JPS58194647A - Control method of antiskid - Google Patents

Abstract

PURPOSE:To control an antiskid in accordance with a road surface even if the road surface is changed in 1 cycle, by selecting decleration obtaining a false car body speed to a small value when a relaxing time of brake oil pressure exceeds a prescribed value. CONSTITUTION:A signal from a car body speed sensor 30 is input to a CPU via an amplifying and waveform shaping unit 32. The CPU measures a time relaxing brake oil pressure by a solenoid timer 44, when this measured time exceeds a prescribed value, a signal is fed to a reference car speed setter unit 42. The unit 42 decides a false car body speed on the basis of a prescribed deceleration, when the signal is fed from the solenoid timer, this deceleration is changed to a small value. Since a false car body speed corresponding to a road surface mu can be determined even if the road surface is changed during 1 cycle of control, an antiskid is more accurately controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid control method for efficiently braking a vehicle by preventing a skid phenomenon caused by wheel locking when sudden braking is applied while the vehicle is running. * between the wheels and the road surface in response to changing conditions
*Related to an anti-skid control method that appropriately brakes a vehicle regardless of the road surface condition, taking into account the fact that the coefficient changes. The relationship between the coefficient of friction μ between the wheels and the road surface and the slip ratio S has characteristics as shown in FIG.

According to this, the maximum friction coefficient μ is obtained near the slip rate S=0.2, and when the wheels are locked by sudden braking, the friction coefficient becomes thick (and the friction coefficient decreases. Therefore, the minimum distance In order to perform braking, it is best to adjust the braking pressure so as to obtain the maximum friction coefficient, that is, to maintain the slip ratio S = 0.2 at all times during braking.Therefore, if the slip ratio is The anti-skid control method is a method of controlling the braking pressure so that it is within an appropriate range.

Various methods have been invented for this control, and one known method is to simulate the vehicle speed after braking. Figure 2 illustrates the method. When sudden braking is applied at point A1 in FIG. 2, the brake oil pressure increases and the wheel rotation speed decreases.

However, slip occurs between the road surface and the wheels, and the actual vehicle speed is greater than the wheel rotation speed. This method of calculating the vehicle speed is based on a preset deceleration (speed reduction rate per unit time) based on the wheel rotation speed at point A1 at the start of braking, and the vehicle speed after braking is calculated by linear approximation. A method of predicting is adopted. Therefore, the actuator of the anti-skid control device is activated at the time when the slip ratio, which is determined from the relationship between the vehicle body speed predicted above and the actually measured wheel rotation speed, reaches or exceeds a certain set value (point 81 in the diagram). to reduce the brake oil pressure and release the control. Then, the wheel rotational speed decreases for a while due to the inertia of the control system, and the slip ratio increases, but the effect of brake release appears, and the wheel rotational speed eventually increases and the slip ratio becomes smaller. The actual vehicle speed is
If the speed is lower than the simulated vehicle speed, there is a point where the simulated vehicle speed and the actually measured wheel rotation speed become equal. In this method,
At this point (point 01 on the diagram) where the points are equal, the actuator of the anti-skid control device is turned off, the brake release is released, and brake hydraulic pressure is applied by foot pressure to apply the brake again. In other words, due to the inertia of the control system, the wheels are accelerated for a while (1), but eventually the braking effect occurs and the wheels move toward the locked direction, so the wheel rotational speed decreases. Top A
Anti-skid control is performed with one period from point 1 to point A2. Note that the simulation of the vehicle body speed after the second cycle is set based on the maximum rotational speed of the wheels.

The deceleration rate is constant in any period.

However, the coefficient of friction between the wheels and the road surface varies depending on the road surface conditions, such as ice, snow, mud, paved roads, etc., and the wheel rotation speed decreases due to braking. The recovery characteristics upon release differ, and the vehicle speed reduction characteristics also vary depending on the road surface conditions.

3 and 4 illustrate this, and FIG. 3 shows the case of a low μ road with a small coefficient of friction.

FIG. 4 shows the case of a high μ road with a large coefficient of friction. In this way, the actuator activation and termination times and the activation time (T) are different between the low μ road and the high μ road. Therefore, in order to perform appropriate braking, it is necessary to monitor the road surface condition, and the simulated vehicle speed to be predicted should be changed accordingly. Even though it is a low μ road, if control was performed using the deceleration of the vehicle body on a high μ road C, the actuator's on time would be delayed and its off time would be too early, resulting in a short operating time. , a locking phenomenon occurs immediately after actuator 1 is turned off. On the other hand, when simulating the deceleration on a low μ road despite the high μ muscle, the actuator on time is too early and the off time is delayed, resulting in the actuator J-Y's operating time being It becomes longer and optimum braking cannot be achieved.

Therefore, the following method is known as a means to eliminate such inconveniences and perform control according to road surface conditions. FIG. 5 is an explanatory diagram of this method. In the first cycle of the anti-skid control method described above, the medium speed characteristic 10 is always set in accordance with the high μ road.

When braking is applied with a constant brake pressure, on a high μ road, the wheel rotation speed decreases relatively slowly as shown in curve 12 due to the large friction between the road surface and the wheels, and when the brake is released, the wheel rotation speed decreases quickly. The vehicle speed recovers toward the vehicle speed. On the other hand, low μ
In the case of a road, the wheel rotation speed decreases relatively quickly and recovers slowly (as shown in curve 14) due to the small friction between the road surface and the wheels. Therefore, the operating time of the actuator is It can be seen that T is shorter on a high μ road than on a low μ road. That is, it can be seen that the actuator operating time is related to the coefficient of friction between the road surface and the wheels.

Taking advantage of this fact, a method is adopted in which it is determined whether the road surface condition is a high μ road or a low μ road during this operation time, and the deceleration of the pseudo vehicle speed for the next cycle is selected. That is,
The vehicle speed for the next cycle was set according to the operating time of actuators 1 to 2 in the previous cycle.

However, with such means, appropriate control cannot be performed when the coefficient of friction of the road surface changes locally. That is, even if it is determined that the road is a low μ road and the pseudo vehicle speed for the next cycle is set, the actual road surface may be a high μ road when the next cycle is reached. The opposite case is also possible.

If the cycle of the road surface condition and the control cycle match, the control will be performed under completely opposite conditions, which is inconvenient. Even if the road surface is uniform and has a low μ road, the first recycle is controlled at a pseudo vehicle speed for a high μ road, and appropriate braking cannot be obtained.

Conventional anti-skid control methods have drawbacks as described above.

The present invention was made for the purpose of improving such drawbacks, and initially the pseudo vehicle speed was set to a high μ which is a high deceleration.
It is predicted using road constants, and if the period during which the control hydraulic pressure of the hydraulic control system is relaxed is longer than a predetermined period, the road surface is determined to be a low μ road, and the pseudo vehicle speed is reduced from the middle. By setting the speed to a smaller value and modifying the pseudo vehicle speed from the initial predicted characteristics, the same effect as when predicting the pseudo vehicle speed with the deceleration for low μ roads from the beginning is obtained, that is, the control hydraulic pressure of the hydraulic control system The objective is to perform anti-skid control appropriately in accordance with the coefficient of friction between the road surface and the wheels by controlling the period in which the friction coefficient is relaxed to be a period corresponding to a low μ road. 1'4 That is, in predicting the vehicle speed after braking, the present invention reduces the maximum wheel rotational speed by a constant deceleration to obtain a pseudo vehicle speed,
The pseudo vehicle speed and the actual wheel rotation speed are compared, and at the time when these values meet a predetermined relationship, the control oil pressure of the hydraulic control system is loosened, and then the actual wheel rotation speed and the pseudo vehicle speed are compared. In an anti-skid control method, the process of controlling the control hydraulic pressure to increase at a time when the relationship between When the set time or more is reached, in predicting the subsequent vehicle speed, the pseudo heavy object speed at that time is reduced by a constant deceleration smaller than the previously set deceleration to obtain a pseudo vehicle speed, The anti-skid control method is characterized in that the pre-control oil pressure is controlled to be increased at a time when the relationship between the pseudo vehicle speed and the measured wheel rotation speed meets a predetermined relationship.

