DE102017204871A1 - Energy-saving positioning method - Google Patents

Abstract

The invention relates to a method for operating a position measuring system (10), wherein the position measuring system comprises a first and a second body (20; 50) which are relatively movable along a one-dimensional trajectory, wherein on the first body (20) an absolute and an incremental measuring graduation (30; 40) is provided, the second body (50) having a first sensor (60) comprising a plurality of separate scanning means (62) with which a plurality of digits of a random number sequence (33) of the absolute measuring graduation (30) The second body (50) has a second sensor (70) by means of which the incremental material measure (40) can be scanned. According to the invention, the method comprises the following steps: a) Determining an absolute first position using a first number of Sensing means of the first sensor, b) determining an absolute second position using the first position u c) determining an absolute third position using a second number of sensing means, the second number being less than the first number, the position sensing system (10) moving during determination of the absolute third position.

Description

The invention relates to a method for operating a position measuring system.

The process according to the invention is in particular that of DE 10 2015 213 784 A1 known absolute position measuring system. From the EP 2 502 030 B1 Furthermore, the combination of an absolute and an incremental position measuring system is known.

A position measuring system according to the invention comprises a first and a second body which are relatively movable along a one-dimensional trajectory, wherein an absolute and an incremental measuring graduation are provided on the first body, the absolute measuring graduation having a multiplicity of first markings which follow the trajectory distributed, wherein they encode a random number sequence, wherein the incremental measuring graduation has a plurality of second markers, which are arranged distributed along the trajectory periodically distributed, wherein the second body comprises a first sensor comprising a plurality of separate scanning means with which a plurality of locations Random number sequence of the absolute material measure can be scanned simultaneously, wherein the second body has a second sensor, by means of which the second marks of the incremental material measure can be scanned.

An advantage of the method according to the invention is that an absolute first position can be determined when the position measuring system is at a standstill. At the same time an absolute third position can be determined during operation. The electrical power requirement during the determination of the absolute third position is significantly lower than that during the determination of the absolute first position. It should be noted that a position measuring system is typically connected via a standardized connection cable to a higher-level control. Part of such a standard is typically the electrical power supply, which is limited upwards. It is usually permissible to record a higher electrical power during the switch-on of the position measuring system than during operation.

1. a) Ermitteln einer absoluten ersten Position unter Verwendung einer ersten Anzahl der Abtastmittel des ersten Sensors;
2. b) Ermitteln einer absoluten zweiten Position unter Verwendung der ersten Position und des zweiten Sensors;
3. c) Ermitteln einer absoluten dritten Position unter Verwendung einer zweiten Anzahl von Abtastmitteln, wobei die zweite Anzahl kleiner als die erste Anzahl ist, wobei sich das Positionsmesssystem während der Ermittlung der absoluten dritten Position bewegt.

According to the independent claim, it is proposed that the method according to the invention comprises the following steps:

1. a) determining an absolute first position using a first number of the scanning means of the first sensor;
2. b) determining an absolute second position using the first position and the second sensor;
3. c) determining an absolute third position using a second number of sensing means, the second number being less than the first number, the position sensing system moving during determination of the absolute third position.

The position measuring system is preferably stationary during step a). Step a) is preferably carried out during the switch-on process, in which an increased power consumption is permitted. By means of step b), a very accurate absolute second position is determined during operation. By means of step c), a comparatively inaccurate absolute third position is determined during operation, which primarily serves to control the second position. The electrical supply power, which is required for the steps b) and c) during operation, is smaller than the maximum permissible electrical supply power according to the usual standards.

The first number of scanning means preferably comprises all available scanning means. The second number of scanning means is preferably one. Step a) is preferably carried out as a first process step. Steps b) and c) are preferably carried out several times alternately or in parallel.

In the dependent claims advantageous refinements and improvements of the invention are given.

It can be provided that the second and the third position are compared with each other, wherein an error message is issued if they do not match. A malfunction is present in particular when the third position deviates from the second position by a predetermined threshold value. It is understood that the second position is considerably more accurate than the third position. The said threshold value is preferably selected depending on the accuracy of the third position.

It can be provided that the scanning means each comprise at least a first receiver coil, wherein the first sensor has a first transmitter winding arrangement, wherein the inductive coupling between the first transmitter winding arrangement and the at least one first receiver coil can be influenced by the absolute measuring scale, wherein an electrical Supply power of the first transmitter winding arrangement in the context of step a) is greater than in the context of step c). As a result, in the context of step c), the electrical supply power can be minimized. The evaluation method described below still allows a reliable reading of the random number sequence.

