Multi-track arrangement for linear-or angular-position measuring systems

Abstract

The invention relates to a device for a length or angular position measuring system, comprising: a first track with a magnetic code; and at least one second track with a geometric code along a measuri

Description

[0001] The invention relates to a device for a length or angle-measuring system, a corresponding measuring system, and a method for producing a device for a length or angle-measuring system. BACKGROUND

[0002] Various measuring systems for position determination are known from the prior art, in particular linear / length measuring systems, angle-measuring systems, or rotary encoders. Linear measuring systems or length measuring systems are configured for determining the position along a route having different end points. In contrast, angle-measuring systems are configured for determining the position along a closed circular path. A measuring system for position determination comprises a scale standard which contains coded position information, and a scanning head having a sensor. Furthermore, the measuring system can comprise a physical evaluation channel and an evaluation circuit. Typically, the position information of the measuring system is forwarded via an interface to a servocontroller for control purposes (for example for controlling position, speed or torque).

[0003] The position measurement takes place by the relative movement of the scanning head and the scale standard. In the process, the sensor measures a physical property, for example a magnetic or electrical measured variable, which is dependent on the coded position information. An item of position information is then calculated from the change in the physical property, by the evaluation circuit. The obtained position information can either be relative, if it is dependent on a starting position, or absolute, if each point of a trajectory is clearly defined by the coded position information of the scale standard. Depending on the measuring system, the scanning head or the scale standard moves. In the case of a circular scale standard, reference is made to rotor and stator.

[0004] For absolute position measurement, what are referred to as Vernier-coded scale standards are known. In this case, the scale standard comprises at least two periodically coded measuring tracks, which have different division periods, such that for each position on the scale standard a unique signal combination of the tracks is present.

[0005] Scale standards are known comprising two or more magnetically coded measuring tracks, which are typically arranged side-by-side in the same plane.

[0006] However, in the case of such multi-track, magnetically coded measuring track assemblies, the problem of cross-talk arises. This problem arises both between magnetic poles of separate tracks and between the magnetic poles of the same track. The prior art discloses solutions which are intended to contribute to the reduction of the cross-talk. These relate in particular to the magnetization or coding process, or to the type of the magnetization pattern.

[0007] For example, the document EP3285267B1 discloses a magnetization device for magnetizing a scale standard having a plurality of tracks. In this case, magnetic shielding of the magnetizing heads is intended to reduce overwriting or cross-talk during the magnetization.

[0008] The document EP2839247B1 discloses a magnetic encoder for producing an index signal which is intended to reduce the influence of the index or the reference track on the incremental track.

[0009] The document EP2579002B1 discloses an encoder having a plurality of rows of magnetically coded tracks. Due to the configuration of the tracks and the positions of the associated sensors, the interference of the magnetic pattern of the rows of the respective sensors should appear as a magnetic pattern having the same division.

[0010] A further approach is to reduce the problem of cross-talk by digital processing of the measuring signal.

[0011] The approaches disclosed in the prior art are associated with very high outlay and are very complex, should solve the problem of cross-talk only in part, and are difficult to scale and / or are subject to technical limitations. Furthermore, they frequently lose their validity in the case of a dynamic change of system parameters, e.g. of the operating point.

[0012] The inventors have addressed the problem of providing a device for length or angle-measuring systems which overcomes the above disadvantages, in particular significantly reduces the problem of cross-talk, and at the same time remains particularly compact. SUMMARY

[0013] The stated problem is solved by a device having the features of claim 1, a system having the features of claim 15, and a method having the features of claim 17. Various embodiments and developments of the present invention are described in the dependent claims.

[0014] Proposed is a device for length or angle-measuring systems, which comprises the following: a first track having magnetic coding along a measuring direction, and at least one second track having geometric coding along the measuring direction.

[0015] A system is also described, which comprises: an assembly according to the above paragraph, and a sensor head having a first sensor element which, together with the first track, forms a first measuring channel, and at least one second sensor element which, together with the second track, forms a second measuring channel.

[0016] Furthermore, a method is described, having the following steps: Providing a substrate made of a magnetic material; magnetizing the substrate for forming a first track having a magnetic coding along a measuring direction; and changing at least one geometric feature of the substrate along the measuring direction for forming at least one second track having a geometric coding along the measuring direction.

[0017] This in particular prevents the problem of cross-talk, in a simple and scalable manner. Furthermore, the measuring system remains particularly compact and can be produced simply and quickly. BRIEF DESCRIPTION OF THE FIGURES

[0018] For improved understanding of the features and advantages of the invention, some embodiments of the invention will be described in more detail in the following with reference to the accompanying Fig. 1 to 17. However, the illustrations of the figures show only some embodiments and are not to be considered limiting, since other, equally effective, embodiments may also exist. It is noted that some of the details and / or features shown in the figures are not reproduced true to scale, for reasons of clarity.

[0019] Fig. 1 is a block diagram of a position measuring system.

[0020] Fig. 2 is a perspective view of a length measuring system according to the prior art.

[0021] Fig. 3 is a perspective view of an angle-measuring system according to the prior art.

[0022] Fig. 4 is a perspective view of a length measuring system comprising a periodically coded scale standard and a periodic sensor element.

[0023] Fig. 5 is a perspective view of an example of a measuring track assembly for a length measuring system comprising a periodically coded magnetic track.

