JP7523366B2 - Vehicle control device and control method - Google Patents

Description

The present invention relates to a vehicle control device and a control method.

Conventionally, in a vehicle capable of generating braking force on each of the four wheels, it is known that when turning, if the actual turning radius (turning line) deviates from the target turning radius (turning line), a braking force is generated on a specific wheel (see, for example, Patent Document 1).

JP 2004-066873 A

However, the above technology leaves room for improvement in terms of quickly returning the vehicle to the target turning line.

The present invention has been made in consideration of the above, and aims to provide a vehicle control device and control method that quickly returns a vehicle to a target turning line when the vehicle deviates from the target turning line.

A vehicle control device according to one aspect of the embodiment controls a vehicle in which four or more drive wheels are rotated by different motors. The vehicle control device includes a motor control unit that controls the torque generated by the motor. When oversteer occurs when the vehicle is turning, the motor control unit performs oversteer control by generating a braking torque in the motor that rotates the front wheel on the outside relative to the turn and increasing the drive torque in the motor that rotates the rear wheel on the inside relative to the turn.

According to one aspect of the embodiment, if the vehicle deviates from the target turning line, the vehicle can be quickly returned to the target turning line.

FIG. 1A is a diagram showing a turning course of a vehicle. FIG. 1B is a diagram showing a control method in the event of oversteer. FIG. 1C is a diagram showing a control method in the event that understeer occurs. FIG. 2 is a schematic diagram illustrating a part of the vehicle according to the embodiment. FIG. 3 is a block diagram showing the configuration of the control device according to the embodiment. FIG. 4 is a map for calculating the vehicle required torque. FIG. 5 is a map for calculating the braking torque to be generated when understeer occurs. FIG. 6 is a map for calculating the drive torque to be generated when understeer is occurring. FIG. 7A is a flowchart illustrating the sideslip prevention process according to this embodiment. FIG. 7B is a flowchart illustrating the sideslip prevention process according to the embodiment.

The vehicle control device and control method according to the embodiment will be described in detail below with reference to the attached drawings. Note that the present invention is not limited to the embodiment.

The control method according to the embodiment will be described with reference to Figs. 1A to 1C. Fig. 1A is a diagram showing a turning course of a vehicle C. Fig. 1B is a diagram showing a control method when oversteer occurs. Fig. 1C is a diagram showing a control method when understeer occurs.

The control method according to the embodiment is executed by a control device 10 (vehicle control device). The control device 10 is mounted on a vehicle C. The vehicle C has, for example, four drive wheels 1. Note that the vehicle C may have four or more drive wheels 1. The vehicle C rotates each drive wheel 1 by a different motor 2. The motor 2 is a so-called in-wheel motor.

In the following, a vehicle C having four drive wheels 1 will be described as an example. The left front drive wheel 1 of the vehicle C may be referred to as the "left front wheel 1FL", the right front drive wheel 1 of the vehicle C may be referred to as the "right front wheel 1FR", the left rear drive wheel 1 of the vehicle C may be referred to as the "left rear wheel 1RL", and the right rear drive wheel 1 of the vehicle C may be referred to as the "right rear wheel 1RR". In addition, the motor 2 that rotates the left front wheel 1FL may be referred to as the "left front wheel motor 2FL", the motor 2 that rotates the right front wheel 1FR may be referred to as the "right front wheel motor 2FR", the motor 2 that rotates the left rear wheel 1RL may be referred to as the "left rear wheel motor 2RL", and the motor 2 that rotates the right rear wheel 1RR may be referred to as the "right rear wheel motor 2RR". In addition, the front drive wheel 1 of the vehicle C may be referred to as the "front wheel 1F", and the rear drive wheel 1 of the vehicle C may be referred to as the "rear wheel 1R".

When vehicle C turns based on the steering angle, it is desirable for vehicle C to turn along a predetermined turning course according to the steering angle, as shown by the dashed arrow, without causing vehicle C to skid. If vehicle C skids, vehicle C may oversteer or understeer.

Oversteer is a state in which vehicle C travels along a course that is cut inward in the turning radius from the specified turning course, as indicated by the dashed double-dashed arrow. Oversteer occurs, for example, when rear wheel 1R skids.

Understeer is a state in which vehicle C travels on a course that bulges outward in terms of the turning radius from the specified turning course, as shown by the dashed arrow. Understeer occurs, for example, when the front wheels 1F skid.

The control method according to the embodiment is designed to suppress sideslip by controlling the torque of the motor 2 when sideslip occurs while the vehicle C is turning.

When oversteer occurs, the control device 10 generates a braking torque in the motor 2 that rotates the front wheel 1F on the outside relative to the turn, as shown in FIG. 1B. Braking torque is torque that generates a braking force in the drive wheel 1. Braking torque is negative torque. The control device 10 also increases the drive torque in the motor 2 that rotates the rear wheel 1R on the inside relative to the turn. Drive torque is torque that generates a drive force in the drive wheel 1. Drive torque is positive torque.

For example, when the vehicle C is turning right, the control device 10 generates a braking torque in the left front wheel motor 2FL and increases the drive torque in the right rear wheel motor 2RR.

This generates a counterclockwise yaw moment in vehicle C, causing vehicle C to turn while approaching the specified turning course.

When understeer occurs, the control device 10 generates a braking torque in the motor 2 that rotates the inner rear wheel 1R relative to the turn, as shown in FIG. 1C. The control device 10 also increases the drive torque in the motor 2 that rotates the outer front wheel 1F relative to the turn.

For example, when the vehicle C is turning right, the control device 10 generates a braking torque in the right rear wheel motor 2RR and increases the driving torque in the left front wheel motor 2FL.

This generates a clockwise yaw moment in vehicle C, causing vehicle C to turn while approaching the specified turning course.

In this way, when oversteer or understeer occurs, the control device 10 suppresses oversteer or understeer by controlling the torque of the motor 2 that rotates the drive wheels 1. Therefore, the control device 10 can quickly return the vehicle C to the specified turning course.

Note that a vehicle C having more than four drive wheels 1 has, for example, three or more drive wheels 1 arranged in the front-to-rear direction on one side of the vehicle C in the left-right direction. Also, multiple drive wheels 1 may be arranged in the left-right direction on one side of the vehicle C in the left-right direction. Also, additional wheels (drive wheels) may be provided near the center of the vehicle C.

In such a case, for example, the control device 10 controls only the torque of the outermost and frontmost front wheel 1F and the torque of the innermost and rearmost rear wheel 1R. Also, for example, the control device 10 controls the torque of the drive wheels 1 other than the outermost and rearmost rear wheel 1R and the innermost and frontmost front wheel 1F. Also, for example, the control device 10 divides the drive wheels 1 into four groups, front right, front left, rear right, and rear left, by dividing the drive wheels 1 into front and rear wheels depending on whether they are forward or rear of the center of the vehicle C, and left and right wheels depending on whether they are left or right of the center of the vehicle C, and controls the torque of the drive wheels 1 corresponding to each group (for example, when controlling the outer front wheels and the outer side is the right wheel side, the drive wheels 1 included in the right front group are controlled as the outer front wheel group).

Next, the vehicle C according to the embodiment will be described with reference to FIG. 2. FIG. 2 is a schematic diagram illustrating a portion of the vehicle C according to the embodiment.

Vehicle C has four drive wheels 1, four motors 2, a battery 3, and a control device 10.

The four drive wheels 1 include a left front wheel 1FL, a right front wheel 1FR, a left rear wheel 1RL, and a right rear wheel 1RR. When a turning request is made to the vehicle C, for example when the steering wheel 5 is operated by the driver, the left front wheel 1FL and the right front wheel 1FR are steered in the turning direction. In other words, the left front wheel 1FL and the right front wheel 1FR are steered wheels. Note that the steered wheels may also be the left rear wheel 1RL and the right rear wheel 1RR.

The four motors 2 include a motor 2FL for the left front wheel, a motor 2FR for the right front wheel, a motor 2RL for the left rear wheel, and a motor 2RR for the right rear wheel.

Each motor 2 is attached to a different drive wheel 1. Each motor 2 is supplied with power from a battery 3. The torque of each motor 2 is controlled based on a control signal input from a control device 10. Specifically, each motor 2 generates a drive torque or a braking torque based on the control signal. The torque generated by each motor 2 is transmitted to each drive wheel 1.

The control device 10 is a controller that individually controls each motor 2. The control device 10 outputs a control signal to each motor 2 in response to, for example, the amount of operation of the accelerator pedal or the amount of operation of the brake pedal, and controls each motor 2.

For example, when the accelerator pedal is operated to request acceleration of the vehicle C, the control device 10 controls each motor 2 so that a drive torque for accelerating the vehicle C is output from each motor 2 to each drive wheel 1. This causes the vehicle C to accelerate.

For example, when the brake pedal is operated and a request is made to decelerate the vehicle C, the control device 10 controls each motor 2 so that a braking torque that decelerates the vehicle C is output from each motor 2 to each drive wheel 1. This causes the vehicle C to decelerate. Note that when a request is made to decelerate, the vehicle C may also decelerate using a mechanical brake.

For example, when the steering wheel 5 is operated to request the vehicle C to turn, the control device 10 steers the left front wheel 1FL and the right front wheel 1FR as described above. Furthermore, when the vehicle C is skidding while turning, the control device 10 executes skid suppression processing. The skid suppression processing will be described later.

Next, the configuration of the control device 10 according to the embodiment will be described with reference to FIG. 3. FIG. 3 is a block diagram showing the configuration of the control device 10 according to the embodiment. Note that in FIG. 3, only the components necessary to explain the features of this embodiment are shown as functional blocks, and descriptions of general components are omitted.

In other words, each component shown in FIG. 3 is a functional concept, and does not necessarily have to be physically configured as shown. For example, the specific form of distribution and integration of each functional block is not limited to that shown, and all or part of it can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

The control device 10 includes a control unit 11 (motor control unit) and a memory unit 12. The memory unit 12 is configured with a storage device such as a non-volatile memory, data flash, or hard disk drive. The memory unit 12 stores map information, various programs, and the like.

The control unit 11 includes a detection unit 13, a calculation unit 14, a determination unit 15, and a setting unit 16. The control unit 11 includes, for example, a computer having a CPU, a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk drive, an input/output port, and various other circuits.

The computer's CPU functions as the detection unit 13, calculation unit 14, determination unit 15, and setting unit 16 of the control unit 11, for example, by reading and executing a program stored in the ROM.

In addition, at least some or all of the detection unit 13, calculation unit 14, determination unit 15, and setting unit 16 of the control unit 11 can be configured with hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

Signals are input to the detection unit 13 from various sensors provided in the vehicle C. The various sensors include a steering angle sensor 30, a yaw rate sensor 31, a vehicle speed sensor 32, an accelerator opening sensor 33, a brake sensor 34, etc.

The detection unit 13 detects the steering angle θ of the steered wheels based on a signal input from the steering angle sensor 30. The steering angle sensor 30 is provided on each of the left front wheel 1FL and the right front wheel 1FR. That is, the detection unit 13 detects the steering angle θ of the left front wheel 1FL and the steering angle θ of the right front wheel 1FR. Note that, below, the steering angle of the front wheel 1F that is on the inside during a turn may be referred to as "θ1", and the steering angle of the front wheel 1F that is on the outside during a turn may be referred to as "θ2".

The detection unit 13 detects the current yaw rate Yawreal of the vehicle C (hereinafter referred to as the "actual yaw rate Yawreal") based on the signal input from the yaw rate sensor 31.

The detection unit 13 detects the vehicle speed Spd based on a signal input from the vehicle speed sensor 32. The detection unit 13 detects the accelerator opening Accel, which is the amount of depression of the accelerator pedal, based on a signal input from the accelerator opening sensor 33.

The detection unit 13 detects the amount of depression of the brake pedal based on the signal input from the brake sensor 34.

