DE102018105922B4 - Arrangement for detecting the relative position of a measuring head - Google Patents

Abstract

The present invention relates to an arrangement (01) for detecting the relative position of a measuring head (02) with respect to a measuring grid plate (03), which has a rectangular grid structure area (04). The arrangement (01) comprises at least two reference mark arrangements (13) arranged outside the grid structure area (04), each reference mark arrangement (13) each having two spaced-apart reference marks (14) extending perpendicularly from a first edge (08) of the Rasterstructure area (04) extend, wherein the reference marks (14) of successive reference mark arrangements (13) have a different distance (Ra) to each other. On the measuring head (02) three position sensing elements (15a, 15b, 15c) each having a reference mark sensor (17) and a Rasterabtastfeld (18) are arranged. At a second and a third edge (09, 10) of the raster structure region (04), a plurality of spaced-apart reference marks (14) are arranged outside the raster structure region (04). The Rasterabtastfelder (18) of the position sensing elements (15a, 15b, 15c) are arranged on the measuring head (02), that they are arranged in any positioning of the measuring head (02) within the grid structure region (04).

Description

The present invention relates to an arrangement for detecting the relative position of an optoelectronically operating measuring head with respect to a measuring grid plate, which has a rectangular grid structure area. The arrangement comprises reference mark arrangements on measuring grid plates and reference mark sensors on the measuring head.

Reference mark arrangements and measuring heads are essential components of measuring and processing machines. When a measuring machine is started, reference marks are used to zero the system, i. H. The scanning probe is placed at a zero point or starting point with respect to a defined measuring grid. The manner of forming the reference mark structures is critical in terms of the time it takes for the control system to zero. Even the savings of a few seconds result in considerable cost savings for highly complex, expensive systems.

From the DD 1 22 135 A1 An arrangement for generating marker pulses in incremental length and angle encoders is known, wherein a scale and a measuring device are moved relative to each other. By means of a light beam, a scan is performed on two scale points, so that a deviating from one magnification scale is mapped to a second scale position. On the scale, a counting track and at least two mark tracks are arranged. Changing marks of the optical properties are arranged on the marking tracks.

In the US 2005/0 042 529 A1 For example, a method for determining field-to-field alignment and a mask therefor is described. The mask has reference structures at four edges of a closed field. The reference structures consist of rectangles with different circumferences.

The DE 41 32 942 C2 shows a measuring device for two measuring directions for measuring the relative position of objects, in which a measuring graduation is scanned by a scanning device for each measuring direction. Each measuring graduation is assigned at least one reference mark. At least one reference mark extends longitudinally over the measuring length of the measuring direction perpendicular to its associated measuring direction. If the measuring process is interrupted, for example due to a power failure, the current position value is lost. Due to the longitudinal extension of the reference mark, the reference position can be retrieved from any current measuring position by the scanning device being moved only in the associated measuring direction of this reference mark in order to scan the reference mark.

From the DE 102 30 614 B3 an arrangement of reference marks on measuring grid plates and of reference marks on a corresponding optoelectronic working measuring head is known. The arrangement serves to detect relative positions of a measuring head to form a measuring grid plate. For at least one edge of a measuring grid parallel at least two reference mark modules are arranged, each having two line-shaped first reference marks. Between the first reference marks of each reference mark module, a pair of marks of line-shaped second reference marks is arranged, whose mutual distance increases from reference mark module to reference mark module and of which each further from the edge zero point second reference mark has a fixed distance to the adjacent first reference mark. At the measuring head, a first and a second reference mark sensor are arranged parallel to each other and a third reference mark sensor rotated by 90 ° to the first and the second reference mark sensor. The third reference mark sensor is laterally offset relative to the first and the second reference mark sensor in the zero point position in the edge direction next to the second reference marks, while the first and second reference mark sensors are symmetrically centered above the first reference marks.

The object of the present invention is to provide an improved arrangement for detecting the relative position of a measuring head in relation to a measuring grid plate, which produces a quick and unambiguous assignment of the measuring head to reference marks.

To solve the problem, an arrangement according to the appended claim 1 is used.

The arrangement according to the invention initially comprises at least two reference mark arrangements arranged outside a grid structure area of the measuring grid plate and spaced from each other. Each reference mark arrangement has in each case at least two reference marks spaced apart from one another, which preferably extend perpendicularly from a first edge of the raster structure region. The reference marks of successive reference mark arrangements have a different distance from each other.

