Driving assist system

Abstract

To provide a technology for reducing a feeling of discomfort which a driver of a vehicle perceives against driving assist control for a step of a road surface.SOLUTION: In a driving assist system that assists in driving of a vehicle, one or more processors acquire a tire force which is input to a wheel of the vehicle and caused by a step of a road surface, and calculate an assist quantity for steering of the wheel on the basis of the acquired tire force.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In vehicles, there is a demand for alleviating the discomfort that drivers feel when driving assistance controls are performed.

[0003] For example, Patent Document 1 discloses a vehicle steering device that steers the wheels in response to the operation of an operating member for steering the vehicle, and that includes a rutted road determination means that determines whether the vehicle is traveling on a rutted road, and a steering promotion control means that, when the rutted road determination means determines that the vehicle is traveling on a rutted road, promotes the steering of the wheels in response to the operation of the operating member more than when the rutted road determination means determines that the vehicle is not traveling on a rutted road. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-302053 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology disclosed in Patent Document 1, when a vehicle is traveling on a rutted road, the steering of the wheels is promoted compared to when the vehicle is not traveling on a rutted road. However, the amount of steering promotion of the wheels is switched uniformly depending on whether the vehicle is traveling on a rutted road or not. Therefore, the driver of the vehicle may feel uncomfortable with the driving assistance control depending on the nature of the bumps in the road surface.

[0006] In view of the above circumstances, an object of the present disclosure is to provide a technology that reduces the sense of discomfort that a vehicle driver feels when driving assistance control is performed for road bumps. [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, wherein the one or more processors acquire tire forces input to the wheels of the vehicle due to road surface irregularities, and calculate an amount of assistance related to wheel steering based on the acquired tire forces. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, it is possible to reduce the discomfort that a driver of a vehicle feels when driving assistance control is performed for a bump in the road surface. [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] 2 is a schematic diagram showing a configuration example of an electric steering system provided in the vehicle shown in FIG. 1. FIG. [Figure 3] 1 is a block diagram illustrating a configuration example of a driving assistance device according to a first embodiment of the present disclosure. [Figure 4] 4 is a flowchart illustrating an example of the operation of the driving assistance device according to the first embodiment of the present disclosure. [Figure 5] 5 is a diagram illustrating the state of the vehicle in the operation example shown in FIG. 4. FIG. [Figure 6] 6 is a diagram illustrating an example of a load applied to the right front wheel shown in FIG. 5. FIG. [Figure 7] 6 is a diagram illustrating an example of a load applied to the right front wheel shown in FIG. 5. FIG. [Figure 8] 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 9] 10 is a flowchart illustrating an example of the operation of a driving assistance device according to a second embodiment of the present disclosure. [Figure 10]FIG. 10 is a diagram illustrating the state of a vehicle in a modified example 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 60 according to an embodiment of the present disclosure will be described with reference to FIG.

[0012] The vehicle 1 is configured as a front-wheel drive four-wheel vehicle that transmits drive torque output from a drive power source 13 that generates drive torque for the vehicle 1 to left and right front wheels 3LF, 3RF. The vehicle 1 may be a vehicle equipped with an internal combustion engine such as a gasoline engine or a diesel engine as the drive power source 13. The vehicle 1 may also be an electric vehicle equipped with a drive motor as the drive power source 13. The vehicle 1 may also be a hybrid electric vehicle equipped with both an internal combustion engine and a drive motor as the drive power source 13.

[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 13, brake devices 7LF, 7RF, 7LR, 7RR (hereinafter collectively referred to as "brake devices 7" unless a distinction is required), and an electric steering system 30 as equipment used to control the operation of the vehicle 1.

[0015] The driving force source 13 outputs a driving torque that is transmitted to the front-wheel drive shaft 5F via a front-wheel differential mechanism (not shown). The driving of the driving force source 13 is controlled by a vehicle control device 11 that includes one or more electronic control units (ECUs). During manual driving, the vehicle control device 11 controls the driving of the driving force source 13 based on the accelerator opening operated by the driver. Furthermore, during execution of driving assistance control or automatic driving control, the vehicle control device 11 controls the driving of the driving force source 13 based on a target driving torque for automatic driving.

[0016] The brake devices 7LF, 7RF, 7LR, and 7RR apply braking force to the front, rear, left, and right wheels 3LF, 3RF, 3LR, and 3RR, respectively (hereinafter, collectively referred to as "wheels 3" unless a distinction is required). The brake devices 7 are configured, for example, as hydraulic friction brake devices, and generate a predetermined braking force by adjusting the hydraulic pressure supplied to each brake device 7. If the vehicle 1 is an electric vehicle or a hybrid electric vehicle, the brake devices 7 are used in conjunction with regenerative braking using a drive motor. The hydraulic pressure supplied to the brake devices 7 is controlled by a hydraulic pressure control unit (not shown).

