JP5833872B2 - Vehicle braking force control device - Google Patents

Description

  The present invention relates to a braking force control device for a vehicle that can generate a desired yaw moment by applying braking force to each wheel independently.

  In recent years, various technologies have been proposed and put into practical use in vehicles in which braking force is independently applied to each wheel to generate a desired yaw moment to improve stability and motion performance. For example, in Japanese Patent Application Laid-Open No. 2007-131251 (hereinafter referred to as Patent Document 1), at the time of rollover prevention control, at the relatively early stage where the absolute value of the actual lateral acceleration is greater than or equal to value Gy1 and less than or equal to value Gy2, Only when the inner front wheel braking force is generated, and when the value is greater than or equal to Gy2 and less than or equal to the value Gy3, the inner rear wheel braking force is generated on the inner rear wheel braking force in addition to the inner front wheel braking force. Increases the roll angle by generating a vehicle height reduction force, and when the absolute value of the actual lateral acceleration exceeds the value Gy3, generates an outer wheel braking force on the front wheels outside the turning direction in addition to the inner rear wheel braking force. Thus, a technique of a vehicle motion control device that suppresses an increase in roll angle by forcibly generating a yawing moment in a direction opposite to the turning direction is disclosed.

JP 2007-131251 A

  In general, by detecting the understeer tendency of the vehicle and adding a yaw moment in the vehicle turning direction by the turning inner wheel brake, the rear wheel also has a sufficient slip angle, and it is possible to increase the cornering force of the four wheels to some extent. is there. However, the lack of cornering force on the front axle (the characteristic that the rear tire grip cannot be used up) due to the basic weight distribution that is biased to the front axle cannot be resolved. Even if it is increased, the cornering force of the four wheels may not be used as much as possible, and there is a risk of eventually going out of the course in a four wheel drift state.

  In the technique disclosed in Patent Document 1 described above, until the absolute value of the actual lateral acceleration becomes a value Gy1 to a value Gy3 or less, a braking force is generated on the turning inner wheel side, and the absolute value of the actual lateral acceleration is more than Gy3. If this increases, the braking force is also generated on the front wheels on the outside of the turn to suppress the increase in lateral acceleration. As a result, the deceleration acting on the vehicle body also increases and the traveling speed also decreases to prevent the vehicle from rolling over. Can be expected. However, when the braking force is generated as in the technique disclosed in the above-mentioned Patent Document 1, the yaw moment in the turning direction applied to the vehicle changes, and an unexpected wheel lock or the like due to the braking force occurs, resulting in a vehicle behavior. There is a risk that problems such as sudden changes and the effect of preventing an understeer tendency may be diminished.

  The present invention has been made in view of the above circumstances, and effectively controls the tire cornering force at the time of turning of the vehicle and can reliably prevent the vehicle from going out of the curve with stable vehicle behavior. An object is to provide a power control device.

One aspect of the vehicle braking force control apparatus according to the present invention is a target vehicle behavior calculation means for calculating a vehicle behavior that is a target of vehicle lateral movement based on a driving state of the vehicle, and detects an actual vehicle behavior of the vehicle lateral movement. And a first addition for calculating a first additional yaw moment to be added to the vehicle based on the target vehicle behavior of the vehicle lateral movement and the actual vehicle behavior of the vehicle lateral movement. A second additional yaw to be added to the vehicle in addition to the first additional yaw moment based on the yaw moment calculating means, the vehicle behavior targeted for the vehicle lateral movement and the actual vehicle behavior of the vehicle lateral movement. A second additional yaw moment calculating means for calculating a moment; and a first brake for calculating a braking force applied to the turning inner wheel and the turning outer wheel based on the first additional yaw moment as the first braking force. A force calculation means, the above should be added to the first vehicle in addition to the additional yaw moment on the basis of the second additional yaw moment, the first of said turning inner wheel and the turning outer wheel calculated by the braking force calculating means Based on the first braking force and the second braking force, second braking force calculating means for calculating the braking force applied to the vehicle without changing the braking force difference between the first braking force and the second braking force. Each wheel braking force calculation means for calculating a braking force applied to each wheel, wherein each wheel braking force calculation means determines only the front-rear weight distribution ratio of the vehicle and the front-rear weight distribution ratio of the second braking force. Set according to either of the ground load distribution .

  According to the braking force control apparatus for a vehicle according to the present invention, it is possible to effectively exert the tire cornering force at the time of turning of the vehicle, and to reliably prevent the course out to the outside of the curve with a stable vehicle behavior.

It is explanatory drawing which shows schematic structure of the vehicle carrying the braking force control apparatus by one Embodiment of this invention. It is a functional block diagram of a control part by one embodiment of the present invention. It is a flowchart of the braking force control program by one Embodiment of this invention. It is characteristic explanatory drawing of the lateral acceleration and steering wheel angle ratio in the steady circle turning test when this control is applied by one Embodiment of this invention. It is explanatory drawing of the control state which generates brake force by one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes a vehicle, and the driving force by an engine 2 disposed at the front of the vehicle is transmitted from an automatic transmission device (including a torque converter and the like) 3 behind the engine 2 via a transmission output shaft 3a. It is transmitted to the center differential device 4.

  The center differential device 4 is inputted to the rear wheel final reduction device 8 via the rear drive shaft 5, the propeller shaft 6 and the drive pinion 7, while the front wheel final deceleration is sent from the center differential device 4 via the front drive shaft 9. Input to the device 10. Here, the automatic transmission 3, the center differential device 4, the front wheel final reduction gear 10, and the like are integrally provided in the case 11.

  The driving force input to the rear wheel final reduction gear 8 is transmitted to the left rear wheel 13rl via the rear wheel left drive shaft 12rl and to the right rear wheel 13rr via the rear wheel right drive shaft 12rr. On the other hand, the driving force input to the front wheel final reduction gear 10 is transmitted to the left front wheel 13fl via the front wheel left drive shaft 12fl and to the right front wheel 13fr via the front wheel right drive shaft 12fr.

  Reference numeral 15 denotes a brake drive unit of the vehicle. A master cylinder 17 connected to a brake pedal 16 operated by a driver is connected to the brake drive unit 15, and the driver operates (depresses) the brake pedal 16. ) And the master cylinder 17 through the brake drive unit 15 to each wheel cylinder of the four wheels 13fl, 13fr, 13rl, 13rr (left front wheel cylinder 18fl, right front wheel cylinder 18fr, left rear wheel cylinder 18rl, right rear wheel) The brake pressure is introduced into the cylinder 18rr), whereby the four wheels are braked and braked.

  The brake drive unit 15 is a hydraulic unit including a pressurizing source, a pressure reducing valve, a pressure increasing valve, and the like, and applies brake pressure to each wheel cylinder 18fl, 18fr, 18rl, 18rr independently according to an input signal. It is formed to be freely introduced.

  The vehicle 1 is provided with an engine control device 21 that controls the engine 2, an automatic transmission 3, a transmission control device 22 that controls the center differential device 4, and a later-described control unit 30 that controls the brake drive unit 15.

  The controller 30 receives the engine output Teg and the engine speed Ne from the engine control device 21 described above, and the turbine control speed Nt, the main transmission gear ratio i, and the driving force distribution by the center differential device 4 from the transmission control device 22. The ratio DD (= front wheel side driving force / total driving force) is input.

Further, the control unit 30 includes a vehicle speed sensor 23, a handle angle sensor 24, a longitudinal acceleration sensor 25, a vehicle speed V from the lateral acceleration sensor 26, a handle angle θH, a longitudinal acceleration (d ² x / dt ² ), and a vehicle body lateral acceleration ( Each signal such as d ² y / dt ² ) is input.

Then, the control unit 30 calculates a target lateral acceleration (d ² y / dt ² ) t as a vehicle behavior that is a target of the vehicle lateral movement based on the vehicle speed V and the steering wheel angle θH, and this target lateral acceleration (d ² y / dt ² ) t and the actual lateral acceleration (d ² y / dt ² ) (that is, the detected value by the lateral acceleration sensor 26 as the actual vehicle behavior detecting means) The additional yaw moment Mzt1 is calculated, and the vehicle 1 is added to the first additional yaw moment Mzt1 based on the target lateral acceleration (d ² y / dt ² ) t and the actual lateral acceleration (d ² y / dt ² ). The second additional yaw moment Mzt2 to be added is calculated, the braking force applied to the turning inner wheel is calculated as the first braking force FB1 based on the first additional yaw moment Mzt1, and the second additional yaw moment Mzt2 is calculated. In turn based on The braking force applied to the vehicle 1 without changing the braking force difference between the wheel and the turning outer wheel is calculated as the second braking force FB2, and based on the first braking force FB1 and the second braking force FB2. The braking force applied to each wheel is calculated and output to the brake drive unit 15.

  Therefore, as shown in FIG. 2, the control unit 30 includes a target lateral acceleration calculation unit 30a, a lateral acceleration deviation calculation unit 30b, a target yaw moment calculation unit 30c, a braking force calculation unit 30d, a transmission output torque calculation unit 30e, The braking / driving force calculating unit 30f, the second front / rear braking force distribution ratio calculating unit 30g, the front / rear braking force distribution ratio calculating unit 30h considering the driving force, the braking force calculating unit 30i for each wheel, and the brake hydraulic pressure calculating unit for each wheel 30j is mainly composed.

The target lateral acceleration calculation unit 30 a receives the vehicle speed V from the vehicle speed sensor 23 and the handle angle θH from the handle angle sensor 24. Then, for example, the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement is calculated by the following equation (1), and is output to the lateral acceleration deviation calculating unit 30b.
(D ² y / dt ² ) t = (1 / (1 + A · V ² )) · (V ² / l) · (θH / n) (1)
Here, A is a stability factor, l is a wheel base, and n is a steering gear ratio. Thus, the target lateral acceleration calculation unit 30a is provided as target vehicle behavior calculation means.

The lateral acceleration deviation calculator 30b receives the actual lateral acceleration (d ² y / dt ² ) from the lateral acceleration sensor 26, and receives the target lateral acceleration (d ² y / dt ² ) t from the target lateral acceleration calculator 30a. Is done. Then, the lateral acceleration deviation Δ (d ² y / dt ² ) is calculated by the following equation (2) and output to the target yaw moment calculating unit 30c.
Δ (d ² y / dt ² ) = (d ² y / dt ² ) − (d ² y / dt ² ) t (2)

The target yaw moment calculating unit 30c receives the steering wheel angle θH from the steering wheel angle sensor 24, and receives the lateral acceleration deviation Δ (d ² y / dt ² ) from the lateral acceleration deviation calculating unit 30b. When the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is smaller than a preset first lateral acceleration deviation threshold e 1 (| Δ (d ² y / dt ² ) | <In the case of e1), or the condition that the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs and the vehicle 1 can be regarded as having an oversteer tendency, the vehicle 1 will have a yaw moment in the turning direction. If it can be determined that it is not necessary to add, the yaw moment is set as the first additional yaw moment Mzt1, and the first additional yaw moment Mzt1 is set to zero. On the other hand, when the above condition is not satisfied and it can be determined that it is necessary to add the yaw moment in the turning direction to the vehicle 1, the first additional yaw moment Mzt1 is expressed by, for example, the following equation (3): To calculate.
Mzt1 = GMZ1 · Δ (d ² y / dt ² ) (3)
Here, GMZ1 is a yaw moment gain set in advance for experiments and calculations.

Further, the target yaw moment calculation unit 30c calculates a second additional yaw moment Mzt2 to be added to the vehicle 1 in addition to the first additional yaw moment Mzt1 as follows. That is, when the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is smaller than a preset second lateral acceleration deviation threshold e 2 (> e 1) (| Δ (d ² y / dt ² ) | <e ² ), or under the condition that the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH are different signs and the vehicle 1 can be regarded as having an oversteer tendency. When it can be determined that it is not necessary to add a yaw moment in the turning direction to the vehicle 1 in addition to the moment Mzt1, this yaw moment is set as the second additional yaw moment Mzt2, and this second additional yaw moment Mzt2 is set to 0. Set to. On the other hand, if the above condition is not satisfied and it can be determined that it is necessary to add a yaw moment in the turning direction to the vehicle 1 in addition to the first additional yaw moment Mzt1, the second additional yaw moment Mzt2 Is calculated by the following equation (4), for example.
Mzt2 = GMZ2 · Δ (d ² y / dt ² ) (4)
Here, GMZ2 is a yaw moment gain set in advance for experiments and calculations.

  Thus, the first additional yaw moment Mzt1 and the second additional yaw moment Mzt2 calculated by the target yaw moment calculation unit 30c are output to the braking force calculation unit 30d. As described above, the target yaw moment calculation unit 30c is provided as the first additional yaw moment calculation means and the second additional yaw moment calculation means.

The braking force calculation unit 30d receives the first additional yaw moment Mzt1 and the second additional yaw moment Mzt2 from the target yaw moment calculation unit 30c. Then, for example, the braking force applied to the turning inner wheel is calculated as the first braking force FB1 by the following equation (5). For example, the turning inner wheel and the turning outer wheel are calculated by the following equation (6). The braking force applied to the vehicle 1 without changing the difference in braking force between is calculated as the second braking force FB2.
FB1 = | Mzt1 | / (w / 2) (5)
Here, w is a tread.

FB2 = GFb · | Mzt2 | (6)
Here, GFb is a conversion gain (predetermined value) to the braking force. The first braking force FB1 calculated in this way is output to the braking force calculation unit 30i for each wheel, and the second braking force FB2 is the front / rear braking force distribution ratio calculation unit 30h considering the driving force and the braking force for each wheel. It is output to the power calculation unit 30i. Thus, the braking force calculation unit 30d is provided as a first braking force calculation unit and a second braking force calculation unit.

The transmission output torque calculation unit 30e receives the engine output Teg and the engine speed Ne from the engine control device 21, and receives the turbine speed Nt and the main transmission gear ratio i from the transmission control device 22. Then, for example, the transmission output torque TD is calculated by the following equation (7) and output to the total braking / driving power calculation unit 30f.
TD = Teg · t · i (7)
Here, t is the torque ratio of the torque converter, and is obtained, for example, by referring to a map of a preset rotational speed ratio e (= Nt / Ne) of the torque converter and the torque ratio t of the torque converter. .

The total braking / driving power calculation unit 30f receives the transmission output torque TD from the transmission output torque calculation unit 30e. Then, for example, the total braking / driving force FD is calculated by the following equation (8) and output to the front / rear braking force distribution ratio calculating unit 30h in consideration of the driving force.
FD = (TD · Gf) / Rt (8)
Here, Gf is the final gear ratio, and Rt is the tire diameter.

The second longitudinal braking force distribution ratio calculating unit 30g receives the longitudinal acceleration (d ² x / dt ² ) from the longitudinal acceleration sensor 25. For example, the front / rear braking force distribution ratio DB2 (= front wheel side braking force / total braking force) of the second braking force FB2 is calculated by the following equation (9), and the front / rear braking force distribution ratio in consideration of the driving force is calculated. It outputs to the calculation part 30h.
DB2 = Fzf / (Fzf + Fzr) (9)
Here, Fzf is the ground load on the front shaft, and Fzr is the ground load on the rear shaft, which are calculated by the following equations (10) and (11), respectively.

Fzf = Fzf0−m · (d ² x / dt ² ) · h / l (10)
Here, Fzf0 is the front shaft ground load in a stationary state, m is the vehicle mass, and h is the height of the center of gravity.

Fzr = m · g−Fzf (11)
Here, g is a gravitational acceleration.

In the present embodiment, the front / rear braking force distribution ratio DB2 of the second braking force FB2 is set according to the ground load distribution of the front / rear shaft, but is set according to the front / rear weight distribution of the vehicle. You may do it. In this case, the front / rear braking force distribution ratio DB2 of the second braking force FB2 is calculated by the following equation (12), for example.
DB2 = Wf / (Wf + Wr) (12)
Here, Wf and Wr indicate front and rear axial weights.