The arrangement further comprises at least three position sensing elements arranged on the measuring head, each having a reference mark sensor and a raster scanning field. First and second position sensing elements are arranged parallel to each other. A third Positionsabtastelement is arranged rotated by 90 ° to the first and the second position sensing element. It is located between the first and second position sensing elements and preferably equidistant from the first and second position sensing elements.

The arrangement is characterized in particular in that at a second and a third edge of the raster structure region a plurality of spaced-apart reference marks are arranged outside the raster structure region. The reference marks preferably extend perpendicularly from the respective edge. The first and second position sensing elements are configured to scan opposing reference marks.

A significant advantage of the arrangement according to the invention is that it allows a fast and reliable determination of the relative position of the measuring head. Upon initialization of the measuring head, a movement preferably takes place toward the first edge of the raster structure area on which the reference mark arrangements are arranged. Characterized in that the reference marks of successive reference mark arrangements have a different distance from one another, when scanning the reference marks of a reference mark arrangement by the associated reference mark sensor from the detection of the specific distance between the reference marks, the relative position of the measuring head to the measuring grid plate for the first edge associated coordinate direction can be clearly determined. Subsequently, individually arranged reference marks can be selectively approached and scanned at the second and the third edge of the grid structure area. The arrangement of the reference mark arrangements and reference marks is preferably carried out so that minimal travel paths for the drive system of the measuring head arise.

According to a particularly preferred embodiment, the reference marks on the second and the third edge of the raster structure region are each arranged in at least two spaced-apart reference mark arrangements. Each reference mark arrangement has two reference marks spaced apart from each other. The reference marks of successive reference mark arrangements have a different distance from each other. Thus, all three edges of the raster structure area are equipped with reference mark arrangements. When the reference marks of a reference mark arrangement are scanned by the associated reference mark sensor, the relative position of the measuring head to the measuring grid plate can be determined unambiguously from the detection of the specific distance between the reference marks for the coordinate direction associated with the respective edge on which the reference mark arrangement is arranged. With stepwise scanning of the reference mark arrangements at the three edges of the grid structure area, the relative position of the measuring head to the grid plate for the X and Y position and additionally the rotation of the measuring head in the X-Y plane can be determined.

In alternative embodiments, all four edges of the raster structure region may also be provided with reference marks or reference mark arrangements.

The Rasterabtastfelder the position sensing elements are preferably arranged on the measuring head, that they are arranged at each positioning of the measuring head for detecting the reference marks within the grid structure region. The Rasterabtastfelder thus remain during the detection of the reference marks in the detection area of the grid structure area.

The reference mark arrangements advantageously have a defined distance from a nearest corner of the raster structure area.

• a₁, a₁+d, a₁+2d, ... a₁+ (n-1) d
• mit a₁=1; d>0; n=ganze Zahl
• gewählt werden.

The distance between the reference marks of successive reference mark arrangements preferably increases by an amount d> 0. The distance a of the reference marks may preferably be an arithmetic constant growing sequence

• a ₁ , a ₁ + d, a ₁ + 2d, ... a ₁ + (n-1) d
• with a ₁ = 1; d>0; n = integer
• to get voted.

The distance between two adjacent reference mark arrangements is preferably the same in each case. According to an advantageous embodiment, the distance between two adjacent reference mark arrangements is selected such that it corresponds to the pole period of a linear motor or planar motor used for driving the measuring head for a movement of the measuring head in the direction of the edge assigned to the reference mark arrangements. By appropriate energization, for example, of two phases of the linear motor or planar motor can be done at an unknown position of the sensor head centering at a defined position within the Polperiode for the edge associated coordinate direction. The reference mark arrangements are placed on the measuring grid plate in such a way that a reference mark arrangement can already be scanned in a defined direction after a short journey. The same applies to the other coordinate directions. On the hand of this In the start mode or in the event of a crash, the measuring head can determine the position-catching regime with the shortest travel paths and thus the system zero position in the shortest possible time since only the closest reference-mark arrangement has to be approached.

The reference marks are preferably formed like a line and preferably have the same stroke length. Other suitable reference mark shapes are possible.

At the edges or the edge of the raster structure area, preferably, as many reference mark arrangements are arranged as the linear motor or planar motor associated with the coordinate direction has stable centering positions with suitable motor-phase energization. Designs with only one, two or more than two reference mark arrangements are possible. Embodiments are likewise possible which have reference marks or reference mark arrangements on all four edges of the raster structure region.

