Driving support device

Abstract

To provide a technique which makes both a turning amount and a turning attitude of a vehicle have desirable characteristics at the same time.SOLUTION: In a driving support device which supports driving of a vehicle, one or a plurality of processors acquires a load which is applied in a vehicle width direction of the vehicle among forces which are applied on vehicle wheels of the vehicle, and a moment around a shaft along a height direction of the vehicle when the vehicle turns, and updates a correlation map which represents a relationship between the load and the moment on the basis of the acquired load and moment.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a driving assistance device. [Background technology]

[0002] In a vehicle, it is required that the amount of turning and the turning attitude are simultaneously made desirable characteristics.

[0003] For example, Patent Document 1 discloses a behavior control device for an electric vehicle, which includes a steering mechanism that turns in response to steering operation, means for calculating a target turning amount and a target slip angle basic value of the vehicle based on the vehicle speed and steering operation amount, means for calculating a driving force difference command value based on the target turning amount and the target slip angle basic value, means for controlling the driving wheels based on the driving force difference command value, means for calculating a target slip angle by correcting the target slip angle basic value based on the amount of deviation of the actual driving force difference of the driving wheels from the driving force difference command value, and means for correcting the steering angle of the steering mechanism based on the target slip angle and target turning amount. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-151623 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology disclosed in Patent Document 1 predicts changes in vehicle behavior from the deviation of the actual driving force difference between the drive wheels from a driving force difference command value, and controls turning behavior. However, there is a problem in that changes in vehicle behavior cannot be adequately detected when there is no driving force difference between the drive wheels. Also, there is a problem in that fluctuations in the vehicle's turning amount cannot be suppressed even when the road surface has a low friction coefficient and the drive wheels do not receive a sufficient road surface reaction force. Another problem is that slip angle requires high accuracy, making accurate calculation difficult. Therefore, there is room for improvement in achieving desirable characteristics for both the vehicle's turning amount and turning attitude.

[0006] In view of the above circumstances, an object of the present disclosure is to provide a technology that simultaneously makes the turning amount and turning posture of a vehicle desirable characteristics. [Means for solving the problem]

[0007] A driving assistance device according to one embodiment of the present disclosure is a driving assistance device that assists in driving a vehicle, and includes one or more processors and one or more memories communicatively connected to the one or more processors. When the vehicle is turning, the one or more processors acquire, from among the forces applied to the wheels of the vehicle, the load applied in the vehicle's width direction and the moment around an axis along the vehicle's height direction, and update a correlation map showing the relationship between the load and the moment based on the acquired load and moment. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, the turning amount and turning attitude of the vehicle can be simultaneously made to be desirable characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a configuration example of a vehicle equipped with a driving assistance device according to an embodiment of the present disclosure. [Figure 2] 1 is a block diagram illustrating a configuration example of a driving assistance device according to a first embodiment of the present disclosure. [Figure 3] 4 is a flowchart illustrating a first operation example of the driving assistance device according to the first embodiment of the present disclosure. [Figure 4] 4 is a diagram illustrating a correlation map updated in the first operation example shown in FIG. 3. FIG. [Figure 5] 6 is a flowchart illustrating a second operation example of the driving assistance device according to the first embodiment of the present disclosure. [Figure 6] FIG. 4 is a block diagram illustrating a configuration example of a driving assistance device according to a second embodiment of the present disclosure. [Figure 7] 10 is a flowchart illustrating an example of the operation of a driving assistance device according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] <1. First embodiment> (1-1. Overall configuration of the vehicle) An example of the overall configuration of a vehicle 1 equipped with a driving assistance device 50 according to an embodiment of the present disclosure will be described with reference to FIG.

[0012] Vehicle 1 is configured as a front-wheel drive four-wheel vehicle that transmits drive torque output from drive power source 9, which generates drive torque for vehicle 1, to the left and right front wheels. Vehicle 1 may be a vehicle equipped with an internal combustion engine such as a gasoline engine or a diesel engine as drive power source 9, an electric vehicle equipped with a drive motor as drive power source 9, or a hybrid electric vehicle equipped with both an internal combustion engine and a drive motor as drive power source 9.

[0013] The combination of drive wheels and the drive method are not limited. For example, vehicle 1 may be a rear-wheel drive vehicle, a four-wheel drive vehicle, or an electric vehicle equipped with a drive motor corresponding to each wheel 3. Furthermore, if vehicle 1 is an electric vehicle or a hybrid electric vehicle, vehicle 1 is equipped with a secondary battery that stores power supplied to the drive motor, and a motor or a generator such as a fuel cell that generates power to charge the battery.

[0014] The vehicle 1 is equipped with a driving force source 9, an electric steering device 15, and brake devices 17LF, 17RF, 17LR, and 17RR (hereinafter collectively referred to as "brake devices 17" unless a distinction is required) as devices used to control the operation of the vehicle 1. The driving force source 9 outputs driving torque that is transmitted to the front drive shaft 5F via a transmission (not shown) and a differential mechanism 7. The operation of the driving force source 9 and the transmission is controlled by a vehicle control unit 41 that includes one or more electronic control units (ECUs: Electronic Control Units).

