WO2013111502A1

WO2013111502A1 - Vehicle control system and vehicle control method

Info

Publication number: WO2013111502A1
Application number: PCT/JP2012/083816
Authority: WO
Inventors: 宏信菊池; 勝彦平山
Original assignee: 日産自動車株式会社
Priority date: 2012-01-25
Filing date: 2012-12-27
Publication date: 2013-08-01
Also published as: JP5929923B2; JPWO2013111502A1

Abstract

This vehicle control system is provided with a skyhook control unit (33a) that controls the pitch rate of a vehicle using a shock absorber posture control amount calculation unit (336) when the absolute value of the amplitude of a detected state quantity is less than a second prescribed value, and controls the pitch rate of the vehicle using a brake posture control amount calculation unit (334) in addition to the shock absorber posture control amount calculation unit (336) when the absolute value of the amplitude is greater than or equal to the second prescribed value.

Description

Vehicle control apparatus and vehicle control method

The present invention relates to a control device and a control method for controlling the state of a vehicle.

A technique described in Patent Document 1 is disclosed as a technique related to a vehicle control device. This publication discloses a technique for controlling the vehicle body posture using a suspension control device capable of changing the damping force.

Japanese Patent Laid-Open No. 7-117435

However, when the vehicle body posture is controlled only by the damping force of the damping force variable shock absorber, a damping force variable shock absorber having a wide controllable area is required, which causes a problem of increasing costs.
The present invention has been made paying attention to the above problems, and an object thereof is to provide a vehicle control device and a vehicle control method capable of controlling the vehicle body posture with an inexpensive configuration.

In order to achieve the above object, the vehicle control apparatus of the present invention controls the pitch rate of the vehicle by the damping force control means when the absolute value of the amplitude of the detected state quantity representing the vehicle body posture is less than a predetermined value. When the absolute value of the amplitude is greater than or equal to the predetermined value, the pitch rate of the vehicle is controlled by the friction brake attitude control means in addition to the damping force control means.

Therefore, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is greater than or equal to a predetermined value, the damping force variable shock absorber's shock absorber posture control amount can be reduced by the brake posture control amount of the friction brake. The controllable region of the shock absorber can be narrowed, and vehicle body posture control can be achieved with an inexpensive configuration.

1 is a system schematic diagram illustrating a vehicle control apparatus according to a first embodiment. FIG. 2 is a control block diagram illustrating a control configuration of the vehicle control device according to the first embodiment. FIG. 3 is a control block diagram illustrating a configuration of roll rate suppression control according to the first embodiment. 3 is a time chart illustrating an envelope waveform forming process of roll rate suppression control according to the first embodiment. FIG. 3 is a control block diagram illustrating a configuration of a traveling state estimation unit according to the first embodiment. It is a control block diagram showing the control content in the stroke speed calculating part of Example 1. FIG. 3 is a block diagram illustrating a configuration of a reference wheel speed calculation unit according to the first embodiment. It is the schematic showing a vehicle body vibration model. FIG. 6 is a control block diagram illustrating actuator control amount calculation processing when performing pitch control according to the first embodiment. It is a control block diagram showing brake pitch control of Example 1. It is the figure which expressed simultaneously the wheel speed frequency characteristic detected by the wheel speed sensor, and the stroke frequency characteristic of the stroke sensor which is not mounted in the Example. It is a control block diagram showing the frequency sensitive control in the sprung mass damping control of the first embodiment. It is a correlation diagram showing the human sensory characteristic in each frequency domain. It is a characteristic view showing the relationship between the vibration mixing ratio of the wing area | region by the frequency sensitive control of Example 1, and damping force. It is a figure showing the wheel speed frequency characteristic detected by the wheel speed sensor in a certain running condition. FIG. 3 is a block diagram illustrating a control configuration of unsprung vibration suppression control according to the first embodiment. FIG. 3 is a control block diagram illustrating a control configuration of a damping force control unit according to the first embodiment. 6 is a flowchart illustrating attenuation coefficient arbitration processing in a standard mode according to the first embodiment. 6 is a flowchart illustrating an attenuation coefficient arbitration process in the sport mode according to the first embodiment. 6 is a flowchart illustrating attenuation coefficient arbitration processing in the comfort mode according to the first embodiment. 6 is a flowchart illustrating attenuation coefficient arbitration processing in a highway mode according to the first exemplary embodiment. It is a time chart showing the attenuation coefficient change at the time of drive | working a wavy road surface and an uneven | corrugated road surface. 6 is a flowchart illustrating a mode selection process based on a running state in an attenuation coefficient arbitration unit according to the first embodiment. FIG. 12 is a control block diagram illustrating actuator control amount calculation processing when performing pitch control according to the second embodiment.

1 Engine 1a Engine controller 2 Brake control unit 2a Brake controller 3 S / A (Damping force variable shock absorber)
3a S / A controller 5 Wheel speed sensor 6 Integrated sensor 7 Rudder angle sensor 8 Vehicle speed sensor 20 Brake 31 Driver input control unit 32 Traveling state estimation unit (state quantity detection means)
33 Sprung damping control unit 33a Skyhook control unit (attitude control means)
33b Frequency response control unit 34 Unsprung vibration suppression control unit 35 Damping force control unit 331 First target attitude control amount calculation unit 332 Engine attitude control amount calculation unit 333 Second target attitude control amount calculation unit 334 Brake attitude control amount calculation unit ( Friction brake attitude control means)
335 Third target attitude control amount calculation unit 336 Shock absorber attitude control amount calculation unit (damping force control means)

[Example 1]
FIG. 1 is a system schematic diagram illustrating a vehicle control apparatus according to the first embodiment. The vehicle includes an engine 1 that is a power source and a brake 20 that generates braking torque due to friction force on each wheel (hereinafter, when displaying brakes corresponding to individual wheels, right front wheel brake: 20FR, left front wheel brake: 20FL). Right rear wheel brake: 20RR, left rear wheel brake: 20RL), and shock absorber 3 (hereinafter referred to as S / A) provided between each wheel and the vehicle body and capable of variably controlling the damping force. When displaying S / A corresponding to an individual wheel, right front wheel S / A: 3FR, left front wheel S / A: 3FL, right rear wheel S / A: 3RR, left rear wheel S / A: 3RL And).

The engine 1 includes an engine controller (hereinafter also referred to as an engine control unit) 1a that controls torque output from the engine 1, and the engine controller 1a includes a throttle valve opening, a fuel injection amount, and an ignition of the engine 1. By controlling the timing and the like, a desired engine operating state (engine speed and engine output torque) is controlled. Further, the brake 20 generates a braking torque based on the hydraulic pressure supplied from the brake control unit 2 that can control the brake hydraulic pressure of each wheel according to the traveling state. The brake control unit 2 includes a brake controller (hereinafter also referred to as a brake control unit) 2a for controlling a braking torque generated by the brake 20, and a master cylinder pressure generated by a driver's brake pedal operation or a built-in motor. A pump pressure generated by the drive pump is used as a hydraulic pressure source, and a desired hydraulic pressure is generated in the brake 20 of each wheel by opening and closing operations of a plurality of solenoid valves.

S / A3 is a damping force generator that attenuates the elastic motion of a coil spring provided between a vehicle unsprung (axle, wheel, etc.) and a sprung (vehicle body, etc.). It is configured to be variable. The S / A 3 includes a cylinder in which fluid is sealed, a piston that strokes in the cylinder, and an orifice that controls fluid movement between fluid chambers formed above and below the piston. Furthermore, orifices having a plurality of types of orifice diameters are formed in the piston, and an orifice corresponding to a control command is selected from the plurality of types of orifices when the S / A actuator is operated. Thereby, the damping force according to the orifice diameter can be generated. For example, if the orifice diameter is small, the movement of the piston is easily restricted, so that the damping force is high. If the orifice diameter is large, the movement of the piston is difficult to be restricted, and thus the damping force is small.

In addition to the selection of the orifice diameter, for example, an electromagnetic control valve is arranged on the communication path connecting fluids formed above and below the piston, and the damping force is set by controlling the opening / closing amount of the electromagnetic control valve. There is no particular limitation. The S / A 3 has an S / A controller 3a that controls the damping force of the S / A 3, and controls the damping force by operating the orifice diameter by the S / A actuator.

Further, a wheel speed sensor 5 for detecting the wheel speed of each wheel (hereinafter, when displaying wheel speeds corresponding to individual wheels, right front wheel speed: 5FR, left front wheel speed: 5FL, right rear wheel speed: 5RR). , Left rear wheel speed: 5RL)), an integrated sensor 6 for detecting longitudinal acceleration, yaw rate and lateral acceleration acting on the center of gravity of the vehicle, and a steering angle which is a steering operation amount of the driver is detected. Steering angle sensor 7, vehicle speed sensor 8 for detecting vehicle speed, engine torque sensor 9 for detecting engine torque, engine speed sensor 10 for detecting engine speed, and master pressure sensor 11 for detecting master cylinder pressure. And a brake switch 12 that outputs an on-state signal when a brake pedal operation is performed, and an accelerator opening sensor 13 that detects an accelerator pedal opening.The signals of these various sensors are input to the S / A controller 3a. The arrangement of the integrated sensor 6 may be at the center of gravity of the vehicle, or may be any place other than that as long as various values at the center of gravity can be estimated. Moreover, it is not necessary to be an integral type, and a configuration in which yaw rate, longitudinal acceleration, and lateral acceleration are individually detected may be employed.

FIG. 2 is a control block diagram showing the control configuration of the vehicle control apparatus according to the first embodiment. In the first embodiment, the controller is composed of an engine controller 1a, a brake controller 2a, and an S / A controller 3a. Within the S / A controller 3a, there are a driver input control unit 31 for performing driver input control for achieving a desired vehicle posture based on driver operations (steering operation, accelerator operation, brake pedal operation, etc.), and various sensors. Based on the estimated traveling state, a traveling state estimating unit 32 that estimates the traveling state based on the detected value, a sprung mass damping control unit 33 that controls the vibration state on the spring based on the estimated traveling state, and the like. An unsprung vibration suppression control unit 34 that controls the unsprung vibration state, a shock absorber posture control amount output from the driver input control unit 31, and an unsprung vibration suppression control amount output from the sprung vibration suppression control unit 33. Based on the unsprung vibration suppression control amount output from the unsprung vibration suppression control unit 34, a damping force to be set in the S / A 3 is determined, and the damping force control unit 3 that performs the S / A damping force control. With the door.

In the first embodiment, a configuration including three controllers as the controller is shown. However, for example, the damping force control unit 35 is excluded from the S / A controller 3a and used as an attitude control controller, and the damping force control unit 35 is configured as an S / A controller. The A controller may be configured to include four controllers, or each controller may be configured from one integrated controller without particular limitation. In the first embodiment, the engine controller and the brake controller in the existing vehicle are used as they are as the engine control unit 1a and the brake control unit 2a, and the S / A controller 3a is separately installed. It is assumed that the vehicle control apparatus according to the first embodiment is realized.

(Overall configuration of vehicle control device)
In the vehicle control apparatus of the first embodiment, three actuators are used to control the vibration state generated on the spring. At this time, since each control controls the sprung state, mutual interference becomes a problem. In addition, the elements that can be controlled by the engine 1, the elements that can be controlled by the brake 20, and the elements that can be controlled by the S / A 3 are different from each other, and how to control them in combination is a problem.
For example, the brake 20 can control a bounce motion and a pitch motion, but if both are performed, a feeling of deceleration is strong and a driver is likely to feel uncomfortable. In addition, S / A3 can control all of roll motion, bounce motion and pitch motion. However, when all control is performed by S / A3, the production cost of S / A3 is increased and the damping force is increased. Since it tends to be high, high-frequency vibration from the road surface side is likely to be input, and it is easy for the driver to feel uncomfortable. In other words, there is a trade-off that the control by the brake 20 does not cause deterioration of the high frequency vibration but increases the feeling of deceleration, and the control by the S / A3 does not cause the feeling of deceleration but invites the input of high frequency vibration. To do.

Therefore, in the vehicle control apparatus of the first embodiment, it is possible to comprehensively judge these problems and realize a control configuration that complements each other's weak points while taking advantage of the advantages as the respective control characteristics. Therefore, in order to realize a vehicle control apparatus that is inexpensive but has excellent vibration control capability, an overall control system was constructed mainly considering the points listed below.
(1) The trade-off relationship is improved by switching between the operation and non-operation for the pitch control of each actuator in accordance with the amplitude of the state quantity representing the vehicle body posture (pitch rate in the first embodiment).
(2) By limiting the control target motion of the brake 20 to the pitch motion, the feeling of deceleration in the control by the brake 20 is eliminated.
(3) The control amount by the engine 1 and the brake 20 is limited and output from the control amount that can be actually output, thereby reducing the burden on the S / A 3 and accompanying the control of the engine 1 and the brake 20. Suppresses discomfort that occurs.
(4) Skyhook control is performed by all actuators. At this time, without using a stroke sensor or a sprung vertical acceleration sensor generally required for skyhook control, the skyhook control can be performed with an inexpensive configuration using wheel speed sensors mounted on all vehicles. Realize.
(5) When performing sprung control by S / A3, scalar control (frequency sensitive control) is newly introduced for the input of high frequency vibration that is difficult to cope with by vector control such as skyhook control.
(6) By appropriately selecting the control state realized by the S / A 3 according to the traveling state, an appropriate control state according to the traveling state is provided.
The above is the outline of the entire control system configured in the embodiment. Hereinafter, individual contents for realizing these will be sequentially described.

(About the driver input controller)
First, the driver input control unit will be described. The driver input control unit 31 achieves the vehicle posture required by the driver by the engine side driver input control unit 31a that achieves the vehicle posture required by the driver by torque control of the engine 1 and the damping force control of S / A3. And an S / A side driver input control unit 31b. In the engine-side driver input control unit 31a, the vehicle behavior desired to be achieved by the driver is determined based on the ground load variation suppression control amount that suppresses the ground load variation of the front wheels and the rear wheels, and signals from the steering angle sensor 7 and the vehicle speed sensor 8. The corresponding yaw response control amount is calculated and output to the engine control unit 1a.
The S / A-side driver input control unit 31b calculates a driver input damping force control amount corresponding to the vehicle behavior that the driver wants to achieve based on signals from the steering angle sensor 7 and the vehicle speed sensor 8, and the damping force control unit 35 Output for. For example, when the driver is turning, if the nose side of the vehicle is lifted, the driver's field of view easily deviates from the road surface. In this case, the four-wheel damping force is used as a driver input damping force to prevent the nose from rising. Output as a controlled variable. In addition, a driver input damping force control amount that suppresses a roll generated during turning is output.

(About roll control by S / A side driver input control)
Here, the roll suppression control performed by the S / A side driver input control will be described. FIG. 3 is a control block diagram illustrating a configuration of roll rate suppression control according to the first embodiment. The lateral acceleration estimation unit 31b1 estimates the lateral acceleration Yg based on the front wheel steering angle δf detected by the steering angle sensor 7 and the vehicle speed VSP detected by the vehicle speed sensor 8. The lateral acceleration Yg is calculated from the following equation based on the vehicle body plan view model.
Yg = (VSP ² / (1 + A · VSP ² )) · δf
Here, A is a predetermined value.

The 90 ° phase advance component creation unit 31b2 differentiates the estimated lateral acceleration Yg and outputs a lateral acceleration differential value dYg. The first addition unit 31b4 adds the lateral acceleration Yg and the lateral acceleration differential value dYg. The 90 ° phase delay component creation unit 31b3 outputs a component F (Yg) obtained by delaying the phase of the estimated lateral acceleration Yg by 90 °. The second adder 31b5 adds F (Yg) to the value added by the first adder 31b4. The Hilbert transform unit 31b6 calculates a scalar quantity based on the envelope waveform of the added value. The gain multiplication unit 31b7 multiplies the scalar amount based on the envelope waveform by the gain, calculates a driver input attitude control amount for roll rate suppression control, and outputs the calculated value to the damping force control unit 35.

FIG. 4 is a time chart showing the envelope waveform forming process of the roll rate suppression control of the first embodiment. When the driver starts steering at time t1, roll rate begins to gradually occur. At this time, the 90 ° phase advance component is added to form an envelope waveform, and the driver input attitude control amount is calculated based on the scalar amount based on the envelope waveform, thereby suppressing the occurrence of roll rate in the initial stage of steering. it can. Next, when the driver enters the steering holding state at time t2, the 90 ° phase advance component disappears, and this time, the phase delay component F (Yg) is added. At this time, even if the roll rate itself does not change much in the steady turning state, a roll rate resonance component corresponding to the roll back is generated after the roll once. If the phase delay component F (Yg) is not added, the damping force from the time t2 to the time t3 is set to a small value, which may cause the vehicle behavior to become unstable due to the roll rate resonance component. In order to suppress this roll rate resonance component, a 90 ° phase delay component F (Yg) is added.

When the driver shifts from the steered state to the straight traveling state at time t3, the lateral acceleration Yg decreases and the roll rate converges to a small value. Again, since the damping force is firmly secured by the action of the 90 ° phase delay component F (Yg), instability due to the roll rate resonance component can be avoided.

(About the running state estimation unit)
Next, the traveling state estimation unit will be described. FIG. 5 is a control block diagram illustrating the configuration of the traveling state estimation unit according to the first embodiment. In the traveling state estimation unit 32 of the first embodiment, basically, based on the wheel speed detected by the wheel speed sensor 5, the stroke speed of each wheel used for the skyhook control of the sprung mass damping control unit 33 described later, Calculate bounce rate, roll rate and pitch rate. First, the value of the wheel speed sensor 5 of each wheel is input to the stroke speed calculation unit 321, and the sprung speed is calculated from the stroke speed of each wheel calculated by the stroke speed calculation unit 321.

FIG. 6 is a control block diagram showing the control contents in the stroke speed calculation unit of the first embodiment. The stroke speed calculation unit 321 is individually provided for each wheel, and the control block diagram shown in FIG. 6 is a control block diagram focusing on a certain wheel. In the stroke speed calculation unit 321, the value of the wheel speed sensor 5, the front wheel steering angle δf detected by the steering angle sensor 7, and the rear wheel steering angle δr (actual rear wheel steering if a rear wheel steering device is provided). The reference wheel speed calculation unit 300 that calculates a reference wheel speed based on the vehicle body lateral speed and the actual yaw rate detected by the integrated sensor 6, and the angle may be appropriately set to 0 in other cases. A tire rotation vibration frequency calculation unit 321a that calculates the tire rotation vibration frequency based on the calculated reference wheel speed, and a deviation calculation unit 321b that calculates a deviation (wheel speed fluctuation) between the reference wheel speed and the wheel speed sensor value. A GEO conversion unit 321c that converts the deviation calculated by the deviation calculation unit 321b into a suspension stroke amount, a stroke speed calibration unit 321d that calibrates the converted stroke amount to a stroke speed, A band elimination filter corresponding to the frequency calculated by the tire rotation vibration frequency calculation unit 321a is applied to the value calibrated by the roke speed calibration unit 321d to remove the tire rotation primary vibration component and calculate the final stroke speed. A signal processing unit 321e.

[Regarding the reference wheel speed calculation unit]
Here, the reference wheel speed calculation unit 300 will be described. FIG. 7 is a block diagram illustrating a configuration of a reference wheel speed calculation unit according to the first embodiment. The reference wheel speed refers to a value obtained by removing various disturbances from each wheel speed. In other words, the difference between the wheel speed sensor value and the reference wheel speed is a value related to a component that fluctuates according to the stroke generated by the bounce behavior, roll behavior, pitch behavior, or unsprung vertical vibration of the vehicle body. In the example, the stroke speed is estimated based on this difference.

The plane motion component extraction unit 301 calculates the first wheel speed V0 that is the reference wheel speed of each wheel based on the vehicle body plan view model with the wheel speed sensor value as an input. Here, the wheel speed sensor value detected by the wheel speed sensor 5 is ω (rad / s), the front wheel actual steering angle detected by the steering angle sensor 7 is δf (rad), and the rear wheel actual steering angle is δr (rad ), The vehicle body lateral speed is Vx, the yaw rate detected by the integrated sensor 6 is γ (rad / s), the vehicle speed estimated from the calculated reference wheel speed ω0 is V (m / s), and the reference to be calculated Wheel speed is VFL, VFR, VRL, VRR, front wheel tread is Tf, rear wheel tread is Tr, distance from vehicle center of gravity to front wheel is Lf, and distance from vehicle center of gravity to rear wheel is Lr. Using the above, the car body plan view model is expressed as follows.

(Formula 1)
VFL = (V-Tf / 2 ・ γ) cosδf + (Vx + Lf ・ γ) sinδf
VFR = (V + Tf / 2 ・ γ) cosδf + (Vx + Lf ・ γ) sinδf
VRL = (V−Tr / 2 ・ γ) cosδr + (Vx−Lr ・ γ) sinδr
VRR = (V + Tr / 2 ・ γ) cosδr + (Vx－Lr ・ γ) sinδr
If it is assumed that the vehicle is traveling normally without skidding, 0 may be input as the vehicle body lateral velocity Vx. When this is rewritten to a value based on V in each equation, it is expressed as follows. In this rewriting, V is described as V0FL, V0FR, V0RL, V0RR (corresponding to the first wheel speed) as a value corresponding to each wheel.
(Formula 2)
V0FL = {VFL-Lf · γsinδf} / cosδf + Tf / 2 · γ
V0FR = {VFR-Lf · γsinδf} / cosδf-Tf / 2 · γ
V0RL = {VRL + Lr · γsinδr} / cosδr + Tr / 2 · γ
V0RR = {VRR + Lf · γsinδf} / cosδr-Tr / 2 · γ

The roll disturbance removing unit 302 calculates the second wheel speeds V0F and V0R as the reference wheel speeds for the front and rear wheels based on the vehicle body front view model with the first wheel speed V0 as an input. The vehicle body front view model removes the wheel speed difference caused by the roll motion that occurs around the roll rotation center on the vertical line passing through the center of gravity of the vehicle when the vehicle is viewed from the front. Is done.
V0F = (V0FL + V0FR) / 2
V0R = (V0RL + V0RR) / 2
As a result, the second wheel speeds V0F and V0R from which disturbance based on the roll is removed are obtained.

The pitch disturbance removal unit 303 calculates the third wheel speeds VbFL, VbFR, VbRL, and VbRR, which are the reference wheel speeds for all the wheels, based on the vehicle side view model, with the second wheel speeds V0F and V0R as inputs. Here, the vehicle body side view model is to remove the wheel speed difference caused by the pitch motion generated around the pitch rotation center on the vertical line passing through the center of gravity of the vehicle when the vehicle is viewed from the lateral direction. It is expressed by the following formula.
(Formula 3)
VbFL = VbFR = VbRL = VbRR = {Lr / (Lf + Lr)} V0F + {Lf / (Lf + Lr)} V0R
In the reference wheel speed redistribution unit 304, VbFL (= VbFR = VbRL = VbRR) is substituted for V in the vehicle body plan view model shown in (Equation 1), and the final reference wheel speeds VFL, VFR, VRL of each wheel are respectively substituted. VRR is calculated and divided by the tire radius r0 to calculate the reference wheel speed ω0.

When the reference wheel speed ω0 for each wheel is calculated by the above processing, a deviation between the reference wheel speed ω0 and the wheel speed sensor value is calculated, and this deviation is a wheel speed variation associated with the suspension stroke. Converted to stroke speed Vz_s. Basically, the suspension does not stroke only in the vertical direction when holding each wheel, but the wheel rotation center moves back and forth with the stroke, and the axle itself equipped with the wheel speed sensor 5 also tilts. It causes a rotation angle difference from the wheel. Since the wheel speed changes with this back-and-forth movement, the deviation between the reference wheel speed and the wheel speed sensor value can be extracted as the fluctuation accompanying this stroke. It should be noted that the degree of fluctuation may be set as appropriate according to the suspension geometry.

When the stroke speed calculation unit 321 calculates the stroke speeds Vz_sFL, Vz_sFR, Vz_sRL, and Vz_sRR for each wheel by the above processing, the sprung speed calculation unit 322 calculates the bounce rate, roll rate, and pitch rate for skyhook control. Calculated.

(About the estimation model)
Skyhook control is to achieve a flat running state by setting a damping force based on the relationship between the S / A3 stroke speed and the sprung speed, and controlling the posture on the sprung. Here, in order to achieve the posture control on the spring by the skyhook control, it is necessary to feed back the sprung speed. Now, the value that can be detected from the wheel speed sensor 5 is the stroke speed, and since the vertical acceleration sensor or the like is not provided on the spring, the sprung speed needs to be estimated using an estimation model. Hereinafter, the problem of the estimation model and the model configuration to be adopted will be described.

FIG. 8 is a schematic diagram showing a vehicle body vibration model. FIG. 8A is a model of a vehicle (hereinafter referred to as a “convex vehicle”) having an S / A having a constant damping force, and FIG. 8B has an S / A having a variable damping force. This is a model for performing skyhook control. In FIG. 8, Ms represents the mass above the spring, Mu represents the mass below the spring, Ks represents the elastic coefficient of the coil spring, Cs represents the damping coefficient of S / A, and Ku represents the unsprung (tire). , Cu represents an unsprung (tire) damping coefficient, and Cv represents a variable damping coefficient. Z2 represents a position on the spring, z1 represents a position under the spring, and z0 represents a road surface position.

When the conveyor vehicle model shown in FIG. 8A is used, the equation of motion for the sprung is expressed as follows. Note that the first derivative (ie, speed) of z1 is represented by dz1, and the second derivative (ie, acceleration) is represented by ddz1.
(Estimation formula 1)
Ms · ddz2 = −Ks (z2−z1) −Cs (dz2−dz1)
When this relational expression is rearranged by Laplace transform, it is expressed as follows.
(Estimation formula 2)
dz2 = − (1 / Ms) · (1 / s ² ) · (Cs · s + Ks) (dz2−dz1)
Here, since dz2-dz1 is the stroke speed (Vz_sFL, Vz_sFR, Vz_sRL, Vz_sRR), the sprung speed can be calculated from the stroke speed. However, when the damping force is changed by the skyhook control, the estimation accuracy is remarkably lowered, and therefore, there is a problem that a large attitude control force (attenuating force change) cannot be given in the convex vehicle model.

Therefore, it is conceivable to use a vehicle model based on skyhook control as shown in FIG. Changing the damping force basically means changing the force that limits the piston moving speed of S / A 3 in accordance with the suspension stroke. Since the semi-active S / A3 that cannot positively move the piston in the desired direction is used, when the semi-active skyhook model is employed and the sprung speed is obtained, it is expressed as follows.
(Estimation formula 3)
dz2 = − (1 / Ms) · (1 / s ² ) · {(Cs + Cv) · s + Ks} (dz2−dz1)
However,
When dz2 · (dz2−dz1) ≧ 0 Cv = Csky · {dz2 / (dz2−dz1)}
When dz2 · (dz2-dz1) <0, Cv = 0
That is, Cv has a discontinuous value.

Now, if you want to estimate the sprung speed using a simple filter, in the semi-active skyhook model, when this model is viewed as a filter, each variable corresponds to a filter coefficient, and the pseudo-differential term { Since (Cs + Cv) · s + Ks} includes a discontinuous variable attenuation coefficient Cv, the filter response becomes unstable and appropriate estimation accuracy cannot be obtained. In particular, when the filter response becomes unstable, the phase shifts. If the correspondence between the phase of the sprung speed and the sign is broken, the skyhook control cannot be achieved. Therefore, even when a semi-active S / A3 is used, it is not dependent on the sign relationship between the sprung speed and the stroke speed, and the sprung is performed using an active skyhook model that can directly use stable Csky. The speed was estimated. When the active sky hook model is adopted and the sprung speed is obtained, it is expressed as follows.

(Estimation formula 4)
dz2 =-(1 / s). {1 / (s + Csky / Ms)}. {(Cs / Ms) s + (Ks / Ms)} (dz2-dz1)
In this case, discontinuity does not occur in the pseudo differential term {(Cs / Ms) s + (Ks / Ms)}, and the {1 / (s + Csky / Ms)} term can be configured by a low-pass filter. Therefore, the filter response is stable and appropriate estimation accuracy can be obtained. Here, even if the active sky hook model is adopted, only semi-active control is actually possible, so the controllable area is halved. Therefore, the magnitude of the estimated sprung speed is smaller than the actual value in the frequency band below the sprung resonance, but the most important in skyhook control is the phase. If the correspondence between the phase and the sign can be maintained, the skyhook can be maintained. Since control is achieved and the magnitude of the sprung speed can be adjusted by other factors, there is no problem.

From the above relationship, it can be understood that the sprung speed can be estimated if the stroke speed of each wheel is known. Next, since the actual vehicle is four wheels instead of one wheel, it is considered to estimate the state of the spring by mode decomposition into roll rate, pitch rate and bounce rate using the stroke speed of each wheel. To do. Now, when the above three components are calculated from the stroke speed of the four wheels, one corresponding component is insufficient, and the solution becomes indefinite. Therefore, a war plate representing the movement of the diagonal wheels is introduced. If the stroke amount bounce term is xsB, the roll term is xsR, the pitch term is xsP, the warp term is xsW, and the stroke amount corresponding to Vz_sFL, Vz_sFR, Vz_sRL, Vz_sRR is z_sFL, z_sFR, z_sRL, z_sRR, Holds.

(Formula 1)

From the above relational expression, the differential dxsB of xsB, xsR, xsP, xsW, etc. is expressed by the following expression.
dxsB = 1/4 (Vz_sFL + Vz_sFR + Vz_sRL + Vz_sRR)
dxsR = 1/4 (Vz_sFL-Vz_sFR + Vz_sRL-Vz_sRR)
dxsP = 1/4 (-Vz_sFL-Vz_sFR + Vz_sRL + Vz_sRR)
dxsW = 1/4 (-Vz_sFL + Vz_sFR + Vz_sRL-Vz_sRR)

Here, since the relationship between the sprung speed and the stroke speed is obtained from the estimation equation 4, among the estimation equations 4, − (1 / s) · {1 / (s + Csky / Ms)} · {(Cs / Ms) s + (Ks / Ms)} is described as G, and modal parameters (CskyB, CskyR, CskyP, CsB, CsR, CsP, KsB, KsR, KsP) are GB, GR, GP, bounce rate is dB, roll rate is dR, and pitch rate is dP, dB, dR, dP can be calculated as the following values.
dB = GB · dxsB
dR = GR · dxsR
dP = GP · dxsP
From the above, the state estimation on the spring in the actual vehicle can be achieved based on the stroke speed of each wheel.

(Spring control unit)
Next, the configuration of the sprung mass damping control unit 33 will be described. As shown in FIG. 2, the sprung mass damping control unit 33 includes a skyhook control unit 33a that performs posture control based on the above-described sprung speed estimation value, and a frequency response that suppresses sprung vibration based on the road surface input frequency. And a control unit 33b.

[Configuration of Skyhook Control Unit]
The vehicle control apparatus according to the first embodiment includes the engine 1, the brake 20, and the S / A 3 as actuators for achieving sprung posture control. Of these, the skyhook control unit 33a controls bounce rate, roll rate, and pitch rate for S / A3, controls bounce rate and pitch rate for engine 1, and controls pitch for brake 20. The rate is controlled. Here, in order to assign a control amount to a plurality of actuators having different actions and control the sprung state, it is necessary to use a common control amount for each. In the first embodiment, the control amount for each actuator can be determined by using the sprung speed estimated by the traveling state estimation unit 32 described above.

The amount of skyhook control in the bounce direction is
FB = CskyB · dB
The amount of skyhook control in the roll direction is
FR = CskyR · dR
The amount of skyhook control in the pitch direction is
FP = CskyP · dP
It becomes. FB is transmitted to the engine 1 and S / A 3 as a bounce attitude control amount, and FR is a control executed only at S / A 3, and thus is transmitted to the damping force control unit 35 as a roll attitude control amount.

Next, the skyhook control amount FP in the pitch direction will be described. The pitch control is performed by the engine 1, the brake 20 and the S / A3.
FIG. 9 is a control block diagram illustrating actuator control amount calculation processing when performing pitch control according to the first embodiment. The skyhook control unit 33a is achieved by the engine 1 and the first target attitude control amount calculation unit 331 that calculates a target pitch rate that is a first target attitude control amount that is a control amount that can be used in common for all actuators. An engine attitude control amount calculation unit 332 for calculating an engine attitude control amount to be performed, a brake attitude control amount calculation unit 334 for calculating a brake attitude control amount achieved by the brake 20, and an S / A attitude control amount achieved by S / A3 An S / A attitude control amount calculation unit 336 that calculates the above, and an operation switching unit 337 that switches operation / non-operation for pitch control of each actuator.

In the skyhook control of this system, since the first priority is to operate so as to suppress the pitch rate, the first target attitude control amount calculation unit 331 outputs the pitch rate as it is (hereinafter, this pitch rate is referred to as the pitch rate). It is described as a first target attitude control amount.) The engine attitude control amount calculation unit 332 calculates an engine attitude control amount that is a control amount that can be achieved by the engine 1 based on the input first target attitude control amount.

In the engine attitude control amount calculation unit 332, a limit value for limiting the engine torque control amount according to the engine attitude control amount is set in order not to give the driver a sense of incongruity. Thus, the engine torque control amount is limited to be within a predetermined longitudinal acceleration range when converted to longitudinal acceleration. Therefore, if the engine torque control amount is calculated based on the first target attitude control amount and a value equal to or greater than the limit value is calculated, the pitch rate skyhook control amount that can be achieved by the limit value (suppressed by the engine 1). A value obtained by multiplying the pitch rate by CskyP (hereinafter referred to as an engine attitude control amount) is output. At this time, the value converted into the pitch rate in the conversion unit 332a is output to the second target attitude control amount calculation unit 333 described later. Further, the engine control unit 1 a calculates an engine torque control amount based on the engine attitude control amount corresponding to the limit value, and outputs the engine torque control amount to the engine 1.

The second target attitude control amount calculation unit 333 calculates a second target attitude control amount that is a deviation between the first target attitude control amount and the value obtained by converting the engine attitude control amount into the pitch rate in the conversion unit 332a, and the brake attitude. It is output to the control amount calculation unit 334. In the brake attitude control amount calculation unit 334, a limit value for limiting the braking torque control amount is set in order to prevent the driver from feeling uncomfortable as in the case of the engine 1 (details of the limit value will be described later). .)

Thus, when the braking torque control amount is converted into the longitudinal acceleration, it is limited to be within a predetermined longitudinal acceleration range (a limit value obtained from the occupant's discomfort, the life of the actuator, etc.). Therefore, when the brake posture control amount is calculated based on the second target posture control amount and a value equal to or greater than the limit value is calculated, a pitch rate suppression amount (hereinafter referred to as a brake posture control amount) that can be achieved by the limit value. Output). At this time, a value converted into a pitch rate by the conversion unit 3344 is output to a third target attitude control amount calculation unit 335 described later. Further, the brake control unit 2 a calculates a braking torque control amount (or deceleration) based on the brake attitude control amount corresponding to the limit value, and outputs it to the brake control unit 2.

In the third target attitude control amount calculation unit 335, a third target attitude control amount that is a deviation between the second target attitude control amount and the brake attitude control amount is calculated and output to the S / A attitude control amount calculation unit 336. . The S / A attitude control amount calculation unit 336 outputs a pitch attitude control amount corresponding to the third target attitude control amount.

The operation switching unit 337 receives the pitch rate calculated by the traveling state estimation unit 32, and when the absolute value of the amplitude of the pitch rate is less than a first predetermined value, the brake posture control amount calculation unit 334 and the shock absorber posture control A request for setting the brake posture control amount and the damping force control amount to zero is output to the amount calculation unit 336 regardless of the second target posture control amount and the third target posture control amount. When the absolute value of the amplitude of the pitch rate is less than the second predetermined value that is larger than the first predetermined value, the brake posture control amount is calculated with respect to the brake posture control amount calculation unit 334 regardless of the second target posture control amount. Output a request to set to zero.

The damping force control unit 35 calculates a damping force control amount based on a bounce posture control amount, a roll posture control amount, and a pitch posture control amount (hereinafter collectively referred to as an S / A posture control amount). , S / A3.

[Brake pitch control]
Here, the brake pitch control will be described. In general, it can be said that it is preferable to perform both of the brakes 20 because both bounce and pitch can be controlled. However, the bounce control by the brake 20 generates braking force at the same time for the four wheels. Therefore, although the control priority is low, there is a tendency for the driver to feel that the control effect is slow and the driver feels uncomfortable although the control effect is difficult to obtain. there were. Therefore, the brake 20 has a configuration specialized for pitch control. FIG. 10 is a control block diagram showing the brake pitch control of the first embodiment. The vehicle body mass is m, the front wheel braking force is BFf, the rear wheel braking force is BFr, the height between the vehicle center of gravity and the road surface is Hcg, the vehicle acceleration is a, the pitch moment is Mp, and the pitch rate is Vp. Then, the following relational expression is established.

BFf + BFr = m · a
m · a · Hcg = Mp
Mp = (BFf + BFr) · Hcg
Here, when the pitch rate Vp is positive, that is, when the braking force is applied when the front wheel side is depressed, the front wheel side is further depressed and the pitch motion is promoted. In this case, the braking force is not applied. On the other hand, when the pitch rate Vp is negative, that is, when the front wheel side is lifted, the braking pitch moment gives a braking force to suppress the front wheel side lift. This contributes to improving the sense of security and flatness by ensuring the driver's field of view and making it easier to see the front. From the above
When Vp> 0 (front wheel sinks) Mp = 0
When Vp ≦ 0 (front wheel lift) Mp = CskyP · Vp
The amount of control is given. Accordingly, since the braking torque is generated only when the vehicle body is lifted up on the front side, the generated deceleration can be reduced as compared with the case where the braking torque is generated in both the lifting and sinking. Moreover, since the actuator operation frequency is only half, a low-cost actuator can be employed.

Based on the above relationship, the brake attitude control amount calculation unit 334 is composed of the following control blocks. The dead zone processing code determination unit 3341 determines the sign of the input pitch rate Vp, and when it is positive, it outputs 0 to the deceleration reduction processing unit 3342 because control is unnecessary, and when it is negative, it determines that control is possible. The pitch rate signal is output to the deceleration reduction processing unit 3342.

[Deceleration feeling reduction processing]
Next, the deceleration feeling reduction process will be described. This process is a process corresponding to the limit by the limit value performed in the brake attitude control amount calculation unit 334. The square processor 3342a squares the pitch rate signal. This inverts the sign and smoothes the rise of the control force. The pitch rate square decay moment calculation unit 3342b calculates the pitch moment Mp by multiplying the squared pitch rate by the skyhook gain CskyP of the pitch term considering the square process. The target deceleration calculating unit 3342c calculates the target deceleration by dividing the pitch moment Mp by the mass m and the height Hcg between the vehicle center of gravity and the road surface.

In the jerk threshold limiting unit 3342d, the calculated rate of change of the target deceleration, that is, whether the jerk is within a preset range of the deceleration jerk threshold and the extraction jerk threshold, and the target deceleration is the longitudinal acceleration limit value. Judgment is made whether or not it is within the range. If any threshold is exceeded, the target deceleration is corrected to a value within the jerk threshold range, and if the target deceleration exceeds the limit value, the limit is set. Set within the value. Thereby, the deceleration can be generated so as not to give the driver a sense of incongruity.

The target pitch moment converting unit 3343 calculates the target pitch moment by multiplying the target deceleration limited by the jerk threshold limiting unit 3342d by the mass m and the height Hcg, and the brake control unit 2a and the target pitch rate converting unit 3344. Output for. A target pitch rate conversion unit 3344 divides the target pitch moment by the skyhook gain CskyP of the pitch term to convert it into a target pitch rate (corresponding to a brake posture control amount), and the third target posture control amount calculation unit 335 Output.

In the first embodiment, when the absolute value of the amplitude of the pitch rate is less than the first predetermined value due to the action of the operation switching unit 337, the pitch control is performed only by the engine 1, and the absolute value of the amplitude of the pitch rate is the first predetermined value. When the absolute value of the amplitude of the pitch rate is greater than or equal to the second predetermined value, it is added to the engine 1 and S / A3. The pitch is controlled by the brake 20.

That is, when the pitch rate is small (the absolute value of the amplitude of the pitch rate is less than the first predetermined value), the controllable area of S / A3 can be narrowed by setting the pitch attitude control amount to zero, and the cost is low. Pitch control can be achieved by S / A3. Here, increasing the damping force control amount basically increases the damping force. An increase in damping force means a hard suspension characteristic, so when high-frequency vibration is input from the road surface, it becomes easy to transmit high-frequency input and impairs passenger comfort (hereinafter referred to as high-frequency vibration characteristics). Described as worse.) On the other hand, the deterioration of high frequency vibration can be suppressed by setting the pitch attitude control amount to zero.

If the pitch rate is moderate (the absolute value of the amplitude of the pitch rate is equal to or greater than the first predetermined value and less than the second predetermined value) or less, the brake attitude control amount is set to zero to increase the braking torque. An increase in the feeling of deceleration can be avoided. At this time, since the engine attitude control amount is determined before the shock absorber attitude control amount, the pitch attitude control amount of the S / A3 is reduced by the pitch rate suppression by the actuator that does not affect the vibration transmission characteristic by the road input of the engine 1. And the deterioration of the high frequency vibration can be suppressed. Furthermore, since it is rare that the pitch rate exceeds the middle level, it is possible to reduce the number of scenes that generate deceleration, and to improve the durability of the brake system.

Further, when the pitch rate is large (the absolute value of the amplitude of the pitch rate is greater than or equal to the second predetermined value), the engine posture control amount and the brake posture control amount are determined prior to the pitch posture control amount. By controlling the pitch rate by the actuator that does not affect the vibration transmission characteristics due to the road surface input, the control amount of S / A 3 can be reduced, and deterioration of high-frequency vibration can be suppressed. Further, since the engine attitude control amount is determined prior to the brake attitude control amount, an increase in the feeling of deceleration accompanying an increase in braking torque can be suppressed.

[Frequency-sensitive control unit]
Next, frequency sensitive control processing in the sprung mass damping control unit will be described. In the first embodiment, the sprung speed is estimated based on the detection value of the wheel speed sensor 5 and the skyhook control is performed based on the estimated sprung speed control. However, when it is considered that the estimation accuracy cannot be sufficiently secured by the wheel speed sensor 5 or depending on the driving situation or the driver's intention, a comfortable driving state (a comfortable ride feeling softer than the vehicle body flatness) is guaranteed. Sometimes you want to. In such cases, vector control where the relationship (phase, etc.) of the sign of stroke speed and sprung speed is important, such as skyhook control, may make it difficult to achieve proper control due to a slight phase shift. Therefore, we decided to introduce frequency-sensitive control, which is sprung mass damping control according to the scalar quantity of vibration characteristics.

FIG. 11 is a diagram in which the wheel speed frequency characteristic detected by the wheel speed sensor and the stroke frequency characteristic of a stroke sensor not mounted in the embodiment are simultaneously written. Here, the frequency characteristic is a characteristic in which the vertical axis represents the magnitude of the amplitude with respect to the frequency as a scalar quantity. Comparing the frequency component of the wheel speed sensor 5 with the frequency component of the stroke sensor, it can be understood that substantially the same scalar amount is taken from the sprung resonance frequency component to the unsprung resonance frequency component. Therefore, the damping force is set based on this frequency characteristic among the detection values of the wheel speed sensor 5. Here, the area where the sprung resonance frequency component exists is felt as if the occupant was thrown into the air by swinging the entire body of the occupant, in other words, the feeling that the gravitational acceleration acting on the occupant was reduced. The frequency region that brings about the waving region (0.5 to 3 Hz), and the region between the sprung resonance frequency component and the unsprung resonance frequency component is not a feeling that gravitational acceleration decreases, The feeling that the human body jumps in small increments when performing (trot), in other words, the frequency range that brings up and down movement that the whole body can follow is the leopard region (3 to 6 Hz), and the region where the unsprung resonance frequency component exists Is not a vertical movement until the mass of the human body follows, but a bull region (6 to 6) is used as a frequency region where vibration is transmitted to a part of the body such as the occupant's thigh. 23 Hz).

FIG. 12 is a control block diagram illustrating frequency sensitive control in the sprung mass damping control according to the first embodiment. The band elimination filter 350 cuts noise other than the vibration component used for the main control from the wheel speed sensor value. The predetermined frequency domain dividing unit 351 divides the frequency band into a wide area, a horizontal area, and a bull area. The Hilbert transform processing unit 352 performs Hilbert transform on each divided frequency band, and converts it into a scalar quantity based on the amplitude of the frequency (specifically, an area calculated from the amplitude and the frequency band).
The vehicle vibration system weight setting unit 353 sets weights at which vibrations in the frequency bands of the fur region, the leopard region, and the bull region are actually propagated to the vehicle. The human sense weight setting unit 354 sets weights at which vibrations in the frequency bands of the fur region, the leopard region, and the bull region are propagated to the occupant.

Here, the setting of human sense weight is explained. FIG. 13 is a correlation diagram showing human sensory characteristics with respect to frequency. As shown in FIG. 13, in the waving region, which is a low frequency region, the occupant's sensitivity is relatively low with respect to the frequency, and the sensitivity gradually increases as the region moves to the high frequency region. Note that the high frequency region above the bull region becomes difficult to be transmitted to the occupant. From the above, the human sense weight Wf of the wafe area is set to 0.17, the human sense weight Wh of the leopard area is set to 0.34 which is larger than Wf, and the human sense weight Wb of the bull area is larger than Wf and Wh. Set to 0.38. Thereby, the correlation between the scalar quantity in each frequency band and the vibration actually propagated to the occupant can be further increased. These two weighting factors may be changed as appropriate according to the vehicle concept and the passenger's preference.

The weight determining unit 355 calculates the ratio of the weight of each frequency band to the weight of each frequency band. If the weight of the wing area is a, the weight of the leopard area is b, and the weight of the bull area is c, the weight coefficient of the wing area is (a / (a + b + c)), and the weight coefficient of the leap area is (b / (a + b + c). )), And the weighting factor of the bull area is (c / (a + b + c)).
The scalar amount calculation unit 356 multiplies the scalar amount of each frequency band calculated by the Hilbert transform processing unit 352 by the weight calculated by the weight determination unit 355, and outputs a final scalar amount. The processing so far is performed on the wheel speed sensor value of each wheel.

The maximum value selection unit 357 selects the maximum value from the final scalar amounts calculated for each of the four wheels. Note that 0.01 in the lower part is set to avoid the denominator becoming 0 because the sum of the maximum values is used as the denominator in the subsequent processing. The ratio calculation unit 358 calculates the ratio using the sum of the scalar value maximum values in each frequency band as the denominator and the scalar value maximum value in the frequency band corresponding to the waving region as the numerator. In other words, the mixing ratio (hereinafter simply referred to as the ratio) of the wafer region included in all vibration components is calculated. The sprung resonance filter 359 performs filter processing of about 1.2 Hz of the sprung resonance frequency with respect to the calculated ratio, and extracts a sprung resonance frequency band component representing a waft region from the calculated ratio. In other words, since the wing area exists at about 1.2 Hz, the ratio of this area is considered to change at about 1.2 Hz. Then, the finally extracted ratio is output to the damping force control unit 35, and a frequency sensitive damping force control amount corresponding to the ratio is output.

FIG. 14 is a characteristic diagram showing the relationship between the vibration mixing ratio of the waft region and the damping force by the frequency sensitive control of the first embodiment. As shown in FIG. 14, the vibration level of sprung resonance is reduced by setting the damping force high when the ratio of the wing area is large. At this time, even if the damping force is set high, the ratio of the leopard area and the bull area is small, so that high frequency vibration or vibration that moves with the leopard is not transmitted to the occupant. On the other hand, when the ratio of the wing region is small, the damping force is set low, so that the vibration transmission characteristic more than the sprung resonance is reduced, the high frequency vibration is suppressed, and a smooth riding comfort is obtained.

Here, an advantage of the frequency sensitive control when the frequency sensitive control is compared with the skyhook control will be described. FIG. 15 is a diagram showing the wheel speed frequency characteristics detected by the wheel speed sensor 5 under a certain traveling condition. This is a characteristic that appears particularly when traveling on a road surface in which small unevenness such as a stone pavement continues. When Skyhook control is performed while traveling on a road surface exhibiting such characteristics, the damping force is determined by the value of the amplitude peak in Skyhook control. There is a problem that a very high damping force is set at an incorrect timing and high-frequency vibration is deteriorated.
On the other hand, when controlling based on a scalar quantity instead of a vector as in frequency sensitive control, a low damping force is set on the road surface as shown in FIG. Become. As a result, even if the amplitude of the vibration in the bull region is large, the vibration transfer characteristic is sufficiently reduced, so that deterioration of high-frequency vibration can be avoided. From the above, high-frequency vibration can be suppressed by frequency-sensitive control based on the scalar amount in a region where control is difficult due to deterioration in phase estimation accuracy even if skyhook control is performed using an expensive sensor or the like. .

(Unsprung vibration control unit)
Next, the configuration of the unsprung vibration suppression control unit will be described. As described in the conveyor vehicle of FIG. 8A, since the tire also has an elastic coefficient and a damping coefficient, a resonance frequency band exists. However, since the mass of the tire is smaller than the mass on the spring and the elastic coefficient is high, it exists on the higher frequency side than the resonance on the spring. Due to this unsprung resonance component, the tire may flutter under the unsprung mass, which may deteriorate the ground contact property. In addition, fluttering under the spring may cause discomfort to the occupant. Therefore, in order to suppress the flutter due to unsprung resonance, a damping force corresponding to the unsprung resonance component is set.

FIG. 16 is a block diagram illustrating a control configuration of unsprung vibration suppression control according to the first embodiment. The unsprung resonance component extraction unit 341 extracts a unsprung resonance component by applying a band-pass filter to the wheel speed fluctuation output from the deviation calculation unit 321b in the traveling state estimation unit 32. The unsprung resonance component is extracted from the region of approximately 10 to 20 Hz of the wheel speed frequency component. In the envelope waveform shaping unit 342, the extracted unsprung resonance component is scalarized, and the envelope waveform is shaped using the EnvelopeFilter. The gain multiplication unit 343 multiplies the scalarized unsprung resonance component by a gain, calculates an unsprung damping damping force control amount, and outputs the calculated amount to the damping force control unit 35. In the first embodiment, the unsprung resonance component is extracted by applying a bandpass filter to the wheel speed fluctuation output from the deviation calculating section 321b in the running state estimating section 32. The unsprung resonance component may be extracted by applying a bandpass filter to the driving force, or the unsprung resonance component may be extracted by the running state estimation unit 32 by estimating and calculating the unsprung speed along with the sprung speed. Good.

(Configuration of damping force control unit)
Next, the configuration of the damping force control unit 35 will be described. FIG. 17 is a control block diagram illustrating a control configuration of the damping force control unit according to the first embodiment. In the equivalent viscosity damping coefficient conversion unit 35a, the driver input damping force control amount output from the driver input control unit 31, the S / A attitude control amount output from the skyhook control unit 33a, and the frequency sensitive control unit 33b output The frequency sensitive damping force control amount, the unsprung damping damping force control amount output from the unsprung damping control unit 34, and the stroke speed calculated by the running state estimation unit 32 are input, and these values are equivalent. Convert to viscous damping coefficient.

In the damping coefficient arbitration unit 35b, the damping coefficient converted by the equivalent viscous damping coefficient conversion unit 35a (hereinafter, each damping coefficient is referred to as driver input damping coefficient k1, S / A attitude damping coefficient k2, frequency sensitive damping coefficient k3, unsprung). (Which is described as damping damping coefficient k4)), which arbitration is performed based on which damping coefficient is controlled, and a final damping coefficient is output. The control signal converter 35c converts the control signal (command current value) for S / A3 based on the attenuation coefficient and stroke speed adjusted by the attenuation coefficient adjuster 35b, and outputs the control signal to S / A3.

[Attenuation coefficient mediation section]
Next, the contents of arbitration by the attenuation coefficient arbitration unit 35b will be described. The vehicle control apparatus according to the first embodiment has four control modes. First, the standard mode assuming a state where an appropriate turning state can be obtained while driving in a general urban area, and second, a state where a stable turning state can be obtained while actively driving a winding road etc. In sport mode, thirdly, comfort mode that assumes a state of driving with priority on ride comfort, such as when starting at a low vehicle speed, and fourthly, highway mode that assumes a state of traveling at high vehicle speed on highways with many straight lines is there.

In the standard mode, priority is given to unsprung vibration suppression control by the unsprung vibration suppression control unit 34 while performing skyhook control by the skyhook control unit 33a.
In the sport mode, priority is given to driver input control by the driver input control unit 31, and skyhook control by the skyhook control unit 33a and unsprung vibration suppression control by the unsprung vibration suppression control unit 34 are performed.
In the comfort mode, the control for giving priority to the unsprung vibration damping control by the unsprung vibration damping control unit 34 is performed while performing the frequency sensitive control by the frequency sensitive control unit 33b.
In the highway mode, priority is given to driver input control by the driver input control unit 31, and control for adding the amount of unsprung vibration suppression control by the unsprung vibration control unit 34 to skyhook control by the skyhook control unit 33a is performed. To do.
Hereinafter, the adjustment of the attenuation coefficient in each mode will be described.

(Arbitration in standard mode)
FIG. 18 is a flowchart illustrating the attenuation coefficient arbitration process in the standard mode according to the first embodiment.
In step S1, it is determined whether or not the S / A attitude damping coefficient k2 is larger than the unsprung damping damping coefficient k4. If larger, the process proceeds to step S4 and k2 is set as the damping coefficient.
In step S2, a scalar amount ratio of the bull region is calculated based on the scalar amounts of the fur region, the leopard region, and the bull region described in the frequency response control unit 33b.
In step S3, it is determined whether or not the ratio of the bull area is equal to or greater than a predetermined value. If the ratio is greater than or equal to the predetermined value, there is a concern about deterioration of riding comfort due to high-frequency vibration. Set. On the other hand, if the ratio of the bull area is less than the predetermined value, even if the damping coefficient is set high, there is little fear of deterioration in riding comfort due to high-frequency vibration, so the routine proceeds to step S5 and k4 is set.

As described above, in the standard mode, priority is given to unsprung vibration suppression control that suppresses unsprung resonance. However, when the damping force required by skyhook control is lower than the damping force required by unsprung vibration suppression control and the ratio of the bull area is large, the damping force of skyhook control is set and Avoid the deterioration of high-frequency vibration characteristics that accompanies the requirements. As a result, it is possible to obtain optimum damping characteristics according to the running state, and at the same time, it is possible to avoid a deterioration in riding comfort against high-frequency vibrations while achieving a flat feeling of the vehicle body.

(Mediation in sport mode)
FIG. 19 is a flowchart showing attenuation coefficient arbitration processing in the sport mode of the first embodiment.
In step S11, the four-wheel damping force distribution ratio is calculated based on the four-wheel driver input damping coefficient k1 set by the driver input control. The right front wheel driver input damping coefficient is k1fr, the left front wheel driver input damping coefficient is k1fl, the right rear wheel driver input damping coefficient is k1rr, the left rear wheel driver input damping coefficient is k1rl, and the damping force distribution ratio of each wheel is If xfr, xfl, xrr, xrl,
xfr = k1fr / (k1fr + k1fl + k1rr + k1rl)
xfl = k1fl / (k1fr + k1fl + k1rr + k1rl)
xrr = k1rr / (k1fr + k1fl + k1rr + k1rl)
xrl = k1rl / (k1fr + k1fl + k1rr + k1rl)
Is calculated by

In step S12, it is determined whether or not the damping force distribution ratio x is within a predetermined range (greater than α and smaller than β). If it is within the predetermined range, it is determined that the distribution to each wheel is substantially equal, and the process proceeds to step S13. If any one is out of the predetermined range, the process proceeds to step S16.
In step S13, it is determined whether or not the unsprung damping damping coefficient k4 is larger than the driver input damping coefficient k1. If it is determined that the unsprung damping damping coefficient k4 is larger, the process proceeds to step S15 and k4 is set as the first damping coefficient k. On the other hand, if it is determined that the unsprung damping damping coefficient k4 is equal to or less than the driver input damping coefficient k1, the process proceeds to step S14, and k1 is set as the first damping coefficient k.

In step S16, it is determined whether or not the unsprung damping damping coefficient k4 is the maximum value max that S / A3 can be set. If it is determined that the maximum value is max, the process proceeds to step S17, and otherwise, the process proceeds to step S18. move on.
In step S17, the maximum value of the four-wheel driver input damping coefficient k1 is the unsprung damping damping coefficient k4, and the damping coefficient that satisfies the damping force distribution ratio is calculated as the first damping coefficient k. In other words, a value that maximizes the damping coefficient while satisfying the damping force distribution rate is calculated.
In step S18, a damping coefficient that satisfies the damping force distribution ratio in a range where all the four-wheel driver input damping coefficients k1 are equal to or greater than k4 is calculated as the first damping coefficient k. In other words, a value that satisfies the damping force distribution ratio set by the driver input control and also satisfies the requirements of the unsprung vibration suppression control side is calculated.

In step S19, it is determined whether or not the first attenuation coefficient k set in each of the above steps is smaller than the S / A attitude attenuation coefficient k2 set by skyhook control. Since the damping coefficient requested on the side is larger, the process proceeds to step S20 and k2 is set. On the other hand, if it is determined that k is equal to or greater than k2, the process proceeds to step S21 and k is set.

As described above, in the sport mode, priority is given to unsprung vibration suppression control that suppresses unsprung resonance as a rule. However, the damping force distribution rate required from the driver input control side is closely related to the vehicle body posture, and particularly because it is closely related to the driver's line-of-sight change due to the roll mode. The highest priority is to secure the damping force distribution ratio. In addition, with respect to the movement that causes the posture change in the vehicle body posture while the damping force distribution ratio is maintained, the sky vehicle body posture can be maintained by selecting Skyhook control with select high.

(Mediation in Conford mode)
FIG. 20 is a flowchart illustrating the attenuation coefficient arbitration process in the comfort mode according to the first embodiment.
In step S30, it is determined whether or not the frequency sensitive damping coefficient k3 is larger than the unsprung damping damping coefficient k4. If it is determined that the frequency sensitive damping coefficient k3 is larger, the process proceeds to step S32 and the frequency sensitive damping coefficient k3 is set. On the other hand, if it is determined that the frequency sensitive damping coefficient k3 is equal to or less than the unsprung damping damping coefficient k4, the process proceeds to step S32 to set the unsprung damping damping coefficient k4.

As described above, in the comfort mode, priority is given to unsprung resonance control that basically suppresses unsprung resonance. Originally frequency sensitive control was performed as sprung mass damping control, and the optimum damping coefficient was set according to the road surface condition, so it was possible to achieve control that ensured riding comfort and lack of grounding feeling due to fluttering under the spring. Can be avoided by unsprung vibration suppression control. In the comfort mode, as in the standard mode, the attenuation coefficient may be switched according to the bull ratio of the frequency scalar quantity. As a result, the ride comfort can be further ensured in the super comfort mode.

(Arbitration in highway mode)
FIG. 21 is a flowchart illustrating the attenuation coefficient arbitration process in the highway mode according to the first embodiment. Since steps S11 to S18 are the same as the arbitration process in the sport mode, the description thereof is omitted.
In step S40, the S / A attitude attenuation coefficient k2 by the skyhook control is added to the first attenuation coefficient k that has been adjusted up to step S18, and is output.

As described above, in the highway mode, the attenuation coefficient is adjusted using a value obtained by adding the S / A attitude attenuation coefficient k2 to the adjusted first attenuation coefficient k. Here, the operation will be described with reference to the drawings. FIG. 22 is a time chart showing a change in attenuation coefficient when traveling on a wavy road surface and an uneven road surface. For example, when trying to suppress the movement of the vehicle body to fluctuate due to slight road surface undulations when driving at high vehicle speeds, it is necessary to detect slight fluctuations in the wheel speed when trying to achieve only with the skyhook control. Therefore, it is necessary to set the skyhook control gain to be quite high. In this case, the movement that fluctuates can be suppressed, but if the road surface is uneven, the control gain is too large and excessive damping force control may be performed. As a result, there is a concern about deterioration in ride comfort and vehicle body posture.

On the other hand, since the first damping coefficient k is always set as in the highway mode, a certain amount of damping force is always secured, and the vehicle body fluctuates even when the damping coefficient by the skyhook control is small. Such movement can be suppressed. Further, since it is not necessary to increase the skyhook control gain, it is possible to appropriately deal with road surface irregularities by using a normal control gain. In addition, since the skyhook control is performed with the first damping coefficient k set, unlike the damping coefficient limit, the damping coefficient decreasing process can be performed in the semi-active control region, and at the time of high-speed traveling It is possible to ensure a stable vehicle posture.

(Mode selection process)
Next, a mode selection process for selecting each travel mode will be described. FIG. 23 is a flowchart illustrating a mode selection process based on the running state in the attenuation coefficient arbitration unit of the first embodiment.
In step S50, it is determined whether or not the vehicle is in the straight traveling state based on the value of the steering angle sensor 7. If it is determined that the vehicle is traveling straight, the process proceeds to step S51. If it is determined that the vehicle is turning, the process proceeds to step S54. move on.
In step S51, it is determined based on the value of the vehicle speed sensor 8 whether or not the vehicle speed is equal to or higher than a predetermined vehicle speed VSP1 representing a high vehicle speed state. If it is determined that the vehicle speed is VSP1 or higher, the process proceeds to step S52 and the standard mode is selected. On the other hand, if it is determined that it is less than VSP1, the process proceeds to step S53 and the comfort mode is selected.
In step S54, based on the value of the vehicle speed sensor 8, it is determined whether or not the vehicle speed is equal to or higher than a predetermined vehicle speed VSP1 representing a high vehicle speed state. If it is determined that the vehicle speed is VSP1 or higher, the process proceeds to step S55 and the highway mode is selected. On the other hand, if it is determined that it is less than VSP1, the process proceeds to step S56 to select the sport mode.

In other words, when driving at a high vehicle speed in a straight running state, the standard mode is selected to stabilize the vehicle body posture by skyhook control and to suppress the high frequency vibration such as leopard and bull. In addition, unsprung resonance can be suppressed. Further, when traveling at a low vehicle speed, by selecting the comfort mode, it is possible to suppress unsprung resonance while suppressing the input of vibrations such as leopard and bull to the occupant as much as possible.

On the other hand, when the vehicle is traveling at a high vehicle speed while turning, the highway mode is selected, so that it is controlled by the value obtained by adding the damping coefficient, so that basically a high damping force can be obtained. As a result, even when the vehicle speed is high, unsprung resonance can be suppressed while positively securing the vehicle body posture during turning by driver input control. In addition, when driving at low vehicle speeds, the sport mode is selected, so that the vehicle posture during turning is positively secured by driver input control, and unsprung resonance is suppressed while skyhook control is performed as appropriate. Can travel in a stable vehicle posture.

As for the mode selection process, the control example in which the driving state is detected and automatically switched is shown in the first embodiment. However, for example, a changeover switch that can be operated by the driver is provided to select the driving mode. You may control to. As a result, ride comfort and turning performance according to the driving intention of the driver can be obtained.

As described above, Example 1 has the following effects.
(1) A running state estimation unit 32 (running state detecting means) that detects the pitch rate of the vehicle and a brake attitude control amount of the brake 20 that uses the vehicle pitch rate as a target pitch rate are calculated and output to the brake 20 A brake attitude control amount calculation unit 334 (friction brake attitude control means) that calculates the shock absorber attitude control amount of S / A3 with the vehicle pitch rate as the target pitch rate, and outputs the S / A3 to S / A3 A posture control amount calculation unit 336 (damping force control unit), a running state estimation unit 32 (state amount detection unit) that detects a state quantity representing the vehicle body posture, and the absolute value of the amplitude of the detected state quantity is a second value. When the absolute value of the amplitude is equal to or greater than the second predetermined value, the S / A attitude control amount calculation unit 33 controls the pitch rate of the vehicle by the S / A attitude control amount calculation unit 336 when the value is less than the predetermined value. With the skyhook control unit 33a for controlling the pitch rate of the vehicle (orientation control means), a by brake attitude control amount calculation unit 334 in addition to.
Therefore, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is equal to or larger than the second predetermined value, the pitch posture control amount of S / A3 can be reduced by the brake posture control amount of the brake 20, so The controllable region can be narrowed, and vehicle body posture control can be achieved with an inexpensive configuration. In addition, the pitch attitude control amount can be kept small, and deterioration of high-frequency vibration can be suppressed.
Further, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is less than the second predetermined value, the brake posture control amount of the brake 20 is zero, so that the number of scenes that generate deceleration during the vehicle body posture control can be reduced. This can reduce the uncomfortable feeling given to the driver.

In general, it can be said that it is preferable to perform both of the brakes 20 because both bounce and pitch can be controlled. However, the bounce control by the brake 20 generates braking force at the same time for the four wheels. Therefore, despite the low control priority, the deceleration effect is strong for the difficulty of obtaining the control effect, and the driver tends to feel uncomfortable. there were. Therefore, the brake 20 has a configuration specialized for pitch control.
Here, when the pitch rate Vp is positive, that is, when the braking force is applied when the front wheel side is depressed, the front wheel side is further depressed and the pitch motion is promoted. In this case, the braking force is not applied. On the other hand, when the pitch rate Vp is negative, that is, when the front wheel side is lifted, the braking pitch moment gives a braking force to suppress the front wheel side lift. This contributes to improving the sense of security and flatness by ensuring the driver's field of view and making it easier to see the front. Further, since the braking torque is generated only when the vehicle body is lifted on the front side, the generated deceleration can be reduced as compared with the case where the braking torque is generated for both lifting and sinking. Moreover, since the actuator operation frequency is only half, a low-cost actuator can be employed.

(2) The running state estimation unit 32 (running state detection means) estimates the pitch rate of the vehicle based on the change in wheel speed.
This eliminates the need for an expensive sensor such as a sprung vertical acceleration sensor or a stroke sensor, and generally reduces the number of parts by estimating the pitch rate from the wheel speed sensor 5 mounted on any vehicle. In addition, the cost can be reduced and the vehicle mountability can be improved.

(3) The traveling state estimation unit 32 (state amount detection means) is means for detecting the pitch rate of the vehicle.
Thereby, when the pitch rate is large, the pitch posture control amount is suppressed by the brake posture control amount, and the roll posture control amount and the bounce posture control amount can be increased by that amount, so the controllability of the skyhook control can be improved.

(4) When the absolute value of the amplitude of the detected state quantity is less than the second predetermined value and the running state estimation unit 32 (sensor) that detects the state quantity representing the vehicle body posture, the vehicle is driven by the damping force of S / A3. When the absolute value of the amplitude is greater than or equal to the second predetermined value, the skyhook control unit 33a (controller) controls the pitch rate of the vehicle by the braking force of the brake 20 in addition to the damping force of S / A3. And).
Therefore, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is equal to or larger than the second predetermined value, the pitch posture control amount of S / A3 can be reduced by the brake posture control amount of the brake 20, so The controllable region can be narrowed, and vehicle body posture control can be achieved with an inexpensive configuration. In addition, the pitch attitude control amount can be kept small, and deterioration of high-frequency vibration can be suppressed.
Further, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is less than the second predetermined value, the brake posture control amount of the brake 20 is zero, so that the number of scenes that generate deceleration during the vehicle body posture control can be reduced. This can reduce the uncomfortable feeling given to the driver.

(5) When the absolute value of the amplitude of the state quantity representing the vehicle body posture is less than the second predetermined value, the skyhook control unit 33a controls the pitch rate of the vehicle by the damping force of S / A3, and the absolute value of the amplitude Is equal to or greater than the second predetermined value, the pitch rate of the vehicle is controlled by the braking force of the brake 20 in addition to the damping force of S / A3.
Therefore, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is equal to or larger than the second predetermined value, the pitch posture control amount of S / A3 can be reduced by the brake posture control amount of the brake 20, so The controllable region can be narrowed, and vehicle body posture control can be achieved with an inexpensive configuration. In addition, the pitch attitude control amount can be kept small, and deterioration of high-frequency vibration can be suppressed.
Further, when the absolute value of the amplitude of the state quantity representing the vehicle body posture is less than the second predetermined value, the brake posture control amount of the brake 20 is zero, so that the number of scenes that generate deceleration during the vehicle body posture control can be reduced. This can reduce the uncomfortable feeling given to the driver.

[Example 2]
FIG. 24 is a control block diagram illustrating actuator control amount calculation processing when performing pitch control according to the second embodiment. The second embodiment is different from the first embodiment in that the operation switching unit 337 switches the operation / non-operation of each actuator based on the roll rate instead of the pitch rate.

In the second embodiment, when the absolute value of the roll rate amplitude is less than the first predetermined value due to the action of the operation switching unit 337, the pitch control is performed only by the engine torque control amount, and the absolute value of the roll rate amplitude is the first value. Pitch control is performed using the damping force control amount in addition to the engine torque control amount when it is greater than or equal to one predetermined value and less than the second predetermined value, and engine torque control is performed when the absolute value of roll rate amplitude is greater than or equal to the second predetermined value The pitch control is performed by the braking torque control amount in addition to the amount and the damping force control amount.

Therefore, in Example 2, in addition to the effects (1), (2), (4), and (5) of Example 1, the following effects are exhibited.
(6) The traveling state estimation unit 32 (state quantity detection unit) is a unit that detects the roll rate of the vehicle.
Thereby, when the roll rate is large, the pitch posture control amount is suppressed by the brake posture control amount, and the roll posture control amount in S / A 3 can be increased by that amount, so that the roll motion can be suppressed early.

(Other examples)
As mentioned above, although the Example of this invention was described based on drawing, the specific structure of this invention is not limited to an Example.
For example, the power source attitude control means, the damping force control means, and the friction brake attitude control means individually calculate control amounts for setting the vehicle pitch rate as the target pitch rate to control the engine, the brake, and the damping force variable shock absorber. The actuator may be configured to switch the operation / non-operation of each actuator in accordance with the absolute value of the detected amplitude of the state quantity.

Claims

Traveling state detection means for detecting the pitch rate of the vehicle;
Friction brake posture control means for calculating a brake posture control amount of a friction brake having a vehicle pitch rate as a target pitch rate, and outputting to the friction brake;
A damping force control means for calculating a shock absorber attitude control amount of a damping force variable shock absorber having a vehicle pitch rate as a target pitch rate, and outputting the calculated amount to the damping force variable shock absorber;
State quantity detection means for detecting a state quantity representing the vehicle body posture;
When the absolute value of the amplitude of the detected state quantity is less than a predetermined value, the damping force control means controls the pitch rate of the vehicle, and when the absolute value of the amplitude is greater than or equal to a predetermined value, the damping force control Attitude control means for controlling the pitch rate of the vehicle by the friction brake attitude control means in addition to the means;
A vehicle control device comprising:
The vehicle control device according to claim 1,
The vehicle control apparatus characterized in that the running state detecting means estimates a pitch rate of the vehicle based on a change in wheel speed.
The vehicle control device according to claim 1 or 2,
The vehicle control apparatus according to claim 1, wherein the state quantity detection means is means for detecting a pitch rate of the vehicle.
In the control apparatus of the vehicle as described in any one of Claim 1 thru | or 3,
The vehicle control apparatus, wherein the state quantity detection means is means for detecting a roll rate of the vehicle.
A sensor for detecting a state quantity representing a vehicle posture;
When the absolute value of the amplitude of the detected state quantity is less than a predetermined value, the pitch rate of the vehicle is controlled by the damping force of the damping force variable shock absorber, and when the absolute value of the amplitude is not less than the predetermined value, A controller for controlling the pitch rate of the vehicle by the braking force of the friction brake in addition to the damping force of the damping force variable shock absorber;
A vehicle control device comprising:
The controller
When the absolute value of the amplitude of the state quantity representing the vehicle body posture is less than a predetermined value, the pitch rate of the vehicle is controlled by the damping force of the damping force variable shock absorber, and when the absolute value of the amplitude is not less than the predetermined value, A method for controlling a vehicle, comprising: controlling a pitch rate of the vehicle by a braking force of a friction brake in addition to the damping force of the damping force variable shock absorber.