort is of particular advantage.

The cost of the device practically does not increase, neither does it its weight and its external appearance.

The object of the invention defined at the outset becomes more advantageous, more alternative Design also solved by the features of claim 8. With this arithmetical The computer calculates the compensation using known formulas for the deflection the correction value for the corresponding measuring point and corrects it. At this Evaluation, however, only calculated deflection errors are compensated, on the other hand, no further errors caused by other influences.

Further details and advantages result from the following Description. The complete wording of the claims is above alone not reproduced to avoid unnecessary repetition, but instead only referred to by naming the claim number, which however all claim features as expressly at this point and as belonging to the invention revealed to have to apply.

The invention is shown below with reference to in the drawings Embodiments explained in more detail. They show: FIG. 1 a schematic, for Partly sectioned side view of a device for three-dimensional measurement and / or Marking and / or probing workpieces, FIG. 2 is a schematic plan view of the device in the direction of arrow II in Fig. 1, Fig. 3 is a schematic side view of the device in the direction of arrow III in -Fig. 1, FIGS. 4a and 4b are each schematic simplified representations of the device in Fig. 1, once without bending the column and on the other hand with the turn of the column.

In Figs. 1-3 there is, for example, a stationary straightening plate 11 with an upper plane surface 12 shown, can be clamped on the workpieces to be measured, marked and / or touched are.

In this example, the straightening plate 11 carries on the visible long side, and also on the opposite long side, which is not visible, one only schematically indicated upper guide rail 13 and lower guide rail 14. Both are seated on the outside of the straightening plate 11 pointing to the left in FIG. 1, up and along the guide rails 13, 14 is a device 15 for three-dimensional measuring and marking and / or probing workpieces lying on the straightening plate 11 along the long side the straightening plate 11 can be moved. The device 15 has one designed, for example, as a carriage Foot 16, which with plain bearings and / or bearing rollers on the guide rails 13, 14 is supported on all sides and on it smoothly in one holizontal direction (X-axis) is movably mounted.

The foot 16 carries a fixed thereon, at right angles to the straightening plate 11 standing column 17 on which a cross slide 18 in the vertical direction (Z-axis) is movable. In the cross slide 18 is a transverse front, slightly outside the middle arm 1.9 in the horizontal direction (Y-direction) and parallel to the plane surface 12 and held at right angles to the course of the guide rails 13, 14 adjustable. The cross arm 19 is hollow on the inside and closed at both ends.

At the right front end in Fig. 1, the transverse arm 19 carries a e.g. Cube-shaped recording head 20 for the measuring, scribing and / or to be recorded therein Probing tools.

The device 15 is equipped with a compensation device 21, are determined and taken into account by means of the errors of the device 15 during measurement, namely those errors that occur at the respective vertical distance b of the neutral fiber of the cross arm 19 and cross slide 18 and at the respective projection length 1, with which the transverse arm 19 protrudes with respect to the neutral fiber of the column 17, a bend the column 17 by the angle rX in the one vertical plane (Fig. 4b) and / or around the angle ß in the right-angled-n, second perpendicular plane (Fig. 3) to Have consequence. The first vertical plane coincides with the FIG. 1, 4a and 4b Drawing plane and contains the neutral fiber of at least the column 17. The second, perpendicular to this at right angles coincides with the plane of the drawing according to Fig. 3. Part of the compensation device 21 is only indicated schematically Computer 22 with display 23, which is connected to device 15 via cable 24, and there with the individual, not further visible and per shifting direction (X-, Y- and Z-axis) provided measuring systems.

Experienced due to the apparent stand construction of the device 15 the cross arm 19 and the column 17 deflections caused by the individual lever arms acting forces are caused.

