JPH07300008A - Suspension control device - Google Patents

Abstract

PURPOSE:To suppress deterioration of comfortableness caused by a phase delay of control. CONSTITUTION:A control pressure Ppuj, which is a control amount based on an attitude change and vertical acceleration, is calculated from a displacement feedback control amount Pxj reflecting the attitude change of roll or the like and from a feedback control amount Pzj reflecting the vertical acceleration (step S345). Thereafter, a bottom frequency fT in a vertical vibration condition (vertical acceleration) of a car body, changed in accordance with a car speed V, is used to serve as a shield frequency of a high frequency component, to perform filtering (step S347), and the control pressure Ppuj is set to a new control amount FPpuj shielding the high frequency component exceeding the bottom frequency 5T. Further, the bottom frequency fT serving as the shield frequency of the high frequency component is changed at each time in accordance with the car speed V (step S346), and the shield frequency fT is conformed to a springing vibration condition changed in accordance with the car speed V.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control device for controlling the attitude of a vehicle through an actuator that suspends the vehicle body.

[0002]

2. Description of the Related Art In a suspension control device of this type, for example, in a fluid pressure type active suspension using a fluid pressure actuator as an actuator interposed between a vehicle body and a wheel to suspend the vehicle body, the operation to the fluid pressure actuator is performed. Suspending conditions such as vehicle height and supporting load can be adjusted by supplying and discharging fluid. Utilizing this, various technologies have been proposed for controlling the attitude of the vehicle, controlling the vehicle height, or ensuring the steering stability. For example, Japanese Patent Laid-Open No. 2-
In 17504, a technique is proposed in which the working fluid is supplied and discharged with a control amount according to the running state amount of the vehicle such as lateral acceleration acting on the vehicle body when the vehicle turns. Then, by controlling in this way, the internal pressure of the fluid pressure actuator is increased or decreased according to the variation of the ground load of each wheel due to the load movement of the vehicle body, etc. Steering stability is achieved.

[0003]

However, the suspension control device proposed in the above publication has the following problems due to the limit of the responsiveness of the devices and the like that compose the system.

The traveling state quantity such as lateral acceleration fluctuates due to the influence of the vehicle body itself such as the steering angle of the steering wheel and the steering angular velocity, as well as the state of the unevenness of the road surface and the coefficient of friction as a disturbance input to the vehicle body. To do. Therefore, when these disturbance inputs fluctuate, the running state amount also follows the changes, and the working fluid is supplied to and discharged from the fluid pressure actuator with a control amount according to the thus varying running state amount. Therefore, if the fluctuation of the disturbance input becomes a high frequency fluctuation that exceeds the limit of the system responsiveness, the fluctuation of the running state quantity, and consequently the fluctuation of the control quantity, becomes a high frequency fluctuation. May occur, and the ride comfort may worsen despite the posture control.

As a method of solving such a problem, for example, a gain such as a vehicle height feedback control gain may be set low, or a low pass filter may be provided so as to remove high frequency components of the control amount. But,
In the former method, vibration of the vehicle body on the spring (vertical direction)
In the low frequency region around 1 Hz, the tilt of sprung mass resonance deteriorates, which causes an increase in posture change speed. Therefore, although the ride comfort in the high frequency region can be improved, the ride comfort in the low frequency region cannot be effectively improved. On the other hand, although the latter method can improve the riding comfort in the low frequency region, it has the following problems. That is, since the vibration state on the spring changes according to the vehicle speed, at a certain vehicle speed, the vertical acceleration on the spring due to the vibration becomes relatively high in the vicinity of the cutoff frequency region of the low pass filter due to the phase delay of the control. Sometimes
The ride quality may deteriorate.

The present invention has been made to solve the above problems, and an object thereof is to improve the riding comfort.

[0007]

In order to achieve the above object, the means adopted by the suspension control device of the present invention is interposed between the vehicle body and the wheels, and is adapted to the vehicle according to a control amount commanded from the outside. Suspension control including an actuator for adjusting the suspension condition of the vehicle and a control unit for instructing the vehicle attitude by instructing a control amount to the actuator on the side where a change in the vehicle attitude that occurs depending on the running state of the vehicle is reduced. An apparatus, comprising: a running state detecting means for detecting a running state of the vehicle; and a speed detecting means for detecting a speed of the vehicle, wherein the control means detects the control amount by the running state detecting means. A calculation unit that calculates according to the traveling state, a control unit that commands the actuator to perform the calculated control amount, and a traveling state amount of the traveling state detected by the traveling state detection means. Is a frequency component for inputting at least one of the calculation control amounts calculated by the calculation unit and outputting the input running state amount or calculation control amount by shielding or attenuating a high frequency component exceeding a predetermined frequency of the input signal. And a limiting frequency changing unit that changes the predetermined frequency in the limiting processing unit according to the vehicle speed detected by the speed detecting unit, and the control unit has the limiting process. So that the section outputs the running state quantity subjected to the frequency component limiting processing to the computing section in preference to the running state detected by the running state detecting means. The gist is to provide the control unit with priority over the control amount calculated by the calculation unit to output to the control unit.

[0008]

In the suspension control device of the present invention having the above-mentioned structure, the control means instructs the control amount to be instructed to the actuator to the side where the change in the posture of the vehicle which occurs according to the running state is reduced. Then, the suspension state is adjusted by the actuator that receives the command of the control amount so that the change in the attitude of the vehicle is reduced, and the attitude of the vehicle is controlled.

At this time, the control amount instructed to the actuator is obtained as follows, and the obtained control amount is instructed by the control unit of the control means. When the limiting processing unit of the control means inputs the running state quantity of the running state detected by the running state detecting means and applies the running state quantity to the frequency component limiting processing, the high frequency exceeding the predetermined frequency by the frequency component limiting processing. The running state quantity in which the frequency component is shielded or attenuated is output in priority to the calculation unit. That is, the control amount commanded to the actuator is calculated by the calculation unit according to the running state amount that has undergone the frequency component limiting process of the limit processing unit. Therefore, since the running state quantity for calculating the control amount is the high frequency component exceeding the predetermined frequency is shielded or attenuated, the high frequency component exceeding the predetermined frequency is also shielded or attenuated. It has been done. Therefore, the riding comfort in the low frequency region where the vibration of the vehicle body (on the spring) is low is improved.

On the other hand, when the limiting processing unit of the control means inputs the arithmetic control amount calculated by the arithmetic unit and performs the frequency component limiting process on the arithmetic control amount, the high frequency exceeding the predetermined frequency by the frequency component limiting process. The calculation control amount in which the frequency component is shielded or attenuated is output in priority to the control unit. In other words, the control amount commanded to the actuator in this case is
After being calculated by the calculation unit of the control means according to the traveling state, the high frequency component exceeding the predetermined frequency is shielded or attenuated by the frequency component restriction process of the restriction processing unit. Therefore, the riding comfort in the low frequency region where the vibration of the vehicle body (on the spring) is low is improved.

Further, in any of the above-mentioned cases, since the predetermined frequency when the limiting processing unit carries out the frequency component limiting processing is changed by the limiting frequency changing unit according to the vehicle speed detected by the speed detecting means, this It is possible to adapt the changed predetermined frequency to the vibration condition on the spring that changes according to the vehicle speed.

[0012] Therefore, the predetermined frequency for the frequency component restriction processing by the restriction processing unit is set to the specific frequency (the vertical acceleration is small and the dynamic performance of the vehicle is determined by the restriction frequency changing unit, which is obtained from the analysis of the vibration behavior on the spring. Frequency with less influence). Therefore, it is possible to suppress the increase in vertical acceleration due to the control phase delay regardless of the vehicle speed and improve the riding comfort.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a suspension control device according to the present invention will be described below with reference to the drawings by taking a fluid pressure type active suspension using a fluid pressure actuator as an example. Prior to detailed description of the suspension control device of the embodiment, the basic concept of the embodiment will be described in advance.

