JPH05319064A - Suspension control device - Google Patents

Abstract

PURPOSE:To provide a suspension control device which compensate a change in response property due to a change in the pressure of fluid pressure cylinders to generate an appropriate expected control force at an optimum time in order to improve comfortability by providing a correction means for correcting at least one of a pressure command value and delay time depending upon the pressure detection value of a pressure detection means. CONSTITUTION:An oscillation input estimation circuit calculates a differential value for road displacement for front wheels and pressure sensors 29RL, 29RR detect the pressure of hydraulic cylinders 18RL, 18RR, and a microcomputer 44 calculates an expected control force based on the differential value as well as delay time for rear wheels based on a car speed detection value. A computer 44 calculates a control force and a delay time correction values based on the pressure detection values of the pressure sensors 29RL, 29RR to increase the expected control force and to shorten the delay time when the response property of a hydraulic system may be reduced. In addition, when the response property of the hydraulic system may be improved, the reverse control is provided to generate an appropriate control force at an optimum time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension controller for predicting and controlling the working fluid pressure of a fluid pressure cylinder interposed between a wheel to be controlled and a vehicle body based on road surface information detected at a position in front of the wheel to be controlled. ..

[0002]

2. Description of the Related Art As a conventional suspension control device, there is one disclosed in Japanese Patent Application Laid-Open No. 56-31861. In this conventional example, in a vibration predicting control device for a vehicle having a fluid actuating mechanism for detecting the vibration of the vehicle and suppressing the vibration of the vehicle body based on the detection result and a control circuit for the fluid actuating mechanism, a speed detector for detecting the vehicle speed is provided. A vibration detector is provided on the front side in the traveling direction of the vehicle, and the phase of the fluid operating mechanism and the control circuit is determined by the detection result of the speed detector and the distance from the vibration detector to the fluid operating mechanism on the rear side in the vehicle traveling direction. It has a configuration in which a preview circuit is provided for compensating for the delay and transmitting the detection result of the vibration detector to the control circuit.

[0003]

However, in the above-mentioned conventional suspension control device, the control force calculated based on the road surface information detected by the vibration detector provided in front of the wheel to be controlled is used as the road surface information. Correct the passing time of the controlled wheel calculated from the distance between the detection point and the controlled wheel and the vehicle speed with the compensation time determined by the advance time according to the vehicle speed that compensates for the phase delay of the fluid operation mechanism and the control circuit. Therefore, if a hydraulic cylinder is applied as the actuator and the fluctuation of the control pressure due to the vibration input in the unsprung resonance frequency range is absorbed by the accumulator,
When the response characteristics (gain, phase) of the hydraulic cylinder change due to changes in the loading state of the vehicle, pressure changes in the hydraulic cylinder due to turning, etc., and the volume of the gas chamber of the accumulator changes accordingly. Since the control system time delay correction time and the control gain are constant, it is not possible to follow changes in the response characteristics of the hydraulic cylinder, and the timing of generating the control force may shift or an appropriate control force may not be obtained. There is an unsolved problem that the ride comfort cannot be exerted.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and generates an adequate control force regardless of the response characteristic change of a fluid pressure cylinder such as a hydraulic cylinder. An object of the present invention is to provide a suspension control device that can exert a riding comfort improving effect.

[0005]

In order to achieve the above object, a suspension control device according to the present invention is interposed between a wheel to be controlled and a vehicle body as shown in the basic configuration diagram of FIG. A fluid pressure cylinder, a pressure control valve that communicates with the pressure chamber of the fluid pressure cylinder to control the working fluid pressure thereof, an accumulator that communicates with the pressure chamber of the fluid pressure cylinder via a throttle, and the wheel to be controlled. Front road surface information detecting means for detecting front road surface information, and a pressure command value for the pressure control valve calculated based on road surface information of the front road surface information detecting means on the road surface detected by the front road surface information detecting means. In a suspension control device having a control means for outputting to the pressure control valve when a delay time until the wheel arrives, a pressure for detecting the pressure of the fluid pressure cylinder. Detection means, is characterized in that at least one of the pressure command value and the delay time in response to the pressure detection value of the pressure detecting means and a correcting means for correcting.

[0006]

In the present invention, the pressure of the fluid pressure cylinder is detected by the pressure detecting means, and based on the detected pressure value, at least the pressure command value for the pressure control valve or the road surface detected by the front road surface information detecting means is controlled by the wheel to be controlled. By compensating for the delay time until the arrival of, the change in the response characteristics of the fluid pressure cylinder is compensated, and an appropriate control force is generated at the optimum time.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, 10 is a vehicle body side member, 11FL to 11RR are front left to rear right wheels, and 12 is an active suspension.

