Vehicle behavior control apparatus

Abstract

To provide a vehicle behavior control apparatus that can suppress a bias in roll stiffness distribution while suppressing a large roll according to the lateral acceleration or taking into consideration the state of a vehicle stability control.SOLUTION: A vehicle behavior control apparatus includes a variable roll stiffness device and a controller. The variable roll stiffness device is configured with roll stiffness of a first axle being one of a front axle and a rear axle and roll stiffness of a second axle being the other of the front axle and the rear axle being variable; The controller controls the variable roll stiffness device so as to increase the roll stiffness of the first axle in accordance with an increase in a lateral acceleration in at least a low acceleration range in a region of the lateral acceleration acting on the vehicle. Further, when the lateral acceleration increases to a high acceleration range beyond the low acceleration range, or a vehicle stability control for suppressing at least one of oversteer and understeer of the vehicle is abnormal, the controller executes a control process of controlling the variable roll stiffness device so as to increase the roll stiffness of the second axle.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a vehicle behavior control device. [Background technology]

[0002] Patent Document 1 discloses a roll control device for a vehicle. This roll control device increases the control amount of the actuator on both the first and second axles (rear and front axles) so as to increase the roll stiffness of the first and second axles in response to an increase in lateral acceleration. When the lateral acceleration increases beyond the low acceleration range to the high acceleration range, the roll control device reduces the gain of the control amount of the actuator on the first axle for lateral acceleration in response to the increase in lateral acceleration so that the roll stiffness allocation rate of the first axle does not exceed a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-051026 A Summary of the Invention [Problem to be solved by the invention]

[0004] According to the technology described in Patent Document 1, it is possible to suppress the bias of roll stiffness distribution in the high acceleration range and suppress the occurrence of unintended oversteer or understeer. However, the method of lowering the roll control gain makes it easier for large rolls to occur in the high acceleration range. Also, even if the lateral acceleration is low, if there is an abnormality in the vehicle stability control, the bias of roll stiffness distribution can be a factor that makes it easier for unintended oversteer or understeer to occur depending on, for example, the road surface conditions.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a vehicle behavior control device that is capable of suppressing large roll in response to lateral acceleration or suppressing bias in roll stiffness distribution while taking into account the state of vehicle stability control. [Means for solving the problem]

[0006] A vehicle behavior control device according to the present disclosure includes a roll stiffness varying device and a controller. The roll stiffness varying device is configured to vary the roll stiffness of a first axle, which is one of the front and rear axles of the vehicle, and the roll stiffness of a second axle, which is the other of the front and rear axles. The controller controls the roll stiffness varying device so as to increase the roll stiffness of the first axle in response to an increase in lateral acceleration at least in a low acceleration range of a range of lateral acceleration acting on the vehicle. In addition, when the lateral acceleration increases beyond the low acceleration range to a high acceleration range, or when there is an abnormality in the vehicle stability control that suppresses at least one of oversteer and understeer of the vehicle, the controller executes a control process to control the roll stiffness varying device so as to increase the roll stiffness of the second axle. Effect of the Invention

[0007] According to the present disclosure, when the acceleration exceeds the low acceleration range and increases to the high acceleration range, it becomes possible to suppress bias in roll stiffness distribution without relying on a method of lowering the roll control gain (i.e., while suppressing the occurrence of large rolls according to lateral acceleration). Furthermore, according to the present disclosure, when there is an abnormality in the vehicle stability control, even in the low acceleration range, unintended oversteer or understeer can be suppressed by suppressing bias in roll stiffness distribution through execution of a control process. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of a vehicle equipped with a behavior control device according to an embodiment; [Diagram 2] FIG. 2 is a diagram conceptually illustrating a basic configuration of roll control according to the embodiment. [Diagram 3] 10 is a flowchart showing an example of a process related to roll control including a control process according to an embodiment; [Figure 4] FIG. 13 is a diagram for explaining a specific example EX3 of the distribution process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1. Vehicle behavior control device Fig. 1 is a diagram showing the configuration of a vehicle 10 equipped with a behavior control device according to an embodiment. As shown in Fig. 1, the vehicle 10 has four wheels 14, which are a left front wheel 14FL and a right front wheel 14FR on a front axle 16F, and a left rear wheel 14RL and a right rear wheel 14RR on a rear axle 16R. In the vehicle 10, for example, the left and right wheels 14FL and 14FR are steered wheels.

