JPH056845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a position measuring device according to the preamble of claim 1.

The positioning device detects the path length traveled so far and stores it in memory, or sets the reference mark to the value "zero".
It is known for the detection of a reference position to run relatively movable machine parts or measuring device parts from a starting position to a reference position.

Such a method is made possible by an incremental length or angle measuring device as described in German patent specification 1964381.

However, this method requires the possibility of unimpeded relative movement of the object to be measured, since the components of the measuring device must be fixed to the object to be measured and adjusted together with the object to the reference mark. It is from.

A mechanical measuring device is known from DE 1673887, which allows the detection of a reference point on a mechanical carriage clamped to the machine bed. There, the carriage must first be driven into a position which will later be determined as a reference point for the zero point. The carriage is then clamped onto the machine bed. The scanning plate of the measuring device is then moved relative to the scale until it reaches the reference mark. When the reference mark is reached, the electronic counter of the measuring device is set to the value zero. The carriage is then unclamped again and the carriage is driven to the desired position. The position of the reference mark indicates a reference position for other processing steps.

However, the known methods for detecting a reference position defined as a starting position which is carried out before a specific machining step cannot be used if a machining step has already taken place and, for example, if the ongoing machining is interrupted. This is no longer possible with incremental measuring devices. For example, in commercially available automatic machines--commonly referred to as industrial robots--interruption of an ongoing machining process can be caused by a power outage. The robot then remains in that momentary position. However, the measured values relating to the original reference position are lost due to a power outage, since the measurements are also interrupted. However, a reference position must be known in order to continue the interrupted machining process. A return movement of the robot from its instantaneous position to its original position is generally excluded, since, for example, the tool is engaged with the workpiece.

SUMMARY OF THE INVENTION The present invention provides a position-measuring device of the type mentioned above, which eliminates the drawbacks of the known devices and which allows the reference position to be determined without movement of the object to be measured after the loss of position information at an unknown instantaneous position. The basis of the task is to improve it so that it can be reproduced.

(Solution Means) According to the present invention, this problem can be solved in the first claim.
solved by the features of the term.

(Effects of the Invention) The position measuring device of the present invention is provided with at least one other scanning unit having the same configuration as the scanning unit as a reference scanning unit,
The reference scanning unit is movable relative to the scale independently of at least one said scanning unit and thus both objects, and is capable of moving from the zero point of the at least one reference mark or reference code graduation by scanning the first incremental graduation. It serves to detect the distance to at least one said scanning unit.

Such a measured object in the form of a tool remains engaged with the workpiece due to a fault during interruptions in the measuring and machining process, so that it cannot be interrupted after elimination of the fault and redetection of the reference position. The processed machining process can immediately be continued again. Retracting the tool from its point of engagement with the workpiece and retracing this point of engagement is time consuming and difficult, and can lead to damage to the workpiece. Furthermore, for example in industrial robots, a program-controlled inspection of each reference position during the individual machining steps is possible, which significantly increases the operational safety of such systems.

Advantageous developments of the invention can be gleaned from the exemplary embodiment section.

(Example) The present invention will be explained in detail based on the illustrated example.

The position-measuring device 1 shown in FIG. 1 is limited to the essential device for the invention and is therefore shown diagrammatically. A position measuring device 1 measures the relative positions of two objects 2 and 3. These objects 2 and 3 may be machines (not shown), such as the bed and carriage of a machine tool.

A hollow body 4 is fixed to the carriage 3 by angles 5a and 5b.

A scale 6 is disposed inside the hollow body 4 using a known method. This scale 6 likewise carries an incremental graduation T1 which is scanned by a scanning unit A1 in a known manner. The scanning unit A1 is fixed to the machine bed 2 and
and the carriage 3 move relative to the scale 6. The scale has a so-called incremental graduation, which will be explained in more detail below, so that the position of the carriage 3 relative to the stationary bed 2 can be detected at any time. This is because the incremental graduation T scanned by scanning unit A1 during movement
This is because the interval of 1 is grasped by an evaluation device (not shown) and indicated as a stroke or position value.

In addition to scanning unit A1, a reference scanning unit
A further scanning unit, designated as RA, is provided and is movable with respect to the scale 6 independently of the bed 2 and carriage 3.

With this reference scanning unit, RA, the position of scanning unit A1 relative to the reference point of scale 6 can be determined at any time. The reference point is determined by a reference mark R1, the reference position being absolutely fixed with respect to the incremental graduation T1 of the scale. This reference point detection will be described below based on FIG.

FIG. 2 is a plan view of the configuration according to FIG. 1. The hollow body 4 has a scanning unit A1 and a scanning unit A1 on its upper surface.
It can be seen that the sealing elements 4a and 4b arranged in the area of RA are sealed, so that scanning units A1 and RA each have a coupling member. In the area of this connecting member the sealing element 4a
and 4b are spread apart and lubricate the outer area of the connecting member, the cross-sectional area of which is approximately equal to a double-edged sword.