The active suspension 12 is a hydraulic cylinder 1 as an actuator that is interposed between the vehicle body side member 10 and the wheel side members 14 of the wheels 11FL to 11RR.
8FL to 18RR and pressure control valves 20FL to 20RR for individually adjusting the operating pressures of these hydraulic cylinders 18FL to 18RR,
A hydraulic pressure source 22 that supplies hydraulic oil of a predetermined pressure to these pressure control valves 20FL to 20RR via a supply side pipe 21S, and collects return oil from the pressure control valves 20FL to 20RR via a return side pipe 21R, and this hydraulic pressure. Accumulators 24F and 24R for accumulating pressure, which are inserted in the supply pressure side pipe 21S between the source 22 and the pressure control valves 20FL to 20RR, and a vehicle speed sensor 26 that detects the vehicle speed and outputs a pulse signal corresponding to the detected vehicle speed.
And stroke sensors 27FL and 27FR which are arranged in parallel with the front wheel side hydraulic cylinders 18FL and 18FR to detect relative displacement between the front wheels 11FL and 11FR and the vehicle body, and vehicle bodies at positions corresponding to the respective wheels 11FL to 11RR. Vertical acceleration sensors 28FL to 28RR for individually detecting the vertical acceleration of each of the rear wheel side hydraulic cylinders 18RL and 18RR.
Pressure sensors 29RL and 29RR that output a pressure detection value having a voltage corresponding to the supplied hydraulic pressure of RR, and vertical acceleration detection values Z _{GFL to} Z of each vertical acceleration sensor 28FL to 28RR.
_While actively controlling each pressure control valve 20FL to 20RR based on _GRR , each sensor 26, 27FL, 27FR, 28FL
A controller 30 for individually predicting the output pressure of the rear wheel side pressure control valves 20RL and 20RR according to the motion state of the front wheels based on the detected values of 28FR, 29FL, and 29FR is provided.

Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a.
A lower pressure chamber L separated by a piston 18c having an axial through hole is formed in 8a.
Thrust is generated according to the pressure difference between the upper and lower surfaces and the internal pressure.
The lower end of the cylinder tube 18a is the wheel-side member 1
4 and the upper end of the piston rod 18b is attached to the vehicle body side member 10. Further, each of the pressure chambers L has a pressure control valve 20FL to 20RR via a hydraulic pipe 38.
Connected to the output port of. Also, the hydraulic cylinder 1
Each of the pressure chambers L of 8FL to 18RR is connected to an accumulator 34 for absorbing unsprung vibration via a throttle valve 32. A coil spring 36, which has a relatively low spring constant and supports a static load of the vehicle body, is disposed between the upper and lower springs of each of the hydraulic cylinders 18FL to 18RR.

Each of the pressure control valves 20FL to 20RR has a conventionally known three-port proportional electromagnetic pressure reducing valve having a cylindrical valve housing in which a spool is slidably mounted and a proportional solenoid integrally provided therein. (For example, JP-A-64-7
No. 4111). Then, by adjusting the command current i (command value) supplied to the exciting coil of the proportional solenoid, the movement distance of the poppet accommodated in the valve housing, that is, the position of the spool is controlled, and the supply port and the output port or the output are controlled. The hydraulic oil flowing between the hydraulic power source 22 and the hydraulic cylinders 18FL to 18RR can be controlled via the port and the return port.

The relationship between the command current i (: i _{FL to} i _RR ) applied to the exciting coil and the control pressure P output from the output port of the pressure control valve 20 _FL (to 20 _RR ) is shown in FIG. As described above, when the minimum current value i _MIN taking noise into consideration, the minimum control pressure P _NIM is reached. When the current value i is increased from this state, the control pressure P increases linearly in proportion to the current value i, and the maximum control pressure P _NIM increases. When the current value is i _MAX , the maximum control pressure P _MAX corresponding to the set line pressure of the hydraulic power source 22 is obtained. This Figure 3
I _N is the neutral command current, and P _CN is the neutral control pressure.

As shown in FIG. 4, each of the stroke sensors 27FL and 27FR has a neutral voltage V _{S of} zero and a vehicle height higher than the target vehicle height when the vehicle height matches a preset target vehicle height. The stroke detection values H _FL and H _FR, which are a positive voltage corresponding to the deviation and a negative voltage corresponding to the deviation when the vehicle height becomes lower than the target vehicle height, are output.

As shown in FIG. 5, each of the vertical acceleration sensors 28FL to 28RL has a zero voltage when the vertical acceleration is zero, and a positive voltage corresponding to the acceleration value when the upward acceleration is detected. When the analog voltage and the downward acceleration are detected, the vertical acceleration detection values Z _{GFL to} Z _GRR , which are negative analog voltages corresponding to the acceleration value, are output.

The controller 30, as shown in FIG.
Stroke detection values S _FL and S _FR input from the stroke sensors 27 _FL and 27 _FR and the vertical acceleration sensor 28.
Acceleration sensor 28FL corresponding to the front wheel side of FL to 28RR
And 28FR vertical acceleration detection value Z output from 28FR
_{Based on the GFL} and Z _GFR , the vibration input estimation circuit 41 that outputs differential values x _1FL ′ and x _1FR ′ of the road surface displacement of the front wheels 11FL and 11FR that accurately follow the road surface shape, and the vertical acceleration sensors 28FL to 28FR The vertical acceleration detected values Z _{GFL to} Z _GFR are integrated to integrate the sprung speed Z _{VFL to} Z _VFL
For example, an integrator circuit 4 configured by a bandpass filter that calculates a _VRR that passes a frequency near the sprung resonance frequency.
2FL to 42RR and the pressure detection values P _HRL and P _HRR input from the pressure sensors 29RL and 29RR are input, and the low frequency components indicating the slow pressure changes due to the passenger getting on and off the pressure detection values P _HRL and P _HRR. Low-pass filters 47RL and 47RR for extracting the vibration, and the vibration input estimation circuit 4
1, differential values x _0FL ′ and x _0FR ′ of road surface displacement, sprung speeds Z _{VFL to} Z _VRR output from integrating circuits 42FL to 42RR, and low frequency pressure detection values output from low pass filters 47RL and 47RR. P _LRL and P
A / D converters 43a to 43 for converting _LRR into digital values
3h, a microcomputer 44 to which the vehicle speed detection value V of the vehicle speed sensor 26 and the A / D conversion outputs of the A / D converters 43a to 43h are input, and this microcomputer 4
The pressure command values P _{FL to} P _RR output from 4 are supplied via D / A converters 45 _{FL to} 45 _RR , and these are converted into drive currents i _{FL to} i _FR for the pressure control valves 20 _{FL to} 20 RR, for example, a floating type. Drive circuits 46FL to 46FR each including a constant voltage circuit are provided.

