Method and control unit for determining the rotational speed of a vehicle wheel and assistance system

Abstract

The invention relates to a method for determining, in particular indirectly, a rotational speed (N1) of a, preferably driven, wheel (1) of a vehicle (100), wherein the vehicle (100) has a drive train (10) with a drive (11) for the wheel (1), and wherein the wheel (1) forms a component (K1) of the drive train (10), comprising: - Determining a model (M) that represents a relationship between rotational speeds (N1, N2, N11) in the drive train (10), - Detecting a rotational speed (N2, N11) of at least one other component (K2, K11) in the drive train (10), which in particular is not the wheel (1), - Determining the rotational speed (N1) of the wheel (1) as a function of the specified model (M) and of the at least one detected rotational speed (N2, N11), wherein in the specified model (M) of the drive train (10) at least one operating parameter (BP) of the drive train (10) is taken into account as a model parameter.

Description

[0001] The invention relates to a method for, in particular indirectly, determining a rotational speed of a preferably driven wheel of a vehicle. Furthermore, the invention relates to a corresponding computer program product for implementing a corresponding method. Furthermore, the invention relates to a corresponding control unit for implementing a corresponding method. Furthermore, the invention relates to a corresponding assistance system, e.g., for vehicle dynamics control, speed control, slip control, brake force distribution, standstill control, etc., as well as to a corresponding vehicle with a corresponding control unit.

[0002] Vehicle wheels are usually equipped with speed sensors that measure the speed and / or angular velocity of the vehicle wheels. The measured values ​​from the speed sensors are relevant for various assistance systems in the vehicle. If the speed sensor fails at a wheel, speed control at that wheel is no longer possible. Various redundancy concepts provide for redundant installation of the speed sensor at this location. However, this requires additional costs and can cause installation space problems.

[0003] A method for estimating the rotational speed of a vehicle wheel is known from DE 100 61 502 A1. However, such a method can be inaccurate.

[0004] The object of the invention is therefore to at least partially overcome at least one of the disadvantages described above. In particular, the object of the invention is to provide an improved method for, in particular indirectly, determining a rotational speed of a, preferably driven, wheel of a vehicle, which method enables improved determination of the rotational speed of the wheel, even if a corresponding rotational speed sensor has failed or is malfunctioning, which determines the rotational speed of the wheel with increased accuracy and which advantageously takes into account the properties and circumstances in a drive train. Furthermore, the object of the invention is to provide a corresponding control unit for carrying out a corresponding method. Furthermore, the object of the invention is to provide a corresponding assistance system, e.g.for vehicle dynamics control, speed control, slip control, brake force distribution, standstill control, etc.

[0005] The problem is solved by a method for, in particular indirectly, determining a rotational speed of a preferably driven wheel of a vehicle, having the features of the independent method claim. Furthermore, the problem is solved by a corresponding computer program product for carrying out a corresponding method. Furthermore, the problem is solved by a corresponding control unit for carrying out a corresponding method. Furthermore, the problem is solved by a corresponding assistance system, e.g., for vehicle dynamics control, speed control, slip control, brake force distribution, standstill control, etc.

[0006] The invention provides a method for determining, in particular indirectly, a rotational speed of a preferably driven wheel of a vehicle, for example, when a corresponding rotational speed sensor has failed or is malfunctioning. The vehicle has a drive train with a drive for the wheel, with the wheel forming a component of the drive train.

[0007] The procedure comprises the following steps: - Determining a, preferably technical, model which represents (in particular computationally represents) a, in particular physical, relationship between rotational speeds (or variables representing rotational speeds, such as angular velocities) in the drive train, - detecting (e.g. by direct or immediate sensing) a rotational speed (or a variable representing the rotational speed, such as an angular velocity) of at least one further component in the drive train, which in particular is not the wheel, such as a drive and possibly one or more further driven wheels in the drive train, - Determining (e.g. by a corresponding calculation according to the model) the speed of the wheel as a function of the specific model and of the at least one detected speed, wherein in the specific model of the drive train at least one operating parameter (or operating variable) of the drive train is taken into account (or represented) as a model parameter (or model variable).

[0008] An operating parameter or operating variable of the drive train can be understood as a characteristic or property of at least one component of the drive train that characterizes the technical behavior in the drive train and that describes in particular the transmission behavior for the drive force between the drive and the wheel.

[0009] The drivetrain can comprise multiple components, such as the wheel, whose rotational speed is determined, and the drive, which provides the driving force to the wheel. In vehicles with multiple wheels driven by a drive, the drivetrain components also include the other wheels in the drivetrain and a corresponding transmission for distributing the driving force among the multiple wheels.

[0010] The invention recognizes that, for a driven wheel, in addition to the wheel's speed, the drive's speed is usually also present. If a drive drives multiple wheels via a transmission, e.g., a differential, the speed is usually the speed of the drive and the wheels connected to it. If a transmission gear is located between the drive and the wheels, it rotates at a multiple i of the wheel speed.

[0011] For constant speeds and load conditions, the following relationship can arise in the example with two wheels driven by a drive: 0.5*(speed of the first wheel+speed of the second wheel)=(speed of the drive) / i.

[0012] This formula can be understood as a model that describes a relationship between the speeds of the two driven wheels and the speed of the drive.

[0013] If angular velocities are used instead of rotational speeds, then the model can be described as follows: 0.5*(angle change of the first wheel + angle change of the second wheel)=(angle change of the anti-reb) / i.

[0014] If a speed sensor on one of the two wheels (first wheel or second wheel) fails, the failed speed sensor can be replaced using the procedure described above.

[0015] The invention further recognizes that the drive train has elasticity. If an additional angle of rotation arises due to a change in the load on the drive train, this additional angle of rotation can be taken into account as a first offset1 or a first correction value in the drive train model.

[0016] In this case, the drivetrain stiffness 1 / K can be considered as the inverse of the drivetrain elasticity K in the model. If a change in the load in the transmission is denoted by Δ_M1, the additional angle of rotation in the transmission can be calculated as a function of the drivetrain stiffness 1 / K and the change in the load in the transmission as Δ_M1. The torque in the drivetrain can be assumed to be known as the external motor torque and is usually provided by the drive. Angle change_Offset1=Δ_M1 / K.

[0017] The invention further recognizes that the drivetrain has an inertia. A second offset2 or a second correction value can result from the fact that the components of the drivetrain are mounted and supported in the corresponding bearings. The force that the components exert on their bearings may not be linearly dependent on position and change in position. To compensate for this effect, a simulation of the support of the drivetrain components in the bearings can be carried out, for example. Furthermore, in addition to the linear moments of inertia in the drivetrain, the rotational moments of inertia can also be taken into account, such as the acceleration of the rotational inertia in the drive and / or the acceleration of the rotational inertia in the transmission. Angular change_Offset2=f(t,Δ_M2).

[0018] The model can then be adjusted to refine the results of the determination. Overall, this can result in the following relationship: 0.5*(Angle change of the first wheel+Angle change of the second wheel)=(Angle change of the anti-reb) / i+Angle change_offset1+Angle change_offset2

[0019] Using the more accurate model, the rotation angle of the wheel with a failed speed sensor can be determined. The speed can then be determined by deriving the rotation angle over time.

[0020] The speed determined in this way can then be used advantageously in a vehicle assistance system that requires the speed of the wheel, e.g. for vehicle dynamics control, speed control, slip control, brake force distribution, standstill management or other vehicle functions.

[0021] In the case of a wheel-individual drive (single-wheel drive), the term for the second wheel is omitted in the example described above.

[0022] The drivetrain operating parameters or the model parameters to be considered (drivetrain stiffness, component support, etc.) for the application of the method can be determined using a variety of learning methods before the speed sensor fails. For example, the drivetrain operating parameters can be determined using a simulation. Field tests are also conceivable to determine the drivetrain operating parameters.

[0023] Another advantage is that the determined speed can be used to verify the measured values ​​from the speed sensor. In an example case of a frozen / rusted parking brake, determining the speed of the frozen wheel can rule out a wheel speed sensor fault and thus identify the correct error. In other words, the determined speed can even contribute to troubleshooting.

[0024] Furthermore, it can be provided that the detection of a rotational speed of at least one further component in the drive train includes a rotational speed of the drive and / or a rotational speed of at least one further, in particular driven, wheel. In this way, a representative model of the drive train can be provided, which advantageously maps the relationships within the drive train, in particular the relationships between the rotational speeds (or variables that map the rotational speeds, such as angular velocities) of drive train components.

[0025] Furthermore, it can be provided that the at least one operating parameter of the drivetrain, which is represented as a model variable in the specific model, includes an elasticity parameter of at least one component of the drivetrain. In this way, it can be advantageously taken into account that the drive torque is not transmitted 1:1 to the wheel, but is modified, usually attenuated, via the elastic couplings in the drivetrain. This can already be taken into account in the model of the drivetrain in the form of a first offset1 or a first correction value in order to improve the determination of the speed.

[0026] Furthermore, it can be provided that the at least one operating parameter of the drivetrain, which is represented as a model variable in the specific model, comprises an inertia parameter of at least one component of the drivetrain. Advantageously, it can also be taken into account that the inertia parameter comprises at least one linear inertia parameter and / or a rotational inertia parameter. An example of an inertia parameter, in particular a linear inertia parameter, can be a linear moment which the wheel or another component of the drivetrain exerts on its bearing due to its mass inertia. This moment can weaken the transmission of the drive force, similar to slip. If this is already taken into account in the model that describes the drivetrain, the speed can be determined more accurately.An example of an inertia parameter, in particular a rotational inertia parameter, can be the acceleration of the rotational inertia in the drive and / or the acceleration of the rotational inertia of the driven wheels.

[0027] In this method, it is conceivable that at least one operating parameter of the drivetrain is determined during a test run. This allows the drivetrain model to be adapted using field data.

[0028] In the method, it is further conceivable for the at least one operating parameter of the drive train to be determined through a simulation. In this way, the drive train model can be adapted using physical relationships and / or variables in the system.

[0029] Advantageously, determining the wheel's rotational speed can be used as a replacement for a failed wheel speed sensor. This enables the functionality of assistance systems and / or functions in the vehicle that require wheel speed, even if the associated speed sensor has failed and / or is malfunctioning.

[0030] Advantageously, determining the wheel's rotational speed can be used to verify the plausibility of sensor values ​​from a wheel speed sensor. This method can thus enable advanced testing functions and even fault investigation in affected vehicle systems.

[0031] Furthermore, the invention provides a computer program product comprising instructions that, when executed by a computer, cause the computer to perform a method that can proceed as described above. Using the computer program product, the same advantages can be achieved that were described above in connection with the method according to the invention. These advantages are incorporated herein by reference in their entirety.

[0032] Furthermore, the invention provides a control unit comprising a computing unit and a memory unit in which a code is stored which, when at least partially executed by the computing unit, carries out a method that can proceed as described above. The control unit can achieve the same advantages as described above in connection with the method according to the invention. These advantages are incorporated herein by reference in their entirety.

[0033] Furthermore, the invention provides an assistance system, e.g., for vehicle dynamics control, speed control, slip control, brake force distribution, standstill control, etc., for a vehicle, comprising a control unit that can be designed as described above. The assistance system can achieve the same advantages as those described above in connection with the method according to the invention. These advantages are incorporated herein by reference.

[0034] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are described in detail with reference to the drawing. The figure shows: Fig. 1 a schematic representation of a vehicle in which a method according to the present disclosure can be carried out.

[0035] The Fig. 1 serves to explain a method according to the invention, which was developed for, in particular, indirectly determining a rotational speed N1 of a preferably driven wheel 1 of a vehicle 100. The method can be carried out, for example, if a corresponding rotational speed sensor S1 on wheel 1 has failed or is malfunctioning.

[0036] As the Fig. 1 schematically indicates, the vehicle 100 has a drive train 10 with a drive 11 for the wheel 1, wherein the wheel 1 forms a component K1 of the drive train 10.

[0037] The drivetrain 10 can fundamentally comprise several components K1, K2, K11, K12. The components of the drivetrain 10 include, firstly, wheel 1, whose rotational speed N1 is determined. The components of the drivetrain 10 can also include the drive 11, which provides the driving force to wheel 1. In vehicles 100 with several wheels 1, 2 driven by a drive 11, the additional wheels 2 also belong to the drivetrain 10, as does a corresponding transmission for distributing the driving force among the several wheels 1, 2.

[0038] In the Fig. 1 shows a drive train 10 with two driven wheels 1, 2 merely as an example.

[0039] Of course, the drive train 10 can also be designed differently and, for example, have several or fewer wheels 1, 2 driven by a drive 11. Vehicles 100 with a separate drive 11 for each wheel 1, 2 are also conceivable.

[0040] The procedure comprises the following steps: - Determining a, preferably technical, model M, which represents a, in particular physical, relationship between rotational speeds N1, N2, N11 or variables representing the rotational speeds, such as angular velocities, in the drive train 10, in particular by calculation, - Detecting, for example, by directly sensing a speed N2, N11 or a variable representing the speed, such as an angular velocity, of at least one further component K2, K11 in the drive train 10, which in particular is not the wheel 1, such as a drive and possibly one or more further driven wheels in the drive train, - Determine, for example, by a corresponding calculation according to the model of the rotational speed N1 of the wheel 1 as a function of the specific model M and of the at least one detected rotational speed N2, N11, wherein in the specific model M of the drive train 10 at least one operating parameter BP or an operating variable of the drive train 10 is taken into account or represented as a model parameter or a model variable.

[0041] An operating parameter BP or operating variable of the drive train 10 can describe a characteristic or property (e.g. elasticity, inertia, etc.) of at least one component K1, K2, K11, K12 of the drive train 10, which characterizes the transmission behavior for the drive force between the drive 11 and the wheel 1.

[0042] The method utilizes the fact that, for a driven wheel 1, in addition to the speed N1 of wheel 1, the speed N11 of the drive 11 is usually also present. If a drive 11 drives several wheels 1, 2 via a transmission 12, e.g., a differential, the speed N11 of the drive 11 and the speed N2 of the wheels 2 connected to it are usually present. If a transmission 12 is located between the drive 11 and the wheels 1, 2, it rotates at a multiple i of the wheel speed.

[0043] For constant speeds and load conditions, the example of Fig. 1 the following relationship / model M results: 0.5*(N1+N2)=(N11) / i.

[0044] The model M describes a relationship between the speeds N1, N2 of the two driven wheels 1, 2 and the speed N1 of the drive 11.

[0045] If angular velocities φ1, φ2, φ11 are used instead of rotational speeds N1, N1, N11, then the model M can be described as follows: 0.5*(Δφ1+Δφ2)=(Δφ11) / i.

[0046] If a speed sensor S1, S2 of one of the two wheels 1, 2 (e.g. of a first wheel 1) fails, the failed speed sensor S1 can be replaced using the relationship described above.

[0047] The method advantageously utilizes the knowledge that the drive train 10 has elasticity for adapting the model M. If an additional angle of rotation arises due to a load change on the drive train 10, this additional angle of rotation can be taken into account as a first offset 1 or a first correction value in the model M of the drive train 10.

[0048] In this case, the stiffness 1 / K of the drive train 10 can be considered as the operating parameter BP as the inverse of the elasticity K of the drive train 10 in the model M. If a change in the load in the transmission 12 is referred to as Δ_M1, the additional angle of rotation in the transmission 12 can be calculated as Δ_M1 depending on the stiffness 1 / K of the drive train 10 and the change in the load in the transmission 12. The torque in the drive train 10 can be assumed to be known, for example. Δφ_Offset1=Δ_M1 / K.

[0049] The method advantageously utilizes the knowledge that the drive train 10 has an inertia for adapting the model M. A second offset 2 or a second correction value can result from the fact that the components K1, K2, K11, K12 of the drive train 10 are mounted and supported in the corresponding bearings. The force that the components K1, K2, K11, K12 exert on their bearings cannot be linearly dependent on position and change in position. To compensate for this effect, a simulation of the support of the components K1, K2, K11, K12 of the drive train 10 in the bearings can be carried out, for example. Furthermore, in addition to the linear moments of inertia in the drive train 10, the rotational moments of inertia can also be taken into account, such as the acceleration of the rotational inertia in the drive and / or the acceleration of the rotational inertia of the driven wheels. Δφ_Offset2=f(t,Δ_M2).

[0050] Then the following relationship / model M can result: 0.5*(Δφ1+Δφ2)=Δφ11 / i+Δφ_Offset1+Δφ_Offset2.

[0051] Using the refined model, the rotation angle φ1 of wheel 1 with a failed speed sensor S1 can be determined. The speed N1 can then be determined by a time derivative dφ1 / dt of the rotation angle φ1.

