DE102011109551A1 - Measuring system for contactless measurement of positions of magnetic element for motor, determines desired curve adapted to magnetization between north and south poles of magnetic elements with respect to reference element - Google Patents

Abstract

The measuring system (1) has a magnetic encoder (2) that performs very high accurate measurement of positions of magnetic elements (8) rotated or displaced with respect to a reference element. The magnetic elements are mutually spaced at a fixed period length along shifting direction or twisting direction. The desired curve adapted to magnetization between north poles and south poles of magnetic elements with respect to the reference element is determined by a Wiegand sensor, based on positions of magnetic elements along shifting direction or twisting direction.

Description

The invention relates to a measuring system with a reference body and a relative to the reference body slidable or rotatable body with a magnetic encoder.

In a variety of technical applications, concepts for non-contact measurement of positions and paths of two relatively movable components are of particular importance. For example, in the field of automotive technology it may be important to quantitatively detect a linear or nearly linear displacement of two components relative to each other, particularly in pedal travel sensors, accumulator sensors in hydraulic or pneumatic accumulators, shock absorber sensors, liquid tank level determinations, headlight position sensor sensors, throttle position sensors , Linear motors, cutting machines for steel beams, woodworking machines or the like. Equally, the quantitative detection of the rotation of two components relative to each other in the manner of a rotational relative movement or angular rotation in a variety of applications, such as in motor vehicle technology, in handling equipment, printing, textile or wood processing machines, robots, wind turbines or a Many other applications will be significant.

Both in the detection of linear or sliding movements of two components relative to each other as well as in the detection of rotations or rotational relative movements of two components to each other various technologies can be used, in particular optical or magnetic systems. Optical scans usually offer the advantage of comparatively high resolution and precision in the acquisition of measured values. In contrast, however, magnetic systems are usually more cost effective and technologically more robust than comparable optical systems, so that there are advantages in magnetic field-based systems, especially for applications in harsh or adverse environmental conditions. Measuring systems which are provided for determining relative position shifts or twists of two components relative to one another, are generally composed of a signal transmitter or encoder mounted on one of the components and a sensor or read head which scans the signal transmitter or encoder and is mounted on the other component. The scanning can be carried out in particular via light or high-frequency signals, electrical or magnetic fields. Perforated disks include perforated disks, gears and magnetic structures. "Encoder" - often referred to as "material measure" - is in this case in particular a magnetic or magnetized structural element to be understood by magnetization or the like impressed magnetic signature whose magnetic field or magnetic signature can be detected and evaluated via the sensor.

Usually one differentiates between so-called incremental encoders on the one hand and so-called absolute donors on the other hand. In the case of an incremental encoder, angle changes (rotational) or changes in position (linear) are detected by an optical or magnetic measuring system and transmitted in the form of pulse-shaped incremental, ie counting signals. The reference to the physical position information is produced by referencing a zero point from which the changes are counted. The advantage is that only change information must be transmitted, which is cheaper, among other things, for fast, dynamic applications. The disadvantage is that in the event of a power failure, the referencing and thus the reference to the physical position information is lost and must be re-referenced. The mere persistence in a rest position is not problematic as long as the position information is kept in the counter. In an absolute encoder on the other hand on an associated reference body or scale, the physical position discretely or continuously clearly mapped, such. B. on a code disk or a coded linear scale. Each discrete physical position is assigned a unique coded value; in an analog scan, each position is assigned a continuous unique analog value. A power failure does not lead to a loss of this assignment. A disadvantage is the increased expenditure for the realization and the transmission (eg by analog signals of corresponding quality or entire digital position words). Usually, at least two tracks are used in an absolute system. A track is provided with a digital code in which a scanned track is only once on the circumference. This defines the absolute position to a basic pitch (a few millimeters). The exact positioning is then carried out via the evaluation of an incremental track.

The invention is therefore based on the object to provide a measuring system of the type mentioned above, with the measurement of the position of a relative to a reference body slidable or rotatable body is made possible in a particularly simple manner and with very high accuracy.

