Travel assistance method and travel assistance device

Abstract

This travel assistance method comprises: setting, on the basis of a vehicle speed and a steering angle, a target slip angle that is the target value of a vehicle body slip angle being an angle of the travel direction of a vehicle with respect to the longitudinal direction of the vehicle body (S2); estimating or detecting an actual slip angle being an actual vehicle body slip angle (S3); and setting and applying a target braking force to the vehicle by correcting a required braking force such that braking forces to be applied to rear wheels are increased or braking forces to be applied to front wheels are decreased if the actual slip angle is larger than the target slip angle, or the braking forces to be applied to the rear wheels are decreased or the braking forces to be applied to the front wheels are increased if the actual slip angle is smaller than the target slip angle, with the vehicle body slip angle of rotating in a vehicle turning direction as a positive sign and the vehicle body slip angle of rotating in a direction opposite to the vehicle turning direction as a negative sign (S4-S6).

Description

Driving support method and driving support device

[0001] The present invention relates to a driving assistance method and a driving assistance device.

[0002] The following Patent Document 1 describes a torque control device that, in order to improve cornering performance, increases torque distribution to the front wheels when the actual yaw rate is greater than the target yaw rate, and increases torque distribution to the rear wheels when the actual yaw rate is smaller than the target yaw rate.

[0003] Japanese Patent Application Publication No. 3-70633

[0004] Although a driver can achieve a desired yaw rate by operating the steering wheel, it is not possible to simultaneously achieve a desired yaw rate and a desired vehicle body slip angle. When the vehicle body slip angle is too large or too small, the driver's line of sight is affected by a deviation from the vehicle's direction of travel. This can cause the driver to steer more than necessary or to steer insufficiently. As a result, it can become difficult to steer the vehicle along a desired driving line. The present invention aims to facilitate steering operations for turning a vehicle along a desired driving line.

[0005] A driving assistance method according to one aspect of the present invention detects the vehicle speed, detects the steering angle of the steering wheel, and sets required braking / driving forces in accordance with the amount of operation of the accelerator pedal or brake pedal by the driver. A target value for the vehicle body slip angle, which is the angle from the longitudinal direction of the vehicle body to the direction of travel of the vehicle, is set as the target slip angle based on the vehicle speed and the steering angle. An actual slip angle, which is the actual vehicle body slip angle, is estimated or detected. The sign of the vehicle body slip angle when the vehicle is rotating in the turning direction is taken to be positive, and the sign of the vehicle body slip angle when the vehicle is rotating in the opposite direction to the turning direction is taken to be negative. If the actual slip angle is larger than the target slip angle, the required braking / driving forces are corrected so as to increase the braking / driving force of the rear wheels or decrease the braking / driving force generated on the front wheels. If the actual slip angle is smaller than the target slip angle, the required braking / driving forces are corrected so as to decrease the braking / driving force of the rear wheels or increase the braking / driving force generated on the front wheels, thereby setting target braking / driving forces, and the target braking / driving forces are generated in the vehicle.

[0006] According to the present invention, steering operations for turning a vehicle along a desired driving line can be facilitated. The objects and advantages of the present invention will be realized and attained by using the elements and combinations set forth in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to be limiting of the invention as claimed.

[0007] FIG. 1 is a schematic configuration diagram of an example of a driving assistance device according to an embodiment. (a) to (d) are explanatory diagrams of vehicle body slip angle. (a) to (d) are schematic diagrams showing examples of target slip angle and actual slip angle when turning left. (a) to (d) are schematic diagrams showing examples of target slip angle and actual slip angle when turning right. It is a block diagram of an example of the functional configuration of the controller of FIG. 1. It is a block diagram of an example of the functional configuration of a braking / driving force correction value calculation unit. It is a flowchart of an example of a driving assistance method according to an embodiment. It is a block diagram of a modified example of the functional configuration of the braking / driving force correction value calculation unit.

[0008] 1 is a schematic diagram of an example of a driving assistance device according to an embodiment. The driving assistance device 10 adjusts the vehicle body slip angle of the vehicle 1 by controlling the braking / driving force of at least one of the front wheels 2F (a left front wheel 2FL and a right front wheel 2FR) and the rear wheels 2R (a left rear wheel 2RL and a right rear wheel 2RR) of the vehicle 1, thereby assisting the driver in steering the vehicle 1. The driving assistance device 10 includes a wheel speed sensor 11, a steering angle sensor 12, a switch (SW) 13, a yaw rate sensor 14, an acceleration sensor 15, a brake sensor 16, an accelerator opening sensor 17, a controller 18, a drive controller 19, an actuator 20, a steering device 21, a braking device 22, and a drive source 23.

[0009] The wheel speed sensor 11 detects a wheel speed Vw of the vehicle 1. For example, the wheel speed sensor 11 may detect the average value of the wheel speeds of the left front wheel 2FL, the right front wheel 2FR, the left rear wheel 2RL, and the right rear wheel 2RR as the wheel speed Vw. The steering angle sensor 12 detects the steering angle θs(s) of the steering wheel. In this specification, the sign of the steering angle θs(s) for left rotation (counterclockwise) is defined as positive, and the sign of the steering angle θs(s) for right rotation (clockwise) is defined as negative. The switch (SW) 13 is an operator that accepts a selection input by an occupant of the vehicle 1 (e.g., the driver) to select the response characteristics of the vehicle 1 that respond to the driver's driving operation.

[0010] For example, switch 13 may be a switch for switching drive modes, which are driving characteristics of vehicle 1. For example, the drive modes may include a first mode (e.g., sport mode) in which the response characteristics of vehicle 1 in response to driving operations by the driver are high, and a second mode (e.g., eco mode) in which the response characteristics of vehicle 1 in response to driving operations are gentle. The response characteristics of vehicle 1 in response to driving operations may be, for example, the response characteristics of the steering angle of the running wheels in response to steering wheel operation, the driving characteristics in response to accelerator pedal operation, or the braking characteristics in response to brake pedal operation. Controller 18 changes the response characteristics of vehicle 1 in response to driving operations by the driver based on the setting state of switch 13.

[0011] The yaw rate sensor 14 detects the yaw rate of the vehicle 1. The acceleration sensor 15 detects the lateral acceleration, which is the acceleration in the vehicle width direction, of the vehicle 1. The brake sensor 16 detects the brake operation amount Br, which is the amount of brake pedal operation by the driver. The accelerator opening sensor 17 detects the accelerator operation amount Ac, which is the amount of accelerator pedal operation by the driver.

[0012] The controller 18 is an electronic control unit (ECU) that performs driving assistance control of the vehicle 1. The controller 18 includes a processor 18a and peripheral components such as a storage device 18b. The processor 18a may be, for example, a central processing unit (CPU) or a micro-processing unit (MPU). The storage device 18b may include a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The storage device 18b may include memories such as a register, a cache memory, and a read-only memory (ROM) and a random access memory (RAM) used as a main storage device. The functions of the controller 18 described below are realized, for example, by the processor 18a executing a computer program stored in the storage device 18b.

[0013] The controller 18 may be formed of dedicated hardware for executing the information processing described below. For example, the controller 18 may include a functional logic circuit configured in a general-purpose semiconductor integrated circuit. For example, the controller 18 may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0014] The drive controller 19 is an electronic control unit that controls the drive force generated by the drive source 23 on at least one of the front wheels 2F and the rear wheels 2R, based on the accelerator operation amount Ac detected by the accelerator opening sensor 17 and the braking / driving force correction value Cr set by the controller 18. Specifically, the drive controller 19 calculates a pre-correction target drive force Fd0 based on the accelerator operation amount Ac. The drive controller 19 corrects the pre-correction target drive force Fd0 with the braking / driving force correction value Cr set by the controller 18, and causes the drive source 23 to generate the target drive force Fd.

[0015] The drive controller 19 includes a processor and peripheral components such as a storage device. The processor may be, for example, a CPU or an MPU. The storage device may include a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The storage device may include registers, cache memory, and memories such as ROM and RAM used as main storage devices. The functions of the drive controller 19 described below are realized, for example, by the processor executing a computer program stored in the storage device. The drive controller 19 may also be formed by dedicated hardware for executing the information processing described below. For example, the drive controller 19 may include functional logic circuits configured in a general-purpose semiconductor integrated circuit. For example, the drive controller 19 may include a PLD such as an FPGA. The drive controller 19 may be a controller separate from the controller 18, or the drive controller 19 and the controller 18 may be integrated into one controller.

[0016] The actuator 20 operates the steering device 21 and the braking device 22 in response to a control signal from the controller 18 to generate a vehicle behavior of the vehicle 1. The actuator 20 includes a steering actuator and a brake control actuator. The steering actuator operates the steering device 21 to control the steering direction and steering amount of the vehicle 1. The brake control actuator operates the braking device 22 to generate a friction braking force and control the longitudinal deceleration of the vehicle 1.

[0017] Next, driving assistance control by the driving assistance device 10 of this embodiment will be described. As described above, the driver can achieve a desired yaw rate by operating the steering wheel, but cannot simultaneously achieve a desired yaw rate and a desired vehicle body slip angle. Please refer to FIGS. 2(a) to 2(d). In this specification, "vehicle body slip angle" is defined as the angle β from the longitudinal direction db of the vehicle 1 to the traveling direction dd of the vehicle 1. In FIGS. 2(a) to 2(d), reference character P indicates the center of gravity of the vehicle 1, and reference character Ld indicates the driving line (driving trajectory) of the vehicle 1 during cornering.

[0018] In this specification, the sign of the vehicle slip angle β for left rotation (counterclockwise) is defined as positive, and the sign of the vehicle slip angle β for right rotation (clockwise) is defined as negative. As shown in Figure 2(a), when the vehicle's longitudinal direction db is pointing outward from the traveling direction dd during a left turn, the sign of the vehicle slip angle β is positive. As shown in Figure 2(b), when the vehicle's longitudinal direction db is pointing inward from the traveling direction dd during a left turn, the sign of the vehicle slip angle β is negative. As shown in Figure 2(c), when the vehicle's longitudinal direction db is pointing outward from the traveling direction dd during a right turn, the sign of the vehicle slip angle β is negative. As shown in Figure 2(d), when the vehicle's longitudinal direction db is pointing inward from the traveling direction dd during a right turn, the sign of the vehicle slip angle β is positive. In the following description, the state in which the fore-and-aft direction db of the vehicle body during a turn is directed more toward the outside of the turn than the direction of travel dd, as shown in Figures 2(a) and 2(c), may be referred to as the "outward-facing state," and the state in which the fore-and-aft direction db of the vehicle body during a turn is directed more toward the inside of the turn than the direction of travel dd, as shown in Figures 2(b) and 2(d), may be referred to as the "inward-facing state."