The calculation unit 14 calculates the vehicle required torque Cartrq. The calculation unit 14 calculates the vehicle required torque Cartrq from the map shown in FIG. 4 based on the vehicle speed Spd and the accelerator opening Accel. FIG. 4 shows a map for calculating the vehicle required torque Cartrq. The calculation unit 14 may calculate the vehicle required torque Cartrq from a formula or the like without using a map. In the following description, the calculation using a map may also be a calculation using a formula or the like.

The calculation unit 14 calculates the estimated turning radius Rad. The calculation unit 14 calculates the estimated turning radius Rad using formula (1) based on the wheelbase L, the steering angle θ1 of the front wheel 1F that is on the inside during turning, and the steering angle θ2 of the front wheel 1F that is on the outside during turning.

Rad=(L/sinθ1+L/tanθ2)/2...(1)

The calculation unit 14 calculates the target yaw rate Yawtag. The calculation unit 14 calculates the target yaw rate Yawtag based on the vehicle speed Spd and the estimated turning radius Rad. The calculation unit 14 calculates the target yaw rate Yawtag using equation (2).

Yawtag= ^Spd2 /Rad...(2)

The calculation unit 14 calculates the yaw rate deviation Delyaw. The calculation unit 14 calculates the deviation between the target yaw rate Yawtag and the actual yaw rate Yawreal as the yaw rate deviation Delyaw.

The determination unit 15 determines whether the brake pedal is depressed and the driver operates the brakes. Specifically, the determination unit 15 determines whether the amount of depression of the brake pedal is greater than a predetermined amount of depression set in advance. If the amount of depression of the brake pedal is greater than the predetermined amount of depression, the determination unit 15 determines that the driver operates the brakes. The predetermined amount of depression is the amount of depression that generates a braking force on the vehicle C.

The determination unit 15 determines whether understeer has occurred. Specifically, the determination unit 15 compares the yaw rate deviation Delyaw with the value obtained by multiplying the target yaw rate Yawtag by the understeer determination coefficient Usgain.

The determination unit 15 determines that new understeer has occurred when the yaw rate deviation Delyaw is greater than the target yaw rate Yawtag multiplied by the understeer determination coefficient Usgain. In other words, the determination unit 15 determines that new understeer has occurred when the real yaw rate Yawreal is sufficiently smaller than the target yaw rate Yawtag. The understeer determination coefficient Usgain is a preset value that allows the determination that new understeer has occurred with respect to the turning line of the vehicle C according to the target yaw rate Yawtag.

The determination unit 15 determines that new understeer has not occurred if the yaw rate deviation Delyaw is equal to or less than the value obtained by multiplying the target yaw rate Yawtag by the understeer determination coefficient Usgain. The determination unit 15 determines that understeer has not occurred or is currently occurring if the yaw rate deviation Delyaw is equal to or less than the value obtained by multiplying the target yaw rate Yawtag by the understeer determination coefficient Usgain.

Note that even if understeer is occurring, the determination unit 15 determines that new understeer has occurred if the yaw rate deviation Delyaw becomes greater than the target yaw rate Yawtag multiplied by the understeer determination coefficient Usgain.

The determination unit 15 determines whether or not oversteer has occurred. Specifically, the determination unit 15 compares the yaw rate deviation Delyaw with the value obtained by multiplying the target yaw rate Yawtag by the oversteer determination coefficient Osgain.

The determination unit 15 determines that new oversteer has occurred when the yaw rate deviation Delyaw is smaller than the target yaw rate Yawtag multiplied by the oversteer determination coefficient Osgain. In other words, the determination unit 15 determines that new oversteer has occurred when the real yaw rate Yawreal is sufficiently larger than the target yaw rate Yawtag. The oversteer determination coefficient Osgain is a preset value that allows the determination that new oversteer has occurred with respect to the turning line of the vehicle C according to the target yaw rate Yawtag.

The determination unit 15 determines that new oversteer has not occurred if the yaw rate deviation Delyaw is equal to or greater than the value obtained by multiplying the target yaw rate Yawtag by the oversteer determination coefficient Osgain. The determination unit 15 determines that oversteer has not occurred or is currently occurring if the yaw rate deviation Delyaw is equal to or greater than the value obtained by multiplying the target yaw rate Yawtag by the oversteer determination coefficient Osgain.

Note that even if oversteer is occurring, the determination unit 15 determines that new oversteer has occurred if the yaw rate deviation Delyaw becomes smaller than the target yaw rate Yawtag multiplied by the oversteer determination coefficient Osgain.

The determination unit 15 determines whether or not understeer is occurring. Specifically, the determination unit 15 determines whether or not the understeer flag Usfrg is "ON". If the understeer flag Usfrg is "ON", the determination unit 15 determines that understeer is occurring.

The determination unit 15 determines whether or not oversteer is occurring. Specifically, the determination unit 15 determines whether or not the oversteer flag Osfrg is "ON". If the oversteer flag Osfrg is "ON", the determination unit 15 determines that oversteer is occurring.

When understeer is occurring, the determination unit 15 determines whether the understeer return condition is satisfied. Specifically, the determination unit 15 determines that the understeer return condition is satisfied when at least one of the following is satisfied: the yaw rate deviation Delyaw is equal to or less than a predetermined threshold value, and a brake operation is performed. The predetermined threshold value is a value obtained by multiplying the target yaw rate Yawtag by the understeer convergence determination coefficient Usfingain. The understeer convergence determination coefficient Usfingain is a preset value, and is a value by which it is possible to determine that understeer has converged. When understeer occurs and the understeer control described below is being executed, the determination unit 15 determines whether to end the understeer control based on the deviation between the target yaw rate Yawtag and the actual yaw rate Yawreal.

When oversteer occurs, the judgment unit 15 judges whether the oversteer return condition is satisfied. Specifically, the judgment unit 15 judges that the oversteer return condition is satisfied when at least one of the following is satisfied: when the sign of the actual yaw rate Yawreal is reversed, and when a brake operation is performed. The sign of the actual yaw rate Yawreal is a sign indicating a plus or minus in the sensor value of the yaw rate sensor 31. The reversal of the sign of the actual yaw rate Yawreal indicates that the direction in which the actual yaw rate Yawreal is generated is reversed. For example, the judgment unit 15 judges that the sign of the actual yaw rate Yawreal has been reversed when the multiplication value of the actual yaw rate Yawreal detected based on the signal output from the yaw rate sensor 31 and the actual yaw rate Yawreal detected a predetermined time ago (for example, the previous detection) is a negative value. When oversteer occurs and the oversteer control described below is being executed, the determination unit 15 determines whether or not to end the oversteer control based on the direction in which the actual yaw rate Yawreal occurs.

When oversteer occurs, the determination unit 15 determines whether or not a counter operation has been performed by the driver. A counter operation is when the steering wheel 5, which has been operated to turn the vehicle C in the turning direction, is operated to rotate in the opposite direction. The determination unit 15 determines that a counter operation has been performed when the direction of the actual yaw rate Yawreal and the direction of the steering angle θ of the front wheels 1F are opposite to each other.

For example, in the example shown in FIG. 1B, when the actual yaw rate Yawreal indicates a right-turning state and the steering angle θ of the front wheels 1F is steering to the left, the determination unit 15 determines that a counter operation has been performed.

When the determination unit 15 determines that understeer has occurred, the setting unit 16 sets the understeer flag Usfrg to "ON". Note that when setting the understeer flag Usfrg to "ON", if the oversteer flag Osfrg is "ON", the setting unit 16 sets the oversteer flag Osfrg to "OFF".

When the determination unit 15 determines that oversteer has occurred, the setting unit 16 sets the oversteer flag Osfrg to "ON". Note that when setting the oversteer flag Osfrg to "ON", if the understeer flag Usfrg is "ON", the setting unit 16 sets the understeer flag Usfrg to "OFF".

When the determination unit 15 determines that the understeer return condition is satisfied while understeer is occurring, the setting unit 16 sets the understeer flag Usfrg to "OFF." When the determination unit 15 determines that the oversteer return condition is satisfied while oversteer is occurring, the setting unit 16 sets the oversteer flag Osfrg to "OFF."

The setting unit 16 sets the torque to be generated by each motor 2. When understeer or oversteer is not occurring, specifically when the understeer flag Usfrg is "OFF" and the oversteer flag Osfrg is "OFF", the setting unit 16 performs normal control. When understeer or oversteer is not occurring, the setting unit 16 sets the torque at each motor 2 to normal torque. The setting unit 16 divides the vehicle required torque Cartrq by the number of motors 2 and sets the divided value as the normal torque at each motor 2. For example, the setting unit 16 sets the torque obtained by dividing the vehicle required torque Cartrq into four equal parts as the normal torque at each motor 2. The normal torque is a positive torque and is a drive torque.

For example, if the driver brakes when understeer or oversteer is occurring, the setting unit 16 performs normal control. In other words, if the driver brakes when understeer or oversteer is occurring, the setting unit 16 returns to normal control. The setting unit 16 sets the normal torque so that the vehicle required torque is generated by the four drive wheels 1.

When understeer occurs, the setting unit 16 performs understeer control. When understeer occurs, the setting unit 16 sets the torque in each motor 2 to understeer torque. The setting unit 16 sets the braking torque and driving torque so that the yaw rate deviation Delyaw becomes small.

Specifically, the setting unit 16 calculates the braking torque from the map shown in FIG. 5 based on the yaw rate deviation Delyaw and the vehicle speed Spd, and sets the calculated braking torque as the understeer torque of the motor 2 that rotates the inner rear wheel 1R in relation to the turn. FIG. 5 is a map for calculating the braking torque to be generated when understeer is occurring.

The setting unit 16 also calculates the drive torque from the map shown in FIG. 6 based on the yaw rate deviation Delyaw and the vehicle speed Spd, and sets the calculated drive torque as the understeer torque in the motor 2 that rotates the outer front wheel 1F with respect to the turn. FIG. 6 is a map for calculating the drive torque to be generated when understeer is occurring.

The setting unit 16 sets the braking torque and driving torque based on the vehicle speed Spd. As a result, for example, when the vehicle speed Spd is high, the braking torque and driving torque are generated so as to quickly return to the predetermined turning course. Also, for example, when the vehicle speed Spd is low, the braking torque and driving torque are generated so as to prevent a sudden change in the passenger's posture. In other words, the control device 10 can generate the braking torque and driving torque according to the traveling state of the vehicle C.

When the vehicle C has more than four drive wheels 1 and there are multiple drive wheels 1 to which braking torque is applied, the setting unit 16 divides the braking torque equally and sets the braking torque at each drive wheel 1 so that the braking torque is applied evenly to the multiple drive wheels 1. When there are multiple drive wheels 1 to which driving torque is applied, the setting unit 16 divides the driving torque equally and sets the driving torque at each drive wheel 1 so that the driving torque is applied evenly to the multiple drive wheels 1. When applying braking torque or driving torque to multiple drive wheels 1, the setting unit 16 may distribute the braking torque to each drive wheel 1 or the driving torque to each drive wheel 1 so that the proportion of drive wheels 1 with a higher application effect is larger. For example, when applying driving torque to multiple left front wheels 1FL, the setting unit 16 sets the driving torque at each left front wheel 1FL so that the proportion of driving torque applied to the wheel that is further left and further forward among the multiple left front wheels 1FL is larger than that of the other left front wheels 1FL.

In addition, when understeer occurs, the setting unit 16 sets the torque of the motor 2 that rotates the inner front wheel 1F relative to the turn and the motor 2 that rotates the outer rear wheel 1R relative to the turn to zero. In other words, the understeer torque of the motor 2 that rotates the inner front wheel 1F relative to the turn and the motor 2 that rotates the outer rear wheel 1R relative to the turn is zero. Therefore, no torque is transmitted from the motor 2 to the inner front wheel 1F relative to the turn and the outer rear wheel 1R relative to the turn.

When understeer occurs, the torque of the motor 2 that rotates the inner front wheel 1F relative to the turn and the motor 2 that rotates the outer rear wheel 1R relative to the turn are set to zero. Therefore, when understeer occurs, in order to suppress a sudden change in the vehicle speed Spd of the vehicle C, the drive torque of the motor 2 that rotates the outer front wheel 1F relative to the turn is increased.

