Method for operating an actively adjustable roll stabiliser

Abstract

The invention relates to a method for operating an actively adjustable roll stabiliser (1) for a motor vehicle, wherein the roll stabiliser (1) comprises an actuator (2) having a drive train formed from a motor (3), a transmission (4), a device (5) for decoupling torsional vibrations and an output element (6), and comprises two stabiliser sections (10a, 10b) which can be coupled at its ends to wheel suspensions (11a, 11b) and of which a first stabiliser section (10a) is connected to a housing (8) of the actuator (2), wherein a second stabiliser section (10b) is connected to the output element (6) in such a way that the second stabiliser section (10b) can be rotated about an axis of rotation (7) relative to the first stabiliser section (10a) by means of the drive train in order to counteract a roll torque (M) acting on the motor vehicle, characterised in that a rotation of the output element (6) is detected by means of a sensor in order to determine a rotation (α) of the actuator (2), in that an external rotation (β) of the roll stabiliser (1) is determined, and in that the motor (3) is controlled taking into account the rotation (α) of the actuator (2), the external rotation (β) of the roll stabiliser (1) and a mechanical stiffness (c) of the stabiliser sections (10a, 10b).

Description

[0001] Method for operating an actively adjustable roll stabilizer

[0002] The invention relates to a method for operating an actively adjustable roll stabilizer for a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to an actively adjustable roll stabilizer for a motor vehicle according to the preamble of claim 9.

[0003] In automotive engineering, particularly chassis technology, it is known that the roll behavior of motor vehicles can be influenced by means of so-called roll stabilizers. In their basic design, these are essentially C-shaped torsion bars, which are mounted in the center of the vehicle body so that they can rotate relative to the vehicle body. Their outer, opposite ends are each coupled to a wheel suspension by means of so-called pendulum supports. The roll stabilizer thus ensures that the vehicle body not only compresses on the outside when cornering (due to centrifugal force), but also that the inside wheel is slightly lowered. Roll stabilizers improve the vehicle's directional stability and reduce the lateral inclination of the vehicle body (roll), making cornering safer and more comfortable.

[0004] To further increase vehicle stability and ride comfort, roll stabilizers can be designed to be actively adjustable. In this case, the roll stabilizer comprises an actuator and is divided into two stabilizer sections that can be rotated relative to each other around a rotational axis using the actuator. By rotating the stabilizer sections relative to each other, a roll movement of the vehicle body is deliberately generated or a roll movement of the vehicle body caused by external influences is specifically counteracted.

[0005] Adjustable roll stabilizers are known from the prior art, the actuator of which comprises an electric motor that is drive-connected to a mechanical transmission, particularly in the form of a multi-stage planetary gear, to achieve suitable speeds or torques. In this context, reference is made to DE 10 2006219 399 A1, for example. The actuator therein has a drive train comprising a motor, a transmission, and an output element, each of which is directly drive-connected to one another. In the assembled state, as shown in Figure 1 therein, the output element of the actuator is connected to a second stabilizer section.Due to the direct drive coupling between the engine, transmission, output element, and second stabilizer section, the disadvantage is that when a vehicle equipped with this system travels straight ahead over an uneven road surface, wheel heave movements caused by rolling over bumps in the road surface introduce disruptive vibrations into the vehicle (here: around the roll axis). The roll stabilizer lacks the means to compensate for such disturbances.

[0006] In contrast, an actively adjustable roll stabilizer previously known from DE 10 2021 201 025 A1 has a torsion damper in the drive train of the actuator, i.e. a device arranged between the transmission and the output element to decouple torsional vibrations.

[0007] The present invention relates, according to the preamble of claim 1, to a method for operating an actively adjustable roll stabilizer, wherein the roll stabilizer comprises an actuator with a drive train formed from a motor, a transmission, a device for decoupling torsional vibrations and an output element, as well as two stabilizer sections which can be coupled at the ends to wheel suspensions, of which a first stabilizer section is connected to a housing of the actuator, wherein a second stabilizer section is connected to the output element in such a way that the second stabilizer section can be rotated about an axis of rotation relative to the first stabilizer section by means of the drive train in order to counteract a rolling moment acting on the motor vehicle.

