JPH05229329A - Damping force control method of car suspension - Google Patents

Abstract

PURPOSE:To improve a feeling of riding comfort by determining the damping force of a suspension optimizing the car riding comfort on the basis of a fuzzy inference deriving from a first variable giving the flossy riding comfort to people aboard and a second variable giving the stiff riding comfort respectively. CONSTITUTION:A vertical behavior in a car body is first detected. Both first and second variables are extracted from this behavior and sought by an engine control unit 5. These first and second variables are those of specifying a road surface state, and it the first variable is large a rider receives a feeling of flossy riding comfort. In contrast with this, if the second variable is large, the riser receives a feeling of stiff riding comfort. On the basis of a fuzzy inference deriving from these first and second variables extracted, the road surface state is carefully specified and at the same time damping force in a suspension suited to the road surface state is determined, and subsequently, the damping force in the car suspension is actually selected in accordance with the determined damping force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension damping force control method capable of optimally controlling the switching of the damping force according to road conditions when the vehicle is running.

[0002]

2. Description of the Related Art Among vehicle suspensions, it is known that the damping force can be switched to, for example, three levels of soft, medium and hard. Switching of the damping force is performed by a manual switch. Or automatically depending on the road surface condition.

Therefore, in the case of a suspension capable of automatically controlling the damping force, that is, an active suspension, it is necessary to detect the road surface condition first. To detect this road surface condition, for example, a vehicle height sensor is used. be able to. That is, based on the output of the vehicle height sensor, when the vertical stroke of the vehicle body becomes larger than the allowable amount, it can be determined that the road surface is a bad road having a step. In this case, the damping force of the suspension is switched to hard, which prevents full bumps and rebounds of the vehicle body. Also, even if the vertical stroke is within the allowable amount, if the output of the vehicle height sensor changes finely and frequently, it can be determined that the road surface is a bad road such as a gravel road. In some cases, the damping force is hard-switched.

With respect to this type of active suspension, control aiming at the so-called skyhook effect by conducting continuous switching of damping force has also been studied.

[0005]

The above-described damping force switching control basically tries to secure the running stability of the vehicle by switching the damping force to a hard one when the road surface is a bad road. Therefore, if the road surface is flat,
The damping force of the suspension is softly switched.

However, even if the road surface is flat, if the road surface is undulating, for example, the damping force is soft and the vehicle body moves gently up and down to give the occupant a fluffy feeling. As a result, the ride becomes uncomfortable. To suppress such a fluffy feeling, the damping force of the suspension can be switched to a hard one, but in this case, even if there are small irregularities on the road surface, the vehicle body will receive a small vibration input due to these irregularities. This makes it easier to receive and gives the occupant a rugged ride.

The skyhook effect of the active suspension described above is still in the research stage due to the slow switching speed of the damping force, and its realization is difficult. The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to reduce the damping force of a vehicle suspension that enables switching control of the damping force in consideration of ride comfort of passengers. It is to provide a control method.

[0008]

The damping force control method of the present invention detects the behavior in the vertical direction of the vehicle body, and from this behavior, makes the occupant rugged with a first variable that gives the occupant a fluffy ride comfort. The second variable that gives the ride comfort is extracted, and the damping force of the suspension that optimizes the riding comfort of the occupant's vehicle is determined based on the fuzzy reasoning from these first and second variables, and switched to this damping force. Control.

[0009]

The behavior of the vehicle body in the vertical direction is first detected, and the first and second variables are extracted and obtained from this behavior.
The first and second variables specify the road surface condition. When the first variable is large, the occupant receives a fluffy ride comfort, while when the second variable is large, the occupant is rugged. Get a ride. When the first and second variables are extracted, the road surface condition is finely specified based on the fuzzy reasoning from the first and second variables, and at the same time, the damping force of the suspension suitable for the road surface condition is determined. The damping force of the vehicle suspension is actually switched according to the determined damping force.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a vehicle electronically controlled air suspension is schematically illustrated. This electronically controlled air suspension suspends wheels, for example, its front wheels FW, with respect to the vehicle body 1. Specifically, this suspension is an empty space provided between the vehicle body 1 and the front axle 2. A pressure cylinder / shock absorber 3 is provided. This pneumatic cylinder / shock absorber 3 is capable of switching not only its spring constant but also its damping force in three stages of, for example, hard, medium and soft, and its spring constant and damping force can be switched at the top. It can be performed by the control actuator 4 provided.

That is, the control actuator 4 is electrically connected to an electronic control unit (ECU) 5, a drive control signal is supplied from the ECU 5 to the control actuator 4, and the control actuator is controlled in response to the drive control signal. No. 4 switches the opening of the orifice in the shock absorber, and as a result, the damping force of the suspension is changed. The spring constant of the suspension can be switched by changing the amount of air passing through the air valve between the main air chamber and the sub air chamber of the pneumatic cylinder.

