JP2016141221A - Vehicle traveling control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle traveling control device capable of reducing a change in acceleration or speed of a vehicle when the understeering of the vehicle is suppressed during the turning of the vehicle.SOLUTION: The vehicle traveling control device includes a turning traveling control unit for controlling a vehicle braking device so as to apply a braking force to a turning-inside driving wheel larger than that to a turning-outside driving wheel, for example, when the traveling state of the vehicle is an understeering state, and controlling a vehicle driving device so as to apply a driving force for compensating for the reduction of acceleration or speed of the vehicle accompanying the controlling of the braking device while controlling the braking device.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a vehicle travel control device.

  Conventionally, a first step of applying a braking force to one of the left and right wheels according to the vehicle behavior, and a second step of increasing the other driving force of the left and right wheels when the vehicle behavior is changed by the first step, Is known (for example, Patent Document 1).

JP 2010-215164 A

  In the prior art, changes in the acceleration and speed of the vehicle are likely to increase between the first step and the second step. Accordingly, one of the problems of the present invention is to obtain a vehicle travel control device in which, for example, a change in acceleration or speed of the vehicle is likely to be smaller when executing control to suppress understeer of the vehicle when the vehicle is turning. is there.

  The vehicle travel control apparatus according to the present invention turns, for example, when a travel state detection unit that detects that the travel state of the vehicle is an understeer state and the understeer state of the vehicle is detected by the travel state detection unit. The braking device of the vehicle is controlled so that a larger braking force is applied to the inner driving wheel than the outer driving wheel of the turn, and the vehicle accompanying the control of the braking device is controlled on the driving wheel while controlling the braking device. And a turning control unit that controls the driving device of the vehicle so as to apply a driving force that compensates for a decrease in the acceleration or speed of the vehicle.

  In the vehicle travel control device, for example, in a state where an acceleration operation unit that performs an operation for accelerating the drive device is operated, the turning travel control unit controls the brake device and drives the drive. Perform control of the device.

  Further, in the vehicle travel control device, for example, while the acceleration operation unit that performs an operation for accelerating the drive device is operated, the control by the turning travel control unit is continued.

  In the vehicle travel control device, for example, in a state where an acceleration operation unit that performs an operation for accelerating the drive device is not operated, the turning travel control unit controls the braking device and drives the drive. Of the control of the device, only the control of the braking device can be executed for a predetermined time, and the predetermined time is set shorter as the road surface friction coefficient is smaller.

FIG. 1 is an exemplary schematic diagram of a vehicle on which the vehicle travel control device of the embodiment is mounted. FIG. 2 is an exemplary block diagram of the vehicle travel control apparatus according to the embodiment. FIG. 3 is a schematic explanatory diagram showing the braking force and driving force at each wheel of the front-wheel drive vehicle controlled by the vehicle travel control device of the embodiment. FIG. 4 is a schematic explanatory diagram showing the braking force and driving force at each wheel of the four-wheel drive vehicle controlled by the vehicle travel control device of the embodiment. FIG. 5 is a graph showing an example of the correlation between the road surface friction coefficient and the braking force in the vehicle travel control apparatus of the embodiment. FIG. 6 is a graph showing an example of the correlation between the yaw rate deviation and the braking force coefficient (K1) in the vehicle travel control apparatus of the embodiment. FIG. 7 is a graph showing an example of the correlation between the operation amount of the acceleration operation unit and the braking force coefficient (K2) in the vehicle travel control apparatus of the embodiment. FIG. 8 is a graph showing an example of the correlation between the steering angle and the coefficient (K3) of the braking force in the vehicle travel control apparatus of the embodiment. FIG. 9 is an exemplary flowchart illustrating a control procedure performed by the vehicle travel control apparatus according to the embodiment. FIG. 10 is a graph showing an example of the correlation between the road surface friction coefficient and the control duration in the vehicle travel control apparatus of the embodiment.

  Hereinafter, exemplary embodiments of the present invention are disclosed. The configuration of the embodiment shown below, and the operation and result (effect) brought about by the configuration are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments. According to the present invention, it is possible to obtain at least one of various effects (including derivative effects) obtained by the configuration.

<Configuration of travel control device>
The vehicle 1 includes a total of four wheels 2 including a front and left wheel 2FL, a front and right wheel 2FR, a rear and left wheel 2RL, and a rear and right wheel 2RR. The vehicle 1 is provided with a wheel cylinder 22 corresponding to each of the four wheels 2. The operation of the wheel cylinder 22 is controlled by the brake actuator 21. The brake actuator 21 applies hydraulic pressure to each of the wheel cylinders 22. The wheel cylinder 22 suppresses the rotation of the rotating member 23 such as a disk or a drum that rotates with the wheel 2 in accordance with the applied hydraulic pressure. Thereby, the wheel 2 is braked. The brake actuator 21 is controlled by a brake ECU 10 (electronic control unit). The brake ECU 10 can control the braking force of each wheel 2 by outputting an electric signal (control signal) to the brake actuator 21. The brake ECU 10 is an example of a travel control device. The brake actuator 21, the wheel cylinder 22, the rotating member 23, and the like are examples of a brake device.

