Vehicle driving assistance systems

Abstract

The system is designed to ensure vehicle stability even if the vehicle slides backward on an uphill slope, without causing the driver to become unsettled. [Solution] When the driving assistance device determines that the vehicle is sliding backward on an uphill road, it switches the driving mode to reverse mode, performs braking and driving control to suppress the sliding backward, and performs steering control to turn the front of the vehicle body in the downhill direction.

Description

Technical Field

[0001] The present invention relates to a driving support device for a vehicle.

Background Art

[0002] Generally, when stopping a vehicle while ascending a slope on an extremely low-μ road surface (a road surface with a low friction coefficient such as a snowy road or an icy road) from a state where the vehicle is ascending the slope, the driver gently presses the brake pedal while paying attention not to lock the wheels and gradually decelerates to stop the vehicle.

[0003] At this time, when the vehicle (mass m) stops on a slope (road surface gradient θ), if the component of the weight along the slope (mg·sinθ) is greater than the static friction coefficient μ of the slope, the tire will slip down (a phenomenon of sliding in the downward direction) while remaining locked.

[0004] When the vehicle experiences slip-down, the driver will become shaken, and it is difficult to recover tire lock by performing pumping brakes or gentle accelerator operations (increasing driving force) with a margin, and often continues to press the brake pedal. In particular, slip-down from an ascending state makes it difficult for the driver to visually recognize the backward direction because the vehicle is facing backward, resulting in a sense of uneasiness.

[0005] As a countermeasure against this, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-274520) discloses a vehicle stop holding device that supports driving operations when smoothly starting a vehicle stopped on a slope without allowing it to slip down (recede). When slip-down is detected, it is estimated that the driver is performing a steering operation, and a technique for releasing or reducing the braking force on the steered wheels is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] The technology disclosed in this document prevents the steering wheels from locking by releasing or reducing the braking force applied to them, and generates a lateral force on the steering wheels to assist the driver's steering operation.

[0008] When a vehicle rolls backward on an uphill slope, it is essentially moving backward. This can cause the driver to become unsettled, making it difficult to steer with precision.

[0009] In particular, on low-friction surfaces, the reaction force from the road surface that the driver experiences when turning the steering wheel is low, resulting in a lighter steering response, a phenomenon known as "steering slippage." As a result, it becomes difficult for the driver to accurately perceive the direction of the steering wheels relative to the vehicle body.

[0010] The present invention aims to provide a vehicle driving assistance device that can ensure the stability of a vehicle without causing the driver to become unsettled, even if the vehicle slides backward while stopped on an uphill road. [Means for solving the problem]

[0011] The present invention relates to a vehicle driving assistance device comprising: a slippage determination unit that determines whether or not the vehicle is slipping on an uphill road; a steering control unit that controls the steering of the vehicle; a braking and driving control unit that controls the braking and driving force of the front and rear drive wheels of the vehicle; a driving mode switching unit that switches the driving mode between drive mode and reverse mode; and a vehicle control unit that performs control to suppress the slippage when the slippage determination unit determines that the vehicle is slipping. The vehicle control unit, when the slippage determination unit determines that the vehicle is slipping, causes the driving mode switching unit to switch the driving mode to reverse mode, causes the braking and driving control unit to perform control to suppress the slippage, and causes the steering control unit to turn the front of the vehicle body in the downhill direction. [Effects of the Invention]

[0012] According to the present invention, when it is determined that the vehicle is sliding backward on an uphill road, the driving mode is switched to reverse mode, control is performed to suppress the sliding backward, and control is performed to turn the front of the vehicle body in the downhill direction to change direction. As a result, the driver can control the vehicle more easily than when it is sliding backward, swaying is suppressed, and the stability of the vehicle can be ensured. [Brief explanation of the drawing]

[0013] [Figure 1] Overall schematic diagram of the driver assistance system [Figure 2] A flowchart showing the driving assistance control routine during downward sliding. [Figure 3] Flowchart showing the direction change control subroutine [Figure 4] A flowchart showing the braking torque setting subroutine. [Figure 5] Chart showing the slip distribution of each wheel during a left turn. [Figure 6] Diagram illustrating the vehicle sliding backward. [Figure 7] An explanatory diagram showing the forward-sloping of a vehicle after changing direction. [Figure 8] An explanatory diagram showing the vehicle's posture in different states during a change of direction. [Modes for carrying out the invention]

