JP7596704B2 - Vehicle behavior control method and vehicle behavior control device - Google Patents

Description

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

The following Patent Document 1 describes how a pitching motion is generated in the vehicle when the driver turns the steering wheel, giving the driver a sense of the vehicle's response to the steering.

JP 2020-121626 A

However, if pitch behavior is applied at the time the steering wheel is turned, there is a problem that the driver may recognize the pitch behavior before he or she realizes that he or she has turned the steering wheel, which may cause the driver to feel uncomfortable.
An object of the present invention is to provide a driver with a natural feeling of vehicle response when the driver operates the steering wheel.

In one embodiment of the present invention, a vehicle behavior control method detects the steering angle of a steering wheel, detects the steering force applied to the steering wheel by the driver, sets a steering angle threshold based on the detected steering force, and generates a pitch behavior in the vehicle when the detected steering angle reaches the steering angle threshold.

The present invention provides the driver with a natural feeling of vehicle response when operating the steering wheel.

1 is a schematic configuration diagram of an example of a vehicle braking/driving force control device according to an embodiment; 1 is a schematic configuration diagram of an example of a steering device for a vehicle according to an embodiment; FIG. 2 is a block diagram showing an example of a functional configuration of a braking/driving force controller. FIG. 4 is a diagram illustrating an example of steering force characteristics relative to steering angle. FIG. 4 is an explanatory diagram of an example of a method for setting a steering angle threshold value. FIG. 4 is an explanatory diagram of an example of a method for setting a steering angle threshold value. FIG. 11 is a characteristic diagram showing a combination of a pitch angle change amount and a lower limit value of a pitch angular velocity of a pitch behavior that can be recognized by a driver. FIG. 5B is an explanatory diagram of an approximation line of the characteristic line of FIG. 5A. 10 is a flowchart of an example of a steering angle threshold setting process. 13 is a flowchart of an example of a process for generating a pitch behavior.

Below, an embodiment of the present invention will be described with reference to the drawings. Note that each drawing is a schematic view and may differ from the actual product. Furthermore, the embodiment of the present invention shown below is an example of an apparatus and method for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the structure, arrangement, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

(composition)
1 is a schematic diagram of an example of a braking/driving force control device for a vehicle according to an embodiment. A vehicle equipped with the braking/driving force control device 1 includes an accelerator sensor 2, a brake sensor 3, a vehicle speed sensor 4, a steering angle sensor 5, a torque sensor 6, and a braking/driving force controller 10.
The vehicle also includes a brake actuator 11, wheel cylinders 12FR, 12FL, 12RR, and 12RL, a power control unit 13, a drive source 14, and wheels 15FR, 15FL, 15RR, and 15RL.

In the following description, the wheel cylinders 12FR, 12FL, 12RR, and 12RL may be collectively referred to as "wheel cylinders 12."
Furthermore, wheels 15FR, 15FL, 15RR and 15RL are the right front wheel, the left front wheel, the right rear wheel and the left rear wheel, respectively, and may be collectively referred to as "wheels 15."

The accelerator sensor 2 is a sensor formed, for example, by using a pedal stroke sensor, which detects the amount of operation (amount of depression) of an acceleration/deceleration pedal 16 (accelerator pedal) by the driver.
The acceleration/deceleration pedal 16 is a pedal that the driver of the vehicle depresses in response to a braking force request or a driving force request.

The accelerator sensor 2 also outputs an accelerator operation amount signal, which indicates the amount of operation of the acceleration/deceleration pedal 16 by the driver, to the braking/driving force controller 10 .
The configuration of the accelerator sensor 2 is not limited to a configuration formed using a pedal stroke sensor, but may be a configuration that detects the opening degree of the acceleration/deceleration pedal 16 when depressed by the driver, for example.

The brake sensor 3 is, for example, a sensor formed using a pedal stroke sensor, which detects the amount of operation (amount of depression) of a braking pedal 17 (brake pedal) by the driver.
The brake pedal 17 is a pedal that is depressed by the driver of the vehicle in response to a braking force request.

The brake sensor 3 also outputs a brake operation amount signal, which indicates the amount of operation of the brake pedal 17 by the driver, to the braking/driving force controller 10 .
In addition, like the accelerator sensor 2, the configuration of the brake sensor 3 is not limited to a configuration formed using a pedal stroke sensor, and may be, for example, a configuration that detects the opening degree of the brake pedal 17 when depressed by the driver.

The vehicle speed sensor 4 detects the vehicle speed from the wheel speed of the wheels 15. The vehicle speed sensor 4 outputs a vehicle speed signal indicating the detected vehicle speed to the braking/driving force controller 10.
The steering angle sensor 5 is provided in a steering device of the vehicle and detects the steering angle θs of the steering wheel 20. For example, the steering angle sensor 5 may be a rotary encoder that detects the rotation angle of a steering shaft.