Here, the vibration input estimation circuit 41 differentiates the stroke detection values S _FL and S _FR of the stroke sensors 27 _FL and 27 _FR, as shown in FIG.
Calculate _VFL and S _VFR , for example, 2 of unsprung resonance frequency
Differentiating circuits 41a and 4 composed of a high-pass filter set to a cut-off frequency f _HC of about double (about 20 Hz)
1b and the vertical acceleration detection values Z _GFL and Z _GFR of the vertical acceleration sensors 28FL and 28FR are integrated to calculate the differential values x _FL ′ and x _FR ′ of the sprung displacement. Integrator circuits 41c and 41d constituted by low-pass filters set to a cutoff frequency f _LC in the vicinity of 6 (about 0.02 Hz) and differentiating circuits 41a and 4
An adder 41e for adding the stroke velocities S _VFL and S _VFR output from 1b and the differential values x _FL ′ and x _FR ′ of the sprung displacement output from the integration circuits 41c and 41d.
And 41f, and differential values x _0FL ′ and x _0FR ′ of the road surface displacements of the front wheels 11FL and 11FR that accurately follow the road surface shape are output from the adders 41e and 41f.

That is, the stroke sensors 27FL and 27FL
Stroke detection values S _FL and S _FR output from 7FR are
As expressed by the following equations (1) and (2), the unsprung and unsprung relative displacements are expressed. Therefore, from the unsprung displacement x _0FL and x _{0FR of} the front wheels 11FL and 11FR to the unsprung displacement x of the vehicle body. _FL
And x _FR are subtracted. S _FL = x _0FL −x _FL (1) S _FR = x _0FR −x _FR (2) Therefore, the stroke obtained by differentiating the stroke detection values S _FL and S _FR with the differentiating circuits 41a and 41b. The speeds S _VFL and S _VFR are differential values x _0FL ′ and x _0FR ′ of the unsprung displacement, _respectively .
Since the differential values x _FL ′ and x _FR ′ of the sprung displacement are subtracted from these, these and the vertical acceleration detection values Z _GFL and Z
By adding the differential value of the integral of the sprung displacement of the _GFR x _FL 'and x _FR', the true road displacement offset to follows the road surface displacement a differential value x _FL sprung displacement 'and x _FR' It is possible to obtain the differential values x _0FL ′ and x _0FR ′ of.

Further, the microcomputer 44 has a small number of
At least the input side interface circuit 44a and the output side interface circuit
Face circuit 44b, arithmetic processing unit 44c, and storage device
44d. The input interface circuit 44a includes
Converted output of vehicle speed detection value V and A / D converters 43a to 43f
Force is input, and from the output side interface circuit 44b
Pressure command value P for each pressure control valve 20FL to 20RR_FL~
P_RRIs output to the D / A converters 45FL to 45RR. Well
Further, the arithmetic processing unit 44c executes the processing of FIG. 7 described later.
Then, the predetermined sampling time T_S(For example, every 20 msec)
, Vehicle speed detection value V, road surface differential value x_0FL′,
x_0FR′ 、 Vehicle vertical speed Z_VFL~ Z_VRRAnd low frequency pressure
Detection value P_LRLAnd P_LRRBased on the vehicle speed detection value V
Delay time between front and rear wheels τ_RAnd calculate the pressure
Outgoing price P_LRLAnd P_LRRBased on the control force correction coefficient α and
The delay time correction coefficient β is calculated, and the differential value x of the road surface displacement is calculated.
_0FL′, X _0FRBased on ’
Prediction system that occurs in the current hydraulic cylinders 18RL and 18RR
Control power U_RL, U_RRTo calculate the control force for preview control
U_RL, U _RRIs multiplied by the correction coefficient α to correct the
Total time τ_RIs multiplied by the correction coefficient β to make the correction, and then
Control force U for preview control_RL,U_RRDelay time τ
_RTogether with the storage device 44d, a shift register having a predetermined number of lower stages is formed.
Stored in the storage area corresponding to the star while shifting in sequence.
Delay time τ_RWhen sampling when shifting
Interval T_SIs stored while subtracting sequentially, and the delay time τ_RIs zero
Reaching control force U for preview control_RL, U_RRAnd the integration circuit 42FL
~ 42RR body vertical speed Z_VFL~ Z_VRROn the basis of
For active control that demonstrates the calculated skyhook damper function
The value obtained by adding the control force to each pressure control valve 20FL to 20RR
D / A converters 45FL to 45RR as pressure command values for
Output.

