DE102018220612A1 - Steering wheel angle estimation method - Google Patents

Abstract

The invention relates to a method for estimating a steering wheel angle of a steering wheel (28) of a steering system (2) of a vehicle, the steering system (2) comprising at least one rack (10), at least one pinion wheel (12), at least one torsion bar (18) and at least one has a universal joint (24), the at least one toothed rack (10) on the one hand with at least one wheel (6) for moving the vehicle and on the other hand via the at least one pinion wheel (12), the at least one torsion bar (18) and the at least one universal joint (24) is connected to the steering wheel (28), a rack position of the at least one rack (10) being determined, an angle of the at least one pinion wheel (12) being determined from the rack position, the steering wheel angle of the steering wheel (28) starting from is determined from the angle of the pinion gear (12) taking into account an angular offset of the at least one universal joint (24).

Description

The invention relates to a method for estimating a steering wheel angle of a steering wheel of a vehicle and a monitoring system for a steering system of a vehicle.

A steering wheel angle of a steering wheel can be measured directly with a steering wheel angle sensor.

A method and a device for detecting a fatigue state of a driver of a motor vehicle are known from the publication EP 1 997 666 A1 known.

The publication DE 100 57 674 A1 describes a method and a device for determining a steering angle of a motor vehicle.

A method for determining a steering wheel angle of a steering wheel rotatably mounted on a vehicle body is described in the document WO 2007/147383 A1 described.

With this in mind, it was a task to estimate a steering wheel angle without a steering wheel angle sensor.

This object is achieved by a method and a monitoring system with the features of the independent claims. Embodiments of the method and the monitoring system emerge from the dependent patent claims.

The method according to the invention is provided for estimating a steering wheel angle of a steering wheel of a steering system of a vehicle, the steering system having at least one toothed rack, at least one pinion wheel, at least one torsion bar and at least one universal joint. The at least one toothed rack is connected on the one hand to at least one wheel, for example two wheels, for moving the vehicle, which is or are usually arranged on an axle. On the other hand, the at least one rack is connected to the steering wheel via the at least one pinion wheel, the at least one torsion bar and the at least one universal joint. In the method, a rack position of the at least one rack is determined, an angle of the at least one pinion wheel being determined from the rack position. The steering wheel angle of the steering wheel is determined on the basis of the angle of the at least one pinion wheel, taking into account an angular offset or angular error of the at least one universal joint.

In an embodiment, the angular offset of the at least one universal joint is calculated and thus determined using at least one mathematical function or with a mathematical function. This at least one mathematical function for determining the angular offset is usually dependent on the rack position of the rack and / or on an angle of the at least one pinion gear and / or on an angle of the at least one torsion bar and / or on a spatial alignment or orientation of two shafts, that are connected to each other via the at least one universal joint. In an embodiment, this mathematical function is designed and / or can be represented as a trigonometric function, for example at least one sine function or cosine function. Furthermore, this mathematical function, in particular a trigonometric function, can be represented in an embodiment, for example as a polynomial and / or via a model.

The alignment of the two shafts and thus the angle of the at least one universal joint can also be represented via the at least one mathematical function which is dependent on the rack position and / or on the angle of the at least one pinion gear and / or on the angle of the at least one torsion bar. The angular offset or angular error of the at least one universal joint describes a possible deviation of the angle of the at least one universal joint. Usually, the angle of the at least one universal joint changes according to at least one trigonometric function, for example at least one sine function or cosine function, for example a combination of several sine or cosine functions. Furthermore, the angular offset of the at least one universal joint is represented or described with the same at least one mathematical function as the angle and / or with at least one additional mathematical, for example trigonometric function or a corresponding polynomial. Alternatively or additionally, it is possible for the angle and / or angle offset to be determined taking into account a model, it being possible for this model to be represented with the at least one mathematical function.

In an embodiment, the method can be carried out for a steering system in which the at least one torsion bar is connected on the one hand to the at least one pinion gear and on the other hand, for example via a shaft, to which at least one universal joint is connected. In the method, a torsional torque or a steering torque or a torque of the at least one torsion bar is determined via a steering torque sensor or torque sensor. An angle of the at least one torsion bar is determined on the basis of the determined steering torque. An angle offset or angle error of the at least one torsion bar is determined with the steering torque sensor.

On the basis of the angle and angular offset of the at least one torsion bar, it is possible in one embodiment of the method that the steering wheel angle of the steering wheel is additionally determined on the basis of the angle of the at least one pinion gear, taking into account the angular offset of the at least one torsion bar and the angular offset of the at least one universal joint.