  In the vehicle 1 illustrated in FIG. 1, the front wheels 2FL and 2FR are driven by a drive source 3 such as an engine or a motor. In this case, torque (driving force) of the drive source 3 is transmitted to the wheels 2FL and 2FR via the transmission 4, the shaft 5, a differential gear (not shown), and the like. The transmission 4 is a stepped or continuously variable transmission, and is, for example, AT (automatic transmission), CVT (continuously variable transmission), AMT (automated manual transmission), MT (manual transmission), or the like. The wheel 2 driven by the drive source 3 can also be referred to as a drive wheel. FIG. 1 illustrates a so-called front wheel drive vehicle in which the front wheels 2FL and 2FR are driven. However, the travel control device of the present invention is a vehicle having other drive wheels, such as a rear wheel drive vehicle, It can also be applied to a four-wheel drive vehicle. The drive source 3 is an example of a drive device.

  The drive source 3 is controlled by the drive ECU 11. For example, when the drive source 3 is an internal combustion engine, the drive ECU 11 is an engine ECU and controls an electronically controlled throttle valve, an electronically controlled fuel injection valve, and the like (not shown) that are operated by an electrical signal (control signal). As a result, the output torque of the drive source 3 and, in turn, the drive force in the drive wheels are controlled. The drive ECU 11 can control the drive source 3 based on detection signals from at least one of the sensors 31 and 32. For example, when the drive source 3 is a gasoline engine, the sensors 31 and 32 are an air flow meter, a throttle sensor, a rotation speed sensor, and the like.

  At least two of the four wheels 2 are steered according to the rotation of the steering wheel 6. In the vehicle 1 illustrated in FIG. 1, the front wheels 2FL and 2FR are steered. In this case, the rotation of the steering wheel 6 is converted into the operation of the steering member 63 such as a rod or a link through the power steering device 61, the motion conversion mechanism 62, and the like, and the wheel 2FL is changed according to the operation of the steering member 63. , 2FR is steered. The wheel 2 steered by the steered member 63 can also be referred to as a steered wheel. Although a so-called front wheel steering vehicle is illustrated in FIG. 1, the traveling control device of the present invention can also be applied to a vehicle having other steering wheels, for example, a four-wheel steered vehicle. Further, the steering amount (steering angle) based on the operation of the steering wheel 6 is detected by the steering angle sensor 33, and the actual turning amount (steering angle) of the steered wheels is detected by the steering amount sensor 34. Note that the steering angle sensor 33 and the steered amount sensor 34 may be simply referred to as sensors 33 and 34.

  The vehicle 1 is provided with an accelerator sensor 35 that detects an operation amount of the acceleration operation unit 71 and a brake sensor 36 that detects an operation amount of the deceleration operation unit 72. The acceleration operation unit 71 is, for example, an accelerator pedal, the deceleration operation unit 72 is, for example, a brake pedal, and the accelerator sensor 35 and the brake sensor 36 are, for example, a stroke sensor or a position sensor. Note that the accelerator sensor 35 and the brake sensor 36 may be simply referred to as sensors 35 and 36.

  Further, the vehicle 1 is provided with acceleration sensors 37 and 38 and a yaw rate sensor 39. The acceleration sensor 37 detects acceleration in the vehicle longitudinal direction of the vehicle 1, the acceleration sensor 38 detects acceleration in the vehicle width direction of the vehicle 1, and the yaw rate sensor 39 detects angular velocity in the turning direction of the vehicle 1. The acceleration sensors 37 and 38 and the yaw rate sensor 39 may also be simply referred to as sensors 37, 38, and 39.

  Each wheel 2 is provided with a wheel speed sensor 40. Based on the detection result of the wheel speed sensor 40, the rotational speed of each wheel 2, the rotational acceleration, the speed of the vehicle 1, the moving distance of the vehicle 1, and the like are calculated. The wheel speed sensor 40 may be simply referred to as a sensor or the like.

  The brake ECU 10 illustrated in FIG. 2 includes a control element 110 and a storage unit 120. The control element 110 is, for example, a CPU (central processing unit), and the storage unit 120 is, for example, a RAM (random access memory), a ROM (read only memory), a flash memory, an SSD (solid state drive), or the like. is there. The control element 110 includes a brake control unit 111, a turning travel control unit 112, a data transfer control unit 113, and the like. The control element 110 may include a skid control unit (not shown).

  The control element 110 can execute processing in accordance with a program installed and loaded to realize each function. That is, by executing processing according to the program, the control element 110 can function as the brake control unit 111, the turning travel control unit 112, the data transfer control unit 113, and the like. In this case, the program includes modules corresponding to the brake control unit 111, the turning travel control unit 112, the data transfer control unit 113, and the like. In addition, the storage unit 120 stores a program, data corresponding to the detection result by the sensor, data used in arithmetic processing of each unit, data of the result of arithmetic processing, and the like. The storage unit 120 may include a nonvolatile rewritable storage unit. Note that at least some of the functions of the above-described units may be realized by hardware.