The front / rear braking force distribution ratio calculation unit 30h considering the driving force receives the driving force front / rear distribution ratio DD from the center differential device 4 from the transmission control device 22, and receives the second braking force FB2 from the braking force calculation unit 30d. The total braking / driving force FD is input from the total braking / driving power calculating unit 30f, and the front / rear braking force distribution ratio DB2 of the second braking force FB2 is input from the second front / rear braking force distribution ratio calculating unit 30g. Then, for example, the front / rear braking force distribution ratio DB considering the driving force with respect to the second braking force FB2 is calculated by the following equation (13) and output to the braking force calculating unit 30i of each wheel.
DB = DB2 + (FD / FB2). (DD-DB2) (13)

Here, the above equation (13) will be described.
First, an actual front / rear braking / driving force front-rear distribution ratio (= front shaft braking / driving force / total braking / driving force) DA considering the driving force with respect to the second braking force FB2 can be calculated by the following equation (14). .
DA = (FD / DD-FB2 / DB2) / (FD-FB2) (14)
Solving this equation (14) for the front / rear braking force distribution ratio DB2,
DB2 = DA + (FD / FB2). (DD-DA) (15)
In this equation (15), when DA is the front / rear braking force distribution ratio DB2 of the second braking force FB2, which is the front / rear distribution ratio of the braking force to be generated, the driving force is expressed with respect to the second braking force FB2 at that time. The considered front / rear braking force distribution ratio DB is expressed as in equation (13), where DB2 is DB.

The braking force calculation unit 30i for each wheel receives the first braking force FB1 and the second braking force FB2 from the braking force calculation unit 30d, and the second braking force distribution ratio calculation unit 30h taking into account the driving force. The front / rear braking force distribution ratio DB considering the driving force with respect to the braking force FB2 is input. And, for example, according to the following equations (16) to (19), the braking force of each wheel (turning outer front wheel braking force FBfo, turning inner front wheel braking force FBfi, turning outer rear wheel braking force FBro, turning inner rear wheel braking force) FBri) is calculated and output to the brake fluid pressure calculation unit 30j for each wheel. That is, each wheel braking force calculation unit 30i is provided as each wheel braking force calculation means.
FBfo = (FB2 / 2) · DB (16)
FBfi = FB1 ・ DB1 + FBfo (17)
FBro = (FB2 / 2). (1-DB) (18)
FBri = FB1 · (1-DB1) + FBro (19)
Here, DB1 is the front-rear distribution ratio of the first braking force FB1, and is set to a value of 0.5 or the like in advance by experiments, calculations, or the like.

As is apparent from the above equations (16) to (19), in the present embodiment, as shown in FIG. 5, first, the absolute value | Δ (d ² y / dt ² ) | When the first lateral acceleration deviation threshold e1 or more is reached and the first additional yaw moment Mzt1 is applied, braking forces of FBfi and FBri are generated on the turning inner front and rear wheels (the state of Cv1 in FIG. 5). ).

Thereafter, when the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation becomes equal to or greater than the second lateral acceleration deviation threshold value e2, the second additional yaw moment Mzt2 is added. In addition to the braking forces FBfi and FBri of the inner front and rear wheels, the braking force is applied to the four wheels without changing the braking force difference between the inner wheel and the outer wheel (FBfo for the front two wheels and FBfo for the rear two wheels, respectively) FBro braking force) is generated. Therefore, the braking force FBfi of the turning inner front wheel generates FBfo braking force in addition to the initial FBfi (FBfi = FBfi + FBfo), and the braking force FBri of the turning inner rear wheel generates FBro braking force in addition to the initial FBri. (FBri = FBri + FBro) (state of Cv2 in FIG. 5).

The brake fluid pressure calculation unit 30j for each wheel receives the braking force FBfo, FBfi, FBro, FBri for each wheel from the braking force calculation unit 30i for each wheel. And, for example, according to the following formulas (20) to (23), the brake fluid pressure of each wheel (turning outside front wheel brake fluid pressure PBfo, turning inside front wheel brake fluid pressure PBfi, turning outside rear wheel brake fluid pressure PBro, turning inside The rear wheel brake hydraulic pressure PBri) is calculated and output to the brake drive unit 15.
PBfo = FBfo · CBf (20)
PBfi = FBfi · CBf (21)
PBro = FBro · CBr (22)
PBri = FBri · CBr (23)
Here, CBf and CBr are constants determined by brake specifications (wheel cylinder diameter, etc.).

Next, the braking force control program executed by the control unit 30 will be described with reference to the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) S101, necessary parameters, that is, engine output Teg, engine speed Ne, turbine speed Nt, main transmission gear ratio i, and driving force front-rear distribution ratio by the center differential device 4 are described. Each signal such as DD, vehicle speed V, steering wheel angle θH, longitudinal acceleration (d ² x / dt ² ), vehicle body lateral acceleration (d ² y / dt ² ) is read.

Next, the process proceeds to S102, where the target lateral acceleration calculation unit 30a calculates the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement, for example, by the above-described equation (1). To do.

Next, the process proceeds to S103, where the lateral acceleration deviation calculating unit 30b calculates the lateral acceleration deviation Δ (d ² y / dt ² ) by the above-described equation (2).

Next, in S104, the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is smaller than the preset first lateral acceleration deviation threshold e1 in the target yaw moment calculation unit 30c. In the case (| Δ (d ² y / dt ² ) | <e1), or when the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs and the vehicle 1 is oversteered. If it can be determined that it is not necessary to add a yaw moment in the turning direction to the vehicle 1 under the conditions that can be considered, this yaw moment is set as the first additional yaw moment Mzt1, and the first additional yaw moment Mzt1 is set to 0. Set. On the other hand, if the above condition is not satisfied and it can be determined that it is necessary to add a yaw moment in the turning direction to the vehicle 1, the first additional yaw moment Mzt1 is expressed by, for example, the above-described equation (3) To calculate.

Next, the process proceeds to S105, where the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is preset by the target yaw moment calculating unit 30c, and the second lateral acceleration deviation threshold e2 (> e1). Smaller than (when | Δ (d ² y / dt ² ) | <e ² ), or when the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs, the vehicle 1 tends to oversteer. If it can be determined that it is not necessary to add a yaw moment in the turning direction to the vehicle 1 in addition to the first additional yaw moment Mzt1 under the conditions that can be considered to be, the second additional yaw moment Mzt2 The second additional yaw moment Mzt2 is set to 0. On the other hand, if the above condition is not satisfied and it can be determined that it is necessary to add a yaw moment in the turning direction to the vehicle 1 in addition to the first additional yaw moment Mzt1, the second additional yaw moment Mzt2 Is calculated by, for example, the aforementioned equation (4).

  Next, proceeding to S106, the braking force calculation unit 30d calculates the first braking force FB1 to be applied to the turning inner wheel by the above-described equation (5).

  Next, the process proceeds to S107, and the second braking force FB2 applied to the vehicle 1 without changing the braking force difference between the turning inner wheel and the turning outer wheel by the braking force calculation unit 30d is expressed by the above-described equation (6). Calculated by

  Next, the process proceeds to S108, where the front / rear braking force distribution ratio calculation unit 30h considering the driving force, for example, the front / rear braking force distribution ratio DB considering the driving force with respect to the second braking force FB2 by the aforementioned equation (13). Is calculated.

  Next, the processing proceeds to S109, where the braking force calculation unit 30i of each wheel calculates the braking force of each wheel (the turning front wheel braking force FBfo, the turning inside front wheel braking force FBfi, the turning outside by the above-described equations (16) to (19)). The rear wheel braking force FBro and the turning inner rear wheel braking force FBri) are calculated.

  Then, the process proceeds to S110, and the brake fluid pressure calculation unit 30j for each wheel calculates the brake fluid pressure (the turning outer front wheel brake fluid pressure PBfo, the turning inner front wheel brake fluid pressure) according to the above-described equations (20) to (23). PBfi, turning outer rear wheel brake fluid pressure PBro, turning inner rear wheel brake fluid pressure PBri) are calculated and output to the brake drive unit 15 to exit the program.

