Driving assistance apparatus for vehicle

Abstract

To provide a driving support device improved so as to reduce a risk that vehicle speed control is inappropriately executed due to the fact that an actual wheel speed becomes larger than a wheel vehicle speed calculated as a product of a rotational speed of a wheel and a constant even if an outer peripheral length of the wheel increases due to a change in a situation of the wheel.SOLUTION: A driving assistance ECU10 in which a product of a wheel rotation speed estimated based on a meter speed and a constant value stored in advance is calculated as a wheel speed, and a wheel rotation speed is controlled such that the wheel rotation speed becomes a target wheel rotation speed for causing the wheel speed to become a target speed, the driving assistance ECU10 acquiring information on an actual speed of the car from the GNSS receiver when it is determined that the car 102 is traveling at a constant speed; When the difference between the actual vehicle speed and the wheel speed is larger than the reference value, at least one of the constant, the target wheel rotation speed, the target vehicle speed, and the wheel speed used for the vehicle speed control is corrected based on the difference so that the difference becomes smaller than the reference value, and the vehicle speed control is executed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device for a vehicle such as an automobile. [Background technology]

[0002] In vehicle speed control such as constant speed cruise control performed by a driving assistance device, as described in Patent Document 1 below, the vehicle speed is detected based on the wheel speed, which is based on the rotational speed of each wheel, and the vehicle speed is controlled to become a target vehicle speed. The wheel speed is calculated as the product of the rotational speed of each wheel and a constant preset as the outer circumference of the wheel. The constant preset as the outer circumference of the wheel is stored in a storage device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-197071 Summary of the Invention

[0004] [Problem to be solved by the invention] The outer circumference of a wheel changes depending on changes in the wheel condition, such as changes in tire air pressure, tire wear, tire replacement, etc. Therefore, when a change in the wheel condition occurs, the constant stored in the storage device no longer matches the actual outer circumference of the wheel, and the wheel speed calculated as the product of the wheel rotation speed and the constant no longer matches the actual wheel speed, which can reduce the accuracy of vehicle speed control.

[0005] In particular, if the actual circumference of the wheel becomes larger than the constant stored in the storage device due to an increase in tire pressure, the actual wheel speed becomes larger than the wheel speed calculated as the product of the wheel rotation speed and the constant, which makes it difficult to properly control the vehicle speed, and the vehicle speed may become higher than the target vehicle speed.

[0006] The present invention provides an improved driving assistance device that reduces the risk of inappropriate vehicle speed control being performed due to the actual wheel speed being greater than the wheel speed calculated as the product of the wheel rotation speed and a constant, even if the outer circumferential length of the wheel increases due to a change in the wheel condition.

[0007] [Means for solving the problems and effects of the invention] According to the present invention, there is provided a vehicle driving assistance device (100) including: a meter vehicle speed calculation device (meter ECU 40) that calculates a meter vehicle speed (Vm) based on the wheel rotation speeds detected by wheel speed sensors (60fl, 60fr, 60rl, and 60rr); and a control unit (driving assistance ECU 10) that performs vehicle speed control (ACC constant speed traveling control) that calculates the product of the wheel rotation speed (Nwm) estimated based on the meter vehicle speed and a pre-stored constant (Lw) as the wheel speed, and controls the wheel rotation speed so that it becomes a target wheel rotation speed (Nwt) for setting the wheel speed to a target vehicle speed (Vset-Vb).

[0008] When the control unit (driving assistance ECU 10) determines that the vehicle (102) is traveling at a constant vehicle speed (S10), it acquires information on the actual vehicle speed (Va) of the vehicle from the GNSS receiving device (navigation device 70) (S30), calculates the difference (ΔV) between the actual vehicle speed and the wheel speed (S50), and, when the difference is greater than a reference value (Vb) (S60), corrects at least one of the constant (Lw), the target wheel rotation speed (Nwt), the target vehicle speed (Vset-Vb), and the wheel rotation speed (Nwm) used for vehicle speed control based on the difference so that the difference becomes smaller than the reference value, thereby executing vehicle speed control (S170, S170A, S175, S180).