It can be provided that in the context of step c) it is determined by means of the second sensor whether the first sensor has traversed enough points of the random number sequence in order to determine the third position. With the incremental second sensor can be easily determined whether the position measuring system has covered the required distance.

It can be provided that the third position is always determined when the second sensor has moved in the same direction by a predetermined measuring length. This criterion is easy to check. At the same time, this criterion ensures that the absolute third position is frequently determined.

It can be provided that in the context of step c) more digits of the random number sequence are read than are necessary for determining the absolute third position, wherein by means of the surplus places an error detection and / or an error correction is performed. As a result, the reliability of the position measuring system can be increased.

It can be provided that the first sensor is connected to an analog-to-digital converter with which samples can be generated, whereby corresponding samples are stored, which have a constant first movement distance, wherein the graduation λ of the absolute material measure an integer multiple of the first Movement distance is, wherein the pitch γ of the incremental material measure is an integer multiple of the first movement distance. The pitch λ of the absolute material measure and the pitch γ of the incremental material measure are preferably selected to be different from one another such that the above-mentioned condition can be fulfilled. An analog-to-digital converter typically specifies digital samples with a predetermined sample rate. From these comparatively large numbers of samples, those samples which are present in defined positions of the position measuring system are selected and stored. The said defined positions are each spaced apart by the first movement distance. As a result, only a comparatively small number of samples needs to be processed further. Nevertheless, it is ensured that the optimum samples for the evaluation are stored.

It can be provided that the sample values are assigned to a plurality of groups in such a way that the sample values within a group have a second movement distance which is equal to the pitch λ of the absolute material measure. It is thus possible to determine the random number sequence solely by evaluating the sample values of a group, wherein only one single sample value is to be evaluated for each digit of the random number sequence.

It can be provided that the random number sequence is determined on the basis of the group of sample values which has the largest magnitude of the sampled values. As a result, it is achieved with high reliability that the determined random number sequence coincides with the random number sequence actually present on the absolute material measure.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

• 1 eine grobschematische Draufsicht eines erfindungsgemäßen Positionsmesssystems;
• 2 einen grobschematischen Querschnitt des Positionsmesssystems nach 1;
• 3 eine grobschematische Seitenansicht der absoluten Maßverkörperung und des ersten Sensors;
• 4 eine grobschematische Seitenansicht der inkrementellen Maßverkörperung und des zweiten Sensors;
• 5 den Verlauf des Signals eines Abtastmittels bei einer Bewegung entlang der Bewegungsbahn.

The invention will be explained in more detail below with reference to the accompanying drawings. It shows:

• 1 a rough schematic plan view of a position measuring system according to the invention;
• 2 a rough schematic cross section of the position measuring system according to 1 ;
• 3 a rough schematic side view of the absolute measuring scale and the first sensor;
• 4 a rough schematic side view of the incremental measuring scale and the second sensor;
• 5 the course of the signal of a scanning means in a movement along the trajectory.

1 shows a rough schematic plan view of a position measuring system according to the invention 10 , The position measuring system 10 is purely an example part of a linear roller bearing. The first body 20 is accordingly of a guide rail 21 formed, which with a constant cross-sectional shape along a longitudinal axis 11 extends. The trajectory 12 of the position measuring system 10 falls with the longitudinal axis 11 together. A carriage 51 is, for example by means of several rows of endless rotating rolling elements, in the direction of the longitudinal axis 11 movable on the guide rail 21 guided. On the carriage 51 is a measuring head 52 attached, which together with the carriage 51 the second body 50 forms. In the measuring head 52 are a first and a second sensor 60 ; 70 and an evaluation device 53 added. The first and the second sensor 60 ; 70 are to the evaluation device 53 connected, preferably to analog-to-digital converter in the evaluation device 53 , The evaluation device 53 preferably comprises an FPGA and / or a microprocessor, which are set up for carrying out the method according to the invention. The guide rail 21 includes an absolute and an incremental material measure 30 ; 40 , which in each case over the entire length of the guide rail 21 extend.

2 shows a rough schematic cross section of the position measuring system 10 to 1 , The guide rail 21 includes a main body 24 from bearing steel, the hardened raceways 22 has for the Wälzköper. Whose cross-sectional shape is adapted in the present case to cylindrical rolling elements, wherein four rows of rolling elements are provided. The absolute and the incremental material measure 30 ; 40 are on opposite side surfaces of the main body 24 attached. They each come from an associated masking tape 23 covered, which also on the main body 24 is attached. The absolute and the incremental material measure 30 ; 40 In the present case, each of a sheet metal strip of magnetically conductive material, for example of magnetizable steel, formed in accordance with the 3 respectively. 4 is provided with openings. The masking tapes 23 are each designed as a metal strip without openings, which consists of a magnetically non-conductive material, such as non-magnetizable steel.

The first and the second sensor 60 ; 70 is inside the measuring head 52 fixed so that it is the associated measuring standard 30 ; 40 with a small distance opposite.

It should be noted that in addition to the presented inductive measuring principle, the present invention can also be used in conjunction with a magnetic or an optical measuring principle.

3 shows a rough schematic side view of the absolute material measure 30 and the first sensor 60 , In the first transmitter coil arrangement 61 , the first receiver coils 63 and the absolute measuring standard 30 is the central axis 32 the absolute measuring standard 30 located. For the sake of clarity, the parts mentioned in 3 transverse to the central axis 32 shown side by side, where they are actually superposed so that all three central axes 32 are congruent. In the direction of the central axis 32 the three parts mentioned are aligned relative to one another according to the actual conditions. The central axis 32 is parallel to the longitudinal axis (No. 11 in 1 ) arranged.

The first marks 31 the absolute measuring standard 30 are each formed by rectangular openings in the sheet metal strip concerned. The corresponding first rectangle pages 34 are perpendicular to the central axis 32 aligned. Your distance in the direction of the central axis 32 can be an integer multiple of a pitch λ of the absolute material measure 30 It is also conceivable that their position is minimally shifted from this ideal position. The second rectangle sides 35 are parallel to the central axis 32 arranged. Mapped second rectangle sides 35 different first marks 31 are arranged in a flight.

The first marks 31 encode a binary random number sequence 33 , A logical 1 is coded if there is a transition from a magnetically conductive material to a free space or vice versa at a division position. A logical 0 is encoded if there is no corresponding transition at a split position. The coded random number sequence 33 is chosen such that any selection of a number n of immediately consecutive bits results in a position code occurring only once in the random number sequence. The named number n is also referred to as the bit width of the random number sequence.

The first sensor 60 is present according to the DE 10 2015 213 784 A1 whose entire content is referred to and incorporated in the present application. But it is also conceivable, the absolute measuring standard and the first sensor according to the EP 2 502 030 B1 perform.

The first sensor comprises a plurality of first receiver coils 63 with a constant pitch δ along the central axis 32 are arranged distributed. In 3 in each case only one winding circulation is shown, wherein a first receiver coil 63 actually has a plurality of Windungsumläufen. According to the DE 10 2015 213 784 A1 are each two adjacent first receiver coils 63 differentially interconnectable, so that together they are a sampling means 62 form. It is possible to choose which pairs of first receiver coils 63 are interconnected. In 3 the corresponding interconnection is exemplary of a pair of first receiver coils 63 shown. One connection each of the first two receiver coils 63 is interconnected, with the other two terminals a differential amplifier 65 be supplied. The field of the first transmitter coil arrangement 61 thus leads in the area of a logical 1 to a magnitude strong signal, where it leads to a weak signal in the range of a logical 0 (see. 5 ).

The first transmitter coil arrangement 61 is formed by multiple intersecting tracks, which several first transmitter surfaces 64 circumscribe. In 3 only one winding turn is shown, wherein the first transmitter winding arrangement 61 actually has several Windungsumläufe. The first transmitter areas 64 are in the direction of the central axis 32 arranged distributed regularly with the pitch δ, wherein within each first transmitter surface 64 in each case a single first receiver coil 63 is arranged. The magnetic field direction in two immediately adjacent first transmitter surfaces 64 is oriented in the opposite direction. The first transmitter coil arrangement 61 An alternating current is applied to it in the first receiver coils 63 induces a voltage. This voltage is dependent on the relative position between the first and the second body.

The pitches λ and δ are preferably selected differently from each other. λ may be, for example, 1.5 mm, wherein δ is 0.8 mm, for example. This makes it possible to read all the bits required for the determination of the first position, without the second body has to be moved relative to the first body, wherein the reading is possible in any relative position. In this case, preferably successively different pairs of first receiver coils 63 interconnected to each different scanning means 62 to form, with which different bits can be read.

