JPH04115398A - Method for detecting bad road - Google Patents

Abstract

PURPOSE:To decide whether a traveling road of a vehicle is a bad road or not by changing the value of a bad road deciding counter in the other direction in each prescribed restoration value smaller than a displacement value up to a reference value with the lapse of time. CONSTITUTION:In each generation of a deviation from a good road area R in average vertical acceleration GAV, an additional value CU is added to the value of the bad road deciding counter C of a bad road discriminating part 47 in a controller 30, and in other states, the value of the counter C is subtracted in each control cycle, i.e. in each subtraction value CD. In a state continuously and frequently deviating the GAV from a good road area within a short period, the rate of addition of each additional value CU is increased as compared with the rate of subtraction of each subtraction value CD to be executed in each repeat of a control cycle, so that discrimination becomes positive and a bad traveling road face is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides, for example, when controlling the operation of a vehicle active suspension device according to the road surface on which the vehicle is traveling.
The present invention relates to a rough road detection method for detecting the condition of the road surface, that is, whether the road surface is rough or not.

(Prior Art) This type of active suspension system for a vehicle has hydraulic actuators each consisting of a hydraulic cylinder interposed between the vehicle body and each vehicle body, and the vehicle body is actuated via these hydraulic actuators, that is, mainly by hydraulic pressure. It is designed to support.

According to such an active suspension device, if the hydraulic pressure in each hydraulic actuator is controlled in proportion to the relative displacement between the vehicle body and the wheels, the hydraulic actuator can function as a spring. By controlling the hydraulic pressure in proportion to the relative speed between the vehicle body and the wheels, the hydraulic actuator can function as a damper. That is, according to the above-described active suspension device, by appropriately controlling the oil pressure of each hydraulic actuator, the stiffness of the suspension can be arbitrarily varied.

(Problem to be Solved by the Invention) By the way, in controlling the hydraulic pressure of each hydraulic actuator based on the above-mentioned relative displacement and relative speed to vary the stiffness of the suspension, it is necessary to control not only these relative displacements and relative speeds, but also The condition of the road surface on which the vehicle travels, that is,
If the stiffness of the suspension is made variable in consideration of whether the road surface is rough or not, it is thought that undesirable full bumps and full rebounds in the vehicle can be effectively prevented. In order to do this, it is first necessary to accurately detect whether the road surface is rough or not.

Various methods have been proposed in the past for detecting such rough roads, but when applying these conventional methods to active suspension devices, it is necessary to install special sensors for detecting rough roads in this active suspension device. There are disadvantages such as the need to additionally provide a

This invention was made based on the above-mentioned circumstances, and
The purpose is to provide a rough road detection method that does not require additional components such as sensors and is especially suitable for controlling the operation of an active suspension device.

(Means for Solving the Problems) According to the rough road detection method of the present invention, the vertical acceleration of the vehicle body is detected while the vehicle is running, and each time the vertical acceleration deviates from a predetermined area, the value of the rough road determination counter is is changed from the reference value in one direction by a predetermined displacement value, and as time passes, the value of the rough road judgment counter is changed in the other direction by a predetermined return value smaller than the above displacement value up to the reference value. Then, when the value of the rough road determination counter exceeds the rough road determination threshold, the road surface on which the vehicle is traveling is determined to be a rough road.

(Function) According to the above-described rough road detection method, if the vertical acceleration of the vehicle body continuously and frequently deviates from the predetermined range, the value of the rough road determination counter will exceed the rough road determination threshold. , From this, the road surface is determined to be a rough road.

In other words, a situation in which the vertical acceleration of the vehicle body deviates from a predetermined range includes, for example, a wheel running over a protrusion, or
This is a case where the vehicle falls into a pothole, and by checking whether this situation continues frequently, it is possible to determine whether or not the road surface the vehicle is traveling on is rough.

The vertical acceleration of the vehicle body can be obtained from an acceleration sensor included in the active suspension device, the so-called vertical G sensor, so when applying the rough road detection method of the present invention to the active suspension device, special sensors etc. is not additionally required.

(Example) FIG. 1 shows the configuration of a hydraulic active suspension system for a vehicle to which the rough road detection method of the present invention is applied. This figure shows a suspension unit 12 as a hydraulic support means provided for each wheel, that is, front left and right wheels and rear left and right wheels, and a suspension spring 13 of this suspension unit 12 and a single-acting hydraulic cylinder. The hydraulic actuator 14 consisting of
and the wheels 8. In addition, in Figure 1, 1
A suspension unit combined with two wheels is representatively illustrated.