[0015] The electric steering device 15 is provided on the front-wheel drive shaft 5F. The electric steering device 15 includes an electric motor (not shown) and a gear mechanism (not shown), and is controlled by a vehicle control unit 41 to adjust the steering angle of the front wheels. The vehicle control unit 41 controls the driving of the electric steering device 15 so as to control the steering angle of the front wheels based on the steering angle of the steering wheel 13 by the driver. If the vehicle 1 is a vehicle capable of executing automatic driving control, the vehicle control unit 41 controls the electric steering device 15 based on the steering angle of the steering wheel 13 by the driver during manual driving. On the other hand, the vehicle control unit 41 controls the electric steering device 15 based on the steering angle or steering angular velocity set by the driving assistance device 50 during automatic driving.

[0016] Electric steering device 15 may be a steer-by-wire type steering device in which a steering device (not shown) that receives steering input from steering wheel 13 operated by the driver and a wheel steering device (not shown) that steers the steered wheels are mechanically separated (linkless) and controlled in conjunction with each other by vehicle control unit 41. However, the present disclosure is not limited to this.

[0017] Brake devices 17LF, 17RF, 17LR, and 17RR apply braking force to the respective wheels. Brake devices 17 may be, for example, hydraulic brake devices. In this case, the vehicle control unit 41 controls the drive of hydraulic units 16 to adjust the hydraulic pressure supplied to each brake device 17. If vehicle 1 is an electric vehicle or a hybrid electric vehicle, brake devices 17 are used in combination with regenerative braking using a drive motor.

[0018] The vehicle control unit 41 includes one or more electronic control units (ECUs) that control the operation of the driving force source 9, the electric steering device 15, and the hydraulic unit 16. If the vehicle 1 is equipped with a transmission that changes the speed of the output from the driving force source 9 and transmits it to the wheels, the vehicle control unit 41 has a function to control the operation of the transmission. Note that if the vehicle 1 is a vehicle capable of executing automatic driving control, the vehicle control unit 41 is configured to be able to acquire information output from the driving assistance device 50, and is configured to be able to execute automatic driving control of the vehicle 1.

[0019] The vehicle 1 further includes an ambient environment sensor 31, a vehicle state sensor 33, a GNSS (Global Navigation Satellite System) sensor 35, a load detection device 37, a notification device 43, and the like.

[0020] The surrounding environment sensor 31 is one or more sensors that detect information about the surrounding environment of the vehicle 1. The surrounding environment sensor 31 captures an image of the surroundings of the vehicle 1, which corresponds to the surrounding environment of the vehicle 1, and outputs the image data to the driving assistance device 50. The surrounding environment sensor 31 includes, for example, a pair of left and right stereo cameras 31LF, 31RF that capture images of the area ahead of the vehicle 1. The surrounding environment sensor 31 may include, for example, one or more sensors selected from the group consisting of a LiDAR, a radar sensor, and an ultrasonic sensor.

[0021] The vehicle state sensor 33 includes one or more sensors that detect the state of the vehicle 1. The vehicle state sensor 33 includes a steering angle sensor that detects the steering angle of the steering wheel 13. The vehicle state sensor 33 may also include a torque sensor that detects the steering force input by the driver via the steering wheel 13. The vehicle state sensor 33 may also include a yaw rate sensor that detects the yaw rate. The vehicle state sensor 33 may also include at least one of a vehicle speed sensor, an acceleration sensor, an angular velocity sensor, an accelerator position sensor, a brake stroke sensor, a brake pressure sensor, and an engine rotation speed sensor. The vehicle state sensor 33 outputs information indicating the detection result to the driving assistance device 50.

[0022] The GNSS sensor 35 receives satellite signals from positioning satellites such as GPS (Global Positioning System) satellites. The GNSS sensor 35 transmits position information of the vehicle 1 contained in the received satellite signals to the driving assistance device 50. Note that the GNSS sensor 35 may be provided with an antenna, in addition to the GPS sensor, that receives satellite signals from other satellite systems that identify the position of the vehicle 1.

[0023] The load detection devices 37LF, 37RF, 37LR, and 37RR (hereinafter collectively referred to as "load detection device 37" unless a distinction is required) detect tire forces applied to each wheel of the vehicle 1 based on differential signals output from load cells having bridge circuits to which strain gauges are connected. The load detection devices 37LF and 37RF are respectively provided at the connection between the front drive shaft 5F and the front wheels. The load detection devices 37LR and 37RR are respectively provided at the connection between the rear wheel shaft (not shown) and the rear wheels. The load detection device 37 can be a six-component force detector or the like that detects loads (Fx, Fy, Fz) applied in the fore-and-aft direction (hereinafter also referred to as the "x-axis direction"), the vehicle width direction (hereinafter also referred to as the "y-axis direction"), and the height direction (hereinafter also referred to as the "z-axis direction") of the vehicle 1, and moments (Mx, My, Mz) about the x-axis, y-axis, and z-axis, respectively. The load detection device 37 outputs information indicating the detection result to the driving assistance device 50.

