Vehicle driving assistance systems

Abstract

The present invention provides a vehicle driver assistance system that can determine the timing of deceleration in a way that suppresses the driver from feeling uncomfortable during driver assistance driving. [Solution] The vehicle's deceleration control is initiated (step ST9) on the condition that the time available for the vehicle to reach the point of maximum curvature of the curved road falls within the range between an upper threshold and a lower threshold determined by the curve radius at the point of maximum curvature of the curved road (YES determination in step ST8). Therefore, the start timing of the deceleration control can be obtained to correspond to the driver's intended deceleration start timing, and the driver's feeling of discomfort when the vehicle's deceleration control is initiated can be suppressed.

Description

Technical Field

[0001] The present invention relates to a driving support device for a vehicle. In particular, the present invention relates to measures for optimizing the deceleration start timing during driving support running.

Background Art

[0002] Conventionally, a driving support device capable of executing ACC (Adaptive Cruise Control) of a vehicle is known. In ACC, generally, when there is no preceding vehicle in front of the vehicle (own vehicle), the vehicle is driven at a constant speed at the target vehicle speed, while when there is a preceding vehicle, the vehicle follows the preceding vehicle at a vehicle speed lower than the target vehicle speed. Also, as a driving support of a vehicle, as disclosed in Patent Document 1, control is also performed to control the deceleration start timing for automatically decelerating the vehicle before a curve road (hereinafter, this control may also be referred to as speed adjustment support). Specifically, this Patent Document 1 discloses that, based on the section distance (the distance from the current position of the vehicle to the entrance of the curve road) and the vehicle speed at the deceleration start timing, the smaller the section distance, the greater the deceleration of the vehicle during deceleration control and the lateral acceleration of the vehicle during curve road driving, and an operation of the target deceleration is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technology disclosed in Patent Document 1, the target deceleration is calculated using the distance from the vehicle's current position to the entrance of the curve (section distance). Therefore, the longer this section distance, the earlier the deceleration starts. As a result, the actual deceleration start time may be earlier than the deceleration start time intended by the driver (the deceleration start time intended if the driver were driving themselves), which could cause the driver to feel uncomfortable.

[0005] The present invention has been made in view of the above, and its objective is to provide a vehicle driving assistance device that can obtain a deceleration start timing that can suppress the driver from feeling uncomfortable during driving assistance driving. [Means for solving the problem]

[0006] The present invention provides a solution for achieving the above objectives, based on a vehicle driving assistance device comprising a road information recognition unit that recognizes road information to be traveled, and a driving assistance unit that assists the vehicle's driving based on the road information recognized by the road information recognition unit. The vehicle driving assistance device is characterized by comprising, during the assistance of the vehicle's driving, if the road information recognized by the road information recognition unit includes information that a curved road exists on the planned route, a support timing calculation unit that calculates the estimated time until the vehicle reaches the point of maximum curvature of the curved road in the current driving state, and a support determination unit that initiates deceleration control of the vehicle on the condition that the estimated time calculated by the support timing calculation unit falls within the range between an upper threshold and a lower threshold determined by the curve radius at the point of maximum curvature of the curved road.

[0007] Based on this specific condition, if a curved road exists on the planned route while assisting the vehicle's driving, the assistance timing calculation unit first calculates the estimated time it will take for the vehicle to reach the point of maximum curvature of the curved road in the current driving state. Then, the assistance judgment unit determines that if the calculated estimated arrival time is within the range between the upper and lower thresholds determined by the curve radius at the point of maximum curvature of the curved road, then the estimated arrival time (the estimated arrival time at the present time) is an appropriate timing to start deceleration control of the vehicle (the present time is an appropriate time to start deceleration control of the vehicle), and starts deceleration control of the vehicle. In other words, if the estimated arrival time is not within the range between the upper and lower thresholds, the system determines that starting deceleration control of the vehicle at this estimated arrival time would cause the driver to feel uncomfortable, and therefore restricts deceleration control of the vehicle. Through the above operation, the system can obtain a deceleration control start timing that corresponds to the driver's intended deceleration start timing, thus suppressing the driver from feeling uncomfortable when deceleration control of the vehicle is started.

[0008] Furthermore, the upper and lower thresholds for the predicted arrival time are set so that the smaller the radius of the curved road, the longer the time.

[0009] The timing at which deceleration control is initiated based on a threshold for the predicted arrival time is variable (control parameter), depending on the radius of the curve. For example, the smaller the radius of the curve, the earlier the vehicle's deceleration control can be initiated, allowing the vehicle speed at the point of maximum curvature of the curve to be sufficiently reduced (reducing the speed to the target speed without requiring emergency braking).

