The rotation angle of the steering shaft is determined by three gears.

Abstract

The present invention relates to a method for determining the rotation angle (E) of a shaft (2). In order to improve the accuracy of determination over a larger predetermined angle range compared with the prior art, the following steps are provided: - detecting the corresponding rotation angles (W1, W2, W3) of three gears (Z1, Z2, Z3) of a gear assembly, wherein the three gears (Z1, Z2, Z3) with different numbers of teeth (z1, z2, z3) directly mesh with the gear ring (10) of the steering shaft (2); and - determining the rotation angle (E) of the shaft (2) based on the corresponding rotation angles (W1, W2, W3) of the three gears (Z1, Z2, Z3) according to a predetermined extraction rule, wherein the rotation angle (E) of the shaft (2) is explicitly defined by all the corresponding rotation angles (W1, W2, W3) within a predetermined angle range.

Description

Technical Field

[0001] This invention relates to a method for determining the rotation angle of a steering shaft, wherein the rotation angle of the steering shaft is determined from the corresponding rotation angles of a plurality of gears. Other aspects of the invention relate to a control unit and a measuring device for determining the rotation angle of a steering shaft. A fourth aspect of the invention relates to a motor vehicle having said a shaft. Background Technology

[0002] Methods for determining the rotation angle of a steering shaft are known in the prior art. For example, a primary gear connected to the steering shaft drives two secondary gears with different numbers of teeth. The corresponding rotation angles of the two secondary gears can be detected using appropriate angle sensors. From the two rotation angles of the secondary gears, the rotation angle of the steering shaft can be determined separately in multiple rotations using the Nonius principle. A similar device is known, for example, from FR 269 7081A1.

[0003] For example, z1 and z2 are the corresponding number of teeth of the secondary gears Z1 and Z2, where z1 is less than z2, and z1 and z2 are coprime. The number of teeth of the primary gear corresponds to l. The detectable angle range of the shaft in this case can be, for example, z1·z2·360÷l. The larger z1 and z2 are, the larger the detectable angle range, but the angle sensor must be more accurate to avoid a decrease in precision. If g1 is the precision of the first angle sensor S1 that detects the movement of the secondary gear Z1, then the total precision G1 of the rotation angle of the steering shaft is obtained by the formula G1=g1·z1÷l. From the formula, it can be seen that z1÷l, the detectable angle range increases as the precision decreases. This similarly applies to the secondary gear Z2.

[0004] EP 2 743 662 A1 provides a device for a motor vehicle designed to precisely determine the absolute rotation angle of a steering shaft, even when it involves more than one full revolution. Here, a first assembly comprising two gears forms a speed sensor, and a second assembly comprising one gear is used to precisely determine the rotation angle.

[0005] The existing technology has the following disadvantages: the size of the angle range within which the rotation angle of the steering shaft is clearly defined is mutually constrained by the accuracy of the determination of the rotation angle of the steering shaft. Summary of the Invention

[0006] The object of this invention is to determine the rotation angle of the steering shaft with improved accuracy over a larger predetermined angle range compared to the prior art.

[0007] In this method for determining the rotation angle of the steering shaft, the corresponding rotation angles of the three gears of the gear assembly are detected in the first step, wherein the three gears, each with a different number of teeth, directly mesh with the gear ring of the shaft. For example, the corresponding rotation angles are detected using corresponding angle sensors. Specifically, three rotation angles are detected for each of the three gears. In particular, due to the different number of teeth, the three gears rotate at different angular velocities during the rotation of the shaft. "Direct meshing" specifically refers to the direct meshing of the corresponding teeth of each of the three gears with the teeth of the gear ring.