In a vehicle body attitude control device typified by a suspension control device, a response delay of an actuator, a delay in electrical control, and the like always occur, and a response delay of these systems inevitably occurs. In particular, when the control amount (actuator control instruction signal, instruction control value) fluctuates at a high frequency, it becomes difficult to follow the actuator operation without delay with respect to the control amount change.

On the other hand, the control amount (instruction signal to the actuator, instruction control amount) in this type of device is determined according to the running state amount such as lateral acceleration. This running state quantity includes a parameter such as steering angle and steering angular velocity that is caused by the vehicle body itself, and a disturbance input that is input to the wheels as a representative of the unevenness of the road surface. The frequency of this disturbance input is a high frequency. Is also included.

Therefore, depending on the running condition, the frequency of the disturbance input becomes high, and as a result, the control amount also fluctuates at a high frequency, so that the response delay of the system or the actuator occurs. As a result, the phase of the actual control result (actual control value) having the response delay becomes significantly different from the phase of the control amount (instruction signal to the actuator, instruction control value, target control value). (When the phase difference becomes large), for example, although the target control value (target hydraulic pressure of the actuator) is originally desired to be increased, the actual control value may be decreasing. Therefore, if the actuator is simply controlled according to the traveling state without any benefit, the riding comfort may be worsened.

Therefore, if the control value equal to or higher than the predetermined frequency (cutoff frequency) is cut off or attenuated by the filter (limitation processing section), the above-mentioned problem can be avoided. However, when the cutoff frequency is constant, there is no problem at a predetermined vehicle speed, but at different vehicle speeds, a problem (deterioration of riding comfort) due to the following phenomenon occurs.

First, as a first phenomenon, when a vehicle having front wheels and rear wheels is running, the disturbance input to the front wheels always comes after a predetermined time (that is, after a delay of the vehicle wheel base). Since it is also input to the wheels, the frequency at which the vertical vibration (vehicle center of gravity position vibration) becomes a peak (peak) and the frequency at which it becomes a trough always appear regardless of the presence or absence of attitude control, depending on the vehicle speed. (See FIG. 15). Also, the second
The phenomenon (1) includes the inevitable characteristic of the filter itself near the cutoff frequency. More specifically, the filter limits the amplitude of the input signal and outputs it, and at the same time delays the phase of the output signal with respect to the input signal. For example, a low-pass filter of a temporary delay system limits the amplitude of the output signal to 70% with respect to the input signal and cuts the phase of the output signal to 45% in the vicinity of the cut frequency.
゜ Delay. Therefore, due to the unavoidable characteristics of the filter, a phase difference becomes noticeable between the target control value (or the running state amount) that is the input to the filter and the actual control value that is the output of the filter. It means that the riding comfort is deteriorated. Then, these two phenomena synergistically cause deterioration of riding comfort.

For example, in a vehicle having a mountain frequency of 10 Hz when the vehicle speed is 100 km / h and a mountain frequency of 5 Hz when the vehicle speed is 50 km / h, the cutoff frequency is 5 H.
When the vehicle speed is fixed at z, there is no problem that the riding comfort is deteriorated when the vehicle speed is 100 km / h, but the riding comfort may be deteriorated when the vehicle speed is 50 km / h. In other words, deterioration of the vibration characteristics that the vehicle originally has (peak of the center of gravity position frequency of the vehicle)
And the deterioration of the riding comfort caused by the phase delay of the control (of the filter) synergize with each other to further deteriorate the riding comfort.

Therefore, in the embodiments described below, the cut-off frequency is made to coincide with a good frequency of the vibration characteristic of the vehicle itself which is determined by the vehicle speed (frequency at which the trough of the vibration of the center of gravity of the vehicle is taken). Is suppressed, and even if there is a factor that deteriorates the riding comfort due to the control, the deterioration of the riding comfort is minimized as a result. The cutoff frequency should be as large as possible within the frequency range that the control system can follow.

Next, a fluid pressure type active suspension according to an embodiment will be described with reference to the drawings. Figure 1
FIG. 1 is a schematic configuration diagram showing a fluid circuit of a fluid pressure type active suspension 10 of an embodiment. As illustrated, the fluid pressure active suspension 10 includes a reservoir 11 that stores oil as a working fluid, and one end of a connection passage 12 and one end of a working fluid discharge passage 14 are connected to the reservoir 11. The other end of the connection passage 12 is connected to the suction side of a pump 18 driven by the engine 16. The pump 18 is a variable displacement pump in the illustrated embodiment, and one end of a working fluid supply passage 20 is connected to the discharge side thereof. The other end of the working fluid supply passage 20 and the other end of the working fluid discharge passage 14 respectively communicate with the P port and the R port of a pilot operated three-port three-position switching type switching control valve 24 that constitutes the pressure control valve 22. It is connected. In the middle of each working fluid discharge passage 14, the check valve 1 is located closer to the pressure control valve 22 than the communication connection portion 14a where the working fluid discharge passages for other wheels join.
5 are provided. Therefore, the working fluid discharge passage 14
In the above, the check valve 15 allows only the flow of the working fluid from the pressure control valve 22 to the reservoir 11.

The pressure control valve 22 includes a switching control valve 24, a branch passage 26 that branches from the working fluid supply passage 20 to reach the reservoir 11, and a fixed throttle 2 provided in the middle of the passage.
8 and a variable throttle 30 that changes the effective passage cross-sectional area of the branch passage 26 by a built-in solenoid. The variable throttle 30 of the pressure control valve 22 is connected to an electronic control unit 100, which will be described later, and when the electronic control unit 100 controls the current to the solenoid, it cooperates with the fixed throttle 28 and is variable with the fixed throttle 28. Branch passage 26 to the throttle 30
The internal pressure Pp is changed. A connection passage 32 leading to an actuator 36 that is interposed between the vehicle body and the wheels and suspends the vehicle body is connected to the A port of the switching control valve 24. The switching control valve 24 of the pressure control valve 22 is a spool valve that takes in the pressure Pp as a pilot pressure through the fixed throttle 28 and the variable throttle 30 and the pressure Pa in the connection passage 32 through the throttle 34 of the passage. Yes, pressure Pp and pressure P
The direction of the oil flow is switched according to the balance with a, and the oil is supplied to and discharged from the actuator 36.

The other end of the connection passage 32 is communicatively connected to a working fluid chamber 38 of an actuator 36 provided corresponding to the wheel. As shown in the figure, the actuator 36 is a kind of cylinder piston device, is arranged between the suspension member supporting the wheels Wh and the vehicle body to suspend the vehicle body, and the working fluid is supplied to and discharged from the working fluid chamber 38. As a result, the vehicle height of the corresponding portion is increased or decreased as follows.

Generally, the variable diaphragm 30 is the electronic control unit 100.
The solenoid is controlled to change the effective passage area of the branch passage 26. If the pressure Pp in the branch passage 26 and the pressure Pa in the connection passage 32 are equal when the effective passage cross-sectional area of the branch passage 26 has a certain value, the switching control valve 2
4 has a switching position 24b that shuts off communication with all ports.

When the variable throttle 30 is controlled by the electronic control unit 100 so that the pressure Pp becomes low, the pressure P
Since a becomes higher than the pressure Pp, the switching control valve 24 switches to the switching position 24c that connects and connects the port R and the port A, and keeps this position until the pressure Pa and the pressure Pp become equal. Therefore, the working fluid chamber 3 of the actuator 36
Oil is discharged from No. 8, and the vehicle height is lowered by the actuator 36. On the other hand, when the variable throttle 30 is controlled to increase the pressure Pp, the pressure Pa becomes lower than the pressure Pp, so that the switching control valve 24 switches to the switching position 24a that connects the port P and the port A to each other, and the pressure is reduced. This position is maintained until Pa and the pressure Pp become equal. Therefore, oil is supplied from the pump 18 to the working fluid chamber 38 of the actuator 36, and the vehicle height is increased by the actuator 36.