[0008] In such an actuator equipped with a torsional vibration decoupling element in the drivetrain, there is a torsional compliance within the drivetrain between the motor and the output element, since the interposed device for decoupling torsional vibrations allows for at least a certain degree of rotation – depending on the load. While this compliance is advantageous and desirable in terms of achievable ride comfort (elimination of disturbing vibrations), it poses a challenge with regard to actuator control.In order to set a desired target torque with an actuator, it is possible in a relatively simple way to construct an actuator without a torsion damper by first dividing the target torque by a known mechanical stiffness of the roll stabilizer in order to calculate a so-called target angle by which the motor must then be adjusted in order to effectively obtain the desired torque (control of the torque via a position controller).

[0009] In a drivetrain equipped with a torsion damper, this type of control (torque control via a position controller) cannot be implemented because the presence of a torsion damper – usually comprising an elastomer decoupling element – ​​leads to nonlinear stiffness behavior and usually also to hysteresis, which means that a desired torque cannot be achieved simply (as described above) by setting a specific motor rotation angle. In an actuator equipped with a torsion damper in the drivetrain, setting a desired torque to specifically influence the vehicle's roll behavior conventionally requires the additional integration of a torque sensor in the drivetrain in order to create a closed control loop for the torque to be controlled. The integration of such a torque sensor is disadvantageous in several respects.In addition to additional design and installation space requirements, the complexity and susceptibility to failure of the overall system increases.

[0010] It is an object of the present invention to provide a method for operating an actively adjustable roll stabilizer with a device for decoupling torsional vibrations in the drive train, which method enables control of the actuator motor to set a desired torque using simple structural means, in particular while avoiding the use of a torque sensor. In addition, an actively adjustable roll stabilizer for a motor vehicle is to be provided that enables this accordingly. This object is achieved, first, by a method according to the features of claim 1.It is a method for operating an actively adjustable roll stabilizer for a motor vehicle, wherein the roll stabilizer comprises an actuator with a drive train formed from an engine, a transmission, a device for decoupling torsional vibrations and an output element, as well as two stabilizer sections which can be coupled at the ends to wheel suspensions, of which a first stabilizer section is connected to a housing of the actuator, wherein a second stabilizer section is connected to the output element in such a way that the second stabilizer section can be rotated about an axis of rotation relative to the first stabilizer section by means of the drive train in order to counteract a rolling moment acting on the motor vehicle.

[0011] According to the invention, the method is characterized in that, to determine a rotation of the actuator, a rotation of the output element is detected by a sensor, an external rotation of the roll stabilizer is determined, and the motor is controlled taking into account the rotation of the actuator, the external rotation of the roll stabilizer, and the mechanical stiffness of the stabilizer sections. Accordingly, it was initially recognized that, due to a non-linear stiffness behavior including adverse hysteresis effects in the drive train, a desired torque cannot be easily achieved on an actuator equipped with a device for decoupling torsional vibrations by simply setting a specific motor rotation angle—in order to generate a mathematically resulting counter-roll moment based on knowledge of the mechanical stiffness of the stabilizer sections.The idea of ​​the invention was then developed to detect the rotation of the actuator's output element using sensors "across the decoupling element." Thus, not only is the motor rotation angle measured to calculate the rotation angle (multiplied by the known constant gear ratio), but rather the total rotation angle of the drive train formed by the motor, transmission, and torsion damper (=device for decoupling torsional vibrations) is measured, referred to in the context of this patent application as the "torsion of the actuator." Knowing this rotation of the actuator, as well as an additional external rotation of the roll stabilizer, which is already detected, the applied torque can be calculated with additional knowledge of the mechanical stiffness of the stabilizer sections.This signal can then be fed into a motor control system to set a desired torque on the roll stabilizer. This solves the aforementioned problem.