[0009] According to the above configuration, when it is determined that the vehicle is traveling at a constant vehicle speed, information on the actual vehicle speed of the vehicle is acquired from the GNSS receiver, and the difference between the actual vehicle speed and the wheel speed is calculated. Furthermore, when the difference is greater than a reference value, at least one of the constants used for vehicle speed control, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed is corrected based on the difference so that the difference becomes smaller than the reference value, and vehicle speed control is executed.

[0010] Therefore, when the difference between the actual vehicle speed and the wheel speed is larger than the reference value, at least one of the constant used in the vehicle speed control, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed is corrected, and vehicle speed control can be executed so that the difference becomes smaller than the reference value. Therefore, even if the outer circumferential length of the wheel increases due to a change in the wheel condition, the risk of inappropriate execution of vehicle speed control due to the actual wheel speed being larger than the wheel vehicle speed calculated as the product of the wheel rotation speed and the constant can be reduced.

[0011] [Mode of the Invention] In one aspect of the present invention, the control unit (driving assistance ECU 10) is configured to calculate the difference (ΔV) when the meter vehicle speed (Vm) is equal to or greater than the reference vehicle speed (Vmc) (S20).

[0012] When the metered vehicle speed is small, the risk of inappropriate execution of vehicle speed control due to the actual wheel speed being greater than the wheel speed calculated as the product of the wheel rotation speed and a constant is small. According to the above aspect, since the difference is calculated when the metered vehicle speed is equal to or greater than the reference vehicle speed, it is possible to prevent the difference from being calculated unnecessarily when the metered vehicle speed is less than the reference vehicle speed.

[0013] In another aspect of the present invention, the control unit (driving assistance ECU10) is configured to determine (S10) that the vehicle is traveling at a constant vehicle speed when the difference between the maximum vehicle speed and the minimum vehicle speed within a reference time is equal to or less than a reference vehicle speed difference.

[0014] According to the above aspect, it is possible to prevent the vehicle from being determined to be traveling at a constant vehicle speed when the difference between the maximum vehicle speed and the minimum vehicle speed within the reference time exceeds the reference vehicle speed difference.

[0015] Furthermore, in another aspect of the present invention, the vehicle speed control is a control (ACC constant speed driving control) that controls the vehicle speed to a constant set vehicle speed (Vset), and the control unit (driving assistance ECU10) is configured to acquire information on a buffer vehicle speed (Vb) for calculating a meter vehicle speed (Vm) based on the wheel rotation speed, and set the target vehicle speed to the difference (Vset-Vb) between the set vehicle speed and the buffer vehicle speed (S170, S125, S170A).

[0016] According to the above aspect, information on the buffer vehicle speed for calculating the meter vehicle speed based on the wheel rotation speed is acquired, and the target vehicle speed is set to the difference between the set vehicle speed and the buffer vehicle speed, so that the target vehicle speed for the vehicle speed control can be set taking the buffer vehicle speed into consideration.

[0017] Furthermore, in another aspect of the present invention, the reference value is the buffer vehicle speed (Vb) (S60).

[0018] According to the above aspect, since the reference value is the buffer vehicle speed, at least one of the constants used in vehicle speed control, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed can be corrected based on the difference so that the difference between the actual vehicle speed and the wheel speed is smaller than the buffer vehicle speed.

[0019] In the above description, to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are enclosed in parentheses for the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols enclosed in parentheses. Other objects, features, and attendant advantages of the present invention will be easily understood from the following description of the embodiments of the present invention, which will be given with reference to the drawings. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating an embodiment of a vehicle driving assistance device according to the present invention; [Figure 2]10 is a flowchart showing a constant Lw correction routine in the first embodiment. [Figure 3] 4 is a flowchart illustrating an ACC routine in the first embodiment. [Figure 4] 10 is a flowchart showing a correction coefficient Ka setting routine in the second embodiment. [Figure 5] 10 is a flowchart showing an ACC routine in a second embodiment. [Figure 6] 10 is a flowchart showing an ACC routine in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle driving assistance device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] As shown in Fig. 1, a driving assistance device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driving assistance ECU 10. The vehicle 102 is capable of autonomous driving and includes a drive ECU 20, a brake ECU 30, and a meter ECU 40. The ECU stands for an electronic control unit that includes a microcomputer as its main component. The vehicle 102 will be referred to as the host vehicle 102 as necessary to distinguish it from other vehicles.