A gas-liquid spring device 42 is connected to the working fluid chamber 38 by a passage 40, and a throttle 44 is provided in the passage 40. The gas-liquid spring device 42 acts as a suspension spring or an auxiliary suspension spring, and the throttle 44 generates a damping force. A vehicle height sensor 118 that detects the vehicle height of the vehicle body is provided between the suspension member that supports the wheels Wh and the vehicle body.

A pilot operated shutoff valve 46 is provided in the middle of the connection passage 32.
6 takes in pilot pressure Pc controlled by a pilot pressure control device 48 described later. And shutoff valve 4
No. 6 opens when the pilot pressure Pc exceeds a valve opening predetermined value, and closes when the pilot pressure falls below a valve closing predetermined value. A pilot pressure control device 48 is provided in a connection passage 50 that connects the working fluid supply passage 20 and the reservoir 11 to each other, and the pilot pressure control device 48 includes:
Fixed throttle 52 and connection passage 50 provided in the middle of the passage
And a variable throttle 54 that changes the effective passage cross-sectional area by a solenoid. The variable throttle 54 is connected to an electronic control unit 100, which will be described later, and when the electronic control unit 100 controls the current to the solenoid, it cooperates with the fixed throttle 52 to connect the fixed throttle 52 and the variable throttle 54. The pressure Pc in the connecting passage 50 is changed. Therefore, the pilot pressure control device 48 changes the pilot pressure Pc by the variable throttle 54 and supplies it to the shutoff valve 46.
Opens or closes the connection passage 32 according to the pilot pressure Pc.

Further, in the middle of the working fluid supply passage 20,
A check valve 58 is provided which allows only the flow of working fluid from the filter 56 and pump 18 towards the pressure control valve 22. An accumulator 60 is connected to the working fluid supply passage 20 downstream of the check valve 58.

The pressure control valve 22, the connection passage 32,
The diaphragm 44, the actuator 36, the gas-liquid spring device 42, etc. are provided corresponding to each wheel. Note that these constituent members of each wheel (right front wheel, left front wheel, right rear wheel and left rear wheel) are represented by adding reference numerals FR, FL, RR, RL, for example, the pressure control valve 22 is 22FR. , 22F
They will be referred to as L, 22RR and 22RL.

Next, the electrical construction of the fluid pressure type active suspension 10 will be described. As shown in FIG. 2, the pilot pressure control device 48 and the pressure control valve 22FR
22 to 22RL are respectively connected to the electronic control unit 100, and the pilot pressure control unit 48 and the variable throttle 54 and the variable throttle 30 included in each pressure control valve are controlled by the electronic control unit 100. The electronic control unit 100 includes a microcomputer 102 mainly including a central processing unit (CPU) 104. As is well known, the microcomputer 102 has a CPU 104, a read-on memory (ROM) 106, a random access memory (RAM) 108, an input port device 110, and an output port device 112, and these are bidirectional. Are connected to each other by a common bus 114.

The input port device 110 includes various switches and sensors such as an ignition switch (IGS).
W) 116 and vehicle height sensors 118FL and 118F for each wheel
R, 118RL, 118RR, a vehicle speed sensor 120 for detecting a vehicle speed, a front-rear G (acceleration) sensor 122 for detecting a longitudinal acceleration of the vehicle body, a lateral G sensor 124 for detecting a lateral acceleration of the vehicle body, and a steering wheel. The steering angle sensor 126 for detecting the steering angle of the vehicle, the vehicle height setting switch 128 for setting the vehicle height control mode to either the high mode or the low mode, and the left front wheel, the left rear wheel, and the right rear wheel. Up and down G sensors 140, 142, and 144 that are provided and detect the vertical acceleration acting on each of these wheels are connected.

Then, the electronic control unit 100 receives various signals from these switches and sensors, specifically, signals indicating whether or not the ignition switch is in the ON state, each wheel (left front wheel, right front wheel, left rear wheel). A signal indicating the vehicle height Xi (i = 1, 2, 3, 4) of the portion corresponding to the wheel and the right rear wheel, the vehicle speed V
Indicating the longitudinal acceleration Gx of the vehicle, a signal indicating the lateral acceleration Gy of the vehicle, a signal indicating the steering angle θ of the steering wheel, and a signal indicating whether the vehicle height control mode is the high mode or the low mode. , Signals indicating vertical accelerations Gza, Gzb and Gzc corresponding to the respective wheels (left front wheel, left rear wheel and right rear wheel) are input.

The input port device 110 appropriately processes the above-mentioned input signal and outputs the processed signal to the CPU and the RAM 108 according to an instruction of the CPU 104 based on a program stored in the ROM 106. The ROM 106 stores maps corresponding to the graphs shown in FIGS. 8 to 13 in addition to the control flows shown in FIGS. 3 to 7 and the control flows not shown, and the CPU stores signals based on the respective control flows. It is designed to perform the processing of. The output port device 112 follows the instruction of the CPU 104 and goes through the drive circuit 130 to generate the pilot pressure control device 48.
Output a control signal to the variable diaphragm 54 of the
Control signals are output to the variable throttles 30 of the pressure control valves 22FR to 22RL via 2 to 138.

Next, regarding the suspension control performed by the fluid pressure type active suspension 10 of this embodiment,
This will be described with reference to the flowcharts of FIG. The suspension control shown is based on the ignition switch 11
It is started by turning on the ignition switch 6, and is ended shortly after the ignition switch is turned off.

In the first step S50, R
The AM 108 is initialized, and gains Kzif, Kzir, etc. used for running state determination, active calculation, etc., which will be described later, are set.
Kdxh, Kdxp, Kdxr, and Kdxw have the minimum value (Kzife, Kzire, Kdxhe, Kdx) for each gain.
be, Kdxre, and Kdxwe). Then, it progresses to step S100. Of these gains, Kzif and Kzi
r represents the integral term gain of the vertical acceleration of the vehicle body on the front wheel side and the rear wheel side, and Kdxh, Kdxp, Kdxr and Kdxw represent the differential term gain thereof.

In the following description, "damping gain" means a gain for the vertical speed of the sprung body (vehicle body), a gain for the relative speed between the sprung mass and the unsprung mass (wheels), or both of these gains. Means both.

In step S100, a control signal is output to the solenoid of the variable throttle 54 of the pilot pressure control device 48 to gradually reduce the effective passage sectional area of the variable throttle, thereby gradually increasing the pilot pressure Pp. In this process, the shutoff valve 46 is opened, the pressure of the working fluid in the working fluid supply passage 20 reaches a predetermined pressure, and the shutoff valve 46 is fully opened, that is, the actuator 3
In the state in which the oil can be supplied to and discharged from 6, the process proceeds to the next step S150.

In step S150, the ignition switch 116 and the vehicle height sensor 118 for each wheel are set.
Besides, vehicle speed sensor 120, front and rear G sensor 122, lateral G
The sensor 124, the steering angle sensor 126, the vehicle height setting switch 128, the vertical G sensors 140 to 144, and the like are scanned,
The corresponding signal is read from each switch or sensor, and then the process proceeds to step S200. That is, in this step S150, the ignition switch 116
Is a signal indicating whether or not the vehicle is on, a signal indicating the vehicle height Xi of each wheel, a signal indicating the vehicle speed V, a signal indicating the longitudinal acceleration Gx of the vehicle body, a signal indicating the lateral acceleration Gy, and a steering angle θ of the steering wheel. Signal, a signal indicating whether the set mode is a high mode or a low mode, signals indicating vertical accelerations Gza, Gzb and Gzc corresponding to each wheel (left front wheel, left rear wheel and right rear wheel), etc. Read various signals of.