Further, the electronically controlled air suspension described above is provided with a linear stroke sensor 6.
The linear stroke sensor 6 continuously detects a relative vertical stroke between the vehicle body 1 and the front axle 2. Specifically, the linear stroke sensor 6 is attached to the front axle 2 side. , A link 7 that interlocks with the vertical movement of the front axle 2 and a rotary potentiometer 9 that is attached to the vehicle body 1 side and that has the link 7 connected to its rotating arm 8.
It consists of and. Rotary potentiometer 9
Converts a relative vertical stroke between the vehicle body 1 and the front axle 2 into a voltage signal via the link 8 and the rotary arm 8,
This voltage signal, that is, the vertical stroke is supplied to the ECU 5 described above.

The ECU 5 has a function of determining the damping force of the electronically controlled suspension based on the output of the linear stroke sensor 6 and controlling the operation of the control actuator 4. This function is shown in the block diagram of FIG. Indicated by. As shown in FIG. 2, the ECU 5 has an analysis unit 10 which receives the output of the linear stroke sensor 6 and analyzes the output, and the analysis unit 10 includes the linear stroke sensor 6. The results obtained by frequency analysis (FFT) of the 6 outputs, that is, the upper and lower strokes, that is, the spectral distribution is created.

Here, for example, the ECU 5 takes in the output of the linear stroke sensor 6 every 30 msec, and the analyzing unit 10 calculates and creates the spectral distribution every 60 msec. When the vertical stroke spectral distribution is created, the extraction calculation unit 11 uses the spectral distribution to determine whether the traveling road surface of the vehicle is a first variable that gives the occupant a fluffy ride comfort or a second variable that gives the occupant a rough ride comfort. Variables are extracted.

The spectral distribution created by the analysis unit 10 is specifically shown in Table 1 below, and the relationship between the output of the linear stroke sensor 6, that is, the amplitude of the vertical stroke and the frequency is, for example, As shown in FIG.
Here, as shown in FIG. 3, when the vehicle travels on a road surface where the amplitude of the vertical stroke reaches its peak in the frequency range of 1 Hz to 2 Hz (near the sprung resonance point of the vehicle), the occupants are fluffy. When the vehicle runs on a road surface where the amplitude of the vertical stroke has a peak in the frequency range of 4 Hz to 8 Hz, the occupant feels a rugged ride. This is 4Hz
This is because a vibration input of 8 Hz to 8 Hz is most easily felt by humans.

Therefore, the first variable, that is, the sprung resonance degree Fa, can be calculated by extracting the spectrum value corresponding to the frequency range of 1 Hz to 2 Hz in Table 1 and calculating the sum thereof. Similarly, the second variable, that is, the rough sensitivity Fb can be calculated by extracting the spectrum value corresponding to the frequency range of 4 Hz to 8 Hz and calculating the sum thereof.

[0017]

[Table 1] Specifically, the sprung resonance degree Fa is calculated by obtaining the spectral value corresponding to the frequency range of 1 Hz to 2 Hz, that is, the moving average value of the sum of SPE 1 to SPE 3 as shown in the following equation. it can.

Fa = (1 / n) Σ (SPE 1 (n) + SPE 2 (n) + SPE 3 (n)) where n represents the number of data of spectrum values. On the other hand, the ruggedness sensitivity Fb is also calculated by obtaining the spectrum value corresponding to the frequency range of 4 Hz to 8 Hz, that is, the moving average value of the sum of SPC 7 to SPC 14, as shown in the following expression.

Fb = (1 / n) · Σ (SPE 7 (n) + SPE 8 (n) + SPE 9 (n) + SPE 10 (n) + SPE 11 (n) + SPE 12 (n) + SPE 13 (n) + SPE 14 (n)) When the sprung resonance degree Fa and the ruggedness sensitivity degree Fb are calculated as described above, these are then supplied to the damping force setting unit 12. In the damping force setting unit 12, the damping force of the electronically controlled air suspension is set based on fuzzy inference using the sprung resonance degree Fa and the ruggedness degree Fb as variables.

The rules for implementing fuzzy inference are:
For example, as shown in FIG. 4, each rule will be described below. Rule 1 As shown by hatching in FIG. 4, when the sprung resonance degree Fa is small and the road surface state is small, the damping force degree Fg is softly determined, which is concerned with the size of the ruggedness sensitivity degree Fb. .. That is, the road surface condition that complies with this rule 1 means a flat road surface with no undulations, that is, a good road. In this case, even if the damping force of the suspension is soft, the rider feels fluffy and comfortable. It does not give a feeling.

Rule 2 When the sprung mass resonance degree Fa is medium and the ruggedness degree Fb is small, the damping force degree Fg is hard determined. That is, the road surface condition that complies with this rule 2 indicates a road surface that is flat but has a certain degree of undulation as described above. In this case, the damping force of the suspension is made hard and the spring of the vehicle is It suppresses the upper resonance, that is, the fluffy ride comfort. In this road condition, even if the damping force of the suspension is hard, since the rough sensitivity Fb is small, vibrations that are easily felt by humans are not input to the vehicle body, and the passengers feel the rough riding. I don't feel comfortable.

Rule 3 When the sprung resonance degree Fa and the ruggedness sensitivity degree Fb are medium, the damping force degree Fg is determined to be medium. The road surface condition that complies with this rule 3 is
It shows a road surface with both undulations and small irregularities,
In this case, the suspension damping force is set to a medium level to simultaneously reduce the fluffy riding comfort and the rugged riding comfort felt by the occupant.

Rule 4 The sprung resonance degree Fa is medium and the ruggedness sensitivity Fb is large.
If is large, the damping force degree Fg is softly determined. That is, the road surface condition that complies with the rule 4 indicates a road surface having moderate undulations and relatively large unevenness. Therefore, in this case, the damping force of the suspension is mainly used to suppress the vibration input from the unevenness. To soften.

Rule 5 If the sprung resonance degree Fa is large regardless of the magnitude of the sensitivity Fb, the damping force degree Fg is hard determined. The road surface condition that complies with this rule 5 indicates a road surface that is flat but has a relatively large swell, and in this case, the damping force of the suspension is made hard to give the occupant a fluffy ride comfort. Prevent feeling.

As described above, when the sprung resonance degree Fa and the ruggedness sensitivity degree Fb are calculated, these values are applied to each rule, and then the final damping of the electronically controlled air suspension is obtained from the results of the consequent section. The force is set. Specifically, for example, the hatched area of the consequent part in the conforming rule is seen by the damping force degree Fg which is the horizontal axis, and they are superposed, and
What is closest to the center of gravity of the shaded area may be selected as the damping force.

However, in the case of this embodiment, E
In order to simplify and speed up the calculation process in the CU 5, as shown in FIG. 5, a map for realizing the above-mentioned rules 1 to 5 is prepared in advance. Therefore, the damping force of the suspension can be set by reading the points indicated by the calculated sprung mass resonance degree Fa and the ruggedness sensitivity degree Fb from the map.

When the damping force is set in this way, a driving control signal corresponding to the set damping force is supplied from the damping force setting section 12 to the control actuator 4 of the electronically controlled air suspension. Control actuator 4
The damping force is actually switched and controlled through the operation of the. Further detailed description of switching the damping force,
If a harder damping force than the current damping force is set, a drive control signal is immediately output to the control actuator 4 to switch the damping force, and the damping force is held for at least 2 seconds. It However, if the damping force is hard at this point and the damping force is reset to soft in such a state, after holding the damping force at medium for 1 second, Switch power to soft.

The present invention is not limited to the above-described embodiment, but various modifications can be made. For example, in one embodiment, the linear stroke sensor is used to detect the behavior of the vehicle body in the vertical direction. However, instead of the linear stroke sensor, the vertical G sensor may detect the vertical acceleration of the vehicle body. .. Also, from the sensor output
Also when extracting and calculating the variable and the second variable, the first and second variables can be extracted and calculated not necessarily by frequency analysis but by passing the sensor output through a bandpass filter.

Further, in carrying out the present invention, the vehicle suspension is not limited to the electronically controlled air suspension shown in the embodiment.

[0030]

As described above, according to the damping force control method for a vehicle suspension of the present invention, the first variable amount and the ruggedness that give the occupant a fluffy ride comfort are obtained from the behavior of the vehicle body in the vertical direction. The second variable that gives the ride comfort is extracted and obtained, and the damping force of the suspension that optimizes the ride comfort of the vehicle is determined based on the fuzzy reasoning from the first and second variables. For this reason, it is possible to perform switching control of damping force with improved riding comfort.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electronic air suspension.

FIG. 2 is a block diagram showing a part inside the ECU of FIG.

FIG. 3 is a graph showing a frequency distribution of vertical strokes on a certain road surface.

FIG. 4 is a diagram showing each rule of fuzzy inference.

FIG. 5 is a map showing a damping force to be set based on a sprung resonance degree and a rugged sensitivity degree.

[Explanation of symbols]

 1 vehicle body 2 front axle 3 pneumatic cylinder / shock absorber 4 control actuator 5 ECU 6 linear stroke sensor

Front page continuation (72) Inventor Kazuya Hayafune 5-3-8, Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. A vehicle suspension in which the damping force is variable, detects the behavior of the vehicle body in the vertical direction, and from this behavior, makes the occupant rugged and the first variable that gives the occupant a fluffy ride comfort. A second variable that gives a riding comfort is extracted, and a damping force of the suspension that optimizes the riding comfort of the vehicle is determined based on fuzzy reasoning from these first and second variables, and switching control of this damping force is performed. A method for controlling a damping force of a vehicle suspension, comprising: