JPH07186667A - Suspension controller - Google Patents

Abstract

PURPOSE:To realize the excellent estimation control by calculating the negative spring control moment on the basis of the pitch angle estimation value and correcting the estimation control force on the basis of the result of the calculation, in the constitution where a control objective wheel generates the estimation control force on the basis of the front road surface information. CONSTITUTION:A controller 30 calculates the differential value of the road surface displacement of a front wheel which correctly follows the road surface shape on the basis of the stroke detection value on the front wheel side and the vertical acceleration detection value at each prescribed sampling time, and calculates the control force for the estimation control which is generated on the hydraulic cylinders 18RL and 18RR on the rear wheel side on the basis of the above-described differential value. The control force for the estimation control is stored in succession through shift into a memory device 42d, together with the delay time between the front and rear wheels which is calculate on the basis of the vehicle speed V. The control force for the estimation control in the case where the delay time reaches zero is corrected according to the negative spring control moment which is calculated from the pitch angle obtained from the front and rear stroke detection values, and each pressure control valve 20FL-20RR is controlled by the corrected control force for estimation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects front road surface information indicating road surface displacement at a position in front of a wheel to be controlled, and based on this road surface information, a stroke of an actuator interposed between a vehicle body and a wheel to be controlled. The present invention relates to an improvement of the suspension control device for predictive control.

[0002]

2. Description of the Related Art As a conventional suspension control device for performing preview control, Japanese Patent Application Laid-open No. 60-
Some are disclosed in Japanese Patent No. 35618. In this conventional example, when vibration is input from the road surface to the front wheels and acceleration is detected on the vehicle body side, the control force in the same direction as the detected acceleration causes the actuator for the rear wheels to move after a lapse of time corresponding to the vehicle speed. There is disclosed a suspension device which prevents vibration input when rear wheels pass through a road surface on which front wheels have passed.

[0003]

However, in the conventional suspension control device, the road surface information is estimated from the front wheel position, and the rear wheel suspension is passed from the road surface based on the value delayed by the time corresponding to the vehicle speed. Because it was configured to generate a control force that cancels the force transmitted to the vehicle body,
Although vibration at the front wheel position cannot be suppressed, vibration at the rear wheel position is suppressed, and pitching in the frequency range of 1 to 3 Hz, which makes the occupant uncomfortable due to large pitch motion, is avoided. However, there is an unsolved problem of making passengers uncomfortable.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and suppresses the pitch motion during the preview control by performing the negative spring control against the pitch motion. It is an object of the present invention to provide a suspension control device capable of improving the riding comfort.

[0005]

In order to achieve the above object, a suspension control device according to the present invention is arranged at least between a rear wheel and a vehicle body, and a stroke between them can be controlled by a control signal. An actuator that generates a control force, a front road surface information detection unit that detects road surface information in front of the wheel, a vehicle speed detection unit that detects a vehicle speed, and the front road surface information of the front road surface information detection unit that is detected by the actuator as the vehicle speed. In a suspension control device including a control means for generating a preview control force calculated based on a value delayed in accordance with vehicle speed detection of the means, a relative displacement for detecting a relative displacement between front and rear wheels and a vehicle body. Detecting means, pitch angle estimating means for estimating a pitch angle based on the relative displacement detection value of the relative displacement detecting means, and pitch of the pitch angle estimating means Negative spring control moment calculation means for calculating a negative spring control moment against the pitch motion of the vehicle body based on the estimated value, and correction means for correcting the preview control force based on the calculation result of the negative spring control moment calculation means. It is characterized by having and.

[0006]

In the present invention, the pitch angle of the vehicle body is estimated from the relative displacement between the front and rear wheels and the vehicle body, and the negative spring control moment against this pitch movement is calculated by the negative spring control moment calculation means. The correction means corrects the preview control force calculated based on the front road surface information by adding a negative spring control moment to suppress the pitch motion that occurs when performing the preview control of the vehicle body.