4 shows a rough schematic side view of the incremental material measure 40 and the second sensor 70 , In the second transmitter winding arrangement 73 , the first and second receiver coil pairs 71 ; 72 and the incremental material measure 40 is the central axis 42 the incremental material measure 40 located. For the sake of clarity, the parts mentioned in 4 transverse to the central axis 42 shown side by side, where they are actually superposed so that all three central axes 32 are congruent. In the direction of the central axis 42 the said parts are aligned relative to each other according to the actual conditions. The central axis 42 is parallel to the longitudinal axis (No. 11 in 1 ) arranged.

The second marks 41 the incremental material measure 40 are each formed by rectangular openings in the sheet metal strip concerned. The corresponding rectangle sides are parallel or perpendicular to the central axis 42 aligned. The apertures are formed equal to each other, wherein they are distributed at a constant pitch γ along the central axis 42 are arranged. The pitch γ is 1.0 mm, for example. The width of the apertures is preferably equal to the width of the webs 43 executed between the breakthroughs.

The second sensor 70 is preferably according to DE 10 2011 106 940 A1 the entire contents of which are referred to and incorporated in the present application.

The second transmitter coil arrangement 73 is formed by multiple intersecting tracks, which several second transmitter areas 74 circumscribe. In 4 only one winding turn is shown, wherein the second transmitter winding arrangement 73 actually has several Windungsumläufe. The second transmitter areas 74 are in the direction of the central axis 42 arranged distributed regularly with the pitch 7/4 γ, wherein within each first transmitter surface 64 in each case a first or a second pair of receiver coils 71 ; 72 is arranged. Each receiver coil pair 71 ; 72 comprises two differentially interconnected individual coils, which are in the direction of the central axis 42 have a distance of γ / 2. In the direction of the middle axis 42 are the first and second receiver coil pairs 71 ; 72 alternately arranged side by side. All first receiver coil pairs 71 are in-phase connected in series, so that in sum results in a correspondingly strong sine wave signal. All second receiver coil pairs 72 are in-phase connected in series, so that in sum results in a correspondingly strong sine wave signal. For example, there are ten first and second receiver coil pairs each 71 ; 72 available. The second transmitter coil arrangement 73 is fed with an alternating current so that they are in the first and the second receiver coil pairs 71 ; 72 induces a voltage. This voltage is dependent on the relative position between the first and the second body.

5 shows the course of the signal 13 a scanning means during a movement along the path of movement. In the vertical is a signal voltage U of the corresponding signal 13 applied. As already explained above, the first sensor is excited with an alternating voltage. The scanning means (No. 62 in 3 ) outputs an alternating voltage with the same frequency whose amplitude depends on the relative position between the first and the second body. In the 5 drawn signal voltage U is proportional to the amplitude of said AC voltage.

In the context of the method according to the invention, a third absolute position is determined. This is determined with the same first sensor, with which also the absolute first position is determined. In order to minimize the electrical power requirement, fewer absolute scanning means are used in the determination of the absolute third position than in the determination of the absolute first position. Ideally, only a single scanning means is used in the second case. In turn, the position measuring system is moved during the determination of the absolute third position.

5 shows the course of the signal explained above 13 over the movement path x of the position measuring system, which in 1 is applied horizontally. In 5 are different samples 81 ; 82 ; 83 marked with squares, circles and crosses. The samples 81 ; 82 ; 83 be with a constant movement distance 14 , which in this case is 0.5 mm recorded. The divisions λ and γ are each an integer multiple of this movement distance 14 , where the movement distance 14 Preferably, the largest common divisor of the pitches λ and γ. The movement distance 14 is determined using the second sensor. Whenever it is determined by means of the second sensor that the second body is at the said movement distance 14 moved relative to the first body, a sample of the first sensor is stored. The samples become present three groups 81 ; 82 ; 83 all samples of a group are marked with the same symbol (square, circle or cross). The number of groups is equal to the quotient of the division λ of the absolute material measure and the movement distance 14 , The samples of a group 81 ; 82 ; 83 have a second movement distance between them, which is equal to the pitch λ of the absolute material measure. To determine the random number sequence 33 the group of samples is selected in which the largest amounts of samples occur. The present is the second group 81 selected from samples marked with squares. When the signal voltage U is substantially zero, the corresponding sample encodes a logical 0. If the magnitude of the signal voltage U is significantly different from zero, the sample in question encodes a logical one.