This object is achieved by the encoder a plurality of seen in a planned displacement or rotation direction periodically with a fixed period length Each magnet element has a magnetization ratio between north pole and south pole components which is adapted to a predetermined nominal curve for the position of the respective magnetic element in the direction of displacement or torsion, and wherein the reference body comprises a weighing sensor is provided.

Advantageous embodiments of the invention are the subject of the dependent claims.

For the following terms and designations, it is assumed that magnetic field-based information can be stored in a suitable material, as usual in magnetic field-based read-write systems by suitably magnetizing a suitable material in its surface area via, for example, a magnetic write head. for example, by properly aligning magnetic dipoles or domains present in the material relative to the write head. Readout via a suitable read head is then possible by determining the relative orientation of this magnetization, ie the magnetic dipoles or domains in the material, relative to a reference direction in the read head. The term "north pole portion" and "south pole portion" is to be understood as meaning a respectively suitably oriented magnetization, that is to say, in particular, on the one hand parallel and, on the other hand, antiparallel to a predetermined reference axis.

Furthermore, "Wiegandsensor" refers to a magnetic field sensitive sensor, which essentially comprises a Wiegand wire, which consists of a special alloy with a hard magnetic metal as a sheath and a soft magnetic metal as the core. The Wiegand wire is wrapped in a coil.

The invention is based on the consideration that in a particularly simple construction reliably and with comparatively high resolution, the determination of the position of a component equipped with the encoder relative to a - usually held stationary - reference component is made possible by a suitable for a magnetic field sensor in the Reference component suitable readable spatially resolved magnetic signature is generated by the encoder. In order to enable a comparatively high-precision position measurement with little effort, a correspondingly suitable complex field should also be provided in the case of what is known as a "single-track" magnetic signal transmitter whose magnetic field characteristic can be read out via an associated sensor.

To make this possible, it is provided to provide a magnetic signature based on the superposition of two signatures, similar to the superimposition of several signals with different frequencies in electrical engineering. The first signature should now be contributed by the respective magnetic pole pair forming magnetic elements, which are seen in the intended direction of displacement or rotation periodically spaced and fixed with a fixed period length to each other. By means of this periodically spaced arrangement with a fixed period length, a first characteristic signature having a wavelength predetermined by the period length is available analogously to a "fundamental wave". In order to enable the desired high spatial resolution even when detecting the absolute position of the encoder, the superimposition of this first characteristic signature is provided with a further characteristic signature. This should be provided quantitatively by a suitable adjustment of the total magnetization of the respective magnetic element, ie in particular by a suitable choice of the respective magnetization ratio between "North Pole Shares" and "South Pole Shares". The magnetization ratio of the respective magnetic element is, in accordance with the positioning of the respective magnetizing element within the encoder seen in the respective displacement or rotation direction, adapted to a predetermined characteristic curve characteristic of this position.

The magnet elements may have in the manner of applied domain structures segmented or blockwise magnetizations kept constant with demand magnetically selected direction of magnetization (distinction between "North Pole Segment" and "South Pole Segment"), said magnetization ratio can be adjusted by a suitable choice of the respective block or segment sizes.

As has now been recognized, the combination of such an encoder with a Wiegandsensor particularly suitable to provide a measuring system for determining position, in addition to the position determination along a relative to the reference body displaceable or rotatable body and the number of full revolutions or at a Sequence of bodies, the number of passed or pushed past the reference bodies body can be counted. The magnetic signature specified by the encoder can be scanned by appropriate sensors to determine position along a revolution or along a body. The measuring system is improved in this way, including the number of complete To count turns or to determine positions on a sequence of bodies.

The Wiegand wire of the Wiegandsensors is respectively reversed by the change of North Polanteilen and Südpolanteilen in the magnetic elements of the encoder - with suitable strength of the magnetic field - passing it for configured magnetic field elements, thereby generating an electrical pulse, which is a robust signal for the detection of the transition represents the Wiegandsensors to the respective magnetic element. Due to the robustness of the voltage pulse generated in this way, this type of detection is also suitable for rapid passing of the reference body on the relative to the reference body slidable or rotatable body.

The Wiegandsensor can be advantageously combined with additional or additional magnetic field sensors. By using at least two magnetic field sensors arranged spaced apart from one another in the direction of displacement or twisting, the signal structure provided by the encoder and the magnetic field characteristic can be evaluated in a particularly targeted manner. In particular, by such a constellation, the superposition of the two periodic components, on the one hand given by the periodic arrangement of the magnetic elements as such and on the other hand given by the preferably periodically varying magnetization of the magnetic elements, are resolved into their individual components, so that a particularly reliable location determination is possible. Depending on the selected distance between the magnetic field sensors, recourse to an associated mathematical function can be used to convert the measured signals and to assign the signal components to the two periodic components.

In an advantageous embodiment of the measuring system, the encoder is configured such that the Wiegandsensor generates a predetermined number of Ummagnetisierungspulsen in passing the body relative to the reference body or rotatable body. In this way, with the help of the Wiegandsensors each of the complete pre-transition of the body can be counted on the reference body. In this case, the counting process is realized in a particularly simple manner if the weighing sensor generates precisely two countable pulses during one revolution of the reference body or during a complete pre-transition to the reference body. This can be achieved by virtue of the fact that the "fundamental wave" has exactly one period during a complete revolution / displacement of the reference body. Increasing the number of periods per revolution / body increases proportionally the number of pulses. At a constant counter width thereby reduces the number of countable revolution or the number of countable linearly arranged one behind the other body. With the same number of revolutions / body to be counted, a correspondingly larger counter would be needed.

In the preferred embodiment of the measuring system with at least two additional magnetic field sensors can be counted in the case of mutually rotatable body and reference body in this way, for example, using the Wiegandsensors full revolutions, while the position is determined within one revolution by the magnetic field sensors. In a juxtaposition of several bodies which are displaceable relative to the reference body, so the transition of each of these individual bodies can be counted on the Wiegandsensor. The position along the respective body can be determined by the magnetic field sensors.

The Ummagnetisierungsimpulse the Wiegandsensors are advantageously counted by a counter, which includes a non-volatile memory to secure the count. In this way, the counter reading is maintained even in the event of a power failure of the measuring system, so that the knowledge about the number of scale or body pushed past the weighing sensor or the number of full revolutions is not lost. In conjunction with the harmonic of the encoder can thus be reconstructed both the absolute position within the corresponding length or revolution and the absolute position in a linear juxtaposition of each provided with the magnetic signature bodies are determined.

The induced by the Ummagnetisierung the Wieganddrahtes in the coil of the Wiegandsensors voltage pulse is advantageously used both as a count signal and to supply the non-volatile, extremely power-saving meter, which is not only the count information received in the absence of external supply, but also kept current. The disadvantage of a classical incremental system is bypassed in this way.

An application example of this is an electrically operated roller shutter, wherein the corresponding drive for opening the roller shutter makes several revolutions and the Wiegandsensor counts the number of revolutions. If the door is moved manually in the event of a power failure, the current opening condition of the roller shutter can be detected immediately when the electrical supply returns.

The determination of the absolute position is possible in a particularly simple manner, if as Distance between the magnetic field sensors advantageously a multiple of a quarter of the period length, more preferably about half the period length, is selected. In particular, the periodic basic signal can be determined by subtraction from the signals of the two magnetic field sensors precisely as a result of said superposition. On the other hand, the additional signal superimposed in the manner of a "harmonic wave" and corresponding to the nominal characteristic curve implemented in the magnetization of the respective magnetic elements can be determined by addition of the two partial signals of the two magnetic field sensors and thus provided particularly precisely.

In particular, if the setpoint curve implemented in the magnetization (the so-called "sub-wave") has a sinusoidal shape and is accordingly suitably selected periodically, the angular position of the encoder relative to the sensors and thus to the corresponding signals, in particular taking into account the slope and amplitude of the sub-wave signal the angular position of the body provided with the encoder can be determined particularly accurately relative to the reference body bearing the sensors. In order to enable a reliable determination of the absolute angle even when the encoder is at rest relative to the sensors, another sensor, that is to say a third sensor, is advantageously provided. This is preferably arranged offset by 90 ° to the first sensors, so that a clearly defined result of the position measurement is ensured.

