Vehicle control method and vehicle control device

Abstract

To improve the stability of vehicle behavior when the vehicle is turning. [Solution] In the vehicle control method, the longitudinal acceleration and lateral acceleration of the vehicle are detected or estimated (S1), and in accordance with the longitudinal acceleration and lateral acceleration, it is selected which of the following to perform is executed: yaw rate control to control the yaw rate of the vehicle, roll control to control the roll angle, and pitch control to control the pitch angle (S2~S7). In roll control, the wheel load of the front outer wheel, which is the front wheel on the outside of the turn, and the wheel load of the rear inner wheel, which is the rear wheel on the inside of the turn, are estimated (S24), and braking force is applied to the front outer wheel and the rear inner wheel with a braking force distribution according to the ratio of the wheel load of the front outer wheel and the wheel load of the rear inner wheel (S25).

Description

[Technical Field]

[0001] This invention relates to a vehicle control method and a vehicle control device. [Background technology]

[0002] Patent Document 1 proposes a technique for controlling the rolling motion of a vehicle by adjusting the distribution ratio of braking force to target wheels, including at least one of the inner rear wheel and the outer front wheel during a turn. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-117216 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] According to the technology described in Patent Document 1, the roll behavior of a vehicle during cornering can be adjusted. However, when a vehicle is cornering, it is preferable to stabilize the yaw behavior and pitch behavior in accordance with changes in the vehicle's state. The present invention aims to improve the stability of vehicle behavior when a vehicle is turning. [Means for solving the problem]

[0005] In a vehicle control method according to one aspect of the present invention, the vehicle's longitudinal acceleration, lateral acceleration, steering angle, and vehicle speed are detected or estimated, the vehicle's actual yaw rate, actual roll angle, and actual pitch angle are detected or estimated, target yaw rate, target roll angle, and target pitch angle are set based on the steering angle and vehicle speed, and the vehicle's yaw rate is controlled by applying braking force to the wheels based on the yaw rate deviation, which is the deviation of the actual yaw rate from the target yaw rate, in accordance with the longitudinal acceleration and lateral acceleration, and roll angle deviation, which is the deviation of the actual roll angle from the target roll angle. The system selects whether to perform roll control, which controls the vehicle's roll angle by applying braking force to the wheels based on the difference, or pitch control, which controls the vehicle's pitch angle by applying braking force to the wheels based on the pitch angle deviation, which is the deviation of the actual pitch angle from the target pitch angle. In roll control, the system estimates the wheel load of the outer front wheel (outside the turn) and the inner rear wheel (inside the turn) based on longitudinal and lateral acceleration, and applies braking force to the outer front wheel and the inner rear wheel with a braking force distribution corresponding to the ratio of the wheel loads of the outer front wheel and the inner rear wheel. [Effects of the Invention]

[0006] According to the present invention, the stability of vehicle behavior during vehicle turns can be improved. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of an example of a vehicle control device according to an embodiment. [Figure 2] This is an explanatory diagram of the vehicle control method according to the embodiment. [Figure 3] Figure 1 is a block diagram showing an example of the controller's functional configuration. [Figure 4] This is an explanatory diagram illustrating an example of the regions of longitudinal and lateral acceleration in which yaw rate control, roll control, and pitch control take precedence, respectively. [Figure 5] This is an explanatory diagram illustrating an example of yaw rate feedforward control. [Figure 6] This is an explanatory diagram illustrating an example of braking force distribution based on longitudinal acceleration and vehicle speed. [Figure 7](a) to (e) are time charts illustrating an example of roll control during a turn. [Figure 8] This is a flowchart illustrating an example of the vehicle behavior control selection process performed by the target control selection unit. [Figure 9] This is a flowchart illustrating an example of the process in yaw rate control. [Figure 10] This is a flowchart illustrating an example of the process in roll control. [Figure 11] This is a flowchart illustrating an example of the process involved in pitch control. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings are schematic and may differ from actual ones. Furthermore, the embodiments of the present invention described below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the structure, arrangement, etc., of the components described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0009] (composition) Figure 1 is a schematic diagram of an example of a vehicle control device according to an embodiment. Vehicle 1 is equipped with a vehicle control device 10 that stabilizes the vehicle behavior of vehicle 1 during cornering. The vehicle control device 10 stabilizes the yaw, roll, and pitch behavior of vehicle 1 during cornering by adjusting the braking force distribution between the right front wheel 2FR, the left front wheel 2FL, the right rear wheel 2RR, and the left rear wheel 2RL.

[0010] In the following description, the right front wheel 2FR and the left front wheel 2FL may be collectively referred to as the "front wheels 2FRL", the right rear wheel 2RR and the left rear wheel 2RL may be collectively referred to as the "rear wheels 2RRL", the right front wheel 2FR and the right rear wheel 2RR may be collectively referred to as the "right wheels 2RFR", and the left front wheel 2FL and the left rear wheel 2RL may be collectively referred to as the "left wheels 2LFR". The right front wheel 2FR, the left front wheel 2FL, the right rear wheel 2RR, and the left rear wheel 2RL may be collectively referred to as the "wheels 2".

[0011] Also, the wheels on the outside of the turn (that is, the wheels attached to the side opposite to the turning direction among the right wheels 2RFR and the left wheels 2LFR) may be referred to as the "outer turning wheels", and the wheels on the inside of the turn (that is, the wheels attached to the same side as the turning direction among the right wheels 2RFR and the left wheels 2LFR) may be referred to as the "inner turning wheels". The front wheels on the outside of the turn may be referred to as the "front outer wheels", the rear wheels on the inside of the turn may be referred to as the "rear inner wheels", the rear wheels on the outside of the turn may be referred to as the "rear outer wheels", and the front wheels on the inside of the turn may be referred to as the "front inner wheels".

[0012] The vehicle control device 10 includes a braking device 12, a steering angle sensor 13, a vehicle speed sensor 14, an acceleration sensor 15, a gyro sensor 16, and a controller 17. The braking device 12 is a braking mechanism that can individually control the braking forces generated on the right front wheel 2FR, the left front wheel 2FL, the right rear wheel 2RR, and the left rear wheel 2RL. For example, the braking device 12 may be a friction brake. Note that regenerative braking forces may be generated in in-wheel motors that individually drive the right front wheel 2FR, the left front wheel 2FL, the right rear wheel 2RR, and the left rear wheel 2RL and used as the braking device 12.

[0013] The steering angle sensor 13 detects the steering angle δs of the steering wheel. The vehicle speed sensor 14 detects the vehicle speed V, which is the body speed of the vehicle 1. The acceleration sensor 15 detects the longitudinal acceleration Gx, which is the acceleration of the vehicle 1 in the longitudinal direction, and the lateral acceleration Gy, which is the acceleration in the lateral direction. As the acceleration sensor 15, a 6-axis sensor capable of detecting the longitudinal acceleration Gx, the lateral acceleration Gy, the vertical acceleration, the yaw rate γ, the roll angular velocity dθr / dt, and the pitch angular velocity dθp / dt may be used.