[0010] The vehicle 10 includes suspensions 20FL, 20FRA, 20RLA, and 20RRA. The suspensions 20FL, 20FRA, 20RLA, and 20RRA suspend a left front wheel 14FL, a right front wheel 14FR, a left rear wheel 14RL, and a right rear wheel 14RR from the vehicle body 12, respectively.

[0011] The suspension 20FL of the left front wheel 14FL is a non-active suspension and includes a spring 22FL and a shock absorber 24FL.

[0012] The suspension 20FRA of the right front wheel 14FR is an active suspension (full active suspension) and includes an actuator 26FR in addition to a spring 22FR and a shock absorber 24FR. The actuator 26FR is configured to actively apply a vertical control force between the vehicle body 12 and the right front wheel 14FR. The actuator 26FR is, for example, an electric or hydraulic type.

[0013] The suspensions 20RLA and 20RRA of the rear axle 16R are also active suspensions and include springs 22RL and 22RR, shock absorbers 24RL and 24RR, and actuators 26RL and 26RR, respectively. The actuators 26RL and 26RR are configured to actively apply vertical control forces between the vehicle body 12 and the left and right wheels 14RL and 14RR of the rear axle 16R, respectively. The actuators 26RL and 26RR are, for example, electric or hydraulic.

[0014] The vehicle 10 is equipped with a controller 30. The controller 30 acquires signals from a sensor group 40 equipped on the vehicle 10. The sensor group 40 includes sensors that measure physical quantities related to the behavior of the vehicle 10, such as an acceleration sensor, a vehicle height sensor, a sprung acceleration sensor, and a wheel speed sensor. The controller 30 also controls the actuators 26FR, 26RL, and 26RR.

[0015] The controller 30 includes a processor 32 and a memory 34 coupled to the processor 32. The processor 32 executes various processes related to behavior control of the vehicle 10. The behavior control includes at least roll control, which will be described later. The memory 34 stores various information required for the processor 32 to execute various processes. For example, the memory 34 stores a program 36 executable by the processor 32 and various information related to the program 36. The processor 32 executes the program 36 to realize behavior control.

[0016] Furthermore, the various processes related to the behavior control of the vehicle 10 may include the following processes related to vehicle stability control. The vehicle stability control is a control for suppressing at least one of oversteer and understeer of the vehicle 10. The vehicle stability control includes, for example, the controller 30 detecting sideslip of the vehicle 10 using the sensor group 40 and controlling at least one of the drive device and the brake device of the vehicle 10 so as to suppress the sideslip. The drive device is, for example, at least one of an electric motor and an internal combustion engine.

[0017] 2. Vehicle roll control In this embodiment, the rear axle 16R corresponds to the "first axle" and the front axle 16F corresponds to the "second axle." The pair of left and right active suspensions 20RLA and 20RRA of the rear axle 16R and the single active suspension 20FRA of the front axle 16F function as a "roll stiffness variable device" that varies the roll stiffness of the rear axle 16R and the roll stiffness of the front axle 16F. The "behavior control device" according to this embodiment is configured to include the roll stiffness variable device and a controller 30. The roll control according to this embodiment is executed by the controller 30 that controls the roll stiffness variable device.

[0018] First, Fig. 2 is a diagram conceptually showing the basic configuration of the roll control according to the embodiment. Fig. 2 shows a modeled vehicle 10 and a lateral acceleration (lateral G) a acting on the center of gravity 11 of the vehicle 10. y and the control force F for roll suppression applied by the roll stiffness variable device. rl and F rr On the left side of Figure 2, the lateral acceleration a y The right side shows the low lateral acceleration a y In addition, Fig. 2 shows the state where the lateral acceleration a y Graphs are shown showing changes in the roll stiffness distribution ratio of the front axle 16F and the rear axle 16R before and after an increase in

[0019] The basic configuration of roll control in the vehicle 10 having the suspension configuration shown in Figures 1 and 2 is as follows. That is, on the side of the rear axle 16R having active suspensions 20RLA and 20RRA on both the left and right wheels 14RL and 14RR, actuators 26RL and 26RR are used to control F rl and F rr In more detail, as shown in FIG. y When this occurs, the actuator 26RL applies a downward control force F to the left rear wheel 14RL. rl is applied, and an upward control force F is applied to the right rear wheel 14RR by the actuator 26RR. rrAs a result, in the vehicle 10 having the above suspension configuration, the lateral acceleration a is applied without causing heave and pitch. y In other words, it is possible to generate a roll moment that suppresses the roll caused by the lateral acceleration a y Therefore, the roll rigidity of the rear axle 16R (first axle) can be increased.

