Device and method for determining a steering angle of a steering system, vehicle comprising the device

Abstract

The invention relates to a device (100) and a method for determining a steering angle of a steering system (102) with a steering shaft (104) which comprises a motor (106) which is coupled to the steering shaft (112) via a motor shaft (108) and a gear unit (110), wherein the gear unit (110) has a specified transmission ratio, wherein according to the method, a rotational angle of the steering shaft (104) is detected in a rotational range of the steering system (102), wherein a rotational angle of the motor shaft (108) is detected in a detection range, wherein depending on the rotational angle of the steering shaft (104) a periodicity is determined which assigns the detected rotational angle of the motor shaft (108) to the detected rotational angle of the steering shaft (104), wherein the steering angle (104) is determined depending on the periodicity and the rotational angle of the motor shaft (108).

Description

[0001] Description

[0002] title

[0003] Device and method for determining a steering angle of a

[0004] Steering system, vehicle comprising the device

[0005] State of the art

[0006] The invention is based on a device and a method for determining a steering angle of a steering system and a vehicle comprising the device.

[0007] To determine the steering angle, the rotation angle of a steering angle sensor can be scaled using a steering gear ratio and used as the steering angle. This method scales an inaccuracy of the steering angle sensor and transfers it to the steering angle.

[0008] Disclosure of the invention

[0009] A method for determining a steering angle of a steering system with a steering shaft, which comprises a motor which is coupled to the steering shaft via a motor shaft and a transmission, wherein the transmission has a predetermined gear ratio, provides that a rotational angle of the steering shaft is detected in a rotational range of the steering system, wherein a rotational angle of the motor shaft is detected in a detection range, wherein a period number is determined depending on the rotational angle of the steering shaft, which period number assigns the detected rotational angle of the motor shaft to the detected rotational angle of the steering shaft, wherein the steering angle is determined depending on the period number and the rotational angle of the motor shaft. This prevents a transfer of an error in the rotational angle measured at the steering shaft to the steering angle.The number of periods is determined, for example, depending on a quotient of the maximum angle of the detection range and the gear ratio by which the angle of rotation of the steering shaft is divided.

[0010] For example, a product of the angle of rotation of the steering shaft and the gear ratio is determined, whereby the number of periods is determined depending on a quotient of the product and the maximum angle of the detection range.

[0011] The steering angle can be corrected using a predefined correction value. This correction value is used, for example, to correct deviations.

[0012] It can be provided that, in a vehicle with steerable wheels, the angle of rotation of the steering shaft and the angle of rotation of the motor shaft are recorded when the steerable wheels are in the straight-ahead position. This allows the angles of rotation to be calibrated or detects any deviation of the angles from the steering angle expected when the wheels are in the straight-ahead position.

[0013] It may be provided that the angle of rotation is stored, particularly in a non-volatile memory. This makes the angle of rotation available for subsequent starts of the steering system.

[0014] Preferably, the angle of rotation is determined at a start of the steering system in a calibration, in particular at the end of a production line for the vehicle, and stored in the memory, wherein the angle of rotation is read from the memory at a start, in particular at each start, after the calibration, and the steering angle is determined as a function of the angle of rotation read from the memory and the angle of rotation and the period number of the motor shaft.

[0015] This means that the angle of rotation at the steering shaft is used as a period counter for the number of periods of the angle of rotation of the motor shaft. A device for determining a steering angle of a steering system with a steering shaft, which comprises a motor which is coupled to the steering shaft via a motor shaft and a transmission, wherein the transmission has a predetermined gear ratio, characterized in that the device comprises a computing device, in particular with a non-volatile memory, and an interface to a sensor for detecting a rotation angle of the steering shaft and to a sensor for detecting a rotation angle of the motor shaft, wherein the computing device is designed to carry out the method.

[0016] A vehicle may be provided, the vehicle comprising a steering system, the steering system comprising a steering shaft and a motor coupled to the steering shaft via a motor shaft and a transmission, the transmission having a predetermined gear ratio, the steering system comprising a sensor for detecting an angle of rotation of the steering shaft and a sensor for detecting an angle of rotation of the motor shaft, the vehicle comprising the device.

[0017] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows:

[0018] Fig. 1 is a schematic representation of a vehicle,

[0019] Fig. 2 Courses of rotation angles of a steering system,

[0020] Fig. 3 is a flowchart showing steps of a method for determining a steering angle of the steering system.

[0021] Figure 1 shows a schematic representation of a vehicle 100.

[0022] The vehicle 100 includes a steering system 102.

[0023] The steering system 102 includes a steering shaft 104.

[0024] The steering system 102 includes a motor 106.

[0025] The steering system 102 includes a motor shaft 108. The steering system 102 includes a gearbox 110. The gearbox 110 has a predetermined gear ratio, e.g., I=9.

[0026] The motor 106 is coupled to the steering shaft 104 via the motor shaft 108 and the transmission 110.

[0027] The steering system 102 includes a sensor 112 for detecting a rotation angle S of the steering shaft 104. The sensor 112 for detecting the rotation angle S of the steering shaft 104 is arranged on the steering shaft 104 in the example. The sensor 112 for detecting the rotation angle S of the steering shaft 104 includes a small gear in the example, wherein a rotation of the steering shaft 104 is detected broken down into two partial angles, which are combined using the vernier algorithm to form an absolute angle, the rotation angle S of the steering shaft 104.

[0028] The sensor 112 for detecting the angle of rotation S of the steering shaft 104 covers at least the entire rotation range of the steering wheel. For example, for a rotation range of + / - 2 steering wheel revolutions, a range of -720° to +720° is provided.

[0029] The steering system 102 includes a sensor 114 for detecting a rotation angle R of the motor shaft 108.

[0030] The sensor 114 for detecting the angle of rotation R of the motor shaft 108 is, for example, a magnetic sensor with an integrated circuit located on a printed circuit board, which detects the rotation of a magnet arranged at the end of the motor shaft 108. The sensor 114 for detecting the angle of rotation R of the motor shaft 108 has a detection range with a maximum angle. In the example, the detection range is one full revolution of the motor shaft 108. This means that the maximum angle of the detection range is 360° in the example. After one full revolution of the motor shaft 108, the angle of rotation jumps from 359.99 to 0°.

[0031] Due to its design, sensor 112 for detecting the angle of rotation S of steering shaft 104 is less accurate than sensor 114 for detecting a rotation angle R of motor shaft 108. When the steering system is started, sensor 114 for detecting the angle of rotation R of motor shaft 108 delivers a rotation angle R of motor shaft 108 within its detection range, e.g., between [0°, 360°]. This corresponds to a rotor position of motor 106. The angle of rotation R of motor shaft 108 corresponds to a rotation angle S of steering shaft 104. One period of the angle of rotation R of the motor shaft corresponds to a rotation angle of steering shaft 104, in the example, [0.40°].

[0032] The vehicle 100 includes steered wheels 116.

[0033] The vehicle 100 includes a device 118 for determining a steering angle L of the steering system 102.

[0034] The device 118 comprises a computing device 120, in particular with a non-volatile memory 122. The device 118 comprises an interface 124 to the sensor 112 for detecting the angle of rotation S of the steering shaft 104 and to the sensor 114 for detecting the angle of rotation R of the motor shaft 108.

[0035] The computing device 120 is designed to carry out a method for determining a steering angle L of the steering system 102.

[0036] Figure 2 shows curves of the angle of rotation R of the motor shaft 108 and the angle of rotation S of the steering shaft 104 and an assignment of the steering angle for the detection range [0°, 360°] and to a value of the rotation range of the motor shaft between -3240° and +3240° indicated in brackets.

[0037] In an initial position 202 of the steering system 102, for example, a rotation angle Si of the steering shaft 104 of 125° and a rotation angle Ri of the motor shaft 108 of 182° are recorded, it being known that when the wheels were in the straight-ahead position, a calibration value 204 of the rotation angle R of the motor shaft 108 of 137° was recorded.