The Rasterabtastfelder the position sensing elements preferably each have a grid of parallel, spaced-apart lines, which run parallel to the scanned with the respective Rasterabtastfeld reference marks.

A preferred embodiment of the arrangement according to the invention will be explained in more detail with reference to the accompanying single figure, which shows a schematic representation of the arrangement according to the invention.

The inventive arrangement 01 serves for detecting the relative position of an opto-electronically operating measuring head 02 with respect to a grid plate 03 , The measuring head 02 is drawn in three different positions. The grid plate 03 has a preferably rectangular grid structure area 04 which is a grid structure 05 which preferably extends throughout the grid structure area 04 extends. The raster structure area 04 has four edges 08 . 09 . 10 . 12 , A first and a third edge 08 . 10 of the raster structure area 04 run in the Y direction. A second and a fourth edge 09 . 12 run in the X direction.

The order 01 further comprises nine reference mark arrangements in the illustrated embodiment 13 , where at the first, second and third edge 08 . 09 . 10 of the raster structure area 04 in each case three reference mark arrangements 13 are arranged. Between the at one of the edges 08 . 09 . 10 successive reference mark arrangements 13 there is an equal distance pb , Each reference mark arrangement 13 consists of two reference marks 14 , The reference marks 14 are outside the raster tree area 04 and extend perpendicularly from the respective edge 08 . 09 . 10 of the raster structure area 04 , They are formed like a line and have the same stroke length. Between the reference marks 14 a reference mark arrangement 13 there is a gap Ra , The along one of the edges 08 . 09 . 10 in successive reference mark arrangements 13 arranged reference marks 14 have a different distance Ra on. In the embodiment shown, the distance at the first edge applies 09 arranged reference mark arrangements 13 Ral <Ra2 <a3. The first reference brand 14 this reference mark arrangement 13 is at a distance Yr from the nearest corner of the raster structure area 04 spaced. The at the first edge 08 arranged reference mark arrangements 13 serve to determine the Y position. The at the second edge 09 arranged reference mark arrangements 13 serve to determine the X position. The first reference brand 14 the first edge 08 nearest reference marker arrangement 13 is at a distance xr from the nearest corner of the raster structure area 04 spaced. The at the third edge 10 arranged reference mark arrangements 13 with respect to the first edge 08 arranged reference mark arrangements 13 an offset in the Y direction.

The order 01 further includes first, second and third position sensing elements 15a . 15b . 15c , which on the measuring head 02 are arranged. The position sensing elements 15a . 15b . 15c , each comprise a reference mark sensor 17 and a raster scan field 18 , The first position sensing element 15a and the second position sensing element 15b are arranged parallel to each other. The third position sensing element 15c is rotated 90 ° to the first and second position sensing elements 15a . 15b arranged. It is located between the first and second position sensing elements 15a . 15b , The raster scan fields 18 each have a grid of parallel, spaced-apart bars, which in the correctly aligned state parallel to those with the respective Rasterabtastfeld 18 to be scanned reference marks 14 run. The first position sensing element 15a is used during the repositioning to scan the reference marks 14 at the first edge 08 , The second position sensing element 15b touches on the third edge 10 located reference marks 14 from. First and second position sensing element 15a . 15b provide the Y position and the rotation in the XY plane. The third position sensing element 15c detects during the repositioning the at the second edge 09 located reference marks 14 and thus serves to determine the X position. The measuring head 02 is shown in three different positions. Shown are a starting position of the measuring head 02 at the beginning of the measurement, one position 02X in which the reference marks 14 at the second edge 09 that is, in the X direction, with the position sensing element 15c sampled as well as a position 02Y in which the reference marks 14 at the first edge 08 ie, in the Y direction, through the position sensing element 15a be recorded. The position 02X and 02Y If the measurement process is interrupted, the current position value of the measuring head is displayed 02 lost, hit. An interruption of the measuring process can occur, for example, due to a power failure or due to an external force. In the positions shown 02X and 02Y are the raster scan fields 18 the position sensing elements 15a . 15c still within the raster structure area 04 the grid plate 03 , but the reference mark sensor is 17 each above the reference marks 14 to scan them.