[0010] Furthermore, if the above conditions are not met, the estimated arrival time will be recalculated.

[0011] If the vehicle's deceleration control is limited because the predicted arrival time is longer than the upper threshold, as the vehicle travels (approaching the point of maximum curvature on the curved road), the predicted arrival time will approach the upper threshold, and the vehicle's deceleration control will start when the predicted arrival time reaches the upper threshold and falls within the range, as calculated by recalculating the predicted arrival time. By performing such recalculations, even if the vehicle's deceleration control is initially limited, the vehicle's deceleration control will then start at an appropriate timing, allowing the driver to obtain a deceleration control start timing that corresponds to the deceleration start timing intended by the driver.

[0012] Furthermore, the support timing calculation unit recalculates the estimated arrival time using at least the current vehicle speed and the distance between the vehicle and the point of maximum curvature as parameters.

[0013] This allows for the accurate calculation of the estimated time to initiate deceleration control of the vehicle at a point that minimizes the driver's sense of unease.

[0014] Furthermore, if the road information recognized by the road information recognition unit includes information that the planned route consists of two consecutive curved roads with different curve directions, and the curved road closer to the vehicle is designated as the first curved road and the curved road further away from the vehicle is designated as the second curved road, the support determination unit initiates deceleration control of the vehicle targeting the second curved road, provided that the predicted arrival time from when the vehicle passes the maximum curvature point of the first curved road until it reaches the maximum curvature point of the second curved road is within the range between the upper and lower threshold values ​​determined by the curve radius at the maximum curvature point of the second curved road.

[0015] According to this, when two consecutive curves with different directions, such as an S-curve, are present, it is possible to avoid the second curve acting as a disturbance and negatively affecting the vehicle's deceleration control targeting the first curve. Furthermore, the vehicle's deceleration control targeting the second curve can be initiated at an appropriate timing. Therefore, even when multiple consecutive curves with different directions are present, it is possible to achieve deceleration control that suppresses the driver from feeling any discomfort with each individual curve. [Effects of the Invention]

[0016] In this invention, the vehicle's deceleration control is initiated when the predicted time until the vehicle reaches the point of maximum curvature of the curved road falls within the range between an upper threshold and a lower threshold determined by the curve radius at the point of maximum curvature of the curved road. Therefore, the vehicle can obtain a deceleration control start timing that corresponds to the driver's intended deceleration start timing, and the driver's discomfort when the vehicle's deceleration control starts can be suppressed. [Brief explanation of the drawing]

[0017] [Figure 1] This is a block diagram showing the schematic configuration of the driver assistance system according to the embodiment. [Figure 2] This is a block diagram illustrating the transmission and reception of information within the driver assistance ECU according to the embodiment. [Figure 3] This figure shows an example of a map for determining arrival time buffer. [Figure 4] This is a flowchart illustrating the driver assistance processing procedure according to the embodiment. [Figure 5] This figure shows a plan view of a vehicle traveling on a curved road and an example of the curvature waveform of the said curved road. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments of the present invention will be described based on the drawings. In this embodiment, a case where the present invention is applied to a vehicle equipped only with an engine (internal combustion engine) as a driving force source will be described. The present invention is not limited to this, and can also be applied to hybrid vehicles, plug-in hybrid vehicles, electric vehicles, fuel cell vehicles, and the like.

[0019] FIG. 1 is a block diagram showing a schematic configuration of a driving support system 1 according to this embodiment. As shown in this FIG. 1, the driving support system 1 is applied to a vehicle (hereinafter sometimes referred to as "own vehicle" to distinguish it from other vehicles), and includes a driving support ECU 10, a navigation ECU 20, an engine ECU 30, and a brake ECU 40.

[0020] These ECUs 10, 20, 30, 40 are electric control devices (Electric Control Unit) having a microcomputer as a main part, and are connected to each other via a CAN (Controller Area Network) not shown so that information can be transmitted and received. The microcomputer includes a CPU 101, a ROM 102, a RAM 103, an interface (I / F) 104, and the like. The CPU 101 realizes various functions by executing instructions (programs, routines) stored in the ROM 102.

[0021] A vehicle speed sensor 11, a surrounding sensor 12, and an operation switch 13 are connected to the driving support ECU 10, and the driving support ECU 10 is configured to receive detection signals and output signals from these. In addition, various other sensors and various switches are also connected to the driving support ECU 10, but here, only the sensors and switches according to the present invention will be described. In addition, the vehicle speed sensor 11, the surrounding sensor 12, and the operation switch 13 may be connected to an ECU other than the driving support ECU 10. In that case, the driving support ECU 10 will receive the detection signal or output signal via the CAN from another ECU to which the vehicle speed sensor 11, the surrounding sensor 12, and the operation switch 13 are connected.

[0022] The vehicle speed sensor 11 detects the traveling speed (vehicle speed) of the host vehicle and outputs a signal representing the vehicle speed SPD.

[0023] The surrounding sensor 12 is configured to acquire information regarding at least the road in front of the host vehicle and the three-dimensional objects present on the road. The three-dimensional objects represent, for example, moving objects such as pedestrians, bicycles, and automobiles, as well as stationary objects such as utility poles, trees, and guardrails. Hereinafter, these three-dimensional objects may also be referred to as "targets". Further, the surrounding sensor 12 is configured to calculate and output the presence or absence of a target and the relative relationship between the host vehicle and the target (i.e., the distance between the host vehicle and the target, the relative speed between the host vehicle and the target, etc.).

[0024] The surrounding sensor 12 includes, for example, a radar sensor and a camera sensor.

[0025] The radar sensor radiates, for example, radio waves in the millimeter wave band (hereinafter, may also be referred to as "millimeter waves") to the peripheral area of the host vehicle including at least the front area of the host vehicle, and receives the millimeter waves (i.e., reflected waves) reflected by the targets present within the radiation range.

[0026] More specifically, the radar sensor includes a millimeter wave transmitting / receiving unit and a processing unit. The processing unit acquires, for each detected target (n), the inter-vehicle distance (vertical distance) Dfx(n), relative speed Vfx(n), lateral distance Dfy(n), relative lateral speed Vfy(n), etc., at every elapse of a predetermined time, based on the phase difference between the millimeter waves transmitted from the millimeter wave transmitting / receiving unit and the reflected waves received by the millimeter wave transmitting / receiving unit, the attenuation level of the reflected waves, the time from transmitting the millimeter waves to receiving the reflected waves, etc.

[0027] The camera sensor comprises a stereo camera and an image processing unit. The stereo camera captures the scenery in the left and right areas in front of the vehicle, acquiring a pair of left and right image data. The image processing unit calculates and outputs the presence or absence of an object and the relative relationship between the vehicle and the object based on the pair of left and right image data captured by the stereo camera. In this case, the driver assistance ECU 10 determines the relative relationship between the vehicle and the object by combining the relative relationship between the vehicle and the object obtained by the radar sensor and the relative relationship between the vehicle and the object obtained by the camera sensor. Furthermore, the camera sensor recognizes lane markers such as white lines on the left and right of the road (hereinafter sometimes simply referred to as "white lines") based on the pair of left and right image data it has captured, and calculates and outputs the shape of the road (for example, radius of curvature, whether it is an S-curve, whether it is a complex curve, etc.) and the positional relationship between the road and the vehicle.

[0028] The information acquired by the surrounding sensor 12 is called target information. The surrounding sensor 12 repeatedly transmits the target information to the driver assistance ECU 10 at predetermined intervals. Note that the surrounding sensor 12 does not necessarily need to include both a radar sensor and a camera sensor; for example, it may include only a radar sensor or only a camera sensor.

[0029] The operation switch 13 is a switch operated by the driver. By operating the operation switch 13, the driver can choose whether or not to perform follow-me distance control and speed adjustment support control (also called "speed management control").

[0030] Here, speed adjustment support control is a driving control (driving assistance) that controls the speed of the vehicle based on the radius of curvature of the curve ahead of the vehicle. As will be described later, the driving assistance ECU 10 sets a target speed and a target acceleration to achieve the target speed during the period when the vehicle is traveling on a road that includes a curved section, and the driving assistance ECU 10 controls the vehicle so that the vehicle's speed and acceleration match these target speed and target acceleration, respectively. The speed adjustment support control, including the setting of these target speed and target acceleration when there is a curve ahead (when there is a curve in the planned route), will be described later.

[0031] The vehicle (own vehicle) is equipped with a navigation system. The navigation system includes the navigation ECU 20. The navigation ECU 20 is configured to guide the vehicle along a route based on the vehicle's position and map information. Therefore, the navigation ECU 20 is connected to a GPS receiver 21 that receives GPS signals to detect the vehicle's position, a map database 22 that stores map information, and a human-machine interface, a touch panel display 23, etc. Based on the GPS signal, the navigation ECU 20 identifies the current position (current location) of the vehicle (Pnow), performs various calculations based on the vehicle's position (Pnow) and the map information stored in the map database 22, and provides route guidance using the display 23.

[0032] The map information stored in map database 22 includes road information. This road information includes road parameters for each section of the road. For example, each section of the road is associated with the road's width, gradient, superelevation (cant), and radius of curvature (or curvature). The radius of curvature of a road is, for example, the radius of curvature of the curve drawn by the center line connecting the centers of the roads in the width direction. The curvature is the reciprocal of the radius of curvature.

[0033] The engine ECU 30 is connected to the engine actuator 31. The engine actuator 31 includes a fuel injector, spark plug, throttle valve, etc. The engine ECU 30 can change the torque generated by the internal combustion engine by driving the engine actuator 31. The torque generated by the internal combustion engine is transmitted to the drive wheels (not shown) via a transmission (not shown). Therefore, the engine ECU 30 can control the driving force of its own vehicle and change the acceleration state (acceleration) by controlling the engine actuator 31.

[0034] The brake ECU 40 is connected to the brake actuator 41. The brake actuator 41 is located in the hydraulic circuit between a master cylinder (not shown) that pressurizes the hydraulic fluid in response to the force applied to the brake pedal, and the friction brake mechanisms provided on the left and right front and rear wheels. The brake actuator 41 adjusts the hydraulic pressure supplied to the wheel cylinders built into the brake calipers of the friction brake mechanisms in response to instructions from the brake ECU 40. This hydraulic pressure causes the wheel cylinders to actuate, pressing the brake pads against the brake discs and generating frictional braking force. Therefore, the brake ECU 40 can control the braking force of its own vehicle and change the acceleration state (deceleration, i.e., negative acceleration) by controlling the brake actuator 41.

[0035] Next, the basic operation of the driver assistance system 1 configured as described above will be explained. As mentioned above, the driver assistance ECU 10 performs follow-me distance control and speed adjustment support control.

[0036] The defining feature of this embodiment lies in the speed adjustment support control. Before describing this speed adjustment support control, we will briefly explain the following vehicle distance control.

[0037] Adaptive Cruise Control (CC) is a driver assistance control system that adds a distance control function to constant speed control (cruise control: CC). Constant speed control is a control system that keeps the vehicle moving at a constant speed according to a target speed without requiring the driver to operate the accelerator pedal. The distance control function is a function that keeps the vehicle following the preceding vehicle while maintaining a predetermined distance between the vehicle and the preceding vehicle. Adaptive Cruise Control itself is well known (see, for example, Japanese Patent No. 4172434 and Japanese Patent No. 4929777, etc.). Therefore, it will be briefly explained below.

[0038] The driver assistance ECU 10 performs follow-vehicle distance control when follow-vehicle distance control is requested by the operation of the operation switch 13.

[0039] When this adaptive cruise control is requested, the driver assistance ECU 10 selects a target vehicle to follow based on target information acquired by the surrounding sensors 12. For example, the driver assistance ECU 10 determines whether the relative position of the detected target (n), identified from the lateral distance Dfy(n) and the inter-vehicle distance Dfx(n), is within a predetermined area for target vehicles to follow, such that the lateral distance decreases as the inter-vehicle distance increases. If the relative position of the target remains within the area for target vehicles for a predetermined period of time or longer, the driver assistance ECU 10 selects that target (n) as the target vehicle to follow (a). If there are multiple target vehicles to follow, the driver assistance ECU 10 selects the vehicle with the smallest inter-vehicle distance Dfx(n) from among them as the target vehicle to follow.

[0040] Furthermore, the driver assistance ECU 10 calculates the target acceleration Gtgt according to either equation (1) or (2) below. The target acceleration Gtgt calculated according to either equation (1) or (2) is also referred to as the "target acceleration Gtgt for follow-vehicle distance control". In equations (1) and (2), Vfx(a) is the relative speed of the vehicle being followed (a), and k1 and k2 are predetermined positive gains (coefficients). ΔD1 is the inter-vehicle deviation obtained by subtracting the target inter-vehicle distance Dtgt from the inter-vehicle distance Dfx(a) of the vehicle being followed (a). The target inter-vehicle distance Dtgt is calculated by multiplying the vehicle speed SPD of the vehicle itself by the target inter-vehicle time Ttgt, which is set by the driver using the operation switch 13.

[0041] The driver assistance ECU10 determines the target acceleration Gtgt using equation (1) below when the value (k1·ΔD1+k2·Vfx(a)) is positive or "0". ka1 is a positive gain (coefficient) for acceleration and is set to a value of "1" or less.

