JPH0277352A - Antiskid control device with acceleration sensor - Google Patents

Abstract

PURPOSE:To positively perform anti-skid control even when a car travels on a bad road by passing output of an acceleration sensor through a lowpass filter selecting a value by which cut-off frequency cuts off wave form depending on vibration of a car body when the car travels on the bad road. CONSTITUTION:A first filter unit 43 and a second filter unit 44 comprise a low-pass filter respectively, and cut-off frequency of the second filter unit 44 is selected as a low frequency than the cut off frequency of the first filter unit 43. With the cut-off frequency of the second filter unit 44, cut-off frequency sufficient to remove car body vibration frequency included in output signals from an acceleration sensor during travelling on a bad road is selected. As a result, when a bad road decision unit 41 judges that the road surface on which a car is travelling is a normal road, a switching unit 42 is switched to the first filter unit 40, and when it is judged that the road surface is bad, the switching unit is switched to the second filter unit 44. Thus, even when the car travels on the bad road, positive and smooth anti-skid control can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides an anti-skid control system that can reliably perform anti-skid control even when the anti-skid control is performed while driving on a rough road such as a bumpy road or a gravel road. Regarding a control device.

Conventional technologyAn anti-skid control device is a device that hydraulically controls the slip rate of the wheels so that the coefficient of friction between the wheels and the road surface is the highest.
) is VW, the vehicle's traveling speed (hereinafter referred to as "vehicle speed")
) is VS, the slip rate S is defined by the first equation.

s-vw S=□ ... (1) VS When an acceleration sensor that detects acceleration in the direction of travel of the vehicle is used for anti-skid control, the vehicle body speed ■S can be determined by integrating the output of the acceleration sensor. can. Further, the wheel speed can be determined from the output signal of a wheel speed sensor attached to the wheel axle. Therefore, the slit 1 ratio S is calculated based on the output signals of the acceleration sensor and the wheel speed sensor. Furthermore, in order to shorten the braking distance, it is necessary to change the anti-skid control depending on the road surface condition, and for this purpose it is necessary to determine the coefficient of friction between the wheels and the road surface. Therefore,
Conventionally, for example, when the brake pedal is depressed and the wheel speed decreases, an acceleration sensor detects the deceleration (negative acceleration). If so, it is determined that the road has a high friction coefficient.

As described above, in the conventional anti-skid control device, the output of the acceleration sensor is used for anti-skid control in order to obtain more accurate friction coefficients between the vehicle speed and wheel speed and the road surface.

Problems to be Solved by the Invention As mentioned above, by using the output signal of an acceleration sensor fixed to the vehicle body for anti-skid control, it is possible to make anti-skid control smoother and contribute to shortening the braking distance. Can be done.

However, if anti-skid control is performed while driving on uneven roads that are not normal roads such as paved roads, or rough roads such as gravel roads, vertical vibrations of the wheels are transmitted to the vehicle body, and these vibrations cause noise in the output of the acceleration sensor. appears. When attempting to determine the vehicle speed from the output of the acceleration sensor, the noise caused by the vehicle vibration described above is integrated, resulting in an error, and when used to determine the friction coefficient, an incorrect friction coefficient may be derived.
There is a problem that anti-skid control cannot be performed accurately.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an anti-skid control device that can reliably perform anti-skid control even when anti-skid control is performed while driving on a rough road such as a bumpy road or a gravel road.

Means for Solving the Problems The present invention detects the acceleration of a vehicle body using an acceleration sensor, and performs anti-skid control by braking the wheels to a slip ratio that increases the coefficient of friction between the wheels and the road surface when braking the wheels. The anti-skid control device with an acceleration sensor is provided with a rough road detection means for detecting running on a rough road, the output of the acceleration sensor is applied to a low-pass filter, the anti-skid control is performed based on the output of the low-pass filter, and the anti-skid control device with an acceleration sensor is provided. An acceleration sensor is an anti-skid control device characterized in that the cutoff frequency of is selected to a value that cuts off a waveform dependent on vibration of the vehicle body when driving on a rough road.

Function: In the present invention, the acceleration of the vehicle body is detected by an acceleration sensor. The anti-skid control device brakes the wheels so that the slip ratio is such that the coefficient of friction between the wheels and the road surface increases when the wheels are braked. Then, the output of the acceleration sensor is given to a low-pass filter, and anti-skid control is performed based on the output. The rough road detection means detects whether or not the vehicle is traveling on a rough road. When the rough road detection means detects that the vehicle is traveling on a rough road, the anti-skid control device receives the output of the acceleration sensor. The cutoff frequency of the filter is selected to a value that blocks vibrations of the vehicle body caused by driving on rough roads.

Embodiment FIG. 1 is a block diagram for explaining a hydraulic path of an anti-skid control device according to an embodiment of the present invention. When the brake pedal 30 is depressed, braking oil pressure is generated in the master cylinder 31, and the braking oil pressure is transmitted through the pipes p1 to p.
4 to the three-position electromagnetic control valves 32a to 32d, and further supplied to the wheel cylinders 33a to 33d via pipes p'+ to p8. As a result, the wheels 34a
~34d starts braking and the speed of the car decreases.

The rotational speed of the wheels 34a to 34d is determined by the wheel speed sensors 1a to 34d.
A vehicle body acceleration signal detected by the vehicle body 1d and also detected by the acceleration sensor 3 fixed to the vehicle body is sent to the anti-skid control circuit 4.

When the anti-skid control circuit 4 determines that the anti-skid control start conditions are satisfied, the anti-skid control circuit 4 applies the control hydraulic pressure generated by the motor 17 to the master cylinder 31 via the pipe p9, and also controls the three-position electromagnetic control valves 32a to 3.
2d is increased, decreased, or maintained to control the braking oil pressure of the wheel cylinders 33a to 33d. By this control n, the slip rate S of the wheels 34a to 34d is
is controlled to a value at which the highest frictional braking force acts on the road surface, for example, 10% to 20%.

FIG. 2 is a block diagram for explaining electrical connections of an anti-skid control device according to an embodiment of the present invention. Wheel speed sensors 1a to 1d provided on each wheel detect the rotational speed of the wheel, and the detection signal is sent to the waveform shaping circuit 5a.
~5d.

The wheel speed sensors 1a to 1d each have, for example, a detection plate made of a ferromagnetic material fixed to a wheel shaft, provided with a large number of equally spaced notches and protrusions in the circumferential direction, and an electromagnetic pickup provided near the detection plate. , or a sensor that outputs a wheel speed signal with a frequency proportional to the wheel speed using an optical sensor.

The wheel speed signal is given to the waveform shaping circuits 5a to 5d, and after being waveform-shaped into a pulse signal, it is sent to the processing circuit 2.

The acceleration sensor 3 fixed to the vehicle body is, for example, a cup gauge type acceleration sensor, and its output voltage is applied to an analog/digital conversion circuit 6 and converted into a digital value.
Digital filter processing is performed within the processing circuit 2 to remove unnecessary components.

The switch 7 is, for example, a brake switch that detects whether the brake pedal is depressed or not, and its output is converted into an appropriate voltage in the anti-skid control circuit 4 by a level conversion circuit 8, and then sent to the processing circuit 2.
sent to.

The power supply circuit 9 is connected to a battery 11 via a power switch 10.
The voltage supplied from the anti-skid control circuit 4 is converted into a voltage for use within the anti-skid control circuit 4.

The anti-skid control signal output from the processing circuit 2 is
The power is given to the solenoid drive circuits 12a to 12d, and after being amplified, the power is sent to actuators 13a to 13d composed of three position solenoid control valves 32a to 32d and wheel cylinders 33a to 33d. 32d to either pressure increase, pressure decrease, or hold state.

When performing anti-skid control, the processing circuit 2 controls the actuators 13a to 13dt! - Don't be active,
Solenoid relay 15 in solenoid relay drive circuit 14
Sends a signal to turn on. Solenoid relay 1
When a drive current flows through the coil 15a of No. 5, the contact 15b becomes conductive, and the electric power from the battery 11 is supplied to the solenoid coils of the three-position electromagnetic control valves 32a to 32d in the actuators 13a to 13d.

The motor relay 16 is a relay for driving the motor 17 for generating control hydraulic pressure, and a motor relay drive signal whose power has been amplified by the motor relay drive circuit 18 is sent to the coil 16.
When a is excited, the contact 16b becomes conductive and the motor 17 rotates.

One lamp is a lamp that lights up when the anti-skid control circuit 4 performs an abnormal operation, and the alarm signal output from the processing circuit 2 is given to the lamp 19 after being power amplified by the lamp drive circuit R20. .

In the anti-skid control device configured as above, the configuration of the present invention will be described below.

FIG. 3 is a functional block diagram for explaining the configuration of an embodiment of the present invention. The acceleration signal processing section 10 is configured within the processing circuit 2. Wheel speed sensors 1a to 1d
A wheel acceleration signal obtained by calculating the time rate of change of the detected wheel speed or an output signal of a rough road sensor, which will be described later, is input to the rough road determining section 41. The rough road determining unit 41 determines whether the road the vehicle is currently traveling on is a normal road, such as a paved road, or a rough road, such as a bumpy road or a gravel road, according to a procedure described later.

The output of the rough road determining section 41 is sent to the switching section 42, which switches the output signal of the analog/digital conversion circuit 6 to the input of either the first filter section 43 or the second filter section 44. The first filter section 43t3 and the second filter m4
4 performs so-called digital filter processing on the acceleration signal converted into a digital signal and sends it to the anti-skid control calculation section.

The first filter section 43 and the second filter section 44 together constitute a low-pass filter, and the cutoff frequency of the second filter section 44 is selected to be lower than the cutoff frequency of the first filter section 43 . The cutoff frequency of the second filter section 44 is selected to be sufficient to remove the vehicle body vibration frequency included in the output signal of the acceleration sensor 3 when driving on a rough road. Therefore, when the rough road determining section 41 determines that the road surface on which the vehicle is currently traveling is a normal road, the switching section 42 is switched to the first filter section 43; filter 44. In this way, by switching the cutoff frequency of the filter that filters the noise contained in the output signal of the acceleration sensor 3 depending on the road surface condition while driving, anti-skid control is performed using the acceleration signal in a state where noise caused by vehicle body vibration is further suppressed. It can be used for calculations.

Next, the calculations executed in the first filter 43 and the second filter 44 will be explained below. analog/
The digital conversion circuit 6 converts an analog signal into a digital signal using a predetermined sampling frequency and outputs the digital signal. The rough road determining unit 41 determines that the road is normal, and the switching unit 42
Assuming that the first filter 43 is selected, the output signal of the analog/digital conversion circuit 6 is sent to the first filter 43. The first filter 43 inputs a digital signal at the end of the sampling period, and for example,
A low-pass filter can be constructed by simply averaging these digital quantities as shown in the second equation. Here, A is the digital amount from the analog/digital conversion circuit 6, the subscript n indicates the sampling time, and Fl indicates the output value of the first filter 43.

All+A11. , ten...+ An-tF1=□
(2) The first filter 43 discards the oldest digital amount, adds the latest digital amount, and repeatedly performs the calculation of the second equation at each sampling period.

Further, the second filter 44 constitutes a low-pass filter by simply averaging 16 temporally continuous digital quantities among the digital quantities from the analog/digital conversion circuit 6 as shown in the third equation. . Here, A and n are the same as in the second equation, and F2 is the output value of the second filter 44.

As described above, by changing the number of data to be simply averaged, the cutoff frequency of the filter can be changed.

The calculations of the first filter 43 and the second filter 44 described above are performed by simply averaging the input digital amounts, but are not limited to this, and include Ike's digital filter processing, For example, cyclic digital filter processing may be performed using past digital filter output values for filter calculations.

FIG. 4 is a flowchart for explaining the anti-skid 1li111n calculation executed in the processing circuit 2. The processing of each step will be explained below. In step m1, it is detected whether the road surface on which the vehicle is currently traveling is a rough road. In step m2, a rough road judgment is performed based on the rough road detection performed in step m1, and if the vehicle is traveling on a normal road, the process proceeds to step m3;
3, the first filter operation described above is performed. Also,
In step rn2, if it is determined that the road surface on which the vehicle is currently traveling is a rough road, the process proceeds to step m4, where a second filter calculation is performed.

In step m5, the wheel speed of each wheel is calculated based on the wheel speed signals from the wheel speed sensors 1a to 1d. Based on the wheel speed determined in step m5, step m
In step 6, the time change rate of the wheel speed is calculated, and the wheel acceleration is calculated. In step m7, a control reference speed, which is a reference for anti-skid control calculation, is calculated. This control reference speed is determined by calculating a speed that is 10% lower than the vehicle speed. That is, the vehicle speed is determined by integrating the vehicle acceleration, which is the output value of the first filter or the second filter, and the control reference speed is calculated by multiplying this vehicle speed by 0 and 9. The control reference speed is a speed that serves as a reference for selecting the output state of the control signal in anti-skid control calculation. Once this control reference speed is calculated, the process proceeds to step m8, where anti-skid control calculation is executed.