Also, for example, the steering angle sensor 5 may be a rotation angle sensor (e.g., a resolver) that detects the rotation angle of an electric motor that applies a rotational driving force to a steering shaft in a steering device of a vehicle. For example, the steering angle sensor 5 may be a rotation angle sensor that detects the rotation angle of a steering assist motor that generates a steering assist torque (assist torque) that assists the steering force by a driver in an electric power steering (EPS) device, or a rotation angle sensor that detects the rotation angle of a reaction motor that applies a reaction torque to the steering wheel 20 in a steer-by-wire (SBW) system.
The steering angle sensor 5 outputs a steering angle signal indicating the detected steering angle θs to the braking/driving force controller 10. For example, the steering angle sensor 5 outputs the steering angle signal to the braking/driving force controller 10 via a CAN (Controller Area Network).

The torque sensor 6 is provided in a steering device of the vehicle and detects the steering torque Ts applied to the steering wheel 20 by the driver.
For example, the torque sensor 6 detects a change in magnetic flux density caused by a relative angular displacement between a multi-pole magnet and a yoke due to twisting of a torsion bar provided on the steering shaft, for example, using a Hall element, and converts the change into an electric signal.
Further, for example, the torque sensor 6 may detect the steering torque Ts based on the drive current of the steering assist motor or the reaction motor.
The torque sensor 6 outputs a steering torque signal indicating the detected steering torque Ts to the braking/driving force controller 10. For example, the torque sensor 6 outputs the steering torque signal to the braking/driving force controller 10 via the CAN.

The braking/driving force controller 10 uses various input information signals to output command signals (braking command signals, drive command signals) for controlling the brake actuator 11 and the drive source 14 .
The braking command signal is a signal indicating a braking force command value for controlling the braking torque generated in the vehicle, and includes a friction braking torque command value, which is a command value for controlling the hydraulic pressure of each wheel cylinder 12 .
The braking/driving force controller 10 calculates a braking force command value in response to a braking force request based on at least the operation of the brake pedal 17 by the driver.

The drive command signal is a signal that indicates the drive torque of the vehicle generated by the drive source 14 and the drive force command value of the drive torque transmitted from the drive source 14 to the front wheels 15FR and 15FL and the rear wheels 15RR and 15RL. The drive source 14 may be an engine, an electric motor, or both.
The braking/driving force controller 10 calculates a driving force command value in response to a driving force request based on at least the operation of the acceleration/deceleration pedal 16 by the driver.

The braking/driving force controller 10 is, for example, an electronic control unit (ECU) that includes a processor and peripheral components such as a storage device.
The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).
The storage device may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device may include a register, a cache memory, a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory) used as a main memory device.

The processor of the driving/braking force controller 10 executes a computer program stored in the storage device, thereby carrying out information processing by the driving/braking force controller 10 as described below.
Furthermore, the information processing by the driving/braking force controller 10 described below may be executed by a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the driving/braking force controller 10 may have a programmable logic device (PLD) such as a field programmable gate array (FPGA).

The brake actuator 11 is a hydraulic control device interposed between a master cylinder (not shown) and each wheel cylinder 12. The brake actuator 11 also changes the hydraulic pressure of each wheel cylinder 12 in response to a braking command signal received from the braking/driving force controller 10. In this way, the brake actuator 11 applies a braking force to each wheel 15.

The wheel cylinder 12 generates a pressing force for pressing a brake pad (not shown) constituting a disc brake against a disc rotor (not shown). The disc rotor is a member that rotates integrally with each wheel 15 and comes into contact with the brake pad to generate frictional resistance.
The wheel cylinders 12FR, 12FL, 12RR, and 12RL are disposed for the front right wheel 15FR, the front left wheel 15FL, the rear right wheel 15RR, and the rear left wheel 15RL, respectively.

The power control unit 13 controls the driving torque generated by the driving source 14 in response to the driving command signal received from the braking/driving force controller 10 .
In addition, the power control unit 13 controls the drive torque transmitted from the drive source 14 to the front wheels 15FR and 15FL and the rear wheels 15RR and 15RL in response to a drive command signal received from the braking/driving force controller 10 .

Figure 2 is a schematic diagram of an example of a steering device of a vehicle according to an embodiment. The steering device according to the embodiment is an electric power steering device that applies a steering assist torque to the steering shaft of the vehicle, and includes the above-mentioned steering angle sensor 5 and torque sensor 6, a steering wheel 20, a steering shaft 21, a universal joint 22, a pinion shaft 23, a steering gear 24, a rack gear 25, a steering rack 26, an EPS controller 27, and a steering assist motor 28.

The steering wheel 20 rotates in response to a steering torque input applied by the driver.
The steering shaft 21 rotates integrally with the steering wheel 20 .
As described above, the steering angle sensor 5 detects the steering angle θs of the steering wheel 20. The steering angle sensor 5 outputs a steering angle signal indicating the detected steering angle θs to the EPS controller 27.

As described above, the torque sensor 6 detects the steering torque Ts applied by the driver to the steering wheel 20. The torque sensor 6 outputs a steering torque signal indicating the detected steering torque Ts to the EPS controller 27.
The pinion shaft 23 is connected to the steering shaft 21 via a universal joint 22 and rotates together with the steering shaft 21 .

The steering gear 24 meshes with a rack gear 25 and steers the front wheels 15FL and 15FR, which are steered wheels, in response to rotation of the pinion shaft 23. As the steering gear 24, for example, a rack-and-pinion type steering gear or the like may be adopted.
The steering assist motor 28 is connected to the steering shaft 21 via a reduction gear, and applies a steering assist torque to the steering shaft 21 .

The EPS controller 27 is an electronic control unit that controls the steering assist torque by the steering assist motor 28. The EPS controller 27 controls the steering assist torque based on the steering torque Ts detected by the torque sensor 6, the vehicle speed Vv detected by the vehicle speed sensor 4, and the steering angle θs detected by the steering angle sensor 5.
The EPS controller 27 includes, for example, a processor and peripheral components such as a storage device. The processor may be, for example, a CPU or an MPU.

The storage device may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device may include a register, a cache memory, a memory such as a ROM and a RAM used as a main memory device.
The processor of the EPS controller 27 executes a computer program stored in the storage device, thereby causing the EPS controller 27 to process information.

Furthermore, the information processing by the EPS controller 27 may be executed by a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the EPS controller 27 may include a PLD such as an FPGA.
The vehicle of the embodiment may be provided with a steering device other than the electric power steering device. For example, the vehicle of the embodiment may be provided with a hydraulic power steering device, or a steer-by-wire (SBW) type steering device in which the steering wheel 20 and the steered wheels 15FL and 15FR are mechanically separated from each other.

Next, a vehicle behavior control method according to an embodiment will be described. The vehicle behavior control method according to the embodiment provides the driver with a sense of response of the vehicle to steering by generating a pitch behavior in the vehicle when the driver steers the steering wheel 20.
By providing the driver with a sense of vehicle response to steering in this way, it becomes easier for the driver to turn the vehicle along a desired driving trajectory. The reason for this will be explained below.

When a driver starts steering from a state where the steering wheel 20 is held steered, while the steering angle θs is still small immediately after starting steering, the driver is not yet aware that he or she is inputting steering into the steering wheel 20 (performing steering), and when the steering angle θs reaches a certain value, the driver recognizes that he or she has input steering.
Hereinafter, the steering angle at which the driver begins to recognize that he or she has input steering will be referred to as the "steering recognition angle."

Thereafter, as the steering angle θs becomes larger, the yaw rate generated in the vehicle increases in response to the increase in the steering angle θs, and when the yaw rate reaches a certain level or greater, the driver begins to recognize that the vehicle is behaving in response to the steering input.
The steering angle at which the driver begins to recognize that a vehicle behavior in response to a steering input has occurred is referred to as the "behavior recognition angle."
The magnitude of the yaw rate at which the driver begins to recognize that a vehicle behavior is occurring, i.e., the behavior recognition angle, differs depending on the driver, but the behavior recognition angle is usually larger than the steering recognition angle. Therefore, the driver recognizes that the vehicle behavior in response to the steering input has occurred after the driver recognizes that he or she has input a steering input.

During this time, i.e., while the steering angle θs is changing from the steering recognition angle to the behavior recognition angle, the driver is not aware of whether vehicle behavior is occurring in response to the input steering, so the driver continues steering while imagining that vehicle behavior is occurring.
As a result, the amount of steering may be excessive or insufficient depending on the individual driver and the situation, causing the vehicle to deviate from the desired driving path.

Therefore, the driver is given a sense of the vehicle's response to steering before the steering angle reaches the behavior recognition angle.
There are various possible means for giving the driver a sense of vehicle response to steering, but it is preferable to generate a pitch (pitching) behavior in the vehicle, because the driver is less sensitive to yaw behavior and roll behavior (the driver is less likely to perceive them) compared to pitch behavior.
This allows the driver to quickly realize that the vehicle behavior has occurred in response to the steering input. This provides a guide for steering operation, which prevents excessive or insufficient steering and improves the steering feeling. As a result, the driver can easily turn the vehicle along the desired driving trajectory.

However, as described above, even if the driver starts to operate the steering wheel 20, the driver does not recognize that he or she is inputting steering to the steering wheel 20 until the steering angle θs reaches the steering recognition angle.
For this reason, if a pitch behavior is applied at the time the steering wheel 20 is turned, the driver will sense a response before he or she realizes that he or she has operated the steering wheel 20, which may cause the driver to feel uncomfortable.