  The brake control unit 111 controls the brake actuator 21. The data transmission / reception control unit 113 controls transmission / reception of data (signals) between the brake ECU 10 and another ECU, for example, the drive ECU 11. Data exchange is performed via an interface unit such as a connector or a bus (not shown).

  The turning control unit 112 includes a start condition determination unit 112a, an end condition determination unit 112b, a braking force calculation unit 112c, a driving force calculation unit 112d, and the like. The start condition determination unit 112a is a state that satisfies the condition for starting the control by the turning control unit 112 by comparing each parameter calculated based on the detection values by the sensors 31 to 40 with a predetermined threshold, for example. It is determined whether or not. The end condition determination unit 112b satisfies a condition that satisfies the condition for starting the control by the turning control unit 112 by comparing each parameter calculated based on the detection values by the sensors 31 to 40 with a predetermined threshold, for example. It is determined whether or not. The turning control unit 112 executes control (first control) for braking the vehicle 1 and, in parallel with the first control, a driving force that compensates for a decrease in acceleration or speed of the vehicle 1 due to braking. The control (second control) for applying to the drive wheel can be executed.

  The braking force calculation unit 112c calculates the braking force applied to the driving wheels inside the turning in the control by the turning traveling control unit 112. In addition, the driving force calculation unit 112d reduces the acceleration (speed) of the vehicle 1 that is reduced by applying the braking force calculated by the braking force calculation unit 112c to the driving wheels inside the turning in the control by the turning traveling control unit 112. ) Is calculated. The “compensation” here may be any compensation for driving force having a magnitude of 100% or less of the braking force. That is, it is sufficient that the driving force is increased by this compensation as compared with the case where no compensation is made. However, compensation exceeding 100 percent is not performed.

  The turning control unit 112 can acquire or calculate the value of each parameter used in turning control based on the detection results (detection values) of the sensors 31 to 40. In the example of FIG. 2, the turning control unit 112 is mounted as a part of the brake ECU 10 and mounted on the same control element 110 as the brake control unit 111, but is not limited thereto, and the brake ECU 10 The ECU may be included in another ECU, or may be implemented as an element different from the brake control unit 111.

<Determination of braking force and driving force in turning control (1)>
Here, with reference to FIG. 3, in the travel control device of the present embodiment, the braking force applied to the driving wheel inside the turning and the driving force applied to the driving wheel in the control by the turning travel control unit 112 will be described. To do. First, a case where the present invention is applied to the front wheel drive vehicle illustrated in FIG. 3 will be described. In FIG. 3, the vehicle front-rear direction is the vertical direction of FIG. 3, the vehicle width direction is the left-right direction of FIG. 3, and the upper side of FIG. Here, first, a case where the vehicle 1 turns leftward as shown in FIG. 3 is exemplified.

ここに、Ｖ：車両速度、Ｓｔ：舵角、ｎ：ステアリングギヤ比、Ｌ：ホイールベース、Ｋｈ：スタビリティファクタである。 Turning control section 112, in order to suppress the understeer during turning of the vehicle 1, deviation Yr _d between the target yaw rate Yr _t and the actual yaw rate Yr _s is controlled to approach zero. Deviation Yr _d can be expressed by the following equation (1).

Here, V: vehicle speed, St: rudder angle, n: steering gear ratio, L: wheelbase, Kh: stability factor.

ここに、Ｉ：車両のヨー方向の慣性モーメント、Ｔ：トレッド、δ_ｆ：駆動輪の舵角、Ｌ_ｆ：重心位置Ｃｇから駆動輪（車輪２ＦＬ，２ＦＲ）までの車両前後方向の距離、である。制動力算出部１１２ｃは、式（１）および式（２）から、車両１の旋回の内側の駆動輪（車輪２ＦＬ）に加える制動力Ｆｂ_ｆを、算出することができる。旋回走行制御部１１２は、車両１の旋回の内側の駆動輪（車輪２ＦＬ）に、式（１）および式（２）から算出された制動力Ｆｂ_ｆが生じるよう、ブレーキアクチュエータ２１を制御する。これにより、車両１のアンダーステアが低減される。なお、旋回の内輪の制動力が外輪の制動力よりも、｜Ｆｂ_ｆ｜だけ大きい状態であれば、同様の結果が得られる。 Further, the turning of the vehicle 1, a braking force Fb _f applied to the inside of the drive wheels of the turning vehicle 1 (wheel 2FL), a deviation Yr _d of formula (1), the following equation (2) containing a The equation of motion shown holds.

