METHOD FOR DETECTING A POSITION OF A SIGNAL GENERATOR IN A POSITION MEASURING SYSTEM, AND POSITION MEASURING SYSTEM

Abstract

A method for detecting a position of a signal generator in a position measuring system which includes at least one Hall sensor, a set of position intensity data is provided for a plurality of predetermined positions. A current measurement signal is detected for each measuring direction at the one Hall sensor or at each of the several Hall sensors for a current position of the signal generator, and the current position of the signal generator is determined from the position intensity data and all current measurement signals. The position intensity data for the position measuring system is stored in a control unit.

Claims

1. A method for detecting a position of a signal generator in a position measuring system, which comprises a position detection device with a Hall sensor or at least two Hall sensors, wherein the one Hall sensor detects two measurement signals or several Hall sensors each detect one measurement signal in at least one measuring direction when the signal generator moves relative to the one Hall sensor or to the Hall sensors, comprising steps of: providing a set of position intensity data for a plurality of predetermined positions within a measurement range of the one Hall sensor or of each of the Hall sensors in each measuring direction, measuring a current measurement signal for each measuring direction at the one Hall sensor or each of the Hall sensors for a current position of the signal generator, and determining the current position of the signal generator from the position intensity data and all current measurement signals.

2. The method according to claim 1, wherein the position intensity data contains additional parameters, in particular temperature and/or ageing data.

3. The method according to claim 2, wherein the additional parameters include temperature and/or ageing data.

4. The method according to claim 1, wherein the providing of the set of position intensity data comprises moving the signal generator along the measurement range of the respective Hall sensor in a predetermined path and recording the measured signal and a related position.

5. The method according to claim 1, wherein the providing of the set of position intensity data comprises calculating the position intensity data.

6. The method according to claim 1, wherein the determination of the current position of the signal generator is effected according to a nearest-neighbour classification or nearest-neighbour regression or a random-forest classification or random-forest regression.

7. The method according to claim 1, wherein the set of position intensity data is compiled outside of the position measuring system and is transferred to a control unit of the position measuring system and stored there.

8. The method according to claim 1, wherein a quantity of position intensity data obtained is reduced by a downsampling method and an accuracy of a predicted position is improved by averaging over predicted most probable positions weighted by their probabilities.

9. The method according to claim 1, wherein when using a single Hall sensor, measuring is carried out in various measuring directions to generate different measurement signals.

10. The method according to claim 1, wherein it is carried out on a microcontroller, which sits on a circuit board on which at least one Hall sensor is also affixed.

11. A position measuring system with a position detection device, which comprises at least one Hall sensor, wherein the one Hall sensor detects a measurement signal in at least one measuring direction or several Hall sensors each detect a measurement signal in at least one measuring direction, and comprises a signal generator, wherein in the case of several Hall sensors, the Hall sensors are arranged successively along a movement path of the signal generator, and with a control unit for carrying out the method according to claim 1, wherein the position intensity data for the position measuring system is stored in the control unit.

12. The position measuring system according to claim 11, wherein the at least one Hall sensor is constructed such that it comprises at least two subsensors, which detect magnetic field components in a first measuring direction and a second measuring direction orthogonal to this and provide measurement signals in each case.

13. The position measuring system according to claim 11, wherein the position measuring system is arranged in a drive of a valve and a valve position is determined.

14. The position measuring system according to claim 13, wherein the signal generator is an axially polarized magnet, which is arranged on a valve tappet that is displaceable linearly along the movement path such that its poles lie in the movement path, wherein the movement path runs parallel to one of the measuring directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 shows a schematic representation of a position measuring system according to the disclosure, here of a valve, for carrying out a method according to the disclosure;

[0059] FIG. 2 shows schematically the position detection device of the position measuring system from FIG. 1;

[0060] FIG. 3 shows steps of the method according to the disclosure for providing a set of position intensity data;

[0061] FIG. 4 shows further steps of the method according to the disclosure;

[0062] FIG. 5 shows steps of the method according to the disclosure for position determination; and

[0063] FIG. 6 shows a schematic representation of the saved position intensity data, the measurement results of a position detection device with three Hall sensors and the position of the signal generator determined by the position measuring system.

DETAILED DESCRIPTION

[0064] The drawings are not true to scale.

