JPH10309919A - Vehicle height control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a vehicle from getting into a state that is liable to cause vehicle behavior uncomfortable to the driver with the use of a vehicle height controller for adjusting vehicle height control mechanisms provided for all the wheels to control the vehicle height. SOLUTION: All the wheels of a vehicle are provided with air suspensions 12, 14, 16 and 18. The suspensions 12, 14, 16 and 18 are controlled for the control of the vehicle height and are continued to be driven until predetermined requirements set for the respective wheels are satisfied. The vehicle rolling state is detected based on detection values by vehicle height sensors 82, 84, 86 and 88 provided for all the wheels. Those requirements set for all the wheels are then evaluated in terms of suppression of the vehicle rolling and updated to values aiming for better evaluation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle height control device, and more particularly to a vehicle height control device that adjusts a vehicle height by extending and contracting a vehicle height adjustment mechanism provided for each wheel.

[0002]

2. Description of the Related Art Conventionally, there is known a vehicle having a vehicle height adjusting function as disclosed in Japanese Patent Publication No. 6-4372. The above-mentioned conventional vehicle is provided with an air suspension for each wheel. Each air suspension is provided with an air chamber. The air suspension is
It can be extended by supplying air to the air chamber. The air suspension can be reduced by discharging air from the air chamber.

In the above-described conventional vehicle, when it is recognized that the vehicle height is lower than the target vehicle height, a rising control for supplying air to a plurality of air suspensions is executed. When it is recognized that the vehicle height is higher than the target vehicle height, a descending control for sequentially discharging air from the plurality of air suspensions is executed. Therefore, according to the above-described conventional vehicle, the vehicle height can be controlled to the target vehicle height at each wheel position regardless of a change with time or a change in the load of the vehicle.

[0004]

However, the vehicle height at each wheel position changes when the air suspension of the other wheel is driven, even if the air suspension provided on that wheel is not driven. Specifically, for example, when the air suspension of the right front wheel of the vehicle is driven in the extension direction, the vehicle heights of the other three wheels are increased in the extension direction even though the air suspensions of those wheels are not driven. Changes to

For this reason, in the above conventional vehicle, for example, when the vehicle height at the left and right rear wheel positions is equally reduced, air is supplied to the left rear wheel air suspension prior to the right rear wheel air suspension. That is,
If the height of the left rear wheel is increased before the height of the vehicle at the right rear wheel position is increased, the internal pressure of the air chambers of the air suspensions of the left and right rear wheels may become non-uniform at the end of the lift control. There is. Similarly, in a conventional vehicle, the internal pressure of the air chamber of the air suspension of each wheel may be non-uniform by executing the ascending control or the descending control with the four wheels as control objects.

[0006] The air suspension exhibits a spring constant corresponding to the internal pressure of the air chamber. Therefore, according to the above-described conventional vehicle, the spring constants of the air suspensions of the four wheels may become non-uniform with execution of the above-described ascent control or descent control. If the spring constant of the air suspension provided for each wheel becomes non-uniform, unpleasant behavior for the driver is likely to occur in the vehicle while the vehicle is running. In this regard, the above-described conventional control method is not always an ideal method for maintaining good riding comfort of the vehicle.

The present invention has been made in view of the above points, and controls the vehicle height at each wheel position to a target vehicle height without forming a situation in which the driver is likely to cause unpleasant vehicle behavior. It is an object to provide a vehicle height control device.

[0008]

The above object is achieved by the present invention.
As described in the above, in a vehicle height control device that controls the vehicle height by expanding and contracting a vehicle height adjustment mechanism disposed for each wheel, based on the vehicle height and a control threshold, the vehicle height adjustment mechanism Vehicle height control means for controlling, sprung behavior detecting means for detecting sprung behavior of the vehicle, control threshold value evaluating means for evaluating the control threshold value based on the sprung behavior,
A control threshold updating unit that updates the control threshold to a value that provides good evaluation.

In the present invention, the vehicle height adjusting mechanism provided for each wheel is controlled based on the vehicle height and a control threshold. The wheel load shared by each wheel changes when the balance of the state of the vehicle height adjustment mechanism provided for each wheel changes. Therefore, the balance of the wheel load shared by each wheel is affected by the control threshold value used for controlling the vehicle height adjustment mechanism.

When the balance of the wheel loads shared by the wheels is good, the sprung behavior of the vehicle becomes stable. On the other hand, when the balance of those wheel loads deteriorates,
The behavior that the driver feels uncomfortable easily occurs on the spring of the vehicle. In the present invention, the control threshold value is used to evaluate whether or not the vehicle exhibits excellent characteristics in suppressing the sprung behavior of the vehicle. Then, the control threshold value is updated to a value that gives a better evaluation. If such a control threshold value is used for controlling the vehicle height adjustment mechanism, a state is formed in which it is difficult for the driver to generate unpleasant sprung behavior with the execution of the vehicle height adjustment.

[0011] The above object is achieved by the present invention as defined in claim 2.
2. The vehicle height control device according to claim 1, wherein the control threshold value updating means generates a new generation threshold value using a genetic algorithm, and a new generation threshold value setting means. Evaluation comparing means for comparing the evaluation with the evaluation of the control threshold value; and when the evaluation of the threshold value of the new generation is superior to the evaluation of the control threshold value, Control threshold changing means for setting the threshold as a new control threshold.

In the present invention, the control threshold value is updated to a new generation threshold value which has a higher evaluation. The new generation threshold is generated according to a genetic algorithm. According to the genetic algorithm, a new generation threshold value that inherits a gene suitable for achieving an object can be generated based on a control threshold gene generated in the past. For this reason, in the present invention, the control threshold value quickly evolves to a value with which excellent evaluation can be obtained.

[0013] The above object is as described in claim 3.
2. The vehicle height control device according to claim 1, wherein the sprung behavior detecting means includes a roll state detecting means for detecting a roll state of the vehicle body, and the control threshold value evaluating means is configured based on the roll state. This is achieved by a vehicle height control device that evaluates the control threshold.

In the present invention, the control threshold value is evaluated based on a roll state generated on a spring of the vehicle body. If the wheel loads shared by the wheels are not properly balanced, the vehicle is more likely to roll than when the balance is proper. Therefore, as described above, when the control threshold value is evaluated based on the roll state, it is possible to evaluate the balance of the wheel load.

According to a fourth aspect of the present invention, in the vehicle height control device according to the third aspect, the sprung behavior detecting means includes a vertical acceleration detecting means for detecting a vertical acceleration of the vehicle body. The vehicle height control device is provided, wherein the control threshold evaluation means evaluates the control threshold based on the roll speed and the vertical acceleration.

In the present invention, the control threshold value is evaluated based on a roll state and a vertical acceleration generated on a spring of the vehicle body. When the vehicle travels in an environment in which vertical acceleration frequently occurs, the vehicle is likely to roll even if the wheel loads shared by the wheels are properly balanced. Therefore, when the vehicle frequently undergoes vertical acceleration, it can be determined that the balance of the wheel loads shared by the wheels is appropriate even if the vehicle rolls to some extent. On the other hand, when a roll occurs in the vehicle even though the vertical acceleration does not act so much on the vehicle, it can be determined that the balance of the wheel loads shared by the wheels is inappropriate even if the roll is not so frequent. . In the present invention, from such a viewpoint,
The control threshold value is evaluated based on both the roll state and the vertical acceleration.

[0017]

FIG. 1 shows a system configuration diagram of a vehicle height control device according to one embodiment of the present invention. The vehicle height control device according to the present embodiment includes an electronic control unit 10 (hereinafter referred to as an ECU 10).
). The ECU 10 includes a CPU, an RO,
M, RAM, input / output interface and the like are built in.

The vehicle height control device includes an air suspension 12.
~ 18. Air suspension 12-18
Are disposed on the right front wheel FR, left front wheel FL, right rear wheel RR or left rear wheel RL of the vehicle, respectively. The air suspensions 12 to 18 are respectively provided with air chambers 20 to 2.
6 and shock absorbers 28-34.
The air chambers 20 to 26 are provided with shock absorbers 28 to
Diaphragms 36 to 42 fixed to the outer peripheral surface of
Housings 44-fixed to the diaphragms 36-42
50.

The upper and lower ends of the shock absorbers 28 to 34 are respectively connected to the vehicle body and wheels FR, FL, R
Fixed to R and RL. Therefore, shock absorber 2
8 to 34 include wheels FR, FL, RR, and RL, respectively.
Between the car and the vehicle (hereinafter referred to as wheel load)
Is working. On the other hand, the air sealed in the air chambers 20 to 26 generates an urging force in a direction for preventing the shock absorbers 28 to 34 from contracting, that is, an urging force opposing the wheel load.

The urging force generated by the air chambers 20-26 increases as the shock absorbers 28-34 shrink, and decreases as the shock absorbers 28-34 expand. Thus, in the air suspensions 12 to 18, the air chambers 20 to 26
Functions as a spring element that receives wheel loads on the wheels FR, FL, RR, RL.

The shock absorbers 28 to 34 have built-in damping force variable actuators 52 to 58, respectively. The damping force variable actuators 52 to 58 are mechanisms for changing the magnitude of the damping force generated by the shock absorbers 28 to 34. The damping force variable actuators 52 to 58 are connected to the ECU 10. The damping force variable actuators 52 to 58 operate in an appropriate state in response to a drive signal output from the ECU 10.

The air chambers 20 to 26 of the air suspensions 12 to 18 are provided with opening / closing valves 60 to 66, respectively.
Through the intake / exhaust passage 68. On-off valve 60 ~
Reference numeral 66 denotes a two-position solenoid valve that keeps the valve closed in a normal state. The on-off valves 60 to 66 are opened when a drive signal is supplied from the ECU 10. A rectifying mechanism 70 communicates with the intake / exhaust passage 68. The rectifying mechanism 70
Is connected to an air dryer 72. Rectifying mechanism 70
A check valve that allows only a fluid flow from the air dryer 72 side to the intake / exhaust passage 68 side;
And an orifice for controlling the flow rate of the fluid exchanged between the intake and exhaust passages 68.

The discharge side of the compressor 76 communicates with the air dryer 72 via a check valve 74. Check valve 7
Reference numeral 4 denotes a one-way valve that allows only a fluid flow from the compressor 76 side to the air dryer 72 side. The compressor 76 has a motor 78 as its power source. The motor 78 drives the compressor 76 by receiving a drive signal from the ECU 10. The compressor 76 discharges high-pressure air from its discharge side when driven by a motor 78. The high-pressure air discharged from the compressor 76 is dehumidified by the air dryer 72,
The air is supplied to the intake / exhaust passage 68.

The air dryer 72 includes the check valve 7 described above.
4 and an atmosphere release valve 80 communicate with each other. Atmospheric release valve 8
Numeral 0 is a two-position solenoid valve that maintains a closed state in a normal state. When a drive signal is supplied from the ECU 10, the atmosphere release valve 80 is opened to allow the air dryer 72 to communicate with the atmosphere. The vehicle height control device according to the present embodiment includes vehicle height sensors 82 to 88. The vehicle height sensors 82 to 88 are provided for each of the wheels FR, FL, RR, RL. The vehicle height sensors 82 to 88 output electric signals corresponding to the vehicle height at each wheel position (hereinafter, referred to as wheel position vehicle height H). Output signals of the vehicle height sensors 82 to 88 are supplied to the ECU 10. The ECU 10 detects the wheel position and the vehicle height based on the output signals of the vehicle height sensors 82 to 88.

The vehicle height control device includes a vertical acceleration sensor 90-
96 are provided. The vertical acceleration sensors 90 to 96 are provided for each of the wheels FR, FL, RR, RL. The vertical acceleration sensors 90 to 96 output electric signals corresponding to vertical acceleration G (hereinafter, referred to as wheel position vertical acceleration G) generated in the vehicle body at each wheel position. Vertical acceleration sensor 9
Output signals 0 to 96 are supplied to the ECU 10. E
The CU 10 detects the wheel position vertical acceleration G based on the output signals of the vertical acceleration sensors 90 to 96.

Next, the operation of the vehicle height control device will be described. When the vehicle height H detected by the vehicle height sensors 82 to 88 is lower than the target vehicle height, the vehicle height control device executes a raising control for increasing the vehicle height H at the wheel position. When the vehicle height H detected by the vehicle height sensors 82 to 88 is higher than the target vehicle height, the vehicle height control device performs a lowering control for lowering the vehicle height H. .

In the raising control, the motor 78 is operated while the air release valve 80 is kept closed, and the opening / closing valves 60 to 66 of the wheels FR, FL, RR, RL are sequentially and appropriately opened. This is realized by setting the state. According to the above processing, the high-pressure air discharged from the compressor 76 is supplied to the air chambers 20 to 26 of the air suspensions 12 to 18.
Are supplied sequentially.

The higher the internal pressure of the air chambers 20 to 26, the greater the urging force in the direction facing the wheel load. Accordingly, when high-pressure air is supplied to the air chambers 20 to 26, and as a result, the amount of air inside the air chambers 20 to 26 increases, the air suspensions 12 to 18 change in the direction of increasing the wheel height H. .
For this reason, according to the above-described ascending control, each wheel FR, F
The wheel height H of the wheel positions L, RR, and RL can be increased on average, that is, the average height of the vehicle can be increased without deteriorating the vehicle attitude.

In the above-described lowering control, the motor 78 is maintained in a non-operating state, the atmosphere release valve 80 is opened, and
This is achieved by sequentially and appropriately opening the on-off valves 60 to 66 of the wheels FR, FL, RR, RL. According to the above processing, the air in the air chambers 20 to 26 of the air suspensions 12 to 18 can be sequentially released to the atmosphere. The wheel position vehicle height H decreases as the amount of air inside the air chambers 20 to 26 of the corresponding air suspensions 12 to 18 decreases. Therefore, according to the above-described descending control, it is possible to reduce the average vehicle height without deteriorating the vehicle attitude.

Incidentally, each wheel FR, FL, RR, RL
Of the wheel position H of the other wheel is changed by changing the wheel position H of the other wheel even if the internal pressure of the air chamber 20 to 26 corresponding to the wheel does not change, that is, the wheel position H corresponds to the other wheel. It changes as the internal pressure of the air chambers 20 to 26 changes. Specifically, for example, the left and right front wheels FL,
When high-pressure air is supplied to the air chamber 20 of the right front wheel FR when the wheel position H of the FR is equally reduced, the wheel position H of the right front wheel FR reaches the target vehicle height by the time. The wheel position H of the left front wheel FL rises to some extent. In this case, thereafter, the air chamber 2 of the left front wheel FL
2, the wheel position H of the left front wheel FL may reach the target vehicle height just by supplying a small amount of high-pressure air.

The air suspensions 12 to 18 exhibit a spring constant corresponding to the internal pressure of the air chambers 20 to 26. Therefore, when a large amount of high-pressure air is supplied to the air chamber 20 of the right front wheel FR and a small amount of high-pressure air is supplied to the air chamber 22 of the left front wheel FL in the process of ascent control as described above, The spring constants of the air suspensions 12 and 14 become uneven.

FIG. 2 shows a case where the wheel positions H of all the wheels are properly controlled to the target vehicle height, and the respective wheels FR, FL, FL
The figure which illustrated the wheel load which RR and RL share is shown.
In the vehicle shown in FIG. 2, it is assumed that the load of the vehicle is distributed to the front and rear wheels by 50% and to the left and right wheels by 50%. "25%" shown in FIG. 2 means that when all the air suspensions 12 to 18 show a uniform spring constant, the wheel load distributed to each wheel FR, FL, RR, RL occupies the total load of the vehicle. Indicates the ratio. On the other hand, “10%” and “40%” shown in parentheses in FIG. 2 indicate that the respective wheels FR, FR, when the spring constants of the air suspensions 12 to 18 become non-uniform during the vehicle height control. FL, RR, R
The ratio of the wheel load distributed to L to the total load of the vehicle is shown.

As shown in parentheses in FIG. 2, the left front wheel F
When the wheel load of L and the wheel load of the right rear wheel RR are 40% of the total load of the vehicle, and the wheel load of the right front wheel FR and the wheel load of the left rear wheel RL are 10% of the total load,
Although the wheel loads of the wheels FR, FL, RR, RL are not uniform, the weight balance in the front-rear direction and the weight balance in the left-right direction are balanced. For this reason, when the wheel loads of the wheels FR, FL, RR, and RL have such a ratio, the wheel loads are not uniform even though the wheel loads are non-uniform.
In some cases, the vehicle heights H of all wheel positions may be equal to the target vehicle height. That is, according to the system of the present embodiment, if the vehicle height control is performed only on the condition that the wheel position H is equal to the target vehicle height, the air suspensions 12 to 18 are completed when the vehicle height control ends. May be non-uniform.

If the spring constants of the air suspensions 12 to 18 are non-uniform, the vehicle rolls and the like during the running of the vehicle will
Unpleasant vehicle behavior is likely to occur for the driver. In other words, when the behavior of the roll or the like is likely to occur while the vehicle is running, it can be determined that the spring constants of the air suspensions 12 to 18 are not uniform. FIG. 3 shows a frequency characteristic of a roll speed generated during running of the vehicle. The characteristics indicated by the solid lines in FIG. 3 indicate characteristics realized when the spring constants of the four air suspensions 12 to 18 are uniform. The characteristic shown by the broken line in FIG.
The characteristics realized when the spring constants 2 to 18 are non-uniform are shown. As shown in FIG. 3, the roll speed gain near 4 Hz is greater when the spring constants of the air suspensions 12 to 18 are non-uniform than when the spring constants are uniform. Therefore, in the system of the present embodiment, the air suspension 1 is determined based on whether the roll speed shows a large gain near 4 Hz.
The uniformity of the spring constants of 2 to 18 can be evaluated.

The vehicle height control apparatus of this embodiment evaluates the uniformity of the spring constants of the air suspensions 12 to 18 by the above-described method, and sets the parameters of the vehicle height control (hereinafter, referred to as "height") so as to improve the evaluation. (Referred to as a control threshold). Hereinafter, with reference to FIG. 4 to FIG. 13, a characteristic portion of the vehicle height control device of the present embodiment will be described.

FIGS. 4 to 6 show flowcharts of an example of a control routine executed by the ECU 10 to realize the above functions. This routine is a main routine that is repeatedly started each time the execution is completed. ECU10
Stores a program corresponding to this routine in the ROM. After the vehicle is started, the ECU 10 executes the following processing according to the program. ECU
Step 10 is a step 10 after this routine is started.
0 is executed.

[0037] In step 100, attempts timer T _GA whether the predetermined time T ₀ or more is determined. The trial timer _TGA is a timer that is automatically incremented after being set to “0” by initial processing when the vehicle is started. The predetermined time T ₀ is an interval at which trial for changing the control threshold value of the vehicle height control is performed. In this embodiment, the predetermined time T ₀ is set to one hour. If it is determined that T _GA ≧ T ₀ does not hold as a result of the above determination, it is determined that the time for trial has not yet come. in this case,
Next, the process of step 102 is performed.

In step 102, R is set as “individual 1”.
The data group stored in the AM is set as a control threshold for the vehicle height control. FIG. 7 shows a data group that the ECU 10 stores in the RAM. As shown in FIG.
In 10, m data groups from “individual 1” to “individual m” are stored. Hereinafter, these data groups are simply referred to as “individual k” (k = 1 to m). The ECU 10 calculates eight control threshold values HFLU (k) and HFR as the individual k.
U (k), HRLU (k), HRRU (k), H
FLD (k), HRRD (k), HRLD (k) and HRRD (k) are stored. ECU1
0 stores the evaluation values XU (k) and XD (k) of the individual k in association with each of the individuals k.

FIG. 8 shows an example of the data structure of individual control thresholds stored as components of the individual k. In this embodiment, each control threshold value is set to 8 as shown in FIG.
It is composed of a binary signal of bits. Of the control thresholds stored as components of individual k, HFLU
(K), HFRU (k), HRLU (k), HR
RU (k) is such that when the vehicle height increase control is executed, the wheel position H of the left front wheel FL, the right front wheel FR, the left rear wheel RL and the right rear wheel RR respectively reaches the target vehicle height. This is a threshold value used to determine whether or not there is an error. on the other hand,
The remaining four control thresholds HFLD (k), HFRD
(K), HRLD (k) and HRRD (k)
When the vehicle height lowering control is executed, the left front wheel F
L, a front right wheel FR, a left rear wheel RL, and a right rear wheel RR are threshold values used to determine whether the vehicle height H has reached the target vehicle height.

The evaluation value XU (k) of the individual k is calculated by using the control thresholds HFLU (k) to HRRU (k) of the individual k, and the air suspension 12 to
This is an evaluation value for evaluating the uniformity appearing in the spring constant of No. 18. Similarly, the evaluation value XD (k) is calculated based on the control thresholds HFLD (k) to HRRD (k) of the individual k when the descending control is executed.
This is an evaluation value for evaluating the uniformity appearing in the spring constant of No. 18. As will be described later, the arithmetic expressions of the evaluation values XU (k) and XD (k) are determined such that their spring constants become smaller as the uniformity becomes better.

In this embodiment, the individual 1 has a control threshold value H indicating the smallest evaluation value XU (k) in the ascending control.
FLU (k) to HRRU (k), and control threshold value HFLD indicating the smallest evaluation value XD (k) in descending control
(K) to HRRD (k) are stored. Also,
Evaluation values XU (k), XD
(K) is increased so that the control threshold HFLU
(K) to HRRD (k) are stored. Therefore,
In step 102, the combination with the highest evaluation among the combinations of the control thresholds stored in the ECU 10 is set as the control threshold for the vehicle height control.

In step 104, each wheel FR, FL,
A process of converting a sampling value obtained based on output signals of the vehicle height sensors 82 to 88 of RR and RL into a vehicle height region is executed. FIG. 9 is a diagram showing an example of output signals of the vehicle height sensors 82 to 88 superimposed on a map referred to when converting output signals of the vehicle height sensors 82 to 88 into a vehicle height region. During traveling of the vehicle, all wheels are constantly displaced vertically in order to absorb traveling vibration. For this reason, the output signals emitted from the vehicle height sensors 82 to 88 during running of the vehicle generally change as shown in FIG. ECU1
0 indicates that the output signals of the vehicle height sensors 82 to 88 are detected as sampling values of the wheel position vehicle height H at that time every predetermined sampling time (5 seconds in this embodiment).

In the above step 104,
The detected sampling value is used to calculate the vehicle height area at each wheel position.
The process of converting to the area is executed. For example, the output shown in FIG.
The force signal is output from the vehicle height sensor 82 disposed on the right front wheel FR.
If it is a signal, according to the above processing, the time t₀Smell
The vehicle height region of the right front wheel FR is recognized as “3”. Step
In step 106, the sampling timer T_SPredetermined count value
Time T₁It is determined whether or not this is the case. sampling
Timer T_SIs initialized by initial processing,
A timer that is automatically incremented. Also,
Fixed time T ₁Are height sensors 82 to 8 which are constantly changing.
8 based on the output signal of step 8
Average at each wheel position based on the vehicle height area obtained in 04
Is the time to wait for estimating
You.

Therefore, in the above step 106, T _S ≧ T ₁
Is determined not to hold, it can be determined that it is not yet time to estimate the average vehicle height area. In this case, step 1 follows step 106 above.
Twelve processes are executed. On the other hand, if it is determined that T _S ≧ T ₁ holds, it can be determined that the time has come to estimate the average vehicle height area. In this case, the process of step 108 is performed next.

[0045] At step 108, the count value of the sampling timer T _S, the process for subtracting a predetermined time (T _1/4) is executed. After the process of step 108 is performed, the predetermined time (T _1/4) until lapse, T _S ≧ T ₁ in step 106 is determined not satisfied. Therefore, the condition of step 106 is
The predetermined time (T _1/4) is established each time elapses.

In step 110, a vehicle height area ratio RATE represented by the following equation is calculated for each wheel position. still,
During the following formula, N _TOTAL is the total number of detected vehicle height region at each wheel position during a predetermined past time T _1. Also, n
(0-5), n (6-15) or the like, the number of data of a predetermined past time 0 region 5 region detected by the respective wheel positioned between the T _1, or, the number of data of the sixth region 15 region It is. Further, (**) used in the following equation is a code that collectively represents the codes FR, FL, RR, RL of the corresponding wheel positions.

RATE0-5 (**) = n (0-5) / N _TOTAL (1) RATE6-15 (**) = n (6-15) / N _TOTAL (2) RATE10 -15 (**) = n (10-15) / N _TOTAL (3) RATE0-9 (**) = n (0-9) / N _TOTAL (4) System of this embodiment , The target vehicle height at the standard time corresponds to the vehicle height region 8. Therefore, RATE0-5 (**) shown in the above equation (1) and RATE6-15 (**) shown in the above equation (2) are used when the vehicle height is decreasing, or This is a ratio that tends to be a large value when the height is not reduced. Similarly, the above (3)
RATE10-15 (**) shown in the formula and RATE0-9 (**) shown in the above formula (4) are respectively
This is a ratio that tends to be a large value when the vehicle height is excessively increasing or when the vehicle height is not excessively increasing.

By the way, the process of step 110 is as follows.
Predetermined time as described above (T _1/4) is executed each time elapses. Accordingly, the (1) to (4) height area ratio shown in equation, whenever the predetermined time has elapsed (T _1/4), the detected vehicle height region during the past recent predetermined time T ₁ Updated based on data. In step 112, the flag XHI
It is determined whether "1" is set in GHT. The flag XHIGHT is a flag indicating whether or not the vehicle height control is being executed. In this step 112, XHIG
If it is determined that HT = 1 is not established, it is determined that the vehicle height control has not been started yet. In this case, the process of step 114 is performed next. On the other hand, XHIGH
If it is determined that = 1 holds, it is determined that the vehicle height control has already been started, and then the process of step 142 is executed.

In step 114, it is determined whether or not the conditions for starting the vehicle height control are satisfied. This step 114
Specifically, it is determined whether or not the condition for starting the vehicle height control is satisfied by executing the processing according to the routine shown in FIG. FIG. 10 shows a flowchart of an example of a control routine executed by the ECU 10 in order to determine whether or not the start condition of the vehicle height control is satisfied. The routine shown in FIG. 10 is started each time execution of step 114 is requested. When the routine shown in FIG. 10 is started, first, the process of step 116 is executed.

In step 116, RATE0-5 corresponding to the wheel to be processed in the current processing cycle is executed.
It is determined whether (**) is equal to or greater than a predetermined value A%.
As a result of the above determination, when RATE0-5 (**) ≧ A is satisfied, it is determined that the wheel position vehicle height H at the position of the processing target wheel is lower than the target vehicle height. In this case, the process of step 118 is executed next. On the other hand, as a result of the above determination, if RATE0-5 (**) ≧ A is not satisfied, it is determined that the wheel position vehicle height H is not lower than the target vehicle height. In this case, the process of step 120 is executed next.

In step 118, flags XUP ** (** are FR, FL, RR,
“1” is set to any of RL).
The flag XUP ** is a flag indicating that the wheel position vehicle height H is decreasing at the position of the wheel to be processed.
In step 120, the flag XUP ** corresponding to the wheel to be processed is reset to "0". Step 12
When the process of 0 is executed, thereafter, it is determined that the wheel position H at the wheel position is not lower than the target vehicle height.

In step 122, it is determined whether or not RATE10-15 (**) corresponding to the wheel to be processed is equal to or greater than a predetermined value B%. As a result of the above determination, RATE
If 10-15 (**) ≧ B is satisfied, it is determined that the wheel position vehicle height H at the position of the processing target wheel is excessively higher than the target vehicle height. In this case, the process of step 124 is executed next. On the other hand, if RATE10-15 (**) ≧ B is not satisfied as a result of the above determination, it is determined that the wheel position vehicle height H does not excessively increase relative to the target vehicle height. In this case, the process of step 126 is executed next.

At step 124, "1" is set to the flag XDOWN ** corresponding to the wheel to be processed.
The flag XDOWN ** is a flag indicating that the wheel position H is excessively increased at the position of the processing target wheel. In step 126, the flag XDOWN ** corresponding to the wheel to be processed is reset to "0".
After the processing of step 126 is executed, it is determined that the wheel position H at the position of the wheel has not risen excessively compared to the target vehicle height.

In step 128, all the wheels FR, F
It is determined whether or not the processing of steps 116 to 126 has been executed for L, RR, and RL. As a result, if it is determined that the processing has not been completed for all the wheels, the wheels for which the processing has not been completed are to be processed,
The processing after step 116 is executed again. On the other hand, when it is determined that the processing has been completed for all the wheels, the processing of step 130 is executed next.

In step 130, it is determined whether or not there is a wheel satisfying XUP ** = 1. as a result,
If it is determined that XUP ** = 1 holds for any of the wheels, the process of step 132 is executed next. On the other hand, if it is determined that there is no wheel satisfying XUP ** = 1, the process of step 134 is executed next.

In step 132, it is determined that the condition for starting the vehicle height control is satisfied. When the process of step 132 ends, the current routine ends. In step 134, it is determined whether or not there is any wheel that satisfies XDOWN ** = 1. As a result, when it is determined that XDOWN ** = 1 is established for any of the wheels, the process of step 132 is executed next. On the other hand, if it is determined that there is no wheel satisfying XDOWN ** = 1, the process of step 136 is executed next.

At step 136, it is determined that the condition for starting the vehicle height control is not satisfied. When the process of step 136 ends, the current routine ends. According to the above processing, when the wheel position vehicle height H at any of the wheel positions is excessively low or excessively high,
When it is necessary to execute the ascending control or the descending control at any of the wheel positions, it can be determined that the condition for starting the vehicle height control is satisfied.

During the main routine of this embodiment, if it is determined in step 114 (see FIG. 4) that the conditions for starting the vehicle height control are satisfied, then the process of step 138 is executed. On the other hand, if it is determined that the start condition of the vehicle height control is not satisfied, the current routine is terminated without any further processing. In step 138, "1" is set to the flag XHIGHT. According to the above process, the flag XHIGHT can be set to "1" immediately after the vehicle control start condition is satisfied.

At step 140, a process for starting the vehicle height control is executed. After the processing of step 140 is executed, the ECU 10 thereafter executes the ascending control when there is a wheel satisfying XUP ** = 1, and also executes XDOW
If there is a wheel satisfying N ** = 1, the descent control is started. When the ascending control is started in the system of the present embodiment, the wheels satisfying XUP ** = 1, that is,
The wheel whose wheel position H is decreasing is selected as the wheel to be controlled. During the execution of the ascent control, high-pressure air is supplied to the air suspensions 12 to 18 of the control target wheels in a predetermined order. The supply of high-pressure air to each of the air suspensions 12 to 18 is continued until the average value of the vehicle height region of the control target wheel (hereinafter, referred to as the average vehicle height region) increases by a predetermined region (for example, two regions). . Then, when the average vehicle height area of one control target wheel increases by a predetermined area, supply of high-pressure air to the air suspensions 12 to 18 of the other control target wheels is started.

During the execution of the ascent control, the above processing is repeated to increase the wheel height H of all the control target wheels. Flag X corresponding to the wheel to be controlled
UP ** is reset to "0" when a predetermined condition described later is satisfied. Wheels for which the flag XUP ** has been reset to "0" are excluded from the control target wheels. As described later, the ascending control is performed using flags X corresponding to all the wheels.
It continues until UP ** is reset to "0".

When the descent control is started in the system of the present embodiment, the wheels satisfying XDOWN ** = 1, that is, the wheels whose wheel height H is excessively increased, are selected as the control target wheels. You. During the descent control,
The air suspensions 12 to 12 of the wheels to be controlled in a predetermined order
Air is released from 18. Each air suspension 12
Release of air from -18 is continued until the average vehicle height area of the control target wheel decreases by a predetermined area (for example, two areas). Then, when the average vehicle height area of one control target wheel decreases by a predetermined area, the release of air from the air suspensions 12 to 18 of the other control target wheels is started.

During the execution of the descending control, the above processing is repeated to lower the wheel positions H of all the controlled wheels. Flag X corresponding to the wheel to be controlled
DOWN ** is reset to "0" when a predetermined condition described later is satisfied. Wheels for which the flag XDOWN ** has been reset to "0" are excluded from the control target wheels. The descending control is continued until the flags XDOWN ** corresponding to all the wheels are reset to "0" as described later.

In step 142, it is determined whether a condition for terminating the vehicle height control is satisfied. Present step 142
Specifically, it is determined whether the condition for terminating the vehicle height control is satisfied by executing the processing according to the routine shown in FIG. FIG. 11 shows a flowchart of an example of a control routine executed by the ECU 10 to determine whether or not the end condition of the vehicle height control is satisfied. The routine shown in FIG. 11 is started each time execution of step 142 is requested. When the routine shown in FIG. 11 is started, first, the process of step 144 is executed.

In step 144, a flag XUP ** corresponding to the wheel to be processed in the current processing cycle is set.
Is set to "1", that is, whether or not the wheel is a control target wheel of the ascent control. If it is determined that XUP ** = 1 is established as a result of the above determination, the process of step 146 is performed next. On the other hand, if it is determined that XUP ** = 1 does not hold, steps 146 and 148 are jumped, and the process of step 150 is executed.

In step 146, it is determined whether RATE6-15 (**) corresponding to the wheel to be processed is equal to or greater than the control threshold value H ** U (1) which is a component of the individual 1 described above. Is determined. As a result of the above determination, RATE
When 6-15 (**) ≧ H ** U (1) holds,
It is determined that the wheel position vehicle height H at the position of the wheel to be processed has already sufficiently increased with respect to the target vehicle height. In this case, the process of step 148 is executed next. On the other hand, as a result of the above determination, RATE6-15 (**) ≧ H
** If U (1) is not satisfied, it is determined that the wheel position H at that wheel position has not yet sufficiently increased with respect to the target vehicle height. In this case, step 148 is jumped, and then the processing of step 150 is executed.

At step 148, the flag XUP ** corresponding to the wheel to be processed is reset to "0". When the process of step 148 is executed, the wheel is excluded from the control target wheels of the ascent control in the next and subsequent processing cycles. In step 150, a flag XDOWN corresponding to the wheel to be processed in the current processing cycle is set.
It is determined whether or not ** is set to "1", that is, whether or not the wheel is a control target wheel of the descending control. If it is determined that XDOWN ** = 1 is established as a result of the above determination, the process of step 152 is executed next. On the other hand, if it is determined that XDOWN ** = 1 is not established, steps 152 and 154 are jumped, and the process of step 156 is executed.

In step 152, it is determined whether RATE0-9 (**) corresponding to the wheel to be processed is equal to or greater than the control threshold value H ** D (1) which is a component of the individual 1 described above. Is determined. As a result of the above determination, RATE0
If -9 (**) ≧ H ** D (1) holds, it is determined that the wheel position vehicle height H at the position of the wheel to be processed has already sufficiently decreased with respect to the target vehicle height. You. In this case, the process of step 154 is executed next. On the other hand, as a result of the above determination, RATE0-9 (**) ≧ H ** U
When (1) is not established, it is determined that the wheel position vehicle height H has not yet sufficiently decreased with respect to the target vehicle height.
In this case, step 154 is jumped, and then the process of step 156 is executed.

In step 154, the flag XDOWN ** corresponding to the wheel to be processed is reset to "0". When the process of step 154 is performed, the wheel is excluded from the control target wheels of the descending control in the next and subsequent processing cycles. In step 156, all wheels F
Steps 144-1 for R, FL, RR, RL
It is determined whether the process of 54 has been executed. As a result, if it is determined that the processing has not been completed for all the wheels, the processing from step 144 onward is executed again for the wheels for which the processing has not been completed. On the other hand, if it is determined that the processing has been completed for all the wheels, the processing of step 158 is executed next.

At step 158, it is determined whether or not there is a wheel satisfying XUP ** = 1. as a result,
If it is determined that XUP ** = 1 does not hold for all wheels, the process of step 160 is executed next. In step 160, it is determined whether or not there is a wheel that satisfies XDOWN ** = 1. As a result, when it is determined that XDOWN ** = 1 is not established for all the wheels, the process of step 162 is executed next.

At step 162, it is determined that the condition for terminating the vehicle height control is satisfied. When the process of step 162 ends, the current routine ends. On the other hand, when it is determined in step 158 that there is a wheel satisfying XUP ** = 1, and in step 16
If it is determined that the wheel satisfies XDOWN ** = 1 at 0, the process of step 164 is executed following those steps.

At step 164, it is determined that the condition for terminating the vehicle height control is not satisfied. When the process of step 164 ends, the current routine ends. According to the above processing, when XUP ** = 1 and XDOWN ** = 1 hold for all the wheels, that is, when the wheel position H of all the wheels FR, FL, RR, and RL is the target When it can be estimated that the vehicle height is controlled to be close to the vehicle height, it can be determined that the condition for terminating the vehicle height control is satisfied.

In the main routine of this embodiment, if it is determined in step 142 (see FIG. 4) that the condition for terminating the vehicle height control has not yet been satisfied, step 1 is repeated.
04 and subsequent processes are executed. On the other hand, if it is determined that the condition for terminating the vehicle height control is satisfied, then step 166 is executed.
Is performed. In step 166, a process of resetting the flag XHIGHT to "0" is executed to indicate that the vehicle height control has been completed. This step 1
When the process at 66 ends, the current routine ends.

During the main routine of this embodiment, the above steps are performed.
In step 100 (see FIG. 4), T_GA≧ T ₀Is determined that
If so, the processing of step 168 shown in FIG.
Is executed. In step 168, the trial counter C_GA
Is cleared. Trial counter C_GAIs the system of the present embodiment.
In the system, a predetermined time T₀Executed every (1 hour)
This is a counter for counting the number of trial repetitions.

At step 170, a process of incrementing the trial counter _CGA is executed. Step 172
Then, a process of generating a new generation individual m + 1 by a genetic algorithm (hereinafter referred to as GA) is executed based on the m individuals stored in the RAM. In the present step 172, specifically, a new generation is generated by executing processing according to the routine shown in FIG.

FIG. 12 is a flowchart showing an example of a control routine executed by the ECU 10 to generate a new generation individual m + 1 according to the GA based on the individuals 1 to m. The routine shown in FIG. 12 is started each time the execution of step 172 is requested. When the routine shown in FIG. 12 is started, first, the process of step 174 is executed. In step 174, two individuals are stochastically selected from the m individuals (individual 1 to individual m) stored in the RAM. Each of these individuals stores eight control thresholds composed of an 8-bit binary signal. ECU
10 crosses the control threshold values stored in each of the two individuals selected in step 174 to generate a control threshold value that is a component of the new generation individual m + 1.

In step 176, the new generation individual m + 1
Is selected. In the present embodiment, the ECU 10 performs mating between individuals using a technique such as exchange using a control threshold value as a unit, crossover using a control threshold bit data as a unit, sudden displacement, or the like. In this step 176, one or more mating methods used in the current processing cycle are stochastically selected from these options.

In step 178, a combination of control thresholds to be crossed, a combination of bit data to be crossed, and the like are stochastically selected. Specifically, as the mating method, the exchange is performed in units of the control threshold, or when sudden displacement is selected, a combination of control thresholds to be mated or a control threshold that causes sudden displacement Is selected. When crossover in units of bit data is selected as the mating method, a combination of bit data to be mated is selected.

At step 180, a new generation individual m + 1
Is generated. In this step 180,
Specifically, in accordance with the mating method or the like selected in the above steps 174 to 178, a new generation individual m having eight control thresholds like the other individuals based on the two individuals m
A process for generating +1 is executed. When the process of step 180 is completed, the current routine is completed. Hereinafter, the eight control thresholds that constitute the new generation individual m + 1 are defined as HFLU (m + 1), HFRU (m + 1),
HRLU (m + 1), HRRU (m + 1), HFL
D (m + 1), HFRD (m + 1), HRLD (m
+1) and HRRD (m + 1).

In the main routine of this embodiment, when the processing of step 172 (see FIG. 5), that is, the processing of generating a new generation individual m + 1 is completed, the processing of step 182 is executed next. In step 182, the eight control threshold values stored in the new generation individual m + 1 are used to control the four control threshold values used for the wheels FR, FL, RR, RL during the ascent control, and During the descending control, four control threshold values used corresponding to the wheels FR, FL, RR, RL are set. ECU10
Performs a trial of the vehicle height control using these control threshold values.

In step 184, each wheel FR, FL,
A process of converting a sampling value obtained based on output signals of the vehicle height sensors 82 to 88 of RR and RL into a vehicle height region is executed. The processing in step 184 is performed with reference to the map shown in FIG. 9 as in the case of step 104 described above. In step 186, the sampling timer T _S
Count of whether or not a predetermined time above T ₁ is determined. If T _S ≧ T ₁ does not hold as a result of the above determination, steps 188 and 190 are jumped, and the process of step 192 is executed. On the other hand, T _S ≧ T ₁
Is determined to hold, the process of step 188 is executed next.

At step 188, the sampling timer
T_SA predetermined time (T₁/ 4) Subtraction processing
Is executed. According to the above processing, the sampling tie
Ma T _SIs a predetermined time T₁(3T₁
/ 4). In step 190, each wheel position
Each time, the vehicle height area ratio RATE6 expressed by the above equation (2)
-15 (**) and the vehicle height represented by the above formula (4)
The area ratios RATE0-9 (**) are calculated.

At step 192, the flag XHIGH
Is set to "1". As a result, when it is determined that XHIGH = 1 is not established, it is determined that the trial based on the new generation individual m + 1 has not yet been started. In this case, the process of step 194 is performed next. On the other hand, when it is determined that XHIGH = 1 is established, it is determined that the trial based on the new generation individual m + 1 has been started. In this case, step 1
Steps 94 to 204 are jumped, and then the processing of step 206 is executed.

In step 194, XHIGH is set to "1" to indicate that the trial has been started.
According to the above process, after the trial based on the new generation individual m + 1 is started, the flag XHIGHHT is immediately set to “1”.
It can be. In step 196, the flag XU
It is determined whether "1" is set in PTEST. The flag XUPTEST becomes “1” when the trial of the ascent control is started based on the new generation individual m + 1.
Is a flag to be set. Therefore, X in this step 196
When it is determined that UPEST = 1 is not established, it can be determined that the trial of the ascent control has not been executed yet. In this case, the process of step 198 is executed next.

In step 198, the flag XUPTES
A process of setting “1” to T is executed. When the process of step 198 is completed, the process of step 200 is executed next. In step 200, a process for starting a trial of the ascent control is executed. In this step 200, specifically, flags XUP * corresponding to all wheels
* Is set to "1", and a process of changing the target vehicle height at all wheel positions by a predetermined value higher than the target vehicle height at the standard time is executed. After the process of step 200 is executed, the ECU 10 thereafter executes a predetermined control method using the same control method as the above-described ascending control, that is, the predetermined order with respect to the air suspensions 12 to 18 of the wheels for which XUP ** = 1 holds. The vehicle height H at each wheel position is gradually raised toward the target vehicle height by a control method of supplying high-pressure air at the same time. The trial of the ascent control is continued until the flags XUP ** corresponding to all the wheels are reset to "0" as described later.

In the main routine of this embodiment, the flag XHIGHHT is set while the trial of the rising control is being executed.
Is maintained at “1”. Therefore, the process of step 196 is not executed again during the execution of the ascent control. When the trial of the ascent control ends, the flag XHIGHT is reset to “0” as described later. Therefore, when the trial of the ascent control is completed, the above step 1 is repeated again.
96 processes are executed.

As described above, the flag XUPTEST is set to "1" at the time when the trial of the ascent control is started (see step 198). Therefore, when step 196 is performed immediately after the end of the trial of the ascent control, it is determined that XUPTEST = 1 is established. In this case, the process of step 202 is performed after step 196.

In step 202, the flag XUPTES
A process for resetting T to “0” is executed. When the process of step 198 is completed, the process of step 204 is executed next. In step 204, a process for starting a trial of the descending control is executed. This step 204
Then, specifically, the flag XDO corresponding to all the wheels
A process is performed to set WN ** to "1" and to return the target vehicle height at all wheel positions to the target vehicle height at the standard time from the value increased when starting the trial of the ascent control. When the process of step 204 is performed,
The CU 10 is a control method similar to the above-described descending control, that is, a control method in which air is discharged in a predetermined order from the air suspensions 12 to 18 of the wheels for which XDOWN ** = 1 holds, and the wheel position of each wheel position is determined. The vehicle height H is gradually lowered toward the target vehicle height. The trial of the descending control is continued until the flags XDOWN ** corresponding to all the wheels are reset to "0" as described later.

In step 206, it is determined whether or not a condition for terminating the trial of the ascending control or the descending control (hereinafter referred to as a trial termination condition) is satisfied. In this step 206, specifically, it is determined whether or not the trial end condition is satisfied by executing the processing according to the routine shown in FIG. FIG. 13 shows a flowchart of an example of a control routine executed by the ECU 10 to determine whether or not the trial end condition is satisfied. The routine shown in FIG. 13 is started each time the execution of step 206 is requested. When the routine shown in FIG. 13 is started,
First, the process of step 208 is performed.

At step 208, a flag XUP ** corresponding to the wheel to be processed in the current processing cycle is set.
Is set to "1", that is, whether or not the wheel is the control target wheel of the ascent control trial. If it is determined that XUP ** = 1 is established as a result of the above determination, the process of step 210 is next performed. On the other hand, when it is determined that XUP ** = 1 does not hold, steps 210 and 212 are jumped, and the process of step 214 is executed.

In step 210, RATE 6-15 (**) corresponding to the wheel to be processed is controlled by a control threshold value H ** U (m) which is a component of the new generation individual m + 1.
+1) is determined. As a result of the above determination,
When RATE6-15 (**) ≧ H ** U (m + 1) holds, the wheel position H at the position of the wheel to be processed is set to the new generation control threshold value H ** U (m + 1). According to this, it can be determined that the target vehicle height has already been sufficiently increased. In this routine, in this case, the process of step 212 is executed next.

On the other hand, in step 210, RATE6
If it is determined that −15 (**) ≧ H ** U (m + 1) does not hold, the control threshold H ** U (m +
According to 1), it can be determined that the wheel position H of the control target wheel has not yet sufficiently increased. In this routine, in this case, step 212 is jumped, and then the process of step 214 is executed.

At step 212, the flag XUP ** corresponding to the wheel to be processed is reset to "0". When the process of step 212 is performed, the wheels are excluded from the control target wheels for the trial of the ascent control in the next and subsequent processing cycles. In step 214, the flag XD corresponding to the wheel to be processed in the current processing cycle
It is determined whether or not OWN ** is set to "1", that is, whether or not the wheel is a control target wheel for a trial of the descending control. As a result of the above determination, XDOWN **
If it is determined that = 1 holds, then step 21
6 is executed. On the other hand, if it is determined that XDOWN ** = 1 is not established, steps 216 and 2
18 is jumped, and then the process of step 220 is executed.

In step 216, RATE0-9 (**) corresponding to the wheel to be processed is set to the control threshold value H ** D (m +) which is a component of the new generation individual m + 1.
1) It is determined whether it is more than or equal to. As a result of the above determination, R
If ATE0-9 (**) ≧ H ** D (m + 1) holds, the wheel position H at the position of the wheel to be processed
However, according to the control threshold value H ** D (m + 1) of the new generation, it can be determined that the vehicle is already sufficiently lowered with respect to the target vehicle height. In this routine, in this case, the process of step 218 is executed next.

On the other hand, in step 216, RATE0
If it is determined that −9 (**) ≧ H ** D (m + 1) is not established, the control threshold H ** U (m +
According to 1), it can be determined that the wheel position H of the control target wheel has not yet sufficiently increased. In this routine, in this case, step 218 is jumped, and then the process of step 220 is executed.

At step 218, the flag XDOWN ** corresponding to the wheel to be processed is reset to "0". When the process of step 218 is performed, the wheel is excluded from the control target wheels in the trial of the descending control in the next and subsequent processing cycles. In step 220, the above-mentioned step 20 is performed for all the wheels FR, FL, RR, RL.
It is determined whether or not the processes of 8-218 have been executed. As a result, if it is determined that the processing has not been completed for all the wheels yet, the processing from step 208 onward is executed again for the wheels for which the processing has not been completed. On the other hand, if it is determined that the processing has been completed for all the wheels, the processing of step 222 is executed next.

In step 222, it is determined whether or not there is a wheel satisfying XUP ** = 1. as a result,
If it is determined that XUP ** = 1 does not hold for all wheels, the process of step 224 is executed next. In step 224, it is determined whether or not there is a wheel that satisfies XDOWN ** = 1. As a result, when it is determined that XDOWN ** = 1 is not established for all the wheels, the process of step 226 is executed next.

At step 226, it is determined that the trial end condition is satisfied. When the process of step 226 ends, the current routine ends. On the other hand, when it is determined in step 222 that there is a wheel satisfying XUP ** = 1, and in step 224,
If it is determined that there is a wheel that satisfies XDOWN ** = 1, step 228 follows those steps.
Is performed.

At step 228, it is determined that the trial termination condition is not satisfied. When the process of step 228 ends, the current routine ends. According to the above processing, XUP ** = 1 for all wheels, and
When XDOWN ** = 1 holds, that is, when it can be estimated that the wheel positions H of all the wheels FR, FL, RR, RL have reached the vicinity of the target vehicle height set at the start of the trial. , It can be determined that the trial end condition has been satisfied.

In the main routine of this embodiment, if it is determined in step 206 (see FIG. 5) that the trial termination condition has not been satisfied, the processing in step 184 and thereafter is executed again. On the other hand, when it is determined that the trial end condition is satisfied, the process of step 230 is executed next. At step 230, a process of resetting the flag XHIGHT to "0" is executed to indicate that the trial of the ascending control or the trial of the descending control has been completed. When the process of step 230 is completed, the process of step 231 shown in FIG. 6 is executed.

In step 231, the vertical acceleration sensor 9
The vertical acceleration G of the vehicle is detected based on the output signals 0 to 96. In step 232, the vehicle height sensors 82 to 8
The roll speed Rs of the vehicle body is calculated based on the eight output signals. In step 234, the vertical processing value G _FILT and Rs _FILT are calculated by processing the vertical acceleration G detected in step 231 and the roll speed Rs calculated in step 232 by a digital filter. The digital filter used in step 234 has a band-pass characteristic that passes frequencies near 4 Hz.

In step 236, step 234 is performed.
Integrated value β = ∫G of the filtered value G _FILT obtained in
_FILT dt is calculated. In step 238, the integral value α = ∫Ra _FILT dt filtering value Ra _{FI LT} determined in step 234 is calculated. The vehicle of the present embodiment is 4
It has a characteristic that it is easy to roll by receiving a vertical acceleration G that changes at a frequency near Hz. Further, as shown in FIG. 3, the roll speed Rs generated in the vehicle of this embodiment is
Since the spring constants of the air suspensions 12 to 18 become non-uniform, it is easy to change the gain especially in the vicinity of 4 Hz. Therefore, according to the system of the present embodiment,
It can be determined that the larger the β = ∫G _FILT dt, the more the vehicle is running in an environment where rolls are likely to occur. Also, α = ∫Ra
_The larger the _FILT dt, the more frequently it can be determined that the vehicle is rolling.

[0102] At step 240, the count value of the evaluation timer T _EV whether the predetermined time T ₂ or more is discriminated. The predetermined time T ₂ are, after the air suspension 12 to 18 is controlled by the increase control trial or descending control trial,
This is the time during which the running of the vehicle should be continued in order to evaluate the state of the air suspensions 12-18. Therefore, if it is determined in this step 240 that T _EV ≧ T ₂ does not hold, it can be determined that sufficient time has not yet passed after the trial has been completed. In this case, the processes of steps 231 to 238 are executed again. on the other hand,
When it is determined that T _EV ≧ T ₂ is satisfied, it can be determined that, after the trial is completed, a time sufficient for performing appropriate evaluation has elapsed. In this case, next step 24
2 is executed.

In step 242, the evaluation value X = α / β of the current trial is calculated. As described above, α is a characteristic value representing the frequency of the roll. On the other hand, β is a characteristic value indicating the ease with which a roll is generated due to the traveling environment. Therefore, the evaluation value X becomes a larger value as the vehicle itself shows characteristics that easily cause roll. Therefore, according to the system of the present embodiment, it can be determined that the smaller the evaluation value X is, the better the balance of the spring constants of the air suspensions 12 to 18 is.

At step 244, the flag XUPTES
It is determined whether "1" is set in T. As described above, XUPTEST is set to “1” immediately after the start of the trial of the ascent control. Therefore, this step 244
If it is determined that XUPTEST = 1 holds in
It can be determined that the evaluation value X obtained this time is an evaluation value related to the trial of the ascent control executed based on the new generation individual m + 1. In this case, the process of step 246 is executed next.

In step 246, step 242 is performed.
Is used as an evaluation value relating to the trial of the ascent control, that is, the control threshold values HFLU (m + 1) and HFRU which are constituent elements of the individual m + 1 of the new generation.
(M + 1), HRLU (m + 1) and HRRU
It is stored as the evaluation value XU (m + 1) for (m + 1). When the process of step 246 is completed, the process of step 184 shown in FIG. 5 is executed. According to the above processing, the trial of the ascent control based on the individual m + 1 is executed, and the evaluation value XU (m +
After 1) is stored, a trial of the descending control based on the individual m + 1 can be started.

In the main routine of this embodiment, if it is determined in step 244 that XUPTEST = 1 does not hold, the evaluation value X obtained this time is replaced by the new generation individual m +
It can be determined that the evaluation value is an evaluation value related to the trial of the descending control executed based on No. 1. In this case, the process of step 248 is executed next. In step 248, the evaluation value X calculated in step 242 is used as an evaluation value relating to the trial of the descending control, that is, the control threshold values HFLD (m + 1), HF, which are components of the new generation individual m + 1.
RD (m + 1), HRLD (m + 1) and HRR
It is stored as an evaluation value XD (m + 1) of D (m + 1). When the above processing ends, the processing of step 250 is executed next.

At step 250, the following three processes are executed. (i) m + 1 sets of control threshold values HFLU (k), HFRU (k), HRLU (k) stored in individuals 1 to m and the new generation individual m + 1
And HRRU (k) as components of individuals 1 to m + 1 in ascending order of evaluation value XU (k). (Ii) m + 1 sets of m + 1 stored in individuals 1 to m and new generation m + 1 Control threshold group HFLD (k), HF
RD (k), HRLD (k) and HRRD (k)
From the individual 1 to the individual m + 1 in ascending order of the evaluation value XD (k).
And (iii) a process of deleting the individual m + 1 newly formed by the above process, that is, the individual m + 1 having a control threshold value of the lowest evaluation as a component.

In step 252, it is determined whether or not the count value of the trial counter _CGA is equal to or greater than a predetermined value α. The predetermined value α is the number of times that the trial of the ascending control and the trial of the descending control should be repeated. If it is determined that C _GA ≧ α is not established as a result of the above determination, it can be determined that the trial has not been sufficiently repeated. In this case, the process of step 170 shown in FIG. 5 is executed next. On the other hand, C _GA ≧ α
Is satisfied, it can be determined that the trial has already been sufficiently repeated. In this case, then step 2
The processing of 54 is executed.

At step 254, processing for clearing the trial counter _CGA is executed. When the process of step 254 is completed, the current processing cycle is completed. According to the above processing, as the trial is repeated, the individual 1
-It is possible to evolve the control threshold value stored in the individual m to a combination that hardly causes the vehicle to roll. At normal times, the vehicle height control can be executed based on the individual 1 having the highest evaluation among the individuals.
Therefore, according to the vehicle height control device of the present embodiment, in addition to being able to accurately control the wheel height H at all wheel positions to the target vehicle height, the springs of the air suspensions 12 to 18 can be constantly controlled. The balance of the constants can be maintained in a good balance in which the vehicle is hardly rolled.

In the above embodiment, the new generation individual m + 1 is evaluated based on the vertical acceleration G and the roll speed Rs of the vehicle body. However, the present invention is not limited to this. No, new generation individuals m + 1
May be evaluated based only on the roll speed Rs. In the above embodiment, the air suspensions 12 to 96 are provided with the "vehicle height adjusting mechanism" according to the first aspect.
In addition, the control threshold value ~ H ** which is a component of the individual 1
U (1) and ~ H ** D (1) correspond to the "control threshold value" of the first aspect, respectively, and the ECU 10 executes the processing of steps 104 to 116 described above. The “vehicle height control means” according to claim 1 executes the processing of the above steps 231 to 240 to thereby “the sprung behavior detection means”.
Executes the processing of step 242, thereby causing the “control threshold value evaluation means” to execute the processing of step 250.
The described "control threshold updating means" is realized respectively.

In the above embodiment, the ECU 1
0 executes the processing of steps 172 to 180, whereby the “new generation generating means” according to claim 2 executes the processing of step 250, and “evaluation comparing means” according to claim 2. And "control threshold value changing means" are each realized. Further, in the above-described embodiment, the ECU 10 performs the processing in steps 232, 2
The "roll state detecting means" according to claim 3 is executed by executing the processing of steps 34 and 238, and the "vertical acceleration detecting means" according to claim 4 is executed by executing the processing of step 231. Each has been realized.

[0112]

As described above, according to the first aspect of the present invention, it is possible to form a state in which it is difficult for the driver to feel uncomfortable with sprung behavior as the vehicle height is adjusted.
According to the second aspect of the present invention, the control threshold value can be rapidly evolved. Therefore, according to the present invention,
A state in which the sprung behavior that the driver feels uncomfortable is unlikely to occur can be quickly formed.

According to the third aspect of the invention, the control threshold value is evaluated by focusing on the roll state of the vehicle body.
It is possible to form a state in which it is difficult to generate a roll. According to the fourth aspect of the invention, the control threshold value is evaluated by focusing on the roll state and the vertical acceleration of the vehicle body, so that the roll is generated more accurately than the third aspect of the invention. It is possible to form a state that is difficult to cause.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a vehicle height control device according to an embodiment of the present invention.

FIG. 2 shows a case where each wheel F is controlled when the wheel height H of all the wheels is controlled to a target vehicle height by the vehicle height control device shown in FIG.
It is the figure which illustrated wheel load which R, FL, RR, and RL share.

FIG. 3 is a diagram illustrating a frequency characteristic of a roll speed generated during running of a vehicle.

FIG. 4 is a flowchart (part 1) of an example of a main routine executed in the vehicle height control device according to one embodiment of the present invention.

FIG. 5 is a flowchart (part 2) of an example of a main routine executed in the vehicle height control device according to one embodiment of the present invention.

FIG. 6 is a flowchart (part 3) of an example of a main routine executed in the vehicle height control device according to one embodiment of the present invention.

FIG. 7 is a diagram showing a data structure of an individual stored in the ECU shown in FIG. 1;

8 is a diagram showing a data structure of a control threshold value, which is a component of an individual, stored in the ECU shown in FIG.

FIG. 9 is a diagram in which an example of an output signal of the vehicle height sensor is superimposed on a map referred to when converting an output signal of the vehicle height sensor into a vehicle height region.

FIG. 10 is a flowchart of an example of a control routine executed in the vehicle height control device according to the embodiment of the present invention to determine whether a start condition of vehicle height control is satisfied.

FIG. 11 is a flowchart illustrating an example of a control routine that is executed by the vehicle height control device according to the embodiment of the present invention to determine whether a vehicle height control termination condition is satisfied;

FIG. 12 is a flowchart of an example of a control routine executed to generate a new generation of individuals in the vehicle height control device according to one embodiment of the present invention.

FIG. 13 is a flowchart of an example of a control routine executed to determine whether a trial end condition is satisfied in the vehicle height control device according to the embodiment of the present invention.

[Explanation of symbols]

10 electronic control unit 12 to 18 air suspension 20 through 26 the air chamber 76 compressor 72 the air dryer 82 to 88 the vehicle height sensors 90 to 96 vertical acceleration sensor T _GA attempts timer T _S sampling timer C _GA trial counter T _EV Evaluation timer H ** U (K) The control threshold value of the ascent control stored in the individual k H ** D (k) The control threshold value of the descending control stored in the individual k XU (k) The control of the ascent control stored in the individual k Evaluation value relating to threshold value XD (k) Evaluation value relating to control threshold value of descent control stored in individual k RATE0-5 (**) Ratio of detection of vehicle regions from 0 region to 5 regions RATE6-15 ( **) Ratio of detection of vehicle regions from 6 regions to 15 regions RATE0-9 (**) Ratio of detection of 5 vehicle regions from 0 region RATE10-15 (**) Ratio of detection of vehicle area from 15 areas to 15 areas

Claims (4)

[Claims] 1. A vehicle height control device for controlling a vehicle height by expanding and contracting a vehicle height adjustment mechanism provided for each wheel, wherein the vehicle height adjustment mechanism is controlled based on a vehicle height and a control threshold value. Vehicle height control means for controlling, sprung behavior detecting means for detecting sprung behavior of the vehicle, control threshold value evaluating means for evaluating the control threshold value based on the sprung behavior, the control threshold And a control threshold value updating means for updating the value to a value that gives a good evaluation. 2. The vehicle height control device according to claim 1,
The control threshold updating means, a new generation generating means for generating a new generation threshold using a genetic algorithm, and comparing the evaluation of the new generation threshold with the evaluation of the control threshold Evaluation comparing means, and when the evaluation of the threshold of the new generation is superior to the evaluation of the control threshold, the threshold of the new generation is set as a new control threshold. A vehicle height control device, comprising: control threshold value changing means. 3. The vehicle height control device according to claim 1, wherein the sprung behavior detecting means includes a roll state detecting means for detecting a roll state of the vehicle body, and the control threshold value evaluating means includes a control unit for controlling the roll threshold. A vehicle height control device, wherein the control threshold value is evaluated based on a state. 4. The vehicle height control device according to claim 3, wherein the sprung behavior detecting means includes a vertical acceleration detecting means for detecting a vertical acceleration of a vehicle body, and the control threshold value evaluating means includes a control unit for controlling the roll. A vehicle height control device for evaluating the control threshold value based on a state and the vertical acceleration.