As magnetic field sensors, any suitable sensors can be used, in particular those whose signal is expediently proportional to a component of the flux density or of the magnetic field. Advantageously, Hall sensors are provided as sensors.

In order to enable a particularly high spatial resolution in the determination of the absolute position, the magnetization of the magnetic elements is advantageously chosen such that the predetermined characteristic nominal curve is particularly approximated. For this purpose, the magnetic elements advantageously each have a suitable, preferably continuous, varying magnetization in the direction of displacement or rotation.

The magnetic elements could also each be spatially limited and spaced from each other. However, in order to further promote the accuracy in the position measurement, adjacent magnetic elements seen in the direction of displacement or rotation are advantageously dimensioned and positioned in such a way that they adjoin one another directly. Thus, in the displacement or twisting direction, the size or the length of each magnetic element expediently corresponds to the period length.

The magnetic encoder can be provided for detecting positions in a linear arrangement, ie as a so-called linear scale for detecting a displacement position. In such an embodiment, the magnetic elements are expediently arranged for detecting positions on a common linear scale such that the period length does not change over the entire length of this scale.

In an alternative advantageous embodiment of the magnetic encoder is designed suitable for use in wave or hollow shaft applications suitable. In this case, the encoder for detecting the angular position in the rotation of a body is provided in relation to a reference body, wherein the encoder for mounting on a shaft, so in particular with free for the implementation of the shaft central area, is configured. Especially for such hollow shaft applications previously comparatively precise working magnetic-based measuring systems could be provided only with increased effort, especially with recourse to at least two tracks, so that this application of the now provided encoder offers particular advantages.

In order to make this possible, the magnetic elements are arranged in a particularly advantageous embodiment for detecting rotational positions on a common circumference that the period length forms a plate of the circumference. By "periodic arrangement" is to be understood in particular that the magnetic elements, with respect to their respective reference points such as their respective centers, central points or the like, are arranged at a fixed, constant angular distance from each other.

In this case, "divisor" in particular in accordance with the mathematical definition means that the total length of the circumference on which the magnetic elements are arranged yields an integral multiple of the period length. Especially in the event that the magnetic elements are arranged adjacent to each other, they thus span the circumference completely and completely in this advantageous embodiment, and by the vote of the period length on the circumference is complete even with repeated complete rotation of the respective wave - a reliable counting Revolutions provided - the desired positioning measurement also in the idle state of the components to each other possible.

Based on this arrangement, a particularly high angular resolution in determining the twist angle with high reliability is possible in a particularly advantageous development by providing the superposition of two periodic signal characteristics with each other. For this purpose, the setpoint curve for the magnetization ratio of the magnetic elements in turn is also configured periodically in a particularly advantageous development, wherein the period length of the setpoint curve also forms a divisor of the circumference or in a particularly advantageous manner equal to the length of the circumference. Thus, the setpoint curve, which is given for example as a sinusoid, in their period length be completely matched to the circumference, so that the desired superposition of two frequency components in. By the combination of the set in the Magnetierungsverhältnissen the magnetic elements setpoint curve with the per se periodic arrangement of the magnetic elements the magnetic field characteristic is reached. Especially with such a superimposition of two periodic components, a particularly reliable signal evaluation and thus a particularly high accuracy in the angle measurement is made possible by resorting to the methods available for this purpose.

In principle, the arrangement of the encoder, for example, on the front side of a shaft is possible if the angle of rotation of the shaft to be determined. Advantageously, however, the magnetic elements of the encoder are arranged circumferentially on a support cylinder. This can in turn be made hollow in its central region, so that the overall arrangement is particularly suitable for use with hollow shaft applications.

In an alternatively possible embodiment as a linear system in which the magnetic elements are applied to a linear body, the modulation period should be an integer multiple of the pole period. In a preferred embodiment, the measuring system comprises a plurality of linearly aligned linear bodies or linear bodies. In this way, larger distances can be measured or determined along longer distances positions, as would be the case with only one linear body. By a juxtaposition of bodies thus in principle arbitrarily large distances can be detected positionally.

