Methods for roll stabilization

Abstract

Method for roll stabilization of a vehicle body, wherein the body has four wheel suspensions, each with a vibration damper, wherein the vibration dampers are arranged between the body and a wheel suspension movably mounted relative to the body, wherein the vibration dampers are designed such that a damping force is adjustable for each vibration damper, wherein two front vibration dampers are arranged on opposite sides of a front section of the body, wherein two rear vibration dampers are arranged on opposite sides of a rear section of the body, wherein a first roll velocity is determined for a front section of the body and a second roll velocity is determined for a rear section of the body, wherein, depending on the two measured roll velocities, a damping force for at least one vibration damper is adjusted in such a way as to counteract a roll movement of the body. characterized by the fact that The damping force for an in-phase oscillation of the front and rear sections of the body is determined.

Description

[0001] The invention relates to a method for roll stabilization according to claim 1 and a control unit according to claim 11.

[0002] From DE 10 2011 005 348 A1, a roll stabilization system for a two-track, two-axle vehicle is known. This system includes an electronic control unit which, taking into account height signals of individual vehicle wheels relative to the vehicle body obtained in a suitable manner, controls the roll stabilization system when the vehicle is located with only one wheel of only one axle on a contact surface that is significantly raised or lowered compared to the contact surface of the other three wheels, and / or when driving onto or down such a surface. The control unit then activates the roll stabilization system in such a way that the load on the vehicle body caused by a torsional moment introduced by the wheel suspensions is reduced compared to the same vehicle operating condition without such control of the roll stabilization system.

[0003] JP 3 473 673 B2 discloses the subject matter of the preamble of claim 1.

[0004] DE 10 2005 040 643 A1 teaches how to determine the damping force for a tensile load or for a compressive load of several vibration dampers.

[0005] The object of the invention is to provide an improved method for roll stabilization of a vehicle body.

[0006] The object of the invention is solved by the method according to claim 1 and by the control unit according to claim 11.

[0007] One advantage of the described method is that it achieves more precise and accurate roll stabilization. This advantage is gained by considering the roll velocity of a front section of the vehicle body and a roll velocity of a rear section when determining the damping force for at least one vibration damper. A more accurate model for the vibration characteristics of the vehicle body is used, in which the body is divided into a front and a rear section. This allows the front and rear sections of the vehicle body to roll at different speeds around a longitudinal axis. Therefore, the newly proposed method enables the determination of more efficient roll damping with greater accuracy.

[0008] For this purpose, in-phase and out-of-phase vibrations of the front and rear sections of the body are taken into account when calculating the damping force. This results in increased accuracy in determining the damping force.

[0009] In one embodiment, a front moment of inertia is used to determine the damping force for the front section of the body, and a rear moment of inertia is used for the rear section of the body, with the front and rear moments of inertia being coupled to each other via a predetermined torsional stiffness. This enables a precise determination of the damping force for damping the vehicle's roll motion.

[0010] In a further embodiment, both the damping force for a tensile load and the damping force for a compressive load of the at least one vibration damper are determined, in particular calculated, and controlled accordingly to dampen the roll motion. This allows for a further improvement in roll stabilization.

[0011] In a further embodiment, the damping forces for at least two vibration dampers, and in particular for all vibration dampers, are determined, and especially calculated. This results in improved roll stabilization.

[0012] In one embodiment, a damping moment for the front section is determined, and in particular calculated, depending on the first and second roll velocities. Damping forces for the two vibration dampers of the front section are then determined and adjusted based on this damping moment, distributing the damping moment between the two vibration dampers. This results in improved control of the damping forces of the front section.

[0013] In a further embodiment, a damping moment for the rear section is determined, and in particular calculated, depending on the first and second roll velocities, wherein the damping forces of the two vibration dampers of the rear section are adjusted in such a way that the damping moment is distributed between the two vibration dampers. This results in improved control of the damping forces.

[0014] Depending on the chosen design, the damping forces for the two vibration dampers of the front and rear sections are set to the same value. One vibration damper in one section is subjected to a tensile force, while the other damper in the same section is subjected to a compressive force. This ensures that the vibration dampers are loaded evenly.

[0015] In another embodiment, identical damping values ​​are used for the vibration dampers, in particular for the vibration dampers of the front section and the vibration dampers of the rear section of the body. This allows for a simple and quick calculation of the damping forces.

[0016] In another embodiment, different damping values ​​are used when calculating the damping force for the front and rear vibration dampers. This results in a more precise adjustment of the damping forces.

[0017] The invention will be explained in more detail below with reference to the figure.

[0018] The figure schematically depicts a vehicle body 1, divided into a front section 2 and a rear section 3. The front section 2 and the rear section 3 are considered ideally rigid plates, operatively connected to each other via an element 4, which forms a torsionally rigid connection between the front and rear sections 2 and 3. Thus, according to the model used, the front section 2 and the rear section 3 can only twist relative to each other. The twisting is possible along a central longitudinal axis 5, which passes through the midpoint (with respect to width) of sections 2 and 3 and the element 4. The longitudinal axis 5 extends along an X-axis. A Y-axis, representing a transverse direction to the vehicle body 1, is shown perpendicular to the X-axis. A Z-axis is arranged perpendicular to the XY-plane.At the front section 2, a wheel suspension 8, 9 is provided at opposite front corner areas 6, 7, which is movably attached to the body 1. Each front wheel suspension 8, 9 is operatively connected to the body 1 via a vibration damper 10, 11. In addition, a wheel 12, 13 is attached to each of the first and second front wheel suspensions 8, 9.

[0019] Similarly, a first and a second rear wheel suspension 14, 15 are provided, each movably mounted relative to the body 1 and each connected to the rear section 3 of the body 1 via a first and a second rear vibration damper 16, 17, respectively. The first and the second rear vibration damper 16, 17 are arranged in a third and fourth corner region 20, 23 of the rear section 3 of the body 1, respectively. A wheel 18, 19 is also attached to each rear wheel suspension 14, 15. A first sensor 20 is assigned to each wheel 12, 13, 18, 19. A second sensor 21 is also assigned to each corner region 6, 7, 22, 23. The front and rear vibration dampers 10, 11, 16, 17 are designed such that the damping force of each vibration damper 10, 11, 16, 17 can be set and changed by a control signal from a control unit 25. For example, a vibration damper canbe designed in the form of an actuator and / or a hydraulic shock absorber.

[0020] The first and second sensors 20, 21 are designed to measure displacement and / or acceleration. Thus, sensors 20, 21 can be used to measure the velocities in the Z-direction, i.e., perpendicular to the plane of the vehicle body 1, for the wheels 12, 13, 18, 19 and for the corner sections 6, 7 of the front section 2 and the corner sections 22, 23 of the rear section 3. It is important that the velocities in the Z-direction are determined. Whether these are ultimately determined using acceleration sensors or by means of the time derivative of height sensors is irrelevant for the procedure described here. Using sensors 20, 21, four velocities of the four corner sections 6, 7, 22, 23 of the vehicle body 1 are calculated based on the measured accelerations of the corner sections and the wheels.According to the model used, the front section 2 can rotate about the longitudinal axis 5 relative to the reference plane XY and thus also relative to the rear section 3. Therefore, a front roll velocity ẋ can occur. V for the front section around the longitudinal axis 5 and a rear roll speed ẋ H The following formulas are used to calculate the distances for the rear section 3 around the longitudinal axis 5: x˙V=(vAufbauFL−vAufbauFR)YV x˙H=(vConstructionRL−vConstructionRR)YH, where with v Aufbau FL the speed of the first front corner area 6, with v Aufbau FR the speed of the second front corner area 7, with v Aufbau RL the speed of the third corner area 22, with v Aufbau RR The velocity of the fourth corner area is denoted by 23. With Y VThe first track width between the first wheel 12 of the first front wheel suspension 8 and the second wheel 13 of the second front wheel suspension 9 is designated with Y. H A second track width is designated between the third wheel 18 of the first rear wheel suspension 14 and the fourth wheel 19 of the second rear wheel suspension 15.

[0021] In a further step, rotational stiffnesses can be calculated, which change in vehicles with air suspension where the spring rate is variable. The rotational stiffness for the front axle, i.e., for the front section 2, is calculated using the following formula: cV=(cFL+cFR)⋅(YV2)2+cStabi v, where with C V the stiffness of the front section 2, with C FL the stiffness of the first front vibration damper 10, with C FR the stiffness of the second front vibration damper 11, with Y V the first track width and with CStabi V The stiffness of a stabilizer (not shown) is defined. The stiffness of the stabilizer is a fixed value, which is stored, for example, in a memory 24. The memory 24 is connected to a control unit 25, which is connected to sensors 20 and 21 via an input 26. Furthermore, the control unit 25 is connected to vibration dampers 10, 11, 16, and 17 via an output 27.