Further, the storage device 44d stores a program necessary for the arithmetic processing of the arithmetic processing device 44c in advance, and the correction preview control forces U _RL, U _RR calculated for each predetermined sampling time T _S. A shift register area for storing a predetermined number while sequentially shifting the control delay time τ _R and a control force correction map showing a relationship between the low frequency pressure detection value P _L and the control force correction coefficient α, and A delay time correction map showing the relationship between the low frequency pressure detection value P _L and the delay time correction coefficient β is stored,
Further, the calculation results required in the calculation process of the calculation processing device 44c are sequentially stored. Here, the control force correction map is shown in FIG.
As shown in, when the low frequency pressure detection value P _L is the neutral pressure P _CN , the control force correction coefficient α becomes “1”, and the neutral pressure P _CN
When it becomes higher, α becomes smaller than “1”, and the neutral pressure P _CN
It is set non-linearly so that α becomes larger than “1” when it becomes lower. Similarly, in the delay time correction map, as shown in FIG. 9, when the low frequency pressure detection value P _L is the neutral pressure P _CN , the delay time correction coefficient β becomes “1” and becomes higher than the neutral pressure P _CN. Non-linearity is set so that β becomes larger than “1” when β becomes smaller than “1” and becomes lower than the neutral pressure P _CN . Thus, the control force correction coefficient α
The reason for setting the delay time correction coefficient β is that the ride comfort is improved according to the frequency response characteristics of the hydraulic system (pressure control valve, hydraulic cylinder, etc.) when the pressure of the hydraulic cylinders 18FL to 18RR is at the neutral pressure P _CN. Assuming that the gain of the preview control and the delay time τ _R are tuned so as to increase, the frequency response characteristic of the hydraulic system shows that the accumulator 3 changes when the pressure of the hydraulic cylinders 18FL to 18RR changes.
The gas spring constant of No. 4 changes as shown in FIG. That is, when the pressure of the hydraulic cylinders 18FL to 18RR is high, the response is high when the volume of the accumulator gas chamber is small (the gas spring constant is large), and the response is deteriorated when the neutral pressure is low. Thus, to advance the frequency response characteristic due to the pressure change in the hydraulic cylinders 18FL~18RR measured, the same control effect as well the pressure of the hydraulic cylinder 18FL~18RR is varied from the neutral pressure P _CN is neutral pressure P _CN is out The correction coefficients α and β are set to.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. 7 showing the processing procedure of the arithmetic processing unit 44c in the microcomputer 44. That is,
Process of Figure 7 is predetermined sampling time T _S (e.g., 20ms
ec) is executed as a timer interrupt process. First, in step S1, the current vehicle speed detection value V (n) of the vehicle speed sensor 26 is read, and then the process proceeds to step S2 to detect the vehicle speed detection value V.
It is determined whether or not (n) is equal to or higher than a preset vehicle speed setting value V _S , and when V (n) <V _S , the timer interrupt process is terminated and the process returns to a predetermined main program. , V (n) ≧ V _S , the process proceeds to step S3.

In step S3, the differential values x _0FL ′, x _0FR ′ of the road surface displacement from the vibration input estimation circuit 41 and the vehicle body vertical velocities Z _{VFL to} Z from the integration circuits 42FL to 42FR.
_VFR is read, then the process proceeds to step S4, and the low frequency pressure detection value P from the low pass filters 47RL and 47RR is read.
Reads the _LRL and P _LRR, then proceeds to step S5, the low frequency pressure detection value P _LRL and 8 that are stored in advance in the storage device 44d based on low frequency pressure detection value P _LRL and P _LRR The diagram which is stored in advance in the storage device 44d by calculating the control force correction coefficient α by referring to the control force correction map showing the relationship between P _LRR and the control force correction coefficient α, and then moving to step S6 Low frequency pressure detection value P shown in 9
_The delay time correction coefficient β is calculated with reference to the delay time correction map _showing the relationship between the _LRL and P _LRR and the delay time correction coefficient β.

Next, in step S7, the correction delay time τ _S is calculated by performing the following equation (3) based on the delay time correction coefficient β. τ _S = β ・ τ ₁ + τ ₂ + τ ₃ (3) where τ ₁ is the preset response delay time of the hydraulic system,
τ ₂ is a preset controller calculation dead time, τ ₃
Is a phase delay time by a preset filter.

Next, in step S8, the differential value x _0FL ′ of the road surface displacement read in step S3 described above,
x _0FR ′ is read out, and based on these, the following equation (4) and
(5) is calculated and the rear wheel pressure control valves 20RL and 2
The preview control forces U _pRL and U _pRR for 0 _RR are calculated. U _pRL =-[C _p + {1 / (ω ₁ + s)} K _p ] x _0FL ′ ... (4) U _pRR =-[C _p + {1 / (ω ₁ + s)} K _p ] x _0FR ′ (5) where C _p is the damping constant and K _p is the spring constant, and C _p ≦ C, K _p ≦ K for the damping constant C and the spring constant K of the actual suspension. And ω ₁ ≧ 0.

Here, the reason why the _preview control forces U _pRL and U _pRR are calculated according to the above equations (4) and (5) is that they are active in the unsprung resonance frequency region as in the case of a normal active suspension. When control is not performed and vibration is suppressed mainly in the sprung resonance frequency region of 5 Hz or less, the motion model of one wheel has a spring element K, a damping element C, and a control element U on the road surface as shown in FIG. Can be considered as a one-degree-of-freedom model in which the sprung mass M is arranged above these, and the external force F acts on this sprung mass M. In FIG. 11, X ₀ is the road surface displacement and X is the sprung displacement.

The equation of motion of this one-wheel one-degree-of-freedom model can be expressed by M ″ X ₀ = C (X ₀ ′ −X ′) + K (X ₀ −X) −F + U (6) Solving this equation (6) for the sprung displacement X, Becomes

For example, in the above formula (4), x_0FL′ = S
x_0FLTherefore, this equation (4) is changed to ω ₁= 0, C_p= C,
K_pSubstituting into equation (7) with = K, equation (7) yieldsBecomes

Since the estimation accuracy of the road surface displacement by the road surface input estimating circuit 41 in the equation (8) is sufficiently high as described above,
Since (X ₀ −x _0FL ) _≈0 , the equation (8) becomes The effect of uneven road surface is hardly transmitted to the vehicle body,
A good ride quality can be obtained.

Then, the process proceeds to step S9 and the above-mentioned step is performed.
Preview control force U calculated in step S8 _pRLAnd U_pRRTo
Corrected preview control force U multiplied by a positive coefficient α_pRL(= Α ・ U
_pRL) And U_pRR(= Α ・ U_pRR) Is calculated. Next
Then, the process proceeds to step S10, and based on the vehicle speed detection value V,
The following formula (10) is calculated and the front wheels 11FL and 11FR pass.
Delay until the rear wheels 11RL and 11RR reach the surpassed road surface
Time τ_RTo calculate.

Τ _R = (L / V) −τ _S (10) where L is the wheel base. Then, the process proceeds to step S11, and the corrected _preview control forces U _pRL and U _pRR calculated in step S9 and the delay time τ _R calculated in step S10 are set at the head position of the shift register area formed in the storage device 44d. The correction _preview control forces U _pRL, U _pRR and the delay time τ _R stored up to the previous time are sequentially shifted while being stored. At this time, when the shift for the delay time tau _R, the delay time of each shift position tau _R
The value obtained by subtracting the sampling time T _S from each is updated and stored as a new delay time τ _R.

Next, in step S12, the corrected _preview control forces U _pRL and U _pRR stored in the shift register area, that is, the oldest, that is, the delay time τ _R becomes zero, are read out, and these and the above steps are _executed. Based on the sprung speeds Z _{VFL to} Z _VRR read in S3, the total control forces U _{FL to} U _RR are calculated according to the following formulas (11) to (14), and the oldest corrected preview control force read out is calculated. The values U _pRL, U _pRR and the corresponding delay time τ _R are erased from the shift register area.

[0030] _{U FL = U N -K B ·} Z VFL ............ (11) U FR = U N -K B · Z VFR ............ (12) U RL = U N -K B · Z VRL _{+ U pRL ............ (13) U} RR = U N -K B · Z VRR + U pRR ............ (14) wherein, U _N control force necessary to maintain the vehicle height to the target vehicle height , K _B are bounce control gains.

Next, in step S13, the control forces U _{FL to} U _RR calculated in step S12 are output as pressure command values to the D / A converters 45 _{FL to} 45 _RR , respectively, and then timer interrupt processing is performed. Upon completion, the program returns to the predetermined main program. Thus, now, it is assumed that the vehicle goes straight constant speed running at the set vehicle speed V _S or more of the vehicle speed to maintain a target vehicle height flat good road. In this state, since the vehicle maintains the target vehicle height on a flat and good road, the stroke detection values S _FL and S _FR of the stroke sensors 27FL and 27FR arranged on the front wheel side are substantially zero. And the vehicle body side member 1
0 does not oscillate, so each vertical acceleration sensor 28
The acceleration detection values Z _{GFL to} Z _GRR of FL to 28 _RR are substantially zero. Therefore, the differentiation circuit 4 of the vibration input estimation circuit 41
Stroke differential value S _VFL output from 1a and 41b
And S _VFR and the differential values x _FL ′ and x _FR ′ of the sprung displacement output from the integrating circuits 41c and 41d, respectively, become substantially zero, so the differential value of the road surface displacement output from the adders 41e and 41f. x _0FL ′ and x _0FR ′ are also substantially zero. On the other hand, since the vertical acceleration detection values Z _{GFL to} Z _GRR are substantially zero, the sprung speeds Z _{VFL to} Z _VRR output from the integrating circuits 42FL to 42RR are also substantially zero.

