Vehicle attitude control device

Abstract

The present invention is provided to a vehicle 1 having front / rear / left / right wheels 3a-3d suspended by a suspension device 11 having an anti-dive and anti-lift geometry, and is provided with brake devices 30a-30d respectively provided to the wheels 3a-3d, and a brake control unit 31 for controlling operation of the front / rear / left / right brake devices 30a-30d. The brake control unit 31 comprises a pitch / roll determination unit 40 for determining the pitch state of the vehicle 1 on the basis of rotational speeds of the wheels 3a-3d and front / rear direction acceleration of the vehicle 1, and an additional braking force computation unit 41 for computing a braking force of each of the brake devices 30a-30d so as to suppress the determined pitch state with regard to when the wheels 3a-3d have run up onto a raised road surface as well as after the foregoing have ran up. An additional moment that is set on the basis of a vehicle travel state is added every time a pitch determination condition is satisfied, to compute a total additional moment.

Description

Vehicle attitude control device

[0001] The present invention relates to a vehicle attitude control technology that utilizes a brake device.

[0002] A method using a four-wheel active suspension system is known as a technology for stabilizing a vehicle's posture when traveling over rough roads and improving passenger comfort. The four-wheel active suspension system controls the reaction force of the suspension system for each wheel to control the vehicle's posture. However, four-wheel active suspension systems have the drawback of being relatively expensive. Therefore, for vehicles that do not have four-wheel active suspension systems, a posture control system has been proposed that uses the anti-dive and anti-lift forces of the suspension system to control the braking force (braking force) of the four wheels.

[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 while the vehicle is turning, and the time change rate of the deviation exceeds a predetermined value, braking force is applied to the wheel on the inside of the turn, thereby making it possible to improve the turning behavior of the vehicle.

[0004] Japanese Patent Application Laid-Open No. 2020-50024

[0005] In Patent Document 1, the yaw rate of a vehicle is controlled by controlling the braking force of each of the four wheels. However, there is a demand for a device that can also inexpensively control the pitch, which is the longitudinal behavior of the vehicle. Vehicle attitude control requires the detection of vehicle attitude. However, vehicles without a four-wheel active suspension system often do not have a stroke sensor in the suspension system, making it difficult to detect vehicle attitude.

[0006] Furthermore, even if braking control is performed to suppress pitch, it is difficult to rapidly converge pitch due to control delays, etc. The present invention has been made in consideration of these problems, and an object of the present invention is to provide a vehicle attitude control device that can rapidly suppress pitch in a vehicle that does not have a stroke sensor in its suspension device.

[0007] In order to achieve the above object, the vehicle attitude control device of the present invention is provided on a vehicle in which front, rear, left and right wheels are suspended by suspension devices having anti-dive and anti-lift geometry, and includes braking devices provided on the front, rear, left and right wheels, respectively; a braking control unit that controls the operation of the front, rear, left and right braking devices and is capable of applying braking forces independently to the front, rear, left and right wheels; a speed detection unit that detects the rotational speeds of the front, rear, left and right wheels, respectively; and a longitudinal acceleration detection unit that detects longitudinal acceleration of the vehicle, and the braking control unit detects a longitudinal acceleration of the vehicle based on the rotational speed of each of the wheels and the longitudinal acceleration of the vehicle. and a posture control unit that applies braking forces by the front, rear, left, and right braking devices based on the pitch state, wherein the pitch determination unit has a plurality of types of pitch determination conditions that determine the pitch state based on the rotational acceleration of each of the wheels and the longitudinal acceleration of the vehicle, and calculates an overall additional moment of the vehicle by adding an additional moment that is set each time the pitch determination condition is satisfied, and the additional moment is set based on the vehicle running state when the pitch determination condition is satisfied.

[0008] The vehicle attitude control device of the present invention uses information detected by a relatively inexpensive detector that detects wheel rotational speed and vehicle longitudinal acceleration, and can apply an additional moment to reduce vehicle pitch when a wheel runs over a convex road surface and pitch determination conditions are met. Furthermore, because the additional moment is set based on the vehicle running state when the pitch determination conditions are met, it becomes possible to appropriately suppress pitch in a short period of time.

[0009] 1 is a schematic configuration diagram of a vehicle attitude control device according to one embodiment of the present invention; FIG. 2 is an explanatory diagram of anti-dive force and anti-lift force in a vehicle suspension device; FIG. 3 is an image diagram of a pitch moment generated when a front wheel runs over a road surface and an additional moment corresponding thereto; FIG. 4 is an image diagram of a pitch moment generated when a rear wheel runs over a road surface and an additional moment corresponding thereto; FIG. 5 is an image diagram of a roll moment generated when a right wheel runs over a road surface and an additional moment corresponding thereto; FIG. 6 is an image diagram of a roll moment generated when a left wheel runs over a road surface and an additional moment corresponding thereto; FIG. 7 is a flowchart showing a method for calculating an additional moment when a front wheel runs over a road surface; FIG. 8 is a flowchart showing a method for calculating an additional moment when a rear wheel runs over a road surface; FIG. 9 is a flowchart showing a method for calculating an additional moment when one right wheel runs over a road surface; FIG. 10 is a flowchart showing a method for calculating an additional moment when two right wheels run over a road surface; FIG. 11 is a flowchart showing a method for calculating an additional moment when two right wheels and one left wheel run over a road surface; FIG. 12 is a flowchart showing a method for calculating an additional moment when one left wheel runs over a road surface; 1 is a flowchart showing a method for calculating the additional moment when two wheels on the left side and one wheel on the right side go over a run-up area. FIG. 2 is a flowchart showing the procedure for calculating the set value xxMy1 set for the additional pitch moment My1. FIG. 3 is an image diagram of the pitch moment remaining after the front wheels go over a run-up area and the corresponding additional moment. FIG. 4 is an image diagram of the pitch moment remaining after the rear wheels go over a run-up area and the corresponding additional moment. FIG. 5 is a flowchart showing a method for calculating the additional moment after the front wheels go over a run-up area. FIG. 6 is a flowchart showing a method for calculating the additional moment after the rear wheels go over a run-up area. FIG. 7 is a time chart showing an example of the progression of the pitch angle when the front wheels go over a run-up area and the timing of each control. FIG. 8 is a flowchart showing a control procedure for determining whether pitch / roll control is performed.