Subsequent to step S150, the running state of the vehicle is determined in step S200 as will be described later, and the damping gain is determined and smoothing is performed in step S250 as described later. Then, in step S300, step S1 is performed in order to perform vehicle height maintenance control, posture control, and vehicle ride comfort control.
The active calculation is performed based on various signals read in 50 to determine the active control amount (the target pressure Pu in each actuator 36 controlled by each pressure control valve).
i) is calculated. The active calculation for calculating the target pressure Pui will be described later in detail with reference to the flowcharts of FIGS. 6 and 7 and the graphs of FIGS. 8 to 13.
In step S350 subsequent to step S300, the control signals corresponding to the active control amount are sent to the drive circuits 132 to 13 corresponding to the pressure control valves 22FL to 22RR.
Output to 8. Through the output of this control signal, the pressure control valve 2
Drive control of 2FL to 22RR, and then step S
Return to 150.

Next, the processing for determining the running state of the vehicle in step S200 and the determination and smoothing of the damping gain in step S250 will be described with reference to the flowchart shown in FIG. In the flowchart shown in FIG. 4, the gain control flag FG has a gain control step for increasing / decreasing the damping gain according to a change in longitudinal acceleration as will be described later, which is either an increase / decrease step or a value maintaining step. It shows that. Then, as shown in FIG. 8, the gain control flag FG indicates that the damping gain is gradually increased when the value is 1, and the damping gain is increased when the value is 2. It shows that it is in the second stage where it is kept constant, and if the value is 3, it means that it is in the third stage where the damping gain is gradually reduced.

First, the processing for determining the running state of the vehicle in step S200 will be described with reference to FIGS. 9 and 10. Step S, which is the initial step of the process
In 202, the integral term gain Kzife of the vertical acceleration Gz of the vehicle body on the front wheel side with respect to the vehicle speed V is calculated based on the map corresponding to the graph shown in FIG.

In the following step S204, the steering angular velocity is calculated as the time differential value θd of the steering angle θ, and the calculated value of the steering angular velocity and the vehicle speed V are used based on the map corresponding to the graph shown in FIG. The change rate Gypr of the estimated lateral acceleration is calculated. Subsequent step S206
, The absolute value of the change rate Gypr of the estimated lateral acceleration (|
It is determined whether or not Gypr |) is greater than or equal to the reference value Gypre (constant). Here, if it is determined that | Gypr | ≧ Gypre, the process proceeds to step S210, and |
If it is determined that Gypr | ≧ Gypre is not established, the routine proceeds to 208.

In step S208, the time differential value Gxd of the longitudinal acceleration Gx of the vehicle body is calculated, and the absolute value (| Gxd |) of the time differential value Gxd of the vehicle longitudinal acceleration is not less than the reference value Gxde (constant). Whether or not it is determined. When it is determined in this step S208 that | Gxd | ≧ Gxde, the gain control flag FG is set to the value 1 in step S210, and the flow advances to step S214. On the other hand, when it is determined in step S208 that | Gxd | ≧ Gxde is not satisfied, the process proceeds to step S212.
In this step S212, the gain control flag FG
It is determined whether or not the value of 1 is 1, and when it is determined that FG = 1 is not established, the process proceeds to step S220, which will be described later, and FG =
If it is determined to be 1, the process proceeds to step S214.

In step S214, the change rate Gyp of the estimated lateral acceleration in steps 206 and 208 before that is calculated.
Larger r or time derivative G of longitudinal acceleration Gx of the vehicle
Since it is determined that xd (rate of change) is large, any change in acceleration acting on the vehicle body is large. Therefore, the following process is performed to increase the control amount of the actuator 36 in response to the change. That is, in this step S214, the integral term gains Kzif, Kzir and the differential term gains Kdxh, Kdxp of the vertical accelerations of the vehicle body on the front wheel side and the rear wheel side are obtained.
, Kdxr, Kdxw are newly calculated by incrementing corresponding minute values according to the following formulas,
Each of these gains is once increased. The calculated gains are used in the active calculation described later.

Kzif = Kzif + ΔKzif Equation 1 Kzir = Kzir + ΔKzir Equation 2 Kdxh = Kdxh + ΔKdxh Equation 3 Kdxp = Kdxp + ΔKdxp Equation 4 Kdxr = Kdxr + wKdxr = 5Kdxr Kdxw + ΔKdxw… Equation 6

Step S2 following this step S214
16, the integral term gain Kzif is the upper limit value Kzi
Determine whether it is greater than or equal to fu (constant). here,
If it is determined that Kzif ≧ Kzifu is not satisfied, step S in FIG.
The process proceeds to 300 and the subsequent processing is performed. However, if it is determined in step S216 that Kzif ≧ Kzifu, the count value Tc of the timer is set to 0 and the gain control flag FG is set to 2 in step S218.

After making a negative decision in the previous step S212, the gain control flag F is set in step S220.
It is determined whether or not the value of G is 2. Where FG
If it is determined that FG = 2 is not satisfied, then the process proceeds to step S230, which will be described later. Then, in the affirmative determination in step S220 or in step S222 subsequent to step S218, the respective gains Kzif, Kzir, Kdxh, Kdxp, Kdxr and Kdxw are respectively set to maximum values Kzifu, Kziru, Kdxhu, Kdx.
Set to pu, Kdxru and Kdxwu. That is, each gain is once incremented in step S214, and the integral term gain Kzif is set to its upper limit Kzifu in step S216.
As described above, in step S222, each gain is limited to its maximum value. After that, step S
At 224, the count value Tc of the timer is incremented by one.

Step S226 following step S224
In step 1, it is determined whether or not the count value Tc of the timer is greater than or equal to the reference value Tce (constant). Where Tc ≧
If it is determined that it is not Tce, the process proceeds to step S300 in FIG. 3, and if it is determined that Tc ≧ Tce, the value 3 is set in the gain control flag FG in step S228. Further, in step S230 after the negative determination is made in step S220, the value of the gain control flag FG is set to 3
Is determined. Here, if it is determined that FG = 3 is not established, then the processing advances to step S238, which will be described later, and FG =
If it is determined to be 3, the process proceeds to step S232.

In addition, in the affirmative determination in step S230 or in step S232 following step S228, a predetermined time has elapsed since each gain was set to its maximum value in step S222.
The following processing is performed to reduce the control amount of the actuator 36. That is, in this step S232, the integral and differential term gains (Kzif, Kzir, Kdxh, Kdxp, Kdxr, and Kdxw) of the vertical accelerations of the front wheel side and the rear wheel side are respectively calculated according to the following mathematical expressions. Decrement only and reduce each of these gains.

Kzif = Kzif−ΔKzifd Equation 7 Kzir = Kzir−ΔKzird Equation 8 Kdxh = Kdxh−ΔKdxhd Equation 9 Kdxp = Kdxp−ΔKdxpd Equation 10 Kdxr = Kdxr−ΔKdxrd Equation 8 Kdxw-ΔKdxwd Equation 12

In the subsequent step S234, it is determined whether or not the integral term gain Kzif is less than or equal to the reference value Kzife, and if it is determined that Kzif≤Kzife is not satisfied, then FIG.
To step S300, and the subsequent processing is performed. However, if it is determined in step S234 that Kzif ≤ Kzife, in step S236, the gain control flag F
The value 0 is set in G, and in the following step S238,
The gains Kzif, Kzir, Kdxh, Kdxp, Kdxr, and Kdxw are respectively Kzife, Kzire, Kdxhe, Kdxpe,
Set to Kdxre and Kdxwe. That is, step S2
Each gain is decremented at 32 and step S234.
Since the integral term gain Kzif is less than or equal to the reference value Kzife, each gain is limited to its minimum value in step S238. After step S238, the process proceeds to step S300 in FIG.

As is apparent from the above description of each step, steps S202 to S208 correspond to step S200 in the general flowchart of FIG. 3 for judging the running state of the vehicle. Also, steps S210 to 238.
3 corresponds to step S250 in the general flow chart of FIG. 3 in which each damping gain is determined and smoothed according to the running state of the vehicle. The first step of gradually increasing the damping gain is a phenomenon caused by the processing of step S214 of incrementing the value, and the third step of gradually reducing the damping gain is caused by the processing of step S232 of decrementing the value. It is a phenomenon. Then, in this embodiment, the increment value in step S214 and the decrement value in step S230 are associated with each other in the following relationship. Therefore, as shown in FIG. 9, the degree of increase or decrease is different between the first stage and the third stage, the damping gain is relatively quickly increased when the damping gain is increased, and the damping gain is reduced when the damping gain is decreased. Is relatively moderately reduced.

ΔKzif> ΔKzifd Formula 13 ΔKzir> ΔKzird Formula 14 ΔKdxh> ΔKdxhd Formula 15 ΔKdxp> ΔKdxpd Formula 16 ΔKdxr> ΔKdxrd Formula 17 ΔKdxw> ΔKdxwd Formula 18

Next, an example of the active control amount (target pressure Pui) calculation performed in step S300 will be described with reference to FIGS.

As shown in FIG. 5, step S32 which is the first process of step S300 following step S250.
2, the heave target value R based on the target posture of the vehicle body
xh is calculated based on the map corresponding to the graph shown in FIG. 11, and then the process proceeds to step S324. Note that FIG.
1 is the heave target value R when the vehicle height control mode set by the vehicle height setting switch 128 is the normal mode.
The xh pattern is shown by a solid line, and the pattern in the high mode is shown by a dotted line.

In step S324, step S
Left front wheel, right front wheel, left rear wheel, read in 150,
Based on the vehicle heights X1 to X4 at the position corresponding to the right rear wheel, the displacement mode conversions for heave (Xxh), pitch (Xxp), roll (Xxr), and warp (Xxw) are calculated according to the following formulas. It proceeds to step S326.

Xxh = (X1 + X2) + (X3 + X4) Equation 19 Xxp =-(X1 + X2) + (X3 + X4) Equation 20 Xxr = (X1-X2) + (X3-X4) Equation 21 Xxw = (X1-X2)-(X3-X4) Equation 22

In step S326, the deviation of the displacement mode is calculated according to the following equation, and then the process proceeds to step S328. In calculating the deviation in the displacement mode, the vehicle speed V and the heave target value Rxh calculated in step S322 as described above are used.

Exh = Rxh-Xxh Formula 23 Exp = Rxp-Xxp Formula 24 Exr = Rxr-Xxr Formula 25 Exw = Rxw-Xxw Formula 26

In this case, the pitch target value Rxp and the roll target value Rxr may be zero. Also, the warp target value R
xw may also be 0, or may be Xxw calculated in step S324 immediately after the activation of the active suspension or an average value of Xxw calculated in the past several cycles. The absolute value of Exw (| Exw |) ≤
In the case of W1 (a positive constant), Exw = 0.

In step S328, steps S214, 222, and 23 of the flowchart shown in FIG. 4 are performed.
Using the differential term gains (Kdxh, Kdxp, Kdxr and Kdxw) on the front and rear wheels calculated in 2 or 238, the PI of displacement feedback control is calculated according to the following equation.
D compensation calculation is performed, and then the process proceeds to step S330.

Cxh = Kpxh * Exh + Kixh * Ixh (n) + Kdxh {Exh (n) -Exh (n-n1)} Equation 27 Cxp = Kpxp * Exp + Kixp * Ixp (n) + Kdxp {Exp (n) -Exp (n) -n1)} Equation 28 Cxr = Kpxr * Exr + Kixr * Ixr (n) + Kdxr {Exr (n) -Exr (n-n1)} Equation 29 Cxw = Kpxw * Exw + Kixw * Ixw (n) + Kdxw {Exw (n) -Exw (n-n1)} Equation 30

In the above equations, Ek (n) (k = x
h, xp, xr, xw) is the current Ek, and Ek (n-n1) is n1
It is Ek before the cycle. Also, Ik (n) and Ik (n-1)
Let Ik be the current and one cycle before, respectively, I
k (n) can be described as follows with Tx as a time constant.

Ik (n) = Ek (n) + Tx.multidot.Ik (n-1) Equation 31

In this case, the absolute value of Ik (| Ik |) is
| Ik | ≦ Ikmax, where Ikmax is a predetermined value. Furthermore, the coefficients Kpk, Kdk and Kik (k = xh, xp, xr, xw)
Are proportional constants, differential constants and integral constants, respectively.

In step S330, the inverse conversion of the displacement mode is calculated according to the following mathematical expression, and then the process proceeds to step S332.

Px1 = 1/4 · Kx1 (Cxh−Cxp + Cxr + Cxw) Equation 32 Px2 = 1/4 · Kx2 (Cxh−Cxp−Cxr−Cxw) Equation 33 Px3 = 1/4 · Kx3 (Cxh + Cxr + Cxw) Formula 34 Px4 = 1/4 · Kx4 (Cxh + Cxp−Cxr + Cxw) Formula 35

Note that KX1, KX2, K in the above equations
X3 and KX4 are proportional constants.

In step S332, the front-rear direction and the lateral direction of the vehicle are shown in FIGS. 12 and 13, respectively.
Based on the map corresponding to the graph shown in
gx and Pgy are calculated, and then the process proceeds to step S334.

In step S334, the PD compensation calculation of the horizontal G feedforward control is performed for the pitch (Cgp) and the roll (Cgr) according to the following mathematical expression, and then the process proceeds to step S336 shown in FIG.

Cgp = Kpgp.Pgx + Kdgp {Pgx (n) -Pgx (n-n1)} Formula 36 Cgr = Kpgr.Pgy + Kdgr {Pgy (n) -Pgy (n-n1)} Formula 37

In the above equations, Pgx (n) and Pgy (n) are the current Pgx and Pgy, respectively, and Pgx
(n-n1) and Pgy (n-n1) are Pgx before n1 cycles, respectively.
And Pgy. Further, Kpgp and Kpgr are proportional constants, and Kdgp and Kdgr are differential constants.

In step S336 shown in FIG. 6,
The inverse G-mode inverse conversion is calculated according to the following formula, and then the process proceeds to step S338.

Pg1 = Kg1 / 4 · (−Cgp + K2f · Cgr + K1f · Gypr) Equation 38 Pg2 = Kg2 / 4 · (−Cgp−K2f · Cgr−K1f · Gypr) Equation 39 Pg3 = Kg3 / 4 · (Cgp + K2r ·) Cgr + K1r · Gypr) Equation 40 Pg4 = Kg4 / 4 · (Cgp−K2r · Cgr−K1r · Gypr) Equation 41

Note that Kg1, Kg2, Kg in the above equations
3 and Kg4 are proportional constants, K1f and K1r,
K2f and K2r are constants as distribution gains between the front and rear wheels.

In step S338, the vertical accelerations Gza, G detected by the vertical G sensors 140-144.
Based on zb and Gzc, the vertical accelerations Gz1 to Gz4 of the parts corresponding to the respective wheels are calculated according to the following mathematical formulas, and then the process proceeds to step S340.

Gz1 = Gza Equation 42 Gz2 = Gza−Gzb + Gzc Equation 43 Gz3 = Gzb Equation 44 Gz4 = Gzc Equation 45

In step S340, the vertical accelerations Gz1 to Gz4 are integrated to calculate integrated values Iz1 to Iz4.
In the following step S342, Kzpf and Kzpr
Is the proportional gain of the vertical acceleration on the front wheel side and the vertical acceleration on the rear wheel side, respectively.
.About.Czp4 are calculated, and then the process proceeds to step S343.

Czp1 = Kzpf.Gz1 Equation 46 Czp2 = Kzpf.Gz2 Equation 47 Czp3 = Kzpr.Gz3 Equation 48 Czp4 = Kzpr.Gz4 Equation 49

In step S343, step S
Each integrated value Iz1 to I of the vertical acceleration of the vehicle body calculated in 340
z4 and step S21 of the flowchart shown in FIG.
Based on the front-wheel-side and rear-wheel-side integral term gains Kzif and Kzir calculated at 4, 222, 232 or 238, the vertical acceleration integral terms, that is, the sprung speed terms Czi1 to Czi4, are calculated according to the following equation. Then, step S344.
Go to.

