JPH05262118A - Damping force control device of shock absorber - Google Patents

Abstract

PURPOSE:To effectively damp the vibrations of a vehicle body by changing the damping force without causing the control delay even in the case where the frequency of the undulation of the road surface is high, and avoid the increase in the cost. CONSTITUTION:A preview sensor 18 to detect the absolute displacement of the road surface forward of wheels 14, 16 mounted on a vehicle body 10, a vehicle speed sensor 36 and an electronic control device 38 are provided. The electronic control device 38 computes the damping factor according to the skyhook control theory for the imaginary vehicle model based on the absolute displacement Xop of the road surface to be detected by the preview sensor 18, and the damping force of shock absorbers 24, 26 is controlled through actuators 40, 42 based on the damping factor by executing the specified time delay taking into consideration the time required for the wheels 14, 16 to travel to the previewed position and the control delay.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber for a vehicle such as an automobile, and more particularly to a damping force control device for a shock absorber.

[0002]

2. Description of the Related Art As one of damping force control devices for a shock absorber of a vehicle such as an automobile, for example, Japanese Patent Laid-Open No. 3-276 is known.
As described in Japanese Patent Publication No. 807, a damping force control device configured to calculate a damping coefficient based on the skyhook control theory and control the damping force of a shock absorber based on the calculation result has been conventionally known. There is. According to this damping force control device, the damping force of the shock absorber is controlled to the optimum damping force in relation to the absolute space, so that the vibration of the vehicle body is effectively damped and the riding comfort of the vehicle is improved. be able to.

[0003]

However, since there is a calculation delay in the damping force control device and a response delay in the shock absorber and the actuator, when the vehicle travels on a rough road at a relatively high speed, for example. When the frequency of the undulation change of the road surface is high, the change of the damping force of the shock absorber cannot follow the change of the undulation of the road surface.Therefore, even the conventional damping force control device based on the skyhook control theory is effective for the vibration of the vehicle body It is difficult to improve the riding comfort of the vehicle by attenuating it temporarily.

Further, in order to solve such a problem, if the damping force control device is made to have high performance with high calculation speed or the shock absorber and actuator are made to have high performance with high responsiveness, the cost of damping force control of the shock absorber is reduced. There is a problem that will increase.

In view of the above-mentioned problems in the conventional shock absorber damping force control device, the present invention can reduce the damping force of the shock absorber without delay of control even when the frequency of the undulation change of the road surface is high. For the purpose of providing a damping force control device for a shock absorber improved so that the vibration of the vehicle body can be effectively damped by changing the vibration and the cost of damping force control can be prevented from increasing. There is.

[0006]

According to the present invention, a damping force control device for a shock absorber in which a damping force is increased or decreased by an actuator is provided, and a preview in front of a wheel mounted on a sprung member is provided. Based on the skyhook control theory, a road surface displacement detecting means for detecting the absolute displacement of the road surface at a position, a vehicle speed detecting means, and a virtual vehicle model in the preview position based on the absolute displacement of the road surface detected by the road surface displacement detecting means. Control for calculating a damping coefficient, delaying a predetermined time considering the time required for the wheel to move to the preview position and a control delay, and controlling the damping force of the shock absorber via the actuator based on the damping coefficient And a damping force control device for the shock absorber.

[0007]

As shown in FIG. 5, the road surface displacement detecting means 120 is present at the preview position Pp ahead of the wheel 110 of the actual vehicle 100 by the distance L, and the sprung mass 130 having the mass Mp is provided at that position. And a virtual vehicle model 160 suspended by shock absorber 150. The spring constant of the suspension spring 140 of the virtual model 160 and the damping coefficient of the shock absorber 150 are Kp and Cp, respectively, and the absolute displacement of the road surface at the preview position Pp detected by the road surface displacement detecting means 120 is Xop, and s is the Laplace operator. Then, the sprung displacement Xp of the virtual model is expressed by the following expression 1, and thus the sprung speed Xpd of the virtual model is expressed by the following expression 2.

[0008]

[Number 1] Xp = (Cp · s + Kp ) Xop / (Mp · s 2 + Cp · s + Kp)

[Number 2] ^{Xpd = (Cp · s 2 +} Kp · s) Xop / (Mp · s 2 + Cp · s + Kp)

The relative velocity Ypd between the unsprung 170 and the sprung 130 in the virtual model 160 is determined by the sprung velocity Xpd.
And the rate of change in absolute displacement of the road surface (differential value of absolute displacement Xopd
) And is expressed by the following mathematical formula 3.

[Number 3] Ypd = Xpd-Xopd = -Mp · s 3 · Xop / (Mp · s 2 + Cp · s + Kp)

From equations 2 and 3, the damping coefficient Cp * of the shock absorber according to the skyhook control theory in the virtual model 160 is expressed by the following equation 4.

[Number 4] Cp * = Cp · Xpd / Ypd = - (Cp · s + Kp) Xop · s / (Mp · s 3 · Xop) = - (Cp · s + Kp) Xop / (Mp · Xoptd)

The damping coefficient Cp * obtained by the equation 4 is the optimum damping coefficient at the preview position Pp, and the actual vehicle 100 is located behind the preview position by the distance L in the traveling direction of the vehicle. Therefore, the control delay, that is, the calculation delay of the control means and the response delay of the shock absorber etc.
c, the distance between the preview position Pp and the front wheel of the vehicle is Lp, the wheelbase of the vehicle is Lw, and the vehicle speed is V, the absolute displacement of the road surface at the preview position Pp is detected by the road surface displacement detecting means 120. Letting Tf and Tr be the delay times from the time of detection to the time of outputting a control signal to the actuators of the front and rear wheel shock absorbers, these delay times are expressed by the following equations 5 and 6, respectively. It

[0012]

## EQU5 ## Tf = Lp / V-Tc

## EQU6 ## Tr = (Lp + Lw) / V-Tc

According to the above-mentioned structure, the control means skies the virtual vehicle model (160) at the preview position (Pp) based on the absolute displacement (Xp) of the road surface detected by the road surface displacement detection means (120). The damping coefficient (Cp *) according to the hook control theory is calculated, and the damping coefficient (C) is delayed by a predetermined time (Tf, Tr) considering the time required for the wheels (110) to move to the preview position and the control delay.
The damping force of the shock absorber is controlled via an actuator based on p *), and the damping force of the shock absorber is set at the preview position (Pp
Since the control is reliably performed based on the damping coefficient (Cp *) at the time of moving to), the damping force of the shock absorber changes appropriately without delay even when the frequency of the undulation change of the road surface is high. As a result, the vibration of the vehicle body is effectively damped.

Further, according to the above-mentioned structure, the delay of the control is not required even if the damping force control device is not made to have high performance with high calculation speed or the shock absorber and the actuator are made to have high performance with high responsiveness. Since the damping force of the shock absorber is appropriately changed and the vibration of the vehicle body is effectively damped without causing the occurrence of the above, an increase in the cost of damping force control is reliably avoided.

[0015]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of a damping force control device for a shock absorber according to the present invention.

In FIG. 1, reference numeral 10 denotes a vehicle body of a vehicle traveling on a road surface 12, and 14 and 16 denote front wheels and rear wheels of the vehicle, respectively. A preview sensor 18 is provided at the front end of the vehicle body 10 as a road surface displacement detecting means for detecting the absolute displacement Xp of the road surface 12 in front of the front wheels 14. The preview sensor 18 includes a road surface sensor 20 that detects a relative displacement Y of the road surface as a distance from the road surface 12,
The vertical acceleration sensor 22 detects the vertical acceleration Ztd of the vehicle body 10 near the road surface sensor. The preview sensor 18 is provided in front of the vehicle by a distance Lp from the front wheels 14, and the wheel base is shown by Lw in FIG.

Although not shown in detail in FIG. 1, the vehicle body 10 includes a suspension including damping shock absorbers 24 and 26 disposed between the vehicle body 10 and the suspension members of the front wheels 14 and the rear wheels 16. Suspended by. Each suspension has a vehicle body 10 and a front wheel 1
Stroke sensors 28 and 30 for detecting relative displacements Hf and Hr between the vehicle 4 and the rear wheel 16 are provided, and the vertical accelerations of these portions are provided above the front wheel 14 and the rear wheel 16 of the vehicle body 10, respectively. Vertical acceleration sensors 32 and 34 for detecting Gf and Gr are provided, and a vehicle speed sensor 36 for detecting a vehicle speed V is further provided.

A signal indicating the state quantity detected by each of the above-mentioned sensors is input to the electronic control unit 38, and the electronic control unit 38 detects the state quantity detected by each sensor as described in detail later. By controlling the corresponding actuators 40 and 42, the damping forces of the shock absorbers 24 and 26 are continuously increased or decreased.

The preview sensor 18 (road surface sensor 20
1 and the vertical acceleration sensors 22) are provided in front of the left and right front wheels, respectively, and the stroke sensors 28, 30 and the vertical acceleration sensors 32, 34 are also provided corresponding to the left and right wheels, respectively, as shown in FIG. Electronic control unit 38
2, which shows one specific example of the above as a block diagram, these sensors corresponding to the right wheel and the left wheel,
Shock absorbers 24 and 26, actuator 40
The symbols 42 and 42 are respectively labeled with symbols r and l.

The electronic control unit 38 includes a microcomputer 50 as shown in FIG. Microcomputer 50 may be of a general configuration as shown in FIG. 2, and central processing unit (CPU) 52.
, Read only memory (ROM) 54, random access memory (RAM) 56, and input port device 58
And an output port device 60, which are connected to each other by a bidirectional common bus 62.

The input port device 58 has a signal indicating the relative displacement Yr and Yl of the road surface from the road surface sensors 20r and 20l of the preview sensors 18r and 18l, and a vertical acceleration Ztdr of the vehicle body near the corresponding road surface sensor from the vertical acceleration sensors 22r and 22l. And signals indicating Ztdl, and strokes Hfr, Hfl, Hrr, Hrl of the corresponding wheels from stroke sensors 28r, 28l, 30r, 30l provided for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. Vertical acceleration sensors 32r, 32l, 34r, 34 provided corresponding to the indicated signal, the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel.
Vertical acceleration G of the vehicle body above the corresponding wheel from l
A signal indicating fr, Gfl, Grr, Grl, and a signal indicating the vehicle speed V are input from the vehicle speed sensor 36.

The input port device 58 appropriately processes the signal input thereto, and in accordance with the instruction of the CPU 52 based on the program stored in the ROM 54, the CPU and the RAM.
The processed signal is output to 56. R
The OM 54 stores a control program based on the flowchart shown in FIG. The CPU 52 is adapted to perform various calculations and signal processing as will be described later based on the flowchart shown in FIG. The output port device 60 is C
According to the instruction from the PU 52, the actuators 40r and 40l are provided corresponding to the wheels through the drive circuits 64-70.
, 42r, 42l are adapted to output control signals.

The operation of the illustrated embodiment will now be described with reference to the flow chart shown in FIG. The control by the electronic control unit 38 is started by closing an ignition switch, which is not shown in the figure, and is ended after a while after the ignition switch is opened.

First, in step 10, the RAM 5
Initialization such as clearing of 6 is performed, and in step 20, signals from each sensor are read, and in step 30
In this case, the vertical accelerations Ztdr and Ztdl detected by the vertical acceleration sensors 18r and 18l are integrated by the second order to calculate Zr and Zl, and the road surface at the preview position at the preview position is calculated according to the following formulas 7 and 8. Absolute displacement X
opr and Xopl are calculated and stored in the RAM 56 in time series.

[0026]

## EQU00007 ## Xopr = Yr-Zr

(8) Xopl = Yl−Zl

In step 40, the above equations (5) and (6) are used.
Then, the delay times Tf and Tr are calculated respectively, and in step 50, the absolute displacements Xpor and Xopl of the road surface calculated in step 30 before the delay time calculated in step 40 are selected. In step 60, the sprung mass velocities Xpdfr, Xpdfl, Xpdrr, and Xpdrl of the virtual model are calculated in accordance with the equation 9 corresponding to the above equation 2, and the unsprung velocity is calculated in accordance with the following equation 10 corresponding to the above equation 3. Relative speed between the sprung and the sprung Ypdfr, Tpdfl, Y
pdrr and Ypdrl are calculated.

[0028]

[Expression 9] Xpdj = (Cpj · s ² + Kpj · s) Xopj / (Mpj · s ² + Cpj · s + Kpj) (j = fr, fl, rr, rl)

[Number 10] Ypdj = Xpdj -Xopdj = -Mpj · s 3 · Xopj / (Mpj · s 2 + Cpj · s + Kpj) (j = fr, fl, rr, rl)

In step 70, the damping coefficient Cp * of each shock absorber according to the skyhook control theory in the virtual model is calculated according to the following equation 11 corresponding to the above equation 4.
j (j = fr, fl, rr, rl) is calculated.

[Equation 11] Cp * j = Cpj · Xpdj / Ypdj

In step 80, the vertical acceleration sensor 3
Vertical velocities Xdfr, Xdfl, X of the vehicle body are integrated by integrating vertical accelerations Gfr, Gfl, Grr, Grl of the vehicle body detected by 2r, 32l, 34r, 34l.
drr and Xdrl are calculated, and the stroke sensor 28
The strokes Hfr, Hfl, Hrr, and Hrl detected by r, 28l, 30r, and 30l are differentiated to differentiate the relative velocities Ydfr, Ydfl, and Ydr between the wheels and the vehicle body.
r and Ydrl are calculated.

At step 90, the damping coefficient C * j of each shock absorber according to the skyhook control theory is calculated according to the following equation 12 based on the vehicle speed Xdj and the relative speed Ydj calculated at step 80. ..

[Equation 12] C * j = Cj * Xdj / Ydj

In step 100, a is calculated based on the damping coefficients Cp * j and C * j calculated in steps 70 and 90.
And b are positive constants, the control damping coefficient Coutj is calculated according to the following equation 13, and in step 110, each actuator is controlled by the control current corresponding to the control damping coefficient Coutj. The steps are repeated.

[Equation 13] Coutj = (a * C * j + b * Cp * j) / (a + b)

FIG. 6 is a flow chart showing the control flow of another embodiment of the damping force control system for a shock absorber according to the present invention. In FIG. 6, steps corresponding to the steps shown in FIG. 3 are given the same step numbers as the step numbers given in FIG.

In this embodiment, in step 70, the damping coefficient Cp * j of each shock absorber according to the skyhook control theory in the virtual model is calculated according to the above equation (11).
(J = fr, fl, rr, rl) are calculated, and those values are RA
It is stored in M56 in time series. In step 95 which follows step 90, the damping coefficient Cp * j calculated in step 70 is called from the RAM 56 before the delay time calculated in step 40.

Thus, according to the two embodiments shown, as shown in FIG. 4 for the right wheel, the road surface absolute displacements Xpr and X detected by the preview sensor 18 are shown.
Virtual vehicle model 1 at preview position Pp based on pl
For 60, the damping coefficient Cp * according to the skyhook control theory
j is calculated, a predetermined delay time Tf in consideration of the time required for the front wheels 14 and the rear wheels 16 to move to the preview position and the control delay, and the damping coefficient calculated before Tr or the damping coefficient Cp * j equivalent to this. The control damping coefficient Coutj is calculated according to the damping coefficient C * j calculated based on the stroke and the vertical acceleration for each wheel, and the shock absorbers 24 and 26 are controlled by the control current corresponding to the control damping coefficient Coutj.
Damping force is controlled via an actuator. Therefore, the damping force of each shock absorber is sure to be the damping coefficient Cp * when the corresponding wheel moves to the preview position Pp.
Since it is controlled based on j, the damping force of the shock absorber is appropriate without delay in control even when the frequency of the undulation change of the road surface is high, for example, when the vehicle travels on a rough road at a relatively high speed. The vibration of the vehicle body is effectively dampened.

In particular, according to the illustrated embodiment, the control damping coefficient Coutj is calculated by the weighted average of the damping coefficient C * j by the vehicle state feedback and the damping coefficient Cp * j based on the detection result of the preview sensor. Because
The damping force can be controlled more stably than when the damping force of each shock absorber is controlled only based on the damping coefficient Cp * j based on the detection result of the preview sensor.

In the above-described embodiment, the damping coefficient Cp * j is the preview sensor 18 for both the front and rear wheels.
However, for the rear wheel, the corresponding state quantity of the front wheel (for example, sprung speed X
dfr, Xdfl and relative velocity Ydf between unsprung and sprung
r, Ydfl) may be used as the preview information. In that case, the damping coefficients Cp * rr and Cp * rl of the shock absorbers for the right rear wheel and the left rear wheel according to the skyhook control theory of the preview are the following numbers, respectively. 14 and Equation 15 are calculated.

[0038]

[Equation 14] Cp * rr = Cprr × Xpdrr / Ypdrr

[Equation 15] Cp * rl = Cprl-Xpdrl / Ypdrl

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to these embodiments, and various other embodiments within the scope of the present invention. It will be apparent to those skilled in the art that

[0040]

As is apparent from the above description, according to the present invention, the damping force of the shock absorber surely depends on the damping coefficient based on the skyhook control theory when the wheel moves to the preview position. Since it is controlled, the damping force of the shock absorber is appropriately changed without causing a control delay even when the frequency of the undulation change of the road surface is high,
This makes it possible to effectively dampen vehicle vibrations,
Since it is not necessary to use a high-performance damping force control device with high calculation speed or a high-performance shock absorber and actuator with high responsiveness, it is possible to reliably avoid an increase in the cost of damping force control. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a damping force control device for a shock absorber according to the present invention.

FIG. 2 is a block diagram showing one specific example of the electronic control device shown in FIG.

FIG. 3 is a flowchart showing a control flow achieved by the electronic control device shown in FIG.

FIG. 4 is an explanatory diagram showing a control logic of the embodiment shown in FIGS. 1 to 3;

FIG. 5 is an explanatory diagram showing a control logic of a damping force control device for a shock absorber according to the present invention.

FIG. 6 is a flowchart showing a control flow of another embodiment of the damping force control device for a shock absorber according to the present invention.

[Explanation of symbols]

 10 ... Vehicle body 18 ... Preview sensor 20 ... Road surface sensor 22 ... Vertical acceleration sensor 24, 26 ... Shock absorber 28, 30 ... Stroke sensor 32, 34 ... Vertical acceleration sensor 36 ... Vehicle speed sensor 38 ... Electronic control device 40, 42 ... Actuator 50 … Microcomputer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Hiraiwa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Shunichi Doi 1 Toyota Central Research Laboratories at 41 Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture

Claims (1)

[Claims] 1. A damping force control device for a shock absorber in which a damping force is increased or decreased by an actuator, and a road surface displacement detection means for detecting an absolute displacement of a road surface at a preview position in front of a wheel, which is mounted on a sprung member, and a vehicle speed. Based on the detection means and the absolute displacement of the road surface detected by the road surface displacement detection means, the damping coefficient by the skyhook control theory is calculated for the virtual vehicle model at the preview position, and the wheels move to the preview position. A damping force control device for a shock absorber, comprising: a control unit that controls a damping force of the shock absorber via the actuator based on the damping coefficient after a predetermined time delay in consideration of a required time and a control delay.