[0024] The notification device 43 is driven by the driving assistance device 50 and notifies the driver of the vehicle 1 of various information by means of image display, audio output, or the like. The notification device 43 may include, for example, a display device provided in the instrument panel, or may include a speaker provided in the vehicle 1. The display device may be a display device provided in a navigation device. The notification device 43 may also include a HUD (Head Up Display) that displays information on the front window of the vehicle 1.

[0025] (1-2. Driving assistance devices) A driving assistance device 50 according to a first embodiment will be described with reference to FIG.

[0026] (1-2-1. Configuration example) The driving assistance device 50 functions as a device that assists in driving the vehicle 1 by having one or more processors, such as CPUs (Central Processing Units), execute a computer program. The computer program is a computer program that causes the processor to execute operations, described below, that should be performed by the driving assistance device 50. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 52, described below, or may be recorded on a recording medium built into the driving assistance device 50 or any recording medium that can be externally attached to the driving assistance device 50.

[0027] Recording media for recording computer programs may include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical recording media such as CD-ROMs, DVDs, and Blu-ray (registered trademark), magneto-optical media such as floptical disks, memory elements such as RAMs and ROMs, flash memories such as USB memories and SSDs, and other media capable of storing programs.

[0028] The driving assistance device 50 is connected to an ambient environment sensor 31, a vehicle state sensor 33, a GNSS sensor 35, a load detection device 37, a vehicle control unit 41, and a notification device 43 via a dedicated line or a communication means such as a CAN (Controller Area Network) or a LIN (Local Inter Net).

[0029] The driving assistance device 50 includes a processing unit 51, a storage unit 52, and a correlation map storage unit 53.

[0030] (Processing section) The processing unit 51 includes one or more processors such as a CPU and various peripheral components. Part or all of the processing unit 51 may be configured with updatable components such as firmware, or may be a program module executed by instructions from the CPU or the like.

[0031] (Storage part) The storage unit 52 is configured with one or more storage elements such as RAM or ROM connected to the processing unit 51 so as to be able to communicate with the processing unit 51. However, there is no particular limitation on the type and number of the storage units 52. The storage unit 52 stores information indicating the computer program executed by the processing unit 51, various parameters used in the calculation process, detection results, calculation results, etc.

[0032] (Correlation map storage unit) The correlation map storage unit 53 is configured by a storage element such as a RAM or a ROM, or a storage medium such as an HDD, a CD, a DVD, an SSD, a USB flash drive, or a storage device, which is communicably connected to the processing unit 51. The correlation map storage unit 53 stores a correlation map that is updated by an update unit 62, which will be described later.

[0033] (1-2-2. Functional configuration of the processing unit) The functional configuration of the processing unit 51 of the driving assistance device 50 will be described. The processing unit 51 includes an acquisition unit 61, an update unit 62, a calculation unit 63, a determination unit 64, and a notification processing unit 65. These units each have a function realized by execution of a computer program by one or more processors such as a CPU. However, some or all of the acquisition unit 61, the update unit 62, the calculation unit 63, the determination unit 64, and the notification processing unit 65 may be configured using analog circuits.

[0034] (Acquisition Department) The acquisition unit 61 acquires, from among the forces (tire forces) applied to each wheel of the vehicle 1, a load Fy applied in the vehicle width direction of the vehicle 1 and a moment Mz around an axis along the height direction of the vehicle 1. Specifically, the acquisition unit 61 acquires the load Fy and moment Mz detected by the load detection device 37 from the load detection device 37. The load Fy and moment Mz are acquired at predetermined time intervals after the vehicle 1 turns, and are stored in the correlation map storage unit 53 as time-series data.

[0035] The acquisition unit 61 acquires the steering angle from the vehicle state sensor 33. The acquisition unit 61 may acquire the steering force or the yaw rate from the vehicle state sensor 33.

[0036] (Update section) The update unit 62 updates the correlation map indicating the relationship between the load Fy and the moment Mz based on the load Fy and the moment Mz acquired by the acquisition unit 61. Specifically, the update unit 62 updates the correlation map indicating the relationship between the load Fy and the moment Mz every time the acquisition unit 61 acquires the load Fy and the moment Mz. Details will be described later. The correlation map is stored (overwritten and saved) in the correlation map storage unit 53.

[0037] (Calculation section) The calculation unit 63 acquires the time series data of the load Fy and the time series data of the moment Mz acquired by the acquisition unit 61 within a predetermined time after the vehicle 1 turns from the correlation map storage unit 53. The calculation unit 63 also calculates a regression line by performing linear regression on the acquired time series data of the load Fy and the time series data of the moment Mz. Specifically, the calculation unit 63 calculates linear regression parameters using the least squares method with the moment Mz as an explanatory variable and the load Fy as a target variable.

[0038] (Judgment Department) The determination unit 64 determines whether the vehicle 1 is turning. Specifically, the determination unit 64 determines whether the vehicle 1 is turning based on the steering angle acquired by the acquisition unit 61. However, alternatively or additionally, at least one of the steering force and the yaw rate may be used for the determination.

