Device for determination of positions and faults in guidance

The present invention relates to a device for determining the position and determination of management errors.

On modern precision machine tools or coordinate measuring machines is sometimes the demand, besides the exact determination of the position along a machine axis and the possibly present guide error the respective axis to capture. The metrological determination of one of several management errors is as straightness designated. From the measured guiding errors can then in a suitable Evaluation of each position measured during operation be corrected by calculation.

In EP 0082244 A1, this problem is discussed in detail. The Figures 3 and 4 of this document also show a suitable device, which enables both a high-resolution incremental measurement to determine the respective position along an axis and the above-mentioned determination of management errors and the straightness perform. To this end, a scale is provided, which in addition to a Position measuring graduation in the form of a conventional incremental in Measuring direction and a perpendicular thereto disposed guide error measuring graduation includes. The guidance error measuring graduation consists of graduation marks, which are oriented parallel to the measuring direction and extending over the corner region a carrier body having a square section extending. For scanning the different measuring scales are photoelectric measuring systems mentioned, is to not to elaborate.

Another device for the simultaneous position and guidance error measurement is known from EP 0660085 A1. Here, a material measure scanned with the aid of a CCD line, wherein the measuring graduation includes multiple tracks. Symmetrical adjacent to an average non-periodic Bar code structure are arranged two tracks with strokes, which are oriented parallel to the measuring direction. The scanning of the latter two tracks, which are aligned perpendicular to the measurement direction actual are, in turn, enables the detection of potential lead errors or straightness. The absolute position is determined However, in this case with a relatively coarse resolution; for high precision applications this device is therefore not suitable.

Object of the present invention is to provide a device for determining the position specify and identify guiding errors, the starting of a conventional high-resolution position measuring as few modifications required to a high-precision determination guiding errors along at least one predetermined make axis.

This object is achieved by a device having the features of Claim 1.

give Advantageous embodiments of the inventive device the listed from the measures in the dependent claims are.

According to the invention has now been a high-resolution position measuring, as it is known for example from EP 0387520 B1, to the effect modified so that a simultaneous detection of leadership failures so is possible. On the side of the scale of the apparatus are adjacent to a usual position measurement division in the form of a Incremental least two guide error measuring graduations arranged each oriented perpendicular to the position measurement scale. For scanning the different measuring graduations are preferably of two identical trained scanning units provided that rotated only by 90 ° are to be arranged. One of the two scanning units serves as a position determination scanning unit, which in a known manner, the position measuring graduation in the measuring direction for generating position Metßsignalen scans. The second scanning unit acts as a guide error scanning scans to generate guidance error measuring signals the FührungsfehlerMeßteilungen from. The guide error scanning unit is together with the Position determination scanning unit along the measuring direction opposite the scale mobile.

In comparison to the known position measuring from EP 0387520 B1 is thus only the additional arrangement of the two guide error measuring graduations on the scale, and a second - identical - scanning required now in a device, both the position determination as to accomplish the determination of the tracking error.

Both the generation of the position measurement signals and the generation the guide error measuring signals based on an interferential scanning, ie it is for both measurements respectively a correspondingly high Resolution or precision ensured.

Furthermore, the arrangement of the position measuring graduation proves and two guide error measuring graduations on the scale as an extremely space-saving, ie it is also on the side of the scale no large construction volumes required.

The inventive apparatus further may be modified in various forms or expand; for example by adding more scanning units for detecting additional guidance error or use of alternative scanning principles etc ...

Further advantages and details of the present invention will become apparent based from the following description of several embodiments of the accompanying drawings.

It shows<dl tsize="8"><dt>figure 1</dt><dd>a schematic plan view of a first Embodiment of the device according to the invention;</dd><dt>figure 2</dt><dd>a perspective view of the scale and portions of the guide error scanning the example of Figure 1;</dd><dt>figure 3</dt><dd>the beam path for guiding measurement error in a second embodiment of the present invention Device.</dd></dl>

1 shows a first embodiment of the device according to the invention shown schematically in a plan view. Of these, particular on sides of the respective scanning units 20, 30 for reasons of better Clarity not shown all the elements.