In FIG. 3, a portion of the scale 6 is shown enlarged. The scale 6 is made of glass and includes a layer that does not transmit light. Here the light is
Although the invention should not be limited to photoelectric position measuring devices, it will be described with reference to those that fall within the optical domain.

Incremental graduations T1 are formed on the scale 6 by a photographic method. One reference point R1 is placed on the scale 6 in a similar manner at a location defined as a reference point. Of course, multiple reference marks can also be provided.

The scanning of the incremental graduation T1 takes place in a known manner. With reference to FIG. 4, it will be explained how the reference position is detected with the method according to the invention.

A scanning unit A1 on the scale 6 in side view scans an incremental graduation T1. Scanning unit A1 and scale 6 at any location
is assumed to be in the rest position. This rest position can be caused by an interruption in the energy supply of the machine. However, as a result of power outages, incremental measuring devices generally also lose position values.

In order to reproduce this position value, it is necessary at a technical level (see the document mentioned at the beginning) to align the reference mark with the corresponding scanning field of the scanning unit.
It is then necessary to run the carriage in such a way that a reference pulse is generated which sets the evaluation device to a predetermined value, for example "zero". The carriage can thus be repositioned. The drawbacks arising from this prior art have already been discussed and the method for detecting a reference position according to the invention has been devised.

The carriage 3 with the scale 6 occupies an unknown position relative to the bed 2 and the scanning unit A1, and the carriage is moved from this location to another location.
The reference mark R from the scanning unit A1 is used to detect the position of the scanning unit A1 with respect to the reference mark R1 and thus of the carriage 3 with respect to the bed 2.
1 distance must be specified.

For this purpose, an additional reference scanning unit RA is operated manually or by means of a drive (not shown) on the scale 6.
is run against. The reference scanning unit RA and the scanning unit A1 also have indicator units 7 and 8. When these indicator units 7 and 8 are brought into matching position, they form a so-called zero indicator 78. The zero indicator has a different structure, and the scanned reference mark is also strictly a zero indicator.

After passing one of the zero indicators (zero indicator 8 or reference mark R1 formed by both indicator units 7 and 8), the evaluation device is set to a predetermined position value, for example "zero". The reference scanning unit RA then moves in the direction of another zero indicator, and the graduation increments passed by the reference scanning unit are detected and summed in the evaluation device. After passing the zero indicator (R1 or 78), the counting is stopped and the distance from the zero indicator 78, ie the first scanning unit A1, to the reference mark R1 is indicated as a reference value. In this way, the position of the respective first scanning unit is detected by moving the reference scanning unit relative to the unknown position of the first scanning unit to a position coincident with this first scanning unit.

The reference position is thereby re-established without having to move one of the mechanical components.

The reference scanning unit RA must be guided as required. This means that - as shown in the example - looking inside the position-measuring device 1, the reference scanning unit RA can of course also be guided directly to the machine outside the position-measuring device 1.

In Fig. 5, the scale 65 corresponds to Fig. 3.
is shown, with an incremental graduation T
A further incremental graduation TR5 is provided next to 5. This incremental graduation TR5 can be made like the incremental graduation T5, but need not have the same lattice constant. If both incremental graduations T5 and TR5 have the same grating constant, instead of two separate incremental graduations T5 and TR5 - in contrast to FIG. 5 - a single wide incremental graduation can be provided.

In addition to the scanning unit A15, other scanning units are also provided for scanning the incremental graduation T5, of which only the scanning unit A25 is shown. Many scanning units scan a common incremental graduation, and in very long machines several mechanical carriages run independently of one another in one axis. Each of the scanning units and A25 has a separate reference position with respect to the scale zero point or reference point R15. Each scanning unit A15 or A25 has its own indicator unit 85 or 95. The distance from the zero point of the graduation or from the reference mark R1 can be determined for each scanning unit A15, A25, etc. in the manner described above by means of a correspondingly connected evaluation device.

Within the scope of the present invention, it is also possible to use multiple scanners on the scale if the scanning path length for the reference scanning unit is to be kept short or if a unique reference mark is to be assigned to each scanning unit A15, A25, etc. Provide a reference mark.

For this case, the individual reference marks must be encoded, ie for each individual reference mark the individual distance from the scale zero point must be known and decoded by the reference scanning unit RA5. can be done.

The example in FIG. 6 shows a particularly advantageous configuration of the invention.

The incremental graduation T6 is arranged on the scale 66 and the scanning units A16 and A26
scanned by The scale 66 has no reference marks and thus forms an incremental position measuring device of the simplest construction. However, the scale must be stored within the housing as described above.