[0008] In the second step, the rotation angle of the steering shaft is determined based on the corresponding rotation angles of the three gears according to a predetermined extraction rule, wherein the rotation angle of the steering shaft is explicitly limited to a predetermined angle range by all the corresponding rotation angles. The predetermined angle range specifically includes multiple full revolutions of the shaft. The three corresponding rotation angles of the three gears can be considered as tuples, particularly triplets. The rotation angle of the steering shaft can be explicitly assigned to the shaft within the predetermined angle range by using all the corresponding rotation angles or by using the tuples. The method of assigning the rotation angle of the steering shaft based on all the corresponding rotation angles and / or based on the tuples can, for example, be based on a value table. The predetermined extraction rule can therefore include: determining the rotation angle of the steering shaft from a value table based on all the corresponding rotation angles.

[0009] The rotation angle of the steering shaft can be measured over multiple revolutions. For example, the rotation angle of the steering shaft is between 0 degrees and multiples of 360 degrees, such as 3600 degrees, which corresponds to 10 full revolutions. The corresponding rotation angles of the three gears are particularly related to the current rotational speed of the respective gear. Therefore, the rotation angles of the three gears are preferably always within the range of 0 degrees and 360 degrees.

[0010] One improved scheme specifies that the predetermined extraction rule includes selecting two different gear pairs from three gears, wherein the first gear of the three gears is included in two gear pairs. Here, the complete number of revolutions of the first gear can be clearly determined within the corresponding partial angle range by means of the corresponding rotation angles of the two gear pairs. For example, the first gear pair in the two gear pairs includes the first and second gears of the three gears, and the second gear pair in the two gear pairs includes the first and third gears of the three gears. The complete number of revolutions of the first gear within the first partial angle range of the first gear pair can be clearly determined by the first rotation angle of the first gear and the second rotation angle of the second gear. The complete number of revolutions of the first gear within the second partial angle range of the second gear pair can be clearly determined by the first rotation angle of the first gear and the third rotation angle of the third gear. By selecting two gear pairs, the complete number of revolutions of the first gear can be determined particularly easily because, in this case, for the corresponding gear pairs, the extraction rule known in the art for determining the rotation angle of the steering shaft based on two gears can be determined. The complete number of revolutions of the gear specifically indicates, in each case, how many 360-degree revolutions the corresponding gear has made from the zero position. For example, the number of complete turns of a gear corresponds to the absolute angle of the corresponding gear, which in particular represents the angle of the gear relative to the zero position in multiple turns divided by 360 degrees.

[0011] An improved scheme specifies that a first value for the total number of revolutions of the first gear is determined from the corresponding rotation angles of the gears in the first gear pair of two gear pairs, and a second value for the total number of revolutions of the first gear is determined from the corresponding rotation angles of the gears in the second gear pair of two gear pairs. The first and second values ​​for the total number of revolutions of the first gear can be equal to or different from each other. In particular, the first and second values ​​deviate from each other only when the total number of revolutions of the first gear is outside one or both of the corresponding partial angle ranges. In this case, the total number of revolutions of the first gear cannot be explicitly determined solely by the gear pair. In particular, the first value for the total number of revolutions of the first gear can be determined from the first and second rotation angles. In particular, the second value for the total number of revolutions of the first gear can be determined from the first and third rotation angles.

[0012] An improved approach specifies that, in each case, a first value and a second value for the complete number of turns of the first gear are determined using the von Neumann principle. Specifically, the first value for the complete number of turns of the first gear in the first gear pair is determined using the von Neumann principle. Preferably, the second value for the complete number of turns of the first gear in the second gear pair is determined using the von Neumann principle. The von Neumann principle provides a simple and unique extraction rule for determining the first and second values ​​for the complete number of turns of the first gear for the corresponding gear pair.

[0013] An improved scheme specifies that if a first value is less than a second value, a first predetermined summation value is added to the first value; if the second value is less than the first value, a second predetermined summation value is added to the second value, and corresponding predetermined values ​​are iteratively added to the first and second values ​​until the first and second values ​​correspond. Preferably, the first / second values ​​are changed by adding the first / second predetermined summation values ​​in an iterative loop. Preferably, the iterative loop specifies that the corresponding predetermined summation value is added to the smaller of the two values. Specifically, in each iteration step, it is checked which of the two values ​​in the current iteration step is less than the other. The iteration loop can be stopped as long as the first and second values ​​correspond.