As shown in Figure 1 seen the inventive device for position determination comprising and determination of management errors a scale 10 and two relative to the scale 10 in the measuring direction x Portable Scanning units 20, 30. In practice, this is the benchmark against 10 the two scanning units 20, 30 arranged to be movable; It is essential, however, are merely possible relative movement of the scale 10 and scanning units 20, 30. The two scanning units 20, 30 are referred to as position determination scanning unit 20 or guide error scanning unit 30 designated. Both scanning units 20, 30 are assembled against each other the scale 10 movable - or vice versa - and this, as in a - not shown - housing. In principle, the joint mobility of the two scanning units 20, 30 against are the scale 10 of course also made elsewhere, is about by suitable mechanical coupling elements etc .. In figure 1 the forcible joint movement of the two scanning units 20, 30 40b schematically indicated by the coupling elements 40a.

The scale 10 and the two scanning units 20, 30 are, for example, connected to machine components in the measuring direction relative to each other are x movable. In addition to high-precision relative position should also the machine side guiding errors along the respective measuring length ML are determined on the inventive device. Of the two Scanning units 20, 30 in the case of movement relative to scale 20 generated position and guidance error measuring signals are for further processing a - not shown - evaluation unit supplied. On the concrete analysis or further processing of the generated signals is to this point no further details, but as only the already above-mentioned EP 082 441 A1 referenced 0.

The scale 10 of the device according to the invention is in this embodiment designed as a reflection scale, ie the various on arranged measuring scales 11, 12a, 12b are respectively known as reflection measuring graduations in the form of reflection phase divisions. Such reflection measuring scales are made in the respective measuring direction x alternately arranged partial areas 11.1, 11.2, 12A.1, 12a.2, 12b.1, 12b.2 with different step heights. In the case of the reflection phase division is it about to periodically arranged line-shaped, reflecting partial areas 11.1, 12A.1, 12b.1 or lines of gold, which are arranged on a reflecting surface, including also Gold. The arranged between strokes subareas 11.2 12a.2, 12b.2 are hereinafter referred to as gaps.

On the scale 10 of the inventive device is shown in Embodiment, on the upper side of a support element 13 centrally a position measuring graduation 11 is provided consisting of periodically Measuring direction arranged, highly reflective lines 11.1 and gaps 11.2. The longitudinal direction of the bars 11.1 and 11.2 gaps here is perpendicular to the measuring direction x is oriented, the corresponding direction is a y-direction defined. The length of the bars 11.1 corresponds to the width b_PMT of the Track with the position measuring graduation 11. The graduation period of the position measuring graduation 11 is with TP_PMT designated.

Both sides adjacent to the position measuring graduation 11 in the illustrated Embodiment of the apparatus erfindungsgmäßen two guidance error measuring graduations- 12a, 12b provided on the support element 13 of the scale 10th The guidance error measuring graduations 12a, 12b are in this case perpendicular arranged for position measurement division 11th This means that the bars 12A.1, 12a.2 or bars and gaps 12a.2, 12b.2 of the two guide error measuring graduations 12a, 12b parallel to the measuring direction x over the entire Measuring length ML extend. The width of the two tracks with the guide error measuring graduations 12a, 12b is selected to be identical and subsequently with b_GMT designated; the distance between the two tracks with the guide error measuring graduations 12a, 12b is the central track with the position measuring graduation 11 each denoted by d. Both guidance error measuring graduations 12a 12b exhibit the same graduation period TP_GMT on. Basically, the two could Guidance error measuring graduations 12a, 12b and immediately afterwards are arranged at the central position measuring graduation 11, ie d = 0 selected will.

In a preferred embodiment, the graduation periods TP_MT. TP_GMT the different measuring graduations 11, 12a, 12b are all identical educated.