[0017] The vehicle 1 is equipped with tire force sensors 9LF, 9RF, 9LR, and 9RR (hereinafter collectively referred to as "tire force sensors 9") corresponding to the respective wheels 3LF, 3RF, 3LR, and 3RR. The tire force sensors 9LF and 9RF are provided at the connection between the front drive shaft 5F and the front wheels 3LF and 3RF, respectively. The tire force sensors 9LR and 9RR are provided at the connection between the rear wheel shaft 5R and the rear wheels 3LR and 3RR, respectively. The tire force sensors 9 are load sensors that detect the load applied to each wheel 3. For example, the tire force sensor 9 may be a six-component force detector that detects loads (Fx, Fy, Fz) applied in the longitudinal 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 tire force sensor 9 outputs information indicating the detection result to the driving assistance device 60.

[0018] The vehicle 1 is equipped with a surrounding environment sensor 15. The surrounding environment sensor 15 is one or more sensors that detect information about the surrounding environment of the vehicle 1. The surrounding environment sensor 15 captures an image of the surroundings of the vehicle 1 as the surrounding environment of the vehicle 1, and outputs the image data to the driving assistance device 60. The surrounding environment sensor 15 is equipped with, for example, a pair of left and right stereo cameras 15L, 15R that capture images of the area ahead of the vehicle 1. Note that the surrounding environment sensor 15 may include, for example, one or more sensors selected from a LiDAR, a radar sensor, and an ultrasonic sensor.

[0019] The vehicle 1 is equipped with a vehicle condition sensor 17. The vehicle condition sensor 17 is one or more sensors that detect the condition of the vehicle 1. The vehicle condition sensor 17 includes an acceleration sensor that detects acceleration acting in the longitudinal direction, width direction, and height direction of the vehicle 1. The vehicle condition sensor 17 may also include a vehicle speed sensor that detects the speed of the vehicle 1. The vehicle condition sensor 17 outputs information indicating the detection result to the driving assistance device 60.

[0020] (1-2. Electric steering system) An example of the overall configuration of the electric steering system 30 according to this embodiment will be described with reference to FIG.

[0021] The electric steering system 30 includes a motor and a gear mechanism, which will be described later, and is controlled by the vehicle control device 11 to adjust the steering angle of the left and right front wheels 3LF, 3RF. During manual driving, the vehicle control device 11 controls the steering angle of the front wheels 3LF, 3RF based on the steering angle of the steering wheel 31 operated by the driver. Furthermore, during execution of driving assistance control or automatic driving control, the vehicle control device 11 controls the steering angle of the front wheels 3LF, 3RF based on a target steering angle set in accordance with a target driving trajectory.

[0022] The electric steering system 30 includes a steering device 33 and a wheel turning device 40. The steering device 33 receives steering input from a steering wheel 31 operated by the driver. The wheel turning device 40 steers the front wheels (steerable wheels) 3LF, 3RF. Note that the electric steering system 30 shown in FIG. 2 is a steer-by-wire type steering system in which the steering device 33 and the wheel turning device 40 are mechanically separated (linkless) and controlled in conjunction with each other by the vehicle control device 11. However, the electric steering system 30 in the present disclosure is not limited to the steer-by-wire type.

[0023] The steering device 33 includes a steering wheel 31, a steering shaft 32 connected to the steering wheel 31, and a reaction motor 34 coaxially mounted at an axially intermediate position of the steering shaft 32. The reaction motor 34 applies a reaction force (rotational resistance) to the driver operating the steering wheel 31 via the steering shaft 32 and the steering wheel 31. The drive of the reaction motor 34 is controlled by the vehicle control device 11. The output torque of the reaction motor 34 is transmitted to the steering wheel 31 via the steering shaft 32.

[0024] The wheel steering device 40 includes a rack shaft 51 arranged to extend in the vehicle width direction of the vehicle 1, and knuckle arms 53L, 53R connected to both ends of the rack shaft 51 via tie rods 52L, 52R, respectively. The left and right front wheels 3LF, 3RF are connected to the knuckle arms 53L, 53R, respectively.

[0025] Rack shaft 51 is supported by housing 49 so as to be movable in the width direction of vehicle 1. Rack gear 54 is provided on rack shaft 51. Rack gear 54 is engaged with pinion gear 55. Pinion gear 55 is connected to pinion shaft 56. Steering motor 57 is coaxially incorporated into pinion shaft 56 at an intermediate position in the axial direction.

