JPH05319054A - Suspension control device - Google Patents

Abstract

PURPOSE:To generate an adequate foreseeing control force and to improve the riding feeling by providing a correcting means to correct at least one side of the foreseeing control force and the delay time depending on the temperature of an operating oil. CONSTITUTION:The differential value of the road surface displacement of the front wheels is calculated by a vibration input inference circuit 41, the temperature of an operating oil fed to pressure control valves 20FL to 20RR is detected by a temperature sensor 29, and a foreseeing control force is calculated depending on the differential value by a microcomputer 44. Furthermore, a delay time for rear wheels is calculate depending on the car speed detecting value, and the correcting value of the control force and the correcting value of the delay time are calculated depending on the temperature detecting value of the temperature sensor 29, and when the response property of a hydraulic system is decreased by the increase of the viscosity of the operating oil, the foreseeing control force is increased, and the delay time is reduced. And when the response property of the hydraulic system is increased by the reduction of the viscosity of the operating oil, the foreseeing control force is reduced, and the delay time is increased. By such a way, an adequate control force is generated at an optimum point of 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, when the temperature of the working fluid decreases in cold regions, the viscosity of the working fluid increases, and the response characteristics (gain, phase) of the fluid working mechanism change, the response characteristic of the fluid working mechanism changes. It is not possible to achieve sufficient riding comfort improvement effect because the timing of generating control force is deviated or proper control force cannot be obtained. There is a problem.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and generates an appropriate control force at an optimum time regardless of the response characteristic change of the fluid pressure cylinder due to the working fluid temperature. It is an object of the present invention to provide a suspension control device that can exert a sufficient 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 a pressure chamber of the fluid pressure cylinder and controls the working fluid pressure thereof, a front road surface information detecting unit that detects road surface information in front of the wheel to be controlled, and the front road surface. The pressure command value for the pressure control valve calculated based on the road surface information of the information detecting means is output 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 has elapsed. In the suspension control device including a control means for controlling the temperature of the working fluid, the temperature command means detects the temperature of the working fluid, and the pressure command value and the delay time are determined according to the temperature detection value of the temperature detection means. Is characterized in that a correcting means for correcting at least one time.

[0006]

In the present invention, the temperature of the working fluid supplied to the fluid pressure cylinder is detected by the temperature detecting means, and based on the detected temperature value, at least the pressure command value for the pressure control valve or the front road surface information detecting means is detected. By correcting the delay time until the wheel to be controlled reaches the road surface, the change in the response characteristic of the fluid pressure cylinder due to the change in the viscosity of the working fluid 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 them, a temperature sensor 29 for outputting a temperature detection value formed of a voltage according to the hydraulic oil temperature provided in the supply side pipe 21S, and each vertical direction. The pressure control valves 20FL to 20RR are actively controlled based on the vertical acceleration detection values Z _{GFL to} Z _GRR of the acceleration sensors 28FL to 28RR, and also based on the detection values of the sensors 26, 27FL, 27FR, 28FL to 28FR and 29. A controller 30 for predicting the output pressures of the rear wheel side pressure control valves 20RL and 20RR individually according to the motion state of the front wheels 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 temperature detection value T _H input from the temperature sensor 29, and a low-pass filter 47 that extracts a low frequency component representing a slow temperature change due to a change in the environment of the temperature detection value T _H , 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. A / D converters 43a to 43g for converting _TL into digital values, a vehicle speed detection value V of the vehicle speed sensor 26, and respective A / D converters 43a to 43g.
A microcomputer 44 to which 3 g of A / D conversion output is input, and pressure command values P _{FL to} P _RR output from this microcomputer 44 are D / A converters 45 _{FL to} 45 _RR.
Are supplied through the pressure control valves 20FL to 20RR.
To drive currents i _{FL to} i _FR for the drive circuits 46 FL to 46 composed of floating type constant voltage circuits, for example.
It has FR and.

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.