[0023] The microcomputer of each ECU includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are interconnected via a Controller Area Network (CAN) 104 to enable data exchange (communication). Therefore, the detected values ​​of sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0024] The driving assistance ECU 10 is a central control device that performs driving assistance control such as adaptive cruise control, collision avoidance assistance control, etc. Adaptive cruise control is sometimes called adaptive cruise control, and is abbreviated as "ACC" in this application.

[0025] ACC includes two types of control: constant speed cruise control and adaptive cruise control. Constant speed cruise control adjusts the acceleration / deceleration of the vehicle so that the vehicle speed matches a target vehicle speed (set vehicle speed) Vset without requiring the driver to perform braking or driving operations. Adaptive cruise control causes the host vehicle to follow a preceding vehicle traveling immediately ahead of the host vehicle while maintaining the inter-vehicle distance between the host vehicle and the preceding vehicle at a target inter-vehicle distance Dset.

[0026] The driving assistance ECU 10 is connected to a camera sensor 12, a radar sensor 14, and a setting operation device 16. The camera sensor 12 and the radar sensor 14 each include a plurality of camera devices and a plurality of radar devices. The camera sensor 12 and the radar sensor 14 function as a target information acquisition device 18 that acquires target information around the vehicle 102.

[0027] Although not shown in the figure, each camera device of the camera sensor 12 includes a camera unit that captures images of the surroundings of the vehicle 102 and a recognition unit that analyzes image data captured by the camera unit to recognize targets such as white lines on the road and other vehicles. The recognition unit supplies information about the recognized targets to the driving assistance ECU 10 at predetermined time intervals.

[0028] Each radar device of the radar sensor 14 uses millimeter wave band radio waves to detect the distance between the vehicle and a three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle, etc., and supplies information representing these at predetermined time intervals to the driving assistance ECU 10. Note that instead of or in addition to the radar sensor 14, a LiDAR (Light Detection And Ranging) may be used.

[0029] The setting operation device 16 is provided in a position operable by the driver, like a steering wheel (not shown in Fig. 1), and is designed to be operated by the driver. Although not shown in Fig. 1, the setting operation device 16 includes an ACC switch and a set vehicle speed setting device. The driving assistance ECU 10 executes ACC when the ACC switch is on. The set vehicle speed Vset is set by the driver operating the set vehicle speed setting device.

[0030] The drive ECU 20 is connected to a drive unit 22 that accelerates the vehicle 102 by applying drive force to drive wheels 24. The drive ECU 20 normally controls the drive unit 22 so that the drive force generated by the drive unit 22 changes in response to the driving operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it controls the drive unit 22 based on the command signal. Thus, the drive ECU 20 and the drive unit 22 work together to function as a drive control device 26.

[0031] The braking ECU 30 is connected to a braking device 32 that applies braking force to wheels 34 to decelerate the vehicle 102. The braking ECU 30 normally controls the braking device so that the braking force generated by the braking device 32 changes in response to the braking operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it controls the braking device 32 based on the command signal to perform automatic braking.

[0032] Therefore, the brake ECU 30 and the brake device 32 cooperate with each other to function as a brake control device 36. When a braking force is applied to the wheels by automatic braking or the like, a brake lamp (not shown in Fig. 1) is turned on.

[0033] A display 42 that displays the status of control by the driving assistance ECU 10 is connected to the meter ECU 40. The display 42 may be, for example, a multi-information display that displays meters such as a vehicle speed meter 42A that displays the meter vehicle speed Vm and various other information. As will be described later, the display 42 displays the status of the ACC when it receives a signal from the driving assistance ECU 10.

[0034] The driving operation sensor 50 and the vehicle condition sensor 60 are also connected to the CAN 104. Information detected by the driving operation sensor 50 and the vehicle condition sensor 60 (referred to as sensor information) is transmitted to the CAN 104. The sensor information transmitted to the CAN 104 can be used appropriately in each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to the CAN 104 from that specific ECU.

