DE102021109174A1 - Axle module for a vehicle and method for controlling an axle module - Google Patents

Abstract

The invention relates to an axle module (1) for a vehicle (6), having a wheel axle (2) which can be rotated about an axis of rotation (R) relative to the vehicle (6), but which can be fixed axially; two wheels (3), a first wheel (9) being arranged at a first axial end of the wheel axle (2) and a second wheel (11) being arranged at a second axial end of the wheel axle (2), the first wheel (9) and the second wheel (11) are rotatable about the wheel axle (2), a sensor (19) for detecting a position of the wheel axle (2) relative to the vehicle (6), and a drive torque distribution unit (21) which is arranged to to transmit first drive torque to the first wheel (9) and to transmit a second drive torque to the second wheel (11). The invention also relates to a vehicle (6) with such an axle module (1) and a method (100) for controlling such an axle module (1).

Description

The present invention relates to an axle module for a vehicle, in particular for an autonomous vehicle, a vehicle, in particular an autonomous vehicle, with such an axle module, and a method for controlling an axle module.

State of the art

Axle modules for vehicles are well known in the prior art. It is known to connect two wheels via an axle element, such as a wheel axle, with the wheels being steered as a function of one another for cornering. Furthermore, so-called wheel modules are known in which each wheel can be controlled or steered individually. Such wheel modules are used in particular for autonomous vehicles, with each wheel having a separate actuator for the drive and for the steering.

In addition, the so-called torque vectoring principle is known from the prior art, with which a vehicle can also be steered via the wheels. The torque vectoring principle is based on a controlled redistribution of the drive torque and not on changing the wheel position. Torque vectoring is mainly used as an additional system in well-known steering systems for vehicles.

It has now been found that there is a further need to improve a known axle module for a vehicle, in particular there is a further need to provide an axle module for a vehicle, in particular an autonomous vehicle, which can be manufactured in a space-saving and cost-effective manner.

Against this background, it is an object of the present invention to provide an improved axle module for a vehicle, in particular to provide an axle module for an autonomous vehicle that can be manufactured in a space-saving and cost-effective manner.

Disclosure of Invention

These and other objects that may be mentioned or recognized by a person skilled in the art upon reading the following description are solved by the subject-matters of the independent claims. Advantageous embodiments and developments can be found in the dependent claims and the following description.

The axle module according to the invention for a vehicle, in particular for an autonomous vehicle, has a wheel axle, two wheels, a sensor and a drive torque distributor unit. The wheel axle can be rotated about an axis of rotation relative to the vehicle, for example a vehicle body or a vehicle frame, but is axially fixed or fastened. A first of the two wheels is located at a first axial end of the wheel axle and a second of the two wheels is located at a second axial end of the wheel axle opposite the first axial end. The first wheel and the second wheel can be rotated about the wheel axis. The sensor, preferably a position sensor, is used to detect a position, in particular to determine a steering angle of the wheel axle relative to the vehicle. The drive torque distributor unit is set up to transfer a first drive torque to the first wheel and to transfer a second drive torque to the second wheel.

The advantage of the solution according to the invention lies in particular in the fact that individual drive torques can be transmitted to the wheels, and the wheel axle can be rotated relative to the vehicle but is arranged axially fixed. A rotary movement of the axis module around the axis of rotation can be generated by the targeted distribution of the respective drive torque. As a result, a targeted setting of the rotational movement, and thus a targeted setting of a steering angle, is made possible. This allows the axle module to perform a steering movement without requiring a separate actuator to steer the wheels.

In the event that the first drive torque and the second drive torque differ from one another, the torque difference causes the wheel axle to rotate about the axis of rotation. As a result, the entire axle module is turned in and, in particular, a steering movement that is gentle on the wheels and the respective surface is achieved.

In other words, one can say that the steering movement with the axle module according to the invention is brought about by a rotational movement of the entire axle module relative to the vehicle, induced in particular by the difference in the respective drive torques that are transmitted to the wheels. The wheels cannot be turned relative to the wheel axle, ie they cannot be turned, the wheels can only rotate about the wheel axle as the axis of rotation in order to produce a rolling movement for driving forwards and/or backwards. This eliminates the need for a separate actuator for steering the wheels.

The axle module is particularly compact in its design and also inexpensive to produce, and can therefore be used in particular for autonomously controlled vehicles, e.g. autonomously controlled robots are used.

The sensor is preferably designed as a position sensor. However, any other type of sensor and/or measuring device that directly or indirectly allows inferences to be drawn about the position of the wheel axle relative to the vehicle body can also be used as the sensor.

According to one embodiment, the drive torque distribution unit has a drive motor, a transmission and a drive control unit. The drive motor is set up to generate a predetermined total drive torque. The drive control unit is set up to control the transmission in such a way that the first drive torque is transmitted to the first wheel and the second drive torque is transmitted to the second wheel.

The drive motor is preferably provided for the axle module and transmits the total drive torque generated to the transmission. The transmission is controlled by the drive control unit and transmits the first drive torque to the first wheel and the second drive torque to the second wheel. The drive control unit can be designed, for example, as a so-called drive control unit (DCU) and can preferably be coupled to a vehicle control unit in order to be in communication with it, e.g. via a bus system of the vehicle.

According to an alternative embodiment, the drive torque distributor unit has two drive motors and two drive control units. The two drive control units are preferably set up to receive control signals from an external control unit, for example a vehicle control unit. A first of the two drive control units is set up to control a first of the two drive motors in such a way as to transmit the first drive torque to the first wheel. A second of the two drive control units is set up to control a second of the two drive motors in such a way as to transmit the second drive torque to the second wheel. Alternatively, the two drive motors can also be controlled by a common drive control unit.

Thus, each of the two wheels has a separate drive and is controlled via a separate drive control unit in order to transmit the respective drive torque to the wheel. The drive can be designed in particular as a wheel hub drive, which can be used in a particularly space-saving manner.

According to one embodiment, the wheels are arranged essentially symmetrically to the axis of rotation of the wheel axle. A symmetrical structure of the axle module simplifies the steering of the vehicle, since the necessary torque difference of the respective drives can be easily determined due to the symmetry.

According to an alternative embodiment, the first wheel has a first distance from the axis of rotation and the second wheel has a second distance from the axis of rotation that differs from the first distance. A non-symmetrical structure of the axis module may be necessary due to the space available. The asymmetrical structure of the axle module can be taken into account when distributing the drive torques, in particular by means of a controller, to the two wheels.

According to one embodiment, the drive torque distributor unit is set up to be able to be coupled to a vehicle control unit. The drive torque distribution unit can communicate with the vehicle control unit, for example to receive or send signals. The vehicle control unit can be used to determine the first drive torque and the second drive torque based on the actual position of the wheel axle, which is transmitted to the vehicle control unit by the sensor, and send them to the drive torque distributor unit. For this data exchange, the vehicle control unit and the drive torque distributor unit are preferably connected via signal lines, such as CAN, for example. Alternatively, the respective setpoint drive torque can also be determined by the drive torque distributor unit or by the respective drive control unit.

A further aspect of the invention relates to a vehicle, in particular an autonomous vehicle. The vehicle has at least one vehicle body, for example a vehicle frame, at least one vehicle axle, a vehicle control unit, and at least one vehicle battery. The vehicle axle is designed as an axle module described above and below and is attached to the vehicle body in a rotatable but axially fixed manner via a coupling element. The drive torque distribution unit is connected to the vehicle control unit, and the at least one vehicle battery for supplying energy is connected to the vehicle control unit and/or the drive torque distribution unit.

The drive torque distribution unit can receive the calculated required drive torques from the vehicle control unit in order to apply them to the wheels. The at least one vehicle battery supplies both the driving tool control unit and the drive torque distribution unit with energy. Preferably, the vehicle control unit and/or the drive torque distribution unit are connected to a number of vehicle batteries, in particular to different vehicle batteries which, for example, can have different voltage levels.

• Ermitteln einer Soll-Position der Radachse relativ zum Fahrzeugkörper;
• Bestimmen einer Ist-Position der Radachse mittels des Sensors;
• Bestimmen einer Positionsdifferenz zwischen der Soll-Position und der Ist-Position;
• Ermitteln, basierend auf der Positionsdifferenz, des ersten Antriebsmoments für das erste Rad,
• Ermitteln, basierend auf der Positionsdifferenz, des zweiten Antriebsmoments für das zweite Rad, und
• Übermitteln des ersten Antriebsmoments und des zweiten Antriebsmoments an die Antriebsmomentverteilereinheit.

A further aspect of the invention relates to a method for controlling an axle module described above and below. The method has at least the following steps, which do not necessarily have to be carried out in the order given:

• Determining a target position of the wheel axle relative to the vehicle body;
• determining an actual position of the wheel axle using the sensor;
• determining a position difference between the target position and the actual position;
• determining, based on the position difference, the first drive torque for the first wheel,
• determining, based on the position difference, the second drive torque for the second wheel, and
• Transmitting the first drive torque and the second drive torque to the drive torque distributor unit.

The target position of the wheel axle relative to the vehicle body can be determined in particular by the vehicle control unit. For example, the vehicle control unit can receive signals for a destination of the vehicle from an external device and determine the desired position of the wheel axle based on this. The actual position of the wheel axle is determined by the sensor. In particular, the sensor can be a position sensor that is used to detect a steering angle of the wheel axle. However, all other sensors and/or measuring devices that can be used directly or indirectly to detect the position of the wheel axle can also be used as a sensor. The sensor is also preferably connected to the vehicle control unit in order to send the detected actual position of the wheel axle to the vehicle control unit. The determination of the position difference between the target position and the actual position is preferably carried out by the vehicle control unit. In addition, the vehicle control unit then determines the first drive torque and the second drive torque based on the determined position difference, and transmits these to the drive torque distributor unit, which applies the first drive torque to the first wheel and the second drive torque to the second wheel.

A further aspect of the invention relates to a control unit for controlling an axle module described above and below. The control unit is set up to execute a method, described above and below, for controlling an axle module described above and below. Furthermore, a further aspect of the invention relates to a program element which, when executed in a vehicle control unit of a vehicle described above and below, instructs the vehicle control unit to execute the method for controlling an axle module, also described above and below.

With regard to the possible configurations of the axle module, the vehicle and/or the control device, and with regard to possible variations of the method, the above statements and those described below apply.

character list

• 1 eine schematische Darstellung eines Achsmoduls gemäß einer Ausführungsform der Erfindung in einer Vorderansicht;
• 2a und 2b eine schematische Darstellung eines Achsmoduls gemäß einer Ausführungsform der Erfindung, wobei 2a bespielhaft die Verteilung von Antriebskräften für eine Linkskurve darstellt und 2b beispielhaft die Lenkstellung des Achsmoduls für eine Linkskurve darstellt;
• 3a und 3b eine schematische Darstellung eines Achsmoduls gemäß einer Ausführungsform der Erfindung, wobei 3a beispielhaft die Verteilung von Antriebskräften für eine Rechtskurve darstellt und 3b beispielhaft die Lenkstellung des Achsmoduls für eine Rechtskurve darstellt;
• 4 eine schematische Darstellung eines Achsmoduls gemäß einer Ausführungsform der Erfindung, die beispielhaft die Verteilung von Antriebskräften für eine Geradeausfahrt darstellt;
• 5 eine schematische Darstellung eines Fahrzeugs gemäß einer Ausführungsform der Erfindung; und
• 6 ein schematisches Flussdiagramm für ein Verfahren zur Steuerung eines Achsmoduls gemäß einer Ausführungsform der Erfindung.

Further measures improving the invention are presented in more detail below together with the description of a preferred exemplary embodiment of the invention with reference to the figures. It shows:

• 1 a schematic representation of an axle module according to an embodiment of the invention in a front view;
• 2a and 2 B a schematic representation of an axle module according to an embodiment of the invention, wherein 2a exemplarily represents the distribution of driving forces for a left turn and 2 B represents an example of the steering position of the axle module for a left turn;
• 3a and 3b a schematic representation of an axle module according to an embodiment of the invention, wherein 3a exemplarily represents the distribution of driving forces for a right turn and 3b exemplarily represents the steering position of the axle module for a right turn;
• 4 a schematic representation of an axle module according to an embodiment of the invention, which represents an example of the distribution of drive forces for straight-ahead driving;
• 5 a schematic representation of a vehicle according to an embodiment of the invention; and
• 6 a schematic flowchart for a method for controlling an axle module according to an embodiment of the invention.

The figures are only of a schematic nature and serve only to understand the invention. The same elements are provided with the same reference numbers.

1 shows a schematic representation of an axle module 1 according to an embodiment of the invention in a front view. The axle module 1 has an axle element 2, a so-called wheel axle 2, which is connected to a wheel 3 at each of its axial ends. in the in 1 In the exemplary embodiment shown, the wheels 3 are each connected to the wheel axle 2 via a separate wheel hub drive 4 in such a way that they can each rotate about the wheel axle. As a result, a drive movement is possible. A relative twisting and/or tilting of the wheels 3, for example a wheel deflection as in a classic steering movement, is not possible.

The wheel hub drives 4 are each controlled by a drive control unit 15, 16 in order to transmit a predetermined drive torque to the wheels 3 in order to implement a drive movement. Depending on a diameter of the respective wheel 3, a drive force results from the predetermined drive torque, from which the drive movement results. The wheel hub drives 4 and the drive control units 15, 16 can also be collectively referred to as a drive torque distributor unit 21.

The wheel axle 2 is also connected to a coupling element 5 in a rotationally and axially fixed manner. The coupling element 5 is also attached to a vehicle body (not shown) of a vehicle 6 (see FIG 5 ) Stored in such a way that the coupling element 5, and thus the axle module 1, is rotatable about an axis of rotation R relative to the vehicle 6, but is mounted axially fixed. this is in 1 shown as an example with a bearing 7 . A steering of the vehicle 6 is based exclusively on the fact that the axle module 1 rotates relative to the vehicle 6 . A rotational movement of the axle module 1 is realized by an individual, in particular unequal, distribution of drive torques to the wheels 3 . This is related to the 2 until 4 explained in more detail below.

the 2 until 4 show various schematic representations of the axle module 1, wherein 2 shows schematic representations for the consideration of a left turn, 3 shows schematic representations for viewing a right turn, and 4 shows a schematic representation for the consideration of straight-ahead driving. In the 2 until 4 it is assumed that the wheels 3 have the same diameter.

2a shows schematically the axle module 1. A first wheel hub drive 8 transmits a first drive torque to a first wheel 9, resulting in a first drive force FA1. A second wheel hub drive 10 transmits a second drive torque to a second wheel 11, resulting in a second drive force FA2. The axle module 1 shown here is constructed essentially symmetrically. This means that the first wheel 9 and the second wheel 11 are at essentially the same distance h from a center point MP of the wheel axle 2 , which is also a pivot point 12 about which the wheel axle 2 can be rotated relative to the vehicle 6 . Thus, the pivot point 12 is the area where the coupling element 5 is attached to the wheel axle 2 .

In 2a the second driving force FA2 is smaller than the first driving force FA1, which is also illustrated by the different lengths of the arrows. The different drive torque distribution and the resulting different drive forces FA1, FA2 cause a steering torque ML around the pivot point 12, the amount of which results from the difference between the drive forces FA1, FA2 and the distance h from the pivot point 12: $$ML=\mathrm{<figure-callout\; id="1"\; label="f\; A"\; filenames="DE102021109174A1\_0002.png,DE102021109174A1\_0003.png"\; state="\{\{state\}\}">f</figure-callout>}A1\ast H-\mathrm{<figure-callout\; id="2"\; label="f\; A"\; filenames="DE102021109174A1\_0002.png,DE102021109174A1\_0003.png"\; state="\{\{state\}\}">f</figure-callout>}A2\ast H=\left(\mathrm{<figure-callout\; id="1"\; label="f\; A"\; filenames="DE102021109174A1\_0002.png,DE102021109174A1\_0003.png"\; state="\{\{state\}\}">f</figure-callout>}A1-fA2\right)\ast H$$

Due to the fact that in 2a the first drive force FA1 on the first wheel 9 is greater than the second drive force FA2 on the second wheel 11, the resulting steering torque ML causes the wheel axle 2 to rotate counterclockwise about the pivot point 12. This counterclockwise rotation of the wheel axis 2 causes a Left turn of the vehicle 6 (see 2 B) .

In 3a the second drive force FA2 on the second wheel 11 is greater than the first drive force FA1 on the first wheel 9. This results in a steering torque ML, which causes the wheel axle to rotate clockwise about the pivot point 12. This clockwise rotation of the wheel axle 2 causes the vehicle 6 to turn to the right (see 3b) .

In 4 the first drive force FA1 on the first wheel 9 is equal to the second drive force FA2 on the second wheel 11. Since the two drive forces FA1, FA2 are equal, no steering torque ML is generated. Thus, the wheel axle 2 does not rotate about the pivot point 12 and the vehicle 6 can drive straight ahead.

An amount of difference between the first driving force FA1 and the second driving force FA2 affects the degree of rotation of the wheel axle 2 about the fulcrum 12, and thus the degree of the turn to be made. This means that there is a small difference between the driving forces FA1, FA2 Lich generates a small steering torque ML, which causes only a small rotation of the wheel axle 2 about the pivot point 12 and thus results in a wide curve. A large difference between the driving forces FA1, FA2 generates a large steering torque ML, which causes the wheel axle 2 to rotate sharply about the pivot point 12 and thus results in a tight curve.

5 shows an example of a schematic, functional representation of a vehicle 6 according to an embodiment of the invention. The vehicle 6 has a front axle 13, which is designed as the axle module 1, and a rigid rear axle 14. The first wheel hub drive 8 is connected to a first drive control unit 15, and the second wheel hub drive 10 is connected to a second drive control unit 16.

The drive control units 15, 16 are designed to control the respective wheel hub drive 8, 10 in order to transmit the respective drive torque to the respective wheel 9, 11. The drive control units 15, 16 are in turn connected to a vehicle control unit 18 for data exchange via communication or signal lines 17, for example CAN.

In addition, the axle module 1 has a sensor 19 which is designed to detect a position of the wheel axle 2 and thus of the axle module 1 relative to the vehicle 6 . The sensor 19 is also connected to the vehicle control unit 18 via a signal line 17 . The vehicle control unit 18 and the drive control units 15, 16 and the wheel hub drives 8, 10 are supplied with the necessary energy by a vehicle battery 20.

In the 1 until 4 an axle module 1 is shown with a drive torque distributor unit 21, which has a separate wheel hub drive 4 for each of the two wheels 3, each wheel hub drive 8, 10 being controlled by its own drive control unit 15, 16. However, it is also conceivable that the drive torque distributor unit 21 has only one drive motor, which generates a total drive torque that is then distributed individually to the wheels 4, for example via a transmission. For this purpose, the transmission is controlled by a drive control unit. A control method for controlling the axis module 1 is described below with reference to FIG 6 described.

6 FIG. 1 shows, by way of example, a flowchart for a method 100 for controlling an axle module 1 according to an embodiment of the invention. In a step S1 of the method 100, a target position of the wheel axle 2 relative to the vehicle 6 is determined. For example, the vehicle control unit 18 receives a target position for the vehicle from an external device and calculates a route to reach the target position based on information stored in the vehicle control unit 18 . Vehicle control unit 18 can determine the target position of wheel axle 2 based on the route.

In a step S2, the sensor 19 determines the actual position of the wheel axle 12 and transmits this via the signal line 17 to the vehicle control unit 18. The vehicle control unit 18 then determines in a step S3 a difference between the target position of the wheel axle 2 and the actual Position of the wheel axle 2 and based on this difference in a step S4 determines the first drive torque for the first wheel 9 and in a step S5 the second drive torque for the second wheel 11. In a step S6 the vehicle control unit 18 transmits the determined first and second drive torques to the drive torque distributor unit 21, which transmits it to the wheels 3.