[0042] The driver assistance ECU 10 determines the target acceleration Gtgt using equation (2) below when the value (k1·ΔD1+k2·Vfx(a)) is negative. kd1 is the gain (coefficient) for deceleration, and in this example it is set to "1". Gtgt (for acceleration)=ka1 (k1 ΔD1+k2 Vfx(a)) …(1) Gtgt (for deceleration)=kd1 (k1 ΔD1+k2 Vfx(a)) …(2) Furthermore, if there are no targets in the area of ​​the vehicle to be followed, the driver assistance ECU 10 performs constant speed control. That is, the driver assistance ECU 10 determines the target acceleration Gtgt based on the target vehicle speed and vehicle speed SPD so that the vehicle speed SPD of the own vehicle matches the target vehicle speed set by the operation of the operation switch 13. If the target vehicle speed matches the vehicle speed SPD, the driver assistance ECU 10 sets the target acceleration Gtgt to "0". If the target vehicle speed is higher than the vehicle speed SPD, the driver assistance ECU 10 gradually increases the target acceleration Gtgt. If the target vehicle speed is lower than the vehicle speed SPD, the driver assistance ECU 10 gradually decreases the target acceleration Gtgt. The target acceleration Gtgt calculated in this way is also referred to as the "target acceleration Gtgt for constant speed control". The driver assistance ECU 10 controls the engine actuator 31 using the engine ECU 30 so that the vehicle's acceleration matches the target acceleration Gtgt, and also controls the brake actuator 41 using the brake ECU 40 as needed.

[0043] Next, we will describe the speed adjustment support control, which is a feature of this embodiment. Figure 2 is a block diagram illustrating the transmission and reception of information within the driver assistance ECU 10 when performing speed adjustment support control.

[0044] As shown in Figure 2, the functional units of the driver assistance ECU 10 for speed adjustment support control include a road information recognition unit 51, a support amount calculation unit 52, a support timing calculation unit 53, a support judgment unit 54, and a vehicle control unit 55. These units perform the following processing (calculations) at predetermined intervals.

[0045] The road information recognition unit 51 acquires (recognizes) the current position of the vehicle and road information relating to the road ahead of the vehicle's current position. Specifically, the road information recognition unit 51 acquires the vehicle's position Pnow and road information included in the map information of the map database 22 via the navigation ECU 20. For example, the road information includes information on various parameters of a section that makes up the area from the vehicle's position Pnow to a point several hundred meters ahead of the vehicle. The road information recognition unit 51 outputs information on "radius of curvature R and road shape" as various parameters for each of the above sections, as well as information on the vehicle's position Pnow, to the support amount calculation unit 52 and the support timing calculation unit 53. Note that information on the road ahead (road information) may also be acquired from the surrounding sensor 12.

[0046] The support amount calculation unit 52 calculates the target vehicle speed for the curved road based on the information of "radius of curvature R and road shape" and vehicle speed received from the road information recognition unit 51. This target vehicle speed is calculated at the point with the greatest curvature on the curved road ahead (hereinafter referred to as the point of maximum curvature). The unit also calculates the target acceleration (target negative acceleration: deceleration) based on this target vehicle speed, the current vehicle speed, the distance from the vehicle's position Pnow to the point of maximum curvature, etc. This target vehicle speed and target acceleration are calculated as values ​​that keep the vehicle's lateral acceleration below a predetermined allowable lateral acceleration (for example, 0.15g). A detailed explanation follows below.

[0047] In order to calculate the target acceleration G1, the support amount calculation unit 52 first calculates the target vehicle speed V1 for each of the aforementioned sections according to the following equation (3). Target vehicle speed V1={R×(Mg+g×i)}1 / 2…(3) R: radius of curvature Mg: Allowable lateral acceleration g:Gravity acceleration≒9.8 i: Superelevation The support amount calculation unit 52 then calculates the distance L from the vehicle's position Pnow to the point of maximum curvature. Furthermore, the support amount calculation unit 52 obtains information on the current vehicle speed SPD from the vehicle speed sensor 11. For each of the above sections, the support amount calculation unit 52 calculates the target acceleration based on the target vehicle speed V1, the current vehicle speed SPD, and the distance L. The target acceleration is the acceleration (deceleration) required for the vehicle's speed at the point where it reaches the point of maximum curvature on the curve ahead to match the target vehicle speed on the curve. This target acceleration is applied as the deceleration when the vehicle is decelerated at the start timing of the deceleration control described later.

[0048] In this specification, acceleration includes acceleration during acceleration (positive acceleration values) and acceleration during deceleration (negative acceleration values).