Here, I: inertia moment in the yaw direction of the vehicle, T: tread, δ _f : rudder angle of the drive wheel, L _f : distance in the vehicle front-rear direction from the center of gravity position Cg to the drive wheel (wheels 2FL, 2FR) is there. Braking force calculating unit 112c, from equation (1) and (2), the braking force Fb _f applied to the inside of the drive wheels of the turning vehicle 1 (wheel 2FL), it can be calculated. The turning traveling control unit 112 controls the brake actuator 21 so that the braking force Fb _f calculated from the equations (1) and (2) is generated on the driving wheel (wheel 2FL) inside the turning of the vehicle 1. Thereby, the understeer of the vehicle 1 is reduced. Similar results can be obtained if the braking force of the turning inner wheel is larger than the braking force of the outer wheel by | Fb _f |.

ここに、α：係数である。係数αは、例えば１以下に設定される。旋回走行制御部１１２は、車両１の駆動輪（車輪２ＦＬ，２ＦＲ）に、式（３）で算出された駆動力ΔＦｄを追加する。駆動力ΔＦｄは、各駆動輪に分配される。なお、図３中のＦｄは、駆動力である。 Furthermore, the driving force calculation unit 112d calculates a driving force ΔFd that compensates for the acceleration (speed) of the vehicle 1 that decreases with the braking force Fb _f by the following equation (3).

Here, α is a coefficient. The coefficient α is set to 1 or less, for example. The turning traveling control unit 112 adds the driving force ΔFd calculated by Expression (3) to the driving wheels (wheels 2FL, 2FR) of the vehicle 1. The driving force ΔFd is distributed to each driving wheel. Note that Fd in FIG. 3 is a driving force.

Although not shown, the same control can be performed when the front-wheel drive vehicle 1 turns in the right direction. However, in this case, the braking force Fb _f calculated from the equations (1) and (2) is applied to the front and right wheels 2FR, and the driving force ΔFd calculated from the equation (3) is applied to the front wheels 2FL. , 2FR.

ここに、Ｌ_ｒ：重心位置Ｃｇから駆動輪までの車両前後方向の距離である。なお、この場合にあっても、旋回の内輪の制動力が外輪の制動力よりも、｜Ｆｂ_ｒ｜だけ大きい状態であれば、同様の結果が得られる。 Although not shown, in the case of a rear wheel drive vehicle, the braking force calculation unit 112c calculates the driving wheel (inside the turning of the vehicle 1) from the equation (1) and the equation (4) similar to the equation (2). it is possible to calculate the braking force Fb _r applied to the wheels 2RL or wheels 2RR).

Here, L _r is the distance in the vehicle front-rear direction from the center of gravity position Cg to the drive wheel. Even in this case, the same result can be obtained as long as the braking force of the turning inner wheel is larger than the braking force of the outer wheel by | Fb _r |.

旋回走行制御部１１２は、車両１の駆動輪（車輪２ＲＬ，２ＲＲ）に、式（３）で算出された駆動力ΔＦｄを追加する。駆動力ΔＦｄは、各駆動輪に分配される。 The driving force calculating unit 112d is the driving force ΔFd to compensate for acceleration (velocity) of the vehicle 1 decreases along with the braking force Fb _r, is calculated by the following equation (5).

The turning traveling control unit 112 adds the driving force ΔFd calculated by Expression (3) to the driving wheels (wheels 2RL, 2RR) of the vehicle 1. The driving force ΔFd is distributed to each driving wheel.

  Next, the braking force and driving force applied in the control by the turning control unit 112 when the vehicle 1 is a four-wheel drive vehicle will be described with reference to FIG. 4, the vehicle front-rear direction is the vertical direction of FIG. 4, the vehicle width direction is the left-right direction of FIG. 4, and the upper side of FIG. 4 is the front side of the vehicle 1. Here, first, the case where the vehicle 1 turns leftward as shown in FIG. 4 is illustrated.

ここに、ｍ：車両１の重量、Ｇ_ｘ：車両前後方向の車両１の加速度、Ｇ_ｙ：車幅方向の車両１の加速度、ｈ：車両１の重心の路面からの高さである。 The load movement amount ΔWx due to the pitch of the vehicle 1 and the load movement amount ΔWy due to the roll of the vehicle 1 can be expressed by the following equations (6) and (7).

Here, m is the weight of the vehicle 1, G _{x is} the acceleration of the vehicle 1 in the vehicle longitudinal direction, G _{y is} the acceleration of the vehicle 1 in the vehicle width direction, and h is the height of the center of gravity of the vehicle 1 from the road surface.

When load movement amounts ΔWx and ΔWy occur while the vehicle 1 is turning, the load W _{fl of} the wheel 2FL, the load W _{fr of the} wheel 2FR, the load W _{rl of the} wheel 2RL, and the load W _{rr of the} wheel 2RR are expressed by the following formulas ( 8) to (11).