[0014] The gyro sensor 16 detects the yaw rate γ, the roll angular velocity dθr / dt, and the pitch angular velocity dθp / dt. The controller 17 is an electronic control unit (ECU) that controls the braking force generated on the wheels 2 by the braking device 12. For example, the controller 17 includes a computer that includes a processor 17a and peripheral components such as a memory device 17b. The processor 17a may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0015] The storage device 17b may include any of semiconductor storage devices, magnetic storage devices, or optical storage devices. The storage device 17b may include memory such as ROM (Read Only Memory) and RAM (Random Access Memory) used as main memory, as well as registers and cache memory. The functions of the controller 17 described below are realized, for example, by the processor 17a executing a computer program stored in the storage device 17b.

[0016] The controller 17 may be formed by dedicated hardware for performing each of the information processing operations described below. For example, the controller 17 may include functional logic circuits configured in a general-purpose semiconductor integrated circuit. For example, the controller 17 may have a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0017] Figure 2 is an explanatory diagram of the vehicle control method according to the embodiment. Figure 2 shows the state changes of the vehicle 1 during a turning operation. Arrow P1 shows the vehicle 1 during turn-in, transitioning from a straight state to a turning state; arrow P2 shows the vehicle 1 during turning; and arrow P3 shows the vehicle 1 during turn-out (or corner-out), transitioning from a turning state to a straight state. During turn-in (P1), vehicle 1 decelerates, resulting in a nose dive where the pitch angle, which lowers the front of the vehicle, becomes larger.

[0018] Next, when vehicle 1 enters a turning state (P2), a roll angle is generated in the direction of downward movement of the outer side of the vehicle body due to lateral acceleration. Finally, during turn-out (P3), vehicle 1 accelerates while turning, resulting in understeer where the actual turning angle is insufficient compared to the steering angle of the steering wheels. Therefore, in order to improve the stability of vehicle behavior during cornering, it is preferable to suppress nose dive during turn-in (P1), suppress the roll angle that lowers the outer side of the vehicle during cornering, and suppress understeer (insufficient yaw rate) during turn-out (P3).

[0019] The controller 17 then controls the pitch angle, roll angle, and yaw rate of the vehicle 1 by adjusting the distribution of braking force applied to the wheels 2 in accordance with the changes in the state of the vehicle 1 during turning. At that time, the controller 17 estimates the state of the vehicle 1 during turning based on the longitudinal acceleration Gx and the lateral acceleration Gy, and decides which of the pitch angle, roll angle, or yaw rate to prioritize for control according to the estimated state of the vehicle 1.

[0020] For example, during turn-in (P1), the pitch angle that lowers the front of the vehicle (nose dive) can be suppressed by distributing more braking force to the rear wheels (2RRL) than to the front wheels (2FRL). Alternatively, the braking force applied to the front wheels (2FRL) may be set to 0, and braking force applied only to the rear wheels (2RRL). Furthermore, for example, during cornering (P2), the roll angle that lowers the outer side of the vehicle during cornering can be suppressed by increasing the braking force distribution to the front outer wheel 2FR and rear inner wheel 2RL compared to the rear outer wheel 2RR and front inner wheel 2FL. For example, braking force may be applied only to the front outer wheel 2FR and rear inner wheel 2RL. Alternatively, braking force may be applied to only one of either the front outer wheel 2FR or the rear inner wheel 2RL.

[0021] Furthermore, for example, during turnout (P3), understeer may be suppressed by increasing the braking force distribution to the left wheel 2LFR, which is the inner turning wheel, compared to the right wheel 2RFR, which is the outer turning wheel. For example, the braking force applied to the outer turning wheel 2RFR may be set to 0, and braking force may be applied only to the inner turning wheel 2LFR. In this way, the controller 17 can improve the stability of the vehicle's behavior during a turn by adjusting the distribution of braking force applied to the wheels 2 according to the state of the vehicle 1 during a turn (or according to which stage it is in: turn-in, turn-out, or turn-in).

[0022] Next, the details of the controller 17 will be described. Figure 3 is a block diagram of an example of the functional configuration of the controller 17. The controller 17 includes a target control selection unit 20, a wheel load estimation unit 21, a vehicle behavior acquisition unit 22, a target behavior setting unit 23, a yaw control amount calculation unit 24, a roll control amount calculation unit 25, a pitch control amount calculation unit 26, and a braking force distribution unit 27.

[0023] The target control selection unit 20 determines, based on the longitudinal acceleration Gx and lateral acceleration Gy, which of the following controls should be prioritized for stabilizing the vehicle behavior of the vehicle 1: yaw rate control, which controls the yaw rate of the vehicle 1 by applying braking force to the wheels 2; roll control, which controls the roll angle of the vehicle 1 by applying braking force to the wheels 2; and pitch control, which controls the pitch angle of the vehicle 1 by applying braking force to the wheels 2.

[0024] The controller 17 may also detect longitudinal acceleration Gx and lateral acceleration Gy using the acceleration sensor 15, or it may estimate longitudinal acceleration Gx and lateral acceleration Gy from information such as wheel speed. In the following explanation, yaw rate control, roll control, and pitch control may be collectively referred to as "vehicle behavior control."

[0025] In "yaw rate control," the yaw rate of vehicle 1 is controlled by applying braking force to wheel 2 based on the yaw rate deviation Δγ, which is the deviation of the actual yaw rate γa from the target yaw rate γt. In "roll angle control," the roll angle of vehicle 1 is controlled by applying braking force to wheel 2 based on the roll angle deviation Δθr, which is the deviation of the actual roll angle θra from the target roll angle θrt. "Pitch angle control" refers to the process of controlling the pitch angle of vehicle 1 by applying braking force to wheel 2 based on the pitch angle deviation Δθp, which is the deviation of the actual pitch angle θpa from the target pitch angle θpt.

[0026] Figure 4 is an explanatory diagram illustrating an example of the ranges of longitudinal acceleration Gx and lateral acceleration Gy for which the target control selection unit 20 selects yaw rate control, roll control, and pitch control, respectively. In the example in Figure 4, the sign of the lateral acceleration Gy generated during a left turn is defined as positive, and the sign of the lateral acceleration Gy generated during a right turn is defined as negative. For example, if the longitudinal acceleration Gx is greater than or equal to the first threshold Th1 and the absolute value of the lateral acceleration |Gy| is greater than or equal to the second threshold Th2, the target control selection unit 20 selects yaw rate control as the vehicle behavior control to be executed with priority.

[0027] For example, if the longitudinal acceleration Gx is greater than or equal to the first threshold Th1 and the lateral acceleration Gy is greater than or equal to the second threshold Th2 (region R1), the target control selection unit 20 may determine that it is a turnout transition from a left-turning state to a straight-ahead state and select yaw rate control. In yaw rate control performed when transitioning from a left-turn state to a straight-ahead state, the braking force distribution to the inner turning wheels 2FL and 2RL may be greater than that to the outer turning wheels 2FR and 2RR, for example, as shown in arrow C1. For example, braking force may be applied only to the inner turning wheels 2FL and 2RL.

[0028] For example, if the longitudinal acceleration Gx is greater than or equal to the first threshold Th1 and the lateral acceleration Gy is less than or equal to the value obtained by inverting the sign of the second threshold (-Th2) (region R2), the target control selection unit 20 may determine that it is a turnout transition from a right-turning state to a straight-ahead state and select yaw rate control. In yaw rate control that transitions from a right-turn state to a straight-ahead state, the braking force distribution to the inner turning wheels 2FR and 2RR may be greater than that to the outer turning wheels 2FL and 2RL, as shown in arrow C2, for example. For example, braking force may be applied only to the inner turning wheels 2FR and 2RR.

[0029] For example, if the longitudinal acceleration Gx is less than the first threshold Th1 and the absolute value of the lateral acceleration |Gy| is greater than or equal to the second threshold Th2, the target control selection unit 20 selects roll control as the vehicle behavior control to be executed with priority.

[0030] For example, if the longitudinal acceleration Gx is less than the first threshold Th1 and the lateral acceleration Gy is greater than or equal to the second threshold Th2 (region R3), the target control selection unit 20 may determine that the vehicle is turning left and select roll control. In roll control performed during a left turn, the braking force distribution to the front outer wheel 2FR and rear inner wheel 2RL may be greater than that to the rear outer wheel 2RR and front inner wheel 2FL, as shown in arrow C3. For example, braking force may be applied only to the front outer wheel 2FR and rear inner wheel 2RL. Alternatively, braking force may be applied to only one of either the front outer wheel 2FR or the rear inner wheel 2RL.

[0031] For example, if the longitudinal acceleration Gx is less than the first threshold Th1 and the lateral acceleration Gy is less than or equal to the second threshold with the sign reversed (-Th2) (region R4), the target control selection unit 20 may determine that the vehicle is turning to the right and select roll control. In roll control performed during a right turn, the braking force distribution to the front outer wheel 2FL and rear inner wheel 2RR may be greater than that to the rear outer wheel 2RL and front inner wheel 2FR, as shown in arrow C4, for example. For example, braking force may be applied only to the front outer wheel 2FL and rear inner wheel 2RR. Alternatively, braking force may be applied to only one of either the front outer wheel 2FL or the rear inner wheel 2RR.

[0032] For example, if the longitudinal acceleration Gx is less than or equal to the third threshold Th3 (a negative value) and the absolute value of the lateral acceleration |Gy| is less than the second threshold Th2 (region R5), the target control selection unit 20 determines that the vehicle 1 is in the turn-in phase and selects pitch control as the vehicle behavior control to be executed with priority. In pitch control, for example, as shown in arrow C5, the braking force distribution to the rear wheels 2RRL may be greater than that to the front wheels 2FRL. For example, braking force may be applied only to the rear wheels 2RRL. The target control selection unit 20 outputs to the braking force distribution unit 27 the decision result of selecting one of the vehicle behavior control systems from yaw rate control, roll control, and pitch control to be executed with priority. The first threshold Th1, second threshold Th2, and third threshold Th3 mentioned above may be set as appropriate based on vehicle specifications and actual vehicle compatibility.

[0033] Refer to Figure 3. The wheel load estimation unit 21 estimates the wheel loads Wfr, Wfl, Wrr, and Wrl for the right front wheel 2FR, left front wheel 2FL, right rear wheel 2RR, and left rear wheel 2RL, respectively, based on the longitudinal acceleration Gx, lateral acceleration Gy, and vehicle specifications of vehicle 1. For example, the wheel load estimation unit 21 may estimate the wheel loads Wfr, Wfl, Wrr, and Wrl based on the following equations (1) to (4).

[0034] Wfr=(m×lr / l÷2)+(-(m×Gx×H / l÷2)+(m×Gy×H / T÷2))…(1) Wfl=(m×lr / l÷2)+(-(m×Gx×H / l÷2)-(m×Gy×H / T÷2))…(2) Wrr=(m×lf / l÷2)+(+(m×Gx×H / l÷2)+(m×Gy×H / T÷2))…(3) Wrl=(m×lf / l÷2)+(+(m×Gx×H / l÷2)-(m×Gy×H / T÷2))…(4)

[0035] The symbol m indicates the weight of vehicle 1, the symbol l indicates the wheelbase, the symbols lf and lr indicate the distance from the vehicle's center of gravity to the front axle and rear axle, respectively, the symbol H indicates the height of the vehicle's center of gravity, and the symbol T indicates the tread width.

[0036] The vehicle behavior acquisition unit 22 acquires information on the actual yaw rate γa, actual roll angle θra, and actual pitch angle θpa of the vehicle 1. For example, the vehicle behavior acquisition unit 22 may use the gyro sensor 16 to detect the actual yaw rate γa, the actual roll angle θra, and the actual pitch angle θpa. For example, the roll angular velocity and pitch angular velocity detected by the gyro sensor 16 may be integrated to detect the actual roll angle θra and the actual pitch angle θpa.

[0037] Alternatively, the vehicle behavior acquisition unit 22 may estimate the actual yaw rate γa, actual roll angle θra, and actual pitch angle θpa based on the vehicle specifications. For example, the vehicle behavior acquisition unit 22 may calculate the actual yaw rate γa, actual roll angle θra, and actual pitch angle θpa based on the following equations (5) to (7).

[0038] The symbol I represents the vehicle's yaw radius of inertia, the symbols Kf and Kr represent the equivalent cornering power of the front and rear wheels, the symbol s represents the Laplace operator, and the symbol K ro This indicates roll stiffness, C ro The symbol I indicates the roll damping coefficient. ro This indicates the roll moment of inertia, M ro The symbol K indicates the roll moment. pi This indicates pitch stiffness, C pi The symbol I indicates the pitch damping coefficient. pi This indicates the pitch moment of inertia, M pi This indicates the pitch moment.

[0039]

number

[0040]

Number

[0041] Note that the controller 17 may detect the vehicle speed V and the steering angle δf using the vehicle speed sensor 14 and the steering angle sensor 13, estimate the vehicle speed sensor 14 from information such as wheel speed, or estimate the steering angle δf from the rotation angle of the steering assist motor of the electric power steering device or the steering motor of the steer-by-wire system. Further, the controller 17 differentiates the roll angular velocity and the pitch angular velocity acquired from the gyro sensor 16 or the 6-axis sensor to calculate the roll angular acceleration and the pitch angular acceleration, and multiplies these by the roll moment of inertia I ro and the pitch moment of inertia I pi respectively, to calculate the roll moment M ro and the pitch moment M pi may be calculated.

[0042] The target behavior setting unit 23 sets the target yaw rate γt, the target roll angle θrt, and the target pitch angle θpt based on the steering angle δf and the vehicle speed V. For example, the target behavior setting unit 23 sets the vehicle speed-sensitive parameters a, b, c, d, e, f, g, h, and i based on the vehicle speed V, and sets the target yaw rate γt, the target roll angle θrt, and the target pitch angle θpt based on the following equations (8) to (9).

[0043]

Number

[0044] The yaw control amount calculation unit 24 calculates the yaw rate deviation Δγ = γt - γa, which is the deviation between the target yaw rate γt and the actual yaw rate γa, and calculates the yaw control amount ΔBγ for controlling the yaw rate of the vehicle 1 based on the yaw rate deviation Δγ. For example, the yaw control amount calculation unit 24 calculates the yaw control amount ΔBγ for reducing (or making zero) the yaw rate deviation Δγ.

[0045] For example, the yaw control amount calculation unit 24 may calculate the yaw control amount ΔBγ as the difference in braking force between the rotating inner ring and the rotating outer ring, or it may calculate the yaw control amount ΔBγ as the braking force applied to the rotating inner ring. For example, the yaw control amount calculation unit 24 may calculate the yaw control amount ΔBγ = G1 × Δγ by multiplying the yaw rate deviation Δγ by a predetermined gain G1.

[0046] Furthermore, the yaw control amount calculation unit 24 determines whether or not the output condition is met, which is the condition for outputting a yaw control amount ΔBγ to the wheel 2 (i.e., for generating a braking force difference on the wheel 2 based on the yaw control amount ΔBγ). For example, it may be determined that the output condition is met if the yaw rate deviation Δγ is greater than or equal to a predetermined value, and that the output condition is not met if it is less than the predetermined value.

[0047] For example, it may be determined that the output condition is met when the vehicle speed V, steering speed, and master pressure are below predetermined values, and that the output condition is not met when they are above the predetermined values. The yaw control amount calculation unit 24 outputs the yaw control amount ΔBγ = G1 × Δγ to the braking force distribution unit 27 when the output condition is met, and outputs the yaw control amount ΔBγ = 0 to the braking force distribution unit 27 when the output condition is met.

[0048] The roll control amount calculation unit 25 calculates the roll angle deviation Δθr = θrt - θra, which is the deviation of the actual roll angle θra from the target roll angle θrt, and calculates the roll control amount ΔBr for controlling the roll angle of the vehicle 1 based on the roll angle deviation Δθr. For example, the roll control amount calculation unit 25 calculates the roll control amount ΔBr to reduce (or make zero) the roll angle deviation Δθr.

[0049] For example, the roll control amount calculation unit 25 may calculate the roll control amount ΔBr by determining the difference in braking force between the front outer ring and the rear inner ring and between the rear outer ring and the front inner ring, or by determining the braking force applied to the front outer ring and the rear inner ring, or by determining the roll control amount ΔBr by determining the braking force applied to either the front outer ring or the rear inner ring. For example, the roll control amount calculation unit 25 may calculate the roll control amount ΔBr = G2 × Δθr by multiplying the roll angle deviation Δθr by a predetermined gain G2.

[0050] Furthermore, the roll control amount calculation unit 25 determines whether or not the output condition is met, which is the condition for outputting a roll control amount ΔBr to the wheel 2 (i.e., for generating a braking force difference on the wheel 2 based on the roll control amount ΔBr). For example, it may be determined that the output condition is met when the roll angle deviation Δθr is greater than or equal to a predetermined value, and that the output condition is not met when it is less than the predetermined value.

[0051] For example, it may be determined that the output condition is met when the vehicle speed V, steering speed, and master pressure are below predetermined values, and that the output condition is not met when they are above the predetermined values. The roll control amount calculation unit 25 outputs the roll control amount ΔBr = G2 × Δθr to the braking force distribution unit 27 when the output conditions are met, and outputs the roll control amount ΔBr = 0 to the braking force distribution unit 27 when the output conditions are met.

[0052] The pitch control amount calculation unit 26 calculates the pitch angle deviation Δθp = θpt - θpa, which is the deviation of the actual pitch angle θpa from the target pitch angle θpt, and calculates the pitch control amount ΔBp for controlling the pitch angle of the vehicle 1 based on the pitch angle deviation Δθp. For example, the pitch control amount calculation unit 26 calculates the pitch control amount ΔBp to reduce (or make zero) the pitch angle deviation Δθp.

[0053] For example, the pitch control amount calculation unit 26 may calculate the pitch control amount ΔBp as the difference in braking force between the rear wheel 2RRL and the front wheel 2FRL, or it may calculate the pitch control amount ΔBp as the braking force applied to the rear wheel 2RRL. For example, the pitch control amount calculation unit 26 may calculate the pitch control amount ΔBp = G3 × Δθp by multiplying the pitch angular deviation Δθp by a predetermined gain G3.

[0054] Furthermore, the pitch control amount calculation unit 26 determines whether the output condition is met, which is the condition for outputting a pitch control amount ΔBp to the wheel 2 (i.e., for generating a braking force difference on the wheel 2 based on the pitch control amount ΔBp). For example, it may be determined that the output condition is met if the pitch angle deviation Δθp is greater than or equal to a predetermined value, and that the output condition is not met if it is less than the predetermined value.

[0055] For example, it may be determined that the output condition is met when the vehicle speed V, steering speed, and master pressure are below predetermined values, and that the output condition is not met when they are above the predetermined values. The pitch control amount calculation unit 26 outputs a pitch control amount ΔBp = G3 × Δθp to the braking force distribution unit 27 if the output condition is met, and outputs a pitch control amount ΔBp = 0 to the braking force distribution unit 27 if the output condition is met.

[0056] In the example above, the yaw control amount calculation unit 24, the roll control amount calculation unit 25, and the pitch control amount calculation unit 26 calculated the yaw control amount ΔBγ, roll control amount ΔBr, and pitch control amount ΔBp, respectively, through feedback control based on the yaw rate deviation Δγ, roll angle deviation Δθr, and pitch angle deviation Δθp. Alternatively, the yaw control amount calculation unit 24, the roll control amount calculation unit 25, and the pitch control amount calculation unit 26 may calculate the yaw control amount ΔBγ, the roll control amount ΔBr, and the pitch control amount ΔBp by feedforward control based on longitudinal acceleration Gx and lateral acceleration Gy.

[0057] Figure 5 is an explanatory diagram of an example of yaw rate feedforward control. For example, the yaw control amount calculation unit 24 includes a first control amount calculation unit 30 that calculates a first control amount C1 based on longitudinal acceleration Gx, a second control amount calculation unit 31 that calculates a second control amount C2 based on lateral acceleration Gy, a multiplier 32, a gain multiplication unit 33, and a limiting unit 34. The first control variable calculation unit 30 and the second control variable calculation unit 31 calculate the first control variable C1 and the second control variable C2, which become greater than 0 when longitudinal acceleration Gx and lateral acceleration Gy exceeding predetermined values ​​are detected.