In addition, the steering recognition angle at which the driver begins to recognize that he/she has input a steering wheel changes according to the steering force applied by the driver to the steering wheel 20. The larger the steering force, the smaller the steering recognition angle at which the driver recognizes the steering wheel input, and the smaller the steering force, the larger the steering recognition angle required.
Therefore, in the vehicle behavior control method of the embodiment, the steering force applied to the steering wheel 20 by the driver is detected, and the steering angle threshold value δ is set based on the detected steering force. The steering angle threshold value δ may be, for example, a "steering recognition angle" which is the steering angle at which the driver begins to recognize that he or she has input a steering command.

When the detected steering angle θs reaches the steering angle threshold δ, the vehicle is caused to pitch, so that the driver can feel a natural response of the vehicle when operating the steering wheel 20.
The pitch behavior of the vehicle can be generated by controlling the braking force and/or the driving force applied to the wheels 15. In this embodiment, the braking/driving force controller 10 controls the braking force and/or the driving force applied to the wheels 15 to generate the pitch behavior.

Figure 3 is a block diagram of an example of the functional configuration of the driving/braking force controller 10. The driving/braking force controller 10 includes a driving/braking force control unit 30, a driving force command value calculation unit 31, a braking force command value calculation unit 32, a steering force characteristic detection unit 33, a steering angle threshold setting unit 34, a recognition time calculation unit 35, a pitch behavior calculation unit 36, and a required moment calculation unit 37.

The braking/driving force control unit 30 calculates a driving torque command value Td, which is a command value for the driving torque to be generated in the vehicle, based on at least the accelerator operation amount signal Aa input from the accelerator sensor 2, and outputs the calculated value to a driving force command value calculation unit 31.
The drive torque command value is a command value for the drive torque generated by the drive source 14 and the drive torque transmitted from the drive source 14 to the front wheels 15FR and FL and the rear wheels 15RR and 15RL.

In addition, the braking/driving force control unit 30 calculates a braking torque command value Tb, which is a command value for the braking torque to be generated in the vehicle, based on at least the brake operation amount signal Ab input from the brake sensor 3, and outputs the calculated value to the braking force command value calculation unit 32.
The braking torque command value is a command value for the friction braking torque to be generated by the friction brakes (brake actuator 11, master cylinder, and each wheel cylinder 12) of the vehicle.

The driving force command value calculation unit 31 calculates a driving force command value based on the driving torque command value Td input from the braking/driving force control unit 30. The driving force command value calculation unit 31 outputs a driving command signal indicating the calculated driving force command value to the power control unit 13.
Braking force command value calculation unit 32 calculates a braking force command value based on the braking torque command value Tb input from braking/driving force control unit 30. Braking force command value calculation unit 32 outputs a braking command signal indicative of the calculated braking force command value to brake actuator 11.

The steering force characteristic detection unit 33 detects a steering force characteristic Cs, which is a characteristic of the steering torque Ts relative to the steering angle θs, based on the steering angle θs received from the steering angle sensor 5 and the steering torque Ts received from the torque sensor 6 .
4A is a diagram illustrating an example of a steering force characteristic Cs. The horizontal axis represents the steering angle θs, and the vertical axis represents the steering torque Ts. Characteristic lines 40 and 41 respectively show the characteristics when the vehicle speed Vv is relatively high VH and relatively low VL.

The steering force characteristic detection unit 33 obtains a plurality of combinations of the steering angle θs and the steering torque Ts detected by the steering angle sensor 5 and the torque sensor 6 at the same time, and detects the steering force characteristic Cs based on the plurality of combinations of different values. For example, the steering force characteristic detection unit 33 may detect the steering force characteristic Cs by interpolating values between the plurality of combinations of different values.
As shown in the figure, the steering force characteristic Cs has a characteristic that the steering torque Ts increases as the steering angle θs increases.

Furthermore, the steering torque Ts is greater when the vehicle speed Vv is relatively high VH than when the vehicle speed Vv is relatively low VL.
This is because the electric power steering device, which is the steering device of the embodiment, controls the magnitude of the steering assist torque according to the vehicle speed Vv, and the steering torque Ts required for steering changes accordingly. For example, when a large steering assist torque is generated to facilitate steering when the vehicle speed Vv is relatively low (VL), the steering torque Ts required for steering becomes small. On the other hand, when the steering assist torque is reduced to stabilize driving when the vehicle speed Vv is relatively high (VH), the steering torque Ts required for steering becomes large.

3, the steering angle threshold setting unit 34 sets the steering angle threshold δ. For example, the steering angle threshold setting unit 34 sets, as the steering angle threshold δ, a steering recognition angle at which the driver starts to recognize that the driver has input a steering input when the driver starts steering from a steering angle θs of 0 (i.e., a state in which the steering angle is maintained while traveling straight).
As described above, the steering recognition angle changes according to the steering torque applied by the driver to the steering wheel 20. The steering angle threshold setting unit 34 sets the steering angle threshold δ based on the steering force characteristic Cs detected by the steering force characteristic detection unit 33.

4B and 4C are diagrams illustrating an example of a method for setting the steering angle threshold δ. The hatched areas 42 and 43 indicate areas obtained by integrating the values of the steering torque Ts indicated by the characteristic lines 40 and 41 over the range from 0 [deg] to the steering angle threshold δ with respect to the steering angle θs.
The areas of these regions 42 and 43 represent the amount of work. The inventors of the present application have found that even if the steering force characteristic Cs differs, the amount of work at which the driver begins to recognize that he or she has input a steering operation is approximately equal.

Therefore, the steering angle threshold setting unit 34 may set, as the steering angle threshold δ, the steering angle θs at which the workload becomes a predetermined value in the steering force characteristic Cs detected by the steering force characteristic detection unit 33. The predetermined value may be set based on the workload at which the driver begins to recognize that he or she has input a steering command, which is obtained, for example, through an experiment or the like.
In addition, since the dimension of the workload is steering angle θs × steering torque Ts, the steering angle threshold setting unit 34 may simply set the result of dividing a predetermined value of the workload by the steering torque Ts as the steering angle threshold δ.

In addition, when the magnitude of the steering assist force is not controlled according to the vehicle speed Vv, as in the case of a hydraulic power steering device, it is not necessary to detect the steering force characteristic Cs in real time. In this case, the steering force characteristic detection unit 33 may be omitted, and the steering angle threshold value δ may be set to a fixed value.
However, in reality, the steering force characteristic Cs changes depending on the aging of the steering device and the condition of the tires and road surface. Therefore, in the hydraulic power steering device, it is preferable to detect the steering force characteristic Cs and dynamically set the steering angle threshold δ.

3, the recognition time calculation unit 35 calculates a recognition time tδ, which is a time until the driver starts to recognize that he or she has input a steering input, when further steering is performed to increase the steering angle θs. That is, the recognition time calculation unit 35 calculates a recognition time tδ until the steering angle θs reaches the steering angle threshold value δ.
For example, the recognition time calculation unit 35 calculates the steering angular velocity ω by differentiating the steering angle θs detected by the steering angle sensor 5, and calculates the division result by dividing the steering angle threshold δ by the steering angular velocity ω as the recognition time tδ.

The pitch behavior calculation unit 36 calculates the magnitude of the pitch behavior to be generated in the vehicle. The pitch behavior to be generated in the vehicle is preferably a behavior in which the pitch angle changes in a direction in which the vehicle body tilts forward, which is in line with the driver's sensation.
The pitch behavior calculation unit 36 calculates the magnitude of the pitch behavior so as to generate a pitch behavior of the vehicle that can be recognized by the driver when a recognition time tδ has elapsed from the current time.
A characteristic line 44 in FIG. 5A shows an example of a characteristic of a combination of a lower limit value of the pitch angle change amount Δθδ of the pitch behavior that can be recognized by the driver and a lower limit value of the pitch angular velocity dθδ/dt.

As the pitch angular velocity dθδ/dt decreases, the lower limit of the pitch angle change amount Δθδ of the pitch behavior that the driver can recognize increases, and as the pitch angular velocity dθδ/dt increases, the lower limit of the pitch angle change amount Δθδ decreases.
In addition, the smaller the pitch angle change amount Δθδ, the larger the lower limit of the pitch angular velocity dθδ/dt of the pitch behavior that the driver can recognize, and the larger the pitch angle change amount Δθδ, the smaller the lower limit of the pitch angular velocity dθδ/dt.
Therefore, in order to prevent excessive pitch behavior from being imparted to the vehicle and to allow the driver to recognize the pitch behavior of the vehicle, it is desirable to impart the pitch behavior on the characteristic line 44 in Fig. 5A. In this embodiment, the pitch behavior on the characteristic line 44 in Fig. 5A is imparted.

The pitch behavior calculation unit 36 calculates the pitch angular acceleration d2θδ/dt2 required to make the pitch behavior of the vehicle at a time when the recognition time tδ has elapsed from the current time point correspond to any combination of the pitch angle change amount Δθδ and the pitch angular velocity ^dθδ / ^dt on the characteristic line 44.
In other words, when a constant pitch angular acceleration ^d2θδ / ^dt2 is applied to the vehicle for the recognition time tδ from the current time, the pitch angular acceleration ^d2θδ / ^dt2 is calculated so that the driver can recognize the pitch behavior of the vehicle when the recognition time tδ has elapsed.

When such a pitch angular acceleration is expressed as d ² θδ/dt ² , the pitch angular velocity dθδ/dt and the pitch angle change amount Δθδ of the pitch behavior that can be recognized by the driver are given by the following equations (1) and (2), respectively.
dθδ/dt=( ^d2θδ / ^dt2 )×tδ...(1)
Δθδ=( ^d2θδ / ^dt2 )× ^tδ2 /2...(2)

The relationship between the pitch angle velocity dθδ/dt and the pitch angle change amount Δθδ of the pitch behavior that the driver can recognize can be approximated by an approximation line 45 that is a linear approximation of the characteristic line 44, as shown in FIG. 5B. The approximation line 45 can be defined by the following equation (3).
Δθδ=a×dθδ/dt+b...(3)
By substituting the above expressions (1) and (2) into the above expression (3) and rearranging, the pitch angular acceleration d ² θδ/dt ² can be obtained as shown in the following expression (4).
d ² θδ/dt ² =2b/(tδ ² -2×a×tδ) ...(4)

By eliminating d ² θδ/dt ² from the above equations (1) and (2), the following equation (5) is obtained.
Δθδ=(tδ×(dθδ/dt))/2...(5)
The above equation (5) shows that when the recognition time tδ is long (i.e., when the steering angular velocity ω is small), a pitch behavior with a large pitch angle change amount and a small pitch angular velocity dθδ/dt is given, and when the recognition time tδ is short (i.e., when the steering angular velocity ω is large), a pitch behavior with a small pitch angle change amount and a large pitch angular velocity dθδ/dt is given.

3, the required moment calculation section 37 calculates a required moment Mr, which is a pitch moment (pitching moment) required for generating the pitch angular acceleration d ² θδ/dt ² calculated by the pitch behavior calculation section 36.
For example, the required moment calculation section 37 calculates the required moment Mr by multiplying the moment of inertia of the vehicle by the pitch angular acceleration d ² θδ/dt ² .
At this time, the required moment calculation unit 37 may estimate the weight and center of gravity position of the occupants and luggage based on the detection results of the load sensor and the amount of suspension sinking, etc., and correct the vehicle moment of inertia with these estimated values.

Required moment calculation section 37 outputs the calculated required moment Mr to braking/driving force control section 30 .
Braking/driving force control section 30 reduces the drive torque of front wheels 15FR and 15FL, thereby applying required moment Mr calculated by required moment calculation section 37 in a direction that tilts the vehicle body forward.
Additionally or alternatively, braking/driving force control section 30 may apply required moment Mr in a direction in which the vehicle body tilts forward by increasing the braking torque of front wheels 15FR and 15FL.

If the mounting position of the rear wheels 15RR and 15RL on the vehicle body is higher than the central axis of the rear wheels 15RR and 15RL, the braking/driving force control unit 30 may apply a required moment Mr in a direction in which the vehicle body tilts forward by increasing the driving force of the rear wheels 15RR and 15RL.
Braking/driving force control section 30 calculates a driving torque for applying required moment Mr to the vehicle based on the vehicle specifications and required moment Mr, and outputs a driving torque command value Td to driving force command value calculation section 31 .

In addition or instead, the braking/driving force control unit 30 calculates a braking torque to apply the required moment Mr to the vehicle based on the vehicle specifications and the required moment Mr, and outputs a braking torque command value Tb to the braking force command value calculation unit 32.

The driving force command value calculation unit 31 outputs a driving force command value corresponding to the input driving torque command value Td to the power control unit 13. The power control unit 13 generates a pitch behavior in the direction in which the vehicle body tilts forward by reducing the driving torque of the front wheels 15FR and 15FL and/or increasing the driving force of the rear wheels 15RR and 15RL based on the driving force command value.

In addition to or instead of this, the braking force command value calculation unit 32 outputs a braking force command value corresponding to the input braking torque command value Tb to the brake actuator 11. The brake actuator 11 increases the braking torque of the front wheels 15FR and 15FL based on the braking force command value, thereby generating a pitch behavior in the direction in which the vehicle body tilts forward.

(Variation 1)
In addition, when the steering angular velocity ω is relatively large, the recognition time tδ, which is the time until the driver starts to recognize the steering input, becomes short, so that it may not be possible to generate a pitch behavior that the driver can recognize in time. In this case, if a pitch behavior is generated after the driver recognizes the steering input, the driver may feel uncomfortable.
For this reason, the required moment calculation unit 37 may differentiate the steering angle θs to obtain the steering angular velocity ω, and if the steering angular velocity ω is equal to or greater than a predetermined speed, set the required moment Mr to zero to prevent pitch behavior from occurring.