[0026] Steering motor 57 is an electric motor that steers the left and right front wheels 3LF, 3RF. The driving of steering motor 57 is controlled by vehicle control device 11. The output torque of steering motor 57 is transmitted to rack shaft 51 via pinion shaft 56, pinion gear 55, and rack gear 54. As a result, the left and right front wheels 3LF, 3RF are steered.

[0027] A clutch mechanism 37 is provided between steering shaft 32 and pinion shaft 56. Clutch mechanism 37 is engaged by vehicle control device 11 in the event of a failure of reaction motor 34 or steering motor 57, etc., to directly connect steering shaft 32 and pinion shaft 56 and enable the driver to steer front wheels 3LF, 3RF.

[0028] Electric steering system 30 includes steering angle sensor 35, steering torque sensor 36, and turning angle sensor 58. Steering angle sensor 35 detects the steering angle (rotation angle) of steering wheel 31. Steering torque sensor 36 detects steering torque, which is the torque input to steering wheel 31 by the driver. Note that steering torque corresponds to the reaction torque that the driver receives from steering wheel 31. Steering angle sensor 58 detects the steering angles (wheel angles) of left and right front wheels 3LF, 3RF. Steering angle sensor 35, steering torque sensor 36, and turning angle sensor 58 output information indicating the detection results to vehicle control device 11.

[0029] (1-3. Driving assistance devices) A driving assistance device 60 according to this embodiment will be described with reference to FIG.

[0030] (1-3-1. Configuration example) The driving assistance device 60 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 60. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 62, described below, or may be recorded on a recording medium built into the driving assistance device 60 or any recording medium that can be externally attached to the driving assistance device 60.

[0031] 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.

[0032] The tire force sensor 9, the vehicle control device 11, the surrounding environment sensor 15, and the vehicle state sensor 17 are connected to the driving assistance device 60 via a dedicated line or communication means such as a CAN (Controller Area Network) or a LIN (Local Inter Net). Note that the driving assistance device 60 is not limited to an electronic control device mounted on the vehicle 1, but may be a server or the like that can communicate with the vehicle 1 via any wireless communication.

[0033] The driving assistance device 60 includes a processing unit 61 and a storage unit 62 .

[0034] (Processing section) The processing unit 61 includes one or more processors such as a CPU and various peripheral components. Part or all of the processing unit 61 may be configured with updatable components such as firmware, or may be a program module or the like that is executed by instructions from the CPU or the like.

[0035] (Storage part) The storage unit 62 is configured with one or more storage elements such as RAM or ROM connected to the processing unit 61 so as to be able to communicate with the processing unit 61. However, there is no particular limitation on the type and number of the storage units 62. The storage unit 62 stores information such as computer programs executed by the processing unit 61, various parameters used in arithmetic processing, detection data, and arithmetic results.

[0036] (1-3-2. Functional configuration of the processing unit) The functional configuration of the processing unit 61 of the driving assistance device 60 will be described. The processing unit 61 includes an acquisition unit 71, a determination unit 72, a calculation unit 73, and a control unit 74. 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 71, determination unit 72, calculation unit 73, and control unit 74 may be configured using analog circuits.

[0037] (Acquisition Department) The acquisition unit 71 acquires tire forces input to the wheels 3 of the vehicle 1 due to bumps in the road surface on which the vehicle 1 is traveling. Specifically, the acquisition unit 71 acquires tire forces input to each of the wheels 3LF, 3RF, 3LR, and 3RR due to bumps in the road surface from the tire force sensors 9LF, 9RF, 9LR, and 9RR provided corresponding to each of the wheels 3LF, 3RF, 3LR, and 3RR. The tire forces acquired by the acquisition unit 71 are stored in the memory unit 62.

[0038] The step includes a step caused by a rut, an unevenness, a curb, etc. formed on the road surface. However, the step in the present disclosure is not particularly limited as long as it is a step present on the road surface.

[0039] The acquisition unit 71 acquires the traveling direction of the vehicle 1. Specifically, the acquisition unit 71 acquires the steering angle (rotation angle) of the steering wheel 31 of the vehicle 1 from the steering angle sensor 35. The steering angle acquired by the acquisition unit 71 is stored in the memory unit 62.

[0040] The acquisition unit 71 may acquire the cant of the road surface on which the vehicle 1 is traveling. The cant means the road gradient in the width direction of the road surface. Specifically, the acquisition unit 71 acquires the cant of the road surface from an acceleration sensor included in the vehicle state sensor 17. Alternatively, the acquisition unit 71 may acquire the cant of the road surface by image processing image data from the stereo cameras 15L, 15R, etc. included in the surrounding environment sensor 15. The cant acquired by the acquisition unit 71 is stored in the storage unit 62.

[0041] The acquisition unit 71 may acquire the speed of the vehicle 1 from a vehicle speed sensor included in the vehicle state sensor 17. The vehicle speed acquired by the acquisition unit 71 is stored in the storage unit 62.

[0042] (Judgment Department) The determination unit 72 determines whether or not there is a step on the road surface on which the vehicle 1 is traveling, based on the tire forces acquired by the acquisition unit 71. Specifically, the determination unit 72 determines whether or not the wheels 3 of the vehicle 1 are approaching a step, based on the increase rate of the load Fy applied in the vehicle width direction of the vehicle 1, among the tire forces acquired by the acquisition unit 71. Note that the determination of whether or not there is a step may be performed by performing image processing on image data from the stereo cameras 15L, 15R, etc. included in the surrounding environment sensor 15, instead of the tire forces.

[0043] The determination unit 72 determines whether or not to provide assistance with steering of the wheels of the vehicle 1 based on the load Fy applied in the vehicle width direction of the vehicle 1, out of the tire forces acquired by the acquisition unit 71.

[0044] The determination unit 72 determines the degree (magnitude) of the difference in level of the road surface based on the moment Mx about the axis in the longitudinal direction of the vehicle 1, among the tire forces acquired by the acquisition unit 71. Furthermore, the determination unit 72 determines whether or not to provide assistance with steering of the vehicle 1, based on the determined degree of the road surface.

[0045] (Calculation section) The calculation unit 73 calculates the amount of assistance related to the steering of the wheels 3 of the vehicle 1 based on the tire forces acquired by the acquisition unit 71. Specifically, the calculation unit 73 calculates the amount of assistance related to the steering of the wheels 3 of the vehicle 1 based on the moment Mz around an axis along the height direction of the vehicle 1, among the tire forces acquired by the acquisition unit 71. In this way, the calculation unit 73 calculates the amount of assistance that reflects the nature of the bump in the road surface. Details will be described later.

[0046] The calculation unit 73 may correct the tire forces acquired by the acquisition unit 71 based on the cant of the road surface acquired by the acquisition unit 71. Specifically, the calculation unit 73 may correct, from among the tire forces acquired by the acquisition unit 71, a moment Mx about an axis along the front-rear direction of the vehicle 1 based on the cant of the road surface acquired by the acquisition unit 71. Furthermore, the calculation unit 73 may correct, from among the tire forces acquired by the acquisition unit 71, a load Fy applied in the vehicle width direction of the vehicle 1 based on the cant of the road surface acquired by the acquisition unit 71. Details will be described later.

[0047] (Control unit) Control unit 74 controls the drive of electric steering system 30 based on the assist amount calculated by calculation unit 73. Specifically, control unit 74 controls the drive of steering motor 57 based on the assist amount calculated by calculation unit 73, thereby controlling the drive of electric steering system 30.

[0048] (1-3-3. Example of operation of driving assistance device) An example of the operation of the driving support device 60 according to this embodiment will be described with reference to a flowchart in FIG.

[0049] In this operation example, as shown in Fig. 5, a case will be described in which the right front wheel 3RF of the vehicle 1 gradually approaches the edge of a step caused by a rut. At this time, the steering wheel 31 of the vehicle 1 is assumed to be in a right-hand turn state. Also, as shown in Fig. 6, a force F directed from the outside to the inside in the vehicle width direction of the vehicle 1 is assumed to be applied to the side of the right front wheel 3RF. However, the present disclosure is not limited to this operation example, and can be similarly applied to, for example, a case in which the left front wheel 3LF of the vehicle 1 gradually approaches the edge of a step caused by a rut.

[0050] In step S10, the acquisition unit 71 acquires the traveling direction of the vehicle 1. Specifically, the acquisition unit 71 acquires the steering angle (rotation angle) of the steering wheel 31 of the vehicle 1 from the steering angle sensor 35 via the vehicle control device 11. Then, the acquisition unit 71 acquires (recognizes) the traveling direction of the vehicle 1 based on the acquired steering angle. Thereafter, the process proceeds to step S11. The steering angle is acquired at predetermined time intervals and stored in the storage unit 62 as time-series data of the steering angle.

[0051] Here, if the vehicle speed of the vehicle 1 is equal to or less than a predetermined value, the processes from step S11 onwards may be executed. Specifically, in the above-mentioned step S10, the acquisition unit 71 acquires the vehicle speed of the vehicle 1 from the vehicle state sensor 17. Then, the determination unit 72 determines whether the vehicle speed acquired by the acquisition unit 71 is equal to or less than a predetermined value. If the vehicle speed is equal to or less than the predetermined value, the process proceeds to step S11. On the other hand, if the vehicle speed is not equal to or less than the predetermined value, the process ends. Note that the predetermined value can be set appropriately taking into consideration an appropriate and safe speed for the wheel 3 to overcome a step.

[0052] In step S11, the acquisition unit 71 acquires the tire forces input to the wheels 3 of the vehicle 1. Specifically, the acquisition unit 71 acquires the loads (Fx, Fy, Fz) and moments (Mx, My, Mz) applied to each wheel 3LF, 3RF, 3LR, 3RR from the tire force sensors 9LF, 9RF, 9LR, 9RR corresponding to each wheel 3LF, 3RF, 3LR, 3RR. Thereafter, the process proceeds to step S12. The tire forces are acquired at predetermined time intervals and stored in the memory unit 62 as time-series data of the tire forces.

[0053] Here, if the road surface on which the vehicle 1 is traveling has a cant (road gradient in the width direction of the road surface), a larger slip angle is imparted to the front wheels 3LF, 3RF than to the rear wheels 3LR, 3RR so as to resist the inclination caused by the road gradient. Therefore, if the vehicle condition sensor 17 detects a cant of the road surface, an offset correction may be performed to remove the influence of the lateral force component generated by the road gradient from the moment Mx and the load Fy among the tire forces acquired in step S11. For example, if the cant is such that the ground contact position of the rear wheel 3LR is lower than the ground contact position of the rear wheel 3RR, the acquisition unit 71 acquires the cant of the road surface (e.g., the inclination angle of the road gradient detected by an acceleration sensor) from the vehicle condition sensor 17. Then, the calculation unit 73 calculates the corrected moment Mx' using the following equation (1). The calculation unit 73 also corrects the corrected load Fy' using the following equation (2). Here, r is the effective radius of the wheel, θ is the inclination angle of the road gradient, and Wr is the load of the rear wheel axle. In this way, the calculation unit 73 corrects the tire forces (moment Mx and load Fy) based on the cant of the road surface acquired by the acquisition unit 71. As a result, in the processes from step S12 onwards, the corrected moment Mx' and load Fy' are used as the moment Mx and load Fy.

[0054]

number

[0055]

number

[0056] In step S12, the determination unit 72 determines whether or not the wheel 3 of the vehicle 1 is approaching (in contact with) a step, based on the tire force acquired in step S11. Specifically, the determination unit 72 determines whether or not the increase rate of the load Fy applied in the vehicle width direction of the vehicle 1, among the tire forces acquired in step S11, is equal to or greater than a first threshold. If the increase rate of the load Fy is equal to or greater than the first threshold, the determination unit 72 determines that the wheel 3 is approaching a step (step S12: YES), and the process proceeds to step S13. On the other hand, if the increase rate of the load Fy is less than the first threshold, the determination unit 72 determines that the wheel 3 is not approaching a step (step S12: NO), and the process returns to step S10. The load Fy used in the determination in this step is the load detected for each of the wheels 3LF, 3RF, 3LR, and 3RR. Therefore, if there is at least one wheel (for example, the right front wheel 3RF) among the wheels 3 whose rate of increase in the load Fy is equal to or greater than the first threshold value, an affirmative determination is made in step S12.

[0057] The rate of increase in the load Fy means the amount of increase in the load Fy relative to the amount of change in the steering angle in a predetermined time interval. The first threshold is a threshold for excluding from the scope of driving assistance control a case where the wheel 3 suddenly comes into contact with a step that cannot be traversed or a case where the wheel 3 suddenly comes into contact with a step that is unsafe for the wheel 3 to traverse, and can be set as appropriate.

[0058] In step S13, the determination unit 72 determines whether or not to provide assistance with steering of the wheels 3 of the vehicle 1. Specifically, the determination unit 72 determines whether or not the load Fy applied in the vehicle width direction of the vehicle 1, among the tire forces acquired in step S11, is less than a second threshold value. If the load Fy is less than the second threshold value (positive determination), the determination unit 72 determines whether or not a moment Mx about an axis in the longitudinal direction of the vehicle 1 is less than a third threshold value. If the moment Mx is less than the third threshold value (positive determination), the determination unit 72 determines that assistance should be provided (step S13: YES), and the process proceeds to step S14. Note that if the load Fy is equal to or greater than the second threshold value or if the moment Mx is equal to or greater than the third threshold value, the determination unit 72 determines that assistance should not be provided (step S13: NO), and the process ends. The load Fy and moment Mx used in the determination in step S13 are the load and moment detected for each of the wheels 3LF, 3RF, 3LR, and 3RR. Therefore, if there is at least one wheel (for example, the right front wheel 3RF) among all the wheels 3 whose load Fy is less than the second threshold value and whose moment Mx is less than the third threshold value, a positive determination is made in step S13.