The advantages achieved by the invention are in particular that by the periodic arrangement of the magnetic elements with fixed period length on the one hand and the position-specific predetermined magnetization by appropriate choice of the respective magnetization ratio between "North Polanteil" and "South Polanteil" according to the predetermined setpoint curve on the other hand targeted a superposition of signal components different frequencies and thus a comparatively high information density with a single magnetic system (a single so-called "magnetic track") is possible, in comparatively simple construction with a Wiegandsensor a particularly reliable position determination even with multiple revolutions of a body or at a stringing of Bodies is possible.

In addition, the superimposition signal is formed by the corresponding magnetization and sensor arrangement so that the fundamental wave allows a clear assignment between analog value Sin / Cos → arctan, and also on the through the n-pole pairs a periodic harmonic wave is "modulated" for fine resolution ( eg also via Acrtan function) can be used. An elaborate multi-track magnetization and a likewise elaborate multi-track reading head can be dispensed with.

It is also advantageous that by a corresponding sampling of the pole pairs also relatively simple fast incremental signals are available. One application here are motor feedback applications: high-resolution position information at standstill, fast incremental control signals during rotation.

However, a significant advantage over other absolute encoders is that it generates an absolute position with the accuracy of an incremental encoder from just one track. There are no overlay effects with a digital track, and it has a higher information density than a single magnet.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

1 a measuring system for measuring the position of a body rotatable relative to a reference body,

2 a diagram with a plurality of signal curves,

3 a measuring system for measuring the position of a relative to the reference body displaceable arrangement of two or more bodies,

4 a diagram illustrating the behavior of a Wiegandsensors a Measuring system with a magnetic encoder in a first embodiment, and

5 a diagram illustrating the behavior of a Wiegandsensors a measuring system with a magnetic encoder in a second embodiment.

Identical parts are provided with the same reference numerals in all figures.

The measuring system 1 according to 1 is intended for measuring the absolute position of a relative to a reference body rotatable body in the manner of measuring the absolute angle of rotation. The measuring system 1 according to the embodiment is thus provided for the detection of rotational relative positioning of reference body on the one hand and on the other hand body to be measured; In the case of a geometrical change of individual components, however, the signal engineering structure is also readily suitable for alternative measuring systems for measuring the absolute position of a body displaceable in the linear direction relative to a reference body.

The measuring system 1 includes a magnetic encoder 2 , which can be firmly connected in the embodiment with the actually monitored body. The magnetic encoder 2 has in its outer area a magnetic signature in the form of a magnetic field, which is used to generate further usable metrological signals with a magnetic field sensor arrangement 4 interacts. The magnetic field sensor arrangement 4 , the output side of which is connected to an evaluation unit, not shown, in particular an evaluation, is firmly connected to the provided reference body. It includes a weighing sensor 32 as well as two magnetic field sensors 30 , which are designed as Hall sensors.

A shift or - as specifically provided in the present embodiment - a rotation of the magnetic encoder 2 and thus the body to be monitored connected to it with respect to the magnetic field sensor arrangement 4 and thus the reference body thus results due to the changing, via the magnetic field sensor arrangement 4 detectable signature of the magnetic encoder 2 in suitable measuring signals that can be used to determine a position characteristic value.

The magnetic encoder 2 and thus also the measuring system 1 Overall, in a suitable form for hollow shaft applications form, so that the magnetic encoder 2 flanged directly onto a shaft and thus can be used for a variety of measuring systems for detecting rotational or angular positions. This includes the magnetic encoder 2 a carrier cylinder 6 , on the outer circumference of a plurality of magnetic elements 8th are arranged. Inside is the carrier cylinder 6 but as a hollow cylinder with central bore 10 executed so that it can be plugged in a suitable manner on a correspondingly sized shaft. Of course, a correspondingly reversed arrangement with arranged on the reference body encoder 2 and on the body to be monitored arranged magnetic field sensor arrangement 4 possible.