The concept of this control method will be explained with reference to the drawings.

FIG. 6 illustrates the relationship between the wheel rotation speed and the simulated vehicle body speed, which is a predicted characteristic, with respect to time, and the relationship between the operation time of the actuator that loosens the control hydraulic pressure of the hydraulic control system.

First, we will discuss the case where the road surface is a low μ road.

Let's say that the brakes are applied now at point P1. The wheel rotational speed is measured by a sensor and is attenuated as shown by curve 22. -h1 The vehicle speed after braking is predicted to obtain a pseudo vehicle speed as follows. At point P1 at the start of braking, the wheel rotational speed and the vehicle body speed match, so the wheel rotational speed at that time is taken as the initial vehicle body speed, and then the vehicle speed is linearly adjusted at a constant deceleration as shown at 1120. Assume that it is attenuated. The deceleration in this case is set to a constant for high μ roads, such as 1, for example IG-(").

Next, at point 01, where the pseudo vehicle speed and the actually measured wheel rotation speed reach a predetermined relationship, the actuator is operated to avoid reducing the control oil pressure. Here, the predetermined relationship is determined when the slip ratio reaches a certain set value, or when the deviation between the pseudo vehicle speed and the wheel rotational speed reaches a set value.

Further, the timing to turn off the actuator and increase the control oil pressure is determined, as described above, when the slip ratio reaches a certain set value, or when the deviation between the two reaches a set value, etc. For the sake of simplicity, assume that the actuator is turned off at a time when the rotational speed of the wheels matches the pseudo vehicle speed. As mentioned above, in the case of a low μ road,
The operating time of the actuator is longer than that on a high μ road.

In the case of a high μ road, the slip between the road surface and the wheels is small, so the degree of deceleration of the wheel rotation speed after braking is smaller than that on a low μ road, and conversely, when the control hydraulic pressure is relaxed, the wheel returns to its original state. The speed is large and exhibits a characteristic as shown by curve 24, and the operating time of the actuator is short as shown by 13. Therefore, if the operating time of the actuator becomes longer than the reference setting value TS, it can be determined that the road is low at that point, that is, at point 81. If it is a low μ road, the slip will be large, so the deceleration that predicts the pseudo vehicle speed should originally use a small constant for low μ roads. Therefore, the actuator would normally be turned off at point R1.
The operating time of the actuator must be ■4 hours.

However, in the conventional method, the actuator was turned off at the 01 point and the operating time was 15 hours, which was shorter than the appropriate value.

Therefore, as shown in the straight line 23, the characteristics after the 81st point are reduced by a smaller deceleration to obtain a pseudo-vehicle speed, and as a result, at point R1, if the pseudo-vehicle speed and wheel rotation speed are matched, the actuator The operating time T4 suitable for a low μ road can be obtained.

On the other hand, when the road surface is a high μ road, the actuator operating time is shorter than the set value TS, so normal measures are taken using the initially set pseudo vehicle speed for high μ roads.

In the second cycle control, under the assumption that the maximum speed at which the wheel rotational speed has recovered is equal to the vehicle speed at that time, the vehicle speed is predicted using the set deceleration using the maximum wheel speed as the initial value. Find the pseudo vehicle speed.

According to a further preferred implementation g, the slope of the pseudo vehicle speed function 23 is newly set according to the difference between the pseudo vehicle speed and the actually measured wheel rotation speed at the judgment time of the actuator 1-2 operation time, that is, at 81 points. is changing. . This is because if the difference between the two is large, it indicates that the recovery speed of the wheel is slow, that is, the slip is large and the coefficient of friction of the road surface is small.

