WO2024116409A1

WO2024116409A1 - Vehicle vibration damping method and vehicle vibration damping device

Info

Publication number: WO2024116409A1
Application number: PCT/JP2022/044603
Authority: WO
Inventors: 宏信菊池; 裕登井上
Original assignee: 日産自動車株式会社
Priority date: 2022-12-02
Filing date: 2022-12-02
Publication date: 2024-06-06

Abstract

Provided is a vehicle vibration damping method for reducing vibrations of a vehicle (100) by controlling at least one of a force in the vertical direction of the vehicle (100) or a moment in the pitch direction thereof, wherein: a first target value, which is a target value of the force in the vertical direction, and a second target value, which is a target value of the moment in the pitch direction, are set; when the sign of the first target value and the sign of the second target value are equal to each other, the force in the vertical direction is controlled on the basis of the first target value and the moment in the pitch direction is controlled on the basis of the second target value; and, when the signs are different from each other, switching between controlling the force in the vertical direction on the basis of the first target value and controlling the moment in the pitch direction on the basis of the second target value is performed on the basis of the magnitudes of the gains of the force in the vertical direction and the moment in the pitch direction relative to the vertical acceleration or longitudinal acceleration on a vehicle body spring.

Description

Vehicle vibration damping method and vehicle vibration damping device

The present invention relates to a vehicle vibration damping method and a vehicle vibration damping device.

Patent Document 1 below describes a technology that selects the larger of the first and second target damping forces that suppress vibrations in the heave and pitch directions of the vehicle body, and outputs a control signal to the damper according to the selected target damping force.

JP 2001-1736 A

However, if the larger of the damping forces that suppress vibrations in the vertical direction and the pitch direction of the vehicle body is simply selected and applied to the vehicle body, it may not be possible to efficiently suppress vibrations on the vehicle body springs.
An object of the present invention is to improve the efficiency of vibration suppression on the vehicle body springs when reducing vehicle vibration by controlling at least one of the force in the vertical direction or the moment in the pitch direction of the vehicle.

According to one aspect of the present invention, a vehicle vibration control method is provided that reduces vehicle vibration by controlling at least one of the vehicle's vertical force or pitch moment. In the vehicle vibration control method, a first target value, which is a target value of the vertical force, and a second target value, which is a target value of the pitch moment, are set, and when the sign of the upward vertical force and the sign of the pitch moment that lowers the front of the vehicle are the same, it is determined whether the sign of the first target value and the sign of the second target value are equal. If the signs are the same, the vertical force is controlled based on the first target value and the pitch moment is controlled based on the second target value. If the signs are different, the priority between the vertical force and the pitch moment is determined based on the magnitude of the gain of the vertical force and the pitch moment relative to the vertical acceleration or the front-rear acceleration on the vehicle's body springs. If the priority of the vertical force is higher than the priority of the pitch moment, the vertical force is controlled based on the first target value and the control of the pitch moment based on the second target value is limited. If the priority of the pitch moment is higher than the priority of the vertical force, the pitch moment is controlled based on the second target value and the control of the vertical force based on the first target value is limited.

According to the present invention, when vibrations of a vehicle are reduced by controlling at least one of the force in the vertical direction and the moment in the pitch direction of the vehicle, it is possible to improve the efficiency of vibration suppression on the vehicle body springs.
The objects and advantages of the invention will be realized and attained by means of the elements and combinations recited in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

1 is a schematic configuration diagram of a vehicle equipped with a vehicle vibration damping device according to an embodiment; FIG. 2 is a schematic diagram of a suspension structure. FIG. 2 is a block diagram of an example of a functional configuration of a controller. FIG. 11 is a frequency characteristic diagram of the gain of the vertical acceleration and the longitudinal acceleration of an occupant's head relative to the vertical speed and pitch rate of the vehicle body. FIG. 4 is a block diagram of an example of a functional configuration of a chattering suppression unit. 13 is a block diagram of an example of a functional configuration of a limiting coefficient calculation unit. FIG. 6A and 6B are diagrams illustrating examples of limit coefficient settings. FIG. 4 is a block diagram of an example of a functional configuration of a target torque determination unit. 2 is a flowchart of an example of a vehicle vibration damping method according to an embodiment. 13 is a flowchart of an example of a priority order determination process. 13A and 13B are schematic diagrams showing the results of a simulation.

(composition)
Referring to Fig. 1, a vehicle 100 includes a steering angle measurement device 1, a steering device 2, an accelerator pedal 3, a brake pedal 4, an inertial measurement unit (IMU) 5, wheel speed measurement devices 6FR, 6FL, 6RR, and 6RL, a right front wheel 7FR, a left front wheel 7FL, a right rear wheel 7RR, and a left rear wheel 7RL, front wheel drive shafts 8FR and 8FL, rear wheel drive shafts 8RR and 8RL, a controller 10, a power converter 11, a front wheel drive source 12F, a rear wheel drive source 12R, and a battery 13. In the following description, the right front wheel 7FR and the left front wheel 7FL may be collectively referred to as "front wheels 7F", and the right rear wheel 7RR and the left rear wheel 7RL may be collectively referred to as "rear wheels 7R".

The steering angle measurement device 1 measures the steering angle δf of the steering wheel 2a, which steers the steered wheels (i.e., the front wheels 7F) to change the traveling direction of the vehicle 100, and outputs it to the controller 10. The steering angle measurement device 1 may measure the steering angle of the front wheels 7F instead of the steering angle δf of the steering wheel 2a. In this case, the steering angle δf may be calculated by multiplying the steering angle by the steering gear ratio. If the vehicle 100 is equipped with a driving assistance device that automatically controls the steering angle of the front wheels 7F, the steering angle measurement device 1 may acquire the steering angle δf or the command value of the steering angle generated by the driving assistance device instead of the measured value of the steering angle δf or the steering angle.

The steering device 2 is composed of a steering wheel 2a, a steering shaft 2b connected to it, and a steering mechanism (not shown) that can change the angle of the front wheels 7F relative to the vehicle 100. The steering angle measurement device 1 is connected to the steering device 2, and measures the change in angle of the steering shaft 2b that accompanies the rotation of the steering wheel 2a by the driver. In a typical vehicle, the rotation of the steering shaft 2b is converted by the steering device into a change in the angle of the front wheels 7F relative to the vehicle 100. On the other hand, in a steer-by-wire system, the drive shaft may be omitted.

The accelerator pedal 3 is a member operated by the driver to adjust the acceleration/deceleration of the vehicle 100. The accelerator pedal 3 has a sensor that measures its stroke amount (hereinafter referred to as "accelerator operation amount Ac") and transmits the measured accelerator operation amount Ac to the controller 10. When acceleration/deceleration control is performed by the driving support device separately from the driver's operation of the accelerator pedal 3, the controller 10 may obtain the acceleration/deceleration command from the driving support device as the accelerator operation amount Ac. The brake pedal 4 is a member operated by the driver to adjust the deceleration of the vehicle 100. The brake pedal 4 has a sensor that measures its stroke amount (hereinafter referred to as "brake operation amount Br") and transmits the measured brake operation amount Br to the controller 10. When deceleration control is performed by the driving support device separately from the driver's operation of the brake pedal 4, the controller 10 may obtain the deceleration command from the driving support device as the brake operation amount Br.

The IMU 5 detects the time rates of change dφ, dθ, and dψ of the roll angle φ, pitch angle θ, and yaw angle ψ of the vehicle 100, as well as the longitudinal acceleration ddx, lateral acceleration ddy, and vertical acceleration ddz, and transmits them to the controller 10.
The wheel speed measurement devices 6FR, 6FL, 6RR, and 6RL (hereinafter sometimes collectively referred to as "wheel speed measurement device 6") measure the wheel speeds ωFR, ωFL, ωRR, and ωRL of the right front wheel 7FR, the left front wheel 7FL, the right rear wheel 7RR, and the left rear wheel 7RL, respectively, and output them to the controller 10. The front wheel drive shafts 8FR and 8FL are installed at positions corresponding to the right front wheel 7FR and the left front wheel 7FL, respectively, and transmit the driving force and braking force generated by the front wheel drive source 12F to the right front wheel 7FR and the left front wheel 7FL. A degree of rotational freedom is provided between the front wheel 7F and the front wheel 7F, allowing the steering device 2 to change the steering angle of the front wheel 7F. The rear wheel drive shafts 8RR and 8RL are installed at positions corresponding to the right rear wheel 7RR and the left rear wheel 7RL, respectively, and transmit the driving force and braking force generated by the rear wheel drive source 12R to the right rear wheel 7RR and the left rear wheel 7RL. In the case of a vehicle capable of rear wheel steering, a degree of rotational freedom is provided between the rear wheel 7R and the rear wheel drive shafts 8RR and 8RL, making it possible to change the steering angle of the rear wheel 7R.

The controller 10 is an electronic control unit (ECU) that independently controls the braking/driving force generated on the front wheels 7F and the braking/driving force generated on the rear wheels 7R. The controller 10 includes a processor 10a and peripheral components such as a storage device 10b. The processor 10a may be, for example, a central processing unit (CPU) or a micro-processing unit (MPU). The storage device 10b may include a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The functions of the controller 10 described below are realized, for example, by the processor 10a executing a computer program stored in the storage device 10b.
The controller 10 determines target braking/driving torques Tft, Trt of the front wheel drive source 12F and the rear wheel drive source 12R based on the steering angle δf, accelerator operation amount Ac, brake operation amount Br, roll angle φ, pitch angle θ, yaw angle ψ's time rates of change dφ, dθ, dψ, longitudinal acceleration ddx, lateral acceleration ddy, vertical acceleration ddz, and wheel speeds ωFR, ωFL, ωRR, and ωRL obtained from the steering angle measurement device 1, accelerator pedal 3, brake pedal 4, IMU 5, and wheel speed measurement device 6, respectively, and outputs them to the power converter 11.

The power converter 11 converts the power supplied from the battery 13 electrically connected to the power converter 11 into power to be supplied to the front wheel drive source 12F and the rear wheel drive source 12R so as to realize the target braking/driving torques Tft, Trt commanded by the controller 10. The front wheel drive source 12F and the rear wheel drive source 12R are also used as generators, and regenerative power is supplied to the battery 13 through the power converter 11 to charge it. Although a single power converter 11 is shown for the front wheel drive source 12F and the rear wheel drive source 12R in FIG. 1, the power converter 11 can supply power independently so that the front wheel drive source 12F and the rear wheel drive source 12R can generate braking and driving forces independently.

The front-wheel drive source 12F and the rear-wheel drive source 12R generate driving force and braking force for the front wheels 7F and the rear wheels 7R, respectively. For example, the front-wheel drive source 12F and the rear-wheel drive source 12R may each include an electric motor and a reduction gear to which the rotating shaft is connected. The electric motor is connected to the power converter 11 and converts the power supplied from the power converter 11 into the rotational force of the rotor of the electric motor. Alternatively, the electric motor is used as a generator, and electricity is extracted from the rotational force and used to charge the battery 13. The reduction gear converts the rotational speed between the rotor and the front-wheel drive shafts 8FR and 8FL or the rear-wheel drive shafts 8RR and 8RL, thereby converting the rotational torque generated in the rotor into the driving torque or braking torque of the front-wheel drive shafts 8FR and 8FL or the rear-wheel drive shafts 8RR and 8RL. Note that the power source of the front-wheel drive source 12F and/or the rear-wheel drive source 12R is not limited to an electric motor, and may be, for example, an internal combustion engine.

2 is a schematic diagram of a suspension structure of the front wheels 7F and rear wheels 7R relative to the vehicle body 20 of the vehicle 100. The wheels are connected via a link mechanism so that the degree of freedom of movement relative to the vehicle body 20 is one degree of freedom, excluding the degree of freedom of movement used for steering. In addition, one end of the

spring mechanisms

21f, 21r that generate a force proportional to the relative displacement from a stationary position between the vehicle body 20 and the wheel, and one end of the

damper mechanisms

22f, 22r that generate a force proportional to the relative speed between the vehicle body 20 and the wheel are connected to the link mechanism or the axle, and the other end is connected to the vehicle body 20, so that the relative motion between the vehicle body 20 and the wheel is passively suppressed.
Due to the configuration of the link mechanism between the vehicle body 20 and the wheels, there are points (hereinafter referred to as "instantaneous rotation centers") 23f, 23r at which the relative position change between the vehicle body 20 and the wheels becomes zero instantaneously. The angle between the straight line connecting the instantaneous rotation center 23f to the wheel center of the front wheel 7F and the horizontal line along the vehicle longitudinal direction is called the anti-dive angle θf, and the angle between the straight line connecting the wheel center of the rear wheel 7R and the horizontal line is called the anti-squat angle θr. In this specification, it is assumed that the anti-dive angle θf and the anti-squat angle θr are positive.

The braking/driving force Fxf acting on the front wheels 7F is calculated by dividing the braking/driving torque Tf of the front wheel drive source 12F by the rotation radius rtf of the tire of the front wheel 7F, and the braking/driving force Fxr acting on the rear wheels 7R is calculated by dividing the braking/driving torque Tr of the rear wheel drive source 12R by the rotation radius rtr of the tire of the rear wheel 7R. The signs of the braking/driving forces Fxf and Fxr are defined so that the sign of the drive torque is "positive" and the sign of the braking torque is "negative".
For example, when the driving

sources

12F and 12R are motors and drive torque is transmitted to each wheel via a reduction gear, a differential gear, and a drive shaft, the application point of the braking and driving forces Fxf and Fxr is the wheel center. When the braking and driving forces Fxf and Fxr act on the wheel center, a vertical force Fzf=-Fxf×tan θf acts on the front wheel 7F, and a vertical force Fzr=Fxr×tan θr acts on the rear wheel 7R. The signs of the vertical forces Fzf and Fzr are defined so that the sign of the upward force is "positive" and the sign of the downward force is "negative". Fz2f, Fz2r, Fx2f, and Fx2r are internal forces between the vehicle body 20 and the wheels, and Fz1f and Fz1r are internal forces between the road surface and the wheels. Also, Usf and Usr are control forces acting by actuators in the suspension, and these are also internal forces between the vehicle body 20 and the wheels.

3 is a block diagram of an example of a functional configuration of the controller 10. The controller 10 includes a target value setting unit 30, a frequency component analysis unit 31, a vehicle speed calculation unit 32, a priority order determination unit 33, a chattering suppression unit 34, a limit coefficient calculation unit 35, and a target torque determination unit 36.
The target value setting unit 30 calculates the required amounts of force and moment used to suppress vibrations of the body of the vehicle 100.
Now, if the required amount of force in the vertical direction, the required amount of moment in the pitch direction, and the required amount of force in the fore-aft direction are respectively the first target value Fz2, the second target value Mp2, and the third target value Fx2, the relationship between the target values Fz2, Mp2, and Fx2 and the braking/driving torques Tf and Tr is given by the following equation.

In equation (1), "lf" and "lr" are the distances from the center of gravity of the vehicle 100 to the front wheel 7F and the rear wheel 7R, respectively, and "μ" is the front/rear torque distribution.
The first target value Fz2, the second target value Mp2, and the third target value Fx2 can be set by multiplying the vertical speed dz, pitch rate dθ, and longitudinal speed dx of the vehicle 100 by predetermined feedback gains (-Cdz), (-Cdp), and (-Cdx), respectively.

Here, when the front wheels 7F and the rear wheels 7R are driven by independent drive sources, the degree of freedom of the controllable parameters is "2." For this reason, of the feedback gains (-Cdz), (-Cdp), and (-Cdx), the feedback gain (-Cdx) for calculating the third target value Fx2 in the fore-aft direction is set to "0."
In addition, to prevent the braking/driving forces generated at the front wheels 7F and the rear wheels 7R from affecting the longitudinal acceleration, the braking/driving torques Tf and Tr of the front wheels 7F and the rear wheels 7R are set to satisfy the following equation, and the braking/driving forces due to the braking/driving torques Tf and Tr are offset by each other.
Tf = -rtf/rtr x Tr
Therefore, the degree of freedom of control is one, and only one of the braking/driving torques Tf, Tr of the front wheels 7F and the rear wheels 7R can be freely set.
In this specification, the braking/driving torque Tr of the rear wheels 7R that satisfies the first target value Fz2 and the second target value Mp2 is calculated, and the braking/driving torque Tf of the front wheels 7F is calculated using the above equation.
The target value setting unit 30 calculates the vertical velocity dz based on the vertical acceleration ddz acquired by the IMU 5, and multiplies the vertical velocity dz by a feedback gain (-Cdz) to calculate a first target value Fz2=(-Cdz)×dz. Also, the target value setting unit 30 multiplies the pitch rate dθ acquired by the IMU 5 by a feedback gain (-Cdp) to calculate a second target value Mp2=(-Cdp)×dθ.

The vehicle speed calculation unit 32 calculates the vehicle speed V, which is the speed of the center of gravity of the body of the vehicle 100, based on the wheel speeds ωFR, ωFL, ωRR, and ωRL. The vehicle speed calculation unit 32 multiplies the average wheel speed ωF = (ωFR + ωFL)/2 of the front wheels 7F by the rotation radius rtf of the tires of the front wheels 7F to calculate the first vehicle speed VF = rtf x ωF. The vehicle speed calculation unit 32 multiplies the average wheel speed ωR = (ωRR + ωRL)/2 of the rear wheels 7R by the rotation radius rtr of the tires of the rear wheels 7R to calculate the second vehicle speed VR = rtr x ωR. The first vehicle speed VF and the second vehicle speed VR are averaged to obtain the vehicle speed V = (VF + VR)/2.

The frequency component analysis unit 31 calculates frequency components of the vehicle behavior. The frequency component analysis unit 31 acquires the vertical acceleration ddz and the pitch rate dθ from the IMU 5. The frequency component analysis unit 31 calculates the vertical velocity dz based on the vertical acceleration ddz, and extracts the frequency component dzf of the vertical velocity dz in the first frequency band Δf1 by performing bandpass filter processing on the vertical velocity dz. In addition, the frequency component analysis unit 31 extracts the frequency component dθf of the pitch rate dθ in the second frequency band Δf2 by performing bandpass filter processing on the pitch rate dθ.
The first frequency band Δf1 is set so as to include frequency components that cause the vertical velocity dz to significantly affect the vertical acceleration or the longitudinal acceleration on the vehicle body springs of the vehicle 100. For example, the first frequency band Δf1 is set so that the effect of the vertical velocity dz in the first frequency band Δf1 on the vertical acceleration or the longitudinal acceleration on the vehicle body springs is greater than the effect in frequency bands other than the first frequency band Δf1.
Moreover, the second frequency band Δf2 is set so as to include frequency components that cause the pitch rate dθ to significantly affect the vertical acceleration or the longitudinal acceleration on the vehicle body springs of the vehicle 100. For example, the second frequency band Δf2 is set so that the effect of the pitch rate dθ in the second frequency band Δf2 on the vertical acceleration or the longitudinal acceleration on the vehicle body springs is larger than the effect in frequency bands other than the second frequency band Δf2.

4 is a frequency characteristic diagram of the gain of the vertical acceleration and the longitudinal acceleration of the occupant's head relative to the vertical velocity dz and the pitch rate dθ of the vehicle body. Gain Gxz is the gain of the longitudinal acceleration of the head at the position of the occupant's forehead relative to the vertical velocity dz, gain Gxp is the gain of the longitudinal acceleration of the head relative to the pitch rate dθ, gain Gzz is the gain of the vertical acceleration of the head relative to the vertical velocity dz, and gain Gzp is the gain of the vertical acceleration of the head relative to the pitch rate dθ.
The range indicated by the arrow 40 contains peaks of the gains Gxz and Gzz, and the vertical velocity dz greatly affects the vertical acceleration or longitudinal acceleration on the body springs of the vehicle 100. Therefore, the first frequency band Δf1 is set to include the range indicated by the arrow 40. Furthermore, the range indicated by the arrow 41 contains peaks of the gains Gxp and Gzp, and the pitch rate dθ greatly affects the vertical acceleration or longitudinal acceleration on the body springs of the vehicle 100. Therefore, the second frequency band Δf2 is set to include the range indicated by the arrow 41.

3, the priority determination unit 33 determines the priority between suppression of vibration of the vehicle 100 based on the first target value Fz2 and suppression of vibration of the vehicle 100 based on the second target value Mp2, and calculates the target braking/driving torque Tr0 based on the determination result.
The priority determination unit 33 determines whether the sign of the first target value Fz2 and the sign of the second target value Mp2 are equal. Here, the sign of the upward vertical force and the sign of the moment in the pitch direction (diving pitch) that lowers the front of the vehicle 100 are defined as being the same sign. For example, the sign of the upward vertical force and the sign of the moment in the pitch direction that lowers the front of the vehicle 100 may be defined as being positive. Instead of determining the sign of the first target value Fz2 and the sign of the second target value Mp2, it may be determined whether the sign of the vertical velocity dz and the sign of the pitch rate dθ are equal.
When the sign of the first target value Fz2 and the sign of the second target value Mp2 are the same, the target braking/driving torque Tr0 is calculated based on the following equation (1).

When the sign of the first target value Fz2 and the sign of the second target value Mp2 are the same, the first and second terms on the right side of the formula (1) also have the same sign, and the torque component based on the first target value Fz2 and the torque component based on the second target value Mp2 do not cancel each other out. On the other hand, when the signs of the two are different, the torque component based on the first target value Fz2 and the torque component based on the second target value Mp2 cancel each other out, resulting in a reduction in the vibration suppression effect. Therefore, when the sign of the first target value Fz2 and the sign of the second target value Mp2 are different, it is determined which has a higher priority: calculating the target braking/driving torque Tr0 using only the first target value Fz2 as the required force to suppress the vertical speed, or calculating the target braking/driving torque Tr0 using only the second target value Mp2 as the required force to suppress the pitch rate.
First, the priority order determination unit 33 determines whether the vehicle speed V is equal to or greater than a threshold value Vth. If the vehicle speed V is equal to or greater than the threshold value Vth, the priority order determination unit 33 calculates the target braking/driving torque Tr0 using only the second target value Mp2 as the required force based on the following equation (2).

Since the higher the vehicle speed V, the farther the driver's gaze point becomes and the greater the change in the gaze point due to the pitching of the vehicle body, the pitch rate can be suppressed to suppress the change in the gaze point. Also, in a driving assistance system using a camera or radar, when the vehicle speed V is high, it is necessary to detect objects that are farther away, so the detection accuracy of the sensor can be improved by suppressing pitching.
In addition, when the absolute value |dθf| of the frequency components of the pitch rate dθ in the second frequency band Δf2 is larger than the threshold value dθth, the target braking/driving torque Tr0 is calculated based on the following equation (2). As a result, when the pitch rate dθ contains many frequency components that significantly affect the vertical acceleration or longitudinal acceleration on the vehicle body springs, vibrations in the pitch direction are preferentially suppressed, thereby making it possible to effectively suppress vibrations for the occupants and improve ride comfort.
On the other hand, when the absolute value |dzf| of the frequency component of the vertical velocity dz in the first frequency band Δf1 is greater than the threshold value dzth, the target braking/driving torque Tr0 is calculated using only the first target value Fz2 as the required force based on the following equation (3).

When the absolute value |dθf| of the frequency component is greater than the threshold value dθth and the absolute value |dzf| of the frequency component is greater than the threshold value dzth, or when the absolute value |dθf| of the frequency component is equal to or less than the threshold value dθth and the absolute value |dzf| of the frequency component is equal to or less than the threshold value dzth, it is considered that the priority determination based on the frequency component is not possible, and the priority is determined based on the vehicle specifications. Specifically, the priority determination unit 33 determines which has a higher priority, whether to calculate the target braking/driving torque Tr0 using only the first target value Fz2 as the required force or to calculate the target braking/driving torque Tr0 using only the second target value Mp2 as the required force, based on the absolute value |θf-θr| of the difference between the anti-dive angle θf and the anti-squat angle θr determined by the vehicle specifications such as the geometric relationship between the suspension and the tires of the vehicle.
When the anti-dive angle θf and the anti-squat angle θr are equal, the magnitude of the vertical forces generated by the front wheels 7F and the rear wheels 7R are equal. Therefore, vibration can only be suppressed in the vertical direction by converting the braking/driving forces of the front wheels 7F and the rear wheels 7R into vertical forces. Therefore, when the absolute value |θf-θr| of the difference between the anti-dive angle θf and the anti-squat angle θr is less than the threshold value, the priority order determination unit 33 calculates the target braking/driving torque Tr0 based on the above equation (3).

On the other hand, when the difference between the anti-dive angle θf and the anti-squeezing angle θr is large, a moment can be generated by converting the braking/driving force of the front wheels 7F and the rear wheels 7R into vertical forces. Therefore, when the absolute value |θf-θr| of the difference between the anti-dive angle θf and the anti-squeezing angle θr is equal to or greater than a threshold value, the priority determination unit 33 calculates the target braking/driving torque Tr0 based on the above formula (2).

The chattering suppression unit 34 suppresses chattering when switching between the target braking/driving torque Tr0 (equation (3)) calculated using only the first target value Fz2 as the required force and the target braking/driving torque Tr0 (equation (2)) calculated using only the second target value Mp2 as the required force. FIG. 5 is a block diagram of an example of the functional configuration of the chattering suppression unit 34. The chattering suppression unit 34 includes a rate limiter 50 and a low-pass filter (LPF) 51. The rate limiter 50 limits the time rate of change of the target braking/driving torque Tr0 to a limit value or less. The rate limiter 50 may limit the time rate of change with the same limit value L when the target braking/driving torque Tr0 increases and decreases, or may limit with different limit values L1 and L2. The LPF 51 applies low-pass filtering to the target braking/driving torque Tr0 whose time rate of change has been limited by the rate limiter 50, and outputs the target braking/driving torque Tr1 after low-pass filtering. By appropriately setting the limit values L, L1, and L2 of the rate limiter 50 and the cutoff frequency of the LPF 51, it is possible to suppress sudden changes in the target torque even if switching occurs continuously.

3, the limiting coefficient calculation unit 35 calculates a limiting coefficient C that limits the target braking/driving torque Tr1 in accordance with the driver's operation input and the vehicle body behavior of the vehicle 100.
6 is a block diagram of an example of a functional configuration of the limiting coefficient calculation unit 35. The limiting coefficient calculation unit 35 includes a driver input determination unit 60, a vehicle body behavior determination unit 61, a wheel speed difference dependent limiting coefficient setting unit 62, and a limiting coefficient setting unit 63.
The driver input determination unit 60 sets the value of the driver input flag Cd to "0" when the accelerator operation amount Ac exceeds the threshold value Acth, when the brake operation amount Br exceeds the threshold value Brth, or when the steering angle δf exceeds the threshold value δfth, and sets the value of the driver input flag Cd to "1" when the accelerator operation amount Ac does not exceed the threshold value Acth, the brake operation amount Br does not exceed the threshold value Brth, and the steering angle δf does not exceed the threshold value δfth.
The vehicle body behavior determination unit 61 sets the value of the vehicle body behavior flag Cm to "0" when the longitudinal acceleration ddx exceeds the threshold value ddxth, when the lateral acceleration ddy exceeds the threshold value ddyth, or when the yaw rate dψ exceeds the threshold value dψth, and sets the value of the vehicle body behavior flag Cm to "1" when the longitudinal acceleration ddx does not exceed the threshold value ddxth, the lateral acceleration ddy does not exceed the threshold value ddyth, and the yaw rate dψ does not exceed the threshold value dψth.

The wheel speed difference dependent limiting coefficient setting unit 62 sets a front/rear wheel speed difference dependent limiting coefficient Cfr that limits the target braking/driving torque Tr0 when the wheel speed difference Δωfr = ωF - ωR between the front wheels 7F and the rear wheels 7R is excessively large (for example, when slippage occurs at the front wheels 7F and/or the rear wheels 7R). Figure 7 (a) shows an example of setting the front/rear wheel speed difference dependent limiting coefficient Cfr. The front/rear wheel speed difference dependent limiting coefficient Cfr has a value in the range from "0" to "1". The front/rear wheel speed difference dependent limiting coefficient Cfr is "1" when the wheel speed difference |Δωfr| is equal to or less than the threshold value Δωfr1, decreases from "1" to "0" as the wheel speed difference |Δωfr| increases in the range where the wheel speed difference |Δωfr| is equal to or more than the threshold value Δωfr1 and equal to or less than the threshold value Δωfr2, and becomes "0" when the wheel speed difference |Δωfr| is equal to or more than the threshold value Δωfr2. The thresholds Δωfr1 and Δωfr2 may be set appropriately using vehicle specifications, simulations, and experiments with an actual vehicle.

The wheel speed difference dependent limiting coefficient setting unit 62 sets a left/right wheel speed difference dependent limiting coefficient Clrf that limits the target braking/driving torque Tr0 when the wheel speed difference Δωlrf between the right front wheel 7FR and the left front wheel 7FL is excessive (for example, when slippage occurs in either the right front wheel 7FR or the left front wheel 7FL). FIG. 7B shows an example of setting the left/right wheel speed difference dependent limiting coefficient Clrf. The left/right wheel speed difference dependent limiting coefficient Clrf has a value in the range from "0" to "1". The left/right wheel speed difference dependent limiting coefficient Clrf is "1" when the wheel speed difference |Δωlrf| is equal to or less than the threshold value Δωlrf1, decreases from "1" to "0" as the wheel speed difference |Δωlrf| increases in the range where the wheel speed difference |Δωlrf| is equal to or more than the threshold value Δωlrf1 and equal to or less than the threshold value Δωlrf2, and becomes "0" when the wheel speed difference |Δωlrf| is equal to or more than the threshold value Δωlrf2. The threshold values Δωlrf1 and Δωlrf2 may be set appropriately using vehicle specifications, simulations, and experiments using an actual vehicle.
Similar to the method of setting the left/right wheel speed difference dependent limiting coefficient Clrf, the wheel speed difference dependent limiting coefficient setting unit 62 sets a left/right wheel speed difference dependent limiting coefficient Clrr that limits the target braking/driving torque Tr0 when the wheel speed difference Δωlrr between the right rear wheel 7RR and the left rear wheel 7RL is excessively large (for example, when slippage occurs at either the right rear wheel 7RR or the left rear wheel 7RL).

The limit coefficient setting unit 63 selects the minimum value from the front/rear wheel speed difference dependent limit coefficient Cfr and the left/right wheel speed difference dependent limit coefficients Clrf and Clrr, and multiplies the selected minimum value by the driver input flag Cd and the vehicle body behavior flag Cm to calculate the product as limit coefficient C=Cd×Cm×min(Cfr, Clrf, Clrr). The limit coefficient setting unit 63 outputs the limit coefficient C to the target torque determination unit 36.
3, the target torque determination unit 36 calculates a limited target braking/driving torque Trt for the rear wheels 7R by limiting the target braking/driving torque Tr1 output by the chattering suppression unit 34 with the limiting coefficient C. In addition, the target braking/driving torque Tft for the front wheels 7F is calculated so that all or part of the braking/driving force generated at the rear wheels 7R by the target braking/driving torque Trt is offset by the braking/driving force of the front wheels 7F.
8 is a block diagram of an example of a functional configuration of the target torque determination unit 36. The target torque determination unit 36 includes a target torque correction unit 70, a rate limiter 71, an LPF 72, and a front wheel torque calculation unit 73.

A target torque correction unit 70 calculates a product C×Tr1 by multiplying the target braking/driving torque Tr1 by a limiting coefficient C. A rate limiter 71 limits the time rate of change of the product C×Tr1. An LPF 72 performs low-pass filtering on the output of the rate limiter 71 to calculate a target braking/driving torque Trt for the rear wheels 7R.
Furthermore, the target torque correction unit 70 calculates a target braking/driving torque Tft that generates a braking/driving force on the front wheels 7F that offsets all or part of the braking/driving force generated on the rear wheels 7R by the target braking/driving torque Trt, based on the target braking/driving torque Trt of the rear wheels 7R. For example, the target torque correction unit 70 may calculate the target braking/driving torque Tft based on the following equation.
Tft = -(rtf/rtr) x Trt
Referring to Fig. 1, the controller 10 outputs target braking/driving torques Tft and Trt to the power converter 11. The power converter 11 supplies electric power to the front-wheel drive source 12F and the rear-wheel drive source 12R so as to realize the target braking/driving torques Tft and Trt commanded by the controller 10. The front-wheel drive source 12F and the rear-wheel drive source 12R generate braking/driving forces corresponding to the target braking/driving torques Tft and Trt on the front wheels 7F and the rear wheels 7R, respectively.

(motion)
9 is a flowchart of an example of a vehicle vibration damping method according to an embodiment. In step S1, the controller 10 acquires information measured by the IMU 5. In step S2, the target value setting unit 30 sets a first target value Fz2 and a second target value Mp2. In step S3, the vehicle speed calculation unit 32 calculates the vehicle speed V, which is the speed of the center of gravity of the body of the vehicle 100. In step S4, the frequency component analysis unit 31 calculates frequency components dzf and dθf of the vehicle behavior.
In step S5, the priority order determination unit 33 performs a priority order determination process. In the priority order determination process, the priority order between suppression of vibration of the vehicle 100 based on the first target value Fz2 and suppression of vibration of the vehicle 100 based on the second target value Mp2 is determined, and the target braking/driving torque Tr0 is calculated based on the determination result. The details of the priority order determination process will be described later with reference to FIG. 10.

In step S6, the chattering suppression unit 34 suppresses chattering at the switching between the target braking/driving torque Tr0 calculated using only the first target value Fz2 as the required force and the target braking/driving torque Tr0 calculated using only the second target value Mp2 as the required force. In step S7, the limiting coefficient calculation unit 35 calculates the limiting coefficient C. In step S8, the target torque determination unit 36 calculates the target braking/driving torque Trt for the rear wheels 7R by limiting the target braking/driving torque Tr1 after suppressing chattering using the limiting coefficient C. In addition, the target braking/driving torque Tft for the front wheels 7F is calculated based on the target braking/driving torque Trt for the rear wheels 7R.
In step S9, the power converter 11, the front wheel drive source 12F and the rear wheel drive source 12R generate braking/driving forces for the front wheels 7F and the rear wheels 7R according to the target braking/driving torques Tft and Trt, respectively.

10 is a flowchart of an example of a priority order determination process. In step S10, the priority order determination unit 33 determines whether the sign of the first target value Fz2 and the sign of the second target value Mp2 are the same. If the signs are the same (step S10: Y), the process proceeds to step S11. If the signs are different (step S10: N), the process proceeds to step S12. In step S11, the priority order determination unit 33 calculates the target braking/driving torque Tr0 based on the above formula (1).
In step S12, the priority order determination unit 33 determines whether the vehicle speed V is equal to or greater than the threshold value Vth. If the vehicle speed V is equal to or greater than the threshold value Vth (step S12: Y), the process proceeds to step S13. If the vehicle speed V is less than the threshold value Vth (step S12: N), the process proceeds to step S14. In step S13, the priority order determination unit 33 calculates the target braking/driving torque Tr0 based on the above formula (2).

In step S14, the priority determination unit 33 determines whether the absolute value |dθf| of the frequency component of the pitch rate dθ in the second frequency band Δf2 is greater than the threshold value dθth, and whether the absolute value |dzf| of the frequency component of the vertical velocity dz in the first frequency band Δf1 in the first frequency band Δf1 is greater than the threshold value dzth. If the absolute value |dθf| is greater than the threshold value dθth and the absolute value |dzf| is greater than the threshold value dzth (step S14: Y), the process proceeds to step S15. If the absolute value |dθf| is equal to or less than the threshold value dθth or the absolute value |dzf| is equal to or less than the threshold value dzth (step S14: N), the process proceeds to step S16. In step S15, the priority determination unit 33 calculates the target braking/driving torque Tr0 based on either the above formula (2) or (3) according to the absolute value |θf-θr| of the difference between the anti-dive angle θf and the anti-squat angle θr.