[0024] Fig. 6 shows graphs illustrating a generated electrical signal of (a) a Hall sensor and (b) a magneto resistive or magnet impedance sensor during scanning of a magnetic pole pair.

[0025] Fig. 7 is a schematic view from above of a measuring track assembly comprising two tracks having different division periods.

[0026] Fig. 8 shows a graph of the magnetic field strength as a function of the distance between the scale standard and sensor for different division periods (pole lengths).

[0027] Fig. 9 is a schematic view of a magnet having two poles, and its magnetic field lines.

[0028] Fig. 10 is a perspective view of a scale standard for the angle measurement with (a) an axial magnetic pole pair and (b) a diametrical magnetic pole pair.

[0029] Fig. 11 is a cross-sectional view of an embodiment of a scale standard with (a) an axial magnetic pole pair and (b) a diametrical magnetic pole pair, wherein the scale standard comprises a second (Vernier) measuring track having a sinusoidal geometry.

[0030] Fig. 12 is a cross-sectional view of a further embodiment of a scale standard with (a) an axial magnetic pole pair and (b) a diametrical magnetic pole pair, which have a geometrical modulation of a plurality of (Vernier) measuring tracks without or with superposition of the additional measuring tracks.

[0031] Fig. 13 is a cross-sectional view of a further embodiment of a scale standard comprising a magnetic track and two superposed, geometrically modulated measuring tracks on the inside edge.

[0032] Fig. 14 shows cross-sectional views of further embodiments of a scale standard having (a) merely a magnetic measuring track, (b) merely a geometric track, and (c) a combination of a magnetic and a geometric track.

[0033] Fig. 15 is a cross-sectional view of an embodiment of a scale standard for a length measuring device comprising two geometrically coded measuring tracks.

[0034] Fig. 16 is a cross-sectional view of a further embodiment of a scale standard for a length measuring device comprising two measuring tracks geometrically coded by superpositioning.

[0035] Fig. 17 is a diagram of an embodiment of a method for producing a scale standard for a measuring system. DETAILED DESCRIPTION

[0036] Fig. 1 is a general block diagram of a position measuring system, in the present case a length measuring system. The measuring system comprises a scale standard 1 and a scanning head 2 (sensor head). The position information of the measuring system is forwarded via an interface 4 to a servocontroller 3 for regulating for example the position, the speed and / or the torque, or for control.

[0037] The scale standard 1 contains coded information, which can be introduced in a wide variety of forms. In this case, the scale standard 1 can be configured both as a passive and as an active element. Examples of active elements for the scale standard are angular position sensors (resolvers) and rotary encoders, which have a meandering structure which is supplied with an alternating current signal.

[0038] The scanning head 2 comprises a sensor 2.1. The sensor 2.1 can be based on various physical measuring principles, for example on a magnetic, inductive, optical, capacitive, or the “giant magnetic impedance” (GMI) measuring principle. In this case, the sensor 2.1 can scan (acquire) the entire length or surface or the scale standard 1 or also only a part or a segment thereof. During scanning, the sensor 2.1 generates one or more analogue signals.

[0039] The scanning head 2 furthermore comprises an electronics circuit having evaluation electronics 2.2 (sensor circuit), which converts the analogue sensor signals, by suitable methods, into digital or analogue position information. The sensor circuit 2.2 can comprise an evaluation circuit having a multiplexer, wherein the multiplexer is connected to the sensor elements and is configured to provide measuring signals via a single physical evaluation channel.

[0040] The position measuring system can be a linear measuring system or a length measuring system. Fig. 2 shows a linear or length measuring system. The scale standard 1 is configured as a linear, strip-shaped element which extends along a length direction x which also represents the measuring direction. It has a linear coding which also extends in the measuring direction x. The sensor head 2 is arranged above the scale standard 1 and can move along the measuring direction x in order to detect the scale standard 1.

[0041] Fig. 3, in contrast, shows an angle-measuring system having an annular scale standard 1 and a corresponding, also annular, sensor head 2. The scale standard 1 has a circular coding along a radial direction, which corresponds to the measuring direction. In the example shown, the sensor head 2 is arranged in parallel with and spaced apart from the scale standard 1. Furthermore, both elements have the same axis, which is arranged perpendicularly to the planes in which the scale standard 1 and the sensor head 2 each extend and which passes through a center of the scale standard or of the sensor head. During measuring, the sensor head can rotate about the axial axis and thus serve as the rotor, while the scale standard remains fixed and serves as the stator. Alternatively, the scale standard can rotate about the axis and the sensor head can remain fixed.

[0042] Typically, the scale standard 1 and the sensor head 2 are spaced apart by a substantially constant distance in a direction that extends perpendicularly to the plane in which the scale standard 1 extends, as shown in Fig. 1 to 3. Thus, both optical and also magnetic, capacitive or inductive measurements can be carried out.

[0043] Fig. 4 is a schematic view of a linear measuring system according to the prior art, which is based on an inductive measuring principle. In this case, the coded information is introduced into the scale standard 1 (the standard) through different regions having different permeabilities p (reluctances) and / or different conductivities a. In the example shown, the linear scale standard 1 extends along a measuring direction x, wherein two adjacent regions in the measuring direction have a different permeability or conductivity. The coding is periodic, wherein a period has a sequence of a first region having a permeability po or conductivity oo, and a second region having a permeability pi or conductivity 01, and a division period A. An incremental position measurement proceeding from a starting position of the sensor head can be carried out by relative movement of the scale standard 1 and a sensor head.