Scanning units A16 and A2 for scale zero point
The reference position of 6 is detected by another position-measuring device, which position-measuring device has an incremental graduation.
It has its own scale 106 with TR6 and reference marks R16, which graduations and marks are scanned by a reference scanning unit RA6. both scales 6
6 and 106 or two corresponding position measuring devices are mounted on the machine in such a way that the reference mark R16 of the scale 106 exactly coincides with the zero point of the incremental graduation T6 of the other scale 66. Scanning units A16 and A26 and reference scanning unit RA
6 similarly indicates indicator configuration units 86, 96.
and 76. The reference point detection is similar to the process described above and therefore will not be described in detail here to avoid repetition.

A particular advantage of the configuration according to FIG. 6 is that the position-measuring device 1 according to the invention can consist of two simple standard incremental measuring devices, of which the graduations of other reference marks can be absolutely determined. The advantage is that only one reference mark is required. With appropriate adjustments, this requirement can be easily met.

A further embodiment is shown in FIG. 7, in which the separate graduation is formed as a reference code graduation TRC. Instead of an incremental graduation with reference marks defining reference positions, a so-called absolute graduation is formed on the scale 67 as a reference code graduation TRC of the incremental graduation T7 used for the specific measurement. The scanning unit is not shown here, since it corresponds to that described above, with the reference code graduation TRC being scanned by a correspondingly designed scanning unit. The absolute position - with respect to the zero point of the reference code graduation TRC - is determined in an evaluation device (not shown) as soon as the indicator unit of the scanning unit for the incremental graduation T7 coincides with the indicator unit of the scanning unit for the reference code graduation TRC. Readable at any time.

The incremental angle measuring device shown in axial cross-section in FIG. 8 is fixed by a housing G to a second object to be measured 02, for example, the housing of an industrial robot (not shown). Inside the housing G, a shaft W is rotatably supported by a first bearing L1 and carries a first partial disk S1 with a first incremental graduation T18, the first incremental graduation being attached to the housing G. scanned photoelectrically by a fixed first scanning unit A18;
The first scanning unit has a first illumination device B1, a first capacitor K1, a first scanning plate AP1 with two first scanning fields (not shown) and two first optoelectronic elements P1. The first incremental graduation T18 in the form of a radial grating consists of alternating light-transparent and light-opaque stripes for the transmitted light measurement method. On the first scanning plate AP1, two first graduation scanning fields are assigned to the first incremental graduation T18 of the first partial disk S1, the first graduation scanning field being the first graduation scanning field for identification of the direction of rotation of the first disk S1. The graduations of the two first graduation scanning fields, to which a first photoelectric element P1 belongs in each case, are offset by 1/4 of the pitch of one incremental graduation T18.
Matches 18. A shaft W protruding from the housing G
is connected to a first object to be measured 01 in the form of an industrial robot.

In the specific measuring process, the axis W and therefore the first partial disk S
When turning 1, the first incremental scale T18
is the first scanning field AP1 fixed to the housing.
The upper and lower first graduations are rotated relative to the scanning fields. The light emerging from the first illumination device B1 is modulated by the first incremental graduation T18 and the mutually moving graduations of the two first graduation scanning fields and impinges on the two associated first photovoltaic elements P1. The element supplies two periodic analog signals offset from each other, which are converted into pulses in a not shown evaluation device of the angle measuring device. These pulses are input to a counter of the evaluation device for counting and can be displayed as digital position measurements in a post-reading indicating device or can be input directly to the numerical control device of the industrial robot.

On the axis W there is a reference mark R which absolutely belongs to the second incremental graduation T2 and to the first incremental graduation T18, concentrically with respect to the first partial disk S1.
A second partial disk S2 is fixed. Second incremental scale T2 and second partial disk S
The reference mark R on 2 is likewise the second scanning unit A.
2, the second scanning unit has a second illumination device B2, a second capacitor K2, a second scanning plate AP2, as well as three second photoelectric elements P2 and has an axis W in the housing G. It is rotatably supported on the second partial disk S2 and the housing G by a second bearing L2.

Second scanning plate AP of second scanning unit A2
2, two second partial scanning fields (not shown) are assigned to the second incremental graduation T2 on the second partial disk S2, and the second partial scanning fields are used to identify the direction of rotation of the second scanning plate K2. 1/ of the pitch of the second incremental scale T2 belonging to
4, the graduations of both second graduation scanning fields coincide with the second incremental graduation T2. A second photoelectric element P2 in a second scanning unit A2 is assigned to each of the two second graduation scanning fields.

The reference mark R on the second partial disk S2 consists of a group of lines with an irregular line graduation, which includes a reference mark with an identical line graduation on the second scanning plate AP2 of the second scanning unit A2. To which the scan field belongs. A second photoelectric element P2 of a second scanning unit A2 is assigned to the reference mark scanning field on the second scanning plate AP2.

