Method and system for roll stabilization of a motor vehicle

Abstract

A method for roll stabilization of a motor vehicle by means of an adjustable roll stabilizer (1), wherein the adjustable roll stabilizer (1) has an actuator (2) which is operable to twist two stabilizer segments (6a, 6b) connected to the actuator relative to one another about a rotational axis (3) in a manner that depends on at least one system-theoretical torque and, taking into account the system stiffness of the roll stabilizer (1), controls the actuator (2), wherein a comparison between the current system torque and the system-theoretical torque is carried out in order to check and / or adapt the correctness of the stored system stiffness.

Description

Technical Field

[0001] The invention relates to a method for roll stabilization of a motor vehicle by means of an adjustable roll stabilizer, and to a system for roll stabilization. Background Art

[0002] It is known from motor vehicle technology, in particular chassis technology, to influence the rollover or rolling behavior of a motor vehicle by means of a so-called roll stabilizer. In the basic structure, the roll stabilizer is a substantially C-shaped torsion bar spring which is rotatably mounted in the middle region relative to the vehicle structure and whose opposite outer ends are respectively connected to the wheel suspension by means of coupling elements (so-called swing struts). Due to this structure, the roll stabilizer ensures that the body of the vehicle is not only pressed down on the side outside the bend (due to centrifugal force) when cornering, but also that the wheel inside the bend is slightly lowered. The roll stabilizer increases the driving directional stability of the vehicle and reduces the lateral inclination (rolling) of the vehicle structure, thereby making cornering safer and more comfortable.

[0003] In order to further improve vehicle stability and driving comfort, it is known to implement such a roll stabilizer in an adjustable manner. In this case, the roll stabilizer includes an actuator and is divided into two stabilizer sections that can be twisted relative to each other around a rotation axis by means of the actuator. Due to the twisting of the stabilizer sections relative to each other, a rolling movement of the vehicle structure is generated in a targeted manner or a rolling movement of the vehicle structure caused by external influences is counteracted in a targeted manner. From the prior art, an adjustable roll stabilizer is known, the actuator of which has an electric motor, which is in drive connection with a mechanical transmission, in particular in the form of a multi-stage planetary transmission, in order to obtain a suitable rotational speed or torque. In this regard, reference is made by way of example to DE 10 2016 219 399 A1.

[0004] In addition to the structural design of an adjustable roll stabilizer, its suitable control is also a technical challenge. For example, a device for adjusting the roll behavior of a motor vehicle is known from DE 10 2009 043 070 A1. Reference is also made to EP 1 577 127 A2.

[0005] For the roll stabilization of a motor vehicle by means of an adjustable roll stabilizer, wherein the adjustable roll stabilizer has an actuator which is operable to twist two stabilizer sections connected to the actuator relative to one another about a rotational axis, in such a way that the actuator is controlled taking into account at least one system-theoretical torque and taking into account the system stiffness of the roll stabilizer, it is precisely necessary to obtain this stiffness (system stiffness) as an input variable. In this context, the system stiffness includes in particular the torsional stiffness of the stabilizer (specifically, the stabilizer sections), the bending stiffness of the stabilizer arms (the regions of the stabilizer sections extending from the rotational axis), the radial stiffness of the rubber mounts on the vehicle side, the possible flexibility in the running gear of the vehicle in which the adjustable roll stabilizer is installed, etc. The system stiffness can only be calculated in advance in the form of nominal values on an exemplary roll stabilizer or on a vehicle equipped with a roll stabilizer, where deviations can occur, for example, due to manufacturing tolerances between systems (i.e., due to the manufacturing tolerances of an adjustable roll stabilizer in one motor vehicle relative to another adjustable roll stabilizer in another motor vehicle). In addition, some components influencing the system stiffness are subject to aging phenomena which affect the system stiffness during the service life in terms of operation of the adjustable roll stabilizer. In a method for roll stabilization as described, for example, previously, the value assumed for the system stiffness is incorporated into the control of the actuator, such that a deviation from the actual system stiffness results in an incorrect or at least suboptimal control of the actuator. Summary of the Invention

[0006] Accordingly, it is an object of the present invention to provide a method for roll stabilization of a motor vehicle of the type described at the beginning, which method is able to continuously take into account the (actual) system stiffness. In addition, a corresponding system for roll stabilization should be provided.

[0007] The object described is achieved first by a method for roll stabilization of a motor vehicle. Here, according to the invention, a method for roll stabilization of a motor vehicle by means of an adjustable roll stabilizer is concerned, wherein the adjustable roll stabilizer has an actuator which is operable to twist two stabilizer sections connected to the actuator relative to one another about a rotational axis, in such a way that the actuator is controlled taking into account at least one system-theoretical torque and taking into account the system stiffness of the roll stabilizer, and wherein a comparison is carried out between the current system torque and the system-theoretical torque in order to check and / or adapt the correctness of the stored system stiffness.

[0008] In this context, the "system-theoretical torque" is to be understood as the torque acting about the axis of rotation, which is to be supported by the adjustable roll stabilizer at the level of the actuator, and which torque is thus applied to the actuator (e.g. comprising an electric motor and a transmission) in the direction of rotation about the axis of rotation. The system-theoretical torque is input as an input variable into the controller of the adjustable roll stabilizer. Defined in this way, the "current system torque" is the torque actually (ultimately) supported by the roll stabilizer with respect to the axis of rotation of the actuator, i.e. this torque is applied to the actuator.

[0009] The recognition on which the idea of the invention is based is that the actual (current) system stiffness can be determined on the basis of variables which are present as measurable values in the method for roll stabilization. Specifically suitable is, on the one hand, continuously comparing the current system torque with the instantaneously required system-theoretical torque. In a preferably used method, the current system torque can be determined in a relatively simple manner on the basis of the current motor current of the actuator (electric motor as actuator). Since in the case of using this method the control is carried out in such a way that the system-theoretical torque is divided by the system stiffness and the resulting angle is fed to the azimuth-rotational speed controller, a permanent deviation between the system-theoretical torque and the current system torque results when the system stiffness is stored incorrectly. Therefore, according to the invention, the comparison between the current system torque and the system-theoretical torque provides a relatively easy possibility of checking and / or adapting the correctness of the stored system stiffness. The object stated at the beginning is thus achieved.

[0010] Conveniently, here the permanent deviation between the system torque and the system-theoretical torque is regarded as an indication of an incorrect stored system stiffness as a standard. Therefore, it is not the deviation at a single point in time that is important, but the deviation over a determinable, suitably long period of time. For the presence of the deviation, a threshold value can be determined, in particular to avoid being affected by measurement inaccuracies.

[0011] According to an advantageous refinement of the method, it can be proposed that the observed deviation over time between the current system torque and the system-theoretical torque is integrated and the deviation is fed to the current value of the system stiffness in order to correct the current value in the sense of a relearning function. Thus, by this measure, in addition to purely carrying out the check, the method also provides the possibility of correcting the stiffness value (original value) calculated once during the service life. In addition, even in the case of changing conditions (stiffness change due to aging), proper actuation of the actuator can be ensured by the relearning described hereby.

[0012] What is costly in terms of construction is to detect, in terms of measurement technology, the system torque prevailing in the adjustable roll stabilizer. According to an advantageous design of the method, the current system torque is detected, in particular indirectly, by means of the motor current of the actuator. It is shown that the torque applied to the motor of the actuator can thus be deduced at least within a relatively short measurement period.

[0013] According to an advantageous design of the described relearning function, advantageously, the constant of the integrator is also associated with the number of completed learning cycles. In this way, relatively rapid learning can be achieved just at the beginning of the service life of the adjustable roll stabilizer, whereby manufacturing tolerances can be compensated, in particular, at an earlier time point. Furthermore, in the later stages of the life cycle phase of the adjustable roll stabilizer, the possible learning speed can be reduced in this way, which is advantageous in that only relatively slow aging phenomena need to be compensated or anticipated in the later stages of the life cycle phase.