The generation of the scanning using the two scanning units 20, 30 each based on an interferential operating principle, as for example, in EP 0387520 B1 of the applicant is described in detail. A corresponding measurement system is used by the applicant under the product name LIP 382 sold, whether in relation to the signal generation at this point we should only refer to the above-mentioned document.

Of the various components of the scanning units 20, 30 are in Figure 1 for reasons of clarity, only the respective Scanning graduations 21, 22 shown. From the illustrated orientation of the scanning graduations 21, 31 relative to the various partitions 11, 12a, 12b the scale 10 it can be seen that the left scanning unit 20 for scanning the position division 11 serves. The scanning graduation 21 of the position determination scanning unit 20 for this purpose is identical to the position measuring graduation 11 based on the scale 10th In the case of the relative movement in Measurement direction x are therefore on the position determination scanning unit 20 periodically modulated incremental signals with the signal period TP_PMT/ 4 generated, which are further processed in a manner known can. The thus generated position measurement signals accordingly serve to precise determination of the relative position of the scanning unit 20 against the scale 10 in the measuring direction x and is therefore identical to the known Description of EP 0387520 B1. In the case of using the above-mentioned system is a LIP-382 Graduation period TP_MT = 0.512μm and a resulting signal period of incremental position measurement signals of from 0.128μm ago.

In measuring direction slightly offset and perpendicular to the position determination scanning unit 20 is arranged the guide error scanning 30th correspondingly by 90 ° relative to the scanning graduation 21 of the position determination scanning unit 20 twisted, ie in the y-direction, is consequently also the Scanning 31 scanning these 30 arranged, ie identical for orientation the two guide error measuring graduations 12a, 12b on the scale 10. Resulting in the case of movement in the measuring direction x now due any management errors a relative movement in the y direction, ie, perpendicular to the measuring direction x, this movement is using the guide error scanning 30 precisely determined. The guidance error measuring signals filters in the case of any relative movement in the y direction likewise periodically modulated incremental signals is that due to sampling the two guide error measuring graduations 12a, 12b, the signal period TP_GMT/ 4 exhibit. These signals are in a manner known further processed by the above-mentioned evaluation unit. If above mentions the graduation periods of all involved measuring graduations 11, 12a, 12b be selected to be identical, is in the case of using the LIP-382 system and TP_GMT = 0.512μm a signal period of the incremental guide error measuring signals of 0.128μm ago.

By appropriate dimensioning of the widths b_GMT, b_PMT the various Graduation tracks 11, 12a, 12b and the distances d in the Scale 10 can be ensured now that two identically designed Scanning units 20, 30 based on the known principle disclosed in EP 0 387 520 B1 is based, can be used. These have turned only 90 ° are to each other. In addition, only the two additional Guidance error measuring graduations 12a, 12b on the scale 10 is required. Without much additional effort thus causes the known measuring system 0,387,520 B1 repurpose from EP to the inventive device.

Alternative to the arrangement of two separate guide error scanning units 20, 30 according to the above example can be the invention Device also vary. For example it is also possible for the optical integrating function of the two scanning in a single scanning, which is movable relative to the scale or vice versa. In this Case could be in particular a more compact system on the scanning side realize.

In Figure 2 is a further schematic partial view of the invention Device shown in a perspective view. shown here are only some of the components of the guide error scanning 30 from FIG 1, the spatial orientation of the various components or the scanning beam in the direction error measurement better illustrate. The position determination scanning unit not shown in Figure 2 includes as previously explained, the identical components, however rotated by 90 ° to the components shown in Figure 2 are arranged.