The cross arm 19 is usually arranged in the interior, parallel to the neutral fiber and also diagonally running Duervertension so prestressed, that a deflection of the cross arm 19 is compensated for. In the following Therefore, the transverse arm 19 can be considered fault-free with regard to a possible deflection be accepted. The cross slide 18 is both in terms of storage for the cross arm 19 and the storage on the column 17 so rigid that in this area also does not impair the measurement accuracy to the same extent Feh - 1s occur. At the respective vertical distance b of the cross slide 18 with cross arm 19 can therefore in each case from a permanent right angle in the area of the cross slide 18 can be assumed.

As is illustrated in FIG. 4a, what is massaged in the center of gravity 25 has an effect Total weight of the Duerarmes 19 there with the vertically directed weight FQ under a lever arm a, which indicates the distance from the neutral fiber of the column 17. The distance a is dependent on the respective projection length 1 of the transverse arm 19. How is illustrated in Fig. 4b, a moment of the size FQ acts on the column 17 æ a.

Under the action of this moment, the column 17 in the said first perpendicular plane, which here coincides with the plane of the drawing, to the right turned around the corner. The size of the deflection depends on the vertical distance b, the neutral fiber of the cross arm 19 and cross slide 18 from the Has plane surface 12. In the same way, the column 1-7 experiences a turn below the angle (Fig. 3) usually to the left, if only because the cross arm 19 arranged in the cross slide 18 at a distance from the neutral fiber of the column 17 is and thus in the center of mass effective weight forces under a lever arm act at a distance to the left of the neutral fiber of the column 17.

The bend of the column 17 by the angle according to FIG. 4a has in the area the center of the recording head 20, on the device 15 before The beginning of the measurements is zeroed, an error h Z in the Z direction and an error A y in the Y direction result. The column bend at the angle (Fig. 3) has a, In contrast, this results in significantly smaller errors A x in the X direction.

The mentioned error deviations #Y, #Z and #X can be passed through Calculate trigonometric functions depending on the respective actual values of a and b, as follows: # Y = b. tan # # Z = a. tan α # X = b. tan ß.

If one looks at an idealized, completely error-free device 15 Fig. 4a, result when touching a workpiece and measuring a measuring point with the coordinates X1, Y1 and Z1 no error deviations. In fact it is a bend of the column 17 at the angle "given, which falsified the measurement leads, with these error deviations # Y and #Z being more considerable and significantly larger as the error deviation #X caused by the column deflection at the angle ß (Fig. 3) is conditional. If one only considers the error deviations t Y and b Z in Fig.

4b, it is due to this error when touching a workpiece the measured and displayed dimension Z1 in the Z direction is smaller by # Z and the dimension Y1 in the Y direction by # Y larger than without errors. Equally measured, the dimension X1 is around # X larger than without errors.

To correct this, if the individual error deviations in all three coordinate directions are determined and known, the error deviation add d Z in the vertical measuring direction to the actual measured value Z1, on the other hand, the other two error deviations a Y and a X from the respective measured value Subtract Y1 or X1.

According to this method, the device 15 is used for computational compensation the mistake preceded. One proceeds in such a way that the device-dependent error deviations especially 4 Y and Z, but also the smaller error deviation t X, in the individual Displacement directions Y, Z or

X determined for each individual measuring point Y1, Z1, X1. Then you give the determined error deviations A Y, 4Z, n X into the computer 22 and linked this for correction with the actual displayed in the Y, Z or X direction Actual value by calculation. The error deviation C \ Z dem is measured Display value Z1 is added, while the remaining error deviations Ay Y and aX can be subtracted from the respectively measured, displayed value Y1 or X1. The single ones Error deviations AY, AZ and t X of each individual measuring point are in each case determined according to the aforementioned angular functions, i.e. as a function of individual overhang lengths 1 or a of the transverse arm 19 and individual vertical distances b of the Duerarmes 19 with Cross slide 18.

The bending of the column 17 at the first angle «(Fig.4b) in the a vertical plane is determined with the help of a first transducer 1, while the bending of the column 17 at the second angle β with the help of a second MeB value transducer 2 is determined. The two transducers 1 and 2 exist of inclinometers, in particular from electronic level scales, which are related to each other are aligned at right angles and are placed on the cross slide 18.