In step S16, the priority determination unit 33 determines whether the absolute value |dθf| is greater than the threshold value dθth. If the absolute value |dθf| is greater than the threshold value dθth (step S16: Y), the process proceeds to step S17. If the absolute value |dθf| is equal to or less than the threshold value dθth (step S16: N), the process proceeds to step S18. In step S17, the priority determination unit 33 calculates the target braking/driving torque Tr0 based on the above formula (2).
In step S18, it is determined whether the absolute value |dzf| is greater than the threshold value dzth. If the absolute value |dzf| is greater than the threshold value dzth (step S18: Y), the process proceeds to step S19. If the absolute value |dzf| is equal to or less than the threshold value dzth (step S18: N), the process proceeds to step S20. In step S19, the priority determination unit 33 calculates the target braking/driving torque Tr0 based on the above formula (3).
In step S20, the priority determination unit 33 calculates the target braking/driving torque Tr0 based on either the above formula (2) or (3) in accordance with the absolute value |θf-θr| of the difference between the anti-dive angle θf and the anti-squat angle θr.

(simulation result)
Fig. 11(a) is a schematic diagram of the simulation result of the frequency characteristic of the gain of the vertical displacement of the vehicle body relative to the vertical displacement of the tire contact point, and Fig. 11(b) is a schematic diagram of the simulation result of the frequency characteristic of the gain of the pitch angle change of the vehicle body relative to the pitch angle change of the tire contact point. The dashed line shows the simulation result when the target braking/driving torque is always calculated by the above formula (1), and the solid line and dotted line show the simulation result when the above formula (2) and (3) are switched, respectively, when the signs of the first target value Fz2 and the second target value Mp2 are different. It can be seen that the vehicle behavior is more suppressed by switching the target braking/driving torque when the signs of the first target value Fz2 and the second target value Mp2 are different, compared to the case where the above formula (1) is always used.

(Modification)
In the above embodiment, an example has been described in which the braking/driving forces generated by the front-wheel drive source 12F and the rear-wheel drive source 12R are controlled to control at least one of the vertical force and the pitch moment, but the present invention is not limited to such an example. The present invention can also be applied to cases in which the vertical force or the pitch moment is controlled by controlling, for example, the braking forces generated by the braking device on the front wheels 7F and the rear wheels 7R, the stroke of the active suspension, or the front/rear distribution of the force and damping force generated by the active suspension.

(Effects of the embodiment)
(1) In the vehicle vibration control method, a first target value which is a target value of a force in a vertical direction and a second target value which is a target value of a moment in a pitch direction are set, and when the sign of the upward vertical force and the sign of the moment in a pitch direction which lowers the front of the vehicle 100 are set to be the same, it is determined whether the sign of the first target value and the sign of the second target value are equal. If the signs are the same, the vertical force is controlled based on the first target value and the pitch moment is controlled based on the second target value. If the signs are different, the vertical force and the pitch moment are controlled by adjusting the body springs of the vehicle 100. A priority order between the vertical force and the pitch moment is determined based on the magnitude of the gain for the vertical acceleration or the fore-aft acceleration, and if the priority order of the vertical force is higher than the priority order of the pitch moment, the vertical force is controlled based on a first target value and the control of the pitch moment based on a second target value is restricted, and if the priority order of the pitch moment is higher than the priority order of the vertical force, the pitch moment is controlled based on the second target value and the control of the vertical force based on the first target value is restricted.

This allows for efficient vehicle vibration control by comparing the vertical force of the vehicle body with the moment in the pitch direction, and if the directions of the vertical forces required for vibration control match, both control forces are used as is, but if they do not match, the control force is appropriately switched to one of the two.In addition, the ride comfort for passengers can be improved by prioritizing the control force that has the greatest effect on the vehicle body springs, out of the vertical force and pitch direction moment of the vehicle body.

(2) A priority order between the vertical force and the pitch moment may be determined based on the frequency components of the vertical force and the pitch moment input to the vehicle 100. This makes it possible to determine whether or not there is a large effect on the vehicle body springs based on the frequency components.
(3) In a case where the magnitude of the frequency component of the vertical force in a first frequency band determined according to the frequency characteristics of the gain imparted by the vertical force to the vertical acceleration or the longitudinal acceleration on the vehicle body springs is equal to or greater than a threshold value, and the magnitude of the frequency component of the pitch moment in a second frequency band determined according to the frequency characteristics of the gain imparted by the pitch moment to the vertical acceleration or the longitudinal acceleration on the vehicle body springs is equal to or greater than a threshold value, or where the magnitude of the frequency component of the vertical force in the first frequency band is less than a threshold value and the magnitude of the frequency component of the pitch moment in the second frequency band is less than a threshold value, the priority between the vertical force and the pitch moment may be determined based on the anti-dive angle and anti-squat angle determined by the geometric relationship between the suspension and tires of the vehicle 100.
As a result, in cases where it is difficult to determine the priority between the vertical force and the pitch moment based on the frequency components, it is possible to give priority to the one that is easier to generate in the braking/driving force of the wheels.

(4) When the vehicle speed of the vehicle 100 is higher than a threshold, it may be determined that the pitch moment has a higher priority than the up-down force. This can reduce the change in the driver's viewpoint caused by the behavior of the vehicle body, and can reduce errors in the detection of distant objects by the camera or radar of the driving support device.
(5) The time rate of change of the target braking/driving torque calculated using only the first target value as the required force and the target braking/driving torque calculated using only the second target value as the required force may be limited to a limit value or may be subjected to low-pass filtering. This can reduce sudden changes in the vehicle behavior.

(6) At least one of the control of the vertical force based on the first target value or the control of the pitch moment based on the second target value may be limited when the difference in rotation speed between the front and rear wheels exceeds a first threshold value, when the difference in rotation speed between the left and right wheels exceeds a second threshold value, when the yaw rate generated in the vehicle 100 exceeds a third threshold value, when the lateral acceleration exceeds a fourth threshold value, when the longitudinal acceleration exceeds a fifth threshold value, when the steering angle of the steering wheel exceeds a sixth threshold value, when the accelerator operation amount exceeds a seventh threshold value, or when the brake operation amount exceeds an eighth threshold value.
This makes it possible to prevent the vibration damping control from making the vehicle unstable and from affecting the acceleration/deceleration and cornering movements intended by the driver.

