DE102012213717A1 - Inkrementalwegsensor - Google Patents

Abstract

The invention relates to an Inkrementalwegsensor in which a plurality of increments is arranged on a scale body, wherein the increments are each formed by a sequence of alternating magnetic poles and wherein an evaluation circuit is provided which a distance or angle measurement by counting a sequence of alternating magnetic poles performs, which are detectable by a sensor. In the sequence of alternating magnetic poles, at least one reference position which can be determined by the sensor is arranged.

Description

The invention relates to an incremental displacement sensor for linear and angular measurement.

For length and distance measurement, so-called absolute value sensors and incremental travel sensors are known.

Absolute value sensors are length or angle encoders, the z. B. on machine tools, in handling and automation technology and on measuring and testing equipment. The problem here is that these sensors have a low resolution and low accuracy, since the sensed element over the entire measuring range must be unique.

Inkrementalwegsensoren are sensors for detecting a distance and the corresponding path direction and an angle change and the corresponding direction of rotation. In this case, a number of so-called increments, which are set to a fixed amount of a path or an angle, are detected or counted. Information about a distance traveled is derived from the respective count value. These sensors are problematic because when switching on the respective absolute position is not known.

The object of the present invention is therefore to provide an incremental displacement sensor which, with a simple design and a high accuracy of measurement, enables investigations of one or more reference positions without a substantial additional outlay.

This object is achieved by an incremental displacement sensor with the features of the characterizing part of claim 1 in conjunction with the features of the preamble of this claim. In particular, the object is achieved with an incremental displacement sensor which comprises a measuring body with which it is possible to determine at least one reference position in addition to the counting of the increments. Subordinate claims relate to preferred embodiments of the invention and do not limit their scope exclusively to these.

In the following description of the invention, the exemplary embodiments and the claims, the following terms are used with the meaning explained in each case:
"Incremental method" is a measurement method in which a repetitive sequence of increments forms a scale body and the number of increments passed to a sensor during the movement is detected and counted. By evaluating the count values, it is possible to make a statement about an operating state of connected position and distance measuring sensors and, connected thereto, of higher-level systems to be monitored.

"Inkrementalwegsensor" is a structural unit comprising at least one, having the increments of the scale body and the information of the increments detecting measuring unit.

"Maßkörper" is a material measure that carries on a suitable surface a regular sequence of increments. The respective increments may according to the task have the same geometry, but differ in optical, magnetic, capacitive or inductive parameters with each other. Further, the scale body is a linear or closed to a circle arrangement.

According to the invention, a reference position in the incremental displacement sensor according to the invention is determined by detecting and evaluating an irregularity in the normally existing arrangement of the increments. For this purpose, the present incremental displacement sensor has a plurality of increments on a measuring body, wherein the increments are each formed by a sequence of alternating magnetic north and south poles and an evaluation circuit is provided which measures a displacement or angle measurement by counting a sequence of alternating magnetic north. and south poles detectable by a sensor. In the sequence of alternating magnetic poles, a reference position which can be determined by the sensor is arranged.

The usual sequence of increments is a regular yes-no arrangement. In the present incremental method, this sequence may be formed by an array of alternating magnetic poles with an intervening irregularity of the sequence. This irregularity serves as a reference position.

According to the invention, an incremental displacement sensor preferably uses a magnetic incremental method in which an alternating polarity S-N-S-N is successively mounted on a gauge as described above. This incremental displacement sensor cooperates with the connected parts or devices in such a way that it can provide information about a counted distance or over a number of revolutions, a speed, a revolution speed or the constancy of the same via the counting of increments.

According to the invention, an irregularity in the sequence of increments is present in the measuring body at a certain point, which is why an evaluation circuit initially generates an error signal. In the case of the magnetic arrangement used, this can be, for example, the finding that an increment in terms of its magnetic field strength is not within a predetermined value range. Thus, this increment can be unmagnetised, it can also have a higher or a lower magnetic field strength than the poles forming the increments.

The incremental displacement sensor works with an evaluation circuit which recognizes these irregularities detected by a sensor and derives information therefrom which can be processed for higher-level control systems or else only for purposes of evaluation / display.

The incremental displacement sensor according to the invention operates in such a way that its evaluation circuit gains information about reference positions beyond mere error detection (erroneous measurement) on the basis of specific patterns in the sequence of increments.

It is possible to recognize a reference position in that before and after an increment which corresponds to a desired value, in each case an increment is arranged which deviates from the nominal values. It is also possible to follow several increments that have a field strength other than the setpoint values.

Furthermore, the arrangement of two gleichpoliger increments one behind the other provide such information.

