Brake control system

Abstract

To control a posture of a vehicle which is under braking, in a brake control device of a vehicle.SOLUTION: A brake control device 10 controls a brake force of a vehicle by operating a regeneration brake device and a friction brake device. The brake control device 10 comprises a posture target calculation part 12 for calculating a target of a pitching posture of the vehicle and a target of a sinking posture of the vehicle on the basis of a target of the deceleration of the vehicle. The brake control device 10 comprises a distribution ratio calculation part 13 for calculating a fore-and-aft distribution ratio and a friction regeneration ratio so as to make a posture of the vehicle follow a posture indicated by the target of the pitching posture and the target of the sinking posture. The brake control device 10 comprises an indication value calculation part for calculating an indication value for operating the friction brake device and the regeneration brake device on the basis of a requirement brake force being the target of the brake force of the vehicle, the fore-and-aft distribution ratio and the friction regeneration ratio.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a braking control device for a vehicle.

Background Art

[0002] When braking a vehicle, the vehicle may pitch in the nose dive direction. In a vehicle, a force acting in a direction to suppress pitching motion is generated by the application of braking force. Specifically, when the braking force applied to the front wheels is the front wheel braking force and the braking force applied to the rear wheels is the rear wheel braking force, an anti-dive force corresponding to the front wheel braking force acts on the vehicle body, and an anti-lift force corresponding to the rear wheel braking force acts on the vehicle body. Even when the total braking force of the entire vehicle is the same when the anti-dive force and the anti-lift force act, if the distribution ratio between the front wheel braking force and the rear wheel braking force changes, the magnitudes of the anti-dive force and the anti-lift force acting on the vehicle body may change. As a result, the pitching posture of the vehicle may change.

[0003] The vehicle braking control device disclosed in Patent Document 1 is applied to a vehicle including a friction braking device and a regenerative braking device. In this braking control device, when varying the regenerative braking force and varying the distribution ratio between the front wheel braking force and the rear wheel braking force, a limit is provided for the change rate of the regenerative braking force. Thereby, it is configured to gently change the distribution ratio between the front wheel braking force and the rear wheel braking force.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The point at which a braking force acts on a wheel when frictional braking force is applied to it is different from the point at which a braking force acts on a wheel when regenerative braking force is applied to it. Therefore, even if the magnitude of the overall braking force on the wheel is the same, the anti-dive force and anti-lift force acting on the vehicle body will differ depending on whether frictional braking force is applied to the wheel or regenerative braking force is applied to the wheel.

[0006] For example, when the regenerative braking force is distributed in large quantities, the rate at which the vehicle's pitching posture changes in response to changes in braking force becomes faster. On the other hand, when the regenerative braking force is distributed in small quantities, the rate at which the vehicle's pitching posture changes in response to changes in braking force becomes slower. Also, when a large quantity of regenerative braking force is distributed to the rear wheels, the anti-lift force decreases, resulting in less dive of the vehicle.

[0007] Brake control devices like the one described in Patent Document 1, which do not take into account the relationship between the distribution of regenerative braking force and the vehicle's attitude, have room for improvement in controlling the vehicle's attitude. [Means for solving the problem]

[0008] A braking control device for solving the above problems is applied to a vehicle comprising: a regenerative braking device that generates regenerative braking force to be applied to at least one of the front wheels and rear wheels of the vehicle; and a friction braking device that generates friction braking force to be applied to the front wheel and friction braking force to be applied to the rear wheel, and controls the braking force of the vehicle by operating the regenerative braking device and the friction braking device, wherein for the wheel to which regenerative braking force can be applied among the front wheel and the rear wheel, the ratio of the friction braking force applied to the wheel to the braking force applied to the wheel is set to friction braking force The gist of the system is that it comprises: an attitude target calculation unit that calculates an attitude target for the vehicle's pitching attitude and an attitude target for the vehicle's sinking attitude based on an attitude target for the vehicle's deceleration degree; a distribution ratio calculation unit that calculates the front-to-rear distribution ratio and the friction regeneration ratio so that the vehicle's attitude follows the attitude indicated by the pitching attitude target and the sinking attitude target; and an instruction value calculation unit that calculates instruction values ​​for operating the friction braking device and the regenerative braking device based on the required braking force which is the vehicle braking force target, the front-to-rear distribution ratio and the friction regeneration ratio.

[0009] According to the above configuration, frictional braking force and regenerative braking force can be controlled according to the front-to-rear distribution ratio and friction regeneration ratio calculated so that the vehicle's attitude follows the attitude target corresponding to the deceleration target. This makes it possible to correlate the pitching attitude and sinking attitude with the deceleration target. By controlling the vehicle's attitude in response to deceleration, it is possible to suppress the discrepancy between the vehicle's attitude estimated by the occupants from the deceleration and the actual vehicle's attitude. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram showing the braking control device of the first embodiment and the vehicle that is controlled by the braking control device. [Figure 2] Figure 2 is a diagram illustrating the distribution of braking force. [Figure 3] Figure 3 is a schematic diagram illustrating the forces acting on a vehicle due to braking force. [Figure 4]Figure 4 is a block diagram illustrating the functions performed by the braking control device of the first embodiment. [Figure 5] Figure 5 is a flowchart showing the processing flow performed by the braking control device of the first embodiment. [Figure 6] Figure 6 shows examples of the front-to-rear distribution ratio and friction regeneration ratio calculated by the braking control device of the first embodiment. [Figure 7] Figure 7 illustrates the relationship between the pitch angle and bounce amount controlled by the braking control device of the first embodiment. [Figure 8] Figure 8 shows examples of the front-to-rear distribution ratio and friction regeneration ratio calculated by the modified braking control system. [Figure 9] Figure 9 is a block diagram illustrating the functions performed by the braking control device of the second embodiment. [Figure 10] Figure 10 illustrates the control concept in the braking control device of the second embodiment by showing an example of the ideal braking force distribution ratio between the front wheel braking force and the rear wheel braking force. [Figure 11] Figure 11 shows the average rate of change of pitch angle controlled by the braking control device of the second embodiment. [Figure 12] Figure 12 shows the average rate of change of bounce amount controlled by the braking control device of the second embodiment. [Figure 13] Figure 13 is a timing chart showing the changes in pitch angular velocity, pitch angle, and braking force controlled by the braking control device of the second embodiment. [Figure 14] Figure 14 illustrates the change in pitch rate when wheel slip occurs. [Figure 15] Figure 15 is a flowchart showing the processing flow performed by the braking control device of the third embodiment. [Figure 16] Figure 16 illustrates the friction regeneration ratio calculated by the braking control device of the third embodiment. [Figure 17] Figure 17 is a timing chart showing the changes in braking force and pitch rate controlled by the braking control device of the third embodiment.

Embodiment for Carrying out the Invention

[0011] (First Embodiment) Hereinafter, a first embodiment of the braking control device will be described with reference to FIGS. 1 to 7. FIG. 1 shows a braking control device 10 and a vehicle 90 equipped with the braking control device 10.

[0012] <Vehicle> The vehicle 90 is, for example, a four-wheel vehicle having two front wheels and two rear wheels as wheels. The vehicle 90 includes a suspension device for suspending the wheels. The vehicle 90 includes a front-wheel suspension device attached to the left front wheel and the right front wheel. The vehicle 90 includes a rear-wheel suspension device attached to the left rear wheel and the right rear wheel.

[0013] As shown in FIG. 1, the vehicle 90 includes a friction braking device 70 and a regenerative braking device 80. The friction braking device 70 and the regenerative braking device 80 are braking devices that apply a braking force to the wheels. The braking control device 10 has a function of operating the friction braking device 70. The vehicle 90 includes a regenerative control device 20 having a function of operating the regenerative braking device 80.

[0014] The vehicle 90 includes an in-vehicle network. The vehicle 90 includes a plurality of processing circuits connected to the in-vehicle network. The braking control device 10 and the regenerative control device 20 are examples of processing circuits. Each processing circuit connected to the in-vehicle network can communicate with each other via the in-vehicle network.

[0015] The vehicle 90 includes a braking operation member 92. The braking operation member 92 is attached at a position where the driver of the vehicle 90 can operate it. The braking operation member 92 is, for example, a brake pedal.

[0016] Vehicle 90 is equipped with various sensors. Figure 1 shows brake sensor SE1 as an example of these sensors. Detection signals from the various sensors are input to the braking control device 10 via the in-vehicle network.

[0017] The brake sensor SE1 can detect the amount Bp of the braking operating member 92. The amount Bp of the braking operating member 92 can be referenced when calculating the target value of the braking force to be applied to the vehicle 90. The brake sensor SE1 may also be a sensor that detects the pressure applied to the braking operating member 92 in order to operate it.

[0018] <Brake device> The friction braking device 70 can generate a frictional braking force to be applied to the wheels. An example of the friction braking device 70 is a hydraulic braking device. The friction braking device 70 is equipped with a braking mechanism corresponding to each wheel. The braking mechanism consists of a rotating body that rotates integrally with the wheel, a friction material that can be pressed against the rotating body, and a wheel cylinder that presses the friction material against the rotating body according to the hydraulic pressure. An example of the braking mechanism is a disc brake. The braking mechanism may also be a drum brake. Another example of the friction braking device 70 is an electric braking device that mechanically transmits the driving force of an electric motor to press the friction material against the rotating body.

[0019] The regenerative braking system 80 can generate regenerative braking force to be applied to the wheels. The regenerative braking system 80 is connected to the battery of the vehicle 90. One example of the regenerative braking system 80 is a motor generator. By making the motor generator function as a generator, regenerative braking force can be applied to the wheels. Another example of the regenerative braking system 80 is an in-wheel motor. The electricity generated by the application of regenerative braking force is used to charge the battery.

[0020] In vehicle 90, the friction braking system 70 can independently adjust the front wheel friction braking force Fxfb, which is the friction braking force applied to the front wheels, and the rear wheel friction braking force Fxrb, which is the friction braking force applied to the rear wheels.