[0035] The driving operation sensor 50 includes a driving operation amount sensor, a braking operation amount sensor, a brake switch, a blinker switch, a steering angle sensor for detecting a steering angle, a steering torque sensor, etc.

[0036] The vehicle state sensor 60 includes wheel speed sensors 62fl, 62fr, 62rl, and 62rr, which detect the rotational speeds Nfl, Nfr, Nrl, and Nrr [rpm] of a left front wheel 64fl, a right front wheel 64fr, a left rear wheel 64rl, and a right rear wheel 64rr, respectively. The vehicle state sensor 60 also includes a longitudinal acceleration sensor, a lateral acceleration sensor, a yaw rate sensor, and the like.

[0037] The ROM of the meter ECU 40 stores a constant Lwc, which is the outer circumference of each wheel, and a buffer vehicle speed Vb. The CPU of the meter ECU 40 calculates wheel speeds Vfl, Vfr, Vrl, and Vrr of the left front wheel 64fl, the right front wheel 64fr, the left rear wheel 64rl, and the right rear wheel 64rr as the product of the rotational speeds Nfl, Nfr, Nrl, and Nrr and Lwc. The CPU of the meter ECU 40 calculates a vehicle speed Vv, which is used to calculate a meter vehicle speed Vm to be displayed on the speedometer 42A, based on at least one of the wheel speeds Vfl, Vfr, Vrl, and Vrr, in a manner known in the art.

[0038] Furthermore, the CPU of the meter ECU 40 calculates a meter vehicle speed Vm as the sum of the vehicle speed Vv and the buffer vehicle speed Vb, and displays the meter vehicle speed Vm on the vehicle speed meter 42A. Therefore, the meter ECU 40 functions as a meter vehicle speed calculation device that calculates the meter vehicle speed Vm based on the rotational speeds Nfl, Nfr, Nrl, and Nrr of each wheel. The buffer vehicle speed Vb is a positive constant that prevents the meter vehicle speed Vm from exceeding the actual vehicle speed.

[0039] Furthermore, the navigation device 70 is also connected to the CAN 104. The navigation device 70 includes a GNSS receiver, a storage device that stores map information and road information, and a communication device that acquires the latest map information and road information from an external device. In particular, the GNSS receiver detects the position of the vehicle 102 and outputs a signal that indicates the actual vehicle speed Va as the rate of change of the vehicle's position.

[0040] [First embodiment] <Constant Lw correction routine (Figure 2)> Next, a constant Lw correction routine in the first embodiment will be described with reference to the flowchart shown in Fig. 2. The correction of the constant Lw according to the flowchart shown in Fig. 2 is repeatedly executed at predetermined time intervals by the CPU of the driving assistance ECU 10 while the ACC switch is on. Note that the relationship between the constant Lw and the corrected constant Lwa for making the meter vehicle speed Vm greater than the actual vehicle speed Va is determined in advance and stored as a map in the ROM of the driving assistance ECU 10.

[0041] First, in step S10, the CPU determines whether or not the vehicle 102 is traveling at a constant speed. If a negative determination is made, the control temporarily ends, and if a positive determination is made, the control proceeds to step S20.

[0042] It may be determined that the vehicle is traveling at a constant speed when the ACC constant speed control is being executed, or it may be determined that the vehicle is traveling at a constant speed when the ACC constant speed control is not being executed but the difference between the maximum vehicle speed and the minimum vehicle speed within a reference time up to the present is equal to or less than a reference value (a positive constant).

[0043] In step S20, the CPU determines whether the meter vehicle speed Vm is equal to or greater than a reference vehicle speed Vmc (a positive constant). If a negative determination is made, the control temporarily ends, and if a positive determination is made, the control proceeds to step S30.

[0044] In step S30, the CPU acquires information on the actual vehicle speed Va from the GNSS receiver of the navigation device .

[0045] In step S40, the CPU calculates the wheel rotation speed Nvm estimated based on the meter vehicle speed Vm according to the following equation (1). Nvm = (Vm - Vb) / Lwc ... (1)

[0046] In step S50, the CPU calculates the difference ΔV between the actual vehicle speed Va and the product (wheel speed) of the wheel rotation speed Nvm and the constant Lwc according to the following equation (2). ΔV=Va-Nvm×Lwc …(2)

[0047] In step S60, the CPU determines whether the difference ΔV is greater than the buffer vehicle speed Vb, and therefore whether the actual vehicle speed Va is greater than the meter vehicle speed Vm and the constant Lw needs to be corrected. If a positive determination is made, the control proceeds to step S90, and if a negative determination is made, the control proceeds to step S70.

