Vehicle attitude control device

Abstract

This attitude control device for a vehicle is provided in a vehicle 1 in which front, rear, left, and right wheels 3a to 3d are suspended by means of a suspension device 11 having an anti-dive and anti-lift geometry. The attitude control device for a vehicle is provided with brake devices 30a to 30d that are respectively provided for the wheels 3a to 3d, a brake control unit 31 that operatively controls the front, rear, left, and right brake devices 30a to 30d, wheel speed sensors 33a to 33d that respectively detect the rotational speeds of the wheels 3a to 3d, and a longitudinal acceleration sensor 35 that detects the acceleration of the vehicle 1 in the longitudinal direction thereof. The attitude control device for a vehicle is further provided with a pitch / roll determination unit 40 that, on the basis of the rotational speeds of the wheels 3a to 3d and the longitudinal acceleration of the vehicle 1, determines the pitch and roll states of the vehicle 1, and an added braking force computation unit 41 that computes a braking force to be added by each of the brake devices 30a to 30d so as to suppress the determined pitch and roll.

Description

Technical Field

[0001] The present invention relates to a vehicle attitude control technology using a braking device.

Background Art

[0002] As a technology for stabilizing the attitude of a vehicle and improving the comfort of passengers when driving on a rough road, a method of using a four-wheel active suspension device is known. The reaction force of the suspension device of each wheel is controlled by the four-wheel active suspension device to control the attitude of the vehicle. However, there is a problem that the four-wheel active suspension device is relatively expensive. Therefore, in a vehicle without a four-wheel active suspension device, an attitude control device that controls the braking force (brake force) of the four wheels by using the anti-dive force and anti-lift force in the suspension device has been proposed.

[0003] For example, in Patent Document 1, when the deviation between the target yaw rate and the actual yaw rate of the vehicle exceeds a predetermined value during a turning operation of the vehicle and the time change rate of the deviation also exceeds a predetermined value, by applying a braking force to the wheels on the inside of the turn, it is possible to improve the turning behavior of the vehicle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, the yaw rate of a vehicle is controlled by controlling the braking force of four wheels, but there is a demand for a device that can also control pitch and roll at low cost. In particular, when performing vehicle attitude control, it is necessary to detect the attitude of the vehicle. However, in a vehicle that does not have a four-wheel active suspension device, it often does not have a stroke sensor in the suspension device, making it difficult to detect the attitude of the vehicle.

[0006] The present invention has been made in view of such problems, and an object thereof is to provide a vehicle attitude control device that controls the braking force of four wheels according to the attitude of the vehicle and controls pitch and roll in a vehicle that does not have a stroke sensor in the suspension device.

Means for Solving the Problems

[0007] To achieve the above object, a vehicle attitude control device of the present invention is provided in a vehicle in which front, rear, left, and right wheels are suspended by a suspension device having anti-dive and anti-lift geometries, and includes braking devices respectively provided on the front, rear, left, and right wheels, a braking control unit that operates and controls the front, rear, left, and right braking devices and can apply braking force independently to the front, rear, left, and right wheels, a speed detection unit that respectively detects the rotational speeds of the front, rear, left, and right wheels, and a front-rear acceleration detection unit that detects the front-rear direction acceleration of the vehicle. The braking control unit includes a pitch-roll determination unit that determines the pitch and roll states of the vehicle based on the rotational speed of each wheel and the front-rear direction acceleration of the vehicle, and a pitch-roll control unit that applies braking force by each of the front, rear, left, and right braking devices based on the pitch and roll states.

[0008] Thereby, based on the rotational speed of each wheel and the front-rear direction acceleration of the vehicle, the pitch and roll states of the vehicle are determined, and braking force is applied by each of the front, rear, left, and right braking devices so as to cancel the pitch and roll states. Therefore, pitch and roll can be reduced based on detection information from relatively inexpensive detection units such as the speed detection unit and the front-rear acceleration detection unit.

[0009] Preferably, when the pitch-roll control unit determines that the vehicle has a pitch or roll state equal to or greater than a predetermined level during vehicle travel by the pitch-roll determination unit, the addition of the braking force of the braking device based on the pitch and roll states may be maintained for a predetermined time. Thereby, when it is determined that the vehicle has a pitch or roll state equal to or greater than a predetermined level, by maintaining the addition of the braking force of the braking device based on the pitch and roll states for a predetermined time, excessive fluctuations in the addition of the braking force can be suppressed.

[0010] Preferably, the pitch-roll determination unit includes a plurality of types of determination conditions for determining the pitch and roll states based on the rotational acceleration of each wheel and the longitudinal acceleration of the vehicle, and adds the additional moments set each time the determination conditions are satisfied to calculate the total additional moment of the vehicle. Thereby, the pitch and roll states of the vehicle can be easily determined, and the additional moment can be easily calculated.

[0011] Preferably, the additional moment set each time the determination conditions are satisfied is the pitch moment directed rearward of the vehicle, the pitch moment directed forward of the vehicle, the roll moment when one wheel on the right side of the vehicle rides on a convex road surface, the roll moment when two wheels on the right side of the vehicle ride on a convex road surface, the roll moment when two wheels on the right side and one wheel on the left side of the vehicle ride on a convex road surface, the roll moment when one wheel on the left side of the vehicle rides on a convex road surface, the roll moment when two wheels on the left side of the vehicle ride on a convex road surface, and the roll moment when two wheels on the left side and one wheel on the right side of the vehicle ride on a convex road surface.

[0012] Thereby, the pitch state and roll state of the vehicle can be easily determined separately, and the roll state can be easily and accurately determined according to the riding state of the vehicle. Preferably, when the driver of the vehicle performs a braking operation equal to or greater than a predetermined level, the pitch-roll control unit may suppress the addition of braking force based on the pitch and roll states.

[0013] Thereby, in response to a sudden braking operation by the driver, the braking by the pitch-roll control unit can be suppressed, and the braking requested by the driver can be prioritized. Preferably, the vehicle includes a braking control unit that controls the braking force of the braking device to improve the driving safety of the vehicle, and when the pitch-roll control unit is executing the control of the braking force of the braking device by the braking control unit, the addition of braking force based on the pitch and roll states may be suppressed.

[0014] Thereby, during braking control by the braking control unit, the braking by the pitch-roll control unit can be suppressed, and the control for improving the driving safety of the vehicle, such as improving the driving stability of the vehicle or avoiding a collision by the braking control unit, can be preferentially executed.

Advantages of the Invention

[0015] The vehicle attitude control device of the present invention can reduce the pitch and roll of the vehicle by using detection information from a relatively inexpensive detection unit that detects the wheel rotation speed and the longitudinal acceleration of the vehicle. Therefore, in a vehicle that does not have a stroke sensor in the suspension device, for example, the braking force of the four wheels can be controlled according to the attitude of the vehicle to appropriately control the pitch and roll.

Brief Description of the Drawings

[0016]

Figure 1

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Figure 10

Figure 11

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Figure 15

Mode for Carrying Out the Invention

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a vehicle attitude control device 10 according to an embodiment of the invention. The attitude control device 10 according to an embodiment of the present invention is mounted on a four-wheeled vehicle (hereinafter referred to as vehicle 1) having wheels 3a to 3d (driving wheels) on the front, rear, left, and right of the vehicle body. Between each of the wheels 3a to 3d of the vehicle 1 and the vehicle body, a suspension device 11 having an anti-dive and anti-lift geometry is provided to suspend the wheels 3a to 3d with respect to the vehicle body respectively.

[0018] Each of the wheels 3a to 3d of the vehicle 1 is provided with a brake device 30a to 30d (braking device) respectively. The brake devices 30a to 30d are controlled by a brake control unit 31 (braking control unit), and it is possible to apply an arbitrary different braking force (braking power) to each of the wheels 3a to 3d.

[0019] Note that each of the wheels 3a to 3d is driven by, for example, an electric motor or an engine. For example, the front wheels 3a, 3b and the rear wheels 3c, 3d can be driven by an electric motor respectively, and the front wheels 3a, 3b can be driven by an engine. The present invention is applicable to various driving power sources such as a plug-in hybrid vehicle, a hybrid vehicle, an electric vehicle that drives the wheels 3a to 3d only by an electric motor, and an engine vehicle that drives the wheels 3a to 3d only by an engine, and also to vehicles with various driving forms such as four-wheel drive or two-wheel drive.

[0020] The vehicle 1 is provided with a longitudinal acceleration sensor 35 (longitudinal acceleration detection unit) for detecting the acceleration in the longitudinal direction of the vehicle body, and wheel speed sensors 33a to 33d (speed detection units) for detecting the rotational speeds of the respective wheels 3a to 3d. The attitude control device 10 is composed of the longitudinal acceleration sensor 35, the wheel speed sensors 33a to 33d of the respective wheels 3a to 3d, and the brake control unit 31.

[0021] Note that in the present embodiment, the detection values of the longitudinal acceleration sensor 35 and the wheel speed sensors 33a to 33d are configured to be input to the brake control unit 31, but for example, a configuration in which they are input via a main control unit 20 that controls the entire vehicle may also be used. The brake control unit 31 includes an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, and the like. The brake control unit 31 receives the operation amount of the brake pedal from a brake pedal sensor (not shown), and controls the braking force (brake force) by the brake devices 30a to 30d based on the operation amount of the brake pedal and the like.

[0022] Further, detection information is input to the brake control unit 31 from the longitudinal acceleration sensor 35 and the wheel speed sensors 33a to 33d. The attitude control device 10 includes a pitch-roll determination unit 40 that estimates the attitude of the vehicle 1, specifically the pitch and roll states of the vehicle 1, based on the detection information of the longitudinal acceleration sensor 35 and the wheel speed sensors 33a to 33d of each wheel 3a to 3d, and an additional braking force calculation unit 41 (pitch-roll control unit) that calculates the braking force to be applied to each wheel 3a to 3d so as to reduce the estimated pitch and roll. The attitude control device 10 estimates the pitch and roll of the vehicle based on the detection information of the longitudinal acceleration sensor 35 and the wheel speed sensors 33a to 33d, and executes pitch-roll control to set the braking force to be applied to each wheel 3a to 3d so as to reduce the pitch and roll.

[0023] Figure 2 is an explanatory diagram of the anti-dive force and anti-lift force. First, the relationship between the anti-dive force and anti-lift force in the suspension device of the vehicle 1, and the pitch moment and roll moment will be described. As shown in Figure 2, let the distance in the longitudinal direction of the vehicle between the ground contact points of the front wheels 3a and 3b of the vehicle 1 and the center of gravity A of the vehicle body be a, the distance in the longitudinal direction of the vehicle between the ground contact points of the rear wheels 3c and 3d of the vehicle 1 and the center of gravity A be b, the height of the center of gravity A from the ground be hCG, the total braking force of the entire vehicle be F, the ratio of the braking force on the front wheel 3a, 3b side be λ, the anti-lift angle be βf, and the anti-dive angle be βr. Then, the pitch moment My, which is the sum of the pitch moment generated by the deceleration of the vehicle 1 and the pitch moment generated by the anti-dive force and anti-lift force of the suspension device 11, is obtained by the following (Equation 1).

[0024] My = F×hCG - (λF×|tan(βf)|×a + (1 - λ)F×|tan(βr)|×b) ···(Equation 1) Also, let the front track (the distance between the left and right front wheels 3a and 3b) be tf, the rear track (the distance between the left and right rear wheels 3c and 3d) be tr, the braking force (brake force) of the left front wheel 3a be Fbfl, the braking force of the right front wheel 3b be Fbfr, the braking force of the left rear wheel 3c be Fbrl, and the braking force of the right rear wheel 3d be Fbrr. Then, the roll moment Mx generated by the anti-dive force and anti-lift force of the suspension device 11 is obtained by the following (Equation 2).

[0025] Mx = tf / 2(Fbfl - Fbfr)×tan(βf) + tr / 2(-Fbrl - Fbrr)×tan(βr) ···(Equation 2) Figs. 3 to 6 are images of the additional moment in the attitude control device 10 of the present embodiment. Fig. 3 is an image of the pitch moment generated when the front wheels 3a and 3b ride up and the additional moment with respect thereto when the rear wheels 3c and 3d ride up.

[0026] As shown by the solid arrow in Fig. 3, the pitch moment generated when the front wheels 3a and 3b of the vehicle 1 ride up on a convex road surface is a moment that rotates around the center of gravity of the vehicle 1 toward the rear side. In contrast, the attitude control device 10 may add an additional pitch moment My1 that rotates toward the front side of the vehicle shown by the dashed arrow so as to cancel this pitch moment. As shown by the solid arrow in Fig. 4, the pitch moment generated when the rear wheels 3c and 3d of the vehicle 1 ride up on a convex road surface is a moment that rotates around the center of gravity of the vehicle 1 toward the front side. In contrast, the attitude control device 10 may add an additional pitch moment My2 that rotates toward the rear side of the vehicle shown by the dashed arrow so as to cancel this pitch moment.

[0027] Also, as shown by the solid arrows in Fig. 5, the roll moment generated when the right wheels 3b and 3d of the vehicle 1 climb over a convex road surface is a moment that rotates around the center of gravity of the vehicle 1 to the left in the vehicle width direction. As shown in Fig. 5, (a) the case where only one wheel (for example, the right front wheel 3b) has climbed over the convex road surface, (b) the case where two wheels (the right front wheel 3b and the right rear wheel 3d) have climbed over the convex road surface, and (c) the case where three wheels (the right front wheel 3b, the right rear wheel 3d, and for example, the left front wheel 3a) have climbed over the convex road surface can be considered.

[0028] Therefore, in the cases of Figs. 5(a) to (c), as shown by the dashed lines in Fig. 5, additional roll moments Mx1, Mx2, and Mx3 that cancel out the roll moment may be added. In the case of (a) in Fig. 5, it is the additional roll moment Mx1, in the case of (b), it is the additional roll moment Mx2, and in the case of (c), it is the additional roll moment Mx3. Also, as shown by the solid arrows in Fig. 6, the roll moment generated when the left wheels 3a and 3c of the vehicle 1 climb over a convex road surface is a moment that rotates around the center of gravity of the vehicle 1 to the right in the vehicle width direction. As shown in Fig. 6, (a) the case where only one wheel (for example, the left front wheel 3a) has climbed over the convex road surface, (b) the case where two wheels (the left front wheel 3a and the left rear wheel 3c) have climbed over the convex road surface, and (c) the case where three wheels (the left front wheel 3a, the left rear wheel 3c, and for example, the right front wheel 3b) have climbed over the convex road surface can be considered.

[0029] Therefore, in the cases of (a) to (c), as shown by the dashed lines in Fig. 6, additional roll moments Mx4, Mx5, and Mx6 that cancel out the roll moment may be added. In the case of (a) in Fig. 6, it is the additional roll moment Mx4, in the case of (b), it is the additional roll moment Mx5, and in the case of (c), it is the additional roll moment Mx6. Note that in Figs. 5 and 6, (b) and (c), the × mark indicates that it has climbed over the convex road surface. In Figs. 5 and 6, (b) and (c), the arrows indicating the moment are shown in the top view, but actually, it is a roll moment in the vertical direction similar to (a).

[0030] A method for determining the attitude of the vehicle 1, which is executed in the brake control unit 31, will be described. The pitch / roll determination unit 40 of the brake control unit 31 determines the attitude regarding each of the above pitches / rolls based on the longitudinal acceleration of the vehicle 1 and the wheel rotation speeds of the respective wheels 3a to 3d.

[0031] The attitude in which the front wheels 3a and 3b of the vehicle 1 ride over a convex road surface as shown in FIG. 3 is a case where the conditions in Table 1 below are satisfied. The conditions in Table 1 are when the rotational accelerations of the left and right front wheels 3a and 3b exceed a predetermined threshold (FRwa > Xwa1, FLwa > Xwa2), the wheel rotational accelerations of the left and right rear wheels 3c and 3d are less than the predetermined threshold (|wsaRL| < Xwa3, |wsaRR| < Xwa4), and the longitudinal acceleration of the vehicle exceeds the predetermined threshold (La < Xaa1), that is, when all five conditions are satisfied.

[0032] The attitude in which the rear wheels 3c and 3d of the vehicle 1 ride over a convex road surface as shown in FIG. 4 is a case where the conditions in Table 2 below are satisfied. The conditions in Table 2 are when the rotational accelerations of the left and right rear wheels 3c and 3d exceed a predetermined threshold (RLwa > Xwa5, RRwa > Xwa6), the wheel rotational accelerations of the left and right front wheels 3a and 3b are less than the predetermined threshold (|wsaFL| < Xwa7, |wsaFR| < Xwa8), and the longitudinal acceleration of the vehicle exceeds the predetermined threshold (La < Xaa2), that is, when all five conditions are satisfied.

[0033] The attitude in which one wheel on the right side of the vehicle 1 rides over a convex road surface as shown in FIG. 5(a) is a case where the conditions in Table 3 below are satisfied. The conditions in Table 3 are met when all of the following five conditions are satisfied: when the rotational acceleration of the right front wheel 3b exceeds a predetermined threshold (FRwa > Xwa9), the wheel rotational accelerations of the other wheels 3a, 3c, and 3d are less than the predetermined threshold (|wsaFL| < Xwa10, |wsaRL| < Xwa11, |wsaRL| < Xwa12), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa3). Or, when all of the following five conditions are satisfied: when the rotational acceleration of the right rear wheel 3d exceeds a predetermined threshold (RRwa > Xwa13), the wheel rotational accelerations of the other wheels 3a, 3b, and 3c are less than the predetermined threshold (|wsaFR| < Xwa14, |wsaFL| < Xwa15, |wsaRL| < Xwa16), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa4), these are also the conditions in Table 3.

[0034] The posture in which the two right wheels 3b and 3d of the vehicle 1 ride over a convex road surface as shown in Fig. 5(b) is the case when the conditions in Table 4 below are satisfied. The conditions in Table 4 are met when all of the following five conditions are satisfied: when the rotational accelerations of the two right wheels 3b and 3d exceed a predetermined threshold (FRwa > Xwa17, RRwa > Xwa18), the rotational accelerations of the two left wheels 3a and 3c are less than the predetermined threshold (|wsaFL| < Xwa19, |wsaRL| < Xwa20), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa5).

[0035] The posture in which the two right wheels and one left wheel of the vehicle 1 ride over a convex road surface as shown in Fig. 5(c) is the case when the conditions in Table 5 below are satisfied. The conditions in Table 5 are met when all of the following five conditions are satisfied: when the rotational accelerations of the left and right front wheels 3a and 3b exceed a predetermined threshold (FLwa > Xwa21, FRwa > Xwa22), the rotational acceleration of the right rear wheel 3d exceeds a predetermined threshold (RRwa > Xwa23), the rotational acceleration of the left rear wheel 3c is less than the predetermined threshold (|wsaRL| < Xwa24), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa6).

[0036] The posture in which one wheel on the left side of the vehicle 1 has climbed onto a convex road surface as shown in Fig. 6(a) is the case when the conditions in Table 6 below are satisfied. The conditions in Table 6 are that when the rotational acceleration of the left front wheel 3a exceeds a predetermined threshold (FLwa > Xwa25), the rotational accelerations of the other wheels 3b, 3c, 3d are less than the predetermined threshold (|wsaFR| < Xwa26, |wsaRL| < Xwa27, |wsaRR| < Xwa28), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa7). Or, when the rotational acceleration of the left rear wheel 3c exceeds a predetermined threshold (RLwa > Xwa29), the rotational accelerations of the other wheels 3a, 3b, 3d are less than the predetermined threshold (|wsaFR| < Xwa30, |wsaFL| < Xwa31, |wsaRR| < Xwa32), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa8). These are also the conditions in Table 6 when all five conditions are satisfied.

[0037] The posture in which two wheels 3a, 3c on the left side of the vehicle 1 have climbed onto a convex road surface as shown in Fig. 6(b) is the case when the conditions in Table 7 below are satisfied. The conditions in Table 7 are that when the rotational accelerations of the left-side wheels 3a, 3c exceed a predetermined threshold (FLwa > Xwa33, RLwa > Xwa34), the rotational accelerations of the two right-side wheels 3b, 3d are less than the predetermined threshold (|wsaFR| < Xwa35, |wsaRR| < Xwa36), and the acceleration in the longitudinal direction of the vehicle exceeds a predetermined threshold (La < Xaa9). These are the conditions when all five conditions are satisfied.

[0038] The posture in which two wheels 3a, 3c on the left side and one wheel on the right side of the vehicle 1 have climbed onto a convex road surface as shown in Fig. 6(c) is the case when the conditions in Table 8 below are satisfied. The conditions in Table 8 are when all of the following five conditions are met: when the rotational acceleration of the front wheels 3a and 3b exceeds a predetermined threshold (FRwa > Xwa37, FLwa > Xwa38), when the acceleration of the left rear wheel 3c exceeds a predetermined threshold (RLwa > Xwa39), when the rotational acceleration of the right rear wheel 3d is less than a predetermined threshold (|wsaRR| < Xwa40), and when the acceleration of the vehicle in the longitudinal direction exceeds a predetermined threshold (La < Xaa10).

[0039] Note that the threshold values Xwa1 to Xwa40 and Xaa1 to Xaa10 are values set as appropriate respectively. Figures 7 to 14 are flowcharts showing the calculation methods of the additional pitch moments My1, My2 and the additional roll moments Mx1 to Mx6. Figure 7 shows the additional pitch moment My1 when the front wheels 3a and 3b lift off, Figure 8 shows the additional pitch moment My2 when the rear wheels 3c and 3d lift off, Figure 9 shows the additional roll moment Mx1 when one wheel on the right side lifts off, Figure 10 shows the additional roll moment Mx2 when two wheels on the right side lift off, Figure 11 shows the additional roll moment Mx3 when two wheels on the right side and one wheel on the left side lift off, Figure 12 shows the additional roll moment Mx4 when one wheel on the left side lifts off, Figure 13 shows the additional roll moment Mx5 when two wheels on the left side lift off, and Figure 14 shows the calculation method of the additional roll moment Mx6 when two wheels on the left side and one wheel on the right side lift off.

[0040] These flowcharts are each repeatedly executed with a short control cycle (for example, about several msec). As shown in Figure 7, first in step S10, it is determined whether the conditions in Table 1 above are satisfied. If the conditions in Table 1 are satisfied, the process proceeds to step S20. If the conditions in Table 1 are not satisfied, the process proceeds to step S60.

[0041] In step S20, the brake timer XT1 is counted up. Then, the process proceeds to step S30. In step S30, it is determined whether the brake timer XT1 is less than a braking time threshold value XTime1 set as appropriate. If the brake timer XT1 is less than the braking time threshold value XTime1, the process proceeds to step S40. If the brake timer XT1 is greater than or equal to the braking time threshold value XTime1, the process proceeds to step S50.

[0042] In step S40, the additional pitch moment My1 is set to xxMy1 set as appropriate. Then, this routine returns. In step S50, the additional pitch moment My1 is set to 0, and the brake timer XT1 is reset to 0. Then, this routine returns. In step S60, it is determined whether the brake timer XT1 is not 0. If the brake timer XT1 is not 0, the process proceeds to step S70. If the brake timer XT1 is 0, the process proceeds to step S80.

[0043] In step S70, the brake timer XT1 is incremented. Then, the process proceeds to step S90. In step S80, the additional pitch moment My1 is set to 0. Then, this routine returns. In step S90, it is determined whether the brake timer XT1 is less than the braking time threshold value XTime1. If the brake timer XT1 is less than the braking time threshold value XTime1, the process proceeds to step S100. If the brake timer XT1 is greater than or equal to the braking time threshold value XTime1, the process proceeds to step S110.

[0044] In step S100, the additional pitch moment My1 is set to xxMy1. Then, this routine returns. In step S110, the additional pitch moment My1 is set to 0, and the brake timer XT1 is reset to 0. Then, this routine returns. By controlling as described above, when the conditions in Table 1 are satisfied, the additional pitch moment My1 is set to xxMy1 until the brake timer XT1 reaches the braking time threshold XTime1.

[0045] As shown in FIG. 8, the additional pitch moment My2 is set in the same manner as the additional pitch moment My1. That is, when the conditions in Table 2 are satisfied, the additional pitch moment My2 is set to xxMy2 until the brake timer XT2 reaches the braking time threshold XTime2. As shown in FIG. 9, the additional roll moment Mx1 is set in the same manner as the additional pitch moment My1.

[0046] That is, when the conditions in Table 3 are satisfied, the additional roll moment Mx1 is set to xxMx1 until the brake timer XT3 reaches the braking time threshold XTime3. For the additional roll moment Mx2, as shown in FIG. 10, for the additional roll moment Mx3, as shown in FIG. 11, for the additional roll moment Mx4, as shown in FIG. 12, for the additional roll moment Mx5, as shown in FIG. 13, and for the additional roll moment Mx6, as shown in FIG. 14, all are set in the same manner as the additional roll moment Mx1.

[0047] The finally added pitch moment My and roll moment Mx of Vehicle 1 are calculated by the following (Equation 3) and (Equation 4). My = My1 + My2 ··· (Equation 3) Mx = Mx1 + Mx2 + Mx3 + Mx4 + Mx5 + Mx6 ··· (Equation 4) Next, the additional braking forces Fbfl, Fbfr, Fbrl, and Fbrr of each wheel are calculated from the additional moment values. The calculation formulas for the additional moments are obtained by transforming the above (Equation 1) and (Equation 2) into the following (Equation 5) and (Equation 6).

[0048]

Number

[0049]

Number

[0050] In addition, the total additional braking force X Total Force (= XX Force) is obtained from the following (Equation 7). The left - right difference of the additional braking force, X Dif Force, is obtained from the following (Equation 8).

[0051]

Number

[0052]

Number

[0053] Note that X Dif Force = XX Dif × the required yaw moment input from the main control unit 20, and XX Dif is the gain of the said required yaw moment set as appropriate. Regarding the pitch moment My, roll moment Mx, total additional braking force X Total Force, and left - right difference of the additional braking force X Dif Force, when they are matrix - formed, the following (Equation 9) is obtained.

[0054]

Number

[0055] Figure 15 is a flowchart showing the control procedure for the execution determination of the above pitch - roll control. The control shown in Figure 15 is started at the time of system startup and is repeatedly performed during the running of the vehicle 1. First, in step S1600, it is determined whether the brake control unit 31 or each of the brake devices 30a to 30d is in an abnormal (faulty) state. Whether these units are abnormal can be determined by a known self-diagnosis function. If the brake control unit 31 or each of the brake devices 30a to 30d is abnormal, the process proceeds to step S1640. If the brake control unit 31 and each of the brake devices 30a to 30d are normal, the process proceeds to step S1610.

[0056] In step S1610, it is determined whether the driver's brake operation amount (operating force) exceeds a predetermined threshold value X Cmd Force set as appropriate. If the brake operation amount exceeds the threshold value X Cmd Force, the process proceeds to step S1640. If the brake operation amount is equal to or less than the threshold value X Cmd Force, the process proceeds to step S1620. In step S1620, it is determined whether other traveling control devices (traveling safety devices) of the vehicle 1, such as an Electric Stability Control system (ESC), an Anti-lock Brake System (ABS), and a Collision Damage Mitigation Brake System (AEB), are in an operating state (under control). If other traveling control devices are in an operating state, the process proceeds to step S1640. If other traveling control devices are not in an operating state (standby state), the process proceeds to step S1630.

[0057] In step S1630, the pitch-roll control by the above-described attitude control device 10 is turned on. Then, this routine returns. In step S1640, the pitch-roll control by the above-described attitude control device 10 is turned off. Then, this routine returns. As described above, in the embodiment of the present invention, it becomes possible to perform attitude control (pitch-roll control) for reducing the pitch and roll of the vehicle 1 by controlling the braking force of the four-wheel brake devices 30a to 30d of the vehicle 1.

[0058] Regarding the pitch and roll of the current vehicle 1, they are estimated based on the rotational accelerations of the respective wheels 3a to 3d and the longitudinal acceleration of the vehicle 1. Thereby, based on the detection information by relatively inexpensive detectors such as the four wheel speed sensors 33a to 33d and the longitudinal acceleration sensor 35, the pitch and roll of the vehicle 1 can be estimated. The pitch / roll determination unit 40 includes tables 1 to 8 having determination conditions for determining the pitch / roll state of the vehicle 1 based on the rotational accelerations of the respective wheels 3a to 3d and the longitudinal acceleration of the vehicle 1, and determines whether the conditions of each of the tables 1 to 8 are satisfied.

[0059] When any of the conditions of each of the tables 1 to 8 is satisfied, the additional braking force calculation unit 41 sets the additional moments Mx1, Mx2, My1 to My6 corresponding to each table, and adds these additional moments to calculate the overall additional moment of the vehicle 1. Thereby, the pitch and roll states of the vehicle 1 can be easily determined, and the additional moment can be easily calculated.

[0060] Regarding the additional moments My1, My2, Mx1 to Mx6 set for each of the tables 1 to 8, specifically, they are as follows. · Table 1 has a determination condition for generating a pitch moment directed toward the rear of the vehicle, and sets an additional pitch moment My1 directed toward the front of the vehicle. · Table 2 has a determination condition for generating a pitch moment directed toward the front of the vehicle, and sets an additional pitch moment My2 directed toward the rear of the vehicle. · Table 3 has a determination condition for generating a roll moment in a state where one wheel on the right side of the vehicle 1 has climbed onto a convex road surface, and sets an additional roll moment Mx1 directed toward the right side of the vehicle. · Table 4 has a determination condition for generating a roll moment in a state where two wheels on the right side of the vehicle 1 have climbed onto a convex road surface, and sets an additional roll moment Mx2 directed toward the right side of the vehicle. · Table 5 has the determination conditions for the generation of roll moment in the state where two wheels on the right side of the vehicle and one wheel on the left side are riding on a convex road surface, and sets an additional roll moment Mx3 directed toward the right side of the vehicle. · Table 6 has the determination conditions for the generation of roll moment in the state where one wheel on the left side of the vehicle is riding on a convex road surface, and sets an additional roll moment Mx4 directed toward the left side of the vehicle. · Table 7 has the determination conditions for the generation of roll moment in the state where two wheels on the left side of the vehicle are riding on a convex road surface, and sets an additional roll moment Mx5 directed toward the left side of the vehicle. · Table 8 has the determination conditions for the generation of roll moment in the state where two wheels on the left side and one wheel on the right side of the vehicle are riding on a convex road surface, and sets an additional roll moment Mx6 directed toward the left side of the vehicle.

[0061] Thus, based on the rotational accelerations of the respective wheels 3a to 3d and the longitudinal acceleration of the vehicle 1, the pitch and roll states of the vehicle 1 can be easily and accurately determined. Also, the determination of each of Tables 1 to 8 based on the rotational accelerations of the wheels 3a to 3d and the longitudinal acceleration of the vehicle 1 is performed at a relatively short period in order to quickly respond to the attitude change of the vehicle 1. However, as shown in the left portion of the flowcharts of FIGS. 7 to 14, when the brake timer counts up and becomes non-zero by satisfying the determination conditions of each of Tables 1 to 8, until the brake timer completes the count-up, even if it is determined that the determination conditions of the respective Tables 1 to 8 are not satisfied midway, the additional moment corresponding to the respective Tables 1 to 8 is continuously set.

[0062] Thus, while the responsiveness when the determination conditions of each of Tables 1 to 8 are satisfied is made good, once the determination conditions are satisfied, the additional moment is set and the addition of the braking force is maintained for a predetermined time until the brake timer completes the count-up, so that excessive fluctuations (switching) of the added braking force can be suppressed. Also, when the brake control unit 31 or each brake device 30a to 30d is abnormal, when the driver's brake operation amount exceeds the threshold value X Cmd Force, or when other driving control devices (driving safety devices) other than the present attitude control device 10 such as ESC, ABS, and AEB are operating, in any of these cases, the pitch / roll control by the attitude control device 10 is not executed.

[0063] In particular, since the pitch / roll control is not executed when the brake operation force is equal to or greater than a predetermined value, when the driver performs a sudden brake operation, the pitch / roll control of the present embodiment can be suppressed and the braking by the brake operation can be prioritized. Also, when other driving control devices other than the attitude control device are operating (such as during brake control), the pitch / roll control of the present embodiment can be suppressed, other driving control devices can be prioritized, and the driving safety function by the other driving control devices can be appropriately ensured.

[0064] The description of the embodiment ends here, but the aspects of the present invention are not limited to the above embodiment. For example, in the above embodiment, when the brake operation amount exceeds the threshold value X Cmd Force or when other driving control devices are operating, the pitch / roll control of the present embodiment is not executed, but the braking force may be slightly suppressed and added by the pitch / roll control of the present embodiment. The present invention can be widely applied to a vehicle capable of independently braking four wheels on the front, rear, left, and right.

Explanation of Reference Numerals

[0065] 1 Vehicle 3a to 3d Wheels 10 Attitude Control Device 11 Suspension Device 30a to 30d Brake Devices (Braking Devices) 31 Brake Control Unit (Braking Control Unit) 33a to 33d Wheel Speed Sensors (Speed Detection Units) 35 Front - Rear Acceleration Sensor (Front - Rear Acceleration Detection Unit) 40 Pitch / Roll Determination Unit 41 Additional braking force calculation unit (pitch / roll control unit)

Claims

1. A vehicle equipped with a suspension device having anti-dive and anti-lift geometry, with front, rear, left, and right wheels suspended, braking devices respectively provided on the front, rear, left, and right wheels, a braking control unit that operates and controls the front, rear, left, and right braking devices and can apply braking force independently to the front, rear, left, and right wheels, a speed detection unit that respectively detects the rotational speeds of the front, rear, left, and right wheels, a front-rear acceleration detection unit that detects the front-rear acceleration of the vehicle, comprising: the braking control unit includes a pitch-roll determination unit that determines the pitch and roll states of the vehicle based on the rotational speed of each wheel and the front-rear acceleration of the vehicle, and a pitch-roll control unit that applies braking force by the front, rear, left, and right braking devices based on the pitch and roll states, the pitch-roll determination unit includes a plurality of types of determination conditions for determining the pitch and roll states based on the rotational acceleration of each wheel and the front-rear acceleration of the vehicle, and adds an additional moment set each time the determination conditions are satisfied to calculate the total additional moment of the vehicle A vehicle attitude control device characterized by the above.

2. When the pitch-roll determination unit determines a pitch or roll state of the vehicle equal to or greater than a predetermined value during vehicle travel, the pitch-roll control unit maintains the application of the braking force of the braking device based on the pitch and roll states for a predetermined time The vehicle attitude control device according to claim 1, characterized by the above.

3. (Deleted)

4. The additional moment set each time the determination conditions are satisfied is a pitch moment directed towards the rear of the vehicle, a pitch moment directed towards the front of the vehicle, a roll moment in a state where one wheel on the right side of the vehicle has climbed onto a convex road surface, a roll moment in a state where two wheels on the right side of the vehicle have climbed onto a convex road surface, a roll moment in a state where two wheels on the right side and one wheel on the left side of the vehicle have climbed onto a convex road surface, a roll moment in a state where one wheel on the left side of the vehicle has climbed onto a convex road surface, a roll moment in a state where two wheels on the left side of the vehicle have climbed onto a convex road surface, a roll moment in a state where two wheels on the left side and one wheel on the right side of the vehicle have climbed onto a convex road surface The vehicle attitude control device according to claim 1, characterized by the above.

5. When there is a braking operation of a predetermined level or more by the driver of the vehicle, the pitch-roll control unit suppresses the addition of braking force based on the pitch and roll states. The vehicle attitude control device according to claim 1, characterized in that.

6. The vehicle includes a braking control unit that controls the braking force of the braking device to improve the driving safety of the vehicle. When the pitch-roll control unit is executing the control of the braking force of the braking device by the braking control unit, the pitch-roll control unit suppresses the addition of braking force based on the pitch and roll states. The vehicle attitude control device according to claim 1, characterized in that.

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