[0014] The following describes one embodiment of the present invention based on the drawings. The vehicle (own vehicle) M shown in Figure 1 is a four-wheel drive vehicle. The power unit 1 consists of a drive source and a transmission. The drive source may be an engine, an electric motor, or both. A center differential mechanism (center differential) 2 is connected to the output shaft of the power unit 1. From the center differential 2, output shafts 2a and 2b are connected to the front differential mechanism (front differential) 3F and the rear differential mechanism (rear differential) 3R in the front-rear direction.

[0015] The front axle shafts 4F extend horizontally from the front differential 3F to the left and right. The left and right front axle shafts 4F are connected to the left and right front drive wheels Fl, Fr. These front drive wheels Fl, Fr also serve as steering wheels. On the other hand, the rear axle shafts 4R extend horizontally from the rear differential 3R to the left and right. The left and right rear axle shafts 4R are connected to the left and right rear drive wheels Rl, Rr. In the following, when comprehensively referring to each drive wheel Fl, Fr, Rl, Rr, they are collectively referred to as drive wheels Aw.

[0016] Also, a steering mechanism 11 is arranged parallel to the front axle shaft 4F. Tie rods 12 extend horizontally from the steering mechanism 11 to the left and right. The left and right tie rods 12 are respectively connected to the front drive wheels Fl, Fr. Further, a steering shaft 13 extends from the middle of the steering mechanism 11 towards the driver's seat side. A steering wheel 14 is fixed to the end of the steering shaft 13 on the driver's seat side.

[0017] When the driver operates the steering wheel 14, the tie rods 12 extending horizontally from the steering mechanism 11 via the steering shaft 13 slide to the left and right, and the front drive wheels Fl, Fr are steered by the sliding of these tie rods 12. An electric power steering (EPS) motor 15 is connected via a transmission mechanism (not shown) to a portion of the steering shaft 13 close to the steering mechanism 11.

[0018] The drive source and transmission provided in the power unit 1 are controlled based on an output control signal and a shift control signal output from a power control unit (PW_ECU) 31. The PW_ECU 31 and a Bk_ECU 33 described later constitute the drive control unit of the present invention.

[0019] Also, the assist torque (EPS torque) added by the EPS motor 15 to the steering shaft 13 is controlled by an EPS control unit (EPS_ECU) 32 as a steering control unit.

[0020] Furthermore, the vehicle M is equipped with a brake control unit (Bk_ECU) 33. A hydraulic control unit (HCU) 35 is connected to the output side of this Bk_ECU 33. The HCU 35 is a hydraulic circuit that adjusts the brake fluid pressure according to the drive signal from the Bk_ECU 33. This brake fluid pressure is supplied to the brake actuators provided in the brake mechanism (not shown) of each drive wheel Aw. The braking torque of each drive wheel Aw is adjusted by this brake fluid pressure.

[0021] Each of the above-mentioned ECUs 31 to 33 is connected to the DSS (Driving Support System) control unit (DSS_ECU) 34 via an in-vehicle network using, for example, CAN (Controller Area Network) communication, allowing for bidirectional communication. This DSS_ECU 34 corresponds to the vehicle control unit of the present invention.

[0022] Each of these ECUs 31-34 is composed of a microcontroller. The microcontroller includes a CPU, RAM, ROM, rewritable non-volatile memory (flash memory or EEPROM), and peripheral devices. The microcontroller's RAM is provided as the CPU's work area, where various data from the CPU is temporarily stored. The ROM stores programs and fixed data necessary for the CPU to execute various processes. The CPU is also called an MPU (Microprocessor) or processor. Alternatively, a GPU (Graphics Processing Unit) or GSP (Graph Streaming Processor) may be used instead of the CPU. Alternatively, a selective combination of CPU, GPU, and GSP may be used.

[0023] Each of these ECUs 31-33 is basically controlled according to the control signals from DSS_ECU34. Sensor switches 16 are connected to the input side of DSS_ECU34. Sensor switches 16 is a general term for sensors and switches that acquire the parameters necessary to control the operations performed by each of the ECUs 31-33. These sensors and switches include brake switches, accelerator position sensors, wheel speed sensors, front and rear acceleration sensors, vehicle speed detection units, steering angle sensors, and yaw rate sensors.