[0012] To detect the actuator's rotation, the angle of rotation of the output element around the rotation axis is advantageously measured. This can be implemented in various ways.

[0013] The external rotation of the roll stabilizer is the degree by which the stabilizer sections are rotated relative to each other around the axis of rotation at their ends, meaning at the coupling point with the respective wheel suspension. The external rotation of the roll stabilizer is advantageously determined by comparing, in particular by examining the differences between, the heights of the wheel suspensions or the respective areas of the stabilizer sections closest to the wheels.

[0014] From a design point of view, it can advantageously be provided that each of the stabilizer sections is assigned a height sensor with which a height of a region of the respective stabilizer section close to the wheel is detected.

[0015] According to an advantageous development of the method, the detected rotation of the actuator and the determined external rotation of the roll stabilizer are fed to a position controller.

[0016] Advantageously, it can be provided that a moment applied to the roll stabilizer is calculated by multiplying the difference between the actuator's rotation and the external rotation of the roll stabilizer by the mechanical stiffness of the stabilizer sections. It is expedient to implement position control by appropriately controlling the motor, taking the calculated moment into account.

[0017] In a manner known per se, the stabilizer sections are expediently coupled to a wheel suspension of the motor vehicle at a radial distance from the axis of rotation in order to influence the rolling behavior of the motor vehicle.

[0018] The object mentioned above is also achieved by an actively adjustable roll stabilizer for a motor vehicle according to the features of claim 9. This is suitable for carrying out the method as described above and, according to the invention, has two stabilizer sections which can each be coupled to the wheel suspension of the motor vehicle, each of which is connected to an actuator and can be rotated relative to one another about a rotational axis by means of the actuator in order to influence the roll behavior of the motor vehicle. The actuator has a motor arranged in a housing, wherein the housing is connected to a first stabilizer section, an output element which is rotatable about the rotational axis and can be driven by the motor and is connected to a second stabilizer section, a device acting between the motor and the output element for decoupling torsional vibrations, and a position controller.The actively adjustable roll stabilizer is characterized according to the invention by a sensor device for detecting a rotation of the actuator, a device for determining the external rotation of the roll stabilizer or for receiving such information, wherein the position controller is operable to determine a torque applied to the roll stabilizer from the rotation of the actuator, the external rotation of the roll stabilizer and a mechanical stiffness of the stabilizer sections and to control the motor taking the torque into account.

[0019] The sensor device for detecting a rotation of the actuator preferably comprises a rotation angle sensor with which a rotation angle of the output element about the rotation axis can be detected. The device for determining the external rotation of the roll stabilizer preferably comprises a sensor arrangement that detects the heights of the wheel suspensions and is operable to derive the external rotation of the roll stabilizer from a comparison, in particular a differential analysis, of the heights.

[0020] The invention will be explained in more detail below with reference to the accompanying drawing. Further advantageous effects of the invention will also emerge from this. The drawing shows the only

[0021] Figure 1 shows an actively adjustable roll stabilizer for a motor vehicle in a simplified perspective view from the rear above.

[0022] The sole Figure 1 shows an actively adjustable roll stabilizer 1 for a motor vehicle in a simplified perspective view. For orientation, a direction of travel FR is indicated by an arrow pointing in a preferred direction of travel (forward direction of travel) of a motor vehicle to be equipped with the roll stabilizer 1. The actively adjustable roll stabilizer 1 is accordingly part of a chassis (not shown in full) of a motor vehicle (not shown). The roll stabilizer 1 is also part of an axle of the motor vehicle; for example, the front axle and / or rear axle of the motor vehicle can be equipped with such an adjustable roll stabilizer 1.

[0023] As Figure 1 shows, a first wheel 12a (on the left with respect to the direction of travel FR shown) and a second wheel 12b (on the right with respect to the direction of travel FR shown) are each connected to a vehicle body of the motor vehicle (not shown for illustration reasons) via a first wheel suspension 11a and a second wheel suspension 11b, respectively, which are not to be explained in more detail.

