JP2829214B2 - Anti-skid control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device having an acceleration sensor for detecting, for example, the acceleration of a vehicle, and more particularly to a good anti-skid control by removing the influence of an offset of the acceleration sensor on the anti-skid control. The present invention relates to an anti-skid control device capable of performing control.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a conventional anti-skid control device. In the figure, 1 is a controller, 2 is a vehicle acceleration, and the detected data is RO.
Microcomputer 5 including M, RAM, CPU, etc.
The wheel speed sensors 4, 7, 8, which detect the speed of each wheel of the vehicle (not shown) and output a sine wave detection signal having a frequency proportional to the wheel speed, respectively. 9 and 11 are these wheel speed sensors 3,
6,8, and a detection signal from 10 is converted into a pulse each Sei Namikata form circuit supplies the pulse to the microcomputer 5, respectively, solenoid based on a command from 12,15,17 and 19 microcomputer 5 1
A current control circuit for controlling a current supplied to 3, 16, 18 and 20 is a power supply terminal connected to the solenoids 13, 16, 18 and 20.

Here, the characteristics of the acceleration sensor 2 will be described with reference to FIG. FIG. 6 is a characteristic diagram showing an example of the characteristic of the acceleration sensor 2. In the figure, the vertical axis represents the detection voltage VG of the acceleration sensor 2, and the horizontal axis represents the vehicle body acceleration. The solid line represents ideal characteristics, and the broken line represents characteristics when the offset amount v is included. In ideal characteristics, the detected voltage VG is directly proportional to the vehicle acceleration, and shows a predetermined value VGS when the vehicle acceleration is zero. Note that the offset amount v has a different value due to variations in components and the acceleration sensor 2 and aging.

Next, referring to the flowchart of FIG.
The control operation of the microcomputer 5 of the conventional anti-skid control device shown in FIG. While the vehicle is running, the acceleration of the vehicle from the acceleration sensor 2 is detected and supplied to the microcomputer 5 as detection data, and the wheel speed sensors 3, 6, 8 and 10
, A sine wave signal having a frequency proportional to the wheel speed is supplied to the waveform shaping circuits 4, 7, 9 and 11, respectively. The sine wave signals from the wheel speed sensors 3, 6, 8 and 10 are supplied to the microcomputer 5 after being converted into pulses in the waveform shaping circuits 4, 7, 9 and 11, respectively. In step S1, a wheel speed VW is calculated. Then, control goes to a step S2. That is, here, the microcomputer 5 measures the cycle of the wheel speed pulse supplied from the waveform shaping circuits 4, 7, 9 and 11 by a separate interruption process (not shown), and calculates the wheel speed VW from the reciprocal of the cycle. .

In step S2, a wheel acceleration GW is calculated by calculating a difference between the wheel speed VW calculated in step S1 and the wheel speed VW calculated last time. Then, control goes to a step S3. In step S3, the detection voltage VG detected by the acceleration sensor 2 is converted into digital data by an A / D converter (not shown), and the converted detection data is read. Then, control goes to a step S4.

In step S4, the detected data from the A / D converter is used as the vehicle body acceleration GB, and the vehicle body acceleration G
Based on B, the wheel speed VW, and the wheel acceleration GW, the pressure increase, pressure decrease, and holding of the brake hydraulic pressure P of the brake (not shown) are determined according to a predetermined algorithm. Then, control goes to a step S5. In step S5, a current instruction value is output to each of the current control circuits 12, 15, 17 and 19 according to the contents determined in step S4. This allows current from the power supply 14 to flow through each of the solenoids 13, 16, 18, and 20,
The brake hydraulic pressure P of the brake is increased, reduced, or held, and anti-skid control is performed. Steps S1 to S
The processing up to 5 is performed cyclically every predetermined time TL.

Next, the operation of the anti-skid control device shown in FIG. 5 will be described with reference to a waveform diagram of FIG. 8A, the solid line in FIG. 8A is the detected voltage VG of the acceleration sensor 2, the solid line a in FIG. 8B is the actual vehicle speed, and FIG.
The broken line b of B is the vehicle speed VB estimated based on the output of the acceleration sensor 2, the solid line c of FIG.
The solid line of C indicates the braking oil pressure of the wheel, and the solid line of FIG. 8D indicates the current command value output from the microcomputer 5, all of which indicate three states of the pressure decreasing current, the pressure increasing current, and the holding current, respectively.

Now, the brake pedal of the vehicle is operated,
When the braking hydraulic pressure P of the wheel increases and the braking force exceeds the frictional force between the road surface and the tire, the wheel rapidly shifts to the locked state. At this time, the wheel acceleration GW indicates a large deceleration, and the slip amount (the difference between the vehicle speed VB and the wheel speed VW)
The microcomputer 5 detects the occurrence of the locking tendency from the wheel acceleration GW and the slip amount, and supplies the current control circuits 12, 15, 17 and 19 with a current instruction value indicating a pressure reduction. As a result, the brake hydraulic pressure P is reduced by the action of the solenoids 13, 16, 18, and 20, and the wheels shift from the locking tendency to the recovery state.
That is, the wheel acceleration GW shifts from the deceleration side to the acceleration side,
The slip amount shifts from the increasing direction to the decreasing direction.

On the other hand, when the wheels shift from the locking tendency to the recovery state, the microcomputer 5 sets the wheel acceleration GW.
This is detected from the slip amount and the current control circuit 1
A current command value indicating holding is given to 2, 15, 17 and 19. As a result, the braking oil pressure P is held by the action of the solenoids 13, 16, 18, and 20. And
The wheel condition has fully recovered from the locking tendency, and the vehicle speed V
After approaching B, the pressure is increased sequentially. In other words, the microcomputer 5 repeats the operation of giving the current control value to the current control circuits 12, 15, 17, and 19 for a short time, and then giving the current control value indicating the hold. As a result, the braking oil pressure P sequentially increases, and when the braking force eventually exceeds the frictional force, the wheels shift to the locked state again, and the microcomputer 5 sends the current instruction values indicating the pressure reduction to the current control circuits 12, 15, 17. And 19 respectively. Thereafter, by repeating the above-described operations sequentially, the braking force of the wheel is controlled to be close to the maximum value of the frictional force between the road surface and the tire.

In the anti-skid control device, it is indispensable to find the vehicle speed VB of the vehicle. However, it is technically very difficult to directly detect the vehicle speed VB. Body speed V
B is obtained by estimation. Here, the calculation method of the vehicle body speed VB will be described with reference to FIG. 8 again. When the wheels do not tend to be locked, the wheel speed VW substantially coincides with the actual vehicle speed.
Can be obtained as VB = VW. Next, when the locking tendency occurs, the vehicle speed VB is decreased by the detection data from the acceleration sensor 2, that is, the inclination according to the vehicle acceleration VG. That is, the vehicle speed VB is obtained by integrating the vehicle acceleration VG. Next, after the wheels recover from the locking tendency and reach the vehicle body speed VB, the vehicle body speed VB is obtained again with VB = VW. Thereafter, the series of calculations described above are repeated to determine the vehicle speed. Japanese Patent Application Laid-Open No. 2-77352 discloses a method of indirectly obtaining a vehicle speed VB by using an acceleration sensor and integrating detection data detected by the acceleration sensor.

[0011]

Since the conventional anti-skid control device is constructed as described above, since the characteristics of the acceleration sensor are not always ideal, a vehicle body obtained by integrating detection data from the acceleration sensor is obtained. Since the speed includes a large error, especially since the anti-skid control device works effectively on a road surface with low frictional force,
Depending output value when acceleration is zero is, that, the offset value is large, whereby there is a problem such that it is impossible to perform good anti-skid control.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an anti-skid control device capable of removing an influence of an offset of an acceleration sensor and performing good anti-skid control. With the goal.

[0013]

An anti-skid control device according to the present invention includes an acceleration sensor for detecting the acceleration of a vehicle, a wheel speed detecting means for detecting a wheel speed of each wheel of the vehicle, the acceleration sensor, Control means for controlling the braking force on each of the wheels based on the output of the wheel speed detection means, the control means comprising: acceleration or deceleration of each wheel, wheel speed of each wheel for a predetermined time Difference, the change amount of the wheel speed of each wheel, and the change amount of the output of the acceleration sensor are all equal to or less than a predetermined value, and when the wheel speed of each wheel is equal to or more than a predetermined value, the average of the output of the acceleration sensor is obtained. The value is stored as an offset value, and the vehicle speed of the vehicle is obtained based on a value obtained by subtracting the offset value from the output of the acceleration sensor.