[0059] The second threshold is a threshold for excluding the wheel 3 from the driving assistance control when the wheel 3 cannot overcome a step or when it is unsafe for the wheel 3 to overcome a step, and can be set as appropriate. Therefore, when the load Fy corresponding to the lateral force of the wheel 3 is equal to or greater than the second threshold, the wheel 3 is excluded from the driving assistance control from the standpoint of safety, and no assistance is provided for steering the wheel 3, which will be described later.

[0060] The third threshold is a threshold for determining the level (size) of the step using the moment Mx, and can be set as appropriate. Here, the reason why the level of the step can be determined using the moment Mx will be explained. As shown in FIG. 7, when the level of the step is small (for example, when the rut is shallow), the force F applied to the right front wheel 3RF generates a load component Fz in the height direction in addition to the load component Fy in the width direction of the vehicle 1. As a result, the moment Mx about the axis in the longitudinal direction of the vehicle 1 is weakened. Therefore, by focusing on the moment Mx, the level (size) of the step can be determined. That is, when the moment Mx is less than the third threshold, it is possible to determine that the step is small. On the other hand, when the moment Mx is equal to or greater than the third threshold, it is possible to determine that the step is large. Note that when the step is large, it is not subject to driving assistance control from the viewpoint of safety, and assistance regarding steering of the wheel 3, which will be described later, is not performed.

[0061] In step S14, the calculation unit 73 calculates the amount of assistance related to the steering of the wheels 3 based on the tire force acquired in step S11. Specifically, the calculation unit 73 calculates the assist torque T for assisting the steering torque, which is the torque input to the steering wheel 31 by the driver, using the following equation (3). In the following equation (3), Mzi means the moment Mz about the axis in the height direction of the vehicle 1 applied to the wheel approaching a step caused by a rut. For example, when the front wheels 3LF, 3RF are approaching a step caused by a rut as shown in FIG. 5, it means the moment Mz about the axis in the height direction of the vehicle 1 applied to the front wheel 3i (i is an index representing LF, RF). SR is a steering gear ratio determined according to the electric steering system 30, and is stored in advance in the storage unit 62. Σ is the sum for the wheels approaching a step caused by a rut. For example, when front wheels 3LF and 3RF are approaching a step caused by a rut as shown in FIG. 5, Σ means the sum for front wheel 3i (i is an index representing LF and RF).

[0062]

number

[0063] In this way, the assist torque T is calculated using the tire force (specifically, the moment Mz) that the wheel 3 receives from the step, and therefore is an amount that reflects the characteristics of each step. After that, the process proceeds to step S15.

[0064] In step S15, control unit 74 controls the driving of electric steering system 30 of vehicle 1 based on the assist amount calculated in step S14. Specifically, control unit 74 generates a control signal for causing steering motor 57 to output an output torque corresponding to the steering torque to which assist torque T calculated by the above equation (3) has been applied. Control unit 74 then outputs the generated control signal to steering motor 57 via vehicle control device 11. As a result, steering of wheels 3 in accordance with the step is performed. Thereafter, the process ends.

[0065] (effect) As described above, the processing unit 61 of the driving assistance device 60 according to the first embodiment acquires the tire force input to the wheels 3 of the vehicle 1 due to a step on the road surface. Then, the processing unit 61 calculates the amount of assistance related to steering of the wheels 3 based on the acquired tire force.

[0066] With this configuration, the amount of assistance related to steering of the wheels 3 reflects the characteristics of each step. Therefore, compared to when the amount of assistance is switched uniformly when a step is present on the road surface, it is possible to reduce the sense of discomfort felt by the driver in response to driving assistance control for road steps. In particular, compared to when a stroke sensor provided in a suspension device or a strain sensor attached to a tie rod is used, more precise driving assistance control is possible because the tire force input to the wheels 3 is directly used.

[0067] <2. Second Embodiment> A driving assistance device 60 according to a second embodiment of the present disclosure will be described below. The driving assistance device 60 according to this embodiment will be described mainly focusing on the differences from the first embodiment.

[0068] (2-1. Example of configuration of driving assistance device) 8, the driving assistance device 60 further includes a preference information storage unit 63. The preference information storage unit 63 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 61. The preference information storage unit 63 stores a preference map, which will be described later.