[0044] In principle, the scale standard 1 comprises one or more periodically or aperiodically coded measuring tracks. In the case of periodic coding, the division period A corresponds to one period of the coding. The scale standard 1 is scanned (sensed) by a sensor 2.1. Thus, the scanning is not sampling, but rather a detection of the scale standard. It is the case that the sensor 2.1 contains a sensor element 2.1.1 for each track of the scale standard. A sensor element 2.1.1 is formed of at least one emitter coil 2.1.1.1 and one or more receiver coils 2.1.1.2. It is the case that a sensor element 2.1.1 can have one or more emitter coils 2.1.1.1 and an emitter coil 2.1.1.1 can be used both by just one sensor element 2.1.1 and by a plurality of sensor elements 2.1.1 together.

[0045] The sensor element 2.1.1 covers at least one division period A of the measuring track. The sensor element can also cover a plurality of division periods n A (with n e N), wherein n denotes the number of division periods. Thus, possibly occurring errors can be averaged, which reduces the general measuring error. The emitter coils 2.1.1.1 and the receiver coils 2.1.1.2 can for example be implemented as conductor tracks in the form of a meandering structure (pancake coils) in or on a rigid or flexible substrate (e.g. a printed circuit board). In the example shown, the sensor element 2.1.1 comprises a single emitter coil 2.1.1.1 which has the form of a cuboid, and two meander-shaped, offset receiver coils 2.1.1.2 which are arranged within the emitter coil 2.1.1.1.

[0046] A measuring track of the scale standard 1 in combination with the sensor element 2.1.1 forms a measuring channel. The electronic circuit 2.2 feeds an alternating current into the emitter coil(s) 2.1.1.1 of the sensor element 2.1.1, for example at a frequency in the range of a few kHz to 100 MHz. Owing to the inductive coupling (mutual induction) between the emitter 2.1.1.1 and receiver coils 2.1.1.2, an alternating current of the same frequency is induced in the receiver coils 2.1.1.2. In this case, the mutual induction is modulated in the case of a relative movement of the scale standard 1 with respect to the scanning head 2 (the sensor structure).

[0047] In the case of different permeabilities p, those regions of the scale standard 1 having higher magnetic permeability (pi >po) will amplify the mutual induction or the alternating current induced in the receiver coils 2.1.1.2.

[0048] In the case of different conductivities a, those regions of the scale standard 1 having higher conductivity (oi >oo) will reduce the mutual induction or the alternating current induced in the receiver coils 2.1.1.2.

[0049] The alternating currents induced in the receiver coils 2.1.1.2 or the measured signals are demodulated by the evaluation electronics 2.2 and converted into position information. The position information thus obtained is forwarded via an interface 4 to a servocontroller 3 for various control purposes. In one example, the interface is a synchronous serial interface (SSI) and comprises a power amplifier (line driver), e.g. of the type RS485, as well as a cable and a connector.

[0050] As described above, for position measuring the sensor head can move along the measuring direction above the surface of the scale standard, and in the process detect changes of one or more physical variables, such as the inductance or the magnetic field strength, wherein the evaluation circuit calculates position information from the sensor signals. Alternatively, the sensor head can be fixed, while the scale standard itself moves, for example rotates.

[0051] Fig. 5 is a schematic view of a scale standard for a measuring system, in the present case a length measuring system. The scale standard, in the present case configured as a standard, comprises a substrate and a magnetic measuring track assembly. The magnetic measuring track assembly consists of one or more measuring tracks which are coded with a periodic or aperiodic (random) pattern. In this case, a measuring track refers to a track which is coded in such a way that the scanning (sensing) thereof by a sensor allows for determination of the absolute and / or relative position of the sensor on the measuring track. In the example of Fig. 1, the magnetic measuring track assembly comprises a single measuring track having a periodic division. A division period corresponds to the length A of a magnetic pole or the length 2*A of a magnetic pole pair.

[0052] A magnetic measuring track assembly can consist of a magnetically hard material, such as ferrites or alloys based on aluminum, nickel, cobalt, neodymium, iron-boron. The measuring track assembly can be produced by various methods, such as synthesis, forming, vulcanizing and rolling. In addition, in order to increase the mechanical stability and / or the magnetic properties, the measuring track assembly can be manufactured on a substrate or be retrospectively adhesively bonded thereto.

[0053] Following production of the scale standard, a scale (measuring track) having a periodic or aperiodic pattern of magnetic pole pairs is magnetized in the magnet material of the magnetic measuring track assembly. The magnetization can take place both in the direction of movement or of rotation (axially or radially) of the measuring system, and orthogonally thereto. The magnetization of the substrate for producing the measuring track is remanent magnetization. The measuring track thus has a magnetic coding along a given measuring direction, and is formed by a plurality of magnetic portions, wherein two adjacent portions have different magnetization.

[0054] Magnetic measured variables include for example the field strength, the flux density, the reluctance, the permeability, the saturation magnetization, the dipole moment, and the polarization.

[0055] Typical magnetic sensors use Hall, magneto resistive (MR) or magnetic impedance (Ml) effects in order to scan the magnetic scale. During scanning, they generate an electrical signal which is a reproduction of the magnetic pattern of the measuring track assembly.