ここに、δ_ｆ：前側の駆動輪の舵角、δ_ｒ：後側の駆動輪の舵角、Ｌ_ｆ：重心位置Ｃｇから前側の駆動輪（車輪２ＦＬ，２ＦＲ）までの車両前後方向の距離、Ｌ_ｒ：重心位置Ｃｇから後側の駆動輪（車輪２ＲＬ，２ＲＲ）までの車両前後方向の距離、である。 Then, the turning of the vehicle 1 in this case, the inside of the drive wheels (wheels 2FL, 2RL) of turning of the vehicle 1 to the applied braking force _Fb f, and Fb _r, and deviation Yr _d of formula (1), the The equation of motion represented by the following equation (12) is established.

Where δ _{f is} the steering angle of the front driving wheel, δ _{r is} the steering angle of the rear driving wheel, L _f is the distance in the vehicle longitudinal direction from the center of gravity Cg to the front driving wheels (wheels 2FL and 2FR). , L _r : Distance in the vehicle front-rear direction from the center of gravity position Cg to the rear drive wheels (wheels 2RL, 2RR).

したがって、制動力算出部１１２ｃは、式（１）、式（１２）、および式（１３）から、車両１の旋回の内側の駆動輪（車輪２ＦＬ，２ＲＬ）に加える制動力Ｆｂ_ｆ，Ｆｂ_ｒを、算出することができる。旋回走行制御部１１２は、車両１の旋回の内側の駆動輪（車輪２ＦＬ，２ＲＬ）に、式（１）、式（１２）、および式（１３）から算出された制動力Ｆｂ_ｆ，Ｆｂ_ｒが生じるよう、ブレーキアクチュエータ２１を制御する。これにより、車両１のアンダーステアが低減される。また、四輪駆動の車両１が右方向に旋回する場合も同様に制御されうる。ただし、この場合は、車両１の旋回の内側の駆動輪（車輪２ＦＲ，２ＲＲ）に加える制動力Ｆｂ_ｆ，Ｆｂ_ｒの配分は、次の式（１４）により決定する。

そして、式（１）、式（１２）、および式（１４）によって算出された制動力Ｆｂ_ｆが前側かつ右側の車輪２ＦＲに加えられ、制動力Ｆｂ_ｒが後側かつ右側の車輪２ＲＲに加えられる。なお、この場合にあっても、旋回の内輪の制動力が外輪の制動力よりも、｜Ｆｂ_ｆ｜または｜Ｆｂ_ｒ｜だけ大きい状態であれば、同様の結果が得られる。 Here, inside of the drive wheels (wheels 2FL, 2RL) of turning of the vehicle 1 braking force _Fb f applied to the allocation of Fb _r, as in the following equation (13), the load acting on the front and rear of the drive wheels Determine by ratio.

Therefore, the braking force calculation unit 112c applies the braking forces Fb _f and Fb _r applied to the driving wheels (wheels 2FL and 2RL) on the inner side of the turning of the vehicle 1 from the equations (1), (12), and (13). Can be calculated. The turning travel control unit 112 applies braking forces Fb _f and Fb _r calculated from the equations (1), (12), and (13) to the driving wheels (wheels 2FL, 2RL) inside the turning of the vehicle 1. The brake actuator 21 is controlled so as to occur. Thereby, the understeer of the vehicle 1 is reduced. The same control can be performed when the four-wheel drive vehicle 1 turns to the right. However, in this case, the inside of the drive wheels of the turning vehicle 1 (wheel 2FR, 2RR) braking force _Fb f applied to the allocation of Fb _r is determined by the following equation (14).

Then, equation (1), equation (12), and the braking force Fb _f calculated by Equation (14) is applied to the front and right wheels 2FR, in addition to the braking force Fb _r is rear and right wheel 2RR It is done. Even in this case, the same result can be obtained if the braking force of the turning inner wheel is larger than the braking force of the outer wheel by | Fb _f | or | Fb _r |.

ここに、α：係数である。係数αは、例えば１以下に設定される。
旋回走行制御部１１２は、車両１の駆動輪（車輪２ＦＬ，２ＦＲ，２ＲＬ，２ＲＲ）に、式（１５）で算出された駆動力ΔＦｄを追加する。駆動力ΔＦｄは、各駆動輪に分配される。なお、図４中のＦｄは、駆動力である。 Furthermore, the driving force calculating unit 112d is the driving force ΔFd for compensating the braking force _Fb f, Fb _r in association with Decreased vehicle 1 acceleration (velocity) is calculated by the following equation (15).

Here, α is a coefficient. The coefficient α is set to 1 or less, for example.
The turning travel control unit 112 adds the driving force ΔFd calculated by Expression (15) to the driving wheels (wheels 2FL, 2FR, 2RL, 2RR) of the vehicle 1. The driving force ΔFd is distributed to each driving wheel. Note that Fd in FIG. 4 is a driving force.