For example, when the vehicle C is turning right and understeer occurs, the setting unit 16 generates a braking torque in the right rear wheel motor 2RR that rotates the right rear wheel 1RR, and increases the drive torque in the left front wheel motor 2FL that rotates the left front wheel 1FL. The setting unit 16 also sets the torque in the left rear wheel motor 2RL that rotates the left rear wheel 1RL and the right front wheel motor 2FR that rotates the right front wheel 1FR to zero.

When the vehicle C is turning left and understeer occurs, the setting unit 16 generates a braking torque in the left rear wheel motor 2RL that rotates the left rear wheel 1RL, and increases the drive torque in the right front wheel motor 2FR that rotates the right front wheel 1FR. The setting unit 16 also sets the torque in the right rear wheel motor 2RR that rotates the right rear wheel 1RR and the left front wheel motor 2FL that rotates the left front wheel 1FL to zero.

The setting unit 16 may generate a slight braking torque without setting the torque of the motor 2 that rotates the inner front wheel 1F for turning to zero. The setting unit 16 may also generate a slight driving torque without setting the torque of the motor 2 that rotates the outer rear wheel 1R for turning to zero. In other words, when understeer occurs, the setting unit 16 reduces the torque of the motor 2 that rotates the inner front wheel 1F for turning and the torque of the motor 2 that rotates the outer rear wheel 1R for turning to less than the normal torque. In this case, it is preferable for the setting unit 16 to set each torque so that the increase in torque and the decrease in torque net each other to zero.

When the total torque of the driving torque and the braking torque calculated as the understeer torque is greater than the vehicle required torque Cartrq, the setting unit 16 limits the driving torque. That is, the setting unit 16 sets the braking torque to be given priority over the driving torque. Specifically, the setting unit 16 limits the driving torque so that the total torque of the driving torque and the braking torque becomes the vehicle required torque Cartrq without changing the braking torque. That is, when understeer occurs, the upper limit torque of the driving torque of the motor 2 that rotates the outer front wheel 1F with respect to the turn is the torque obtained by adding the braking torque to the vehicle required torque Cartrq.

When oversteer occurs and no counter operation is performed, the setting unit 16 performs oversteer control. When oversteer occurs, the setting unit 16 sets the torque of each motor 2 to the oversteer torque.

Specifically, the setting unit 16 sets a predetermined braking torque as the oversteer torque in the motor 2 that rotates the outer front wheel 1F with respect to the turn. The setting unit 16 also sets a predetermined drive torque as the oversteer torque in the motor 2 that rotates the inner rear wheel 1R with respect to the turn. The predetermined braking torque and the predetermined drive torque are each a value that is set in advance. The predetermined braking torque and the predetermined drive torque are values that are set so that the sign of the real yaw rate Yawreal is reversed and the vehicle C returns to the predetermined turning line. The predetermined braking torque and the predetermined drive torque may be calculated from a map or the like based on the yaw rate deviation Delyaw and the vehicle speed Spd.

In addition, when oversteer occurs and no counter operation is being performed, the setting unit 16 sets the torque of the motor 2 that rotates the inner front wheel 1F relative to the turn and the motor 2 that rotates the outer rear wheel 1R relative to the turn to zero. In other words, the oversteer torque of the motor 2 that rotates the inner front wheel 1F relative to the turn and the motor 2 that rotates the outer rear wheel 1R relative to the turn is zero. Therefore, no torque is transmitted from the motor 2 to the inner front wheel 1F relative to the turn and the outer rear wheel 1R relative to the turn.

When oversteer occurs and no counter operation is being performed, the torque of the motor 2 that rotates the inner front wheel 1F relative to the turn and the motor 2 that rotates the outer rear wheel 1R relative to the turn are set to zero. Therefore, when oversteer occurs and no counter operation is being performed, the drive torque (oversteer torque) of the motor 2 that rotates the inner rear wheel 1R relative to the turn is increased to suppress a sudden change in vehicle speed Spd of the vehicle C.

For example, when the vehicle C is turning right, oversteer occurs, and a counter operation is not being performed, the setting unit 16 generates a braking torque in the left front wheel motor 2FL that rotates the left front wheel 1FL, and increases the drive torque in the right rear wheel motor 2RR that rotates the right rear wheel 1RR. The setting unit 16 also sets the torque in the right front wheel motor 2FR that rotates the right front wheel 1FR and the left rear wheel motor 2RL that rotates the left rear wheel 1RL to zero.

When the vehicle C is turning left, oversteer occurs, and a counter operation is not being performed, the setting unit 16 generates a braking torque in the right front wheel motor 2FR that rotates the right front wheel 1FR, and increases the drive torque in the left rear wheel motor 2RL that rotates the left rear wheel 1RL. The setting unit 16 also sets the torque in the left front wheel motor 2FL that rotates the left front wheel 1FL and the right rear wheel motor 2RR that rotates the right rear wheel 1RR to zero.

The setting unit 16 may generate a slight driving torque without setting the torque of the motor 2 that rotates the inner front wheel 1F for the turn to zero. The setting unit 16 may also generate a braking torque without setting the torque of the motor 2 that rotates the outer rear wheel 1R for the turn to zero. In other words, when oversteer occurs and a counter operation is not being performed, the setting unit 16 reduces the torque of the motor 2 that rotates the inner front wheel 1F for the turn and the torque of the motor 2 that rotates the outer rear wheel 1R for the turn to less than the normal torque. In this case, it is preferable for the setting unit 16 to set each torque so that the increase in torque and the decrease in torque net each other to zero.

The setting unit 16 limits the drive torque when the total torque of the predetermined braking torque and the predetermined braking torque is greater than the vehicle required torque Cartrq. That is, the setting unit 16 sets the braking torque to be given priority over the drive torque. In this case, the setting unit 16 limits the drive torque so that the total torque of the predetermined braking torque and the predetermined drive torque becomes the vehicle required torque Cartrq without changing the predetermined braking torque. That is, when oversteer occurs and a counter operation is not performed, the upper limit torque of the drive torque of the motor 2 that rotates the inner rear wheel 1R relative to the turn becomes the torque obtained by adding the predetermined braking torque to the vehicle required torque Cartrq.

When oversteer occurs and a counter operation is performed, the setting unit 16 performs control during the counter operation. The setting unit 16 sets the torque of each motor 2 to the counter torque.

Specifically, the setting unit 16 sets the torque of each motor 2 so that the vehicle required torque Cartrq is generated by the motor 2 that rotates the front wheel 1F, which is the steered wheel. For example, the setting unit 16 sets a torque of 1/2 of the vehicle required torque Cartrq as a counter torque for the left front wheel motor 2FL that rotates the left front wheel 1FL and the right front wheel motor 2FR that rotates the right front wheel 1FR. The setting unit 16 also sets the torque of the left front wheel motor 2FL that rotates the left rear wheel 1RL and the right rear wheel motor 2RR that rotates the right rear wheel 1RR to zero. In other words, when oversteer occurs and a counter operation is performed, the setting unit 16 reduces the braking torque of the motor 2 that rotates the outer front wheel 1F relative to the turn. In addition, when oversteer occurs and a counter operation is performed, the setting unit 16 preferentially generates a drive torque by the motor 2 that rotates the front wheels 1F, which are the steered wheels.

A control signal for controlling each motor 2 is output to each motor so that the torque set by the setting unit 16 is generated in each motor 2. This controls the torque generated in each motor 2.

Next, the skid suppression processing according to the embodiment will be described with reference to FIG. 7A and FIG. 7B. FIG. 7A and FIG. 7B are flowcharts explaining the skid suppression processing according to the embodiment.

The control device 10 calculates the vehicle required torque Cartrq (S100). The control device 10 calculates the vehicle required torque Cartrq based on the vehicle speed Spd and the accelerator opening Accel.

The control device 10 calculates the estimated turning radius Rad (S101) and calculates the target yaw rate Yawtag (S102). The control device 10 calculates the target yaw rate Yawtag based on the vehicle speed Spd and the estimated turning radius Rad. The control device 10 detects the actual yaw rate Yawreal (S103).

The control device 10 calculates the yaw rate deviation Delyaw based on the target yaw rate Yawtag and the actual yaw rate Yawreal (S104), and determines whether new understeer has occurred (S105). The control device 10 determines that new understeer has occurred if the yaw rate deviation Delyaw is greater than the value obtained by multiplying the target yaw rate Yawtag by the understeer determination coefficient Usgain.

If new understeer has occurred (S105: Yes), the control device 10 sets the understeer flag Usfrg to "ON" (S106).

If new understeer has not occurred (S105: No), the control device 10 determines whether new oversteer has occurred (S107). The control device 10 determines that new understeer has occurred if the yaw rate deviation Delyaw is smaller than the target yaw rate Yawtag multiplied by the oversteer determination coefficient Osgain.

If new oversteer has occurred (S107: Yes), the control device 10 sets the oversteer flag Osfrg to "ON" (S108). If new oversteer has not occurred (S107: No), the control device 10 determines that new understeer and new oversteer have not occurred, and proceeds to step S109 to continue processing.

The control device 10 determines whether or not understeer is occurring (S109). Specifically, the control device 10 determines whether or not the understeer flag Usfrg is "ON". If the understeer flag Usfrg is "ON" and understeer is occurring (S109: Yes), the control device 10 determines whether or not the understeer return condition is satisfied (S110).

When the understeer return condition is satisfied (S110: Yes), the control device 10 sets the understeer flag Usfrg to "OFF" (S111) and performs normal control (S112). For example, the control device 10 sets the torque obtained by dividing the vehicle required torque Cartrq into four equal parts as the normal torque. For example, when the yaw rate deviation Delyaw, which is the deviation between the target yaw rate Yawtag and the actual yaw rate Yawreal, falls below a predetermined threshold, the control device 10 ends the understeer control and performs normal control. When the driver depresses the brake pedal while understeer is occurring, the control device 10 ends the understeer control and performs normal control.

When the understeer return condition is not satisfied (S110: No), the control device 10 performs understeer control (S113). Specifically, the control device 10 sets the understeer torque so that a braking torque is generated in the motor 2 that rotates the inner rear wheel 1R for turning, and the driving torque in the motor 2 that rotates the outer front wheel 1F for turning increases. The control device 10 also sets the understeer torque so that the torque in the motor 2 that rotates the outer rear wheel 1R for turning and the torque in the motor 2 that rotates the inner front wheel 1F for turning become zero.

If the control device 10 is not determining whether understeer is occurring (S109: No), it determines whether oversteer is occurring (S114). Specifically, the control device 10 determines whether the oversteer flag Osfrg is "ON" or not. If the oversteer flag Osfrg is "ON" and oversteer is occurring (S114: Yes), the control device 10 determines whether the oversteer return condition is satisfied (S115).

When the oversteer recovery condition is met (S115: Yes), the control device 10 sets the oversteer flag Osfrg to "OFF" (S116) and performs normal control (S112). For example, when the control device 10 determines that the direction of the actual yaw rate Yawreal has reversed, it ends the oversteer control and performs normal control. When the driver depresses the brake pedal while oversteer is occurring, the control device 10 ends the oversteer control and performs normal control.

When the oversteer recovery condition is not satisfied (S115: No), the control device 10 judges whether or not a counter operation has been performed (S117). When a counter operation has been performed (S117: Yes), the control device 10 performs counter operation control (S118). When the control device 10 is performing oversteer control and the driver has performed a counter operation, the control device 10 performs counter operation control. Specifically, the control device 10 sets the counter torque so that a drive torque that is 1/2 of the vehicle required torque Cartrq is generated at each of the front wheels 1F.

When a counter operation is not being performed (S117: No), the control device 10 performs oversteer control (S119). Specifically, the control device 10 sets the oversteer torque so that a braking torque is generated in the motor 2 that rotates the outer front wheel 1F for the turn, and the driving torque in the motor 2 that rotates the inner rear wheel 1R for the turn increases. The control device 10 also sets the oversteer torque so that the torque in the motor 2 that rotates the inner front wheel 1F for the turn and the torque in the motor 2 that rotates the outer rear wheel 1R for the turn become zero.