The control valve 17 of the suspension unit 12 is inserted between an oil passage 16 communicating with the hydraulic chamber 15 of the hydraulic actuator 14, and a supply oil passage 14 and a discharge oil passage 6, which will be described later. One end of a branch passage 16a is connected to the middle of the oil passage 16, and an accumulator 2o is connected to the other end of the branch passage 16a. Gas is sealed in the accumulator 2o, and due to the compressibility of the gas, a so-called gas spring action is exerted. A throttle 19 is disposed in the middle of the branch path 16a, and the throttle 19 regulates the amount of hydraulic oil flowing between the accumulator 20 and the hydraulic chamber 15 of the hydraulic actuator 14. The desired vibration damping effect will be achieved.

The other end of the supply oil passage 4 described above is connected to the discharge side of the oil pump l, and the suction side of the oil pump l communicates with the inside of the reserve tank 3 via the oil passage 2. Therefore, when the oil pump 1 is driven, the reserve tank 3
The hydraulic oil stored therein is discharged to the supply oil path 4 side. In the supply oil passage 4, an oil filter 9, a check valve 10, and an accumulator 11 for maintaining line pressure are arranged in order from the oil pump l side. The check valve 10 allows only the flow of hydraulic oil from the oil pump 1 side toward the suspension unit 12 side, and allows high-pressure hydraulic oil to be stored in the accumulator 11.

The control valve 17 is of a type that changes its valve opening degree in proportion to the supplied current value, and depending on this valve opening degree, the control valve 17 changes the valve opening degree between the supply oil passage 4 side and the discharge oil passage 6 side. It is possible to control the supply and discharge of the amount of oil, that is, the supply and discharge of oil pressure to and from the hydraulic actuator 14. And control valve 17
The structure is such that the larger the current value supplied to the hydraulic actuator 14, the greater the hydraulic pressure within the hydraulic actuator 14, that is, the supporting force generated by the hydraulic actuator 14. The hydraulic oil discharged from the control valve 17 to the discharge oil path 6 side is returned to the reservoir tank 3 described above.

The control valve 17 is electrically connected to the output side of the controller 30, and is driven by a drive signal from the controller 30.
Its operation is controlled. Therefore, various sensors are connected to the input side of the controller 30, and these sensors include a vertical G sensor 31 that is attached to the vehicle body 7 and detects the vertical acceleration G of the vehicle body 7, and a vertical G sensor 31 that detects the vehicle height. A steering wheel angle sensor 33 detects the steering angle θH of a steering wheel (not shown) of the vehicle, a vehicle speed sensor 34 detects the vehicle speed V of the vehicle, and the like.

Although only one vertical G sensor 31 is shown in FIG. 1, in reality, the vertical G sensor 31 is used to detect the vertical acceleration G of the vehicle body 7 at each wheel 8. There are 4 of them.

Further, four vehicle height sensors 32 are also provided, and each vehicle height sensor 32 measures the relative displacement between each wheel 8 and the vehicle body 7, that is, the vertical stroke of the vehicle body 7 at each wheel 8. It is designed to detect each.

Next, the operation of the suspension unit 12 controlled by the controller 30 will be explained with reference to the block diagram of FIG. 2.

First, the vertical stroke Sa obtained from the vehicle height sensor 32 paired with one wheel 8 is supplied to the subtraction section 40, and
A target stroke SO corresponding to the target vehicle height of the vehicle body 7 is also supplied to the subtraction unit 40 .

Here, the target stroke So is, for example, the vehicle speed sensor 3
Depending on the vehicle speed V etc. obtained in step 4, in other words, the vehicle height is lowered when the vehicle is running in a high speed range, whereas it is raised when the vehicle is running in a low speed range. is set to

The aforementioned subtraction section 40 calculates the deviation ΔS between the target stroke SO and the vertical stroke Sa, and this deviation ΔS is supplied to the next first hydraulic control amount calculation section 41. In this first hydraulic control amount calculation section 41, the subtraction section 40
The first hydraulic control amount Ps is calculated by multiplying the deviation ΔS1 obtained in , that is, the relative displacement between the wheels 8 and the vehicle body 7 by a predetermined spring element gain Ks. When the hydraulic pressure of the hydraulic actuator 14 is controlled based on the first hydraulic control amount Ps obtained in this way, the hydraulic actuator 14 exerts an equivalent spring force as a suspension that is proportional to the above-mentioned relative displacement. It will be demonstrated.

On the other hand, the deviation ΔS obtained by the subtraction unit 40 is subjected to differentiation processing in the differential calculation unit 42, and as a result, from the differential calculation unit 42,
The relative speed X between the wheels 8 and the vehicle body 7 is output. This relative speed 2. A hydraulic control amount PD is calculated. Based on the second hydraulic control amount PD obtained in this way, the hydraulic actuator 1
4 is controlled, this hydraulic actuator 14
will exhibit an equivalent damping force as a suspension that is proportional to the relative speed X.

The first and second hydraulic control amounts Ps and PD calculated as described above are supplied to the adding section 44 and added together, thereby obtaining a total hydraulic control amount Pl.

Next, the total hydraulic control amount P1 is calculated by the limit hydraulic control amount calculation unit 4.
5, and this limited oil pressure control amount calculating section 45 calculates the limited oil pressure control amount P2.

Specifically, the limit hydraulic control amount P2 is calculated by multiplying the total hydraulic control amount P1 by a predetermined limit gain, and
Here, the limit gain of 1 is calculated by the limit gain calculation unit 46.

In the case of this embodiment, the limit gain calculation unit 46 determines the limit gain to be 1 based on the vertical stroke Sa and the mode discrimination signal indicating whether the road is rough or not, which is determined by the rough road discrimination unit 47. Specifically, the limit gain of 1 can be found from the map shown in FIG. FIG. 3 shows two characteristics: a good road mode (solid line) and a bad road mode (dashed line). When it is determined that the road is rough, 1 is determined as the limit gain from the solid line good road mode based on the vertical stroke Sa. On the other hand, when the rough road is determined as a rough road by the determination by the rough road determining section 47, the vertical stroke Sa is determined to be 1. The limit gain Kl is determined from the rough road mode indicated by the broken line based on Sa.

Here, to explain the two modes in FIG. 3, the limit gain in the good road mode is set to 1, but when the amount of change in the vertical stroke Sa is within a predetermined range 681, it is set to 0, and the amount of change is within a predetermined range 681. When it changes beyond ΔS1,
It increases as the amount of change increases. When the amount of change in the vertical stroke Sa exceeds a predetermined range 682, the limit gain 1 is set to its maximum value, for example 1.0.

On the other hand, the limit gain of 1 in the rough road mode is set to take a larger value with respect to the amount of change in the vertical stroke Sa than in the good road mode. In other words, the limit gain Kl in the rough road mode takes, for example, a value greater than or equal to 0 even if the amount of change in the vertical stroke Sa increases, and as the amount of change in the vertical stroke Sa increases, This is expected to increase.

When the aforementioned limited hydraulic control amount calculation unit 45 calculates the limited hydraulic pressure control amount P2 by taking 1 into consideration for the limit gain, the controller 30 sends a control signal corresponding to the limited hydraulic control amount P2 to the control valve 17. This causes the hydraulic pressure in the hydraulic actuator 14 to be controlled through the actuation of the control valve 17. In other words, the hydraulic actuator 14 performs the functions of a spring and a damper as a suspension, respectively, based on the limited hydraulic control amount P2.

Here, as is clear from the map in FIG. 3, when the road is good, the limit gain is set to 1 based on the good road mode, so if the amount of change in the vertical stroke Sa of the hydraulic actuator 14 is small. For example, even if the total hydraulic control amount P1 is calculated, in this case, the limited hydraulic control amount P2 will be 0 or a value almost close to O. Therefore, the hydraulic actuator 14 does not generate an equivalent spring force and damping force, and in this case, the relative displacement and relative speed between the wheels 8 and the vehicle body 7, that is, when the vehicle is running, the As shown in FIG. By doing so, it is possible to effectively absorb and attenuate the noise, thereby improving the riding comfort.

On the other hand, even on a good road, the vertical stroke Sa
As the amount of change increases, the limit gain increases by 1 as the amount of change increases, that is, the total hydraulic control amount P
Since the restriction rate of 2 becomes small, the restriction hydraulic pressure control amount P2 takes a large value. Therefore, in this case, the hydraulic actuator 14 exerts a large equivalent spring force and damping force depending on the amount of change in its vertical stroke Sa and the relative speed X.

When the amount of change in the vertical stroke Sa further increases, the limit gain 1 takes its maximum value 1.0, and in this situation, the total hydraulic control amount P1 and the limit hydraulic control amount P2
Accordingly, the hydraulic actuator 14 exerts even greater spring force and damping force.

On the other hand, in the case of a rough road, the limit gain Kl is read from the rough road mode, so even if the amount of change in the vertical stroke Sa is small, in this case, compared to the case of a good road, the limit gain Kl is read from the rough road mode.
The limit gain has a large value of 1. Therefore, when driving on a rough road, since the restriction rate of the total hydraulic control amount P2 is small, the limited hydraulic pressure control amount P2 takes a large value, and as a result, the hydraulic actuator 14 has a large spring force from the beginning. and damping force.

In this way, the hydraulic actuator ■4 is made to exert a large spring force and damping force from a region where the amount of change in the vertical stroke Sa is small, and the vertical stroke S
By increasing the spring force and damping force as the amount of change in a increases, the vertical stroke of the vehicle body 7, that is, the hydraulic actuator 14, can be restricted, and the full bump and full rebound of the vehicle body can be restricted. This means that the occurrence of can be effectively suppressed.

Although FIG. 2 shows a block diagram of hydraulic pressure control regarding one hydraulic actuator 14, it goes without saying that the hydraulic pressures of other hydraulic actuators 14 are controlled in the same manner.

By the way, in determining the limit gain to 1 from the good road mode and the bad road mode shown in FIG. However, in the following, this rough road discrimination section 47
A specific rough road detection method implemented in the following will be explained.

First, as is clear from FIG. 2, each upper and lower G sensor 31
The vertical acceleration detected by G1. G2. G3 and G4 are respectively supplied to a calculation unit 48, and the calculation unit 48 calculates an average value GAY of the vertical acceleration G based on the following equation.

GAV=Σ1Gnl/n Here, n indicates the subscript of the vertical acceleration G.

The average vertical acceleration GAV determined by the above equation is then passed through the bypass filter 49 and then sent to the rough road determination section 4 described above.
The rough road determining section 47 determines whether or not the vehicle is in the rough road mode based on fluctuations in the average vertical acceleration GAV. Here, the bypass filter 49 described above is a filter for passing only the high frequency component of the average vertical acceleration GAY.

In the case of this embodiment, the rough road mode determination routine executed by the rough road determining section 47 is shown in the flowcharts of FIGS. 4 and 5, and the flowchart and the graph of FIG. 6 will be described below. The above determination routine will be explained with reference to .

First, the rough road mode determination routine is repeatedly executed at every predetermined control cycle, and when this determination routine is executed for the first time, the values of various flags and counters are set to initial values, that is, 0. It is assumed that this has been set.

In step S1 of FIG. 4, the value of the rough road judgment counter C is subtracted by the subtraction value CD as a return value, and this calculation is performed as follows.
It can be expressed by the following formula.

C=C−CD Here, the rough road judgment counter C is 0 in the case of this embodiment.
It is a counter that can take only the above values. Therefore, if the value of the rough road determination counter C is already at the initial value (reference value), even if step s1 is implemented, the value of the rough road determination counter C is maintained at the initial value, that is, 0.

In the next step S2, it is determined whether or not the rough road mode flag MF is set, that is, whether MF=1, but here as well, the rough road mode flag MF is still reset to 0. In this case, the determination is negative (No) and the next step S3 is executed.

The rough road mode flag MF is a flag indicating whether or not the road surface on which the vehicle is traveling is rough; in this case, the rough road mode flag MF
When is set to 1, it is determined that the road is rough.

In step S3, a flag indicating whether the average vertical acceleration GAY deviates from the predetermined good road region R (0<R<K) shown in FIG. 6, that is, an opaflav HF is set. However, the determination here is also negative for the same reason as in step $2 described above, and the process proceeds to the next step S4.

In step S4, it is determined whether the average acceleration GAV is greater than or equal to a predetermined value for dividing the good road region R, that is, whether the following equation holds true.

If GAV≧, and the determination in step S4 is negative, the process returns to step Sl, and the aforementioned steps are repeated.

However, if the determination in step S4 is positive (Yes), that is, as shown in FIG. 6, for example, at time tl, if the average vertical acceleration GAV or more, Proceeding to step S5, in this step, a predetermined displacement value, that is, an addition value CI+ is added to the value of the rough road determination counter C described above. In other words, the following equation will be implemented.

C=C+CLI Here, the addition value CU is set to a value larger than the above-mentioned subtraction value CD, that is, a value that satisfies CO>CD.

In addition, in step S5, not only is the value of the rough road determination counter C added, but also the above-mentioned over flag HF is added by 1.
is set.

Then, in the next step S6, it is determined whether the value of the rough road determination counter C has reached a predetermined rough road determination threshold CM or more. The rough road determination threshold CM is set to a value that is sufficiently larger than the above-mentioned addition value CU, so the determination at this point is negative, and the process returns to step S1 again. Steps are repeated.

In this case, when step 31 is executed, the value of the rough road determination counter C is subtracted by the subtraction value CD, and then the next step S2. S3 will be executed sequentially, but at this time, since l has already been set in the over flag HF in step S5 described above, the determination in step S3 is positive, and therefore, from step S3, Step S7 will be executed instead of step S4.

In step S7, it is determined whether GAV<K is satisfied, that is, whether the average vertical acceleration GAY has returned to the above-mentioned good road region R (see FIG. 6). If the determination in this step is negative, it means that the average vertical acceleration GAV is still changing between time tl and time t2 in FIG.
Returning to step S1, steps S1 and subsequent steps are repeated. However, if the determination in step $7 is positive, the next step S8 is executed, in which the opaflav HF is reset to O, and
The process returns to step St. Here, as is clear from the above explanation, while step S7 is being repeatedly executed, step S1 is also being repeatedly executed, so the value of the rough road determination counter C is reduced as time passes. This means that each CD is subtracted.

Then, after step S8 is performed, step S1
When the subsequent steps are repeatedly performed, since the determination in step S3 becomes negative again, the steps after step S4 are performed.

To summarize the actions carried out in each step described above, each time the average vertical acceleration GAY deviates from the good road area R, the value of the rough road judgment counter C is incremented by an additional value CU. Then, the value of the rough road determination counter C is decremented by the subtraction value CD in each control cycle, that is, each time step Sl is executed. Therefore, as shown after time t3 in FIG. 6, if the average vertical acceleration GAV deviates from the good road region R continuously and frequently within a short period of time, the rough road The value of the judgment counter C is subtracted by the subtraction value CD at each repetition of the control cycle, but is incremented by the addition value CU at a higher rate.As a result, at a certain time t4, the step The determination in S6 is positive, and in this case,
Steps S6 to S9 are executed, and it is determined that the road surface the vehicle is traveling on is a rough road. That is, in step S9, the aforementioned limit gain is switched to 1 and calculated from the rough road mode shown in FIG. 3, and the rough road mode flag MF is set to 1.

After step S9 has been carried out, the steps will be carried out again from step S1, but in this case, the next step S
The determination in step 2 is positive, and the steps after step S1 in FIG. 5 are executed.

In step SlO, it is determined whether the value of the rough road determination counter C has become smaller than the good road return threshold CL. Here, as is clear from FIG. 6, since the good road return threshold CL is set to a smaller value than the rough road discrimination threshold CM, the judgment here is negative, and therefore, in this case, , step S11 is bypassed and step 512 is executed.

In step S12, it is determined whether the over flag HF is set to 1 or not. Regarding the determination here,
When the steps after step S12 are performed,
Step S6 in FIG. Since step S7 has been executed and step S5 is always executed before steps S6 and S7 are executed, the determination in step S12 is positive. Therefore, step S13 is executed from step S12, and in step S13, it is determined whether the average vertical acceleration GAY has returned to the good road region R or not. If the determination here is still negative, step S
1, and the steps after step S1 are repeated. In this case, the value of the rough road determination counter C is subtracted by the subtraction value CD each time it is repeated. On the other hand, if the determination in step 513 is positive, the overflag HF is reset to 0 in the next step SL4.
If the determination in step S12 is negative, the steps after step S15 will be executed.

In step S15, it is determined whether the average vertical acceleration GAY has deviated from the good road region R. If the determination here is negative, the process immediately returns to step Sl, whereas the determination in step S15 is correct. If so, in step S16, as in the case described above, the value of the rough road determination counter C is incremented by the addition value CU, and the over flag HF is
is set to 1, and the process returns to step S1.

Therefore, from steps Sl, S2 and SIO to step S
When steps 12 and subsequent steps, that is, the process of returning to the good road mode, are repeatedly performed, the value of the rough road judgment counter C is decremented by the subtraction value CD each time step S1 is performed, and the average Vertical acceleration GAV is in good road area R
An additional value CU is added to the value of the rough road judgment counter C only when the value deviates from the above.

Then, while the above-described process of returning to the good road mode is repeatedly executed, when the determination in step S10 becomes positive and step Sll is executed, that is,
At time t5 shown in FIG. 6, the rough road mode is returned to the good road mode. That is, step Sll
Then, the aforementioned limit gain is switched to 1 and calculated from the good road mode shown in FIG. 3, and the bad road mode flag MF is reset to 0. When returning from the bad road mode to the good road mode in this way, as is clear from FIG. 6, the bad road discrimination value CM and the good road discrimination value C
Since hysteresis HY is provided based on the difference between L and L, hunting does not occur when switching between the good road mode and the bad road mode.

When step Sll is executed, step S14 is always executed before it, so that step
After ll is executed, steps S12 to S
13. Through S14, the process returns to step S1, and the steps after step S1 are repeated as described above.

Based on the average vertical acceleration GAV, the rough road determination unit 47
When determining whether or not the road is rough, the average vertical acceleration GAY supplied to the rough road determining section 47 passes through the bypass filter 49 and has its low frequency components cut. does not adversely affect the judgment of rough roads, and also does not adversely affect the ride comfort control performed by the active suspension system when the vehicle travels on a undulating road.

This invention is not limited to the one embodiment described above, and various modifications are possible. For example, in the rough road detection method of the present invention, in an active suspension device,
It is not necessarily used only to vary the above-mentioned limit gain of 1 calculation mode depending on whether the road is rough or not. For example, in a suspension device including a shock absorber, the damping force of the shock absorber is It can also be used to switch between

Further, in one embodiment, the average vertical acceleration GAY is supplied to the rough road determination section 47, but one vertical G sensor 3
It is also possible to determine whether the road is rough based on the vertical acceleration G from 1. In this case, since the vertical acceleration G supplied from the vertical G sensor 31 to the rough road determining section 47 varies as shown by the broken line in FIG. 6, the good road region R in this case is -K<R< It will be shown by K.

Furthermore, in one embodiment, each time the average vertical acceleration GAV deviates from the good road area R, the value of the rough road determination counter C is added to the value C.
In contrast to this, the value of the rough road determination counter C is subtracted by a predetermined subtraction value from the reference value, and when the value of the rough road determination counter C is less than or equal to the rough road determination threshold It may be determined that the road is rough when (in this case, the subtraction value CD in one embodiment is replaced with an addition value).

(Effects of the Invention) As explained above, according to the rough road detection method of the present invention, each time the vertical acceleration of the vehicle body deviates from a predetermined range, the value of the rough road determination counter is incremented by a predetermined displacement value from the reference value. While changing the value in one direction, as time passes, the value of the rough road judgment counter is changed in the other direction by a predetermined return value smaller than the above displacement value up to the reference value.
From the value of the rough road determination counter, it can be determined whether or not the road surface on which the vehicle is traveling is rough. In other words, since the value of the rough road determination counter represents the history of fluctuations in vertical acceleration, that is, the state of the road surface, when the value of the rough road determination counter exceeds the rough road determination threshold, Therefore, it is possible to accurately determine whether the road is rough. Further, since vertical acceleration can usually be detected by a vertical G sensor included in an active suspension device, there is also an advantage that an additional sensor is not required when performing rough road judgment. .

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a schematic configuration diagram of an active suspension device, FIG. 2 is a block diagram for explaining the operation of the controller, and FIG. A graph showing the limit gain, FIGS. 4 and 5 are flowcharts showing a rough road mode determination routine, and FIG. 6 is a graph showing changes in average vertical acceleration with respect to time, the value of the rough road determination counter, and road surface mode. It is. 7... Vehicle body, 8... Wheels, 14... Hydraulic actuator, I7... Control valve, 3o... Controller, 32... Vehicle height sensor. Figure 1 Applicant Mitsubishi Motors Corporation Agent Patent Attorney Kan Nagato Figure 3 Figure 3 Upper and Lower Strog Figure 5

Claims (1)

[Claims] While the vehicle is running, the vertical acceleration of the vehicle body is detected, and each time this vertical acceleration deviates from a predetermined range, the value of the rough road judgment counter is changed in one direction by a predetermined displacement value from the reference value. As time passes, the value of the rough road determination counter is changed in the other direction by a predetermined return value smaller than the displacement value up to the reference value, and when the value of the rough road determination counter exceeds the rough road determination threshold, A rough road detection method characterized by determining a road surface on which a vehicle is traveling as a rough road.