[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 in which the present invention is applied to an active suspension that performs preview control using front road surface information. In the figure, 10 is a vehicle body side member, 11FL, 11FR. Front left wheel, front right wheel, 11RL,
Reference numeral 11RR indicates a rear left wheel and rear right wheel, and 12 indicates an active suspension.

The active suspension 12 is a hydraulic cylinder 1 as an actuator which 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 through 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 thereto.
And stroke sensors 27FL to 27RR arranged in parallel with the hydraulic cylinders 18FL to 18RR to detect relative displacement between the wheels 11FL to 11RR and the vehicle body, and the left and right front wheels 11FL,
Vertical acceleration sensors 28FL, 28 for individually detecting vertical accelerations of the vehicle body at positions corresponding to 11FR, respectively.
The front wheel side is actively controlled based on the FR and the detection values of the vertical acceleration sensors 28FL and 28FR, and the sensor 26,
The road surface condition that the front wheels have passed is estimated based on the detected values of 27FL to 27RR and 28FL, 28FR, and the output pressures of the rear wheel side pressure control valves 20RL and 20RR are individually predicted and controlled accordingly, and the preview control is performed. And a controller 30 that corrects the output pressures of the pressure control valves 20FL to 20RR of the front and rear wheels so as to suppress the pitch motion associated with the above.

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 sprung portion and the unsprung portion 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 housed 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 provided. 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 to 27RR 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 positive voltages corresponding to the deviations and have negative voltages corresponding to the deviations when the vehicle height becomes lower than the target vehicle height, are configured to be output.

As shown in FIG. 5, each of the vertical acceleration sensors 28FL and 28FR has a voltage of zero 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.
A / D that converts the stroke detection values S _{FL to} S _RR input from the stroke sensors 27 _FL to 27 _RR into digital values
Converters 41a to 41d and vertical acceleration sensor 28FL
And 28FR vertical acceleration detection value Z output from 28FR
A / D converters 41e and 41f for converting _GFL and Z _GFR into digital values, a vehicle speed detection value V of the vehicle speed sensor 26, and a microcomputer to which the A / D conversion outputs of the A / D converters 41a to 41f are input. 44 and pressure command values P _{FL to} P _RR output from this microcomputer 44 are supplied via D / A converters 45 _{FL to} 45 _RR , and these are supplied to drive currents i _{FL to} i for pressure control valves 20 _{FL to} 20 RR.
For example, control valve drive circuits 46FL to 46FR configured by a floating type constant voltage circuit for converting into _FR are provided.

Here, the number of microcomputers 44 is small.
Input interface circuit 44a, output interface
Case circuit 44b, arithmetic processing unit 44c, and storage unit 4
4d and executes the processing of FIG.
Pulling time T_SEach time (for example, 20 msec), the front wheel side
Trooke detection value S_FLAnd S_RRAnd vertical acceleration detection value Z_{GF L}
And Z_GRRFront wheels that accurately follow the road surface shape based on
Differential value x of road displacement of 11FL and 11FR_1FL'And x
_1FR′ Is calculated and based on this, the actuator on the rear wheel side is calculated.
Of the hydraulic cylinders 18RL and 18RR
Control force for viewing control U _RL, U_RRTo calculate this preview control
Power U_RLAnd U_RRBefore calculated based on the detected vehicle speed V
Delay time between rear wheels τ_RTogether with the memory device 44d
Sequentially shifts to the storage area corresponding to the predetermined number of shift registers.
Store while delaying, delay time τ_RShift about
Sampling time T_SStore while subtracting sequentially
Delay time τ_RControl force U for preview control when zero has reached zero_RL，
U_RRThe stroke detection value S before and after_FL~ S_RROn the basis of
A negative spring control model that calculates the pitch angle θ and resists pitch movement.
Calculation and generate this negative spring control moment.
Correction based on the control force, and
D / as the pressure command value for the force control valves 20FL to 20RR
Output to the A converters 45FL to 45RR.