A photoelectric zero sensor N having a third illumination device B3 and a third photoelectric element P3 is fixed to the housing G as an indicator unit. A second scanning unit A2, which is rotatably mounted on the axis W, fixes an imaging optical system OT as an indicator unit, which optical system is connected between the third illumination unit B3 and the third optoelectronic element P3. The rotation of the second scanning unit A2 in a particular position causes the light emitted by the third illumination device B3 to be focused on the third photoelectric element P3, so that the third photoelectric element P3 Two scanning units emit a zero signal characterizing a predetermined absolute position of the scanning unit A2.

As mentioned at the outset, in the case of an incremental position measuring device it is not possible from the beginning of the measurement to determine a reference position for the first partial disk S1 which can serve as a starting position for the measurement and which can be reproduced even after a failure. is important.

The measured object 01, which is capable of relative movement before the start of the measurement or even after a failure in which the position measurement is lost in the case of an incremental position measuring device - for example due to a power outage;
02 is assumed to be in a stationary state.

The first partial disk S1 is in a position where the position of the scale zero point relative to the housing G is unknown.

To obtain this reference position, the instantaneous position of the first partial disk S1 with respect to the housing G must be determined. For this purpose, a calibration run is started, during which the second scanning unit A2, including the imaging optics OT of the electrical zero sensor N, is rotated via the transmission Z by the motor M fixed in the housing G. . First, for example, the imaging system OT of the zero sensor N reaches a position coincident with the third illumination device B3 and the third photoelectric element P3, so that the third photoelectric element P3 sets the counter of the evaluation device to the value zero and at the same time Connect the zero signal to start.

From this point on, the second incremental graduation T2 of the stationary second partial disk is replaced by the rotating second scanning plate.
The periodic analog signals scanned by the two second graduation scanning fields of AP2 and generated by the associated second photoelectric element P2 are evaluated and the counter pulses are input to a counter.

After starting the counter and counting the graduation increments of the second incremental graduation T2, the stationary reference mark R of the second partial disk S2 is scanned by the associated reference mark scanning field on the rotating second scanning plate AP2. The counter of the evaluation device is stopped by the signal of the second optoelectronic element P2, which is assigned to the second scanning unit A2. The count values detected in the counter for the adjustment path in the form of the angle of rotation of the second scanning unit between the zero sensor N and the reference mark R on the second partial disk S2 directly give an absolute position value. , whose position value indicates the position instantaneously occupied by the first partial disk S1 and the second partial disk S2 with respect to the housing G, since the reference mark R is directly associated with the first partial disk S1 on the first partial disk S1. This is because it indicates the zero point of the incremental scale T18. Motor M stops and the calibration process ends.

From the moment of scanning of the reference mark R on the second partial disk S2, the counter for the specific measuring process can again be loaded with a counting pulse, which is the counting pulse of the first partial disk S1 with respect to the housing G. This is caused by the scanning of the first incremental graduation by the two first graduation scanning fields on the first scanning plate AP1, which is fixed to the housing during rotation, and by the two first photoelectric elements P1 assigned to the first scanning unit A18. In the event of a failure, for example a power outage, the reference position of the first partial disk S1 with respect to the housing G can be reproduced by said calibration process even if the first partial disk S1 cannot be moved from its instantaneous position. This is because the tool, which is operatively connected to the shaft W, for example via the arm of an industrial robot, is engaged with the workpiece to be machined in the event of a failure.

The rotation of the second scanning unit A2 is carried out over a swivel range somewhat larger than 360° and in both directions of rotation due to the conductor E1 connected to the second illumination unit B2 and the second photoelectric element P2 for the calibration or regeneration process. It will be held on. The rotation angle measuring device is connected to the evaluation device and the power supply device via a conductor E2.

In a manner not shown, the second scanning unit A2 can also be powered by a slip ring instead of a conductor, in which case the second scanning unit A2 can be rotated any number of times in both rotational directions.

Instead of the reference mark R, a plurality of reference marks can also be provided on the second partial disc B2, the reference marks requiring code identification.

Such coded reference marks are described, for example, in DE-A-3039483.
For scanning the code marks for reference marks, an associated code mark scanning field is present on the second scanning plate AP2.

The presence of only one reference mark on the second partial disk S2 has the advantage of a particularly simple manufacturing of the second partial disk S2, since the single reference mark does not require a code for identification. It is from. As will be explained below, the presence of a plurality of reference marks on the second partial disk S2 means that only a small angular step has to be returned during the calibration or reproduction process for the scanning of the next reference mark by the second scanning unit A2. , and has the advantage of being carried out in both rotational directions. This reversing operation allows a program-controlled inspection of individual machining processes, for example of each reference position, in a quick and simple manner by means of the transmission Z, which is designed as a reversing transmission.

The incremental angle measuring device shown as an axial cross section in Fig. 9 is the 8th in terms of basic structure and operation method.
This corresponds to the measuring device shown in the figure and therefore will not be described again.