[0048] In step S70, the CPU determines whether the difference ΔV is a positive value, that is, whether the product of the rotational speed Nvm of the wheel and the constant Lwc is smaller than the actual vehicle speed Va. When a negative determination is made, this control ends once without obtaining the corrected constant Lwa, and when an affirmative determination is made, this control proceeds to step S80.

[0049] In step S80, the CPU determines whether the difference ΔV is increasing. When a negative determination is made, this control ends once without obtaining the corrected constant Lwa, and when an affirmative determination is made, this control proceeds to step S90.

[0050] In step S90, the CPU determines the corrected constant Lwa for making the meter vehicle speed Vm greater than the actual vehicle speed Va from a map of the relationship between the difference ΔV and the corrected constant Lwa based on the difference ΔV. In step S100, the CPU stores the corrected constant Lwa in the RAM.

[0051] <ACC routine (Figure 3)> Next, the ACC routine in the first embodiment will be described with reference to the flowchart shown in FIG. 3. The ACC according to the flowchart shown in FIG. 3 is repeatedly executed by the CPU of the driving support ECU 10 at predetermined time intervals in a situation where the ACC switch is on.

[0052] First, in step S110, the CPU determines whether there is a preceding vehicle in front of the vehicle 102. When a negative determination is made, this control proceeds to step S130, and when an affirmative determination is made, this control proceeds to step S120.

[0053] In step S120, the CPU executes the follow - up inter - vehicle distance control of the ACC. That is, the CPU controls the running of the vehicle 102 with respect to the preceding vehicle so that the inter - vehicle distance D between the vehicle 102 and the preceding vehicle acquired by the target information acquisition device 18 becomes the set target inter - vehicle distance Dset.

[0054] In step S130, the CPU determines whether the set vehicle speed Vset of the ACC constant speed cruise control is equal to or greater than the reference set vehicle speed Vsetc (a positive constant). If a negative determination is made, the control proceeds to step S160, and if a positive determination is made, the control proceeds to step S140.

[0055] In step S140, the CPU determines whether the corrected constant Lwa is stored in the RAM. If a negative determination is made, the control proceeds to step S160, and if a positive determination is made, the control proceeds to step S150.

[0056] In step S150, the CPU sets the constant Lw to the corrected constant Lwa, and in step S160, the CPU sets the constant Lw to the constant Lwc stored in the ROM.

[0057] In step S170, the CPU calculates the target wheel rotation speed Nwt according to the following equation (3). Nwt=(Vset-Vb) / Lw …(3)

[0058] In step S180, the CPU outputs command signals to the drive ECU 20 and the brake ECU 30 so that the wheel rotation speed Nwm becomes the target wheel rotation speed Nwt, thereby executing constant speed cruise control of the ACC so that the vehicle speed Vv becomes the target vehicle speed Vset-Vb.

[0059] In the first embodiment, when it is determined that the vehicle 102 is traveling at a constant speed (S10) and that the meter vehicle speed Vm is equal to or greater than the reference vehicle speed Vmc (S20), information on the actual vehicle speed Va is acquired from the GNSS receiver of the navigation device 70 (S30). A wheel rotation speed Nvm estimated based on the meter vehicle speed Vm is calculated (S40), and a difference ΔV between the actual vehicle speed Va and the wheel speed calculated as the product of the wheel rotation speed Nvm and a constant Lwc is calculated (S50).

[0060] When the difference ΔV is larger than the buffer vehicle speed Vb (S60), and therefore the meter vehicle speed Vm is smaller than the actual vehicle speed Va, a corrected constant Lwa for making the meter vehicle speed Vm larger than the actual vehicle speed Va is calculated based on the difference ΔV and stored in RAM (S90, S100).