Further, the storage device 44d stores a program necessary for the arithmetic processing of the arithmetic processing device 44c in advance, and the preview control control forces U _RL and U _RR are delayed for a predetermined sampling time T _S. A shift register area for storing a predetermined number while sequentially shifting with _R is formed, and further, the calculation result necessary in the calculation process of the calculation processing device 44c is sequentially stored.

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,
The process of FIG. 7 is started as a timer interrupt process every predetermined time (for example, 10 msec) when the ignition switch is turned on and the power of the controller 30 is turned on. First, in step S1, the vehicle speed detection value is detected. V,
Stroke detection value S _{FL to} S _RR and vertical acceleration detection value Z
_After reading _{GFL and} Z _GFR , the process proceeds to step S2.

In step S2, the vertical acceleration detection values Z _GFL and Z _GFR are integrated by performing low-pass filter processing at a cut-off frequency of 0.2 Hz, for example, to calculate vehicle vertical speeds Z _VFL and Z _VFR , Next, in step S3, the stroke detection values S _FL and S _FR on the front wheel side are differentiated by performing high-pass filtering at a cut-off frequency of 20 Hz, for example, to differentiate the relative speed S.
Calculate _VFL and S _VFR .

Next, in step S4, the vehicle body vertical speeds Z _VFL and Z _{VFR are changed} to the relative speeds S _VFL and S _VFR.
Is subtracted to calculate road surface estimated values x _0L ′ and x _0R ′, which are stored in the shift register area formed in a predetermined storage area of the storage device 44d while being sequentially shifted. x _0L ′ = Z _VFL −S _VFL ………… (1) x _0R ′ = Z _VFR −S _VFR ………… (2) Here, the stroke detection value S _FL output from the stroke sensors 27FL and 27FR and Since S _FR represents the relative displacement between the unsprung portion and the unsprung portion, it becomes a value obtained by adding the unsprung portion displacement and the unsprung portion displacement of the front wheels 11 _FL and 11 _FR , and the relative speed obtained by differentiating the stroke detection values S _FL and S _FR. Since S _VFL and S _VFR are also values obtained by adding the unsprung speed and the sprung speed respectively, the relative speed S _VFL is calculated from the vehicle body vertical speed Z _VFL and Z _GFR by integrating the vertical acceleration detection values Z _GFL and Z _GFR.
And S _VFR are subtracted from each other to cancel the sprung speeds Z _VFL and Z _GFR to obtain road surface estimated values x _0L ′ and x _0R ′ which are differential values of the true road surface displacement following the road surface displacement. .

Next, at step S5, the following equation (3) is calculated based on the detected vehicle speed V, and the front wheels 11
Calculate the delay time τ until the rear wheels 11RL and 11RR reach the road surface where FL and 11FR have passed. τ = (L / V) −τ _S (3) where L is the wheel base, τ _S is the control system delay time, and the hydraulic system response delay τ ₁ and the controller calculation dead time τ It is represented by the sum of ₂ and the phase delay τ ₃ due to the filter.

Then, the process proceeds to step S6, the shift register of the storage device 44d is referred to, and the step S6 is executed.
Road surface estimated value before delay time τ calculated in 5 x _0L ′ (t−τ)
And x _0R ′ (t−τ) are read out, and these are set as the current rear wheel road surface estimated values x _0L ′ (t) and x _0R ′ (t). Next, in step S7, the following equations (4) and (5) are calculated based on the read road surface estimated values x _0L ′ and x _0R ′, and the rear wheel pressure control valves 20RL and 20RR are calculated. The predictive control forces U _pRL and U _pRR for

U _pRL = − [C _p + {1 / (ω ₁ + s)} K _p ] x _0L ′ ... (4) U _pRR = − [C _p + {1 / (ω ₁ + s)} K _p ] x _0R ′ (5) where C _p is the damping force control gain, K _p is the spring force control gain, and ω ₁ is the cutoff frequency f _C of the low pass filter for control multiplied by 2π. The time constant is C _p ≦ for the damping constant C and the spring constant K of the actual suspension.
C, K _p ≦ K, 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. Are arranged in parallel, a sprung mass M is arranged above them, and an external force F is applied to the sprung mass M.
Can be considered as a one-degree-of-freedom model in which
In FIG. 8, X ₀ is road surface displacement and X is 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, X = a _{(Cs + K) X 0 /} (Ms 2 + Cs + K) -F / (Ms 2 + Cs + K) + U / (Ms 2 + Cs + K) ...... (7) Become.

For example, in the equation (4), x _0L ′ =
Since sx _0L , this formula (4) is _expressed by ω ₁ = 0 and C _p =
Substituting into equation (7) with C and K _p = K, we obtain (7)
Expression, X = (Cs + K) (X 0 -x 0L) / (Ms 2 + Cs + K) - F / (Ms 2 + Cs + K) ......... becomes (8). The estimation accuracy of the road surface estimated values x _0L ′ and x _0R ′ in the equation (8) is sufficiently high as described above, and (X ₀ −x _0L ) _≈0
Therefore, the equation (8) becomes X≈−F / (Ms ² + Cs + K) ... (9), and the influence of the road surface unevenness is hardly transmitted to the vehicle body,
A good riding comfort can be obtained.

Next, the process proceeds to step S8 and the following (10) is performed based on the front, rear, left and right stroke detection values S _{FL to} S _RR.
The pitch angle θ is calculated by calculating the formula. θ = {(S _FL + S _FR ) / 2− (S _RL + S _RR ) / 2} / (L _F + L _R ) ... (10) Next, the process proceeds to step S9 and the calculated pitch angle θ
Is low-pass filtered and the unsprung resonance frequency (10H
z)) or more components are cut, and then step S1
Before and after shifting to 0, the negative spring control moment against the pitch motion is generated by performing the calculation of the following formulas (11) and (12) based on the pitch angle θ that cuts the component above the unsprung resonance frequency. Front wheel side correction control forces U _AFL, U _AFR and rear wheel side correction control forces U for the wheel hydraulic cylinders 18FL to 18RR
Calculate _{ARL and} U _ARR .

U _AFL = U _AFR = K _N · f (θ) / 2 (L _F + L _R ) ... (11) U _ARL = U _ARR = −K _N · f (θ) / 2 (L _F + L _R ) ... (12) Here, K _N is a control gain, and f (θ) is a low-pass filtered pitch angle. As described above, by calculating the control forces U _{AFL to} U _ARR that generate the negative spring control moment against the pitch motion based on the formulas (11) and (12), the damping force of the pitch motion remains unchanged and the spring Only the constant can be reduced.

[0028] That is, the motion equation in the pitch _{direction, Iθ "+2 (C F L} F + C R L R) θ '+ 2 (K F L F + K R L R) θ + {- (U AFL + U AFR) L F + (U _ARL + U _ARR ) _LR } = 0 ... (13) where θ ″ is the pitch angular acceleration, K
The _F and K _R on the front wheel side and rear wheel side coil spring 36
Is the spring constant of.

Here, assuming that pitch negative spring control is performed, and the negative spring coefficient is K _N ,-(U _AFL + U _AFR ) L _F + (U _ARL + U _ARR ) L _R = -K _N θ (14 ), The equation of motion of the equation (13) is: Iθ ″ +2 (C _F L _F + C _R L _R ) θ ′ + {2 (K _F L _F + K _R L _R ) −K _N } θ = 0 (15) Comparing this equation (15) with the above equation (13), the damping force of the second term on the left side does not change at all,
Only the spring constant of the third term on the left-hand side is decreased by the negative spring coefficient K _N , and the pitch resonance frequency is lowered, resulting in a slow pitch motion, so that the occupant's discomfort can be alleviated.

In practice, in order to eliminate the adverse effect of unsprung vibration, a low pass filter cuts off components above the unsprung resonance frequency with respect to the pitch angle θ.
Expression - is represented by _{(U AFL + U AFR) L} F + (U ARL + U ARR) L R = -K N f (θ) ...... (16).