Equivalent components are designated by the same reference numerals with a ``9'' corresponding to FIG.

A second partial disk S29 is concentrically attached to the first partial disk S19 on the axis W9 and is fixed to a first reference mark R19 attached to the first incremental scale T19 of the first partial disk S19 (10th). In the plane of the second partial disk S29, a ring-shaped third partial disk S39 is disposed concentrically around its periphery, and the third partial disk S39 is attached to the housing G9 via a transparent support plate TP9. fixed, and the second incremental scale T29 and the second incremental scale T2
It has a second reference mark R29 attached absolutely to 9. (Figure 11).

The first reference mark R19 of the second partial disk S29 as well as the second incremental graduation T29 and the second reference mark R29 of the third partial disk S39 are likewise scanned photoelectrically by the second scanning unit A29 and the second The scanning unit has a second illumination device B29, a second capacitor K29, a second scanning plate AP29, a second photoelectric element P29, a third photoelectric element P39, and is connected by a bearing L29 on the shaft 9 in the housing G9. It is rotatably supported on the two-part disc S29 and the third disc S39.

The second incremental graduation T of the third partial disk S39 is placed on the second scanning plate A29 of the second scanning device A29.
29 with two second graduation scanning fields TF21,
TF22 is assigned, the second graduation scanning field being offset from one another by 1/4 of the pitch of the associated second incremental graduation T29 for identification of the direction of rotation of the second scanning plate AP29. The graduations of the two second graduation scanning fields TF21, TF22 coincide with the second incremental graduation T29.

The first reference mark R19 of the second partial disk S29 and the second reference mark R29 of the third partial disk S39 each consist of the same group of lines with predetermined irregular lines, and Second scanning plate
A first reference mark scanning field RF1 and a second reference mark scanning field RF2 having the same line group are attached to the line group on AP29 (the first
Figure 2). A second photoelectric element P29 is located in the first reference mark scanning field RF1 on the second scanning plate A29.
and both second partial scanning fields TF21, TF2
2 and the second reference mark scanning field RF2 respectively have a third photoelectric element P39 of the second scanning device A29.
is attached.

This angle measuring device also determines the instantaneous position of the first partial disk S19 with respect to the housing G9 in order to obtain a reference position. For this purpose, a calibration run is started, during which the second scanning device A29 is driven via the transmission 29 by the motor M9, which is fixed to the housing G9. First, for example, a second reference mark scanning field RF2 on a rotating second scanning plate AP29 is connected to a third segment disk S3 fixed to the housing.
The third photoelectric element P39 of the second scanning device A29 which scans the second reference mark R29 on the second scanning device A29 and which rotates as a result supplies a signal which sets the counter of the evaluation device and simultaneously starts it. From this point on, the associated third photoelectric element P39 is rotated by the associated second graduation scanning field TF21, TF22 during the scanning of the second incremental graduation T29 of the third partial disk S39 fixed to the housing. The periodic analog signal occurring on plate AP29 is evaluated and the counting pulses are input to a counter.

After starting the counter and counting the scale increments of the second incremental scale T29,
A first reference mark R19 on a stationary second partial disk S29 is scanned by a first reference mark scanning field RF1 on a rotating second scanning plate AP29 and a second photoelectric field of a second scanning device A29 is scanned. Element P
The counter of the evaluation device is stopped by the signal No. 29. First reference mark R19 counted by counter
and the second scanning device A between the second reference mark R29 and the second reference mark R29.
The count value for adjustment path length of 29 is housing G9
gives the absolute position instantaneously occupied by the first partial disc relative to the reference mark R19,
R29 is the directly attached incremental scale T1
This is because it indicates the scale zero point of 9, T29. The second scanning device A29 is returned to its starting position again and the motor M9 is stopped. This concludes the calibration process.

From the moment of scanning of the first reference mark R19, the counter for the specific measuring process is again supplied with counting pulses, which are applied to the first scanning plate AP19 fixed to the housing during rotation of the first partial disk S19 with respect to the housing G9. Scanning of the first incremental graduation T19 with the first partial scanning field above and the two first photoelectric elements P assigned to the first scanning device A19
19, the reference position for the first partial disk S19 is maintained even if the first partial disk S19 cannot be moved from its instantaneous position during a fault, for example during a power failure, due to the scanning of the first incremental target T19. It can be reproduced through the calibration process. This is because a malfunction occurs, for example, when the tool, which is connected to the axis W9 via the arm of the indicator unit, engages in the workpiece to be machined.

First reference mark R19 on second partial disk S29
Second sight mark R on chisel and third partial disc S39
29 has the advantage of a particularly simple manufacture of the two partial disks S29, 39.