[0069] The preference map includes preference information related to the steering operation of the driver of the vehicle 1. Specifically, the preference map includes information indicating a preference coefficient A determined in advance according to a preference mode M and a moment Mx, and has the moment Mx and the preference mode M as inputs and the preference coefficient A as an output.

[0070] The preference mode M includes a plurality of modes indicating the preferences of the driver of the vehicle 1 regarding steering operation. For example, the preference mode M may include a first preference mode M1 in which the steering wheel 31 has a stronger than standard feel, a second preference mode M2 ​​in which the steering wheel 31 has a standard feel, and a third preference mode M3 in which the steering wheel 31 has a weaker than standard feel. However, the present disclosure is not limited to this, and the number and contents of the preference modes M can be set arbitrarily. The driver can set the preference mode M via a human-machine interface (HMI) provided in the vehicle 1. Note that the HMI may include a switch or the like for switching the preference mode M, and information input by the driver via the switch or the like is output to the driving assistance device 60. Alternatively, the preference mode M may be set using a learning model generated by machine learning using the driving history of the driver's steering operation, etc., as learning data.

[0071] The moment Mx is a value corresponding to a moment around an axis in the longitudinal direction of the vehicle 1, and a plurality of values ​​are prepared in advance in the preference map.

[0072] The preference coefficient A takes a positive value with a maximum of 1. The smaller the value of the preference coefficient A, the greater the response of the steering wheel 31 when the wheels 3 go over a step, making it easier for the driver to recognize the road surface conditions, but the greater the burden on the driver. On the other hand, the larger the value of the preference coefficient A, the less the response of the steering wheel 31 when the wheels 3 go over a step, making the burden on the driver lighter.

[0073] (2-2. Example of operation of driving assistance device) An example of the operation of the driving assistance device 60 according to this embodiment will be described with reference to Fig. 9. This example of the operation is preferably performed instead of steps S14 and S15 after a positive determination is made in step S13 shown in Fig. 4. However, step S20, which will be described later, may be performed in parallel with steps S10 to S13.

[0074] In step S20, the acquisition unit 71 acquires preference information related to the steering operation of the driver of the vehicle 1. Specifically, the acquisition unit 71 acquires the moment Mx used to determine the degree of the step in step S13 shown in Fig. 4. The acquisition unit 71 also acquires the preference mode M input by the driver via, for example, an HMI. The acquisition unit 71 also acquires a preference map from the preference information storage unit 63. Then, the acquisition unit 71 inputs the moment Mx and preference mode M acquired by the acquisition unit 71 into the preference map, and acquires a preference coefficient A corresponding to the input as an output from the preference map.

[0075] In step S21, the calculation unit 73 reflects the preference information acquired in step S20 in calculating the amount of assistance related to the steering of the wheels 3 based on the tire force acquired in step S11 shown in FIG. 4. Specifically, the calculation unit 73 calculates the assist torque T for assisting the steering torque, which is the torque input to the steering wheel 31 by the driver, using the following equation (4). In the following equation (4), Mzi refers to the moment Mz around the axis in the height direction of the vehicle 1 applied to the wheel approaching a step caused by a rut. For example, when the front wheels 3LF and 3RF are approaching a step caused by a rut as shown in FIG. 5, Mzi refers to the moment Mz around the axis in the height direction of the vehicle 1 applied to the front wheel 3i (i is an index representing LF and RF). SR refers to the steering gear ratio determined according to the electric steering system 30 and is stored in advance in the storage unit 62. A refers to the preference coefficient acquired in step S20. Σ is the sum for the wheels approaching a step caused by a rut. For example, when front wheels 3LF and 3RF are approaching a step caused by a rut as shown in FIG. 5, Σ means the sum for front wheel 3i (i is an index representing LF and RF).

[0076]

number

[0077] In this way, the calculation unit 73 calculates the assist torque T that reflects the driver's preference for the response of the steering wheel 31 when the wheels 3 approach a step. After that, the process proceeds to step S22.

[0078] In step S22, the control unit 74 controls the driving of the electric steering system 20 of the vehicle 1 based on the assist amount calculated in step S21. For details, the description of step S15 in the first embodiment is cited. Thereafter, the process ends.

[0079] (effect) As described above, the processing unit 61 of the driving assistance device 60 according to the second embodiment acquires the tire force input to the wheels 3 of the vehicle 1 due to a step in the road surface. The processing unit 61 also acquires preference information regarding the steering operation of the driver of the vehicle 1. Then, when calculating the amount of assistance regarding the steering of the wheels 3 based on the acquired tire force, the processing unit 61 reflects the acquired preference information in the amount of assistance.