If oversteer is not occurring (S114: No), the control device 10 performs normal control (S112) because neither understeer nor oversteer is occurring.

The order of the skid suppression process is not limited to the above-mentioned order. For example, the control device 10 may calculate the estimated turning radius Rad before calculating the vehicle required torque Cartrq. Also, for example, the control device 10 may determine whether oversteer has occurred before determining whether understeer has occurred.

Next, the effects of the control device 10 according to the embodiment will be described.

The control device 10 controls a vehicle C in which four or more drive wheels 1 are rotated by different motors 2. The control device 10 includes a control unit 11 that controls the torque generated by the motors 2. When oversteer occurs when the vehicle is turning, the control unit 11 performs oversteer control by generating a braking torque in the motor 2 that rotates the outer front wheel 1F relative to the turn, and increasing the drive torque in the motor 2 that rotates the inner rear wheel 1R relative to the turn.

As a result, if oversteer occurs when the vehicle C is turning, the control device 10 can quickly return the vehicle C to the specified turning course. The control device 10 can also return the vehicle C to the specified turning course by adjusting the torque in the motor 2. Therefore, for example, if oversteer occurs when the vehicle C is turning, the vehicle C can be returned to the specified turning course without using a braking system that individually adjusts the hydraulic pressure of the mechanical brakes provided on each drive wheel 1. Therefore, the control device 10 can return the vehicle C to the specified turning course by adjusting the torque in each motor 2 without using a braking system that individually adjusts the hydraulic pressure of the mechanical brakes.

When the control unit 11 determines that the sign of the actual yaw rate Yawreal of the vehicle C has reversed, it ends the oversteer control.

This allows the control device 10 to suppress the generation of excessive yaw moment required to return the vehicle to the specified turning course. As a result, the control device 10 can stabilize the behavior of the vehicle C and stabilize the driving performance of the vehicle C.

When the control unit 11 is performing oversteer control, if the driver performs a counter operation, it performs counter operation control to reduce the braking torque.

As a result, when oversteer occurs and the driver performs a counter operation, the control device 10 can suppress the generation of excessive yaw moment to return the vehicle to the specified turning course. Therefore, the control device 10 can stabilize the behavior of the vehicle C and stabilize the driving performance of the vehicle C. Therefore, the control device 10 can improve safety when oversteer occurs and the driver performs a counter operation.

When controlling during counter operation, the control unit 11 gives priority to generating drive torque by the motor 2 that rotates the front wheel 1F.

As a result, during counter operation control, the control device 10 can generate a drive torque on the front wheels 1F, which are the steered wheels, and return the vehicle C to a specified turning course in response to the driver's counter operation.

The control unit 11 determines whether to end the oversteer control based on the direction in which the actual yaw rate Yawreal occurs.

This allows the control device 10 to terminate oversteer control at the appropriate time, and suppresses the generation of excessive yaw moment required to return to the specified turning course.

The control unit 11 determines whether to end the understeer control based on the deviation between the target yaw rate Yawtag and the actual yaw rate Yawreal.

This allows the control device 10 to terminate understeer control at an appropriate time, stabilizing the behavior of the vehicle C when returning to the specified turning course and stabilizing the driving performance of the vehicle C.

The control device 10 controls a vehicle C in which four or more drive wheels 1 are rotated by different motors 2. The control device 10 controls the torque generated by the motors 2. When understeer occurs when the vehicle is turning, the control unit 11 performs understeer control by generating a braking torque in the motor 2 that rotates the inner rear wheel 1R relative to the turn and increasing the drive torque in the motor 2 that rotates the outer front wheel 1F relative to the turn.

As a result, if understeer occurs when vehicle C is turning, the control device 10 can quickly return vehicle C to the specified turning course. In addition, the control device 10 can return vehicle C to the specified turning course by adjusting the torque in the motor 2. The control device 10 can return vehicle C to the specified turning course by adjusting the torque in each motor 2 without using a braking system that individually adjusts the hydraulic pressure of the mechanical brakes.

When the control unit 11 determines that the yaw rate deviation Delyaw between the target yaw rate Yawtag of vehicle C and the actual yaw rate Yawreal of vehicle C is equal to or less than a predetermined threshold, it ends the understeer control.

This allows the control device 10 to stabilize the behavior of the vehicle C when returning to the specified turning course, thereby stabilizing the driving performance of the vehicle C.

When the control device 10 generates a braking torque due to the occurrence of at least one of oversteer and understeer during vehicle turning, the control device 10 adjusts the driving torque so that the sum of the braking torque and the driving torque does not exceed the vehicle required torque Cartrq.

This allows the control device 10 to suppress the generation of excessive drive torque relative to the vehicle required torque Cartrq. Therefore, the control device 10 can suppress the generation of a sudden increase in vehicle speed Spd when returning to a specified turning course, and stabilize the posture of the passengers.

When the driver depresses the brake pedal while at least one of oversteer and understeer is occurring during vehicle turning, the control device 10 returns to normal control.

This makes it possible to suppress the generation of yaw moment that would result in excessive return to a predetermined turning course when the driver depresses the brake pedal. Therefore, the control device 10 can stabilize the behavior of the vehicle C and stabilize the driving performance of the vehicle C. Therefore, the control device 10 can improve safety when the driver depresses the brake pedal.

In the above embodiment, the skid suppression control is performed after skid occurs. However, when the vehicle C turns, skid prevention control may be performed to prevent skid from occurring. That is, the control device 10 may perform skid prevention control, and then, when skid occurs, perform skid suppression control. In addition, part of the skid suppression control may be applied to the vehicle C that performs autonomous driving.

