Vehicle attitude control device

Abstract

Provided is an attitude control device for a vehicle, the attitude control device being provided in a vehicle 1 equipped with front, rear, left, and right wheels 3a to 3d suspended by means of a suspension device 11 having an anti-dive and anti-lift geometry. The attitude control device comprises: 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 longitudinal acceleration of the vehicle 1. The attitude control device further comprises: a pitch / roll determination part 40 that determines the pitch state of the vehicle 1 on the basis of the rotational speeds of the wheels 3a to 3d and the longitudinal acceleration of the vehicle 1; and an added braking force computation part 41 that computes the braking force of each of the brake devices 30a to 30d so as to suppress the determined pitch state for both when and after the wheels 3a to 3d run onto a bump in the road surface.

Description

[Technical Field]

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

[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 of each wheel to control the vehicle's posture. However, one problem with four-wheel active suspension systems is that they are 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-50024 Summary of the Invention [Problem 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 the four wheels, but there is a demand for a device that can also inexpensively control the pitch, which is the longitudinal behavior of the vehicle. When controlling the vehicle's attitude, it is necessary to detect the vehicle's attitude. However, in vehicles that do not have a four-wheel active suspension system, the suspension system often does not have a stroke sensor, making it difficult to detect the vehicle's attitude.

[0006] Furthermore, even if braking control is performed to suppress pitch, it is difficult to rapidly converge the pitch due to control delays and the like. The present invention has been made in view of the above-mentioned 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. [Means for solving the problem]

[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 comprises 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 longitudinal acceleration of the vehicle, and the braking control unit includes 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 pitch determination unit that determines a pitch state of the vehicle based on the pitch state. and an attitude control unit that applies braking force by each braking device of the above-mentioned, wherein the pitch determination unit has a plurality of types of 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 up additional pitch moments that are set each time the determination conditions are satisfied, and the additional pitch moments that are set each time the determination conditions are satisfied include a first additional pitch moment that suppresses a first periodic pitch moment that occurs when the wheel runs over a convex road surface, and a second additional pitch moment that suppresses a second periodic pitch moment that follows after the wheel runs over a convex road surface.

[0008] This allows the pitch state of the vehicle to be determined based on the rotational speed of each wheel and the longitudinal acceleration of the vehicle, and braking forces are applied by the front, rear, left, and right braking devices to cancel out the pitch. Therefore, the pitch can be reduced based on information detected by relatively inexpensive detectors such as a speed detector and a longitudinal acceleration detector. In particular, the system calculates a first additional pitch moment to be applied when the wheel runs over a convex road surface, and also calculates a second additional pitch moment to be applied after the wheel has passed over the convex road surface. Therefore, if the pitch is not sufficiently suppressed by applying the first additional pitch moment when the wheel runs over a convex road surface, the pitch can be further suppressed by adding the second additional pitch moment.

[0009] Preferably, the first additional pitch moment includes a first front wheel additional pitch moment directed toward the front of the vehicle based on the pitch state of the vehicle when the front wheels of the vehicle run over a convex road surface, and a first rear wheel additional pitch moment directed toward the rear of the vehicle based on the pitch state of the vehicle when the rear wheels of the vehicle run over a convex road surface, and the second additional pitch moment includes a second front wheel additional pitch moment directed toward the front of the vehicle based on the pitch state of the vehicle after the front wheels of the vehicle run over a convex road surface, and a second rear wheel additional pitch moment directed toward the rear of the vehicle based on the pitch state of the rear wheels of the vehicle run over a convex road surface.

[0010] This allows the additional pitch moment to be calculated and braking force to be applied when the front wheels of the vehicle run over a convex road surface and after the front wheels run over a convex road surface, and when the rear wheels run over a convex road surface and after the rear wheels run over a convex road surface, thereby rapidly suppressing pitch when all wheels of the vehicle pass over a convex road surface. Preferably, when the pitch determination unit determines that the pitch state of the vehicle is equal to or greater than a predetermined value while the vehicle is traveling, the attitude control unit maintains the application of braking force of the braking device based on the pitch state for a predetermined period of time.