[0024] The actively adjustable roll stabilizer 1 essentially consists of a first stabilizer section 10a and a second stabilizer section 10b, which are connected to one another via a substantially cylindrical actuator 2 arranged therebetween. The actively adjustable roll stabilizer 1 forms a C-shaped torsion bar spring in a manner known per se. An end of the first stabilizer section 10a facing away from the actuator 2 is coupled to the first wheel suspension 11a via a pendulum support (not designated in more detail), while an end of the second stabilizer section 10b facing away from the actuator 2 is coupled to the second wheel suspension 11b via a corresponding pendulum support. As indicated graphically by the respective double arrows, height movements of the first wheel 12a or the second wheel 12b are transmitted via the respective wheel suspension 11a or 11b and the pendulum supports to the first stabilizer section 10a ormechanically coupled to the second stabilizer section 10b.

[0025] The actuator 2, arranged between the first stabilizer section 10a and the second stabilizer section 10b, has a substantially cylindrical basic shape and extends along a rotation axis 7. A motor 3, a gearbox 4, a torsional damper 5, and an output element 6 are arranged coaxially within a housing 8 of the actuator 2 and are drivingly connected to one another, thus forming a drive train. Also located within the housing 8 of the actuator 2 is an electronic monitoring and control unit, including a position controller 9. The motor 3 is controlled by means of the position controller 9, with the position controller 9 receiving input signals for controlling the motor 3, among other things, from a rotation angle sensor 13, also arranged on the actuator 2, and from height sensors 14a, 14b. In addition, the position controllers 9 receive further signals, which in particular specify a torque to be set.

[0026] In a manner known per se, the motor 3 is an electric motor. This is drive-connected to the transmission 4, which, in a manner also known per se, is preferably designed as a multi-stage planetary gear with preferably three planetary gear stages in order to translate an input speed specified by the motor 3 into a lower output speed with a correspondingly higher torque. The output element 6 of the actuator 2 is rotatably mounted relative to the housing 8 of the actuator 2 and is drive-connected to the output of the transmission 4 by means of a device 5 for decoupling torsional vibrations (in short: a torsional damper). When the motor 3 is operated, the output element 6 is correspondingly set in rotation about the rotational axis 7 via the transmission 4 and the torsional damper 5, whereby the second stabilizer section 10b, which is rigidly connected to the output element 6, is also rotated about the rotational axis 7.

[0027] While the transmission 4 specifies a fixed speed ratio between the engine and the transmission output, the torsional damper 5, located between the transmission output and the output element 6, ensures a certain degree of rotational flexibility due to its torsional elasticity. The torsional damper preferably has a characteristic characterized by a load-dependent, variable stiffness, with a low stiffness under a low moment load, while its stiffness increases with increasing moment load ("progressive spring characteristic").The torsion damper 5 thus has the effect, in a manner known per se, that height movements of the wheels 12a, 12b caused when driving over uneven road surfaces can be at least partially dampened by at least partially absorbing these movements under an inward rotation of the torsion damper 5 and thus not even being introduced into the transmission and the engine, where these vibrations can lead to adverse disturbing effects (e.g. noise development due to flank impact within the transmission).

[0028] In the actively adjustable roll stabilizer 1 shown in Figure 1, a rotation a of the actuator 2 is detected by a sensor in that a rotation angle sensor 13 is arranged on an axial end of the actuator 2 facing the second stabilizer section 10b, which sensor detects a rotation a of the output element 6 about the rotation axis 7.

[0029] In contrast to conventional actuators for roll stabilizers, in which only a rotation of the motor is measured (by detecting the angle of rotation of the motor shaft) and the rotation of the transmission output is calculated using a known constant gear ratio, the roll stabilizer 1 according to the invention therefore has the option of being able to measure the rotation of the actuator 2 “across the torsion damper 5”, so that despite the presence of a torsion damper 5, an entire rotation a of the actuator 2, i.e. a rotation between the housing 8 and the output element 6, can be detected.

[0030] In addition, an external rotation ß of the roll stabilizer 1 is determined. For this purpose, each of the stabilizer sections 10a and 10b is assigned a ride height sensor 14a or 14b, with which a ride height h1 or h2 of a region of the respective stabilizer section 10a or 10b near the wheel is detected. The external rotation ß of the roll stabilizer 1 is determined by a comparison, in particular by a differential analysis, of the ride heights h1, h2 of the wheel suspensions 11a, 11b.

[0031] While in an unloaded state the first stabilizer section 10a and the second stabilizer section 10b lie in a common horizontal plane, in a twisted state (under load) the first stabilizer section 10a' and the second stabilizer section 10b' are located in planes inclined to one another about the rotation axis 7 (by a twist ß), as indicated graphically in Figure 1 by dashed lines. From a single twist ß occurring on each side of the roll stabilizer 1 a of the first stabilizer section 10a 'and a single twist ßb of the second stabilizer section Wb' results in the external twist ß of the roll stabilizer 1 . Therefore, ß = ß a + ßb, where the division into ß a and ß aIn the context of the present application, it primarily serves to graphically visualize the rotation. Rather, the (total) external rotation ß, which can be detected by means of height sensors 14a, 14b, and is of importance to the invention as an actual operating parameter.

[0032] The detected rotation a of actuator 2 (internal rotation) and the determined external rotation ß of the roll stabilizer are fed to the position controller 9. A moment M applied to the roll stabilizer 1 is calculated by multiplying the difference between the rotation a of actuator 2 and the external rotation ß of the roll stabilizer 1 by a known mechanical stiffness c of the stabilizer sections 10a, 10b. Taking the calculated moment M into account, the position controller 9 can then control the motor 3 in order to set a desired moment on the roll stabilizer through position control.

[0033] The rotation angle measurement on the actuator via the torsion damper proposed according to the invention advantageously makes it possible to use a decoupling element (torsion damper) that promotes driving comfort within the drive train of the actuator, but to dispense with a complex torque sensor.

[0034] Reference symbol

[0035] 1 actively adjustable roll stabilizer

[0036] 2 actuators

[0037] 3 Engine

[0038] 4 gearboxes

[0039] 5 torsion dampers

[0040] 6 Output element

[0041] 7 Rotation axis

[0042] 8 housings

[0043] 9 Position controller

[0044] 10a first stabilizer section

[0045] 10b second stabilizer section

[0046] 10a' first stabilizer section (twisted state)

[0047] 10b' second stabilizer section (twisted state)

[0048] 11 a first wheel suspension

[0049] 11 b second wheel suspension

[0050] 12a bike

[0051] 12b bike

[0052] 13 Angle sensor

[0053] 14a Height level sensor

[0054] 14b Height sensor a Torsion actuator ß a , ßb Twisting of first or second stabilizer section, ß Outer twisting of roll stabilizer c Stiffness

[0055] FR Direction of travel h1 Height of first wheel h2 Height of second wheel

[0056] M Moment

Claims

Patent claims 1. A method for operating an actively adjustable roll stabilizer (1) for a motor vehicle, wherein the roll stabilizer (1) comprises an actuator (2) with a drive train formed by a motor (3), a transmission (4), a device (5) for decoupling torsional vibrations, and an output element (6), as well as two stabilizer sections (10a, 10b) that can be coupled at their ends to wheel suspensions (11a, 11b), of which a first stabilizer section (10a) is connected to a housing (8) of the actuator (2), wherein a second stabilizer section (10b) is connected to the output element (6) such that the second stabilizer section (10b) can be rotated about a rotation axis (7) relative to the first stabilizer section (10a) by means of the drive train in order to counteract a rolling moment (M) acting on the motor vehicle, characterized in thatthat in order to determine a rotation (a) of the actuator (2), a rotation of the output element (6) is detected by a sensor, that an external rotation (ß) of the roll stabilizer (1) is determined, and that the motor (3) is controlled taking into account the rotation (a) of the actuator (2), the external rotation (ß) of the roll stabilizer (1) and a mechanical stiffness (c) of the stabilizer sections (10a, 10b).