The vehicle C in the above embodiment may have an electric brake system. In a vehicle C having an electric brake system, for example, control for generating a braking torque is executed by the electric brake system. The above-mentioned skid suppression control is effective even in a vehicle C that does not have an electric brake system. Therefore, by executing skid suppression control in a vehicle C that does not have an electric brake system, it is possible to reduce costs by eliminating the electric brake system.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

1 Drive wheel 2 Motor 3 Battery 5 Steering 10 Control device (vehicle control device)
11 Control unit (motor control unit)
30 steering angle sensor 31 yaw rate sensor 32 vehicle speed sensor 33 accelerator opening sensor 34 brake sensor

Claims (13)

A vehicle control device for controlling a vehicle in which four or more drive wheels are rotated by different motors,
a motor control unit for controlling a torque generated by the motor,
The motor control unit includes :
When oversteer occurs during a turn of the vehicle , an oversteer control is performed to generate a braking torque in the motor that rotates the outer front wheel relative to the turn and to increase the drive torque in the motor that rotates the inner rear wheel relative to the turn .
When it is determined that the direction of the actual yaw rate of the vehicle is reversed, the oversteer control is terminated.
A vehicle control device comprising: A vehicle control device for controlling a vehicle in which four or more drive wheels are rotated by different motors,
a motor control unit for controlling a torque generated by the motor,
The motor control unit includes :
When oversteer occurs during a turn of the vehicle , an oversteer control is performed to generate a braking torque in the motor that rotates the outer front wheel relative to the turn and to increase the drive torque in the motor that rotates the inner rear wheel relative to the turn .
When the driver performs a counter operation while the oversteer control is being performed, the braking torque is reduced by performing a counter operation control.
A vehicle control device comprising: The vehicle control device according to claim 2 , wherein the motor control unit, during the counter operation control, preferentially generates a drive torque by a motor that rotates a steered wheel among the drive wheels. A vehicle control device for controlling a vehicle in which four or more drive wheels are rotated by different motors,
a motor control unit for controlling a torque generated by the motor,
The motor control unit includes :
When oversteer occurs during a turn of the vehicle , an oversteer control is performed to generate a braking torque in the motor that rotates the outer front wheel relative to the turn and to increase the drive torque in the motor that rotates the inner rear wheel relative to the turn .
If the driver depresses the brake pedal while oversteer is occurring, normal control is restored.
A vehicle control device comprising: The vehicle control device according to any one of claims 1 to 4, characterized in that, when understeer occurs during a turn of the vehicle, the motor control unit performs understeer control by generating a braking torque in a motor that rotates an inner rear wheel relative to the turn and increasing a driving torque in a motor that rotates an outer front wheel relative to the turn. 6. The vehicle control device according to claim 5, wherein the motor control unit determines whether or not to terminate the oversteer control based on a direction in which an actual yaw rate of the vehicle is occurring, and determines whether or not to terminate the understeer control based on a deviation between a target yaw rate of the vehicle and the actual yaw rate of the vehicle. A vehicle control device for controlling a vehicle in which four or more drive wheels are rotated by different motors,
a motor control unit for controlling a torque generated by the motor,
The motor control unit includes :
When understeer occurs during a turn of the vehicle , a braking torque is generated in the motor that rotates the inner rear wheel with respect to the turn, and a driving torque is increased in the motor that rotates the outer front wheel with respect to the turn, thereby performing an understeer time control.
When it is determined that the deviation between the target yaw rate of the vehicle and the actual yaw rate of the vehicle is equal to or smaller than a predetermined threshold, the understeer control is terminated.
A vehicle control device comprising: A vehicle control device for controlling a vehicle in which four or more drive wheels are rotated by different motors,
a motor control unit for controlling a torque generated by the motor,
The motor control unit includes :
When understeer occurs during a turn of the vehicle , a braking torque is generated in the motor that rotates the inner rear wheel with respect to the turn, and a driving torque is increased in the motor that rotates the outer front wheel with respect to the turn, thereby performing an understeer time control.
If the driver depresses the brake pedal while understeer is occurring, normal control is restored.
A vehicle control device comprising: A method for controlling a vehicle in which four or more drive wheels are rotated by different motors, comprising the steps of:
When oversteer occurs during turning of the vehicle, a braking torque is generated in a motor that rotates an outer front wheel relative to the turning, and a driving torque in a motor that rotates an inner rear wheel relative to the turning is increased ;
When it is determined that the direction of the actual yaw rate of the vehicle is reversed, the generation of the braking torque is terminated and the increase of the driving torque is terminated.
A control method comprising: A method for controlling a vehicle in which four or more drive wheels are rotated by different motors, comprising the steps of:
When oversteer occurs during turning of the vehicle, a braking torque is generated in a motor that rotates an outer front wheel relative to the turning, and a driving torque in a motor that rotates an inner rear wheel relative to the turning is increased ;
When the braking torque is generated and the driving torque is increased, if a counter operation is performed by the driver, the braking torque is decreased.
A control method comprising: A method for controlling a vehicle in which four or more drive wheels are rotated by different motors, comprising the steps of:
When oversteer occurs during turning of the vehicle, a braking torque is generated in a motor that rotates an outer front wheel relative to the turning, and a driving torque in a motor that rotates an inner rear wheel relative to the turning is increased;
If the driver depresses the brake pedal while oversteer is occurring, normal control is restored.
A control method comprising: A method for controlling a vehicle in which four or more drive wheels are rotated by different motors, comprising the steps of:
When understeer occurs during turning of the vehicle, a braking torque is generated in a motor that rotates the inner rear wheel with respect to the turning, and a driving torque in a motor that rotates the outer front wheel with respect to the turning is increased ;
When it is determined that the deviation between the target yaw rate of the vehicle and the actual yaw rate of the vehicle is equal to or smaller than a predetermined threshold value, the generation of the braking torque is terminated and the increase of the drive torque is terminated.
A control method comprising: A method for controlling a vehicle in which four or more drive wheels are rotated by different motors, comprising the steps of:
When understeer occurs during turning of the vehicle, a braking torque is generated in a motor that rotates the inner rear wheel with respect to the turning, and a driving torque in a motor that rotates the outer front wheel with respect to the turning is increased ;
When the driver depresses the brake pedal while the understeer is occurring, the control returns to normal.
A control method comprising:

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