Inductive position sensor

Abstract

A sensor (9) for sensing a rotation angle (22) of a shaft (7, 11) and a torque angle (16), which is dependent on a torque acting on the shaft (7, 11), wherein the shaft (7, 11) is divided into a first shaft section (11), a second shaft section (7) and a torsion element separating the first shaft section (11) and the second shaft section (7), comprising – a coarse track (18), which can be positioned circumferentially around the first shaft section (11) and comprises a coarse-track number, denoted hereafter by the formula symbol A, of coarse-track elements (29) arranged equidistantly in relation to one another; - a fine track (17), which can be positioned circumferentially around the second shaft section (7) and comprises a fine-track number, denoted hereafter by the formula symbol B and greater than the coarse-track number, of fine-track elements (27) arranged equidistantly in relation to one another; and - a sensing device (19), which is set up to sense the rotation angle (22) and the torque angle (16) from an angular position (34) of the coarse track (18) and an angular position (33) of the fine track (17) within a maximum torque-angle range, denoted hereafter by the formula symbol T, and a maximum rotation-angle range (51), denoted hereafter by the formula symbol S; - wherein the coarse-track number and the fine-track number are in a non-integer relationship to one another, characterized in that the coarse-track number and the fine-track number satisfy the following condition: formula (I), where the function gcd() stands for the determination of the greatest common divisor and the formula symbol Θ stands for the degree of a full angle.

Description

[0001] INDUCTIVE POSITION SENSOR

[0002] Description

[0003] The present invention relates to a sensor for detecting a rotation angle of a shaft and a torque angle which is dependent on a torque acting on the shaft, a method using the sensor and a control device for carrying out the method.

[0004] EP 1 081 454 A1 discloses an angle sensor with an oscillator circuit, several receiving coils, and both a coarse track and a fine track in the form of movable inductive coupling elements. The angular position is evaluated using the Vernier algorithm, whereby the coarse and fine tracks must have different pitches. It is essential that the number of periodic repetitions of the elements of the coarse and fine tracks be in a non-integer ratio to each other across the entire measuring range of the angle sensor. However, no specific instructions for selecting the pitch are disclosed.

[0005] The object of the invention is to improve the angle sensor. i

[0006] REPLACEMENT SHEET (RULE 26) The problem is solved by the features of the independent claims. Preferred developments are the subject of the dependent claims.

[0007] According to one aspect of the invention, a sensor for detecting a rotation angle of a shaft and a torque angle which is dependent on a torque acting on the shaft, wherein the shaft is divided into a first shaft section, a second shaft section and a torsion element separating the first shaft section and the second shaft section,

[0008] - a coarse track which can be laid circumferentially around the first shaft section and has a coarse track number of equidistant coarse track elements, designated below by the symbol A;

[0009] - a fine track that can be laid circumferentially around the second shaft section with a number of fine track elements, designated below with the symbol B, arranged equidistant from one another, which is greater than the number of coarse tracks; and

[0010] - a detection device which is designed to detect the angle of rotation and the torque angle from an angular position of the coarse track and an angular position of the fine track within a maximum torque angle range designated hereinafter by the formula symbol T and a maximum rotation angle range designated hereinafter by the formula symbol S;

[0011] - wherein the coarse track number and the fine track number are in a non-integer ratio to each other, characterized in that the coarse track number and the fine track number satisfy the following condition: wherein the function gcd() for the

[0012] Determination of the greatest common divisor and the symbol 0 stands for the degree measure of a full angle (360°).

[0013] Based on the sensor mentioned at the beginning, the motivation behind the specified sensor is to integrate a torque measurement, but to use both the coarse track and the fine track to determine the angle of rotation.

[0014] Based on this motivation, the specified sensor is based on the premise that when a torque acts on the shaft, the coarse and fine tracks are misaligned, thus distorting the angular position detection. While algorithms already exist to correct this distortion, they only work reliably if the torque acting on the shaft complies with an unknown torque angle limit.

[0015] Here, the specified sensor attacks with the idea of ​​bringing the coarse track and the fine track as close as possible to this torque angle limit, which is achieved with the inventive condition.