[0039] The determination unit 64 determines whether the relationship between the load Fy and moment Mz acquired by the acquisition unit 61 is linear based on the result of the linear regression by the calculation unit 63. Specifically, if the deviation between the plot on the correlation map of the load Fy and moment Mz acquired by the acquisition unit 61 and the regression line calculated by the calculation unit 63 is less than a threshold, the determination unit 64 determines that the relationship between the load Fy and the moment Mz is linear. On the other hand, if the deviation is equal to or greater than a threshold, the determination unit 64 determines that the relationship between the load Fy and the moment Mz is not linear (nonlinear). Note that the deviation is the residual between the regression line and the plot, but the present disclosure is not limited to this. The threshold can be set appropriately taking into account the roughness of the road surface, for example, a value estimated from the detection value of the acceleration sensor and the variance of the load Fy and moment Mz.

[0040] When it is determined that the relationship between the load Fy and the moment Mz is linear, the determination unit 64 determines whether or not to output a warning regarding the slipperiness of the vehicle 1 based on the slope of the regression line calculated by the calculation unit 63. Specifically, when the slope is less than a threshold value, the determination unit 64 determines to output a warning that the vehicle 1 is in a slippery state. Note that the slipperiness is an index evaluated based on how much moment Mz the vehicle 1 generates to generate the load Fy, and is an index evaluated, for example, based on the amount of steering operation that the driver must make to turn the steering wheel in order for the vehicle to turn a certain curve.

[0041] When it is determined that the relationship between the load Fy and the moment Mz is not linear (nonlinear), the determination unit 64 determines the content of the warning regarding the slip of the vehicle 1 based on the change over time of the load Fy acquired by the acquisition unit 61. Specifically, when the load Fy increases over time, the determination unit 64 determines to output a warning that the vehicle 1 is in a near-slip state. On the other hand, when the load Fy decreases over time, the determination unit 64 determines to output a warning that the vehicle 1 is in a slip state. Note that the near-slip state refers to a state in which the wheel has transitioned from a linear region to a nonlinear region and the frictional force between the wheel and the road surface is approaching a limit value. The slip state refers to a state in which the frictional force between the wheel and the road surface has exceeded the limit value and the wheel contact surface and the road surface are beginning to slip.

[0042] (Notification processing unit) The notification processing unit 65 controls the driving of the notification device 43 to warn the driver of the vehicle 1 about the slipperiness of the vehicle 1 or about a slip of the vehicle 1. The notification processing unit 65 issues the notification by outputting a sound or voice, or by displaying an image or text.

[0043] (1-2-3. First Operation Example of Driving Assistance Device) With reference to FIG. 3, a first operation example of the driving assistance device 50 according to the first embodiment will be described along with a flowchart.

[0044] In step S10, the determination unit 64 determines whether the vehicle 1 is turning. Specifically, the determination unit 64 determines whether the vehicle 1 is turning based on the steering angle of the steering wheel 13 acquired by the acquisition unit 61. Note that, instead of the steering angle, the steering force or the yaw rate may be used, or at least one of the steering force and the yaw rate may be used together with the steering angle. If it is determined that the vehicle 1 is turning (step S10: YES), the process proceeds to step S11. On the other hand, if it is determined that the vehicle 1 is not turning (step S10: NO), the process ends. Note that, if it is determined that the vehicle 1 is not turning (traveling straight), the determination unit 64 preferably initializes the correlation map stored in the correlation map storage unit 53. This is because the road surface condition or the wheel condition (tire pressure, etc.) is always different. Therefore, it is preferable that the correlation map be dynamically created and updated every time the vehicle 1 approaches a curve.

[0045] In step S11, the acquisition unit 61 acquires, from among the tire forces applied to each wheel of the vehicle 1, the load Fy applied in the vehicle width direction of the vehicle 1 and the moment Mz around an axis along the height direction of the vehicle 1. Specifically, the acquisition unit 61 acquires the detection results of the load Fy and moment Mz by the load detection device 37 from the load detection device 37. Thereafter, the process proceeds to step S12.

[0046] In step S12, the update unit 62 updates the correlation map showing the relationship between the load Fy and the moment Mz based on the load Fy and the moment Mz acquired in step S11. Specifically, the update unit 62 plots the load Fy and the moment Mz acquired in step S11 on the correlation map stored in the correlation map storage unit 53, and updates (overwrites and saves) the correlation map. As a result, one plot is obtained on the correlation map. Note that the correlation map is preferably initialized before the processing of step S10 is performed. Thereafter, the process returns to step S10.

[0047] The series of processes from step S10 to S12 is repeated from when the vehicle 1 starts turning until it finishes turning. Specifically, the correlation map is updated each time the load Fy and moment Mz are acquired at a predetermined time interval after the vehicle 1 starts turning, resulting in a correlation map such as that shown in FIG. 4 being obtained. Note that the predetermined time interval is, for example, approximately 0.5 to 2 seconds, but can be set appropriately depending on the vehicle speed of the vehicle 1, etc. Also, while FIG. 4 shows six plots P1 to P6, the number of plots is not limited to this and is preferably approximately 1,000 to 2,000. Note that it is preferable that a correlation map be created and updated for each wheel of the vehicle 1. In this case, a "positive determination" in FIGS. 5 and 7, which will be described later, means a positive determination for at least one of the wheels of the vehicle 1.