[0021] In vehicle 90, the regenerative braking system 80 can independently adjust the front wheel regenerative braking force Fxfd, which is the regenerative braking force applied to the front wheels, and the rear wheel regenerative braking force Fxrd, which is the regenerative braking force applied to the rear wheels.

[0022] <Regenerative Control System> The regenerative braking control device 20 activates the regenerative braking device 80 based on the requested regenerative braking force. As will be described in detail later, the requested regenerative braking force is calculated by the braking control device 10 as the requested regenerative braking force value FxdR. The regenerative braking control device 20 can transmit the effective regenerative braking force value Fxd, which represents the magnitude of the regenerative braking force actually applied to the vehicle 90, to the braking control device 10.

[0023] If the maximum regenerative braking force that the regenerative braking device 80 can generate is smaller than the regenerative braking force request value FxdR, the actual regenerative braking force value Fxd may be smaller than the regenerative braking force request value FxdR. For example, if the remaining charge of the battery installed in the vehicle 90 is greater than a threshold, the regenerative control device 20 may limit the maximum regenerative braking force to a smaller value in order to reduce the power generated when applying regenerative braking force.

[0024] <Braking force> Let's explain each braking force. The sum of the front wheel friction braking force Fxfb and the front wheel regenerative braking force Fxfd is called the front wheel braking force Fxf. The sum of the rear wheel friction braking force Fxrb and the rear wheel regenerative braking force Fxrd is called the rear wheel braking force Fxr. The vehicle braking force Fx, which is the braking force applied to the vehicle 90, is the sum of the front wheel braking force Fxf and the rear wheel braking force Fxr. The effective regenerative braking force Fxd corresponds to the sum of the front wheel regenerative braking force Fxfd and the rear wheel regenerative braking force Fxrd.

[0025] The front wheel braking force Fxf and rear wheel braking force Fxr can be expressed using the vehicle braking force Fx and the front-to-rear distribution ratio n. The front wheel friction braking force Fxfb and front wheel regenerative braking force Fxfd can be expressed using the front wheel braking force Fxf and the front wheel friction regeneration ratio nf. The rear wheel friction braking force Fxrb and rear wheel regenerative braking force Fxrd can be expressed using the rear wheel braking force Fxr and the rear wheel friction regeneration ratio nr.

[0026] Using Figure 2, we will explain the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, the rear-wheel friction regeneration ratio nr, and the braking force applied to the wheels. Figure 2 shows an example where the front-wheel friction braking force Fxfb, the front-wheel regenerative braking force Fxfd, the rear-wheel friction braking force Fxrb, and the rear-wheel regenerative braking force Fxrd are applied. As shown in Figure 2, the front-to-rear distribution ratio n is the sum of the front-wheel braking force Fxf and the rear-wheel braking force Fxr, that is, the ratio of the front-wheel braking force Fxf to the vehicle braking force Fx. The front-to-rear distribution ratio n is a value between "0" and "1". The front-to-rear friction regeneration ratio nf is the ratio of the front-wheel friction braking force Fxfb to the front-wheel braking force Fxf. The front-to-rear distribution ratio nf is a value between "0" and "1". The rear-wheel friction regeneration ratio nr is the ratio of the rear-wheel friction braking force Fxrb to the rear-wheel braking force Fxr. The rear-wheel friction regeneration ratio nr is a value between "0" and "1".

[0027] As will be explained in more detail later, the braking control device 10 can calculate the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr in order to adjust the braking force applied to each wheel. The braking control device 10 can operate the friction brakes 70 and the regenerative brakes 80 so that the braking force distributed according to the calculated values ​​of the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr is applied to the wheels.

[0028] <Vehicle movement> Using Figure 3, we will illustrate the forces acting on the vehicle 90 when it is being braked, and explain the sprung mass motion in the vehicle 90.

[0029] Figure 3 shows vehicle 90 viewed from the side. Figure 3 illustrates the left front wheel FL and the left rear wheel RL. Figure 3 also shows the vehicle's center of gravity GC.

[0030] In the following explanations referring to Figure 3, the explanation may focus on the left front wheel FL, and omit the explanation of the right front wheel, which is symmetrical to the left front wheel FL. Similarly, the explanation may focus on the left rear wheel RL, and omit the explanation of the right rear wheel, which is symmetrical to the left rear wheel RL.

[0031] Figure 3 shows the first distance Lf as the horizontal distance between the vehicle's center of gravity GC and the front axle in the longitudinal direction of vehicle 90. Figure 3 also shows the second distance Lr as the horizontal distance between the vehicle's center of gravity GC and the rear axle in the longitudinal direction of vehicle 90. The sum of the first distance Lf and the second distance Lr corresponds to the wheelbase L of vehicle 90.

[0032] Figure 3 shows arrows illustrating the pitching moment M generated around the vehicle's center of gravity GC when the vehicle 90 is braked. The pitching moment M can be calculated based on the inertial force acting on the vehicle's center of gravity GC, the height from the road surface to the vehicle's center of gravity GC, and the first distance Lf and second distance Lr. When the vehicle 90 is braked, a forward inertial force acts on the vehicle's center of gravity GC. Therefore, the pitching moment M is a force that displaces the front part of the vehicle body 91, which is the part on the front wheel side, downward. The pitching moment M is also a force that displaces the rear part of the vehicle body 91, which is the part on the rear wheel side, upward. In other words, the pitching moment M is a force that tilts the vehicle body 91 forward.

[0033] The degree to which the vehicle 90 is tilted forward is expressed as the pitch angle. In this embodiment, the pitch angle is larger the further down the front of the vehicle 90 is positioned compared to when the vehicle 90 is horizontal. That is, a larger pitch angle indicates that the vehicle 90 is tilted forward more significantly. The closer the pitch angle is to "0", the smaller the degree of tilt. In other words, the closer the pitch angle is to "0", the closer the vehicle 90 is to a horizontal position.

[0034] The motion of the vehicle body 91 rising and falling is called bounce motion. In this embodiment, the amount by which the vehicle's center of gravity GC sinks due to the bounce motion is called the bounce amount. In this embodiment, the bounce amount takes a value of "0" or greater when the vehicle body 91 sinks. That is, the more the vehicle body 91 sinks, the greater the bounce amount becomes. In Figure 3, the arrow indicating the direction in which the vehicle's center of gravity GC sinks is shown as the bounce direction Z.

[0035] Frictional braking force acts at the point of contact between the wheel and the road surface. On the other hand, regenerative braking force acts at the point where the wheel is attached to the axle. Figure 3 shows the first point of application PA1 where the front wheel frictional braking force Fxfb acts, the second point of application PA2 where the front wheel regenerative braking force Fxfd acts, the third point of application PA3 where the rear wheel frictional braking force Fxrb acts, and the fourth point of application PA4 where the rear wheel regenerative braking force Fxrd acts.

[0036] Figure 3 shows the instantaneous center of rotation of the wheels. The instantaneous center of rotation of the left front wheel FL when the vehicle 90 is being braked is shown as the front wheel rotation center Cf. The angle between the straight line connecting the first point of application PA1 and the front wheel rotation center Cf and the road surface is shown as the first angle θfb. The angle between the straight line connecting the second point of application PA2 and the front wheel rotation center Cf and the road surface is shown as the second angle θfd. From the positional relationship between the first point of application PA1 and the second point of application PA2 with respect to the front wheel rotation center Cf, the first angle θfb is larger than the second angle θfd. Also, the instantaneous center of rotation of the left rear wheel RL when the vehicle 90 is being braked is shown as the rear wheel rotation center Cr. The angle between the straight line connecting the third point of application PA3 and the rear wheel rotation center Cr and the road surface is shown as the third angle θrb. The fourth angle θrd is the angle between the straight line connecting the fourth point of application PA4 and the rear wheel rotation center Cr, and the road surface. Based on the positional relationship between the third point of application PA3 and the fourth point of application PA4 with respect to the rear wheel rotation center Cr, the third angle θrb is larger than the fourth angle θrd.

[0037] The position of each instantaneous center of rotation is determined by the characteristics of the suspension system. The positions of each instantaneous center of rotation shown in Figure 3 are examples and do not represent the actual positions of the instantaneous centers of rotation. Therefore, the magnitudes of the first angle θfb, second angle θfd, third angle θrb, and fourth angle θrd do not represent the actual magnitudes of the angles.

[0038] The forces that change the attitude of vehicle 90 will be explained using Figure 3. In Figure 3, the anti-dive force FAD, which acts on vehicle 90 by the front suspension system, is shown with a white arrow. In Figure 3, the anti-lift force FAL, which acts on vehicle 90 by the rear suspension system, is shown with a white arrow. Note that the white arrows indicate the direction of the force and do not represent the actual magnitude of the force.

[0039] This section explains the anti-dive force (FAD). The anti-dive force (FAD) is a force that acts when braking force is applied to the front wheels. The anti-dive force (FAD) is a force that suppresses the front of the vehicle from sinking. The direction in which the anti-dive force (FAD) acts is in the direction that displaces the front of the vehicle away from the road surface.

[0040] This section explains the anti-lift force FAL. The anti-lift force FAL is a force that acts when braking force is applied to the rear wheels. The anti-lift force FAL is a force that suppresses the rear of the vehicle from lifting off the ground. The direction in which the anti-lift force FAL acts is in the direction that displaces the rear of the vehicle closer to the road surface.

[0041] The anti-dive force FAD can be expressed by the following relation (Equation 1). The anti-lift force FAL can be expressed by the following relation (Equation 2).

[0042]

number

[0043] As shown in Figure 3, since the first angle θfb is larger than the second angle θfd, the front wheel friction braking force Fxfb contributes more to the anti-dive force FAD than the front wheel regenerative braking force Fxfd. In other words, if the ratio of the front wheel friction braking force Fxfb to the total front wheel braking force Fxf is increased compared to the ratio of the front wheel regenerative braking force Fxfd to the total front wheel braking force Fxf, in other words, if the front wheel friction regeneration ratio nf is increased, the anti-dive force FAD will increase. On the other hand, if the ratio of the front wheel regenerative braking force Fxfd to the total front wheel braking force Fxf is increased compared to the ratio of the front wheel friction braking force Fxfb to the total front wheel braking force Fxf, in other words, if the front wheel friction regeneration ratio nf is decreased, the anti-dive force FAD will decrease.