[0010] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a schematic diagram of a vehicle attitude control device 10 according to an embodiment of the present invention. The attitude control device 10 according to an embodiment of the present invention is mounted on a four-wheel vehicle (hereinafter referred to as vehicle 1) having wheels 3a to 3d (running wheels) on the front, rear, left and right sides of the vehicle body. Between each of the wheels 3a to 3d of the vehicle 1 and the vehicle body, there is provided a suspension device 11 having anti-dive and anti-lift geometry, which suspends each of the wheels 3a to 3d relative to the vehicle body.

[0011] Brake devices 30a to 30d (braking devices) are provided on the wheels 3a to 3d of the vehicle 1, respectively. The brake devices 30a to 30d are controlled by a brake control unit 31 (braking control section), and are capable of applying different braking forces to the wheels 3a to 3d.

[0012] The wheels 3 a to 3 d are driven by, for example, an electric motor or an engine. The present invention can be applied to various drive sources, such as a plug-in hybrid vehicle (PHEV) or hybrid vehicle in which the front wheels 3 a, 3 b and the rear wheels 3 c, 3 d can be driven by electric motors and the front wheels 3 a, 3 b can be driven by an engine, an electric vehicle in which the wheels 3 a to 3 d are driven only by an electric motor, or an engine vehicle in which the wheels 3 a to 3 d are driven only by an engine, as well as to vehicles with various drive configurations, such as four-wheel drive or two-wheel drive.

[0013] The vehicle 1 is equipped with a longitudinal acceleration sensor 35 (longitudinal acceleration detection unit) that detects the acceleration in the longitudinal direction of the vehicle body, and wheel speed sensors 33a to 33d (speed detection units) that detect the rotational speeds of the wheels 3a to 3d. The attitude control device 10 is made up of the longitudinal acceleration sensor 35, the wheel speed sensors 33a to 33d for the wheels 3a to 3d, and the brake control unit 31.

[0014] In this embodiment, the detection values ​​of the longitudinal acceleration sensor 35 and the wheel speed sensors 33a to 33d are input to the brake control unit 31, but they may also be input via the main control unit 20 that controls the entire vehicle. The brake control unit 31 includes an input / output device, a memory device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc. The brake control unit 31 receives an operation amount of the brake pedal from a brake pedal sensor (not shown), and controls the braking force (braking force) of the brake devices 30a to 30d based on the operation amount of the brake pedal, etc.

[0015] In addition, detection information is input to the brake control unit 31 from a longitudinal acceleration sensor 35 and wheel speed sensors 33 a to 33 d. The attitude control device 10 includes a pitch / roll determination unit 40 (pitch determination unit, roll determination unit) that estimates the attitude of the vehicle 1, more specifically, the pitch and roll states of the vehicle 1, based on the detection information from the longitudinal acceleration sensor 35 and the wheel speed sensors 33 a to 33 d of each of the wheels 3 a to 3 d, and an applied braking force calculation unit 41 (attitude control unit) that calculates the braking force to be applied to each of the wheels 3 a to 3 d 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 from the longitudinal acceleration sensor 35 and the wheel speed sensors 33 a to 33 d, and performs pitch / roll control that sets the braking force to be applied to each of the wheels 3 a to 3 d so as to reduce the pitch and roll.

[0016] 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 of the suspension system of the vehicle 1 and the pitch moment and roll moment will be described. As shown in FIG. 2, if the distance in the vehicle longitudinal direction between the ground contact points of the front wheels 3 a, 3 b of the vehicle 1 and the center of gravity A of the vehicle body is a, the distance in the vehicle longitudinal direction between the ground contact points of the rear wheels 3 c, 3 d of the vehicle 1 and the center of gravity A is b, the height of the center of gravity A from the ground is hCG, the braking force of the entire vehicle is F, the ratio of the braking force on the front wheel 3 a, 3 b side is λ, the anti-lift angle is βf, and the anti-dive angle is βr, the pitch moment My, which is the sum of the pitch moment generated by deceleration of the vehicle 1 and the pitch moment generated by the anti-dive force and anti-lift force of the suspension system 11, can be calculated by the following (Equation 1):

[0017] My = F x hCG - (λF x | tan(βf) x a + (1 - λ)F x | tan(βr) | x b) (Equation 1) Furthermore, if the front track (distance between the left and right front wheels 3a, 3b) is tf, the rear track (distance between the left and right rear wheels 3c, 3d) is tr, the braking force (braking force) of the left front wheel 3a is Fbfl, the braking force of the right front wheel 3b is Fbfr, the braking force of the left rear wheel 3c is Fbrl, and the braking force of the right rear wheel 3d is Fbrr, then the roll moment Mx generated by the anti-dive force and anti-lift force of the suspension device 11 can be calculated using the following (Equation 2).

[0018] Mx=tf / 2(Fbfl-Fbfr)×tan(βf)+tr / 2(-Fbrl-Fbrr)×tan(βr) (Equation 2) Figures 3 to 6 are conceptual diagrams of the additional moments in the attitude control device 10 of this embodiment. Figure 3 is a conceptual diagram of the pitch moment and the corresponding additional moment that occur when the front wheels 3a, 3b climb up, and Figure 4 is a conceptual diagram of the pitch moment and the corresponding additional moment that occur when the rear wheels 3c, 3d climb up.

[0019] As shown by the solid arrows in Figure 3, the pitch moment generated when the front wheels 3a, 3b of the vehicle 1 run over a convex road surface is a moment that rotates the vehicle 1 backward about its center of gravity. In response to this, the attitude control device 10 applies an additional pitch moment My1 that rotates the vehicle forward, as indicated by the dashed arrows, to cancel out this pitch moment. As shown by the solid arrows in Figure 4, the pitch moment generated when the rear wheels 3c, 3d of the vehicle 1 run over a convex road surface is a moment that rotates the vehicle 1 forward about its center of gravity. In response to this, the attitude control device 10 applies an additional pitch moment My2 that rotates the vehicle backward, as indicated by the dashed arrows, to cancel out this pitch moment.

[0020] The additional pitch moments My1 and My2 correspond to the first additional pitch moment of the present invention. Furthermore, as indicated by the solid arrows in Figure 5, the roll moment generated when the right wheels 3b, 3d of the vehicle 1 run over a convex road surface is a moment that rotates the vehicle 1 to the left in the vehicle width direction about the center of gravity. As shown in Figure 5, possible cases are: (a) when only one wheel (for example, the right front wheel 3b) runs over a convex road surface; (b) when two wheels (the right front wheel 3b and the right rear wheel 3d) run over a convex road surface; and (c) when three wheels (the right front wheel 3b, the right rear wheel 3d, and, for example, the left front wheel 3a) run over a convex road surface.

[0021] Therefore, in the cases of Figures 5(a) to 5(c), additional roll moments Mx1, Mx2, and Mx3 that cancel out the roll moments should be added, as shown by the dashed lines in Figure 5. In the case of Figure 5(a), the additional roll moment is Mx1, in the case of Figure 5(b), the additional roll moment is Mx2, and in the case of Figure 5(c), the additional roll moment is Mx3. Also, as shown by the solid arrows in Figure 6, the roll moment that occurs when the left wheels 3a and 3c of the vehicle 1 run over a convex road surface is a moment that rotates the vehicle 1 to the right in the vehicle width direction about the center of gravity. As shown in Figure 6, possible cases are: (a) when only one wheel (e.g., the left front wheel 3a) runs over a convex road surface; (b) when two wheels (the left front wheel 3a and the left rear wheel 3c) run over a convex road surface; and (c) when three wheels (the left front wheel 3a, the left rear wheel 3c, and, for example, the right front wheel 3b) run over a convex road surface.

[0022] Therefore, in cases (a) to (c), additional roll moments Mx4, Mx5, and Mx6 should be added to cancel out the roll moments, as shown by the dashed lines in Figure 6. In the case of Figure 6(a), the additional roll moment is Mx4, in the case of Figure 6(b), the additional roll moment is Mx5, and in the case of Figure 6(c), the additional roll moment is Mx6. Note that in Figures 5 and 6(b) and (c), the x marks indicate riding over a convex road surface. In Figures 5 and 6(b) and (c), arrows indicating moments are shown in the top views, but in reality, they are vertical roll moments similar to those in Figure 5(a).

[0023] A method for determining the attitude of the vehicle 1, which is executed by the brake control unit 31, will now be described. A pitch / roll determination section 40 of the brake control unit 31 determines the attitudes related to each of the pitch and rolls described above based on the longitudinal acceleration of the vehicle 1 and the wheel rotation speeds of the wheels 3 a to 3 d.

[0024] 3, the front wheels 3a, 3b of the vehicle 1 climb up onto a convex road surface when the conditions of the following Table 1 are satisfied. The conditions of Table 1 are when all five conditions are satisfied: the rotational acceleration of the left and right front wheels 3a, 3b exceeds a predetermined threshold (FRwa>Xwa1, FLwa>Xwa2), the wheel rotational acceleration of the left and right rear wheels 3c, 3d is less than a predetermined threshold (|wsaRL|<Xwa3, |wsaRR|<Xwa4), and the acceleration in the front and rear directions of the vehicle exceeds a predetermined threshold (La<Xaa1).

[0025] 4, the rear wheels 3c, 3d of the vehicle 1 climb up onto a convex road surface when the conditions in the following Table 2 are satisfied. The conditions in Table 2 are when all five conditions are satisfied: the rotational acceleration of the left and right rear wheels 3c, 3d exceeds a predetermined threshold (RLwa > Xwa5, RRwa > Xwa6), the wheel rotational acceleration of the left and right front wheels 3a, 3b is less than a predetermined threshold (|wsaFL| < Xwa7, |wsaFR| < Xwa8), and the acceleration in the front and rear directions of the vehicle exceeds a predetermined threshold (La < Xaa2).

[0026] The conditions in Tables 1 and 2 are pitch determination conditions of the present invention. The posture in which one wheel on the right side of the vehicle 1 runs over a convex road surface as shown in Figure 5(a) occurs when the conditions in Table 3 below are satisfied. The conditions in Table 3 occur when all five conditions are satisfied: 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 predetermined thresholds (|wsaFL|<Xwa10, |wsaRL|<Xwa11, |wsaRL|<Xwa12), and the accelerations in the front and rear of the vehicle exceed predetermined thresholds (La<Xaa3). Alternatively, the conditions in Table 3 are met when all five conditions are met: the rotational acceleration of the right rear wheel 3d exceeds a predetermined threshold (RRwa > Xwa13), the wheel rotational acceleration of the other wheels 3a, 3b, and 3c is less than a predetermined threshold (|wsaFR| < Xwa14, |wsaFL| < Xwa15, |wsaRL| < Xwa16), or the acceleration in the front and rear of the vehicle exceeds a predetermined threshold (La < Xaa4).

[0027] 5B, the vehicle 1 assumes a posture in which the two right wheels 3b, 3d climb up onto a convex road surface when the conditions in Table 4 below are met. The conditions in Table 4 are when all five conditions are met: the rotational acceleration of the two right wheels 3b, 3d exceeds a predetermined threshold (FRwa>Xwa17, RRwa>Xwa18), the rotational acceleration of the two left wheels 3a, 3c is less than a predetermined threshold (|wsaFL|<Xwa19, |wsaRL|<Xwa20), and the acceleration in the front and rear of the vehicle exceeds a predetermined threshold (La<Xaa5).

[0028] 5(c), the vehicle 1 assumes a posture in which two wheels on the right side and one wheel on the left side run up onto a convex road surface when the conditions in the following Table 5 are satisfied. The conditions in Table 5 are when all five conditions are satisfied: when the rotational acceleration of the left and right front wheels 3a, 3b exceeds a predetermined threshold (FLwa>Xwa21, FRwa>Xwa22), when the rotational acceleration of the right rear wheel 3d exceeds a predetermined threshold (RRwa>Xwa23), when the rotational acceleration of the left rear wheel 3c is less than a predetermined threshold (|wsaRL|<Xwa24), and when the acceleration in the front and rear directions of the vehicle exceeds a predetermined threshold (La<Xaa6).

[0029] 6A, the posture in which one wheel on the left side of the vehicle 1 runs up onto a convex road surface occurs when the conditions in the following Table 6 are satisfied. The conditions in Table 6 are when all five conditions are satisfied: the rotational acceleration of the left front wheel 3a exceeds a predetermined threshold (FLwa>Xwa25), the rotational accelerations of the other wheels 3b, 3c, and 3d are less than predetermined thresholds (|wsaFR|<Xwa26, |wsaRL|<Xwa27, |wsaRR|<Xwa28), and the accelerations in the front and rear of the vehicle exceed predetermined thresholds (La<Xaa7). Alternatively, the conditions in Table 6 are met when all five conditions are met: the rotational acceleration of the left rear wheel 3c exceeds a predetermined threshold (RLwa > Xwa29), the rotational acceleration of the other wheels 3a, 3b, and 3d is less than a predetermined threshold (|wsaFR| < Xwa30, |wsaFL| < Xwa31, |wsaRR| < Xwa32), or the acceleration in the front and rear of the vehicle exceeds a predetermined threshold (La < Xaa8).

[0030] 6B, the posture in which the two left wheels 3a, 3c of the vehicle 1 climb up onto a convex road surface occurs when the conditions in the following Table 7 are satisfied. The conditions in Table 7 are when all five conditions are satisfied: the rotational acceleration of the left wheels 3a, 3c exceeds a predetermined threshold (FLwa > Xwa33, RLwa > Xwa34), the rotational acceleration of the two right wheels 3b, 3d is less than a predetermined threshold (|wsaFR| < Xwa35, |wsaRR| < Xwa36), and the acceleration in the front and rear of the vehicle exceeds a predetermined threshold (La < Xaa9).

[0031] 6(c), the posture in which the two left wheels 3a, 3c and one right wheel of the vehicle 1 climb up onto a convex road surface occurs when the conditions of the following Table 8 are satisfied. The conditions of Table 8 are when all five conditions are satisfied: when the rotational acceleration of the front wheels 3a, 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 in the front and rear directions of the vehicle exceeds a predetermined threshold (La<Xaa10).

[0032] The threshold values ​​Xwa1 to Xwa40 and Xaa1 to Xaa10 are each appropriately set values. The conditions in Tables 3 to 8 are the roll determination conditions of the present invention. Figures 7 to 14 are flowcharts showing the calculation methods for the additional pitch moments My1, My2 and the additional roll moments Mx1 to Mx6. FIG. 7 shows a method of calculating the additional pitch moment My1 when the front wheels 3a and 3b run up, FIG. 8 shows the additional pitch moment My2 when the rear wheels 3c and 3d run up, FIG. 9 shows the additional roll moment Mx1 when one right wheel runs up, FIG. 10 shows the additional roll moment Mx2 when two right wheels run up, FIG. 11 shows the additional roll moment Mx3 when two right wheels and one left wheel run up, FIG. 12 shows the additional roll moment Mx4 when one left wheel runs up, FIG. 13 shows the additional roll moment Mx5 when two left wheels run up, and FIG. 14 shows the additional roll moment Mx6 when two left wheels and one right wheel run up.

[0033] As shown in Fig. 7, first, in step S10, it is determined whether or not the conditions in Table 1 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. In step S20, the brake timer XT1 is counted up. Then, the process proceeds to step S30.

[0034] In step S30, it is determined whether the brake timer XT1 is less than the braking time threshold XTime1 that has been set appropriately. If the brake timer XT1 is less than the braking time threshold XTime1, the process proceeds to step S40. If the brake timer XT1 is equal to or greater than the braking time threshold XTime1, the process proceeds to step S50. In step S40, the additional pitch moment My1 is set to xxMy1 that has been set appropriately. Then, the process returns from this routine.

[0035] In step S50, the additional pitch moment My1 is set to 0, and the brake timer XT1 is reset to 0. Then, this routine is returned. 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.

[0036] In step S70, the brake timer XT1 is counted up. Then, the process proceeds to step S90. In step S80, the additional pitch moment My1 is set to 0. Then, the process returns from this routine. In step S90, it is determined whether the brake timer XT1 is less than the braking time threshold XTime1. If the brake timer XT1 is less than the braking time threshold XTime1, the process proceeds to step S100. If the brake timer XT1 is equal to or greater than the braking time threshold XTime1, the process proceeds to step S110.

[0037] In step S100, the additional pitch moment My1 is set to xxMy1. Then, this routine is returned. In step S110, the additional pitch moment My1 is set to 0, and the brake timer XT1 is reset to 0. Then, this routine is returned. By controlling in this manner, if the conditions of Table 1 are satisfied, the additional pitch moment My1 is set to xxMy1, which will be described later, until the brake timer XT1 reaches the braking time threshold XTime1.

[0038] 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 of 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.

[0039] That is, when the conditions of Table 3 are satisfied, the additional roll moment Mx1 is set to xxMx1 until the brake timer XT3 reaches the braking time threshold XTime3. The additional roll moment Mx2 is set in the same manner as the additional roll moment Mx1, as shown in Fig. 10, the additional roll moment Mx3 is set in the same manner as the additional roll moment Mx1, as shown in Fig. 11, the additional roll moment Mx4 is set in the same manner as the additional roll moment Mx5, as shown in Fig. 13, and the additional roll moment Mx6 is set in the same manner as the additional roll moment Mx1, as shown in Fig. 14.

[0040] Fig. 15 is a flowchart showing the procedure for calculating the set value xxMy1 to be set for the additional pitch moment My1. In this embodiment, when the conditions of Table 1 are satisfied, xxMy1 to be set for the additional pitch moment My1 is set as shown in Fig. 15. The flow shown in Fig. 15 is executed when step S40 or step S100 of the flow shown in Fig. 7 is reached, before the control in that step.

[0041] First, in step S1600, it is determined whether the brake timer XT1 is equal to 0. If the brake timer XT1 is equal to 0, the process proceeds to step S1610. If the brake timer XT1 is equal to 0, the process proceeds to step S1630. In step S1610, the maximum left and right front wheel accelerations X WACC MAX My1 (maximum wheel acceleration) and the maximum vehicle deceleration X ACC Min My1 are calculated.

[0042] X WACC MAX My1 = max (FR wheel acceleration, FL wheel acceleration, previous value of X WACC MAX My1) (Equation 3) FR wheel acceleration is the maximum right front wheel acceleration, and FL wheel acceleration is the maximum left front wheel acceleration. In (Equation 3), the largest value among the FR wheel acceleration, FL wheel acceleration, and the previous X WACC MAX My1 is set to X WACC MAX My1.

[0043] X ACC Min My1 = min (Longitudinal acceleration, previous value of X ACC Min My1) (Equation 4) Longitudinal acceleration is the longitudinal acceleration of the vehicle. In (Equation 4), the smaller value (negative larger value) between the minimum value of longitudinal acceleration and the previous X ACC Min My1 is set to X ACC Min My1.

[0044] Then, the process proceeds to step S1620. In step S1620, xxMy1 is calculated based on X WACC MAX My1 and X ACC Min My1 calculated in step 1610. xxMy1 can be calculated using a map that calculates xxMy1 from WACC MAX My1 and X ACC Min My1, which map may be confirmed in advance through experiments or the like and stored. Note that xxMy1 can be set so that it increases as the maximum left / right front wheel acceleration WACC MAX My1 or the maximum vehicle deceleration X ACC Min My1 increases. Then, this routine ends, and the process returns to the flow of FIG. 7.

[0045] In step S1630, the set values ​​xxMy1 of the left and right front wheel maximum acceleration X WACC MAX My1, the vehicle maximum deceleration X ACC Min My1, and the additional pitch moment My1 are set to 0. Then, this routine ends, and the process returns to the flow in Fig. 7. In addition to the above-mentioned pitch / roll control, the attitude control device 10 of this embodiment also executes pitch convergence control to converge the pitch remaining after the front wheels 3a, 3b or rear wheels 3c, 3d of the vehicle 1 go over a convex road surface.

[0046] 16 and 17 are conceptual diagrams of the additional moments in pitch convergence control in the attitude control device 10 of this embodiment. Fig. 16 is a conceptual diagram of the pitch moment immediately after the front wheels 3a, 3b go over a convex road surface, and Fig. 17 is a conceptual diagram of the pitch moment and the corresponding additional moment immediately after the rear wheels 3c, 3d go over a convex road surface. Even if control is performed to cancel the pitch moment when the front wheels 3a, 3b of the vehicle 1 go over a convex road surface or when the rear wheels 3c, 3d go over a convex road surface using the above-mentioned pitch / roll control, vibration in the pitch direction may remain due to control delays, etc.

[0047] The attitude control device 10 applies an additional pitch moment My3 that rotates toward the front of the vehicle, as indicated by the dashed arrow, so as to cancel out the pitch moment that rotates backward about the center of gravity of the vehicle 1, which remains after the front wheels 3a, 3b have gone over a convex road surface, as indicated by the solid arrow in Fig. 16. Furthermore, the attitude control device 10 applies an additional pitch moment My4 that rotates toward the rear of the vehicle, as indicated by the dashed arrow, so as to cancel out the pitch moment that rotates forward about the center of gravity of the vehicle 1, which remains after the rear wheels 3c, 3d have gone over a convex road surface, as indicated by the solid arrow in Fig. 17.

[0048] The additional pitch moments My3 and My4 correspond to the second additional pitch moments of the present invention. Figure 18 is a flowchart showing a method for calculating the additional pitch moment My3, and Figure 19 is a flowchart showing a method for calculating the additional pitch moment My4. These flowcharts are repeatedly executed at short control intervals (e.g., about several msec). Figure 20 is a time chart showing an example of the transition of the pitch angle and each control timing (determination flag) when the front wheels 3a and 3b climb up a slope.

[0049] As shown in Fig. 18, first, in step S1710, it is determined whether or not the conditions in Table 1 above are satisfied. If the conditions in Table 1 are satisfied, the process proceeds to step S1720. If the conditions in Table 1 are not satisfied, the process proceeds to step S1800. In step S1720, a braking start time threshold XTimeMy3 and a braking time threshold XTime9 for pitch convergence control are set based on the vehicle speed.

[0050] 20, when the wheels (front wheels 3a, 3b) run over a convex road surface, the pitch angular velocity of the vehicle 1 decreases while periodically fluctuating between + and - from 0. The braking start time threshold XTimeMy3 is the time for the first cycle from when the condition in Table 1 is met (pitch angular velocity = 0) when the front wheels 3a, 3b run over a convex road surface until the pitch angular velocity goes through +, 0, - and then becomes 0 again.