[0011] As a result, when it is determined that the vehicle's pitch state is greater than or equal to a predetermined value, the application of braking force from the braking device based on the pitch state is maintained for a predetermined period of time, thereby suppressing excessive fluctuations in the application of braking force. Preferably, the attitude control unit suppresses application of braking force based on the pitch state when a braking operation by the driver of the vehicle is greater than or equal to a predetermined value.

[0012] This allows the braking by the attitude control unit to be suppressed in response to a sudden braking operation by the driver, and allows the braking requested by the driver to be given priority. Preferably, the vehicle is equipped with a braking control unit that controls the braking force of the braking device to improve the driving safety of the vehicle, and the attitude control unit suppresses the application of braking force based on the pitch state when the braking control unit is controlling the braking force of the braking device.

[0013] As a result, when braking control is performed by the braking control unit, braking by the attitude control unit is suppressed, and control by the braking control unit can be given priority to improving the vehicle's driving safety, such as improving the vehicle's driving stability and avoiding collisions. Preferably, the braking control unit includes a roll determination unit that determines 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 using the front, rear, left, and right braking devices based on the pitch state and the roll state, and the roll determination unit includes a plurality of types of determination conditions that determine the roll state based on the rotational acceleration of each of the wheels and the longitudinal acceleration of the vehicle, and an additional roll moment that is set each time the determination condition is satisfied is added to the overall additional moment of the vehicle.

[0014] This allows the roll state of the vehicle to be determined based on the rotational speed of each wheel and the longitudinal acceleration of the vehicle, and braking forces can be applied by the front, rear, left and right braking devices so as to cancel out the roll state along with the pitch state. [Effects of the Invention]

[0015] The vehicle attitude control device of the present invention can reduce the pitch of the vehicle by using information detected by a relatively inexpensive detector that detects the wheel rotational speed and the vehicle's longitudinal acceleration. Furthermore, if the pitch is not sufficiently suppressed by applying a first additional pitch moment when the wheel runs over a convex road surface, the pitch can be further suppressed by applying a second additional pitch moment after the wheel runs over the convex road surface. Therefore, the pitch remaining after the wheel runs over a convex road surface can be rapidly converged, improving the ride comfort of the vehicle. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram of a vehicle attitude control device according to an embodiment of the present invention; [Figure 2]3 is an explanatory diagram of an anti-dive force and an anti-lift force in a suspension device of a vehicle. FIG. [Figure 3] FIG. 1 is an image diagram of the pitch moment that occurs when the front wheels climb up and the corresponding additional moment. [Figure 4] FIG. 1 is an image diagram of the pitch moment that occurs when the rear wheels climb up and the corresponding additional moment. [Figure 5] FIG. 1 is an image diagram of the roll moment and the corresponding additional moment that occurs when the right wheel runs up. [Figure 6] FIG. 1 is an image diagram of the roll moment and the corresponding additional moment that occurs when the left wheel runs over the road. [Figure 7] 10 is a flowchart showing a method for calculating an additional moment when the front wheels climb up. [Figure 8] 10 is a flowchart showing a method for calculating an additional moment when the rear wheel climbs up. [Figure 9] 10 is a flowchart showing a method for calculating an additional moment when one wheel on the right side runs over the road. [Figure 10] 10 is a flowchart showing a method for calculating an additional moment when the two right wheels climb up. [Figure 11] 10 is a flowchart showing a method for calculating an additional moment when two wheels on the right side and one wheel on the left side run up. [Figure 12] 10 is a flowchart showing a method for calculating an additional moment when one left wheel runs over the road. [Figure 13] 10 is a flowchart showing a method for calculating an additional moment when the two left wheels climb up. [Figure 14] 10 is a flowchart showing a method of calculating an additional moment when two wheels on the left side and one wheel on the right side run up. [Figure 15] FIG. 1 is an image diagram of the pitch moment remaining after the front wheels climb up and the additional moment corresponding to it. [Figure 16]FIG. 10 is an image diagram of the pitch moment remaining after the rear wheels climb up and the additional moment corresponding to the pitch moment. [Figure 17] 10 is a flowchart showing a method for calculating an additional moment after the front wheels climb up. [Figure 18] 10 is a flowchart showing a method for calculating an additional moment after a rear wheel climbs up. [Figure 19] 10 is a time chart showing an example of the transition of the pitch angle and the timing of each control when the front wheels climb up. [Figure 20] 10 is a flowchart showing a control procedure for determining whether to execute pitch-roll control. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will 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. An attitude control device 10 according to one 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 wheel 3a to 3d of vehicle 1 and the vehicle body, there is provided a suspension device 11 having anti-dive and anti-lift geometry and suspending each of the wheels 3a to 3d relative to the vehicle body.

[0018] The wheels 3a to 3d of the vehicle 1 are provided with brake devices 30a to 30d (braking devices), respectively. The braking 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.

[0019] The wheels 3a to 3d are driven by, for example, an electric motor or an engine. The present invention can be applied to various drive sources for traveling, such as a plug-in hybrid vehicle (PHEV) or hybrid vehicle in which the front wheels 3a, 3b and the rear wheels 3c, 3d can be driven by electric motors, respectively, and the front wheels 3a, 3b can be driven by an engine, an electric vehicle in which the wheels 3a to 3d are driven only by an electric motor, or an engine vehicle in which the wheels 3a to 3d are driven only by an engine, as well as to vehicles with various drive configurations, 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) 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 speed of each of the wheels 3a to 3d. The attitude control device 10 is made up of a longitudinal acceleration sensor 35, wheel speed sensors 33a to 33d for the respective wheels 3a to 3d, and a brake control unit 31.

[0021] 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, for example, 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 input of the 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.

[0022] In addition, detection information is input to the brake control unit 31 from a longitudinal acceleration sensor 35 and wheel speed sensors 33a to 33d. 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 33a to 33d of each of the wheels 3a to 3d, and an applied braking force calculation unit 41 (attitude control unit) that calculates the braking force to be applied to each of the wheels 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 from the longitudinal acceleration sensor 35 and the wheel speed sensors 33a to 33d, and performs pitch / roll control that sets the braking force to be applied to each of the wheels 3a to 3d so as to reduce the pitch and roll.

[0023] FIG. 2 is an explanatory diagram of the anti-dive force and the 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, if the distance in the longitudinal direction of the vehicle between the ground contact points of front wheels 3a, 3b of vehicle 1 and the center of gravity A of the vehicle body is a, the distance in the longitudinal direction of the vehicle between the ground contact points of rear wheels 3c, 3d of vehicle 1 and the center of gravity A is b, the height of center of gravity A from the ground is hCG, the braking force of the entire vehicle is F, the ratio of braking force on the front wheel 3a, 3b side is λ, the anti-lift angle is βf, and the anti-dive angle is βr, then the pitch moment My, which is the sum of the pitch moment generated by deceleration of vehicle 1 and the pitch moment generated by the anti-dive force and anti-lift force of suspension device 11, can be calculated using the following (Equation 1).

[0024] My=F×hCG-(λF×|tan(βf)×a+(1-λ)F×|tan(βr)|×b) ...(Formula 1) Furthermore, if the front track (the distance between the left and right front wheels 3a and 3b) is tf, the rear track (the distance between the left and right rear wheels 3c and 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).