The microcomputer 44 has at least an input side interface circuit 44a, an output side interface circuit 44b, an arithmetic processing unit 44c and a storage unit 44d. The input interface circuit 44a includes
The vehicle speed detection value V and the conversion outputs of the A / D converters 43a to 43f are input, and the pressure command values P _FL to the pressure control valves 20FL to 20RR are output from the output side interface circuit 44b.
P _RR is output to the D / A converters 45FL to 45RR. Further, the arithmetic processing unit 44c executes the processing of FIG. 7 described later, and at every predetermined sampling time T _S (for example, 20 msec), the vehicle speed detection value V, the differential value x _0FL ′ of the road surface displacement,
x _0FR ′, vehicle body vertical speeds Z _{VFL to} Z _VRR and low frequency temperature detection value _TL are read, delay time τ _R between the front and rear wheels is calculated based on vehicle speed detection value V, and pressure detection values P _LRL and P _The control force correction coefficient α and the delay time correction coefficient β are calculated based on the _LRR , and the differential value x _0FL ′, x of the road surface displacement is calculated.
_{The preview} control forces U _RL and U _RR generated by the hydraulic cylinders 18RL and 18RR as actuators on the rear wheel side are _calculated based on _0FR ′, and the preview control forces U _RL and U _RR are multiplied by the correction coefficient α. In addition to the correction, the delay time τ _R is multiplied by the correction coefficient β to be corrected, and then the corrected _preview control forces U _{pRL and} U _pRR are formed in the storage device 44d together with the corrected delay time τ _R. The data is stored in the storage area corresponding to the shift register of the number of stages while being sequentially shifted, and the delay time τ _R
Is stored while sequentially subtracting the sampling time T _S when shifting, and the preview control forces U _RL and U _RR for which the delay time τ _R has reached zero, and the vehicle body vertical velocity Z from the integrating circuits 42 FL to 42 _RR. A value obtained by adding the control force for active control that exerts the skyhook damper function calculated based on _{VFL to} Z _VRR is output to the D / A converters 45FL to 45RR as a pressure command value for each pressure control valve 20FL to 20RR. ..

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 _pRL, U _pRR calculated for each predetermined sampling time T _S. Correction delay time τ _R
A shift register area for storing a predetermined number while sequentially shifting is formed together with the control force correction map and the low frequency pressure detection value P indicating the relationship between the low frequency temperature detection value T _L and the control force correction coefficient α in advance. _L and delay time correction coefficient β
Stores a delay time correction map showing the relationship with
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, the low frequency temperature detection value T _L is the reference temperature T _N
The control force correction coefficient α becomes “1” at a certain time, and when it becomes higher than the reference temperature, α becomes smaller than “1”, and when it becomes lower than the reference temperature T _N , α becomes larger than “1”. There is. Similarly, in the delay time correction map, the delay time correction coefficient β becomes “1” when the low frequency temperature detection value T _L is the reference temperature T _N , as shown in FIG.
When the temperature is higher than the reference temperature T _N , β is smaller than “1”, and when the temperature is lower than the reference temperature T _N , β is larger than “1”. Thus, the reason for setting the control force correction coefficient α and the delay time correction coefficient β is to match the frequency response characteristics of the hydraulic system (pressure control valve, hydraulic cylinder, etc.) when the hydraulic oil temperature is at the reference temperature T _N. Assuming that the gain of the preview control and the delay time τ _R are tuned so that the riding comfort improvement effect becomes large, the frequency response characteristic of the hydraulic system shows that the viscosity change of the hydraulic oil changes when the hydraulic oil temperature changes. Changes as shown in FIG. That is, when the hydraulic oil temperature is high and the viscosity is large, the responsiveness is high, and when the hydraulic oil temperature is low, the responsiveness is deteriorated. Therefore, previously the frequency response characteristics of the hydraulic oil temperature change was measured, setting the correction coefficient α and β such that out the same control effect as well working oil temperature is varied from the reference temperature T _N is a reference temperature T _N To do.

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.
_{The VFR} is read, then the process proceeds to step S4, and the low frequency temperature detection value T from the low pass filters 47RL and 47RR is read.
Reading _L, and the then the process proceeds to step S5, a low-frequency detected temperature value T _L shown in FIG. 8 which is stored in advance in the storage device 44d based on the low frequency detected temperature value T _L and the control force correction coefficient α Of the low frequency temperature detection value T shown in FIG. 9 which is stored in advance in the storage device 44d as shown in FIG. _The delay time correction coefficient β is calculated with reference to the delay time correction map showing the relationship between _L 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.

As described above, when the hydraulic oil temperature T _L is constant at the reference temperature T _N in the running condition on a good road, the control force correction coefficient α calculated in step S5 in the process of FIG.
And the delay time correction coefficient β calculated in the process of step S6 becomes "1", and
The _preview control forces U _pRL and U _pRR calculated in step 8 directly become the corrected _preview control forces, and the correction delay time τ _S has a preset hydraulic system response delay time τ ₁ , controller calculation dead time τ ₂ and filter. It is set to the sum of the response delay time τ ₃ .

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, when the hydraulic oil temperature T _L is lower than the reference temperature T _N , such as when traveling in a low temperature region such as a cold region, this is detected by the temperature sensor 29, and these are detected via the low pass filter 47 by the microcomputer. 44
Since the control force correction coefficient α calculated in step S5 and the delay time correction coefficient β calculated in step S6 are set to values larger than “1” as shown in FIGS. 8 and 9, This together with the correction preview control force U _pRL and U _pRR calculated in step S9 the preview control force U _pRL and U _pRR greater value calculated in step S8, the delay time tau _R calculated in step S10 It becomes shorter than the neutral pressure _PCN state described above, and it is possible to compensate for the decrease in responsiveness of the hydraulic system due to the increase in viscosity due to the decrease in hydraulic oil temperature, and to generate an appropriate preview control force at the optimum time.

Similarly, a high temperature area on the tropical side of the subtropical zone in midsummer
Operating temperature T as when traveling in the region_LIs the reference temperature
If it is higher, the control force correction calculated in step S5
Coefficient α and delay time correction coefficient calculated in step S6
Both β are smaller than “1”, which enables preview control.
Force U_pRLAnd U_pRRAnd delay time τ _R
By increasing the
Compensate for the increase in hydraulic system
An appropriate preview control force can be generated at an appropriate 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 case where the low pass filter for extracting the low frequency component from the temperature detection value T _H of the temperature sensor 29 is composed of an analog circuit has been described, but the present invention is not limited to this. The microcomputer 44 may perform digital filter processing. Further, in the above embodiment, the temperature sensor 29
Although the case where the hydraulic oil temperature in the supply side pipe 21S is detected has been described above, the present invention is not limited to this, and the hydraulic oil temperature may be detected at any point from the hydraulic power source 22 to the hydraulic cylinders 18FL to 18RR. It ’s good.

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 temperature of the working fluid is detected by the temperature detecting means, and at least one of the preview control force and the delay time is detected based on the detected temperature value. Since it compensates for changes in the response characteristics of the control system caused by changes in the viscosity of the working fluid due to changes in the working fluid temperature, it is possible to generate an appropriate preview control force at the optimum time. The effect that the riding comfort improving effect can be exhibited 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 temperature detection value and a control force correction coefficient.

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

FIG. 10 is a characteristic diagram showing a frequency response characteristic due to a change in hydraulic oil temperature of a hydraulic control system, wherein (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 29 Temperature sensor 30 Controller

Front page continued (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 wheel to be controlled. Front road surface information detecting means for detecting road surface information further ahead, and a pressure command value for the pressure control valve calculated based on road surface information of the front road surface information detecting means is controlled to the road surface detected by the front road surface information detecting means. In a suspension control device comprising a control means for outputting to the pressure control valve at the time point when a delay time until the target wheel arrives, a temperature detection means for detecting the temperature of the working fluid,
A suspension control device comprising: a correction unit that corrects at least one of the pressure command value and the delay time according to a temperature detection value of the temperature detection unit.