[0049] The support timing calculation unit 53 calculates the distance L to the point of maximum curvature on a curved road based on the information of "radius of curvature R and road shape" and vehicle speed information received from the road information recognition unit 51. The support timing calculation unit 53 also acquires the current vehicle speed SPD information from the vehicle speed sensor 11. Then, the support timing calculation unit 53 calculates the arrival margin time (predicted arrival time in this invention) TTP according to the following equation (4).

[0050] Time to reach destination TTP = L / SPD …(4) In other words, this time to reach point TTP is calculated as the time required for the vehicle to reach the point of maximum curvature on the curved road, assuming that the current vehicle speed SPD is maintained.

[0051] The time to reach the target (TTP) gradually decreases as the vehicle progresses (approaching the entrance to the curve or the point of maximum curvature on the curve). In this embodiment, focusing on the fact that this time to reach the target gradually decreases, the timing for initiating deceleration control of the vehicle is replaced with an indicator such as the time to reach the target (TTP). The brake actuator 41 is controlled by defining the point at which the time to reach the target (TTP) is reached, which suppresses the driver from feeling any discomfort when the vehicle's deceleration control begins, as the start timing for deceleration control of the vehicle.

[0052] The support judgment unit 54 determines whether the arrival margin time TTP calculated by the support timing calculation unit 53 is sufficient to prevent the driver from feeling any discomfort when the vehicle's deceleration control begins.

[0053] Specifically, the support judgment unit 54 utilizes the arrival time determination map shown in Figure 3. This arrival time determination map defines an upper threshold (upper threshold of arrival time TTP) and a lower threshold (lower threshold of arrival time TTP) determined by the curve radius at the point of maximum curvature of the curved road. In Figure 3, the horizontal axis is the curve radius, and the vertical axis is the arrival time TTP. An upper threshold curve is defined as a curve connecting the upper thresholds for each curve radius, and a lower threshold curve is defined as a curve connecting the lower thresholds for each curve radius. This arrival time determination map has upper and lower thresholds for arrival time TTP, which are variable (control parameters) according to the radius of the curved road. For example, based on sensory testing, it is possible to design the system so that the arrival time TTP is longer as the radius of the curved road decreases.

[0054] The support determination unit 54 applies the arrival time TTP calculated by the support timing calculation unit 53 to the arrival time determination map (Figure 3) and determines whether the arrival time TTP is within the range between the upper and lower thresholds for the curve radius at the point of maximum curvature. If the arrival time TTP is within the range between the upper and lower thresholds, it determines that the conditions for starting deceleration control are met and starts deceleration control of the vehicle. In other words, it determines that the arrival time TTP is at an appropriate timing for starting deceleration control of the vehicle and outputs an arrival time signal to the vehicle control unit 55.

[0055] On the other hand, if the time to reach the destination (TTP) is longer than the upper threshold or shorter than the lower threshold, the system determines that initiating deceleration control at the TTP timing would cause the driver to feel uneasy, and therefore restricts the deceleration control. In other words, if the TTP is longer than the upper threshold, initiating deceleration control at that TTP timing would result in the actual deceleration starting earlier than the driver's intended timing, potentially causing the driver to feel uneasy, and thus restricts the deceleration control. In this case, the aforementioned TTP is recalculated, and as the vehicle travels, the TTP gradually shortens until it falls below the upper threshold, at which point the deceleration control is initiated. On the other hand, if the TTP is shorter than the lower threshold, and deceleration control is not initiated until the TTP timing, the actual deceleration starting later than the driver's intended timing would also potentially cause the driver to feel uneasy, and therefore restricts the deceleration control at this timing. In this case, the driver will generally apply the brake pedal (disabling the automatic speed control assistance that slows down the vehicle) before reaching the time limit (TTP).

[0056] When the vehicle control unit 55 receives a signal indicating that the arrival time margin has been reached from the support judgment unit 54, it transmits a deceleration control command signal to the brake ECU 40. The brake ECU 40 then activates the brake actuator 41 and starts decelerating the vehicle upon receiving this deceleration control command signal.

[0057] As the driver assistance system 1 is configured as described above, the assistance judgment unit 54 and the vehicle control unit 55 constitute the driving assistance unit as defined in the present invention, and the driver assistance ECU 10 constitutes the driver assistance device as defined in the present invention.

[0058] Next, the driver assistance processing procedure in the driver assistance system 1 configured as described above will be explained. Figure 4 is a flowchart illustrating this driver assistance processing procedure. The processing in this flowchart is repeated at predetermined intervals by the driver assistance ECU 10 when the operation switch 13 is operated and speed adjustment support control is being performed.

[0059] First, in step ST1, road information is acquired. This road information is obtained from map information stored in the map database 22. Alternatively, it may be acquired from the output signal from the surrounding sensor 12.