[0025] Mx=tf / 2(Fbfl-Fbfr)×tan(βf)+tr / 2(-Fbrl-Fbrr)×tan(βr) ...(Formula 2) 3 to 6 are conceptual diagrams of the additional moments in the attitude control device 10 of this embodiment. Fig. 3 is a conceptual diagram of the pitch moment that occurs when the front wheels 3a and 3b climb up, and Fig. 4 is a conceptual diagram of the pitch moment that occurs when the rear wheels 3c and 3d climb up, and the corresponding additional moments.

[0026] 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 around the center of gravity. In response to this, the attitude control device 10 adds an additional pitch moment My1 that rotates the vehicle forward, as indicated by the dashed arrow, to cancel out this pitch moment. As indicated by the solid arrow in Figure 4, the pitch moment that occurs when rear wheels 3c, 3d of vehicle 1 run over a convex road surface is a moment that rotates the vehicle 1 forward about the center of gravity. In response to this, the attitude control device 10 adds an additional pitch moment My2 that rotates the vehicle toward the rear, as indicated by the dashed arrow, to cancel out this pitch moment.

[0027] The additional pitch moments My1 and My2 correspond to the first additional pitch moment of the present invention. Furthermore, the additional pitch moment My1 corresponds to the first front wheel additional pitch moment of the present invention, and the additional pitch moment My2 corresponds to the first rear wheel additional pitch moment of the present invention. Furthermore, as indicated by the solid arrows in Fig. 5, the roll moment that occurs when the wheels 3b, 3d on the right side 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 Fig. 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.

[0028] Therefore, in the cases of Figures 5(a) to 5(c), it is sufficient to add additional roll moments Mx1, Mx2, and Mx3 that cancel out the roll moments, 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. Furthermore, as indicated by the solid arrows in Fig. 6, the roll moment that occurs when the left wheels 3a, 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 Fig. 6, possible cases are (a) when only one wheel (for example, 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.

[0029] Therefore, in the cases of (a) to (c), additional roll moments Mx4, Mx5, and Mx6 that cancel out the roll moments should be added, as shown by the dashed lines in Fig. 6. In the case of (a) in Fig. 6, the additional roll moment is Mx4, in the case of (b) the additional roll moment is Mx5, and in the case of (c) the additional roll moment is Mx6. In Figures 5 and 6(b) and (c), the cross marks indicate that the vehicle is riding on a convex road surface. In Figures 5 and 6(b) and (c), arrows indicating the moment are shown on the top view, but in reality, they are vertical roll moments similar to those in (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 that when the rotational accelerations of the left and right front wheels 3a and 3b exceed a predetermined threshold value (FRwa > Xwa1, FLwa > Xwa2), the wheel rotational accelerations of the left and right rear wheels 3c and 3d are less than the predetermined threshold value (|wsaRL| < Xwa3, |wsaRR| < Xwa4), and the longitudinal acceleration of the vehicle exceeds the predetermined threshold value (La < Xaa1), which is a case where 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 that when the rotational accelerations of the left and right rear wheels 3c and 3d exceed a predetermined threshold value (RLwa > Xwa5, RRwa > Xwa6), the wheel rotational accelerations of the left and right front wheels 3a and 3b are less than the predetermined threshold value (|wsaFL| < Xwa7, |wsaFR| < Xwa8), and the longitudinal acceleration of the vehicle exceeds the predetermined threshold value (La < Xaa2), which is a case where 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 five conditions are satisfied, such as 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, 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 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, 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 the convex road surface as shown in Fig. 5(b) is the case when the following conditions in Table 4 are satisfied. The conditions in Table 4 are met when all five conditions are satisfied, such as 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 the convex road surface as shown in Fig. 5(c) is the case when the following conditions in Table 5 are satisfied. The conditions in Table 5 are met when all five conditions are satisfied, such as 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 the convex road surface as shown in Fig. 6(a) is when the conditions in Table 6 below are satisfied. The conditions in Table 6 are also the conditions in Table 6 when all of the following five conditions are satisfied: 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 of the vehicle in the front-rear direction 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 of the vehicle in the front-rear direction exceeds a predetermined threshold (La < Xaa8).