The first level 1 is parallel to the direction of displacement (Y-axis) of the transverse arm 19 and transversely to the other two displacement directions (X-axis, Z-axis) aligned.

The second level 2 is parallel to the direction of displacement (X-axis) the column 17 and aligned at right angles to the first level 1. Instead of of the electronic spirit levels, other suitable transducers can also be used will. Electronic spirit levels have the advantage of that these determine the respective inclination with high precision regardless of the respective overhang length 1. The advantage of this method of computational error compensation is that error deviations caused not only by the deflection at the angle «and / or R are compensated, but also other errors that have an impact, e.g.

those from the guide system between foot 16 and guide rails 13, 14 are caused in the X-direction, furthermore errors caused by temperature fluctuations or temperature influences in the measuring room where the device 15 is located, furthermore only in the course of the process wear-related errors or errors occurring during operation, conditional through improper handling, e.g. through damage to the device 15 or stress with external forces through excessive pulling down of the freely cantilevered Cross arm 19 or the like.

When measuring, one proceeds in such a way that before the start of the measurement the device 15 is set to zero in its machine zero. This setting is necessary so that the computer 22 can correct reset functions to be carried out and always carries out its calculations with reference to the machine zero point. In the case of no the computer 22 undertakes the described computational error compensation for the individual Coordinate values from the counter and thus calculates the measurement task given to it. In the case of the computational error compensation explained, the latter is connected upstream. The computer must first receive the coordinate values supplied to it in the manner explained correct, i.e. the actual display values arithmetically with the determined Link error deviations 6 Y, 4Z and a X before calculating the entered task will.

In another exemplary embodiment, not shown, the electronic spirit levels 1 and 2 do not. Instead one proceeds in such a way that one the device-dependent error deviations once, i.e. not when measuring each one Measuring point, with a precisely known measuring standard in several, sufficiently many Measuring positions of the device 15 determined in the measuring room and the so determined Error deviation image is stored in the computer. Here you can see the error deviation image e.g. determine with a step gauge that is placed on the plane surface 12 and has various stepped surfaces that appear as if one wanted to use the device 15 measure, sampled and measured. Since you get the error-free actual measured value knows for this measuring standard, one can determine the respective error deviation from it and so store a complete error deviation image of the device 15 in the computer. A laser interferometer can also be used to determine this.

If a measured value is then entered into the Computer accepted, the computer searches for the location X1, Y1 in the memory and Z1 assigned correction value and corrects the read-in measured value.

Compared to the former method, this is the second method somewhat less favorable for computational error compensation than, for example, during the course Errors occurring during the operating time of the device are not taken into account here.

This can be errors due to temperature influences or wear of the management systems. If you want to include these errors, you have to create of the error deviation image take place at correspondingly small time intervals and more frequently.

Finally, error compensation can also be carried out in this way be that in the computer 22 known, formula-based dependencies for the deflection of the column 17 in the two perpendicular, perpendicular Stores levels, regardless of the actual error deviation image of the device 15. Here, the computer 22 is calculated using known formulas for the deflection X and ß the correction value for the corresponding measuring point and corrected this. However, there is only compensation for the calculated errors below Consideration the deflection, but not other errors, e.g. caused by temperature influences, Play or wear in the guide systems or the like.