[0014] Alternatively or additionally, it is conceivable that during the operation of the roll stabilizer, in particular during the ignition cycle of a motor vehicle equipped with the roll stabilizer, the relearning in the form of a correction of the stiffness value is preferably limited depending on the number of completed operational applications. The purpose of this measure is not to change the driving behavior of the vehicle too much during the ignition cycle.

[0015] According to an advantageous refinement of the method, the adjustable roll stabilizer is controlled based on the obtained system-theoretical torque. For this purpose, advantageously, the system-theoretical torque is converted into a torsional angle for the torque requirement by means of a known system stiffness. For this purpose, the system-theoretical torque is divided by the system stiffness. The torsional angle obtained for the torque requirement represents the reference variable for controlling the actuator.

[0016] Since the motor vehicle also traverses uneven ground during its operational use, disturbance variable compensation is also advantageously incorporated into the control of the actuator. In this sense, the zero-torque angle (corresponding to the external torsional angle of the roll stabilizer, for example due to an uneven road) is advantageously calculated, and this zero-torque angle is added to the torsional angle for the torque requirement to form the theoretical angle to be set.

[0017] Furthermore, the controller of the adjustable roll stabilizer is advantageously designed such that the theoretical angle obtained by adding the torsional angle and the zero-moment angle for the torque requirement is fed to the azimuth-rotational speed controller, where the azimuth-rotational speed controller calculates the theoretical motor torque for the actuator. Finally, conveniently, the calculated theoretical motor torque of the actuator is fed to a field-oriented control device, which controls the motor assigned to the actuator, and the motor output torque of this motor is converted into a system (actual) torque by means of the transmission of the actuator.

[0018] Furthermore, the object stated at the beginning is achieved by a system for performing roll stabilization. Here, the system is a system for performing roll stabilization, which is designed to implement a method of the above type. Description of the Drawings

[0019] The invention is further explained below with the aid of the drawings. Other advantageous embodiments of the invention also result therefrom. In the drawings:

[0020] Figure 1 An adjustable roll stabilizer for a motor vehicle is shown in a schematic view,

[0021] Figure 2 A graphical illustration showing the control strategy of the adjustable roll stabilizer is shown,

[0022] Figure 3 A graphical illustration showing the learning function of the stiffness value on which the control strategy is based is shown. Detailed Description of the Embodiment

[0023] To demonstrate the application area of the invention, Figure 1 First, an adjustable roll stabilizer 1 is shown in a schematic view. The adjustable roll stabilizer 1 is part of a running gear of a motor vehicle (not shown) that is not fully shown. The reference numerals only indicate the vehicle structure 10 of the motor vehicle. The roll stabilizer 1 is also part of an axle of the motor vehicle, for example, the front axle and / or the rear axle of the motor vehicle can be equipped with the adjustable roll stabilizer 1.

[0024] As Figure 1 shown, the left wheel 7a and the right wheel 7b arranged on the opposite vehicle side are each connected to the vehicle structure 10 by means of a steering mechanism 8a or 8b that is not elaborated in detail. Thus, the wheel 7a and the steering mechanism 8a or the wheel 7b and the steering mechanism 8b each form a unit and are each connected to one end of the associated stabilizer section 7a or 7b of the adjustable roll stabilizer 1 by means of a swing strut 9a or 9b. The left stabilizer section 6a and the right stabilizer section 6b are connected to each other in the vehicle middle by means of an actuator 2 shown as a substantially cylindrical body.

[0025] In a manner known per se, the adjustable roll stabilizer 1 is rotatably supported relative to the vehicle structure 10 about a rotational axis 3, for which purpose a left stabilizer support 11a and a right stabilizer support 11b are used, which left and right stabilizer supports are U-shaped (shown schematically) around the region of the respective stabilizer section 6a or 6b facing the actuator 2. Figure 1 (Shown schematically) in a U-shape around the region of the respective stabilizer section 6a or 6b facing the actuator 2.

[0026] The actuator 2, shown here as a cylinder, generally includes a housing (not shown in detail) that is generally rotationally symmetric relative to the rotational axis 3. An electric motor 4, a multi-stage planetary transmission 9, and a rotational speed sensor 13 (each only indicated by reference numerals) are arranged in the housing. The stabilizer sections 6a and 6b are in driving connection with each other via the electric motor 4 and the multi-stage planetary transmission 5. When the actuator 2 is stationary, the two stabilizer sections 6a, 6b are rigidly interconnected via the stationary electric motor 4 and the multi-stage planetary transmission 5 drivingly connected thereto. However, by operating the electric motor 4, the stabilizer sections 6a, 6b can be twisted relative to each other about the rotational axis 3 depending on the rotational direction of the electric motor 4. Here, the multi-stage planetary transmission 5 presets a fixed transmission ratio between the drive device (electric motor 4) and the driven device (right stabilizer section 6b coupled to the transmission output). Thus, the adjustable roll stabilizer 1 can be adjusted in a manner known per se.

[0027] Depending on the operating state of the adjustable roll stabilizer 1 or a vehicle equipped with an adjustable roll stabilizer, the stabilizer sections 6a, 6b interconnected by the actuator 2 may be twisted, and depending on this twist, a moment M acting about the rotational axis 3 is formed. 系统 This moment M 系统 is applied to the actuator 2 in the form of a system moment.

[0028] With the aid of the roll stabilizer 1, the roll moment M acting between the vehicle structure 10 and the wheels 7a, 7b can be supported. By adjusting the roll stabilizer 1, the supportable roll moment M can be influenced. 侧倾 To control the roll stabilizer 1 as required, a height sensor 12a or 12b is assigned to each of the left wheel 7a or the right wheel 7b. These height sensors enable the detection of the wheel lift movement of the respective wheel and output the detection result in the form of the height z of the left wheel 侧倾 or in the form of the height z of the right wheel 7a or in the form of the height z of the right wheel 7b . In addition, the rotation of the electric motor 4 can be detected by the rotational speed sensor 13 and output as the motor rotational speed n in the form of a rotational speed signal.

[0029] The following elaborates in detail on the control of the roll stabilizer 1 with the aid of the control strategy shown in Figure 2 shown inFigure 1 The control of the adjustable roll stabilizer 1 shown schematically therein. Correspondingly, in the control of the adjustable roll stabilizer 1, so-called system-theoretical torques are included as input variables. Here, the system-theoretical torques are variables preset by the vehicle and corresponding to the torque M acting about the axis of rotation 3 系统 (see Figure 1 ). This torque should be supported by the adjustable roll stabilizer 1 at the level of the actuator, and thus this torque should be applied to the actuator 2 (including the electric motor 4 and the transmission 5) in the rotational direction about the axis of rotation 3. By kinematically coupling the adjustable roll stabilizer 1, the wheel suspensions 7a, 7b, 8a, 8b, 9a, 9b and the connecting elements 11a, 11b to the vehicle structure 10, the adjustable roll stabilizer 1 thus (at the vehicle level) supports the axle-related (see Figure 1 , extending about the longitudinal vehicle extension direction) roll torque M 侧倾 .

[0030] The system-theoretical torques are converted into a torsional angle for the torque requirement by means of a known system stiffness, where the known system stiffness is composed of the individual stiffnesses, in particular of the stiffnesses of the stabilizer itself (stabilizer sections, transmissions, housings, possibly decoupling elements, swivel struts, stabilizer supports, etc.).

[0031] At the same time, variables for compensating for disturbances are incorporated into the control of the adjustable roll stabilizer. For this purpose, wheel movement data in the form of height signals (detected by height sensors assigned to the wheels) and a characteristic value table for the decoupling angle (with previously calculated data specific to the vehicle) are used to determine the so-called "zero torque angle", i.e., the angle corresponding to the external torsional angle of the adjustable roll stabilizer (e.g., due to road unevenness) and which may cause no torque to be generated in the actuator of the adjustable roll stabilizer. Subsequently, the two angles calculated in this way (i.e., the torsional angle for the torque requirement and the zero torque angle) are added to form a theoretical angle.

[0032] Subsequently, the theoretical angle is fed to the azimuth-rotation controller of the cascade. This azimuth-rotation controller includes a position controller that calculates the theoretical rotational speed based on the obtained theoretical angle (additionally taking into account the feedback signal of the motor), and then sends this theoretical rotational speed to the rotational speed controller. The rotational speed controller calculates the theoretical motor torque for controlling the electric motor based on the theoretical rotational speed and the feedback (rotational speed) from the electric motor. Subsequently, the theoretical motor torque is fed to the field-oriented control device, which then controls the electric motor 4 of the actuator 2 while taking into account the feedback signal of the electric motor. The motor output torque generated by the electric motor 4 is (now mechanically) converted into a system torque by means of a transmission 5 (multi-stage planetary transmission), and this system torque acts between the stabilizer sections (see Figure 1 the reference signs 6a and 6b).

[0033] In Figure 2 the control schematic diagram shown is advantageously applied to the adjustable roll stabilizer 1 as shown in Figure 1 . Since the system theoretical torque obtained under the control principle described there is converted into a theoretical angle by means of the system stiffness, the theoretical motor torque is calculated based on this theoretical angle by means of the azimuth-rotation controller, where a corresponding motor current is applied to the motor, and then the roll stabilizer is adjusted - without feedback of the obtained system torque.

[0034] For example, as can be seen from the above description of the method for performing roll stabilization, system stiffness (the passive component of the roll stabilization system) is required as an input variable for this purpose. The system stiffness can be calculated in advance only in the form of the nominal value of the corresponding adjustable roll stabilizer on the motor vehicle. Due to manufacturing tolerances, deviations may occur, and in addition, the system stiffness is subject to aging phenomena for at least some of the components. Therefore, the initially assumed value of the system stiffness does not necessarily correspond to the actual system stiffness.

[0035] Figure 3 In the embodiment, a learning function of the system stiffness for performing active roll stabilization is schematically shown in a graphical illustration. Essentially, the learning function is based on the comparison between the current system torque and the system theoretical torque (correspondingly at the actuator level), where the shown relearning function provides the possibility of first checking the correctness of the stored system stiffness and (in the case of relevant deviations) correcting the current value of the system stiffness in the sense of the relearning function.

[0036] For example, from Figure 3It can be concluded that the actuator torque 21 (the current torque applied to the actuator, corresponding to the system torque) and the system theoretical torque (the control variable input from the vehicle level to the system for roll stabilization) are input into the comparator 29. In the comparator 29, the original comparison according to the present invention is carried out between the current system torque and the system theoretical torque. At the same time, it is checked whether the actuator torque 21 numerically reaches the threshold value represented in the figure as the minimum torque 30 for stiffness learning. Only when this is the case (i.e., the corresponding minimum torque is reached), can the observed deviation between the current actuator torque 21 and the system theoretical torque 22 be integrated over time on the integrator 35 and fed to the final value 36 of the system stiffness in a subsequent cycle (addition cycle), and this system stiffness is finally output in the form of the current stiffness 28 as an output variable in the right graph area.

[0037] The initial stiffness 23 and the final effective stiffness 24 are input into the relearning function. In addition, the learning cycle timer 25 and the ignition cycle timer 26 are set, thereby adding different operating conditions to the learning behavior of the system. On the one hand, in this way, the constant of the integrator 35 depends on the number of learning cycles that have been achieved, especially in order to enable relatively fast learning at the beginning of the service life, but to reduce the learning speed in the later stage of the life cycle phase. The learning speed is influenced by the multiplier 38, which is connected downstream of the comparator 29 and the learning cycle timer 25.

[0038] The ignition cycle timer 26 ensures that: during the period of operational application (i.e., during the ignition cycle), the relearning in the form of correcting the stiffness value is restricted depending on the number of operational applications that have been completed.

[0039] The method described provides the following possibility: to monitor and correct, through relearning, the system values on which roll stabilization is based, specifically the system stiffness of an adjustable roll stabilizer. The integrator 35 increases or decreases the stiffness value in the case of a permanent deviation (and when additional conditions are met), thereby ensuring relearning.

[0040] List of Reference Signs

[0041] 1 Adjustable roll stabilizer

[0042] 2 Actuator

[0043] 3 Axis of rotation

[0044] 4 Electric motor

[0045] 5 Multistage planetary transmission

[0046] 6a, 6b Left (or right) stabilizer section

[0047] 7a, 7b left (or right) wheel

[0048] 8a, 8b left (or right) steering mechanism

[0049] 9a, 9b left (or right) swing strut

[0050] 10 vehicle structure

[0051] 11a, 11b left (or right) stabilizer support

[0052] 12a, 12b height sensor for left (or right) wheel

[0053] 13 rotational speed sensor

[0054] z 7a , z 7b height of left (or right) wheel

[0055] M 侧倾 roll moment (related to the axle)

[0056] M 系统 system moment

[0057] n motor rotational speed

[0058] 21 actuator moment

[0059] 22 system theoretical moment

[0060] 23 initial stiffness

[0061] 24 final effective stiffness

[0062] 25 learning cycle timer

[0063] 26 ignition cycle timer

[0064] 27 learning cycle timer increment

[0065] 28 current stiffness

[0066] 29 comparator

[0067] 30 minimum moment for stiffness learning

[0068] 31 RC theoretical moment delay

[0069] 32 learning cycle timer / integrator constant

[0070] 33 ignition cycle timer / stiffness change

[0071] 34 stiffness in the current ignition cycle as integrator initial value

[0072] 35 Integrator

[0073] 36 Final Value

[0074] 37 Integrator

[0075] 38 Multiplier

Claims

1. A method for roll stabilization of a motor vehicle by means of an adjustable roll stabilizer (1), wherein the adjustable roll stabilizer (1) has an actuator (2) which is operable to twist two stabilizer segments (6a, 6b) connected to the actuator relative to one another about a rotational axis (3) in a manner depending on at least one system-theoretical torque and, taking into account the system stiffness of the roll stabilizer (1), controlling the actuator (2), wherein a comparison is carried out between the current system torque and the system-theoretical torque in order to check and / or adapt the correctness of the stored system stiffness, the observed deviation between the current system torque and the system-theoretical torque is integrated over time, and the deviation is fed to the current value of the system stiffness in order to correct the current value in the sense of a relearning function.

2. The method according to claim 1, wherein A permanent deviation between the system torque and the system-theoretical torque is regarded as an indication of incorrectness of the stored system stiffness.

3. The method according to claim 1 above, characterized in that, The current system torque is detected indirectly by means of the motor current of the actuator (2).

4. The method according to claim 1, wherein The constant of the integrator (35) is also correlated with the number of learning cycles already completed in such a way that relatively rapid learning is possible at the start of the service life of the adjustable roll stabilizer (1), but the learning speed is reduced at a later stage in the life cycle phase of the adjustable roll stabilizer (1).

5. The method according to claim 1, wherein During operation of the roll stabilizer, during the ignition cycle of a motor vehicle equipped with the roll stabilizer, the relearning in the form of a stiffness value is restricted depending on the number of operationally applied times already completed.

6. The method according to claim 1, characterized in that, The actuator (2) is controlled by means of an orientation-speed controller.

7. The method according to claim 1, characterized in that, The system-theoretical torque is divided by the system stiffness in order to convert the system stiffness into a twist angle for torque requirements.

8. The method according to claim 7, characterized in that, A zero torque angle is calculated and added to the twist angle for torque requirements to form a theoretical angle to be set.

9. The method according to claim 8, characterized in that The actuator (2) is controlled by means of an orientation-speed controller, and the theoretical angle obtained by adding the twist angle for torque requirements and the zero torque angle is fed to the orientation-speed controller, wherein the orientation-speed controller calculates the motor-theoretical torque of the actuator (2).

10. The method according to claim 9, wherein The calculated motor-theoretical torque of the actuator (2) is fed to a field-oriented control device which controls a motor (4) assigned to the actuator (2), and the motor output torque of the motor is converted by means of a transmission (5) of the actuator (2) into the current system torque.

11. A system for roll stabilization, which is designed to carry out the method according to one of the preceding claims.

Images