[0044] As shown in relational equation (Equation 2), the anti-lift force FAL is greater when the vehicle braking force Fx is greater, given that the front-to-rear weight distribution ratio n is the same. The anti-lift force FAL is greater when the front-to-rear weight distribution ratio n is smaller, given that the vehicle braking force Fx is the same. In other words, the anti-lift force FAL is greater when the rear wheel braking force Fxr is greater.

[0045] As shown in Figure 3, since the third angle θrb is larger than the fourth angle θrd, the rear-wheel friction braking force Fxrb contributes more to the anti-lift force FAL than the rear-wheel regenerative braking force Fxrd. In other words, if the ratio of rear-wheel friction braking force Fxrb to rear-wheel braking force Fxr is increased compared to the ratio of rear-wheel regenerative braking force Fxrd to rear-wheel braking force Fxr, in other words, if the rear-wheel friction regeneration ratio nr is increased, the anti-lift force FAL will increase. On the other hand, if the ratio of rear-wheel regenerative braking force Fxrd to rear-wheel braking force Fxr is increased compared to the ratio of rear-wheel friction braking force Fxrb to rear-wheel braking force Fxr, in other words, if the rear-wheel friction regeneration ratio nr is decreased, the anti-lift force FAL will decrease.

[0046] <Braking control device> The braking control device 10 is composed of a processing circuit that controls the vehicle 90. The braking control device 10 controls the braking force of the vehicle 90 by activating the regenerative braking device 80 and the friction braking device 70 according to the target deceleration degree of the vehicle 90.

[0047] The braking control device 10 is composed of multiple functional units that perform various types of control. Figure 1 shows, as an example of a functional unit, a target deceleration calculation unit 11, a target attitude calculation unit 12, a distribution ratio calculation unit 13, a command value calculation unit 14, and a friction control unit 15. Each functional unit of the braking control device 10 is capable of sending and receiving information from one another.

[0048] <Target deceleration calculation section> The target deceleration calculation unit 11 can calculate the target deceleration DVT as a target for the degree of deceleration of the vehicle 90. Deceleration indicates the rate of change of the vehicle 90's speed. In this embodiment, deceleration takes a positive value when the vehicle 90 is decelerating. Deceleration takes a larger value the greater the change in the vehicle 90's speed in the deceleration direction.

[0049] The target deceleration calculation unit 11 calculates the target deceleration DVT based on the manipulated variable Bp. The target deceleration calculation unit 11 calculates a larger target deceleration DVT the larger the manipulated variable Bp is. Furthermore, the target deceleration calculation unit 11 can also calculate the required braking force FxR based on the manipulated amount Bp as the target vehicle braking force Fx for making the vehicle 90 decelerate in line with the target deceleration DVT.

[0050] <Posture target calculation section> The attitude target calculation unit 12 calculates target pitching attitude and target sinking attitude of the vehicle 90 based on the target deceleration DVT. For example, the target pitching attitude could be a target value for the pitch angle. The target pitching attitude could also be a target value for the pitch moment that achieves the target pitch angle. For example, the target sinking attitude could be a target value for the bounce amount. The target sinking attitude could also be a target value for the bounce force that achieves the target bounce amount.

[0051] The functions of the posture target calculation unit 12 will be explained in detail using Figure 4. The attitude target calculation unit 12 obtains the target deceleration DVT calculated by the target deceleration calculation unit 11. The attitude target calculation unit 12 calculates the target pitch angle Θreq as the target value of the pitch angle. The attitude target calculation unit 12 calculates the target pitch moment Mreq to achieve the target pitch angle Θreq. Here, the moment in the backward rotation direction generated by the action of the front wheel anti-dive force FAD and the rear wheel anti-lift force FAL is defined as the controllable moment Ma. The controllable moment Ma is the moment that acts in the direction of suppressing the pitching moment M. The target pitch moment Mreq can be said to be the target value of the moment obtained by suppressing the pitching moment M with the controllable moment Ma. The attitude target calculation unit 12 calculates the target bounce amount DZreq as the target value of the bounce amount. The attitude target calculation unit 12 calculates the target bounce force Zreq to achieve the target bounce amount DZreq.

[0052] The attitude target calculation unit 12 calculates a target pitch angle Θreq such that the pitching motion of the vehicle 90 increases as the target deceleration DVT increases. Based on the target pitch angle Θreq, the attitude target calculation unit 12 calculates a target pitch moment Mreq such that it increases as the target deceleration DVT increases. The attitude target calculation unit 12 calculates a target bounce amount DZreq such that the bounce motion of the vehicle 90 increases as the target deceleration DVT increases. Based on the target bounce amount DZreq, the attitude target calculation unit 12 calculates a target bounce force Zreq such that it increases as the target deceleration DVT increases.

[0053] The attitude target calculation unit 12 may calculate the target pitch moment Mreq using a function corresponding to the target deceleration DVT based on the relationship between the target pitch angle Θreq and the target pitch moment Mreq, with the target deceleration DVT as input. Similarly, the attitude target calculation unit 12 may calculate the target bounce force Zreq using a function corresponding to the target deceleration DVT based on the relationship between the target bounce amount DZreq and the target bounce force Zreq, with the target deceleration DVT as input.

[0054] An example of how the target pitch moment Mreq and target bounce force Zreq are calculated will be described. For example, the attitude target calculation unit 12 stores a calculation map 12a for calculating the target pitch moment Mreq and target bounce force Zreq corresponding to the target deceleration DVT. The calculation map 12a has relationships set up in advance, calculated through experiments or the like, as the relationship between the target deceleration DVT, the target pitch moment Mreq, and the target bounce force Zreq. Figure 4 illustrates the relationship between the target deceleration DVT, the target pitch moment Mreq, and the target bounce force Zreq shown in the calculation map 12a.

[0055] The attitude target calculation unit 12 calculates a larger target pitch moment Mreq based on the calculation map 12a, where the larger the target deceleration DVT, the larger the target pitch moment Mreq. Figure 4 shows an example of the relationship between the target deceleration DVT and the target pitch moment Mreq, where the target pitch moment Mreq increases linearly as the target deceleration DVT increases. The relationship between the target deceleration DVT and the target pitch moment Mreq is not limited to the example shown in Figure 4.

[0056] The attitude target calculation unit 12 calculates a larger target bounce force Zreq based on the calculation map 12a, where the larger the target deceleration DVT, the larger the target bounce force Zreq. Figure 4 shows an example of the relationship between the target deceleration DVT and the target bounce force Zreq, where the target bounce force Zreq increases linearly as the target deceleration DVT increases. The relationship between the target deceleration DVT and the target bounce force Zreq is not limited to the example shown in Figure 4.

[0057] <Allocation Ratio Calculation Unit> The distribution ratio calculation unit 13 performs a distribution ratio calculation process. In the distribution ratio calculation process, the distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr so that the vehicle 90's posture follows the posture indicated by the target pitch posture and the target sink posture. That is, the distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr so that the vehicle 90's pitch angle follows the target pitch angle Θreq and the vehicle 90's bounce amount follows the target bounce amount DZreq. Details of the process performed by the distribution ratio calculation unit 13 will be described later.

[0058] <Indication value calculation unit and friction control unit> The instruction value calculation unit 14 obtains the required braking force FxR, the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr. Based on the required braking force FxR, the front-to-rear distribution ratio n, the front-to-rear friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr, the instruction value calculation unit 14 calculates instruction values ​​to activate the friction braking system 70 and the regenerative braking system 80.

[0059] The instruction value calculation unit 14 calculates the friction braking force requirement value FxbR as the instruction value for activating the friction braking device. The friction braking force requirement value FxbR includes an instruction value corresponding to the front wheel friction braking force Fxfb and an instruction value corresponding to the rear wheel friction braking force Fxrb. The friction control unit 15 activates the friction braking device 70 according to the friction braking force requirement value FxbR.

[0060] The instruction value calculation unit 14 calculates a regenerative braking force request value FxdR as an instruction value to activate the regenerative braking system. The regenerative braking force request value FxdR includes an instruction value corresponding to the front wheel regenerative braking force Fxfd and an instruction value corresponding to the rear wheel regenerative braking force Fxrd. The regenerative braking force request value FxdR is transmitted to the regenerative control device 20. The regenerative braking system 80 is activated by the regenerative control device 20 according to the regenerative braking force request value FxdR.

[0061] <Calculation process for allocation ratio> An example of how the distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr will be described.

[0062] Figure 5 shows the processing flow when the distribution ratio calculation unit 13 performs the distribution ratio calculation process. This processing routine is repeatedly executed at predetermined intervals while the vehicle 90 is braking. When this processing routine is started, in step S101, the distribution ratio calculation unit 13 first obtains the target pitch moment Mreq corresponding to the target pitch angle Θreq and the target bounce force Zreq corresponding to the target bounce amount DZreq. Based on the target pitch moment Mreq and target bounce force Zreq calculated by the attitude target calculation unit 12, the distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr.

[0063] An example of the processing performed by the allocation ratio calculation unit 13 in step S101 will be described below. The front wheel friction regeneration ratio nf can be expressed as the following relational equation (Equation 3) based on the equation of motion of the vehicle 90. The rear wheel friction regeneration ratio nr can be expressed as the following relational equation (Equation 4) based on the equation of motion of the vehicle 90.

[0064]

number

[0065]

number

[0066] Figure 6 shows a Cartesian coordinate system in which the front-to-rear distribution ratio n is plotted on the horizontal axis as the first axis, and the front-to-rear friction regeneration ratio nf and rear-to-rear friction regeneration ratio nr are plotted on the vertical axis as the second axis. In Figure 6, the function of relational equation (Equation 3) is shown as a solid line. In Figure 6, the function of relational equation (Equation 4) is shown as a dashed line. The distribution ratio calculation unit 13 finds the solution by setting the front-to-rear friction regeneration ratio nf and rear-to-rear friction regeneration ratio nr to equal values. That is, the horizontal axis coordinate value "X" of the intersection point (X,Y) of the solid and dashed lines shown in Figure 6 is taken as the front-to-rear distribution ratio n, and the vertical axis coordinate value "Y" of the said intersection point is calculated as the front-to-rear friction regeneration ratio nf and rear-to-rear friction regeneration ratio nr.