[0037] The posture in which two wheels 3a, 3c on the left side of the vehicle 1 have climbed onto the convex road surface as shown in Fig. 6(b) is when the conditions in Table 7 below are satisfied. The conditions in Table 7 are when all of the following five conditions are satisfied: 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 of the vehicle in the front-rear direction exceeds a predetermined threshold (La < Xaa9).

[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 the convex road surface as shown in Fig. 6(c) is 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 accelerations of the front wheels 3a and 3b exceed 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 appropriately set values respectively. Figures 7 to 14 are flowcharts showing the calculation methods of the additional pitch moments My1 and My2 and the additional roll moments Mx1 to Mx6. Figure 7 shows the calculation method of the additional pitch moment My1 when the front wheels 3a and 3b lift off, Figure 8 shows the calculation method of the additional pitch moment My2 when the rear wheels 3c and 3d lift off, Figure 9 shows the calculation method of the additional roll moment Mx1 when one wheel on the right side lifts off, Figure 10 shows the calculation method of the additional roll moment Mx2 when two wheels on the right side lift off, Figure 11 shows the calculation method of 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 calculation method of the additional roll moment Mx4 when one wheel on the left side lifts off, Figure 13 shows the calculation method of 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] 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. In step S20, the brake timer XT1 is counted up. Then, the process proceeds to step S30.

[0041] In step S30, it is determined whether the brake timer XT1 is less than an appropriately set braking time threshold XTime1. 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 an appropriately set xxMy1, and then the routine returns.

[0042] In step S50, the additional pitch moment My1 is set to 0, and the brake timer XT1 is reset to 0. Then, the routine returns. In step S60, it is determined whether or not 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 counted up, and the process proceeds to step S90. In step S80, the additional pitch moment My1 is set to 0. Then, the routine returns. 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.

[0044] In step S100, the additional pitch moment My1 is set to xxMy1, and then the routine returns. In step S110, the additional pitch moment My1 is set to 0, and the brake timer XT1 is reset to 0. Then, the routine returns. By controlling in the above manner, 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 value 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 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.

[0046] That is, when the conditions in Table 3 are met, 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 shown in FIG. 11, the additional roll moment Mx4 is set in the same manner as shown in FIG. 12, the additional roll moment Mx5 is set in the same manner as shown in FIG. 13, and the additional roll moment Mx6 is set in the same manner as the additional roll moment Mx1.

[0047] In addition to the above-mentioned pitch / roll control, the attitude control device 10 of this embodiment performs 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. 15 and 16 are conceptual diagrams of the additional moments in pitch convergence control in the attitude control device 10 of this embodiment. Fig. 15 is a conceptual diagram of the pitch moment and the corresponding additional moment immediately after the front wheels 3a and 3b have gone over a convex road surface, and Fig. 16 is a conceptual diagram of the pitch moment and the corresponding additional moment immediately after the rear wheels 3c and 3d have gone over a convex road surface.

[0048] Even if the above-described pitch-roll control is performed to cancel out 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, vibration in the pitch direction may remain due to control delays, etc. The attitude control device 10 adds 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 go over a convex road surface, as indicated by the solid arrow in Figure 15.

[0049] In addition, the posture control device 10 adds 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 that remains after the rear wheels 3c and 3d go over the convex road surface, as indicated by the solid arrow in Figure 16. The additional pitch moments My3 and My4 correspond to the second additional pitch moment of the present invention. Furthermore, the additional pitch moment My3 corresponds to the second front wheel additional pitch moment of the present invention, and the additional pitch moment My4 corresponds to the second rear wheel additional pitch moment of the present invention.

[0050] Fig. 17 is a flowchart showing a method for calculating the additional pitch moment My3, and Fig. 18 is a flowchart showing a method for calculating the additional pitch moment My4. These flowcharts are repeatedly executed at short control intervals (for example, on the order of several msec). Fig. 19 is a time chart showing an example of the transition of the pitch angle when the front wheels 3a, 3b climb up and the respective control timings (determination flags). 17, 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.

[0051] 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. As shown in FIG. 19, when the wheels (front wheels 3a, 3b) run onto a convex road surface, the pitch angular velocity of the vehicle 1 decreases from 0 while periodically fluctuating between positive and negative values. 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 and 3b run over a convex road surface until the pitch angular velocity goes through +, 0, - and then becomes 0 again.

[0052] 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.

[0053] In step S1730, the brake start timer XTMy3 is counted up, and the process proceeds to step S1740. In step S1740, it is determined whether the brake start timer XTMy3 has exceeded the braking start time threshold XTimeMy3 set in step S1720. If the brake start timer XTMy3 has exceeded 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.

[0054] In step S1750, brake timer XT9 is counted up, and the flow 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.

[0055] In step S1770, the additional pitch moment My3 is set to an appropriately set xxMy3, and then the routine 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. Then, the routine returns.

[0056] In step S1790, the additional pitch moment My3 is set to 0. Then, the routine returns. In step S1800, it is determined whether or not 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.

[0057] In step S1810, the brake start timer XTMy3 is counted up, and the process proceeds to step S1820. In step S1820, it is determined whether the brake start timer XTMy3 has exceeded the braking start time threshold XTimeMy3 set in step S1720. If the brake start timer XTMy3 has exceeded 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.

[0058] In step S1830, brake timer XT9 is counted up, and the flow 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.

[0059] In step S1850, the additional pitch moment My3 is set to an appropriately set xxMy3, and then the routine 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. Then, the routine returns.

[0060] In step S1870, the additional pitch moment My3 is set to 0. Then, the routine returns. In step S1880, the additional pitch moment My3 is set to 0. Then, the routine returns. By controlling as described above, if the conditions in 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 brake time threshold XTime9 (My3=xxMy3 setting period in Figure 19).

[0061] As shown in FIG. 18, 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 brake start time threshold XTimeMy4 until the brake timer XT10 reaches the brake time threshold XTime10.

[0062] The pitch moment My and roll moment Mx finally applied to the vehicle 1 are calculated using the following (Equation 3) and (Equation 4). My=My1+My2+My3+My4...(Formula 3) Mx=Mx1+Mx2+Mx3+Mx4+Mx5+Mx6...(Formula 4) Next, the additional braking forces Fbfl, Fbfr, Fbrl, and Fbrr for each wheel are calculated from the additional moment value. The calculation formulas for the additional moment are obtained by modifying the above (Formula 1) and (Formula 2) to obtain the following (Formula 5) and (Formula 6).

[0063]

number

[0064]

number

[0065] Furthermore, the total additional braking force X Total Force (=XX Force) is calculated using the following equation (7): X Dif Force, which is the difference between the left and right additional braking forces, is calculated using the following equation (8):

[0066]

number

[0067]

number

[0068] It should be noted that X Dif Force=XX Dif×required yaw moment input from the main control unit 20, and XX Dif is an appropriately set gain of the required yaw moment. When the pitch moment My, the roll moment Mx, the total additional braking force X Total Force, and the difference between the left and right additional braking forces X Dif Force are expressed as a matrix, the following (Equation 9) is obtained.

[0069]

number

[0070] 20 is a flowchart showing a control procedure for determining whether to execute the pitch-roll control. The control shown in FIG. 20 is executed when the system is started and is repeatedly executed while the vehicle 1 is traveling. First, in step S2000, it is determined whether the brake control unit 31 or each of the brake devices 30a to 30d is in an abnormal (failed) state. Whether these units are abnormal or not 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.

[0071] 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 the electric stability control system (ESC), antilock braking system (ABS), and collision mitigation 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.

[0072] In step S2030, the pitch / roll control by the attitude control device 10 is turned on, and then this routine is returned. In step S2040, the pitch / roll control by the attitude control device 10 is turned off, and then this routine is returned. As described above, in the embodiment of the present invention, the braking forces of the brake devices 30a to 30d of the four wheels of the vehicle 1 are controlled, thereby enabling posture control (pitch-roll control) to reduce the pitch and roll of the vehicle 1.

[0073] The current pitch and roll of the vehicle 1 are estimated based on the rotational acceleration of each wheel 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 has tables 1 to 8 having determination conditions for determining the pitch / roll state of the vehicle 1 based on the rotational acceleration of each wheel 3a to 3d and the longitudinal acceleration of the vehicle 1, and determines whether the conditions of each table 1 to 8 are met.

[0074] When the conditions of any of tables 1 to 8 are met, the additional braking force calculation unit 41 sets the corresponding additional moments My1, My2, My3, My4, Mx1 to Mx6 for 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 moment.

[0075] The additional moments My1, My2, My3, My4, and Mx1 to Mx6 set for each of the tables 1 to 8 are as follows in detail. Table 1 has the criteria for determining whether a pitch moment toward the rear of the vehicle occurs, and sets additional pitch moments My1 and My3 toward the front of the vehicle. Table 2 has the criteria for determining whether a pitch moment toward the front of the vehicle occurs, 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 the criteria for determining whether a roll moment occurs when the 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 the criteria for determining whether a roll moment occurs when two wheels on the right side of the vehicle and one wheel on the left side are on a convex road surface, and sets an additional roll moment Mx3 toward the right side of the vehicle. Table 6 has the criteria for determining whether a roll moment occurs 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 criteria for determining whether a roll moment occurs when the 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 a determination condition for the occurrence of a roll moment when two wheels on the left side of the vehicle and one wheel on the right side are on a convex road surface, and sets an additional roll moment Mx6 toward the left side of the vehicle.

[0076] 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 3a to 3d and the longitudinal acceleration of the vehicle 1. Furthermore, the determination of each of Tables 1 to 8 based on the rotational acceleration of wheels 3a to 3d and the longitudinal acceleration of vehicle 1 is performed at a relatively short interval in order to quickly respond to changes in the posture of vehicle 1. However, as shown in the left part of the flowcharts in Figures 7 to 14, when the determination condition of each of 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 that the determination condition of that Table 1 to 8 is not met.

[0077] This ensures good responsiveness when the judgment conditions of each of tables 1 to 8 are met, and once the judgment conditions are met, an additional moment is set and the application of braking force is maintained for a predetermined period of time until the brake timer completes counting up, thereby suppressing excessive fluctuations (switching) in the braking force being applied. In this embodiment, an additional pitch moment My1 toward the front of the vehicle is calculated to cancel out the first-cycle pitch moment generated when the front wheel 3a or 3b of the vehicle 1 runs over a convex road surface, and an additional pitch moment My2 toward the rear of the vehicle is calculated to cancel out the first-cycle pitch moment generated when the rear wheel 3c or 3d of the vehicle 1 runs over a convex road surface. In addition, an additional pitch moment My3 toward the front of the vehicle is calculated to cancel out the second-cycle pitch moment remaining after the front wheel 3a or 3b runs over the convex road surface, and an additional pitch moment My4 toward the rear of the vehicle is calculated to cancel out the second-cycle pitch moment remaining after the rear wheel 3c or 3d runs over the convex road surface. Therefore, if the pitch of the vehicle 1 is not sufficiently suppressed by applying the brakes 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 applying the brakes to apply the additional pitch moments My3 and My4. This allows the pitch remaining after the wheels 3a to 3d run onto a convex road surface to converge quickly, thereby improving the ride comfort of the vehicle 1.

[0078] Furthermore, pitch / roll control by the attitude control device 10 is not performed in any of the following cases: the brake control unit 31 or each of the brake devices 30a to 30d is abnormal; the driver's brake operation amount exceeds the threshold X Cmd Force; or a driving control device (driving safety device) other than the attitude control device 10, such as ESC, ABS, or AEB, is in operation.