[0014] One improvement specifies that the first and second predetermined summation values ​​relate to the span of a corresponding partial angular range within which the complete number of rotations of the first gear can be clearly determined by the first and second gear pairs, respectively. Specifically, the first summation value represents the span of a partial angular range within which the complete number of rotations of the first gear can be clearly determined by the first gear pair. Alternatively or additionally, the second predetermined summation value indicates the span of a partial angular range within which the complete number of rotations of the first gear can be clearly determined by the second gear pair. The corresponding predetermined summation value preferably corresponds to the complete number of rotations of the first gear that can be clearly performed by the first gear within a partial angular range of the first gear pair. For example, the second predetermined summation value corresponds to the complete number of rotations of the first gear that can be clearly performed by the first gear within a partial angular range of the second gear pair.

[0015] An improved approach specifies that the first and / or second values ​​are defined as the complete number of revolutions of the first gear only when they correspond. For example, after determining the corresponding values ​​from the corresponding rotation angles of the gears in the corresponding gear pair, the first and second values ​​directly correspond. In this case, the complete number of revolutions of the first gear can be within the corresponding partial angle range of the two gear pairs. For example, the first and second values ​​correspond after iterative addition of corresponding predetermined summation values. In both cases, the first and / or second values ​​of the complete number of revolutions of the first gear can correspond to the actual complete number of revolutions of the first gear. Therefore, the complete number of revolutions of the first gear is explicitly determined from the first gear pair and the second gear pair.

[0016] One improved method specifies combining the rotation angle of the first gear with the number of complete revolutions of the first gear to obtain the total angle of the first gear, and then determining the rotation angle of the steering shaft from the total angle of the first gear. For example, the number of complete revolutions of the first gear is multiplied by 360 degrees, and then the rotation angles of the first gear are added together to form the total angle of the first gear. The total angle of the first gear can be in a predetermined proportion relative to the rotation angle of the steering shaft. Using the predetermined ratio, the rotation angle of the steering shaft can be determined from the total angle of the first gear.

[0017] An improved embodiment of the present invention specifies that the gear with the smallest number of teeth among the three gears is selected as the first gear. Specifically, the gear with the smallest number of teeth relative to the other gears among the three gears is selected as the first gear. Specifically, the second and third gears each have a number of teeth greater than that of the first gear.

[0018] One improvement specifies that the reasonableness of the steering shaft's rotation angle is verified by comparing the determined rotation angle of the steering shaft with a predetermined rotation angle range, wherein the predetermined rotation angle range is at least twice as large as the predetermined rotation angle range within which the steering shaft can move. In other embodiments, the predetermined angle range may be at least 3, 4, 5, 8, 10, 15, 20, or 50 times larger than the predetermined rotation angle range within which the shaft can move. In other words, the angle range within which the steering shaft's rotation angle is explicitly defined by means of all the corresponding rotation angles of the three gears can be at least a corresponding multiple larger than the predetermined rotation angle range within which the shaft can actually move. If the determined rotation angle of the steering shaft is outside the predetermined rotation angle range, it can be inferred that the steering shaft's rotation angle has been incorrectly determined. In this case, the determined rotation angle of the steering shaft is unreasonable. The larger the multiple by which the predetermined angle range is greater than the predetermined rotation angle range, the greater the likelihood that the determined rotation angle of the steering shaft is outside the predetermined rotation angle range in the case of an incorrect determination of the steering shaft's rotation angle. This allows for particularly reliable identification of errors in the determination of the steering shaft's rotation angle. Compared to existing technologies, this makes it possible for the first time to identify reasonableness by a larger range of predetermined angles, where the rotation angle of the steering shaft is clearly measurable.

