JP2002293121A - Suspension control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suspension control device capable of improving control accuracy. SOLUTION: When relative speed is in a relative speed region of an initial set value >=V2, a relative speed-damping characteristic (segment C-F in Figure 5) corresponding to command current I2 having a smaller value than command current I1 which is obtained in advance by using the initial set value V2 as relative speed in a control rule approximated to a sky hook damper theory is used for a control, in place of a relative speed-damping characteristic (segment B-E in Figure 5) corresponding to the command current I1 . Damping force at actual relative speed can be lowered from an E point to an F point (that is, a size corresponding to target damping force before a correction of Fsky (B-D) shown by a point B) to improve control accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a suspension control device used for a vehicle.

[0002]

2. Description of the Related Art An example of a conventional suspension control device is disclosed in Japanese Patent Application Laid-Open No. 5-330325.
The device of the second embodiment disclosed in this publication includes a shock absorber of variable damping coefficient interposed between the vehicle body and the axle, an actuator for adjusting the damping coefficient of the shock absorber, and a device mounted on the vehicle body. An acceleration sensor for detecting an acceleration in the vertical direction of the vehicle body, an integration circuit for integrating the acceleration detected by the acceleration sensor to obtain a velocity in the vertical direction of the vehicle body, and obtaining an absolute value of the vertical acceleration of the vehicle body, The vertical speed of the vehicle body obtained by integration is divided by this absolute value, and this value is taken as the relative speed between the vehicle body and the axle, and the damping of the shock absorber is given to the actuator based on the relative speed (relative speed M described later). The body is damped by adjusting the coefficient.

In this case, the shock absorber determines a target damping coefficient by a method approximating a control method based on the skyhook damper theory described later, and responds to a control signal (current) supplied to the actuator based on the target damping coefficient. To change the damping coefficient. By setting the magnitude of the damping coefficient to a predetermined value, a damping force having a magnitude corresponding to (for example, substantially proportional to) the relative speed is generated (the relative speed-damping force characteristic is secured).
At the same time, the relative speed-damping force characteristic can be adjusted by changing the damping coefficient and thus the target damping coefficient.

[0004] The above-mentioned prior art suspension control device performs control by approximating a control method based on the skyhook damper theory. Here, in the skyhook damper theory, V: Absolute vertical speed of the vehicle body (spring up) X: Absolute vertical speed of the axle (unsprung) C _Z : Damping of the shock absorber (damper) provided between the absolute coordinate system If the coefficients, and the damping coefficient C ₁ of the shock absorbers disposed between the vehicle body and the axle (damper) so as to obtain as follows.

That is, if V (V−X)> 0, C ₁ = C _Z V / (V−X) (1)

If V (V−X) <0, then C ₁ = 0 (2).

On the other hand, the prior art suspension
The control unit does not use a stroke sensor,
Using the vertical acceleration sensor only
Detect the speed and, based on this vertical acceleration,
Damping coefficient C₁Is to decide. And the control law
As a result, the actual unsprung and unsprung in equation (1) is
Relative speed (VX) is an average of relative speed (VX).
Assuming a constant value (M), the following control rule
Similar. With the prior art suspension control device
Is based on the skyhook damper theory,
Decay coefficient C ₁I'm trying to get

That is, if V (V−X)> 0, C ₁ = K _v V / M (1a) Also, if V (V−X) <0, C ₁ = C _min ( (Small value) ... (2a) In the formulas (1a) and (2a),
K _v : constant [K _v = C _Z / (V−X)], C _min ≠ 0.

[0009]

In the above-mentioned prior art, the target damping constant is determined by assuming that the relative speed between the unsprung part and the sprung part is constant (relative speed M), and the relative damping constant is determined based on the target damping constant. Since the speed-damping force characteristic is determined, an error occurs between the target damping force and the actually generated damping force when the relative speed is low and when the relative speed is high, and it is desired to improve the control accuracy in this region.

The present invention has been made in view of the above circumstances, and has as its object to provide a suspension control device capable of improving control accuracy.

[0011]

According to the first aspect of the present invention,
A shock absorber interposed between a sprung portion and a unsprung portion of the vehicle and capable of adjusting a damping characteristic according to a command current to the actuator; a sprung vibration detecting means for detecting a sprung vibration of the vehicle; Control means for controlling the damping characteristic of the shock absorber based on the relative speed between the sprung and unsprung obtained from the detection signal detected by the sprung vibration detecting means, wherein the damping characteristic of the shock absorber is: In the relative speed range above the opening point of the damping valve of the shock absorber, the relative speed changes substantially in proportion to the relative speed, and the rate of change is changed according to the magnitude of the command current. The means is a suspension control device that sets the command current based on a target damping force obtained based on a predetermined initial setting value equal to or higher than an opening point of the damping valve. When the relative speed is greater than the initial set value, the control means uses a target damping force smaller than the target damping force for setting the command current instead of the target damping force corresponding to the initial setting value. It is characterized by.
According to a second aspect of the present invention, in the configuration of the first aspect,
When the relative speed is smaller than the initial setting value, a target damping force larger than the target damping force is used for setting the command current instead of the target damping force corresponding to the initial setting value. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A suspension control device according to one embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, a spring 3 and a damping characteristic are provided between a vehicle body 1 (spring-up) and four (only one is shown) wheels 2 (unsprung) constituting an automobile (vehicle). Adjustable shock absorber 4 is interposed in parallel,
These support the vehicle body 1.

An acceleration sensor 6 (spring-spring vibration detecting means) for detecting a vertical acceleration (sprung acceleration) a with respect to the absolute coordinate system of the car body 1 is mounted on the vehicle body 1. The sprung acceleration a (detection signal) detected by the acceleration sensor 6 is supplied to a controller 7 (control means). In addition, the shock absorber 4 and the spring 3 are composed of four wheels 2
Are provided for each of the three, but only one of them is shown for convenience.

The shock absorber 4 includes a damping force generator (not shown) having a damping valve (not shown), and an actuator 8 for driving the damping force generator. As shown in FIG. 5, the relationship between the relative speed and the damping force of the shock absorber 4 changes at the boundary of the valve opening point V1 of the damping valve, and the damping force is relatively reduced in the relative speed region above the valve opening point V1. Damping characteristics that are approximately proportional to the speed (line JE, line KF
Reference). The slope (rate of change) of the damping characteristic in the relative speed region above the valve opening point V1 is changed according to the magnitude of the command current supplied to the actuator 8.

For example, as shown in FIG. 5, when I ₁ is determined as the command current, in the relative speed range from 0 to the valve opening point V1, a substantially quadratic curve is formed as shown by points A and J. In the relative speed region above the valve opening point V1,
As shown by points J, B, and E, the characteristic shows that the damping force is proportional to the relative speed. Similarly, if I ₂ (I ₁ > I ₂ ) is determined as the command current, a substantially quadratic curve-like characteristic as shown by points A and K is shown in the relative speed range from 0 to the valve opening point V1. In the relative speed region above the valve opening point V1, points C and C
D and F show characteristics in which the damping force is proportional to the relative speed, and the relative speed-damping characteristics are different at the valve opening point V1. Further, in the valve open point V1 more relative speed region, the command current exhibit characteristics that the damping force in each case of I ₁ and I ₂ is proportional to the relative velocity, changing the command current I ₁ to the command current I ₂ As can be clearly seen from the comparison between the attenuation characteristic shown by the line JE and the attenuation characteristic shown by the line JE, the slope becomes smaller.

The controller 7 uses a method similar to a control method based on the skyhook damper theory to determine a predetermined initial value V that is equal to or higher than the valve opening point V1.
2 (relative speed value), a target damping force is determined, and a relative speed-damping characteristic can be adjusted in accordance with a command current I supplied to the actuator 8 obtained based on the target damping force. . In the present embodiment, the command current I determined by the above-described method is set to I ₁ in advance, and the shock absorber 4 is operated in the normal state [normal
At the time of control], a relative speed-decay characteristic indicated by a line AJE in FIG. 5 is exerted. Command current I ₁
Is generated from the target damping force F _{sky at} the point B corresponding to the initial setting value V2. In the present embodiment, as shown in FIG. 4, which will be described later, if it is determined that the relative speed is slower than the initial set value V2 in step S3, the normal semi-act control is performed (step S4). If No is determined in S3 (the relative speed is not slower than the initial set value V2), the relative speed-damping characteristic control indicated by the line segment A-K-F (this control is referred to as correction semi-act control for convenience). I do.

As shown in FIG. 2, the controller 7 includes the following components (A) to (G). (A) Integrating circuit 10 for obtaining vertical speed (absolute sprung speed) V by integrating sprung acceleration a, (A) Control method based on sprung absolute speed V obtained by integrating circuit 10 and skyhook damper theory Target damping force c obtained by using a method approximating to (indicated by points B and C in FIG. 5, for example).
(C) detecting the valve opening point V1 at which the damping characteristic is switched, estimating the relative speed using the sprung absolute speed V obtained by the integration circuit 10, and obtaining information indicating the relative speed; A valve opening point detector 12 that outputs information indicating the valve opening point V1 as valve opening information d; (d) a valve opening point detector 1
A valve-opening-point determining unit 13 that determines whether the damping valve is in an open state from the valve-opening information d of FIG.
(E) When the damping valve is in the open state and the relative speed is equal to or higher than the initial set value V2, the damping force calculating unit 11 calculates the target damping force c which is predetermined as described above (for example, in FIG. 5, for example, The target damping force corrector 14 (in FIG. 5, for example, a corrected target damping force F _semi2 indicated by a point C in FIG. 5) instead of the pre-correction target damping force F _sky indicated by the point B. The correction semi-active control is performed by the arithmetic processing of the target damping force correction unit 14.), (f)
If the relative speed is less than the initial set value V2, the relative speed is set at an initial value relative to the predetermined target damping force c (for example, the target damping force before correction F _sky indicated by a point B in FIG. 5). instructions damping force calculating unit 15 for calculating the instruction damping force f by multiplying the control gain K ₁ to the corrected target damping force is the target damping force correcting unit 14 for in a case where the set value V2 or more,
(G) The command damping force f calculated by the command damping force calculator 15
A predetermined relative speed-damping characteristic (line A-) obtained from the command damping force f obtained based on the target damping force after correction or the command damping force f obtained based on the target damping force before correction without correction. A damping characteristic calculator 16 for obtaining a command current I (a driving current for the actuator 8) corresponding to a relative speed-damping characteristic indicated by KF and for supplying the obtained command current I to the actuator 8.

The controller 7 selectively performs the above-described normal semi-active control and correction semi-active control, and this selection is performed as shown in the flowchart of FIG. First, determination processing of a control method (normal semi-active control and correction semi-active control) is started.
(Step S1), the valve-opening point detecting unit 12 detects the valve-opening point V1 at which the damping characteristic switches, and estimates the relative speed using the sprung absolute speed V obtained by the integration circuit 10 (this relative speed is calculated as The means for estimating is referred to as relative speed estimating means 17 for convenience.) [Step S2].

In the next step S3, it is determined whether or not the relative speed is lower than the initial set value V2. Step S3
Yes (the relative speed is slower than the initial set value V2)
When the determination is made, the normal semi-act control is performed as described above (step S4), and when it is determined as No (the relative speed is not slower than the initial set value V2) in step S3, the line segment A-K-F is determined. Performs the correction semi-active control indicated by
(Step S5).

As the relative speed estimating means 17, for example, a circuit shown in FIG. 3 is used. In FIG. 3, the relative speed estimating means 17 calculates the acceleration a from the acceleration sensor 6.
And a phase adjustment filter 20 for adjusting the phase of the actual relative speed to the same phase near the sprung resonance frequency band as described later, and the phase-adjusted signal g1 through a low-pass filter 21a and a high-pass filter 21b. Gain adjustment filter 21 for processing to generate signal g2
And an absolute value calculating means 22 for obtaining an absolute value of the signal g2. The phase adjustment filter 20 includes a phase advance element, and advances the phase of the sprung acceleration a that advances by a predetermined angle with respect to the actual relative speed by a predetermined angle, for example, by setting the phase difference to 180 degrees. The phase of the sprung acceleration a is made to match the phase of the relative speed, and the phase-adjusted signal is used as the estimated relative speed (signal g1). The gain adjustment filter 21 includes a low-pass filter 21a and a high-pass filter 21b connected in parallel to the output of the phase adjustment filter 20. The gain adjustment filter 21 adds the outputs from the low-pass filter 21a and the high-pass filter 21b to add the band-pass signal g.
2 (estimated relative velocity), and the band-pass signal g2
(Estimated relative speed) is output to the absolute value calculation circuit 22. The absolute value calculation circuit 22 calculates the absolute value of the bandpass signal g2 (estimated relative speed) and outputs this as the estimated relative speed.