LIST OF REFERENCE NUMBERS

01 -

arrangement

02 -

probe

03 -

Measuring grid plate

04 -

Grid structure area

05 -

grid structure

06 -

-

07 -

-

08 -

first edge

09 -

second edge

10 -

third edge

11 -

-

12 -

fourth edge

13 -

Reference marker arrangements

14 -

reference marks

15 -

position sensing member

16 -

-

17 -

Reference mark sensor

18 -

Rasterabtastfeld

Pb -

Distance between the reference mark arrangements

Ra -

Distance between the reference marks

Yr -

Distance of the reference mark arrangements for the Y direction from the corner of the raster structure area

Xr -

Distance of the reference mark arrangements for the X direction from the corner of the raster structure area

02X -

Measuring head in position for scanning the reference marks in the X direction

02Y -

Measuring head in position for scanning the reference marks in the Y direction

Claims (11)

Arrangement (01) for detecting the relative position of an optoelectronically operating measuring head (02) with respect to a measuring grid plate (03), which has a grid structure region (04), wherein the arrangement (01) comprises the following components: - at least two outside the grid structure region (04) arranged and spaced reference mark arrays (13), each reference mark array (13) each having at least two spaced-apart reference marks (14) extending from a first edge (08) of the raster pattern region (04) therefrom, the reference marks (14). of reference mark arrays (13) contiguous along the first edge (08) have a different distance (Ra) from each other; at least three position sensing elements (15a, 15b, 15c) arranged on the measuring head (02) each having a reference mark sensor (17) and a raster scanning field (18), wherein a first and a second position sensing element (15a, 15b) are arranged parallel to one another and one third position sensing element (15c) rotated 90 ° to the first and second position sensing elements (15a, 15b) and disposed between the first and second position sensing elements (15a, 15b), characterized in that - at a second and a third edge ( 09, 10) of the raster structure region (04) a plurality of spaced reference marks (14) outside the raster structure region (04) are arranged, wherein the reference marks (14) from the respective edge (09, 10) of the raster structure region (04) extending therefrom ; - The first and the second position sensing element (15a, 15b) for the scanning of opposing reference marks (14) are formed. Arrangement (01) after Claim 1 , characterized in that the reference marks (14) on the second and the third edge (09, 10) of the grid structure region (04) in each case at least two spaced-apart reference mark arrangements (13) are arranged, each reference mark arrangement (13) each at least two from each other spaced reference marks (14), wherein the reference marks (14) of successive reference mark arrangements (13) have a different distance (Ra) to each other. Arrangement according to Claim 1 or 2 characterized in that the reference marks (14) are perpendicular to the first, second and third edges (08, 09, 10) of the grid structure region (04) extending away from the latter. Arrangement (01) according to one of Claims 1 to 3 , characterized in that the distance (Ra) between the reference marks (14) of successive reference mark arrangements (13) in each case by an amount d> 0 increases. Arrangement (01) according to one of Claims 1 to 4 characterized in that the distance (Pb) between two adjacent reference mark arrangements (13) is the same in each case. Arrangement (01) after Claim 5 , characterized in that the distance (Pb) between two adjacent reference mark arrangements (13) of the pole period of a linear motor used for driving the measuring head (02) for a movement of the measuring head (02) in the direction of the respective reference mark arrangements (13) associated edge (08 , 09, 10). Arrangement (01) according to one of Claims 2 to 6 , characterized in that at the first, second and third edge (08, 09, 10) of the grid structure region (04) each have three or four reference mark arrangements (13) are arranged. Arrangement (01) according to one of Claims 1 to 7 Characterized in that the Rasterabtastfelder (18) of the position sensing members (15a, 15b, 15c) are arranged on the measuring head (02) that it (during scanning of the reference marks (14) with the associated reference mark sensor (17) within the grid pattern region 04 ) are arranged. Arrangement (01) according to one of Claims 1 to 8th , characterized in that the reference mark arrangements (13) have a defined distance from a nearest corner of the grid structure area (04). Arrangement (01) according to one of Claims 1 to 9 characterized in that the third position sensing element (15c) is equally spaced from the first and second position sensing elements (15a, 15b). Arrangement (01) according to one of Claims 1 to 10 , characterized in that the number of reference marks (14) of successive reference mark arrangements (13) increases by at least one reference mark (14) along the same edge (08, 09, 10), the distance between the reference marks (14) of the same reference mark arrangements (13 ) preferably remains the same.

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