[0019] The invention also includes a control unit for determining the rotation angle of the steering shaft, the control unit being configured to perform the aforementioned method. Specifically, the control unit has a receiver unit for detecting the corresponding rotation angles of the three gears from three angle sensors.

[0020] A third aspect of the invention relates to a measuring device for determining the rotation angle of a steering shaft. The measuring device includes: a gear ring arrangeable on the shaft; a gear assembly comprising three gears mechanically operably connected to the gear ring at different gear ratios; and two angle sensors for detecting the respective rotation angles of the first and second gears of the three gears.

[0021] To accurately determine the rotation angle of the steering shaft within a wider predetermined angle range compared to existing technologies, the measuring device includes a third angle sensor for detecting the third rotation angle of the third gear among the three gears. Furthermore, each of the three gears, with different numbers of teeth, directly meshes with the gear ring.

[0022] An improved version of the measuring device specifies that it further includes the aforementioned control unit. The angle sensor can be designed to transmit the detected rotation angle to the receiver unit of the control unit.

[0023] The measuring device can be part of the steering system, wherein a gear ring is arranged on the steering shaft of the steering system. The gear ring particularly has external teeth. Preferably, the gear ring is arranged on the steering shaft in a rotationally symmetrical manner with respect to the axis of rotation of the steering shaft. In particular, the steering shaft is formed as the steering shaft of the vehicle. In this case, the steering angle of the vehicle can be determined from the rotation angle of the steering shaft.

[0024] The measuring device may be part of a driver assistance system configured to perform a method for determining the rotation angle of a steering shaft of the type described above. For example, a driver assistance system may include Electronic Stability Program, or ESP for short, which requires the rotation angle of the vehicle's steering shaft as an input variable.

[0025] Furthermore, the present invention includes a motor vehicle having the aforementioned measuring device. Specifically, the steering shaft is formed as the steering shaft of the motor vehicle. The rotation angle of the steering shaft is preferably related to the steering angle of the motor vehicle's wheels. In this case, the steering angle of the wheels can be inferred from the rotation angle of the steering shaft.

[0026] Other features of the invention will be derived from the accompanying drawings and description. Features and combinations of features referenced in the above description, as well as features and combinations of features shown separately in and / or in the accompanying drawings, can be used not only in the correspondingly specified combinations, but also in other combinations or individually, without departing from the scope of the invention. Therefore, embodiments of the invention that arise and can be produced by separate combinations of features of the discussed embodiments, but are not explicitly shown and discussed in the drawings, should also be considered as included and disclosed. Attached Figure Description

[0027] In the attached diagram:

[0028] Figure 1 A vehicle with a steering shaft and a measuring device for determining the rotation angle of the steering shaft is shown in a schematic side view;

[0029] Figure 2 The measuring device is shown in the cross-section through the steering shaft;

[0030] Figure 3 The diagram shows multiple actual rotation angles of the steering shaft, plotted as curves of the rotation angles of the steering shaft determined by three gears; and

[0031] Figure 4 An exemplary flowchart is shown for a method of determining the rotation angle of a steering shaft. Detailed Implementation

[0032] Figure 1 A vehicle 3, particularly a motor vehicle, preferably a motor car, such as a passenger car or a heavy-duty truck, is shown in a schematic side view. The vehicle 3 currently has one or more steering wheels 30, particularly the two front wheels. The steering angle of the steering wheels 34 or 30 can be controlled, in particular, by a steering mechanism 7. In this case, the steering mechanism 7 includes a steering wheel 6 that can be rotated by the driver of the vehicle 3 and a steering shaft 2 that is currently formed as the steering axis of the vehicle 3. At the steering shaft 2, a measuring device 1 is arranged for determining the rotation angle E of the steering shaft 2. The rotation angle E of the steering shaft 2 can be directly related to the steering angle of the steering wheels 30, for example, by a scaling factor. In this case, the measuring device 1 also includes a control unit 4, which is designed to perform the method for determining the rotation angle E of the steering shaft 2. The measuring device 1 may include a driver assistance system 5. For example, the driver assistance system 5 includes another control unit 8 for providing driver assistance functions. Driver assistance features include Electronic Stability Program (ESP), servo steering system, or active steering system, which provide steering assistance in a manner that depends on the rotation angle E of steering axis 2.

[0033] Figure 2 The measuring device 1 is shown in cross-section through shaft 2. Figure 2 Control unit 4 is not shown. A gear ring 10 is arranged on shaft 2. The gear ring 10 is designed as a gear, preferably as a spur gear. The gear ring 10 has teeth on its radially outer side, wherein the number of teeth l of the gear ring 10 represents the number of teeth in the gear ring 10. The gear ring 10 meshes directly with three other gears Z1, Z2, Z3 in this case. Each of the three gears Z1, Z2, Z3 has a corresponding number of teeth on its radially outer side. In particular, the three gears Z1, Z2, Z3 are designed as spur gears. The three gears Z1, Z2, Z3 mesh directly with the gear ring 10, wherein "directly" specifically means that at least one corresponding tooth of each of the three gears Z1, Z2, Z3 meshes with a corresponding tooth of the gear ring 10. Preferably, the three gears Z1, Z2, Z3 mesh with the gear ring 10 independently of each other. The three gears Z1, Z2, Z3 together with the gear ring 10 form a gear assembly 11.

[0034] Each of the three gears Z1, Z2, Z3 is assigned a corresponding angle sensor S1, S2, S3. For example, angle sensors S1, S2, S3 are arranged at the corresponding gear Z1, Z2, Z3. The first angle sensor S1 can be designed to detect the first rotation angle W1 of the first gear Z1. The second angle sensor S2 can be designed to detect the second rotation angle W2 of the second gear Z2. The third angle sensor S3 can be designed to detect the third rotation angle W3 of the third gear Z3. The rotation angle E of the steering shaft 2 is explicitly defined by the corresponding rotation angles W1, W2, W3 of the three gears Z1, Z2, Z3. These three rotation angles W1, W2, W3 specifically represent the current angle of the corresponding gear Z1, Z2, Z3 relative to the zero position. In this case, the values ​​of the three rotation angles W1, W2, W3 range specifically from 0 degrees to 360 degrees. Conversely, the rotation angle E of the steering shaft 2 is determined over multiple full revolutions. Figure 2 The rotation angle E of the steering shaft 2 shown can correspond to, for example, 30°, 390°, or 750°. The three gears Z1, Z2, and Z3 have different numbers of teeth. In other words, each of the three gears Z1, Z2, and Z3 preferably has a different number of teeth. For example, the number of teeth z2 of the second gear Z2 is greater than the number of teeth z1 of the first gear Z1. For example, the number of teeth z3 of the third gear Z3 is greater than the number of teeth z2 of the second gear Z2.

[0035] Figure 4 A flowchart illustrates an exemplary sequence of method steps for determining the rotation angle E of the steering shaft 2. The control unit 4 is preferably configured to perform one, more, or all of the method steps discussed below. In step V0, two different gear pairs (Z1, Z2 and Z1, Z3) are selected from the three gears Z1, Z2, Z3. In this case, the first gear Z1 is particularly included in two gear pairs (Z1, Z2) and (Z1, Z3). For example, the first gear pair (Z1, Z2) includes the first gear Z1 and the second gear Z2. For example, the second gear pair (Z1, Z3) includes the first gear Z1 and the third gear Z3.

[0036] In step V1, specifically using the Nonius algorithm, the complete number of revolutions U1 of the first gear Z1 in the first gear pair (Z1, Z2) is determined. For this, the following formula 1 can be applied, where A1 represents the complete number of revolutions A1 of the second gear Z2 in the first gear pair (Z1, Z2):

[0037] z1·U1-z2·A1=(z2·W2-z1·W1)÷360°Formula 1

[0038] For Equation 1 above, a solution greater than 0 and less than z2 is sought. Under this auxiliary condition, Equation 1 can be clearly solved despite the presence of two unknowns (U1, A1). In particular, if the complete number of revolutions U1 of the first gear Z1 is greater than 0 and less than z2, it can be clearly determined from the first gear pair (Z1, Z2). The complete number of revolutions of gears Z1, Z2, and Z3 specifically indicates how many 360-degree revolutions the corresponding gear has made from the zero position in each case. For example, the complete number of revolutions of a gear corresponds to the absolute angle of the corresponding gear, which specifically represents the angle of the corresponding gear relative to the zero position over multiple revolutions divided by 360 degrees. Using Equation 1, the complete number of revolutions can be determined, for example, within a partial angular range corresponding to z2·360°.

[0039] In step V2, specifically using the Nonius algorithm, the complete number of revolutions U2 of the first gear Z1 from the second gear pair (Z1, Z2) is determined. For this, the following formula 2 can be applied, where A2 represents the complete number of revolutions A2 of the third gear Z3 in the second gear pair (Z1, Z3):

[0040] z1·U2-z3·A2=(z3·W3-z1·W1)÷360 formula 2

[0041] For Equation 2 above, we seek a solution that is greater than 0 and less than z3. Under this auxiliary condition, Equation 2 can be clearly solved even though it involves two unknowns (U2, A2). In particular, if the complete number of revolutions U2 of the first gear Z1 is greater than 0 and less than z3, it can be clearly determined from the second gear pair (Z1, Z3). Using Equation 2, the complete number of revolutions can be determined, for example, within a partial angular range of z3·360°.

[0042] In the third step V3, it is checked whether U1 and U2 are equal. If so, the method continues in step V7. In step V7, if U1 and / or U2 are equal, it can be defined as the complete number of revolutions U of gear Z1.

[0043] In step V4, it can be checked whether U1 is greater than U2 or whether U2 is greater than U1. Depending on the result of the check, the method continues with either step V5 or step V6. In the current case, if U1 is greater than U2, the method continues with step V5. In the current case, if U2 is greater than U1, the method continues with step V6.

[0044] In step V5, a second predetermined sum, z3 in the current case, is added to U2. This produces a new value for U2, specifically U2 = U2 + z3 in the current case. In step V6, the second predetermined sum, z3 in the current case, is added to U1. This produces a new value for U1, specifically U1 = U1 + z2 in the current case. The first and second predetermined sums specifically predefine the maximum detectable number of turns of the first gear Z1 within the respective angular range of the gear pair (Z1, Z2), (Z1, Z3). The method then continues with step V3, where the value of U1 or U2 may have changed relative to the first execution of step V3. Steps V3 through V6 can be performed iteratively until U1 and U2 are equal. Specifically, in steps V5 and V6, the corresponding sums are iteratively added to U1 and / or U2 until U1 and U2 are equal.

[0045] By iteratively adding the values, the complete number of revolutions U of gear Z1 can be determined within a certain angular range that is greater than the range of the gear pairs (Z1, Z2) and (Z1, Z3). The complete number of revolutions U of gear Z1 can be directly related to the rotation angle E of the steering shaft 2 using Formula 3:

[0046] E = (W1 + U·360°)z1 / l Formula 3

[0047] The selection of gears Z1, Z2, and Z3 should be understood as merely an example. Specifically, each of the three gears Z1, Z2, and Z3 can be selected as either the first gear Z1, the second gear Z2, or the third gear Z3. Preferably, within the meaning of the above formula, one of the gears Z1, Z2, and Z3 with the smallest number of teeth z1 is selected as the first gear Z1. In this case, the accuracy of determining the rotation angle E of the steering shaft 2 can be improved.