[0060] In step ST2, based on the road information, it is determined whether or not there is a curve ahead of the vehicle. If there is no curve ahead of the vehicle and the result in ST2 is NO, it is determined that deceleration control of the vehicle is not necessary, and the system returns to the starting position.

[0061] On the other hand, if a curved road exists in front of the vehicle and a YES determination is made in step ST2, the process proceeds to step ST3, where the target vehicle speed at the point of maximum curvature on the curved road (curved road target vehicle speed) is calculated. This target vehicle speed is calculated by the support amount calculation unit 52, and in this embodiment, it is calculated by equation (3) described above. Alternatively, the target vehicle speed may simply be determined in a one-to-one relationship with the radius of curvature at the point of maximum curvature.

[0062] In step ST4, distance information to the point of maximum curvature is acquired. This information is also obtained from map information stored in the map database 22. In step ST5, current vehicle speed information is acquired. This vehicle speed information is obtained by a signal representing the vehicle speed SPD output from the vehicle speed sensor 11.

[0063] In step ST6, the target acceleration is calculated. This target acceleration is determined as the acceleration (deceleration) required for the vehicle speed at the point where the vehicle reaches the point of maximum curvature on the curve ahead to match the target vehicle speed (target vehicle speed on the curve).

[0064] In step ST7, the time to reach the destination (TTP) is calculated. This time to reach the destination (TTP) is calculated in the support timing calculation unit 53 using equation (4) described above.

[0065] After the time to reach TTP is calculated in this way, in step ST8, this time to reach TTP is applied to the time to reach determination map (Figure 3) to determine whether the time to reach TTP falls within the range between the upper and lower thresholds on the time to reach determination map for the curve radius at the point of maximum curvature. If the time to reach TTP does not fall within the range between the upper and lower thresholds, step ST8 is judged as NO, and the process returns to step ST4, where the time to reach TTP is recalculated using the processing operation described above. In this recalculation of the time to reach TTP, the vehicle speed SPD of the vehicle, the target vehicle speed corresponding to the curvature at the point of maximum curvature on the curved road (curved road target vehicle speed), and the distance L to the point of maximum curvature on the curved road are used as parameters.

[0066] On the other hand, if the time to reach the destination (TTP) is within the range between the upper and lower thresholds, and a YES determination is made in step ST8, the process moves to step ST9, where a deceleration control command signal is sent to the brake ECU 40 to start deceleration control of the vehicle.

[0067] After initiating deceleration control of the vehicle, if the vehicle passes the point of maximum curvature on the curved road that was the target of this deceleration control, a YES determination is made in step ST10, and the aforementioned processing operation is then performed on the curved road located ahead. In other words, if the curved road closer to the vehicle is designated as the first curved road and the curved road further away from the vehicle is designated as the second curved road, the vehicle's deceleration control will be initiated only if the time limit TTP (time to reach the point of maximum curvature of the second curved road) between the point of maximum curvature of the first curved road and the point of maximum curvature of the second curved road falls within the range between the upper and lower thresholds determined by the curve radius at the point of maximum curvature of the second curved road.

[0068] This type of operation will be repeated throughout the period in which speed adjustment support control is being implemented.

[0069] Figure 5 shows a plan view of the vehicle traveling on a curved road and an example of the curvature waveform of the said curved road. Figure 5 shows a case where the first curved road section is a left curve, the second curved road section is a right curve, and the third curved road section is a left curve, all in succession. In the figure, MCP1 indicates the point of maximum curvature in the first curved road section, MCP2 indicates the point of maximum curvature in the second curved road section, and MCP3 indicates the point of maximum curvature in the third curved road section.

[0070] In this embodiment, until the vehicle reaches the point of maximum curvature MCP1 in the first curved section, processing operations are performed according to the flowchart described above for the first curved section, and deceleration control of the vehicle is started at a predetermined timing. However, deceleration control of the vehicle for the second and third curved sections is restricted. In other words, deceleration control of the vehicle (deceleration control for the first curved section) is performed without considering the information of "radius of curvature R and road shape" for the second and third curved sections.

[0071] Furthermore, until the vehicle passes the point of maximum curvature MCP1 in the first curved section and reaches the point of maximum curvature MCP2 in the second curved section, the system performs processing operations according to the flowchart described above for the second curved section and starts deceleration control of the vehicle at a predetermined timing. However, deceleration control of the vehicle for the third curved section is restricted. In other words, deceleration control of the vehicle (deceleration control for the second curved section) is performed without considering the information of the "radius of curvature R and road shape" of the third curved section.