<Determination of braking force and driving force in turning control (2)>
Equation (1), (2), (4), from (12) or the like, the braking force _Fb f, Fb _r is the yaw rate and the deviation Yr _d of the steering angle [delta] _f, may vary depending on the [delta] _r, etc. I understand. Further, the inventors' diligent research has revealed that the braking forces Fb _f and Fbr _r also change depending on the friction coefficient of the road surface, the operation amount of the acceleration operation unit 71, the speed of the vehicle 1, the change speed of the steering angle, and the like. doing. Therefore, the braking force calculating unit 112c, the braking force _Fb f, predetermined parameters and the braking force to change the size of the Fb _{r Fb} f, based on the correlation between the Fb _r, the braking force _Fb f, the Fb _r Can be calculated. The correlation is acquired in advance based on the above-described theoretical examination, examination by experiment, simulation, or the like, and is stored in the storage unit 120 as a function (formula), a map, a table, or the like. In addition, the function (formula) may be stored in a program, or may be incorporated as a logical operation circuit in hardware.

Specifically, in the case of a front-wheel drive vehicle, the braking force calculation unit 112c can calculate the braking force Fb _f by Expression (16).
Fb _f = f (μ) × K1 × K2 × K3 (16)
Here, mu: road surface friction coefficient, f (μ): a function of road surface friction coefficient mu (Fig. 5), K1: coefficient corresponding to the yaw rate deviation Yr _d (FIG. 6), K2: operating amount of an acceleration operating section 71 As Is a coefficient according to (Fig. 7), K3: a coefficient according to the steering angle St (Fig. 8). Also in this case, the driving force calculation unit 112d can calculate the driving force ΔFd that compensates for the acceleration (speed) of the vehicle 1 that decreases with the braking force Fb _f by the above formulas (3) and (5). it can. Incidentally, a formula (16) and the characteristics of FIGS. 6-8 (correlation) is an example, the braking force Fb _f include, but are not limited, it may be calculated based on other parameters, other May be calculated based on the characteristics (correlation). Further, in the case of rear-wheel drive vehicle, the braking force Fb _r is calculated by the equation similar to equation (16), the above equation based on the braking force Fb _r (3), the braking force ΔFd by (5) Can be calculated. Further, in the case of a four-wheel drive vehicle, the total value of the braking force for both the front wheels and the rear wheels is calculated by the same expression as Expression (16), and the distribution shown in Expressions (13) and (15) braking force _Fb f, Fb _r is calculated, the braking force ΔFd can be calculated by equation (14). Instead of the road surface friction coefficient μ, acceleration in the vehicle width direction of the vehicle 1 may be used, or the road surface friction coefficient μ may be calculated based on the acceleration in the vehicle width direction of the vehicle 1. The coefficients K1, K2, and K3 can also be referred to as gains.

<Procedure for turning control>
Here, an example of the procedure of the turning traveling control will be described with reference to FIG. At each time step, at least one of S1 to S4 in FIG. 9 is executed. First, the start condition determination unit 112a determines whether the start condition is satisfied based on the parameter value acquired or calculated by the turning control unit 112 (S1). If the start condition is not satisfied in S1 (No in S1), the turning traveling control is not executed and the process ends. The start condition in S1 is set as follows, for example.
[1-1] sgn (Yr _t ) · Yr _d ≧ Yth and [1-2] V ≧ Vth and [1-3] St ≧ Sth and [1-4] Bs ≦ Bth
Here, sgn (Yr _t ) is a sign function. When Yr _t > 0, sgn (Yr _t ) = 1, when Yr _t = 0, sgn (Yr _t ) = 0, and Yr _t <0. When sgn (Yr _t ) = − 1. Further, Yth: threshold of the yaw rate deviation Yr _d, Vth: the threshold of the vehicle speed V, Sth: threshold of the steering angle St, Bs: operation amount of the reduction operation unit 72, Bth: the threshold of the manipulated variable Bs of deceleration operation unit 72 is there.

  From [1-1], it can be determined whether or not the vehicle 1 is in an understeer tendency. [1-1] is set so that turning control of the present embodiment is started in a state where the vehicle 1 is in an understeer tendency. The threshold Yth is set to a value close to 0 (zero), for example. The sign function sgn () takes into account that the sign such as yaw rate changes depending on the turning direction. The start condition determination unit 112a is an example of a traveling state detection unit.

  Moreover, by [1-2], the time of low-speed driving | running | working, such as the time of parking or leaving can be excluded from turning control.

Moreover, for example, the state where the steering angle St is small can be excluded from the turning control by [1-3]. Note that the steering angles δ _f and δ _{r of the} wheels 2 may be used instead of the steering angle St, or the speed (angular speed) of the steering angle may be used.

  Further, when the braking operation is performed by the driver according to the setting [1-4], the turning traveling control is not executed. The turning traveling control unit 112 aims to reduce understeer of the vehicle 1 when the vehicle 1 travels while turning, and is excluded from the control target when the driver tries to brake the vehicle 1. Note that the inequality signs in the above formulas [1-1] to [1-4] may not include the equal sign. In addition, each determination formula (inequality) of the start condition of the turning control is not limited to the examples of the above formulas [1-1] to [1-4]. Further, another condition may be added, or some of the above conditions may be reduced.