[0022] The stiffness for the rear section 3 is calculated according to the following formula: cH=(cRL+cRR)⋅(YH2)2+cStabi H

[0023] With C H is the stiffness of the rear section 3, with C RL the stiffness of the first rear vibration damper 16, with C RR the stiffness of the second rear vibration damper 17, with Y H the second track gauge and with C Stabi HThis refers to the stiffness of a rear stabilizer (not shown). The stiffness of the rear stabilizer is stored in data memory 24.

[0024] Furthermore, a rotational stiffness c is required for the rotational connection between the front section 2 and the rear section 3. K the body 1 is used, which is known and stored in data memory 24. Furthermore, a first moment of inertia J is also used. V for the front section 2 and a second moment of inertia J H known for the rear section 3 and stored in data storage 24.

[0025] Using the described data and formulas, the natural frequencies of the body 1 can be calculated according to the following first rule: det(C−ω2M)=0⇒|(cV+cK)−ω2⋅JV−cK−cK(cH+cK)−ω2⋅JH|=0

[0026] In a subsequent step, the two natural frequencies and the two resulting natural vibration vectors are calculated.

[0027] The following values ​​are assumed as a calculation example: JV=330.13 kg⋅m2JH=390.87 kg⋅m2cV=33444 N⋅m / radcH=52386 N⋅m / radcK=1718873 N⋅m / radM=[330.1300390.87]C=[1752317−1718873−17188731771259] where M denotes the inertia matrix and C denotes the stiffness matrix.

[0028] Furthermore, the first rule is solved numerically with the aforementioned values ​​by the control unit 25 in real time during the operation of the vehicle, for example in the form of C programming: det|1752317−ω2⋅330.13−1718873−17188731771259−ω2⋅390.87|=0

[0029] The two solutions are the two natural frequencies: ω1 = 1.7 Hz and ω2 = 15.7 Hz.

[0030] The corresponding eigenvectors u1, u2 satisfy the following conditions: [C−ω12M]u1=0 [C−ω22M]u2=0

[0031] Numerically, these can be expressed as follows: u1=( 11752317−ω1⋅330.13−1718873)=( 10.9966)⇒Mode1, primary "wavering" u2=(ω2⋅390.87−1771259−1718873 1 )=(−1.18 1)⇒Mode 2, primary "tortieren"

[0032] The modal matrix is ​​therefore: Φ=[u1 u2]=[1−1.180.99661]

[0033] In a subsequent step, the new coordinates are calculated according to the following formulas for the natural frequencies: (xWankxTord)=Φ−1⋅(xVxH)⇒xWank=0.4596⋅xV+0.5423⋅xHxTord=−0.4580⋅xV+0.4596⋅xH

[0034] In the new coordinate system, the equations are decoupled: ϕTMϕ+ϕTKϕ+ϕTCϕ=0

[1001] ⋅[x¨Wank x¨Tord]+[2⋅D1⋅ω1002⋅D2⋅ω2]⋅[x¨Wank x¨Tord]+[ω1200ω22]⋅[x¨Wank x¨Tord]=0

[0035] This means that the damping matrix K in the normal coordinate system is equal to 1 when a first damping measure D1 of the first natural frequency, which corresponds to a roll of the vehicle, and a second damping measure D2 of the second natural frequency, which corresponds to a twist, are equal to 1. K=inv(ϕT)⋅[2⋅D1⋅ω1002⋅D2⋅ω2]⋅ϕ=[38491−31394−3139440030]

[0036] Depending on the chosen design, the damping values ​​for the first and second natural modes of vibration can also be selected differently and, for example, range between 0.8 and 1.3. This determines the front and rear torques, which, together with the specified damping values ​​D1 and D2, dampen the two vibration modes of the structure: roll and torsion.

[0037] Subsequently, in a further process step, torques for the front and rear vibration dampers 10, 11, 16, 17 are calculated according to the following formulas: (MVMH)=K⋅(x˙Vx˙H)⇒MV=38491⋅x˙V−31394⋅x˙HMH=−31394⋅x˙V+40030⋅x˙H, where with M V a front damping moment of the front vibration dampers 10, 11 and with M H a rear damping moment of the rear vibration dampers 16, 17 is designated. Depending on the selected embodiment, the damping moments can also be determined based on the first roll velocity of the front section and the second roll velocity of the rear section using tables, characteristic curves or maps stored in memory 24.

