JPH09243346A - Road surface condition detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge a road surface in a short time simplify preparations and a control program. SOLUTION: A road surface condition detecting device is provided with a wheel speed detecting means (a) which detects the speed of at least one of plural wheels; a vehicle speed change detecting means (b) for detecting the amount of change in the wheel speed in a predetermined time; a change calculating means (c) for calculating the absolute values of the amounts of changes in the wheel speed; a road surface judging means (d) which, when the calculation value obtained by the change calculating means (c) is equal to or greater than a predetermined threshold, judges a road surface to be in a bad condition and which if the value is less than the threshold judges the road surface to be not bad; and a low-pass filter (e) by which signals input from the change calculating means (c) are cut off at frequencies at least higher than unsprung resonance frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface state detecting device that determines whether or not a traveling road surface is a bad road based on a change in wheel speed when the vehicle is traveling.

[0002]

2. Description of the Related Art Conventionally, for example, as a road surface state detecting device for determining whether or not a traveling road surface is a bad road in control such as vehicle traction control, anti-skid control, damping force control, and the like, for example, Japanese Patent Laid-Open No. 3-273967. The one described in Japanese Patent Publication is known. This conventional road surface state detecting device determines whether or not the number of times that the amplitude of the change with time of the acceleration detected by the wheel acceleration detecting means exceeds a predetermined threshold value α within a predetermined time is larger than a predetermined threshold value β. A rough road judging means for judging whether the road is a bad road or not, and a threshold changing means for changing the threshold α depending on whether the vehicle is braking or not.

[0003]

However, in the above-described conventional road surface state detecting device, two threshold values α and β are set as threshold values for making a bad road determination, Moreover, since the number of times the amplitude exceeds the threshold value α is further compared with the threshold value β, there are problems listed below. It is difficult to determine a bad road in a short time, and only a road surface having a certain length can be determined. That is, accurate judgment cannot be performed on a road surface in which a bad road and a good road are alternately present with a short length. The thresholds α and β are determined by simulating appropriate values in advance and then determined by further repeating an experiment with an actual vehicle, but such advance preparation becomes complicated and complicated. In the control program, at least two steps for comparison and determination are required, which complicates the control program.

The present invention has been made by paying attention to the above-mentioned conventional problems, and road surface determination can be performed in a short time.
Further, it is an object of the present invention to enable simplification of advance preparation and control program.

[0005]

Means for Solving the Problems In order to achieve the above object, a road surface state detecting device of the present invention, as shown in the claim correspondence diagram of FIG. 1, determines the wheel speed of at least one wheel among a plurality of wheels. A wheel speed detecting means a for detecting, a wheel speed change amount detecting means b for detecting a wheel speed change amount within a predetermined time, a change amount integrating means c for integrating the absolute value of the wheel speed change amount, and this change amount integrating The road surface determination means d is provided for determining that the road is an unfavorable road when the integrated value obtained by the means c is equal to or more than a predetermined threshold value and is determined to be a bad road. Further, in the invention according to claim 2, the wheel change amount detecting means b detects the wheel speed change amount a plurality of times during one rotation of the wheel, and the change amount integrating means c detects the wheel speed during one rotation. It is configured to integrate the absolute value of the wheel speed variation detected at. In the invention according to claim 3, the change amount integrating means c is configured to input a signal via a low-pass filter e having a cutoff frequency at least higher than the unsprung resonance frequency.

[0006]

With the road surface state detection device of the present invention, the amount of change in wheel speed within a predetermined time is detected, the absolute value of the amount of change is integrated, and the integrated value is compared with a threshold value to integrate. If the value is greater than or equal to the threshold value, it is determined to be a bad road, and if the value is less than or equal to the threshold value, it is determined to be a bad road (good road). That is, when traveling on a non-bad road (good road), the slip amount of the wheel is small, and the change amount of the wheel speed detected by the wheel speed change amount detection stage b is small. Therefore, the integrated value of the wheel speed change amount accumulated by the change amount accumulating means c becomes a small value and is less than the threshold value, and the road surface determining means d determines that the road is a bad road (good road). On the other hand, when the vehicle is traveling on a rough road, the wheel slip amount increases, and as a result, the wheel speed change amount detected by the wheel speed change amount detecting means b increases, so the integrated value of the change amount integrating means c also increases. . Therefore, the integrated value becomes equal to or greater than the threshold value, and the road surface determination means d determines that the road is bad. According to the second aspect of the present invention, the above road surface determination is performed by obtaining an integral value every time the wheel makes one revolution. Therefore, on a short surface,
Road surface determination can be performed. For example, accurate road surface determination can be performed even on a road surface in which short roads and good roads are alternately present. In the invention according to claim 3,
The signal input by the change amount integrating means c is a low-pass filter e.
As a result, high frequency components higher than the cutoff frequency higher than the unsprung resonance frequency are cut. Therefore, high frequency noise due to road surface or tire surface, or noise due to household appliances etc. is cut,
Problems caused by accumulating this noise are prevented.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) As shown in FIG. 2, Embodiment 1 includes a wheel speed sensor 1 and a control unit 2, and the wheel speed sensor 1 is provided coaxially with a wheel (not shown). It is arranged in the vicinity of a gear-shaped rotor and outputs a pulse signal SS by a magnetic change caused by the rotation of the rotor. Further, the control unit 2 calculates the wheel speed from the pulse signal SS from the wheel speed sensor 1. Along with this, the rough road is judged based on this wheel speed,
Based on this rough road determination result, for example, a solenoid that controls the brake hydraulic pressure to perform antilock brake control or traction control control, or
It controls the drive of a motor for controlling the damping force of the shock absorber or an actuator 3 such as an actuator for driving the engine such as a fuel injection valve or a throttle valve for performing traction control.

Next, the road surface condition determination by the control unit 2 will be described. The control unit 2 has a configuration for performing road surface condition determination, as shown in the block diagram of FIG. A change amount calculation unit 2b, a low-pass filter 2c, a change amount absolute value integration unit 2d, and a road surface determination unit 2e are provided. When performing the road surface state determination, the wheel speed calculation unit 2a
May input signals from one wheel speed sensor 1 or pulse signals SS from all wheel speed sensors 1.
Alternatively, the road surface determination may be performed for each signal SS.

The road surface condition determination operation by these configurations is
This will be described with reference to the flowchart of FIG. In step S1, the count value Cp obtained by counting the number of pulses of the pulse signal SS obtained from the wheel speed sensor 1 is cleared. The counter function is included in the wheel speed calculator 2. In step S2, the integrated value Sa is cleared. Note that this integration function is included in the change amount absolute value integration unit 2d. In step S3, 1 is added to the count value Cp based on the rise of one pulse of the pulse signal SS from the wheel speed sensor 1. In step S4, the pulse signal SS from the wheel speed sensor 1 is read. That is, one pulse of the pulse signal SS is read. Step S
In step 5, the wheel speed VW indicated by one pulse is obtained based on the read pulse signal SS. In step S6, the current wheel speed VWn to the previous wheel speed VWn-
Subtract 1 to obtain the wheel speed variation Dw. In step S7, the obtained wheel speed change amount Dw is filtered by the low-pass filter 2c at 20 Hz. In step S8, the integrated value Sa of the absolute values of the wheel speed variation Dw is
Ask for. In step S9, the count values Cp and n (n
= Number of pulses for one rotation of the wheel), and if less than n, return to step S3 to continue integration, and if n, proceed to step S10. In step S10, the integrated value Sa and the threshold value γ are compared. If the integrated value Sa is less than the threshold value γ, the road surface flag Rflag is set to 0, that is, it is determined as a good road, and if the threshold value γ is exceeded. The road surface flag Rflag is set to 1, that is, it is determined to be a bad road.

That is, the control flow described above will be briefly described. Every time one pulse signal SS from the wheel speed sensor 1 is input, the variation amount of the wheel speed VW (the wheel speed when the previous pulse was input is input. VWn-1 and the wheel speed VWn due to the current pulse) are calculated, and the change amount of each change is performed while the wheel makes one rotation, that is, while the pulse signal SS from the wheel speed sensor 1 is input for n pulses. Absolute values are integrated, and if the integrated value Sa exceeds the threshold value γ, it is determined as a bad road, and if it is less than the threshold value γ, it is determined as a good road.

FIG. 5 is an output example of the integrated value Sa when traveling on a bad road according to a concrete example in which the device of the above-described embodiment is actually prepared, and FIG. 6 is an integration example when traveling on a good road according to the concrete example. As an output example of the value Sa, as can be seen by comparing the two, the integrated value Sa shows a large value and the change amount is large when the vehicle travels on a rough road, while the integrated value Sa on a good road is large.
Is small and the amount of change is small. In addition, these figures are obtained by plotting the integrated value Sa for each rotation of the wheel and connecting them. T in the figures corresponds to one rotation of the tire. This integrated value Sa by length
Is less than the threshold value γ, it is determined as a good road.

Next, the operation of the embodiment will be described. When the vehicle travels on a good road, the amount of slip of the wheels is small. Therefore, the change amount of the wheel speed VW and the integral value Sa of the change amount are sa.
Becomes a small value as shown in FIG. Therefore,
The integrated value Sa of the amount of change per one rotation of the wheel does not exceed the threshold value γ and is determined to be a good road. On the other hand, when driving on a rough road, the slip amount of the wheels increases,
Amount of change in wheel speed VW and integrated value S of the amount of change
a has a large value as shown in FIG. Therefore,
The integral value Sa of the amount of change per one rotation of the wheel exceeds the threshold value γ, and it is determined that the road is rough. As described above, in the present embodiment, the vehicle behavior component that correlates with the road surface state is obtained from the amount of change in wheel speed VW (that is, the slip amount), and the road surface is determined based on the magnitude of this slip amount. .

As described above, in the present embodiment,
It has the effects listed below. Since only one threshold value (threshold value γ) is used to judge the road surface condition, the preparation for determining the threshold value becomes easy and the control program becomes simple. Can be done in a short time. Since the road surface determination is performed for each rotation of the wheel, the responsiveness of the road surface determination can be improved. By the way, FIGS. 7 and 8 show a comparative example in which the integrated value Sa is plotted every 0.1 rotation of the tire using the same configuration as the specific example of the above-described embodiment. Is when traveling on a bad road, and FIG. 8 is when traveling on a good road. In the case of this comparative example, a noise component related to signal generation in the wheel speed sensor 1 may be superposed, so that the integrated waveform when traveling on a bad road vibrates greatly as shown in the drawing, and the vertical change with respect to the threshold value γ is frequent. As a result, the judgment of good road and bad road will be frequently switched, and even if the judgment is made too small in this way, this judgment can be handled depending on the control response of the output side. Since this is not possible because it is not possible in terms of control, it is preferable to set the time for integrating the integrated value Sa to an optimum time according to the response on the output side. In integrating the wheel speed change amount, the high-frequency component is removed by performing the filtering process by the low-pass filter 2c, so that the high-frequency noise caused by the road surface, the tire surface, or the like, or 50 due to household electric appliances, etc.
Further, noise of 60 Hz or high-frequency noise due to a motor mounted on a vehicle can be removed to prevent erroneous determination that a vehicle is traveling on a good road but is judged to be a bad road.

Next, a second embodiment of the present invention will be described. The second embodiment is different from the above-described first embodiment only in the processing sequence of the control flow of the road surface determination control in the control unit 2, and the other configurations are the same, so the description of the configuration will be omitted. Along with
The same processing and determination steps as those in the flowchart of the first embodiment shown in FIG. 4 are designated by the same step numbers as those in the first embodiment, and the description thereof will be omitted. FIG. 9 shows the second embodiment.
6 is a flowchart showing the road surface determination control of FIG. The second embodiment differs from the first embodiment in the processing order for performing the determination in step S9 for determining whether or not the wheel has made one rotation. In this embodiment, after the road surface determination is performed (step S9).
After S, S11, S12), the determination in step S9 is performed. Also in the second embodiment, the same operational effect as in the first embodiment can be obtained.

Although the embodiment has been described above, the present invention is not limited to this embodiment. For example, in the embodiment, the low-pass filter 2c performs the filtering process before inputting the change amount absolute value accumulating unit 2d. As a result, erroneous judgment due to high frequency noise is prevented and the judgment accuracy is improved. Even if the low-pass filter 2c is not provided, the intended effect, that is, the simplification of advance preparation, the simplification of the control program, and the reduction of the judgment time by setting the threshold value to one can be achieved. Further, in the embodiment, the road surface determination is performed every one rotation of the wheel,
For example, the value to be compared with the count value Cp in step S9 does not have to be a pulse for one rotation of the wheel, or is directly related to the rotation speed of the wheel such as 1 second or 2 seconds. It may be performed at an unrelated time.

[0016]

As described above, in the road surface state detecting device of the present invention, the wheel speed change amount detecting means for detecting the wheel speed change amount and the change amount for integrating the absolute value of the wheel speed change amount. Within a predetermined time, there are provided an integrating means and a road surface determining means for judging that the road is a bad road when the integrated value by the change amount integrating means is equal to or more than a predetermined threshold value, and is less than the threshold value. It is configured to determine the road surface condition by comparing the integrated value of the amount of change in wheel speed in
Since the road surface determination can be performed even if only one threshold value is used for the comparison determination, the effect that the preparation for setting the threshold value can be simplified, and the effect that the control program can be simplified, There is an effect that an appropriate road surface determination can be performed by shortening the time required for the determination and the traveling distance. According to the second aspect of the present invention, the amount of change in wheel speed is obtained a plurality of times during one rotation of the wheel, and the wheel performs road surface determination by integrating the absolute value of the amount of change in one rotation. Since it is configured, it is possible to perform road surface determination by traveling on an extremely short road surface, for example, even on a road surface where short roads and bad roads are alternately present,
An effect that an accurate road surface determination can be performed is obtained. Further, according to the third aspect of the invention, since the low-pass filter that cuts the high-frequency component above the cutoff frequency of the frequency higher than the unsprung resonance frequency in the signal input by the change amount integrating means is provided, the high frequency due to the road surface or tire surface is high. Noise, high-frequency noise due to home appliances, or high-frequency noise due to the operation of an in-vehicle actuator is cut, and an effect of preventing the erroneous determination due to the integration of this noise can be obtained.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a road surface state detecting device of the present invention.

FIG. 2 is a configuration diagram showing a configuration of the first embodiment.

FIG. 3 is a block diagram showing a configuration of a control unit according to the first embodiment.

FIG. 4 is a flowchart illustrating a control flow according to the first embodiment.

FIG. 5 is a specific value output diagram during traveling on a rough road in a specific example.

FIG. 6 is an output diagram of an integrated value when traveling on a good road in a specific example.

FIG. 7 is an integrated value output diagram during traveling on a rough road in a comparative example.

FIG. 8 is an integrated value output diagram during traveling on a good road in a comparative example.

FIG. 9 is a flowchart showing the control flow of the second embodiment.

[Explanation of symbols]

 a wheel speed detection means b wheel speed change amount detection means c change amount integration means d road surface determination means e low pass filter 1 wheel speed sensor 2 control unit 2a wheel speed calculation unit 2b wheel speed change amount calculation unit 2c low pass filter 2d absolute change amount Value integration unit 2e Road surface determination unit 3 Actuator

Claims (3)

[Claims] 1. A wheel speed detecting means for detecting a wheel speed of at least one wheel among a plurality of wheels, a wheel speed change amount detecting means for detecting a wheel speed change amount within a predetermined time, and a wheel speed change amount A change amount accumulating means for accumulating absolute values, and a road surface judging means for judging a bad road when the integrated value by the change amount accumulating means is a predetermined threshold value or more, and a non-bad road when it is less than this threshold value. And a road surface condition detecting device. 2. The wheel change amount detecting means detects the wheel speed change amount a plurality of times during one rotation of the wheel, and the change amount integrating means detects the wheel speed change amount during one rotation of the wheel. The road surface condition detecting device according to claim 1, wherein the absolute value of is integrated. 3. The change amount integrating means is configured to input a signal via a low-pass filter having a cutoff frequency at least higher than the unsprung resonance frequency. 2. The road surface condition detecting device according to 2.