[0048] (1-2-4. Second Operation Example of Driving Assistance Device) A second operation example of the driving assistance device 50 according to the first embodiment will be described with reference to a flowchart in FIG. 5. The second operation example is preferably performed in parallel with the first operation example. That is, the processing unit 51 of the driving assistance device 50 preferably performs various determinations (described later) in parallel with updating the correlation map.

[0049] In step S20, the determination unit 64 determines whether a predetermined time has elapsed since the vehicle 1 turned. If it is determined that the predetermined time has elapsed (step S20: YES), the process proceeds to step S21. On the other hand, if it is determined that the predetermined time has not elapsed (step S20: NO), the process repeats step S20. The predetermined time can be set appropriately taking into account the number of plots that allows linear regression to be sufficiently performed.

[0050] In step S21, the calculation unit 63 performs linear regression on the time-series data of the load Fy and the time-series data of the moment Mz acquired at predetermined time intervals within a predetermined time after the vehicle 1 turns. As a result, the calculation unit 63 calculates a regression line L that indicates the relationship between the load Fy and the moment Mz as shown in Fig. 4. The process then proceeds to step S22.

[0051] In step S21, the calculation section 63 may appropriately perform one or more of the first to third outlier processing steps described below.

[0052] As a first outlier processing, when the deviation between a plot (e.g., plot P5) on the correlation map of the load Fy and moment Mz acquired within a predetermined time after the vehicle 1 turns and the regression line L is equal to or greater than a threshold, the calculation unit 63 processes the load Fy and moment Mz (e.g., plot P5) as an outlier. The outlier is caused by noise in the load detection device 37, such as a six-component force detector. The predetermined time can be set appropriately depending on the change over time in the steering angle of the steering wheel 13 or the change over time in the load Fy. The deviation is, for example, the residual between the regression line L and the plot (e.g., plot P5), but the present disclosure is not limited to this.

[0053] As a second outlier processing, the calculation unit 63 inputs, as an explanatory variable, the moment Mz acquired in a second time interval after the first time interval into a first regression line L1 calculated in the same manner as the linear regression described above in a first time interval after the vehicle 1 has turned. Then, if the difference between the value of the objective variable corresponding to this explanatory variable and the load Fy acquired simultaneously with the moment Mz in the second time interval is equal to or greater than a threshold, the calculation unit 63 processes the load Fy and the moment Mz as outliers. The outlier is caused by a rough road, such as the presence of unevenness on the road surface.

[0054] As the third outlier processing, the calculation unit 63 calculates a first regression line L1 in a first time interval after the vehicle 1 turns, similar to the second outlier processing. The calculation unit 63 also calculates a second regression line L2 in a second time interval after the first time interval. If the difference between the slope of the first regression line L1 and the slope of the second regression line L2 is equal to or greater than a threshold, or if the difference between the intercept of the first regression line L1 and the intercept of the second regression line L2 is equal to or greater than a threshold, the calculation unit 63 identifies a plot (e.g., plot P5) on the correlation map of the load Fy and the moment Mz that was processed as an outlier in at least one of the first outlier processing and the second outlier processing. The calculation unit 63 then performs linear regression again, excluding the identified plot (e.g., plot P5) from the time-series data of the load Fy and the time-series data of the moment Mz acquired from the time the vehicle 1 turns until the present time.

[0055] Returning to FIG. 5, in step S22, the determination unit 64 determines whether the relationship between the load Fy and the moment Mz is linear based on the linear regression in step S21. Specifically, if the deviation between the plots on the correlation map of the load Fy and the moment Mz acquired at predetermined time intervals after the vehicle 1 turns and the regression line L in step S21 is less than a threshold, the determination unit 64 determines that the relationship between the load Fy and the moment Mz is linear. For example, in the correlation map shown in FIG. 4, the determination unit 64 determines that the plots P1, P2, and P3 are in a linear region. On the other hand, if the deviation between the plots and the regression line L is equal to or greater than a threshold, the determination unit 64 determines that the relationship between the load Fy and the moment Mz is not linear (nonlinear). For example, in the correlation map shown in FIG. 4, the determination unit 64 determines that the plots P4 and P6 are in a nonlinear region. If it is determined that the relationship is linear (step S22: YES), the process proceeds to step S23. On the other hand, if it is determined that the relationship is not linear (step S22: NO), the process proceeds to step S25. Note that if it is determined that the relationship between the load Fy and the moment Mz of any one of the wheels 3 is not linear, the process proceeds to step S25.

[0056] In step S23, the determination unit 64 determines whether or not to output a warning regarding the slipperiness of the vehicle 1 based on the slope of the regression line L in step S21. Specifically, if the slope is less than a threshold, the determination unit 64 determines to output a warning indicating that the vehicle 1 is in a slippery state. If it is determined to output a warning (step S23: YES), the process proceeds to step S24. On the other hand, if it is determined not to output a warning (step S23: NO), the process ends.

[0057] In step S24, the notification processing unit 65 controls the driving of the notification device 43 to warn the driver of the vehicle 1 about the slipperiness of the vehicle 1. As a result, a warning such as "The road surface is slippery" is given to the driver. Then, the process ends.

[0058] On the other hand, if a negative determination is made in step S22, in step S25, the determination unit 64 determines the content of a warning regarding a slip of the vehicle 1 based on the change in the load Fy over time. Specifically, if the load Fy acquired at a predetermined time interval after the relationship between the load Fy and the moment Mz becomes nonlinear increases over time, the determination unit 64 determines to output a warning that the vehicle 1 is in a near-slip state, and the process proceeds to step S26. For example, in the correlation map shown in FIG. 4, plot P4 corresponds to a near-slip state. On the other hand, if the load Fy acquired at a predetermined time interval after the relationship between the load Fy and the moment Mz becomes nonlinear decreases over time, the determination unit 64 determines to output a warning that the vehicle 1 is in a slip state, and the process proceeds to step S27. For example, in the correlation map shown in FIG. 4, plot P6 corresponds to a slip state.

[0059] In step S25, if no peak (maximum value) appears in the relationship between the load Fy and the moment Mz on the correlation map, the determination unit 64 may determine to output a warning that the vehicle 1 is near a slip state. On the other hand, if the peak (maximum value) appears, the determination unit 64 may determine to output a warning that the vehicle 1 is in a slip state.

[0060] In step S26, the notification processing unit 65 controls the driving of the notification device 43 to warn the driver of the vehicle 1 that the vehicle 1 is in a near-slip state. This causes a warning to be given to the driver, such as "You are about to slip." Then, the process ends.

[0061] In step S27, the notification processing unit 65 controls the driving of the notification device 43 to warn the driver of the vehicle 1 that the vehicle 1 is in a slipping state. This causes a warning such as "You are slipping" to be given to the driver. Then, the process ends.

[0062] (effect) As described above, when the vehicle 1 is turning, the processing unit 51 of the driving assistance device 50 according to the first embodiment acquires, from among the forces applied to the wheels of the vehicle 1, the load Fy applied in the vehicle width direction of the vehicle 1 and the moment Mz about an axis along the height direction of the vehicle 1. Then, based on the acquired load Fy and moment Mz, the processing unit 51 of the driving assistance device 50 updates the correlation map indicating the relationship between the load Fy and the moment Mz.

[0063] According to this configuration, by using a correlation map dynamically updated from tire forces acquired by a six-component force detector or the like, rather than the driving force difference and slip angle of the driving wheels, it is possible to issue a warning to the driver in real time about slippage or the like of the vehicle 1 approaching a curve. This allows the driver to control the speed by braking or accelerating, or to apply or return the steering angle by steering, in real time. As a result, it is possible to simultaneously achieve desirable characteristics for the amount of turning and the turning attitude of the vehicle 1.

[0064] <2. Second Embodiment> (2-1. Example of configuration of driving assistance device) A driving assistance device 50 according to a second embodiment of the present disclosure will be described below. The driving assistance device 50 according to this embodiment will be described mainly focusing on the differences from the first embodiment.

[0065] (Map data storage unit) 6, the driving assistance device 50 further includes a map data storage unit 54 in which map data is stored. The map data storage unit 54 is configured by a storage element such as a RAM or a ROM, or a storage medium such as an HDD, a CD, a DVD, an SSD, a USB flash drive, or a storage device, which is communicably connected to the processing unit 51. The map data includes information indicating a reference path, which is a trajectory that serves as a reference when the vehicle 1 travels on a road under driving assistance control or autonomous driving control.

[0066] (Processing section) The processing unit 51 of the driving assistance device 50 further includes a setting unit 66 and a correction unit 67 in addition to the above-described acquisition unit 61, update unit 62, calculation unit 63, determination unit 64, and notification processing unit 65. Each of these units is a function realized by execution of a computer program by one or more processors such as a CPU. However, some or all of these units may be configured using analog circuits.

[0067] (Settings section) The setting unit 66 sets a driving route to the destination using map data stored in the map data storage unit 54, based on an operation in which the driver of the vehicle 1 activates the autonomous driving mode and inputs the destination into a navigation device or the like provided in the vehicle 1. The setting unit 66 also uses the map data stored in the map data storage unit 54 to set a reference path (specifically, position coordinates of the reference path), which is a trajectory that serves as a reference for when the vehicle 1 travels the driving route to the destination. Note that if the destination and driving route are not specified, the setting unit 66 sets the reference path so that the vehicle 1 can travel autonomously at the center position of the driving lane of the vehicle 1.

[0068] The setting unit 66 sets a target steering angle for the vehicle 1 to travel along the set reference path. The setting unit 66 also outputs the set target steering angle to the vehicle control unit 41. As a result, the vehicle control unit 41 controls the traveling of the vehicle 1 by controlling the electric steering device 15 based on the acquired target steering angle. Note that the setting unit 66 may also set a target acceleration / deceleration for the vehicle 1 to travel along the reference path, in addition to the target steering angle. In this case, the setting unit 66 outputs the set target acceleration / deceleration to the vehicle control unit 41. As a result, the vehicle control unit 41 controls the traveling of the vehicle 1 based on the acquired target acceleration / deceleration.