Thus, according to the embodiment of the present invention, the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement is calculated based on the vehicle speed V and the steering wheel angle θH, Based on the target lateral acceleration (d ² y / dt ² ) t and the actual lateral acceleration (d ² y / dt ² ), a first additional yaw moment Mzt 1 to be applied to the vehicle 1 is calculated, and the target lateral acceleration is calculated. Based on (d ² y / dt ² ) t and the actual lateral acceleration (d ² y / dt ² ), a second additional yaw moment Mzt 2 to be added to the vehicle 1 in addition to the first additional yaw moment Mzt 1 The braking force applied to the turning inner wheel based on the first additional yaw moment Mzt1 is calculated as the first braking force FB1, and the turning inner wheel and the turning outer wheel are calculated based on the second additional yaw moment Mzt2. Without changing the braking force difference between The braking force applied to both 1 is calculated as the second braking force FB2, and the braking force applied to each wheel is calculated on the basis of the first braking force FB1 and the second braking force FB2, and applied to the brake drive unit 15. Output. For this reason, the yaw moment in the turning direction applied to the vehicle does not change, unexpected wheel locks due to braking force occur, the vehicle behavior changes suddenly, and the effect of preventing the understeer tendency is diminished. It is possible to effectively maximize the cornering force of the tire when turning the vehicle and reliably prevent the vehicle from going out of the curve with stable vehicle behavior.

The present embodiment will be specifically described with reference to the characteristics explanatory diagram of the lateral acceleration and the steering wheel angle ratio in the steady circle turning test of FIG.
The characteristic explanatory diagram of the lateral acceleration and the steering wheel angle ratio in the steady circle turning test of FIG. 4 shows the lateral acceleration (d ² y / dt ² ) when the vehicle 1 turns along a circle with a predetermined constant radius: Ratio of horizontal axis and handle angle (= handle angle θH / handle angle θH0 at extremely low speed): an example of the characteristics of the vertical axis, and a line L0 indicated by a broken line in FIG. 4 is a reference steer characteristic line. A line translated from the reference steer characteristic line L0 by the first lateral acceleration deviation threshold e1 with respect to the horizontal axis in the direction in which the lateral acceleration (d ² y / dt ² ) decreases becomes L1, the second The line translated by the lateral acceleration deviation threshold e2 is L2.

In a normal vehicle, as the vehicle speed V increases and the lateral acceleration (d ² y / dt ² ) increases, a predetermined constant value is obtained unless the steering wheel angle θH is cut off from the steering wheel angle θH0 at an extremely low speed. The steering wheel angle ratio tends to increase because it becomes difficult to turn along a circle with a radius of.

That is, in the general vehicle characteristics, as shown by the broken line Nsu0, when the lateral acceleration (d ² y / dt ² ) increases, the tire cornering force is deviated from the reference steering characteristic line due to the nonlinearity of the tire cornering force, and the lateral acceleration (d ² y / dt ² ), a characteristic with a larger handle angle ratio is drawn.

  In the control according to the present embodiment, when the state after the point P1 deviated by the first lateral acceleration deviation threshold e1 from the reference steering characteristic line L0, the braking force of FBfi and FBri is generated on the turning inner front and rear wheels. One additional yaw moment Mzt1 is added to prevent an understeer tendency of the vehicle. As a result, the characteristics of the vehicle are improved to characteristics close to the line L1 as indicated by Nsu1.

  Even if the vehicle characteristic is improved to Nsu1, if the state after the point P2 deviated from the reference steering characteristic line L0 by the second lateral acceleration deviation threshold e2 is reached, the braking force FBfi of the turning inner front and rear wheels, In addition to FBri, braking force is generated on the four wheels without changing the braking force difference between the turning inner wheel and the turning outer wheel, and the second additional yaw moment Mzt2 is added to prevent the vehicle from understeering. Is done. Thereby, the characteristic of the vehicle is improved to a characteristic approaching the line L2 as indicated by Nsu2.