  In the flow of FIG. 9, when the start condition of S1 is satisfied, that is, when all the above [1-1] to [1-4] are satisfied (Yes in S1), the braking force is applied to the driving wheels of the turning inner wheel. Is applied (S2), and a driving force that compensates for a decrease in the acceleration (speed) of the vehicle 1 due to S3 is applied to the driving wheels (S3). The turning traveling control unit 112 can execute S2 and S3 in parallel. The braking force and driving force in S2 and S3 are determined by (1), (2), etc. of the determination of the braking force and driving force in the above-described turning traveling control. S2 is an example of the first control, and S3 is an example of the second control.

After S3, the end condition determining unit 112b determines whether or not the end condition is satisfied based on the parameter value acquired or calculated by the turning control unit 112 (S4). If the termination condition is not satisfied in S4 (No in S4), the process returns to S2. The termination condition in S4 is set as follows, for example.
[2-1] sgn (Yr _t ) · Yr _d ≦ 0 or [2-2] Bs> Bth or [2-3] As ≦ Ath and Kt ≧ Kth
Here, As: operation amount of the acceleration operation unit 71, Ath: threshold value of the operation amount As of the acceleration operation unit 71, Kt: duration from the start of turning traveling control, Kth: control time from the start of turning traveling control It is a threshold value.

  From [2-1], it can be determined whether or not the vehicle 1 is in an oversteer tendency. [2-1] is set so that the turning control of the present embodiment is terminated in a state where the vehicle 1 is in an oversteer tendency.

  Further, when the braking operation is performed by the driver according to the setting of [2-2], the turning traveling control is ended. The turning traveling control unit 112 aims to reduce understeer of the vehicle 1 when the vehicle 1 travels while turning, and is excluded from the control target when the driver tries to brake the vehicle 1.

  Moreover, in the state where the operation of the acceleration operation unit 71 is performed according to [2-3], the turning traveling control of the present embodiment is continued. If the turning control is immediately terminated when the condition of [2-1] is satisfied, the vehicle 1 is again in an understeering state, and the understeering state and the turning traveling control of this embodiment are executed. Thus, there is a possibility that the state in which the understeer tendency is eliminated repeatedly occurs, and the change in the acceleration of the vehicle 1 becomes relatively large or the vehicle 1 slightly meanders. In this respect, in the present embodiment, the turning traveling control of the present embodiment is continued in the state where the operation of the acceleration operation unit 71 is performed according to [2-3], and thus such an inconvenient phenomenon occurs. hard. The threshold Ath is set to a value close to 0 (zero), for example.

  In [2-3], even when the operation of the acceleration operation unit 71 is not performed, the duration Kt from the start of the turning traveling control is equal to or more than the threshold value Kth (predetermined time). If it is short, the turning traveling control of this embodiment is continued. The duration time Kt is an elapsed time after the condition of S1 is established. According to the inventors' diligent research, the effect of the braking control (first control, S2) related to the traveling control of the present embodiment is effective even in a traveling state in which no driving force is generated in the wheel 2. It turns out. However, the purpose of the turning control according to the present embodiment is to reduce the understeer tendency of the vehicle 1 while the vehicle 1 is turning, and from the state where the operation of the acceleration operation unit 71 is not performed. When the operation of the acceleration operation unit 71 is started, the vehicle 1 may be slightly oversteered, which is not preferable. Therefore, by setting the continuation time Kt from the start of the turning control as in [2-3], the operation of the acceleration operation unit 71 is not performed for a certain time (the continuation time Kt). By executing the turning traveling control of the present embodiment only for the time until reaching the threshold value Kth), the understeer tendency of the vehicle 1 is reduced even in a situation where the operation of the acceleration operation unit 71 is not performed. In addition, the vehicle 1 can easily be prevented from falling into an unstable behavior as the operation of the acceleration operation unit 71 is started. Note that the above-described S3 (FIG. 9, second control) is not essential for the control in a state where the operation of the acceleration operation unit 71 described here is not performed. In addition, by the setting of [2-3], the effect of the prior control before the control for preventing the skidding of the vehicle 1 is executed by the skidding prevention control device or the skidding control section (not shown) mounted on the vehicle 1. May be obtained. Thereby, it may be easy to make a smooth transition due to the skid prevention control, or the effect of the skid prevention control may be more easily obtained. The threshold value Kth is an example of a predetermined time, and may be referred to as a limit time, a set time, a time threshold value, or the like.

  Furthermore, the threshold value Kth of the duration Kt of [2-3] can be set shorter as the road surface friction coefficient μ becomes lower, as illustrated in FIG. In a state where the road surface friction coefficient μ is low, the behavior of the vehicle 1 is likely to become unstable by the turning traveling control of the present embodiment. Therefore, by setting the threshold value Kth of the duration time Kt short according to the road surface friction coefficient μ, it is easy to suppress the behavior of the vehicle 1 from becoming more unstable. Note that the inequality signs in the above formulas [2-1] to [2-3] may not include the equal sign. In addition, each determination formula (inequality) of the start condition of the turning control is not limited to the examples of the above formulas [2-1] to [2-3]. Further, another condition may be added, or some of the above conditions may be reduced.