[0067] Returning to Figure 5, in step S101, as illustrated above, the distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n, the front-to-rear friction regeneration ratio nf, and the rear-to-rear friction regeneration ratio nr. As a result, the instruction value calculation unit 14 calculates the friction braking force requirement value FxbR and the regenerative braking force requirement value FxdR. Based on the friction braking force requirement value FxbR, the friction control unit 15 activates the friction braking device 70. Also, based on the regenerative braking force requirement value FxdR, the regenerative braking device 20 activates the regenerative braking device 80.

[0068] After calculating the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr in step S101, the distribution ratio calculation unit 13 proceeds to step S102. In step S102, the distribution ratio calculation unit 13 obtains the regenerative braking force value Fxd. Once the distribution ratio calculation unit 13 obtains the regenerative braking force value Fxd from the regenerative control device 20, it proceeds to step S103.

[0069] In step S103, the distribution ratio calculation unit 13 recalculates the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr. For example, the distribution ratio calculation unit 13 solves the simultaneous equations of relational equation (Equation 3) and relational equation (Equation 4) so ​​that the regenerative braking force request value FxdR is less than or equal to the regenerative braking force execution value Fxd. The distribution ratio calculation unit 13 updates the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr based on the newly calculated values. As a result, the instruction value calculation unit 14 calculates the friction braking force request value FxbR and the regenerative braking force request value FxdR based on the recalculated values. After recalculating the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr in the process of step S103, the distribution ratio calculation unit 13 terminates this processing routine.

[0070] <Operation and Effects of the First Embodiment> The operation and effects of the first embodiment will be described. The anti-dive force FAD and anti-lift force FAL are values ​​that change depending on the front-to-rear weight distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr, as shown in the above relational equations (Equation 1) and (Equation 2). By adjusting the front-to-rear weight distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr, the anti-dive force FAD and anti-lift force FAL generated on the vehicle 90 can be adjusted. In other words, by setting the front-to-rear weight distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr, the attitude of the vehicle 90 can be controlled.

[0071] Test runs of the vehicle 90 controlled by the braking control device 10 confirmed the following: The pitch angle could be varied according to the deceleration. The bounce amount could be varied according to the deceleration. A predetermined regular relationship could be established between the pitch angle and the bounce amount. The actual deceleration, pitch angle, and bounce amount of the vehicle 90 can be detected using sensors such as an acceleration sensor and a gyro sensor. An example is illustrated using Figure 7.

[0072] Figure 7 illustrates the relationship between pitch angle and bounce amount when the braking control device 10 of the first embodiment is applied, using a solid line. As a comparative example, Figure 7 shows an example where the control of this embodiment based on the target pitch moment Mreq and target bounce force Zreq is not performed, using a dashed line.

[0073] In the comparative example, as shown by the dashed line in Figure 7, the bounce amount may fluctuate irregularly with respect to the pitch angle. For example, there are cases where the bounce amount decreases even as the pitch angle increases.

[0074] In contrast, the braking control device 10 can vary the pitch angle in proportion to the deceleration. It can also vary the bounce amount in proportion to the deceleration. As a result, a proportional relationship can be established between the pitch angle and the bounce amount, as shown by the solid line in Figure 7.

[0075] According to the braking control device 10, the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr are calculated so that the attitude of the vehicle 90 follows the target pitch angle Θreq and target bounce amount DZreq corresponding to the target deceleration DVT. The front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr are calculated based on the target pitch moment Mreq and the target bounce force Zreq. The friction braking force and regenerative braking force can be controlled according to the calculated front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr. This makes it possible to correlate the pitch angle and bounce amount with respect to the target deceleration DVT. By controlling the attitude of the vehicle 90 in response to deceleration, it is possible to suppress the discrepancy between the attitude of the vehicle 90 estimated by the occupant of the vehicle 90 from the deceleration and the actual attitude of the vehicle 90.

[0076] In the braking control device 10, the target pitch angle Θreq, target pitch moment Mreq, target bounce amount DZreq, and target bounce force Zreq are calculated based on the target deceleration DVT. The target deceleration DVT is calculated based on the manipulated variable Bp. Therefore, the braking control device 10 can improve the responsiveness of the vehicle 90's attitude to the driver's actions. This can suppress the driver from feeling any discomfort with the vehicle 90's behavior as a result of their actions.

[0077] (Second Embodiment) The braking control device of the second embodiment will be described with reference to Figures 9 to 13. The braking control device of the second embodiment includes an attitude target calculation unit 112 instead of the attitude target calculation unit 12 of the first embodiment. That is, the second embodiment differs from the first embodiment in that the attitude target calculation unit 112 calculates the target pitch moment Mreq and the target bounce force Zreq. Other configurations in the second embodiment are common to the first embodiment. Descriptions of configurations common to the first embodiment will be omitted as appropriate.

[0078] In the second embodiment, the objective is to control the attitude of the vehicle 90 so that the driver of the vehicle 90 can easily perceive the deceleration of the vehicle 90. Specifically, at the start of braking, the pitch angular acceleration is increased to increase the pitch angular velocity. During braking, the pitch angular velocity is gradually decreased in accordance with the increase in the degree of deceleration. In addition, the change in pitch angle is reduced in accordance with the increase in the degree of deceleration. Furthermore, the amount of bounce is increased in accordance with the increase in the degree of deceleration during braking.

[0079] As shown in Figure 9, the attitude target calculation unit 112 includes a pitching gain calculation unit 112a and a sinking gain calculation unit 112b. The attitude target calculation unit 112 acquires the target deceleration DVT calculated by the target deceleration calculation unit 11. The target deceleration DVT is input to the pitching gain calculation unit 112a and the sinking gain calculation unit 112b.

[0080] The pitching gain calculation unit 112a calculates the pitch angle gain KtΘ based on the target deceleration DVT. The attitude target calculation unit 112 calculates the target pitch angle Θreq by multiplying the pitch angle gain KtΘ by the pitch angle base Θbase.

[0081] The pitch angle gain KtΘ is a value used to adjust the target pitch angle Θreq according to the target deceleration (DVT). The pitch angle base Θbase serves as the basis for calculating the target pitch angle Θreq. The pitch angle base Θbase can be described as the relationship between the target pitch angle Θreq and the target deceleration DVT when the pitch angle gain KtΘ is "1". The pitch angle base Θbase is stored in the attitude target calculation unit 112 as a pre-calculated value. For example, the pitch angle base Θbase can be the relationship between the pitch angle and deceleration when braking force is generated on the vehicle 90 with equal pressure distribution between the front and rear. Generating braking force with equal pressure distribution between the front and rear means setting the front wheel regenerative braking force Fxfd and the rear wheel regenerative braking force Fxrd to "0", and generating the front wheel friction braking force Fxfb and the rear wheel friction braking force Fxrb so that the hydraulic pressure in the wheel cylinders of the front and rear wheels are equal. The hydraulic pressure in the front wheel cylinder is an example of the pressing force corresponding to the magnitude of the friction braking force applied to the front wheel. The hydraulic pressure in the rear wheel cylinder is an example of the pressing force corresponding to the magnitude of the friction braking force applied to the rear wheel.

[0082] The sinking gain calculation unit 112b calculates the bounce amount gain KtZ based on the target deceleration DVT. The attitude target calculation unit 112 calculates the target bounce amount DZreq by multiplying the bounce amount gain KtZ by the bounce amount base DZbase.

[0083] The bounce amount gain KtZ is a value used to adjust the target bounce amount DZreq according to the target deceleration DVT. The bounce amount base DZbase serves as the basis for calculating the target bounce amount DZreq. The bounce amount base DZbase can be described as the relationship between the target bounce amount DZreq and the target deceleration DVT when the bounce amount gain KtZ is "1". The bounce amount base DZbase is stored in the attitude target calculation unit 112 as a pre-calculated value. For example, the bounce amount base DZbase can be the relationship between the bounce amount and deceleration when braking force is applied to the vehicle 90 with a front-to-rear equal pressure distribution.

[0084] The attitude target calculation unit 112 calculates the target pitch moment Mreq based on the target pitch angle Θreq. The attitude target calculation unit 112 calculates the target bounce force Zreq based on the target bounce amount DZreq.

[0085] The functions of the posture target calculation unit 112 will be explained in detail using Figure 9. The attitude target calculation unit 112 calculates the target pitch angle Θreq such that the pitch increase rate when the target deceleration DVT is small is greater than the pitch increase rate when the target deceleration DVT is large. Here, the pitch increase rate refers to the rate at which the target pitch angle Θreq changes in the direction that increases the pitching motion of the vehicle 90 in response to an increase in the target deceleration DVT. In other words, when the deceleration of the vehicle 90 increases at the same speed, the rate of change of the pitch angle is high in the region of small deceleration and low in the region of large deceleration.

[0086] More specifically, the attitude target calculation unit 112 calculates the target pitch angle Θreq such that, when the target deceleration DVT is small, the pitch increase rate is greater than the reference pitch rate. On the other hand, when the target deceleration DVT is large, the attitude target calculation unit 112 calculates the target pitch angle Θreq such that the pitch increase rate is less than or equal to the reference pitch rate. Here, the above reference pitch rate refers to the rate by which the pitch angle changes in the direction in which the pitching motion of the vehicle 90 increases with respect to the increase in deceleration when braking force is generated on the vehicle 90 with front-to-rear equal pressure distribution.

[0087] The attitude target calculation unit 112 calculates the target bounce amount DZreq such that the bounce increase rate when the target deceleration DVT is small is smaller than the bounce increase rate when the target deceleration DVT is large. Here, the bounce increase rate refers to the rate at which the target bounce amount DZreq changes in the direction in which the bounce motion of the vehicle 90 increases in response to an increase in the target deceleration DVT.