Then, the differential value x of the road surface displacement_0FL'And x
_0FR′ And sprung speed Z_VFL~ Z_{VR R}Is the vehicle speed detection value V
It is also input to the microcomputer 44. This
As you can see, the microphone is
A predetermined sampling time T_SEvery
In the processing of FIG. 7 to be executed, it is sequentially performed in step S11.
Corrected preview control force U stored in the shift register area_pRL
And U_{pR R}Continues to be zero, so step S10
Delay time τ calculated by_RCorrection preview control after the passage of
Force U_pRLAnd U_pRRIs also zero, while the sprung speed is
Z _VFL~ Z_VRRIs also zero, it is calculated in step S12
Total control power U_FL~ U _RRIs neutral to maintain target vehicle height
Pressure control force U_NOnly the values corresponding to
Interface circuit 44b and D / A converters 45FL-4FL
It is output to the drive circuits 46FL to 46RR via 5RR.

[0033] Therefore, by being converted into the command current i _FL through i _RR corresponding to the pressure command value P _FL to P _RR drive circuit 46FL~46RR supplied to the pressure control valve 20FL~20RR of the front wheel side. As a result, the neutral pressure P _CN required to maintain the target vehicle height is output from the pressure control valves 20FL to 20RR to the front and rear wheel hydraulic cylinders 18FL, 18FR and 18RL, 18RR, and these hydraulic cylinders 18FL to At 18RR, a thrust force for maintaining the stroke between the vehicle body side member 10 and the wheel side member 14 at the target vehicle height is generated.

[0034] Thus, the good road traveling state, the hydraulic pressure supplied to the hydraulic cylinders 18RL and 18RR of the rear wheels is maintained at the neutral pressure P _CN, is calculated in step S5 in the processing of FIG. 7 Control force correction coefficient α and step S
Both the delay time correction coefficients β calculated in the process of 6 are “1”
_Therefore , the _preview control forces U _pRL and U _pRR calculated in step S8 in the process of FIG. 7 become the corrected _preview control forces as they are, and the correction delay time τ _S has a preset response delay time τ ₁ of the hydraulic system. Controller calculation dead time τ ₂
And the filter response delay time τ ₃ are set.

When the front left and right wheels 11FL and 11FR pass through a so-called ramp step road in which the road surface rises stepwise at the same time in this straight road straight traveling state, the front wheels 11FL are ridden by stepping up the front left and right wheels. And 1
1FR bounces, which causes the stroke sensor 27
The stroke detection values S _FL and S _{FR of} FL and 27 _FR suddenly increase from zero in the positive direction, and upward acceleration is generated in the vehicle body side member 10.
And 28FR, the acceleration detection values Z _GFL and Z _GFR increase in the positive direction.

Since the stroke detection values S _FL and S _FR and the vertical acceleration detection values Z _{GF L} and Z _GFR are input to the vibration input estimation circuit 41, the vibration input estimation circuit 41 described above. As described above, the differential values x _0FL ′ and x _0FR ′ of the road surface displacement which are truly positive values according to the road surface shape and are not affected by the vertical movement of the vehicle body side member 10 are output to the microcomputer 44.

Therefore, in the microcomputer 44
Is the differential value x of the road surface displacement in the process of step S8._0FL'And
X_0FRCalculated according to Eqs. (4) and (5) based on
Preview control force U_pRLAnd U_pRRBecomes negative and these
Preview control force U_pRLAnd U_pRRIs calculated in step S10
Rear wheel 11RL on the road surface where front wheels 11FL and 11FR passed
And delay time τ until 11RR arrives_RShift with
It is stored at the beginning of the register area, and it is zero until the last time.
Preview control power U_pRL And U_pRRAnd delay time τ _RIn order
Next, shift one by one, and at this time, each delay time τ_RFrom Sun
Pulling time T _SThe new delay time τ_RWhen
And update.

At this point, the data is stored in the shift register area.
Each preview control force U up to the last time_pRLAnd U_pRRIs
Since it is zero, the control force U on the rear wheel side_RLAnd U_RRIs neutral control
Force U _NMaintain, but above the front wheels in the 11FL and 11FR positions
Acceleration detection value Z of the downward acceleration sensor 28FL and 28FR
_GFLAnd Z_GFRIs increasing in the positive direction, so step
Front wheel side total control force U calculated in S8_FLAnd U_FRDan
Neutral control force U according to the speed at which the vehicle rises due to differential riding_N
It is further lowered, and the drive circuits 46FL and 46FR are correspondingly reduced.
Command current i output from_FLIs reduced by this
Control pressure P output from force control valves 20FL and 20FR_CBut
Neutral pressure P_CNLower, hydraulic cylinders 18FL and 18
FR thrust is reduced, reducing front wheel stroke
By doing so, the front wheel 1 is able to exert the skyhook damper function.
The body side member 10 by climbing the step of 1FL and 11FR
Oscillation can be suppressed.