Finally, it is also possible to generate sequences of increments in which a structure of the increments of unmagnetized, magnetized in predetermined field strength, weakly magnetized and excessively magnetized increments follow one another in a specific order. Since there are a different number of possibilities for such arrangements compared to the target arrangement, not only a first but also a further or a limited number of reference positions can be integrated into the dimensional body, which can be distinguished on the basis of the respective codes.

According to the invention, the evaluation circuit is programmed with the corresponding patterns for the sequence of increments of the reference position so that they can recognize the respective patterns from the serial sequence of the signals, evaluate them and forward them to a higher-level control device.

It can be provided to program the actual speed or speed monitoring so that the changed information arriving in the region of the reference positions is additionally recorded with regard to their time interval and the same information can be generated as would be possible with a regular sequence of increments ,

Another possibility is to make the evaluation circuit fault-tolerant, so that it does not start from a measurement error or a speed deviation when receiving information about reference positions that have the length of several increments.

The invention will be explained in more detail below with reference to embodiments and drawings. Showing:

1 The representation of an incremental travel sensor according to the invention, which consists of a linearly extending scale body, a sensor element and an evaluation circuit,

2 an incremental displacement sensor according to the invention, which consists of a disk-shaped measuring body, a sensor element and an evaluation circuit,

3 a representation of a Maßkörpers, as it is applied in the prior art for incremental measuring methods,

4 an arrangement for a scale body according to the invention with an integrated reference position, in which the regular sequence of increments is represented by two increments which do not correspond to the control sequence,

5 a representation of a sequence of increments, which shows a further embodiment for marking a reference position,

6 another arrangement of increments, in which a reference position is marked by a changed sequence of the increments,

7 Another arrangement of increments, in which a reference position is included by changing increments, and

8th an array of increments in which a first and a second reference position are marked by irregularities in the arrangement of the increments.

An existing incremental displacement sensor for performing an incremental measuring method comprises according to 1 a measure body 1 who on any carrier part 2 is mounted and performs its movement. The measure body 1 has magnetic increments due to a regular sequence of north poles 3 and southern Poland 4 be formed.

A sensor 5 is at a small distance to the measure body 1 arranged and can the same when passing it in the direction x detect the magnetic coding and its measuring signals to an evaluation circuit 6 to transfer.

In a rotating embodiment of the dimensional body 7 is the same according to 2 on a wave 8th arranged and can turn in any direction. The formation of northern Poland 9 and southern Poland 10 again moves in the direction x at a sensor 11 , passing the corresponding measuring signals to an evaluation circuit 12 passes.

The incremental displacement sensor according to the invention uses the above-described incremental arrangements of the prior art and leads by deviation from the rule-compliant alternating magnetization an additional coding of the Maßkörpers 1 one. While in the prior art according to 3 on a south pole 13 one north pole each 14 and on a north pole 14 one south pole each 13 is following in accordance with the present incremental displacement sensor 4 For example, in the series of increments or poles, an arrangement of two unmagnetized increments 15 inserted. As the evaluation circuit 6 respectively. 12 time-definite, it can deduce from the incoming measurement signals and the duration of these measurement signals that they are not erroneous measurements but, because exactly the duration of two increments is taken up, it is instead a reference position.

Another form of marking a reference position may be that according to 5 a north pole 14 first a comparatively weakly magnetized South Pole 16 , then a weakly magnetized North Pole 17 follows and then the normal sequence is continued. With appropriate programming of the evaluation circuit and this mark is detected as a reference position.

Another possibility of displaying a reference position can according to 6 in that, contrary to the regular sequence, there is a north pole extending over two increments 18 followed by a south pole extending over two increments 19 are arranged. This form of marking a reference position has the advantage that it can be concluded from the pole change with high precision to the reference position.

Another way of marking a reference position can according to 7 be effected in that the regular sequence of magnetic poles by a first increment 20 without magnetization, below an arrangement of a north pole 14 and a south pole 13 is present, which in turn is an unmagnetized increment 21 follows. Also this type of marking can be traced back to the pole change with high precision mark the reference position.

In another embodiment, the marking of reference positions can according to 8th instead of a normal magnetized south pole 13 a weakly magnetized south pole 22 be provided, which is a normal magnetized south pole 23 is downstream and in turn a weakly magnetized South Pole 24 and a normal magnetized south pole 25 follow.

Consequently, a first reference position is formed by the fact that compared to the control sequence instead of the expected north pole 14 a south pole 23 and instead of the next following North Pole again a South Pole 25 is present, with the weakly magnetized south poles 22 and 24 are arranged in the manner shown in between. Thus, four increments marking a south pole follow each other. This arrangement forms a first reference position.