[0088] More specifically, the attitude target calculation unit 112 calculates the target bounce amount DZreq such that the bounce increase rate is smaller than the reference bounce rate when the target deceleration DVT is small. On the other hand, when the target deceleration DVT is large, the attitude target calculation unit 112 calculates the target bounce amount DZreq such that the bounce increase rate is greater than or equal to the reference bounce rate. Here, the reference bounce rate refers to the rate at which the bounce amount changes in the direction in which the bounce motion of the vehicle 90 increases with respect to the increase in deceleration when braking force is applied to the vehicle 90 with front-to-rear equal pressure distribution.

[0089] <Pitch angle gain> An example of how the pitching gain calculation unit 112a calculates the pitch angle gain KtΘ will be described. For example, the pitching gain calculation unit 112a stores a calculation map for calculating the pitch angle gain KtΘ corresponding to the target deceleration DVT. The calculation map has a relationship set in advance between the target deceleration DVT and the pitch angle gain KtΘ, which has been calculated through experiments or other means. Figure 9 illustrates the relationship between the target deceleration DVT and the pitch angle gain KtΘ shown in the calculation map.

[0090] The relationship between the target deceleration DVT and the pitch angle gain KtΘ, as illustrated in Figure 9, will be explained. In the range where the target deceleration DVT is less than the first deceleration dv1, the pitch angle gain KtΘ is a constant value greater than "1".

[0091] In the range where the target deceleration DVT is greater than or equal to the first deceleration dv1, the pitch angle gain KtΘ decreases as the target deceleration DVT increases. More specifically, in the range where the target deceleration DVT is greater than or equal to the first deceleration dv1 and less than the second deceleration dv2, the pitch angle gain KtΘ decreases at a constant gradient. The pitch angle gain KtΘ corresponding to the second deceleration dv2 is less than "1". In the range where the target deceleration DVT is greater than or equal to the second deceleration dv2, the pitch angle gain KtΘ decreases in such a way that the rate at which the pitch angle gain KtΘ decreases in relation to the increase in the target deceleration DVT is smaller compared to the predetermined gradient mentioned above. In other words, with the second deceleration dv2 as the boundary, the rate at which the pitch angle gain KtΘ decreases in relation to the increase in the target deceleration DVT is changed between the range where the target deceleration DVT is less than or equal to the second deceleration dv2 and the range where the target deceleration DVT is greater than or equal to the second deceleration Dv2.

[0092] Note that the first deceleration dv1 is a smaller value than the second deceleration dv2, for example, a value that is only slightly larger than "0". The second deceleration dv2 will be discussed later. The relationship between the target deceleration DVT and the pitch angle gain KtΘ is not limited to the example shown in Figure 9. For example, the pitch angle gain KtΘ may decrease at a predetermined gradient in the range from the target deceleration DVT to the second deceleration dv2.

[0093] The attitude control realized by the target pitch angle Θreq calculated by the attitude target calculation unit 112 will be explained using Figure 11. Figure 11 shows the relationship between the average rate of change of the pitch angle (ΔΘ / ΔDV) and the target deceleration DVT. The solid line in Figure 11 shows the relationship when braking force is generated so that the attitude of the vehicle 90 follows the target pitch angle Θreq calculated by the attitude target calculation unit 112. The dashed line in Figure 11 shows the relationship when braking force is generated on the vehicle 90 with front-to-rear equal pressure distribution as a comparative example. The average rate of change of the pitch angle corresponds to the pitch increase rate. The average rate of change of the pitch angle shown by the dashed line corresponds to the reference pitch rate.

[0094] As shown by the solid line in Figure 11, the attitude target calculation unit 112 calculates the target pitch angle Θreq such that, in the range where the target deceleration DVT is smaller than the first deceleration dv1, the average rate of change of the pitch angle is increased more significantly than in the comparative example shown by the dashed line. In the range where the target deceleration DVT is greater than or equal to the first deceleration dv1 and smaller than the second deceleration dv2, the attitude target calculation unit 112 calculates the target pitch angle Θreq such that the average rate of change of the pitch angle is gradually reduced. As a result, in the range where the target deceleration DVT is large, the pitch increase rate shown by the solid line is less than or equal to the reference pitch rate shown by the dashed line. In the range where the target deceleration DVT is greater than or equal to the second deceleration dv2, the attitude target calculation unit 112 calculates the target pitch angle Θreq such that the average rate of change of the pitch angle remains constant. In other words, in the range where the target deceleration DVT is greater than or equal to the second deceleration dv2, the pitch angle gain KtΘ is calculated so as to stop the change in the average rate of change of the pitch angle.

[0095] Figure 10 will be used to explain the concept behind setting the second deceleration dv2. Figure 10 shows, with a dashed line, an ideal braking force distribution ratio where the front and rear wheels lock simultaneously during braking. Furthermore, the solid line illustrates the change in braking force when the gradient that reduces the pitch angle gain KtΘ in the range where the target deceleration DVT shown in Figure 9 is greater than or equal to the first deceleration dv1 and less than the second deceleration dv2 is applied to all target deceleration ranges.

[0096] Here, in vehicle 90, the anti-dive coefficient Ad due to frictional braking force can be expressed as the following relation (Equation 11). The anti-lift coefficient Al due to frictional braking force can be expressed as the following relation (Equation 12). Furthermore, the anti-dive coefficient Adr due to regenerative braking force can be expressed as the following relation (Equation 13). The anti-lift coefficient Alr due to regenerative braking force can be expressed as the following relation (Equation 14).

[0097]

number

[0098] <Bounce amount gain> Returning to Figure 9, an example of how the sinking gain calculation unit 112b calculates the bounce amount gain KtZ will be described. For example, the sinking gain calculation unit 112b stores a calculation map for calculating the bounce amount gain KtZ corresponding to the target deceleration DVT. The calculation map has a relationship set in advance between the target deceleration DVT and the bounce amount gain KtZ, which has been calculated through experiments or other means. Figure 9 illustrates the relationship between the target deceleration DVT and the bounce amount gain KtZ shown in the calculation map.

[0099] The relationship between the target deceleration DVT and the bounce amount gain KtZ, as illustrated in Figure 9, will be explained. In the range where the target deceleration DVT is less than the first deceleration dv1, the bounce amount gain KtZ is a constant value less than "1".

[0100] In the range where the target deceleration DVT is greater than or equal to the first deceleration dv1, the bounce amount gain KtZ increases as the target deceleration DVT increases. More specifically, in the range where the target deceleration DVT is greater than or equal to the first deceleration dv1 and less than the second deceleration dv2, the bounce gain KtZ increases at a constant gradient. The bounce gain KtZ corresponding to the second deceleration dv2 is greater than "1". In the range where the target deceleration DVT is greater than or equal to the second deceleration dv2, the bounce gain KtZ increases in such a way that the rate at which the bounce gain KtZ increases in relation to the increase in the target deceleration DVT is smaller compared to the predetermined gradient mentioned above. In other words, with the second deceleration dv2 as the boundary, the rate at which the bounce gain KtZ increases in relation to the increase in the target deceleration DVT is changed between the range where the target deceleration DVT is less than or equal to the second deceleration dv2 and the range where the target deceleration DVT is greater than or equal to the second deceleration dv2.

[0101] The relationship between the target deceleration DVT and the bounce gain KtZ is not limited to the example shown in Figure 9. For example, the bounce gain KtZ may increase at a predetermined gradient in the range from the target deceleration DVT to the second deceleration dv2.

[0102] The attitude control achieved by the target bounce amount DZreq calculated by the attitude target calculation unit 112 will be explained using Figure 12. Figure 12 shows the relationship between the average rate of change of the bounce amount (ΔDZ / ΔDV) and the target deceleration DVT. The solid line in Figure 12 shows the relationship when braking force is generated so that the attitude of the vehicle 90 follows the target bounce amount DZreq calculated by the attitude target calculation unit 112. The dashed line in Figure 12 shows the relationship when braking force is generated on the vehicle 90 with front-rear equal pressure distribution as a comparative example. The average rate of change of the bounce amount corresponds to the bounce increase rate. The average rate of change of the bounce amount shown by the dashed line corresponds to the reference bounce rate.

[0103] As shown by the solid line in Figure 12, the attitude target calculation unit 112 calculates the target bounce amount DZreq such that the average rate of change of the bounce amount is smaller than in the comparative example shown by the dashed line when the target deceleration DVT is small. When the target deceleration DVT is smaller than the first deceleration dv1, the attitude target calculation unit 112 allows the bounce amount to change in the direction of decreasing from "0", that is, the bounce amount to change in the direction of lifting the vehicle 90. When the target deceleration DVT is greater than or equal to the first deceleration dv1 and less than the second deceleration dv2, the attitude target calculation unit 112 calculates the target bounce amount DZreq such that the average rate of change of the bounce amount is gradually increased. As a result, when the target deceleration DVT is large, the bounce increase rate shown by the solid line is greater than or equal to the reference bounce rate shown by the dashed line. When the target deceleration DVT is in the range of the second deceleration dv2 or higher, the attitude target calculation unit 112 calculates the target bounce amount DZreq such that the average rate of change of the bounce amount remains constant. In other words, when the target deceleration DVT is in the range of the second deceleration dv2 or higher, the bounce amount gain KtZ is calculated so as to stop the change in the average rate of change of the bounce amount.

[0104] <Operation and Effects of the Second Embodiment> The operation and effects of the second embodiment will be explained using Figure 13. In the example shown in Figure 13, braking begins at timing t11. That is, the attitude of the vehicle 90 is controlled based on the target pitch moment Mreq and target bounce amount DZreq calculated by the attitude target calculation unit 112 from timing t11.

[0105] Figures 13(a) and (b) show examples of the control described in the second embodiment, indicated by solid lines. As a comparative example, Figures 13(a) and (b) show an example where the attitude of the vehicle 90 is not controlled, indicated by dashed lines.