[0024] Here, we will briefly explain the functions of the sensors and switches provided in the sensor / switch unit 16. The brake switch detects the driver's depression of the brake pedal and outputs an ON signal when the driver depresses the brake pedal. The accelerator pedal position sensor detects the amount the driver depresses the accelerator pedal. The wheel speed sensor detects the wheel speed Vw of each drive wheel Aw. The vehicle speed is calculated from the average value of the wheel speeds Vw.

[0025] The longitudinal acceleration sensor detects the longitudinal acceleration (G) during vehicle movement and, based on this acceleration, the direction of the road surface gradient, indicating whether the vehicle M is moving uphill or downhill. The vehicle speed detection unit detects the vehicle's speed (vehicle speed Vv). If position information from a GNSS (Global Navigation Satellite System) satellite can be obtained, the vehicle speed detection unit estimates the vehicle speed Vv from the amount of movement per unit time based on this position information from the GNSS satellite. Alternatively, the vehicle speed detection unit estimates the vehicle speed Vv based on the change in acceleration detected by the longitudinal acceleration sensor. Alternatively, the vehicle speed detection unit may estimate the vehicle speed Vv from the amount of movement per unit time of a point of interest captured by the forward recognition camera unit 23, which will be described later.

[0026] The steering angle sensor detects the steering angle generated by the driver's operation of the steering wheel 14. The yaw rate sensor detects the yaw rate acting on the vehicle body.

[0027] Furthermore, the DSS_ECU34 is connected to the input side of a forward recognition camera unit 23 and a rear recognition unit 24. The forward recognition camera unit 23 is a stereo camera and includes a main camera and a sub-camera. The forward recognition camera unit 23 captures reference image data with the main camera and comparison image data with the sub-camera. The forward recognition camera unit 23 then recognizes the same object in both images based on the parallax between the reference image data and the comparison image data, calculates the distance data (distance from the vehicle M to the object), and acquires information about the driving environment in front. The rear recognition unit 24 includes a monocular camera and a rear radar. The rear recognition unit 24 acquires information about the driving environment behind based on the rear environment image captured by the monocular camera and scan data from the rear radar.

[0028] Incidentally, when attempting to stop a vehicle M on an extremely low-friction surface (such as snow or ice), the driver will lightly press the brake pedal to slow down the vehicle M gradually and bring it to a stop, preventing the tires from locking. However, if this extremely low-friction surface is an uphill road, and the weight component of the vehicle M along the slope (mg·sinθ) exceeds the static friction coefficient of the uphill road due to the road gradient θ, the vehicle will slide backward with the tires locked. As shown in Figure 6, on an uphill road, the vehicle M will slide backward.

[0029] Generally, if a vehicle M starts to roll backward, the driver will try to stop it by pressing the brake pedal or the accelerator pedal. If the brake pedal is pressed when the tires have reduced grip, the tires will lock up. If the accelerator pedal is pressed, tire slip will occur. Furthermore, on low-friction surfaces, so-called "steering loss" can easily occur, leading to a loss of steering control.

[0030] In this way, if the vehicle M slides backward, the driver becomes unsettled, making it difficult to perform controlled braking (pumping the brakes), gentle acceleration, or steering maneuvers.

[0031] When the DSS_ECU34 detects that the vehicle M is sliding when the driver has stopped it on an uphill road with an extremely low friction surface, it rotates the front of the vehicle M in the direction of sliding to improve visibility in the sliding direction and provide driving assistance to reduce driver sway.

[0032] Specifically, the driver assistance control in the DSS_ECU34 is performed according to the downward-sliding driver assistance control routine shown in Figure 2. The following explanation will use a road with left-hand traffic regulations as an example.

[0033] The DSS_ECU34 first checks whether its own vehicle M is stopped on an uphill road (step S1). Whether the road is an uphill road is determined based on the road surface gradient θ detected by the front and rear acceleration sensors provided in the sensor / switch set 16. Furthermore, whether the own vehicle M is stopped is determined based on the vehicle speed obtained from the wheel speed Vw detected by the wheel speed sensor.

[0034] Then, if DSS_ECU34 determines that vehicle M is not stopped on an uphill road, or that the road on which it is stopped is not an uphill road (NO), it exits the routine. Also, if DSS_ECU34 determines that its own vehicle M is stopped on an uphill road (YES: state A in Figure 8), it checks whether the brake switch provided on the sensor / switch 16 is ON or OFF (step S2).

[0035] The brake switch outputs an ON signal when the driver is pressing the brake pedal. If DSS_ECU34 determines that the brake switch is OFF and the driver is not pressing the brake pedal (NO), it exits the routine. Even if the vehicle is stopped on an uphill road, if the driver is not pressing the brake pedal, it is assumed that the driver does not require driver assistance through control intervention.

[0036] Furthermore, if the brake switch is ON (YES), the driver determines that they are trying to maintain the stationary state of their vehicle M and checks whether or not backward sliding is occurring (step S3). The processing in step S3 corresponds to the backward sliding determination unit of the present invention.

[0037] Furthermore, the term "sliding backward" here refers to a situation where the vehicle M is moving backward due to the driver's braking lock. Therefore, situations where the vehicle M is moving backward due to insufficient braking torque caused by insufficient braking pressure from the driver are excluded.

[0038] Whether or not the vehicle M is sliding backward is determined based on the vehicle speed Vv [Km / h] detected by the vehicle speed detection unit provided in the sensor / switch unit 16 and the wheel speed Vw [Km / h] detected by the wheel speed sensor. If the vehicle speed Vv is detected by the vehicle speed detection unit (0>Vv) but the wheel speed Vw is not detected by the wheel speed sensor (a locked state, Vw=0), then it is determined that sliding backward is occurring (YES). On the other hand, if both the vehicle speed Vv and the wheel speed Vw are detected (Vv>0, and Vw>0), or if the vehicle speed Vv is 0 [Km / h] (stopped), then it is determined that sliding backward is not detected (NO), and the routine is exited.

[0039] If a slippage is detected (step S3: YES), the DSS_ECU34 checks in steps S4 to S6 whether the driver requires driver assistance through control intervention.

[0040] First, the DSS_ECU34 checks whether the brake switch remains ON (step S4). If the brake switch remains ON (YES), it determines that the tires are locked and therefore requires driver assistance, and branches off to step S7. On the other hand, if the brake switch is OFF (NO), the tires are rotating, and the DSS_ECU34 determines that the driver is performing an operation to escape the vehicle sliding backward.

[0041] The DSS_ECU34 checks whether the driver is operating the accelerator when the brake switch is OFF (step S5). Whether the driver is operating the accelerator is determined based on the output signal from the accelerator opening sensor provided in the sensor / switch 16. Note that the driving mode at this time is drive mode (forward). Therefore, the driver is attempting to move uphill by operating the accelerator.

[0042] The DSS_ECU34 determines that the driver is not operating the accelerator (NO) and is not taking any action to avoid rolling backward, and branches to step S7. On the other hand, if the driver is operating the accelerator (YSE), the DSS_ECU34 estimates that the driver is taking action to avoid rolling backward and checks whether or not rolling backward has been avoided (step S6). Whether or not rolling backward has been avoided is determined, for example, based on the forward driving environment information captured by the forward recognition camera unit 23. Alternatively, it is determined based on the vehicle speed Vv and the wheel speed Vw.

[0043] When DSS_ECU34 determines whether a vehicle is sliding based on driving environment information, it examines the change in the distance per unit time between an image of a point of interest (a fixed three-dimensional object) and the vehicle M. If the distance between the point of interest and the vehicle M does not change or decreases, it determines that the vehicle has been avoided. On the other hand, if the distance between the point of interest and the vehicle M increases, it determines that the vehicle has not been avoided.

[0044] Furthermore, when DSS_ECU34 determines whether a vehicle is sliding based on the vehicle speed Vv and wheel speed Vw, it examines the direction of movement due to the vehicle speed Vv and the direction of rotation due to the wheel speed Vw. DSS_ECU34 then determines that sliding has not been avoided if the direction of movement due to the vehicle speed Vv and the direction of rotation due to the wheel speed Vw are opposite. On the other hand, if the direction of movement due to the vehicle speed Vv and the direction of rotation due to the wheel speed Vw are the same, or if the vehicle speed Vv is 0 [Km / h], it determines that sliding has been avoided.