[0038] The front damping moment M V The front damping moment is applied to the front section 2 of the body 1 by means of the front vibration dampers 10, 11. The front damping moment is achieved by means of the first track width Y. Vand the center of mass of the front section 2 of the body along the longitudinal axis 5 is converted into a damping force. Depending on the selected configuration, the front vibration dampers 10, 11 are controlled in such a way that the front damping moment is applied equally by both front vibration dampers 10, 11, i.e., each front vibration damper generates half of the front damping moment or the corresponding front damping force. For this purpose, the damping force of the front vibration dampers 10, 11 is adjusted accordingly by the control unit 25. In this process, one vibration damper exerts a tensile force and the other a compressive force to dampen roll, i.e., rotation about the longitudinal axis 5. Depending on the selected configuration, the damping forces of the front vibration dampers 10, 11 can also be set to different values, but the total front damping moment or...the front damping force is generated.

[0039] The rear damping moment M H The force is exerted on the rear section 3 of the body 1 by means of the rear vibration dampers 16, 17. The rear damping moment is controlled by the second track width Y. Hconverted into a rear damping force. Depending on the selected configuration, the rear vibration dampers 16, 17 are controlled in such a way that the rear damping moment is applied equally by both rear vibration dampers 16, 17, i.e., each rear vibration damper generates half of the rear damping moment or rear damping force. The control unit adjusts the damping force of the rear vibration dampers accordingly. One vibration damper exerts a tensile force and the other a compressive force as damping force to dampen roll, i.e., rotation about the longitudinal axis 5. Depending on the selected configuration, the damping forces of the rear vibration dampers 16, 17 can also be set to different values, but the total rear damping moment or rear damping force is always generated.

[0040] The damping moments can be determined and, in particular, calculated in real time, for example every 2 ms, by the control unit 25. Furthermore, the control unit 25 can control the vibration dampers every 2 ms in such a way that the vibration dampers generate the desired damping moment.

Claims

[1] Method for roll stabilization of a vehicle body, wherein the body has four wheel suspensions, each with a vibration damper, wherein the vibration dampers are arranged between the body and a wheel suspension movably mounted relative to the body, wherein the vibration dampers are designed such that a damping force is adjustable for each vibration damper, wherein two front vibration dampers are arranged on opposite sides of a front section of the body, wherein two rear vibration dampers are arranged on opposite sides of a rear section of the body, wherein a first roll velocity is determined for a front section of the body and a second roll velocity is determined for a rear section of the body, wherein, depending on the two measured roll velocities, a damping force for at least one vibration damper is adjusted in such a way as to counteract a roll movement of the body. characterized by , that The damping force is determined for an in-phase oscillation of the front and rear sections of the body. [2] Method according to claim 1, wherein a damping force is determined for an antiphase oscillation of the front and rear sections of the body. [3] Method according to one of the preceding claims, wherein for determining the damping force a front mass inertia of the front section and a rear mass inertia of the rear section are taken into account, wherein the front and the rear mass inertia are coupled to each other via a predetermined torsional stiffness. [4] Method according to one of the preceding claims, wherein the damping force is determined for a tensile load or for a compressive load of the at least one vibration damper. [5] Method according to one of the preceding claims, wherein the damping forces for the at least two vibration dampers, in particular for all vibration dampers, are determined. [6] Method according to claim 5, wherein a damping moment is determined for the front section depending on the first and the second roll velocity, wherein damping forces for the two vibration dampers of the front section are determined depending on the damping moment and are adjusted in such a way that the damping moment is distributed between the two vibration dampers. [7] Method according to claim 5, wherein a damping moment is determined for the rear section depending on the first and the second roll velocity, wherein damping forces of the two vibration dampers of the rear section are adjusted in such a way that the damping moment is distributed between the two vibration dampers. [8] Method according to claim 6 or 7, wherein the damping forces for the two vibration dampers are set to be equal. [9] Method according to one of the preceding claims, wherein the same damping values ​​are used when calculating the damping forces for the front and rear vibration dampers. [10] Method according to any one of claims 1 to 8, wherein different damping measures are used when calculating the damping forces for the front and rear vibration dampers. [11] Control unit for controlling a damping force of at least one vibration damper, wherein the control unit is configured to perform a method according to one of the preceding claims.

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