[0106] In Figure 13(c), the vehicle braking force Fx is shown by a dashed line. The regenerative braking force effective value Fxd is shown by a solid line. The regenerative braking force effective value Fxd for comparison is shown by a dashed line. As shown by the dashed line in Figure 13(c), the vehicle braking force Fx gradually increases from timing t11. In other words, the target deceleration DVT is increasing.

[0107] In the initial stages of braking, when the target deceleration DVT is relatively small, the pitch angular acceleration is large, as shown in Figure 13(a), and the pitch angular velocity becomes larger earlier compared to the comparative example. As a result, as shown in Figure 13(b), the pitch angle becomes larger earlier. Thus, according to the second embodiment, the pitch angular velocity is increased from the initial stages of braking, that is, from the moment the driver of the vehicle 90 begins to operate the braking operating member 92. And the pitch angle becomes larger.

[0108] As shown in Figure 13(a), the pitch angular velocity, which is increased in the initial stages of braking, is gradually reduced. Therefore, as shown in Figure 13(b), the amount of change in the pitch angle gradually decreases. Thus, according to the second embodiment, during the middle stages of braking, i.e., while the target deceleration DVT is gradually increasing, the pitch angular velocity is reduced in accordance with the increase in the target deceleration DVT.

[0109] According to the second embodiment, as shown particularly from timing t12 onwards in Figure 13(c), the proportion of the friction braking force effective value Fxb is increased and the proportion of the regenerative braking force effective value Fxd is decreased. This adjusts the anti-dive force FAD and anti-lift force FAL generated on the vehicle 90, thereby achieving attitude control as shown in Figures 13(a) and (b).

[0110] By controlling the vehicle 90 to follow the target value calculated by the attitude target calculation unit 112 of the second embodiment, the following sensations can be provided to the driver of the vehicle 90 during the initial and middle stages of braking.

[0111] During the initial stages of braking, the pitch angle of vehicle 90 changes significantly, altering the information visible to the driver of vehicle 90. For example, the dashboard of vehicle 90 appears to move downwards. The driver can perceive the deceleration of vehicle 90 due to the change in visual information. Furthermore, the large change in the pitch angle of vehicle 90 causes the upper body to be pushed by the seat, encouraging the driver to lean forward.

[0112] During the mid-stage of braking, the gradual decrease in the pitch angular velocity of the vehicle 90 suppresses the shaking of the driver's head. For example, it can reduce the stimulation received by the otolith organs. This suppresses disruption of the driver's sense of balance. Therefore, it can prevent the driver from misjudging the deceleration of the vehicle 90. Furthermore, the gradual decrease in the pitch angular velocity of the vehicle 90 reduces the acceleration that causes the driver's upper body to tilt forward by the seat. This allows the driver to feel a sense of unity with the seat of the vehicle 90. In addition, as the degree of deceleration increases, the amount of bounce of the vehicle 90 increases, allowing the driver to feel that the deceleration is increasing from the sinking of the vehicle body 91. The driver can also feel a sense of stability from the sinking of the vehicle body 91.

[0113] (Third embodiment) During vehicle braking, the actual braking force applied to the wheels may be limited. For example, if a high-priority control is in operation, other controls may not be able to adjust the braking force. Examples of high-priority controls include anti-lock braking control and brake force distribution control. Anti-lock braking control, or ABS control, is a control that adjusts the braking force to suppress wheel lock. Brake force distribution control, or EBD control, is a control that limits the braking force of one wheel to prevent one of the front or rear wheels from locking up first. For example, the braking control device 10 shown in Figure 1 has a function to perform ABS control. For example, the braking control device 10 has a function to perform EBD control.

[0114] If the braking force acting on the wheels is limited, it may not be possible to make the vehicle 90 follow the posture indicated by the target pitching posture and the target sinking posture. An example is illustrated using Figure 14.

[0115] Figure 14 shows an example where ABS control and EBD control are initiated for the rear wheels at timing t21. Before timing t21, the vehicle 90's attitude is controlled so that the pitch rate, which indicates the rate of change of pitch angle per unit time, gradually decreases. However, after timing t21, the degree of freedom of the front-to-rear distribution ratio n is lost, making it impossible to reduce the pitch rate, and the pitch rate increases excessively.

[0116] Therefore, the third embodiment differs from the above embodiments in that it further includes a function in which the distribution ratio calculation unit 13 performs a limiting recalculation process when the braking force is limited on either the front wheel or the rear wheel, and the braking force is not limited on the other wheel. The purpose of the limiting recalculation process is to control the attitude of the vehicle 90 by controlling the braking force of the wheel whose braking force is not limited. The limiting recalculation process may be applied to the first embodiment or to the second embodiment. In the following description, configurations common to the first or second embodiment will be omitted as appropriate.

[0117] Incidentally, when ABS control is initiated, the application of regenerative braking force to the wheel targeted by ABS control may be terminated. In such cases, for example, the regenerative braking force value Fxd may be obtained by the process in step S102, as explained using Figure 5, and the friction regeneration ratio of the wheel targeted by ABS control may be recalculated as "1" in the subsequent step S103.

[0118] <Recalculation process when limit is reached> Figure 15 shows the processing flow when the distribution ratio calculation unit 13 performs the recalculation process when the limit is reached. This processing routine is repeatedly executed at predetermined intervals, for example, when the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr have been calculated by the process shown in Figure 5.

[0119] When this processing routine is started, in step S201, the distribution ratio calculation unit 13 first determines whether or not there is a limit on the rear wheel braking force. Examples of determining that there is a limitation on rear wheel braking force are described below. When ABS control and EBD control are being performed on the rear wheels, the distribution ratio calculation unit 13 can determine that there is a limitation on rear wheel braking force. When slip occurs on the rear wheels, the distribution ratio calculation unit 13 can determine that there is a limitation on the rear wheels. When the difference between the rear wheel speed and the vehicle speed is greater than a specified slip determination value, the distribution ratio calculation unit 13 can determine that there is a limitation on the rear wheels. When the ratio of rear wheel braking force is greater than the ideal braking force distribution ratio, the distribution ratio calculation unit 13 can determine that there is a limitation on the rear wheels. The distribution ratio calculation unit 13 can acquire information indicating whether ABS control is being performed, information indicating whether EBD control is being performed, information indicating the wheel in which slip is occurring, wheel speed, vehicle speed, and other elements.

[0120] In step S201, if there is a limitation on the rear wheel braking force (S201: YES), the distribution ratio calculation unit 13 proceeds to step S202. In step S202, the distribution ratio calculation unit 13 determines whether or not there is a limitation on the front wheel braking force.

[0121] An example of how the system determines that there is a limitation in front wheel braking force is described below. When ABS control and EBD control are being performed on the front wheels, the distribution ratio calculation unit 13 can determine that there is a limitation in front wheel braking force. When slip occurs on the front wheels, the distribution ratio calculation unit 13 can determine that there is a limitation on the front wheels. When the difference between the front wheel speed and the vehicle speed is greater than a specified slip detection value, the distribution ratio calculation unit 13 can determine that there is a limitation on the front wheels.

[0122] In step S202, if there is a limitation on the front wheel braking force (S202: YES), the distribution ratio calculation unit 13 terminates this processing routine. That is, if there is a limitation on both the front wheel braking force and the rear wheel braking force, the distribution ratio calculation unit 13 terminates this processing routine.

[0123] On the other hand, if there is no restriction on the front wheel braking force (S202:NO), the distribution ratio calculation unit 13 proceeds to step S203. In other words, if there is a restriction on the rear wheel braking force but no restriction on the front wheel braking force, the distribution ratio calculation unit 13 proceeds to step S203.

[0124] In step S203, the distribution ratio calculation unit 13 recalculates the front-wheel friction regeneration ratio nf and the front-to-rear distribution ratio n. For example, the distribution ratio calculation unit 13 calculates the front-wheel friction regeneration ratio nf and the front-to-rear distribution ratio n in such a way that the vehicle 90 follows the target pitching posture by suppressing the increase in the front-wheel braking force Fxf. Details of this process will be described later. Once the distribution ratio calculation unit 13 has recalculated the front-wheel friction regeneration ratio nf and the front-to-rear distribution ratio n, it terminates this processing routine.

[0125] In step S201, if there is no restriction on the rear wheel braking force (S201: NO), the distribution ratio calculation unit 13 proceeds to step S204. In step S204, the distribution ratio calculation unit 13 determines whether or not there is a restriction on the front wheel braking force.

[0126] In step S204, if there is no restriction on the front wheel braking force (S204: NO), the distribution ratio calculation unit 13 terminates this processing routine. That is, if there is no restriction on both the front wheel braking force and the rear wheel braking force, the distribution ratio calculation unit 13 terminates this processing routine.

[0127] On the other hand, if there is a limit on the front wheel braking force (S204: YES), the distribution ratio calculation unit 13 proceeds to step S205. That is, if there is a limit on the front wheel braking force but no limit on the rear wheel braking force, the distribution ratio calculation unit 13 proceeds to step S205.

[0128] In step S205, the distribution ratio calculation unit 13 recalculates the rear-wheel frictional regeneration ratio nr and the front-to-rear distribution ratio n. For example, the distribution ratio calculation unit 13 calculates the rear-wheel frictional regeneration ratio nr and the front-to-rear distribution ratio n so that the attitude of the vehicle 90 follows the target pitching attitude by suppressing an increase in the rear-wheel braking force Fxr. Details of this process will be described later. When the distribution ratio calculation unit 13 recalculates the rear-wheel frictional regeneration ratio nr and the front-to-rear distribution ratio n, it ends this processing routine.

[0129] <Details of S203 and S205> An example of the process of step S203 and the process of step S205 will be described. Note that the process of step S203 and the process of step S205 correspond to the recalculation process during restriction.

[0130] The process of step S203 aims to make the attitude of the vehicle 90 follow the target pitching attitude by adjusting the braking force gradient ΔFxf of the front wheels. The process of step S205 aims to make the attitude of the vehicle 90 follow the target pitching attitude by adjusting the braking force gradient ΔFxr of the rear wheels. Here, regarding the target pitching attitude, the change amount of the target pitch moment Mreq is defined as the target pitch moment change amount ΔM.