When the above-described relative speed estimation is performed, the following items can be used to easily estimate the relative speed or to more reliably estimate the relative speed. That is, (1) since the road surface is presumed to be good on the highway, the vertical speed of the piston provided in the shock absorber 4 is relatively low when traveling on the highway. (2) When the vehicle speed is high, it is estimated that the vehicle is traveling on a road with good road surface conditions, such as a highway, so that the vertical speed of the piston is estimated to be relatively low. (3) When the number of times that the sprung acceleration exceeds the threshold value within a predetermined time is small, it is estimated that the vertical speed of the piston is relatively low. (4) When the value of the sprung acceleration is small, it is estimated that the road surface condition is relatively good and the vertical speed of the piston is relatively low.

Next, the target damping force correcting section 14 will be described. When the target damping force correction unit 14 determines that there is a relative speed region equal to or more than the initial set value V2 based on the valve opening information d (information indicating the valve opening point V1 and information indicating the relative speed), as shown below. To the target damping force. First, a pre-correction target damping force F _sky [damping force (point B)] is calculated from the sprung absolute speed V obtained by the integration circuit 10. Here, the pre-correction target damping force F _sky at the point B is calculated.

However, actually, the relative speed is not limited to the initial set value V2. Therefore, the actually generated damping force differs from the target damping force. For example, if the actual relative speed is
Let it be the value shown on the right. In this case, the actual relative speed is larger than the initial set value V2, and as shown in FIG. 2, the actually generated damping force (damping force at point E) becomes larger. For this reason, if the damping force is generated as it is, the target damping force cannot be obtained, and the control accuracy is reduced. Therefore, correction is performed to suppress such a decrease in control accuracy. This correction will be described with reference to FIG.

For convenience of explanation, the command current I is set to I _{1 in} advance.
Is defined, the command current I by the correction as an example a case where the I _2. In FIG. 2, a triangle AEG and a triangle AB
D, the triangle AFG and the triangle ACD are similar, and have the following relationship. F _sky (BD): F _semi2 ( _CD ) = F _semi ( _EG ): F _sky (FG) ... (3) F _sky (BD): target damping force before correction, F _semi2 ( _CD ): Target damping force after correction F _semi ( _EG ): Damping force generated after correction F _sky (FG): Damping force generated before correction

If the spring force is ignored, the generated damping force F before correction is
_{Since semi} is given by equation (4), the corrected target damping force F
_semi2 is expressed by Expression (5) obtained by _modifying Expression (3). F _semi = m · a (4) m: body mass a: body absolute acceleration F _semi = (F _sky ) ² / m · a (5)

By generating a command current I so as to generate a damping force of the corrected target damping force F _semi2 (that is, the command current I ₂ ) (changing the command current I from I ₁ to I ₂ ), The error between the damping force and the generated damping force can be reduced.
That is, without changing (correcting) the command current I, the relative speed corresponding to the command current I ₁ previously obtained by using the initial set value V2 as the relative speed in the control law.
In the damping characteristic (the line segment BE in FIG. 5), the damping force with respect to the actual relative speed generates the damping force indicated by the point E, and becomes excessively large as compared with the target damping force.

On the other hand, in the present embodiment, the command current I is changed from I ₁ to I ₂ as described above,
Relative speed-damping characteristics corresponding to ₂ (line CF in FIG. 5)
Is used, the damping force at the actual relative speed is changed from the point E to the point F (that is, F is indicated by point B).
_sky (the size equivalent to the pre-correction target damping force of BD)
And control accuracy can be improved.

Further, in this embodiment, suspension control is performed well without using a vehicle height sensor, so that the apparatus can be reduced in cost and the performance can be improved because the vehicle height sensor is not used. Can be planned.

In the above embodiment, the valve opening information d
By (information indicating the information indicating the valve opening point V1 and the relative speed), when the relative speed is determined to be the initial setting value V2 or more relative velocity range, the command current I changed from I ₁ to I ₂ , Relative speed-damping characteristic corresponding to the command current I ₁ (FIG. 5
Relative speed in place of the line J-B) corresponding to the command current I ₂ in - was an example in which such attenuation characteristics (line C-F in FIG. 5) is used, instead of the content Alternatively, in addition to the above contents, the following contents may be implemented. That is, based on the valve opening information d (information indicating the valve opening point V1 and information indicating the relative speed), the relative speed is changed to the valve opening point V1.
If it is determined that the relative speed region to the initial setting value V2 from the command current I to change the command current I ₃ of the I ₁ value greater than from I _1, the relative speed corresponding to the command current I ₁ -The command current I ₃ instead of the attenuation characteristic (the line JB in FIG. 5)
Is used (line segment LN in FIG. 5). With this configuration, when the actual relative speed is smaller than the initial set value V2, it is suppressed that the damping force actually generated becomes smaller than the target damping force and the damping force becomes insufficient. For this reason, good control accuracy can be ensured.

In the above embodiment, the case where the vehicle in which the suspension control device is used is an automobile is described as an example. Alternatively, the vertical acceleration of the vehicle body is replaced with the lateral acceleration of the vehicle body of the railway vehicle, By replacing the absolute speed with the right and left absolute speeds of the vehicle body and replacing the axle with a bogie, it can be used for railway vehicles.

[0031]

According to the first aspect of the invention, when the relative speed is larger than the initial set value, the target damping force is compared with the target damping force obtained in advance in accordance with the initial setting value. Since the smaller target damping force is used for setting the command current, the damping force obtained at the actual relative speed becomes smaller, and the value can be made closer to the target damping force obtained in advance corresponding to the initial set value. For this reason, control accuracy can be improved. In other words, it is possible to generate a damping force having a magnitude closer to the damping force expected by the control based on the control theory in which the relative speed is set to a constant value by approximating the control method based on the skyhook damper theory. It is possible to prevent the ride comfort from deteriorating due to an excessively large or insufficient damping force and the occurrence of a wander phenomenon. In addition, since suspension control is favorably performed without using a vehicle height sensor, the cost of the device can be reduced, and the performance can be improved. According to the second aspect of the present invention, when the relative speed is smaller than the initial set value, the target damping force that is larger than the target damping force is replaced with the target damping force corresponding to the initial set value. Since the damping force is used for setting, the damping force obtained at the actual relative speed increases, and the value can be made closer to the target damping force obtained in advance in accordance with the initial setting value, thereby improving control accuracy. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a suspension control device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a controller of the suspension control device of FIG. 1;

FIG. 3 is a block diagram showing a relative speed estimating means (a valve opening point detecting unit) used in the controller of FIG. 1;

FIG. 4 is a flowchart showing calculation contents of a controller of FIG. 1;

FIG. 5 is a diagram showing a relative speed-damping characteristic of the shock absorber of FIG.

[Explanation of symbols]

 4 Shock absorber 7 Controller 14 Target damping force correction unit 15 Command damping force calculation unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D001 AA02 DA03 DA17 EA22 EA24 EA34 EA44 EB32 EC09 ED04 ED10 3J069 AA50 EE64

Claims (2)

[Claims] 1. A shock absorber interposed between a sprung portion and a unsprung portion of a vehicle and capable of adjusting a damping characteristic according to a command current to an actuator, and a sprung vibration detecting a sprung vibration of the vehicle. Detecting means for controlling a damping characteristic of the shock absorber based on a relative speed between the sprung and unsprung obtained from a detection signal detected by the sprung vibration detecting means, Of the shock absorber changes substantially proportionally to the relative speed in the relative speed region above the opening point of the damping valve of the shock absorber, and the rate of change is changed according to the magnitude of the command current. Wherein the control means sets the command current based on a target damping force obtained based on a predetermined initial setting value equal to or higher than an opening point of the damping valve. When the relative speed is greater than the initial set value, the control means sets a target damping force smaller than the target damping force in place of the target damping force corresponding to the initial setting value to the command current. A suspension control device for use in setting a suspension. 2. The target damping force according to claim 1, wherein when the relative speed is smaller than the initial set value, the target damping force is larger than the target damping force instead of the target damping force corresponding to the initial set value. A suspension control device, wherein a force is used for setting a command current.