JPH09243345A - Road surface condition detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge a road surface in a short time and to simplify preparations and a control program. SOLUTION: A road surface condition detecting device is provided with a wheel speed detecting means (a) which outputs a signal corresponding to the speed of at least one of plural wheels; an amplitude calculating means (b) which, when signals are input thereto via a band-pass filter (d) extracting unsprung vertical resonance frequency components in signals output from the wheel speed detecting means (a), calculates the absolute values of amplitude of the vertical resonance frequency components for a predetermined time; and a road surface judging means (c) which judges the road surface to be in a bad condition if the calculation value obtained by the amplitude calculating means (b) is equal to or greater than a predetermined threshold, and which judges the road surface to be not bad if the value is less than the threshold.

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-mentioned object, a road surface state detecting device of the present invention, as shown in the claim correspondence diagram of FIG. 1, has a wheel speed of at least one wheel among a plurality of wheels. Wheel speed detecting means a for outputting a corresponding signal
And an amplitude accumulating means b for accumulating the absolute values of the amplitudes of the unsprung upper and lower resonance frequency components contained in the output signal of the wheel speed detecting means a for a predetermined time, and the integrated value of the amplitude accumulating means b is a predetermined value. A road surface determination means c is provided for determining a bad road when the threshold value is equal to or more than the threshold value and determining a non-bad road when the threshold value is less than the threshold value. According to the second aspect of the invention, the amplitude accumulating means b is configured to input the output signal of the wheel speed detecting means a via the bandpass filter d for extracting the unsprung upper and lower resonance frequency components. Further, in the third aspect of the invention, the predetermined time for the amplitude accumulating means b to integrate the absolute value of the amplitude is the time for the wheel to rotate once.

[0006]

In the road surface state detecting device of the present invention, the absolute value of the amplitude of the unsprung upper and lower resonance frequency components in the output signal of the wheel speed detecting means a within a predetermined time is calculated by the amplitude integrating means b.
In the road surface determination means c, the integrated value is compared with a threshold value, and when the integrated value is equal to or more than the threshold value, it is determined as a bad road, and when the integrated value is less than the threshold value, it is determined as a non-bad road (good road). To do.
In other words, it was found that the amplitude of the unsprung upper and lower resonance frequency components on the bad road is larger than that on the good road, and the fluctuation of the unsprung upper and lower resonance frequency components included in the wheel speed is larger on the bad road than on the good road. ing. The integrated value of the fluctuation component of the unsprung upper and lower resonance frequencies represents the slip amount of the wheel. Therefore, when traveling on a good road, since the slip amount of the wheels is small, the integrated value of the absolute value of the amplitude integrated by the amplitude integrating means b becomes a small value, which is less than the threshold value.
The road surface determination means c determines that the road is a bad road (good road). on the other hand,
When the vehicle travels on a rough road, as a result of an increase in the amount of slip of the wheels, the amplitude of the unsprung upper and lower resonance frequency components of the output signal of the wheel speed detecting means a becomes large, and the integrated value of the amplitude integrating means b also becomes a large value. Therefore, the integrated value becomes equal to or greater than the threshold value, and the road surface determination means c determines that the road is bad. According to the second aspect of the present invention, the unsprung upper and lower resonance frequency components are extracted from the output signal of the wheel speed detecting means a by the band pass filter d.
By. In the invention according to claim 3, the road surface determination is performed every time the wheel makes one rotation. Therefore, it is possible to perform the road surface determination on a short road surface, and for example, it is possible to perform the accurate road surface determination even on a road surface where short roads and good roads are alternately present.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, as shown in FIG. 2, a wheel speed sensor 1 and a control unit 2 are provided.
And The wheel speed sensor 1 is a well-known device which is arranged in the vicinity of a gear-shaped rotor provided coaxially with a wheel (not shown) and outputs a pulse signal SS by a magnetic change caused by the rotation of the rotor.

Further, the control unit 2 is, for example, a solenoid for controlling a brake hydraulic pressure for performing antilock brake control or traction control control, a motor for controlling a damping force of a shock absorber, or a traction control. It controls driving of an actuator 3 such as an actuator for driving an engine such as a fuel injection valve or a throttle valve. In performing such control, a pulse signal SS from the wheel speed sensor 1 is detected in order to detect a running state. It is configured to input and calculate the wheel speed, determine the road surface, and switch the control based on the road surface determination result.

Next, the road surface condition determination by the control unit 2 will be described. The control unit 2 has a configuration for performing the road surface condition determination, as shown in the block diagram of FIG. 2b, an amplitude integration unit 2c, and a road surface determination unit 2d. In addition, when determining the road surface condition,
The pulse signal SS may be input from all the wheel speed sensors 1 provided for each wheel, and the road surface state determination may be performed for each signal SS, or one wheel speed sensor 1
It is also possible to input the pulse signal SS only from to determine the road surface state, and the latter is used in this embodiment.

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 that performs this counting is the wheel speed calculator 2a.
Included in. In step S2, the integrated value a is cleared. This integration function is included in the amplitude integration unit 2c. 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. In step S5, the wheel speed VW indicated by one pulse is obtained based on the read pulse signal SS. In step S6, the unsprung upper and lower resonance frequency component amplitudes of 10 to 15 Hz are extracted by the bandpass filter. In step S7,
The integrated value Sa of the absolute value of the extracted amplitude is obtained. In step S8, the count value Cp is compared with n (n = the number of pulses for one rotation of the wheel). If less than n, the process returns to step S3 to continue the integration, and if n, the process proceeds to step S9. In step S9, the integrated value Sa and the threshold value γ are compared, and if the integrated value Sa is less than the threshold value γ, the road surface flag Rfla.
g is set to 0, that is, it is determined to be a good road. On the other hand, 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, to briefly explain the above control flow, while the wheel makes one revolution, that is, while the pulse signal SS from the wheel speed sensor 1 is input for n pulses,
For each pulse of the signal, the absolute values of the amplitudes of the unsprung upper and lower resonance frequency components are integrated, and when the integrated value Sa exceeds the threshold value γ, it is determined as a bad road, and when it is less than the threshold value γ, it is a good road. It is a judgment.

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 embodiment is actually produced, 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. Since the slip amount of the wheel is small during running on a good road, the absolute value of the amplitude of the unsprung upper and lower resonance frequency components contained in the pulse signal SS, and its absolute value. The integrated value Sa of the values is shown in FIG.
It becomes a small value as shown in. 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 the vehicle travels on a rough road, the slip amount of the wheel increases, so that the absolute value of the amplitude of the unsprung upper and lower resonance frequency components and the integrated value Sa of the absolute value become large values as shown in FIG. Therefore, the integral value Sa per one rotation of the wheel exceeds the threshold value γ, and it is determined that the road is bad. As described above, in the present embodiment, the vehicle behavior component that correlates with the road surface state is determined by the fluctuation amount of the unsprung upper and lower resonance frequency components included in the pulse signal SS of the wheel speed sensor 1, that is, the absolute value of the amplitude. (=
The amount of slip) is used to determine the road surface based on the magnitude of the integrated value Sa of this absolute value.

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. Since the bandpass filter is used to extract the unsprung upper and lower resonance frequency components from the pulse signal SS from the wheel speed sensor 1, the configuration is simplified as compared with the configuration in which the lowpass filter and the highpass filter are combined. Further, it is possible to prevent erroneous determination by removing high frequency noise due to road surface or tire surface, 50 or 60 Hz noise due to household electric appliances, or high frequency noise due to a vehicle-mounted motor or the like.

Although the embodiment has been described above, the present invention is not limited to this embodiment. For example, in the embodiment, as a bandpass filter, 10
Although a frequency band of ˜15 Hz is shown, this frequency band is set according to the upper and lower resonance frequency characteristics of the unsprung vehicle.

Further, in the embodiment, the road surface condition is determined for each rotation of the wheel, but the present invention is not limited to this, and the value to be compared with the count value Cp in step S9 is The number of pulses for two rotations of the wheel or 0.5 rotations is set to 2n, 0.5n, or an arbitrary numerical value not directly related to the rotation speed of the wheel (for example, 1
The number may be set to 0, 20, 50, 100) or may be divided into times such as 1 second and 2 seconds that are not directly related to the rotation speed of the wheels. However,
If this time is too short, the control performed on the output side may fail to respond. Therefore, it is preferable to set the optimum time by matching with the control response.

[0017]

As described above, in the road surface state detecting device of the present invention, the absolute value of the amplitude of the unsprung upper and lower resonance frequency components included in the output signal of the wheel speed detecting means is set for a predetermined time. An amplitude accumulating means for accumulating and a road surface judging means for judging a bad road when the integrated value by the amplitude accumulating means is equal to or more than a predetermined threshold value and determining a non-bad road when less than the threshold value are provided. The road surface condition is configured by comparing the integrated value of the absolute values of the amplitudes of the unsprung upper and lower resonance frequency components in time with a threshold value, and the road surface condition is determined even if only one threshold value is used for comparison judgment. Since the determination can be made, the effect that the preparation for setting the threshold value can be simplified, the effect that the control program can be simplified, the time required for the determination and the traveling distance can be shortened to be appropriate. Na The effect that the road surface can be determined is obtained. In the invention according to claim 2, since a bandpass filter is used to extract the unsprung upper and lower resonance frequencies in the signal input by the amplitude accumulating means, a combination of a lowpass filter and a highpass filter is used. Compared with this, the effect that the configuration can be simplified can be obtained.

According to the third aspect of the present invention, the road surface is determined by integrating the absolute value of the amplitude of the unsprung resonance frequency component every time the wheel makes one revolution. Therefore, the vehicle travels on an extremely short road surface. It is possible to perform the road surface determination only by itself, and it is possible to obtain an effect that the road surface can be accurately determined even on a road surface where a short road and a bad road are alternately present.

[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 an embodiment.

FIG. 3 is a block diagram showing a configuration of a control unit.

FIG. 4 is a flowchart showing a control flow of the 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.

[Explanation of symbols]

 a wheel speed detection means b amplitude integration means c road surface determination means d band pass filter 1 wheel speed sensor 2 control unit 2a wheel speed calculation unit 2b band pass filter 2c amplitude integration unit 2d road surface determination unit 3 actuator

Claims (3)

[Claims] 1. A wheel speed detecting means for outputting a signal corresponding to a wheel speed of at least one of a plurality of wheels, and an unsprung upper and lower resonance frequency component included in an output signal of the wheel speed detecting means. Amplitude accumulating means for accumulating the absolute value of the amplitude for a predetermined time, and if the integrated value of the amplitude accumulating means is a predetermined threshold value or more, it is judged as a bad road, while if it is less than this threshold value, it is judged as a non-bad road. A road surface state detection device, comprising: a road surface determination means. 2. The amplitude accumulating means is configured to input the output signal of the wheel speed detecting means via a band pass filter for extracting the unsprung upper and lower resonance frequency components. The road surface condition detection device described. 3. The road surface state detecting device according to claim 1, wherein the predetermined time for the amplitude accumulating means to integrate the absolute value of the amplitude is a time for one rotation of the wheel.