(Variation 2)
In the above embodiment, when further steering is performed to increase the steering angle θs, a pitch behavior is generated in which the pitch angle changes in a direction in which the vehicle body tilts forward. In addition to this or instead, when return steering is performed to decrease the steering angle θs, a pitch behavior may be generated in which the pitch angle changes in a direction in which the vehicle body tilts backward.

(Variation 3)
In the above-described embodiment, the pitch behavior is generated by controlling the driving torque and/or braking torque generated in the wheels 15. In addition to or instead of this, the pitch behavior may be generated by driving an actuator of an active suspension.

(Operation)
An example of the vehicle behavior control method according to the embodiment will be described with reference to the flowcharts of FIG. 6 and FIG.
FIG. 6 is a flowchart of an example of a process for setting the steering angle threshold δ.
In step S<b>1 , the steering angle sensor 5 detects the steering angle θs of the steering wheel 20 .
In step S2, the torque sensor 6 detects the steering torque Ts applied to the steering wheel 20 by the driver.

In step S3, the steering force characteristic detection section 33 of the braking/driving force controller 10 generates a steering force characteristic Cs, which is the characteristic of the steering torque Ts relative to the steering angle θs, based on the steering angle θs and the steering torque Ts.
In step S<b>4 , the steering angle threshold setting unit 34 sets the steering angle threshold δ based on the steering force characteristic Cs generated by the steering force characteristic detection unit 33 .
The process then ends.

FIG. 7 is a flowchart of an example of a process for generating a pitch behavior.
In step S10, the steering angle sensor 5 detects the steering angle θs of the steering wheel 20.
In step S11, the recognition time calculation unit 35 differentiates the steering angle θs detected by the steering angle sensor 5 to calculate the steering angular velocity ω.

In step S12, the recognition time calculation unit 35 calculates a division result obtained by dividing the steering angle threshold value δ by the steering angular velocity ω as the recognition time tδ.
In step S13, the pitch behavior calculation unit 36 calculates the pitch angular acceleration d ² θδ/dt ² to be generated in the vehicle so as to generate a pitch behavior of the vehicle that is recognizable by the driver when the recognition time tδ has elapsed from the current time.

In step S14, the required moment calculation section 37 calculates a required moment Mr, which is a pitch moment required for generating the pitch angular acceleration d ² θδ/dt ² calculated by the pitch behavior calculation section 36.
In step S15, braking/driving force control section 30 applies required moment Mr calculated by required moment calculation section 37 in a direction that causes the vehicle body to tilt forward.
The process then ends.

(Effects of the embodiment)
(1) The steering angle sensor 5 detects the steering angle θs of the steering wheel 20. The torque sensor 6 detects the steering force Ts applied to the steering wheel 20 by the driver. The steering force characteristic detection unit 33 and the steering angle threshold setting unit 34 of the braking/driving force controller 10 set the steering angle threshold δ based on the detected steering force Ts. The braking/driving force control unit 30 causes the vehicle to pitch when the detected steering angle θs becomes equal to the steering angle threshold δ.

This allows the driver to realize that the vehicle behavior has occurred in response to the steering input (performed by the driver himself), making it possible to prevent excessive or insufficient steering and improving the steering feeling. As a result, the driver can easily turn the vehicle along a desired driving trajectory.
In addition, since a pitch behavior is generated in the vehicle when the driver recognizes a steering input, a natural feeling of vehicle response can be given to the driver.

(2) The recognition time calculation unit 35 may determine the time when the steering angle of the steering wheel 20 becomes the steering angle threshold δ based on the detected steering angle θs. The pitch behavior calculation unit 36, the required moment calculation unit 37, and the braking/driving force control unit 30 may generate a pitch behavior of the vehicle such that the pitch behavior of the vehicle becomes equal to or greater than a predetermined magnitude at the time when the steering angle θs becomes the steering angle threshold δ.
By generating a pitch behavior of a predetermined magnitude or more, the driver can easily recognize the pitch behavior. In addition, since the pitch behavior is generated in the vehicle when the steering angle of the steering wheel 20 reaches the steering angle threshold value δ, that is, when the driver recognizes the steering input, the driver can be given a natural feeling of vehicle response.

(3) The steering angle threshold setting unit 34 may set a larger steering angle threshold δ as the detected steering force Ts decreases.
The smaller the steering force Ts, the larger the steering angle θs at which the driver can recognize the steering input. Therefore, by setting a larger steering angle threshold δ as the steering force Ts becomes smaller, it is possible to more accurately determine whether the driver recognizes the steering input.

(4) The required moment calculation section 37 may increase the pitch angular velocity dθδ/dt of the pitch behavior generated in the vehicle as the steering angular velocity ω increases.
When the steering angular velocity ω is large, the driver is unlikely to feel uncomfortable even if a pitch behavior with a larger pitch angular velocity dθδ/dt occurs. Therefore, the driver can easily recognize the pitch behavior while suppressing the driver from feeling uncomfortable.

(5) The required moment calculation unit 37 may reduce the pitch angle change amount Δθδ of the pitch behavior caused to occur in the vehicle as the steering angular velocity ω increases.
In this way, when a pitch behavior with a large pitch angular velocity dθδ/dt is to be generated, the pitch behavior can be imparted without causing any discomfort by making the pitch angle change amount Δθδ small.

(6) The required moment calculation section 37 may prohibit the pitch behavior when the steering angular velocity ω is equal to or greater than a predetermined velocity.
When the steering angular velocity ω is relatively large, the recognition time tδ, which is the time until the driver begins to recognize the steering input, becomes short, so that the generation of pitch behavior that the driver can recognize may not be completed in time. In this case, the generation of pitch behavior after the driver recognizes the steering input can be prohibited to prevent the driver from feeling uncomfortable.

(7) When further steering is performed to increase the steering angle θs, the braking/driving force control section 30 may cause a change in pitch angle in the forward tilt direction as the pitch behavior described above.
This allows pitch behavior to occur without affecting the turning motion of the vehicle.

(8) The braking/driving force control unit 30 may generate the above-mentioned pitch behavior by reducing the driving force of the front wheels 15FR, 15FL, increasing the braking force of the front wheels 15FR, 15FL, or increasing the driving force of the rear wheels 15RR, 15RL, thereby causing a change in pitch angle in the forward tilt direction.
This allows pitch behavior to occur without affecting the turning motion of the vehicle.

1...driving/braking force control device, 2...accelerator sensor, 3...brake sensor, 4...vehicle speed sensor, 5...steering angle sensor, 6...torque sensor, 10...driving/braking force controller, 11...brake actuator, 12, 12FL, 12FR, 12RL, 12RR...wheel cylinder, 13...power control unit, 14...drive source, 15, 15FL, 15FR, 15RL, 15RR...wheel, 16...acceleration/deceleration pedal, 17...braking pedal, 20...steering wheel , 21...Steering shaft, 22...Universal joint, 23...Pinion shaft, 24...Steering gear, 25...Rack gear, 26...Steering rack, 27...EPS controller, 28...Steering assist motor, 30...Braking and driving force control unit, 31...Driving force command value calculation unit, 32...Braking force command value calculation unit, 33...Steering force characteristic detection unit, 34...Steering angle threshold setting unit, 35...Recognition time calculation unit, 36...Pitch behavior calculation unit, 37...Demand moment calculation unit

Claims (9)

Detects the steering angle of the steering wheel,
Detecting a steering force applied to the steering wheel by a driver;
setting a steering angle threshold for determining whether or not the driver has recognized that the driver himself/herself has input a steering force based on the detected steering force;
When the detected steering angle reaches the steering angle threshold value, a pitch behavior is generated in the vehicle.
A vehicle behavior control method comprising: determining a time when the steering angle of the steering wheel becomes the steering angle threshold value based on the detected steering angle;
generating a pitch behavior of the vehicle such that the pitch behavior of the vehicle is equal to or greater than a predetermined magnitude at a time point when the steering angle becomes the steering angle threshold value;
2. The vehicle behavior control method according to claim 1 . The vehicle behavior control method according to claim 1 or 2, characterized in that the smaller the detected steering force, the larger the steering angle threshold is set. The vehicle behavior control method according to any one of claims 1 to 3, characterized in that the greater the steering angular velocity of the steering wheel, the higher the pitch angular velocity of the pitch behavior generated in the vehicle. The vehicle behavior control method according to claim 4, characterized in that the greater the steering angular velocity, the smaller the pitch angle change amount of the pitch behavior caused in the vehicle. A vehicle behavior control method according to any one of claims 1 to 3, characterized in that the pitch behavior is not generated when the steering angular velocity of the steering wheel is equal to or greater than a predetermined speed. The vehicle behavior control method according to any one of claims 1 to 6, characterized in that when further steering is performed to increase the steering angle, a change in pitch angle in the forward tilt direction is generated as the pitch behavior. The vehicle behavior control method according to claim 7, characterized in that the pitch behavior is caused by a change in pitch angle in the forward tilt direction by either reducing the driving force of the front wheels, increasing the braking force of the front wheels, or increasing the driving force of the rear wheels. a first sensor for detecting a steering angle of a steering wheel;
a second sensor for detecting a steering force applied to the steering wheel by a driver;
a controller that sets a steering angle threshold based on the detected steering force to determine whether or not the driver recognizes that the driver himself/herself has input steering , and causes the vehicle to make a pitch behavior when the detected steering angle reaches the steering angle threshold;
A vehicle behavior control device comprising:

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