2. Method according to claim 1, characterized in that for the sensory detection of the rotation (a) of the actuator (2) an angle of rotation of the output element (6) about the axis of rotation (7) is detected.

3. Method according to claim 2, characterized in that the external rotation (ß) of the roll stabilizer (1) is determined by a comparison, in particular by a difference analysis of the heights (h1, h2) of the wheel suspensions (11 a, 11 b) or of the respective regions of the stabilizer sections (10a, 10b) close to the wheel.

4. Method according to one of the preceding claims, characterized in that each of the stabilizer sections (10a, 10b) is assigned a height sensor (14a, 14b), with which a height (h1, h2) of a region of the respective stabilizer section (10a, 10b) close to the wheel is detected.

5. Method according to one of the preceding claims, characterized in that the detected rotation (a) of the actuator (2) and the determined external rotation (ß) of the roll stabilizer (1) are fed to a position controller (9).

6. Method according to one of the preceding claims, characterized in that a moment (M) applied to the roll stabilizer (1) is calculated by multiplying a difference between the rotation (a) of the actuator (2) and the external rotation (ß) of the roll stabilizer (1) by the mechanical stiffness (c) of the stabilizer sections (10a, 10b).

7. Method according to claim 6, characterized in that by suitable control of the motor (3) a position control is carried out taking into account the calculated torque (M).

8. Method according to one of the preceding claims, characterized in that the stabilizer sections (10a, 10b) are each coupled to a wheel suspension (11a, 11b) of the motor vehicle radially away from the axis of rotation (7) in order to influence a rolling behavior of the motor vehicle.

9. An actively adjustable roll stabilizer (1) for a motor vehicle, suitable for carrying out the method according to one of the preceding claims, comprising two stabilizer sections (10a, 10b) which can each be coupled to wheel suspensions (11a, 11b) of the motor vehicle, each of which is connected to an actuator (2) and can be rotated relative to one another about a rotational axis (7) by means of the actuator (2) in order to influence a roll behavior of the motor vehicle, wherein the actuator (2) comprises: a motor (3) arranged in a housing (8), wherein the housing (8) is connected to a first stabilizer section (10a), an output element (6) which is rotatable about the rotational axis (7) and drivable by the motor (3), which output element is connected to a second stabilizer section (10b), a device (5) acting between the motor (3) and the output element (6) for decoupling torsional vibrations, and a position controller (9), characterized by a sensor device (13) for detecting a rotation (a) of the actuator (2), a device (14a, 14b) for determining the external rotation (ß) of the roll stabilizer (1) or for receiving such information, wherein the position controller (9) is operable to determine a moment (M) applied to the roll stabilizer (1) from the rotation (a) of the actuator (2), the external rotation (ß) of the roll stabilizer (1) and a mechanical stiffness (c) of the stabilizer sections (10a, 10b) and to control the motor (3) taking the moment (M) into account.

10. Actively adjustable roll stabilizer according to claim 9, characterized in that the sensor device for detecting a rotation of the actuator comprises a rotation angle sensor (13) with which a rotation angle (a) of the output element (6) about the rotation axis (7) can be detected.

11. Actively adjustable roll stabilizer according to claim 9 or 10, characterized in that the device for determining the external rotation (ß) of the roll stabilizer comprises a sensor arrangement (14a, 14b) which detects the height levels (h1, h2) of the wheel suspensions (11a, 11b) and which is operable to derive the external rotation (ß) of the roll stabilizer (1) from a comparison, in particular a difference analysis of the height levels (h1, h2).

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