[0014]

According to the present invention, the acceleration or deceleration of each wheel, the difference between the wheel speeds of each wheel, the change amount of the wheel speed of each wheel, the change amount of the output of the acceleration sensor, the wheel When the speed is equal to or lower than the predetermined value, the average value of the output of the acceleration sensor is stored as an offset value, and a value obtained by subtracting the offset value from the output of the acceleration sensor is integrated to obtain the vehicle body speed of the vehicle. As a result, the effect of the offset of the acceleration sensor can be removed, and good anti-skid control can be performed.

[0015]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an anti-skid control device according to the present invention. In the drawing, portions corresponding to those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the figure, 1A is a controller, a waveform shaping circuit 4,
7, 9 and 11, a microcomputer 5A, and current control circuits 12, 15, 17 and 19.

Next, referring to the flowchart of FIG.
The operation of the anti-skid control device shown in FIG. While the vehicle is running, the acceleration of the vehicle from the acceleration sensor 2 is detected and supplied to the microcomputer 5A as detection data, and a frequency proportional to the wheel speed from each of the wheel speed sensors 3, 6, 8 and 10 is detected. Are supplied to the waveform shaping circuits 4, 7, 9 and 11, respectively. The sine wave signals of the wheel speed sensors 3, 6, 8 and 10 are supplied to the microcomputer 5A after being converted into pulses in the waveform shaping circuits 4, 7, 9 and 11, respectively. In step S1, the wheel speed VW
Is calculated. Then, control goes to a step S2. That is, the microcomputer 5A measures the cycle of the wheel speed pulse supplied from the waveform shaping circuits 4, 7, 9 and 11 by a separate interruption process (not shown), and calculates the wheel speed VW from the reciprocal of the cycle. .

In step S2, a wheel acceleration GW is calculated by calculating a difference between the wheel speed VW calculated in step S1 and the wheel speed VW calculated last time. Then, control goes to a step S3. In step S3, the detection voltage VG detected by the acceleration sensor 2 is converted into digital data by an A / D converter (not shown), and the converted detection data is read. Then, control goes to a step S10.

In step S10, the offset GS0 is learned from the detected data GSI from the A / D converter.
By subtracting the offset value GS0 from the input value GSI, the vehicle body acceleration GB from which the offset value GS0 has been removed
Get. Then, control goes to a step S4. Step S4
Then, the wheel speed VW, the wheel acceleration GW and the vehicle body acceleration G
From B, pressure increase, pressure decrease, and holding of the brake hydraulic pressure P are determined according to a predetermined algorithm described later. Then, control goes to a step S5.

Next, in step S5, a current instruction value is output to each of the current control circuits 12, 13, 17 and 19 according to the determined contents. As a result, the current from the power supply 14 flows through each of the solenoids 13, 16, 18, and 20, and the brake hydraulic pressure P of the brake (not shown) is increased, reduced, or held, thereby performing anti-skid control. Step S1,
The processes up to S2, S3, S10, S4, and S5 are cyclically performed at predetermined time intervals TL.

Next, a method of removing the offset of the acceleration sensor 2 will be described with reference to a functional block diagram of the microcomputer 5A shown in FIG. In the figure,
Reference numeral 21 denotes an offset removal function block as a whole,
Reference numeral 22 denotes an input terminal to which the detection data GSI from the AD converter shown in FIG. 1 is supplied, and reference numeral 23 denotes a detection data GSI supplied from the AD converter via the input terminal 22.
Is integrated 256 times to obtain a value GS1 of 1/256 of the result, 24 is a switch that opens and closes based on a switching signal from a condition determination unit 25, and 25 is learning conditions (a) to (e) described later. Is a condition determining unit that determines whether or not the condition is satisfied, and controls the opening and closing of the switch 24 according to the determination.

The filter 26 filters the average data GSI from the averaging section 23 to store an erroneous value as an offset value for some reason. If the erroneous learning is performed, the influence of the erroneous learning on the anti-skid control is obtained. The filter section 27 for reducing the filter output GS2 from the filter section 26 by clipping the filter output GS2, as in the case of the filter section 26, stores an erroneous value as an offset value for some reason when erroneous learning is performed. A clipping section 28 for reducing the influence of the erroneous learning on the anti-skid control; 28, an addition circuit for subtracting the output of the clipping section 27 from the detection data GSI from the input terminal 22, ie, the offset value GS0; 28,
That is, the vehicle acceleration GB is calculated by the microcomputer 5A.
Output terminal to be supplied to other functional block units.