In an embodiment, the angular offset of the at least one torsion bar is determined taking into account a torsion or the torsional moment, for example taking into account a torsional rigidity of the at least one torsion bar.

Furthermore, the method can be carried out in a supplementary embodiment for a steering system which, in addition to the at least one toothed rack, the at least one pinion gear and the at least one universal joint, and possibly in addition to the at least one torsion bar, if there is one, also a superimposed steering with a planetary gear and an electric motor, the planetary gear being connected on the one hand to the at least one universal joint and on the other hand to the steering wheel. In this case, a translation of the electric motor and / or the superposition steering is determined. As an alternative or in addition, an overlay angle or additional angle of the overlay steering is determined.

It is thus possible for the steering wheel angle of the steering wheel to be additionally determined taking into account the superimposition angle or additional angle of the superimposition steering. Furthermore, it is possible for a sum to be calculated from the angle of the at least one pinion gear and at least one angular offset of the at least one torsion bar and / or the at least one universal joint. It is possible that the sum is calculated from the angle of the at least one pinion gear and only the angular offset of the at least one torsion bar, that the sum is calculated from the angle of the at least one pinion gear and only the angular offset of the at least one universal joint, or that Sum is calculated from the angle of the at least one pinion gear, the angular offset of the at least one torsion bar and the angular offset of the at least one universal joint. This resulting sum is multiplied by the translation of the electric motor and / or the superimposed steering and a product is formed from it. In this case, the steering wheel angle of the steering wheel is determined taking into account the named product plus the superimposition angle of the superimposition steering.

The monitoring system according to the invention is provided for a steering system of a vehicle, the steering system having at least one toothed rack, at least one pinion gear and at least one universal joint, the at least one toothed rack on the one hand with at least one wheel for moving the vehicle and on the other hand via the at least one pinion wheel and the at least one universal joint of the steering column is or will be connected to the steering wheel. The monitoring system is designed to estimate a steering wheel angle of the steering wheel and has a control unit and a rack position sensor, the rack position sensor being designed to determine a rack position of the at least one rack. The surveillance system, i. H. at least the rack position sensor and / or the control unit is or are designed to determine an angle of the at least one pinion gear from the rack position. The control device is designed to determine an angular offset of the at least one universal joint. The control device is designed to determine the steering wheel angle of the steering wheel on the basis of the angle of the at least one pinion wheel, taking into account the angular offset of the at least one universal joint.

This monitoring system is provided in a configuration for a steering system which additionally has at least one torsion bar which is or is connected on the one hand to the at least one pinion gear and on the other hand to the at least one universal joint. In this case, the monitoring system has a steering torque sensor or torque sensor, which is designed to determine a torsional moment of the at least one torsion bar and from this an angular offset of the at least one torsion bar. The control device is designed to additionally determine the steering wheel angle of the steering wheel on the basis of the angle of the at least one pinion wheel, taking into account the angular offset of the at least one torsion bar and the angular offset of the at least one universal joint.

With the method presented, it is possible to estimate the steering wheel angle of a steering unit of the steering system which is designed as a steering wheel and which can be operated or operated manually and which has a steering column or a steering train or a steering train. The exact position of the steering wheel angle can be estimated on the basis of measured variables and model data of the steering column or the steering column. The performance of functions that otherwise require signals from a steering wheel angle sensor as input or input is retained. In addition, in a network of the steering system, the signal from the steering wheel angle sensor can simply be replaced by the estimated value of the steering wheel angle, so that no development work is required during development.

When the method is implemented, the position of the rack and pinion indicates where the at least one pinion gear is absolutely and therefore also what angle the at least one pinion gear has or takes. The mechanical transmission ratio between the at least one rack and the at least one pinion gear is also taken into account.

Depending on the definition, the torsion bar is assigned to the steering torque sensor as a transmission element of the steering column and / or is designed as a component of the steering torque sensor. The steering torque sensor indicates how large the torsional torque or torque and thus the torsion is in the area of the torsion bar of the steering column. With information about a torsional stiffness of the torsion bar, which is assigned to the steering column and / or the steering torque sensor as a sensor module, the angle below the at least one universal joint or between the at least one pinion gear and the at least one universal joint can then be calculated.

A formula for calculating an angular error or an angular offset of the steering wheel angle by the torsional rigidity of the steering torque sensor is: $$\begin{array}{l}\text{Angular error}=\left(\text{measured torsional moment}\right)/(\text{Torsional stiffness of the}\\ \text{Torsion bar})\end{array}$$

The torsional stiffness can be a single-digit, in particular low single-digit number of Nm / degrees, z. B. 2 Nm / degree.