[0016] In a further development of the specified sensor, the coarse track and the fine track are configured to change an electrical and / or magnetic property of the space depending on their relative angular position, and wherein the detection device for detecting the angular position of the coarse track or the fine track is configured to generate an electrical coarse track signal or fine track signal depending on the electrical and / or magnetic property of the space.

[0017] These signals can be easily processed using information technology to determine both the torque with the aid of a spring stiffness of the torsion element, which is assumed to be known because it can be freely selected, and the angle of rotation.

[0018] In a further development of the specified sensor, the number of fine tracks and the number of coarse tracks have a common divisor. In this way, the maximum measurable torque angle can be maximized. In an additional development of the specified sensor, the detection device is configured to compare the coarse track signal with a value denoted below by the formula symbol E. A electrical coarse gauge signal error and the fine gauge signal with a value indicated below with the symbol E B and wherein the number of coarse tracks and the number of fine tracks are selected such that a value designated below by the symbol E T designated error in the torque angle of the following condition

[0019] EE is sufficient: E f ~±(— +— +C), where any real value can be chosen for the symbol C for an AB.

[0020] In this way, a buffer can be taken into account for measurement errors that occur when measuring the torque. The measurement error E T at constant E A and E B The idea behind setting A and B as small as possible is to choose them as large as possible. The arbitrary real value C can represent a fundamentally unknown value that describes additional measurement errors during use of the sensor.

[0021] In another development of the specified sensor, the maximum angle of rotation range is selected such that it satisfies the following condition: S=±19 - - r, preferably S=±9.5 - -7. gcd(A,ß) gcd(A ,B)

[0022] The maximum achievable unique rotation angle S without the aid of information from a satellite gear is characterized by the fact that it is always less than or equal to a full rotation. It is determined by the following formula: S = — gcd A, B ? )

[0023] From the formula it is clear that in order to achieve a large S it is advantageous to choose A and B so that the greatest common divisor is as small as possible.

[0024] The maximum achievable unique angle of rotation S is characterized by being greater than a full rotation of 360°, typically on the order of several full rotations of ±1000°. Due to direct proportionality, the formula clearly shows that to achieve a large maximum achievable unique angle of rotation S, it is advantageous to choose A and B such that the greatest common factor is as small as possible.

[0025] The scale factors 19 and 9.5 are empirically determined by taking into account the typically expected measurement accuracy of the coarse and fine track signals, as well as the satellite gear.

[0026] In this way, the function for detecting the angle of rotation of the specified sensor is achieved as specified in the standard

[0027] ISO 26262 (2018) Road vehicles - "Functional safety. International Organization for Standardization" specified Automotive Safety Integrity Levels (ASIL). The ISO 26262 standard defines four Automotive Safety Integrity Levels (ASIL A to D), with ASIL D being the highest safety level. With the condition When using a signal from the satellite gear with an assumed SPFM (Single Point Fault Metric) of >97%, the safety level ASIL C can be achieved, while with the condition and when using a signal from the satellite

[0028] Gear with an assumed SPFM of >98%, with the help of additional diagnostics even the safety level ASIL D can be achieved.

[0029] In another development of the specified sensor, the maximum torque angle range is selected such that it meets the following condition:

[0030] In order to achieve the largest possible available unique torque angle range T, it is clear from the formula that A and B must be selected such that the quotient of the greatest common divisor of A and B and the product of A and B should be as large as possible. In yet another development of the specified sensor, the number of coarse tracks and the number of fine tracks are selected from: A=9 and B=6, or A=10 and B=6, or A=12 and B=8, or A=12 and B=9, or A=15 and B=6, or A=15 and B=10, or A=18 and B=12.

[0031] For this selection of coarse and fine track numbers, the best results can be achieved for the measurable torque angle range T and the measurable rotation angle range S (or SM with the aid of the satellite gear). The competing requirements from the system level of T, SM, and E Tto the selection of A and B, require selecting the most advantageous combination of A and B for the respective application.

[0032] For the selection A=9 and B=6, a torque angle range T of ±10°, an angle range SM of ±1140° with a torque angle error E T of ±0.16°.

[0033] For the selection A=10 and B=6, a torque angle range T of ±6°, an angle range SM of ±1710° with a torque angle error E T on ±0.15° cover.

[0034] For the selection A=12 and B=8, a torque angle range T of ±7.5°, an angle range SM of ±855° with a torque angle error E T of ±0.12°.

[0035] For the selection A=12 and B=9, a torque angle range T of ±5°, an angle range SM of ±1140° with a torque angle error E T of ±0.12°.

[0036] For the selection A=15 and B=6, a torque angle range T of ±6°, an angle range SM of ±1140° with a torque angle error E T of ±0.14°. For selection A=15 and B=10, a torque angle range T of ±6°, an angle range SM of ±684° with a torque angle error E T of ±0.10°.

[0037] For the selection A=18 and B=12, a torque angle range T of ±5°, an angle range SM of ±570° with a torque angle error E T of ±0.09°.

[0038] From this selection, the combination A=12 and B=9 has proven to be the most suitable in the field of steering angle technology in vehicles.

[0039] According to a further aspect of the invention, a method for detecting a rotation angle of a shaft with one of the said sensors comprises the steps:

[0040] - Detecting the angular position of the coarse track;

[0041] - Detecting the angular position of the fine track;

[0042] - Determine, based on the detected angular position of the coarse track, a number of full periods that the angular position of the fine track has already passed through;

[0043] - Correct the angular position of the fine track based on the determined number of full periods of the angular position of the fine track.

[0044] In a further training, the specified procedure includes the following steps:

[0045] - detecting an angular position of a satellite gear; and

[0046] - Determine based on the detected angular position of the

[0047] satellite gear a number of full periods that the angular position of the fine track has already passed through; and

[0048] - Correct the angular position of the fine track based on the determined number of full periods of the angular position of the fine track.

[0049] According to a further aspect of the invention, a control device is configured to carry out one of the specified methods. In a further development of the specified device, the specified device comprises a memory and a processor. The specified method is stored in the memory in the form of a computer program, and the processor is provided to execute the method when the computer program is loaded from the memory into the processor.

[0050] According to a further aspect of the invention, a computer program comprises program code means for carrying out all steps of the specified method when the computer program is executed on an electronic device or one of the specified devices.

[0051] According to a further aspect of the invention, a computer program product contains a program code which is stored on a computer-readable data carrier and which, when executed on a data processing device, carries out the specified method.

[0052] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become more clearly understood in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings.

[0053] Fig. 1 is a structural view of a vehicle with a sensor for detecting a rotation angle and a torque,

[0054] Fig. 2 is a structural view of the sensor for detecting a rotation angle and a torque from Fig. 1,

[0055] Fig. 3 is a structogram to illustrate a determination of the angle of rotation in the sensor of Fig. 2, Fig. 4 is a diagram of the time course of a coarse track signal and a fine track signal in the sensor of Figs. 2 and 3,

[0056] Fig. 5 is a diagram of the time course of a resulting position signal from the coarse track signal and the fine track signal of Fig. 4,

[0057] Fig. 6 is a diagram of the time course of another position signal in the sensor of Figs. 2 and 3 and the resulting position signal of Fig. 5, and

[0058] Fig. 7 is a diagram of the time course of a rotation angle signal from the further position signal in the sensor of Figs. 2 and 3 and the resulting position signal of Fig. 6.

[0059] In the figures, identical technical elements are provided with identical reference symbols and are described only once. The figures are purely schematic and, above all, do not represent the actual geometric relationships.

[0060] Reference is made to Fig. 1, which schematically shows a perspective view of a vehicle 1 with a steering system 2.

[0061] In the present embodiment, the vehicle 1 comprises a chassis 5 supported on two front wheels 3 and two rear wheels 4. The front wheels 3 can be turned via the steering system 2 so that the vehicle 1 can be driven around a curve.

[0062] The steering system 2 comprises a steering wheel 6 mounted on a first steering shaft 7, which in turn is arranged to rotate about a rotational axis 8. The first steering shaft 7 is guided into a sensor 9 for detecting a position, here in the form of an angular position, and is connected there in a manner not further specified to a torsion element 10. The torsion element has a freely selectable spring rate, which should preferably be constant and linear, and thus converts an applied torque into a measurable torque angle. Adjoining this torsion element 10 on the side opposite the first steering shaft 7 on the rotational axis 8 is a second steering shaft 11, which in turn ends in a steering gear 12.If the steering wheel 6 is turned with a torque in the form of a steering torque 13, the steering torque 13 is transmitted accordingly via the steering shafts 7, 11 to the steering gear 12, which in response thereto turns the front wheels 3 with a wheel angle 14 for cornering.

[0063] The steering process is assisted by an auxiliary motor 15, which also rotates the second steering shaft 11. For this purpose, the steering torque 13 is derived from a rotation angle difference 16 between the first steering shaft 7 and the second steering shaft 11, which is detected by the inductive sensor 9. The auxiliary motor 15 then rotates the second steering shaft 11 depending, among other things, on the detected steering torque 13.

[0064] To detect the aforementioned rotation angle difference 16 and thus the steering torque 13, the sensor 9 comprises a fine track 17 connected to the first steering shaft 7 and a coarse track 18 connected to the second steering shaft 11, which will be discussed in more detail later. The sensor 9 further comprises a measuring circuit 19 that is fixedly connected to the vehicle 1 and detects an angular position of the fine track 17 and an angular position of the coarse track 18 and determines the rotation angle difference 16 from this. This will also be discussed in more detail later. Based on the rotation angle difference 16, a control device 20 can then control the auxiliary motor 15 with a suitable control signal 21.

[0065] In addition to the rotation angle difference 16, the measuring circuit 19 of the sensor 9 also determines a rotation angle 22 of the entire steering shaft 7, 11, for use, for example, in a vehicle dynamics system. The structure of the sensor 9, which forms the basis for the explanation of the present embodiment, is explained in more detail below with reference to Fig. 2.

[0066] While the coarse track 18 is non-rotatably attached directly to the second steering shaft 11, the fine track 17 is held on the first steering shaft 7 via a support sleeve 23. A drive gear 24 is also non-rotatably attached to this support sleeve 23, which drives an output gear 25 for a multi-angle detection device 26 in a manner to be described below.

[0067] In the present embodiment, the fine-gauge 17 is designed as an impeller wheel with a fine-gauge number of fine-gauge vanes 27 made of metal. The individual fine-gauge vanes 27 are distributed equidistantly in the circumferential direction around the first steering shaft 7 and are held on a fine-gauge carrier 28. For the purposes of the following explanations, a fine-gauge number of twelve fine-gauge vanes 27 will be assumed, although significantly more fine-gauge vanes 27 are shown in Fig. 2.

[0068] Analogously, the coarse track 18 in the present embodiment is also designed as an impeller with a coarse track number of coarse track vanes 29 made of metal. The individual coarse track vanes 29 are also held on a coarse track carrier 30, distributed equidistantly in the circumferential direction around the first steering shaft 7, similar to the fine track 17. For the following explanations, a coarse track number of eight coarse track vanes 29 will be assumed. Not all of these coarse track vanes 29 are visible in the perspective of Fig. 2.

[0069] Using the coarse-gauge vane 29 and the fine-gauge vane 27, the measuring circuit 19 can determine the angle of rotation 22. For this purpose, the measuring circuit 19 can be designed as described in EP 3 865 824 A1.

[0070] The measuring circuit 19 has a fine track side 31 directed toward the fine track vanes 27 and a coarse track side 32 directed toward the coarse track vanes 29. On each side of the measuring circuit 19, a transmitting coil (not shown) exciting a preferably high-frequency magnetic field and at least one receiving coil (not shown) in which a voltage is induced by the magnetic field are arranged. On the fine track side 31, a fine track signal 33 shown in Fig. 3 is thus excited in the corresponding receiving coil, while on the coarse track side 32, a coarse track signal 34 shown in Fig. 3 is excited in the corresponding receiving coil.

[0071] In this configuration of the measuring circuit 19, the vanes 27, 29 disrupt the magnetic field generated by the respective transmitting coil, causing the fine track signal 33 and the coarse track signal 34 to change depending on the rotation angle of the respective track 17, 19. This basic configuration can be expanded, for example, to make the measuring system more robust against measurement errors. Such an expansion is discussed in the previously cited EP 3 865 824 A1. However, such expansions are not essential for understanding the present embodiment.

[0072] As a result, in order to understand the embodiment, it is only important that the wings 27, 29 of the tracks 17, 18 provide track signals 33, 34 which change periodically with the angular position of the respective track 17, 18.

[0073] In addition to the track signals 33, 34, the multi-angle detection device 26 also outputs a magnetic angle signal 35 shown in Fig. 3. This magnetic angle signal 35 is generated in a magnetic sensor element 37 based on a radially magnetized magnet 36, which is arranged on the side of the output gear 25 facing the circuit board 19 and is rotated by the output gear 25 above the magnetic sensor element 37.

[0074] The rotation angle 22 of the entire steering shaft 7, 11 is then calculated on the circuit board 19 from the track signals 33, 34 and the magnetic angle signal 35 and output via an output interface 38. This calculation is discussed in detail below with reference to Figs. 3 to 7.

[0075] First, the individual signals 33 to 35 are converted into sawtooth signals in corresponding conversion devices, so that a coarse-gauge sawtooth signal 39, a fine-gauge sawtooth signal 40 and a magnetic sawtooth signal 41 are present.

[0076] The coarse sawtooth signal 39 and the fine sawtooth signal 40 are then combined in a combining device based on a suitable Vernier algorithm to form an intermediate angle signal 42.

[0077] This combination will be explained in more detail with reference to Figs. 4 and 5, in which the signal values ​​43 of the individual signals are qualitatively plotted against the angle of rotation 22 to be measured.

[0078] The sawtooth signals 39, 40 are generated in such a way that their respective signal value 43 increases directly proportionally to the angle of rotation 22 with a proportionality factor of one.

[0079] Based on the above mentioned number of fine tracks of

[0080] With 12 fine-track vanes and a coarse-track number of 8 coarse-track vanes, the fine-track sawtooth signal 40 has a fine-track period length 44 of 30°, while the coarse-track sawtooth signal 39 has a coarse-track period length 45 of 45°. Since the lowest common multiple of these two period lengths is 90°, the intermediate angle signal 42 can be measured from these two sawtooth track signals 39, 40 over an intermediate angle period length 46 of 90°.

[0081] The Bezout coefficients of a corresponding linear combination 50 of the fine-track sawtooth signal 40 and the coarse-track sawtooth signal 39 to form the intermediate angle signal 42 are 3 for the fine-track sawtooth signal 40 and 2 for the coarse-track sawtooth signal 39, so that the intermediate angle signal 42 can be composed of this linear combination. If the intermediate angle signal 42 is less than or equal to 0, the linear combination may need to be subjected to the intermediate angle period length 46. The resulting intermediate angle signal 42 is shown in Fig. 4.

[0082] However, the intermediate angle signal 42 can be corrupted, particularly if a torque is applied to the entire steering shaft 7, 11. This would lead to measurement errors. To avoid these measurement errors, a modulo division 47 is applied to the intermediate angle signal 42, the divisor of which is the fine-track sawtooth signal 40. The quotient 48 of this modulo division 47 is then applied to the fine-track sawtooth signal 40, and the remainder of the modulo division 47 is discarded. If the coarse-track sawtooth signal 39 is therefore shifted relative to the fine-track sawtooth signal 40 and the intermediate angle signal 42 is thus subject to an error, this error is filtered out using the method described above. It should be noted that the track 17, 18 of the sawtooth signal 39, 40, which is used as a basis for determining the corresponding corrected intermediate angle signal 49, should be arranged on the side facing the steering wheel 6 in order to detect the steering angle 13 without errors.Although the coarse-gauge sawtooth signal 39 could in principle also be used for the previously determined correction method, the fine-gauge sawtooth signal 40 has a higher resolution and is therefore suitable for the correction.

[0083] Finally, the final rotation angle 22 is determined in another linear combination 50, this time from the corrected intermediate angle signal 49 and the magnetic sawtooth signal 41. If all of the previously described sawtooth signals are generated such that the signal values ​​43 are directly proportional to the rotation angle 22 with the proportionality factor 1, the rotation angle 22 can be read directly from the result of the second linear combination, as shown in Fig. 7. The rotation angle 22 is reliably measured here in an angular range 51 between ±855°.

Claims

Patent claims 1. Sensor (9) for detecting a rotation angle (22) of a shaft (7, 11) and a torque angle (16) which is dependent on a torque acting on the shaft (7, 11), wherein the shaft (7, 11) is divided into a first shaft section (11), a second shaft section (7) and a torsion element separating the first shaft section (11) and the second shaft section (7), comprising - a coarse track (18) which can be laid circumferentially around the first shaft section (11) and has a coarse track number, designated below by the formula symbol B, of coarse track elements (29) arranged equidistant from one another; - a fine track (17) which can be laid circumferentially around the second shaft section (7) and has a number of fine track elements (27) arranged equidistant from one another, designated below by the symbol A, which is greater than the number of coarse tracks; and - a detection device (19) which is designed to detect the angle of rotation (22) and the torque angle (16) from an angular position (34) of the coarse track (18) and an angular position (33) of the fine track (17) within a maximum torque angle range designated hereinafter by the formula symbol T and a maximum rotation angle range (51) designated hereinafter by the formula symbol S; - wherein the number of coarse tracks and the number of fine tracks are in a non-integer ratio to each other, characterized in that the number of coarse tracks and the number of fine tracks satisfy the following condition: where the function gcd() stands for the determination of the greatest common divisor and the symbol 0 stands for the degree measure of a full angle. 16 REVISED SHEET (RULE 91) ISA / EP 2. Sensor (9) according to claim 1, wherein the coarse track number and the fine track number have a common divisor.

3. Sensor (9) according to claim 1 or 2, wherein the coarse track (18) and the fine track (17) are configured to change an electrical and / or magnetic property of the space depending on their angular position (34, 33), and wherein the detection device (18) for detecting the angular position (34, 33) of the coarse track (18) or the fine track (17) is configured to generate an electrical coarse track signal (39) or fine track signal (40) dependent on the electrical and / or magnetic property of the space.

4. Sensor (9) according to claim 3, wherein the detection device (19) is arranged to compare the coarse track signal (39) with a value designated below by the formula symbol E A electrical coarse gauge signal error and the fine gauge signal (40) with a value hereinafter designated by the symbol E Band wherein the number of coarse tracks and the number of fine tracks are selected such that a value designated below by the symbol E T designated error in the torque angle (16) satisfies the following condition: where the symbol C can be chosen to be any real value.

5. Sensor (9) according to one of the preceding claims, wherein the maximum rotation angle range (51) is selected such that it satisfies the following condition: S=±19 - preferably S=±9.5 - - -. gcd(A,B) gcd(A,B) 6. Sensor (9) according to one of the preceding claims, wherein the maximum torque angle range (51) is selected such that it satisfies the following condition:

7. Sensor (9) according to one of the preceding claims, wherein the Coarse track number and fine track number is selected from: - A=9 and B=6, or - A=10 and B=6, or - A=12 and B=8, or - A=12 and B=9, or - A=15 and B=6, or - A=15 and B=10, or - A=18 and B=12.

8. A method for detecting a rotation angle (22) of a shaft (7, 11) with a sensor (9) according to one of the preceding claims, comprising: - detecting the angular position (34) of the coarse track (18); - detecting the angular position (33) of the fine track (17); - Determining, based on the detected angular position (34) of the coarse track (18), a number of full periods (44) that the angular position (33) of the fine track (17) has already passed through; and - Correcting the angular position (33) of the fine track (17) based on the determined number of full periods (44) of the angular position (33) of the fine track (17).

9. The method according to claim 8, wherein, in order to correct the angular position (33) of the fine track (17), the angular position (33) of the fine track (17) is added to the determined number of full periods (44).

10. Control device (19) for carrying out a method according to one of the preceding claims.

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