[0131] The braking force gradient ΔFxf of the front wheels and the braking force gradient ΔFxr of the rear wheels can be expressed by the following relational expression (Expression 15). In relational expression (Expression 15), "*" corresponds to "f" or "r". Accordingly, "n*" corresponds to "nf" or "nr". In relational expression (Expression 15), "A**" corresponds to "Ad" when "*" is "f". "A**" corresponds to "Al" when "*" is "r". The same meaning as above is represented for "*" and "A**" shown hereinafter. In relational expression (Expression 15), "h" represents the height of the center of gravity from the road surface to the vehicle center of gravity GC shown in FIG. 3. The center of gravity height h corresponds to the moment arm with respect to the pitching motion of the vehicle 90.

[0132]

number

[0133] In the following, we will explain the relationship between the center of gravity height h and the anti-dive coefficient Ad, or the relationship between the center of gravity height h and the anti-lift coefficient Al, by dividing the explanation into two cases, [A] and [B]. [A] When the height of the center of gravity h is greater than or equal to the anti-dive coefficient Ad, or when the height of the center of gravity h is greater than or equal to the anti-lift coefficient Al (h≧A**).

[0134] In this case, based on the relation (Equation 16), "n*ay" is greater than or equal to "1" (n*ay≧1). That is, the minimum value of "n*ay" is "1". Therefore, in step S203, the front wheel friction regeneration ratio nf can be recalculated as "1". As a result of the processing in step S203, the front wheel regenerative braking force Fxfd is set to "0" (Fxfd = (1-nf)Fxf), and only the front wheel friction braking force Fxfb acts on the front wheels. In other words, the target pitch moment change amount ΔM is achieved by controlling the braking force gradient ΔFxf of the front wheels by adjusting the front wheel friction braking force Fxfb.

[0135] On the other hand, in step S205, the rear-wheel friction regeneration ratio nr can be recalculated as "1". As a result of the processing in step S205, the rear-wheel regenerative braking force Fxrd is set to "0" (Fxrd = (1-nr)Fxr), and only the rear-wheel friction braking force Fxrb acts on the rear wheels. In other words, the target pitch moment change amount ΔM is achieved by controlling the braking force gradient ΔFxr of the rear wheels by adjusting the rear-wheel friction braking force Fxrb.

[0136]

number

[0137] Next, we will explain the process for recalculating the front-to-back distribution ratio n. The front-to-rear brake distribution ratio n can be expressed by the braking force gradient ΔFxf of the front wheels after the point in time when the braking force of either the front or rear wheel is limited, and the braking force Fxflim of the front wheels at the point in time when the braking force of either the front or rear wheel is limited. By rearranging the equation representing the front-to-rear brake distribution ratio n based on relation (Equation 15), the following relation (Equation 18) can be derived. In relation (Equation 18), the braking force gradient ΔFxf of the front wheels represents the increase in braking force of the front wheels after the point in time when the braking force of either the front or rear wheel is limited. Furthermore, the front-to-rear brake distribution ratio n can be expressed by the braking force gradient ΔFxr of the rear wheels after the point in time when the braking force of either the front or rear wheel is limited, and the braking force Fxrlim of the rear wheels at the point in time when the braking force of either the front or rear wheel is limited. By rearranging the equation representing the front-to-rear brake distribution ratio n, the following relation (Equation 19) can be derived. In relational equation (Equation 19), the rear wheel braking force gradient ΔFxr represents the increase in rear wheel braking force after the point in time when the braking force of either the front or rear wheel system is limited.

[0138]

number

[0139] In step S205, the front-to-rear weight distribution ratio n can be calculated based on the relational equation (Equation 19). Specifically, the front-to-rear weight distribution ratio n can be calculated based on the target pitch moment change ΔM, the rear wheel friction regeneration ratio nr, the center of gravity height h, and the anti-lift coefficients Al,Alr.

[0140] [B] When the center of gravity height h is less than the anti-dive coefficient Ad, or when the center of gravity height h is less than the anti-lift coefficient Al (h <A**)。 In this case, based on the relation (Equation 16), "n*ay" becomes less than "1" (n*ay < 1). That is, in order to achieve the target pitch moment change ΔM, adjusting only the braking force gradient ΔFx* is insufficient; it becomes necessary to adjust the friction regeneration ratio n* to generate regenerative braking force.

[0141] Therefore, in steps S203 and S205, the friction regeneration ratio n* is set to a value as close as possible to the asymptote. Within the range of "n*ay", "n*" is set to the largest possible value, and the braking force gradient ΔFx* is adjusted based on the above relational equation (Equation 15).

[0142] The front-to-rear distribution ratio n can be recalculated in the same way as in the case of [A] above. That is, in the process of step S203, the front-to-rear distribution ratio n can be calculated based on the relational expression (Equation 18). In the process of step S205, the front-to-rear distribution ratio n can be calculated based on the relational expression (Equation 19).

[0143] <Operation and Effects of the Third Embodiment> The operation and effects of the third embodiment will be explained using Figure 17. Figure 17 shows an example where there is a limit on rear-wheel braking force but no limit on front-wheel braking force. In the example shown in Figure 17, the front-wheel friction regeneration ratio nf is "1".

[0144] In the example shown in Figure 17, braking begins at timing t31. From timing t32 onward, the rear wheel braking force is limited. For example, this occurs when the rear wheel slips at timing t32.

[0145] Figure 17(a) shows the front wheel friction braking force Fxfb as a solid line and the rear wheel friction braking force Fxrb as a dashed line. Figure 17(b) shows the change in pitch rate. Figure 17 shows an example of controlling the attitude of the vehicle 90 in accordance with the pitching attitude target calculated by the attitude target calculation unit 112 of the second embodiment.

[0146] As shown by the dashed line in Figure 17(a), after timing t32, the rear wheel friction braking force Fxrb is restricted, and the degree of freedom for the front-to-rear distribution ratio n is lost. At this time, according to the third embodiment, the front wheel friction regeneration ratio nf and the front-to-rear distribution ratio n are recalculated by performing a recalculation process when restricted (S203). As a result, as shown by the solid line in Figure 17(a), the increase in the front wheel friction braking force Fxfb is suppressed after timing t32. As a result, as shown in Figure 17(b), the pitch rate can be kept low even after timing t32. Thus, according to the third embodiment, even when the braking force is restricted in either the front or rear wheel, an excessive increase in the pitch rate can be suppressed.

[0147] According to the third embodiment, even if the braking force is limited in either the front or rear wheel, the attitude of the vehicle 90 can be made to follow the target pitching attitude by adjusting the braking force gradient of the other wheel.

[0148] (Example of change) Each of the above embodiments can be implemented with the following modifications. Each of the above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0149] In each of the above embodiments, an example of a braking control device 10 applied to a vehicle 90 equipped with a regenerative braking device 80 that generates regenerative braking force applied to the front and rear wheels. The vehicle only needs to be equipped with a regenerative braking device that generates regenerative braking force applied to at least one of the front and rear wheels. Note that "at least one of the front and rear wheels" means "front wheel only," "rear wheel only," or "both front and rear wheels."

[0150] For example, the braking control device 10 can be applied to a vehicle equipped with a regenerative braking system that generates regenerative braking force applied to the rear wheels. In this case, an example in which the distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n, the front wheel friction regeneration ratio nf, and the rear wheel friction regeneration ratio nr will be explained using Figure 8.

[0151] Figure 8 shows a Cartesian coordinate system in which the front-to-rear distribution ratio n is taken as the horizontal axis as the first axis, and the front-to-rear friction regeneration ratio nf and rear-to-rear friction regeneration ratio nr are taken as the vertical axis as the second axis. In Figure 8, the function of relational equation (Equation 3) is shown as a solid line. In Figure 8, the function of relational equation (Equation 4) is shown as a dashed line. Here, since the vehicle is not equipped with a regenerative braking system that generates regenerative braking force to be applied to the front wheels, the front-to-rear braking force Fxf is equal to the front-to-rear friction braking force Fxfb. That is, the front-to-rear friction regeneration ratio nf is "1". The distribution ratio calculation unit 13 calculates the front-to-rear distribution ratio n by setting the front-to-rear friction regeneration ratio nf to "1". That is, the horizontal axis coordinate value "X" of the coordinate (X,1) on the solid line shown in Figure 8 is calculated as the front-to-rear distribution ratio n. Based on the calculated front-to-rear distribution ratio n, the distribution ratio calculation unit 13 calculates the rear-to-rear friction regeneration ratio nr.

[0152] As described above, the braking control device 10 can also be applied to vehicles equipped with a regenerative braking device that generates regenerative braking force to be applied to one of the wheels, either the front or rear wheels. In this case as well, the pitch angle and bounce amount of the vehicle can be controlled based on the target deceleration DVT, similar to the embodiment described above. This provides the effect of controlling the vehicle's attitude in response to deceleration.

[0153] In each of the above embodiments, an example was shown in which the distribution ratio calculation process by the distribution ratio calculation unit 13 involves obtaining the regenerative braking force value Fxd and recalculating the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr. If the regenerative braking force value Fxd and the regenerative braking force request value FxdR do not deviate from each other, the distribution ratio calculation unit 13 may choose not to recalculate the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr. If the deviation between the regenerative braking force value Fxd and the regenerative braking force request value FxdR is smaller than a predetermined judgment value, the distribution ratio calculation unit 13 may choose not to recalculate the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr.

[0154] The distribution ratio calculation unit 13 may obtain the maximum value of the regenerative braking force. The distribution ratio calculation unit 13 can also use the maximum value of the regenerative braking force to calculate the front-to-rear distribution ratio n, the front-wheel friction regeneration ratio nf, and the rear-wheel friction regeneration ratio nr so that the regenerative braking force requirement value FxdR is less than or equal to the maximum value of the regenerative braking force.

[0155] The attitude target calculation unit 12 may have multiple calculation maps with different characteristics. The attitude target calculation unit 12 may change the relationship between deceleration, pitching attitude and sinking attitude by switching the calculation map used.

[0156] As an example, we will describe a case where it is possible to switch between the first mode and the second mode. The calculation map for the first mode is the calculation map 12a in the embodiment shown as illustrated in Figure 4.