After that, the front wheels 11FL and 11FR are ramped.
After passing the Tep road, the front wheels 11FL and 11FR again
For the control force U for maintaining the target vehicle height_FLAnd U_FRBack to
Return, but for the rear wheels 11RL and 11RR, step
Delay time τ calculated in S10 _RWhen zero becomes zero, that is, the rear wheel
When 11RL and 11RR pass the ramp step road
Then, in step S12, the front wheels 11FL and 11FR ride on a step
Negative preview control force U calculated when raising_pFLAnd U_pRRRead by
Issued, and based on these, the total control force U for the rear wheels_RL
And U_RRIs calculated, the total control force U_RLas well as
U_RRIs the neutral pressure control force U_NWill be lower, the rear wheels
Significantly reduces the impact force when riding on 11RL and 11RR steps
Can be summed up, and as expressed by the above equation (9),
The effect of uneven road surface is hardly transmitted to the vehicle body, and
The ride comfort can be secured. Moreover, the rear wheels 11RL and
And the vehicle body side member on the rear wheel side by riding on the step of 11RR
When an upward acceleration occurs at 10, this acceleration is
The product is detected by the vertical acceleration sensors 28RL and 28RR.
Sprung speed Z integrated by the branch circuits 42RL and 42RR_{VR L}
And Z_VRRIs input to the microcomputer 44
Then, in step S12, the skyhook damper function is demonstrated.
The active control force that suppresses the rise of the vehicle body side member 10 is generated.
Which controls the pressure control valves 20RL and 20RR.
Is supplied to the hydraulic cylinders 18RL and 18RR.
The supplied hydraulic pressure is controlled, and the swing of the vehicle body is suppressed.

However, passengers boarding or loading cargo, etc.
Increases the loading weight, which increases the vehicle height
When the vehicle sinks below the high level, the vehicle height control controls the pressure.
The pressure command value for valves 20FL to 20RR increases and the hydraulic pressure
Control pressure P for Linda 18FL to 18RR_CIs the neutral pressure P_CN
Increase the target cylinder height with hydraulic cylinders 18FL to 18RR.
Will generate thrust to maintain. Like this, oil
The hydraulic pressure of the pressure cylinders 18RL and 18RR will increase.
And this is detected by the pressure sensors 29FL and 29RR.
Via the low pass filters 47RL and 47RR
Since it is input to the computer 44, it is calculated in step S5.
The control force correction coefficient α issued and calculated in step S6
As shown in FIGS. 8 and 9, the delay time correction coefficient β is
It is set to a value less than “1”, and
Corrected preview control force U calculated in S9 _pRLAnd U_pRRIs
Preview control force U calculated in step S8_pRLAnd U_pRRYo
Becomes smaller and is calculated in step S10.
Delay time τ_RIs the neutral pressure P mentioned above._CNLonger than the state,
The hydraulic pressure is increased by increasing the pressure in the hydraulic cylinders 18RL and 18RR.
Compensating for the increase in system responsiveness,
A preview control force can be generated.

Similarly, when the occupant disembarks or the load is unloaded, the loaded weight decreases, and when the vehicle height suddenly becomes higher than the front vehicle height, the vehicle height control controls the pressure control valves 20FL to 20RR. The pressure command value decreases and the control pressure P _C for the hydraulic cylinders 18FL to 18RR is reduced below the neutral pressure P _CN , but in this case, the control force correction coefficient α calculated in step S5 and step S5.
Both the delay time correction coefficient β calculated in 6 becomes larger than “1”, thereby increasing the _preview control forces U _pRL and U _pRR and shortening the delay time τ _R to decrease the control pressure P _C. It is possible to compensate for the decrease in the responsiveness of the hydraulic system due to and generate an appropriate preview control force at the optimum time.

By the way, in the above equations (4) and (5), ω
₁= 0 and control force U_pRLAnd U_{pR R}If you calculate
Power U_pRLAnd U_pRRRoad surface displacement (wheel displacement) x_0FLOver
X _0FRSteady-state gain for (gay when s = 0
However, there is no problem with temporary unevenness.
However, like the ramp step road described above, the road surface displacement X
_0FL(≒ x_0FL) And X_0FR(≒ x_0FR) Has changed
If you drive on a road that does not
Even control power U_pRLAnd U_pRRDoes not become "0" and control power
U_pRLAnd U_pRRAnd suspension spring constant K
Stroke as long as it fits and return based on vehicle height
If not, that is, the initial value of the vehicle height is h, (X₀-X
₀) -H = U / K ≠ 0. Therefore,
After traveling on such a road surface, when you come out on a flat road surface
In order to return the vehicle height to its original value, the control force U_pRLOver
And U_pRREstimated wheel vertical velocity x₀Stationary gain for
Ω in Eqs. (4) and (5) so that₁> 0
You can select it.

On the other hand, when either one of the front wheels 11FL and 11FR, for example, only the front left wheel 11FL rides on the temporary convex portion, the preview control is performed only on the hydraulic cylinder 18RL on the left wheel side to climb the convex portion. With respect to the hydraulic cylinder 18RR on the right wheel side that does not cause the above, control for maintaining the neutral pressure is performed. Further, when the front wheels 11FL and 11FR fall into a temporary recessed portion, the control opposite to the above can be performed to suppress the swinging of the vehicle body, and the continuous irregularities such as irregular road surfaces are not limited to the temporary unevenness. Even when traveling on a rough road surface, the rear wheels can be preview-controlled according to the behavior of the front wheels.

In the above embodiment, the pressure sensor
Pressure detection value P of 29RL and 29RR_{HR L}And P_HRRTo low
The analog circuit is a low-pass filter that extracts the frequency component.
Although the case of configuring has been described, it is not limited to this.
Instead of the digital
Filter processing may be performed. In addition, in the above embodiment
For the hydraulic cylinders 18RL and 18RR,
When pressure sensors 29FL and 29RR are applied as steps
However, the present invention is not limited to this.
Control force U output from the microcomputer 44 _RLOver
And U_RRIs converted to the pressure of hydraulic cylinders 18RL and 18RR
Alternatively, the pressure may be indirectly detected.

Further, in the above embodiment, the micro
With the computer 44, the preview control force U _pRLAnd U_pRRLate
Total time τ_RTogether with the shift register area
Stored and delay time τ_RPreview control force U at which
_pRL~ U_pRRThe case of performing preview control based on
However, the differential value x of the road displacement is not limited to this._0FL'as well as
x_0FR′ Is the delay time τ_RTogether with shift register area
Stored while shifting next time, and changed the road surface when the delay time became zero.
Differential value x_0FL'And x_0FRPrediction control force U based on
_pRLAnd U_pRRMay be calculated.

Furthermore, in the above embodiment, the case has been described in which both the _preview control forces U _pRL and U _pRR and the delay time τ _R are corrected, but the present invention is not limited to this, and only one of them may be corrected. You can Still further, in the above embodiment, the stroke sensor 27 at the front wheel position is used.
Although the case where the front road surface information detecting means is configured by the FL, 27FR, the vertical acceleration sensors 28FL, 28FR, and the vibration input estimating circuit 41 has been described, the present invention is not limited to this, and the front wheels 11FL and 11FR may be located in front of the front position. A non-contact distance sensor such as a sound wave distance sensor or a laser distance sensor is arranged, and the front wheel side hydraulic cylinders 18FL and 18FR and the rear wheel side hydraulic cylinders 18RL and 18RR are foreseen based on the distance detection value of the non-contact type distance sensor. It can also be controlled.

Further, in the above embodiment, the case where the active control of the suspension is carried out only on the basis of the vertical acceleration is explained, but the present invention is not limited to this, and other lateral acceleration sensor and longitudinal acceleration sensor. A control signal for suppressing roll, pitch, and bounce is calculated based on acceleration detection values such as the above, and these are calculated as the pressure command value P _FL.
The total control may be performed by adding / subtracting to P _RR .

Further, in each of the above embodiments, the case where the pressure control valves 20FL to 20RR are applied as the control valves has been described, but the present invention is not limited to this, and other flow rate control type servo valves or the like are applied. I will get it. Further, in the above embodiment, the case where the controller 30 is configured by the microcomputer 62 has been described, but the present invention is not limited to this, and it may be configured by combining electronic circuits such as a shift register and an arithmetic circuit. It goes without saying that it is good.

Further, in the above embodiment, the case where the working oil is used as the working fluid has been described, but the working fluid is not limited to this, and any working fluid may be applied as long as the fluid has a low compression rate.

[0050]

As described above, according to the suspension controller of the present invention, the pressure of the fluid pressure cylinder is detected by the pressure detecting means, and at least the preview control force and the delay time are detected based on the detected pressure value. Since one of them is corrected, it is possible to compensate for the change in response characteristics due to the pressure fluctuation of the fluid pressure cylinder and generate an appropriate preview control force at the optimum time, and to exert an excellent riding comfort improving effect. The effect of being able to do is obtained.

[Brief description of drawings]

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

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

FIG. 3 is a characteristic diagram showing a relationship of control pressure with respect to a command current of a pressure control valve.

FIG. 4 is a characteristic diagram showing an output characteristic of a stroke sensor.

FIG. 5 is a characteristic diagram showing an output characteristic of a vertical acceleration sensor.

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

FIG. 7 is a flowchart showing an example of a processing procedure of a microcomputer.

FIG. 8 is a characteristic diagram showing a relationship between a low frequency pressure detection value and a control force correction coefficient.

FIG. 9 is a characteristic diagram showing a relationship between a low frequency pressure detection value and a delay time correction coefficient.

FIG. 10 is a characteristic diagram showing frequency response characteristics due to pressure change of the hydraulic control system, in which (a) shows a gain characteristic with respect to frequency and (b) shows a phase characteristic with respect to frequency.

FIG. 11 is an explanatory diagram showing a one-wheel one-degree-of-freedom model.

[Explanation of symbols]

 10 Body side member 11FL-11RR Wheel 14 Wheel side member 18FL-18RR Hydraulic cylinder 20FL-20RR Pressure control valve 22 Hydraulic source 26 Vehicle speed sensor 27FL, 27FR Stroke sensor 28FL, 28FR Vertical acceleration sensor 29FL, 29FR Pressure sensor 30 Controller 41 Vibration Input estimation circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ken Kimura 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. A fluid pressure cylinder interposed between a wheel to be controlled and a vehicle body, a pressure control valve communicating with a pressure chamber of the fluid pressure cylinder to control the working fluid pressure, and the fluid pressure cylinder. Accumulator communicating with the pressure chamber of the vehicle through a throttle, front road surface information detecting means for detecting road surface information in front of the control target wheel, and the pressure control valve calculated based on road surface information of the front road surface information detecting means. In the suspension control device including a control means for outputting the pressure command value to the pressure control valve at the time when the delay time until the control target wheel reaches the road surface detected by the front road surface information detecting means, Pressure detection means for detecting the pressure of the cylinder, and a correction hand for correcting at least one of the pressure command value and the delay time according to the pressure detection value of the pressure detection means. A suspension control device having a step.