In order for the pitch control forces U _{AFL to} U _ARR to act as negative springs in the pitch direction without affecting bounce and roll, it is necessary to satisfy the following conditions. Conditions for zero influence on bounce U _AFL + U _AFR + U _ARL + U _ARR = 0 ... (17) Conditions for zero influence on roll U _AFL = U _AFR , U _ARL = U _ARR ...... (18) ) From these equations (16) to (18), the front wheel side control forces _{UAFL, UAFR} and the rear wheel side control forces _{UARL, UARR} for the pitch motion represented by the above equations (11) and (12) are _calculated . Obtainable.

Next, in step S11, the following equations (19) to (22) are calculated to calculate the pressure command values P _{FL to} P _RR for the hydraulic cylinders 18FL to 18RR, and then to step S12. The pressure command values P _{FL to} P _RR calculated after the shift are output to the D / A converters 44 _FL to 44 _RR, and then the timer interrupt process is ended and the process returns to the predetermined main program.

[0033] _{P FL = U N + U AFL} ............ (19) P FR = U N + U AFR ............ (20) P RL = U N + U pRL + U ARL ............ (21) P RR = _{U N + U pRR + U ARR} ............ (22) , where the U _N control force necessary to maintain the vehicle height to the target vehicle height, K _B is a bounce control gain.

In the process of FIG. 7, steps S1 to S1
The process of S4 corresponds to the front road surface information detecting means,
The processing in S5 to S7 corresponds to the control means, and in step S8
The process corresponds to the pitch angle estimating means, and the process of step S10 is performed.
Is a step corresponding to the negative spring control moment calculation means.
The process of S11 corresponds to the correction means. Therefore,
Now, keep the target vehicle height on a good road where the vehicle is flat and run straight at a constant speed
I'm going. In this state, the vehicle is flat and
Since the target vehicle height is maintained on the road,
Stroke sensor 27FL-27RR stroke detection value
S _FL~ S_RRIs approximately zero, and the vehicle body side member 10
Since no rocking occurs, the vertical acceleration sensor 2 on the front wheel side
Acceleration detection value Z of 8FL and 28RR_GFLAnd Z_GFRIs almost zero
Has become. Therefore, the vehicle body vertical speed Z_VFL,Z_VFROver
And relative speed S_VFL,S _VFRAlso becomes approximately zero, so step S
Road surface estimated value x calculated in 4_0L'And x_0R'Is almost zero
It In this way, in the state of continuing to run on a flat and good road
Is stored in the shift register area of the storage device 42d.
Road surface estimated value x_0L′ (T) and x_0R′ (T) continues to be zero
Since the delay time τ calculated in step S6
Road surface estimated value x_0L′ (T−τ) and x_0R′ (T−τ) is also zero
And the rear wheel preview control force calculated in step S7.
U_pRLAnd U_pRRIs also zero.

On the other hand, since the vehicle body does not swing, the pitch angle θ
Is also substantially zero, and the pitch angular velocity θ'is also substantially zero, so that the front wheel side and rear wheel side correction control forces U _{AFL to} U _ARR are also zero, so the pressure command values P _{FL to} P calculated in step S11. _RR
Is a value corresponding only to the neutral pressure control force U _N , and these are the output side interface circuit 42b and the D / A converter 4
It is output to the control valve drive circuits 44FL to 44RR via 3FL to 43RR.

[0036] 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 44FL~44RR supplied to the pressure control valve 20FL~20RR of the front wheel side. As a result, the neutral pressures P _CNF and P _CNR required to maintain the target vehicle height from the pressure control valves 20FL to 20RR are the front and rear wheel hydraulic cylinders 18FL, 18FR and 18RL,
Output to 18RR, these hydraulic cylinders 18FL to 18RR
Thus, 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.

