DEVICE AND METHOD FOR DETERMINING A REFERENCE CURVE FOR THE ROTATIONAL POSITION OF A ROTARY COMPONENT

Description

Technisches Gebiet

[0001] The present invention relates to a method for determining a reference curve for the rotational position of a rotating component by means of such a device according to claim 1. Stand der Technik

[0002] The rotational position of a rotating component is determined using encoders. An encoder is a device that converts a position or motion value into an electrical signal, usually a digital code. Encoders can be rotary or linear and can be absolute or incremental encoders. Unlike absolute encoders, incremental encoders must be referenced after power-up because position changes (changes in position or angle) are not detected when the encoder is off.

[0003] The encoder comprises an encoder disk connected to the rotating component and rotatable about the rotating component's axis of rotation, and an angle measuring device. The angle measuring device comprises a beam source, a sensor unit, and a control unit.

[0004] The beam source generates a measuring beam that strikes or passes through a rasterized encoder disk, allowing the measuring beam to pass through or block it. The sensor unit, designed as an optical detector or read head, detects the passage of the measuring beam and generates a corresponding electrical signal. The sensor unit comprises two offset photodetectors. When the encoder disk rotates, the photodetectors are alternately illuminated. The measured values ​​from the first photodetector are recorded as the first measured values ​​(first output signal), and the measured values ​​from the second photodetector are recorded as the second measured values ​​(second output signal).

[0005] Known encoder disks are circular and have a periodic outer contour with N periods and a zero point, with the unwound outer contour of the encoder disks representing a rectangular function. A disadvantage of known encoder disks is that the accuracy with which the rotational position of the rotating component can be determined depends on the number N of periods. EP 2 388 556 A1 describes a known method for determining a reference curve for the rotational position of a rotating component using a device having an encoder disk. Darstellung der Erfindung

[0006] The object of the present invention is to develop a method for determining a reference curve for the rotational position of a rotating component, which is suitable for determining or adjusting the rotational position of the rotating component with great accuracy.

[0007] This object is achieved according to the invention in the method mentioned at the outset by the features of independent claim 1. Advantageous further developments are specified in the dependent claims.

[0008] The present invention relates to a method for determining a reference curve for the rotational position of a rotary component that is rotatable about a rotational axis, by means of a device comprising an encoder disk that is connected to the rotary component and rotatable about the rotational axis, which encoder disk is circular and has a periodic outer contour with N periods and a zero point, a beam source that emits a measuring beam that is directed onto the outer contour of the encoder disk, a sensor unit that comprises a first measuring surface and a second measuring surface that is different from the first measuring surface, and a control unit that is connected to the sensor unit, wherein the periods of the outer contour are composed of a first functional section and a second functional section, the first functional section and the second functional section are monotonically extending,one of the first and second function sections is monotonically increasing and the other of the first and second function sections is monotonically decreasing, with the steps: , ▪ the measuring beam, which is directed onto the outer contour of the rotating encoder disk and onto the sensor unit, is recorded by the first measuring surface as first measured values ​​and by the second measuring surface as second measured values, ▪ the first measured values ​​and second measured values ​​are transmitted from the sensor unit to the control unit, ▪ the first measured values ​​and associated first time values ​​are displayed by the control unit as a first measuring curve and the second measured values ​​and associated second time values ​​are displayed as a second measuring curve, ▪ the first measuring curve and / or second measuring curve are shifted relative to one another by the control unit until a phase difference of 90° exists between a first phase-shifted measuring curve and a second phase-shifted measuring curve,▪ from the phase-shifted first measurement curve and the phase-shifted second measurement curve, the control unit determines first function values ​​and second function values ​​for several time values ​​and the arctangent function is applied to the quotients of the first and second function values ​​according to the formula φ = , tan − 1 R 1 R 2 applied and ▪ the calculated angle values ​​are displayed by the control unit over time and saved as a reference curve for the rotational position of the rotating component.