[0157] The calculation map in the second mode, for example, has a smaller slope for the target pitch moment Mreq compared to calculation map 12a. That is, it reduces the amount of change in the target pitch moment Mreq with respect to the target deceleration DVT. Furthermore, the calculation map in the second mode, for example, has a smaller slope for the target bounce force Zreq compared to calculation map 12a. That is, it increases the amount of change in the target bounce force Zreq with respect to the target deceleration DVT.

[0158] In other words, the calculation map for the first mode is set to generate more power when regenerative braking is applied compared to the calculation map for the second mode. By switching from the first mode to the second mode, for example, the driver can be made to feel the enjoyment of operating the vehicle 90. Preferably, the driver can choose to switch between the first mode and the second mode.

[0159] The relationship between deceleration, pitching posture, and sinking posture may be set to allow for greater regenerative energy recovery during vehicle braking, as in the first mode described above. Alternatively, the relationship between deceleration, pitching posture, and sinking posture may be set to allow the vehicle's behavior to be preferred by the driver, as in the second mode described above.

[0160] The pitching gain calculation unit 112a in the second embodiment described above may have a plurality of calculation maps with different characteristics. The pitching gain calculation unit 112a may change the relationship between the pitch angle gain KtΘ and the target deceleration DVT by switching the calculation map used. Similarly, the sinking gain calculation unit 112b may have a plurality of calculation maps with different characteristics. The sinking gain calculation unit 112b may change the relationship between the bounce amount gain KtZ and the target deceleration DVT by switching the calculation map used.

[0161] In each of the above embodiments, the attitude target calculation units 12 and 112 are configured to calculate a target pitch angle Θreq and a target pitch moment Mreq to achieve the target pitch angle Θreq as targets for the pitching attitude of the vehicle 90. The targets for the pitching attitude are not limited to the target pitch angle Θreq and the target pitch moment Mreq. For example, a target of pitch angular velocity can be adopted as a target for the pitching attitude. A target of pitch angular acceleration can also be adopted as a target for the pitching attitude. Pitch angular velocity is the rate of change of the pitch angle per unit time. Pitch angular acceleration is the rate of change of the pitch angular velocity per unit time.

[0162] In each of the above embodiments, the attitude target calculation units 12 and 112 are configured to calculate a target bounce amount DZreq and a target bounce force Zreq to achieve the target bounce amount DZreq as targets for the sinking attitude of the vehicle 90. The targets for the sinking attitude are not limited to the target bounce amount DZreq and the target bounce force Zreq. For example, a target bounce velocity can be adopted as a target for the sinking attitude. A target bounce acceleration can also be adopted as a target for the sinking attitude. Bounce velocity is the rate of change of bounce amount per unit time. Bounce acceleration is the rate of change of bounce velocity per unit time.

[0163] The braking control device 10 and the regenerative control device 20, which are processing circuits in each of the above embodiments, may have any of the following configurations: [a] A circuit comprising one or more processors that execute various processes according to a computer program. The processor comprises a processing unit. Examples of processing units include a CPU, DSP, and GPU. The processor comprises memory. Examples of memory include RAM, ROM, and flash memory. The memory stores program code or instructions configured to cause the processing unit to execute the processes. Memory, i.e., computer-readable media, includes any medium that can be accessed by a general-purpose or dedicated computer. [b] A circuit comprising one or more hardware circuits that execute various processes. Examples of hardware circuits include an ASIC (Application Specific Integrated Circuit), a CPLD (Complex Programmable Logic Device), and an FPGA (Field Programmable Gate Array). [c] A circuit comprising a processor that executes a part of the various processes according to a computer program, and hardware circuits that execute the remaining parts of the various processes.

[0164] Some or all of the functions realized by the regenerative control device 20 may be realized by the braking control device 10. Some of the functions implemented by the braking control device 10 may be implemented by other processing circuits connected to the braking control device 10.

[0165] In the third embodiment described above, an example was shown in which, if the braking force of either the front or rear wheel is limited, the attitude of the vehicle 90 is controlled by adjusting the braking force gradient of the other wheel whose braking force is not limited. Instead of the configuration of the third embodiment described above, the attitude of the vehicle 90 may be controlled as follows.

[0166] For example, if the vehicle 90 is equipped with an active suspension, the vehicle's attitude may be controlled by activating the active suspension when the braking force of either the front or rear wheels is limited. In this case, the control that adjusts the front-to-rear distribution ratio n and the friction regeneration ratio n* based on the attitude target calculated by the attitude target calculation unit may be terminated. [Explanation of symbols]

[0167] 10… Brake control device 12, 112... Posture target calculation section 12a...Calculation map 13… Allocation ratio calculation unit 14...Indication value calculation unit 20…Regenerative braking system 70...Friction braking device 80...Regenerative braking device 90... Vehicles 91... Vehicle body

Claims

1. This invention is applied to a vehicle that includes a regenerative braking system that generates regenerative braking force applied to at least one of the front and rear wheels of the vehicle, and a friction braking system that generates friction braking force applied to the front wheel and friction braking force applied to the rear wheel. A braking control device that controls the braking force of the vehicle by activating the regenerative braking device and the friction braking device, The sum of the braking force applied to the front wheel and the braking force applied to the rear wheel is defined as the vehicle braking force, the ratio of the braking force applied to the front wheel to the vehicle braking force is defined as the front-to-rear distribution ratio, and for the front and rear wheels to which regenerative braking force can be applied, the ratio of the friction braking force applied to the wheel to the braking force applied to that wheel is defined as the friction regeneration ratio. A posture target calculation unit calculates a target pitching posture and a target sinking posture for the vehicle based on the target deceleration degree of the vehicle. A distribution ratio calculation unit calculates the front-to-rear distribution ratio and the friction regeneration ratio so that the vehicle's posture follows the posture indicated by the target pitching posture and the target sinking posture, The system includes an instruction value calculation unit that calculates instruction values ​​for operating the friction braking device and the regenerative braking device based on the target required braking force for the vehicle braking force, the front-to-rear distribution ratio, and the friction regeneration ratio. Brake control device.

2. The attitude target calculation unit calculates the pitching attitude target such that the pitching motion of the vehicle increases as the deceleration target is greater in the direction of deceleration, and calculates the sinking attitude target such that the bouncing motion of the vehicle increases as the deceleration target is greater in the direction of deceleration. The braking control device according to claim 1.

3. This applies to a vehicle in which the regenerative braking system generates regenerative braking force to be applied to the front wheels and regenerative braking force to be applied to the rear wheels. The friction regeneration ratio is the front wheel friction regeneration ratio, which is the ratio of the friction braking force applied to the front wheel to the braking force applied to the front wheel. The ratio of the friction braking force applied to the rear wheel to the braking force applied to the said rear wheel is defined as the rear wheel friction regeneration ratio. The instruction value calculation unit instructs the operation of the friction braking device and the regenerative braking device based on the requested braking force, the front-to-rear distribution ratio, the front wheel friction regeneration ratio, and the rear wheel friction regeneration ratio. The aforementioned allocation ratio calculation unit is: The front-to-rear distribution ratio, the front-to-rear friction regeneration ratio, and the rear-to-rear friction regeneration ratio are calculated as solutions to a function representing the front-to-rear friction regeneration ratio based on the equation of motion relating to the vehicle's attitude and a function representing the rear-to-rear friction regeneration ratio based on the equation of motion. In a Cartesian coordinate system in which the front-to-rear distribution ratio is taken as the first axis and the front-wheel friction regeneration ratio and the rear-wheel friction regeneration ratio are taken as the second axis, the coordinate value of the first axis at the intersection of the function representing the front-to-rear friction regeneration ratio and the function representing the rear-wheel friction regeneration ratio is calculated as the front-to-rear distribution ratio. The braking control device according to claim 1 or 2.

4. The ratio by which the target pitching posture changes in a direction that increases the pitching motion of the vehicle, in response to an increase in the target deceleration degree in the direction that slows down the vehicle, is defined as the pitch increase ratio. The bounce increase ratio is defined as the rate at which the target of the sinking posture changes in a direction that increases the bounce motion of the vehicle, in response to an increase in the target of the deceleration degree in the direction that slows down the vehicle. The aforementioned attitude target calculation unit, The target pitching posture is calculated such that the pitch increase rate when the target deceleration is small is greater than the pitch increase rate when the target deceleration is large. The target sinking posture is calculated such that the bounce increase rate when the target deceleration is small is smaller than the bounce increase rate when the target deceleration is large. The braking control device according to claim 1.

5. When the pressing force corresponding to the magnitude of the frictional braking force applied to the front wheels and the pressing force corresponding to the magnitude of the frictional braking force applied to the rear wheels are made equal to generate a frictional braking force on the vehicle, the ratio by which the pitching posture changes in the direction in which the pitching motion of the vehicle increases in response to an increase in the deceleration in the direction that decelerates the vehicle is defined as the reference pitch ratio. When the pressing force corresponding to the magnitude of the frictional braking force applied to the front wheels and the pressing force corresponding to the magnitude of the frictional braking force applied to the rear wheels are made equal to generate a frictional braking force on the vehicle, the ratio by which the sinking posture changes in the direction in which the bouncing motion of the vehicle increases in response to an increase in the deceleration in the direction that decelerates the vehicle is defined as the reference bounce ratio. The aforementioned attitude target calculation unit, The target pitching posture is calculated such that when the target deceleration is small, the pitch increase rate is made larger than the reference pitch rate, while when the target deceleration is large, the pitch increase rate is made less than or equal to the reference pitch rate. When the target deceleration is small, the bounce increase rate is made smaller than the standard bounce rate, while when the target deceleration is large, the bounce increase rate is made equal to or greater than the standard bounce rate, thus calculating the target sinking posture. The braking control device according to claim 4.

6. If slippage occurs in either the front wheel or the rear wheel, and no slippage occurs in the other wheel, The gradient of the braking force applied to the other wheel is adjusted so that the vehicle's posture follows the posture indicated by the target pitching posture. The braking control device according to claim 1.

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