[0056] Fig. 6a shows a measuring system comprising a magnetic pole pair and a Hall sensor, and also a graph which shows the electrical signal generated upon scanning of the magnetic pole pair by the Hall sensor. Fig. 6b) shows a similar measuring system and a corresponding graph, wherein the sensor is configured as a magnet impedance sensor.

[0057] As can be seen from Fig. 6a, in the case of Hall sensors 2 the scanning of a pole pair generates a signal period. In contrast, as shown in Fig. 6b, in the case of MR and Ml sensors 3 the scanning of a single pole generates a signal period, while in the case of scanning of a pole pair two signal periods are generated. It is therefore not possible, using MR and Ml sensors, to distinguish between the north and the south pole.

[0058] The generated electrical signals can then be further processed by evaluation electronics (an evaluation circuit) to give position information. A distinction is made between incremental and absolute measuring systems for both length and angle-measuring systems.

[0059] A scale standard (measuring track assembly) for an incremental measuring system generally comprises a magnetically coded measuring track. In addition, the scale standard can have a reference mark or a reference track.

[0060] A scale standard for an absolute measuring system comprises at least two periodically coded measuring tracks or at least one aperiodically coded measuring track. For absolute position measurement, what are referred to as Vernier-coded scale standards are known. In this case, the scale standard comprises at least two periodically coded measuring tracks, which have different division periods, such that for each position on the scale standard a unique signal combination of the tracks is present. Such Vernier coding can be implemented both for linear measuring systems and for angle-measuring systems.

[0061] Both in the case of scale standards having at least two periodic measuring tracks of different division periods (Vernier coding) and in the case of scale standards having an aperiodic measuring track, cross-talk between the individual tracks or poles occurs. This cross-talk is typically reduced in part by particularly complex magnetization methods, which lead to increased outlay and increase the complexity of the magnetization. A reduction in the cross-talk is in part also possible by means of digital signal processing. However, the outlay for this remains relatively high. Furthermore, these approaches are not particularly flexible and must be adapted in the case of a dynamic change of system parameters, for example of the operating point, which is not always possible, however. The known solutions are not easily scalable and have some physical and technological limitations, which will be described below.

[0062] The magnetic scale standard is limited to an even pole number. This results from Gauss’s law for magnetic fields: V B = 0, according to which the field of the magnetic flux density is solenoidal, since there are no magnetic monopoles.

[0063] This is a problem in particular for scanning a scale standard using MR and Ml sensors 3, because the solenoidal nature of the flux density means that Vernier coding is not possible. For Vernier coding, a measuring track would have to comprise an odd number of division periods, which, however, is not possible for the stated reason. Specifically, for determining the absolute position of a Vernier coding, the greatest common divisor GCD of the number of division periods n of the different tracks must be equal to 1 (GCD (n1, n2) = 1), such that not all tracks can have an even pole number.

[0064] Fig. 7 is a schematic view from above of a scale standard for an angle-measuring system comprising two magnetically coded measuring tracks, which are arranged concentrically in the same plane. The first, outer measuring track 1.1 comprises 16 pole pairs, and the second, inner measuring track 1.2 comprises 3 pole pairs. The measuring tracks are arranged along a radial measuring direction, which is arranged perpendicularly to the thickness of the scale standard. Thus, as explained above, in the case of scanning using a Hall sensor, 16 or 3 sine periods are generated. In the case of scanning using an MR or Ml sensor, 32 or 6 sine periods are generated. Thus, in the case of scanning using MR or Ml sensors, the magnetic pattern thus already repeats after 180°. A Vernier coding is not compatible with this sensor technology.

[0065] Furthermore, the magnetic sensors (Hall, MR and Ml) are sensitive to changes of the magnetic field strength in one of the directions x, y or z of a cartesian coordinate system. A magnetic scale standard comprising a non-periodic measuring track or comprising at least two measuring tracks of different division lengths contains position information in the form of a variation in the amplitude of the magnetic field. In this case, the amplitude is directly proportional to the length of the magnetic pole.

[0066] Thus, in the case of a measuring system having Vernier coding, the optimal operating point of the magnetic sensor of each measuring track can vary significantly. The operating point corresponds to the distance between the sensor and the scale standard in a direction which extends perpendicularly to the plane of the scale standard, and is also referred to as the air gap.

[0067] This problem is illustrated in Fig. 8. Fig. 8 is a graph showing the magnetic field strength as a function of the air gap (in millimetres) for different division periods, wherein a division period corresponds to a pole length. For a given air gap, the amplitude of the magnetic field for two different tracks changes significantly. For example, in the case of an air gap of 4 mm the amplitude of the magnetic field for a track having a division period of 4 mm is approximately 10 times that for a track having a division period of 0.5 mm. The operating point for a multi-track assembly can thus be selected only by compromise between the different tracks of the assembly.

[0068] In principle, a large signal amplitude is desired. The higher the amplitude, the better the signal-to-noise ratio (SNR). However, a problem is also that in the case of too high a magnetic field strength the signal amplitude of the sensor can also become saturated, if for example the operating point changes during operation (dynamic change). Dynamic changes of the operating point, for example due to temperature expansions, are unavoidable. Thus, when selecting the operating point, a compromise must be found between the operating region and performance of the measuring system.

