Vehicle control device, vehicle control method and computer program

Abstract

To provide an improved vehicle control device that can stabilize behavior of a vehicle body during traction control.SOLUTION: A vehicle braking control device, which executes traction control, executes: setting of a target yaw rate and target vehicle body angular acceleration during traction control; calculation of a front and rear force difference of left and right wheels, on the basis of front and rear force of the wheels detected with a tire force sensor during traction control; calculation of an actual yaw rate and actual vehicle body angular acceleration, on the basis of the front and rear force difference of the left and right wheels; and suppression of driving force that is applied to the wheel in which the front and rear force is large of the left and right wheels so as to keep a deviation of yaw rates which is a difference between the target yaw rate and the actual yaw rate and a deviation of the vehicle body angular acceleration which is a difference between the target vehicle body angular acceleration and the actual vehicle body angular acceleration, in a predetermined range, when the deviation of the yaw rates is over a predetermined first threshold or the deviation of the vehicle body angular acceleration is over a predetermined second threshold.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle control device, a vehicle control method, and a computer program. [Background technology]

[0002] Traction control systems (hereinafter referred to as "TCS") are known to prevent wheel spin when accelerating, such as when starting a vehicle. For example, when the accelerator pedal is pressed hard in low-friction conditions where the coefficient of friction between the tires and the road surface is low, the TCS reduces driving force when it detects wheel spin, and then increases driving force again when the wheel rotation speed begins to decrease, repeating this process to ensure that each wheel exerts maximum driving force.

[0003] During traction control by the TCS, upper and lower limits are set for the tire slip ratio, and the driving force is controlled so that the slip ratio falls within the upper and lower limits. Therefore, when the driving force is constant and the road surface changes from a low friction coefficient to a high friction coefficient, the slip ratio decreases, and the traction control intervenes to reduce the slip ratio, increasing the driving force. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-199823 Summary of the Invention [Problem to be solved by the invention]

[0005] If only one of the left and right wheels changes from a low-friction state to a high-friction state during acceleration, the driving force of that wheel increases, creating a difference in driving force between the left and right wheels, and generating a yaw moment on the vehicle body. In a low-friction state, unless the tire slip angle changes significantly, the force in the width direction of the tire (lateral force) does not increase, which can easily disrupt the behavior of the vehicle body.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and an object of the present disclosure is to provide an improved vehicle control device, vehicle control method, and computer program that are capable of stabilizing the behavior of the vehicle body during traction control. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, according to one aspect of the present disclosure, there is provided a vehicle control device that performs traction control, comprising one or more processors and one or more memories communicably connected to the one or more processors, wherein the one or more processors set a target yaw rate and a target vehicle body angular acceleration during the traction control, calculate a longitudinal force difference between left and right wheels based on the longitudinal forces of each wheel detected by a tire force sensor during the traction control, calculate an actual yaw rate and an actual vehicle body angular acceleration based on the longitudinal force difference between the left and right wheels, and when a yaw rate deviation, which is the difference between the target yaw rate and the actual yaw rate, exceeds a predetermined first threshold value, or when a vehicle body angular acceleration deviation, which is the difference between the target vehicle body angular acceleration and the actual vehicle body angular acceleration, exceeds a predetermined second threshold value, suppresses the driving force applied to the wheel of the left and right wheels that has the larger longitudinal force, thereby keeping the yaw rate deviation and the vehicle body angular acceleration deviation within a predetermined range.

[0008] Furthermore, in order to solve the above-described problems, according to another aspect of the present disclosure, there is provided a vehicle control method in which a computer sets a target yaw rate and a target vehicle body angular acceleration during traction control, calculates a longitudinal force difference between the left and right front wheels and a longitudinal force difference between the left and right rear wheels based on the longitudinal forces of each wheel detected by a tire force sensor during the traction control, calculates a yaw rate and a vehicle body angular acceleration based on the longitudinal force difference between the left and right front wheels and the longitudinal force difference between the left and right rear wheels, and when a yaw rate deviation, which is the difference between the target yaw rate and the yaw rate, is equal to or greater than a predetermined first threshold value, or when a vehicle body angular acceleration deviation, which is the difference between the target vehicle body angular acceleration and the vehicle body angular acceleration, is equal to or greater than a predetermined second threshold value, suppresses the driving force applied to the wheel of the front wheels or the rear wheels having the larger longitudinal force, and keeps the yaw rate deviation and the vehicle body angular acceleration deviation within a predetermined range.

[0009] Furthermore, in order to solve the above-described problems, according to another aspect of the present disclosure, there is provided a computer program that causes a computer to execute the following steps: setting a target yaw rate and a target vehicle body angular acceleration during traction control; calculating a lateral force difference between the left and right front wheels and a lateral force difference between the left and right rear wheels based on the lateral forces of each wheel detected by a tire force sensor during the traction control; calculating a yaw rate and a vehicle body angular acceleration based on the lateral force difference between the left and right front wheels and the lateral force difference between the left and right rear wheels; and, when a yaw rate deviation, which is the difference between the target yaw rate and the yaw rate, is equal to or greater than a predetermined first threshold value, or when a vehicle body angular acceleration deviation, which is the difference between the target vehicle body angular acceleration and the vehicle body angular acceleration, is equal to or greater than a predetermined second threshold value, suppressing the driving force applied to one of the front wheels and the rear wheels having the larger longitudinal force, and keeping the yaw rate deviation and the vehicle body angular acceleration deviation within a predetermined range. [Effects of the Invention]

[0010] As described above, according to the present disclosure, the behavior of the vehicle body can be stabilized during traction control. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an example configuration of a vehicle including a vehicle control device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a control device for a vehicle according to the embodiment; [Figure 3] 4 is a flowchart showing a routine of a processing operation by the control device for a vehicle according to the embodiment; [Figure 4] 4 is a flowchart showing a routine of a processing operation by the control device for a vehicle according to the embodiment; [Figure 5] 4 is a flowchart showing a routine of a driving force suppression process performed by the control device for the vehicle according to the embodiment; [Figure 6] 3 is an explanatory diagram showing the operation of the control device for the vehicle according to the embodiment; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] <1. Vehicle configuration> First, an example of the overall configuration of a vehicle equipped with a vehicle control device according to an embodiment of the present disclosure will be described.

[0014] FIG. 1 is a schematic diagram showing an example of the configuration of a vehicle 1. As shown in FIG. The vehicle 1 is configured as a four-wheel drive electric vehicle in which drive motors 3LF, 3RF, 3LR, and 3RR (hereinafter, collectively referred to as "drive motor 3" unless a distinction is required) are provided corresponding to the left front wheel 5LF, the right front wheel 5RF, the left rear wheel 5LR, and the right rear wheel 5RR (hereinafter, collectively referred to as "wheels 5" unless a distinction is required. Furthermore, the left front wheel 5LF and the right front wheel 5RF may be referred to as "front wheels 5F," and the left rear wheel 5LR and the right rear wheel 5RR may be referred to as "rear wheels 5R").

[0015] The drive motors 3LF, 3RF, 3LR, and 3RR are electrically connected to inverters 7LF, 7RF, 7LR, and 7RR, respectively, which control the supply of power from the secondary battery 2 to the drive motors 3LF, 3RF, 3LR, and 3RR. The drive motor 3 functions as a generator, and generates power by regenerating it using the rotational torque of the wheels 5 when the vehicle 1 decelerates. The generated power is controlled by the inverter 7 and charged into the secondary battery 2.

[0016] Each wheel 5 is provided with a tire force sensor 8LF, 8RF, 8LR, 8RR (hereinafter collectively referred to as "tire force sensor 8" unless a distinction is particularly required) and a wheel speed sensor 9LF, 9RF, 9LR, 9RR (hereinafter collectively referred to as "wheel speed sensor 9" unless a distinction is particularly required).

[0017] The tire force sensor 8LF is provided, for example, on an axle connecting the drive motor 3LF and the left front wheel 5LF. The tire force sensor 8RF is provided, for example, on an axle connecting the drive motor 3RF and the right front wheel 5RF. The tire force sensor 8LR is provided, for example, on an axle connecting the drive motor 3LR and the left rear wheel 5LR. The tire force sensor 8RR is provided, for example, on an axle connecting the drive motor 3RR and the right rear wheel 5RR. The tire force sensors 8 are load sensors that detect the load applied to each wheel 5.

[0018] For example, the tire force sensor 8 may be a six-component force detector that detects loads (Fx, Fy, Fz) generated in each of the three axial directions of the wheel 5, namely the fore-and-aft direction (x-axis), width direction (y-axis), and height direction (z-axis), as well as moments (Mx, My, Mz) generated around each of the three axes. In this embodiment, the load generated in the fore-and-aft direction (x-axis direction) of the contact surface of the wheel 5 is referred to as the fore-and-aft force Fx, the load generated in the width direction (y-axis direction) is referred to as the lateral force Fy, and the load generated in the height direction (z-axis direction) is referred to as the ground reaction force Fz.

[0019] The wheel speed sensor 9 is provided on the axle of each wheel 5 and detects the rotation speed of each wheel 5 .

[0020] The vehicle 1 also includes a steering angle sensor 11, an accelerator opening sensor 13, and a yaw rate sensor 15. The steering angle sensor 11 is provided, for example, on a steering column and detects the rotation angle of the steering wheel. The accelerator opening sensor 13 is provided, for example, on an accelerator pedal and detects the accelerator opening. The yaw rate sensor 15 is provided, for example, near the center of gravity of the vehicle body and detects the rotation angular velocity of the vehicle 1 around the z-axis.

[0021] The control device 50 includes one or more electronic control devices that control the braking of the vehicle 1. The control device 50 acquires detection information output from various sensors and executes control to stabilize the vehicle behavior, including traction control.

[0022] <2. Vehicle control device> Next, the vehicle control device 50 according to this embodiment will be described in detail.

[0023] (2-1. Overall configuration of the control device) The control device 50 functions as a device that controls the braking of the vehicle body 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 the operations to be performed by the control device 50, which will be described later. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 53 provided in the control device 50, or may be recorded on a recording medium built into the control device 50 or any recording medium that can be externally attached to the control device 50.