All examples and conditional terms described herein are intended for educational purposes to assist the reader in understanding the present invention and the concepts provided by the inventor for the advancement of technology, and should be construed without being limited to the above specifically described examples and conditions, and the configuration of the examples in this specification with respect to showing the advantages and disadvantages of the present invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and modifications can be made thereto without departing from the spirit and scope of the present invention.

100...vehicle, 1...steering angle measuring device, 2...steering device, 2a...steering wheel, 2b...steering shaft, 3...accelerator pedal, 4...brake pedal, 5...inertial measurement device, 6FL, 6FR, 6RL, 6RR...wheel speed measuring device, 7FL...left front wheel, 7FR...right front wheel, 7RL...left rear wheel, 7RR...right rear wheel, 8FL, 8FR...front wheel drive shaft, 8RL, 8RR...rear wheel drive shaft, 10...controller, 10a...processor, 10b...storage device, 11...power converter, 12F...front wheel drive source, 12R...rear wheel drive source, 13...battery, 20... Vehicle body, 21f, 21r...spring mechanism, 22f, 22r...damper mechanism, 23f, 23r...instantaneous center of rotation, 30...target value setting unit, 31...frequency component analysis unit, 32...vehicle speed calculation unit, 33...priority determination unit, 34...chattering suppression unit, 35...limiting coefficient calculation unit, 36...target torque determination unit, 50...rate limiter, 51, 72...low-pass filter, 60...driver input determination unit, 61...vehicle behavior determination unit, 62...wheel speed difference dependent limiting coefficient setting unit, 63...limiting coefficient setting unit, 70...target torque correction unit, 71...rate limiter, 73...front wheel torque calculation unit

Claims

A vehicle vibration damping method for reducing vibration of a vehicle by controlling at least one of a vertical force or a pitch moment of the vehicle, comprising:
setting a first target value which is a target value of the force in the vertical direction and a second target value which is a target value of the moment in the pitch direction;
determining whether or not the sign of the first target value and the sign of the second target value are equal when the sign of the upward force in the vertical direction and the sign of the moment in the pitch direction that lowers the front part of the vehicle are the same;
When the signs are the same, the vertical force is controlled based on the first target value, and the pitch moment is controlled based on the second target value.
When the signs are different, a priority order between the vertical force and the pitch moment is determined based on a magnitude of a gain of the vertical force and the pitch moment with respect to a vertical acceleration or a longitudinal acceleration on a body spring of the vehicle;
when the priority of the vertical force is higher than the priority of the pitch moment, controlling the vertical force based on the first target value and limiting the control of the pitch moment based on the second target value;
when the priority of the moment in the pitch direction is higher than the priority of the force in the vertical direction, controlling the moment in the pitch direction based on the second target value and limiting the control of the force in the vertical direction based on the first target value.
A vehicle vibration damping method comprising:
The vehicle vibration control method according to claim 1, characterized in that a priority between the vertical force and the pitch moment is determined based on the frequency components of the vertical force and the pitch moment input to the vehicle.
The vehicle vibration control method according to claim 1, characterized in that, when the magnitude of the frequency component of the vertical force in a first frequency band determined according to the frequency characteristics of the gain that the vertical force imparts to the vertical acceleration or the longitudinal acceleration on the vehicle body spring is equal to or greater than a threshold value, and the magnitude of the frequency component of the pitch moment in a second frequency band determined according to the frequency characteristics of the gain that the pitch moment imparts to the vertical acceleration or the longitudinal acceleration on the vehicle body spring is equal to or greater than a threshold value, or when the magnitude of the frequency component of the vertical force in the first frequency band is less than a threshold value, and the magnitude of the frequency component of the pitch moment in the second frequency band is less than a threshold value, the priority between the vertical force and the pitch moment is determined based on an anti-dive angle and an anti-squat angle determined by a geometric relationship between the suspension and tires of the vehicle.
The vehicle vibration control method according to claim 1, characterized in that it is determined that the pitch moment has a higher priority than the vertical force when the vehicle speed of the vehicle is higher than a threshold value.
The vehicle vibration control method according to claim 1, in which the time rate of change of the target braking/driving torque calculated using only the first target value as the required force and the target braking/driving torque calculated using only the second target value as the required force is limited to a limit value or less, or is subjected to low-pass filter processing.
The vehicle vibration control method according to claim 1, characterized in that at least one of the control of the vertical force based on the first target value or the control of the pitch moment based on the second target value is limited when the rotation speed difference between the front and rear wheels exceeds a first threshold, when the rotation speed difference between the left and right wheels exceeds a second threshold, when the yaw rate generated in the vehicle exceeds a third threshold, when the lateral acceleration exceeds a fourth threshold, when the longitudinal acceleration exceeds a fifth threshold, when the steering wheel steering angle exceeds a sixth threshold, when the accelerator operation amount exceeds a seventh threshold, or when the brake operation amount exceeds an eighth threshold.
A vehicle vibration damping device that reduces vibration of a vehicle by controlling at least one of a vertical force or a pitch moment of the vehicle,
An actuator that generates a behavior of the vehicle;
a process of setting a first target value which is a target value of the vertical force and a second target value which is a target value of the pitch direction moment; a process of determining whether or not the sign of the first target value and the sign of the second target value are equal when the sign of the vertical force in an upward direction and the sign of the pitch direction moment which lowers the front of the vehicle are the same; a process of controlling the vertical force based on the first target value by the actuator and controlling the pitch direction moment based on the second target value when the signs are different; a controller that executes a process of determining a priority between the vertical force and the pitch moment based on a magnitude of a gain for a vertical force; a process of controlling the vertical force based on the first target value by the actuator and limiting control of the pitch moment based on the second target value when the priority of the vertical force is higher than the priority of the pitch moment; and a process of controlling the pitch moment based on the second target value by the actuator and limiting control of the vertical force based on the first target value when the priority of the pitch moment is higher than the priority of the vertical force.
A vehicle vibration damping device comprising: