JPH10226328A - Device for detecting unevenness of road surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the continuously projecting and recessed state of a road surface accurately with high accuracy by summing an absolute value of a differ ence between a wheel acceleration and a reference acceleration extending for predetermined time, and determining the projecting and recessed state of the road surface by integration. SOLUTION: During traveling of a vehicle, wheel speed operating circuits 11-14 operate the wheel speeds from output of the speed sensors 3-6 of the respective wheels WH1-WH4, and then the acceleration of each wheel WH1-WH4 is operated by wheel acceleration operating circuits 15-18. By a reference acceleration setting circuit 23, the maximum acceleration is set as a reference acceleration, and the absolute value of a difference between each wheel acceleration and a reference acceleration is operated by absolute value operating circuits 19-22. In integrating circuits 25-28, summing integrating operation of each absolute value is performed, and if the timer fixed by a clocking circuit 39 elapses, the integration output of the integrating circuits 25-28 is led out through switching elements 31-34, and signals having the level corresponding to the projecting and recessed state of the road surface in traveling at each wheel WH1-W114 is led out to lines 35-38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface unevenness detecting device which detects the unevenness of a running road surface when a vehicle such as an automobile is running and determines whether or not the road is rough.

[0002]

2. Description of the Related Art Such unevenness of a road surface is required in anti-skid control and traction control, and a control amount such as an amount of pressure reduction or increase in brake hydraulic pressure is corrected according to the unevenness.

In a typical prior art, the acceleration of a wheel provided in a vehicle is obtained, and the obtained wheel acceleration is level-discriminated at a predetermined discrimination level L1 as shown in FIG. The number of times that the wheel acceleration reaches the discrimination level L1 or more by the counter is counted as shown in FIG. 8 (2), and when the counted value becomes equal to or more than the predetermined number N1, for example, at time t1 in FIG. In, it is determined that the road surface is rough.

In the prior art for determining that the road surface is rough when the number of times that the wheel acceleration reaches a certain discrimination level L1 or more within the predetermined time W1 becomes equal to or more than the predetermined number N1. For example, at time t2 in FIG.
As described below, when the detected wheel acceleration is below the discrimination level L1 and fluctuates greatly within the range below the discrimination level L1, it is not possible to determine the rough state of the road surface.

In order to solve this problem, not only a single discrimination level L1 but also a plurality of discrimination levels are set for the wheel acceleration, and the number of times that the wheel acceleration exceeds each discrimination level for each discrimination level is individually determined. There is a prior art in which a counter is counted for each time W1 to determine the unevenness of the road surface. In this prior art, there is a problem that a level discriminating unit having a plurality of discrimination levels and a counter for each discrimination level are individually required, and the configuration becomes complicated. It cannot be determined with even higher accuracy.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a road surface unevenness detecting device capable of detecting a road surface unevenness state with high accuracy.

[0007]

According to the present invention, there is provided a means for detecting a wheel acceleration, a means for setting a reference acceleration, a wheel acceleration detected by a wheel acceleration detecting means, and a means for setting the reference acceleration. A first calculating means for calculating an absolute value of a difference from the reference acceleration, a time measuring means for measuring a time at every predetermined time W, and a second means for integrating an output of the first calculating means over a time W measured by the time measuring means. 2
A road surface unevenness state detecting device, comprising a calculating means. According to the present invention, the absolute value of the difference between the detected wheel acceleration and the predetermined reference acceleration is calculated by the first calculating means, and the output of the first calculating means over the predetermined time W set by the timing means is calculated by the first calculating means. The two arithmetic means add and integrate. This time W is selected to be less than the cycle T of the wheel acceleration. For example, the time W of the timing means is selected, for example, from 50 to 300 msec, and
0 to 200 msec, more preferably 200
msec. The cycle of the wheel acceleration is, for example, 20 msec. According to another concept of the present invention, the time W of the timing means may be selected to be approximately 10 times the cycle T of the wheel acceleration (W ≒ 10T). Therefore, according to the present invention, it is possible to accurately detect the continuous unevenness of the road surface with high accuracy by the output of the second calculating means.

According to the present invention, the wheel acceleration detecting means includes means for detecting each speed of the plurality of wheels, and wheel acceleration calculating means for calculating the wheel acceleration in response to each output of the wheel speed detecting means. Wherein the reference acceleration setting means responds to the output from the wheel speed detecting means and sets the acceleration of the maximum wheel speed among the wheel speeds detected for each wheel as the reference acceleration. . According to the present invention, the wheel acceleration detecting means detects and calculates the speed of each of the plurality of wheels to obtain the wheel acceleration, and the reference acceleration setting means responds to the output from the wheel speed detecting means, The acceleration of the maximum speed among the detected speeds is set as the reference acceleration. This maximum speed is a value that can be adopted as the vehicle speed. Therefore, in other words, the reference acceleration set by the reference acceleration setting means is the current vehicle acceleration. This makes it possible to obtain an integrated value of the absolute value of the difference that exactly corresponds to the unevenness of the road surface. If the reference acceleration is a fixed value that does not correspond to the vehicle body acceleration, the offset amount, which is the deviation between the fixed value and the current vehicle body acceleration, adversely affects the integrated value of the absolute value of the difference, and the road surface The value cannot accurately correspond to the uneven state linearly. The present invention solves this problem.

Further, the present invention is characterized in that the reference acceleration setting means has a vehicle acceleration sensor provided on the vehicle and detecting the acceleration of the vehicle, and sets an output of the vehicle acceleration sensor as a reference acceleration. According to the present invention, the vehicle body acceleration sensor may be fixed to the vehicle body to directly detect the vehicle body acceleration. Such a vehicle body acceleration sensor can be realized by, for example, a configuration in which the amount of deflection of the elastic cantilever is electrically detected as a physical quantity such as capacitance in accordance with the acceleration of the vehicle body.

Further, according to the present invention, a wheel acceleration detecting means and a first
The second calculating means is provided for each of the plurality of wheels, performs an integrating operation for each wheel, and further includes means for adding an integrated output for each wheel. According to the present invention, instead of detecting the unevenness of the road surface for each wheel,
The average output of the road surface may be detected by adding the integrated outputs by the adding means.

[0011]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention. FIG. 2 is a diagram showing a vehicle body 2 on which a road surface unevenness detecting device 1 is mounted.
3 is a simplified plan view of FIG. To the left and right before and after the body 2,
A plurality of (for example, four) wheels WH1 to WH4 are provided. Each of the wheels WH1 to WH4 is provided with a speed sensor 3 to 6 for generating a pulse having a pulse cycle corresponding to the wheel speed.

FIG. 3 is a side view showing a specific example of the speed sensor 3. The rotor 7 is fixed to the wheel WH1. The detection pieces 8 made of a ferromagnetic material are fixed to the rotor 7 at equal intervals in the circumferential direction. The detected piece 8 is the vehicle body 2
Magnetically coupled to an electromagnetic pickup 9 such as a coil fixed to the coil. Thereby, the electromagnetic pickup 9 derives a pulse corresponding to the detected piece 8.

The remaining speed sensors 4 to 6 have the same configuration as the speed sensor 3.

The wheel speed calculation circuits 11 to 14 respond to the pulses from the speed sensors 3 to 6 and calculate the speed of each of the wheels WH1 to WH4 corresponding to the cycle of the pulses to the speeds Vw1 to Vw1.
w4 is calculated and detected.

The wheel acceleration calculation circuits 15 to 18 respond to the output from the wheel speed calculation circuits 11 to 14, and
Accelerations αw1 to αw4 of speeds Vw1 to Vw4 of WH4
Are calculated and obtained. Wheel acceleration calculation circuit 15-
Wheel accelerations αw1 to αw1
The output representing w4 is provided to one input of the absolute value calculation circuits 19 to 22. The reference acceleration setting circuit 23 responds to the outputs representing the wheel speeds Vw1 to Vw4 from the wheel speed calculation circuits 11 to 14, and calculates the maximum speed among the speeds Vw1 to Vw4 detected for each wheel WH1 to WH4. Set the maximum speed acceleration as the reference acceleration. From the reference acceleration setting circuit 23, a signal representing the set reference acceleration is commonly supplied to the other inputs of the absolute value calculation circuits 19 to 22. The reference acceleration set by the reference acceleration setting circuit 23 is indicated by reference numeral β0.

The absolute value calculating circuit 19 calculates the absolute value γ1 of the difference between the acceleration αw1 of the wheel WH1 from the wheel acceleration calculating circuit 15 and the reference acceleration β0 from the reference acceleration setting circuit 23.
(= | Αw1-β0 |). The remaining absolute value calculation circuits 20 to 22 also have their absolute values γ2 (= | α
w2-β0 |), γ3 (= | αw3-β0 |), and γ4 (= | αw4-β0 |) are calculated and obtained.

The integrating circuit 25 includes absolute value calculating circuits 19 to 2
The operation of resetting the absolute values γ1 to γ4 from 2 and adding them from the initial state each time the control signal is received from the line 29 is repeated. Switching elements 31-34 conduct when control signal 29 is applied, and lines 35-38.
Then, the addition integration outputs of the integration circuits 25 to 28 are derived. The output level derived from the line 35 accurately corresponds to the unevenness of the running road surface for each of the wheels WH1 to WH4 of the vehicle. The timer circuit 39 derives a pulse, which is a control signal, on a line 29 at every predetermined time W.

FIG. 4 is a waveform chart for explaining the operation of the embodiment of the present invention shown in FIGS. The acceleration αw1 detected by the acceleration calculation circuit 15 fluctuates as shown in FIG. The absolute value calculation circuit 19 calculates the absolute value γ1 as described above, and the absolute value γ1 corresponds to the level of the region shown by the oblique lines in FIG.

The integration circuit 25 adds the hatched area shown in FIG. 4A to derive a signal having the waveform shown in FIG. 4B. Timing circuit 39 is line 29
The waveform of the control signal derived as shown in FIG. 4 (3) is shown with reference signs p1 and p2. The integrating circuit 25 derives an integrated output during the period when the control signals p1 and p2 are at a high level in response to the pulses p1 and p2 of these control signals, and is reset when the control signals p1 and p2 fall. And the integration operation is started again. The switching element 31 derives an integrated output when the control signals p1 and p2 are at a high level on a line 35. The operation of each component regarding the remaining wheels WH2 to WH4 is the same.

FIG. 5 is a flowchart for explaining the operation of the embodiment of the present invention shown in FIGS. Moving from step a1 to step a2, the wheel speed calculation circuits 11 to 14 respond to the outputs from the speed sensors 3 to 6 for the respective wheels WH1 to WH4, and output the wheel speeds Vw1 to Vw.
4 is calculated. In step a3, the wheel acceleration calculation circuits 15 to 18 respond to the signals indicating the wheel speeds Vw1 to Vw4 from the wheel speed calculation circuits 11 to 14, and
The accelerations αw1 to αw4 for each of H1 to WH4 are calculated and obtained.

In step a4, the reference acceleration setting circuit 2
3 responds to signals representing wheel speeds Vw1-Vw4,
The maximum speed acceleration is calculated and set as the reference acceleration. In step a5, the absolute value calculation circuits 19 to 22 calculate and obtain the absolute values γ1 to γ4. In step a6, the timer 39 determines whether or not a control signal has been derived at every predetermined time W, and the control signal is derived, so that the integration circuits 25 to 28 execute the next step a6.
The reset and initialization are performed in step 7, and the addition integration operation of the absolute values γ1 to γ4 is performed. Thus, in step a8, the timer 39 counts up to perform a timing operation. When it is determined in step a9 that the time W has elapsed, a control signal is derived to the line 29 and the next step is performed. In a10, the integrated outputs of the integration circuits 25 to 28 are derived via the switching elements 31 to 34. The switching elements 31 to 34 conduct only during a period in which the pulses p1 to p2 of the control signal shown in FIG. In this way, signals having levels corresponding to the unevenness of the road surface during traveling for each of the wheels WH1 to WH4 are obtained on the lines 35 to 38.

In another embodiment of the present invention, the reference acceleration setting circuit 23 may be configured to derive a signal representing a reference acceleration which is a fixed value. In still another embodiment of the present invention, the output from the vehicle body acceleration sensor fixed to the vehicle body 2 may be derived as a signal representing the reference acceleration.

The time W set by the timer 39
Is determined to be a value between 50 and 300 msec according to the experiment of the present inventor, and preferably 100 to 200 msec.
, And more preferably 200 mse
c. This time W corresponds to each wheel WH1-WH4
Cycle of the acceleration of the vehicle, and thus the cycle T
(W> T), for example, the time W is set to a period T
(W 倍 10T).

To perform anti-skid control, the vehicle 2 is provided with a processing circuit realized by a microcomputer or the like to which each output of the wheel speed calculation circuits 11 to 14 and the wheel acceleration calculation circuits 15 to 18 is applied. When it is determined that the conditions for starting skid control are satisfied, the brake hydraulic pressure of the wheel cylinder provided for each of the wheels WH1 to WH4 is controlled to increase, decrease, or hold. For example, the driver depresses the brake pedal to increase the braking oil pressure, thereby increasing the wheel acceleration to the negative side. The absolute value of the wheel acceleration during the deceleration becomes larger than a predetermined decompression start reference value. When the start condition that the speed becomes equal to or less than the predetermined slip reference value is satisfied, the pressure reduction control of the brake hydraulic pressure is started. The slip reference value is set to, for example, 85% of the vehicle speed. When the wheel acceleration and the wheel speed are recovered by the pressure reduction control, the pressure reduction control is terminated, and the process proceeds to the holding control. When the drop in wheel speed was large, the wheel acceleration did not converge even when switching from the pressure reduction control to the holding control,
The pressure once becomes equal to or higher than the pressure increase start reference value, and then reaches a peak value, and then becomes lower than the pressure increase start reference value again. At this time, the brake oil pressure is controlled to be increased only during the pressure increase time depending on the peak value of the wheel acceleration or the like.

In a vehicle equipped with such an anti-skid control device, during anti-skid control, the wheel speed fluctuates due to the negative balance between the braking oil pressure and the road surface drag. Therefore, in this state, it is necessary to stop the operation of detecting the unevenness of the road surface. In another embodiment of the present invention, the integrating circuits 25 to 28 and the switching elements 31 to
Processing circuitry associated with the anti-skid controller for pausing the operation of 34 is further provided to achieve the operation of FIG. When the process proceeds from step b1 to step b2 and the wheel speed obtained from at least one of the wheel speed calculation circuits 11 to 14 of any of the wheels WH1 to WH4 during the anti-skid control drops significantly by a predetermined speed or more by the anti-skid control. Then, the process proceeds to step b7, in which the operations of the integrating circuits 25 to 28 and the switching elements 31 to 34 corresponding to the wheel whose wheel speed drops greatly are stopped to prevent erroneous detection.

In step b3, it is determined whether or not the wheel speed has recovered to the vehicle speed after the pressure of the wheel cylinder of the anti-skid control has been reduced. After the wheel speed has recovered to the vehicle speed, in the next step b4, The timing operation is performed until the predetermined time W2 has elapsed. Also at this time W2, at step b7, the corresponding wheel WH1
The operation of the integration circuits 25 to 28 and the switching elements 31 to 34 for every WH4 is suspended. In step b5,
The calculation operation of the road surface unevenness state shown in FIGS. 1 to 5 is performed. The time W2 is set to a value substantially equal to the time during which the vibration of the wheel speed generated depending on the rigidity of the suspension device for each of the wheels WH1 to WH4 provided in the vehicle body 2 disappears.

FIG. 7 is a block diagram showing the overall configuration of still another embodiment of the present invention. This embodiment is similar to the above-described embodiment, and corresponding portions are denoted by the same reference numerals. It should be noted that the outputs of the integrating circuits 25 to 28 are given to an adding circuit 41 and added, and the added output is led to a line 43 via a switching element 42. Thus, a signal indicating the average unevenness of the road surface on which the vehicle body travels is derived from the line 43. The switching element 42 has the same configuration as the switching elements 31 to 34 described above.

[0028]

According to the first aspect of the present invention, the absolute value of the difference between the wheel acceleration and the reference acceleration is added over a predetermined time W and integrated to determine the unevenness of the road surface. Therefore, the continuous uneven state of the road surface can be accurately detected with high accuracy. Further, according to this configuration, it is not necessary to provide a large number of combinations of the level discriminating means and the counter described in relation to the prior art,
The configuration can be simplified.

According to the second aspect of the present invention, the acceleration of the maximum speed among the speeds detected for each wheel is adopted as the reference acceleration, whereby the integrated value corresponding more accurately to the unevenness of the road surface is obtained. Will be able to gain.

According to the third aspect of the present invention, the output of the vehicle body acceleration sensor provided on the vehicle body is used as the reference acceleration, whereby the unevenness of the road surface can be detected with higher accuracy. Become like

According to the present invention, instead of detecting the unevenness of the road surface for each wheel, the integration operation for each wheel is performed, and the integrated output for each wheel is added. This makes it possible to detect the average unevenness of the entire road surface on which the vehicle is traveling.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a simplified plan view of a vehicle body 2 of an automobile.

FIG. 3 is a side view showing a specific example of the speed sensor 3;

FIG. 4 is a waveform chart for explaining the operation of the embodiment of the present invention shown in FIGS. 1 to 3;

FIG. 5 is a flowchart for explaining the operation of the embodiment of the present invention shown in FIGS. 1 to 4;

FIG. 6 is a flowchart for explaining an operation of another embodiment of the present invention.

FIG. 7 is a block diagram showing an overall configuration of still another embodiment of the present invention.

FIG. 8 illustrates a typical prior art waveform.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 road surface unevenness detecting device 2 vehicle body 3 to 6 speed sensor 11 to 14 wheel speed calculation circuit 15 to 18 wheel acceleration calculation circuit 19 to 22 absolute value calculation circuit 23 reference acceleration setting circuit 25 to 28 integration circuit 31 to 34, 42 Switching element 39 Timing circuit 41 Adder circuit

Claims (4)

[Claims] A means for detecting a wheel acceleration; a means for setting a reference acceleration; a wheel acceleration detected by a wheel acceleration detecting means;
A first calculating means for calculating an absolute value of a difference from the reference acceleration set by the reference acceleration setting means; a time counting means for counting time for each predetermined time W; and an output of the first calculating means being counted by the timing means. And a second calculating means for integrating over a time period W. 2. The wheel acceleration detecting means includes means for detecting each speed of a plurality of wheels, and wheel acceleration calculating means for calculating wheel acceleration in response to each output of the wheel speed detecting means. The reference acceleration setting means is responsive to an output from the wheel speed detection means, and sets an acceleration of a maximum wheel speed among the wheel speeds detected for each wheel as a reference acceleration. A road surface unevenness detection device as described in the above. 3. The reference acceleration setting means includes a vehicle acceleration sensor provided on the vehicle body and detecting an acceleration of the vehicle body, and sets an output of the vehicle acceleration sensor as a reference acceleration. Road surface unevenness detection device. 4. A wheel acceleration detecting means and first and second calculating means are provided for each of a plurality of wheels, perform an integrating operation for each wheel, and further add an integrated output for each wheel. The road surface unevenness detecting device according to any one of claims 1 to 3, further comprising means.