[0065] FIGS. 1 and 2 show a position measuring system 10, here in a valve 11, in particular a process valve, with a schematically represented position detection device 12, which is accommodated here in a control head 14 of the valve 11.

[0066] The position measuring system 10 is naturally also suitable for other purposes, however, in particular in any type of drive with an element that is moved linearly.

[0067] The control head 14 here comprises exclusively components of the valve 11 through which the process medium does not flow.

[0068] A valve tappet 16 protrudes through a bushing 18 at the lower end of the control head 14 and is connected fixedly outside of the control head 14 to a valve element 20.

[0069] The valve element 20 interacts with the components of the valve 11 carrying process media, which components are only indicated here. For example, the valve element 20 can close or release a valve seat or interact with a component that closes or releases the valve seat. In each case the movement of the valve tappet 16 is transmitted immediately and directly to the valve element 20, such that a position of the valve tappet 16 provides clear information about the position of the valve element 20.

[0070] A signal generator 22 is arranged on the valve tappet 16 at the end opposite the valve element 20. The signal generator 22 here is an axially polarized magnet, the poles of which are arranged along the longitudinal axis of the valve tappet 16. The arrangement of the poles represented in FIG. 1 is chosen by way of example; the polarity of the signal generator 22 can naturally also be reversed.

[0071] The longitudinal axis of the valve tappet 16 defines a movement path in the form of a movement axis A.sub.y, wherein the valve tappet 16 moves back and forth linearly along the movement axis A.sub.y in a predetermined movement range to move the valve element 20.

[0072] The signal generator 22 is mounted on the valve tappet 16 in a fixed position and generates a magnetic field that is rotationally symmetrical about the movement axis A.sub.y. Here only a single signal generator 22 is provided in the valve 11.

[0073] The signal generator 22 is part of the position detection device 12. Also belonging to the position detection device 12 are one or more (here three in total, generally n) Hall sensors 24, 26, 28. In this example, all Hall sensors 24, 26, 28 are mounted together on a circuit board 30 (see FIG. 2). All Hall sensors 24, 26, 28 are lined up along a straight line along the movement axis A.sub.y and positioned here at equal distances.

[0074] It should be emphasized that even just a single Hall sensor, for example the Hall sensor 26, is sufficient for the position detection. This singular Hall sensor would then also be mounted on the circuit board 30. The features of the detailing below are also applicable to a singular Hall sensor. When using just a single Hall sensor, this is designed such that it can detect measurement signals B.sub.Mny, B.sub.Mnz in at least two spatial directions perpendicular to one another.

[0075] In this example, even all Hall sensors 24, 26, 28 (even the singular Hall sensor) are designed such that they can detect measurement signals B.sub.Mny, B.sub.Mnz in at least two spatial directions perpendicular to one another, here denoted y- and z-direction. The y-direction coincides here with the direction of the movement axis A.sub.y, while the z-direction points perpendicularly to the surface of the Hall sensor 24.

[0076] Any measurement signals of a subsensor which detects the x-direction perpendicular to the y- and the z-direction are not considered here.

[0077] Each of the Hall sensors 24, 26, 28 supplies an evaluatable measurement signal B.sub.ny, B.sub.nz for each spatial direction selected, thus here the y- and the z-direction. The method is also transferable to other spatial directions perpendicular to one another.

[0078] In the case of Hall sensors 24, 26, 28, which measure a movement in three spatial directions x, y, z lying perpendicular to one another, an axial movement of an axially polarized magnet in an arrangement of this kind results in a measurement signal B.sub.Mny for the movement direction A.sub.y and a measurement signal B.sub.Mnz for the z-direction from the magnet to the Hall sensor 24, 26, 28. Due to the progression of the magnetic field lines, no measurement signal or only a very small measurement signal is measured for the x-direction.

[0079] Formed in the interior of the control head 14 is an attachment structure 32 on which the circuit board 30 is fixedly mounted.

[0080] The positions of the valve tappet 16 and of the Hall sensors 24, 26, 28 in the interior of the control head 14 are fixedly predetermined via the attachment structure 32 and the bushing 18, and thus also the relative positions of the signal generator 22 to the Hall sensors 24, 26, 28.

[0081] The signal generator 22 is an axially polarized permanent magnet here with precisely one north and one south pole.