[0045] If DSS_ECU34 determines that the sliding has been avoided (step S6: YES), it exits the routine. If DSS_ECU34 determines that the sliding has not been avoided (step S6: NO), it branches to step S7.

[0046] When step S7 is initiated from any of steps S4 to S6, the DSS_ECU34 checks whether there is a vehicle (oncoming vehicle) approaching vehicle M from the opposite lane. The presence or absence of an approaching oncoming vehicle is determined based on the forward driving environment information captured by the forward recognition camera unit 23.

[0047] Then, if the DSS_ECU34 determines that there is an oncoming vehicle approaching its own vehicle M (YES), it executes rearward roll suppression control (step S8) and exits the routine. On the other hand, if the DSS_ECU34 determines that there is no oncoming vehicle approaching its own vehicle M (NO), it executes direction change control (step S9) and exits the routine. Note that the rearward roll suppression control executed by the DSS_ECU34 in step S8 is the same process as the "rearward roll suppression control subroutine" described in, for example, Japanese Patent Application Publication No. 2023-13808. Therefore, an explanation is omitted.

[0048] The direction change control in step S9 is performed according to the direction change control subroutine shown in Figure 3. When the DSS_ECU34 executes this subroutine, it forcibly intervenes in the control of each ECU31-33. As a result, the driver will be temporarily unable to operate the brake pedal, accelerator pedal, and steering wheel 14. Therefore, when performing direction change control, the DSS_ECU34 notifies the driver that "direction change control" is starting via a monitor image and sound.

[0049] In this subroutine, the DSS_ECU34 first switches the driving mode to reverse mode (step S11). The driving mode is switched by the DSS_ECU34 sending a reverse mode command signal to the PW_ECU31. Upon receiving the reverse mode command signal from the DSS_ECU34, the PW_ECU31 sets the transmission of the power unit 1 to reverse (state B in Figure 8). Note that the processing in step S11 and step S18, which will be described later, corresponds to the driving mode switching unit of the present invention.

[0050] Next, the DSS_ECU34 sets the braking torque for each drive wheel Aw (step S12). This braking torque is set according to the braking torque setting subroutine shown in Figure 4.

[0051] In this subroutine, DSS_ECU34 first sets the slip ratio λ of each drive wheel Aw during leftward turning (step S21). Figure 5 schematically shows the slip distribution of each drive wheel Aw during leftward turning.

[0052] In other words, when attempting to turn the front of the vehicle M to the left during a rearward roll, the slip ratio λ between the left front drive wheel Fl and the left rear drive wheel Rl, which are bulging outward, is set to "small". The slip ratio λ of the right front drive wheel Fr is set to "medium". Furthermore, the slip ratio λ of the right rear drive wheel Rr is set to "large". In this embodiment, "large" is set to λ ≈ 100[%] (almost a tire lock state), "medium" is set to λ = 70~50[%] (a state where grip force has recovered somewhat), and "small" is set to λ = 30[%] or less (a state where grip force has recovered).

[0053] Grip is restored by setting the slip ratio λ of the turning outer wheels Fl and Rl to "small". On the other hand, by setting the slip ratio λ of the inner right rear drive wheel Rr to "large", the drive wheel Rr is made to follow the turning outer wheels Fl and Rl. At this time, if the slip ratio λ of the inner right front drive wheel Fr is also set to "large", the following ability will improve, but the right front drive wheel Fr is a steering wheel. Therefore, the slip ratio λ is set to "medium" to improve steering ability while maintaining a certain level of grip.

[0054] Then, the outer drive wheels Fl and Rl, which have a small slip ratio λ, are slowly driven. At this time, the steering of the outer front wheel Fl and the inner front wheel Fr causes the front of the vehicle M to slowly turn to the left. The right rear drive wheel Rr follows this movement.

[0055] Next, the DSS_ECU34 sets the braking torque corresponding to the slip ratio λ of each drive wheel Aw (step S22), and proceeds to step S13 in Figure 3.