[0069] (correction section) The correction unit 67 calculates a corrected steering angle by correcting the target steering angle set by the setting unit 66 based on the correlation map stored in the correlation map storage unit 53. The correction unit 67 outputs the calculated corrected steering angle to the vehicle control unit 41. As a result, the vehicle control unit 41 controls the electric steering device 15 based on the obtained corrected steering angle, thereby controlling the traveling of the vehicle 1. Additionally, the correction unit 67 may correct the target acceleration / deceleration in addition to the target steering angle.

[0070] The driving assistance device 50 according to this embodiment updates the correlation map, performs linear regression, and handles outliers in the same manner as in the first embodiment.

[0071] (2-2. Example of operation of driving assistance device) An example of the operation of the driving assistance device 50 according to the second embodiment will be described with reference to a flowchart in FIG.

[0072] In this operation example, a situation will be described in which the vehicle control unit 41 is executing driving assistance control or automatic driving control of the vehicle 1, the vehicle 1 is traveling along a reference path set in advance by the setting unit 66, and the vehicle 1 is approaching a curve. However, the present disclosure is not limited to this.

[0073] In step S30, the acquisition unit 61 acquires the correlation map stored in the correlation map storage unit 53. After that, the process proceeds to step S31. Note that the correlation map acquired in this step is dynamically updated while the vehicle 1 is turning, in parallel with this operation example, as in the first embodiment.

[0074] In step S31, the determination unit 64 determines whether the relationship between the load Fy and the moment Mz (preferably, the latest load Fy and moment Mz) is nonlinear, based on the correlation map acquired in step S30. For details, the description in the first embodiment is cited. If it is determined that the relationship is nonlinear (step S31: YES), the process proceeds to step S32. On the other hand, if it is determined that the relationship is not nonlinear (step S31: NO), the process ends. That is, the traveling of the vehicle 1 is controlled based on one or more of the target steering angle and the target acceleration / deceleration that are preset by the setting unit 66.

[0075] In step S32, the acquisition unit 61 acquires the reference path that has been set in advance by the setting unit 66. After that, the process proceeds to step S33.

[0076] In step S33, the correction unit 67 corrects the target steering angle set by the setting unit 66 based on the plot on the correlation map of the load Fy and moment Mz (preferably the latest load Fy and moment Mz) so that the vehicle 1 can travel along the preset reference path acquired in step S32. Specifically, the correction unit 67 corrects the target steering angle set by the setting unit 66 so that the current traveling trajectory of the vehicle 1 matches the preset reference path. More specifically, the correction unit 67 calculates a corrected steering angle by adding a correction amount according to the degree of deviation between the plot on the correlation map of the load Fy and moment Mz (preferably the latest load Fy and moment Mz) and the regression line L to the target steering angle, and outputs the corrected steering angle to the vehicle control unit 41. In this way, the behavior of the vehicle 1 is controlled so that the vehicle 1 can travel along the preset reference path even if the vehicle 1 is in a near-slip state or a slip state. Thereafter, the process ends.

[0077] In step S33, the target acceleration / deceleration may be corrected in addition to or instead of the target steering angle. In this case, the correction unit 67 corrects the target acceleration / deceleration set by the setting unit 66 based on the plot on the correlation map of the load Fy and the moment Mz (preferably the latest load Fy and moment Mz) so that the vehicle 1 can travel along the preset reference path acquired in step S32. Specifically, the correction unit 67 corrects the target acceleration / deceleration set by the setting unit 66 so that the current traveling trajectory of the vehicle 1 matches the preset reference path. More specifically, the correction unit 67 calculates the corrected acceleration / deceleration by subtracting a correction amount (positive value) corresponding to the degree of deviation between the plot on the correlation map of the load Fy and the moment Mz (preferably the latest load Fy and moment Mz) and the regression line L from the target acceleration / deceleration, and outputs the corrected acceleration / deceleration to the vehicle control unit 41.

[0078] (effect) As described above, when the vehicle 1 is turning, the processing unit 51 of the driving assistance device 50 according to the second embodiment acquires the load Fy applied in the width direction of the vehicle 1 and the moment Mz about an axis along the height direction of the vehicle 1, among the forces applied to the wheels of the vehicle 1. Then, the driving assistance device 50 updates a correlation map indicating the relationship between the load Fy and the moment Mz based on the acquired load Fy and moment Mz. In addition, the processing unit 51 of the driving assistance device 50 acquires a preset reference path of the vehicle 1. Then, based on the plot of the load Fy and the moment Mz on the correlation map, the processing unit 51 of the driving assistance device 50 controls the behavior of the vehicle 1 so that the vehicle 1 can travel along the acquired reference path.

[0079] According to this configuration, the behavior of the vehicle 1 approaching a curve can be automatically controlled by using a correlation map that is dynamically updated based on tire forces acquired by a six-component force detector or the like, rather than the driving force difference and slip angle of the driving wheels. As a result, the amount of turning and the turning attitude of the vehicle 1 can be simultaneously made to have desirable characteristics through automatic control.

[0080] Although preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art to which the present disclosure pertains can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. For example, the functions included in each component or step can be rearranged so as not to be logically inconsistent, and multiple components or steps can be combined or divided into one.