It should be noted that the size of the drive force FA1, FA2 resulting from the respective applied drive torque also depends on a coefficient of friction between the respective wheel 9, 11 and the ground, which can be taken into account in the method described above. It is also possible to adapt the method 100 to an axle module 1 that is not constructed symmetrically. This means an axle module 1 in which the pivot point 12 does not correspond to the center point MP of the wheel axle 2 and/or in which the wheels 4 are at different distances from the pivot point 12 .

Reference List

1

axis module

2

Axle element, wheel axle

3

wheel

4

wheel hub drive

5

coupling element

6

vehicle

7

storage

8th

first wheel hub drive

9

first wheel

10

second wheel hub drive

11

second wheel

12

pivot point

13

front axle

14

rear axle

15

first drive control unit

16

second drive control unit

17

communication line

18

vehicle control unit

19

sensor

20

vehicle battery

21

torque distribution unit

100

procedure

FA1, FA2

driving force

MP

Focus

ML

steering torque

H

Distance

R

axis of rotation

Claims (10)

Axle module (1) for a vehicle (6), having: a wheel axle (2) which can be rotated about an axis of rotation (R) relative to the vehicle (6), but which can be fastened in an axially fixed manner; two wheels (3), a first wheel (9) being arranged at a first axial end of the wheel axle (2) and a second wheel (11) being arranged at a second axial end of the wheel axle (2), the first wheel (9) and the second wheel (11) can be rotated about the wheel axle (2), a sensor (19) for detecting a position of the wheel axle (2) relative to the vehicle (6), and a drive torque distributor unit (21) which is set up to transmit a first drive torque to the first wheel (9) and to transmit a second drive torque to the second wheel (11). Axis module (1) after claim 1 , wherein the drive torque distributor unit (21) has a drive motor, a transmission and a drive control unit, the drive motor being set up to generate a predetermined total drive torque, the drive control unit being set up to control the transmission in such a way that the first drive torque is applied to the to transmit the first wheel (9) and to transmit the second drive torque to the second wheel (11). Axis module (1) after claim 1 , wherein the drive torque distributor unit (21) has two drive motors (8, 10) and two drive control units (15, 16), a first of the two drive control units (15) being set up to control a first of the two drive motors (8) in such a way as to to transmit the first drive torque to the first wheel (9), and wherein a second of the two drive control units (16) is set up to control a second of the two drive motors (10) in such a way to transmit the second drive torque to the second wheel (11) transferred to. Axis module (1) according to one of Claims 1 until 3 , wherein the wheels (3) are arranged substantially symmetrically to the axis of rotation (R) of the wheel axle (2). Axis module (1) according to one of Claims 1 until 3 , wherein the first wheel (9) has a first distance from the axis of rotation (R) and the second wheel (11) has a second distance from the axis of rotation (R) that is different from the first distance. Axis module (1) according to one of Claims 1 until 5 , wherein the drive torque distributor unit (21) is adapted to be coupled to a vehicle control unit (18). Vehicle (6), in particular an autonomous vehicle, comprising: a vehicle body, at least one vehicle axle (13; 14), a vehicle control unit (18); and at least one vehicle battery (20), wherein the vehicle axle (13; 14) as an axle module (1) according to one of Claims 1 until 6 and is rotatably but axially fixed to the vehicle body via a coupling element (5), the drive torque distributor unit (21) being connected to the vehicle control unit (18), and the at least one vehicle battery (20) being connected to the vehicle control unit (18 ) and/or the drive torque distributor unit (21) is connected. Method (100) for controlling an axis module (1) according to one of Claims 1 until 6 , having the following steps: determining a target position of the wheel axle (2); Determining an actual position of the wheel axle (2) by means of the sensor (19); determining a position difference between the target position and the actual position; Determining, based on the position difference, the first drive torque for the first wheel (9), determining, based on the position difference, the second drive torque for the second wheel (11), and transmitting the first drive torque and the second drive torque to the drive torque distributor unit (21 ). Control unit for controlling an axle module (1) according to one of Claims 1 until 6 , wherein the control unit is set up to the method (100) for controlling an axle module (1). claim 8 to execute. Program element that, when in a vehicle control unit (18) of a vehicle (6). claim 7 is executed, the vehicle control unit (18) directs the method (100) according to claim 8 to execute.

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