[0056] When performing direction change control, the DSS_ECU34 outputs a signal to the PW_ECU31 that suppresses the driving force applied to each drive wheel Aw. As a result, the PW_ECU31 suppresses the output from the power source of the power unit 1 and sets the gear ratio of the transmission to approximately the second gear of a stepped transmission. Consequently, the driving force applied to each drive wheel Aw is set to a value lower than the creep force.

[0057] The DSS_ECU34 sets the braking torque for each drive wheel Aw to match the value corresponding to the slip ratio λ. Setting the braking torque low will reduce the tire slip ratio λ, while setting the braking torque high will increase the tire slip ratio.

[0058] When the process proceeds to step S13 in Figure 3, the DSS_ECU34 sets a target path for moving the vehicle M in the direction of the change.

[0059] In other words, the DSS_ECU34 recognizes the road width, road surface shape, etc., based on the downhill driving environment information acquired by the rear recognition unit 24. Then, the DSS_ECU34 sets a target route that optimally guides the vehicle in the direction of the turn, given the recognized road width and road surface shape.

[0060] First, the DSS_ECU34 sets a target destination in the downhill direction of the oncoming lane based on the driving environment information acquired by the rear recognition unit 24. Next, the DSS_ECU34 sets a target route to guide the vehicle M to this target destination by changing direction.

[0061] Subsequently, the DSS_ECU34 outputs a braking torque signal for each drive wheel and a steering angle signal that traces the target path (step S14). The DSS_ECU34 outputs the braking torque signal for each drive wheel Aw to the Bk_ECU33. The DSS_ECU34 also outputs the steering angle signal to the EPS_ECU32.

[0062] Bk_ECU33 outputs a drive signal corresponding to the braking torque signal from DSS_ECU34 to HCU35. HCU35 adjusts the braking torque by operating the brake actuators (not shown) provided in the brake mechanism of each drive wheel Aw according to the drive signal from Bk_ECU33.

[0063] Furthermore, the EPS_ECU32 outputs a drive signal to the EPS motor 15 that follows the steering angle signal from the DSS_ECU34. The EPS motor 15 operates the steering mechanism 11 to steer the front drive wheels Fl and Fr (state C in Figure 8).

[0064] Next, the DSS_ECU34 checks whether the front of the vehicle M has turned in a downward direction (step S15). Whether the front of the vehicle M has turned in a downward direction is determined from the driving environment information acquired by either unit 23 or 24, or from the change in the road surface gradient direction detected by the front and rear acceleration sensors.

[0065] If the DSS_ECU34 determines that the change of direction is not yet complete (NO), it returns to step S14 and repeats the process in steps S14 to S15 until the front of the vehicle M is turned in the downward direction (states D to E in Figure 8). In this embodiment, the change of direction is determined to be complete when the front of the vehicle M is able to move in the downward direction of the road surface.

[0066] Furthermore, if the DSS_ECU34 determines that the vehicle M has completed its conversion (YES: state E in Figure 8), it terminates the reverse mode (step S16).

[0067] Subsequently, the DSS_ECU34 outputs a steering counter-signal to the EPS_ECU32 that directs the front of the vehicle M towards the downhill direction (step S17). The steering angle when counter-steering may be a preset fixed value. The EPS_ECU32 receives the steering counter-signal from the DSS_ECU34 and drives the EPS motor 15 to operate the steering mechanism 11 and steer the front drive wheels Fl and Fr (state F in Figure 8). This prevents the vehicle M from turning sideways to the downhill direction. At this time, the DSS_ECU34 sets the slip ratio of each drive wheel Aw to "small".

[0068] Next, the DSS_ECU34 switches the driving mode to drive mode (step S18). The driving mode switch is performed by the DSS_ECU34 sending a driving mode switching signal to the PW_ECU31. Upon receiving the driving mode switching signal from the DSS_ECU34, the PW_ECU31 switches the transmission of power unit 1 from reverse to drive.

[0069] Next, the DSS_ECU34 performs forward sliding suppression control (step S19). This sliding suppression control directs the vehicle M's attitude toward the downhill direction of the road (state G in Figures 7 and 8). This forward sliding suppression control performs the same processing as the "forward sliding suppression control subroutine" described in, for example, Japanese Patent Application Publication No. 2023-13808, so its explanation is omitted.