[0058] The multiplier 32 and the gain multiplier 33 calculate the yaw control amount ΔBγ = C1 × C2 × K1 by multiplying the product of the first control variable C1 and the second control variable C2 by a predetermined gain K1. The limiting unit 34 determines whether the output conditions for the yaw control amount ΔBγ are met based on the vehicle speed V, steering speed, and master pressure. If the output conditions are met, the limiting unit 34 outputs the yaw control amount ΔBγ = C1 × C2 × K1. If the output conditions are not met, the limiting unit 34 outputs the yaw control amount ΔBγ = 0. The roll control amount calculation unit 25 and the pitch control amount calculation unit 26 may also calculate the roll control amount ΔBr and pitch control amount ΔBp using the same configuration as shown in Figure 5.

[0059] Refer to Figure 3. The braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 in yaw rate control, roll control, or pitch control based on the determination result by the target control selection unit 20, the wheel load estimation unit 21 estimated wheel loads Wfr, Wfl, Wrr, and Wrl, the yaw control amount ΔBγ calculated by the yaw control amount calculation unit 24, the roll control amount ΔBr calculated by the roll control amount calculation unit 25, and the pitch control amount ΔBp calculated by the pitch control amount calculation unit 26.

[0060] When distributing braking force to each wheel 2, the braking force distribution unit 27 determines which of the following vehicle behavior controls—yaw rate control, roll control, or pitch control—the target control selection unit 20 has selected to prioritize. If the output conditions for the control amount of the vehicle behavior control selected by the target control selection unit 20 from among the yaw control amount ΔBγ, roll control amount ΔBr, or pitch control amount ΔBp are met, the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the control amount of the vehicle behavior control selected by the target control selection unit 20.

[0061] On the other hand, if the output conditions for the control amount of the vehicle behavior control selected by the target control selection unit 20 are not met, the braking force to be distributed to each wheel 2 is determined based on the control amounts of other vehicle behavior controls for which the output conditions are met. In this way, the vehicle behavior control selected by the target control selection unit 20 is executed with priority over other vehicle behavior control methods.

[0062] For example, if the vehicle behavior control selected by the target control selection unit 20 is yaw rate control and the output condition for the yaw control amount ΔBγ is met (i.e., the yaw control amount ΔBγ is not 0), the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the yaw control amount ΔBγ. For example, braking force may be applied to each wheel 2 such that the braking force of the inner turning wheel is greater than that of the outer turning wheel by the yaw control amount ΔBγ. For example, braking force ΔBγ may be applied only to the inner turning wheel.

[0063] On the other hand, if the vehicle behavior control selected by the target control selection unit 20 is yaw rate control and the output condition for the yaw control amount ΔBγ is not met (i.e., the yaw control amount ΔBγ is 0), the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the remaining roll control amount ΔBr or pitch control amount ΔBp for which the output condition is met.

[0064] For example, if the vehicle behavior control selected by the target control selection unit 20 is roll control, and the output condition for the roll control amount ΔBr is met (i.e., the roll control amount ΔBr is not 0), the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the roll control amount ΔBr. For example, braking force may be applied to each wheel 2 such that the braking force of the front outer wheel and rear inner wheel is greater than that of the rear outer wheel and front inner wheel by the roll control amount ΔBr. For example, braking force ΔBr may be applied only to the front outer wheel and rear inner wheel. Braking force ΔBr may be applied to either the front outer wheel or the rear inner wheel.

[0065] On the other hand, if the vehicle behavior control selected by the target control selection unit 20 is roll control and the output condition for the roll control amount ΔBr is not met (i.e., the roll control amount ΔBr is 0), the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the remaining yaw control amount ΔBγ or pitch control amount ΔBp for which the output condition is met.

[0066] For example, if the vehicle behavior control selected by the target control selection unit 20 is pitch control, and the output condition for the pitch control amount ΔBp is met (i.e., the pitch control amount ΔBp is not 0), the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the pitch control amount ΔBp. For example, braking force may be applied to each wheel 2 such that the braking force of the rear wheel 2RRL is greater than that of the front wheel 2FRL by the pitch control amount ΔBp. For example, braking force ΔBp may be applied only to the rear wheel 2RRL.

[0067] On the other hand, if the vehicle behavior control selected by the target control selection unit 20 is pitch control and the output condition for the pitch control amount ΔBp is not met (i.e., the pitch control amount ΔBp is 0), the braking force distribution unit 27 determines the braking force to be distributed to each wheel 2 based on the remaining yaw control amount ΔBγ or roll control amount ΔBr for which the output condition is met.

[0068] Furthermore, when roll control is performed, the braking force distribution unit 27 may set the braking force distribution between the front outer wheel and the rear inner wheel based on the wheel loads Wfr, Wfl, Wrr, and Wrl. For example, the braking force distribution unit 27 may apply braking force to the front outer wheel and the rear inner wheel with a braking force distribution that corresponds to the ratio of the wheel load of the front outer wheel to the wheel load of the rear inner wheel. That is, the larger the ratio of the wheel load of the front outer wheel, the larger the braking force applied to the front outer wheel and the smaller the braking force applied to the rear inner wheel. Conversely, the smaller the ratio of the wheel load of the front outer wheel, the smaller the braking force applied to the front outer wheel and the larger the braking force applied to the rear inner wheel.

[0069] For example, when roll control is performed during a left turn as shown in Figure 2 (P2), the braking force ΔBr may be distributed to the front outer wheel 2FR and the rear inner wheel 2RL in a braking force distribution corresponding to the ratio Wfr:Wrl of the wheel load of the front outer wheel 2FR and the wheel load of the rear inner wheel 2RL, thereby applying a braking force ΔBr × Wfr / (Wfr + Wrl) to the front outer wheel 2FR and a braking force ΔBr × Wrl / (Wfr + Wrl) to the rear inner wheel 2RL.

[0070] Furthermore, when yaw rate control is performed, the braking force distribution unit 27 may set the braking force distribution between the front inner wheel and the rear inner wheel based on the wheel loads Wfr, Wfl, Wrr, and Wrl. For example, the braking force distribution unit 27 may apply braking force to the front inner wheel and the rear inner wheel with a braking force distribution that corresponds to the ratio of the wheel load of the front inner wheel to the wheel load of the rear inner wheel. That is, the larger the ratio of the wheel load of the front inner wheel, the larger the braking force applied to the front inner wheel and the smaller the braking force applied to the rear inner wheel. Conversely, the smaller the ratio of the wheel load of the front inner wheel, the smaller the braking force applied to the front inner wheel and the larger the braking force applied to the rear inner wheel.

[0071] For example, when performing yaw rate control when transitioning from a left-turn state to a straight-ahead state as shown in Figure 2 (P3), the braking force ΔBγ can be distributed to the left front wheel 2FL and the left rear wheel 2RL in a braking force distribution corresponding to the ratio Wfl:Wrl of the wheel load of the left front wheel 2FL, which is the turning inner wheel, and the wheel load of the left rear wheel 2RL. This applies a braking force ΔBγ × Wfl / (Wfl + Wrl) to the left front wheel 2FL and a braking force ΔBγ × Wrl / (Wfl + Wrl) to the left rear wheel 2RL.