[0019] Generally, when the vehicle speed is relatively low, the vehicle 1 tends to be in an outward-facing state, and when the vehicle speed is relatively high, the vehicle 1 tends to be in an inward-facing state. When the vehicle 1 is in an outward-facing state, the driver tends to increase the steering amount more than necessary due to a deviation in the driver's line of sight from the traveling direction dd of the vehicle 1. Conversely, when the vehicle 1 is in an inward-facing state, the driver tends to decrease the steering amount. For this reason, if the vehicle body slip angle becomes too large or too small, it may be difficult to steer the vehicle to turn along the desired traveling line. Therefore, the driving assistance device 10 of this embodiment sets a target slip angle βt(s), which is a target value of the vehicle body slip angle, based on the vehicle speed V and the steering angle θs(s). The target slip angle βt(s) is the angle from the target value in the vehicle body longitudinal direction db (hereinafter sometimes referred to as the "target vehicle body longitudinal direction dbt") to the traveling direction dd of the vehicle 1. The driving support device 10 controls the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R so that the actual slip angle βa(s), which is the actual vehicle body slip angle, approaches the target slip angle βt(s).

[0020] 3(a) to 3(d) are schematic diagrams showing examples of target slip angle βt(s) and actual slip angle βa(s) during a left turn. In the example of FIG. 3(a), the vehicle longitudinal direction db is directed toward the outside of the turn relative to the traveling direction dd (βa(s)>0), while the target vehicle longitudinal direction dbt is directed toward the inside of the turn relative to the traveling direction dd (βt(s)<0). In other words, the actual slip angle βa(s) is greater than the target slip angle βt(s). In this case, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) decreases (i.e., so that the vehicle longitudinal direction db rotates toward the inside of the turn). For example, the braking / driving force of the front wheels 2F is reduced or the braking / driving force of the rear wheels 2R is increased. Alternatively, the braking / driving force of the front wheels 2F may be reduced and the braking / driving force of the rear wheels 2R may be increased. In the example of Figure 3(b), both the vehicle longitudinal direction db and the target vehicle longitudinal direction dbt are directed outward from the traveling direction dd, but the vehicle longitudinal direction db is directed outward from the target vehicle longitudinal direction dbt. In other words, the actual slip angle βa(s) is greater than the target slip angle βt(s) (βa(s) > βt(s) > 0). In this case, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) decreases.

[0021] In the example of FIG. 3( c), the vehicle longitudinal direction db is oriented more inwardly than the traveling direction dd (βa(s)<0), while the target vehicle longitudinal direction dbt is oriented more outwardly than the traveling direction dd (βt(s)>0). In other words, the actual slip angle βa(s) is smaller than the target slip angle βt(s). In this case, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) increases (i.e., so that the vehicle longitudinal direction db rotates toward the outside of the turn). For example, the braking / driving force of the front wheels 2F is increased or the braking / driving force of the rear wheels 2R is decreased. It is also possible to increase the braking / driving force of the front wheels 2F and decrease the braking / driving force of the rear wheels 2R. In the example of FIG. 3( d), both the vehicle longitudinal direction db and the target vehicle longitudinal direction dbt are oriented more inwardly than the traveling direction dd, but the vehicle longitudinal direction db is oriented more inwardly than the target vehicle longitudinal direction dbt. In other words, the actual slip angle βa(s) is smaller than the target slip angle βt(s) (βa(s)<βt(s)<0). In this case as well, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) increases.

[0022] 4(a) to 4(d) are schematic diagrams showing examples of target slip angle βt(s) and actual slip angle βa(s) during a right turn. In the example of FIG. 4(a), the vehicle longitudinal direction db is directed toward the outside of the turn relative to the traveling direction dd (βa(s)<0), while the target vehicle longitudinal direction dbt is directed toward the inside of the turn relative to the traveling direction dd (βt(s)>0). In other words, the actual slip angle βa(s) is smaller than the target slip angle βt(s). In this case, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) increases (i.e., so that the vehicle longitudinal direction db rotates toward the inside of the turn). For example, the braking / driving force of the front wheels 2F is reduced or the braking / driving force of the rear wheels 2R is increased. Alternatively, the braking / driving force of the front wheels 2F may be reduced and the braking / driving force of the rear wheels 2R may be increased. In the example of Figure 4(b), both the vehicle longitudinal direction db and the target vehicle longitudinal direction dbt are directed outward from the traveling direction dd, but the vehicle longitudinal direction db is directed outward from the target vehicle longitudinal direction dbt. In other words, the actual slip angle βa(s) is smaller than the target slip angle βt(s) (βa(s)<βt(s)<0). In this case, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) increases.

[0023] In the example of FIG. 4( c), the vehicle longitudinal direction db is oriented more inwardly than the traveling direction dd (βa(s) > 0), while the target vehicle longitudinal direction dbt is oriented more outwardly than the traveling direction dd (βt(s) < 0). In other words, the actual slip angle βa(s) is greater than the target slip angle βt(s). In this case, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so that the actual slip angle βa(s) decreases (i.e., so that the vehicle longitudinal direction db rotates toward the outside of the turn). For example, the braking / driving force of the front wheels 2F is increased or the braking / driving force of the rear wheels 2R is decreased. It is also possible to increase the braking / driving force of the front wheels 2F and decrease the braking / driving force of the rear wheels 2R. In the example of FIG. 4( d), both the vehicle longitudinal direction db and the target vehicle longitudinal direction dbt are oriented more inwardly than the traveling direction dd, but the vehicle longitudinal direction db is oriented more inwardly than the target vehicle longitudinal direction dbt. In other words, the actual slip angle βa(s) is greater than the target slip angle βt(s) (βa(s)>βt(s)>0). In this case as well, the braking / driving force of at least one of the front wheels 2F and the rear wheels 2R is controlled so as to reduce the actual slip angle βa(s).

[0024] This allows the vehicle body slip angle β (actual slip angle βa(s)) of the vehicle 1 to be appropriately controlled, preventing the vehicle body slip angle β from becoming too large or too small. As a result, steering operations for turning the vehicle along a desired driving line are facilitated. Note that in the left-turn examples of FIGS. 3(a) to 3(d), the sign of the vehicle body slip angle β rotating in the turning direction of the vehicle 1 is defined as positive, whereas in the right-turn examples of FIGS. 4(a) to 4(d), the sign of the vehicle body slip angle β rotating in the turning direction of the vehicle 1 is defined as negative. Therefore, even in the case of a right turn, if the vehicle body slip angle β for rotation in the turning direction of the vehicle 1 is defined as positive and the vehicle body slip angle β for rotation in the opposite direction to the turning direction is defined as negative, then if the actual slip angle βa(s) is greater than the target slip angle βt(s) (i.e., if the vehicle body fore-and-aft direction db is pointing outward of the turn than the target vehicle body fore-and-aft direction dbt, as shown in Figures 3(a), 3(b), 4(a), and 4(b)), the braking / driving force of the front wheels 2F will be reduced or the braking / driving force of the rear wheels 2R will be increased. Alternatively, the braking / driving force of the front wheels 2F will be reduced and the braking / driving force of the rear wheels 2R will be increased. On the other hand, when the actual slip angle βa(s) is smaller than the target slip angle βt(s) (i.e., when the vehicle longitudinal direction db is pointing outward of the turning direction relative to the target vehicle longitudinal direction dbt, as shown in Figures 3(c), 3(d), 4(c), and 4(d)), the braking / driving force of the front wheels 2F is increased, or the braking / driving force of the rear wheels 2R is decreased. Alternatively, the braking / driving force of the front wheels 2F is increased and the braking / driving force of the rear wheels 2R is decreased.

[0025] 5 is a block diagram showing an example of the functional configuration of controller 18. Controller 18 includes a vehicle speed calculation unit 30, a required torque calculation unit 31, an actual slip angle estimator 32, a target slip angle calculation unit 33, and a braking / driving force correction value calculation unit 34. The wheel speed Vw detected by wheel speed sensor 11, the steering angle θs(s) detected by steering angle sensor 12, the brake operation amount Br detected by brake sensor 16, the accelerator operation amount Ac detected by accelerator opening sensor 17, and the pre-correction target driving force Fd0 calculated by drive controller 19 are input to controller 18.

[0026] The vehicle speed calculation unit 30 calculates the vehicle speed V of the vehicle 1 based on the wheel speed Vw, and inputs information about the vehicle speed V to the actual slip angle estimator 32 and the target slip angle calculation unit 33. The required torque calculation unit 31 calculates a required braking / driving torque Td according to the brake operation amount Br or accelerator operation amount Ac by the driver, and inputs information about the required braking / driving torque Td to the target slip angle calculation unit 33. The actual slip angle estimator 32 estimates the actual slip angle βa(s) based on at least the vehicle speed V and the steering angle θs(s). For example, the actual slip angle estimator 32 may estimate the actual slip angle βa(s) based on the following equation (1):

[0027] In the above formula, m is the vehicle weight, I is the yaw radius of inertia, l is the wheel base, and l ｆ is the distance from the center of gravity P of the vehicle 1 to the front wheel axle, and l ｒ is the distance from the center of gravity P to the rear wheel axle, and K ｆ is the equivalent cornering power of the front wheels, and K ｒ is the equivalent cornering power of the rear wheels.

[0028] The target slip angle calculation unit 33 estimates the target slip angle βt(s) based on at least the vehicle speed V and the steering angle θs(s). For example, the target slip angle calculation unit 33 may estimate the target slip angle βt(s) based on the following equation (2). K1 in equation (2) is a slip angle gain, and by appropriately adjusting the absolute value and sign of slip angle gain K1, it is possible to set how much the target slip angle βt(s) should be increased or decreased relative to the actual slip angle βa(s). In other words, it is possible to set how much the target vehicle longitudinal direction dbt should be tilted toward the inside or outside of the turn relative to the vehicle longitudinal direction db.

[0029] For example, when the vehicle speed V is relatively low, the vehicle 1 tends to be in an outward-facing state, and when the vehicle speed V is relatively high, the vehicle 1 tends to be in an inward-facing state. Therefore, the target slip angle calculation unit 33 may set the target slip angle βt(s) according to the vehicle speed V. Specifically, if the sign of the vehicle body slip angle β rotating in the turning direction of the vehicle 1 is set to be positive and the sign of the vehicle body slip angle β rotating in the direction opposite to the turning direction is set to be negative, for example, a smaller target slip angle βt(s) may be set when the vehicle speed V is high than when the vehicle speed V is low. For example, the higher the vehicle speed V, the smaller the target slip angle may be set. This makes it possible to prevent the vehicle 1 from being in an inward-facing state when the vehicle speed V is high. Furthermore, when the vehicle speed V is low, the vehicle 1 is prevented from being in an outward-facing state, making it easier for the vehicle 1 to be in an inward-facing state.

[0030] Braking / driving force correction value calculation unit 34 calculates braking / driving force correction value Cr, which corrects the required braking / driving force corresponding to the amount of brake operation Br or accelerator operation Ac by the driver, in accordance with actual slip angle βa(s) and target slip angle βt(s). FIG. 6 is a block diagram of an example of the functional configuration of braking / driving force correction value calculation unit 34. FIG. 6 illustrates an example configuration for calculating braking / driving force correction value Cr, which corrects the driving force of rear wheels 2R, in accordance with actual slip angle βa(s) and target slip angle βt(s). Braking / driving force correction value calculation unit 34 includes a subtractor 40, a gain multiplication unit 41, a sign inversion unit 42, a sign calculation unit 43, multipliers 44 and 46, and a limiter 45.

[0031] A subtractor 40 subtracts the actual slip angle βa(s) from the target slip angle βt(s) to calculate the slip angle difference Δβ = βt(s) - βa(s). A gain multiplication unit 41 multiplies the slip angle difference Δβ by a proportional gain P and outputs the product P x Δβ to a multiplier 44. A sign inversion unit 42 inverts the sign of the steering angle θs(s), and a sign calculation unit 43 outputs a value of "1" if the sign of the steering angle (-1 x θs(s)) after the inversion is positive, and outputs a value of "-1" if the sign is negative. A multiplier 44 normalizes the sign of the slip angle difference Δβ by multiplying the output of the sign calculation unit 43 by the slip angle difference Δβ.

[0032] As a result, whether turning left or right, if the vehicle longitudinal direction db is pointing more toward the outside of the turn than the target vehicle longitudinal direction dbt, the sign of the slip angle difference Δβ is set to positive. As a result, the sign of braking / driving force correction value Cr is set to positive. On the other hand, if the vehicle longitudinal direction db is pointing more toward the inside of the turn than the target vehicle longitudinal direction dbt, the sign of the slip angle difference Δβ is set to negative. As a result, the sign of braking / driving force correction value Cr is set to negative. Limiter 45 places upper and lower limits on the output of multiplier 44 (i.e., the slip angle difference Δβ with its sign normalized), and multiplier 46 multiplies the limited slip angle difference Δβ by the pre-correction target driving force Fd0 to calculate braking / driving force correction value Cr.

[0033] 1 calculates target driving force Fd by adding braking / driving force correction value Cr to pre-correction target driving force Fd0, and controls drive source 23 so that the driving force generated at rear wheel 2R becomes target driving force Fd. Therefore, when vehicle longitudinal direction db is pointing outward of target vehicle longitudinal direction dbt, the driving force at rear wheel 2R increases, and vehicle slip angle β is controlled so that vehicle longitudinal direction db rotates toward the inside of the turn. Conversely, when vehicle longitudinal direction db is pointing inward of target vehicle longitudinal direction dbt, the driving force at rear wheel 2R decreases, and vehicle slip angle β is controlled so that vehicle longitudinal direction db rotates toward the outside of the turn.

[0034] Although the example of braking / driving force correction value calculation unit 34 in Figure 6 calculates braking / driving force correction value Cr that corrects the driving force of rear wheels 2R, braking / driving force correction value calculation unit 34 may also calculate braking / driving force correction value Cr that corrects the driving force of front wheels 2F. In this case, the sign of slip angle difference Δβ is normalized in the opposite direction to that in Figure 6. As a result, when the vehicle longitudinal direction db is pointing outward of the turning direction relative to the target vehicle longitudinal direction dbt, the sign of braking / driving force correction value Cr is set to negative, and when the vehicle longitudinal direction db is pointing inward of the turning direction relative to the target vehicle longitudinal direction dbt, the sign of braking / driving force correction value Cr is set to positive.

[0035] The drive controller 19 in FIG. 1 calculates the target drive force Fd by adding the braking / driving force correction value Cr to the pre-correction target drive force Fd0, and controls the drive source 23 so that the drive force generated at the front wheels 2F becomes the target drive force Fd. Therefore, when the vehicle longitudinal direction db is pointing outward of the turning target vehicle longitudinal direction dbt, the drive force of the front wheels 2F is reduced, and the vehicle slip angle β is controlled so that the vehicle longitudinal direction db rotates toward the inside of the turning. Conversely, when the vehicle longitudinal direction db is pointing inward of the turning target vehicle longitudinal direction dbt, the drive force of the front wheels 2F is increased, and the vehicle slip angle β is controlled so that the vehicle longitudinal direction db rotates toward the outside of the turning target vehicle longitudinal direction dbt. Furthermore, the braking / driving force correction value calculation unit 34 may simultaneously calculate, as the braking / driving force correction value Cr, a braking / driving force correction value CrF that corrects the drive force of the front wheels 2F and a braking / driving force correction value CrR that corrects the drive force of the rear wheels 2R. In this case, when the vehicle longitudinal direction db is pointing more toward the outside of the turn than the target vehicle longitudinal direction dbt, the drive controller 19 reduces the drive force of the front wheels 2F and increases the drive force of the rear wheels 2R. Conversely, when the vehicle longitudinal direction db is pointing more toward the inside of the turn than the target vehicle longitudinal direction dbt, the drive controller 19 increases the drive force of the front wheels 2F and decreases the drive force of the rear wheels 2R. In other words, the sign of the braking / driving force correction value CrF is different from the sign of the braking / driving force correction value CrR. The magnitudes of the braking / driving force correction value CrF and the braking / driving force correction value CrR may be equal or different. To make the magnitudes of the braking / driving force correction value CrF and the braking / driving force correction value CrR equal, the braking / driving force correction value Cr of either the front wheels 2F or the rear wheels 2R may be calculated, and the sign of the calculated braking / driving force correction value Cr may be inverted and set to the braking / driving force correction value (-Cr) of the other wheel. By setting the braking / driving force correction value CrF and the braking / driving force correction value CrR to correction values ​​of the same magnitude but different signs, it is possible to prevent the driving force of the entire vehicle 1 from changing due to correction of the wheel braking / driving forces of the front wheels 2F and rear wheels 2R.

[0036] Furthermore, when the vehicle 1 is decelerating (i.e., when the required braking / driving torque Td is a braking torque), the braking / driving force correction value calculation unit 34 may calculate a braking / driving force correction value Cr that corrects the friction braking force by the brake device 22 or the regenerative braking force by the drive source 23, similar to the braking / driving force correction value Cr that corrects the pre-correction target driving force Fd0 described above. That is, when the vehicle body fore-and-aft direction db is pointing outward of the turning direction relative to the target vehicle body fore-and-aft direction dbt, the braking / driving force correction value Cr that decreases the braking force of the front wheels 2F or the braking / driving force correction value Cr that increases the braking force of the rear wheels 2R may be calculated. The braking / driving force correction value Cr that decreases the braking force of the front wheels 2F and increases the braking force of the rear wheels 2R may also be calculated.

[0037] Conversely, when the vehicle body longitudinal direction db is pointing more inward during a turn than the target vehicle body longitudinal direction dbt, a braking / driving force correction value Cr that increases the braking force of the front wheels 2F or a braking / driving force correction value Cr that decreases the braking force of the rear wheels 2R may be calculated. Alternatively, a braking / driving force correction value Cr that increases the braking force of the front wheels 2F and decreases the braking force of the rear wheels 2R may be calculated. The drive controller 19 calculates a target regenerative braking force in accordance with the amount of operation of the accelerator pedal or the brake pedal by the driver, and controls the drive source 23 to generate a regenerative braking force obtained by correcting the calculated target regenerative braking force with the braking / driving force correction value Cr. Alternatively, the controller 18 calculates a target frictional braking force in accordance with the amount of operation of the accelerator pedal or the brake pedal by the driver, and controls the brake control actuator of the actuator 20 to generate a frictional braking force obtained by correcting the calculated target frictional braking force with the braking / driving force correction value Cr.

[0038] (Operation) Figure 7 is a flowchart of an example of a driving assistance method according to an embodiment. In step S1, the steering angle sensor 12 detects the steering angle θs(s) of the steering wheel. The controller 18 detects the vehicle speed V of the vehicle 1. The drive controller 19 calculates the pre-correction target driving force Fd0. In step S2, the controller 18 estimates the target slip angle βt(s) based on at least the vehicle speed V and the steering angle θs(s). In step S3, the controller 18 estimates the actual slip angle βa(s) based on at least the vehicle speed V and the steering angle θs(s).

[0039] In step S4, controller 18 calculates slip angle difference Δβ=βt(s)−βa(s). In step S5, controller 18 calculates driving / braking force correction value Cr based on the slip angle difference Δβ. In step S6, drive controller 19 calculates target driving force Fd to be generated at the wheels by correcting pre-correction target driving force Fd0 with braking / driving force correction value Cr, and causes drive source 23 to generate target driving force Fd. The process then ends.

[0040] (Modifications) Modifications of the embodiment will be described below. Note that in the following modifications, the sign of the vehicle body slip angle β when the vehicle 1 rotates in the turning direction is defined as positive, and the sign of the vehicle body slip angle β when the vehicle 1 rotates in the opposite direction to the turning direction is defined as negative. Furthermore, the sign of the required braking / driving torque Td, which is a driving torque, is defined as positive, and the sign of the required braking / driving torque Td, which is a braking torque, is defined as negative. (1) When calculating, as the braking / driving force correction value Cr, a correction value that increases the braking / driving force of the front wheels 2F and decreases the braking / driving force of the rear wheels 2R, or when calculating a correction value that decreases the braking / driving force of the front wheels 2F and increases the braking / driving force of the rear wheels 2R, the target slip angle calculation unit 33 may set a larger target slip angle βt(s) when the required braking / driving torque Td is large than when the required braking / driving torque Td is small. For example, the target slip angle βt(s) may be set larger as the required braking / driving torque Td increases. For example, when the required braking / driving torque Td is a driving torque, a larger target slip angle βt(s) may be set than when the required braking / driving torque Td is a braking force, thereby making it possible to suppress understeer during driving and oversteer during braking.

[0041] (2) The target slip angle calculation unit 33 may set the target slip angle larger when the lateral acceleration is large than when the lateral acceleration is small. For example, the target slip angle βt(s) may be set larger as the lateral acceleration increases. This makes it possible to suppress understeer when the lateral acceleration is large. (3) When the drive mode of the vehicle 1 is set by the occupant's operation of the switch 13 (i.e., when the response characteristics of the vehicle 1 responsive to the driver's driving operation are set), the target slip angle calculation unit 33 may set a larger target slip angle βt(s) when the response characteristics are high than when the response characteristics are low. For example, when the drive mode of the vehicle 1 is the first mode, the target slip angle βt(s) may be set larger than when the drive mode is the second mode. This makes it possible to set the vehicle body slip angle β of the vehicle 1 according to the occupant's preference.

[0042] (4) The controller 18 may set a target yaw rate based on the steering angle θs(s) and the vehicle speed V, detect an actual yaw rate that is actually generated in the vehicle 1, and, if the actual yaw rate is smaller than the target yaw rate, correct the required braking / driving force to increase the braking / driving force of the rear wheels 2R or decrease the braking / driving force generated in the front wheels 2F, thereby setting the target braking / driving force. This allows the vehicle body slip angle β to be controlled so that the vehicle 1 turns inward when the actual yaw rate is smaller than the target yaw rate (i.e., when understeer occurs), improving the driving feel.

[0043] (5) Braking / driving force correction value calculation unit 34 may calculate braking / driving force correction value Cr based on slip angular velocity difference Δβ', which is obtained by subtracting the actual slip angular velocity, which is the derivative of the actual slip angle βa(s), from the target slip angular velocity, which is the derivative of the target slip angle βt(s). This improves the responsiveness of braking / driving force correction value Cr to changes in the target slip angle βt(s) and the actual slip angle βa(s). Figure 8 is a block diagram of a modified functional configuration of braking / driving force correction value calculation unit 34. In addition to the functional configuration described with reference to Figure 6, braking / driving force correction value calculation unit 34 includes differentiators 50 and 51, a subtractor 52, a gain multiplier 53, multipliers 54 and 55, and an adder 56.

[0044] Differentiators 50 and 51 and subtractor 52 calculate the slip angular velocity difference Δβ'. Gain multiplication unit 53 multiplies the slip angular velocity difference Δβ' by a differential gain D and outputs the product D×Δβ' to multiplier 54. Multiplier 54 normalizes the sign of the slip angular velocity difference Δβ' by multiplying it by the output of sign calculation unit 43. Multiplier 55 multiplies the output of multiplier 54 (i.e., the slip angular velocity difference Δβ' with its sign normalized) by pre-correction target driving force Fd0, and adder 56 sums the multiplication results of multipliers 46 and 55 to calculate braking / driving force correction value Cr.

[0045] As a result, the braking / driving force correction value calculation unit 34 of this modified example calculates a braking / driving force correction value Cr that increases the driving force of the rear wheels 2R when the actual slip angular velocity is greater than the target slip angular velocity, and decreases the driving force of the rear wheels 2R when the actual slip angular velocity is smaller than the target slip angular velocity. As in the above-described embodiment, the braking / driving force correction value Cr that corrects the driving force of the front wheels 2F can be calculated by normalizing the sign of the slip angular velocity difference Δβ' in the opposite direction to that in Figure 8. Furthermore, in the same way as the braking / driving force correction value Cr that corrects the driving force, a braking / driving force correction value Cr that corrects the braking force may also be calculated.

[0046] (Advantages of the embodiment) (1) The controller 18 detects the speed of the vehicle 1. The steering angle sensor 12 detects the steering angle of the steering wheel. The controller 18 sets the required braking / driving force in accordance with the amount of operation of the accelerator pedal or brake pedal by the driver, and sets a target value for the vehicle body slip angle β, which is the angle from the longitudinal direction db of the vehicle body to the traveling direction dd of the vehicle 1, as a target slip angle βt(s) based on the vehicle speed and steering angle. The controller 18 estimates or detects an actual slip angle βa(s), which is the actual vehicle body slip angle. If the sign of the vehicle body slip angle when the vehicle 1 rotates in the turning direction is positive and the sign of the vehicle body slip angle when the vehicle 1 rotates in the opposite direction to the turning direction is negative, when the actual slip angle βa(s) is greater than the target slip angle βt(s), the controller 18 corrects the required braking / driving force so as to increase the braking / driving force of the rear wheels or decrease the braking / driving force generated on the front wheels, and when the actual slip angle βa(s) is smaller than the target slip angle βt(s), the controller 18 corrects the required braking / driving force so as to decrease the braking / driving force of the rear wheels or increase the braking / driving force generated on the front wheels, thereby setting the target braking / driving force. The drive source 23 or the actuator 20 and the steering device 21 generate target braking / driving forces in the vehicle. This allows the vehicle body slip angle β of the vehicle 1 to be appropriately controlled, preventing the vehicle body slip angle from becoming too large or too small. As a result, steering operations for turning the vehicle along a desired driving line become easier.

[0047] (2) When the actual slip angle βa(s) is smaller than the target slip angle βt(s), the controller 18 may correct the required braking / driving force so as to increase the braking / driving force of the rear wheels and decrease the braking / driving force generated at the front wheels, and when the actual slip angle βa(s) is greater than the target slip angle βt(s), the controller 18 may correct the required braking / driving force so as to decrease the braking / driving force of the rear wheels and increase the braking / driving force generated at the front wheels, thereby setting the target braking / driving force. This makes it possible to prevent changes in the braking / driving force of the entire vehicle 1 due to corrections to the wheel braking / driving forces of the front wheels 2F and the rear wheels 2R. (3) When the vehicle speed is high, the controller 18 may set a smaller target slip angle βt(s) than when the vehicle speed is low. This makes it possible to prevent the vehicle 1 from turning outward when the vehicle speed V is relatively low, and to prevent the vehicle 1 from turning inward when the vehicle speed V is relatively high.

[0048] All examples and conditional terms described herein are intended for educational purposes to aid the reader in understanding the present invention and the concepts provided by the inventor for the advancement of technology, and should be construed without limitation to the specifically described examples and conditions above, and the configuration of examples herein for illustrating the advantages and disadvantages of the present invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the present invention.

[0049] 1...vehicle, 2F...front wheel, 2R...rear wheel, 10...driving assistance device, 11...wheel speed sensor, 12...steering angle sensor, 13...switch, 14...yaw rate sensor, 15...acceleration sensor, 16...brake sensor, 17...accelerator opening sensor, 18...controller, 18a...processor, 18b...storage device, 19...drive controller, 20...actuator, 21...steering device, 22...braking device, 23...drive source, 30...vehicle speed calculation unit, 31...required torque calculation unit, 32...actual slip angle estimator, 33...target slip angle calculation unit, 34...braking / driving force correction value calculation unit, 40, 52...subtractor, 41, 53...gain multiplication unit, 42...sign inversion unit, 43...sign calculation unit, 44, 46, 54, 55...multiplier, 45...limiter, 50, 51...differentiator, 56...adder

Claims

1. Detect the vehicle speed, Detects the steering angle of the steering wheel, A required braking / driving force is set in accordance with an amount of operation of an accelerator pedal or a brake pedal by a driver. a target value of a vehicle body slip angle, which is an angle from a longitudinal direction of a vehicle body to a traveling direction of the vehicle, is set as a target slip angle based on the vehicle speed and the steering angle; Estimating or detecting an actual slip angle, which is an actual vehicle body slip angle, based on at least the vehicle speed and the steering angle; where the sign of the vehicle body slip angle rotating in the turning direction of the vehicle is taken as positive and the sign of the vehicle body slip angle rotating in the opposite direction to the turning direction is taken as negative, when the actual slip angle is larger than the target slip angle, the required braking / driving force is corrected so as to increase the braking / driving force of the rear wheels or to decrease the braking / driving force generated on the front wheels, and when the actual slip angle is smaller than the target slip angle, the required braking / driving force is corrected so as to decrease the braking / driving force of the rear wheels or to increase the braking / driving force generated on the front wheels, thereby setting the target braking / driving force; generating the target braking / driving force in the vehicle; A driving support method comprising:

2. 2. The driving support method according to claim 1, wherein, when the actual slip angle is larger than the target slip angle, the required braking / driving force is corrected so as to increase the braking / driving force of the rear wheels and decrease the braking / driving force generated at the front wheels, and, when the actual slip angle is smaller than the target slip angle, the required braking / driving force is corrected so as to decrease the braking / driving force of the rear wheels and increase the braking / driving force generated at the front wheels, thereby setting the target braking / driving force.

3. 3. The driving support method according to claim 2, characterized in that the sign of the required braking / driving force, which is a driving force, is positive and the sign of the required braking / driving force, which is a braking force, is negative, and the target slip angle is set larger when the required braking / driving force is large than when the required braking / driving force is small.

4. The driving support method according to claim 3 , wherein the target slip angle is set to be larger when the required braking / driving force is a driving force than when the required braking / driving force is a braking force.

5. 5. The driving support method according to claim 1, wherein the target slip angle is set smaller when the vehicle speed is high than when the vehicle speed is low.

6. Detecting a lateral acceleration of the vehicle; When the lateral acceleration is large, the target slip angle is set to be larger than when the lateral acceleration is small. The driving support method according to any one of claims 1 to 5.

7. changing a response characteristic of the vehicle responsive to a driving operation by the driver based on a selection input from the driver; a target slip angle is set to a value larger when the response characteristic is high than when the response characteristic is low; The driving support method according to any one of claims 1 to 6.

8. Calculating a target slip angular velocity which is a differential value of the target slip angle and an actual slip angular velocity which is a differential value of the actual slip angle, When the actual slip angular velocity is larger than the target slip angular velocity, the required braking / driving force is corrected so as to increase the braking / driving force of the rear wheels or to decrease the braking / driving force generated on the front wheels, and when the actual slip angular velocity is smaller than the target slip angular velocity, the required braking / driving force is corrected so as to decrease the braking / driving force of the rear wheels or to increase the braking / driving force generated on the front wheels. The driving support method according to any one of claims 1 to 7.

9. setting a target yaw rate based on the steering angle and the vehicle speed; Detecting an actual yaw rate that is an actual yaw rate occurring to the vehicle; when the actual yaw rate is smaller than the target yaw rate, the target braking / driving force is set by increasing the braking / driving force of the rear wheels or by correcting the required braking / driving force so as to reduce the braking / driving force generated on the front wheels. The driving support method according to any one of claims 1 to 7.

10. A vehicle speed sensor for detecting a vehicle speed; A steering angle sensor for detecting a steering angle of a steering wheel; a controller which sets a required braking / driving force in response to an operation amount of an accelerator pedal or a brake pedal by a driver, sets a target value of a vehicle body slip angle, which is an angle from a longitudinal direction of a vehicle body to a traveling direction of the vehicle, as a target slip angle based on the vehicle speed and the steering angle, estimates or detects an actual slip angle, which is an actual vehicle body slip angle, based on at least the vehicle speed and the steering angle, and corrects the required braking / driving force so as to increase the braking / driving force of the rear wheels or reduce the braking / driving force generated on the front wheels when the actual slip angle is larger than the target slip angle, where the sign of the vehicle body slip angle rotating in the turning direction of the vehicle is set to be positive and the sign of the vehicle body slip angle rotating in the opposite direction to the turning direction is set to be negative, and sets a target braking / driving force by correcting the required braking / driving force so as to reduce the braking / driving force of the rear wheels or increase the braking / driving force generated on the front wheels when the actual slip angle is smaller than the target slip angle; a driving force source or a braking device that generates the target braking / driving force on the vehicle; A driving assistance device comprising:

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