[0081] <First Modification> As a modified example, instead of the tire force detected by a six-component force detector or the like, at least one value of the steering force transmitted to the left and right steered wheels from a steering gear box (not shown) provided in the vehicle 1 and the steering force applied to the steering wheel 13 may be used as an alternative value for the moment Mz. Note that the load Fy is calculated using the distance from the center of gravity of the vehicle 1 to the wheel, as well as the acceleration and yaw rate of the vehicle 1.

[0082] <Second Modification> As a modification, if the electric steering device 15 is a steer-by-wire type, the following process can be executed instead of steps S23 to S27 shown in FIG. 5 or step S33 shown in FIG. 7. For example, if the load Fy and moment Mz of one of the left and right front wheels (steered wheels) are in a nonlinear region of the correlation map and the load Fy and moment Mz of the other wheel are in a linear region of the correlation map, the load Fy of the wheel in the nonlinear region is smaller than the load Fy of the wheel in the linear region. Therefore, to compensate for the decrease in load Fy due to nonlinearity, it is preferable to impart to each wheel a toe angle greater than the toe angle corresponding to the steering angle input by the driver or a toe angle greater than the toe angle corresponding to a steering angle preset based on the reference path. Therefore, the processing unit 51 of the driving assistance device 50 may calculate a corrected toe angle by imparting an appropriate correction amount to the toe angle of each wheel according to the difference between the load Fy of the wheel in the nonlinear region and the load Fy of the wheel in the linear region, and output the corrected toe angle to the vehicle control unit 41. This allows the vehicle control unit 41 to control the driving of the electric steering device 15 so as to control the toe angle of each wheel based on the corrected toe angle.

[0083] <Third Modification> As a modified example, if the vehicle 1 is capable of performing torque vectoring control, which assists turning by generating a torque difference between the left and right wheels while the vehicle 1 is turning, the following processing can be performed instead of the processing of steps S23 to S27 shown in FIG. 3 or instead of the processing of step S33 shown in FIG. 7. That is, when the load Fy of either the left front wheel or the right front wheel is in the nonlinear region, the processing unit 51 of the driving support device 50 performs a correction according to the deficiency of the load Fy due to the nonlinearity when controlling the drive of the left front wheel drive motor (not shown) and the right front wheel drive motor (not shown). Specifically, the processing unit 51 of the driving support device 50 calculates an estimated value of the load Fy for the wheel of the left front wheel or the right front wheel whose load Fy is in the nonlinear region by linear extrapolating the load Fy in the linear region. Furthermore, the processing unit 51 calculates a current value of the load Fy for the wheel in the nonlinear region. Then, the processing unit 51 calculates the deficiency of the load Fy based on the difference between the estimated value and the current value of the load Fy. Then, the processing unit 51 calculates a target moment based on the calculated shortage of the load Fy and the distance from the center of gravity of the vehicle 1 to each wheel, and outputs the calculated target moment to the vehicle control unit 41. As a result, the vehicle control unit 41 controls the driving of the left front wheel drive motor and the right front wheel drive motor so as to generate a longitudinal force equivalent to the calculated target moment by the torque difference.

[0084] The technology of the present disclosure can also be realized as a vehicle 1 equipped with the driving assistance device 50 described in the above-mentioned embodiment, a driving assistance method executed by the driving assistance device 50, a computer program that causes a computer to function as the above-mentioned driving assistance device 50, and a non-transitory tangible recording medium on which the computer program is recorded. [Explanation of symbols]

[0085] 1: vehicle, 50: driving assistance device, 51: processing unit, 52: storage unit, 53: correlation map storage unit, 54: map data storage unit, 61: acquisition unit, 62: update unit, 63: calculation unit, 64: determination unit, 65: notification processing unit, 66: setting unit, 67: correction unit

Claims

1. A driving assistance device that assists driving of a vehicle, one or more processors; and one or more memories communicatively coupled to the one or more processors; the one or more processors: When the vehicle is turning, Among the forces applied to the wheels of the vehicle, a load applied in a vehicle width direction of the vehicle and a moment around an axis along a height direction of the vehicle are obtained; updating a correlation map indicating a relationship between the load and the moment based on the acquired load and moment; Driving assistance device.

2. the one or more processors: determining whether the relationship between the load and the moment is linear based on a linear regression of the time series data of the load and the time series data of the moment obtained within a predetermined time after the vehicle has turned; The driving assistance device according to claim 1 .

3. the one or more processors: If the relationship between the load and the moment is determined to be linear, determining whether to output a warning regarding the slipperiness of the vehicle based on a slope of the regression line obtained by the linear regression; The driving assistance device according to claim 2 .

4. the one or more processors: If it is determined that the relationship between the load and the moment is not linear, determining the content of a warning regarding slippage of the vehicle based on the change in the load over time; The driving assistance device according to claim 2 .

5. the one or more processors: Obtain a preset reference path for the vehicle; controlling a behavior of the vehicle based on a plot of the acquired loads and moments on the correlation map so that the vehicle can travel along the acquired reference path; The driving assistance device according to claim 1 .

Images