[0072] Then, until the vehicle passes the point of maximum curvature MCP2 in the second curved section and reaches the point of maximum curvature MCP3 in the third curved section, the system performs processing operations according to the flowchart described above, targeting the third curved section, and starts deceleration control of the vehicle at a predetermined timing.

[0073] As explained above, in this embodiment, if the calculated arrival time TTP is within the range between the upper and lower thresholds determined by the curve radius at the point of maximum curvature of the curved road, it is determined that the arrival time TTP (the arrival time at the present moment) is at an appropriate time to start the vehicle's deceleration control (the present moment is an appropriate time to start the vehicle's deceleration control), and the vehicle's deceleration control is started. In other words, if the arrival time TTP is not within the range between the upper and lower thresholds, it is determined that starting the vehicle's deceleration control at this arrival time TTP would cause the driver to feel uncomfortable, and the vehicle's deceleration control is restricted. This makes it possible to obtain a deceleration control start timing that corresponds to the driver's intended deceleration start timing, thus suppressing the driver from feeling uncomfortable when the vehicle's deceleration control is started.

[0074] Furthermore, in this embodiment, even when there are two consecutive curved roads with different curvature directions, such as an S-curve, it is possible to achieve deceleration control that suppresses the driver from feeling any discomfort with each curved road. In other words, when the planned route includes information that there are two consecutive curved roads with different curvature directions, and the curved road closer to the vehicle is designated as the first curved road and the curved road further away from the vehicle is designated as the second curved road, the deceleration control for the vehicle targeting the second curved road is initiated on the condition that the time to reach the maximum curvature point of the second curved road after the vehicle has passed the maximum curvature point of the first curved road is within the range between an upper threshold and a lower threshold determined by the curve radius at the maximum curvature point of the second curved road. Therefore, it is possible to avoid the presence of the second curved road having an adverse effect as a disturbance in the deceleration control for the vehicle targeting the first curved road, and the deceleration control for the vehicle targeting the second curved road can also be started at an appropriate timing.

[0075] Furthermore, the present invention is not limited to the embodiments described above, and all modifications and applications are possible within the scope of the claims and equivalents thereof. [Industrial applicability]

[0076] The present invention is applicable to a driver assistance system that controls the timing of deceleration, which automatically slows down a vehicle before it enters a curve. [Explanation of symbols]

[0077] 1…Driver assistance system 10…Driver assistance ECU (Driver assistance device) 51...Road information recognition unit 52...Support amount calculation unit 53...Support timing calculation unit 54...Support Decision Unit (Driving Support Unit) 55...Vehicle Control Unit (Driving Support Unit)

Claims

1. A vehicle driving assistance device comprising a road information recognition unit that recognizes road information for the planned route, and a driving assistance unit that assists the vehicle in driving based on the road information recognized by the road information recognition unit, During the operation of the vehicle, if the road information recognized by the road information recognition unit includes information that a curved road exists on the planned route, the support timing calculation unit calculates the estimated time it will take for the vehicle to reach the point of maximum curvature of the curved road in the current driving state. A vehicle driving assistance device comprising: a support determination unit that initiates deceleration control of the vehicle on the condition that the predicted arrival time calculated by the support timing calculation unit falls within the range between an upper threshold and a lower threshold determined by the curve radius at the point of maximum curvature of the curved road.

2. In the vehicle driving assistance device according to claim 1, A vehicle driving assistance device characterized in that the upper and lower thresholds of the predicted arrival time are set to be longer as the radius of the curved road decreases.

3. In the vehicle driving assistance device according to claim 1 or 2, A vehicle driving assistance device characterized in that, if the above conditions are not met, the estimated arrival time is recalculated.

4. In the vehicle driving assistance device according to claim 1 or 2, The vehicle driving assistance device is characterized in that the support timing calculation unit recalculates the predicted arrival time using at least the current vehicle speed of the vehicle and the distance between the vehicle and the point of maximum curvature as parameters.

5. In the vehicle driving assistance device according to claim 1 or 2, When the road information recognized by the road information recognition unit includes information that the planned travel route consists of two consecutive curved roads with different directions, and the curved road closer to the vehicle is designated as the first curved road and the curved road further away from the vehicle is designated as the second curved road, The vehicle driving support device is characterized in that the support determination unit initiates deceleration control of the vehicle as deceleration control for the vehicle on the second curved road, on the condition that the predicted time from when the vehicle passes the point of maximum curvature of the first curved road until it reaches the point of maximum curvature of the second curved road is within the range between an upper threshold and a lower threshold determined by the curve radius at the point of maximum curvature of the second curved road.

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