At another point in the sequence of increments is another irregularity in the form of a weakly magnetized South Pole 26 present, instead of an expected North Pole 14 is positioned. This is followed by an even weaker magnetized South Pole 27 instead of a normal magnetized south pole 13 , By means of this sequence of irregular increments, a second reference position is marked and at the same time achieved that it is encoded differently than the first reference position and therefore can be clearly differentiated from it.

Thus, the invention advantageously makes it possible to further develop the relative path measurements customary in incremental measuring methods by integrating encoded reference positions, without the size bodies having to be adapted in size.

Generally speaking, according to the present invention, in a normal sequence of increments of a scale body in which north and south poles alternate, reference marks can be generated by sensor-detectable changes in the sequence. For example, these changes can be generated by failing poles, weaker magnetized poles, other pole lengths and twisted poles.

The reference mark should be placed so that it will be reached soon after the system is started, so that it is possible to move from an initial measurement to a measurement in which the increments from the reference mark are counted.

LIST OF REFERENCE NUMBERS

1

 Magnetic tape

2

 support part

3

 North Pole

4

 South Pole

5

 sensor

6

 evaluation

7

 Magnetic tape

8th

 wave

9

 North Pole

10

 South Pole

11

 sensor

12

 evaluation

13

 South Pole

14

 North Pole

15

 increment

16

 South Pole

17

 North Pole

18

 North Pole

19

 South Pole

20

 increment

21

 increment

22

 South Pole

23

 South Pole

24

 South Pole

25

 South Pole

26

 South Pole

27

 South Pole

Claims (10)

Incremental path sensor, in which on a measuring body ( 1 . 7 ) a plurality of increments are arranged, wherein the increments each by a sequence of alternating magnetic north and south poles ( 13 . 14 ) is formed and wherein an evaluation circuit ( 6 . 12 ) which measures a distance or angle measurement by counting a sequence of alternating magnetic north and south poles ( 13 . 14 ) performed by a sensor ( 5 . 11 ) are detectable, characterized in that in the sequence of alternating magnetic north and south poles ( 13 . 14 ) one through the sensor ( 5 . 11 ) Determinable reference position is arranged. Inkrementalwegsensor according to claim 1, characterized in that the reference position by an irregularity of the sequence of magnetic north and south poles ( 13 . 14 ) is formed. Inkrementalwegsensor according to claim 2, characterized in that the reference position is formed by an arrangement consisting of two successive increments, the field strength outside of the north and south poles ( 13 . 14 ) or which are unmagnetized. Incremental sensor according to one of the claims 1 to 3, characterized in that the reference position is formed by increments which form a further south pole ( 16 ) and another north pole ( 17 ), the further south pole ( 16 ) and the further North Pole ( 17 ) are less magnetized and have a lower field strength than that on the scale body ( 1 . 7 ) arranged south poles ( 13 ) and north poles ( 14 ). Incremental path according to claim 1 or 2, characterized in that the reference position is defined by an arrangement of two consecutive increments in the form of two successive north poles ( 18 ) and / or two consecutive southern poles ( 19 ) is formed with the same polarity and field strength. Inkrementalwegsensor according to claim 1 or 2, characterized in that the reference position is formed by four successive increments, wherein these from a first unmagnetized or weakly magnetized pole ( 20 ), a subsequent second pole ( 14 ) with a polarity opposite to the normal sequence, a subsequent third pole ( 13 ) with one to the second pole ( 13 ) opposite polarity and a fourth pole ( 21 ) which is unmagnetized or weakly magnetized. Incremental path sensor according to claim 1 or 2, characterized in that the reference position is formed by four successive increments, these being from one compared to the poles ( 13 . 14 ) of the sequence of weakly magnetized first pole ( 22 ) of a polarity opposite to the preceding pole of the sequence, a subsequent second pole ( 23 ) a magnetization corresponding to the poles of the sequence and a first pole ( 22 ) corresponding polarity, a subsequent third compared to the poles ( 13 . 14 ) of the sequence of weakly magnetized pole ( 24 ) and a first pole ( 22 ) corresponding polarity and a fourth pole ( 25 ) with one of the poles ( 13 . 14 ) of the sequence corresponding magnetization and one of the first pole ( 22 ) corresponding polarity). Inkrementwegsensor according to one of the claims 1 to 7, characterized in that the reference position and at least one further reference position on the scale body ( 1 . 7 ) are arranged, wherein the sequence of increments of the reference position and the further reference position is the same or different. Inkrementalwegsensor according to one of the claims 1 to 8, characterized in that the Maßkörper ( 1 ) relative to the sensor ( 5 ) is linearly movable. Inkrementalwegsensor according to one of the claims 1 to 8, characterized in that the Maßkörper ( 7 ) relative to the sensor ( 11 ) is rotatable.

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