The magnetic encoder 2 is in terms of his for the magnetic field sensor arrangement 4 detectable external magnetic field configured with a characteristic signature, which in a comparatively simple design and in so-called single-lane design, ie with a single magnetic signature, a particularly reliable and comparatively accurate determination of the angular position of the magnetic encoder 2 in relation to the magnetic field sensor arrangement 4 in the manner of an absolute position measurement for the one with the magnetic encoder 2 provided body even in the resting state, ie without current movement of the body relative to the reference body allows. This is the magnetic signature of the magnetic encoder 2 specifically executed in the manner of a superposition of two periodic signature components.

To form these signature components are the magnetic elements 8th suitably designed. Each magnetic element 8th represents a magnetic pole pair with a "north pole portion", in the embodiment according to 1 each sketchy by a hatched area element 12 characterized and with a magnetic "South Pole portion", in 1 through a surface element 14 characterized by a different hatching. The term "north pole component" and "south pole component" here mean localized surface segments with a magnetization whose orientation is relative to a suitable read head in the magnetic field sensor arrangement 4 can be distinguished in the nature of "parallel" or "antiparallel" alignment, as is known per se from other magnetic-based data storage and reading devices.

A first signature component in the magnetic signature of the encoder 2 now results from the fact that the magnetic elements 8th spaced periodically and with fixed period length to each other on the outer circumference of the carrier cylinder 6 are arranged. In addition, the magnetic elements 8th In the exemplary embodiment in this case dimensioned such that adjacent magnetic elements directly adjacent to each other, so that in the embodiment, a continuous, the carrier cylinder 6 completely enclosing wreath of magnetic elements 8th results. The fixed period length or the (with respect to the centers) the same spacing of the magnetic elements 8th to each other corresponds to the requirement that the magnetic elements 8th each having the same outer length in the direction of rotation. in the Embodiment are the magnetic elements 8th chosen such that they each have an angular range on the outer circumference of the carrier cylinder 6 of 20 ° cover. This is the magnetic elements 8th arranged on the common circumference of the carrier cylinder such that the period length (in the embodiment corresponding to an angular range of 20 °) forms a divisor of the circumference; due to the covered angular range of 20 ° in the embodiment, a total of eighteen magnetic elements 8th for complete enclosure of the carrier cylinder 6 intended.

In addition, the magnetic elements 8th for providing the second signature component to be superimposed on the first signature component, as a function of its respective position within the encoder 2 varying magnetization on. In this case, each magnetic element 8th a at a predetermined, for its respective position in the direction of rotation characteristic characteristic curve adapted magnetization ratio between North Pole and Südpolanteil on. In the embodiment according to 1 this is by appropriate variation of the area proportions 12 . 14 shown. The corresponding variation of the north pole or south pole parts can be in the manner of a continuous change of the magnetization within the respective magnetic element 8th or also in the manner of a block, domain or segmental composition by the appropriate choice of individual surface areas with magnetization kept constant within the respective magnetic element 8th respectively.

In the exemplary embodiment, a sine curve with a period length of 360 ° is provided as the characteristic setpoint curve for the magnetization ratios, so that during a complete rotation of the magnetic encoder 2 around its central axis, this setpoint curve or the magnetization curve will pass through exactly once.

The corresponding signature components and the resulting overall signature are shown by way of example in the diagram 2 shown. In this case, the angular position in the circumferential direction of the encoder is on the x-axis as the location characteristic 2 ablated. On the y-axis, however, a characteristic value characteristic of the respective magnetization is plotted. In the exemplary embodiment, the first signature component, corresponding to the curve, serves as components of the magnetic signature 20 , which has a sinusoidal course with a period length of 20 ° due to the arranged with a period length of 20 ° pole pairs in the manner of a fundamental wave. This superimposed in the manner of a harmonic wave is generated by said variation of the magnetization ratio second signature component represented by the curve 22 , The superimposition of these signature components creates the curve as the overall signature 24 ,

The signature is further selected such that the Wiegandsensor with exactly two magnetic elements 8th respectively generates corresponding Ummagnetisierungspulse.

For the high-resolution and precise evaluation of this signature, the magnetic field sensor arrangement comprises 4 of the measuring system 1 next to the Wiegandsensor 32 also two-in the embodiment configured as Hall sensors - magnetic field sensors 30 , which are seen spaced apart in the direction of rotation. To enable a particularly precise and reliable evaluation, the magnetic field sensors 30 seen in the direction of rotation at a distance corresponding to half the period length of the magnetic elements 8th , So at a distance corresponding to a twist angle of 10 ° to each other, arranged. Through this on the period length of the magnetic elements 8th coordinated arrangement of the magnetic field sensors 30 is a comparatively simple and reliable resolution of the overall signature of the encoder 2 and a determination of the two signature shares separately possible.

In an addition of the sensor signals of the two magnetic field sensors 30 Namely, the fundamental component is eliminated, and it is output as the addition signal only attributable to the second signature component signal component. Thus, a direct detection of the sinusoidal magnetization is possible, so that directly and directly the angular position of the magnetic encoder 2 can be determined. If, on the other hand, a subtraction of the two sensor signals is carried out, the second signature component is filtered out and only the first signature component is output as the output signal. With this subtraction signal is thus a movement determination with the accuracy of an incremental graduation corresponding to the period length of the magnetic elements 8th , So in the embodiment of 20 °, possible.

These signals will now be combined with the counted magnetic transducer magnetization pulses, which will determine both the number of full revolutions and the angular position of the magnetic encoder 2 can be detected in the current rotation. Depending on the configuration of the overall signature, more than two magnetic field sensors can also be used 30 be used.

In 3 is a measuring system 1 represented in a further preferred embodiment. The measuring system 1 includes a sensor arrangement 4 with two magnetic field sensors 30 and a weighing sensor 32 , It also includes a linear one Stringing together two bodies, as elongated bodies or linear bodies 34 are formed. Each side of the two linear bodies 34 are dashed another linear body 34 indicated. Depending on the application, any number of corresponding bodies can be used to form a material measure.

The two linear bodies are each provided with a magnetic signature, in which - similar to the in 1 illustrated measuring system - each magnetic element 8th has a Südpol- and Nordpolanteil and a variation of the North Pole or Südpolanteile between the magnetic elements 8th is provided. That is, in this embodiment, too, the magnetization ratios of the magnetic elements between the respective north pole component and south pole component vary according to a predetermined nominal sinusoidal curve in the exemplary embodiment, characterized by the black or white surface components of the magnetic elements 8th ,

The magnetic signature and the Wiegandsensor are coordinated so that the Wiegandsensor in a complete pre-transition of a linear body 34 generates two pulses.

Through the two magnetic field sensors 30 can precisely position each position along a linear body 34 be determined. The Wiegandsensor 32 becomes the repayment of the linear body 34 attached to the sensor assembly 4 in the direction of displacement 40 (or in the opposite direction) are pushed past used. In this way, a precise and absolute position determination along a sequence of in principle any number of linear bodies 34 possible.

The behavior of the Wiegandsensors 32 a measuring system according to the invention 1 with an encoder 2 in a first embodiment is in 4 shown. The abscissa 44 represents a measure of the revolution of the body equipped with the encoder. On the ordinate 48 is the on the Wiegandsensor 32 acting magnetic field strength 52 applied. This consists of a sinusoidal fundamental wave and a superimposed signature (harmonic wave), which modulates the fundamental wave with a degree of modulation of 10% together. Positive values on the ordinate 48 denote a "north pole" magnetization, negative values a "south pole" magnetization. One period of the fundamental corresponds to a full revolution of the body. The harmonic comprises 32 periods at one period of the fundamental.

At the beginning of the rotation process, the Wiegand wire should be fully magnetized or biased in the negative ("south pole") direction. During a rotation of the reference body, the magnetic field increases on average sinusoidally in the positive direction of magnetization. The Wiegand wire does not follow this change due to its design, as long as the strength of the magnetic field is not an upper threshold (shown in dashed lines) 56 has exceeded. Upon reaching this upper threshold 56 (Coercive field strength of the hard magnetic wire sheath), the Wiegand wire jumps from its bias to the opposite triggering magnetization and induces an electrical impulse in the coil wound around the wire 60 , The strength of the pulse is - in contrast to a dynamo - not dependent on the speed of the reference body. From this triggering magnetization, the magnetization of the wire continues to follow the external magnetic field up to its maximum. The wire is now pretensioned again and remains in this state until the external field strength is a lower threshold 72 falls short and an impulse 64 is triggered.

Per half revolution of the reference body so a pulse is triggered. Due to the structure of the harmonic of the magnetic field of the encoder can be the exact time at which the upper threshold 56 or lower threshold 72 of the magnetic field is reached, slightly more or less deviate from the position after exactly half a turn. However, this is not critical, as long as reliably in each half revolution, a pulse occurs, ie, as long as the pulse can be assigned reliably and clearly the respective half turn and the wire can be sufficiently biased in the triggering of the pulse. The magnitude of the pulse depends directly on the amount of the Ummagnetisierungssprunges (from the current bias voltage at the time of triggering towards the opposite tripping magnetization) from. 5 shows in this context a diagram as in 4 but with a degree of modulation of about 40%. In this case as well, one pulse can be reliably assigned to each half revolution and two pulses of opposite sign to each full revolution.

Up to a degree of modulation of approx. 50%, this operating principle should be guaranteed. With a higher degree of modulation there is a risk of "false pulses", ie. h., due to the strong degree of modulation additional Ummagnetisierungen can take place.

LIST OF REFERENCE NUMBERS

1

measuring system

2

encoder

4

sensor arrangement

6

support cylinder

8th

magnetic element

10

central bore

12

surface element

14

surface element

20

Curve

22

Curve

24

Curve

30

magnetic field sensor

32

Wiegand

34

linear body

40

shift direction

44

abscissa

48

ordinate

52

magnetic field strength

56

upper threshold

60

pulse

64

pulse

68

pulse

72

lower threshold

76

magnetization

Claims (12)

Measuring system ( 1 ) with a reference body and with respect to the reference body slidable or rotatable body with a magnetic encoder ( 2 ) arranged periodically with a fixed period length spaced from each other in a designated displacement or rotation direction, each forming a magnetic pole pair magnetic elements ( 8th ), each magnet element ( 8th ) to a given, for the position of the respective magnetic element ( 8th ) in the direction of displacement or torsion characteristic curve has adapted magnetization ratio between North Pole and Südpolanteilen, and wherein the reference body with a Wiegandsensor ( 32 ) is provided. Measuring system ( 1 ) according to claim 1, wherein the reference body with at least two mutually spaced in the direction of displacement or twisting magnetic field sensors ( 30 ) is provided. Measuring system ( 1 ) according to claim 1 or 2, wherein the encoder is configured such that the weighing sensor ( 32 ) generates a predetermined number of Ummagnetisierungspulsen when passing the body by rotation or displacement. Measuring system ( 1 ) according to one of claims 1 to 3 with a counter which counts the Ummagnetisierungspulse, wherein the counter comprises a non-volatile memory for storing the count. Measuring system ( 1 ) according to one of claims 1 to 4, in which between the magnetic field sensors ( 30 ) a distance of about a multiple of a quarter of the period length is provided. Measuring system ( 1 ) according to one of claims 1 to 5, whose magnetic elements ( 8th ) each have a seen in the direction of displacement or rotation varying, preferably continuously varying, magnetization. Measuring system ( 1 ) according to any one of claims 1 to 6, wherein in the direction of displacement or rotation seen adjacent magnetic elements ( 8th ) directly adjoin one another. Measuring system ( 1 ) according to one of claims 1 to 7, whose magnetic elements ( 8th ) are arranged for detecting rotational positions on a common circumference such that the period length forms a divisor of the circumference. Measuring system ( 1 ) according to claim 8, wherein the setpoint curve for the magnetization ratio of the magnetic elements ( 8th ) is also periodic with a period length which forms a plate of the circumference, preferably equal to the circumference. Measuring system ( 1 ) according to claim 8 or 9, whose magnetic elements ( 8th ) peripherally or frontally on a support cylinder ( 6 ) are arranged. Measuring system ( 1 ) according to one of claims 1 to 7, whose magnetic elements ( 8th ) are arranged on a linear body. Measuring system ( 1 ) according to claim 11 with a plurality of linearly aligned linear bodies ( 34 ).

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