In this straight road running state, for example, the front left and right wheels
11FL and 11FR simultaneously step up the road surface
It will be in a state of passing through the so-called ramp step road that is made up of steps
And front wheels 11FL and 1
1FR bounces, which causes the front wheel side stroke
Stroke detection value S of sensors 27FL and 27FR_FLAnd S _FR
Rapidly increases in the negative direction from zero, and the
Directional acceleration is generated, and the vertical acceleration
Acceleration detection value Z of 28FL and 28FR_GFLAnd Z_GFRBut
Increase in the positive direction.

Then, the vertical acceleration detection value Z_GFLAnd Z
_GFRVertical velocity Z that integrates_VFLAnd Z_VFRFrom strike
Roke detection value S_FLAnd S_FRRelative speed S_VFLOver
And S_{VF R}Accurately corresponded to the differential value of the road displacement by subtracting
Road surface estimated value x_0L'And x_0R′ Is calculated. At the same time
The front wheels 11FL and 11FR based on the detected vehicle speed V.
Delay until the rear wheels 11RL and 11RR reach the surpassed road surface
Time τ is calculated, and the road surface estimation value before this delay time τ
x_OL'And x_0R′ Is read from the shift register area. This
At the time of, the previous time stored in the shift register area
Road surface estimated value x_0L'And x_0R′ Is zero, so
Preview control force U for the rear wheels calculated in step S7
_pFLAnd U_pFRMaintains zero condition, but front wheels 11FL and
And the stroke sensors 27FL and 27FL at the 11FR position
Stroke detection value S_FLAnd S_FRIs increasing in the negative direction
Therefore, the pitch angle θ calculated in step S8 becomes negative.
Is generated, which causes the front wheel side correction control force U_AFLAnd U
_AFRIncreases in the negative direction, and the rear wheel side correction control force U _ARLAnd U
_ARRIncreases in the positive direction.

Therefore, it is calculated in step S11.
Front wheel side pressure command value P_FL, P_FRIs the neutral pressure control force U_NThan
Decrease, on the contrary, rear wheel side pressure command value P_RL,P_RRIs neutral pressure control
Force U _NIt will increase more and accordingly, the front wheel side
Of the hydraulic cylinders 18FL and 18FR of the neutral pressure P_NYo
Adjustment control force U_AFLAnd U_AFRThe oil pressure on the rear wheel side
Cylinder 18RL and 18RR pressure is neutral pressure P_NMore correction
Control force U_ARLAnd U_{AR R}Increase the pitch movement of the car body
It is possible to generate a control force against.

After that, the front wheels 11FL and 11FR are ramped.
After passing the Tep road, the front wheels 11FL and 11FR again
Is the neutral control force U for maintaining the target vehicle height_NReturn to
However, for the rear wheels 11RL and 11RR, step S5
At the time when the delay time τ calculated in step 0 becomes zero, that is, the rear wheels 11RL and
And 11RR pass the ramp step road,
Road surface when front wheels 11FL and 11FR climb up a step in S6
Estimated value x_0FL'And x _0FR'Is read out and based on these
And foreseeing the rear wheels according to equations (4) and (5)
Power U_pRLAnd U_pRRIs calculated, so
As expressed by the formula (9), the influence of the road surface unevenness is exerted on the vehicle body.
It is possible to secure a good ride comfort without being transmitted to
Wear.

At the same time, the stroke detection values S _RL and S _RR on the rear wheel side are reduced due to the step-up of the rear wheels 11 _RL and 11 _RR, so that the pitch angle θ calculated in step S8 becomes a positive value and the low-pass filter. The correction control forces U _AFL and U _AFR on the front wheel side, which are calculated based on the pitch angle θ obtained by cutting the frequency components above the unsprung resonance frequency by the processing, also increase in the positive direction, and conversely the correction control forces U on the rear wheel side.
_ARL and U _ARR increase in the negative direction, and accordingly, the pressure of the hydraulic cylinders 18FL and 18FR on the front wheel side increases from the neutral pressure P _N by the correction control force U _AFL and U _AFR ,
The pressures of the hydraulic cylinders 18RL and 18RR on the rear wheel side are reduced by the correction control forces U _ARL and U _ARR, and a control force against pitch movement can be generated without affecting bounce and roll of the vehicle body.

That is, when the control of the present embodiment is performed, the bounce gain characteristic with respect to frequency is shown by the chain line in the case of performing normal preview control, as shown by the characteristic curve L _B1 shown by the solid line in FIG. As in the case of only the normal preview control shown by the characteristic curve L _B2 , the gain of the sprung resonance frequency (about 1 to 2 Hz) is lowered as compared with the case where the preview control shown by the dotted curve characteristic curve L _B3 is not performed. A good ride comfort can be maintained, and the pitch gain characteristic with respect to the frequency can be obtained only by the normal preview control shown by the characteristic curve L _P2 shown by the one-dot chain line, as shown by the characteristic curve L _P1 shown by the solid line in FIG. Compared with the case and the case where the preview control indicated by the characteristic curve L _P3 shown by the dotted line is not performed, the pitch resonance frequency can be lowered, which causes an occupant discomfort.
Since the gain at Hz decreases, it is possible to secure a good riding comfort.

By the way, the above equations (4) and (5) are
At ω₁Predictive control force U when = 0_pRLAnd U_pRRCalculate
Then, the preview control force U_pRLAnd U_pRRRoad surface displacement (wheel change
X)_0FLAnd x_0FRSteady-state gain for
Gain) is K, so there is no temporary unevenness.
There is no problem, but like the ramp step road mentioned above
Road displacement X_0FL(≒ x_0FL) And X_0FR(≒ x_0FR)But
When driving on a road surface that changes and does not return,
Predictive control power U even on rough roads_pRLAnd U_pRRIs “0”
Without predicting control power U_pRLAnd U_pRRAnd suspension
The stroke is kept as long as the spring constant K of
Therefore, the initial value of the vehicle height can
Then, (X₀-X₀) -H = U / K ≠ 0
Becomes Therefore, after driving on such a road surface,
In order to make the vehicle height return to the original level when it appears on a flat road surface
Is the preview control force U_pRLAnd U_pRRWheel vertical speed estimation
Value x ₀So that the steady gain for is 0
In equations (4) and (5), ω₁> 0 should be selected.

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 uneven surface such as irregular road surface is 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.

As described above, according to the above embodiment, the front road surface information detecting means can be applied to the stroke sensors 27FL and 27FR at the front wheels 11FL and 11FR and the vertical acceleration sensors 28FL and 28FR, which are currently in practical use. Since it is possible to use the one that is mounted on the active suspension that has been commercialized, there is an advantage that it is not necessary to newly develop or add a sensor.

In the above embodiment, the case where the active suspension 12 is also provided on the front wheel side has been described, but this may be omitted. In this case, since the control forces U _AFL and U _AFR on the front wheel side for the pitch movement cannot be generated, the bounce is affected but the roll is not affected. , (U _ARL + U _ARR ) L _R = -Kθ
In addition, on the condition that U _ARL = U _ARR , the correction control forces U _ARL and U _ARR for performing negative spring control are _expressed as U _ARL = U _ARR = −K _N
It may be changed to θ / 2L _R.

In the above embodiment, the pitch angle θ
The case where the front and rear wheels are calculated using the average value of the left and right stroke sensors 27FL to 27RR has been described. However, the present invention is not limited to this, and the detection values S _FL, S _RL or S _FR of the front and rear stroke sensors on the left or right side of the vehicle are calculated. _, S _RR may be calculated as follows, in which case the stroke sensor of the rear wheel not used for the calculation can be omitted.

Θ = (S _FL −S _RL ) / (L _F + L _R ) θ = (S _FR −S _RR ) / (L _F + L _R ) Further, in the above embodiment, the active suspension is applied as the actuator. However, the present invention is not limited to this, and a suspension that controls the damping force or spring constant according to the road surface condition by applying a damping force variable shock absorber or air suspension that can change the damping force. It goes without saying that it can also be applied to a control device.

Furthermore, in the above embodiment, the case where the arithmetic processing unit 42c calculates the road surface estimated values x _0FL ′ and x _0FR ′ has been described, but the present invention is not limited to this, and the stroke detection value S _FL is not limited to this. , S _FR and vertical accelerations Z _GFL and Z _GFR of the vehicle body may be differentiated and integrated by a high-pass filter and a low-pass filter, respectively, and then subtracted by a subtractor.

In each of the above embodiments, the micro
On the computer 42, the road surface estimated value x _0FL'And x_0FR′
Are stored in the shift register area while being sequentially shifted.
Although I explained about the case where it was done, it is not limited to this
Estimated value x_0FL'And x_0FRPredictive control force U based on
_pRL, U_pRRIs calculated, and this preview control force U_pRL, U_{pR R}
Are stored in the shift register area while being sequentially shifted.
You may ask.

Further, in the above embodiment, the case where the preview control is performed only on the rear wheel side has been described. However, if the ultrasonic range finder is arranged in front of the front wheel to detect the road surface condition, for example. The same preview control as that on the rear wheel side can be performed on the front wheel side. Furthermore, in each of the above embodiments, the pressure control valves 20FL to 20FL ...
Although the case where 20 RR is applied has been described, the present invention is not limited to this and other flow control servo valves and the like can be applied.

Further, in the above embodiment, the case where the controller 30 is constituted by the microcomputer 42 has been described, but the invention is not limited to this, and it may be constituted by combining electronic circuits such as a shift register and an arithmetic circuit. Needless to say, it is okay. 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.

Furthermore, in the above embodiment, the case where the active suspension is applied as the actuator has been described, but the present invention is not limited to this.
Any actuator can be applied as long as it has a configuration capable of changing the damping characteristics and spring characteristics of a suspension such as a variable damping force type shock absorber.

[0054]

As described above, according to the suspension control device of the present invention, the road surface information in front of the control target wheel is detected by the front road surface information detecting means, and based on this, preview control is performed on the control target wheel. In a suspension control device for generating a force, a pitch angle estimating means estimates a pitch angle, a negative spring control moment calculating means calculates a negative spring control moment based on the estimated pitch angle value, and a correction is made based on the calculation result. Since the preview control force is corrected by the means, it is possible to perform negative spring control against the pitch motion generated in the vehicle body, lower the resonance frequency of the pitch motion, and suppress the slow pitch motion. Yes, without giving the occupant discomfort due to pitch movement,
An effect that good preview control can be performed is obtained.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing a schematic configuration 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 an explanatory diagram showing a one-wheel one-degree-of-freedom model.

FIG. 9 is a characteristic diagram showing a bounce gain.

FIG. 10 is a characteristic diagram showing a pitch gain.

[Explanation of symbols]

 10 Body side member 11FL-11RR Wheel 14 Wheel side member 18FL-18RR Hydraulic cylinder 20FL-20RR Pressure control valve 26 Vehicle speed sensor 27FL-27RR Stroke sensor 28FL, 28FR Vertical acceleration sensor 30 Controller

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

Claims (1)

[Claims] 1. An actuator, which is arranged at least between a rear wheel and a vehicle body, generates a control force capable of controlling a stroke between them by a control signal, and front road surface information for detecting road surface information in front of the wheel. Detecting means, vehicle speed detecting means for detecting vehicle speed, and the actuator with a preview control force calculated based on a value obtained by delaying the front road surface information of the front road surface information detecting means in accordance with the vehicle speed detection of the vehicle speed detecting means. In a suspension control device having control means for generating the relative displacement detection means for detecting relative displacement between front and rear wheels and a vehicle body, and estimating a pitch angle based on a relative displacement detection value of the relative displacement detection means. And a negative spring control for calculating a negative spring control moment against the pitch motion of the vehicle body based on the pitch angle estimation value of the pitch angle estimating means. A suspension control device comprising: a moment calculation means; and a correction means for correcting the preview control force based on a calculation result of the negative spring control moment calculation means.