Next, the operation of the functional block shown in FIG. 3 will be described. Detected data GS via input terminal 22
When I is supplied to the averaging unit 23, it is integrated 256 times, and 1 /
A value of 256, that is, an average value GSI is obtained. On the other hand, in the condition determination unit 25, learning conditions (a) to (described later)
If the determination of (e) is made 256 times, that is, it can be continuously determined for 256TL, the switching signal is transmitted to the switch 24.
To turn it on. That is, the switch 24 is turned on each time the learning condition is satisfied 256 times. When the switch 24 is turned on, the average value GS from the averaging unit 23 is output.
I is supplied to the filter unit 26, and the filter unit 26 performs a filtering process. Here, in the filtering process in the filter unit 26, when the offset value obtained so far is GS2L and the newly input offset value is GS2M, a new filter output GS2N is given as follows.

GS2N = (K1 · GS2M + K2 · GS2L) / (K1 + K2) (1)

The output GS2 of the filter 26 is supplied to a clip section 27 for clipping. Then, the clip unit 27 clips the value of the output GS2 of the filter unit 26 within a range where the offset amount of the acceleration sensor 2 can normally take. The offset value GS0 of the acceleration sensor 2 is learned by the above series of processing, and is stored in, for example, a memory (not shown) of the microcomputer 5A.

In the subsequent anti-skid control, a value obtained by subtracting the offset value GS0 read from the memory from the detection data GSI from the AD converter is used as the vehicle body acceleration GB. That is, the clip portion 27
, Ie, the offset value GS0 is added to the adder 28
And is subtracted from the detection data GSI from the input terminal 22. The output of the adding circuit 28, that is, the vehicle acceleration GB is supplied to another functional block of the microcomputer 5A via the output terminal 29. The memory retains its stored contents even when the power of the apparatus is cut off. Until the learning condition is satisfied, it is assumed that the contents of the memory are initially set to a state where the sensor offset is zero.

Next, the learning conditions (a) to (e) described above will be described. The learning condition (a) is that the wheel acceleration or deceleration GW is equal to or less than a predetermined value, and the learning condition (b) is that the speed difference between the four wheels of the wheel speed VW is equal to or less than a predetermined value, that is, the four wheels have substantially the same speed. The learning condition (c) is that the change amount of the wheel speed VW between the above 256TL is a predetermined value or less, and the learning condition (d) is that the change amount of the detection data (digital data) GSI from the AD converter during the above 256TL is a predetermined value. Hereinafter, the learning condition (e) is that the wheel speed VW is equal to or higher than a predetermined value.

The offset value of the acceleration sensor 2 is the output value of the acceleration sensor 2 when the acceleration is zero, that is, when the vehicle is traveling straight on a level ground at a constant speed. The state can be detected based on the learning condition (e). First, under the learning condition (a), it is detected that the wheels are traveling at a substantially constant speed. That is, when the vehicle is traveling with a large acceleration or deceleration, the wheels slip (the difference between the wheel speed and the vehicle speed).
Occurs, and the wheel speed does not represent the vehicle speed. Therefore, the learning at the time of such a large acceleration or deceleration is prohibited by the learning condition (a). Here, the predetermined value is ideally zero, but in practice, the wheel acceleration GW shows a certain magnitude even at a constant speed due to various disturbances. Use the value corresponding to the size.

Next, it is detected from the learning condition (b) that the vehicle is traveling straight on a flat ground. For example, a wheel speed difference occurs between the driven wheel and the drive wheel when climbing a hill, and a speed difference occurs between the inner wheel and the outer wheel when turning. Therefore, it is determined that the vehicle is traveling straight on a flat ground according to the learning condition (b). Can be detected. Next, based on the learning conditions (c) and (d), it is detected that the vehicle is traveling at a constant speed. Although the constant-speed running state is detected also in the learning condition (a), it is difficult to detect the state in which the vehicle is accelerating or decelerating extremely slowly by the learning condition (a). The slow acceleration and slow deceleration states are detected when the wheel speed VW and the detection data (converted by the AD converter) GSI of the acceleration sensor 2 are substantially constant.

Next, based on the condition (e), it is detected that the vehicle is running at a high speed of a certain level or more. In other words, it is highly probable that the vehicle frequently repeats acceleration and deceleration when traveling at a constant speed, such as traveling in an urban area. Therefore, learning in such a state is prohibited.

Next, the configuration of a program for implementing the above-described offset learning will be described with reference to the flowchart shown in FIG. The flowchart shown in FIG. 4 is for describing the processing in step S10 of the flowchart shown in FIG. 2 in more detail.