[0052] The speed N1 determined in this way can be used advantageously in a vehicle assistance system that requires the speed of the wheel, e.g. for vehicle dynamics control, speed control, slip control, brake force distribution, standstill control, etc., or for other vehicle functions.

[0053] In the case of a wheel-individual drive (so-called single-wheel drive), the term N2 for the second wheel 2 is omitted in the example shown above.

[0054] The operating parameters BP of the drive train or the model parameters to be considered (drive train stiffness, support of components K1, K2, K11, K12, etc.) for using the method can be determined using a variety of learning methods before the speed sensor S1 fails.

[0055] For example, the operating parameters BP of the drive train 10 can be determined using a simulation and / or a test run.

[0056] Another advantage is that the determined speed N1 can be used to verify the measured values ​​of the speed sensor S1, for example, even if the speed sensor S1 has not failed and is delivering sensor values ​​that seem implausible. In the case of a frozen / corroded parking brake, determining the speed N1, N2 of the frozen wheel 1, 2 can rule out a fault in the wheel speed sensor S1, S2, thus allowing the correct fault to be identified more quickly.

[0057] A corresponding computer program product and a corresponding control unit 110 for carrying out a corresponding method also each represent an aspect of the invention. The control unit 110 is shown only schematically in the Fig. 1 shown.

[0058] A corresponding assistance system 102 and a vehicle 100 with a corresponding control unit 110 also each represent an aspect of the invention and are described in the Fig. 1 is also only shown schematically.

[0059] The above explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, without departing from the scope of the present invention. List of reference symbols 100 vehicles 110 Control unit 120 assistance system 10 Drivetrain 11 Drive 12 gearboxes 1 wheel 2 wheels K1 component K2 component K11 component K12 component S1 speed sensor S2 speed sensor M model N1 speed N2 speed N11 speed BP operating parameters P1 elasticity parameter P2 inertia parameter QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 100 61 502 A1

[0003]

Claims

[1] Method for, in particular indirectly, determining a rotational speed (N1) of a preferably driven wheel (1) of a vehicle (100), wherein the vehicle (100) has a drive train (10) with a drive (11) for the wheel (1), and wherein the wheel (1) forms a component (K1) of the drive train (10), comprising: - Determining a model (M) which represents a relationship between speeds (N1, N2, N11) in the drive train (10), - detecting a rotational speed (N2, N11) of at least one further component (K2, K11) in the drive train (10), which in particular is not the wheel (1), - Determining the rotational speed (N1) of the wheel (1) as a function of the specific model (M) and of the at least one detected rotational speed (N2, N11), wherein in the specific model (M) of the drive train (10) at least one operating parameter (BP) of the drive train (10) is taken into account as a model parameter. [2] Method according to claim 1, wherein the detection of a rotational speed (N2, N11) of at least one further component (K2, K11) in the drive train (10) comprises a rotational speed (N11) of the drive (11) and / or a rotational speed (N2) of at least one further, in particular driven, wheel (2). [3] Method according to claim 1 or 2, wherein the at least one operating parameter (BP) of the drive train (10), which is represented as a model variable in the specific model (M), an elasticity parameter (P1) of at least one component (K1, K2, K11, K12) of the drive train (10). [4] Method according to one of the preceding claims, wherein the at least one operating parameter (BP) of the drive train (10), which is represented as a model variable in the specific model (M), an inertia parameter (P2) of at least one component (K1, K2, K11, K12) of the drive train (10), wherein in particular the inertia parameter (P2) comprises at least one linear inertia parameter and / or a rotational inertia parameter. [5] Method according to one of the preceding claims, wherein the at least one operating parameter (BP) of the drive train (10) is determined during a test run and / or by a simulation. [6] Method according to one of the preceding claims, wherein the determination of the rotational speed (N1) of the wheel (1) is used as a replacement for a failed rotational speed sensor (S1) on the wheel (1). [7] Method according to one of the preceding claims, wherein the determination of the rotational speed (N1) of the wheel (1) is used to check the plausibility of sensor values ​​of a rotational speed sensor (S1) on the wheel (1). [8] A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to carry out a method according to any one of the preceding claims. [9] Control unit (110) comprising a computing unit and a memory unit in which a code is stored which, when at least partially executed by the computing unit, carries out a method according to one of the preceding claims. [10] Assistance system (120) for a vehicle (100), comprising a control unit (110) according to the preceding claim.

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