[0020] According to the basic configuration of the roll control, the control force F applied to the left and right wheels 14RL and 14RR is rl and F rr is the lateral acceleration a y That is, the roll stiffness varying device is increased in response to the lateral acceleration a y In FIG. 2, the controller 30 controls the roll stiffness of the rear axle 16R to increase in response to an increase in the lateral acceleration a y The length of the arrow indicating the direction of the lateral acceleration a y The magnitude of the control force F rl and F rr The length of the arrows showing the direction of the control force F rl and F rr This shows the size of .

[0021] According to the basic configuration of roll control, as shown in FIG. 2, the lateral acceleration a y As the roll stiffness of the rear axle 16R is increased in response to the increase in lateral acceleration a y As the lateral acceleration a increases, the roll stiffness distribution rate becomes more biased. y This can lead to unintended oversteer or understeer during cornering. In this regard, the occurrence of unintended oversteer or understeer can be suppressed by lowering the roll control gain in the high acceleration range. However, this method makes it easier for large rolls to occur in the high acceleration range. In addition, it is desirable to take measures to suppress bias in the roll stiffness distribution while taking into account the state of the vehicle stability control.

[0022] Therefore, the process executed by the controller 30 regarding the roll control according to this embodiment includes a "control process." In the control process, the controller 30 calculates the lateral acceleration a y If the acceleration exceeds the low acceleration region R1 and increases to the high acceleration region R2, or if there is an abnormality in the "vehicle stability control", the roll stiffness variable device is controlled to increase the roll stiffness of the front axle 16F (second axle).

[0023] 3 is a flowchart showing an example of a process related to roll control including a control process according to the embodiment. The process of this flowchart is repeatedly executed by the controller 30 (processor 32) while the vehicle 10 is traveling.

[0024] <Step S100> First, in step S100, the controller 30 detects the lateral acceleration a y Specifically, the lateral acceleration a y is an estimated value calculated from, for example, the steering angle and the vehicle speed. However, the lateral acceleration a y The method of acquiring the lateral acceleration a is not particularly limited. y may be, for example, a sensor value measured by an acceleration sensor.

[0025] <Step S102> Next, in step S102, the controller 30 calculates the lateral acceleration a y is a given threshold a yt In other words, it is determined whether the lateral acceleration a y It is determined whether the vehicle is in the high acceleration region R2 or the low acceleration region R1.

[0026] More specifically, the high acceleration region R2 corresponds to an acceleration region near the turning limit of the vehicle 10. y is the threshold a ytIf the lateral acceleration a is less than the turning limit (i.e., it is in the low acceleration region R1), it means that there is a margin for the turning limit. If there is this margin, unintended oversteer or understeer, or large roll will not occur. For this reason, in step S102, y For example, simply, the margin of lateral acceleration a y is the threshold a yt If the vehicle 10 is in the high acceleration range R2, the vehicle is determined to have a small margin for the turning limit. If the vehicle 10 is capable of calculating an estimated coefficient of friction of the road surface on which the vehicle 10 is traveling, the vehicle 10 is determined to have a small margin for the limit lateral acceleration according to the estimated coefficient of friction by using a threshold a yt may be determined taking into account an estimated coefficient of friction.

[0027] <Step S104> lateral acceleration a y is the threshold a yt If it is less than the predetermined value (step S102; No), the controller 30 determines whether or not there is an abnormality in the vehicle stability control in step S104. The method of determining whether or not there is an abnormality is not particularly limited, and any known determination method may be used.

[0028] <Step S106> If the determination result in step S104 is No (i.e., the lateral acceleration a y is the threshold a yt If the vehicle stability control is normal, the process proceeds to step S106. Hereinafter, the time when the process proceeds to step S106 is simply referred to as "normal time."

[0029] In step S106, the controller 30 calculates the required control force F fli , F fri , F rli , and F rri Calculate the required control force F fli , F fri , F rli , and Frri is the required roll moment M r is the control force required for each wheel 14 to achieve

[0030] Required roll moment M r is the roll moment required to suppress the roll behavior by roll control, and is expressed by the following formula (1). In formula (1), α is the roll control gain, β1 is the feedback control gain (FB control gain) for the sprung roll velocity, φ is the roll angle, and s is the Laplace operator. The second term on the right side of formula (1) indicates the feedback term for the sprung roll velocity of the vehicle 10. By having this feedback term, it is possible to reduce the lateral acceleration a y Required roll moment M according to r The required roll moment M r The calculation formula for the required roll moment M may include only the first term on the right side of the formula (1), for example. r is simply the lateral acceleration a y and the roll control gain α.

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[0031] The controller 30 calculates the required roll moment M according to the equation (1). r The required roll moment M is calculated using the following formula (2). r The required control force F for the four wheels 14 fli , F fri , F rli , and F rri In equation (2), T f is the front wheel tread, T r is the rear wheel tread. Required control force F fli , F fri , F rli , and F rri is positive when an upward force is required. The required roll moment M ris taken to be positive if a downward and upward moment is desired.

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[0032] <Step S108> lateral acceleration a y is the threshold a yt If the above is the case (step S102; Yes), or if there is an abnormality in the vehicle stability control (step S104; Yes), the process proceeds to step S108.

[0033] In step S108, the controller 30 calculates the required roll moment M according to the following equation (3): r Formula (3) differs from formula (1) in the FB control gain β relative to the sprung roll speed. Specifically, in formula (3), a value larger than the FB control gain β1 in formula (1) is set as the FB control gain β2.

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[0034] In step S108, the controller 30 performs control processing to calculate the required roll moment M r The required control force F for the four wheels 14 fli , F fri , F rli , and F rri Specifically, the controller 30 converts (distributes) the required control forces F fli , F fri , F rli , and F rri According to formula (4), in comparison with formula (2), the required roll moment M r In order to achieve this, the roll moment generated by the front axle 16F (second axle) is increased by M rf In the example of the vehicle 10 shown in FIG. 1, the suspension 20FL of the left front wheel 14FL is an inactive suspension. Therefore, the increase amount M rfis the required control force F of the right front wheel 14FR having the actuator 26FR. fri This is reflected in

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[0035] The controller 30 adjusts the increment M so as to suppress the imbalance of the roll stiffness distribution. rf Specifically, the controller 30 determines the increment M by, for example, the following method. rf That is, the controller 30 determines the lateral acceleration a y is the threshold a yt If it is greater than or equal to this, the increment M is calculated according to the following formula (5): rf In formula (5), γ is a predetermined gain. By using formula (5), the lateral acceleration a y As the lateral acceleration a y As the vehicle approaches the turning limit, the roll moment generated on the front axle 16F increases. In other words, the lateral acceleration a y As the roll stiffness distribution increases, the roll stiffness distribution shifts toward the front axle. y is the threshold a yt If the vehicle stability control is abnormal and the process proceeds to step S108, the controller 30 may, for example, adjust the lateral acceleration a y The product of itself and a given gain is increased by M rf It may be calculated as:

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[0036] Furthermore, the control process according to the present embodiment may include a "distribution process." In an example involving this distribution process, the controller 30 allocates the required control forces F to the four wheels 14 so as to reduce the roll moment on the rear axle 16R by an amount equal to the roll moment increased on the front axle 16F. fli , F fri , F rli , and F rri Calculate.

[0037] More specifically, M rrl and M rrr are the reduction amounts of the roll moments generated at the two wheels 14RL and 14RR on the rear axle 16R (first axle) side. rf and two reduction amounts M rrl and M rrr There is a relationship between the amount of reduction M and the amount of reduction M as expressed by the following formula (6). rrl and M rrr is the amount of decrease M rrl and the amount of decrease M rrr The sum of this is the increase M rf Therefore, according to the above formula (4), a roll moment equal to the increased roll moment on the front axle 16F side is decreased on the rear axle 16R side.

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[0038] Regarding the allocation process, broadly speaking, the increase M rf The reduction amount M rrl and M rrr The respective ratios may be set arbitrarily. However, the ratios may be determined as described later in "3. Specific examples of allocation processing."

[0039] <Step S110> After step S106 or S108, in step S110, the controller 30 calculates the required control force F fli , F fri , F rli , and F rri Based on this, the actuators 26FR, 26RL, and 26RR of the three wheels 14 are controlled.

[0040] Specifically, in step S110, the controller 30 calculates the required control force F fli , F fri , F rli , and Frri , the required control forces F for the three wheels 14 with the actuators 26. fr、 F rl , and F rr For this conversion, for example, the method described in JP 2023-047810 A can be used. The outline of the conversion according to this method is as follows.

[0041] Regarding the above conversion, the controller 30 first calculates the required control force F fli , F fri , F rli , and F rri is converted into a required value of the center of gravity 3 mode. The center of gravity 3 mode is a motion mode consisting of a heave force, a roll moment, and a pitch moment acting on the center of gravity 11 of the vehicle 10. The required value of the center of gravity 3 mode is the required heave force F ht , required roll moment M rt , and the required pitch moment M pt In formula (7), lf and lr are the distances between the centers of gravity of the front axle 16F and the rear axle 16R, respectively. In addition, the required roll moment M rt is the required roll moment M r The required values ​​for the three center-of-gravity modes may include required values ​​for any behavior control other than the roll control.

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[0042] With respect to the above conversion, the controller 30 then converts the center of gravity three mode demand values ​​into the demand control forces F for the three wheels 14 according to the following equation (8): fr、 F rl , and F rr , that is, converted into required control forces of the three actuators 26.

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[0043] In step S110, the controller 30 calculates the required control force F fr Similarly, the controller 30 controls the actuator 26FR so that the vertical control force applied to the right rear wheel 14RR is equal to the required control force F rr The actuator 26RR is controlled so that the vertical control force applied to the left rear wheel 14RL is the required control force F rl The actuator 26RL is controlled so that the required control force F fr、 F rl , and F rr By controlling each of the actuators 26FR, 26RR, and 26RL based on the above, the desired behavior including all of the roll, pitch, and heave is achieved in the vehicle 10.

[0044] In addition, the above-mentioned control of the actuator 26 is applied to the actuator 26 capable of force (torque) control. In an example having the actuator 26 that performs position (angle) control for the three wheels 14, different from this control example, the controller 30 may control the three actuators 26 as follows. That is, the controller 30 controls each required control force F fr、 F rl , and F rr Then, the controller 30 performs position control of the three actuators 26 in accordance with the calculated position control amounts.

[0045] <Effects> As described above, according to the control process of this embodiment, the lateral acceleration a y When the lateral acceleration a exceeds the low acceleration region R1 and increases to the high acceleration region R2, the roll stiffness of the front axle 16F (second axle) is increased. This increases the roll stiffness of the front axle 16F (second axle) in the high acceleration region R2 without relying on the method of lowering the roll control gain (i.e., the lateral acceleration a y According to this embodiment, it is possible to suppress the occurrence of a large roll corresponding to the lateral acceleration a while suppressing the imbalance of the roll stiffness distribution.y When the vehicle stability control is abnormal even in the low acceleration region R1, the roll stiffness of the front axle 16F (second axle) is increased. As a result, when the vehicle stability control is abnormal, even in the low acceleration region R1, the control process is executed to suppress bias in the roll stiffness distribution, thereby suppressing unintended oversteer or understeer, and the stability of the vehicle 10 is improved.

[0046] According to the distribution process included in the control process, the roll stiffness of the front axle 16F is increased based on the relationship between the expressions (4) and (6) (see step S108). r In order to achieve this, a part of the control force to be generated by the pair of left and right actuators 26RL and 26RR (first actuators) on the rear axle 16R side is distributed to the actuator 26FR (second actuator) on the front axle 16F side. Broadly speaking, the control process may be executed to simply increase the roll moment generated on the front axle 16F side without the distribution process. In contrast, by including the distribution process, it becomes possible to effectively suppress bias in the roll stiffness distribution when increasing the roll moment generated on the front axle 16F side by the same amount, compared to an example without the distribution process.

[0047] Furthermore, according to this embodiment, when the roll stiffness of the front axle 16F is increased by the control process, the FB control gain β for the sprung roll velocity is increased (β2>β1). This makes it possible to suppress bias in the roll stiffness while causing the change in the sprung roll velocity to converge more quickly when roll control is performed using the actuators 26 of the three wheels 14 in conjunction with the control process.

[0048] According to the control process of this embodiment, the roll stiffness of the front axle 16F in the high acceleration region R2 is increased based on the relationship of formula (5) (see step S108). y The higher the increase, the greater the increase in M rf This increases the roll stiffness of the front axle 16F. As a result, the lateral acceleration a yIn accordance with the increase in the roll stiffness, the bias in the roll stiffness can be appropriately suppressed.

[0049] 3. Specific examples of allocation processing First, a specific example EX1 of the distribution process (see step S108) will be described. In this specific example EX1, the controller 30 distributes a part of the control force to be generated by the actuator 26RR (first actuator) of the right rear wheel 14RR of the rear axle 16R located on the same side as one wheel (right front wheel 14FR) of the front axle 16F having the actuator 26FR (second actuator), to the actuator 26FR.

[0050] More specifically, as expressed by the formula (9), the reduction amount M rrr is the increase amount M rf Therefore, from the relationship of the above formula (5), the reduction amount M of the left rear wheel 14RL is set to be equal to rrl becomes 0 as expressed by the formula (10). As a result, a part of the control force to be generated by the actuator 26RR of the right rear wheel 14RR (i.e., the reduction amount M rrr The control force according to the increase M rf The control force according to the rotational speed is distributed to the actuator 26FR.

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[0051] From the viewpoint of preventing the vehicle 10 from rolling over, it is preferable that the sprung center of gravity height is low. According to specific example EX1, it is possible to distribute a part of the control force that should be generated by the first actuator (e.g., actuator 26RR) on the rear axle 16R side to the second actuator (e.g., actuator 26FR) while preventing the generation of force in the heave direction. More specifically, according to the distribution according to specific example EX1, a pitch behavior occurs in accordance with the output of the roll moment, but no force is generated in the heave direction. Therefore, it is possible to suppress behavior that increases the sprung center of gravity height, which is behavior that can lead to rollover. In this way, according to specific example EX1 (as well as specific examples EX2 and EX3 described below), it is possible to prevent rollover while suppressing unintended oversteer or understeer in the high acceleration range R2. In addition, the reduction amount M rrl and M rrr Instead of concrete example EX1, "Decrease amount M rrr >M rrl " may be determined from equation (5) while satisfying the relationship. This relationship also has the effect of suppressing heave.

[0052] Next, in the specific example EX2, the reduction amount M rrl and M rrr is the increase M rf That is, the control force F of the first actuator which generates a roll moment on the rear axle 16R side is set as follows according to the positive or negative of rl and F rr Of these, the downward control force F rl or F rr corresponds to the direction of lowering the sprung center of gravity height, and the lateral acceleration a y This corresponds to a force acting in a direction that prevents the vehicle 10 from overturning due to the action of the force.

[0053] Therefore, in the specific example EX2, the increase amount M rf If negative, the controller 30 decreases the amount M rrl and M rrr On the other hand, the increment M rfWhen is positive, the controller 30 decreases the amount of decrease M according to the relationships of the following equations (11) and (12), that is, the inverse relationships of the relationships of the equations (9) and (10). rrl and M rrr This allows for a distribution process that can more effectively lower the sprung center of gravity height. In addition, the reduction amount M rrl and M rrr Instead of the specific example EX2, "Decrease amount M rrl >M rrr " may be determined from formula (5) while satisfying the relationship. This relationship also provides the effect of lowering the sprung center of gravity height.

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[0054] In addition, the increase amount M rf The allocation process involving consideration of the positive or negative sign of M is not limited to the specific example EX2, and may be executed as in the following specific example EX3. FIG. 4 is a diagram for explaining the specific example EX3 of the allocation process. That is, rf In the allocation process where the positive or negative value of is taken into account, the increment M rf If is positive, the increase M rf The same absolute increase M rf The corresponding reduction amount M rrl Specifically, for example, the reduction amount M rrl and M rrr In FIG. 4, τ is set to the increment M rf (Absolute value of) the reduction amount M rrr Therefore, if the ratio τ is 1, the reduction amount M rrr is the increase amount M rf In the example shown in FIG. rf When is negative, the rate τ is constant at 1, i.e., the decrease M rrl is constant at 0. On the other hand, the increase M rf If is positive, the rate τ is the increase M rfAs the value of M increases, the value of M decreases linearly from 1 to 0. rrl is an increment from 0 to M rf The effect of lowering the sprung center of gravity height can also be obtained by using this specific example EX3.

[0055] 4. Other embodiments In the flowchart shown in FIG. 3, even if the vehicle stability control is normal, the lateral acceleration a y If the lateral acceleration a is in the high acceleration region R2, the control process using the formula (4) is executed. y Alternatively, normal processing utilizing equation (2) may be executed regardless of whether the vehicle stability control is high or low, and control processing may be executed only when the vehicle stability control is abnormal.

[0056] In addition, the required roll moment M r Regarding the calculation of lateral acceleration a, instead of the feedback term of the sprung roll velocity (see equation (1) or (3)), y A feedback term of the time derivative of the above may be used. Then, similarly to the example of the sprung roll velocity, when the roll stiffness of the front axle 16F is increased by the control process, the feedback control gain for the above time derivative may be increased.

[0057] In the example shown in FIG. 1, the suspension 20FL for the left front wheel 14FL is an inactive suspension that does not have an actuator 26. Alternatively, the suspension 20FR for the right front wheel 14FR may be an inactive suspension. Also, unlike the example shown in FIG. 1, the front axle 16F may be the "first axle" and the rear axle 16R may be the "second axle." In this example, the suspension 20RL or 20RR on the side of the rear axle 16R is an inactive suspension. [Explanation of symbols]

[0058] 10 vehicle, 12 body, 14 wheels, 16F front axle, 16R rear axle, 20 suspension, 26 actuator, 30 controller

Claims

1. a roll stiffness varying device configured to vary a roll stiffness of a first axle, which is one of a front axle and a rear axle of a vehicle, and a roll stiffness of a second axle, which is the other of the front axle and the rear axle; A controller; Equipped with The controller: controlling the roll stiffness varying device so as to increase the roll stiffness of the first axle in response to an increase in the lateral acceleration at least in a low acceleration range of a range of the lateral acceleration acting on the vehicle; When the lateral acceleration exceeds the low acceleration range and increases to a high acceleration range, or when an abnormality occurs in a vehicle stability control that suppresses at least one of oversteer and understeer of the vehicle, a control process is executed to control the roll stiffness varying device so as to increase the roll stiffness of the second axle. A vehicle behavior control device comprising:

2. The roll stiffness varying device is A pair of left and right first actuators configured to apply vertical control forces to the left and right wheels of the first shaft; A second actuator configured to apply a vertical control force to one wheel of the second shaft; Including, The controller calculates a required roll moment according to the lateral acceleration, The control process includes a distribution process of distributing a part of a control force to be generated by the pair of left and right first actuators in order to realize the required roll moment to a second actuator.

2. The vehicle behavior control device according to claim 1.

3. In the distribution process, the controller distributes a part of a control force to be generated by one of the pair of left and right first actuators provided for one of the left and right wheels of the first shaft located on the same side as the one wheel of the second shaft, to the second actuator.

3. The vehicle behavior control device according to claim 2.

4. the demanded roll moment includes a feedback term of a roll rate on a sprung load of the vehicle; the feedback term includes a feedback control gain for the roll rate; When the lateral acceleration exceeds the low acceleration range and increases to the high acceleration range, or when the abnormality exists, the controller selects the feedback control gain that is larger than when the lateral acceleration is in the low acceleration range and there is no abnormality.

4. The vehicle behavior control device according to claim 2 or 3.

5. In the control process, the controller controls the roll stiffness varying device so as to increase the roll stiffness of the second axle as the lateral acceleration increases.

4. The vehicle behavior control device according to claim 1, wherein the vehicle behavior control device is a vehicle control device.

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