This anti-skid control calculation calculates a control signal for hydraulically controlling the wheel speed of each wheel so that the slip rate S of the wheel has the highest value of the coefficient of friction between the wheel and the road surface.

FIG. 5 shows a process performed by an embodiment of the present invention.

5 is an output control flowchart in circuit 2. FIG.

When the anti-skid control program is executed in the processing circuit 2, first, in step S1, it is determined whether or not the anti-skid control is currently being executed, and if the anti-skid control is currently being executed, it is determined to start the anti-skid control. Since it is not necessary, the process advances to step s4. In step s1, if anti-skid control is not being performed, the process proceeds to step S2, where it is determined whether conditions for starting anti-skid control are satisfied. As anti-skid control starting conditions, for example, it is determined whether the wheels are locked, or the wheel speed becomes lower than a predetermined rotational speed, and whether the wheel deceleration is greater than the predetermined deceleration. If the conditions for starting the anti-skid control are met, the process advances to step s3, and the wheel cylinder 33 is stored in a predetermined memory area of the processing circuit 2.
A depressurization flag is set to cause a to 33(1) to perform a depressurization operation.

In step S2, if it is determined that the conditions for starting the anti-skid control are not met, the process proceeds to step s18, where the hydraulic pressure generated in the master cylinder 31 by depression of the brake pedal 30 is transferred to the wheel cylinders 33a to 33a.
33d, the three-position electromagnetic control valves 32a to 32d of the actuators 13a to 13d are set to the pressure increasing position.

In step s4, the control conditions for the anti-skid control are determined, and the anti-skid control is canceled, for example, when the foot is removed from the brake pedal 30 or when the vehicle speed becomes 5 Km/h or less. If the anti-skid control termination conditions are not met in step S4, the process proceeds to step s5, and the wheel cylinder 3
A determination is made on flags 3a to 33d that control increases and decreases in oil pressure.

When the anti-skid control starts, the pressure reduction flag is set in step S3, so the process proceeds to step s6, where it is determined whether or not the pressure reduction operation should be completed, and then the process proceeds to step S7, where the pressure in the wheel cylinders 33a to 33d is reduced. In step S6, conditions for ending the pressure reduction operation,
That is, when the wheel speed begins to show signs of recovery, the process proceeds to step s8, and a holding flag is set to keep the oil pressure of the wheel cylinders 33a to 33d constant.

Then, the process advances from step S9 to step slO, and the wheel cylinder pressure is kept constant.

In step s9, when the holding end condition is satisfied in which it is determined that the wheel speed has recovered, the process proceeds to step S11, and a flag is set to increase the oil pressure in the wheel cylinders 33a to 33d. Then, the process proceeds from step s12 to step s13, where the oil pressure in the wheel cylinders 33a to 33d is increased.

In step s12, when the pressure increase is output for a time determined by the pressure increase end condition, for example, the wheel acceleration obtained during wheel recovery, the process proceeds to step s14, where a pulse increase is performed to gradually increase the pressure in the wheel cylinders 33a to 33d. Pressure flag is set. When the pulse pressure increase flag is set, the process proceeds from step sls to step s16, in which a pressure increase pulse having a predetermined time width is sent from the processing circuit 2 to the solenoid drive circuits 12a to 12d, and the actuators 13a to 13d drive the solenoids. Drive circuit 12a~
An operation is performed to increase the pressure for a time corresponding to the pressure increase pulse width given from 12d. In step s15, when the output end conditions for pulse pressure increase are satisfied, the process proceeds to step s17,
A pressure reduction flag is set, and a pressure reduction operation is performed in step s7.

Next, in this embodiment, means for determining a rough road will be explained. FIG. 6 is a flowchart for explaining the process of determining a rough road from wheel acceleration in this embodiment. When the number of times that the acceleration level exceeds a predetermined acceleration level (for example, 2G, where G is gravitational acceleration) within a period of 2 seconds is equal to or greater than a predetermined number of times (for example, 2 times), it is determined that the road is rough.

That is, in the flowchart of FIG.
In step 1, it is first determined whether the measurement time for determining the rough road has elapsed, and if the measurement time has not elapsed, the process proceeds to step n2. In step n2, the wheel acceleration calculated from the wheel speed sensors 1a to 1d is It is determined whether or not the acceleration has exceeded a predetermined acceleration, for example, 2G. If the acceleration has exceeded 2G, the count amount of the counter (2) is increased by 1 in step [Bird 3]. If the wheel acceleration is 2G, the process in step ``13'' is not performed, and the process proceeds from step n2 to step ri1, where it is again determined whether the measurement time has elapsed.In this way, the measurement time is The process proceeds from step nl to step n2 until the wheel acceleration reaches 2.
The number of times G is exceeded is counted.

When the measurement time has elapsed, step n1 to step rI
The process advances to step 4, where it is determined whether the counter value of counter (2) is 2 or more. If it is 2 or more, the process proceeds from step n4 to step n5, where a rough road determination and a process after the rough road determination are performed. That is, as explained in FIG. 3, the first filter 43 is switched to the second filter 44 by the cut portion 42. In step n4, if the value of the counter I is less than 2, the process proceeds from step n4 to step n6, and the process of switching the switching unit 42 is not performed.

Step n6 and step n7 are initialization processing for determining rough roads, and step n6 is initialization of measurement time. For example, the current time at which measurement starts is stored in a predetermined memory of the processing circuit 2. The time stored in this memory is compared with the current time, and if the difference between the two exceeds a predetermined time, it is determined that the measurement time has elapsed.

In step n7, the counter I is initialized, for example, the counter ■ is cleared. When the above-mentioned initialization process is performed, the processes from step 01 to step n3 described above are executed until the measurement time elapses.

FIG. 7 is a flowchart for explaining the process of determining a rough road using a rough road sensor. As a rough road sensor,
For example, a light-emitting means and a light-receiving means are provided at the front or rear of the vehicle body, and among the light emitted from the light-emitting means to the road surface,
The amount of light returning to the light receiving means as a result of diffuse reflection due to the unevenness of the road surface is detected, and when the light detection level exceeds a predetermined value, it is determined that the road surface is highly uneven and the road is rough.

In Stella 7rl, it is determined whether the output from the rough road sensor described above exceeds the level at which it is determined that the road is rough, that is, the rough road level. If the rough road level exceeds the rough road level, proceed to step r2, and proceed to step 6 [2I step rr].
Similar to the process in step 5, rough road determination and processing are performed. If it is determined in step r1 that the output from the rough road sensor does not exceed the rough road level, step r2 described above is not executed, and the process of switching from the first filter 43 to the second filter 44 is not performed.

As described above, according to this embodiment, when it is determined that the road surface on which the vehicle is currently traveling is a rough road, the cutoff frequency of the low-pass filter that filters the noise component contained in the output signal of the acceleration sensor 3 is low. Since this value is selected, noise contained in the output signal of the acceleration sensor 3 due to vehicle body vibration is filtered.

Effects of the Invention As described above, according to the present invention, the cutoff frequency of the low-pass filter is selected to a value that cuts off waveforms dependent on vehicle body vibration while driving on a rough road, so that the output of the acceleration sensor is reduced even when driving on a rough road. Noise components included in the signal are suppressed, and reliable and smooth anti-skid control can be achieved even when driving on rough roads.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the hydraulic path of an anti-skid control device in which one embodiment of the present invention is realized, and FIG.
The figure is a block diagram for explaining the electrical connection of an anti-skid control device that is an embodiment of the present invention, FIG. 3 is a functional block diagram for explaining the configuration of an embodiment of the present invention, and FIG. A flowchart for explaining the anti-skid control calculation executed in the processing circuit 2, FIG. 5 is an output control flowchart in the processing circuit 2 in which an embodiment of the present invention is executed, and FIG. FIG. 7 is a flowchart for explaining the process of determining a rough road using the rough road sensor. la to 1d...Wheel speed sensor, 3...Acceleration sensor. 4...Anti-skid control circuit, 13a to 13d...
・Actuator, 17...Motor, 31...Master cylinder, 34a-34d...Wheel agent Patent attorney Number of strokes Keiichi Part 4 Figure 6 Figure 7

Claims (1)

[Claims] An acceleration sensor that detects the acceleration of a vehicle body using an acceleration sensor, and performs anti-skid control by braking the wheels to a slip ratio that increases the coefficient of friction between the wheels and the road surface when the wheels are braked. The anti-skid control device is equipped with a rough road detection means for detecting running on a rough road, the output of the acceleration sensor is applied to a low-pass filter, the anti-skid control is performed based on the output of the low-pass filter, and the cut-off frequency of the filter is adjusted. An anti-skid control device with an acceleration sensor, characterized in that is selected to a value that blocks a waveform dependent on vibration of a vehicle body when driving on a rough road.