[0051] The braking time threshold XTime9 is the time when the pitch angular velocity becomes positive in the second period. The braking start time threshold XTimeMy3 is output based on the vehicle speed from a pre-stored table 9. The braking time threshold XTime9 is output based on the vehicle speed from a pre-stored table 10. Tables 9 and 10 store the braking start time threshold XTimeMy3 and the braking time threshold XTime9 corresponding to several stages of vehicle speed. Then, the process proceeds to step S1730.

[0052] In step S1730, the brake start timer XTMy3 is counted up. Then, the process proceeds to step S1740. In step S1740, it is determined whether the brake start timer XTMy3 exceeds the braking start time threshold XTimeMy3 set in step S1720. If the brake start timer XTMy3 exceeds the braking start time threshold XTimeMy3, the process proceeds to step S1750. If the brake start timer XTMy3 is equal to or less than the braking start time threshold XTimeMy3, the process proceeds to step S1790.

[0053] In step S1750, the brake timer XT9 is counted up. Then, the process proceeds to step S1760. In step S1760, it is determined whether the brake timer XT9 is less than the braking time threshold XTime9 set in step S1720. If the brake timer XT9 is less than the braking time threshold XTime9, the process proceeds to step S1770. If the brake timer XT9 is equal to or greater than the braking time threshold XTime9, the process proceeds to step S1780.

[0054] In step S1770, the additional pitch moment My3 is set to an appropriately set xxMy3, and the routine then returns. In step S1780, the additional pitch moment My3 is set to 0, and the brake timer XT9 and brake start timer XTMy3 are reset to 0. The routine then returns.

[0055] In step S1790, the additional pitch moment My3 is set to 0. Then, this routine returns. In step S1800, it is determined whether the brake timer XT3 is not 0. If the brake timer XT3 is not 0, the process proceeds to step S1810. If the brake timer XT3 is 0, the process proceeds to step S1880.

[0056] In step S1810, the brake start timer XTMy3 is counted up. Then, the process proceeds to step S1820. In step S1820, it is determined whether the brake start timer XTMy3 exceeds the braking start time threshold XTimeMy3 set in step S1720. If the brake start timer XTMy3 exceeds the braking start time threshold XTimeMy3, the process proceeds to step S1830. If the brake start timer XTMy3 is equal to or less than the braking start time threshold XTimeMy3, the process proceeds to step S1870.

[0057] In step S1830, the brake timer XT9 is counted up. Then, the process proceeds to step S1840. In step S1840, it is determined whether the brake timer XT9 is less than the braking time threshold XTime9 set in step S1720. If the brake timer XT9 is less than the braking time threshold XTime9, the process proceeds to step S1850. If the brake timer XT9 is equal to or greater than the braking time threshold XTime9, the process proceeds to step S1860.

[0058] In step S1850, the additional pitch moment My3 is set to an appropriately set xxMy3, and the routine then returns. In step S1860, the additional pitch moment My3 is set to 0, and the brake timer XT9 and brake start timer XTMy3 are reset to 0. The routine then returns.

[0059] In step S1870, the additional pitch moment My3 is set to 0. Then, the present routine is returned. In step S1880, the additional pitch moment My3 is set to 0. Then, the present routine is returned. By performing the control as described above, if the conditions of Table 1 are satisfied, the additional pitch moment My3 is set to xxMy3 from the time when the brake start timer XTMy3 reaches the brake start time threshold XTimeMy3 until the brake timer XT9 reaches the braking time threshold XTime9 (My3 = xxMy3 setting period in Figure 20).

[0060] 19, the additional pitch moment My4 is set in the same manner as the additional pitch moment My3. That is, when the conditions of Table 2 are satisfied, the additional pitch moment My4 is set to xxMy4 from the time when the brake start timer XTMy4 reaches the braking start time threshold XTimeMy4 until the brake timer XT10 reaches the braking time threshold XTime10.

[0061] The pitch moment My and roll moment Mx to be finally applied to the vehicle 1 are calculated using the following (Equation 5) and (Equation 6). My = My1 + My2 + My3 + My4 ... (Equation 5) Mx = Mx1 + Mx2 + Mx3 + Mx4 + Mx5 + Mx6 ... (Equation 6) Next, the additional braking forces Fbfl, Fbfr, Fbrl, and Fbrr for each wheel are calculated from the additional moment values. The calculation formulas for the additional moments are obtained by modifying the above (Equation 1) and (Equation 2) into the following (Equation 7) and (Equation 8).

[0062]

[0063]

[0064] Further, the total additional braking force X Total Force (=XX Force) is calculated by the following (Equation 9): X Dif Force, which is the difference between the left and right additional braking forces, is calculated by the following (Equation 10).

[0065]

[0066]

[0067] Note that X Dif Force = XX Dif × required yaw moment input from the main control unit 20, where XX Dif is an appropriately set gain of the required yaw moment. When the pitch moment My, roll moment Mx, total additional braking force X Total Force, and left / right difference in additional braking force X Dif Force are put into a matrix, the following (Equation 11) is obtained.

[0068]

[0069] FIG. 21 is a flowchart showing the control procedure for determining whether or not the pitch / roll control is to be performed. The control shown in FIG. 21 is initiated when the system is started and is repeatedly performed while the vehicle 1 is traveling. First, in step S2000, it is determined whether or not the brake control unit 31 or each of the brake devices 30a to 30d is in an abnormal (failed) state. Whether or not these units are abnormal can be determined using 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 S2040. If the brake control unit 31 and each of the brake devices 30a to 30d are normal, the process proceeds to step S2010.

[0070] In step S2010, it is determined whether the driver's brake operation amount (operation force) exceeds an appropriately set predetermined threshold X Cmd Force. If the brake operation amount exceeds the threshold X Cmd Force, the process proceeds to step S2040. If the brake operation amount is equal to or less than the threshold X Cmd Force, the process proceeds to step S2020. In step S2020, it is determined whether other driving control devices (driving safety devices) of the vehicle 1, such as an electric stability control system (ESC), an anti-lock braking system (ABS), or an automatic emergency braking system (AEB), are in operation (under control). If the other driving control devices are in operation, the process proceeds to step S2040. If the other driving control devices are not in operation (standby state), the process proceeds to step S2030.

[0071] In step S2030, the pitch / roll control by the attitude control device 10 is turned on. Then, the present routine is returned. In step S2040, the pitch / roll control by the attitude control device 10 is turned off. Then, the present routine is returned. As described above, in the embodiment of the present invention, attitude control (pitch / roll control) that reduces the pitch and roll of the vehicle 1 is possible by controlling the braking forces of the brake devices 30a to 30d of the four wheels of the vehicle 1.

[0072] The current pitch and roll of the vehicle 1 are estimated based on the rotational acceleration of each of the wheels 3a to 3d and the longitudinal acceleration of the vehicle 1. This makes it possible to estimate the pitch and roll of the vehicle 1 based on information detected by relatively inexpensive detectors such as the four wheel speed sensors 33a to 33d and the longitudinal acceleration sensor 35. 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 acceleration of each of the wheels 3a to 3d and the longitudinal acceleration of the vehicle 1, and determines whether the conditions of each of tables 1 to 8 are satisfied.

[0073] When the conditions of any of tables 1 to 8 are satisfied, the additional braking force calculation unit 41 sets the additional moments My1, My2, My3, My4, Mx1 to Mx6 corresponding to each table, and adds these additional moments together to calculate the overall additional moment of the vehicle 1. This makes it possible to easily determine the pitch and roll states of the vehicle 1 and easily calculate the additional moments.

[0074] The additional moments My1, My2, My3, My4, and Mx1 to Mx6 set for each of Tables 1 to 8 are as follows: Table 1 has a determination condition for the occurrence of a pitch moment toward the rear of the vehicle, and sets additional pitch moments My1 and My3 toward the front of the vehicle. Table 2 has a determination condition for the occurrence of a pitch moment toward the front of the vehicle, and sets additional pitch moments My2 and My4 toward the rear of the vehicle. Table 3 has a determination condition for the occurrence of a roll moment when one wheel on the right side of vehicle 1 is riding on a convex road surface, and sets an additional roll moment Mx1 toward the right side of the vehicle. Table 4 has a determination condition for the occurrence of a roll moment when two wheels on the right side of the vehicle are riding on a convex road surface, and sets an additional roll moment Mx2 toward the right side of the vehicle. Table 5 has a determination condition for the occurrence of a roll moment when 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 toward the right side of the vehicle. Table 6 has the determination conditions for a roll moment occurring when one wheel on the left side of the vehicle is riding on a convex road surface, and sets an additional roll moment Mx4 toward the left side of the vehicle. Table 7 has the determination conditions for a roll moment occurring when two wheels on the left side of the vehicle are riding on a convex road surface, and sets an additional roll moment Mx5 toward the left side of the vehicle. Table 8 has the determination conditions for a roll moment occurring when two wheels on the left side of the vehicle and one wheel on the right side are riding on a convex road surface, and sets an additional roll moment Mx6 toward the left side of the vehicle.

[0075] This makes it possible to easily and accurately determine the pitch and roll state of the vehicle 1 based on the rotational acceleration of each of the wheels 3 a to 3 d and the longitudinal acceleration of the vehicle 1. Furthermore, the determination of each of the tables 1 to 8 based on the rotational acceleration of the wheels 3 a to 3 d and the longitudinal acceleration of the vehicle 1 is performed at a relatively short interval in order to quickly respond to changes in the posture of the vehicle 1. However, as shown in the left part of the flowcharts in Figures 7 to 14, when the determination condition of each of the tables 1 to 8 is met and the brake timer counts up and is no longer 0, the additional moment corresponding to that table 1 to 8 continues to be set until the brake timer completes counting up, even if it is determined midway through that the determination condition of that table 1 to 8 is not met.

[0076] As a result, while maintaining good responsiveness when the judgment conditions of each of Tables 1 to 8 are satisfied, once the judgment conditions are satisfied, an additional moment is set and the application of braking force is maintained for a predetermined time until the brake timer finishes counting up, thereby suppressing excessive fluctuations (switching) in the braking force to be applied. In this embodiment, an additional pitch moment My1 toward the front of the vehicle to cancel out the first-cycle pitch moment generated when the front wheel 3 a or 3 b of the vehicle 1 runs over a convex road surface, an additional pitch moment My2 toward the rear of the vehicle to cancel out the first-cycle pitch moment generated when the rear wheel 3 c or 3 d of the vehicle 1 runs over a convex road surface, and an additional pitch moment My3 toward the front of the vehicle to cancel out the second-cycle pitch moment remaining after the front wheel 3 a or 3 b runs over a convex road surface, and an additional pitch moment My4 toward the rear of the vehicle to cancel out the second-cycle pitch moment remaining after the rear wheel 3 c or 3 d runs over a convex road surface are calculated. Therefore, if the pitch is not sufficiently suppressed by braking to apply the additional pitch moments My1 and My2 when the wheels 3a to 3d run over a convex road surface, the pitch of the vehicle 1 can be further suppressed by braking to apply the additional pitch moments My3 and My4. This makes it possible to quickly converge the pitch that remains after the wheels 3a to 3d run over a convex road surface, thereby improving the ride comfort of the vehicle 1.

[0077] Furthermore, pitch and roll control by the attitude control device 10 is not performed in any of the following cases: when the brake control unit 31 or each of the brake devices 30a to 30d is abnormal; when the amount of brake operation by the driver exceeds the threshold X Cmd Force; or when a driving control device (driving safety device) other than the attitude control device 10, such as ESC, ABS, or AEB, is in operation.

[0078] In particular, since pitch / roll control is not executed when the brake operation force is equal to or greater than a predetermined value, if the driver suddenly applies the brakes, the pitch / roll control of this embodiment can be suppressed and braking by braking can be prioritized. Also, if a driving control device other than the attitude control device is in operation (such as during brake control), the pitch / roll control of this embodiment can be suppressed and the other driving control device can be prioritized, thereby appropriately ensuring the driving safety function of the other driving control device.

[0079] Furthermore, in this embodiment, the additional pitch moment My1 (=xxMy1), which is set until XTime1 has elapsed after the conditions of Table 1 are satisfied, is not set to a constant value, but is set to a different value based on the vehicle running state when the conditions of Table 1 are satisfied. This makes it possible to appropriately set the additional pitch moment based on the vehicle running state, thereby improving the pitch suppression effect.

[0080] The vehicle driving conditions used when calculating the set value xxMy1 of the additional pitch moment My1 are the maximum left and right front wheel acceleration XWACC MAX My1 and the maximum longitudinal deceleration XACC Min My1. The greater the vehicle behavior caused by a change in road surface, the greater the tendency for the maximum left and right front wheel acceleration XWACC MAX My1 and the maximum longitudinal deceleration XACC Min My1 to become. Therefore, by calculating the set value xxMy1 of the additional pitch moment based on the maximum left and right front wheel acceleration XWACC MAX My1 and the maximum longitudinal deceleration XACC Min My1 in response to this tendency, the additional pitch moment can be more appropriately set in accordance with the magnitude of the vehicle behavior, and pitch can be more quickly and effectively suppressed.

[0081] Although the description of the embodiment is now complete, aspects of the present invention are not limited to the above embodiment. For example, in the above embodiment, the set value xxMy1 of the additional pitch moment My1 for suppressing the pitch in the first cycle that occurs when the front wheels pass over a step is calculated based on the vehicle traveling state, and the additional pitch moment My2 in the first cycle when the rear wheels pass over a step, the additional pitch moment My3 in the second cycle when the front wheels pass over a step, the additional pitch moment My4 in the second cycle when the rear wheels pass over a step, the additional roll moments Mx1, Mx2, Mx3 in the first cycle, and the additional roll moments Mx4, Mx5, Mx6 in the second cycle are all set to constant values, it is also possible to calculate all or any of these additional pitch moments My2 to My4 and additional roll moments Mx1 to Mx6 based on the vehicle traveling state.

[0082] This allows the additional pitch moment and additional roll moment to be set appropriately for each vehicle condition, making it possible to more quickly and effectively suppress pitch and roll. Also, in the above embodiment, when the brake operation amount exceeds the threshold X Cmd Force or when another cruise control device is in operation, the pitch / roll control of this embodiment is not executed, but the braking force may be applied by suppressing it to a small value through the pitch / roll control of this embodiment.

[0083] In the above embodiment, the brake devices 30a to 30d are controlled to perform pitch / roll control, i.e., both the pitch moment My and the roll moment Mx are applied, but the present invention may also be applied to a vehicle in which only the pitch moment My is applied. The present invention can be widely applied to a vehicle in which the four wheels (front, rear, left, and right) can be braked independently.

[0084] REFERENCE SIGNS LIST 1 vehicle 3a to 3d wheels 10 attitude control device 11 suspension device 30a to 30d brake device (braking device) 31 brake control unit (braking control unit) 33a to 33d wheel speed sensor (speed detection unit) 35 longitudinal acceleration sensor (longitudinal acceleration detection unit) 40 pitch / roll determination unit (pitch determination unit, roll determination unit) 41 additional braking force calculation unit (attitude control unit)

Claims

1. A vehicle is provided with front, rear, left and right wheels suspended by a suspension device having anti-dive and anti-lift geometry, the vehicle comprising: braking devices provided on the front, rear, left and right wheels, respectively; a braking control unit that operates and controls the front, rear, left and right braking devices and is capable of applying braking forces independently to the front, rear, left and right wheels; a speed detection unit that detects the rotational speeds of the front, rear, left and right wheels, respectively; and a longitudinal acceleration detection unit that detects the longitudinal acceleration of the vehicle, the braking control unit comprising: a pitch determination unit that determines a pitch state of the vehicle based on the rotational speed of each of the wheels and the longitudinal acceleration of the vehicle; and a posture control unit that applies braking forces by the front, rear, left and right braking devices based on the pitch state, the pitch determination unit has a plurality of types of pitch determination conditions that determine the pitch state based on the rotational acceleration of each of the wheels and the longitudinal acceleration of the vehicle, and calculates an overall additional moment of the vehicle by adding an additional moment that is set each time the pitch determination condition is satisfied, the additional moment being set based on the vehicle running state when the pitch determination condition is satisfied. A vehicle attitude control device comprising:

2. The vehicle attitude control device according to claim 1, characterized in that the vehicle running conditions are the maximum wheel acceleration and the maximum vehicle deceleration within a predetermined braking time.

3. The vehicle attitude control device described in claim 1, characterized in that: the braking control unit includes a roll judgment unit which judges the roll state of the vehicle based on the rotational speed of each of the wheels and the longitudinal acceleration of the vehicle; the attitude control unit applies braking forces by each of the front, rear, left and right braking devices based on the pitch state and the roll state; the roll judgment unit includes a plurality of types of roll judgment conditions which judge the roll state based on the rotational acceleration of each of the wheels and the longitudinal acceleration of the vehicle; and an additional moment which is set each time a roll judgment condition is satisfied is added to an overall additional moment of the vehicle.

4. A vehicle attitude control device according to claim 3, characterized in that the additional moment, which is set each time the roll determination condition is satisfied, is set based on the vehicle running state when the roll determination condition is satisfied.

5. A vehicle attitude control device according to claim 1, characterized in that the additional moment includes a first additional pitch moment that suppresses a first period of pitch that occurs when the wheel runs over a convex road surface.

6. A vehicle attitude control device according to claim 5, characterized in that the additional moment includes a second additional pitch moment that suppresses a second pitch period that continues after the wheel goes over a convex road surface.