[0024] Recording media for recording computer programs include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical recording media such as CD-ROMs (Compact Disc Read Only Memory), DVDs (Digital Versatile Discs), and Blu-ray (registered trademark), magneto-optical media such as floptical disks, memory elements such as RAMs (Random Access Memory) and ROMs (Read Only Memory), flash memories such as USB (Universal Serial Bus) memories and SSDs (Solid State Drives), and other media capable of storing programs.

[0025] FIG. 2 is a block diagram showing an example of the configuration of the control device 50. The control device 50 is connected to an inverter 7, a tire force sensor 8, a wheel speed sensor 9, a steering angle sensor 11, an accelerator opening sensor 13, and a yaw rate sensor 15 via a dedicated line or communication means such as a CAN (Controller Area Network) or a LIN (Local Inter Net).

[0026] The control device 50 includes a processing unit 51 and a storage unit 53. The processing unit 51 includes one or more processors such as CPUs and various peripheral components. Part or all of the processing unit 51 may be configured with updatable firmware or the like, or may be a program module or the like that is executed by commands from the CPU or the like.

[0027] The storage unit 53 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 it. However, the type and number of storage units 53 are not particularly limited. The storage unit 53 stores information such as computer programs executed by the processing unit 51, various parameters used in arithmetic processing, detection data, and arithmetic results. A part of the storage unit 53 is used as a work area for the processing unit 51.

[0028] (2-2. Functional configuration of the processing unit) Next, the configuration of the processing unit 51 of the control device 50 will be described. The processing unit 51 includes an acquisition unit 61, a driving state calculation unit 63, a traction control unit 65, a longitudinal force difference calculation unit 67, a target driving state calculation unit 69, and a driving force suppression control unit 71. Each of these units is a function realized by the execution of a computer program by one or more processors. However, part of the acquisition unit 61, the driving state calculation unit 63, the traction control unit 65, the longitudinal force difference calculation unit 67, the target driving state calculation unit 69, and the driving force suppression control unit 71 may be configured by hardware such as an analog circuit.

[0029] Below, the function of each part of the processing unit 51 will be briefly explained, and then the specific processing content of each part will be explained.

[0030] (Acquisition Department) The acquisition unit 61 acquires detection information output from various sensors. For example, the acquisition unit 61 acquires sensor signals output from the tire force sensor 8, the wheel speed sensor 9, the steering angle sensor 11, the accelerator opening sensor 13, and the yaw rate sensor 15 at a predetermined sampling period, and detects the six-component forces generated in each wheel 5, the rotational speed of each wheel 5, the steering angle, the accelerator opening, and the yaw rate (actual yaw rate) of the vehicle body.

[0031] (Driving condition calculation unit) The running condition calculation unit 63 calculates information about the running condition of the vehicle 1. For example, the running condition calculation unit 63 calculates a differential value of the rotational speed of each wheel 5 to calculate the rotational acceleration of each wheel 5 (hereinafter also referred to as "wheel acceleration"). The running condition calculation unit 63 also calculates the vehicle body speed based on the rotational speed of each wheel 5. The running condition calculation unit 63 also calculates the yaw moment of the vehicle body based on the longitudinal force Fx and lateral force Fy generated on each wheel 5, the toe angle θ of each wheel 5, the tread length, and the shortest distance from the center of gravity of the vehicle body to the axle, and calculates the angular acceleration of the vehicle body (hereinafter also referred to as "vehicle body angular acceleration") by dividing the yaw moment by the inertia of the vehicle body. Furthermore, the running condition calculation unit 63 calculates the slip state of each wheel 5 based on the vehicle body speed and the wheel speed. The slip state of the wheel 5 is a state quantity that represents the degree of grip of the wheel 5 with respect to the road surface on which the vehicle is traveling.

[0032] (Traction control unit) The traction control unit 65 executes processing to prevent spinning of each wheel 5 when the accelerator pedal is depressed strongly. For example, the traction control unit 65 executes traction control based on the rotational speed of the wheel 5, the slip state of the wheel 5, the operation amount of the accelerator pedal, the required acceleration, the vehicle speed, the yaw rate, the steering angle, and the vehicle lateral acceleration. Note that the processing content of the traction control is a conventionally known method and is not limited to the above example.

[0033] (Anteroposterior force difference calculation section) The longitudinal force difference calculation unit 67 calculates the difference (longitudinal force difference ΔFx_f) between the forces (longitudinal forces Fx) generated in the direction along the axle 4F for each of the left and right front wheels 5F, and the difference (longitudinal force difference ΔFx_r) between the forces (longitudinal forces Fx) generated in the direction along the axle 4R for each of the left and right rear wheels 5R.

[0034] (Target driving state calculation unit) The target driving state calculation unit 69 sets a target yaw rate and a target vehicle body angular acceleration while traction control is being executed. For example, the target driving state calculation unit 69 calculates the target yaw rate using a predetermined stabilization coefficient based on the steering angle and vehicle body speed. The target yaw rate represents a target value for the yaw rate of the vehicle body determined from the driving operation state of the driver of the vehicle 1. In addition, the target driving state calculation unit 69 calculates the target vehicle body angular velocity based on the steering angle, vehicle body weight, cornering stiffness, and the shortest distance from the center of gravity of the vehicle body to the axle.

[0035] (Driving force suppression control unit) The driving force suppression control unit 71 suppresses the driving force applied to each wheel 5 based on the difference between the target yaw rate and the actual yaw rate (yaw rate deviation) and the difference between the target vehicle body angular acceleration and the actual vehicle body angular acceleration (vehicle body angular acceleration deviation), and performs processing to stabilize the driving state.

[0036] <3. Operation of the control device> Next, an example of the processing operation by the processing unit 51 of the control device 50 according to this embodiment will be specifically described with reference to a flowchart. To make the description easier to understand, the description will be given mainly by taking as an example a situation in which one of the left and right wheels slips when accelerating and traveling straight.

[0037] 3 and 4 show the main routine of the processing operation by the control device 50. FIG. When the processing unit 51 detects that the ignition switch of the vehicle 1 has been turned on (step S11), the acquisition unit 61 of the processing unit 51 starts processing to acquire various detection information based on sensor signals output from the various sensors (step S13). For example, the acquisition unit 61 acquires sensor signals output from the tire force sensor 8, the wheel speed sensor 9, the steering angle sensor 11, the accelerator opening sensor 13, and the yaw rate sensor 15 at a predetermined sampling period, and detects the six-component forces (Fx, Fy, Fz, Mx, My, Mz) generated in each wheel 5, the rotational speeds Vw (Vw_LF, Vw_RF, Vw_LR, Vw_RR) of each wheel 5, the steering angle θs, the accelerator opening Ac, and the yaw rate (actual yaw rate) Yr of the vehicle body.

[0038] Next, the running condition calculation unit 63 of the processing unit 51 calculates the wheel acceleration dVw (dVw_LF, dVw_RF, dVw_LR, dVw_RR) of each wheel 5 based on the rotational speed Vw of each wheel 5 (step S15). For example, the running condition calculation unit 63 differentiates the rotational speed Vw of each wheel 5 to calculate the wheel acceleration dVw of each wheel 5.

[0039] Next, the traveling condition calculation unit 63 calculates the vehicle body speed Vx based on the rotational speed Vw of each wheel 5 (step S17). For example, when a driving force is being applied to each wheel 5, the traveling condition calculation unit 63 calculates the vehicle body speed Vx based on the slowest rotational speed among the rotational speeds Vw of each wheel 5. Furthermore, when a driving force is not being applied to each wheel 5, the traveling condition calculation unit 63 calculates the vehicle body speed Vx based on the fastest rotational speed among the rotational speeds Vw of each wheel 5. When calculating the vehicle body speed Vx, a limit may be placed on the amount of change in the vehicle body speed Vx over time. For example, an upper limit αup of the increase gradient of the vehicle body speed Vx and a lower limit αdn of the decrease gradient of the vehicle body speed Vx may be set, and the change in the vehicle body speed Vx may be restricted by the upper limit αup and the lower limit αdn.

[0040] The method for calculating the vehicle speed Vx is not limited to the above example, and any calculation method, including conventionally known methods, may be used.

[0041] Next, the running condition calculation unit 63 calculates a slip state that indicates the degree of grip of the wheels 5 with respect to the road surface based on the vehicle body speed Vx and the wheel rotation speed Vw (step S19). For example, the running condition calculation unit 63 calculates an acceleration slip speed hV (hV=Vw-Vx), which is the deviation between the rotation speed Vw of each wheel 5 and the vehicle body speed Vx, as a state quantity that indicates the slip state. Furthermore, the running condition calculation unit 63 may calculate a wheel slip ratio Sw (Sw=hV / Vx), which is obtained by non-dimensionalizing the acceleration slip speed hV using the vehicle body speed Vx, as a state quantity that indicates the slip state.

[0042] Next, the traction control unit 65 determines whether or not to execute traction control based on information about the driving state of the vehicle 1 (step S21). For example, the traction control unit 65 determines whether or not the vehicle 1 is accelerating based on at least one of the accelerator pedal position Ac and the required acceleration Gr. The required acceleration Gr is an acceleration command value from automatic driving control or other driving assistance functions, and is obtained from a control device that manages each function. Furthermore, the traction control unit 65 permits the execution of traction control for each wheel 5 when it is determined that the vehicle 1 is accelerating and at least one of the following conditions is met: the accelerator pedal position Ac is equal to or greater than a predetermined value; the operation signal St is in an on state; and the required acceleration Gr is equal to or greater than a predetermined value.

[0043] If the traction control unit 65 does not determine to execute traction control (S21 / No), the process returns to step S15, and calculation of the running state of the vehicle 1 and determination of whether or not to execute traction control are repeated.