  When the termination condition of S4 is satisfied, that is, when at least one of the above [2-1] to [2-3] is established (Yes in S4), the turning control of the present embodiment is terminated. . In the next time step, the determination of the start condition of S1 is executed.

  As described above, in the present embodiment, the turning traveling control unit 112 has a larger braking force on the driving wheels on the inner side of the turning than the driving wheels on the inner side of the turning when the traveling state of the vehicle 1 is an understeer state. The brake actuator 21 (braking device) of the vehicle 1 is controlled to be applied (first control, S2), and the acceleration or speed of the vehicle 1 accompanying the control is controlled on the driving wheel while controlling the brake actuator 21. The drive source 3 (drive device) of the vehicle 1 is controlled so that the drive force that compensates for the decrease is applied (second control, S3). Therefore, according to this embodiment, the understeer state of the vehicle 1 is easily reduced. Further, according to the present embodiment, for example, it is possible to suppress the acceleration or speed of the vehicle 1 from being reduced due to the braking control for reducing the understeer state. That is, according to the present embodiment, when the control for suppressing the understeer of the vehicle 1 is executed when the vehicle 1 turns, changes in the acceleration and speed of the vehicle 1 are likely to be smaller.

  In the present embodiment, the turning control unit 112 performs the first control (S2) and the second control (S3) while the acceleration operation unit 71 is being operated. That is, according to the present embodiment, it is possible to prevent the acceleration or speed of the vehicle 1 from decreasing while the acceleration operation unit 71 is being operated. Therefore, for example, the behavior of the vehicle 1 corresponding to the operation of the acceleration operation unit 71 by the driver can be easily obtained while reducing the understeer state of the vehicle 1. Further, for example, the behavior of the vehicle 1 that does not correspond to the operation of the acceleration operation unit 71 of the driver hardly occurs. In addition, for example, the behavior of the vehicle 1 that deviates from the behavior of the vehicle 1 that the driver assumes for the operation of the acceleration operation unit 71 is difficult to occur.

  In the present embodiment, the control by the turning traveling control unit 112 is continued while the acceleration operation unit 71 is being operated. Therefore, according to the present embodiment, for example, the state of the understeer tendency and the state in which the turning traveling control of the present embodiment is executed to reduce the understeer tendency are repeatedly generated, and the acceleration of the vehicle 1 is changed. It is difficult for an inconvenient situation that the vehicle becomes relatively large or the vehicle 1 slightly meanders.

  In the present embodiment, the turning control unit 112 performs the second control (S3) in a state where the acceleration operation unit 71 that performs an operation for accelerating the drive source 3 (drive device) is not operated. Only the first control (S2) can be executed in a state in which is not executed. Therefore, according to the present embodiment, for example, the understeer state of the vehicle 1 is easily reduced even when the acceleration operation unit 71 is not operated.

  Further, in the present embodiment, the turning control unit 112 ends the first control (S2) when a threshold value Kth (predetermined time) has elapsed since the start of the control, and the threshold value Kth is the road surface friction. The smaller the coefficient μ, the shorter. Therefore, it is difficult for the vehicle 1 to fall into a more unstable state.

  As mentioned above, although embodiment of this invention was illustrated, the said embodiment is an example and is not intending limiting the range of invention. The above embodiment can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the spirit of the invention. Further, the specifications (structure, type, number, etc.) of each configuration, shape, etc. can be changed as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Wheel, 3 ... Drive source (drive device), 10 ... Brake ECU (travel control device), 21 ... Brake actuator (brake device), 22 ... Wheel cylinder (brake device), 23 ... Rotating member ( Braking device), 71... Acceleration operation unit, 112... Turning control unit, 112a... Start condition determination unit (traveling state detection unit).

Claims (4)

A running state detection unit that detects that the running state of the vehicle is an understeer state;
When the driving state detection unit detects the understeer state of the vehicle, the vehicle braking device is controlled so that a larger braking force is applied to the driving wheels on the inner side of the turning than the driving wheels on the outer side of the turning, and A turning control unit for controlling the driving device of the vehicle so as to apply a driving force that compensates for a decrease in acceleration or speed of the vehicle accompanying the control of the braking device to the driving wheel while controlling the braking device;
A vehicle travel control device comprising:   2. The turning traveling control unit executes control of the braking device and control of the driving device in a state where an acceleration operation unit that performs an operation for accelerating the driving device is operated. Vehicle travel control device.   The vehicle travel control device according to claim 2, wherein the control by the turning travel control unit is continued while an acceleration operation unit that performs an operation for accelerating the drive device is operated. In a state where an acceleration operation unit that performs an operation for accelerating the drive device is not operated, the turning travel control unit performs only the control of the brake device among the control of the brake device and the control of the drive device. It can be executed for a predetermined time,
The travel control device for a vehicle according to any one of claims 1 to 3, wherein the predetermined time is set to be shorter as the road surface friction coefficient is smaller.

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