The universal joint is installed between the steering wheel and the steering torque sensor, which is designed or to be referred to as a torsion sensor, for example. The angular error or angular offset from the universal joint is mechanically coupled to a spatial alignment or orientation of the input shaft relative to the output shaft of the universal joint. A mechanical connection between the universal joint and the input shaft and / or output shaft is defined by the spatial orientation of the universal joint. Thus, a position of the angle of the output shaft or on the output shaft of the universal joint cannot rotate in relation to the input shaft. The mathematical function, for example a map or an n-order polynomial function, can additionally describe the angular error of the universal joint.

In a vehicle with an electrical adjustment of the steering column in the vertical direction, information about a current vertical position of the steering wheel can additionally be included in a calculation of the angular error of the universal joint. The vertical position of the adjustment of the steering column indicates the angle at which the output shaft is positioned relative to the input shaft of the universal joint.

In total, the steering wheel angle results from the measured value of the rack position of the at least one EPS rack, from which the angle of the at least one pinion wheel is determined, plus the angular error of the torsion sensor plus the angular error of the universal joint.

In procedures such as are known from the prior art, the steering wheel angle is precisely detected with a steering wheel angle sensor. Since the steering wheel angle can be estimated using the method presented and the steering system, this steering wheel angle sensor can be omitted in the future for cost reasons. Instead, the rack position is measured in the electromechanical steering (EPS).

It is thus possible, among other things, that a function of a chassis control system or a driver assistance system, for which the steering wheel angle sensor has hitherto been used to provide an input variable, can use the EPS angle without any loss in performance due to the use of the method, since with the method angle offset, for example angle losses , are taken into account in the steering column, which are not present in the measured EPS angle of the at least one pinion wheel. The real movement of the Steering wheel, e.g. B. in a hands-on-off transition situation, when the steering wheel can move freely because it is not operated manually, or in a vibration scenario, e.g. B. with a superimposed steering, can also be estimated and thus determined from the measured value of the EPS angle via the steering wheel angle, taking into account the angle offsets or angle errors and / or the superimposition angle. A steering response of the vehicle can also be improved since, for. B. a lateral jerk module of a damper controller with the EPS angle as an input reacts later than with the steering wheel angle as an input, the steering column first having to brace in order to achieve an EPS movement.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own without departing from the scope of the present invention.

• 1 zeigt in schematischer Darstellung eine erste Ausführungsform des erfindungsgemäßen Überwachungssystems für eine erste Ausführungsform eines Lenksystems zur Durchführung einer ersten Ausführungsform des erfindungsgemäßen Verfahrens.
• 2 zeigt in schematischer Darstellung eine zweite Ausführungsform des erfindungsgemäßen Überwachungssystems für eine zweite Ausführungsform eines Lenksystems zur Durchführung einer zweiten Ausführungsform des erfindungsgemäßen Verfahrens.

The invention is illustrated schematically in the drawings using embodiments and is described schematically and in detail with reference to the drawings.

• 1 shows a schematic representation of a first embodiment of the monitoring system according to the invention for a first embodiment of a steering system for performing a first embodiment of the method according to the invention.
• 2nd shows a schematic representation of a second embodiment of the monitoring system according to the invention for a second embodiment of a steering system for performing a second embodiment of the method according to the invention.

The figures are described coherently and comprehensively, the same reference numerals are assigned to the same components.

Both based on the 1 and 2nd schematically illustrated embodiments of the steering system 2nd , 4th are for steering wheels 6 of a vehicle designed here as a motor vehicle and can be designed and / or designated as electric power steering (EPS). Each embodiment of the steering system includes 2nd , 4th a wheel steering angle unit 8th with a rack 10th and a pinion gear 12 , the pinion gear 12 in the rack 10th intervenes. The pinion gear 12 is about a first wave 16 with a torsion bar 18th as a transmission link of a steering column 19th , 21st or a steering column of the steering system 2nd , 4th connected. The torsion bar 18th is about a second wave 22 with a universal joint 24th the steering column 19th , 21st connected.

Both based on the 1 and 2nd schematically illustrated embodiments of the monitoring system according to the invention 3rd , 5 each have a control unit 7 , a rack position sensor 14 for detecting a rack position of the rack 10th and a steering torque sensor 20th on the the torsion bar 18th for detecting a steering torque or torque of the torsion bar 18th is assigned and can, for example, be designed or designated as a torsion sensor.