[0048] To further improve accuracy, and / or to identify measurement errors in the determination of the rotation angle E of steering shaft 2, steps V0 to V7 can be performed independently for two or more different gear pairs. Exemplary gear pairs are (Z1, Z2) and (Z2, Z3) or (Z1, Z3) and (Z2, Z3). For example, similar to steps V0 to V7, the rotation angle E of steering shaft 2 can be determined alternatively or additionally from gear pairs (Z1, Z3) and (Z2, Z3). The formula must be correspondingly suitable for gear pairs (Z1, Z3) and (Z2, Z3). Two different determined values ​​of the rotation angle E of steering shaft 2 can be compared. If a deviation occurs, a measurement error can be determined.

[0049] Figure 3A graph showing the rotation angle E of the steering shaft 2, determined by three gear pairs (Z1, Z2), (Z2, Z3), and (Z1, Z3), is presented for multiple rotation angles E of the steering mechanism. All three graphs start from a point on the graph and rise as the rotation angle E of the steering shaft 2 increases. Once the rotation angle E deviates from the corresponding partial angle range of one of the gear pairs (Z1, Z2), (Z2, Z3), and (Z1, Z3), the corresponding curve drops to a defined rotation angle E of 0°. Therefore, for example, in this case, the rotation angles E of the steering shaft 2 at 360 degrees and 1800 degrees cannot be distinguished based on a single gear pair (Z1, Z2), (Z2, Z3), and (Z1, Z3). However, since the three gear pairs (Z1, Z2), (Z2, Z3), and (Z1, Z3) indicate different values ​​of the rotation angle E of the steering shaft 2 outside the corresponding partial angle ranges, the actual rotation angle E of the steering shaft 2 can be inferred from them. Therefore, steps V0 to V7 provide a method using this implementation, through which the rotation angle E of the steering shaft 2 can be determined particularly easily.

[0050] The predetermined angle range for the rotation angle E of the steering shaft 2 can be definitively determined and can be a predetermined multiple larger than the predetermined rotation angle range within which the steering shaft 2 can move, particularly 2, 3, 4, 5, 8, 10, 15, 20, or 50 times. Here, the predetermined rotation angle range can, for example, correspond to seven full revolutions of the steering shaft 2 or 2520 degrees. The predetermined angle range for the rotation angle E of the steering shaft 2 can, for example, correspond to 10, 15, 20, 30, 50, or 100 revolutions of the steering shaft 2, or 3600 degrees, 5400 degrees, 7200 degrees, 10800 degrees, 18000 degrees, or 36000 degrees. The determined rotation angle E of the steering shaft 2 can be compared with the predetermined rotation angle range. Here, the reasonableness of the rotation angle E of the steering shaft 2 is specifically checked. If the determined rotation angle E of the steering shaft 2 is outside the predetermined rotation angle range, it can be inferred that the rotation angle E of the steering shaft 2 has been incorrectly determined. In this case, the determined rotation angle E is unreasonable. The larger the predetermined angle range is than the predetermined rotation angle range, the greater the likelihood that the determined rotation angle E of the steering shaft 2 will be outside the predetermined rotation angle range in the event of an incorrect determination. This allows for particularly reliable identification of errors in the determination of the rotation angle E. Compared to existing technologies, this possibility of reasonable identification is made possible, especially by using a larger predetermined angle range, where the rotation angle E of the steering shaft 2 is definitively measurable.

