JP3052689B2 - Preview control device for active suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention obtains road surface information ahead of a control wheel to be controlled by a foreseeable distance and, based on the road surface information, obtains a fluid interposed between the control wheel and a vehicle body. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preview control device for an active suspension that performs preview control of a suspension including an actuator such as a pressure cylinder.

[0002]

2. Description of the Related Art An active suspension preview control device for detecting a road surface input at a position ahead of a control wheel and performing preview control of the suspension based on the detected road surface input is disclosed, for example, in JP-A-4-339010. There is one described in JP-A-4-33901. The present applicant has previously filed Japanese Patent Application No. 4-148715. In this active suspension preview control device, for example, as shown in FIGS. 15 and 16, a vertical acceleration sensor x _2f ″ at the upper portion of the front wheel is detected by a vertical acceleration sensor provided at the upper portion of the front wheel of the vehicle. detecting a front wheel of the stroke (x _1f -x _2f) from the body of the neutral state by the stroke sensor provided,
The vehicle speed V is detected by a vehicle speed sensor (not shown) or the like. Then, the integral value x _2f 'the differential value of the stroke (x _1f' of the vertical acceleration of the vehicle body to calculate the 'unsprung vibration velocity x _1f by adding the -x _2f)', the unsprung vibration velocity x _1f ' And a road surface input transmitted from the road surface to the vehicle body via the wheels based on the integral value _x1f . The control force that cancels the road surface input estimation value obtained in this way with respect to the road surface input estimation value is applied after a time difference (wheel base L / vehicle speed V, and response delay) during which the front and rear wheels pass the road surface is delayed. By generating the suspension, the road surface input transmitted from the road surface to the vehicle body via the rear wheels is suppressed, and the riding comfort is improved.
When outputting a control command value for causing the rear suspension to generate a control force that cancels the road surface input estimated value, a suitable control gain for calculating the control command value is determined by the road surface input estimation value. Although the value is multiplied, the control gain is a constant value.

[0003]

However, in such a conventional active suspension preview control device, when the unsprung resonance vibration is large, when the chain is mounted, or when the shimmy phenomenon occurs, the conventional suspension control device has a problem. The vibration of the suspension irrelevant to the road surface input is erroneously detected directly or indirectly as road surface input information, and the road surface input information, that is, the vibration input from the road surface which is estimated to be input to the vehicle body via the control wheels. If the suspension preview control is performed based on the estimated value, there is a problem that the vehicle is vibrated conversely and the riding comfort is reduced. In such a situation, it means that the vibration input has many high-frequency components. However, such a control force that cancels the vibration input having many high-frequency components also has a large amount of high-frequency components. The problem of increased consumption will occur at the same time.

The present invention has been developed in view of these problems. Vibration input from a road surface or a vibration input from a road surface such as when resonance vibration under a spring is large, when a chain is attached, or when shimming occurs. If the estimated value contains many high-frequency components, an active type that can suppress the preview control, reduce the ratio of the preview control, or remove the high-frequency component of the estimated value to suppress a decrease in ride comfort. It is an object of the present invention to provide a suspension preview control device.

[0005]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, obtained the following findings and developed the present invention. That is, in order to perform the above-described control, the magnitude of the high-frequency component in the estimated value of the vibration input from the road surface must be determined in any case.
This is, for example, a low-frequency range (for example, about 10 Hz) that is a target of normal preview control, and a high-frequency range (for example, 10 to 10 Hz) where no preview control is performed or its components are reduced or removed.
The energy of the road surface input estimation value at each of about 20 Hz) may be obtained from the overall power of the power spectral density, the square integral of the vibration input, and the like, and may be compared. As described above, when the control command value is output to the actuator of the control wheel suspension using the value obtained by multiplying the estimated value of the vibration input from the road surface by the gain, the time when the high frequency component is determined to be large is determined. so,
If the gain is set to zero or reduced numerically, the preview control is stopped or the ratio thereof is reduced. On the other hand, when it is determined that the high-frequency component is large, at least the exciting force to the vehicle body can be reduced by removing the high-frequency component obtained as erroneous information from the estimated road surface input value. Conversely, if the high-frequency component is small, such an exciting force can be reduced in a high-frequency range by increasing the distribution ratio for controlling the estimated value itself without removing the high-frequency component.

The active suspension preview control apparatus according to the first aspect of the present invention, as shown in FIG. 1A, is provided between a vehicle body and control wheels to control a control command value. An actuator that generates a control force corresponding to the road surface; a road surface detection unit that is mounted ahead of the control wheel by a foreseeable distance to detect road surface irregularities; and inputs to the control wheel according to a road surface detection value from the road surface detection unit. Control wheel input estimating means for estimating the vibration input to be applied, and a value obtained by multiplying the control wheel vibration input estimating value from the control wheel input estimating means by a gain after a predetermined time delay from the detection of the road surface unevenness. A predictive control device for an active suspension, comprising: a preview control means for outputting a control command value to an actuator of the control wheel, wherein a control wheel vibration input estimation from the control wheel input estimation means is provided. Input level determining means for determining the magnitude of the high-frequency vibration component of the value; and when the input level determining means determines that the high-frequency vibration component of the control wheel vibration input estimated value is large, the rear wheel vibration input Gain changing means for reducing a gain multiplied by the estimated value or setting the gain to zero.

According to a second aspect of the present invention, a preview control device for an active suspension is interposed between a vehicle body and a control wheel and controlled according to a control command value, as shown in FIG. An actuator that generates a force, a road surface detecting unit that is mounted ahead of the control wheel by a foreseeable distance to detect road surface irregularities, and a vibration input that is input to the control wheel according to a road surface detection value from the road surface detecting unit A control command value obtained from a value obtained by multiplying a gain to a control wheel vibration input estimation value from the control wheel input estimation means after a predetermined time delay from the detection of the road surface unevenness. A preview control device for an active suspension, comprising: a preview control means for outputting to the actuator of the control wheel, a control wheel vibration input estimation value from the control wheel input estimation means. Input level determining means for determining the magnitude of the high-frequency vibration component, high-frequency component removing means for removing a high-frequency vibration component from the control wheel vibration input estimation value from the control wheel input estimating means, and a determination result of the input level determining means The larger the high-frequency vibration component of the estimated value of the control wheel vibration input, the larger the ratio of the output value from the high-frequency component removing means or the smaller the high-frequency vibration component of the estimated value of the control wheel vibration input, By changing the distribution ratio so as to increase the ratio of the wheel vibration input estimate itself,
A control distribution ratio changing means for giving a value necessary for calculating a control command value by the preview control means.

According to a third aspect of the present invention, there is provided a preview control device for an active suspension, as shown in FIGS. 1A and 1B, wherein the road surface detecting means is inputted from a road surface to a vehicle body via front wheels. The control wheel is a rear wheel.

[0009]

According to the active suspension preview control apparatus of the first aspect of the present invention, as shown in the basic configuration diagram of FIG. 1A, the road surface detecting means detects irregularities on the road surface, and the control wheel is controlled in accordance with the detected value. An input estimating unit estimates a vibration input input to the control wheel as the unsprung vibration speed or the like, for example. Then, for the estimated value of the control wheel vibration input, for example, the input level determining means performs a low frequency range (about 10 Hz) which is a target of the normal preview control and a high frequency for which the preview control is not performed or its component is reduced or eliminated. Area (10
(About 20 Hz) is calculated from, for example, the overall power of the power spectrum density or the square integral of the vibration input, and the magnitude of the high-frequency vibration component of the estimated value of the control wheel vibration input is calculated based on the ratio between the two. Judge,
If it is determined from the result that the high-frequency vibration component of the estimated value of the control wheel vibration input is larger than a certain level, for example, the gain changing means sets the gain to zero or a small value at a predetermined rate, and The control means obtains a control command value from a value obtained by multiplying the gain by the estimated value of the control wheel vibration input, and delays the control command value by a predetermined time from the detection of road surface irregularities, that is, by a difference of a foreseeable distance from the road surface transit time. And the actuator generates a control force according to the control command value. Therefore, in the active suspension preview control device of the present invention, there are many high frequency components in the estimated value of the vibration input from the road surface, such as when the unsprung resonance vibration is large, when the chain is mounted, or when the shimmy phenomenon occurs. In this case, the preview control is stopped by setting the gain to zero, or the ratio of the preview control is reduced by setting the gain to a small value. Therefore, the vehicle body is added in accordance with the road surface vibration input estimation value obtained as erroneous information. It is possible to prevent or reduce the swinging control force, and it is possible to suppress a decrease in ride comfort in such a case.

In the active suspension preview control apparatus according to the second aspect of the present invention, as shown in the basic configuration diagram of FIG. 1B, the road surface detecting means detects the unevenness of the road surface in the same manner as described above. According to the detected value, the control wheel input estimating means estimates a vibration input to be input to the control wheel, for example, in the same manner as described above. With respect to the control wheel vibration input estimated value obtained in this way, the high frequency component removing means
For example, the high-frequency component is removed by low-pass filter processing or the like. On the other hand, the input level determination means determines the magnitude of the high-frequency vibration component of the control wheel vibration input estimated value in the same manner as described above. On the basis of this determination result, the control distribution ratio changing means increases the ratio of the output value from the high-frequency component removing means or increases the control wheel vibration input estimation as the high-frequency vibration component of the control wheel vibration input estimation value increases. The smaller the high-frequency vibration component of the value is, the larger the ratio of the control wheel vibration input estimated value itself is to change the distribution ratio to obtain a value necessary for calculating the control command value. And outputs it to the actuator after a delay of a predetermined time from the detection of road surface unevenness, that is, the difference between the passage distance of the foreseeable distance from the road surface, and the control force corresponding to the control command value. Occurs. Therefore, in the active suspension preview control device of the present invention, the high frequency component of the estimated value of the vibration input from the road surface is high, such as when the unsprung resonance vibration is large, when the chain is attached, or when the shimmy phenomenon occurs. In many cases, the high-frequency component of the road surface input obtained as erroneous information is removed, and the preview control is executed only for the low-frequency component that is the target of the normal preview control. While improving the vibration characteristics for low frequency components,
A control force that vibrates the vehicle body can be suppressed to prevent a decrease in ride comfort.

In the active suspension preview control apparatus according to the third aspect of the present invention, as shown in the basic structural diagrams of FIGS.
Like No. 5, the stroke of the front wheel and the vertical acceleration of the upper part of the front wheel are detected and detected, and the vibration input to be input to the rear wheel is estimated based on the detected value. Therefore, the preview control apparatus for an active suspension according to the present invention can more accurately detect a vibration generation situation when the unsprung resonance vibration is large, when the chain is mounted, or when the shimmy phenomenon occurs.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing a first embodiment of the present invention. In FIG.
Denotes front left to rear right wheels, and 12 denotes an active suspension.

The active suspension 12 includes hydraulic cylinders 18FL to 18RR as actuators interposed between the vehicle body-side member 10 and the respective wheel-side members 14 of the wheels 11FL to 11RR.
Pressure control valve 20F for individually adjusting the operating pressure of ~ 18RR
L to 20RR and these pressure control valves 20FL to 20RR.
A hydraulic source 22 for supplying hydraulic oil at a predetermined pressure to the supply line via a supply-side pipe 21S, and recovering return oil from the pressure control valves 20FL to 20RR through the return-side pipe 21R; Accumulators 24F, 24R inserted in the supply pressure side pipe 21S between the vehicle pressure sensors 20R to 20RR, a vehicle speed sensor 26 for detecting a vehicle speed and outputting a pulse signal in accordance with the accumulators 24F and 24R, and the wheels 11FL to 1FL.
Vertical acceleration sensors 28FL for individually detecting the vertical acceleration of the vehicle body at positions corresponding to 1RR, respectively.
To 28RR and the front wheel side hydraulic cylinders 18FL and 18F
Stroke sensors 27FL and 27FR, which are disposed in parallel with R and detect relative displacement between the front wheels 11FL and 11FR and the vehicle body-side member 10, and the vertical acceleration sensors 2
Vertical acceleration detection value Z _GFL -Z of 8FL-28RR
Active control for each pressure control valve 20FL-20RR based on _GRR , and each sensor 26, 27FL, 27FR and 2
A controller 30 is provided for selectively performing preview control for the rear wheel-side pressure control valves 20RL and 20RR based on the detected values of 8FL to 28FR in accordance with the motion state of the front wheels.

Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a, and the cylinder tube 18a has a piston 18 having a through hole in the axial direction.
The lower pressure chamber L separated by c forms a thrust corresponding to the pressure receiving area difference between the upper and lower surfaces of the piston 18c and the internal pressure. The lower end of the cylinder tube 18a is attached to the wheel member 14, and the upper end of the piston rod 18b is attached to the vehicle body member 10. Each of the pressure chambers L is connected to a pressure control valve 20FL via a hydraulic pipe 38.
~ 20RR output ports. Each of the pressure chambers L of the hydraulic cylinders 18FL to 18RR is provided with an accumulator 34 for absorbing unsprung vibration through a throttle valve 32.
It is connected to the. Also, the hydraulic cylinders 18FL to 18
A coil spring 36 having a relatively low spring constant and supporting a static load of the vehicle body is disposed between the upper and lower springs of the RR.

Each of the pressure control valves 20FL to 20RR is
Having a cylindrical valve housing with a spool slidably housed therein and a proportional solenoid integrally provided therewith,
Conventionally known three-port proportional electromagnetic pressure reducing valve (for example,
-74111). Then, by adjusting the command current i (command value) supplied to the exciting coil of the proportional solenoid, the moving distance of the poppet housed in the valve housing, that is, the position of the spool, is controlled.
The hydraulic source 22 and the hydraulic cylinders 18FL to 18R via the supply port and the output port or the output port and the return port
It is possible to control the hydraulic oil flowing between R and R.

Here, the command current i (: i _{FL to} i _RR ) applied to the exciting coil and the pressure control valve 20FL (to 20R)
The relationship with the control pressure P output from the output port of R) is
As shown in FIG. 3, the minimum current value i _{MIN in} consideration of noise
Minimum control pressure P _MIN next when the, increasing the current value i from the condition, linearly control pressure P increases in proportion to the current value i, the hydraulic pressure source when the maximum current value i _MAX 22
Is the maximum control pressure P _MAX corresponding to the set line pressure of In FIG. 3, i _N is a neutral command current, and _PCN is a neutral control pressure.

The vertical acceleration sensors 28FL-28
Each of the RLs is, as shown in FIG._FL
~ G_RRIs zero, zero acceleration, upward acceleration G_FL
~ G _RRIs detected, a positive
Log voltage, downward acceleration G _FL~ G_RRIs detected
The vehicle body consists of a negative analog voltage corresponding to the acceleration value
Vertical acceleration detection value Z_GFL~ Z_GRRTo output
It is configured. Here, the vertical acceleration G_FL~ G_RR
Vertical acceleration detection value Z_GFL~ Z_GRRWhat is
A linear function that does not involve a coefficient (that is, the coefficient is “1”)
The vertical acceleration detection value Z_GFL~ Z
_GRRIs the vertical acceleration G_FL~ G_RRTaken as equivalent to
Shall be used.