[0061] Furthermore, in a situation where there is no preceding vehicle ahead of the vehicle 102 and constant speed driving by ACC is being performed, when the set vehicle speed Vset for constant speed driving is equal to or greater than the reference value Vsetc (S130), it is determined whether or not the corrected constant Lwa is stored in RAM (S140). If it is determined that the corrected constant Lwa is stored in RAM, the constant Lw is set to the corrected constant Lwa (S150), and the target wheel rotation speed Nwt is calculated as the value obtained by dividing the target vehicle speed Vset-Vb by the constant Lw (S170).

[0062] Furthermore, command signals are output to the drive ECU 20 and the brake ECU 30 to control the braking / driving forces of each wheel so that the wheel rotation speed Nvm becomes the target wheel rotation speed Nwt and the vehicle speed Vv becomes the target vehicle speed Vset-Vb, thereby executing the constant speed cruise control of the ACC (S170, S180).

[0063] [Second embodiment] <Correction coefficient Ka setting routine (Fig. 4)> Next, a routine for setting the correction coefficient Ka in the second embodiment will be described with reference to the flowchart shown in Fig. 4. The setting of the correction coefficient Ka according to the flowchart shown in Fig. 4 is repeatedly executed by the CPU of the driving assistance ECU 10 at predetermined time intervals while the ACC switch is on.

[0064] 4 and 2, steps S10 to S80 are executed in the same manner as in the first embodiment, except that steps S90A and S100A are executed instead of steps S90 and S100 in the first embodiment. Note that the relationship between the correction coefficient Ka for the target wheel rotation speed Nwt, which is used to make the meter vehicle speed Vm higher than the actual vehicle speed Va, and the difference ΔV is determined in advance and stored as a map in the ROM of the driving assistance ECU 10.

[0065] In step S90A, the CPU determines a correction coefficient Ka for the target wheel rotation speed Nwt to make the meter vehicle speed Vm greater than the actual vehicle speed Va from a map of the relationship between the difference ΔV and the correction coefficient Ka based on the difference ΔV. In step S100A, the CPU stores the correction coefficient Ka in the RAM.

[0066] <ACC routine (Fig. 5)> Next, the ACC routine in the second embodiment will be described with reference to the flowchart shown in FIG. 5. The ACC according to the flowchart shown in FIG. 5 is repeatedly executed by the CPU of the driving support ECU 10 at predetermined intervals in a situation where the ACC switch is on.

[0067] As can be understood from the comparison between FIG. 5 and FIG. 3, steps S110, S120, S130, and S180 are executed in the same manner as in the first embodiment. When an affirmative determination is made in step S110, step S125 is executed. Instead of S140 to S170 of the first embodiment, S140A to S160A and step S175 are executed respectively.

[0068] In step S125, the CPU calculates the target wheel rotation speed Nwt according to the following formula (4). Nwt = (Vset - Vb) / Lwc …(4)

[0069] In step S140A, the CPU determines whether the correction coefficient Ka is stored in the RAM. When a negative determination is made, this control proceeds to step S160A, and when an affirmative determination is made, this control proceeds to step S150A.

[0070] In step S150A, the CPU sets the correction coefficient Kn for the target wheel rotation speed Nwt to the correction coefficient Ka, and in step S160A, the CPU sets the correction coefficient Kn to 1.

[0071] In step S175, the CPU multiplies the target wheel rotation speed Nwt by a correction coefficient Ka to correct the target wheel rotation speed.

[0072] In the second embodiment, similarly to the first embodiment, when it is determined that the vehicle 102 is traveling at a constant speed (S10) and the meter vehicle speed Vm is determined to be equal to or greater than the reference vehicle speed Vmc (S20), the difference ΔV is calculated (S50).

[0073] When the difference ΔV is greater than the buffer vehicle speed Vb (S60), a correction coefficient Ka for the target wheel rotation speed Nwt to make the meter vehicle speed Vm greater than the actual vehicle speed Va is calculated based on the difference ΔV and stored in RAM (S90A, S100A).

[0074] Furthermore, in a situation where there is no preceding vehicle ahead of the vehicle 102 and constant speed driving by ACC is being performed, when the set vehicle speed Vset for constant speed driving is equal to or greater than the reference value Vsetc (S130), it is determined whether or not the correction coefficient Ka is stored in RAM (S140A). If it is determined that the correction coefficient Ka is stored in RAM, the target wheel rotation speed Nwt calculated according to equation (4) is multiplied by the correction coefficient Ka to correct the target wheel rotation speed (S150A, S175).

[0075] Furthermore, command signals are output to the drive ECU 20 and the brake ECU 30 to control the braking / driving force of each wheel so that the wheel rotation speed Nwm becomes the target wheel rotation speed Nwt and the vehicle speed Vv becomes the target vehicle speed Vset-Vb, thereby executing the constant speed cruise control of the ACC (S180).

[0076] [Third embodiment] In the third embodiment, the correction coefficient Ka setting routine is executed according to the flowchart shown in FIG. 4, as in the second embodiment, and the ACC routine is executed according to the flowchart shown in FIG.

[0077] 6 and 5, steps S110 to S160A and step S180 are executed in the same manner as in the second embodiment, except that step S125 is not executed. After step S150A or S160A is completed, in step S170A, the target wheel rotation speed Nwt is calculated based on the target vehicle speed Vset-Vb in accordance with the following equation (5). Nwt = Kn (Vm - Vb) / Lwc ... (5)

[0078] In the third embodiment, when the difference ΔV is larger than the buffer vehicle speed Vb (S60), similarly to the second embodiment, the correction coefficient Kn is set to the correction coefficient Ka for making the meter vehicle speed Vm larger than the actual vehicle speed Va (S150A). Furthermore, the target wheel rotation speed Nwt is calculated based on the target vehicle speed corrected by multiplying the target vehicle speed Vm-Vb by the correction coefficient Kn.

[0079] [Fourth embodiment] In the fourth embodiment, similarly to the first embodiment, the constant Lw correction routine is executed according to the flowchart shown in Fig. 2. The ACC routine is executed similarly to the first embodiment according to the flowchart shown in Fig. 3, except for steps S170 and S180.

[0080] In step S170, the target wheel rotation speed Nwt is calculated according to the following equation (6). Nwt=(Vset-Vb) / Lwc …(6)

[0081] In the step executed after step S170 and before step S180, the wheel rotation speed Nvm is multiplied by the correction coefficient Lwa / Lwc to correct the wheel rotation speed Nvm. Furthermore, in step S180, a command signal is output to the drive ECU 20 and the brake ECU 30 so that the corrected wheel rotation speed Nwm becomes the target wheel rotation speed Nwt, and constant speed traveling control of the ACC is executed so that the vehicle speed becomes the target vehicle speed Vset-Vb.

[0082] As can be seen from the above explanation, according to the present invention, when it is determined that the vehicle 102 is traveling at a constant vehicle speed (S10), information on the actual vehicle speed Va of the vehicle is acquired from the GNSS receiver (S30), and the difference ΔV between the actual vehicle speed and the wheel speed is calculated (S50). Furthermore, when the difference is greater than a reference value Vb, at least one of the constant (Lw), target wheel rotation speed (Nwt), target vehicle speed (Vset-Vb), and wheel rotation speed (Nwm) used in the vehicle speed control (ACC) is corrected based on the difference so that the difference becomes smaller than the reference value, and vehicle speed control is executed.

[0083] Therefore, when the difference ΔV between the actual vehicle speed and the wheel speed is larger than the reference value Vb, at least one of the constant used in vehicle speed control, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed is corrected, and vehicle speed control can be executed so that the difference becomes smaller than the reference value. Therefore, even if the outer circumferential length of the wheel increases due to a change in the wheel condition, it is possible to reduce the risk of inappropriate execution of vehicle speed control due to the actual wheel speed becoming larger than the wheel vehicle speed calculated as the product of the wheel rotation speed and the constant.

[0084] When the vehicle meter speed Vm is small, the risk of inappropriate execution of vehicle speed control due to the actual wheel speed being greater than the wheel speed calculated as the product of the wheel rotation speed and a constant is small. According to the present invention, since the difference is calculated when the vehicle meter speed is equal to or greater than the reference vehicle speed Vmc, it is possible to prevent the difference from being calculated unnecessarily when the vehicle meter speed is less than the reference vehicle speed.