[0009] Using the method according to the invention, a reference curve for the rotational position of the rotating component is determined, from which the rotational position of the rotating component can be determined or adjusted with great accuracy. To determine the reference curve, the measuring beam of the beam source is directed onto the outer contour of the rotating encoder disk and onto the sensor unit, with the first measuring surface recording first measured values ​​and the second measuring surface recording second measured values. Further evaluation and determination of the reference curve takes place in the control unit of the device. The composition of the periods from a monotonically increasing functional section and a monotonically decreasing functional section has the advantage over rectangular periods that the rotational position can be determined with greater accuracy. In the monotonically occurring functional sections, a precise determination of the rotational position is possible.

[0010] The first measurement and time values ​​are displayed by the control unit as a first measurement curve, and the second measurement and time values ​​are displayed as a second measurement curve. The first measurement curve and second measurement curve have a sinusoidal shape and are shifted relative to each other by a phase difference. The phase difference between the first measurement curve and second measurement curve depends on the spatial arrangement of the first measurement surface and second measurement surface. The first measurement curve and second measurement curve are shifted relative to each other by the control unit until a phase difference of 90° exists between a first phase-shifted measurement curve and a second phase-shifted measurement curve.

[0011] The control unit forms the quotient of a first and second function value for several time values ​​and applies the arctangent function according to the formula φ = tan − 1 R 1 R 2 on the quotients. The results of the calculations are angle values ​​that depend on time. These angle values ​​are displayed by the control unit over time and stored as a reference curve for the rotational position of the rotating component. The reference curve has a profile from which the rotational position of the rotating component can be determined or adjusted with high accuracy.

[0012] In a preferred variant, the first measured values ​​are used as the first function values, and the second measured values ​​are used as the second function values. Using the first measured values ​​as the first function values ​​and the second measured values ​​as the second function values ​​reduces the computational effort required to determine the reference curve for the rotational position of the rotating component.

[0013] In an alternative preferred variant, first approximate values ​​are used as first function values ​​and second approximate values ​​are used as second function values, wherein the first approximate values ​​are determined from the first measurement curve and the second approximate values ​​are determined from the second measurement curve. By using first approximate values ​​as first function values ​​and second approximate values ​​as second function values, the accuracy with which the reference curve for the rotational position of the rotating component is determined can be increased.

[0014] In a preferred variant, the transition from the first functional section to the second functional section is continuous. A continuous transition from the first functional section to the second functional section allows the rotational position to be determined at the transitions.

[0015] Particularly preferably, the first functional section and second functional section form a sine function. The sine function consists of monotonic functional sections with a continuous transition. The device comprises a first measuring surface and a second measuring surface, which are different from one another and record first measured values ​​and second measured values. Since the outer contour of the encoder disk can be represented as a sine function, the first and second measuring curves, which are determined using the first measuring surface and second measuring surface, follow a sinusoidal course, wherein the first measuring curve and second measuring curve are shifted relative to one another by a phase difference. The encoder disk makes it possible to determine the rotational position of the rotating component with great accuracy.

[0016] The sensor unit preferably comprises a first measuring surface and a second measuring surface, wherein the first measuring surface is different from the second measuring surface. The method according to the invention requires a first measuring curve and a second measuring curve that are shifted relative to one another. The first measuring curve is determined using the first measuring surface, and the second measuring curve is determined using the second measuring surface.

[0017] In a first variant, the sensor unit comprises a first sensor element comprising the first measuring surface and a second sensor element comprising the second measuring surface. The use of a first sensor element with the first measuring surface and a second sensor element with the second measuring surface enables easy differentiation between the first measured values ​​and the second measured values.

[0018] In a second variant, the sensor unit comprises a sensor element with a measuring range, wherein the first measuring surface and second measuring surface are integrated into the measuring range. The use of a sensor element in which the first and second measuring surfaces are integrated into the measuring range enables the differentiation between the first and second measured values ​​with minimal equipment effort. Ausführungsbeispiele

[0019] Embodiments of the invention are described below with reference to the drawing. These are not necessarily intended to show the embodiments to scale; rather, where useful for explanation, the drawing is schematic and / or slightly distorted. It should be noted that many modifications and changes to the form and detail of an embodiment can be made without departing from the general idea of ​​the invention. The general idea of ​​the invention is not limited to the exact form or detail of the preferred embodiment shown and described below, or to an object that would be limited compared to the object claimed in the claims. For given dimensioning ranges, values ​​lying within the stated limits are also intended to be disclosed as limit values ​​and can be used and claimed as desired.For the sake of simplicity, the same reference symbols are used below for identical or similar parts or parts with identical or similar functions.

[0020] They show: FIG. 1A, Legs device according to the invention, which is designed to determine a reference curve for the rotational position of a rotating component, in a side view ( FIG. 1A ) and in a longitudinal section ( FIG. 1B ); FIGS. 2A, B the device according to the invention of FIG. 1 which has an encoder disk ( FIG. 2A ) and an angle measuring device ( FIG. 2B ) comprises; FIG. 3A, legs sensor unit of the angle measuring device in a first variant ( FIG. 3A ) and a second variant ( FIG. 3B ); FIGS. 4A-C various stages during the implementation of the method according to the invention for determining the reference curve using the device of FIG. 1 ; and FIGS. 5A, B the outer contour of the encoder disk in a first variant ( FIG. 5A ) and a second variant ( FIG. 5B ).

[0021] FIGN. 1A , B show a device according to the invention 10, which is used to determine a reference curve for the rotational position φ of a rotating component 11 is trained. FIG. 1A the device 10 in a side view and FIG. 1B in a longitudinal section.

[0022] The rotating component 11 is rotatable about a rotation axis 12 rotatable, wherein the rotating component 11 is driven by a drive unit 13 around the rotation axis 12. The drive unit 13 comprises a motor 14, which can be designed as a stepper motor, and a gear transmission 15 with a first gear 16 connected to the motor 14 and a second gear 17, which is connected to the rotating component 11. The first gear 16 engages with the second gear 17 and is rotated by the motor 14 about a drive axis 18The movement of the motor 14 is converted via the gear transmission 15 into a movement of the rotating component 11 about the rotation axis 12.

[0023] The motor 14 is connected to a first axle element 19 which is rotatable about the drive axis 18 and which is rotationally fixedly connected to the first gear 16. The rotation component 11 comprises a second axis element 20, which is rotationally fixedly connected to the second gear 17. In the exemplary embodiment, the second axle element 20 is hollow inside and serves to guide an optical beam, for example a laser beam.

[0024] The rotational position φ of the rotating component 11 can be measured using the device 10 according to the invention. The device 10 comprises an encoder disk 21 and an angle measuring device 22.The encoder disk 21 is connected to the rotating component 11 and is designed to be rotatable with the rotating component 11 about the rotation axis 12.

[0025] FIGN. 2A , B show the encoder disk 21 and the angle measuring device 22. FIG. 2A the encoder disk 21 in a view from above and FIG. 2B the angle measuring device 22 in a schematic representation.

[0026] The rotational position φ of the rotating component 11 is determined using the encoder disk 21 and the angle measuring device 22. The encoder disk 21 is circular and has a periodic outer contour 23, which in the embodiment of the FIG. 2A is sinusoidal, with N periods and a zero point 24 The angle measuring device 22 comprises a beam source 25, which has a measuring beam 26 emits a sensor unit 27 and a control unit 28,wherein the sensor unit 27 has a first measuring surface 29A and a second measuring surface 29B The first and second measuring surfaces 29A, 29B are connected to the control unit 28 and can transmit their measured values ​​to the control unit 28. The measured values ​​of the first measuring surface 29A are referred to as first measured values, and the measured values ​​of the second measuring surface 29B are referred to as second measured values. The sensor unit 27 of the angle measuring device 22 can be constructed in different ways.

[0027] The measuring beam 26 is directed toward the first and second measuring surfaces 29A, 29B. The encoder disk 21 is arranged in the beam path of the measuring beam 26 between the beam source 25 and the sensor unit 27 and can at least partially mask the measuring beam 26. During the rotation of the encoder disk 21 about the rotation axis 12, the portions of the measuring beam 26 that impinge on the first measuring surface 29A and the second measuring surface 29B vary due to the periodic outer contour 23 of the encoder disk 21.

[0028] At the FIG. 2B In the embodiment of the angle measuring device 22 shown, the first and second measuring surfaces 29A, 29B have different distances from the axis of rotation 12. In the case of an encoder disk with a periodic outer contour that does not vary in a plane perpendicular to the axis of rotation 12, but rather has an annular outer contour that varies parallel to the axis of rotation 12, the first and second measuring surfaces 29A, 29B are arranged one behind the other in the circumferential direction. Because the outer contour of the encoder disk is arranged between the beam source 25 and the sensor unit 27, the portions of the measuring beam 26 that impinge on the first measuring surface 29A and the second measuring surface 29B vary.

[0029] FIGN. 3A , B show the structure of the sensor unit 27 in a first variant ( FIG. 3A ) and in a second variant ( FIG. 3B ). In the first variant, the sensor unit has a sensor element 31 with a measuring range 32and the first measuring surface 29A and second measuring surface 29B are integrated into the measuring area 32 of the sensor element 31. In the second variant, the sensor unit 27 has a first sensor element 33A, which comprises the first measuring surface 29A, and a second sensor element 33B, which comprises the second measuring surface 29B.

[0030] In order to be able to determine the rotational position φ of the rotary component 11 by means of the device 10 according to the invention, a method according to the invention for determining a reference curve for the rotational position φ of the rotary component 11 is carried out. FIGN. 4A-C show different stages during the implementation of the method according to the invention.

[0031] The beam source 25 emits the measuring beam 26, which is directed onto the outer contour 23 of the rotating encoder disk 21 and onto the sensor unit 27. The measuring beam 26 strikes the first measuring surface 29A, which receives the measuring beam 26 as the first measured values M1.i recorded, and on the second measuring surface 29B, which detects the measuring beam 26 as second measured values M2.j The first and second measured values ​​M1.i, M2.j can be recorded at a constant measuring frequency, with the first and second measured values ​​preferably being recorded at the same measuring frequency. The first measured values ​​M1.i and second measured values ​​M2.j are transmitted to the control unit 28.

[0032] For the method according to the invention, the time course of the first measured values ​​M1.i and the second measured values ​​M2.j is required. The assignment of time values ​​to the first and second measured values ​​can be carried out in different ways. If the sensor unit 27 has a clock for time measurement, first and second time values ​​can be assigned to the first and second measured values ​​already during recording. In this case, first time values T1.i and the second measured values ​​M2.j second time values T2.j assigned. The first and second time values ​​are transmitted to the control unit 28 with the first and second measured values. If the sensor unit 27 does not have a clock for time measurement, the assignment of time values ​​to the first and second measured values ​​can be carried out by the control unit 28. When the first and second measured values ​​are transmitted from the sensor unit 27 to the control unit 28, the control unit 28 creates the first time values ​​T1.i for the first measured values ​​M1.i and the second time values ​​T2.j for the second measured values ​​M2.j. The time difference that elapses between the recording of the measured values ​​and their transmission to the control unit 28 is irrelevant for the accuracy with which the reference curve can be determined, since the time difference occurs with the first and second measured values ​​and the first and second measured values ​​are used at the same time.

[0033] The first measured values ​​M1.i and first time values ​​T1.i are recorded by the control unit 28 as the first measurement curve 41 and the second measured values ​​M2.j and second time values ​​T2.j are shown as a second measurement curve 42 shown. Since the outer contour 23 of the encoder disk 21 can be represented as a sinusoidal function, the first measurement curve 41 and the second measurement curve 42 follow a sinusoidal curve, wherein the first measurement curve 41 and the second measurement curve 42 are shifted relative to one another by a phase difference. The phase difference between the first measurement curve 41 and the second measurement curve 42 depends on the spatial arrangement of the first measurement surface 29A and the second measurement surface 29B; the exact phase difference is not required for the method according to the invention.

[0034] The first measurement curve 41 and second measurement curve 42 are shifted relative to each other by the control unit 28 until a phase difference of 90° is obtained between a phase-shifted first measurement curve43 and a phase-shifted second measurement curve 44 is present. Due to the sinusoidal shape of the first and second measurement curves 41, 42, a phase difference of 90° can be easily determined. For example, a phase difference of 90° exists when the first maximum of the first measurement curve 41 coincides with the first zero of the second measurement curve 42. The phase difference of 90° can be generated by a shift of the first measurement curve 41, by a shift of the second measurement curve 42, or by a shift of the first and second measurement curves 41, 42.

[0035] A reference curve 45The reference curve 45 for the rotational position φ of the rotating component 11 is determined using the phase-shifted first and second measurement curves 43, 44. Two different variants are possible. In a first variant, the reference curve 45 is determined using the first and second measured values, and in a second variant, the reference curve is determined using first and second approximate values.

[0036] The first variant uses the first measured values ​​M1.i, which were measured by the first measuring surface 29A, and the second measured values ​​M2.j, which were measured by the second measuring surface 29B. Due to the shifting of the first and / or second measuring curve 41, 42, a shift of the first and / or second time values ​​T1.i, T2.j is required. The first time values ​​T1.i must be adjusted to the phase-shifted first measuring curve 43 and / or the second time values ​​T2.j must be adjusted to the phase-shifted second measuring curve 44. After adjusting the first and / or second time values, a value table with first measured values, second measured values, and associated time values ​​is available. The control unit 28 calculates the quotient of the first measured value and the second measured value for several time values ​​and applies the arctangent function according to the formula φ = tan − 1 R 1 R 2 on the quotients. The result of the calculations are angle values ​​that depend on time. The angle values ​​are displayed by the control unit 28 over time ( FIG. 4C ) and stored as reference curve 45 for the rotational position φ of the rotating component 11.

[0037] The second variant uses approximate values ​​instead of the first and second measured values. The phase-shifted first measurement curve 43 and the phase-shifted second measurement curve 44 have a phase difference of 90°. The control unit 28 determines first approximate values ​​for several time values ​​from the phase-shifted first measurement curve 43 and second approximate values ​​from the phase-shifted second measurement curve 44. After the determination, a value table with first approximate values, second approximate values, and associated time values ​​is available. The control unit 28 calculates the quotient of the first approximate value and the second approximate value for several time values ​​and applies the arctangent function according to the formula φ = tan − 1 R 1 R 2 on the quotients. The result of the calculations are angle values ​​that depend on time. The angle values ​​are displayed by the control unit 28 over time ( FIG. 4C ) and stored as reference curve 45 for the rotational position φ of the rotating component 11.

[0038] FIGN. 5A , B show the outer contour 23 of the encoder disk 21 in a first variant ( FIG. 5A ) and a second variant ( FIG. 5B ). The first variant shows a sawtooth-shaped outer contour 23 and the second variant a sinusoidal outer contour 23.

[0039] FIG. 5A shows the first variant of the outer contour 23, in which the periods consist of a first functional section 51 and a second functional section 52 The first functional section 51 is monotonically increasing and the second functional section 52 is monotonically decreasing. A transition 53 from the first functional section 51 to the second functional section 52 is non-continuous and a transition 54 from the second functional section 52 to the first functional section 51 is non-continuous.

[0040] The combination of the periods consisting of the monotonically increasing first functional section 51 and the monotonically decreasing second functional section 52 has the advantage over rectangular periods that the rotational position can be determined with greater accuracy. In the monotonically running functional sections 51, 52, a precise determination of the rotational position is possible.

[0041] FIG. 5B shows the second variant of the outer contour 23, in which the periods consist of a first functional section 55 and a second functional section 56 The first functional section 55 is monotonically increasing and the second functional section 56 is monotonically decreasing. A transition 57 from the first functional section 55 to the second functional section 56 is continuous and a transition 58 from the second functional section 56 to the first functional section 55 is continuous.

[0042] The combination of periods consisting of the monotonically increasing first functional section 55 and the monotonically decreasing second functional section 56 has the advantage over rectangular periods that the rotational position can be determined with greater accuracy. In the monotonically increasing functional sections 55, 56, a precise determination of the rotational position is possible. Due to the continuous transitions 57, 58 between the first functional section 55 and the second functional section 56, a determination of the rotational position is also possible at the transitions 57, 58.

Claims

1. Method for determining a reference curve (43) for the rotational position (φ) of a rotary component (11), which is rotatable about an axis of rotation (12), by means of a device (10) comprising an encoder disc (21), which is connected to the rotary component (11) and is rotatable about the axis of rotation (12), the encoder disc being designed as circular and having a periodic outer contour (23) with N periods and a zero point (24), a beam source (25), which emits a measuring beam (26) which is directed onto the outer contour (23) of the encoder disc (21), a sensor unit (27) comprising a first measuring area (29A) and a second measuring area (29B), which is different from the first measuring area (29A), and a control unit (28), which is connected to the sensor unit (27), wherein the periods of the outer contour (23) are made up of a first function portion (51, 55) and a second function portion (52, 56), the first function portion (51, 55) and second function portion (52, 56) following a monotonic progression, one of the first and second function portions increasing monotonically and the other of the first and second function portions decreasing monotonically, the method comprising the following steps: ■ the measuring beam (26), which is directed onto the outer contour (23) of the rotating encoder disc (21) and onto the sensor unit (27), is recorded by the first measuring area (29A) as first measured values (M1.i) and by the second measuring area (29B) as second measured values (M2.j), ■ the first measured values (M1.i) and second measured values (M2.j) are transmitted from the sensor unit (27) to the control unit (28), ■ the first measured values (M1.i) and associated first time values (T1.i) are shown by the control unit (28) as a first measurement curve (41) and the second measured values (M2.j) and associated second time values (T2.j) are shown as a second measurement curve (42), ■ the first measurement curve (41) and second measurement curve (42) are shifted relative to one another by the control unit (28) until there is a phase difference of 90° between a phase-shifted first measurement curve (43) and a phase-shifted second measurement curve (44), ■ the phase-shifted first measurement curve (43) and phase-shifted second measurement curve (44) are used by the control unit (28) to determine first function values (R1) for a number of first time values (T1) and second function values (R2) for a number of second time values (T2) and the arctangent function according to the formula φ = tan − 1 R 1 R 2 is applied to the quotients of the first and second function values (R1, R2) and ■ the calculated function values are shown by the control unit (28) as a progression over time and are stored as a reference curve (45) for the rotational position (φ) of the rotary component (11).

2. Method according to Claim 1, characterized in that the first measured values (M1.i) are used as first function values (R1) and the second measured values (M2.j) are used as second function values (R2).

3. Method according to Claim 1, characterized in that first approximate values are used as first function values (R1) and second approximate values are used as second function values (R2), the first approximate values being determined from the phase-shifted first measurement curve (43) and the second approximate values being determined from the phase-shifted second measurement curve (44).

4. Method according to Claim 1, characterized in that the transition (53, 57) from the first function portion (51, 55) to the second function portion (52, 56) is formed continuously and / or the transition (54, 58) from the second function portion (52, 56) to the first function portion (51, 55) is formed continuously.

5. Method according to Claim 4, characterized in that the first function portion (52) and second function portion (52) form a sine function.

6. Method according to Claim 1, characterized in that the sensor unit (27) has a first sensor element (33A), which comprises the first measuring area (29A), and a second sensor element (33B), which comprises the second measuring area (29B).

7. Method according to Claim 1, characterized in that the sensor unit (27) has a sensor element (31) with a measuring region (32), a first measuring area (29A) and a second measuring area (29B) being integrated in the measuring region (32).