In the embodiment of the present invention, the target lateral acceleration (d ² y / dt ² ) t is used as the target vehicle behavior of the vehicle lateral motion, using the target target lateral acceleration (d ² y / dt ² ) t. The first additional yaw moment Mzt1 and the second additional yaw moment Mzt2 are calculated based on the actual lateral acceleration (d ² y / dt ² ). For example, the following equation (24) Thus, the target yaw rate γt is calculated, and based on the target yaw rate γt and the actual yaw rate γ (detected value from the yaw rate sensor), the yaw rate deviation Δγ is obtained to obtain the first additional yaw moment Mzt1 and the second additional yaw moment. Mzt2 may be calculated.
γt = (1 / (1 + A · V ² )) · (V / l) · (θH / n) (24)

  In the embodiment of the present invention, the second braking force FB2 is determined by the front / rear braking force distribution ratio DB in consideration of the driving force. However, depending on the vehicle characteristics, the driving force may be reduced. You may make it set according to the ground load distribution of a front-back axis | shaft, or the front-back weight distribution, without considering.

  Furthermore, in the embodiment of the present invention, the first additional yaw moment Mzt1 is generated by applying the first braking force FB1 to the turning inner wheel. This is an example in which the braking force is set to 0. In addition, the first additional yaw moment is provided by providing a predetermined braking force difference between the braking force applied to the turning inner wheel and the braking force applied to the turning outer wheel. The same applies to the control for generating Mzt1.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 3 Automatic transmission 4 Center differential device 13fl, 13fr, 13rl, 13rr Wheel 15 Brake drive part 18fl, 18fr, 18rl, 18rr Wheel cylinder 21 Engine control device 22 Transmission control device 23 Vehicle speed sensor 24 Handle angle sensor 25 Front and rear Acceleration sensor 26 Lateral acceleration sensor (actual vehicle behavior detection means)
30 control unit 30a target lateral acceleration calculation unit (target vehicle behavior calculation means)
30b Lateral acceleration deviation calculator 30c Target yaw moment calculator (first additional yaw moment calculator, second additional yaw moment calculator)
30d Braking force calculating unit (first braking force calculating means, second braking force calculating means)
30e Transmission output torque calculation unit 30f Total braking / driving power calculation unit 30g Second front / rear braking force distribution ratio calculation unit 30h Front / rear braking force distribution ratio calculation unit 30i considering driving force 30i Braking force calculation unit for each wheel (each wheel braking force Calculation means)
30j Brake fluid pressure calculator for each wheel

Claims (3)

Target vehicle behavior calculating means for calculating a vehicle behavior to be a target of vehicle lateral movement based on a driving state of the vehicle;
An actual vehicle behavior detecting means for detecting an actual vehicle behavior of the lateral movement of the vehicle;
First additional yaw moment calculating means for calculating a first additional yaw moment to be added to the vehicle based on the vehicle behavior targeted for the vehicle lateral movement and the actual vehicle behavior of the vehicle lateral movement;
A second additional yaw moment to be added to the vehicle in addition to the first additional yaw moment is calculated based on the target vehicle behavior of the lateral vehicle motion and the actual vehicle behavior of the lateral vehicle motion. Additional yaw moment calculation means,
First braking force calculation means for calculating a braking force to be applied to the turning inner wheel and the turning outer wheel as the first braking force based on the first additional yaw moment;
Based on the second additional yaw moment to be applied to the vehicle in addition to the first additional yaw moment, the control between the turning inner wheel and the turning outer wheel calculated by the first braking force calculation means is performed. A second braking force calculating means for calculating a braking force applied to the vehicle without changing the power difference as a second braking force;
And a respective wheel braking force calculating means for calculating a braking force to be added to each of the wheels based on the first braking force and the second braking force,
Each wheel braking force calculation means sets only the front-rear distribution ratio of the second braking force according to either the front-rear weight distribution of the vehicle or the ground load distribution of the front-rear shaft. Power control device. 2. The vehicle braking force control according to claim 1, wherein each wheel braking force calculation unit calculates and corrects only a front-rear distribution ratio of the second braking force with a driving force applied to the front and rear wheels. apparatus. 3. The vehicle control according to claim 1 , wherein the vehicle behavior that is a target of the vehicle lateral movement is one of a target lateral acceleration and a target yaw rate that are calculated based on a driving state of the vehicle. Power control device.

Images