DE202008013715U1 - Device for determining the relative position of two mutually movable objects - Google Patents

Abstract

contraption for determining the relative position of two mutually movable Objects with a material measure attachable to the one object (10) and with an attachable to the other object scanner (12), wherein the scanning device (12) at least one coil (30, 36) whose impedance through the material measure (10) is affected to position-dependent signals generate, characterized in that the scanning device (10) at least one pair of identical coils (30.1, 30.2, 30.3, 30.4, 36.1, 36.2), which in one to the surface of the material measure (10) parallel to each other at a distance from each other are that the material measure (10) by the Impedance of the coils (30, 36) strongly influencing areas (16, 24) and weakly influencing regions (18, 26) is formed, the in the measuring standard (10) are arranged so that these areas (16, 18; 24, 26) are the two coils (30.1, 30.2; 30.3, 30.4; 36.1, 36.2) of an associated pair alternate with each other affect that a voltage jump (Ub) by means of a demand signal (Pulse 1) at the same time ...

Description

The The invention relates to a device for determining the relative Position of two mutually movable objects according to the Preamble of claim 1.

to Determination of the relative position of two mutually movable objects, z. B. two machine parts is on the one object a material measure arranged by a arranged on the other object scanning device is scanned. The material measure can be a Linear measuring standard for the determination of linear Displacement paths or a circular measuring standard for Determination of rotational movements. For an absolute Position measurement can be the material measure have respective position information in coded form. The Sampling thus provides the current position value at any time. In an incremental position measurement are by the scanner the graduation steps of the material measure of one absolute reference position counted to the current one Position to determine.

From the DE 195 23 853 A1 It is known to use as measuring standard successive alternating magnetically poled areas, which are scanned by coils, wherein the magnetic poles of the material measure induce a periodic signal in the coil, which can be evaluated for an incremental position measurement. Absolute position measuring systems usually use an optical scanning and are therefore complicated due to the sensitivity to contamination.

Of the Invention is based on the object, a method and an apparatus for determining the relative position of two mutually movable objects to provide a simple construction and a simple assembly with a low sensitivity to external Unite influences.

These The object is achieved by a device solved with the features of claim 1.

advantageous Embodiments of the invention are referred to in the respective Subclaims specified.

According to the invention the scanning device has at least one pair of two identical coils, in the number of turns, their geometry and their rest Properties are identical. The measuring standard is formed by areas that interact with these coils, wherein the material measure consists of areas that greatly affect the impedance of the coils, and such areas, which have little influence on the impedance of the coils. The two coils each pair of the scanner and also cooperating with these coils Areas of the material measure are so against each other spaced that the strongly influencing and the weakly influencing Areas of the material measure respectively the two Alternately influence coils of an associated pair. to Positioning become the two coils of a pair at the same time subjected to the same voltage jump, wherein the different Affecting the impedance of these two coils through the areas the material measure a different step response which results in two coils. The difference of the step responses the two coils is evaluated as a position-dependent signal.

The Coils may preferably be wound or printed Coils may be formed, the surface parallel to the surface the measuring scale are arranged. The areas the material measure that the impedance of the coils strong influence, are preferably made of a material with good electrical or magnetic conductivity. A simple one Production results from the fact that the material measure as a linear strip-shaped band or disc from an electrically conductive or ferromagnetic Material is formed, with punched, the weakly influencing Forming area that separate the strongly affecting areas, in which the material stops. The strong and weak influencing Areas correspond essentially in their dimensions the area of the coils. A ferromagnetic material for the material measure leads due to the permeability of this material to the influence the impedance of the coils. For a material with good electrical Conductivity are due to the magnetic field of the coils in the strongly influencing areas of the material measure eddy currents generated, which in turn affects the impedance of the coil Create opposing field. The use of a material with good electrical Conductivity leaves a more precise geometric Definition of the areas of influence, why such a material is preferred. It can be used for the material measure For example, a stamped copper sheet, a copper foil or a vapor deposited copper layer can be used.

For an absolute position determination, the two coils of a pair are arranged side by side transversely to the direction of movement of the objects. At the same distance that the two coils of the pair have, the regions of the material measure are arranged in two tracks next to each other. The alternating influence of the two coils of the pair is caused by the fact that Areas of one track are each inverted to the areas of the second track. Each strongly influencing region of the one track corresponds to a stamped free and thus little or no influencing region in the second track. The scanning of these two tracks of the measuring standard by the pair of two coils thus results in a position information of one bit. By arranging a plurality of coil pairs transversely to the direction of movement of the objects and by arranging a corresponding number of track pairs of the material measure, an absolute position determination with a desired code word width of the position information can thus be obtained by a cascading evaluation.

Further It is possible to have the two coils of a pair in the direction of movement to arrange the objects spaced from each other. Accordingly, the Areas with strong influence and weak influence of the Measuring standard in the direction of movement with a arranged such division, that in each case the one coil of the pair with a strongly influencing area comes to cover, if the second coil of the pair with a non-influencing area comes to cover. The two coils of the pair thus deliver sinusoidal and an inverted sinusoidal Signal when scanning against the measuring scale is moved. At the time of sampling is thus out of the respective current amplitude value of the sine signal and the inverted sine signal a difference signal is formed, which is an interpolation of the division the material measure and thus a fine resolution allows. In a conventional manner, in each case to the coil pair for the sinusoidal and the inverted sinusoidal Signal used a second by 90 ° in phase offset coil pair which is thus a cosine and inverted cosinusoidal signal generated. Through this additional 90 ° phase shifted sampling can be indefinite Position states are avoided when the coils of the a coil pair each at the transition from a strongly influencing to a weakly influencing area.

in the The invention will be explained below with reference to an embodiment shown in the drawing Embodiment explained in more detail. Show it:

1 a section of a material measure,

2 one of the material measure associated scanning unit and

3 a circuit diagram of the scanning unit.

In the 1 and 2 a device for determining the relative position of two linearly movable objects is shown, for. B. for determining the position of a CNC-controlled movable carriage on a machine tool. At one of the objects is a material measure 10 attached, of which in 1 a section is shown. At the other object is a scanner 12 attached in 2 is shown.

The linear measuring standard 10 is by a band of a material with good electrical conductivity, z. B. formed from a copper alloy. The band extends linearly in the direction of relative movement of the two objects. The measuring standard 10 has an incremental track running in the longitudinal direction of the belt 14 on, consisting of a predetermined scale alternately successive areas 16 and 18 consists. The areas 16 consist of the solid material of the tape of the material measure 10 while the areas 18 are formed by recesses of the material of the band. The areas 16 and 18 have the same length in the longitudinal direction of the material measure 10 on the same width across the longitudinal extent of the material measure 10 ,

Next has the material measure 10 an absolute encoding based on an inverted code track 20 and a non-inverted code track 22 consists. The code tracks 20 and 22 run parallel to each other in the longitudinal direction of the material measure 10 , The code tracks 20 and 22 are each of longitudinally successive areas 24 and 26 formed, being in the areas 24 the solid material of the electrically conductive material of the material measure 10 exists while the areas 26 are formed by recesses of this material. The areas 24 and 26 each have the same length in the longitudinal direction of the material measure 10 on and a predetermined width transverse to the longitudinal direction. The incremental track 14 and the code tracks 20 and 22 are in the transverse direction of the material measure 10 spaced apart. The areas formed by solid material 24 and the areas formed by recesses 26 follow in the inverted code track 20 according to a binary code on each other z. B. according to a random code. Every area can do this 24 respectively. 26 represent a bit, z. For example, the areas 24 logical 1 and the ranges 26 logical 0. This contains the code track 22 a 1-bit information. It is also possible to have two consecutive areas 24 respectively. 26 to a 2-bit information, etc. The non-inverted code track 22 is different from the inverted code track 20 in that next to each area 24 with solid material in the track 20 an area 26 as a recess in the code track 22 is arranged and corresponding to each area 26 the code track 20 an area 24 of full material in the code track 22 disposed is. The areas 24 and 26 are in the code tracks 20 and 22 thus formed inverted to each other.

In the 2 shown scanning device 12 is surface parallel to the material measure 10 arranged, the material measure 10 and the scanner 12 surface parallel and relative to each other in the longitudinal direction of the measuring graduation 10 are movable against each other.

The scanning device 12 carries electrical coils, especially in the area of the scanning device 12 wound or printed. The coils are in the scanner 12 arranged in tracks corresponding to the tracks 14 . 20 and 22 the measuring standard 10 correspond.

The coils are in their length in the direction of the relative movement of material measure 10 and scanner 12 and in their width according to the areas 16 and 18 respectively. 24 and 26 the measuring standard 10 dimensioned. Comes with the relative movement of material measure 10 and scanner 12 a coil with an area 16 respectively. 24 made of solid material of the material measure 10 to cover, the magnetic field of the coil induces eddy currents in the area when the coil current changes 16 respectively. 24 which generate a magnetic opposing field, so that the impedance of the coil through these areas 16 respectively. 24 is strongly influenced. On the other hand, the coils come with the areas 18 respectively. 26 to cover, through recesses of the material of the material measure 10 are formed, such eddy currents can not be induced and the material measure 10 does not affect the impedance of the coils, or at least significantly less.

In the scanner 12 are in an incremental track 28 Do the washing up 30 arranged. The incremental track 28 falls with the incremental track 14 the measuring standard 10 together. The spools 30 correspond in their dimensions in length and width to the dimensions of the strongly influencing areas 16 and the weakly affecting areas 18 the incremental track 14 the measuring standard 10 , In the longitudinal direction of the incremental track 28 are two coils 30.1 and 30.2 arranged at such a distance from each other that they have a phase shift of 180 ° with respect to the graduation of the incremental track 14 the measuring standard 10 exhibit. This means that the coil 30.1 with a strongly influencing area 16 comes to cover when the coil 30.2 with a weakly affecting area 18 the measuring standard 10 comes to cover and vice versa. The areas 16 the incremental track 14 the measuring standard 10 thus affect the impedance of the coils 30.1 and 30.2 alternately. Will the impedance of a coil 30.1 heavily affected, the impedance of the second coil 30.2 the couple has little or no influence and vice versa.

Another pair of two coils 30.3 and 30.4 is opposite the pair of coils 30.1 and 30.2 phase-shifted by 90 ° with respect to the graduation of the incremental track 14 the measuring standard 10 , The spools 30.3 and 30.4 are thus arranged so that these coils 30.3 and 30.4 each at the transition from a strongly influencing area 16 to a weakly influencing area 18 the incremental track 14 the measuring standard 10 are positioned when the coils 30.1 and 30.2 completely with these areas 16 respectively. 18 come to cover.

Will the scanner 12 relative to the material measure 10 moved, so covers the coil 30.1 the graduation of the areas 16 and 18 the incremental track 14 in a sinusoidal course, while related to the coil 30.2 a sinusoidal curve, the coil 30.3 a cosinusoidal course and the coil 30.4 cover a minus cosinusoidal course.

Next, the scanner 12 in an inverted track 32 and a non-inverted track 34 Do the washing up 36 on. The spools 36 correspond in their dimensions in length and width to the areas 24 and 26 the code tracks 20 and 22 the measuring standard 10 , The inverted track 32 the scanner 12 falls with the inverted code track 20 the measuring standard 10 together, while the non-inverted track 34 with the non-inverted code track 22 the measuring standard 10 coincides. The spools 36 are in the tracks 32 and 34 arranged in the longitudinal direction in the same mutual distance as the strongly influencing areas 24 and the weakly affecting areas 26 in the code tracks 20 and 22 the measuring standard 10 , One coil each 36.1 the inverted track 32 and the coil next to it 36.2 the non-inverted track 34 make a couple. The arrangement of the coils 36.1 and 36.2 and the education of the areas 24 and 26 in the code tracks 20 and 22 the measuring standard 10 have the consequence that the strongly influencing areas 26 the code tracks 20 and 22 the spools 36.1 and 36.2 always alternating with each other. This means that the coil 36.1 with a strongly influencing area 24 comes to cover, so that their impedance is greatly affected when the associated coil 36.2 of the coil pair with a weakly influencing area 26 the non-inverting code track 22 comes to cover, so the impedance of the coil 36.2 is not or only weakly influenced. Conversely, the impedance of the coil 36.2 through an area 24 strongly influenced, so does the coil at the same time 36.1 not affected in their impedance.

Based on the circuit of 3 the operation of the scan is explained.

In the upper half of the 3 is the sample of the incremental track 14 the measuring standard 10 through the coils 30.1 and 30.2 the scanner 12 shown. The sink 30.1 with the inductance L1 and the coil 30.2 with the same inductance L2 are applied in parallel via the same series resistors R1 and R2 connected in series simultaneously with the same voltage jump. For this purpose, a DC voltage Ub of, for example, 5 volts via a transistor M3 is connected in parallel to the series circuits R1, L1 and R2, L2. The transistor M3 is, for example, a P-channel transistor, at whose source the voltage Ub is, while the series circuits of the coils 30.1 and 30.2 are connected to the series resistors R1 and R2 at the drain. An electronic control, not shown, requests the position reading by a demand signal. By this Demand signal (pulse 1), the gate of the transistor M3 is set to 0 volts, whereby a voltage jump of 0 volts to the voltage Ub on the series circuits of the coils 30.1 and 30.2 is switched. This voltage jump is generated at the inductances L1 and L2 of the coils 30.1 and 30.2 a step response that depends on the current impedance of the coils 30.1 and 30.2 depends, that depends on how far the coils 30.1 and 30.2 each with a strongly influencing area 16 or a weakly influencing area 18 the dimensional standard overlap in terms of area. The voltage of the step response of the coil 30.1 is stored on a capacitor C1 via a diode D1. Accordingly, the voltage of the step response of the coil 30.2 stored on a capacitor C2 via a diode D2. The difference of the step responses stored on the capacitors C1 and C2 corresponds to the ratio of sine and minus sine of the phase angle of the scanning device 12 to a graduation period of the incremental track 14 the measuring standard 10 , The voltage difference between the capacitors C1 and C2 is evaluated via a differential amplifier and fed to an AD converter. The voltage difference thus enables interpolation of the graduation of the incremental track 14 the measuring standard 10 ,

about Transistors M1 and M2, the capacitors C1 and C2 then be discharged to the circuit for to reset a new position query.

Like the bottom half of the circuit 3 shows are correspondingly the coils 30.3 with the inductance 13 and 30.4 with the inductance 14 applied via series resistors R3 and R4 to the demand signal (pulse 2) via a transistor M3 with a voltage jump. Also the step response of the coils 30.3 and 30.4 can be stored in a corresponding manner via diodes D3 and D4 on the capacitors C1 and C2, so that the voltage difference of the step responses can be evaluated via the differential amplifier.

The controller selects whether by the demand signal pulse 1 or the demand signal pulse 2, the first coil pair 30.1 . 30.2 or the coil pair offset by 90 ° in phase 30.3 . 30.4 used for position measurement. The selection is made according to which coil pair provides a unique voltage difference, ie not a transition from a strongly influencing area 16 to a weakly influencing area 18 located.

One of the upper half of the 3 corresponding circuit also allows the reading of the inverted code track 20 and the non-inverted code track 22 the measuring standard 10 through the coils 36.1 the inverted track 32 and the coils 36.2 the non-inverted track 34 the scanner 12 , Structure and operation of the circuit correspond to the above description.

Because the code tracks 20 and 22 are designed so that the strongly affecting areas 24 the one code track each weakly affecting areas 26 correspond to the other code track, shows at each adjacent coil pair 36.1 . 36.2 of the tracks 32 and 34 a coil one through an area 24 heavily influenced impedance, while the other coil of the pair one through an area 26 has only weakly influenced impedance. The difference signal of the step responses of the two coils 36.1 . 36.2 a pair thus provides a largely independent of external interference signal, which by the coding of the code tracks 20 and 22 identified absolute position of material measure 10 and scanner 12 indicates.

It goes without saying that the number of coded tracks of the material measure 10 and according to the associated coil tracks of the scanner 12 can also be increased to obtain a larger code word width for the absolute position measurement.

By means of the invention it is possible, in response to a demand signal, to obtain an absolute position value through the coded tracks of the material measure 10 to obtain, whereby the measuring steps of the absolute coding still by the evaluation of the signals of the incremental track 14 can be interpolated and improved in terms of resolution.

10

Measuring standard

12

scanning

14

incremental track

16

strongly affecting areas

18

weak influencing areas

20

inverted Code track

22

non-inverted Code track

24

strongly influencing areas

26

weak influencing areas

28

incremental track

30

Do the washing up

32

inverted track

34

non-inverted track

36

Do the washing up

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19523853 A1 [0003]

Claims (11)

Device for determining the relative position of two objects which can be moved relative to one another, with a material measure attachable to the one object ( 10 ) and with an attachable to the other object scanner ( 12 ), wherein the scanning device ( 12 ) at least one coil ( 30 . 36 ) whose impedance through the material measure ( 10 ) to generate position-dependent signals, characterized in that the scanning device ( 10 ) at least one pair of identical coils ( 30.1 . 30.2 ; 30.3 . 30.4 ; 36.1 . 36.2 ), which in one to the surface of the material measure ( 10 ) parallel direction are arranged at a distance from each other that the material measure ( 10 ) by the impedance of the coils ( 30 . 36 ) strongly influencing areas ( 16 . 24 ) and weakly influencing areas ( 18 . 26 ) formed in the material measure ( 10 ) are arranged so that these areas ( 16 . 18 ; 24 . 26 ) the two coils ( 30.1 . 30.2 ; 30.3 . 30.4 ; 36.1 . 36.2 ) of an associated pair alternately influence one another that a voltage jump (Ub) by means of a demand signal (pulse 1) simultaneously to the two coils ( 30.1 . 30.2 ; 30.3 . 30.4 ; 36.1 . 36.2 ) of the pair can be applied and that the difference of the step responses of the two coils ( 30.1 . 30.2 ; 30.3 . 30.4 ; 36.1 . 36.2 ) is supplied to an evaluation. Device according to Claim 1, characterized in that the regions which strongly influence the impedance ( 16 . 24 ) of the material measure ( 10 ) are formed by a material having high electrical or magnetic conductivity. Apparatus according to claim 2, characterized in that the material measure ( 10 ) consists of a material with high electrical or magnetic conductivity, from which the impedance weakly affecting areas ( 18 . 26 ) are omitted. Device according to one of claims 1 to 3, characterized in that the coils ( 30 . 36 ) or printed on the scanning device ( 12 ) are arranged. Device according to one of the preceding claims, characterized in that the coils ( 30 . 36 ) and the impedance of the coils ( 30 . 36 ) strongly or weakly influencing areas ( 16 . 18 . 24 . 26 ) substantially the same length and width dimensions in the surface of the material measure ( 10 ) or the scanning device ( 12 ) exhibit. Device according to one of the preceding claims, characterized in that the material measure ( 10 ) at least two code tracks ( 20 . 22 ), in which the strongly influencing areas ( 24 ) and the weakly influencing areas ( 26 ) are arranged in a sequence coding the absolute position value, that the regions ( 24 . 26 ) of a code track ( 20 ) with the one in the other track ( 22 ) adjacent thereto are formed inverted to each other and that in the scanning device ( 12 ) Do the washing up ( 36 ) in two corresponding tracks ( 32 . 34 ) are arranged, wherein in each case a coil ( 36.1 ) of one track ( 32 ) with the adjacent coil ( 36.2 ) of the other track ( 34 ) forms a coil pair. Device according to one of the preceding claims, characterized in that in the material measure ( 10 ) strongly influencing areas ( 16 ) and weakly influencing areas ( 18 ) in an incremental track ( 14 ) are arranged in the same graduation in succession and that in a corresponding incremental track ( 28 ) of the scanner ( 12 ) at least a pair of two coils ( 30.1 . 30.2 ; 30.3 . 30.4 ) in such a mutual distance in the direction of the material measure ( 10 ) are arranged that a coil ( 30.1 ; 30.3 ) of the pair with a strongly influencing area ( 16 ) coincides when the other coil ( 30.2 . 30.4 ) of the pair with a weakly influencing area ( 18 ) comes to cover. Device according to claim 7, characterized in that in the incremental track ( 28 ) of the scanner ( 12 ) at least two coil pairs ( 30.1 . 30.2 and 30.3 . 30.4 ) are arranged, wherein the coil pairs in the longitudinal direction of the material measure ( 10 ) are offset from each other so that the coils ( 30.3 . 30.4 ) of the one pair with a transition from a strongly influencing area ( 16 ) to a weakly influencing area ( 18 ) coincide when the coils ( 30.1 . 30.2 ) of the other pair with a strongly influencing area ( 16 ) or a weakly influencing area ( 18 ) come to cover. Apparatus according to claim 7 or 8, characterized in that the difference of the step responses of the two coils ( 30.1 . 30.2 ; 30.3 . 30.4 ) of a pair for interpolating the position measured value within the graduation of the incremental track ( 14 ) is evaluated. Device according to one of the preceding claims, characterized in that the voltage (Ub) via a through the demand signal (pulse 1, pulse 2) through-connected transistor (M3) to the coils ( 30.1 . 30.2 ; 30.3 . 30.4 ; 36.1 . 36.2 ) is placed. Device according to one of the preceding claims, characterized in that by the step response of the coils ( 30.1 . 30.2 ; 30.3 . 30.4 ; 36.1 . 36.2 ) are each charged capacitors (C1, C2), whose voltage is applied to a differential amplifier.