The stroke sensor 27FL27
FR, as shown in FIG. 5, the front wheels 11FL and
Displacement ST between the vehicle body side member 10 and the vehicle body side member 10_FL,
ST _FRIn order to detect the stroke, these stroke sensors 27
From FL and 27FR, the vehicle height reaches the preset target vehicle height
Zero neutral voltage V when coincident_S, Vehicle height is higher than target vehicle height
When it becomes high, the deviation, that is, the relative displacement ST_FL,ST_FR
If the vehicle height is lower than the target vehicle height,
Deviation, ie, the relative displacement ST_FL,ST_FRNegative electricity depending on
Stroke detection value S consisting of pressure_FLAnd S_FRIs output. This
Here, the relative displacement ST_FL,ST_FRDrinking straw against
Detection value S_FLAnd S_FRDoes not involve any coefficients (ie
(The number is “1”).
Troke detection value S_FLAnd S_FRIs the relative displacement ST_FL,S
T_FRShall be adopted as the equivalent.

As shown in FIG. 6, the controller 30
Vertical acceleration detection values Z _GFL -Z _GRR output from vertical acceleration sensors 28FL-28FR, vehicle speed sensor 2
6, the vehicle speed detection value V output from the stroke sensor 27
A microcomputer 44 to which stroke detection values S _FL and S _FR output from FL and 27FR are input, and pressure command values U _{FL to} U _{RR which} are D / A converted and output from the microcomputer 44 are supplied. these and a drive circuit 46FL~46FR constituted by the driving current i _FL through i floating type constant-voltage circuit, for example into a _FR to the pressure control valve 20FL～20RR.

Here, the microcomputer 44 includes at least an input interface circuit 44a having an A / D conversion function, an output interface circuit 44b having a D / A conversion function, an arithmetic processing unit 44c, and a storage unit 44.
d. The input interface circuit 44a, the sensors 26,27FL, 27FR, the detection value V from the _{28FL~28RR, S FL, S FR,} Z GFL ~Z GRR is input, the pressure control valve from the output side interface circuit 44b Control command values U _{FL to} U _RR for 20FL to 20RR are output.

The arithmetic processing unit 44c is provided in a
9 to execute the predetermined sampling time T_S(example
Every 20 msec), the vehicle speed detection value V and the stroke detection value S
_FL, S_FRAnd the vertical acceleration detection value Z_GFL~ Z_GRRRead
Stroke detection value S_FL, S_FRAnd vertical acceleration
Detection value Z_GFL~ Z_GRRInto the rear wheels 11RL and 11RR from
Of road surface displacement as an estimate of the rear wheel vibration input
Derivative x_OFL'And x _OFR'And calculate the road displacement
Derivative x_OFL'And x_OFR'Fast Fourier transformation
In other words, predetermined high and low frequencies obtained by performing so-called FFT processing
Overall power O of the power spectral density distribution in the region
P_Two, OP₁And these overall power O
P_Two, OP₁Ratio of energy in both frequency ranges represented by
(OP_Two/ OP₁) From the differential value x of the road surface displacement_OFL'
And x_OFR'' Of the rear wheel vibration input estimate obtained as
Of the high-frequency components of the rear wheel vibration input
The high-frequency component is small, that is, the existence ratio is set in advance.
If the coefficient ratio does not exceed the differential value x
_OFL'And x_OFR'Based on the preview control force U_pRLAnd U
_pRRBetween the front and rear wheels based on the vehicle speed detection value V.
Delay time τ_RAnd the delay time τ_RBecomes zero
Foreseeable control force U_pRLAnd U_pRRBased on rear wheel pressure control
Normal rear wheel foresight system for controlling the valves 20RL and 20RR
Control, and the high frequency component of this rear wheel vibration input
That is, the existence ratio exceeds the preset coefficient ratio.
In such a case, if the unsprung resonance vibration of the front wheel is large,
Or the shimmy phenomenon occurs when the chain is attached.
Erroneous information that is unrelated to road input, such as
Stop the rear wheel preview control as
Direction acceleration detection value Z _GRLAnd Z_GRRObtained from the integral of
Spring speed x_RL’And x_RR’Based on active control force
U_BRLAnd U_BRRIs calculated and the active control force U_BRLas well as
U_BRRBased on the rear wheel side pressure control valves 20RL and 20R
Normal rear wheel active control for controlling R is selectively performed. What
Please note that the front left and right wheels 11FL and 11FR
Active control is performed by selecting control of the rear wheels 11RL and 11RR.
Now run in parallel.

Further, the storage device 44d stores a program necessary for the arithmetic processing of the arithmetic processing device 44c in advance, and stores the _preview control forces U _pRL and _{Up R} calculated for each predetermined sampling time T _S by a delay time. A shift register area for storing a predetermined number while sequentially shifting along with τ _R is formed, and the operation results required in the operation process of the operation processing unit 44c are sequentially stored.

Next, in this embodiment, the principle for selecting the preview control and the active control of the rear wheels will be described. First,
A method of estimating a vibration input to be input to the rear wheel will be described. The stroke detection values S _FL and S _FR output from the stroke sensors 27FL and 27FR respectively indicate the relative displacement between the unsprung and the sprung, as expressed by the following equations (1) and (2). , _And the unsprung displacements x _FL and x _FR of the vehicle body are subtracted from the unsprung displacements x _0FL and x _{0FR of} 11FR.

S_FL= X_0FL-X_FL ………… (1) S_FR= X_0FR-X_FR (2) Therefore, the stroke sensors 27FL, 27FR
Stroke detection value S _FLAnd S_FRFor example, digital
Differentiating with a differentiation circuit constructed with a high-pass filter etc.
Stroke speed S_VFLAnd S_VFRIs obtained. these
Stroke speed S_VFLAnd S_VFRIs from the above formulas 1 and 2.
And the differential value x of the unsprung displacement, respectively_OFL’And x_OFR’
Differential value of sprung displacement (that is, sprung vibration velocity)
x_FL’And x _FR’
You. Note that the digital high-pass filter is
Built with a program executed on a microcomputer.
The cutoff frequency is used for the program.
This can be set with a temporary variable used.
The cut-off frequency is, for example, around twice the unsprung resonance frequency.
(About 20 Hz).

On the other hand, the sprung vibration speeds x _FL ′ and x _FR ′ correspond to the vertical acceleration detection values Z _GFL and Z G from the front wheel vertical acceleration sensors 28 FL and 28 _FR.
It is obtained by integrating the _GFR with an integrating circuit constructed with, for example, a digital low-pass filter. Accordingly, the sprung vibration speeds x _FL ′ and x _FR ′ obtained by integrating the vertical acceleration detection values Z _GFL and Z _GFR and the stroke speed S _VFL
And S _VFR to obtain the differential values x _0FL ′ and x _0FR ′ of the true road surface displacement following the road surface displacement by canceling the differential values x _FL ′ and x _FR ′ of the sprung displacement. it can. The digital low-pass filter can be constructed by a program executed by the microcomputer, and its cutoff frequency can be set by a temporary variable used in the program. It was set near 1/6 of the sprung resonance frequency (about 0.02 Hz).

The differential value x of the road surface displacement obtained from the differential value of the unsprung displacement of the front wheels 11FL and 11FR in this manner.
_OFL 'and x _OFR' are rear wheels 11RL, since it should be input as a differential value of the same unsprung displacement against 11RR, and the rear wheel vibration input estimate with a thereto. Against the differential value of the road surface displacement x _OFL 'and x _OFR', preview control force U _pRL and U _pRR to pressure control valves 20RL and 20RR of the rear wheels is calculated using the following three formulas and equation 4.

U _pRL = − [C _p + ｛1 / (ω ₁ + s)｝ K _p ] × _0FL ′ (3) U _pRR = − [C _p + {1 / (ω ₁ + s)} K _p ] x _0FR '(4) where C _p is a damping force control gain, K _p is a spring force control gain, and ω ₁ is a value obtained by multiplying a cutoff frequency f _C for control by 2π. Thus, for the actual suspension damping constant C and spring constant K, C _p ≦ C, K _p ≦ K, and ω ₁ ≧ 0. S is a Laplace operator (Laplacian).

Here, the reason why the _preview control forces U _pRL and U _pRR are calculated according to the above equations 3 and 4 is that active control is not performed in the unsprung resonance frequency region as in a normal active suspension. In the case of suppressing vibration mainly in the sprung resonance frequency region of 5 Hz or less, a one-wheel motion model has a spring element K, a damping element C, and a control element U on a road surface in parallel as shown in FIG. The sprung mass M is arranged above the sprung mass M, and can be considered as a one-degree-of-freedom model in which an external force F acts on the sprung mass M. In FIG. 7, X ₀ is a road surface displacement and X is a sprung displacement.

The equation of motion of this one-wheel, one-degree-of-freedom model is:
It can be represented by the following five equations. M ″ X ₀ = C (X ₀ ′ −X ′) + K (X ₀ −X) −F + U (5) By solving the above equation (5) for the sprung displacement X, Becomes

For example, in the above equation (3), x _0FL '= sx
_0FL , these three equations are _expressed as ω ₁ = 0, C _p = C, K _p
= K and substituted into the above equation (6), the equation (6) becomes Becomes

Since the accuracy of estimating the road surface displacement is sufficiently high as described above, (X ₀ −x _0FL ) ≒ 0 in the above equation (7), and equation (7) can be rewritten as equation (8). Therefore, from the equation (8), it is proved that the influence of the road surface unevenness is hardly transmitted to the vehicle body, and that a good riding comfort can be obtained.

Now, the rear wheel road surface vibration input estimated values calculated as the differential values x _OFL 'and x _OFR ' of the road surface displacement as described above are those obtained when the front wheels 11FL and 11RR have passed the road surface. from the three equations and the rear wheel 11R and the calculated predictive control force U _pRL and U _pRR in equation 4
L, in order to effectively generate against 11RR, calculates a time difference therebetween is passed through the road surface, must be delayed the occurrence of the by the time difference control force U _pRL and U _pRR. This delay time τ _R is given by the following equation (9).

Τ _R = (L / V) −τ _S (9) where L is the wheelbase, τ _S is the response delay time of the control system, and the response delay time of the hydraulic system Is set as the sum of the calculation dead time and the response delay time of the filter. Therefore, after the delay time τ _R , the rear wheels 11RL and 11
Since the RR passes, the foreseeable control force U _pRL
After the calculation of U _{pR R} and the delay time τ _R , the control forces U _pRL and _UpR are applied to the actuators of the rear wheels 11RL and 11RR, that is, the hydraulic cylinders 18RL and 18RR.
As a result, it is possible to effectively prevent the input from the passing road surface from being transmitted to the vehicle body via the rear wheels 11RL and 11RR.

As described above, when the unsprung resonance vibration is large, when the chain is mounted, or when the shimmy phenomenon occurs, high frequency vibration is generated, and unnecessary vibration of the front suspension accompanying the high frequency vibration is generated on the road surface. If the input is detected as erroneous information and the preview control of the rear wheels is performed in accordance with the road surface input information, an exciting force acts on the vehicle body. Therefore, in the present invention, it is necessary to determine whether or not the high-frequency component is large among the road surface input information, that is, the rear wheel road surface vibration input estimated value given by the differential values x _OFL ′ and x _OFR ′ of the road surface displacement. However, there is an interesting finding regarding the differential values x _OFL ′ and x _OFR ′ of the road surface displacement.

With respect to the differential values x _OFL ′ and x _OFR ′ of the road surface displacement during normal running obtained in this way, in order to obtain the vibration input energy, for example, a fast Fourier transform (hereinafter also simply referred to as FFT) is used. FIG. 8 shows the distribution of the power spectral density by performing the above. As can be seen from this characteristic diagram, the vibration energy gradually decreases from around the point where the resonance frequency exceeds the unsprung resonance frequency (about 12 Hz). Thus, for example, over-all power OP ₁ obtained as vibration energy sum of the low frequency range is normally rear wheel foreseen control may be performed (e.g., the order of ～10Hz) at least in a normal running state, the misinformation Overall obtained as a sum of vibration energies in a high frequency range (for example, about 10 to 20 Hz) in which rear wheel preview control is not performed or its distribution ratio should be reduced in order to suppress a decrease in ride comfort due to the same level as the power OP ₂ or a degree slightly larger. However, when the unsprung resonance occurs, when the chain is mounted, from the high-frequency vibration generated in the front suspension is a shimmy phenomenon occurs during such an over all power OP ₂ in the high frequency band of the power spectrum density is increased.

If this property is used, when the overall power ratio OP ₂ / OP ₁ in both frequency ranges becomes larger than a predetermined coefficient ratio a (for example, a = 1), high-frequency vibration is caused by the above-mentioned causes. Therefore, in the present invention, control such as stopping the rear wheel preview control, reducing the ratio of the rear wheel preview control, or removing the high frequency component of the estimated value of the rear wheel vibration input is performed in the present invention. By doing so, it is possible to avoid or suppress the generation of a control force that vibrates the vehicle body due to the erroneous information obtained as the high-frequency vibration. In this embodiment, the low frequency range is set to 10 Hz.
The high frequency range is set to a range of about 10 to 20 Hz in these ranges.
Needless to say, it should be appropriately selected according to the resonance frequency of the steering system, each tire specification including the tire size, the drive system reduction ratio, and the like. The coefficient ratio a
Should also be set according to the vibration characteristics of each vehicle caused by these.

Next, based on the principle of the invention, the control according to the present embodiment can improve the vibration characteristics of the vehicle by selectively controlling the normal active control for the front wheels and the preview control and the active control for the rear wheels. The procedure will be described with reference to the flowchart of FIG. 9 executed by the arithmetic processing unit 44c in the microcomputer 44 of the controller 30. In this process, the control flag F indicates that the rear wheel side preview control is in transition to the normal active control, and the flag F = 1 executes the normal active control, and the flag F = 0 executes the preview control.

That is, the process of FIG. 9 is executed as a timer interrupt process every predetermined sampling time T _S (for example, 20 msec). First, in step S1, the current vehicle speed detection value V of the vehicle speed sensor 26 is read. The flow shifts to S2 to read the vertical acceleration detection values Z _{GFL to} Z _GRR from the vertical acceleration sensors 28FL to 28RR, and then to step S3 to move the stroke sensors 27FL and 27FR.
Read the stroke detection values S _FL and S _FR from.

Next, the process proceeds to step S4, in which the stroke speeds S _VFL , S _FR obtained by differentiating the stroke detection values S _FL , S _FR by the digital high-pass filter processing or the like.
_VFR and front-wheel vertical acceleration detection values Z _GFL , Z _GFR
From the front-wheel-side sprung vibration speeds x _FL 'and x _FR ' obtained by integrating
The differential values x _OFL ′ and x _OFR ′ of the road surface displacement are calculated as rear wheel vibration input estimated values from the road surface.

Next, the process proceeds to step S5, where the fast Fourier transform FFT is performed on the differential values x _OFL ', x _OFR ' of the road surface displacement as the rear wheel vibration input estimated values calculated in step S4. To determine the power spectral density distribution. In order to execute the fast Fourier transform FFT by a microcomputer, a known algorithm can be applied.

[0041] Next, the process proceeds to step S6, wherein a power spectrum density distribution of the vibration input obtained in step S5, the high over-all power OP about ₁ and the 10~20Hz the low frequency range of up to about the ~10Hz to calculate the over-all power OP ₂ of the frequency range. Next, step S
7 shifts to an over all power OP ₂ in the high frequency range calculated at step S6, it is determined whether or not the coefficient ratio values above multiplied by a in over-all power OP ₁ in the low frequency range , The overall power OP ₂ of the high frequency range
The coefficient ratio a but the over-all power OP ₁ in the low frequency range
If the value is equal to or more than the value obtained by multiplying by
If not, the process proceeds to step S9.

[0042] At the step S9, the differential value x _OFL 'and x _OFR' with the road surface displacement, and calculates the predictive control force U _pRL and U _pRR the rear wheel side in accordance with the three equations and 4 wherein step S10 Move to In the step S10, the delay time τ _R is calculated according to the equation (9) using the vehicle speed detection value V, and the process proceeds to step S11.

In step S11, step S11
9 is the rear wheel side preview control force U _pRLAnd U_pRRAnd on
The delay time τ calculated in step S10_RAnd the storage device
Stored at the beginning of the shift register area formed in 44d
And foreseeing the rear wheels stored up to the previous time
Power U_pRL, U_pRRAnd delay time τ_RAnd shift sequentially
Then, the process proceeds to step S12. At this time, the delay time τ
_RAbout the delay time of each shift position when shifting
τ_RTo sampling time T_SAre subtracted from each other.
Delay time τ_RUpdate and store as

In step S12, it is determined whether the control flag F is "1". If the control flag F is "1", the flow shifts to step S13. If not, the flow advances to step S14. Transition. In step S14, the oldest _preview control forces U _pRL and U _pRR stored in the shift register area, that is, the rear wheel-side _preview control forces U _pRL and _{R pRR in} which the delay time τ _R has become zero, are read, and the read oldest _preview control forces U _pRL and U _pRR are read.
_pRL, erases the U _pRR and the delay time tau _R for this from the shift register region, the process proceeds to step S15.

In step S15, step S15
4, the front-wheel-side sprung vibration speeds x _FL ′ and x _FR ′ derived when the differential value of the road surface displacement is calculated in step S1
4 using a wheel side of the preview control force U _pRL and U _pRR after being read in accordance with equation (10) to 13 formula below, the pressure control valve 20F
The total control forces U _{FL to} U _RR for L to 20RR are calculated, and the routine goes to Step S16.

[0046] _{U FL = U N -K B ·} x FL '............ (10) U FR = U N -K B · x FR' ............ (11) U RL = U N + K p · U _{pRL ............ (12) U RR =} U N + K p · U pRR ............ (13) wherein, U _N control force necessary to maintain the vehicle height to the target vehicle height, K _B is active control gain, is K _p is a preview control gain.

[0047] On the other hand, in step S13, the delay time tau _R stored in the processing sampling time ΔT
It is determined whether the value obtained by subtracting (τ _R −ΔT) is not zero,
If this value (τ _R -ΔT) is not zero, the aforementioned step S
8 and otherwise, to step S17. In the step S17, the control flag F is set to "0".
Then, the process proceeds to step S14.

In step S8, the rear wheel side
Vertical acceleration detection value Z_GRL, Z _GRRThe digital
The spring on the rear wheel side is integrated by a low-pass filter process etc.
Upper vibration speed x_RL’, X_RR′ Is calculated, and step S18
Move to In the step S18, the step S
Front wheel side derived when calculating the differential value of road displacement in 4
The sprung vibration speed x of_FL’And x_FR′ To the 10
The front wheel side pressure control valve 20FL, 20
Total control force U for FR_FL, U_FR, And
The sprung vibration speed of the rear wheel calculated in step S8
x_RL’, X_RR′ And the following equations 14 and 15
Comprehensive control for wheel side pressure control valves 20RL, 20RR
Force U_RL, U_RRAnd the process proceeds to step S19.
You.

[0049] In _{U RL = U N -K B ·} x RL '............ (14) U RR = U N -K B · x RR' ............ (15) Step S19, the control flag F It is set to "1" and the routine goes to the step S16. Step S
In step 16, the step S15 or the step S18
The control forces U _{FL to} U _RR for each of the pressure control valves 20FL to 20RR calculated in the above are used as pressure command values, respectively, and the D / A converter 4
After outputting to 5FL to 45RR, the timer interrupt process is terminated and the process returns to the predetermined main program.

Next, the active suspension of this embodiment is
The operation of the viewing control device will be described. Now the vehicle is flat
It is assumed that the vehicle is traveling straight ahead at a constant speed while maintaining the target vehicle height on a good road.
Then, in this state, the vehicle reaches the target vehicle height on a flat good road.
The front suspension and front
No unsprung resonance vibration or shimmy phenomenon has occurred on the wheel side
At the same time, it is said that there is no chain attached,
Since the side member 10 does not swing, each vertical acceleration
Acceleration value Z of the sensor 28FL-28FR_GFL~ Z_GRR
And strokes of the stroke sensors 27FL and 27FR
Detection value S_FL, S _FRAre almost zero, and these are the input inputs.
Is converted into a digital value by the interface circuit 44a.
The data is input to the microcomputer 44.

Further, in the state where the vehicle is traveling straight on a flat good road at a constant speed, no unsprung resonance vibration or shimmy phenomenon has occurred on the front suspension and the front wheel side, and the chain is also mounted at the same time. in the state where no, the microcomputer 44, in the process of FIG. 9 which is executed at predetermined sampling time T _S, the step S4~
Overall power OP ₂ in the high frequency range calculated in S6
Is also because the over-all power OP ₁ in the low frequency range should smaller than the value obtained by multiplying the coefficient ratio a, preview control force of the rear wheel side shifts from step S7 to step S9, S10 U _{pR L} , U _pRR and the delay time τ _R are calculated, and the control flag F is “0” indicating the rear-wheel side preview control in step S12, and accordingly, steps S14 to S15
In accordance with the total control forces U _{FL to} U _RR calculated and output in the above, normal active control is performed for the front wheel side pressure control valves 20FL and 20FR, and the rear wheel side pressure control valves 20RL and 20R.
For R, preview control is performed after the delay time τ _R.

That is, while maintaining the target vehicle height in this way,
When the vehicle is traveling straight on a flat road at a constant speed,
Acceleration detection value Z_GFL~ Z_GRRAnd front wheel side stroke detection
Value S _FL, S_FRBecomes substantially zero, so that in step S4
Derived front wheel side sprung vibration speed x_FL’And x_FR'But
On the other hand, the rear wheel side pre-calculation calculated in step S9 becomes zero.
Look control power U_pRL, U_pRRIs also zero, of which zero rear wheels
Side preview control force U_pRL, U_pRRAre sequentially stored in the storage device 44d.
Before and after calculated in step S10 in the shift register area
Delay time between wheels τ_RIs stored in step S11 together with
Each time these shift, the delay time τ_RSampling from
Time T_SIs the new delay time τ_RUpdated as
Is done. Therefore, the control flag F = 0 in step S12.
, The preview control force U read in step S14
_pRL, U_pRRIs also zero.
In the processing, all the second terms on the right side of the expressions 10 to 13 are all
By being zero, each total control force U_FL~ U_RRIs the target car
Neutral pressure control force U corresponding only to high value_NAnd these are
As the pressure command value, D
/ A conversion and output to the drive circuits 46FL to 46RR.
You.

For this reason, the drive circuits 46FL to 46RR convert the currents into command currents i _{FL to} i _RR corresponding to the control forces U _{FL to} U _RR and supply them to the respective pressure control valves 20FL to 20RR.
As a result, the hydraulic cylinders are neutral pressure P _CN required to maintain the target vehicle height from the pressure control valve 20FL～20RR 1
8FL to 18RR.
FL to 18RR generate a thrust for maintaining the stroke between the vehicle body side member 10 and the wheel side member 14 at the target vehicle height.

If, for example, the front left and right wheels 11FL and 11FR simultaneously and temporarily pass through, for example, a convex portion while traveling at a constant speed on this good road, the vehicle body is bound by the bounding of the front left and right wheels running over the convex portion. An upward acceleration is generated in the side member 10, and this is detected by the vertical acceleration sensors 28FL and 28FR of the front left and right wheels. At the same time, the stroke accompanying the bounding of the front left and right wheels is detected by the stroke sensors 27FL and 27FL.
Detected at 27FR.

For this reason, for each sampling time T _S at which the processing of FIG. 9 is executed by the microcomputer 44, the vertical acceleration sensors 28FL, 28
The differential values x _OFL ′ and x _OFR ′ of the road surface displacement corresponding to the vertical acceleration detection values Z _GFL and Z _GFR from the _FR and the stroke detection values S _FL and S _FR from the stroke sensors 27FL and 27FR are calculated. At this time, the differential value x of the road surface displacement
_{Since OFL} 'and x _OFR ' are due to the transient climbing of a convex part on a flat road, it is assumed that the front suspension and the front left and right wheels have not yet generated high-frequency vibrations due to the above-described causes. over all power OP ₂ of high frequencies in S5~S7, like it is determined that the over-all power OP ₁ in the low frequency range smaller than a value obtained by multiplying the coefficient ratio a, the differential value x of the step S9 road surface displacement Foresight control force _UppRL , U according to _OFL 'and _xOFR '
_{The pRR} is calculated, the delay time τ _R according to the vehicle speed is calculated in step S10, and these are stored in the shift register area of the storage device 44d while being sequentially shifted in step S11.

Here, on the front wheel side, the vertical acceleration detection values Z _GFL , Z _GFR output from the vertical acceleration sensors 28FL, 28FR increase in the positive direction due to the acceleration acting upward due to the riding on the convex portion. The sprung vibration speed x _FL ', x _FR ' derived in step S4
Also increases in the positive direction, thus the front-wheel general control force U _FL calculated in step _S15, U _FR will be decreased from the neutral pressure control force U _N, is output from the drive circuit 46FL and 46FR accordingly Command currents i _{FL and} i _FR decrease,
This pressure control valve 20FL, the hydraulic cylinder 18FL control pressure P _C output from 20FR is lowered from neutral pressure P _CN, is reduced thrust 18FR, consequently possible to reduce the front wheel side stroke and By doing so, it is possible to perform a so-called normal active control that suppresses the swing of the vehicle body side member 10 due to the front wheels 11FL and 11FR riding on the convex portions. On the other hand, the rear-wheel wheel-side preview control force after a delay time tau _R is zero when the front wheel rides on the convex portion for the side U _pRL, since U _pRR maintains the state of zero, the rear wheel hydraulic cylinder At 18RL, 18RR, the state of generating a thrust for maintaining the target vehicle height is continued.

Then, the front wheels 11FL and 11FR are
After passing through the top of the convex part, it will be in a rebound state
A downward acceleration is generated in the vehicle body side member 10,
The microcomputer 44 executes the processing shown in FIG.
Sampling time T_SEach time, in reverse to the above, the descending speed on the front wheel side
Front-wheel active total control force U_FL,U_FRBut
Calculated with the opposite sign to the above, and the front wheel side
Rear wheel preview control force U that suppresses changes in descending speed_pRL, U
_pRRIs also calculated, and this rear wheel side preview control force U_{pR L}, U
_pRRAre sequentially shifted while the shift
Stored in the register area. Therefore, step S15
Front wheel side total control force U calculated by_FLAnd U _FRIs a convex part
Neutral pressure control force U according to the following vehicle lowering speed_NMore increased
Output from the drive circuits 46FL and 46FR.
Command current i_FLIncreases, thereby controlling the pressure
Control pressure P output from valves 20FL and 20FR_CIs medium
Standing pressure P_CNThe hydraulic cylinders 18FL and 18
FR thrust increased, resulting in rebound
By increasing the stroke on the front wheel side, the front wheel 11
Of the vehicle body side member 10 after the FL and 11FR convex portions
Normally active control is possible, which suppresses oscillation. On the other hand,
Delay time τ_RRear-wheel preview control force when
U_pRL, U_pRRIs maintained at zero, so the rear wheel side hydraulic pressure
The cylinders 18RL and 18RR are designed to maintain the target vehicle height.
The condition for generating the force is continued.

[0058] However, the rear wheel side, sequentially from the time the delay time tau _R has elapsed that is calculated in step S10 in FIG. 9, before the delay time tau _R, that is, before the aforementioned left and right wheels 11FL, 11FR convex portion , The rear wheel side _preview control forces U _pRL , _{Up RRR} are read out, and based on these, the rear wheel side total control forces U _RL, U _RR are calculated in step S15,
These are used as rear-wheel-side pressure command values as pressure control valves 20RL,
Output to 20RR. As a result, the front wheels 11FL, 11F
Rear wheel R has a delay time tau _R delayed from the start ride protrusion 11RL, rear-wheel side control force from the time the 11RR rides on the convex portion U _RL, by U _RR is decreased from the neutral pressure control force U _N, command current i _RL output from the drive circuit 46RL and 46RR is lowered from neutral current i _N, the control pressure P _C to thereby output from the pressure control valve 20RL and 20RR is lowered from neutral pressure P _CN, hydraulic cylinder 18R
L and 18RR thrusts are reduced, and as a result, it is possible to reduce the strokes of the rear left and right wheels, thereby suppressing the swinging of the vehicle body side member 10 caused by the rear left and right wheels 11RL and 11RR running over the convex portions. , So-called rear wheel preview control.

[0059] At this time, the three equations and equation 4 at the set is rear wheel side predictive control force U _pRL, U _pRR is sufficiently vibration input transmitted from the rear wheel side to the vehicle body as shown by the Formula 8 Since it can be canceled or suppressed, good riding comfort is maintained. On the other hand, when one of the front wheels 11FL and 11FR, for example, only the front left wheel 11FL rides on the transient convex portion, the above-described swing suppression control is performed only on the hydraulic cylinders 18FL and 18RL on the left wheel side. Control for maintaining the neutral pressure is performed for the right wheel hydraulic cylinders 18FR and 18RR that do not cause riding.

The front wheels 11FL and 11FR are temporarily
When the vehicle falls into the recess, the control is performed in the reverse
Swaying of the body can be suppressed, and transient irregularities
Not only when traveling on uneven road surfaces such as irregular roads
Can predictively control the rear wheels according to the behavior of the front wheels.
You. By the way, when driving on a flat, good road as described above,
Also unsprung resonance with front suspension and front left and right wheels
Vibration or shimmy phenomenon
In this case, the vertical acceleration detection value Z_GFL, Z_GFRas well as
Stroke detection value S _FL, S_FROf the high frequency component increases.
Also, this tendency is observed even when driving with the chain attached.
appear. In such a situation, a file that is unrelated to road surface input
The vibration of the front suspension system is regarded as erroneous information of the road surface input.
Get it. Therefore, the upper and lower
Direction acceleration detection value Z_GFL, Z_GFRAnd stroke detection value
S_FL, S_FRDifferential value x of road surface displacement obtained from_OFL'as well as
x_OFR'Has also increased. Therefore,
Overall in high frequency range obtained in steps S5 and S6
Power OP_TwoIs a low frequency overall power OP₁In charge of
The value is equal to or more than the value obtained by multiplying the numerical ratio a.
The rear wheel side sprung vibration speed x_RL’, X_RR’
In step S18, the active control gain K_BMultiplied by
Rear wheel side total control force U_RL, U_RRIs calculated, and at the same time
Similarly, the front wheel side total control force U_FL, U_FRIs calculated. this
Their total control power U_FL~ U_RRIs pressure control as pressure command value
When output to valves 20FL to 20RR, each hydraulic cylinder
18FL ~ 18RR has normal skyhook damper effect
Works as an active suspension that demonstrates
Is also the road surface vibration input estimated value obtained as the erroneous information.
Differential value x of road displacement_OFL’And x_OFR’
Of unnecessary vibration force on the vehicle body for predictive control
At the same time, the normal active control
Movement is effectively suppressed to ensure a good ride.
Wear. Note that during the rear wheel side normal active control,
In step S19, the control flag F is set to "1" indicating this.
Is set.

Incidentally, the shimmy phenomenon and the unsprung resonance vibration are not permanent, and eventually converge and no longer occur. At this time, the over-all power OP ₂ in the high frequency band obtained in step S5, S6 is less than the value obtained by multiplying the coefficient ratio a in over-all power OP ₁ in the low frequency range, again in step S9 and S10 Preview control force U _{pR L,} stores update them to calculate the U _pRR and the delay time tau _R in the shift register area in step S11. However, at this point, while normally shifts to active control from the wheel side Preview Control after the previous, the new preview control force U _pRL, because U _pRR and the delay time tau _R is not calculated and stored and updated, So-called old data is preserved. Therefore, the sampling time ΔT of this processing if not passed the latest delay time is repeated n times, the step preview control force suited to the rear wheel side predictive control in S14 U _pRL, U _pRR delay time tau _R also cause read Will not be. Therefore, in the step S12, the step S
Step S1 based on the control flag F = 1 set in step 19
3 to determine whether the value (τ _R -ΔT) obtained by subtracting the sampling time ΔT from the latest delay time τ _R stored and updated is zero, and at least at this time, this value (τ _R- .DELTA.T) is not zero, the aforementioned step S8
Then, the process shifts to step S18 to continue the rear-wheel-side normal active control. The value (τ) calculated in step S13
_R− ΔT) is temporarily stored in the storage device 44d.
This value is read out in the next processing, and the above determination is made by further reducing the sampling time ΔT.

After a lapse of the delay time τ _R to be compared with the elapsed time, the value (τ _R −ΔT) becomes zero in the step S13, and the process proceeds to the step S17.
Here, the control flag F is reset to "0" indicating the rear wheel side preview control, and the process first proceeds to steps S14 and S15 to execute the rear wheel side preview control again. In the above control,
In rear wheel road surface vibration input is an estimate differential value x _OFL road displacement 'and x _OFR' high frequency range over all power OP ₂ is also over-all power OP ₁ in the low frequency band coefficient ratio a times value above In some cases, stopping the preview control on the rear wheel side and switching to the normal active control is performed by, for example,
When it is considered that the rear wheel side _preview control forces U _pRL and U _pRR obtained by multiplying the equations 4 and 15 by the control gain K _p are added to calculate the rear wheel side total control forces U _RL and U _RR , this control gain K _p
Is equal to zero (for details, refer to a third embodiment described later). Therefore, this embodiment is regarded as applying the invention according to claim 3 to the invention according to claim 1, and the control wheels to be controlled are the rear wheels 11RL and 11R.
R, and the road surface detecting means detects a vibration input input to the vehicle body via the front wheels 11FL and 11FR as a stroke and a vertical acceleration, so that steps S2 and S3 in the processing of FIG. Step S4 corresponds to the control wheel input estimating means, steps S5 to S7 correspond to the input level determining means, and steps S9 to S16 correspond to the foreseeing control means. Steps S8 and S18 correspond to gain changing means. Also, the time of detecting the unevenness of the road surface corresponds to the time of inputting vibration to the front wheels, and the foreseeing distance corresponds to the wheel base between the front and rear wheels.

In the first embodiment, when shifting from the preview control on the rear wheel side to the active control, especially when the shimmy phenomenon and the unsprung resonance vibration occur only in the front suspension system, these various factors are considered. As a result, high-frequency components as erroneous information of road surface vibration input increase, and as a result,
Even at the time when the over-all power OP ₂ in the high frequency range becomes over-all power OP ₁ coefficient ratio a multiplied value or more low frequency region, wheel side preview control force U _pRL after up to this point, U
_{Since the pRR} and the delay time τ _R are appropriate for the rear wheel _preview control, if the rear wheel _preview control can be continued from this time until the delay time τ _R elapses, the vehicle body The swing is more stable.

Next, a second embodiment of the active suspension preview control apparatus of the present invention will be described with reference to FIG. In the second embodiment, the load on the microcomputer required for the FFT is reduced to enable higher-speed processing. The configuration of the vehicle and the configuration of the active suspension 12 applied in this embodiment are substantially the same as those of the first embodiment shown in FIG. The structure of the controller 30 for controlling the active suspension 12 is substantially the same as that of the first embodiment shown in FIG.

The contents of the processing performed by the microcomputer 44 in the controller 30 are different. Here, the rear wheel differential value of the road surface displacement which is calculated as the road surface input x _{OF L} 'and x _OFR' and the rear wheel side predictive control force U _pRL and U _pRR, the delay time tau _R, comprehensive control force U _FL ~U The calculation processing of the _RR and the like is performed in the same manner as in the first embodiment, but the method of calculating the vibration input energy in the high frequency range and the vibration energy in the low frequency range is different. Specifically, in order to reduce the burden of calculating the overall power in both frequency ranges from the FFT, the rear wheel road surface input estimated values corresponding to each frequency range are extracted, and the energy of each frequency range is calculated from the square integration value. Is calculated instead.

Therefore, the microcomputer 44 executes the processing shown in FIG. 10 instead of the processing shown in FIG.
Here, step S5 in FIG. 9 is replaced with step S5 in FIG.
25, similarly, step S6 becomes step S26,
Although step S7 is only changed to step S27, for easy understanding, step S1 is performed in step S21, step S2 is performed in step S22,..., Step S19 is performed in step S39. The specific predetermined contents are the same as in the first embodiment. The same steps will be briefly described, but the overall processing will be described. First, the current vehicle speed detection value V is read in step S21, and then the vertical acceleration detection values Z _{GFL to} Z _{GR R} are read in step S22. Is read, and then, in step S23, the stroke detection values S _FL and S _FR are read.

In the next step S24, the differential values x _OFL ', x
_OFR 'is calculated. Next, the process proceeds to step S25, in which the cutoff frequency does not overlap with the differential value x _OFL ′, x _OFR ′ of the road surface displacement as the estimated value of the rear wheel surface vibration input calculated in step S4, for example, a digital band pass. The filter processing calculates the differential value components _xBP1OFL 'to _xBP2OFR ' of the road surface displacement in the high / low frequency range. Specifically, for example, the low frequency band components xBP _1OFL ′, xBP ′ among the differential values x _OFL ′, x _OFR ′ of the road surface displacement are subjected to digital bandpass filter processing in which the low frequency range of -10 Hz is a pass frequency band. 'seek, by a digital band-pass filtering said 10~20Hz is passing frequency band in the same manner, the differential value x _OFL road displacement' _1OFR, the high frequency range component xBP of x _OFR '
_2OFL ', xBP _2OFR ' Each digital bandpass filter is constructed by a program executed by a microcomputer as is known, and the cutoff frequency of each filter is set by a temporary variable used in the program.

Next, the process proceeds to step S26, in which the square integral value SI ₁ of the differential value components xBP _1OFL 'to xBP _2OFR ' of the road surface displacement in the high and low frequency ranges calculated in step S25 with respect to the frequency f in each frequency range is obtained. , SI ₂ is the following 16 formula,
It is calculated from equation (17). SI ₁ = ∫ (xBP _1OFL ') ² df + ∫ (xBP _1OFR ') ² df... (16) SI ₂ = ∫ (xBP _2OFL ') ² df + ∫ (xBP _2OFR ') ² df ... 17) Next, proceeding to step S27, the square integral S of the differential value of the road surface displacement in the high frequency range calculated in step S26 is obtained.
I ₂ is the square integral S of the differential value of the road surface displacement in the low frequency range
Determining whether a said coefficient ratio multiplied value above which a to I _1, square integrated value SI ₂ of the high frequency range by multiplying the coefficient ratio a to the square integration value SI ₁ of the low frequency range values If so, the process proceeds to step S28; otherwise, the process proceeds to step S29.

In step S29, the above equation (3) and
According to the formula, the rear wheel preview control force U_{pR L}And U_pRRCalculate
Then, the process proceeds to step S30, and according to the above equation (9).
Delay time τ_RIs calculated, and then the process proceeds to step S31.
Then, the preview control on the rear wheel side calculated in step S29 is performed.
Force U_pRLAnd U_pRRAnd the delay calculated in step S30.
Delay time τ_RAnd a shift register formed in the storage device 44d.
Data at the beginning of the data area, and
Rear-wheel-side preview control force U_pRL, U_pRRAnd at the time of delay
Interval τ_RAre sequentially shifted, and the process proceeds to step S32.
You. At this time, the delay time τ_RWhen shifting
Is the delay time τ of each shift position as in the first embodiment.
_RTo sampling time T_SAre subtracted from each other
Delay time τ _RUpdate and store as

In step S32, the control flag F =
1 is determined, and if the control flag F = 1, the process proceeds to step S33; otherwise, the process proceeds to step S34. At step S34, preview control force of the wheel side after the delay time stored in the shift register region tau _R becomes zero U _pRL and reads the U _pRR, and read out the oldest predictive control force U _pRL, U _{The pRR} and the delay time τ _{R corresponding thereto} are erased from the shift register area, and then the process proceeds to step S35, where the total control forces U _{FL to} U _FL for the pressure control valves 20FL to 20RR are calculated according to the above equations (10) to (13).
After calculating _RR , the process proceeds to step S36.

[0071] On the other hand, in step S33, the delay time tau _R stored in the processing sampling time ΔT
It is determined whether or not the value (τ _R −ΔT) obtained by subtracting is not zero. If the value (τ _R −ΔT) is not zero, the process proceeds to step S28, and if not, the process proceeds to step S3.
Item 7 In the step S37, the control flag F is reset to "0", and then the process proceeds to the step S34.

In step S28, the vertical acceleration detection values Z _GRL and Z _GRR of the rear wheel are integrated by the digital low-pass filter processing or the like, and the sprung vibration speeds x _RL ′ and x _{RR of the} rear wheel are integrated. ', And then proceeds to step S38 to calculate the total control force U for the front wheel-side pressure control valves 20FL and 20FR according to the equations (10) and (11).
_FL, calculates the U _FR, the equation (14), 15 pressure control valve for the rear wheels in accordance with formula 20RL, comprehensive control force U _RL for 20RR, the process proceeds to the step S39 to calculate the U _RR, the control flag F Is set to "1", and the routine goes to the step S34.

At the step S34, at the step S34
35 or each pressure control valve 2 calculated in step S38.
The control forces U _{FL to} U _RR for 0 _{FL to 20 RR} are output to the D / A converters 45 _{FL to} 45 _RR as pressure command values, respectively, and then the timer interrupt processing is terminated to return to the predetermined main program. The operation of the vehicle suspension control by the arithmetic processing in this embodiment is almost the same as that of the first embodiment. The transition from the preview control on the rear wheel side to the normal active control and the transition in the opposite direction are performed in the same manner as in the first embodiment. However, the fast Fourier transform performed in the first embodiment has a smaller computational load than the general Fourier transform or the discrete Fourier transform because of the smaller number of multiplications. Even if it has a high capability, the operation processing time is considerable, and thus the load on the operation is large. On the other hand, extracting the components of the necessary frequency range by the digital band-pass filter processing and calculating the square integral thereof as described above requires much less computational load than the fast Fourier transform, and the computation processing time is also reduced. Can be shortened. Here, the square integral value of the vibration waveform is F
It is well known that the energy is expressed in the same manner as the overall power by the FT. Therefore, in step S27, the ratio of the energy in the high and low frequency bands, that is, the input level is determined, and the energy in the high frequency band is reduced to the low frequency band. It can be seen that the control gain of the preview control is set to zero when the energy is larger than the coefficient ratio of the energy, and the preview control is stopped. Therefore, in this embodiment, it is considered that the invention according to claim 3 is applied to the invention according to claim 1, the control wheels to be controlled are the rear wheels 11RL and 11RR, and the road surface detecting means is the front wheels 11FL and 11FL. Since the vibration input input to the vehicle body via the 11FR is detected as the stroke and the vertical acceleration, steps S22 and S22 in the processing of FIG.
23 corresponds to the road surface detecting means of the present invention according to claim 1,
Similarly, step S24 corresponds to control wheel input estimating means, steps S25 to S27 correspond to input level determining means, steps S29 to S34 correspond to preview control means, and steps S28 and S35 correspond to gain changing means. I do. Also, the time of detecting the unevenness of the road surface corresponds to the time of inputting vibration to the front wheels, and the foreseeing distance corresponds to the wheel base between the front and rear wheels.

In the second embodiment, when shifting from the preview control on the rear wheel side to the active control, especially when the shimmy phenomenon and the unsprung resonance vibration occur only in the front suspension system, these various factors are considered. As a result, high-frequency components as erroneous information of road surface vibration input increase, and as a result,
The high-frequency range of the square integration value SI ₂ is low frequency range of the square even when the coefficient ratio becomes a doubled value or integrated value SI _1, wheel side preview control force U _pRL after up to this point, U _pRR and delay Since the time τ _R is appropriate for the rear-wheel side preview control, if the rear-wheel side preview control can be continued from this time until the delay time τ _R elapses, the swing of the vehicle body is reduced. More stable.

Next, a third embodiment of the active suspension preview control apparatus of the present invention will be described with reference to FIGS. In the third embodiment, the overall power ratio OP ₂ / O in the high and low frequency ranges calculated in the first embodiment is described.
By gradually changing the control gain according to the rear wheel predictive control according to P _1, discontinuous transition or smoothly performed by controlling the transition to the opposite direction from the rear wheel predictive control to the normal rear wheel active control To avoid sex.

The configuration of the vehicle and the configuration of the active suspension 12 applied in this embodiment are almost the same as those of the first embodiment shown in FIG. Active suspension 1
The structure of the controller 30 for controlling the second embodiment is substantially the same as that of the first embodiment shown in FIG. The contents of the processing performed by the microcomputer 44 in the controller 30 are different. Here, the rear wheel differential value of the road surface displacement which is calculated as the road surface input x _{OF L} 'and x _OFR' and the rear wheel side predictive control force U _pRL and U _pRR, the delay time tau _R, front-wheel-side total control force U _FL , _UFR, etc., are performed in the same manner as in the first embodiment, but the method of calculating the rear-wheel-side total control forces U _RL , U _RR is different. Specifically, the rear wheel side total control force U _RL ,
U _RR, the target vehicle height achieved control force U _N rear-wheel-side preview control force U _pRL and U _{pR R} in adds a value obtained by multiplying the predictive control gain K _p, further the rear wheel side sprung vibration velocity x _RL obtained by subtracting a value obtained by multiplying the active control gain K _B in 'and x _RR'.

Accordingly, the arithmetic processing unit 44c executes the processing shown in FIG.
Every _S (for example, 20 msec), the vehicle speed detection value V, the stroke detection values S _FL , S _FR and the vehicle body vertical acceleration detection values Z _{GFL to} Z G
_{The GRR} is read, and the rear wheels 11RL and 11RL are read from the stroke detection values S _FL and S _FR and the vehicle vertical acceleration detection values Z _{GFL to} Z _GRR.
Calculate the differential values of road surface displacement x _OFL ′ and x _OFR ′ as rear wheel input estimation values that will be input to RR, and _perform fast Fourier transform FFT on the differential values of road surface displacement x _OFL ′ and x _OFR ′. Overall power OP ₂ , O of the power spectral density in the predetermined high and low frequency range obtained by performing the processing
P ₁ is obtained and these overall powers OP ₂ , OP ₁
The rear wheel vibration obtained as the differential values x _OFL ′ and x _{OF R} ′ of the road surface displacement from the energy ratio of both frequency ranges represented by (i.e., the overall power ratio OP ₂ / OP ₁ ) The existence ratio of the high-frequency component of the input estimated value is obtained, and when the high-frequency component of the rear wheel vibration input estimated value is small, that is, when the existence ratio is smaller than a preset coefficient ratio, the ratio of the rear wheel preview control is reduced. When the high-frequency component of the rear wheel vibration input estimated value is large, that is, when the existence ratio exceeds a preset coefficient ratio, the control command value is increased so that the ratio of the rear wheel active control is increased. A certain total control force U _FL ~
The gain K _p used to calculate the U _RR, set by the control map or calculation formula described later K _B.

At this time, the preview control gain K_pIs
Stored in the storage device 44d of the microcomputer 44
Is set according to the control map of FIG. This control
The map is the overall power OP of the high frequency range._TwoLow
Overall power OP in the frequency range₁Ratio OP to_Two/
OP₁Preview control gain K_pFrom the characteristic diagram
And overall power ratio OP_Two/ OP₁Is "1" or less
In the region of, the preview control gain K_pIs the set value K_pOMaintained in
And overall power ratio OP_Two/ OP₁Exceeds “1”
The overall power ratio OP_Two/ OP₁Is a predetermined value
q for preview control gain K_pIs half the set value K_pO/ 2
So that the slope-(K_pO/ 2) / (1-q) constant and lini
The preview control gain is reduced according to this slope curve.
K_pIs the overall power ratio OP at which is “0”_Two/ OP
₁In the above region, the preview control gain K _pIs maintained at “0”
It is. The decreasing curve of the control gain is expressed by the following equation (18).
expressed.

K_p=-(K_pO/ 2) / (q-1) · (OP_Two/ OP₁) + (Q-1 + K_pO/ 2) / (q-1) (18) On the other hand, the active control gain K_BIs the set value K_BOFor
Set by equation (19). K_B= (K_pO-K_p) / K_pO・ K_BO ............ (19) Therefore, the active control gain K_BIs the overall power ratio O
P_Two/ OP₁In FIG. 12 as indicated by the dashed line.
Become That is, the preview control gain K_pIs the set value K _pOKeep in
Overall power ratio OP_Two/ OP₁Is "1" or more
Active control gain K in the lower region_BIs maintained at “0”,
Look control gain K_pIs the predetermined inclination− (K_pO/ 2) /
The overall power ratio OP that decreases by (1-q)_Two/ O
P₁Is greater than “1”, the overall power ratio
OP_Two/ OP₁As the control gain K increases,_pof
Set value K_pOIncreases with the reversal of the decrease rate of
Control gain K_pPower is maintained at “0”
Ratio OP_Two/ OP₁In the area of, the set value K_BOMaintained in
You.

Here, the processing of FIG. 11 is executed as a timer interruption processing every predetermined sampling time T _S (for example, 20 msec). First, in step S41, the current vehicle speed detection value V of the vehicle speed sensor 26 is read, Step S42
To read the vertical acceleration detection values Z _{GFL to} Z _GRR from the vertical acceleration sensors 28FL to 28RR, and then to step S43 to move to the stroke sensor 27F.
The stroke detection values S _FL and S _FR from L and 27 _FR are read.

Next, the flow shifts to step S44, where the stroke speeds S _VFL and S _VFL obtained by differentiating the stroke detection values S _FL and S _FR by the digital high-pass filter processing or the like are obtained.
S _{VF R} and front-wheel-side vertical acceleration detection values Z _GFL , Z
_From the front-wheel-side sprung vibration speeds x _FL 'and x _FR ' obtained by integrating the _GFR by the digital low-pass filter processing or the like, the differential value x
_OFL ′, x _OFR ′ are calculated.

Next, the flow shifts to step S45, where the fast Fourier transform FFT is performed on the differential values x _OFL ', x _OFR ' of the road surface displacement as the rear wheel road surface vibration input estimated value calculated in step S44. To determine the power spectral density distribution. In order to execute the fast Fourier transform FFT by a microcomputer, a known algorithm can be applied.

Then, the flow shifts to step S46, from the power spectrum density distribution of the vibration input obtained in step S45, the overall power OP _{1 in} the low frequency range up to about 10 Hz and the high overall power OP _{1 in} about 10 to 20 Hz. to calculate the over-all power OP ₂ of the frequency range. Next, the routine proceeds to step S47, the over-all power OP ₂ in the high frequency range calculated at step S46, and calculates the ratio OP ₂ / OP ₁ for over all power OP ₁ in the low frequency range, the 12 According to the control map or the calculation formula 1
The rear wheel preview control gain _Kp is set according to equation (8).

[0084] and then proceeds to step S48, the used differential value x _OFL of the road displacement 'and x _OFR', calculates a predictive control force U _pRL and U _pRR the rear wheel side in accordance with the three equations and 4 expression . Next, the flow shifts to step S49, where the delay time τ _R is calculated in accordance with the above equation 9 using the vehicle speed detection value V.

Next, the flow shifts to step S50, where the rear-wheel-side _preview control forces U _pRL and U _pRL calculated in step S48 are calculated.
_{The pRR} and the delay time τ _R calculated in step S49 are stored at the head position of the shift register area formed in the storage device 44d, and the _preview control forces U _pRL and U _{pRR for the} rear wheels stored up to the previous time are stored. And the delay time τ _R are sequentially shifted. At this time, when the shift for the delay time tau _R, Update stores a value delay time tau _R from the sampling time T _S and each subtraction of the shift position as a new delay time tau _R.

[0086] and then proceeds to step S51, the oldest i.e. the delay time tau _R stored in the shift register region reads the preview control force U _pRL and U _pRR the rear wheels became zero was and read the oldest foreseen control force U _pRL, erases the U _pRR and the delay time tau _R for this from the shift register area. Next, the process proceeds to step S52, where the vertical acceleration detection values Z _GRL and Z _GRR on the rear wheel side are integrated by the digital low-pass filter processing or the like, and the sprung vibration speeds x _RL ′ and x _RR ′ on the rear wheel side. Is calculated.

Then, the flow shifts to step S53, where the front-wheel-side sprung vibration speeds x _FL ′ and x _FR ′ derived when the differential value of the road surface displacement is calculated in step S44 are set in step S47. The wheel side preview control gain K _p , the rear wheel side _preview control force _{Up pRL} read in step S51.
And U _pRR, the step S52 sprung vibration speed of the rear wheels calculated in x _RL ', x _RR' using the following 20 formula to 23
The total control forces U _{FL to} U _RR for the pressure control valves 20 _{FL to 20 RR} are calculated according to the equations.

[0088] _{U FL = U N -K BO ·} x FL '............ (20) U FR = U N -K BO · x FR' ............ (21) U RL = U N + K p · U _{pRL - (K pO -K p)} / K pO · K BO · x RL '= U N + K p · U pRL -K B · x RL' ............ (22) U RR = U N + K p · U _pRR - goes to _{(K pO -K p) / K} pO · K BO · x RR '= U N + K p · U pRR -K B · x RR' ............ (23) then step S54, The control forces U _{FL to} U _RR for the respective pressure control valves 20FL to 20RR calculated in step S53 are used as pressure command values, respectively, as D / A converters 45.
After outputting to FL-45RR, the timer interrupt process is terminated and the process returns to the predetermined main program.

Next, the operation of the active suspension preview control device of this embodiment will be described. Now, assuming that the vehicle is traveling straight ahead at a constant speed while maintaining the target vehicle height on a flat good road, in this state, since the vehicle is maintaining the target vehicle height on a flat good road, Since no unsprung resonance vibration or shimmy phenomena occur on the suspension and the front wheel side, and no chain will be attached at the same time, no swing occurs in the vehicle body side member 10. acceleration detection value of 28FL~28FR Z _{GF L} ~Z
_{The GRR} and the stroke detection values S _FL and S _FR of the stroke sensors 27FL and 27FR are substantially zero, and these are converted into digital values by the input interface circuit 44a and input to the microcomputer 44.

Further, in the state where the vehicle is traveling straight on a flat good road at a constant speed, no unsprung resonance vibration or shimmy phenomenon or the like occurs on the front suspension and the front wheels, and the chain is mounted at the same time. in the state where no, the microcomputer 44, in the process of FIG. 11 which is executed at predetermined sampling time T _S, the step S4
Since the ratio OP ₂ / OP ₁ for over all power OP ₁ in the low frequency range of over-all power OP ₂ in the high frequency range is calculated by 4~S46 should smaller than "1" as described above, the rear-wheel-side preview control gain K _p in step S47 is set to the set value K _pO according to the control map. Then, step S48, the rear wheel side in S49 predictive control force U _pRL, according U _pRR and the delay time tau _R is calculated, and each general control force U _FL ~U _RR calculated output in step S51 to S54, the front wheels Normal active control is performed on the pressure control valves 20FL and 20FR on the side, and control described later is executed on the pressure control valves 20RL and 20RR on the rear wheel side.

That is, while maintaining the target vehicle height in this way,
When the vehicle is traveling straight on a flat road at a constant speed,
Acceleration detection value Z_GFL~ Z_GRRAnd front wheel side stroke detection
Value S _FL, S_FRBecomes substantially zero, so that step S44
The sprung vibration speed x of the front wheel derived from_FL’And x_FR’
Becomes zero, while the rear wheel side calculated in step S48 is
Control power U_pRL, U_pRRIs also zero, of which zero
Rear wheel preview control force U _pRR, U_pRRAre sequentially stored in the storage device 44
d in the shift register area at step S49.
Τ between front and rear wheels_RAnd stored in step S50
And the delay time τ_RFrom sump
Ring time T_SIs the new delay time τ_Rage
Will be updated. Therefore, it is read in step S51.
Preview control force U_pRL, U_pRRIs also zero. On the other hand,
Rear wheel sprung vibration speed calculated in step S52
x_RL’, X_RRIs also the vertical acceleration detection value Z._GRL, Z
_GRRIs zero because is zero. Also, the rear wheel side preview system
Your gain K_pIs the set value K_pOIs set to
The rear wheel active control gain K given by the above equation (19)_BAlso zero
Becomes As described above, in the step S53, the 2
The second term on the right side of Equations 0 and 21 is all zero, and
The second and third terms on the right side of Equations (23) and (23) are all zero.
From each total control force U_FL~ U_RRCorresponds only to the target vehicle height
Neutral pressure control force U _NThese are the pressure command values
D / A converted by the output side interface circuit 44b
The signals are output to the driving circuits 46FL to 46RR.

For this reason, the drive circuits 46FL to 46RR convert the currents into command currents i _{FL to} i _RR corresponding to the control forces U _{FL to} U _RR and supply them to the respective pressure control valves 20FL to 20RR.
As a result, the hydraulic cylinders are neutral pressure P _CN required to maintain the target vehicle height from the pressure control valve 20FL～20RR 1
8FL to 18RR.
FL to 18RR generate a thrust for maintaining the stroke between the vehicle body side member 10 and the wheel side member 14 at the target vehicle height.

When the front left and right wheels 11FL and 11FR simultaneously and temporarily pass through, for example, a convex portion while traveling at a constant speed on the good road, the vehicle body is bounded by the bounding of the front left and right wheels running over the convex portion. An upward acceleration is generated in the side member 10, and this is detected by the vertical acceleration sensors 28FL and 28FR of the front left and right wheels. At the same time, the stroke accompanying the bounding of the front left and right wheels is detected by the stroke sensors 27FL and 27FL.
Detected at 27FR.

For this reason, the microcomputer 44
Sampling time T during which the process of No. 9 is executed_SEach time,
In step S44, the vertical acceleration sensor 28FL, 2
Vertical acceleration detection value Z from 8FR_GFL, Z_GFRas well as
Stroke from stroke sensor 27FL, 27FR
Detection value S_FL, S_FRDifferential value x of road surface displacement according to_OFL’
X_OFR'Is calculated. At this time, the differential value of the road surface displacement
x_OFL’And x_OFR’Is a transient raised power on a flat good road
The front suspension is still
High frequency vibration caused by the above-mentioned factors
Assuming that no occurrence has occurred, in steps S45 to S47
Overall power ratio O still smaller than "1"
P_Two/ OP₁Rear-wheel preview control gain K according to_pIs
Set value K _pOIs continuously set in step S48.
Differential value x of surface displacement_OFL’And x_{OF R}’Preview control
Force U_pRL, U_pRRIs calculated, and in step S49, the vehicle speed is calculated.
Delay time τ according to_RAre calculated, and these are calculated in step S
50, the shift amount of the storage device 44d is sequentially shifted.
Stored in the register area.

Here, on the front wheel side, the
Therefore, the acceleration acting upward causes the vertical acceleration
Vertical direction output from the degree sensors 28FL and 28FR.
Speed detection value Z_GFL, Z_GFRIncreases in the positive direction,
The sprung vibration velocity x derived in step S44_FL’,
x_FR′ Also increases in the positive direction, and therefore is calculated in step S53.
Front wheel side total control force U_FL,U_FRIs the neutral pressure control force U_N
And the driving circuit 46F
Command current i output from L and 46FR_FL,i_FRIs reduced
Slightly, this allows the pressure control valves 20FL, 20FR
Output control pressure P _CIs neutral pressure P_CNThe hydraulic pressure
The thrust of the Linda 18FL, 18FR is reduced, resulting in
To be able to reduce the front wheel stroke
Due to the riding on the convex part of the front wheels 11FL and 11FR
So-called ordinary active control for suppressing the swing of the vehicle body side member 10
Becomes possible. On the other hand, on the rear wheel side, the front wheel
The delay time τ_RIs zero
Control force U_pRL, U_pRRMaintains zero state and at the same time
Rear wheel active control gain K given by equation (19)_BIs still zero
, The second expression on the right-hand side of the above expressions 22 and 23
The term and the third term are still zero, and the rear wheel-side total control force U_RL,
U_RRIs still the neutral pressure control force U_NAnd the rear wheel side hydraulic cylinder
18RL, 18RR generate thrust to maintain the target vehicle height.
The state of producing is continued.

Thereafter, the front wheels 11FL and 11FR are
After passing through the top of the convex part, it will be in a rebound state
A downward acceleration is generated in the vehicle body side member 10,
11 is executed by the microcomputer 44.
Sampling time T_SEach time, on the contrary to the above, the front wheel side descends
Front-wheel active total control force U that suppresses speed changes_FL, U _FR
Is calculated with the opposite sign to the above, and
Rear-wheel-side preview control force U for suppressing a change in the descending speed of the vehicle_pRL,
U_pRRIs also calculated, and this rear wheel side preview control force U _pRL, U
_pRRAre sequentially shifted while the shift
Stored in the register area. Therefore, in step S53,
Issued front wheel side total control force U_FLAnd U_FRIs after passing the convex part
Neutral pressure control force U according to vehicle body lowering speed_NMore increased,
In response to this, the output from the drive circuits 46FL and 46FR is output.
Command current i_FLAnd the pressure control valve 2
Control pressure P output from 0FL and 20FR_CIs neutral pressure
P _CNHydraulic cylinders 18FL and 18FR
Thrust is increased, resulting in the front wheel being in a rebound condition
By increasing the side stroke, the front wheels 11FL
Of the vehicle body-side member 10 after riding on the convex part of the 11FR and 11FR
In general, active control becomes possible. On the other hand,
Delay time τ_RIs zero, the rear-wheel-side preview control force U
_pRL, U_pRRIs maintained at zero and the rear wheel side active control
Inn K_BIs also maintained at zero, so the rear wheel side hydraulic cylinder 1
At 8RL and 18RR, keep the target vehicle height as above
The state in which thrust is generated is continued.

However, regarding the rear wheel side, FIG.
Sequentially from the time the delay time tau _R has elapsed in step S50 of the calculation, before the delay time tau _R, that is, before the aforementioned left and right wheels 11FL, wheel-side preview control force after the time when 11FR has passed the convex portion U _pRL , U _pRR are read out, and based on these, the rear wheel-side total control forces U _RL, U _RR are calculated in step S53, and these are used as rear wheel side pressure command values to control the pressure control valve 20R.
L, 20RR. At this time, the rear-wheel-side preview control gain K _p is maintained at the set value K _pO, from being maintained on the rear wheel side active control gain K _B is still zero at the same time, the 22
Wherein is the zero third term on the right side of the 23 formula, the second term of the right side of the rear wheel-side preview control force U _pRL, wheel side overall control after only U _pRR and the rear-wheel-side preview control gain K _p acts Force U _RL , U _RR
As a result, the rear wheels 11RL and 11RR are delayed by the delay time τ _R from the time when the front wheels 11FL and 11FR start riding on the convex portion.
There rear wheel side control force from the time that rides on the convex portion U _RL, by U _RR is decreased from the neutral pressure control force U _N, the drive circuit 4
The command current i _RL output from 6RL and 46RR becomes lower than the neutral current i _N , whereby the pressure control valve 20RL
And the control pressure P _C to be outputted is lower than the neutral pressure P _CN from 20RR, is reduced thrust of the hydraulic cylinders 18RL and 18RR, by enabling consequently to reduce the stroke of the rear left and right wheel This enables so-called rear wheel preview control, which suppresses the swing generated on the vehicle body side member 10 due to the rear left and right wheels 11RL and 11RR riding on the convex portions.

The rear wheel _preview control forces U _pRL and _{Up RRR} set by the equations (3) and (4) sufficiently cancel the vibration input transmitted from the rear wheel to the vehicle body as shown by the equation (8). Alternatively, since it can be suppressed, good riding comfort is maintained. On the other hand, when one of the front wheels 11FL and 11FR, for example, only the front left wheel 11FL rides on the transient convex portion, the above-described swing suppression control is performed only on the hydraulic cylinders 18FL and 18RL on the left wheel side. Control for maintaining the neutral pressure is performed for the right wheel hydraulic cylinders 18FR and 18RR that do not cause riding.

The front wheels 11FL and 11FR are temporarily
When the vehicle falls into the recess, the control is performed in the reverse
Swaying of the body can be suppressed, and transient irregularities
Not only when traveling on uneven road surfaces such as irregular roads
Can predictively control the rear wheels according to the behavior of the front wheels.
You. By the way, when driving on a flat, good road as described above,
Also unsprung resonance with front suspension and front left and right wheels
Vibration or shimmy phenomenon
In this case, the vertical acceleration detection value Z_GFL, Z_GFRas well as
Stroke detection value S _FL, S_FRThe high frequency component of
In addition, this tendency occurs even while driving with the chain attached.
Live. In such a situation, the flow is unrelated to the road surface input.
Of suspension suspension system as erroneous information of road surface input
I get it. Therefore, the high frequency component is increased
Direction acceleration detection value Z_GFL, Z_GFRAnd stroke detection value S
_FL, S _FRDifferential value x of road surface displacement obtained from_OFL’And x
_OFR'Has also increased. Therefore,
In the high frequency range obtained in steps S45 and S46
Lupawa OP_TwoLow power overall power OP₁To
Ratio OP to_Two/ OP₁Greatly exceeds the above “1”
Therefore, in step S47, the rear wheel preview control gain K
_pIs set to zero, and the rear wheel side active control gain K_B
Is the set value K_BOIs set to

[0100] Thus, preview control force U _pRL to be read at the step S51, regardless of the size of the U _pRR ', 22 expression calculated at step S53, 23 Expressions second term becomes zero, the 22 wherein wheel sprung vibration velocity x _RL after being calculated in step S52 is 23 formula ', x _RR' active control gain K _B (= setting value K _BO) rear wheels comprehensive control from a value obtained by multiplying the relative The forces U _RL and U _RR are calculated, and at the same time, the front wheel side total control forces U _FL and U _FR are calculated in the same manner as described above. When these total control forces U _{FL to} U _RR are output as pressure command values to the pressure control valves 20FL to 20RR, each hydraulic cylinder 1
8FL to 18RR operate as an active suspension exhibiting a normal skyhook damper effect, and are based on at least differential values _xOFL 'and _xOFR ' of road surface displacement, which are estimated rear wheel vibration inputs obtained as the erroneous information. It is possible to avoid the generation of unnecessary excitation force on the vehicle body of the preview control performed at the same time, and at the same time, it is possible to effectively suppress the vertical movement of the vehicle body by normal active control and secure a good ride comfort .

The shimmy phenomenon and the unsprung resonance vibration do not occur at a certain moment, but rather occur to some extent depending on the vehicle speed, the steering angle and the like. Therefore, during the occurrence start period, the differential value x _OFL ′, x
The high frequency component of _OFR 'also increases gradually. Further, even when the chain is mounted, the high-frequency components of the differential values x _OFL ′, x _OFR ′ of the road surface displacement gradually increase as the vehicle speed increases. Therefore, in the processing of FIG. 11 performed for each predetermined sampling time T _{S, the} ratio OP ₂ / OP _{1 of the} overall power OP ₂ in the high frequency range obtained in steps S 45 to _S 47 to the overall power OP _{1 in} the low frequency range. Eventually, the overall power ratio OP ₂ / OP ₁ will further increase beyond the aforementioned “1”. During this period, preview control gain K _p is the slope - (K _pO / 2)
/ (1-q) decreases linearly at a constant, the active control gain K _B simultaneously, increases in positive and negative inverse of decrease rate for the set value K _pO the preview control gain K _p. Therefore, this transition period, the timer interrupt process is being foreseen control force is read in step S51 in the processing time in FIG. 11 U _pRL, U _pRR and wheel side sprung vibration velocity x _RL after being calculated in step S52 ',
x _RR ′ are taken into account to calculate the rear-wheel-side total control forces U _RL , U _RR , and the rear-wheel-side pressure control valves 20RL, 2
0RR and hydraulic cylinders 18RL, although control of the 18RR is performed, the distribution ratio of progressively smaller becomes simultaneously active control is the distribution ratio of the preview control for the rear wheels is gradually increased, the preview control gain K _p becomes zero At this point, the control is completely shifted to the active control on the rear wheel side, so that the control discontinuity is improved in its transient characteristics.

On the other hand, the overall power ratio OP ₂ /
Point OP ₁ is In the transition period to be gradually decreased, the distribution ratio of the distribution ratio is gradually reduced becomes simultaneously preview control active control of the rear wheels is gradually increased, that the active control gain K _B becomes zero The control is completely shifted to the preview control on the rear wheel side, so that the discontinuity of the control is also improved in the transient characteristics.

In the present embodiment, during the transition period from the rear wheel side preview control to the normal active control and the transition period in the opposite direction, the latest preview control force U is sequentially stored in the shift register area of the storage device. _pRL, since U _pRR and the delay time tau _R are updated stored, as described above in the first embodiment and the second embodiment, the delay time tau _R stored need to delay the transition to control of the respective Absent.

In the above control, the _overall power OP ₂ in the high frequency range of the differential values x _OFL ′ and x _OFR ′ of the road surface displacement, which are estimated values of the rear wheel road surface vibration input, are _{compared with the overall} power OP _{1 in} the low frequency range. If the ratio OP ₂ / OP ₁ is (in this example a = 1) certain coefficient ratio a is greater than or equal to gradually present to reduce the control gain K _p to gradually reduce the ratio of the preview control for the rear wheels In this embodiment, this embodiment is regarded as applying the invention according to claim 3 to the invention according to claim 1, and the control wheels to be controlled are rear wheels 11RL,
11RR, and the road surface detecting means is the front wheels 11FL and 11F.
Since the vibration input input to the vehicle body via the R is detected as the stroke and the vertical acceleration, as shown in FIG.
Steps S42 and S43 correspond to the road surface detecting means according to the first aspect of the present invention. Similarly, step S44 corresponds to the control wheel input estimating means.
Steps S47 to S47 correspond to the input level determining means, and step S47 corresponds to the gain changing means.
Steps S54 to S54 correspond to preview control means. Also, the time of detecting the unevenness of the road surface corresponds to the time of inputting vibration to the front wheels, and the foreseeing distance corresponds to the wheel base between the front and rear wheels.

Next, a fourth embodiment of the active suspension preview control apparatus of the present invention will be described with reference to FIGS. In the fourth embodiment, when high-frequency vibration of the front suspension system or the front wheels occurs in the third embodiment, the high-frequency component included as erroneous information in the road surface vibration input estimated value is subjected to, for example, digital low-pass filter processing. The high-frequency component removing means removes the rear wheel, thereby improving the controllability of the rear wheel preview control. At this time, according to the overall power ratio OP ₂ / OP ₁ in the high / low frequency range calculated in the third embodiment, the weight coefficient for the road surface vibration input estimated value from which the high frequency component has been removed, and the road surface vibration A weighting coefficient that uses the input estimated value as it is is set, but the road surface vibration input from which the high-frequency component has been removed from the normal rear wheel side preview control using the road surface vibration input estimated value as it is in the third embodiment is set. During the transition period to the rear-wheel side preview control using the estimated value or the transition period in the opposite direction, while keeping the sum of the two weighting factors unchanged and gradually changing each weighting factor, It seeks to avoid discontinuities. The digital low-pass filter is constructed by a program executed by a microcomputer as in the first embodiment, and its cutoff frequency can be set by a temporary variable used in the program. In this case, the frequency was set to about 5 to 15 Hz in accordance with the unsprung resonance frequency, the front and rear resonance frequency of the suspension system, the resonance frequency of the steering system, tire specifications including tire size, drive system reduction ratio, and the like.

The structure of the vehicle and the structure of the active suspension 12 applied in this embodiment are almost the same as those of the first embodiment shown in FIG. Active suspension 1
The structure of the controller 30 for controlling the second embodiment is substantially the same as that of the first embodiment shown in FIG. The contents of the processing performed by the microcomputer 44 in the controller 30 are different. Here, the rear differential value of the road surface displacement which is calculated as wheel road surface input x _{OF L} 'and x _OFR' and delay time tau _R, the first embodiment also processing such as the front wheel side comprehensive control force U _FL ~U _RR It is performed in the same manner as example, but the rear-wheel-side preview control force U _pRL and U _pRR calculation method is different. Specifically,
Rear-wheel-side preview control force U _pRL and U _pRR, the three equations and 4
Differential values of road displacement x _OFL 'and x _OFR ' used in the equation
In place of the term, the differential values x _OFL 'and x
'A value in multiplied by the weight coefficient alpha, the digital low-pass filtered high frequency component removed XLP _{OF L} of the differential value of the road surface displacement' _OFR using sum of and XLP _OFR value obtained by multiplying the weighting coefficient β in '. Specifically rear wheel predictive control force U _pRL and U _pRR is calculated using the following 24 formula and 25 formula.

U_pRL=-(C_p+ ｛1 / (ω₁+ S)｝ K_p) (αx_OFL’+ ΒxLP_OFL’) ………… (24) U_pRR=-[C_p+ ｛1 / (ω₁+ S)｝ K_p) (αx_OFL’+ ΒxLP_OFL′) (25) Accordingly, the arithmetic processing unit 44c is configured as shown in FIG.
By executing the processing, a predetermined sampling time T_S(Eg 2
0 msec), the vehicle speed detection value V and the stroke detection value S_FL,
S_FRAnd vehicle body vertical acceleration detection value Z_GFL~ Z_GRRRead
Only, stroke detection value S_FL, S_FRAnd vertical acceleration detection
Outgoing price Z_GFL~ Z_GRRInput to rear wheels 11RL and 11RR
Differential value of road displacement as the estimated rear wheel input
x_OFL'And x_OFR'And calculate the differential value of this road displacement
x_OFL'And x_OFR'Fast Fourier transform FFT
The power of the predetermined high and low frequency range obtained by performing the processing
Overall power OP with spectral density_Two, OP₁Seeking
These overall power OP_Two, OP₁Represented by
Energy ratio between the two frequency ranges (ie, the over-
Lupower Ratio OP_Two/ OP₁) From the road surface displacement
High-frequency component of estimated rear wheel vibration input value obtained as differential value
And the differential value x of each road surface displacement _OFL'
And x_OFR'' Low-pass filtered
High frequency component xLP with frequency component removed_OFL’And xLP
_OFR′, And calculates the high-frequency component of the rear wheel vibration input estimated value.
Is small, that is, the existence ratio is smaller than a preset coefficient ratio.
If it is small, there is little erroneous information
The differential value x of the road surface displacement which is the estimated value of the rear wheel road surface input
_OFL'And x_OFR'' Large control distribution ratio using
The estimated value of rear wheel vibration input has many high-frequency components,
When the abundance ratio exceeds a preset coefficient ratio
In the case of rear wheel
Differentiation of road displacement by removing its high frequency component from force estimate
Value high-frequency removal component xLP_OFL’And xLP_OFR’
The rear wheel preview control force is set so that the control distribution ratio increases.
U_pRL’And U_pRR’, The weighting factors α,
β is set by a control map or calculation formula described later, and
The control command value is obtained by using the calculated value and the detected value.
Total control force U_FL~ U_RRIs calculated.

At this time, one of the weighting factors α multiplied by the differential values x _OFL ′ and x _OFR ′ of each road surface displacement in the above equations 24 and 25 is stored in the storage device 4 of the microcomputer 44.
This is set according to the control map of FIG. 14 stored in 4d. This control map is a characteristic diagram of the weighting coefficient α with respect to the ratio OP ₂ / OP ₁ of the overall power OP _{2 in} the high frequency range to the overall power OP _{1 in} the low frequency range, and the overall power ratio OP ₂ In a region where / OP ₁ is equal to or smaller than a predetermined value h slightly smaller than “1”, the weighting coefficient α is maintained at a set value “1”, and the overall power ratio OP ₂ / OP ₁ becomes smaller than the predetermined value h. When you cross over,
As the ratio OP ₂ / OP ₁ over-all power becomes the weighting factor α is "0.5" at a predetermined value i, the slope -0.5 / (i
-H) The overall power ratio OP at which the weighting coefficient α becomes “0” in accordance with this slope and linearly decreases at a constant
₂ / OP ₁ is at least a region predetermined value j, the weight coefficient α is maintained at "0". Accordingly, the decreasing curve of the weight coefficient α is represented by the following equation (26).

Α = −0.5 h / (i−h) · (OP ₂ / OP ₁ ) + (i−1.5 h) / (i−h) (26) and the high frequency component removed XLP _{oF L} 'and XLP _OFR' other weight coefficient β to be multiplied to the differential value of the road surface displacement 25 formula, like the microcomputer 44
Is set in accordance with the control map of FIG. 14 stored in the storage device 44d of the above.