[0069] This problem also arises in the case of magnetic measuring tracks having aperiodic division. Such aperiodic tracks have a plurality of divisions of different lengths, which generate different magnetic field strengths. Specifically, each division generates its own magnetic field strength having a certain amplitude, which is directly proportional to the division length.

[0070] A magnetic measuring track assembly is described in the following which overcomes the above-mentioned disadvantages of the prior art and, in particular, is easy to produce and is scalable. Furthermore, this assembly makes it possible to prevent cross-talk both during the magnetization and also later during operation, and any periodic and / or aperiodic patterns are permitted, including tracks having an odd number of division periods.

[0071] For this purpose, two different effects for the coding of measuring tracks are combined with one another: on the one hand the effect of the magnetic field vectors generated by a magnetized track (magnetic track), and on the other hand the effect of a magnetic change, in particular geometric modulation, of the magnetized track. In this case, a magnetized or magnetic track denotes a track which is formed by a plurality of magnetic portions, wherein two adjacent portions have different magnetization. For example, a magnetic track comprises one or more magnetic pole pairs.

[0072] A mechanical change refers to a change, in particular the change in the shape, surface and / or structure of an object, by the action of a force. Geometric modulation refers to the change in the shape of an object by the action of a force.

[0073] Fig. 9 is a schematic view of a scale standard 1 in the form of a magnet, wherein the magnetic poles are directed along an X-axis. For the sake of clarity, Fig. 9 shows merely a 2D view of the magnetic lines of the magnetic field generated by the magnet. However, it is clear that the magnetic field acts in all directions and thus is a 3D effect. The magnetic field lines begin at the North pole of the magnet and end at the South pole. At each point in space, the magnetic field can be characterized by a magnetic field vector B and its components Bx, By (not shown in Fig. 9) and Bz, wherein x, y and z denote the cartesian coordinates.

[0074] The magnetic field strength and its vectors are directly dependent on the magnetically hard material used or on the alloy of the magnet, on the magnetization method / process or the magnetization facility, and on the geometry of the magnet.

[0075] Due to the change in the geometry (height, width, length) of the magnet in any direction, the magnetic field strength and its vectors also change correspondingly. Precisely this effect is used in the present case for coding a measuring track. The magnetic field can be calculated by analysis methods. However, it is usually calculated with the support of computer simulations, e.g. based on the finite element method (FEM). Therefore, additional geometric coding can be formed on the substrate by varying at least one geometric feature of the substrate along the measuring direction of the sensor. In one example, the geometric coding is formed by varying the external shape of the substrate. In a further example, this additional coding is periodic.

[0076] Fig. 10 is a perspective view of a scale standard 1 for an angle-measuring system having an axial magnetic pole pair (Fig. 10a) and having a diametrical magnetic pole pair (Fig. 10b). The pole pairs thus correspond to a first magnetic track. For the sake of completeness, it is noted at this point that the examples and principles set out in the following can also be applied for scale standards of length measuring systems (see also Fig. 15 and 16).

[0077] Fig. 11a is a schematic cross-sectional view of a scale standard 1 for an angle-measuring system having an axial magnetic pole pair. Compared with the example of Fig. 10a, the circular cylindrical scale standard 1 of Fig. 11a has an outer circular edge 1.1 in the plane shown, which is easily deformable. A width of the scale standard is no longer constant, but rather varies depending on the inscribed angle. More precisely, the outer edge 1.1 of the scale standard has a periodic variation, such that the outer edge 1.1 is sinusoidal, having three sine periods. The radius of the outside edge of the scale standard in the plane shown is calculated on the basis of the following formula: (W) sx 4- - w) (1)

[0078] wherein w is the angle in degrees where 0° <w <360°; t is the number of division periods which are generated by geometric modulation; A is the amplitude of the sine wave; and r is the radius of the sine wave. The index denotes merely the first geometrically generated track. In the example of Fig. 11a, the following parameters were used: ti = 3, Ai = 0.1 and n = 0.9. In this case, the original outside radius of the scale standard before deformation is calibrated to one.

[0079] The periodic variation of the outside radius of the scale standard forms a further measuring track in addition to the first magnetic track which is formed by the pole pair. Together with the magnetized pole pair (two poles), this additional measuring track having three periods forms a Vernier coding, since the greatest common divisor GCD (3, 2) is equal to one.

[0080] It is clear that an additional geometric track can be formed by varying other geometric parameters of the scale standard. For example, a height, a width or a thickness of the scale standard can be varied, in order to generate a geometric track. The geometric track is formed along the measuring direction.

[0081] Thus, by adjusting the geometry of the scale standard, an additional measuring track having a different division can be added, without having to perform an additional magnetization. Since there is just one magnetic track, the cross-talk between a plurality of magnetic tracks is prevented, as a result of which the accuracy of the sensor measurement is greatly improved. The desired geometry can be produced both directly during production of the magnetic track, e.g. by sintering or injection moulding, and also subsequently, e.g. by milling, etching, cutting or turning. In this case, whether the processing of the geometry takes place before or after magnetization of the magnetic track likewise does not play a role.

[0082] The following figures show further examples of scale standards which comprise a combination of a magnetic and a geometric coding.

[0083] Fig. 11b is a schematic cross-sectional view of a scale standard 1 for an angle-measuring system having a diametrically magnetic pole pair. In addition to the pole pair (first magnetic track), the scale standard comprises a second and a third track, which are formed by variation of the geometry of the substrate. In particular, both the outside edge 1.1 and the inside edge 1.2 have a sinusoidal geometry having three periods. The radius f2(w) of the outside edge of the scale standard in the plane shown and the radius fi(w) of the inside edge of the scale standard 1 is calculated on the basis of the following formula: fx(w) ~ r2 + - sin(^ - w), umi / aO) rg + 4g ‘ sin(fg ' w)5 (2) O)

[0084] wherein t2 = 3; A2 = 0.1; n = 0.9; t3 = 3; A3 = 0.1; and rs = 0.6.

[0085] In this case, the external radius of the scale standard, which corresponds to the radius of the scale standard without deformation, is calibrated to 1 and the internal radius is calibrated to 0.5.

[0086] In the example shown, both the magnetic track and the geometric tracks are arranged along the measuring direction, which extends axially.

[0087] Fig. 12a is a schematic cross-sectional view of a further scale standard 1 for an angle-measuring system having a radially magnetic pole pair. Compared with the example of Fig. 11a, the scale standard 1 of Fig. 12a comprises not only one but rather two additional geometrically modulated tracks, specifically on an outside edge 1.1 and an inside edge 1.2 of the circular cross-section. The outside edge 1.1 has a sinusoidal geometry having five periods, and the inside edge 1.2 has a sinusoidal geometry having three periods. The radius f4(w) of the outside edge of the scale standard 1 in the plane shown and the radius fs(w) of the inside edge of the scale standard 1 are calculated on the basis of the following formula: LUv) ~ r4 4 (4) ™ r$ -F ‘ « w), (5)

[0088] where t4 = 3; A4 = 0.1; u = 0.9; ts = 3; As = 0.1; and rs = 0.6.

[0089] Thus, the scale standard of Fig. 12a comprises a first magnetic track having to periods, a second geometric track having three periods, and a third geometric track having five periods, wherein the greatest common divisor of the periods is also one. Thus, the scale standard of Fig. 12a also forms a Vernier coding. It should be noted that all the tracks are arranged along the same measuring direction.

[0090] Fig. 12b is a schematic cross-sectional view of a further scale standard 1 for an angle-measuring system having a radially magnetic pole pair. Compared with the example of Fig. 12a, Fig. 12b shows a superposition of two geometric modulations on the inside edge 1.2. The geometry of the inside edge of the scale standard of Fig. 12b thus results from an overlap of a sinusoidal geometry having three periods and a sinusoidal geometry having five periods. Thus, two geometric tracks are formed on the inside edge. The radius fe(w) of the inner edge of the scale standard 1 is calculated on the basis of the following formula: / -^(^) ™ -i- ' $in(t4 ■ w) T • w)|, (6)

[0091] with the parameters stated above. It is again the case that the original external radius is calibrated to 1, and the original internal radius is calibrated to 0.5. The geometry of the inside edge of the circular scale standard according to Fig. 12b can therefore as a superposition of the two separate modulated geometries of the inside and the outside edge of Fig. 12a.

[0092] Any number of measuring tracks can be created geometrically on a scale standard by means of such superposition. Furthermore, the amplitudes A of the geometric coding can be adjusted, such that the signal amplitudes for all the tracks are in the same range (tolerance range), even if the number of periods or the division lengths are different, which is not readily possible in the case of purely magnetic tracks. An adjustment of the respective amplitude of the geometry is also possible in the case of superposition of two or more geometric tracks.

[0093] According to an example, the magnetic measuring track of the scale standard has the largest number of division periods. The at least one geometrically modulated measuring track for generating a Vernier coding correspondingly has fewer division periods. The number of magnetic poles or magnetic portions of the scale standard is denoted by n, wherein it is the case that n is an element of the natural, even numbers (n e Ng). According to an example, the number of periods for the magnetic track is greater than the number of periods for the geometric track, in particular is greater than the number of periods for the geometric track by a factor of 1.5. According to a further example, the following conditions apply: n >1.5 * ti ; ti >1.5 * t2 ; ti >1.5 * ti+1, wherein ti is the number of periods for the i-th track, created by geometric change. Thus, cross-talk or mutual impairment of the two or more measuring channels relative to one another can be sufficiently reduced or eliminated. Furthermore, the coded information of the measuring tracks can be scanned more precisely.

[0094] Fig. 13 is a schematic cross-sectional view of a further scale standard 1 for an angle-measuring system. The scale standard 1 comprises a first magnetic measuring track, which is arranged along a radial direction and comprises 32 magnetic portions. The magnetic portions are diametrically magnetized poles, which are arranged alternately. Furthermore, the scale standard 1 comprises two modulated and superposed Vernier tracks on the inside edge 1.2. The radius f(w) of the inside edge of the scale standard 1 is, as already set out above, calculated on the basis of the following formula: / X» s; r + pU - - w) T 4» - sln(t8 - (7)

[0095] where r = 0.7; t? = 8; A? = 0.1; ts = 3; As = 0.2. The external radius of the scale standard is calibrated to 1 and the internal radius is calibrated to 0.5.

[0096] The magnetic measuring track of the measuring track assembly in Fig. 13 is the finest track and thus also decisive for the precision of a measuring system. The geometrically modulated Vernier measuring tracks are consulted for determining the absolute value of the measuring system.