[0070] Subsequently, the DSS_ECU34 checks whether the vehicle M has stopped sliding backward (step S20). Whether the sliding has stopped is determined, for example, based on the forward driving environment information captured by the forward recognition camera unit 23, or based on the vehicle speed Vv.

[0071] If DSS_ECU34 determines that the sliding is continuing (NO), it repeats the process in steps S19 to S20. If DSS_ECU34 determines that the sliding has stopped (YES), it exits the routine.

[0072] Thus, in this embodiment, when the DSS_ECU34 detects that the vehicle M, which is stopped on an uphill road, is sliding backward, it executes control to change the direction of the vehicle M. Due to the direction change control by the DSS_ECU34, the front of the vehicle M slowly turns around (states D to E in Figure 8), and this front of the vehicle is directed downward (state E in Figure 8).

[0073] As a result, when the driver stops their vehicle M on an uphill road, even if it rolls backward, the vehicle M will automatically change direction to the forward direction, which is relatively easier to control than reversing. This provides visual reassurance, prevents shaking, and eliminates anxiety. Furthermore, because it becomes easier for the driver to control the vehicle, the stability of the vehicle M can be ensured.

[0074] Furthermore, the present invention is not limited to the embodiments described above. For example, the processing of steps S19 and S20 of the direction change control subroutine described above may be omitted, and after the DSS_ECU34 completes the direction change of its own vehicle M, the driving operation of its own vehicle M may be transferred to the driver. [Explanation of symbols]

[0075] 1... Power unit, 2… Center differential mechanism (center differential), 2a, 2b...output shaft, 3F... Front differential mechanism (front differential), 3R...Rear differential mechanism (rear differential) 4F...Front axle shaft, 4R... Rear axle shaft, 11…Steering mechanism, 12...Tie rod, 13... Steering axis, 14... Handle, 15…EPS motor, 16... Sensors and switches, 23…Forward recognition camera unit, 24...Rear recognition unit, 31…Power control unit (PW_ECU), 32...EPS control unit (EPS_ECU), 33...Brake control unit (Bk_ECU), 34…DSS control unit (DSS_ECU), Aw... Drive wheels, Fl...Left front drive wheel, Fr... Right front drive wheel, M... Own vehicle, Rl... Left rear drive wheel, Rr...Right rear drive wheel, Vv...vehicle speed, Vw...wheel speed, θ...road surface gradient, λ...Slip ratio

Claims

1. A sliding detection unit that determines whether or not the vehicle is sliding down on an uphill road, A steering control unit that controls the steering of the vehicle, A braking and driving control unit that controls the braking and driving force of each of the front and rear drive wheels of the vehicle, A driving mode switching unit that switches the driving mode between drive mode and reverse mode, If the sliding detection unit determines that the vehicle is sliding, the vehicle control unit performs control to suppress the sliding. In a vehicle driver assistance system equipped with, If the vehicle control unit determines that the vehicle is sliding down using the sliding detection unit, it will switch the driving mode to reverse mode using the driving mode switching unit, perform control to suppress the sliding down using the brake / drive control unit, and perform control to turn the front of the vehicle body downwards using the steering control unit. A vehicle driving assistance device characterized by the following features.

2. When the vehicle control unit turns the front of the vehicle body in a downward direction, the brake-drive control unit sets the slip ratio of the drive wheel on the outside of the turn to be small. The vehicle driving assistance device according to claim 1.

3. When the vehicle control unit turns the front of the vehicle body downwards, the brake and drive control unit sets the slip ratio of the drive wheel on the inside of the turn to be greater than the slip ratio of the drive wheel on the outside of the turn. The vehicle driving assistance device according to feature 2.

4. The steering wheels of the aforementioned vehicle are the front wheels. When the vehicle control unit turns the front of the vehicle body downwards, the brake and drive control unit sets the slip ratio of the rear wheel on the turning side to be greater than the slip ratio of the front wheel on the turning side. The vehicle driving assistance device according to feature 3.

5. The aforementioned slippage detection unit determines that slippage is occurring based on the wheel speed of each drive wheel and the vehicle speed of the vehicle itself, if the wheel speed is not detected but the vehicle speed is detected. The vehicle driving assistance device according to feature 1.

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