Czi1 = Kzif · Iz1 Equation 50 Czi2 = Kzif · Iz2 Equation 51 Czi3 = Kzir · Iz3 Equation 52 Czi4 = Kzir · Iz4 Equation 53

In step S344, step S
Based on the proportional term Czpj (j = 1, 2, 3, 4) calculated in 342 and the integral term Czij calculated in step S343, a feedback control amount Pzj based on vertical acceleration is calculated according to the following mathematical formula. Then, it progresses to step S345 shown in FIG.

Pzj = Czpj + Czij Equation 54 (j = 1, 2, 3, 4)

In step S345, step S
The pressures Pxj and Pzj calculated in 330 and 344 are added to calculate the control pressure Ppuj of each pressure control valve that is the target of the filtering process described later, and then step S
Proceed to 346. In this step S346, the time constant K necessary for the filtering process (frequency component limiting process) in step S347, which will be described later, is obtained in the following manner. Prior to the description of step S346, the vehicle speed V and the sprung vibration state ( The vertical acceleration) will be described.

As described above, the disturbance input to the front wheels is always input to the rear wheels after the lapse of a predetermined time, and this elapsed time depends on the vehicle speed and the wheel base. Acceleration), for example, the vibration condition (vertical acceleration) on the spring at the position of the center of gravity of the vehicle changes according to the vehicle speed as shown in FIG. 15, and the vertical acceleration has peaks and valleys at frequencies corresponding to the vehicle speed. Be seen. The frequencies fP and fT of the peaks and valleys can be specified by the following mathematical expressions with the vehicle speed V as a variable.

Peak frequency fP = V / HB Equation 55 Valley frequency fT = V / (2.HB) Equation 56

HB in the equations 1 and 2 is the wheel base.

Therefore, in step S346, the frequency fT of the valley in the vertical vibration state (vertical acceleration) of the vehicle body
Is calculated from the read vehicle speed V and the wheel base HB stored in the ROM according to the above equation 56, and T1 is the sampling cycle from the processing of step S347 in the previous routine to the processing of this routine. Or the control target pressure P described later.
The time constant K is calculated according to the following mathematical expression as one of the changing cycles of uj. Then, it progresses to step S347.

K = T12πfT Equation 57

In step S347, the above-mentioned step S347 is performed.
Using the time constant K obtained in 346, the control pressure Ppuj in step S345 is subjected to a filtering process (frequency component limiting process) according to the following mathematical formula, and then step S3.
Proceed to 48.

FPpuj = FPpuj + (Ppuj−FPpuj) · K Equation 58

That is, in step S347, the control pressure Ppuj of each pressure control valve is determined by the vehicle running condition such as the proportional term and integral term of the vertical acceleration of the front and rear wheels, in addition to the posture changes such as heave, pitch, roll, and warp. Is calculated according to the vehicle speed V, and the high frequency component exceeding the frequency fT of the vertical vibration valley of the vehicle body determined according to the vehicle speed V is shielded.

Then, in step S348 following step S347, the standard pressure Pbj in the working fluid chamber of each actuator stored in the ROM (the pressure in the working fluid chamber when the vehicle in the standard loading state is stopped).
Then, based on the pressure Pgj calculated in step S336 and the pressure FPpuj calculated in step S347, the control target pressure Puj of each pressure control valve is calculated according to the following mathematical formula, and then the process proceeds to step S350 in FIG.

Puj = Pbj + Pgj + FPpuj Equation 59 (j = 1, 2, 3, 4)

Therefore, in steps S322 to 330 of the active control amount calculation routine shown in FIGS. 6 and 7, the displacement feedback control amount Pxj based on the posture change is obtained.
Is calculated, the feedforward control amount Pgj based on the longitudinal acceleration and the lateral acceleration is calculated in steps S332 to 336, the feedback control amount Pzj based on the vertical acceleration is calculated in steps S338 to 344, and each pressure control is performed in steps S345 to 347. A high-frequency component that shields the control pressure Ppuj of the valve from the frequency fT of the vertical vibration valley of the vehicle body, which is determined according to the vehicle speed V, is shielded.
The control target pressure Puj is calculated as the sum of the standard pressure Pbj and each control amount in step S348, and each pressure control valve is controlled in step S350 based on this control target pressure.

As described above, in the fluid pressure type active suspension 10 of this embodiment, each pressure control valve 22 is used.
Control target pressure Puj for controlling the control pressure Ppuj (Pxj +
Pzj) in step S, which is one mode of the calculation unit of the control means.
322 to 345, and then, in step S347, which is one mode of the limiting processing unit, FPpuj in which high-frequency components exceeding the frequency fT of the vertical vibration valley of the vehicle body are shielded. Moreover, the frequency fT of the trough of the vertical vibration of the vehicle body, which is the shielding frequency when shielding the high frequency component, is set in step S346, which is one mode of the limiting frequency changing unit, by the vehicle speed sensor 120, which is one mode of the speed detecting means. The shielding frequency fT is changed each time in accordance with the detected vehicle speed V, and is adapted to the vibration condition on the spring which changes in accordance with the vehicle speed V.

Therefore, according to the fluid pressure type active suspension 10 of the present embodiment, the frequency fT of the trough of the vertical vibration of the vehicle body which appears in the relatively low frequency region where the control system can respond (the vertical acceleration of the vehicle body is small and the vehicle motion is small). By matching the shielding frequency with the frequency (which has a small effect on the performance) as described above, the controllability in the region where the control system can respond is secured. Further, for the high frequency component exceeding the valley frequency fT, which makes it difficult for the control system to respond, the high frequency component is attenuated in step S347 which is one mode of the control processing unit, so that the fluid pressure type of the present embodiment is used. Active suspension 10
According to this, it is possible to reduce the deterioration of the riding comfort caused by the response delay of the control system.

Further, the fluid pressure type active suspension 10 of this embodiment has the following advantages.

Each pressure control valve 22 controls the internal pressure of the working fluid chamber 38 according to the control target pressure. However, the response delay as the above-mentioned control system is the delay due to the operating speed of this pressure control valve. In addition, it is affected by the characteristic of the control processing unit itself (the characteristic of delaying the phase of the output with respect to the input). That is, when the control target pressure is output to the pressure control valve, since the control target pressure has passed through the control processing unit, there is a phase delay in the control target pressure itself in the frequency range exceeding the shielding frequency range. Moreover, although the control amount itself is attenuated and becomes smaller as the cutoff frequency is exceeded, the phase difference becomes large, and thus the phase delay of the control target pressure itself is one factor causing the response delay as the control system.

Therefore, in the fluid pressure type active suspension 10 of this embodiment, the control target pressure itself in the vicinity of the cutoff frequency of the control processing unit is originally set in the unresponsive region due to the limit of the operating speed of the pressure control valve 22 and the like. The region where the phase difference is remarkable is matched, that is, the shielding frequency is matched with the frequency fT of the valley of the vertical vibration of the vehicle body. Therefore, according to the fluid pressure type active suspension 10 of the present embodiment, it is possible to prevent the phase difference of the control target pressure itself from adversely affecting the responsiveness of the control system, and to control the control amount in the frequency range exceeding the shielding frequency. Since the (control target pressure) itself can be rapidly attenuated, it is possible to reduce the deterioration of the riding comfort due to the response delay of the control system.

In this case, the shielding frequency may be set to a value smaller than the frequency fT of the trough of the vertical vibration of the vehicle body. However, in this case, the frequency range for active control becomes small. Therefore, in the fluid pressure type active suspension 10 of the present embodiment, the frequency fT of the trough of the vertical vibration of the vehicle body is a frequency that has little influence on the vehicle's motion performance in terms of the vibration characteristics of the vehicle, and the phase difference of the control target pressure itself is taken into consideration. Focusing on the frequency range that does not need to be set, the shielding frequency is set to the frequency f of the valley of the vertical vibration of the vehicle body.
Matched to T. Therefore, according to the fluid pressure type active suspension 10 of the present embodiment, in the frequency region in which response control is possible, the frequency range for active control is increased, while the influence of the phase difference of the control target pressure itself on the response of the control system. Besides, it is possible to reduce the deterioration of the riding comfort in the high frequency region due to the response delay of the control system. Moreover, the frequency fT of the valley fluctuates depending on the vehicle speed V, but by changing the shielding frequency accordingly, the ride comfort can be improved regardless of the vehicle speed V.

Further, in the fluid pressure type active suspension 10 of the present embodiment, in addition to the integral term gains (Kzif, Kzir) which are damping gains, the differential term gains Kdxh, Cxh, Cxp, Czr and Cxw of the displacement feedback control quantities Cxh,
Kdxp, Kdxr, and Kdxw are increased according to the routine shown in FIG. 4 according to the pattern shown in FIG. 8 when the vehicle makes a sharp turn or sudden acceleration / deceleration, and is a low value (minimum value) in other running states. Configured to maintain. Therefore, it is possible to reduce the attitude change of the vehicle at the time of sudden steering or sudden acceleration / deceleration, particularly, the attitude change speed of the vehicle, and it is possible to improve the riding comfort of the vehicle at the time of normal traveling.

Further, in the fluid pressure type active suspension 10 of the present embodiment, as shown in FIG. 8, each differential term gain is rapidly increased and maintained at a constant value when the vehicle makes a sharp turn or sudden acceleration / deceleration. , Is relatively moderately reduced.
Therefore, it is possible to effectively reduce the attitude change speed of the vehicle when sudden steering or sudden acceleration / deceleration is performed without a response delay, and further, the attitude change speed reducing performance of the vehicle after the end of sudden steering or sudden acceleration / deceleration is achieved. It is possible to reliably prevent sudden changes.

Next, another embodiment will be described. In this embodiment (second embodiment), the processing content of step S347, which is one mode of the restriction processing unit, that is, the processing target in the filtering process (frequency component restriction process), its execution order, and the arithmetic unit is one mode. Step S322-3
The content of calculation in 45 is different from that of the above-described embodiment (first embodiment). That is, in the second embodiment, the filtering process of step S347, which is an aspect of the restriction processing unit, is performed after steps S322 to 345 that are an aspect of the arithmetic operation unit, for example, step S150 in the above-described embodiment.
Between step S200 and step S200, the output (running state amount) that reflects the running state of the vehicle among the sensor outputs read in step S150 as the processing target in the filtering process, specifically, the vehicle height Xi of each wheel. Signal, vehicle speed V
, A signal indicating the longitudinal acceleration Gx of the vehicle body, a signal indicating the lateral acceleration Gy, a signal indicating the steering angle θ of the steering wheel, and a vertical acceleration Gza corresponding to each wheel (left front wheel, left rear wheel and right rear wheel), Signals indicating Gzb and Gzc, etc. are provided, and a configuration for performing filtering processing on these signals is provided. In addition, in the second embodiment, the running state quantity thus filtered is output to steps S322 to 345 which is one mode of the arithmetic unit, that is, the processing contents in steps S322 to 345 which is one mode of the arithmetic unit are output. The control pressure Ppuj (Pxj + Pzj) is calculated based on the running state amount subjected to the filtering process.

Even with this configuration, the control pressure Ppuj
Let (Pxj + Pzj) be a controlled variable in which high frequency components exceeding the frequency fT of the vertical vibration valley of the vehicle body are shielded, and
The shielding frequency can be changed each time according to the vehicle speed V to suit the vibration situation on the spring. Therefore, the second
Also in the embodiment described above, similarly to the first embodiment described above, it is possible to suppress the increase in the vertical acceleration due to the phase delay of the control regardless of the vehicle speed V and improve the riding comfort.

Next, a modification of the above embodiment will be described. In each of the above-described embodiments, the filtering process (frequency component limiting process) is realized by the arithmetic process using the mathematical formula represented by Formula 58. However, a shielding frequency such as a Butterworth type filter or a digital or analog low-pass filter is used. It can be modified to a configuration using various filters that can be changed. Moreover, it is possible to adopt a configuration in which these filters are provided either before or after the microcomputer 102 in the electronic control unit 100 shown in FIG. That is, in the former configuration, the vehicle height Xi, the longitudinal acceleration Gx and the vertical acceleration Gz of the vehicle body
The a, Gzb, Gzc, etc. are subjected to the filtering process by the shielding frequency (the frequency of the valley) according to the vehicle speed V through the above filter, and the output is applied to the microcomputer 1
02 to the input port device 110, and the control amount of each pressure control valve 22 is calculated based on the input. On the other hand, in the latter configuration, after the control amount of each pressure control valve 22 is calculated by the microcomputer 102 based on the vehicle height Xi, the longitudinal acceleration Gx of the vehicle body and the vertical accelerations Gza, Gzb and Gzc, etc. (Control signal) to the output port device 112
It is subjected to a filtering process by the shielding frequency (valley frequency) according to the vehicle speed V via the above-mentioned filter input from the above and then output to each pressure control valve 22. According to these configurations, steps S346, 3 in the active calculation are performed.
Since the processing of 47 can be omitted, the calculation load of the microcomputer 102 can be reduced.

Here, a modified example in which an analog low-pass filter with a variable shield frequency is provided at the subsequent stage of the microcomputer 102 will be described with reference to the drawings. 14
As shown in FIG. 3, the low-pass filter 600 has two input paths, one path calculates the vehicle speed V from the vehicle speed sensor 120, and the other path calculates from the output port device 112 of the microcomputer 102 to the microcomputer 102. The control amount SP of the pressure control valve 22 of the actuator 36 for each wheel is input. The vehicle speed V is input as a pulse signal generated by the vehicle speed sensor 120 each time the wheels rotate by a predetermined angle.

The low-pass filter 600 includes a first resistor 602 (resistance value R) and a coil 60 in the input path of the controlled variable SP.
4 (inductance L), and has a frequency / voltage converter (F / V conversion circuit) 606 in the input path of the vehicle speed V.
The input path of the vehicle speed V is branched into two systems downstream of the F / V conversion circuit 606, and the output voltage-converted by the F / V conversion circuit 606 is input to the − side (inverting input terminal) in each path. Comparing comparators 608 and 610 are provided. The reference voltage 2VEE is applied to the comparator 608 from the + side (non-inverting input terminal), and half the reference voltage VEE is applied to the comparator 610 from the + side (non-inverting input terminal). On the other hand, the transistor 612 and the second resistor 602 are connected to the first resistor 602 in the input path of the controlled variable SP.
The circuit in which the resistor 614 (resistance value R) is connected in series, and the circuit in which the transistor 616 and the third resistor 618 (resistance value R) are connected in series are respectively connected in parallel, and the output of the comparator 608 described above. The terminal is a transistor 612
, And the output terminal of the comparator 610 is connected to the base of the transistor 616. Therefore, the control amount output to each pressure control valve 22 via the coil 604 is a control amount obtained by frequency-shielding (filtering) the control amount SP at the cutoff frequency (shielding frequency) fc represented by the following mathematical formula. .

Fc = (1 / 2π) · (R ′ / L) Equation 60

R'in this formula is the first to third
Is a combined resistance of the resistors 602, 614, and 618, and L is the inductance of the coil 604.

The cutoff frequency fc of the low-pass filter 600 that filters the control amount SP in this way
The reference voltages given to the comparators 608 and 610 are different from each other.
It changes as shown in. Therefore, the control amount output to each pressure control valve 22 is also a control amount obtained by filtering the control amount SP with a cutoff frequency fc that is variable according to the vehicle speed V, and the ride comfort is the same as in the above-described embodiments. It is possible to improve.

[0112]

[Table 1]

In this case, A and B in the vehicle speed column in Table 1
Indicates that the output of the F / V conversion circuit 606 is the comparator 60.
The voltage for inverting the output of 8, 610 (reference voltage V
It is the vehicle speed when it matches EE, 2VEE). Then, the cutoff frequency fc when the vehicle speed V = A matches the frequency of the valley when the vehicle speed is 50 km / h as shown in FIG. 15, and when the vehicle speed V = B. In order to match the frequency of the valley when the cut-off frequency fc is 100 km / h, and further to match the frequency of the valley when the vehicle speed V exceeds B, for example, 120 km / h. First to third resistors 602 and 6
The resistance R of 14,618 and the inductance L of the coil 604 are predetermined.

The low-pass filter 600 having the above structure
It is needless to say that it is also possible to provide the above in the preceding stage of the microcomputer 102 and to output the output of each sensor to the microcomputer 102 after filtering by the cutoff frequency fc.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment and can be implemented in various modes without departing from the scope of the present invention. Of course.

For example, the active pressure calculation, that is, the calculation of the target pressure Puj in the working fluid chamber 38 of each actuator 36 is performed in a specific manner based on the detection results of various sensors and various gains. The operation mode of Puj is determined by each actuator 36 depending on the running state of the vehicle.
Any mode can be adopted as long as the calculation can control the vehicle height of the vehicle body, its posture, and the riding comfort of the vehicle by controlling the target pressure in the working fluid chamber 38.

Further, in the present embodiment, the control valve is constructed as the pressure control valve 22 which directly introduces the pressure in the connection passage 32 and the branch passage 26 to perform switching, but this control valve is provided in the working fluid chamber 38. Needless to say, it may be configured as a flow rate control valve in which the pressure is detected by a pressure sensor and is electrically switched by a solenoid or the like based on the detected value.

Further, in the modified example using the low-pass filter 600, two comparators for changing the cutoff frequency fc according to the vehicle speed V are used and the respective reference voltages are set to VEE and 2VEE. Resistance 60
By providing two parallel circuits that determine the combined resistance with 2,
Although the cutoff frequency fc can be changed in three steps according to the vehicle speed V, the invention is not limited to this. That is,
A plurality of comparators (three or more) are provided to make each reference voltage multistage, and a circuit (a series circuit of a resistor and a transistor) that determines a combined resistance with the first resistor 602 is connected in parallel to the first resistor 602 by the number of installed comparators. It can also be configured to be provided in. With this configuration, the cut-off frequency fc can be changed in multiple stages according to the vehicle speed V, so that the control amount output to each pressure control valve 22 is finely changed according to the vehicle speed V. The control amount SP can be a filtered control amount at the cutoff frequency fc, and the ride comfort can be improved through this.

[0119]

As described above in detail, in the suspension control device of the present invention, the control amount when instructing the actuator is the control amount that has been subjected to the frequency component limiting process for shielding or attenuating the high frequency component exceeding the predetermined frequency. To do. The predetermined frequency at the time of shielding or attenuating the frequency component limiting process is set to a frequency having a small vertical acceleration and a small influence on the motion performance of the vehicle, such as the frequency fT of the vertical vibration valley of the vehicle body. , This frequency is changed each time according to the vehicle speed reflected in the vertical vibration of the vehicle body. As a result, according to the suspension control device of the present invention, the increase in vertical acceleration due to the phase delay of control when adjusting the suspension condition by the actuator that receives the command of the control amount is suppressed regardless of the vehicle speed, and the ride comfort is improved. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fluid pressure type active suspension 10 which is one embodiment of a suspension control device according to the present invention.

2 is a block diagram showing an electronic controller for controlling the pilot pressure controller and the pressure control valve shown in FIG. 1. FIG.

FIG. 3 is a general flow chart showing a suspension control flow achieved by the electronic control device shown in FIG.

FIG. 4 is step S2 of the flowchart shown in FIG.
9 is a flowchart showing a routine for determining the running state of the vehicle, which is performed at 00 and 250.

5 is a step S3 of the flowchart shown in FIG.
10 is a flowchart showing the first half of the active calculation routine performed at 00.

FIG. 6 is a step S3 of the flowchart shown in FIG.
10 is a flowchart showing a middle stage part of a routine of active calculation performed at 00.

FIG. 7 is step S3 of the flowchart shown in FIG.
10 is a flowchart showing the remaining part of the routine of the active calculation performed at 00.

FIG. 8 is a time chart showing an increase / decrease pattern of a gain Kzife.

FIG. 9 is a graph showing a relationship between a vehicle speed V and a gain Kzife.

FIG. 10 is a graph showing a relationship between a vehicle speed V, a steering angular velocity θd, and a rate of change Gypr of estimated lateral acceleration.

FIG. 11 is a graph showing a relationship between a vehicle speed V and a target displacement amount Rxh.

FIG. 12 is a graph showing the relationship between longitudinal acceleration Gx and target pressure Pgx.

FIG. 13 is a graph showing a relationship between lateral acceleration Gy and target pressure Pgy.

FIG. 14 is a schematic configuration diagram for explaining a suspension control device of a modified example.

FIG. 15 is a graph showing the results of frequency analysis of vibration conditions (vertical acceleration) on the spring at the vehicle center of gravity position for different vehicle speeds.

[Explanation of symbols]

 10 ... Fluid pressure type active suspension 12 ... Connection passage 14 ... Working fluid discharge passage 16 ... Engine 18 ... Pump 20 ... Working fluid supply passage 22 ... Pressure control valve 24 ... Switching control valve 24a ... Switching position 24b ... Switching position 24c ... Switching position 26 ... Branch passage 28 ... Fixed throttle 30 ... Variable throttle 32 ... Connection passage 34 ... Throttle 36 ... Actuator 38 ... Working fluid chamber 42 ... Gas-liquid spring device 46 ... Shutoff valve 48 ... Pilot pressure control device 50 ... Connection passage 52 ... Fixed Aperture 54 ... Variable aperture 60 ... Accumulator 100 ... Electronic control device 110 ... Input port device 112 ... Output port device 118 ... Vehicle height sensor 120 ... Vehicle speed sensor 122 ... Front / rear G sensor 124 ... Side G sensor 126 ... Steering angle sensor 128 ... Vehicle High setting switch 130 ... Drive circuit 132-138 ... Drive Circuit 140-144 ... vertical G sensor Wh ... wheel

Claims (1)

[Claims] 1. An actuator which is interposed between a vehicle body and a wheel and adjusts a suspension condition of the vehicle in accordance with a control amount commanded from the outside, and a posture change of the vehicle which occurs depending on a running state of the vehicle. Is a suspension control device having a control means for controlling the attitude of the vehicle by instructing a control amount to the actuator on the side where the vehicle speed is reduced, the traveling state detecting means for detecting the traveling state of the vehicle, and the speed of the vehicle. And a speed detection unit for detecting the control amount, wherein the control unit calculates the control amount according to the traveling state detected by the traveling state detection unit, and commands the calculated control amount to the actuator. The control unit and at least one of the traveling state amount of the traveling state detected by the traveling state detecting unit or the arithmetic control amount calculated by the arithmetic unit are input, and the input traveling state amount or A control processing unit that processes the input control signal by a frequency component limiting process that shields or attenuates a high frequency component exceeding a predetermined frequency and outputs the signal, and detects the predetermined frequency in the limit processing unit by the speed detection unit. And a limit frequency changing unit that changes the limit value according to the vehicle speed, and the control unit controls the limit processing unit to determine the running state amount that has been subjected to the frequency component limiting process by the running state detecting unit. In order to output to the arithmetic unit in priority to the state, the arithmetic control amount processed in the frequency component limiting process is output to the control unit in preference to the control amount calculated by the arithmetic unit. Suspension control device.