Claims

1. A method for determining the rotation angle (E) of a steering shaft (2), comprising the following steps: -Detect the corresponding rotation angles (W1, W2, W3) of the three gears (Z1, Z2, Z3) of the gear mechanism, where, Three gears (Z1, Z2, Z3) with different numbers of teeth (z1, z2, z3) mesh with the gear ring (10) of the steering shaft (2), and - Based on predetermined extraction rules, the rotation angle (E) of the steering shaft (2) is determined based on the corresponding rotation angles (W1, W2, W3) of the three gears (Z1, Z2, Z3), wherein the rotation angle (E) of the steering shaft (2) is explicitly defined within a predetermined angle range by all corresponding rotation angles (W1, W2, W3). Furthermore, the predetermined extraction rule includes selecting two different gear pairs (Z1, Z2) and (Z1, Z3) among the three gears (Z1, Z2, Z3), wherein the first gear (Z1) among the three gears (Z1, Z2, Z3) is included in the two gear pairs (Z1, Z2) and (Z1, Z3), and wherein the complete number of revolutions (U) of the first gear (Z1) can be clearly determined within the corresponding partial angle range by the corresponding rotation angles (W1, W2, W3) of the two gear pairs (Z1, Z2) and (Z1, Z3). Furthermore, the first value (U1) of the number of complete revolutions of the first gear (Z1) is determined from the corresponding rotation angles (W1, W2) of the gears (Z1, Z2) of the first gear pair (Z1, Z2) in the two gear pairs (Z1, Z2) and (Z1, Z3), and the second value (U2) of the number of complete revolutions of the first gear (Z1) is determined from the corresponding rotation angles (W1, W3) of the gears (Z2, Z3) of the second gear pair (Z1, Z3) in the two gear pairs (Z1, Z2) and (Z1, Z3); If the first value (U1) is less than the second value (U2), then the first predetermined summation value is added to the first value (U1); if the second value (U2) is less than the first value (U1), then the second predetermined summation value is added to the second value (U2); the corresponding predetermined summation values ​​are iteratively added to the first value (U1) and the second value (U2) until the first value (U1) and the second value (U2) correspond.

2. The method according to claim 1, Its features are, In each case, the first value (U1) and the second value (U2) of the complete number of revolutions of the first gear (Z1) are determined by the phenius principle.

3. The method according to claim 1, Its features are, The first predetermined sum and the second predetermined sum are related to the span of the corresponding partial angle range, within which the complete number of revolutions (U) of the first gear can be clearly determined by the first gear pair (Z1, Z2) and the second gear pair (Z1, Z3), respectively.

4. The method according to any one of claims 1 to 3, Its features are, The first value (U1) and / or the second value (U2) are defined as the complete number of revolutions of the first gear (Z1) only when the first value (U1) and the second value (U2) correspond.

5. The method according to any one of claims 1 to 3, Its features are, - Combine the rotation angle (W1) of the first gear (Z1) and the total number of revolutions (U) of the first gear (Z1) to give the total angle of the first gear (Z1), and - The rotation angle (E) of the steering shaft (2) is determined from the total angle of the first gear (Z1).

6. The method according to any one of claims 1 to 3, Its features are, The gear with the fewest teeth (z1) among the three gears (Z1, Z2, Z3) is selected as the first gear (Z1).

7. The method according to any one of claims 1 to 3, Its features are, The reasonableness of the rotation angle (E) of the steering shaft (2) is verified by comparing the determined rotation angle (E) of the steering shaft (2) with a predetermined rotation angle range, wherein the predetermined angle range is at least twice as large as the predetermined rotation angle range within which the steering shaft (2) can move.

8. A control unit for determining the rotation angle (E) of a steering shaft (2), the control unit being configured to perform the method according to any one of claims 1 to 7.

9. A measuring device (1) for determining the rotation angle (E) of a steering shaft (2), comprising: - A gear ring (10) that can be mounted on the steering shaft (2), - A gear mechanism comprising three gears (Z1, Z2, Z3) mechanically operably connected to a gear ring (10) at different transmission ratios, and having - Two angle sensors (S1, S2) are used to detect the corresponding rotation angles (W1, W2, W3) of the first gear (Z1) and the second gear (Z2) out of three gears (Z1, Z2, Z3). - The control unit (4) according to claim 8, Its features are, The measuring device (1) includes a third angle sensor (S3) for detecting the third rotation angle (W3) of the third gear (Z3) among the three gears (Z1, Z2, Z3), and - Each of the three gears (Z1, Z2, Z3) with different numbers of teeth (z1, z2, z3) meshes with the gear ring (10).

10. A vehicle (3) having a measuring device (1) according to claim 9.

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