[0097] In the example of Fig. 13, the conditions n >1.5 * t? and t? 1.5 * ts also apply, as shown above. Furthermore, the greatest common divisor of the number of the periods of the tracks is equal to one.

[0098] The geometric modulation of additional measuring tracks makes it possible to produce a magnetic scale standard having a Vernier coding, which can be used both in combination with a Hall sensor and in combination with a magneto resistive sensor or a magnet impedance sensor. Furthermore, since the measuring track assembly requires just one magnetic track, there is also no cross-talk between the tracks. Thus, the performance of a measuring system can be significantly improved. Since just one magnetic track is required, likewise no elaborate and highly complex magnetization devices and algorithms are required for eliminating the cross-talk between different measuring tracks. Thus, the general complexity of the measuring system is reduced. Furthermore, just one track needs to be magnetized, which saves time during production and allows for a particularly compact scale standard.

[0099] The examples shown above all show a geometric modulation of additional measuring tracks having a sinusoidal shape. However, it is clear that the sine shape can be replaced by any other shape. For a track having periodic coding, it is sufficient for the desired period to be detectable for the sensor. According to one example, the geometric feature of the substrate whereby the geometric track is varied for production can be represented mathematically as a polynomial or as a combination of a sine function and a polynomial function.

[0100] Fig. 14a is a cross-sectional view of a scale standard for an angle-measuring system comprising a magnetic measuring track. Fig. 14b is a cross-sectional view of a further scale standard for an angle-measuring system comprising a geometric measuring track. This geometric measuring track is formed by changing the geometry, specifically the radial width, of the substrate. In one example, this change is produced by a mechanical method, such as milling, etching, cutting or turning. The change in the geometry relates both to the outside edge 1.1 and to the inside edge 1.2 of the scale standard. Thus, the geometric track comprises three periodic portions along a radial direction, which portions each have a wider and a narrower region, and forms a periodic track having three periods. Fig. 14c is a cross-sectional view of a scale standard for an angle-measuring system, which is formed by superposition of the effects from Fig. 14a and 14b. The scale standard thus comprises both the magnetic track of Fig. 14a and the geometric track of Fig. 14b. The example of Fig. 14c can also be used for any number of periods of the magnetic and the geometric track. In one example, the geometric track is formed by a plurality of portions, wherein two adjacent portions differ by a change in a geometric feature of the scale standard along the measuring direction (for example the width of the scale standard).

[0101] The above examples can be implemented both in angle-measuring systems and in length measuring systems. Fig. 15 is a side view of a scale standard (standard) for a length measuring system. The measuring direction corresponds to the length direction of the scale standard, which extends along the x-direction. The scale standard 1 comprises a first magnetic track along the measuring direction, which comprises a plurality of alternating magnetic portions. In the example shown, the magnetic track comprises 20 poles. Furthermore, the scale standard 1 comprises a second geometric track which is formed by a periodic change in the first, upper edge 1.1. In the example shown, the first, upper edge 1.1 has the geometry of a sine shape having eight periods, and thus corresponds to a second measuring track having eight division periods. The scale standard 1 also comprises a third geometric track which is formed by a periodic change in a second, lower edge 1.2, which is arranged opposite the first, upper edge 1.1. In the example shown, the second, lower edge 1.2 has the geometry of a sine shape having three periods, and thus corresponds to a third measuring track having three division periods. The upper edge 1.1 and the lower edge 1.2 extend along the measuring direction (length direction). Thus, the elongate scale standard 1 comprises two periodic, geometric tracks having 3 and 8 division periods, respectively, in addition to the magnetic track. The greatest common divisor of the number of the periods of the different tracks is equal to one, such that the measuring tracks form a Vernier coding. In the example shown, the geometric track has a higher number of periods than the magnetic tracks, and is therefore decisive for the precision of the measuring system. The geometrically modulated Vernier measuring tracks are consulted for determining the absolute value of the measuring system.

[0102] Fig. 16 is a side view of a further scale standard for a length measuring system. Compared with the example of Fig. 16, the upper edge 1.1 has a superposition of the two sinusoidal measuring tracks of Fig. 15. Thus, two additional different measuring tracks having 3 and 8 periods, respectively, which can preferably be produced in single method, can be formed by changing one single contour. Thus, a particularly easy and quick production method can be provided. The example of Fig. 16 can be extended to any geometric measuring tracks. In one example, the number of periods of two geometric measuring tracks changes by at least a factor of 1.5. It is thus possible to ensure that the changes in the magnetic field, caused by the geometric track, can be precisely detected by the sensor.