[0072] Alternatively, the braking force distribution unit 27 may set the braking force distribution according to the ratio of the tire's friction circle margin = (resulting force of the tire's longitudinal and lateral forces) / (road surface friction coefficient μ × wheel load) instead of the wheel load ratio. For example, when performing roll control, braking force may be applied to the front outer wheel and the rear inner wheel in a braking force distribution that corresponds to the ratio of the friction circle margin of the front outer wheel to the friction circle margin of the rear inner wheel. For example, when performing yaw rate control, braking force may be applied to the front inner wheel and the rear inner wheel in a braking force distribution that corresponds to the ratio of the friction circle margin of the front inner wheel to the friction circle margin of the rear inner wheel.

[0073] Alternatively, the braking force distribution unit 27 may set the braking force distribution based on the longitudinal acceleration Gx and the vehicle speed V. Figure 6 is an explanatory diagram of an example of a configuration in which the braking force distribution in roll control is set based on the longitudinal acceleration Gx and the vehicle speed V. Braking force distribution is also possible in yaw rate control using a similar configuration. The braking force distribution unit 27 includes a first parameter calculation unit 40 that calculates a first variable parameter V1 based on the vehicle speed V, a second parameter calculation unit 41 that calculates a second variable parameter V2 based on the longitudinal acceleration Gx, multipliers 42 and 43, a gain multiplier 44, an adder 45, and a subtractor 46.

[0074] Multipliers 42 and 43, gain multiplier 44, and adder 45 calculate the braking force Bri = 0.5 × ΔBr × (1 + (V1 × V2)) distributed to the rear inner wheel. Subtractor 46 calculates the braking force Bfo = 0.5 × ΔBr × (1 - (V1 × V2)) distributed to the front outer wheel. The first variable parameter V1 is set to be greater than 0 when the vehicle speed V is above a predetermined value. Therefore, when the vehicle speed V is below the predetermined value (i.e., at low vehicle speeds), the same braking force of 0.5 × ΔBr is applied to the rear inner wheel and the front outer wheel. The second variable parameter V2 is set to increase as the longitudinal acceleration Gx increases. Therefore, the braking force is distributed such that the braking force distributed to the rear inner wheel increases as the longitudinal acceleration Gx increases.

[0075] Refer to Figure 3. When the vehicle behavior control selected by the target control selection unit 20 from among yaw rate control, roll control, or pitch control is switched, the braking force distribution unit 27 prioritizes executing the vehicle behavior control after the switch. For example, as shown in Figure 2, when vehicle 1 changes from a turning state to a straight-ahead state (i.e., when changing from the state indicated by arrow P2 to the state indicated by arrow P3), if the target control selection unit 20 selected roll control in the previous control cycle and selected yaw rate control in the current control cycle, the braking force distribution unit 27 will prioritize executing yaw rate control in the current control cycle.

[0076] In other words, if the vehicle behavior control selected by the target control selection unit 20 in accordance with the longitudinal acceleration Gx and lateral acceleration Gy detected in the previous control cycle (hereinafter referred to as "first control") differs from the vehicle behavior control selected by the target control selection unit 20 in accordance with the longitudinal acceleration Gx and lateral acceleration Gy detected in the current control cycle (hereinafter referred to as "second control"), the braking force distribution unit 27 will prioritize executing the second control in the current control cycle.

[0077] When the vehicle behavior control performed by the braking force distribution unit 27 switches from the first control to the second control, the braking force distribution unit 27 limits the rate of change of the braking force of each wheel 2 that accompanies the transition from the first control to the second control (i.e., it slows down the change). For example, when the vehicle behavior control performed by the braking force distribution unit 27 transitions from roll control to yaw rate control, the rate of change of the braking force of each wheel 2 is limited so that the braking force applied to each wheel 2 gradually changes from a state where the braking force of the front outer wheel and rear inner wheel is greater than that of the rear outer wheel and front inner wheel by a roll control amount ΔBr, to a state where the braking force applied to each wheel 2 is greater than that of the turning inner wheel by a yaw control amount ΔBγ.

[0078] For example, as shown in Figure 2, when roll control is performed during a left turn (P2) and then yaw rate control is performed during a turnout (P3), the rate at which the braking force applied to the right front wheel 2FR changes from ΔBr×Wfr / (Wfr+Wrl) to 0 may be limited, the rate at which the braking force applied to the left rear wheel 2RL changes from ΔBr×Wrl / (Wfr+Wrl) to ΔBγ×Wrl / (Wfl+Wrl) may be limited, and the rate at which the braking force applied to the left front wheel 2FL changes from 0 to ΔBγ×Wfl / (Wfl+Wrl) may be limited.

[0079] Figures 7(a) to 7(e) are time charts illustrating an example of roll control during cornering. Figures 7(a) to 7(e) show longitudinal acceleration Gx, lateral acceleration Gy, wheel loads on the front outer wheel and rear inner wheel, braking force distributed to the front outer wheel, and braking force distributed to the rear inner wheel, respectively. At time point t1, roll control is initiated when the absolute value of the lateral acceleration |Gy| is equal to or greater than the second threshold Th2 while the longitudinal acceleration Gx is less than the first threshold Th1.

[0080] During the period from time t1 to time t2, the deceleration of vehicle 1 increases as shown in Figure 7(a). As a result, as shown in Figure 7(c), the wheel load on the front outer wheel increases while the wheel load on the rear inner wheel decreases, resulting in a front-biased load distribution where the wheel load on the front outer wheel is higher than that on the rear inner wheel. Consequently, as shown in Figures 7(d) and 7(e), the braking force distribution ratio applied by roll control becomes larger for the front outer wheel than for the rear inner wheel.

[0081] From time t2 onward, the deceleration of vehicle 1 decreases, and then vehicle 1 begins to accelerate. As a result, as shown in Figure 7(c), the wheel load on the front outer wheel decreases while the wheel load on the rear inner wheel increases, and from time t3 onward, the load distribution becomes rearward, with the rear inner wheel having a higher wheel load than the front outer wheel. Consequently, as shown in Figures 7(d) and 7(e), the braking force distribution ratio applied to the rear inner wheel increases due to roll control, while the braking force distribution ratio applied to the front outer wheel decreases. From time t3 onward, the braking force distribution ratio of the rear inner wheel becomes greater than that of the front outer wheel. Subsequently, at time t4, roll control terminates when the absolute value of the lateral acceleration |Gy| falls below the second threshold Th2.

[0082] (operation) Figure 8 is a flowchart of an example of the vehicle behavior control selection process by the target control selection unit 20. In step S1, the longitudinal acceleration Gx and lateral acceleration Gy are detected by the acceleration sensor 15. Alternatively, the longitudinal acceleration Gx and lateral acceleration Gy may be estimated as described above. In step S2, the target control selection unit 20 determines whether the longitudinal acceleration Gx is greater than or equal to the first threshold Th and the absolute value of the lateral acceleration |Gy| is greater than or equal to the second threshold Th2.

[0083] If the longitudinal acceleration Gx is not greater than or equal to the first threshold Th, or if the absolute value of the lateral acceleration |Gy| is not greater than or equal to the second threshold Th2 (step S2:N), the process proceeds to step S4. If the longitudinal acceleration Gx is greater than or equal to the first threshold Th and the absolute value of the lateral acceleration |Gy| is greater than or equal to the second threshold Th2 (step S2:Y), the process proceeds to step S3. In step S3, the target control selection unit 20 selects yaw rate control as the vehicle behavior control to be executed with priority. The process then ends.

[0084] In step S4, the target control selection unit 20 determines whether the absolute value of the lateral acceleration |Gy| is greater than or equal to the second threshold Th2. If the absolute value of the lateral acceleration |Gy| is not greater than or equal to the second threshold Th2 (step S4:N), the process proceeds to step S6. If the absolute value of the lateral acceleration |Gy| is greater than or equal to the second threshold Th2 (step S4:Y), the process proceeds to step S5. In step S5, the target control selection unit 20 selects roll control as the vehicle behavior control to be executed with priority. The process then ends.

[0085] In step S6, the target control selection unit 20 determines whether the longitudinal acceleration Gx is below the third threshold. If the longitudinal acceleration Gx is not below the third threshold (step S6:N), the target control selection unit 20 terminates the process without selecting any of the yaw rate control, roll control, or pitch control. If the longitudinal acceleration Gx is below the third threshold (step S6:Y), the process proceeds to step S. In step S7, the target control selection unit 20 selects pitch control as the vehicle behavior control to be executed with priority. The process then ends.

[0086] In Figure 8, the priority order for selecting yaw rate control, roll control, and pitch control is determined. Therefore, yaw rate control, roll control, and pitch control are executed in that order of priority. However, the present invention is not limited to the order shown in Figure 8, and yaw rate control, roll control, and pitch control may be executed in other priority orders.

[0087] Figure 9 is a flowchart of an example of the process in yaw rate control. In step S10, the vehicle behavior acquisition unit 22 detects or estimates the actual yaw rate γa. In step S11, the target behavior setting unit 23 sets the target yaw rate γt. In step S12, the yaw control amount calculation unit 24 determines whether the output condition for outputting braking force by yaw rate control to the wheel 2 is met. If the output condition is not met (step S12:N), the process ends without outputting braking force by yaw rate control. If the output condition is met (step S12:Y), the process proceeds to step S13.

[0088] In step S13, the yaw control amount calculation unit 24 outputs a yaw control amount ΔBγ = G1 × Δγ corresponding to the yaw rate deviation Δγ = γt - γa to the braking force distribution unit 27. In step S14, the wheel load estimation unit 21 estimates the wheel load of each wheel. In step S15, the braking force distribution unit 27 distributes the braking force ΔBγ to the front inner wheel and the rear inner wheel in a braking force distribution according to the ratio of the wheel loads of the front inner wheel and the rear inner wheel. In step S16, the braking force distribution unit 27 controls the braking device 12 to apply the braking force distributed in step S15 to the front inner wheel and the rear inner wheel.

[0089] Figure 10 is a flowchart of an example of the process in roll control. In step S20, the vehicle behavior acquisition unit 22 detects or estimates the actual roll angle θra. In step S21, the target behavior setting unit 23 sets the target roll angle θrt. In step S22, the roll control amount calculation unit 25 determines whether the output condition for outputting a braking force due to roll control to the wheel 2 is met. If the output condition is not met (step S22:N), the process ends without outputting a braking force due to roll control. If the output condition is met (step S22:Y), the process proceeds to step S23.

[0090] In step S23, the roll control amount calculation unit 25 outputs a roll control amount ΔBr = G2 × Δθr corresponding to the roll angle deviation Δθr = θrt - θra to the braking force distribution unit 27. In step S24, the wheel load estimation unit 21 estimates the wheel load of each wheel. In step S25, the braking force distribution unit 27 distributes the braking force ΔBr to the front outer wheel and the rear inner wheel in a braking force distribution according to the ratio of the wheel loads of the front outer wheel and the rear inner wheel. In step S26, the braking force distribution unit 27 controls the braking device 12 to apply the braking force distributed in step S25 to the front outer wheel and the rear inner wheel.

[0091] Figure 11 is a flowchart of an example of the process in pitch control. In step S30, the vehicle behavior acquisition unit 22 detects or estimates the actual pitch angle θpa. In step S31, the target behavior setting unit 23 sets the target pitch angle θpt. In step S32, the pitch control amount calculation unit 26 determines whether the output condition for outputting braking force due to pitch control to the wheel 2 is met. If the output condition is not met (step S32:N), the process ends without outputting braking force due to pitch control. If the output condition is met (step S32:Y), the process proceeds to step S33.

[0092] In step S33, the pitch control amount calculation unit 26 outputs a pitch control amount ΔBp = G3 × Δθp corresponding to the pitch angle deviation Δθp = θpt - θpa to the braking force distribution unit 27. In step S34, the braking force distribution unit 27 distributes the braking force ΔBp to the right rear wheel 2RR and the left rear wheel 2RL at the same distribution ratio. In step S35, the braking force distribution unit 27 controls the braking device 12 to apply the braking force distributed in step S34 to the right rear wheel 2RR and the left rear wheel 2RL.

[0093] (Effects of the embodiment) (1) In the vehicle control method, the longitudinal acceleration, lateral acceleration, steering angle, and vehicle speed of the vehicle are detected or estimated, the actual yaw rate, actual roll angle, and actual pitch angle of the vehicle are detected or estimated, the target yaw rate, target roll angle, and target pitch angle of the vehicle are set based on the steering angle and vehicle speed, and in accordance with the longitudinal acceleration and lateral acceleration, the system selects which of the following to perform: yaw rate control, which controls the vehicle's yaw rate by applying braking force to the wheels based on the yaw rate deviation, which is the deviation of the actual yaw rate from the target yaw rate; roll control, which controls the vehicle's roll angle by applying braking force to the wheels based on the roll angle deviation, which is the deviation of the actual roll angle from the target roll angle; and pitch control, which controls the vehicle's pitch angle by applying braking force to the wheels based on the pitch angle deviation, which is the deviation of the actual pitch angle from the target pitch angle.

[0094] In roll control, the wheel load of the outer front wheel (outer wheel during turning) and the wheel load of the inner rear wheel (inner wheel during turning) are estimated based on longitudinal and lateral acceleration. Braking force is then applied to the outer front wheel and the inner rear wheel in a braking force distribution that corresponds to the ratio of the wheel loads of the outer front wheel and the inner rear wheel. This allows for the distribution of braking force to be changed in response to changes in the vehicle's state during cornering, thereby suppressing the vehicle's behavior and improving its stability. Furthermore, in roll control, braking force is distributed to the front outer wheel and rear inner wheel according to the wheel load, which suppresses slippage caused by applying a large braking force to the wheel with the smallest wheel load.

[0095] (2) If the longitudinal acceleration is greater than or equal to the positive first threshold and the absolute value of the lateral acceleration is greater than or equal to the second threshold, yaw rate control may be given priority. If the longitudinal acceleration is less than the first threshold and the absolute value of the lateral acceleration is greater than or equal to the second threshold, roll control may be given priority. If the longitudinal acceleration is less than or equal to the negative third threshold and the absolute value of the lateral acceleration is less than the second threshold, pitch control may be given priority. This makes it possible to change the distribution of braking force in accordance with the changes in the state of the vehicle accompanying the turn and suppress the behavior that occurs in the vehicle.

[0096] (3) If the first control selected from among yaw rate control, roll control, or pitch control according to the previously detected or estimated longitudinal acceleration and lateral acceleration is different from the second control selected according to the currently detected or estimated longitudinal acceleration and lateral acceleration, the second control may be given priority and the rate of change when the braking force applied to each wheel changes as a result of the transition from the first control to the second control may be limited. This makes it possible to suppress the sudden change in braking force distribution that occurs when the control switches, which can result in large accelerations or jerks.

[0097] (4) In yaw rate control, the yaw rate of the vehicle may be controlled by adjusting the braking force distribution between the inner wheel and the outer wheel during a turn. This can suppress the occurrence of understeer or oversteer during a turn (for example, the occurrence of understeer during turnout). (5) In pitch control, the pitch angle of the vehicle may be controlled by adjusting the braking force distribution between the front and rear wheels. This can suppress pitch behavior during cornering (for example, during turn-in). [Explanation of Symbols]

[0098] 1...Vehicle, 2FR...Right front wheel, 2FL...Left front wheel, 2RR...Right rear wheel, 2RL...Left rear wheel, 10...Vehicle control device, 12...Braking device, 13...Steering angle sensor, 14...Vehicle speed sensor, 15...Accelerometer, 16...Gyro sensor, 17...Controller, 17a...Processor, 17b...Memory device, 20...Target control selection unit, 21...Wheel load estimation unit, 22...Vehicle behavior acquisition unit, 23...Target behavior setting unit, 24...Yaw control amount calculation unit, 25...Roll control amount calculation unit, 26...Pitch control amount calculation unit, 27...Braking force distribution unit, 30...First control amount calculation unit, 31...Second control amount calculation unit, 32, 42, 43...Multiplier, 33, 44...Gain multiplication unit, 34...Limiting unit, 40...First parameter calculation unit, 41...Second parameter calculation unit, 45...Adder, 46...Subtractor

Claims

1. The vehicle's longitudinal acceleration, lateral acceleration, steering angle, and vehicle speed are detected or estimated. The actual yaw rate, actual roll angle, and actual pitch angle of the vehicle are detected or estimated. Based on the steering angle and the vehicle speed, the target yaw rate, target roll angle, and target pitch angle of the vehicle are set. Select which of the following will be executed: yaw rate control, which controls the vehicle's yaw rate by applying braking force to the wheels based on the yaw rate deviation, which is the deviation of the actual yaw rate from the target yaw rate, in accordance with the longitudinal acceleration and the lateral acceleration; roll control, which controls the vehicle's roll angle by applying braking force to the wheels based on the roll angle deviation, which is the deviation of the actual roll angle from the target roll angle; and pitch control, which controls the vehicle's pitch angle by applying braking force to the wheels based on the pitch angle deviation, which is the deviation of the actual pitch angle from the target pitch angle. In the roll control described above, the wheel load of the front outer wheel (the front wheel on the outside of the turn) and the wheel load of the rear inner wheel (the rear wheel on the inside of the turn) are estimated based on the longitudinal acceleration and the lateral acceleration, and braking force is applied to the front outer wheel and the rear inner wheel in a braking force distribution corresponding to the ratio of the wheel load of the front outer wheel and the wheel load of the rear inner wheel. A vehicle control method characterized by the following:

2. If the longitudinal acceleration is greater than or equal to a positive first threshold and the absolute value of the lateral acceleration is greater than or equal to a second threshold, the yaw rate control is given priority and executed. If the longitudinal acceleration is less than the first threshold and the absolute value of the lateral acceleration is greater than or equal to the second threshold, the roll control is given priority and executed. If the longitudinal acceleration is below a negative third threshold and the absolute value of the lateral acceleration is less than a second threshold, the pitch control is prioritized and executed. The vehicle control method according to feature 1.

3. If the first control selected from the yaw rate control, roll control, or pitch control according to the previously detected or estimated longitudinal acceleration and lateral acceleration is different from the second control selected according to the currently detected or estimated longitudinal acceleration and lateral acceleration, the second control is given priority and executed. The speed at which the braking force applied to each wheel changes during the transition from the first control to the second control is limited. The vehicle control method according to feature 1.

4. The vehicle control method according to any one of claims 1 to 3, characterized in that the yaw rate of the vehicle is controlled by adjusting the distribution of braking force between the wheel on the inside of the turn and the wheel on the outside of the turn in the yaw rate control.

5. The vehicle control method according to any one of claims 1 to 3, characterized in that the pitch angle of the vehicle is controlled by adjusting the distribution of braking force between the front wheels and the rear wheels in the pitch control.

6. A process for estimating or obtaining detected values ​​of the vehicle's longitudinal acceleration, lateral acceleration, steering angle, and vehicle speed. A process for estimating the actual yaw rate, actual roll angle, and actual pitch angle of the vehicle, or for obtaining these detected values, A process for setting the target yaw rate, target roll angle, and target pitch angle of the vehicle based on the steering angle and the vehicle speed, A process to select which of the following to execute: yaw rate control, which controls the vehicle's yaw rate by applying braking force to the wheels based on the yaw rate deviation, which is the deviation of the actual yaw rate from the target yaw rate, in accordance with the longitudinal acceleration and the lateral acceleration; roll control, which controls the vehicle's roll angle by applying braking force to the wheels based on the roll angle deviation, which is the deviation of the actual roll angle from the target roll angle; and pitch control, which controls the vehicle's pitch angle by applying braking force to the wheels based on the pitch angle deviation, which is the deviation of the actual pitch angle from the target pitch angle. In the roll control described above, the wheel load of the front outer wheel, which is the front wheel on the outside of the turn, and the wheel load of the rear inner wheel, which is the rear wheel on the inside of the turn, are estimated based on the longitudinal acceleration and the lateral acceleration, and braking force is applied to the front outer wheel and the rear inner wheel in a braking force distribution corresponding to the ratio of the wheel load of the front outer wheel and the wheel load of the rear inner wheel. A vehicle control device characterized by comprising a controller that performs the following actions.

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