[0085] Furthermore, according to the present invention, when the difference between the maximum vehicle speed and the minimum vehicle speed within the reference time is equal to or less than the reference vehicle speed difference, it is determined that the vehicle is traveling at a constant vehicle speed (S10). Therefore, when the difference between the maximum vehicle speed and the minimum vehicle speed within the reference time exceeds the reference vehicle speed difference, it is possible to prevent the vehicle from being determined to be traveling at a constant vehicle speed.

[0086] Furthermore, according to the present invention, information on the buffer vehicle speed Vb for calculating the meter vehicle speed Vm based on the wheel rotation speed is acquired, and the target vehicle speed is set to the difference Vset-Vb between the set vehicle speed and the buffer vehicle speed (S170, S125, S170A). Therefore, the target vehicle speed for vehicle speed control can be set taking the buffer vehicle speed into consideration.

[0087] Furthermore, according to the present invention, since the reference value is the buffer vehicle speed Vb (S60), at least one of the constants used in vehicle speed control, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed can be corrected based on the difference so that the difference ΔV between the actual vehicle speed and the wheel speed becomes smaller than the buffer vehicle speed.

[0088] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various other embodiments are possible within the scope of the present invention.

[0089] For example, in the first to fourth embodiments described above, the constant (Lw), the target wheel rotation speed (Nwt), the target vehicle speed (Vset-Vb), and the wheel rotation speed (Nwm) are corrected, respectively. However, two or more of the constant, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed may be corrected.

[0090] In the first to fourth embodiments described above, the constant (Lw) and other parameters are corrected when it is determined that the difference ΔV is greater than the buffer vehicle speed Vb. However, the reference value does not have to be the buffer vehicle speed Vb. Furthermore, the constant (Lw) and other parameters may also be corrected when the difference ΔV is smaller than a negative reference value.

[0091] Furthermore, in the first to fourth embodiments described above, the vehicle speed control is ACC, but the vehicle speed control may be any control that controls the vehicle speed to a target vehicle speed. [Explanation of symbols]

[0092] 10... driving assistance ECU, 12... camera sensor, 14... radar sensor, 18... target information acquisition device, 22... drive device, 32... braking device, 50... meter ECU, 60fl, 60fr, 60rl and 60rr... wheel speed sensors, 100... driving assistance device, 102... vehicle

Claims

1. A vehicle driving assistance device including: a meter vehicle speed calculation device that calculates a meter vehicle speed based on the rotational speed of a wheel detected by a wheel speed sensor; and a control unit that calculates a wheel speed by multiplying the wheel rotational speed estimated based on the meter vehicle speed by a pre-stored constant, and executes vehicle speed control to control the wheel rotational speed so that the wheel speed becomes a target wheel rotational speed for setting the wheel speed to a target vehicle speed, a control unit that acquires information on the actual vehicle speed of the vehicle from a GNSS receiving device when it is determined that the vehicle is traveling at a constant vehicle speed, calculates the difference between the actual vehicle speed and the wheel speed, and, when the difference is greater than a reference value, performs the vehicle speed control by modifying at least one of the constant, the target wheel rotation speed, the target vehicle speed, and the wheel rotation speed based on the difference so that the difference becomes smaller than the reference value.

2. 2. The vehicle driving assistance system according to claim 1, wherein the control unit is configured to calculate the difference when the meter vehicle speed is equal to or greater than a reference vehicle speed.

3. 2. The vehicle driving assistance device according to claim 1, wherein the control unit is configured to determine that the vehicle is traveling at a constant vehicle speed when a difference between a maximum vehicle speed and a minimum vehicle speed within a reference time is equal to or less than a reference vehicle speed difference.

4. 2. The vehicle driving assistance device according to claim 1, wherein the vehicle speed control is a control for controlling the vehicle speed to a constant set vehicle speed, and the control unit is configured to acquire information on a buffer vehicle speed for calculating the meter vehicle speed based on the rotational speed of the wheels, and to set the target vehicle speed to a difference between the set vehicle speed and the buffer vehicle speed.

5. 5. The vehicle driving assistance system according to claim 4, wherein the reference value is the buffer vehicle speed.

Images