First, in step S11, a counter (not shown) of the microcomputer 5A for counting 256 times is counted up. Then, control goes to a step S12. In step S12, the detection data GSI from the AD converter is integrated. Then, control goes to a step S13. In step S13, it is determined whether or not the learning condition is satisfied. If it is satisfied, the process proceeds to step S17, and if not, the process proceeds to step S15. Step S1
At 5, the counter is reset. And step S16
Move to In step S16, the integrated value is reset. Then, control goes to a step S17.

In step S17, it is determined whether or not the count value of the counter has reached "256". If the count value has reached 256, the process proceeds to step S18, and if not, the process proceeds to step S21. In step S18, when the above-mentioned learning condition is continuously satisfied 256 times, a filtering process is performed. Then, control goes to a step S19. Step S
At 19, clip processing is performed. Then, control goes to a step S20. In step S20, the offset value GS0 obtained by the clip processing is stored in the memory. Then, control goes to a step S21. In step S21, the offset value GS0 is obtained from the detection data GSI from the AD converter.
Is subtracted to obtain the vehicle body acceleration GB. The vehicle acceleration GB is used in the anti-skid control.

As described above, in the present embodiment, when a predetermined learning condition is satisfied, the detection data GSI from the A / D converter is filtered and clamped to obtain an offset value GS0 of the acceleration sensor 2. This offset value GS0 is used as the detection data GS from the AD converter.
I to obtain the vehicle body acceleration GB.
Since B is used for the anti-skid control, the influence of the offset of the acceleration sensor 2 is removed, and thereby good anti-skid control can be performed.

[0034]

As described above, according to the present invention, the acceleration sensor for detecting the acceleration of the vehicle, the wheel speed detecting means for detecting the wheel speed of each wheel of the vehicle, the acceleration sensor and the wheel speed Control means for controlling the braking force on each wheel based on the output of the detection means, the control means for a predetermined time, acceleration or deceleration of each wheel, the difference between the wheel speed of each wheel, If both the change amount of the wheel speed of each wheel and the change amount of the output of the acceleration sensor are equal to or less than a predetermined value, and the wheel speed of each wheel is equal to or more than a predetermined value, the average value of the output of the acceleration sensor is offset. Since the vehicle speed is stored based on the value obtained by subtracting the offset value from the output of the acceleration sensor, the influence of the offset of the acceleration sensor is removed. There is an effect that it is possible to perform a good anti-skid control.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an anti-skid control device according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the anti-skid control device according to the present invention.

FIG. 3 is a functional block diagram showing an embodiment of an anti-skid control device according to the present invention.

FIG. 4 is a flowchart for explaining the operation of the anti-skid control device according to the present invention.

FIG. 5 is a configuration diagram showing a conventional anti-skid control device.

FIG. 6 is a characteristic diagram showing a relationship between a detection voltage of a general acceleration sensor and a vehicle acceleration.

FIG. 7 is a flowchart for explaining the operation of a conventional anti-skid control device.

FIG. 8 is a waveform chart for explaining the operation of the conventional anti-skid control device.

[Explanation of symbols]

 1A Controller 2 Acceleration sensor 3, 6, 8, 10 Wheel speed sensor 4, 7, 9, 11 Waveform shaping circuit 5A Microcomputer 12, 15, 17, 19 Current control circuit 13, 16, 18, 20 Solenoid

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-270666 (JP, A) JP-A-1-218954 (JP, A) JP-A 1-218955 (JP, A) JP-A-1- 218956 (JP, A) JP-A-4-163264 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60T 8/70 B60T 8/66

Claims (1)

(57) [Claims] An acceleration sensor for detecting an acceleration of the vehicle; a wheel speed detecting means for detecting a wheel speed of each wheel of the vehicle; and an acceleration sensor for detecting a speed of the wheel based on outputs of the acceleration sensor and the wheel speed detecting means. Control means for controlling the braking force, the control means for a predetermined time, the acceleration or deceleration of each of the wheels, the difference between the wheel speeds of each of the wheels, the amount of change in the wheel speed of each of the wheels, When any of the change amounts of the output of the acceleration sensor is equal to or less than a predetermined value, and when the wheel speed of each of the wheels is equal to or more than a predetermined value, the average value of the output of the acceleration sensor is stored as an offset value. An anti-skid control device, wherein the vehicle speed of the vehicle is obtained based on a value obtained by subtracting the offset value.