In the first embodiment of the steering system 2nd is the universal joint 24th about a third wave 26 directly with a steering wheel 28 connected as a manual steering unit. Here is the second wave 22 as the input shaft of the universal joint 24th and the third wave 26 as the output shaft of the universal joint 24th intended. Here are the waves mentioned 16 , 22 , 26 also as transmission links of the steering column 19th intended.

In the first embodiment of the method according to the invention for the first embodiment of the steering system 2nd becomes the steering wheel angle of the steering wheel 28 starting from a rack position of the rack 10th , for example EPS rack, determined with the rack position sensor 14 is determined. The rack position becomes an angle of the pinion gear 12 determined. With the steering torque sensor 20th becomes a torsional moment of the torsion bar 18th and thus the torque of the torsion bar 18th determined. In addition, with the control unit 7 taking into account a mathematical function, an angular offset of the universal joint 24th determined. The steering wheel angle results from the angle of the pinion wheel 12 taking into account the angular offset of the torsion bar 18th due to the torsional moment of the torsion bar 18th and the angular offset of the universal joint 24th , with the angular offset of the torsion bar 18th and the universal joint 24th a deviation, for example an error, between the angle of the pinion gear 12 or pinion and the steering wheel angle is taken into account and / or corrected: $$\begin{array}{l}\text{Steering wheel angle}=\left(\text{Angle of the pinion gear 12}\right)+(\text{Angular offset of the}\\ \text{Torsion bar 18})+\left(\text{Angle offset of the universal joint 24}\right)\end{array}$$

In the 2nd illustrated second embodiment of the steering system 4th includes in addition to the first embodiment of the steering system 2nd a planetary gear 30th between the universal joint 24th and the steering wheel 28 .

Here is the universal joint 24th about a third wave 32 with the planetary gear 30th and the planetary gear 30th about a fourth wave 34 with the steering wheel 28 connected. This is the planetary gear 30th an electric motor 36 assigned for an overlay control. Here is the second wave 22 as the input shaft of the universal joint 24th and the third wave 32 as the output shaft of the universal joint 24th intended. Here are all waves 16 , 22 , 32 , 34 as transmission links of the steering column 21st educated. In addition, the second embodiment of the monitoring system 5 an angle sensor 38 on the electric motor 36 assigned.

In the second embodiment of the method according to the invention for the second embodiment of the steering system 4th also the angle of the pinion gear 12 , the angular offset of the universal joint 24th and the angular offset of the planetary gear 30th determined. In addition, a further angle correction is taken into account by the superimposed steering, which comprises two parts. For this purpose, a mechanical translation of the superimposed steering, for example a translation of a superimposed transmission of the superimposed steering, is determined as the first component. This mechanical translation occurs between the third wave 32 towards the universal joint 24th and the fourth wave 34 towards the steering wheel 28 . As a second component, a superposition angle of the superimposed steering is determined as an additional angle, this superimposed angle becomes the superimposed steering of the electric motor 36 provided. In this case, the overlay angle is configured by the angle sensor 38 determined.

Overall, this results for the second embodiment of the steering system 4th , here for the steering column or the steering column 21st with superimposed steering, the steering wheel angle from a sum of the angle of the pinion wheel 12 which results from a measurement of the rack position of the rack 10th can be determined, the angular offset of the steering torque sensor 20th and the angular offset of the universal joint 24th . This sum, also determined according to the first embodiment of the method, is multiplied by the translation of the superposition gear. The overlay angle is added to a resulting product: $$\begin{array}{l}\text{Steering wheel angle}=[\left(\text{Angle of the pinion gear 12}\right)+(\text{Angular offset of the}\\ \text{Torsion bar 18})+\left(\text{Angle offset of the universal joint 24}\right)]*\text{translation}+\\ \text{Overlap angle}.\end{array}$$

Rigidity and thus torsion of the mechanical transmission links or connecting elements in the respective steering column 19th , 21st , ie the universal joint 24th , the planetary gear 30th and the waves 16 , 22 , 26 , 32 , 34 , depending on the design of the steering column 19th , 21st , ie whether it is torsionally soft or torsionally rigid, is taken into account or neglected. A calculation for this is analogous to the calculation of the angular offset of the steering torque sensor, for example designed as a torsion sensor 20th and thus the torsion bar 18th .