The respective scanning units accordingly comprise a light source 32, collimating optics 35, a scanning grating 31, a retroreflective unit 33 as well as a plurality of detector elements 34a, 34b, 34c. Of the light source 32 emitted radiation beam will first use the collimator optics 35 collimated before it on which is constructed as transmission division Scanning 31 arrive. There occurs a splitting of the incident Ray beam into a plurality of sub-beams of different diffraction orders. At least two orders of diffraction, preferably the +/- 1st orders, then meet the guide error measuring graduations 12a, 12b, are again diffracted there and in the direction of the retroreflective unit 33 reflected. The center distance of the two guide error measuring graduations 12a, 12b is therefore to choose in this embodiment, so, that it the distance of the incident on the scale diffraction orders equivalent. The optical design of the retroreflective unit 33 ensures that the incident partial beams back towards the two guide error measuring graduations 12a, 12b are reflected. The Retroreflexionsbaueinheit 33 is dimensioned to be suitable triple prism or as an optically corresponding prismatic reflector assembly; Fairs. Another details made in this connection to EP 0387520 B1 referenced. After re-reflection on the two guide error measuring graduations 12a, 12b meet the different partial beams Finally, again interfering in the scanning graduation 31 that ultimately couples Partial beams in different directions in space to the total three detector elements 34a, 34b, 34c towards deflects. At the three detector elements 34a, 34b, 34c are in the case of a relative movement of the guide error scanning unit 30 relative to the scale 10 on the output side in the y direction finally periodically modulated incremental signals. In between the signals at the three detector elements 34a, 34b, 34c is in this connection a phase shift of 120 ° before.

is a second embodiment of the inventive device explained with reference to FIG. 3 While the first described Embodiment was designed as an incident light system is based on Figure 3 illustrates that the device according to the invention, of course, may also be formed as a transmitted light system. Figure 3 shows Here, a sectional view of the scale 100 and the guide error scanning unit 300 in the yz plane, in particular to the scanning beam the Führungsfehler- or to explain in this case, the straightness. Scale 100 and scanning unit 300 are in the measuring direction x to each other movably arranged. With regard to the - not shown - the arrangement Position determination scanning unit is about to Figure 2 in EP 0 387 referenced 520 B1, the conditions in the scanning beam for position measurement shows in the xz plane.

On the side of the scale 100 are again on a now transparent Support member 113 includes a centrally located position measurement division 111 and both sides adjacent guide error measuring graduations 112a, 112b provided. The respective divisions 111, 112a, 112b are now in transmitted light system as a transmission-divisions, preferably as a phase transmission partitions, educated. How about the average of the two guide error measuring graduations recognizable, these consist arranged periodically Webs and gaps in the respective measuring direction, said ridges and gaps have different step heights.

The guide error scanning unit 300 comprises, as in the previous exemplary embodiment, a light source 132, collimating optics 135, a scanning 131, designed as a triple prism retroreflective unit 133 and three optoelectronic detector elements 134a, 134b, 134c. From the light source 132 and exiting in parallel by the collimator optics 135 directed beams of rays arrive first turn on the scanning 131, split where it bent in different partial beams or will. Then take the diffracted partial beams on the respective guide error measuring graduations 112a, 112b on the scale 100 and are now bent of this in transmission again. undergo after back-reflection by the retroreflective unit 133 the partial beams again the two guide error measuring graduations 112a, 112b, before the plane of the scanning 131 finally capable of generating interference Pairs of partial beams present. With the help of the scanning 131 Finally, there is a deflection of each interfering partial beams in the direction of the detector elements 134a, 134b, 134c, where the Case the relative movement of the scale 100 and the guide error scanning 300 phase-shifted in the Y direction Incremental rest.

In addition to this second embodiment of the device according to the invention are of course also other alternatives in the present Invention implemented. So it would be possible, for example, also which is known from EP 0311144 B1 sensing on sides of the respective use scanning units to the various scanning signals to produce. Also in this case would only be a second, identical scanning unit arranged necessary, rotated by 90 ° to the normal scanning is and the two also additional guidance error measuring graduations- scans, adjacent to the position measuring graduation on the scale to arrange would.

Other known sensing principles can be personalized with minor modifications Adjust accordingly and within the framework of the present invention Insert.

Furthermore, the inventive device can of course modify dahigehend that thus more failure modes can be detected can, for example, guiding errors on rotations about certain Axes based. For this purpose, then according to additional guidance error scanning units provide or guide error measuring graduations as for example in Figures 3 and 5 of the above-mentioned EP 0 082 was 441 proposed etc ..