[0038] With the ratio l=9 and assuming that there is an error of 2° in the angle of rotation S of the steering shaft 104, a steering angle L' at the level of the motor shaft, which is determined directly from the angle of rotation S of the steering shaft 104, would also be subject to an error: L' = S*l

[0039] L'=(125+2)*9=1125+18=1143°

[0040] The error in the angle of rotation of the steering shaft scales up from 2° to an error of 18° due to the gear ratio.

[0041] By the method described below for determining the steering angle L of the steering system 102, the steering angle L is determined at the level of the motor shaft depending on the angle of rotation R of the motor shaft 108, without an error in the angle of rotation S of the steering shaft 104 being reflected in the steering angle of the motor shaft 108:

[0042] L = P*E+R-KR with the period number P = I nt(S*l / E) , where Int denotes the integer divisor of S*l / E and E denotes the maximum angle of the detection range of the sensor 114.

[0043] In the example for R = 182°:

[0044] P = Int (127*9 / 360) = 3

[0045] L = 3*360 + 182° - 137°=1125°

[0046] This means that the angle of rotation S of the steering shaft 104 is used as a period counter for the period number P.

[0047] The method includes a step 302.

[0048] In step 302, the calibration value 204 of the rotation angle R of the motor shaft 108 is recorded and stored. The rotation angle R is determined, for example, when the steering system 102 is started during a calibration, in particular at the end of a production line for the vehicle 100, and stored in the memory 122.

[0049] The angle of rotation R is detected in particular during calibration in a straight-ahead position of the steerable wheels 116 or the steering wheel of the vehicle 100.

[0050] In the example, the angle of rotation R is stored in memory 122. Memory 122 is notably non-volatile. Therefore, calibration value 204 is available after the steering system 102 is switched off and on again.

[0051] The calibration value 204 is read from the memory at a start, in particular at each start after calibration.

[0052] For example, step 302 is performed only once at the end of the line during vehicle production.

[0053] The following steps are carried out during initialization, for example, every time the vehicle is restarted.

[0054] The method includes a step 304.

[0055] In step 304, the rotation angle R of the motor shaft 108 is detected.

[0056] The method includes a step 306.

[0057] In step 306, the rotation angle S of the steering shaft 104 is detected.

[0058] The method includes a step 308.

[0059] In step 308, the preliminary period number P is determined depending on the angle of rotation S of the steering shaft 104. The period number P assigns the detected angle of rotation S of the steering shaft 104 to the detected angle of rotation R of the motor shaft 108. The period number P is determined as an integer, e.g., depending on a product of the steering angle S and the gear ratio I, which is divided by the maximum angle of the detection range E:

[0060] P = Int (S*l / E)

[0061] In step 310, the preliminary steering angle L is determined, particularly during initialization during each operation of the steering system 102, using the angle of rotation S of the steering shaft 104, which is used to initially determine the period number P, the angle of rotation R of the motor shaft 108, and the calibration value 204 stored in the memory 122: If R >= KR:

[0062] L = P*E + R - KR; otherwise L = P*E + R + 360 - KR where KR denotes the calibration value 204.

[0063] The method includes a step 312.

[0064] In step 312 the exact steering angle L is determined.

[0065] After initialization, the exact steering angle L is determined incrementally using the then detected rotation angle R of the motor shaft 108.

[0066] This means that in the example, the steering angle L is determined in the initialization starting from the period number P determined for the first time and after the initialization starting from the steering angle L determined for the first time incrementally with the angle of rotation R of the motor shaft.

[0067] It can be provided that the correctness of the provisionally determined period number P is checked and, if necessary, the provisional steering angle L is corrected, i.e., that the exact steering angle L is the corrected provisional steering angle L. The inaccuracy in the detection of the angle of rotation S of the steering shaft 104 at the limits of the detection range of the angle of rotation R of the motor shaft 108 can lead to a falsified period number P. The correction is determined, for example, depending on the comparison of the difference between the initially calculated steering angle L and the product of the angle of rotation S with the gear ratio I, with a limit:

[0068] If L - S*l > 180:

[0069] L = L - 360;

[0070] Otherwise: If L - S*l < -180:

[0071] L = L + 360;

[0072] Otherwise: L = L

[0073] It can be provided that the steering angle L is corrected with a steering system-specific predetermined correction value.

[0074] It can be provided that, particularly during initialization, the difference between S*l and the precise steering angle L is compared with an expected value in order to detect any errors in angle detection or calculation.

[0075] It may be provided that the method begins when the steering system 102 is started and ends when the steering system 102 is switched off, in particular after the calibration value 204 has been stored in the memory 122.

Claims

Claims 1. A method for determining a steering angle of a steering system (102) with a steering shaft (104), which comprises a motor (106) which is coupled to the steering shaft (112) via a motor shaft (108) and a transmission (110), wherein the transmission (110) has a predetermined gear ratio, characterized in that an angle of rotation of the steering shaft (104) is detected (306) in a rotation range of the steering system (102), wherein an angle of rotation of the motor shaft (108) is detected in a detection range (304), wherein a period number is determined (308) depending on the angle of rotation of the steering shaft (104), which period number assigns the detected angle of rotation of the motor shaft (108) to the detected angle of rotation of the steering shaft (104), wherein the steering angle (104) is determined (316) depending on the period number and the angle of rotation of the motor shaft (108).

2. Method according to claim 1, characterized in that the number of periods is determined as a function of a quotient of the maximum angle of the detection range and the transmission ratio by which the angle of rotation of the steering shaft (104) is divided (308).

3. Method according to one of the preceding claims, characterized in that a product of the angle of rotation of the steering shaft (104) and the gear ratio is determined, the number of periods being determined as a function of a quotient of the product and the maximum angle of the detection range (308).

4. Method according to one of the preceding claims, characterized in that the steering angle is corrected with a predetermined correction value (314).

5. Method according to one of the preceding claims, characterized in that in a vehicle (100) which comprises steerable wheels, the The angle of rotation of the steering shaft and the angle of rotation of the motor shaft are recorded when the steerable wheels are in the straight position (302).

6. Method according to one of the preceding claims, characterized in that the angle of rotation is stored (302), in particular in a non-volatile memory (122).

7. The method according to claim 6, characterized in that the angle of rotation is determined at a start of the steering system (102) in an initialization, in particular at the end of a production line for the vehicle, and is stored in the memory (122) (302), wherein the angle of rotation is read from the memory (122) at a start, in particular at each start following the calibration (304), and the steering angle is determined as a function of the angle of rotation read from the memory (122) and the angle of rotation and the period number of the motor shaft (108) (316).

8. A device (118) for determining a steering angle of a steering system (102) with a steering shaft (104), which comprises a motor (106) which is coupled to the steering shaft (104) via a motor shaft (108) and a transmission (110), wherein the transmission (110) has a predetermined gear ratio, characterized in that the device (118) comprises a computing device (120), in particular with a non-volatile memory (122), and an interface (124) to a sensor (112) for detecting a rotational angle of the steering shaft (104) and to a sensor (114) for detecting a rotational angle of the motor shaft (108), wherein the computing device (120) is designed to carry out the method according to one of claims 1 to 7.

9. Vehicle (100), characterized in that the vehicle (100) comprises a steering system (102), wherein the steering system (102) comprises a steering shaft (104) and a motor (106) which is coupled to the steering shaft (104) via a motor shaft (108) and a transmission (110), wherein the transmission (110) has a predetermined gear ratio, wherein the steering system (102) comprises a sensor (112) for detecting a rotation angle of the steering shaft (104) and a sensor (114) for detecting a rotation angle of the motor shaft (108) wherein the vehicle (100) comprises the device (120) according to claim 8.

Images