[0079] In particular, pitch / roll control is not performed when the brake operation force is greater than a predetermined value, so when the driver suddenly applies the brakes, the pitch / roll control of this embodiment can be suppressed and braking by braking operation can be prioritized. Furthermore, when a driving control device other than the attitude control device is in operation (such as brake control), the pitch / roll control of this embodiment is suppressed, and the other driving control device is given priority, thereby appropriately ensuring the driving safety function provided by the other driving control device.

[0080] 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, 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. Furthermore, 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 only pitch control, which applies the pitch moment My, may be performed.

[0081] The present invention can be widely applied to vehicles in which the four wheels (front, rear, left, and right) can be braked independently. [Explanation of symbols]

[0082] 1 vehicle 3a~3d wheels 10 Attitude control device 11 Suspension device 30a~30d Brake device (braking device) 31 Brake control unit (braking control section) 33a to 33d Wheel speed sensors (speed detection units) 35 Front and rear acceleration sensor (front and rear acceleration detection section) 40 Pitch / roll determination unit (pitch determination unit, roll determination unit) 41 Additional braking force calculation unit (attitude control unit)

Claims

1. The vehicle is provided with front, rear, left and right wheels suspended by suspension devices having anti-dive and anti-lift geometry, 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; a longitudinal acceleration detection unit for detecting longitudinal acceleration of the vehicle; Equipped with The braking control unit 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; an attitude control unit that applies braking forces by the front, rear, left, and right braking devices based on the pitch state, the pitch determination unit is provided with a plurality of types of determination conditions for determining the pitch state based on the rotational acceleration of each of the wheels and the longitudinal acceleration of the vehicle, and calculates a total additional moment of the vehicle by adding up additional moments that are set each time the determination conditions are satisfied; The additional moment that is set each time the judgment condition is satisfied is: a first additional pitch moment that suppresses a first period pitch moment that occurs when the wheel rides over a convex road surface; and and a second additional pitch moment that suppresses a second periodic pitch moment that continues after the wheel has traveled over a convex road surface. A vehicle attitude control device characterized by:

2. The first additional pitch moment is a first front wheel additional pitch moment toward the front of the vehicle based on a pitch state of the vehicle when the front wheels of the vehicle run over a convex road surface; and a first rear wheel additional pitch moment toward the rear of the vehicle based on a pitch state of the vehicle when the rear wheels of the vehicle go over a convex road surface, The second additional pitch moment is a second front wheel additional pitch moment toward the front of the vehicle based on a pitch state of the vehicle after the front wheels of the vehicle run over a convex road surface; and a second additional rear wheel pitch moment toward the rear of the vehicle based on a pitch state of the vehicle after the rear wheels of the vehicle have gone over a convex road surface.

2. The attitude control device according to claim 1,

3. The attitude control unit maintains application of braking force of the braking device based on the pitch state for a predetermined time when the pitch determination unit determines that the pitch state of the vehicle is equal to or greater than a predetermined value while the vehicle is traveling.

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

4. The attitude control unit suppresses application of a braking force based on the pitch state when a braking operation by a driver of the vehicle is greater than or equal to a predetermined value.

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

5. The vehicle includes a braking control unit that controls the braking force of the braking device to improve the traveling safety of the vehicle, The attitude control unit suppresses application of braking force based on the pitch state when the braking control unit is executing control of the braking force of the braking device.

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

6. The braking control unit a roll determination unit that determines a 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 the front, rear, left, and right braking devices based on the pitch state and the roll state, The roll determination unit has a plurality of types of determination conditions for determining the roll state based on the rotational acceleration of each of the wheels and the longitudinal acceleration of the vehicle, and adds an additional moment that is set each time the determination condition is satisfied to the overall additional moment of the vehicle.

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

Images