[0103] Fig. 17 is a diagram of a method 100 for producing scale standard for a measuring system. In a first step 102, a substrate made of a magnetic material is provided. The substrate can be configured as an elongate substrate for a length measuring system or as an annular substrate for an angle-measuring system. Magnetically hard materials such as ferrites or alloys based on aluminum, nickel, cobalt, neodymium, iron-boron can be used as the material. In one example, the substrate is produced by synthesis, forming, vulcanising, rolling, sintering or injection moulding. In a further step 104, the substrate is magnetized. The magnetization of the substrate forms a first track on the substrate having a magnetic coding. The substrate can be magnetized having a periodic or aperiodic pattern of magnetic pole pairs. The magnetization can take place both in the direction of movement or of rotation (axially or radially) of the measuring system, and also normally thereto. In addition, the magnetized substrate can be arranged on a further substrate, for example adhesively bonded thereto. Thus, the mechanical stability can be increased and / or the magnetic properties can be improved. In the next step 106, a changes is made to a geometric feature of the substrate along a measuring direction. The geometric feature can be a thickness, a width or a length of the substrate. Thus, a second track having geometric coding along the measuring direction is formed. Therefore, no additional magnetic tracks are required, as a result of which cross-talk between tracks can be completely eliminated. In one example, the step of changing the geometric feature of the substrate takes place before the step of magnetization of the substrate. The step of producing the substrate and the step of changing the geometric feature of the substrate can for example take place simultaneously. Alternatively, the step of changing the geometric feature can take place after the step of producing the substrate and before the step of magnetization. In one example, the substrate is produced by sintering or injection moulding, which allows for simple production of a scale standard, having the desired geometry, in a single step. The change in the geometric feature of the substrate can also take place after the magnetization of the substrate. For example, the second geometric track can also be formed by milling, etching, cutting and / or turning the substrate. It is also possible to form any number of geometric measuring tracks using this method. By means of the described method, a scale standard for a length or angle-measuring system, which has a first magnetic track and a second geometric track, can be produced particularly easily and quickly. The method is suitable in particular for producing the scale standards shown in Fig. 11 to 16.

[0104] The described scale standard having a first magnetic track and a second geometric track makes it possible to prevent cross-talk between magnetic measuring tracks. Furthermore, this scale standard offers the possibility of forming any number of measuring tracks on a compact substrate. Both periodic and aperiodic measuring tracks can be formed. Furthermore, varying the geometry makes it possible to also form tracks having an odd number of division periods, which can be used together with magneto resistive and magnet impedance sensors. Selecting the parameters for the geometric track, in particular the amplitude, also makes it possible to optimise the operating region for the tracks. The production of a scale standard of this kind is also particularly easy and quick.

Claims

1. Device for a length or angle-measuring system, which comprises: a first track having magnetic coding, andat least one second track having geometric coding along a measuring direction.

2. Device according to claim 1,wherein the magnetic coding is formed by a plurality of magnetic portions, wherein two adjacent portions have different magnetization.

3. Device according to either claim 1 or claim 2, wherein the first track and the second track are arranged on a magnetic substrate, andwherein the geometric coding is formed by varying at least one geometric feature of the substrate along the measuring direction.

4. Device according to claim 3, wherein the geometric coding is formed by varying the external shape of the substrate.

5. Device according to claim 4, wherein the geometric coding is formed by periodically varying the external shape of the substrate.

6. Device according to any of claims 3 to 5, wherein the geometric feature of the substrate follows one of the following functions: a sine function, a polynomial function, and a combination of a sine function and a polynomial function.

7. Device according to any of claims 3 to 6, wherein an amplitude of the variation of the geometric feature of the substrate along the measuring direction is selected such that a first signal amplitude of the signal generated by the first track and asecond signal amplitude of the signal generated by the second track are the same, within a given tolerance range.

8. Device according to any of claims 1 to 7, wherein the magnetic coding comprises a first number of magnetic portions and the geometric coding is periodic and comprises a second number of periods, and wherein the first number differs from the second number.

9. Device according to claim 8, wherein the first number is larger than the second number, in particular larger than the second number by a factor of 1.5.

10. Device according to either claim 8 or claim 9, wherein a greatest common divisor of the first and the second number is equal to 1.

11. Device according to any of claims 1 to 10, wherein the assembly a[A1 ] third track, a second track having a geometric coding along the measuring direction, wherein the third track is arranged on the magnetic substrate, and wherein the further geometric coding is formed by varying at least one of the geometric features of the substrate along the measuring direction.

12. Device according to claim 11, wherein the geometric coding and the further geometric coding are periodic and comprise a second and third number of periods, respectively, andwherein the second number differs from the third number.

13. Device according to claim 12, wherein the second and the third track are formed by varying the same geometric feature of the substrate along the measuring direction.

14. Device according to any of claims 11 to 13, wherein the external shape of thesubstrate is formed by the superposition of the second and third track.

15. System, which comprises:a device according to any of claims 1-14, anda sensor head havinga first sensor element which, together with the first track, forms a first measuring channel, andat least one second sensor element which, together with the second track, forms a second measuring channel.

16. System according to claim 15, wherein the first and the second sensor element are selected from the group comprising the following: a Hall sensor, a magneto resistive sensor, and a magnet impedance sensor.

17. Method, having the following steps:providing a substrate made of a magnetic material,magnetizing the substrate for forming a first track having a magnetic coding, andchanging at least one geometric feature of the substrate along a measuring direction for forming at least one second track having a geometric coding along the measuring direction.

18. Method according to claim 17, wherein the step of producing the substrate and the step of changing the geometric feature of the substrate take place simultaneously.

19. Method according to claim 17, wherein the step of changing the geometricfeature of the substrate takes place after the step of magnetizing the substrate.

20. Method according to claim 17, wherein the step of changing the geometric feature of the substrate takes place after the production of the substrate and before the step of magnetizing the substrate.

21. Method according to any of claims 17 to 20, wherein the changing of the geometric feature of the substrate comprises at least by one of the following steps: milling, etching, cutting and turning.

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