[0080] According to this configuration, the amount of assistance related to steering of the wheels 3 reflects the characteristics of each step. Therefore, compared to when the assistance amount is switched uniformly when there is a step on the road surface, it is possible to reduce the sense of discomfort felt by the driver in response to the driving assistance control for the road step. Furthermore, because the driver's steering preference is also reflected in the calculation of the assistance amount, it is possible to further reduce the sense of discomfort felt by the driver.

[0081] 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.

[0082] (First Modification) As shown in FIG. 10 , the present disclosure is also applicable to a case where a wheel 3 (e.g., a right front wheel 3RF) is approaching a step caused by a rut or the like that curves (e.g., a left curve) ahead in the traveling direction of the vehicle 1, and the steering wheel 31 of the vehicle 1 is in a neutral position. When the wheel 3 approaches a step caused by a rut or the like even though the steering wheel 31 is in a neutral position, not only the load Fy in the vehicle width direction of the vehicle 1 but also the moment Mz around the axis in the height direction of the vehicle 1 increases. Therefore, if the increased moment Mz is applied as is to equation (3) or (4) in the above-described embodiment, the amount of assist may be greater than necessary, which may cause the driver to feel uncomfortable. Therefore, when it is determined that a step that curves ahead in the traveling direction of the vehicle 1 exists, the calculation unit 73 may correct the moment Mz obtained in the same manner as in the above-described embodiment using equation (5) below and then calculate the amount of assist using equation (3) or (4). In the following formula (5), B may be a fixed value that is arbitrarily set between greater than 0 and less than 1. Alternatively, B may be a value that varies between greater than 0 and less than 1 depending on the steering torque of the driver. In this case, a map showing the relationship between the driver's steering torque and B (for example, a relationship in which B increases as the steering torque increases) is stored in advance in the storage unit 63, and may be referred to as appropriate when calculating the assist amount. Note that the determination of whether or not such a step exists can be performed as appropriate by, for example, image processing of image data from the stereo cameras 15L, 15R, etc. included in the surrounding environment sensor 15.

[0083]

number

[0084] (Second Modification) As a modified example, the determination of the level of the step in the above-described step S13 may use both the load Fy and the load Fz instead of the moment Mz. This is because when the level of the step is small (for example, when the rut is shallow), the force F applied to the wheel 3 includes the load Fz in addition to the load Fy.

[0085] (Third Modification) If electric steering system 30 is a steer-by-wire type, calculation section 73 of driving assist device 60 may calculate assist amount T' to be applied to the output torque of steering motor 57, instead of the above-mentioned assist torque T. Specifically, calculation section 73 may calculate assist amount T' using the following equation (6). Σ is the sum for the wheels approaching a step caused by a rut. For example, when front wheels 3LF, 3RF are approaching a step caused by a rut as shown in FIG. 5, it means the sum for front wheel 3i (i is an index representing LF, RF). In a third modified example, assist amount T' for the output torque of steering motor 57 does not need to be fed back to steering device 33. In other words, the assist by driving assist device 60 does not need to be transmitted to the driver.

[0086]

number

[0087] (Fourth Modification) In the third modified example described above, if the steered wheels are independently controllable, the control unit 74 may independently control each steered wheel based on the assist amount calculated for each steered wheel in the same manner as in the above equation (6).

[0088] The technology of the present disclosure can also be realized as a vehicle 1 equipped with the driving assistance device 60 described in the above-mentioned embodiment, a driving assistance method executed by the driving assistance device 60, a computer program that causes a computer to function as the above-mentioned driving assistance device 60, and a non-transitory tangible recording medium on which the computer program is recorded. [Explanation of symbols]

[0089] 1: vehicle, 9: tire force sensor, 30: electric steering system, 60: driving assistance device, 61: processing unit, 62: storage unit, 63: preference information storage unit, 71: acquisition unit, 72: determination unit, 73: calculation unit, 74: control 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: obtaining a tire force input to a wheel of the vehicle due to a road surface bump; calculating an assist amount for steering the wheels based on the acquired tire forces; Driving assistance device.

2. the one or more processors: calculating the assist amount based on a moment around an axis along a height direction of the vehicle among the acquired tire forces; The driving assistance device according to claim 1 .

3. the one or more processors: Obtain the cant of the road surface; correcting the tire force based on the acquired cant; The driving assistance device according to claim 1 .

4. the one or more processors: determining the extent of the step based on the acquired tire force; determining whether to provide steering assistance based on the determined degree; The driving assistance device according to claim 1 .

5. the one or more processors: acquiring preference information regarding steering operation of a driver of the vehicle; When calculating the assist amount, the preference information is reflected in the assist amount. The driving assistance device according to claim 1 .

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