[0044] On the other hand, when the traction control unit 65 determines that traction control is to be performed (S21 / Yes), it repeats the process of reducing the driving force when the slip ratio Sw of the wheel 5 for which traction control is to be performed increases to a predetermined upper limit value, and increasing the driving force when the slip ratio Sw of the wheel 5 decreases to a predetermined lower limit value, thereby controlling the driving force within the range between the upper limit value and the lower limit value.

[0045] Next, the longitudinal force difference calculation unit 67 calculates the longitudinal force difference ΔFx_f between the left and right front wheels 5F and the longitudinal force difference ΔFx_r between the left and right rear wheels based on the longitudinal force Fx generated in each wheel 5 (step S23).

[0046] Next, the target running state calculation unit 69 calculates a target yaw rate Yr_tgt and a target vehicle body angular acceleration α_tgt according to the running state of the vehicle 1 (step S25). For example, the target running state calculation unit 69 calculates the target yaw rate Yr_tgt using a predetermined stabilization factor set in advance based on the steering angle θs and the vehicle body speed Vx. The stabilization factor A is set in advance using the following equation (1) based on the vehicle body weight W, cornering stiffness Kf, Kr, the shortest distances Lf, Lr from the center of gravity of the vehicle body to the front and rear axles, respectively, and the distance l between the front and rear wheels.

[0047]

number

[0048] W: Vehicle weight K f : Front wheel cornering stiffness K r : Rear wheel cornering stiffness L f : The shortest distance between the vehicle's center of gravity and the front axle L r : The shortest distance between the vehicle's center of gravity and the rear axle l: Distance between front and rear axles

[0049] The target running state calculation unit 69 calculates the steering angle θs, the vehicle weight W, the cornering stiffness K f ,K r , the shortest distance L from the center of gravity of the vehicle body to the front and rear wheel axles f ,L r The target vehicle body angular acceleration α_tgt is calculated based on the above.

[0050] Cornering Stiffness K f ,K r indicates the rise gradient of the cornering force relative to the sideslip angle in the range of very small sideslip angles. Cornering stiffness K f ,K r , vehicle weight W and shortest distance L f ,L rare stored in advance in the storage unit 53 or the like as information on the specifications of the vehicle 1.

[0051] Next, the driving force suppression control unit 71 calculates a yaw rate deviation ΔYr and a vehicle body angular acceleration deviation Δα (step S27). The yaw rate deviation ΔYr is the deviation between the target yaw rate Yr_tgt and the actual yaw rate Yr, and the vehicle body angular acceleration deviation Δα is the deviation between the target vehicle body angular acceleration α_tgt and the actual vehicle body angular acceleration α. ​​The actual vehicle body angular acceleration α is calculated, for example, by dividing the yaw moment of the vehicle body, which is calculated based on the longitudinal force Fx and lateral force Fy generated on each wheel 5, the toe angle θ of each wheel 5, the tread length LT, and the shortest distance L from the center of gravity of the vehicle body to the axle, by the inertia of the vehicle body.

[0052] Next, the driving force suppression control unit 71 suppresses the driving force based on the calculated yaw rate deviation ΔYr and vehicle body angular acceleration deviation Δα, and executes processing to stabilize the running state (step S29).

[0053] FIG. 5 shows a flowchart of the driving force suppression process according to this embodiment. First, the driving force suppression control unit 71 determines whether the yaw rate deviation ΔYr exceeds a predetermined first threshold ΔYr_thr (step S41). The first threshold ΔYr_thr is set in advance to any appropriate value depending on the inertia of the vehicle 1. Since the yaw rate is expressed as a function of the steering angle and the vehicle body speed, the first threshold ΔYr_thr may be a variable value depending on the vehicle body speed Vx.

[0054] When the driving force suppression control unit 71 determines that the yaw rate deviation ΔYr exceeds a predetermined first threshold ΔYr_thr (S41 / Yes), the driving force suppression control unit 71 calculates a control intervention amount gain based on the vehicle body angular acceleration deviation Δα, and further multiplies the calculated gain by a correction gain according to the yaw rate deviation ΔYr to determine the control intervention amount gain (step S43). The value of the control intervention amount gain based on the vehicle body angular acceleration deviation Δα is determined by referring to map information or the like that is set in advance so that the vehicle body angular acceleration deviation Δα below a certain level converges quickly, for example, so that the vehicle body behavior can be suppressed from the initial movement. The correction gain according to the yaw rate deviation ΔYr is determined by referring to map information or the like that is set in advance so that the vehicle body behavior becomes gentler, for example, so that the intervention amount becomes large and the vehicle body behavior does not become drastic.

[0055] On the other hand, if the driving force suppression control unit 71 does not determine that the yaw rate deviation ΔYr exceeds the predetermined first threshold ΔYr_thr (S41 / No), it determines whether the vehicle body angular acceleration deviation Δα exceeds a predetermined second threshold Δα_thr (step S45). The second threshold Δα_thr is set in advance based on the detection errors of the longitudinal force Fx and the lateral force Fy of each wheel 5 and the vehicle moment of inertia. The second threshold Δα_thr may be a variable value that varies depending on the vehicle body speed Vx.

[0056] If the driving force suppression control unit 71 does not determine that the vehicle body angular acceleration deviation Δα exceeds the predetermined second threshold value Δα_thr (S45 / No), the driving force suppression control unit 71 exits the routine without adjusting the driving force. On the other hand, if the driving force suppression control unit 71 determines that the vehicle body angular acceleration deviation Δα exceeds the predetermined second threshold value Δα_thr (S45 / Yes), the driving force suppression control unit 71 determines a control intervention amount gain based on the vehicle body angular acceleration deviation Δα (step S47). The value of the control intervention amount gain based on the vehicle body angular acceleration deviation Δα is determined by referring to the map information described above, etc.

[0057] After determining the control intervention amount gain in steps S43 and S45, the driving force suppression control unit 71 limits the driving force of the wheel 5 in the high friction state by a load amount obtained by multiplying the control intervention amount gain by the difference between the left and right longitudinal forces of the front wheels 5F or the rear wheels 5R (step S49). For example, the driving force suppression control unit 71 determines the amount of suppression of the driving force to be limited by multiplying the control intervention amount gain by the difference between the left and right longitudinal forces ΔFx_f of the front wheels 5F. The driving force suppression control unit 71 also calculates the corrected driving force by subtracting the driving force to be limited from the driving force set for the wheel 5 in the high friction state by processing of the traction control unit 65.

[0058] Next, the driving force suppression control unit 71 adjusts the driving force of the wheel 5 in the high friction state in accordance with the corrected driving force (step S51). For example, the driving force suppression control unit 71 controls the drive of the inverter 7 that supplies power to the drive motor 3 of the wheel 5 in the high friction state based on the driving force (driving torque) to suppress the driving force of the wheel 5 in the high friction state. As a result, the actual yaw rate Yr of the vehicle body and the actual vehicle body angular acceleration α caused by the longitudinal force difference occurring in the front wheel 5F or the rear wheel 5R decrease.

[0059] 4, while executing the driving force suppression process, the driving force suppression control unit 71 determines whether the yaw rate deviation ΔYr is equal to or smaller than the first threshold value ΔYr_thr and whether the vehicle body angular acceleration deviation Δα is equal to or smaller than the second threshold value Δα_thr (step S31). If the yaw rate deviation ΔYr exceeds the first threshold value ΔYr_thr or the vehicle body angular acceleration deviation Δα exceeds the second threshold value Δα_thr (S31 / No), the driving force suppression control unit 71 returns to step S29 and continues the driving force suppression process.

[0060] On the other hand, if the driving force suppression control unit 71 determines that the yaw rate deviation ΔYr is equal to or less than the first threshold ΔYr_thr and that the vehicle body angular acceleration deviation Δα is equal to or less than the second threshold Δα_thr (S31 / Yes), it determines whether the lateral forces Fy of the left and right rear wheels 5R are on an increasing trend (step S33). For example, the driving force suppression control unit 71 determines whether the differential values ​​dFy / dt of the lateral forces Fy of the left and right rear wheels 5R are equal to or less than the third threshold dFy / dt_thr. The driving force suppression control unit 71 may also determine whether the ratio Fy / Fz of the lateral forces Fy of the left and right rear wheels 5R to the ground reaction forces Fz is equal to or greater than a predetermined fourth threshold.

[0061] If the lateral force Fy of the rear wheels 5R does not tend to increase even after the drive force suppression process is initiated, there is a risk that the behavior of the vehicle body may still become unstable. Therefore, if the drive force suppression control unit 71 does not determine that the lateral force Fy of the left and right rear wheels 5R is tending to increase (S33 / No), it returns to step S29 and continues the drive force suppression process. On the other hand, if the drive force suppression control unit 71 determines that the lateral force Fy of the left and right rear wheels 5R is tending to increase (S33 / Yes), it stops the drive force suppression process (step S35).

[0062] Thereafter, the processing unit 51 determines whether the ignition switch is turned off (step S37), and if the ignition switch is not turned off (S37 / No), the processing returns to step S15 and repeats the processing of each step described above. On the other hand, if the ignition switch is turned off (S37 / Yes), the processing unit 51 ends the series of processes.

[0063] <4. Effect> Next, the operation when the driving force suppression process according to this embodiment is executed will be described.

[0064] Figure 6 shows a schematic diagram of the longitudinal forces Fx (Fx_L, Fx_R) of the left and right front wheels 5LF, 5RF, the lateral forces Fy (Fy_L, Fy_R), the friction coefficients μ (μ_L, μ_R) between the left and right front wheels 5LF, 5RF and the road surface, the slip ratios Sw (Sw_L, Sw_R) of the left and right front wheels 5LF, 5RF, the yaw rate deviation ΔYr of the vehicle body, and the angular acceleration deviation Δα of the vehicle body over time when traction control is being performed.

[0065] The example shown in FIG. 6 is a case where the left wheel enters a high friction state while traction control is being executed as a result of the driver strongly depressing the accelerator pedal, and shows an example where it is assumed that the steering angle θs is zero.

[0066] At time t0, traction control begins. Between time t0 and time t1, the friction coefficients μ_L and μ_R of the left and right front wheels 5LF and 5RF are equal. During this time, the traction control unit 65 adjusts the driving force so that the slip ratios Sw_L and Sw_R of the left and right front wheels 5LF and 5RF fall within a predetermined range. Accordingly, the longitudinal forces Fx_L and Fx_R of the left and right front wheels 5LF and 5RF repeatedly increase and decrease. Note that while the friction coefficients μ_L and μ_R of the left and right front wheels 5LF and 5RF are equal, the lateral forces Fy_L and Fy_R of the left and right front wheels 5LF and 5RF are equal.

[0067] At time t1, when the friction coefficient μ_L of the left front wheel 5LF increases, the longitudinal force Fx_L of the left front wheel 5LF begins to increase. At this time, conventional traction control adjusts the driving force so that the slip ratio Sw_L of the left front wheel 5LF continues to fall within a predetermined range, and the longitudinal force Fx_L of the left front wheel 5LF repeatedly increases and decreases while remaining greater than the longitudinal force Fx_R of the right front wheel 5RF. Furthermore, the lateral forces Fy_L and Fy_R generated at the left and right front wheels 5LF and 5RF increase. At this time, the lateral force Fy_L of the left front wheel 5LF, which has a larger friction coefficient μ_L, becomes smaller than the lateral force Fy_R of the right front wheel 5RF. Conventional traction control increases the vehicle yaw rate deviation ΔYr, which is the difference between the target yaw rate Yr_tgt (zero in the example shown in FIG. 6 ) and the actual yaw rate Yr. Furthermore, a vehicle body angular acceleration deviation Δα occurs, which is the difference between the target vehicle body angular acceleration α_tgt (zero in the example shown in FIG. 6) and the actual vehicle body angular acceleration α.

[0068] On the other hand, the control device 50 according to this embodiment reduces the driving force of the left front wheel 5LF in accordance with the longitudinal force difference ΔFx_f between the left and right front wheels 5F when, at time t1, the friction coefficient μ_L of the left front wheel 5LF increases and the longitudinal force Fx_L_rev of the left front wheel 5LF begins to increase, and then, when the vehicle body yaw rate deviation ΔYr_rev exceeds a predetermined first threshold ΔYr_thr or the vehicle body angular acceleration deviation Δα_rev exceeds a second threshold Δα_thr, the control device 50 reduces the driving force of the left front wheel 5LF in accordance with the longitudinal force difference ΔFx_f between the left and right front wheels 5F. As a result, the slip ratio Sw_L_rev of the left front wheel 5LF falls below the range of slip ratios maintained by traction control, and an increase in the longitudinal force Fx_L_rev of the left front wheel 5LF is suppressed. As a result, the vehicle body yaw rate deviation ΔYr and the vehicle body angular acceleration deviation Δα are reduced, and an increase in the lateral forces Fy_L, Fy_R of the left and right front wheels 5LF, 5RF is suppressed.

[0069] In this way, the vehicle control device 50 according to this embodiment suppresses the driving force of the wheel in the high friction state when the left wheel 5LF is in a high friction state during execution of traction control, causing the yaw rate deviation ΔYr to exceed the first threshold value ΔYr_thr or the vehicle body angular acceleration deviation Δα to exceed the second threshold value Δα_thr. This makes it possible to bring the longitudinal forces of the left and right wheels closer together and stabilize the behavior of the vehicle body even when the friction states of the left and right wheels are different.

[0070] <5. Effects> As described above, the vehicle control device 50 according to this embodiment includes one or more processors and one or more memories communicably connected to the one or more processors, and the one or more processors set the target yaw rate Yr_tgt and the target vehicle body angular acceleration α_tgt during traction control, calculate the longitudinal force difference ΔFx between the left and right wheels based on the longitudinal force Fx of each wheel 5 detected by the tire force sensor 8 during traction control, and calculate the actual yaw rate Yr and the actual vehicle body angular acceleration α_tgt based on the longitudinal force difference ΔFx of the left and right wheels. and when the yaw rate deviation ΔYr, which is the difference between the target yaw rate Yr_tgt and the actual yaw rate Yr, is equal to or greater than a predetermined first threshold ΔYr_thr, or when the vehicle body angular acceleration deviation Δα, which is the difference between the target vehicle body angular acceleration α_tgt and the actual vehicle body angular acceleration α, is equal to or greater than a predetermined second threshold Δα_thr, suppressing the driving force applied to the wheel of the left or right wheel having the greater longitudinal force, thereby keeping the yaw rate deviation ΔYr and the vehicle body angular acceleration deviation Δα within a predetermined range (less than or equal to the first threshold ΔYr_thr or less than or equal to the second threshold Δα_thr).

[0071] Therefore, the control device 50 directly detects the longitudinal force difference ΔFx between the left and right wheels 5 measured using the tire force sensors 8 provided on each wheel 5, and suppresses the driving force of the wheel in a high friction state, thereby directly controlling the amount of yaw moment generated in the vehicle body. This makes it possible to quickly detect the longitudinal force difference ΔFx between the left and right wheels and quickly approximate the slip ratio, thereby shortening the running time after the longitudinal force difference ΔFx between the left and right wheels occurs. Therefore, it is possible to reduce the risk of the vehicle body's behavior becoming unstable.

[0072] Furthermore, in the vehicle control device 50 according to this embodiment, if the lateral force Fy of the left and right rear wheels 5R begins to increase after the yaw rate deviation ΔYr and the vehicle body angular acceleration deviation Δα have been brought within a predetermined range, the one or more processors stop suppressing the drive force applied to the wheel with the greater longitudinal force of the left and right wheels. Therefore, while directly monitoring the lateral force Fy of the rear wheels 5R using the tire force sensor 8R, the control device 50 can directly control the amount of yaw moment generated in the vehicle body until the behavior of the vehicle body is reliably stabilized.

[0073] Although the 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 set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0074] In addition, the technology disclosed herein can also be realized as a vehicle equipped with the control device described in the above embodiments, a control method using the control device, a program that causes a computer to function as the above control device, and a non-temporary tangible recording medium on which the program is recorded. [Explanation of symbols]

[0075] 1: Vehicle 4: Axle 5: Wheels 8: Tire force sensor 9: Wheel speed sensor 11: Steering angle sensor 13: Accelerator opening sensor 15: Yaw rate sensor 20: Hydraulic control unit 50: Control device 51: Processing section 53: Storage section 61: Acquisition part 63: Driving state calculation unit 65: Traction control unit 67: Front and rear force difference calculation section 69: Target driving state calculation unit 71: Vehicle behavior stabilization control unit

Claims

1. In a vehicle control device that performs traction control, one or more processors; and one or more memories communicatively coupled to the one or more processors; the one or more processors: setting a target yaw rate and a target vehicle body angular acceleration during the traction control; calculating a difference between longitudinal forces of the left and right wheels based on longitudinal forces of each wheel detected by a tire force sensor during the traction control; calculating an actual yaw rate and an actual vehicle body angular acceleration based on a longitudinal force difference between the left and right wheels; When a yaw rate deviation, which is a difference between the target yaw rate and the actual yaw rate, exceeds a predetermined first threshold value, or when a vehicle body angular acceleration deviation, which is a difference between the target vehicle body angular acceleration and the actual vehicle body angular acceleration, exceeds a predetermined second threshold value, suppressing the driving force applied to one of the left and right wheels having a larger longitudinal force, thereby keeping the yaw rate deviation and the vehicle body angular acceleration deviation within a predetermined range; A vehicle control device that executes the above.

2. the one or more processors: When the yaw rate deviation exceeds the predetermined first threshold value, the suppression amount of the driving force is set based on the value of the yaw rate deviation and the value of the vehicle body angular acceleration deviation. The vehicle control device according to claim 1 .

3. the one or more processors: When the yaw rate deviation is equal to or smaller than the predetermined first threshold value and the vehicle body angular acceleration deviation exceeds the predetermined second threshold value, the suppression amount of the driving force is set based on the value of the vehicle body angular acceleration deviation. The vehicle control device according to claim 1 .

4. the one or more processors: When the lateral forces of the left and right rear wheels tend to increase after the yaw rate deviation and the vehicle body angular acceleration deviation are brought within a predetermined range, the suppression of the driving force applied to the wheel with the larger longitudinal force is stopped. The vehicle control device according to claim 1 .

5. The computer Setting a target yaw rate and a target vehicle body angular acceleration during traction control; calculating a difference between longitudinal forces of the left and right front wheels and a difference between longitudinal forces of the left and right rear wheels based on the longitudinal forces of each wheel detected by a tire force sensor during the traction control; calculating a yaw rate and a vehicle body angular acceleration based on the longitudinal force difference between the left and right front wheels and the longitudinal force difference between the left and right rear wheels; When a yaw rate deviation, which is the difference between the target yaw rate and the yaw rate, is equal to or greater than a predetermined first threshold value, or when a vehicle body angular acceleration deviation, which is the difference between the target vehicle body angular acceleration and the vehicle body angular acceleration, is equal to or greater than a predetermined second threshold value, suppressing the driving force applied to one of the front wheels and the rear wheels which has a larger longitudinal force, and keeping the yaw rate deviation and the vehicle body angular acceleration deviation within a predetermined range; A method for controlling a vehicle.

6. On the computer, Setting a target yaw rate and a target vehicle body angular acceleration during traction control; calculating a lateral force difference between the left and right front wheels and a lateral force difference between the left and right rear wheels based on the lateral forces of the wheels detected by the tire force sensors during the traction control; calculating a yaw rate and a vehicle body angular acceleration based on the lateral force difference between the left and right front wheels and the lateral force difference between the left and right rear wheels; When a yaw rate deviation, which is a difference between the target yaw rate and the yaw rate, is equal to or greater than a predetermined first threshold value, or when a vehicle body angular acceleration deviation, which is a difference between the target vehicle body angular acceleration and the vehicle body angular acceleration, is equal to or greater than a predetermined second threshold value, suppressing the driving force applied to one of the front wheels and the rear wheels having a larger longitudinal force, and keeping the yaw rate deviation and the vehicle body angular acceleration deviation within a predetermined range; A computer program that executes

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