Reference symbol list

2.4

Steering system

3, 5

Surveillance system

7

Control unit

6

wheel

8th

Wheel steering angle unit

10th

Rack

12

Pinion gear

14

Rack position sensor

16

wave

18th

Torsion bar

19th

Steering column

20th

Steering torque sensor

21st

Steering column

22

wave

24th

universal joint

26

wave

28

steering wheel

30th

Planetary gear

32, 34

wave

36

Electric motor

38

Angle sensor

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 1997666 A1 [0003]
• DE 10057674 A1 [0004]
• WO 2007/147383 A1 [0005]

Claims (9)

Method for estimating a steering wheel angle of a steering wheel (28) of a steering system (2, 4) of a vehicle, wherein the steering system (2, 4) has at least one rack (10), at least one pinion wheel (12), at least one torsion bar (18) and at least one has a universal joint (24), the at least one toothed rack (10) on the one hand with at least one wheel (6) for moving the vehicle and on the other hand via the at least one pinion wheel (12), the at least one torsion bar (18) and the at least one universal joint (24) is connected to the steering wheel (28), a rack position of the at least one rack (10) being determined, an angle of the at least one pinion wheel (12) being determined from the rack position, the steering wheel angle of the steering wheel (28) starting from is determined from the angle of the pinion gear (12) taking into account an angular offset of the at least one universal joint (24). Procedure according to Claim 1 , in which the angular offset of the at least one universal joint (24) is determined via at least one mathematical function, which is determined by the rack position of the rack (10) and / or by an angle of the at least one pinion wheel (12) and / or by an angle of the at least a torsion bar (18) and / or a spatial alignment of two shafts (22, 26, 32), which are connected to one another via the at least one universal joint (24). Procedure according to Claim 1 or 2nd , for a steering system (2, 4), in which the at least one torsion bar (18) is connected on the one hand to the at least one pinion gear (12) and on the other hand to the at least one universal joint (24), a torsional moment of the at least one torsion bar (18 ) is determined, wherein an angular offset of the at least one torsion bar (18) is ascertained, the steering wheel angle of the steering wheel (28) starting from the angle of the at least one pinion wheel (12) additionally taking into account the angular offset of the at least one torsion bar (18) and the Angular offset of the at least one universal joint (24) is determined. Procedure according to Claim 3 , in which the angular offset of the at least one torsion bar (18) is determined taking into account a torsion or a torsional moment of the at least one torsion bar (18). Method according to one of the preceding claims, for a steering system (4) which has a superimposed steering system with a planetary gear (30) and an electric motor (36), the planetary gear (30) on the one hand with the at least one universal joint (24) and on the other hand with the Steering wheel (28) is connected, wherein a translation of the superimposed steering is determined. Procedure according to Claim 5 , in which the steering wheel angle of the steering wheel (28) is additionally determined taking into account an overlay angle of the overlay steering. Procedure according to Claim 5 or 6 , in which a sum is calculated from the angle of the at least one pinion wheel (12) and at least one angular offset of the at least one torsion bar (18) and / or the at least one universal joint (24), this sum being multiplied by the translation of the superimposed steering and from this a product is formed, the steering wheel angle of the steering wheel (28) being determined taking into account the product plus a superimposition angle of the superimposition steering. Monitoring system for a steering system (2, 4) of a vehicle, the steering system (2, 4) having at least one toothed rack (10), at least one pinion gear (12), at least one torsion bar (18) and at least one universal joint (24), the at least one rack (10) is connected on the one hand to at least one wheel (6) for moving the vehicle and on the other hand via the at least one pinion wheel (12) and the at least one universal joint (24) to a steering wheel (28), the monitoring system (3 , 5) is designed to estimate a steering wheel angle of the steering wheel (28), has a control unit (7) and a rack position sensor (14), the rack position sensor (14) being designed to determine a rack position of the at least one rack (10), wherein the monitoring system (3, 5) is designed to determine an angle of the at least one pinion gear (12) from the rack position, the control device (7) being designed to e to determine an angular offset of the at least one universal joint (24), and the control device (7) is designed to determine the steering wheel angle of the steering wheel (28) based on the angle of the at least one pinion wheel (12), taking into account the angular offset of the at least one universal joint ( 24) to be determined. Surveillance system according to Claim 8 , for a steering system (2, 4) which has at least one torsion bar (18), the at least one torsion bar (18) on the one hand with the at least one pinion wheel (12) and on the other hand is connected to the at least one universal joint (24), the monitoring system (3, 5) having a steering torque sensor (20) which is designed to generate a torsional moment of the at least one torsion bar (18) and an angular offset thereof determining at least one torsion bar (18), the control device (7) being designed to additionally determine the steering wheel angle of the steering wheel (28) based on the angle of the at least one pinion wheel (12), taking into account the angular offset of the at least one torsion bar (18) and to determine the angular offset of the at least one universal joint (24).

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