JP7523367B2 - Vehicle control device and control method - Google Patents

Description

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

Conventionally, a vehicle control device is known that controls the torque of a motor that rotates the left and right wheels depending on the load on the left and right wheels when turning (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 05-328542

However, with the above vehicle control system, there is a risk of skidding occurring when turning with the brake pedal depressed and the load on the front wheels increased.

The present invention has been made in consideration of the above, and aims to provide a vehicle control device and control method that prevents skidding during turns.

A vehicle control device according to one aspect of the embodiment controls a vehicle in which multiple 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 the vehicle is in a front-loaded state in which the load on the front wheels is greater than the load on the other drive wheels and the vehicle is turning, the motor control unit performs a first control that sets the torque in the motor that rotates the front wheels to be large.

According to one aspect of the embodiment, it is possible to prevent skidding during turns.

FIG. 1A is a schematic diagram showing a vehicle in a turning state. FIG. 1B is a schematic diagram illustrating the vehicle in a state where the driving force at the front wheels is increased relative to the turning state of FIG. 1A. 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. 5A is a flowchart illustrating the skid prevention control according to this embodiment. FIG. 5B is a flowchart illustrating the skid prevention control according to this 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.

A control method according to the embodiment will be described. 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 multiple drive wheels 1. For example, the vehicle C has four drive wheels 1. The vehicle C rotates each drive wheel 1 by a different motor 2. The motors 2 are so-called in-wheel motors.

In the following, the front drive wheels 1 of vehicle C may be referred to as "front wheels 1F" and the rear drive wheels 1 of vehicle C may be referred to as "rear wheels 1R."

The front wheels 1F of the vehicle C are steered wheels, and when a turning request is made to the vehicle C, for example when the steering wheel 5 (see FIG. 2) is operated by the driver, the front wheels 1F are steered in the turning direction.

At that time, as shown in FIG. 1A, the cornering force CF at the front wheel 1F and the sum of the component F2 perpendicular to the forward direction of the front wheel of the driving force F1 at the front wheel 1F are in a balanced state with the centrifugal force F3 at the front wheel 1F when the front wheel 1F is turning. The cornering force CF is a force that acts perpendicular to the forward direction T1 of the front wheel 1F and toward the center of the turning circle, among the forces generated by the elastic deformation of the front wheel 1F at the ground contact portion of the front wheel 1F (driving wheel 1). FIG. 1A is a schematic diagram showing a vehicle C in a turning state. Note that in FIG. 1A, the cornering force CF is shifted for the sake of explanation.

The cornering force CF at the front wheel 1F is calculated using formula (1) based on the cornering coefficient Cc, the weight m on the front wheel 1F, and the slip angle SA. The cornering coefficient Cc is a predetermined constant. The slip angle SA is the angle between the direction in which the driving force F1 acts on the front wheel 1F and the traveling direction T1 of the front wheel 1F.

CF=Cc×m×SA...(1)

The cornering force CF increases as the slip angle SA increases. Note that the cornering force CF has a maximum cornering force CFmax and will never exceed this maximum cornering force CFmax. The maximum cornering force CFmax at the front wheel 1F is calculated using formula (2) based on the friction coefficient μ, the weight m applied to the front wheel 1F, and the gravitational acceleration g.

CFmax=μ×m×g...(2)

For example, when the centrifugal force F3 at the front wheel 1F becomes large, the traveling direction T1 of the front wheel 1F shown in FIG. 1A moves counterclockwise. As a result, the slip angle SA becomes large, and the cornering force CF also becomes large. When the cornering force CF becomes the maximum cornering force CFmax, the cornering force CF will not become larger than the maximum cornering force CFmax. Therefore, when the centrifugal force F3 at the front wheel 1F becomes larger than the sum of the maximum cornering force CFmax and the vertical component F2 of the driving force F1 in the front wheel traveling direction, the front wheel 1F of the vehicle C will skid and will enter an understeer state.

For example, when the vehicle C turns after the driver depresses the brake pedal, the vehicle C is in a front-loaded state. A front-loaded state is a state in which the load on the front wheels 1F is greater than the load on the other driving wheels 1, for example, the rear wheels 1R. When the load on the front wheels 1F increases due to the front load, the centrifugal force F3 applied to the front wheels 1F increases. Also, when the vehicle C turns, the front wheels 1F, which are the steered wheels, are first steered in response to, for example, the operation of the steering wheel 5. Therefore, in the turning start state immediately after the start of turning, only the front wheels 1F are transitioning to a turning motion. When the rear wheels 1R are not in a turning state and only the front wheels 1F are in a turning state, the centrifugal force F3 is applied only to the front wheels 1F.

When the vehicle C turns in a front-loaded state, particularly when the vehicle is in a front-loaded state due to braking or the like and is in a turning start state, the centrifugal force F3 at the front wheels 1F becomes relatively large. This makes it easy for the front wheels 1F to skid and become understeered. Note that even if the vehicle C is in either a front-loaded state or a turning start state, the centrifugal force F3 at the front wheels 1F becomes large.

When the vehicle C is in a front-loaded state, the control device 10 increases the driving force F1 at the front wheel 1F as shown by the solid arrow in FIG. 1B. FIG. 1B is a schematic diagram illustrating the vehicle C in a state in which the driving force F1 at the front wheel 1F has been increased relative to the turning state in FIG. 1A. In FIG. 1B, the increased driving force F1 and the vertical component F2 of the increased driving force F1 in the front wheel traveling direction are shown by solid lines. In FIG. 1B, for the sake of explanation, the driving force F1 at the front wheel 1F in FIG. 1A and the vertical component F2 in the front wheel traveling direction are shown by dashed lines. Also, in FIG. 1B, the cornering force CF, the driving force F1 in FIG. 1A, and the vertical component F2 in the front wheel traveling direction are shifted for the sake of explanation.

For example, the control device 10 increases the driving force F1 at the front wheels 1F by increasing the driving torque at the motor 2 that rotates the front wheels 1F (distributing more driving torque to the front wheels 1F). Driving torque is torque that generates a driving force at the driving wheels 1. Driving torque is positive torque. Note that in the following, torque that generates a braking force at the driving wheels 1 may be referred to as braking torque. Braking torque is negative torque. The control device 10 sets the driving torque at the motor 2 that rotates the front wheels 1F to be larger the greater the load on the front wheels 1F compared to the rear wheels 1R.

By increasing the driving torque of the motor 2 that rotates the front wheels 1F, the control device 10 can increase the component F2 perpendicular to the front wheel traveling direction of the driving force F1, and can suppress the increase in the cornering force CF (slip angle SA). Therefore, the control device 10 can ensure a margin until the cornering force CF becomes the maximum cornering force CFmax. Therefore, the control device 10 can prevent the vehicle C from skidding. For example, the control device 10 can prevent the vehicle C from understeer.

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

The left front wheel motor 2FL rotates the left front wheel 1FL. The right front wheel motor 2FR rotates the right front wheel 1FR. The left rear wheel motor 2RL rotates the left rear wheel 1RL. The right rear wheel motor 2RR rotates the right rear wheel 1RR.

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 driving 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.

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, a G sensor 35, a steering sensor 36, a temperature sensor 37, 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 a signal input from the brake sensor 34. The detection unit 13 detects the acceleration ax in the X direction of the vehicle C based on a signal input from the G sensor 35. The X direction of the vehicle C is the front-rear direction of the vehicle C. The acceleration ax in the X direction has a positive value when it is acceleration toward the front of the vehicle C.

The detection unit 13 detects the steering operation amount Strangl based on the signal input from the steering sensor 36. The steering operation amount Strangl is an operation amount based on the position of the steering wheel 5 when the vehicle C is traveling straight ahead.

The detection unit 13 detects the temperature of the motor 2 based on a signal input from the temperature sensor 37. The temperature sensor 37 is provided in each motor 2, and the detection unit 13 detects the temperature of each motor 2.

The calculation unit 14 calculates the estimated turning radius Rad. The calculation unit 14 calculates the estimated turning radius Rad using formula (3) 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...(3)

The calculation unit 14 calculates the upper vehicle speed Spdlmt. Specifically, the calculation unit 14 calculates the upper vehicle speed Spdlmt using equation (4) based on the estimated turning radius Rad and the upper centrifugal acceleration CNTYDNG. The upper centrifugal acceleration CNTYDNG is a preset value that can suppress the occurrence of skidding in the vehicle C. If the centrifugal force F3 increases and the cornering force CF increases, the vehicle C may skid. The centrifugal force F3 is proportional to the centrifugal acceleration and is related to the centrifugal acceleration. Therefore, the calculation unit 14 calculates the upper vehicle speed Spdlmt that corresponds to the upper centrifugal acceleration CNTYDNG.

Spdlmt=(Rad×CNTYDNG) ^1/2 ...(4)

The calculation unit 14 calculates the vehicle required torque Cartrq. Specifically, when the detected vehicle speed Spd is equal to or greater than the upper limit vehicle speed Spdlmt, the calculation unit 14 calculates the vehicle required torque Cartrq by feedback control based on the deviation between the vehicle speed Spd and the upper limit vehicle speed Spdlmt. The calculation unit 14 sets a target vehicle speed so that the vehicle speed Spd is equal to or less than the upper limit vehicle speed Spdlmt, and calculates the vehicle required torque Cartrq that becomes the target vehicle speed. In this case, the vehicle required torque Cartrq is a torque that limits the vehicle speed Spd to be equal to or less than the upper limit vehicle speed Spdlmt, and is a negative torque. In other words, the vehicle required torque Cartrq is a braking torque. The vehicle required torque Cartrq is a braking torque for making the vehicle speed Spd equal to or less than the upper limit vehicle speed Spdlmt.

When the detected vehicle speed Spd is smaller than the upper limit vehicle speed Spdlmt, 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.

The calculation unit 14 calculates the front wheel load ratio Frwigtrt. Specifically, the calculation unit 14 calculates the front wheel load ratio Frwigtrt using formula (5) based on the distance lr from the center of gravity of the vehicle C to the rear wheel 1R, the wheelbase L, the height h from the ground to the center of gravity of the vehicle C, the acceleration ax in the X direction of the vehicle C, and the gravitational acceleration g.

Frwigtrt=(lr/L)+h×ax/(L×g)...(5)

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 (6).

Yawtag= ^Spd2 /Rad...(6)

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 calculation unit 14 calculates the front wheel required drive torque Frtrqrq. Specifically, the calculation unit 14 calculates the front wheel required drive torque Frtrqrq using equation (7) based on the front wheel required drive base torque BASETRQ, the front wheel load ratio Frwigtrt, and the yaw rate deviation Delyaw. The front wheel required drive base torque BASETRQ is a preset value.

Frtrqrq=BASETRQ×Frwigtrt×Delyaw...(7)

When vehicle C starts turning, the yaw rate deviation Delyaw, which is the deviation between the target yaw rate Yawtag and the actual yaw rate Yawreal, becomes large. Therefore, when vehicle C starts turning, the front wheel required drive torque Frtrqrq becomes large. Also, the front wheel required drive torque Frtrqrq becomes larger as the front wheel load ratio Frwigtrt becomes larger. In other words, the front wheel required drive torque Frtrqrq becomes larger as the load on the front wheels 1F is greater than that on the rear wheels 1R.

The calculation unit 14 calculates the lower limit torque Rrtrqmn of the motor 2 that rotates the rear wheel 1R. The calculation unit 14 calculates the lower limit torque Rrtrqmn, for example, based on the temperature of the motor 2 that rotates the rear wheel 1R. The calculation unit 14 calculates the lower limit torque Rrtrqmn when the temperature of the motor 2 that rotates the rear wheel 1R is higher than a preset upper limit temperature. The lower limit torque Rrtrqmn may be calculated according to the temperature of the motor 2 that rotates the rear wheel 1R. For example, the lower limit torque Rrtrqmn increases as the temperature of the motor 2 that rotates the rear wheel 1R increases. The calculation unit 14 calculates the lower limit torque Rrtrqmn as the torque obtained by multiplying the larger of the lower limit torque Mtrltrqmn of the left rear wheel motor 2RL that rotates the left rear wheel 1RL and the lower limit torque Mtrrtrqmn of the right rear wheel motor 2RR that rotates the right rear wheel 1RR. Note that the lower limit torque Rrtrqmn is a negative value. Therefore, as the temperature of the motor 2 that rotates the rear wheel 1R increases, the absolute value of the lower limit torque Rrtrqmn decreases.

The determination unit 15 determines whether the vehicle speed Spd is equal to or greater than the upper limit vehicle speed Spdlmt.

The determination unit 15 determines whether the state of the vehicle C is a front-loaded turning state. Specifically, the determination unit 15 determines whether the state of the vehicle C is a front-loaded state and a turning state. When the state of the vehicle C is a front-loaded state and a turning state, the determination unit 15 determines that the vehicle C is in a front-loaded turning state.

The determination unit 15 determines that the state of the vehicle C is in a front loaded state when the front wheel load ratio Frwigtrt is equal to or greater than the load determination value FRWRTOV. The load determination value FRWRTOV is a preset value.

When the steering operation amount Strangl is equal to or greater than the steering operation judgment value STRQNGLTH, the judgment unit 15 judges that the state of the vehicle C is in a turning state. The steering operation judgment value STRQNGLTH is a preset value. The steering operation judgment value STRQNGLTH is set for left turning and right turning, respectively.

The determination unit 15 determines whether or not the predetermined torque condition is satisfied. Specifically, the determination unit 15 determines that the predetermined torque condition is satisfied when the vehicle required torque Cartrq is a positive value and is smaller than the front wheel required drive torque Frtrqrq. The determination unit 15 determines that the predetermined torque condition is not satisfied when the vehicle required torque Cartrq is equal to or less than zero. The determination unit 15 determines that the predetermined torque condition is not satisfied when the vehicle required torque Cartrq is equal to or greater than the front wheel required drive torque Frtrqrq.

The determination unit 15 determines whether the provisional torque TemtrqR of the rear wheel 1R, which will be described later, is smaller than the lower limit torque Rrtrqmn.

The setting unit 16 sets the provisional torque Temtrq. The setting unit 16 sets the provisional torque Temtrq when the state of the vehicle C is a front-loaded turning state and does not satisfy the specified torque condition. Specifically, the setting unit 16 sets the front wheel required drive torque Frtrqrq as the provisional torque TemtrqF of the front wheels 1F. The setting unit 16 sets the torque obtained by subtracting the front wheel required drive torque Frtrqrq from the vehicle required torque Cartrq as the provisional torque TemtrqR of the rear wheels 1R.

The setting unit 16 sets the torque to be generated by each motor 2.

When the state of vehicle C is not a front-loaded turning state, the setting unit 16 sets the torque generated by each motor 2 to a normal torque. For example, a state of vehicle C that is not a front-loaded turning state includes a case where vehicle C is not turning, i.e., traveling straight ahead. A state of vehicle C that is not a front-loaded turning state includes a case where vehicle C is not in a front-loaded turning state and is turning. The normal torque is a torque that is generated equally by each wheel with respect to vehicle required torque Cartrq. For example, the setting unit 16 sets a torque obtained by dividing vehicle required torque Cartrq into four equal parts as the normal torque for each motor 2.

When the state of the vehicle C is a front-loaded turning state and a predetermined torque condition is satisfied, the setting unit 16 sets the torque generated by each motor 2 to a first front-loaded turning torque. The first front-loaded turning torque is a torque that generates the vehicle required torque Cartrq only by the motor 2 that rotates the front wheels 1F. In other words, with the first front-loaded turning torque, the torque in the motor 2 that rotates the rear wheels 1R becomes zero.

The setting unit 16 sets the torque obtained by dividing the vehicle required torque Cartrq in half as the first front-loaded turning torque in the left front wheel motor 2FL and the first front-loaded turning torque in the right front wheel motor 2FR. The setting unit 16 also sets the first front-loaded turning torque in the left rear wheel motor 2RL and the first front-loaded turning torque in the right rear wheel motor 2RR to zero.

When the vehicle required torque Cartrq is a positive value and is smaller than the front wheel required drive torque Frtrqrq, if the drive torque generated by the entire vehicle C becomes the front wheel required drive torque Frtrqrq, the vehicle C may suddenly accelerate. Therefore, when the state of the vehicle C is a front-loaded turning state and the specified torque condition is satisfied, the setting unit 16 sets the torque generated by each motor 2 to the first front-loaded turning torque. This prevents a torque greater than the torque required by the driver from being output as the drive torque of the vehicle C, and avoids the feeling of runaway.

When the state of the vehicle C is a front-loaded turning state, the predetermined torque condition is not satisfied, and the provisional torque TemtrqR of the motor 2 that rotates the rear wheels 1R is equal to or greater than the lower limit torque Rrtrqmn, the setting unit 16 sets the torque generated by each motor 2 to the second front-loaded turning torque. This causes the first control to be performed, which increases the torque of the motor 2 that rotates the front wheels 1F.

Specifically, the setting unit 16 sets the provisional torque Temtrq as the second front-loaded turning torque. The setting unit 16 sets the provisional torque TemtrqF of the front wheels 1F, specifically the torque obtained by dividing the front wheel required drive torque Frtrqrq in half, as the second front-loaded turning torque in the left front wheel motor 2FL and the second front-loaded turning torque in the right front wheel motor 2FR. The setting unit 16 sets the provisional torque TemtrqR of the rear wheels 1R in half, as the second front-loaded turning torque in the left rear wheel motor 2RL and the second front-loaded turning torque in the right rear wheel motor 2RR.

As described above, when turning starts, the yaw rate deviation Delyaw becomes large, and the front wheel required drive torque Frtrqrq becomes large. Therefore, when turning starts, the second front-loaded turning torque in the left front wheel motor 2FL and the second front-loaded turning torque in the right front wheel motor 2FR become large. In addition, by setting the second front-loaded turning torque, the deviation between the actual yaw rate Yawreal and the target yaw rate Yawtag is eliminated, and when the yaw rate deviation Delyaw becomes small, the front wheel required drive torque Frtrqrq becomes small. When the yaw rate deviation Delyaw becomes small, the second front-loaded turning torque in the left front wheel motor 2FL and the second front-loaded turning torque in the right front wheel motor 2FR become small.

Even if it is not at the start of a turn, if the turning radius becomes smaller during a turn or the amount of steering wheel 5 operation increases during a turn, the yaw rate deviation Delyaw increases, and the front wheel required drive torque Frtrqrq increases, so the second front-load turning torque at the left front wheel motor 2FL and the second front-load turning torque at the right front wheel motor 2FR increase.

Furthermore, the greater the front wheel load ratio Frwigtrt, the greater the front wheel required drive torque Frtrqrq. Therefore, the greater the load on the front wheels 1F compared to the rear wheels 1R, the greater the second front-load turning torque in the left front wheel motor 2FL and the second front-load turning torque in the right front wheel motor 2FR.

When the vehicle required torque Cartrq is negative, i.e., when the vehicle speed Spd is limited to be equal to or lower than the upper limit vehicle speed Spdlmt, the setting unit 16 sets the second weighted turning torque so that the vehicle speed Spd is equal to or lower than the upper limit vehicle speed Spdlmt. This performs a second control in which the torque of each motor 2 is controlled so that the vehicle speed Spd is equal to or lower than the upper limit vehicle speed.

For example, when the front wheel required drive torque Frtrqrq is "50 Nm" and the vehicle required torque Cartrq is "-30 Nm", the setting unit 16 sets "50 Nm" as the second front-loaded turning torque (provisional torque TemtrqF of the front wheels 1F) of the motor 2 that rotates the front wheels 1F. In addition, in order to realize the vehicle required torque Cartrq as the overall torque of the vehicle C, the setting unit 16 sets "-80 Nm" obtained by subtracting "50 Nm", the front wheel required drive torque Frtrqrq, from "-30 Nm", as the second front-loaded turning torque (provisional torque TemtrqR of the rear wheels 1R) of the motor 2 that rotates the rear wheels 1R. In other words, when the vehicle required torque Cartrq is negative, the second front-loaded turning torque of the motor 2 that rotates the rear wheels 1R becomes a braking torque. In this way, when the conditions for implementing both the first control and the second control are met, the first control takes priority, and in the second control, a braking torque is generated in the motor 2 that rotates the rear wheel 1R.

When the state of the vehicle C is a front-loaded state, the predetermined torque condition is not satisfied, and the provisional torque TemtrqR of the motor 2 rotating the rear wheel 1R is smaller than the lower limit torque Rrtrqmn, the setting unit 16 sets the torque generated by each motor 2 to the third front-loaded turning torque. This performs a first control in which the torque of the motor 2 rotating the front wheel 1F is increased. Also, a second control is performed in which the torque of each motor 2 is controlled so that the vehicle speed Spd is equal to or lower than the upper limit vehicle speed Spdlmt.

Specifically, the setting unit 16 sets the lower limit torque Rrtrqmn as the third front-loaded turning torque of the motor 2 that rotates the rear wheel 1R. That is, the setting unit 16 limits the braking torque of the motor 2 that rotates the rear wheel 1R to the lower limit torque Rrtrqmn with respect to the provisional torque TemtrqR of the rear wheel 1R. When the second control is performed, if the braking torque that limits the vehicle speed Spd to the upper limit vehicle speed Spdlmt is smaller than the lower limit torque Rrtrqmn, the braking torque of the motor 2 that rotates the rear wheel 1R is limited to the lower limit torque Rrtrqmn.

The setting unit 16 also limits the drive torque of the motor 2 that rotates the front wheels 1F based on the limit amount of the braking torque of the motor 2 that rotates the rear wheels 1R. The setting unit 16 sets the torque obtained by subtracting the control amount from the provisional torque TemtrqF of the motor 2 that rotates the front wheels 1F as the third front-loaded turning torque of the motor 2 that rotates the front wheels 1F, using the absolute value of the deviation between the provisional torque TemtrqR of the motor 2 that rotates the rear wheels 1R and the lower limit torque Rrtrqmn as the limit amount. That is, when the second control is performed and the braking torque that limits the vehicle speed Spd to the upper limit vehicle speed Spdlmt is smaller than the lower limit torque Rrtrqmn, the drive torque of the front wheels 1F in the first control is limited based on the limit amount of the braking torque of the motor 2 that rotates the rear wheels 1R.

For example, if the front wheel required drive torque Frtrqrq is "50 Nm", the vehicle required torque Cartrq is "-30 Nm", and the lower limit torque Rrtrqmn is "-60 Nm", the provisional torque TemtrqR of the motor 2 that rotates the rear wheels 1R is "-80 Nm", which is obtained by subtracting the front wheel required drive torque Frtrqrq of "50 Nm" from the vehicle required torque Cartrq of "-30 Nm".

In this case, because the provisional torque TemtrqR of the motor 2 that rotates the rear wheels 1R is smaller than the lower limit torque Rrtrqmn, the setting unit 16 sets the lower limit torque Rrtrqmn, "-60 Nm," as the third front-loaded turning torque of the motor 2 that rotates the rear wheels 1R. The setting unit 16 also calculates "20 Nm" as the limit amount of the limit torque, and sets "30 Nm," which is the torque obtained by subtracting the limit amount from "50 Nm," which is the provisional torque TemtrqF (front wheel required drive torque Frtrqrq) of the motor 2 that rotates the front wheels 1F, as the third front-loaded turning torque of the motor 2 that rotates the front wheels 1F.

The setting unit 16 sets the torque obtained by dividing the lower limit torque Rrtrqmn in half as the third front-loaded turning torque in the left rear wheel motor 2RL and the third front-loaded turning torque in the right rear wheel motor 2RR. The setting unit 16 sets the torque obtained by dividing the torque obtained by subtracting the control amount from the provisional torque TemtrqF of the front wheels 1F in half as the third front-loaded turning torque in the left front wheel motor 2FL and the third front-loaded turning torque in the right front wheel motor 2FR.

A control signal for controlling each motor 2 is output to each motor 2 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 prevention control according to the embodiment will be described with reference to Figures 5A and 5B. Figures 5A and 5B are flowcharts explaining the skid prevention control according to the embodiment.

The control device 10 calculates the estimated turning radius Rad (S100) and calculates the upper limit vehicle speed Spdlmt (S101). The control device 10 determines whether the vehicle speed Spd is equal to or greater than the upper limit vehicle speed Spdlmt (S102).

If the vehicle speed Spd is equal to or greater than the upper limit vehicle speed Spdlmt (S102: Yes), the control device 10 calculates the vehicle required torque Cartrq by feedback control based on the deviation between the vehicle speed Spd and the upper limit vehicle speed Spdlmt (S103). If the vehicle speed Spd is smaller than the upper limit vehicle speed Spdlmt (S102: No), the control device 10 calculates the vehicle required torque Cartrq based on the vehicle speed Spd and the accelerator opening Accel, for example by using a map (S104).

The control device 10 determines whether the state of the vehicle C is in a front-loaded turning state (S105). If the state of the vehicle C is not in a front-loaded turning state (S105: No), the control device 10 sets the torque of each motor 2 to a normal torque (S106).

When the state of vehicle C is a front-loaded turning state (S105: Yes), the control device 10 calculates the yaw rate deviation Delyaw (S107) and calculates the front-wheel drive required torque (S108).

The control device 10 determines whether the state of the vehicle C satisfies a predetermined torque condition (S109). If the state of the vehicle C satisfies the predetermined torque condition (S109: Yes), the control device 10 sets the torque of each motor 2 to the first front-loaded turning torque (S110).

When the state of vehicle C does not satisfy the predetermined torque condition (S109: No), the control device 10 calculates the provisional torque Temtrq (S111). The control device 10 calculates the lower limit torque Rrtrqmn (S112).

The control device 10 determines whether the provisional torque TemtrqR of the rear wheels 1R is smaller than the lower limit torque Rrtrqmn (S113). If the provisional torque TemtrqR of the rear wheels 1R is smaller than the lower limit torque Rrtrqmn (S113: Yes), the control device 10 sets the torque of each motor 2 to the third front-loaded turning torque (S114).

When the provisional torque TemtrqR of the rear wheels 1R is equal to or greater than the lower limit torque Rrtrqmn (S113: No), the control device 10 sets the torque of the rear wheels 1R in each motor 2 to the second front-loaded turning torque (S115).

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 drive wheels 1 are rotated by different motors 2. The control device 10 includes a control unit 11. The control unit 11 controls the torque generated by the motors 2. When the state of the vehicle C is a front-loaded state in which the load on the front wheels 1F is greater than the load on the other drive wheels 1, and the vehicle C is in a turning state, the control unit 11 performs a first control that sets the torque in the motor 2 that rotates the front wheels 1F to be large.

As a result, the control device 10 can increase the component F2 perpendicular to the front wheel traveling direction of the driving force F1 at the front wheels 1F, and can suppress the increase in the cornering force CF (slip angle SA) at the front wheels 1F. Therefore, the control device 10 can ensure a margin until the cornering force CF becomes the maximum cornering force CFmax. Therefore, the control device 10 can prevent the occurrence of skidding when the vehicle C turns, and can prevent the occurrence of understeer in the vehicle C.

The first control performed by the control unit 11 sets the torque of the motor 2 that rotates the front wheels 1F based on the yaw rate deviation Delyaw, which is the deviation between the target yaw rate Yawtag and the actual yaw rate Yawreal of the vehicle C.

This allows the control device 10 to precisely control the drive torque of the motor 2 that rotates the front wheels 1F based on the yaw rate of the vehicle C. Therefore, the control device 10 can further prevent skidding from occurring when the vehicle C is turning. Furthermore, when the vehicle is in a front-loaded state and turning state, the control device 10 can precisely control the drive torque of the motor 2 that rotates the front wheels 1F to stabilize the running of the vehicle C.

The first control performed by the control unit 11 sets the torque of the motor 2 that rotates the front wheel 1F to be greater the greater the load on the front wheel 1F compared to the rear wheel 1R.

This allows the control device 10 to secure a margin until the cornering force CF reaches the maximum cornering force CFmax. Therefore, the control device 10 can prevent skidding from occurring when the vehicle C is turning, and can prevent understeer from occurring in the vehicle C.

The first control performed by the control unit 11 is performed when the vehicle C is in a turning start state. This allows the control device 10 to prevent understeer from occurring in the vehicle C even when the vehicle C is starting to turn, which is a time when understeer is likely to occur.

The control unit 11 performs a second control to set the torque of each motor 2 so that the vehicle speed Spd is equal to or less than the upper limit vehicle speed Spdlmt at which the centrifugal acceleration of the vehicle C is equal to or less than the upper limit centrifugal acceleration CNTYDNG.

By limiting the vehicle speed Spd when the vehicle C turns, the control device 10 can suppress the centrifugal force F3 from increasing, and can also ensure a margin until the cornering force CF reaches the maximum cornering force CFmax. Therefore, the control device 10 can further prevent skidding from occurring.

When the conditions for implementing both the first control and the second control are met, the control unit 11 prioritizes the first control, and in the second control, generates a braking torque in the motor 2 that rotates the rear wheel 1R.

As a result, the control device 10 can increase the component F2 perpendicular to the front wheel travel direction of the driving force F1 at the front wheels 1F, and further restrict the vehicle speed Spd using the braking torque at the rear wheels 1R, thereby preventing the centrifugal force F3 from increasing, and ensuring a margin until the cornering force CF at the front wheels 1F reaches the maximum cornering force CFmax. Therefore, the control device 10 can further prevent skidding from occurring.

When performing the second control, if the braking torque that limits the vehicle speed Spd to the upper limit vehicle speed Spdlmt is smaller than the lower limit torque Rrtrqmn, the control unit 11 limits the braking torque of the motor 2 that rotates the rear wheels 1R to the lower limit torque Rrtrqmn. In addition, the control unit 11 limits the drive torque of the front wheels 1F in the first control based on the limit amount of the braking torque of the motor 2 that rotates the rear wheels 1R.

This allows the control device 10 to generate maximum braking torque while preventing skidding from occurring.

The control device 10 according to the above embodiment calculates the front wheel required drive torque Frtrqrq using equation (7) based on the front wheel load ratio Frwigtrt when the vehicle C is in a front-loaded turning state, but this is not limited to the above. The control device 10 according to the modified example may calculate the front wheel required drive torque Frtrqrq using equation (7) based on the front wheel load ratio Frwigtrt only when the vehicle C starts turning.

For example, the control device 10 according to the modified example determines whether or not it is the start of a turn after step S107 in FIG. 5B, and if it is the start of a turn, proceeds to step S108 and calculates the front wheel required drive torque Frtrqrq using equation (7). If it is not the start of a turn, the control device 10 according to the modified example sets the front wheel required drive base torque BASETRQ as the front wheel required drive torque Frtrqrq. For example, the control device 10 according to the modified example determines that it is the start of a turn when the yaw rate deviation Delyaw is greater than a predetermined deviation that is set in advance. The control device 10 may determine that it is the start of a turn based on the amount of change in the steering angle θ at a predetermined time. For example, the control device 10 determines that it is the start of a turn when the amount of change in the steering angle θ becomes greater than a preset value.

As a result, the control device 10 according to the modified example sets the front wheel required drive torque Frtrqrq based on the front wheel load ratio Frwigtrt only in situations where the vehicle C is likely to slip, and performs torque control using the front wheel required drive torque Frtrqrq. Therefore, the control device 10 according to the modified example generates torque in each drive wheel 1 according to the situation of the vehicle C, and can suppress any discomfort felt by the driver.

The control device 10 according to the above embodiment calculates the upper limit vehicle speed Spdlmt based on the estimated turning radius Rad and the upper limit centrifugal acceleration CNTYDNG. Alternatively, the control device 10 according to the modified example may detect the centrifugal acceleration acting in the lateral direction of the vehicle C using a G sensor, and calculate the upper limit vehicle speed Spdlmt based on the estimated turning radius Rad and the detected centrifugal acceleration acting in the lateral direction of the vehicle C. In other words, the upper limit vehicle speed Spdlmt is calculated for the current centrifugal acceleration acting in the lateral direction of the vehicle C.

When the steering device of the vehicle C is a steer-by-wire system and the vehicle speed Spd is limited to the upper limit vehicle speed Spdlmt, torque control of each motor 2 may be started before the actuator adjusts the steering angle θ of the front wheels 1F. Note that the control delay of the actuator with respect to the operation of the steering wheel 5 is set to an extent that the driver does not feel a delay in the turning movement of the vehicle C.

As a result, control of the vehicle speed Spd begins before the steering angle of the drive wheels 1 is actually changed, making it possible to prevent skidding of the vehicle C.

The control device 10 according to the modified example may execute the above-mentioned skid prevention control during turning, regardless of whether the vehicle C is in a front-loaded state or not. In this case, the control device 10 sets the torque of each motor 2 during turning so that the vehicle speed Spd is equal to or lower than the upper limit vehicle speed Spdlmt at which the centrifugal acceleration of the vehicle C corresponds to the upper limit centrifugal acceleration CNTYDNG.

In the above embodiment, the torque is equally distributed between the left and right front wheels 1F and the left and right rear wheels 1R, but this is not limited to the above. The amount of torque distributed between the left and right drive wheels 1 may be different. For example, the amount of torque distributed to the drive wheel 1 on the outside of a turn may be greater than the amount of torque distributed to the drive wheel 1 on the inside of a turn.

In the above embodiment, a vehicle C having four drive wheels 1 has been described as an example, but a vehicle C having more than four drive wheels 1 may have, for example, three or more drive wheels 1 arranged in the front-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.

In such a case, for example, the control device 10 controls only the torque of the outermost and frontmost front wheel 1F and 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 groups the wheels 1F and rear wheels 1R depending on whether they are forward or rearward from the center of the vehicle C, and groups the wheels 1F and right or left depending on whether they are to the left or right of the center of the vehicle C, and controls the torque of the drive wheels 1 corresponding to each group.

In the above embodiment, the skid prevention control is performed before skid occurs. However, when the vehicle C turns, skid suppression control may be performed to suppress the occurrence of skid after skid occurs. 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.

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 1F Front wheel 1R Rear wheel 2 Motor 10 Control device 11 Control unit (motor control unit)
13 Detection unit 14 Calculation unit 15 Determination unit 16 Setting unit C Vehicle

Claims (8)

A vehicle control device for controlling a vehicle in which a plurality of drive wheels are rotated by different motors,
a motor control unit that sets a torque generated by the motor to a normal torque and controls the motor ,
The motor control unit includes :
When the state of the vehicle is a front -loaded state in which the load on the front wheels is larger than the load on the other drive wheels and the vehicle is in a turning state, a first control is performed to set a front-loaded turning torque that is different from the normal torque and that increases the torque of a motor that rotates the front wheels ;
In the first control, a torque of a motor that rotates the front wheels is set based on a deviation between a target yaw rate and an actual yaw rate of the vehicle.
A vehicle control device comprising: A vehicle control device for controlling a vehicle in which a plurality of drive wheels are rotated by different motors,
a motor control unit that sets a torque generated by the motor to a normal torque and controls the motor ,
The motor control unit includes :
When the state of the vehicle is a front -loaded state in which the load on the front wheels is larger than the load on the other drive wheels and the vehicle is in a turning state, a first control is performed to set a front-loaded turning torque that is different from the normal torque and that increases the torque of a motor that rotates the front wheels ;
In the first control, the torque of the motor that rotates the front wheels is set to be larger as the load on the front wheels is larger than that on the rear wheels.
A vehicle control device comprising: The vehicle control device according to claim 1 or 2 , wherein the first control performed by the motor control unit is performed when the vehicle is in a turning start state. The vehicle control device according to any one of claims 1 to 3, characterized in that the motor control unit performs a second control to set a torque in each motor so that the vehicle speed is equal to or lower than an upper limit vehicle speed corresponding to an upper limit centrifugal acceleration of the vehicle. 5. The vehicle control device according to claim 4, wherein, when conditions for implementing the first control and the second control are both satisfied, the motor control unit prioritizes the first control, and in the second control, generates a braking torque in a motor that rotates a rear wheel. 6. The vehicle control device according to claim 5, wherein, when performing the second control, if a braking torque that limits the vehicle speed to the upper limit vehicle speed is smaller than a lower limit torque, the motor control unit limits the braking torque in the motor that rotates the rear wheels to the lower limit torque, and limits the drive torque of the front wheels in the first control based on a limit amount of the braking torque in the motor that rotates the rear wheels. A method for controlling a vehicle in which a plurality of drive wheels are rotated by different motors, comprising the steps of:
When the state of the vehicle is a front-loaded state in which the load on the front wheels is larger than the load on the other drive wheels and the vehicle is turning, a first control is performed to set a front-loaded turning torque that is different from a normal torque and that increases the torque of a motor that rotates the front wheels ;
In the first control, a torque of a motor that rotates the front wheels is set based on a deviation between a target yaw rate and an actual yaw rate of the vehicle.
A control method comprising: A method for controlling a vehicle in which a plurality of drive wheels are rotated by different motors, comprising the steps of:
When the state of the vehicle is a front-loaded state in which the load on the front wheels is larger than the load on the other drive wheels and the vehicle is turning, a first control is performed to set a front-loaded turning torque that is different from a normal torque and that increases the torque of a motor that rotates the front wheels ;
In the first control, the torque of the motor that rotates the front wheels is set to be larger as the load on the front wheels is larger than that on the rear wheels.
A control method comprising:

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