Β = (1−α) (27) Accordingly, the other weight coefficient β changes as shown in FIG. 14 with respect to the overall power ratio OP ₂ / OP ₁ , that is, In a region where the overall power ratio OP ₂ / OP _{1 in} which one weight coefficient α is maintained at “1” is equal to or less than a predetermined value h, the other weight coefficient β is maintained at “0”, and one weight coefficient α is maintained at the predetermined slope -0.5 / (i-h) ratio OP ₂ / OP ₁ over-all power that decreases in exceeds a predetermined value h region, with an increase in the over-all power of the ratio OP ₂ / OP ₁ Therefore, the weight coefficient α increases at the positive / negative inversion value of the decreasing rate,
In a region where the overall power ratio OP ₂ / OP _{1 in} which _one weight coefficient α is maintained at “0” is equal to or larger than a predetermined value j,
It is kept at "0".

Here, the process of FIG. 13 is executed as a timer interrupt process for each predetermined sampling time T _S (for example, 20 msec). First, in step S61, the current vehicle speed detection value V of the vehicle speed sensor 26 is read. Step S62
To read the vertical acceleration detection values Z _{GFL to} Z _GRR from the vertical acceleration sensors 28FL to 28RR, and then to step S63 to move to the stroke sensor 27F.
The stroke detection values S _FL and S _FR from L and 27 _FR are read.

Next, the flow shifts to step S64, where the stroke speeds S _VFL and S _VFL obtained by differentiating the stroke detection values S _FL and S _FR by the digital high-pass filter processing or the like are obtained.
S _{VF R} and front-wheel-side vertical acceleration detection values Z _GFL , Z
_From the front-wheel-side sprung vibration speeds x _FL 'and x _FR ' obtained by integrating the _GFR by the digital low-pass filter processing or the like, the differential value x
_OFL ′, x _OFR ′ are calculated.

Then, the flow shifts to step S65, where the fast Fourier transform FFT is performed on the differential values x _OFL ', x _OFR ' of the road surface displacement as the rear wheel road surface vibration input estimated value calculated in step S64. To determine the power spectral density distribution. In order to execute the fast Fourier transform FFT by a microcomputer, a known algorithm can be applied as in the above.

[0114] Next, the process proceeds to step S66, the said from power spectrum density distribution of the vibration input obtained in step S65, the high over-all power OP about ₁ and the 10~20Hz the low frequency range of up to about the ~10Hz to calculate the over-all power OP ₂ of the frequency range. Next, the routine proceeds to step S67, the over-all power OP ₂ in the high frequency range calculated at step S66, the calculated ratio OP ₂ / OP ₁ for over all power OP ₁ in the low frequency range, the 14 According to the control map or the calculation formula 2
The weight coefficients α and β are set in accordance with Equations 6 and 27.

Then, the flow shifts to step S68, where x _OFL 'and x _OFR ' obtained in step S64 are subjected to high-frequency component removal means such as digital low-pass filter processing to remove the high-frequency removal component of the differential value of the road surface displacement. xLP _OFL '
And xLP _OFR ′. Next, the process proceeds to step S69, in which the differential values x _OFL ′ and x _OFR ′ of the road surface displacement, and the high-frequency removal components x LP _OFL ′ and x x of the differential value of the road surface displacement
LP _OFR ', using the weighting coefficients α and beta, and calculates the predictive control force U _pRL and U _pRR the rear wheel side in accordance with the 24 equations and 25 formula.

Next, the flow shifts to step S70, where the delay time τ _R is calculated in accordance with the equation (9) using the vehicle speed detection value V. Next, the process proceeds to step S71, where
The rear wheel-side _preview control forces U _pRL and _{Up RRR} calculated in 69 and the delay time τ _R calculated in step S70 are stored at the head position of the shift register area formed in the storage device 44d and stored up to the previous time. It has been rear wheel side predictive control force U _pRL, sequentially shifts the U _pRR and the delay time tau _R. At this time, when the shift for the delay time tau _R, Update stores a value delay time tau _R from the sampling time T _S and each subtraction of the shift position as a new delay time tau _R.

Next, the flow shifts to step S72, where the oldest, that is, the rear-wheel _preview control forces U _pRL and _{UpR in} which the delay time τ _R has become zero, which is stored in the shift register area, is read and read. the oldest foreseen control force U _pRL, erases the U _pRR and the delay time tau _R for this from the shift register area. Next, proceeding to step S73, the sprung vibration speeds x _FL ′ and x _FR ′ of the front wheel derived at the time of calculating the differential value of the road surface displacement in step S64, and the rear wheel side read in step S72. Control powers U _pRL and U
_Using pRR, the total control forces U _{FL to} U _RR for the pressure control valves 20FL to 20RR are calculated according to the above equations 10 to 13. At this time, the control gain K _B, K _p may be a predetermined value constant previously set.

Next, the flow shifts to step S74, in which the pressure control valves 20FL to 20RR calculated in step S73 are calculated.
Control forces U _{FL to} U _RR as pressure command values for D /
After outputting to the A converters 45FL to 45RR, the timer interrupt process is terminated and the process returns to the predetermined main program. Next, the operation of the active suspension preview control device of the present embodiment will be described. Now, assuming that the vehicle is traveling straight ahead at a constant speed while maintaining the target vehicle height on a flat good road, in this state, since the vehicle is maintaining the target vehicle height on a flat good road, Since no unsprung resonance vibration or shimmy phenomena occur on the suspension and the front wheel side, and no chain will be attached at the same time, no swing occurs in the vehicle body side member 10. 28FL
２８28FR acceleration detection values Z _{GF L} ＺZ _GRR and stroke detection values S _FL ,
S _FR has become substantially zero, they are input are converted into digital values by the input interface circuit 44a to the microcomputer 44.

[0119] In this way, the vehicle is driven on a flat good road at a constant speed.
While traveling forward, and the front suspension and
And unsprung resonance vibration and shimmy phenomena
If you do not have a chain attached at the same time,
A predetermined sampling time T_Severy
In the process of FIG.
Overall power in high frequency range calculated in 4 to S66
OP_TwoLow power overall power OP₁Against
Ratio OP_Two/ OP₁Is smaller than the predetermined value h as described above.
Therefore, in step S67, one of the weight coefficients
α is set to “1”, and the other weight coefficient β is set to “0”.
You. Then, in step S68, the differentiation of the road surface displacement is temporarily performed.
Value high-frequency removal component xLP_OFL’And xLP_OFR’Is calculated
However, in the following steps S69 and S70, a preview of the rear wheel side is made.
Control force U_pRL, U_pRRAnd delay time τ_RIs calculated and updated.
The total control calculated and output in steps S71 to S74
Force U _FL~ U_RR, The front wheel pressure control valve 20FL and
And 20FR for normal active control, rear wheel side pressure
The control described later is performed on the control valves 20RL and 20RR.
Be executed.

That is, while maintaining the target vehicle height in this way,
When the vehicle is traveling straight on a flat road at a constant speed,
Acceleration detection value Z_GFL~ Z_GRRAnd front wheel side stroke detection
Value S _FL, S_FRBecomes substantially zero, so that step S64
The sprung vibration speed x of the front wheel derived from_FL’And x_FR’
Becomes zero, and therefore the road calculated in step S64
Differential value x of surface displacement_OFL’And x_OFR’Is zero, of course
The high-frequency removal component xLP_OFL’And xLP_OFR’
Is also zero. Moreover, this high-frequency removal component xLP _OFL’
And xLP_OFR’Is also zero,
Rear-wheel preview control force calculated in step S68
U_pRL, U_pRRIs also zero, of which the zero rear wheel side prediction
Control force U_pRR, U_pRRIs the shift level of the storage device 44d.
The distance between the front and rear wheels calculated in step S70 is
Delay time τ_RAre stored in step S71 together with
Delay time τ_RTo sampling time T
_SIs the new delay time τ_RUpdated as
You. For this reason, the preview control force read out in step S72
U_pRL, U_pRRIs also zero. Also, the rear wheel side preview system
Your gain K_pIs the set value K_pOIs set to
The rear wheel active control gain K given by the above equation (19)_BAlso zero
Becomes As described above, before the calculation in step S73 is performed.
The second term on the right side of Equations 10 and 11 is all zero, and
Since the second term on the right side of Equations 2 and 13 is all zero,
Total control force U_FL~ U_RRIs neutral only corresponding to the target vehicle height
Pressure control force U_NAnd these are output as pressure command values on the output side.
D / A conversion by interface circuit 44b and drive circuit
Output to 46FL to 46RR.

For this reason, the driving circuits 46FL to 46RR convert the currents into command currents i _{FL to} i _RR corresponding to the control forces U _{FL to} U _RR and supply the converted currents to the respective pressure control valves 20FL to 20RR.
As a result, the hydraulic cylinders are neutral pressure P _CN required to maintain the target vehicle height from the pressure control valve 20FL～20RR 1
8FL to 18RR.
FL to 18RR generate a thrust for maintaining the stroke between the vehicle body side member 10 and the wheel side member 14 at the target vehicle height.

However, when the vehicle is traveling straight on a good road at a constant speed, for example, a so-called ramp step road having a step where the road surface rises in a step-like manner is formed by the front left and right wheels 11FL and 11FL.
When the FRs pass at the same time, the front wheels 11FL and 11FR bounce due to the stepping of the front left and right wheels, whereby the stroke sensors 27FL and 27F
As the stroke detection values S _FL and S _{FR of} R rapidly increase from zero in the positive direction, an upward acceleration is generated in the vehicle body side member 10, and the vertical acceleration sensors 28 FL and 28
The acceleration detection values Z _GFL and Z _{GFR of} FR increase in the positive direction.

The stroke detection values S_FLas well as
S_FRAnd the vertical acceleration detection value Z_{GF L}And Z_GFRAnd shake
Input to the dynamic input estimating circuit 41,
64, the vertical movement of the vehicle body side member 10
Road surface displacement that is unaffected and is a positive value according to the road surface shape
Derivative x of_0FL’And x_0FR'Is calculated. At this time
Differential value x of calculated road surface displacement_OFL’And x_OFR’
Is it due to a step on the ramp step road
The front suspension and front left and right wheels still have
It is assumed that no high-frequency vibrations due to various reasons have occurred.
In steps S65 to S67, the value is still smaller than the predetermined value h.
Overall power ratio OP_Two/ OP ₁According to
One weighting factor α is set to “1” and the other weighting factor α is
Only the coefficient β continues to be set to “0”. Then step S
At 68, the high frequency removal component xLP of the differential value of the road surface displacement_OFL’
And xLP_OFRIs also calculated, but in the following step S69
Calculated rear wheel side preview control force U_pRL, U_pRRIs the weight of the other
Since the coefficient β is zero, the differential value x
_OFL’And x_OFR’
In step S70, a delay time τ corresponding to the vehicle speed_RIs calculated
These are recorded while being sequentially shifted in step S71.
The data is stored in the shift register area of the storage device 44d.

Here, on the front wheel side, the vertical acceleration detection values Z _GFL , Z _GFR output from the vertical acceleration sensors 28FL, 28FR are increased in the forward direction by the acceleration acting upward due to the stepping on the ramp step road. Since it increases, the sprung vibration speeds x _FL ′, x _FR ′ derived in step S64 also increase in the positive direction. Therefore, the front-wheel-side total control forces U _FL, U _FR calculated in step S73 are the neutral pressure control forces. will be reduced from the U _N, command current i _FL outputted from the driving circuit 46FL and 46FR accordingly, i _FR is reduced, whereby the pressure control valve 20F
L, the hydraulic cylinder 18FL control pressure P _C output from 20FR is lowered from neutral pressure P _CN, it is reduced thrust 18FR, by allowing to consequently reduce the front wheel side stroke, the front wheel The so-called ordinary active control, which suppresses the swing of the vehicle body-side member 10 due to the climbing of the step of 11FL and 11FR, can effectively act according to the principle of the skyhook damper. On the other hand, the rear-wheel wheel-side preview control force after a delay time tau _R is zero when the front wheel rides on the step for side U _pRL, since U _pRR maintains the state of zero, calculated in Step S73 Said 1
2 where 13 expression in the second term on the right side is still rear-wheel-side total control force becomes zero U _RL, U _RR is still neutral pressure control force U _N, and the rear-wheel-side hydraulic cylinders 18RL, the target vehicle height in 18RR The state of generating the maintained thrust is continued.

After that, even when the front wheels 11FL and 11FR have passed through the step, the front wheels 11FL and 11FR do not enter the rebound state on the ramp step road, and the acceleration to the vehicle body side member 10 due to the riding on the step eventually converges. To zero. With the decrease of the acceleration, in the processing of FIG. 13 performed by the microcomputer 44 every predetermined sampling time T _S , the sprung vibration speeds x _FL ′ and x _FR ′ derived in step S64 converge to zero. from the neutral pressure control force U _N smaller than the set have a front-wheel-side total control force U _FL, U _{FR is} increased in step S73 until the neutral pressure control force U _N for each of the sampling time T _S, in which the vertical acceleration detection value generated with Z _GFL and Z _GFR, stroke detected value S _FL, wheel side preview control force after in response to changes in S _FR U _pRL, but U _pRR is calculated in step S69, step Since the weighting coefficients α and β set in S67 maintain the above-mentioned state, the rear-wheel-side preview control force _{UpR L} , which corresponds to only the differential values x _OFL ′ and x _OFR ′ of the road surface displacement as described above, U _pRR is of sequentially shift While memory device with a delay time tau _R in Step S71 4
4d is stored in the shift register area.

[0126] Therefore, the front-wheel-side total control force U _FL and U _FR calculated in step S73 is increased to the neutral pressure control force U _N in accordance with a decrease in the vehicle body vertical acceleration after passing over the step,
In response to this, the command current i _FL output from the drive circuits 46FL and 46FR increases, and the pressure control valve 2
0FL control pressure P _C is output from and 20FR increased to neutral pressure P _CN, hydraulic cylinders 18FL and 18FR
The thrust of the vehicle is increased, and as a result, the stroke on the front wheel side is increased, so that the target vehicle height is achieved while suppressing the swing of the vehicle body side member 10 after the front wheels 11FL and 11FR climb over the step. It becomes possible. On the other hand, even in this state, the rear wheel preview control force U at which the delay time τ _R becomes zero
_pRL, since U _pRR is maintained to the rear wheel side active control gain K _B also zero and maintains the state of zero, the rear wheel side hydraulic cylinder 1
At 8RL and 18RR, the state of generating the thrust for maintaining the target vehicle height is continued as described above.

However, regarding the rear wheel side, FIG.
Sequentially from the time the delay time tau _R calculated in step S70 in has elapsed, before the delay time tau _R, that is, before the aforementioned left and right wheels 11FL, wheel-side preview control force after the time when 11FR has passed the step U _{pRL, UpR} is read in step S71,
Based on these, in step S53, the rear-wheel-side total control force U
_{RL and} U _RR are calculated, and these are output to the pressure control valves 20RL and 20RR as rear wheel side pressure command values. The rear wheel side comprehensive control force U _RL, the U _RR, front wheels 11FL, 11FR
There wheels 11RL after delayed _R delayed time τ from the start ride step, from the time the 11RR rides up the step, the rear wheel side control force U _RL, by U _RR is decreased from the neutral pressure control force U _N, the driving circuit lower than the command current i _RL neutral current i _N output from 46RL and 46RR, control pressure P _C to thereby output from the pressure control valve 20RL and 20RR is lowered from neutral pressure P _CN, hydraulic cylinder 18R
The thrusts of the left and right wheels 18RL and 18RR are reduced, and as a result, the strokes of the rear left and right wheels 11RL and 11RR can be reduced, thereby suppressing the swing generated in the vehicle body side member 10 due to the stepping of the rear left and right wheels 11RL and 11RR. This enables so-called rear wheel preview control.

Since the weighting coefficient β applied to the high frequency elimination components xLP _OFL ′ and xLP _OFR ′ of the differential value of the road surface displacement in the above equations 24 and 25 is zero, the equations 3 and 4 result. The rear wheel side preview control force U _pRL , which is set equivalently,
The _UpRR can sufficiently cancel or suppress the vibration input transmitted from the rear wheel side to the vehicle body as shown by the above equation 8, so that good ride comfort is maintained.

On the other hand, when either one of the front wheels 11FL and 11FR, for example, only the front left wheel 11FL rides on a transient convex portion or a step, the above-described rocking suppression control is performed only for the left wheel hydraulic cylinders 18FL and 18RL. Hydraulic cylinder 18F on the right wheel side, which does not cause protrusions and steps
For R and 18RR, control is performed to maintain the neutral pressure.

The front wheels 11FL and 11FR are temporarily
When the vehicle falls into the recess, the control is performed in the reverse
Swaying of the body can be suppressed, and transient irregularities
Not only when traveling on uneven road surfaces such as irregular roads
Can predictively control the rear wheels according to the behavior of the front wheels.
You. By the way, when driving on a flat, good road as described above,
Also unsprung resonance with front suspension and front left and right wheels
Vibration or shimmy phenomenon
In this case, the vertical acceleration detection value Z_GFL, Z_GFRas well as
Stroke detection value S _FL, S_FRThe high frequency component of
In addition, this tendency occurs even while driving with the chain attached.
Live. In such a situation, the flow is unrelated to the road surface input.
Of suspension suspension system as erroneous information of road surface input
I get it. Therefore, the high frequency component is increased
Direction acceleration detection value Z_GFL, Z_GFRAnd stroke detection value S
_FL, S _FRDifferential value x of road surface displacement obtained from_OFL’And x
_OFR'Has also increased. Therefore,
In the high frequency range obtained in steps S65 and S66
Lupawa OP_TwoLow power overall power OP₁To
Ratio OP to_Two/ OP₁Greatly exceeds the predetermined value j.
Therefore, in step S67, one weighting coefficient α is
It is set to "0" and the other weighting factor is set to "1".

Accordingly, the rear-wheel-side preview control powers _UpPRL , _UP calculated by the equations (24) and (25) in step S69.
_pRR is a value corresponding only to the high frequency elimination components xLP _OFL ′ and xLP _OFR ′ of the differential value of the road surface displacement from which the high frequency component which is the erroneous information has been eliminated, and this rear wheel read after the delay time τ _{R in} step S72. In step S73, the rear wheel-side total control forces U _RL , U _RR are calculated according to the side _preview control forces U _pRL , U _pRR . Next, with these rear wheel side total control forces U _RL and U _RR output in step S74 as pressure command values, the pressure control valves 20RL and 20RR are connected to the respective hydraulic cylinders 18R.
L and 18RR are controlled. At this time, since the erroneous information due to the various causes has been removed, the rear wheel 11R is controlled.
Even if the L and 11RR are foreseeably controlled, the control force does not vibrate the vehicle body, whereby the vertical movement of the vehicle body can be effectively suppressed and a good ride comfort can be secured.

As described above, the shimmy phenomenon and the unsprung resonance vibration do not occur at a certain moment, but rather occur to some extent depending on the vehicle speed, the steering angle and the like. Accordingly, during the occurrence start period, the high-frequency components of the differential values x _OFL ′, x _OFR ′ of the road surface displacement also gradually increase.
Further, even when the chain is mounted, the high-frequency components of the differential values x _OFL ′, x _OFR ′ of the road surface displacement gradually increase as the vehicle speed increases. Therefore, the predetermined sampling time T
_In the processing in FIG.
High frequency overall power OP ₂ obtained in S67
Ratio OP to overall power OP _{1 in} the low frequency range
₂ / OP ₁ also becomes possible to increase gradually, eventually the ratio OP ₂ / OP ₁ in the over-all power further increases beyond the predetermined value h. Meanwhile, one weighting coefficient α has a slope −
0.5 / (i-h), it decreases linearly at a constant rate, and at the same time, the other weighting coefficient β increases with the positive / negative inversion value of this decreasing rate, and the sum of the two is always maintained at "1". Therefore, in this transition period, the differential value x of the road surface displacement which does not remove the high-frequency component interpreted as erroneous information by the calculation of the equations 24 and 25 in step S69 at the time of the processing of FIG.
_OFL ', x _OFR ' and the high-frequency removal component xLP of the differential value of the road surface displacement from which the high-frequency component interpreted as the erroneous information has been removed.
_OFL 'and XLP _OFR' and the consideration to and wheel side preview control force after changing their control distribution ratio appropriately while the sum of "1" of the weight of both U _pRL, U _pRR is calculated, along with this In accordance with the rear-wheel-side total control forces U _RL and U _RR calculated in step S73, the rear-wheel-side pressure control valves 20RL and 20R
R and hydraulic cylinders 18RL, although control of the 18RR is made, since this changes the control distribution ratio in the transition phase takes place gradually with the increase of the specific OP ₂ / OP ₁ over-all power, between the two control modes The control discontinuity is improved in the transient characteristics.

On the other hand, the overall power ratio OP_Two/
OP₁During the transition period when
The weighting factors α and β are increased or decreased in the
Is also output here because the sum of
Rear wheel side total control force U_RL, U _RRDone according to the rear wheel side
Preview control is based on the transient characteristics between the two control modes.
Control discontinuities are improved.

In the transition period from the rear-wheel preview control to the normal active control in this embodiment and the transition period in the opposite direction, the shift register of the storage device is provided in the same manner as in the third embodiment. The latest _preview control force U _pRL , U
Since _pRR and the delay time tau _R are updated stored, as described above in the first and second embodiments, it is not necessary to delay the transition to only the respective control delay time tau _R stored.

In the above control, the _overall power OP ₂ in the high frequency range of the differential values x _OFL ′ and x _OFR ′ of the road surface displacements, which are estimated values of the rear wheel road surface vibration input, are _{compared with the overall} power OP _{1 in} the low frequency range. the weight for a specific OP ₂ / OP ₁ is that in the case (in this example a = h) certain coefficient ratio a is greater than or equal to gradually change the control distribution ratio of the high frequency component removed to remove the high frequency component of the vibration input Coefficient β or weighting coefficient α applied to the vibration input without removing high-frequency components
In this embodiment, the control wheels to be controlled are the rear wheels 11RL and 11RR, and the road surface detecting means is the front wheel. Since the vibration input input to the vehicle body via the 11FL and 11FR is detected as a stroke and a vertical acceleration, steps S62 and S63 of the processing in FIG. Step S64 corresponds to the rear wheel input estimating means, steps S65 to S67 correspond to the input level determining means, and at the same time, step S67 corresponds to the control distribution ratio changing means, and step S68 corresponds to the high frequency. Steps S69 to S74 correspond to the preview control means. Also, the time of detecting the unevenness of the road surface corresponds to the time of inputting vibration to the front wheels, and the foreseeing distance corresponds to the wheel base between the front and rear wheels.

In the third and fourth embodiments, the ratio of the overall power in the high frequency range to the overall power in the low frequency range set as the energy evaluation of the input vibration is used. Although the case where the Fourier transform is performed has been described, it is also possible to use the square integration value as in the second embodiment as the energy evaluation of the input vibration. In addition, a method other than such evaluation using energy can be applied to the input vibration level determination.

In each of the embodiments, a case has been described in which each integration process is performed by a digital low-pass filter process performed by a microcomputer, and each differentiation process is performed by a digital high-pass filter process. However, the present invention is not limited to this. For example, the cut-off frequency may be replaced by band-pass filter processing in which the cutoff frequency is set near the upper and lower limits of each pass frequency band.

In each of the embodiments, the case where the microcomputer 44 performs the filtering process has been described. However, each of the fixedly provided filters is used, and for example, the differential of the road surface displacement which is the estimated value of the rear wheel road surface vibration input is used. In calculating the value, the output from these filters can be added or subtracted by using various adders and adder / subtracters to perform the substitution.

In each embodiment, the microcomputer 44 _{stores the preview} control forces U _pRL and U _pRR while sequentially shifting them together with the delay time τ _R in the shift register area, and the delay time τ _R becomes zero. Preview control force U _pRL ~
There has been described a case where the preview control based on the U _pRR, high-pass filtering the vertical acceleration or the differential value x _0FL 'and x _0FR' sequentially shifted into the shift register region with delay time tau _R of road surface displacement is not limited thereto and stored while, so as to calculate the rear-wheel-side preview control force U _pRL and U _pRR based differential value x _0FL the vertical acceleration or the road surface displacement delay time tau _R becomes zero 'and x _0FR' Is also good.

In the above embodiment, the case where the active control of the suspension is performed only based on the vertical acceleration is described. However, the present invention is not limited to this. The control signal for suppressing the roll and the pitch may be calculated on the basis of the acceleration detection value, and the control signal may be added to or subtracted from the active control force to perform the total control.

In each of the above embodiments, the case where the pressure control valves 20FL to 20RR are applied as the control valve has been described. However, the present invention is not limited to this, and other flow control type servo valves and the like may be applied. What you get. Also,
In the above embodiment, the case where the controller 30 is constituted by a microcomputer has been described. However, the present invention is not limited to this. The controller 30 may be constituted by combining electronic circuits such as a shift register and an arithmetic circuit. Needless to say.

In the above embodiment, the case where the working oil is used as the working fluid has been described. However, the working fluid is not limited to this, and any working fluid may be used as long as the fluid has a low compression ratio. Further, in the above embodiment, the case where the preview control is performed using only the rear wheel as the control target wheel, but the preview control may be performed using only the front wheel or the front and rear wheels as the preview control target wheel. In this case, as described in JP-A-4-339010 or JP-A-4-339011, the road surface unevenness may be detected by a road surface detecting means provided further forward than the front wheels.

[0143]

As described above, according to the suspension control apparatus of the present invention, the estimation of the road surface vibration input obtained as erroneous information when unsprung resonance vibration or shimmy phenomenon occurs or when the chain is mounted is performed. When the high-frequency component of the value increases, the control gain is set to zero in order to stop the preview control, or the control gain is reduced in order to reduce the control distribution ratio of the preview control, or due to erroneous control information. By removing the high-frequency component of a certain road surface vibration input estimation value, it is possible to avoid or suppress the occurrence of the excitation force of the vehicle body due to the preview control due to the erroneous information, especially when removing the high-frequency component of the road surface vibration input estimation value. In this case, it is possible to improve the vibration characteristics of the vehicle body by the preview control for the low-frequency component, and to obtain an effect that a good ride comfort can be secured.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram showing a schematic configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a control current and a command current of a pressure control valve.

FIG. 4 is a characteristic diagram showing output characteristics of a vertical acceleration sensor.

FIG. 5 is a characteristic diagram illustrating output characteristics of a stroke sensor.

FIG. 6 is a block diagram illustrating an example of a controller.

FIG. 7 is an explanatory diagram showing a one-wheel, one-degree-of-freedom model.

FIG. 8 is an explanatory diagram illustrating an example of a correlation between a vibration frequency and a power spectrum density distribution with respect to a road surface vibration input estimated value.

FIG. 9 is a flowchart showing a first embodiment of a processing procedure by the microcomputer.

FIG. 10 shows a second processing procedure performed by the microcomputer.
6 is a flowchart illustrating an embodiment.

FIG. 11 shows a third processing procedure performed by the microcomputer.
6 is a flowchart illustrating an embodiment.

FIG. 12 is a control map of each control gain used in the processing of FIG. 11;

FIG. 13 is a fourth processing procedure performed by the microcomputer;
6 is a flowchart illustrating an embodiment.

FIG. 14 is a control map of each weight coefficient used in the processing of FIG.

FIG. 15 is a schematic configuration diagram of a conventional rear wheel preview control device.

FIG. 16 is a schematic block diagram of conventional rear wheel preview control.

[Explanation of symbols]

 10 is a vehicle-side member 11FL-11RR is a wheel 12 is an active suspension 14 is a wheel-side member 18FL-18RR is a hydraulic cylinder 20FL-20RR is a pressure control valve 22 is a hydraulic source 26 is a vehicle speed sensor 27FL, and 27FR is a stroke sensor 28FL-28RR. Is a vertical acceleration sensor 30 is a controller

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideo Tobata Nissan Motor Co., Ltd. (2) Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Michito Hirahara 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-4-372415 (JP, A) JP-A-60-151111 (JP, A) JP-A-6-8718 (JP, A) JP-A-6-8719 (JP, A) JP-A-4-339011 (JP, A) JP-A-4-339010 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 17/015 B60G 23/00

Claims (3)

(57) [Claims] 1. An actuator interposed between a vehicle body and a control wheel to generate a control force according to a control command value, and a road surface mounted at a foreseeable distance ahead of the control wheel to detect road surface irregularities. Detecting means; control wheel input estimating means for estimating a vibration input input to the control wheel according to a road surface detection value from the road surface detecting means; Preview control means for outputting a control command value obtained from a value obtained by multiplying a control wheel vibration input estimated value from an input estimating means by a gain to an actuator of the control wheel. Input level determining means for determining the magnitude of the high-frequency vibration component of the control wheel vibration input estimated value from the wheel input estimating means; Gain changing means for decreasing a gain multiplied by the rear wheel vibration input estimated value or setting the gain to zero when the high frequency vibration component of the dynamic input estimated value is determined to be large. Active suspension preview control device. 2. An actuator interposed between a vehicle body and a control wheel to generate a control force in accordance with a control command value, and a road surface mounted forward of the control wheel by a foreseeable distance to detect unevenness of the road surface. Detecting means; control wheel input estimating means for estimating a vibration input input to the control wheel according to a road surface detection value from the road surface detecting means; Preview control means for outputting a control command value obtained from a value obtained by multiplying a control wheel vibration input estimated value from an input estimating means by a gain to an actuator of the control wheel. Input level determining means for determining the magnitude of the high-frequency vibration component of the control wheel vibration input estimation value from the wheel input estimating means; and control wheels from the control wheel input estimating means. A high-frequency component removing unit that removes a high-frequency vibration component from the vibration input estimated value; and a high-frequency component of the control wheel vibration input estimated value based on the determination result of the input level determining unit. The distribution ratio is changed so that the ratio of the output value of the control wheel vibration input value or the high-frequency vibration component of the control wheel vibration input estimate value is small, so that the ratio of the control wheel vibration input estimate value itself is increased. A preview control device for an active suspension, comprising: control distribution ratio changing means for giving a value necessary for calculating a control command value. 3. The road surface detecting means detects a vibration input from a road surface to a vehicle body via a front wheel, and the control wheel is a rear wheel. 4. A preview control device for an active suspension according to claim 1.