The angle measuring device can also include a number of reference marks R1. Correspondingly designed partial disks are illustrated in FIGS. 13, 14 and 15. On the axis W9, concentrically with the first partial disk S19, a second partial disk S29 has a first reference mark R1 _i (i=1,2, _. A ring-shaped third partial disk S39 is disposed concentrically around the periphery within the plane of the second partial disk S29, and the third partial disk S39 is fixed to the housing G9 via a transparent support plate TP9. and the second incremental scale T29
and a second reference mark R2 _i (i=1, 2,
. . n), and for the purpose of identification, a second code mark C2 _i is attached to each second reference mark R2 _i (FIG. 14).

First reference mark R1 _i and second partial disk S29
The first code mark C1 _i as well as the second incremental graduation T29 and the second reference mark R2 _i belong to
and the associated second code mark C2 _i are likewise photoelectrically scanned by a second scanning unit A29;
The second scanning unit is formed as described above and has a second partial disk S29 and a third partial disk S39.
is rotatably supported against.

The first reference mark R1 _i of the second partial disk S29 and the second reference mark R2 _i of the third partial disk S39 each consist of the same group of lines with a predetermined irregular line graduation, and the second scanning device A first reference mark scanning field RF1, a second reference mark scanning field RF1 and a second reference mark scanning field RF2 with the same line graduation are attached to the line group on the second scanning plate of A29 (15th figure). The absolute position of the first reference mark R1 _i with respect to the scale zero point of the first incremental graduation T19 is determined by the associated first code mark 1 _i and with respect to the scale zero point of the second incremental graduation T29. The absolute position of _i is characterized by an associated second code mark C2 _i , in which the absolute position of the associated first reference mark R1 _i and second reference mark R2 _i is encoded, respectively. information, such as a so-called barcode. The first code mark C1 _i has the first code mark scanning field on the second scanning plate AP29.
CF1 and a second code mark C2 _i is associated with a second code mark scanning field CF2.

A second photoelectric element P29 is provided in the first reference mark scanning field RF1 and the first code mark scanning field CF1 on the second scanning plate AP29, respectively.
and both second reference mark scanning fields TF21,
TF22; second reference mark scanning field RF2;
and the second code mark scanning field CR2 respectively have a third photoelectric element P in the second scanning device A29.
39 is attached.

To obtain the reference position, the instantaneous position of the first partial disk S19 with respect to the housing G9 must be determined. For this purpose, a calibration run is carried out as described above.

To obtain the reference position, the first code mark scanning field CF1 on the second scanning plate AP29 is moved from the first code mark C1 _i belonging to the scanned first reference mark R1 _i to the absolute position of the first reference mark R1 _i . Read position value. During the scanning of the second reference mark R2 _i , this second reference mark R2 _i is simultaneously read out from the associated second code mark C2 _i from the associated second code mark scanning field CF2 on the second scanning plate AP29. These two absolute position values of the first reference mark R1 _i and of the second reference mark R2 _i are input to the evaluation device. The absolute position value of the first reference mark R1 _i, the absolute position value of the second reference mark R2 _i and the count value corresponding to the angular distance between the first reference mark R1 _i and the second reference mark R2 _i are positive. are combined in the direction.
In the evaluation device, there is an absolute position value occupied by the first partial disk S19 in the housing 9 at an instant.
The second scanning device A29 is again returned to approximately its starting position and the motor M9 is stopped, thereby ending the calibration.

It is possible for the second scanning device A29 to consist of two scanning units. In this case, the transparent carrier plate TP9 can be formed directly as the third partial disk S39, so that the ring-shaped third partial disk S39, which is difficult to manufacture, can be omitted.

According to FIG. 13, a third incremental graduation T39 is also provided on the second partial disk S29, which third incremental graduation T39 corresponds to the third incremental graduation T39 on the rotating second scanning plate AP29 during the calibration or regeneration process. It is scanned by a three-scale scanning field TF3. During this scanning, the analog signal obtained by the associated second optoelectronic element of the second scanning device A29 is logically linked to the reference signal obtained from the first reference mark R1 _i , so that this reference signal adjusted for evaluation.

Actually, the first partial disk S19 and the second partial disk S2
9 cannot be assembled completely accurately and concentrically, errors may occur due to eccentricity errors.

As is clear from FIG. 16, the first partial disk S19
In order to eliminate eccentricity errors between the first partial disk S19 and the second partial disk S29, at least one reference mark RO _i is also arranged on the first partial disk S19, and the position-fixed first scanning device A19 The distance between the reference mark R1 _i previously detected by scanning and the other reference mark R2 _i is corrected by the eccentricity error.

In practice, the calibration is accurate to a few bits, which indicates the uncertainty of the last digit of the measurement result.

This inaccuracy is due to eccentricity which cannot be practically ruled out during the assembly of the first partial disk S19 and the second partial disk S29.

The position of the first reference mark R1 _i with respect to the incremental scale T19 is generally taken as the zero point of the scale,
The last digit of the measurement result is chosen so that it does not appear as a "zero" during calibration. If the last digit of the measurement result is not "zero", the difference is an eccentricity error.

The additional reference mark RO _i provided on the first part S19 is positioned precisely on the zero point of the scale so as to determine the zero point of the scale already in fact and without error during the production of the scale. In an advantageous manner, other additional reference marks RO _i are mounted concentrically with respect to the incremental graduation T19, for example 270 on the partial disk S19, so that one reference mark RO _i appears at every angle of 50.

As soon as the partial disk S19 has been turned by a maximum of 5°, a pulse is generated by the scanning device A19 at one of the reference marks RO _i , which pulse sets the last digit of the measurement result to "zero".

As already mentioned the counter is again a reference mark
actuated by RO _i , resulting in partial disk S19
The angle is determined, including the eccentricity error.

If, for example, an angular constant of 51.38° is detected during calibration, the position of the partial disk S19 is determined with an error of 0.38°, since the reference mark R1 _i should be relative to the zero point of the scale. It is.

When counting starts again after calibration, the absolute angle
At 55.00°, the reference mark RO _i appears. However, the instructions show a measured value of 55.38°. At this moment, according to the invention, the last digit is set to "zero", whereby the measurement is corrected by the eccentricity error.

It is within the scope of the invention if the calibration process does not involve the described reference marks R1 _i and R2 _i , but rather any zero indicators are utilized and eccentricity errors are not fundamentally excluded.

Instead of a photoelectric zero indicator, a magnetic, facile or inductive based zero indicator can also be used.

As already indicated with different graduation formations, the invention is not restricted to incremental position measuring devices, but rather mixed forms can also be used.

Likewise, the physical scanning principle is not essential to the invention; magnetic, inductive, photoelectric, piezoelectric position measuring devices can be operated as reflected or transmitted light types and combinations thereof.

[Brief explanation of the drawing]

Figure 1 shows a length measuring device attached to a mechanical component to be measured, Figure 2 is a plan view of the length measuring device shown in Figure 1, and Figure 3 shows the length measuring device shown in Figures 1 and 2. An enlarged view of the scale, FIG. 4 is a side view of the scale according to FIG. 3 with two scanning components, FIG. 5 is a scale with two incremental graduations and a reference mark, FIG. Two scales with incremental graduations, one of which has a reference mark; FIG. 7 is a scale with incremental graduations and a reference code graduation; FIG. 8 is an axial cross-sectional view of the angle measuring device. , FIG. 9 is an axial sectional view of another angle measuring device, FIG. 10 is a front view of a portion of the second partial disk, FIG. 11 is a front view of a portion of the third partial disk, and FIG. 12 is a front view of a portion of the third partial disk. 13 is a front view of a portion of the other second partial disk, FIG. 14 is a front view of a portion of the other third partial disk, and FIG. 15 is a front view of a portion of the other second partial disk. A front view of the scanning plate, FIG. 16, is a front view of a portion of the first partial disc with additional reference marks. Code in the figure, 2, 3...Object, 6, 65, 6
6,106,67...Scale, A1...Scanning unit, R1...Reference mark, RA, RA5, RA
6...Reference scanning unit, T1, TR, TR6,
TRC...scale, TRC...reference code scale.

Claims (1)

[Claims] 1. For the measurement of the position of two objects 2, 3 capable of relative movement and for the reproduction of a reference position at an unknown position of the object 2, 3 to be measured at any moment. position measuring device, in which at least one scale 6, 65, 66, 67 is connected to the first object 3 and a first incremental graduation T ₁ , T ₅ , T 6 of the scale 6, 65, 66, ₆₇ , at least one scanning unit A1, A15, for scanning _T7 ,
A16 is connected to the second object 2 and at least one reference mark R1, R15, R16 or reference is attached to the first incremental graduation T ₁ , T ₅ , T ₆ , T ₇ of the scale 6, 65, 66 code scale
In the position measuring device, which is equipped with a TRC, at least one reference scanning unit RA, RA5, RA6 which is similar in its configuration to said scanning unit is provided.
Further scanning units are provided, the reference scanning unit being at least one of the scanning units A1, A15, A16 and thus the scales 6, 65, 66, 10, 7, independently of the two objects 2, 3. 6
7 and the first incremental graduation T ₁ or other graduations TR5, TR6, TRC
at least one reference mark R by scanning
1, R15, R16 or reference code scale
A position measuring device characterized in that it detects the distance from the zero point of the TRC to at least one of the scanning units A1, A15, A16. 2 First scanning unit A1 and reference scanning unit
RA has indicator units 8, 7, both indicator units forming a zero indicator unit 78 when coincident.
Position measuring device as described in section. 3. A plurality of said mutually movable scanning units A15, A16, A25, A26 for scanning the first graduations T5, T6 of the scales 65, 66 are equipped with indicator units 85, 86, 95, 96, and Position measuring device according to claim 1, wherein the indicator units 75, 76 of the reference scanning units RA5, RA6 can be brought into a position coincident with each of the other scanning units A15, A16, A25, A26. . 4. Position measuring device according to claim 1, wherein the reference scanning units RA, RA5, RA6 are movable manually or automatically by separate drives relative to the scales 6, 65, 106. 5 Separate graduations TR with reference marks R15, R16 for reference scanning units RA5, RA6
5, TR6 or reference code scale TRC is provided, in which case the zero point of the reference mark R15, R16 or reference code scale TRC is the first scale T5, T6,
2. A position measuring device according to claim 1, which is attached absolutely to T7. 6. Position measuring device according to claim 1 or 5, in which separate scales TR6 are provided on a unique scale 106. 7 a plurality of said scanning units A15, movable independently of each other for scanning the first graduations T5, T6;
A16, A25, A26 are provided and separate scale TR with reference marks R15, R16
5. Reference scanning unit RA for scanning TR6
5, RA6 are provided, the indicator units 75, 76 of which are connected to each scanning unit A1.
5, A16, A25, A26 in a position coinciding with each indicator unit 85, 86, 95, 96.
6. The position measuring device according to any one of item 1, item 3, and item 6. 8. Claim 1, wherein the scanning unit of the first graduation T7 has an indicator unit, which can be brought into a position coinciding with the indicator unit of the scanning unit for the reference code graduation TRC. The position measuring device according to item 1 or 5. 9. Position measuring device according to claim 1, wherein the distance detection is performed during one movement of the object. 10. Any one of claims 1, 5, 6 or 8, in which each one of the graduations, together with its associated scanning unit, assumes an emergency function in the event of a failure of the other scanning unit. The position measuring device described in . 11 A second scale in the form of a partial disk S2 is likewise fastened concentrically to the first scale in the form of a partial disk S1, and a reference scanning unit A2 including an indicator unit 0T is attached to the second partial disk S2. is rotatably supported concentrically with the drive device M,
7. Position-measuring device according to claim 1, which is rotatable in the Z direction and, in particular, for measuring angles. 12. The zero sensor N consists of an illumination device B3 and an attached photoelectric element P3, which are fixed to the second object and between them form an image of the illumination device B3 onto the photoelectric element P3 as an indicator unit. The imaging optical system OT is rotatably mounted, in particular for measuring angles.
The position measuring device according to item 1. 13 a The first scale carrier S19 provided with the first scale T19 is fixed to the second scale carrier S20,
The second graduation carrier is a first reference mark R1i, i=1, 2, 3, which is attached absolutely to the first graduation T19.
...n, b the second object O29 and the third graduation carrier S39 are fixed together, the third graduation carrier having a second graduation T29 with at least one second reference mark R2i;
c at least one first scale of the second graduation carrier S29;
For scanning the reference mark R1i and for scanning the second graduation T29 of the third graduation S39 with at least one second reference mark R2i, a second
The scanning device A29 scans the second scale carrier S29 and the third scale carrier S29.
d the adjustment path of the first scanning device A29 is adjustable in accordance with the distance between the first reference mark R1i and the second reference mark R2i, in particular the angle 2. A position measuring device according to claim 1 or 2, which measures: 14 a. A second graduation carrier in the form of a second partial disk S29 is fixed concentrically to a first graduation carrier in the form of a first partial disk S19; b. A third graduation carrier in the form of a ring-shaped third partial disk S39. a third graduation carrier of the shape of a shape is fixed to the second object O29 concentrically with the second partial disk S29; c the second scanning device A29 is attached to the second partial disk S29 and the third partial disk S39; 14. Position-measuring device according to claim 13, which is rotatable by means of drives M9, Z9 concentrically relative to each other and for measuring angular positions. 15 Each first code mark C1i is attached to the first reference scale mark R1i, and each second code mark C2i is attached to the second reference mark R1i,
14. Position-measuring device according to claim 13, in particular for measuring angles, in which the code marks C1i, C2i have in decoded form the absolute position values of the associated reference marks R1i, R2i. 16. Position measuring device according to claim 13, wherein the second graduation carrier S2 has a third incremental graduation T3. 17 First partial disk S19 and second partial disk S29
At least one reference mark R0 is also provided on the first partial disk S19 for canceling eccentricity errors between
₁ is arranged and the first scanning device A is fixed in position.
19. The method according to claim 14, wherein by scanning the mark by 19 the previously determined distance between the reference mark and another reference mark R1i is corrected by an eccentricity error, in particular for measuring angles. Position measuring device. 18. Position measuring device according to claim 17, in particular for measuring angles, in which the correction is carried out by rounding up the last digit of the distance measurement. 19. The position measuring device according to claim 1, wherein the first incremental scale T5 and the further scale TR5 are integrated into one scale.