Blank page

Claims (8)

Claims 1. Method for error compensation in three-dimensional Measuring and / or scribing devices that are provided with a on or on a straightening plate (11) horizontally (X-axis) displaceable foot (16) with at right angles to the straightening plate (11) standing column (17) on which a cross slide (18) can be moved vertically (Z-axis) is, in which a transverse arm (19), which at the end has a recording head (20) for measuring or Carrying probing or scribing tools, horizontally (Y-axis) and parallel to the Straightening plate (11) and transversely to the column (17) is slidably mounted, with the individual position measuring systems provided on the device for each direction of displacement (X, Y and Z axes) linked to a computer (22), d u r c h g e n n n z e i c h n e t that the device-dependent error deviations (#X, #Y, #Z) in the individual displacement directions (X, Y, Z) determined once or for each individual measuring point and then determined these Enter error deviations (#X, #Y, #Z) into the computer (22) and to correct them with the actual value displayed for each displacement direction (X, Y, Z) (X display, Y display, Z display) arithmetically linked, especially the error deviation (#Z) in the vertical Direction added, the remaining error deviations (#X, #Y) subtracted. 2. The method according to claim 1, d a d u r c h g e k e n nz e i c h n e t that the error coordinates (#X, #Y, #Z) of a measuring point in all displacement directions (X, Y, Z) each as a function of individual ones Overhang lengths (l, a) of the transverse arm (19) and vertical distances (b) of the transverse arm (19) determined with cross slide (18) from the lower end of the column. 3. The method according to claim 2, d a d u r c h g e k e n nz e i c h n e t, that the curve resulting from the inclination of the cantilevered cross arm (193 the column (17) at a first angle (α) in one, the central axis the column (17) and the Ouerarmes (19) containing vertical plane and / or below a second angle (o) in another, perpendicular to it, perpendicular plane determined and that according to the relationship (#X = b. tan ß, #Y = b.tan α, #Z = a. tan α) the error deviations are determined for each measuring point and for each coordinate linked to the displayed value, where (a) that of the respective overhang (1) of the transverse arm (19) depending on the center of gravity of the transverse arm (19) from the neutral one Fiber of column (17) and (b) the vertical distance of the neutral fiber of the transverse arm (19) mean with cross slide (18) from the lower end of the column. 4. The method according to claim 3, d a d u r c h g e k e n nz e i c h n e t that the bend of the column (17) at the first angle (#) in one, the vertical plane containing the central axis of the column (17) and of the transverse arm (19) by means of a first transducer (1) in this direction and the bend the column (17) at the second angle (ß) in the other, perpendicular to it perpendicular plane by means of a second transducer (2) in this other direction determined. 5. The method according to claim 4, d a d u r c h g e k e n nz e i c h n e t that one has two inclinometers (1, 2) aligned at right angles to one another, in particular electronic levels, used. which one on the cross arm (19) or in particular on the cross slide. (18), the first inclinometer (1) parallel to the Direction of displacement (Y-axis) of the transverse arm (19) and transversely to the other two directions of displacement (X-axis, Z-axis) is aligned and wherein the second inclinometer (2) is parallel to the direction of displacement (X-axis) of the column (17) and at right angles to the first Inclinometer (1) is aligned. 6. The method of claim 1, d a d u r c h g e k e n nz e i c h n e t that the device-dependent error deviations can be compared with an exactly known Measuring standard in several, sufficiently many measuring positions of the device (15) in the measuring room and the error deviation image thus determined is stored in the computer (22). 7. The method according to claim 6, d a d u rc h g e k e n nz e i c h n e t that the error deviation image can be obtained with a step gauge or a laser interferometer determined. 8. Method for error compensation in three-dimensional measuring and / or Marking devices that are provided with a horizontal on or on a straightening plate (11) (X-axis) displaceable foot (16) with a right-angled to the straightening plate (11) Column (17) on which a cross slide (18) can be moved vertically (Z-axis), in which a cross arm £ 19), which at the end has a mounting head (20) for measuring or probing or marking tools, horizontally (Y-axis) and parallel to the straightening plate (11) and across the column (17). is slidably mounted, whereby the individual, per shift direction (X-, Y- and Z-axis) provided on the device side Distance measurement systems linked to a computer, so that we can do it e t that one in the computer (22) known, formula-based dependencies for the bending of the column (17) in two perpendicular, perpendicular Stores levels regardless of the actual error deviation image of the device (15).