It should also be noted that the direction of movement is preferably constant in the context of the determination of the absolute third position, whereby a reversal of the direction is also possible. The movement speed may be constant or variable during the determination of the absolute third position.

LIST OF REFERENCE NUMBERS

λ

Division of the absolute dimensional standard

δ

Division of the first sensor

γ

Division of the incremental material measure

x

Movement path along the trajectory

U

signal voltage

10

Position measuring system

11

longitudinal axis

12

trajectory

13

signal

14

first movement distance

20

first body

21

guide rail

22

career

23

masking tape

24

main body

30

absolute measuring standard

31

first mark

32

Central axis of the absolute dimensional standard

33

Random number sequence

34

first rectangle side

35

second rectangle side

40

incremental material measure

41

second mark

42

Central axis of the second measuring scale

43

web

50

second body

51

carriages

52

probe

53

evaluation

60

first sensor

61

first transmitter winding arrangement

62

sampling

63

first receiver coil

64

first transmitter area

65

amplifier

70

second sensor

71

first receiver coil pair

72

second receiver coil pair

73

second transmitter winding arrangement

74

second transmitter area

81

Sample from the first group

82

Sample from the second group

83

Sample from the third group

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102015213784 A1 [0002, 0026, 0027]
• EP 2502030 B1 [0002, 0026]
• DE 102011106940 A1 [0032]

Claims (9)

A method of operating a position sensing system (10), the position sensing system comprising first and second bodies (20; 50) relatively moveable along a one-dimensional trajectory (12), the first body (20) having an absolute and a first body incremental scale (30; 40), wherein the absolute measure (30) comprises a plurality of first markers (31) distributed along the path of movement (12) encoding a random number sequence (33), the incremental scale Measuring scale (40) has a multiplicity of second markings (41) arranged periodically distributed along the movement path (12), the second body (50) having a first sensor (60) comprising a plurality of separate scanning means (62), with which multiple digits of the random number sequence (33) of the absolute material measure (30) can be scanned simultaneously, wherein the second body (50) a second sensor (70), by means of which the second markings (41) of the incremental measuring graduation (40) can be scanned, the method comprising the following steps: a) determining an absolute first position using a first number of the scanning means of the first sensor; b) determining an absolute second position using the first position and the second sensor; c) determining an absolute third position using a second number of sensing means, the second number being less than the first number, the position sensing system (10) moving during the determination of the absolute third position. Method according to Claim 1 wherein the second and the third positions are compared with each other, whereby an error message is output if they do not match. The method of any one of the preceding claims, wherein the sensing means (62) each comprise at least a first receiver coil (63), the first sensor (60) having a first transmitter coil assembly (61), the inductive coupling between the first transmitter coil assembly (61) and the at least one first receiver coil (63) can be influenced by the absolute measuring graduation (30), wherein an electrical supply power of the first transmitter coil arrangement (61) in the context of step a) is greater than in the context of step c). Method according to one of the preceding claims, wherein it is determined in the context of step c) by means of the second sensor (70) whether the first sensor (60) has run over enough locations of the random number sequence (33) to determine the third position. Method according to Claim 4 , wherein the third position is always determined when the second sensor (70) has moved in the same direction by a predetermined measuring length. Method according to one of the preceding claims, wherein in the context of step c) more digits of the random number sequence (33) are read than are necessary for determining the absolute third position, wherein by means of the surplus places an error detection and / or error correction is performed. Method according to one of the preceding claims, wherein the first sensor (60) is connected to an analog-to-digital converter, with which samples can be generated, whereby corresponding samples (81; 82; 83) are stored which have a constant first movement distance (14 ), wherein the pitch λ of the absolute material measure (30) is an integer multiple of the first movement distance (14), wherein the pitch γ of the incremental material measure (40) is an integer multiple of the first movement distance (14). Method according to Claim 7 wherein the samples are associated with a plurality of groups (81; 82; 83) such that the samples within a group (81; 82; 83) have a second movement distance equal to the pitch λ of the absolute measure (30). Method according to Claim 8 in which the random number sequence (33) is determined on the basis of the group (81; 82; 83) of samples having the largest magnitude of the sampled values.

Images