[0082] The position detection device 12 also comprises a control unit 34 (see FIG. 1), which is connected to the Hall sensors 24, 26, 28 in a signal-transmitting manner and which is likewise arranged here on the circuit board 30. The control unit 34 could also be arranged at another point in the position measuring system 10 or outside of it, however, and connected to the Hall sensors 24, 26, 28 in a suitable manner.

[0083] If the valve tappet 16 is moved along the movement axis A.sub.y, the signal generator 22 moves by an extent proportional to the movement of the valve element 20.

[0084] Since the signal generator 22 moves relative to the Hall sensors 24, 26, 28, the measurement signal B.sub.Mny, B.sub.Mnz generated by the Hall sensors 24 changes.

[0085] To convert the measurement signals B.sub.Mny, B.sub.Mnz of the individual Hall sensors 24, 26, 28 into a clear position of the signal generator 22 on the movement axis A.sub.y, a model B(B.sub.ny, B.sub.nz) of the position detection device 12 is stored in the control unit 34, which model comprises a set of position intensity data B.sub.ny, B.sub.nz, which produces a connection between predetermined positions p, in an overall measurement range 36 and measurement signals B.sub.Mny, B.sub.Mnz supplied by the Hall sensors 24, 26, 28 (see FIG. 6).

[0086] The position intensity data B.sub.ny, B.sub.nz here comprises characteristic curves of the Hall sensors 24, 26, 28 for different parameters, for example different ambient temperatures or ageing times of the Hall sensors 24, 26, 28 and the signal generator 22.

[0087] In the example shown in FIG. 6, B.sub.1y, B.sub.1z describe the characteristic curves of the Hall sensor 24 in y- and z-direction, B.sub.2y, B.sub.2z describe the characteristic curves of the Hall sensor 26 in y- and z-direction and B.sub.3y, B.sub.3z describe the characteristic curves of the Hall sensor 28 in y- and z-direction, in each case for identical other parameters.

[0088] In FIG. 6, characteristic curves of the Hall sensors 24, 26, 28 from the position intensity data B.sub.ny, B.sub.nz are represented, which have been selected for the respectively applicable other parameters. Each characteristic curve is present for the entire measurement range 36 of the respective Hall sensor 24, 26, 28.

[0089] The characteristic curves of the Hall sensors 24, 26, 28 are detected in this case over their entire measurement range 36, thus also in the far field. An effective overall measuring distance of 100 mm, for example, can be realized in this way with just three commercially available Hall sensors.

[0090] The set of position intensity data B.sub.ny, B.sub.nz can be determined in any way.

[0091] One option is to move the signal generator 22 along the entire measuring distance and to detect the current measured values B.sub.Mny, B.sub.Mnz as well as the other relevant parameters for a plurality of known positions p.sub.i of the signal generator 22 and save them as characteristic curves in each case.

[0092] Another option is to produce an analytical connection for the respective characteristic curves, if applicable by means of fitting curves and/or empirical formulae, and to calculate the respective characteristic curves.

[0093] A combination of both methods is also possible. Thus the fundamental characteristic curves can be determined for one type of position measuring system 10, for example, by passing along the route with the signal generator 22, while other parameters such as ambient temperature and ageing phenomena are inserted into the characteristic curves by analytical or empirically determined correction factors.

[0094] Once the position intensity data B.sub.ny, B.sub.nz has been determined for all Hall sensors 24, 26, 28, the set of position intensity data B.sub.ny, B.sub.nz is provided. In the case that the position intensity data B.sub.ny, B.sub.nz was generated on the position measuring system 10 itself, this is stored in the control unit 34.

[0095] In the case that the position intensity data B.sub.ny, B.sub.nz was determined in an external device (not represented), the set of position intensity data B.sub.ny, B.sub.nz is transferred as a whole to the control unit 34 and stored there.

[0096] These options are summarized in FIG. 3.

[0097] In the control unit 34, the position intensity data B.sub.ny, B.sub.nz is stored e.g. in the form of a matrix B, which contains a value for each of the predetermined points p.sub.i for each Hall sensor 24, 26, 28 and each measuring direction y, z and if applicable for other parameters.

[0098] The other parameters considered can be saved e.g. also as correction values, in particular if the adaptation can be carried out by a simple arithmetic operation.

[0099] It is also possible to save e.g. a plurality of matrices, which were each compiled for specific values of the individual parameters.

[0100] In order to determine a current position p of the signal generator 22 in ongoing operation, the current measurement signals B.sub.Mny, B.sub.Mnz of all Hall sensors 24, 26, 28 are detected for all measuring directions y, z. Data for the other parameters, for example the ambient temperature, is also detected or read from data stored in the control unit 34, for example for ageing conditions.

[0101] The current measurement signals B.sub.Mny, B.sub.Mnz for the current position p are summarized here for a measurement vector {right arrow over (B.sub.M)} (see also FIG. 6).

[0102] The position p is determined from the position intensity data B.sub.ny, B.sub.nz for the current measurement signals B.sub.Mny, B.sub.Mnz (see also FIG. 4).

[0103] This is effected exclusively with the use of the position intensity data B.sub.ny, B.sub.nz and the current measurement signals B.sub.Mny, B.sub.Mnz without further arithmetic operations with the current measurement signals B.sub.Mny, B.sub.Mnz, for example by a suitable comparison of the current measurement signals B.sub.Mny, B.sub.Mnz with the position intensity data B.sub.ny, B.sub.nz.

[0104] As FIG. 6 shows, the current measurement signals B.sub.Mny, B.sub.Mnz lie at one of the positions p, approximately on the characteristic curves of the position intensity data B.sub.ny, B.sub.nz. For all other positions pi there is a greater or lesser deviation d.sub.ny(p.sub.i), d.sub.nz(p.sub.i). By looking at these deviations d.sub.ny(p.sub.i), d.sub.nz(p.sub.i), the “best-matching” position p.sub.i can be determined from the position intensity data B.sub.ny, B.sub.nz. This position p.sub.i then corresponds in a good approximation to the current position p of the signal generator 22.

[0105] To determine the position p, a nearest-neighbour classification or regression is used, for example, as outlined in FIG. 5.

[0106] In this method, a distance d, of the respective current measurement signal B.sub.Mny, B.sub.Mnz from the characteristic curves of the set of position intensity data B.sub.ny, B.sub.nz that are applicable for the detected or selected parameters is determined for each predetermined position p.sub.i.

[0107] In the matrix B, all values of the selected characteristic curves of the position intensity data B.sub.ny, B.sub.nz belonging to a predetermined position p.sub.i, for example, are summarized respectively in one column. The distances d, can be determined, for example, in a known manner via the Euclidean distance by forming the amount of the difference of each column of matrix B and the measurement vector {right arrow over (B.sub.M)}.

[0108] The distances d.sub.i and the respectively related position p.sub.i are saved in a list. This list is sorted in ascending order according to the magnitude of the distances d.sub.i.

[0109] The position p.sub.i with the smallest distance d.sub.i can be adopted as the current position p, or averaging can be carried out, for example via the positions p.sub.i for the k smallest distances d.sub.i, which is then adopted as current position p. In this case, a choice of k=1, for example, has proved suitable if very many positions pi are provided, k=3 if the measurement data used to determine the position intensity data B.sub.ny, B.sub.nz is noisy or weak, and k=2 in most other cases.

[0110] This algorithm is optionally optimized further e.g. by reducing the range of data being considered. Here a decision tree for instance based on simple comparisons is used that utilizes the characteristic forms of the characteristic curves. The centre of the range to be investigated can be defined, for example, via a threshold value of one or two measurement signals B.sub.Mny, B.sub.Mnz. How many steps or branches the decision tree should have depends here on the specific circumstances of the application.

[0111] Another optimization is the reduction of the position intensity data by a downsampling method. The measuring resolution reduced thereby is compensated for by weighting of the averaging over the positions p.sub.i with the distances d.sub.i (weighted kNN). This means that the accuracy of the predicted position is improved by averaging over the predicted most probable positions weighted by their probabilities.

[0112] This is advantageous in particular if the method is to be carried out on the microcontroller, in particular on a microcontroller with limited memory space, which is e.g. already integrated into the position measuring system, i.e. a microcontroller that does not have the capacity of an external control device. This microcontroller preferably sits on the circuit board on which the Hall sensor or Hall sensors also sit.

[0113] The comparison of the current measurement signals B.sub.Mny, B.sub.Mnz with the position intensity data B.sub.ny, B.sub.nz can naturally be effected in any suitable manner. Thus, for example, instead of the nearest-neighbour classification or regression described above, a random-forest classification or regression could be used.