By doing this, depending on the friction coefficient of the road surface,
By continuously changing the pseudo vehicle speed function, more fine-grained optimal control is possible.

Hereinafter, the present invention will be explained in detail based on Examples.

FIG. 7 is a block diagram showing steps for implementing the method of the present invention.

The wheel rotation speed sensor 30 is a device that is attached to an axle and uses electromagnetic coupling to convert the rotation speed of the wheel into a sinusoidal electrical signal. The output from the wheel rotation speed sensor 30 is sent to an amplification and waveform shaping section 32, where it is amplified and converted into a rectangular wave. This rectangular wave signal is input to the counter section 34, and the wheel rotation speed C1 is constantly determined by calculating the number of rectangular pulses per unit time. It will be sent out on 42. The reference vehicle speed has the same meaning as the above-mentioned pseudo vehicle speed, and the edict of the reference vehicle speed is used because it is a reference value for comparison of wheel rotational speed. The reference vehicle speed setting unit 42 is a block that has a function of predicting the attenuation characteristic of the vehicle speed after braking and setting a pseudo vehicle speed. The stop lamp switch 40 is
A braking start signal is applied to the reference heavy speed setting section 42 in conjunction with the operation of a foot brake (not shown). Reference vehicle speed setting section 4
2 receives this braking start signal, inputs the wheel rotational speed at that time from the counter section 34, and sets a reference vehicle speed characteristic according to a preset deceleration based on the current speed. This reference vehicle speed characteristic is input to the comparator 36 as a value that changes over time, and is compared with the wheel rotation speed at that time. The comparison section 36 sends a signal to the drive section 38 when the comparison amount reaches a predetermined value. Upon receiving the signal, the drive unit 38 performs the following steps to release the brake.
The actuator 46 that drives the pressure reducing device inserted into the brake hydraulic circuit is activated. At this time, the comparison unit 36
A solenoid timer 44 is activated to measure the activation time of the actuator. This operating time is input to the reference vehicle speed setting section 42, and when this time has passed a preset time, the subsequent vehicle speed characteristics are newly set using a new reduction speed. Then, this numerical value is always sent to the comparison section 36, and the wheel rotation speed at that time,
When the reference vehicle speed and wheel rotation speed are compared, an actuator off signal is sent to the drive unit 38 to turn off the actuator 46 and restore braking. The above is one cycle of the anti-skid control method according to one embodiment of the method of the present invention.

A case in which the above-mentioned control method is implemented by processing by a digital computer will be described in detail.

FIG. 8 is a flowchart showing the processing contents of the main routine. First, when the road surface is a low μ road,
The gist of the present invention is to change the setting of the predicted characteristic of the reference vehicle speed to the reference vehicle speed characteristic for a low μ road.When the main switch is turned on, the computer starts program processing from a predetermined entry address. In step 100, variables used in this routine are collectively set to initial values. Step 102 is a step of detecting a signal from the stop lamp switch 40, and if the stop lamp is on, it means that braking was applied at that time. If the signal is on, the process advances to step 103.

Initially, since the vehicle is running, the stop lamp switch is in the off state. In this case, the process proceeds to step 140 and step 14 is performed without activating the actuator.
Proceed to step 2. Step 142 functions to update the initial value of the variable by using the wheel rotation speed at that time detected by the counter unit 34 as the reference vehicle speed. That is, it is used as the initial speed at the start of braking to calculate later predicted characteristics. In addition, actuator operating time i11
Clear the solenoid timer that is activated when the vehicle is running, and set the deceleration to a constant for high μ roads to predict the speed characteristics of the vehicle. This is because, at the beginning of control in this control method, it is assumed that the vehicle speed is always attenuated by a constant for high μ roads. As described above, during non-braking driving, the vehicle body speed is initially set using the latest wheel rotational speed. When braking is applied here, the stop lamp switch is turned on and the process proceeds to step 103.

Step 103 is a step of determining whether the actuator is on or off. Initially, the actuator is off, so the process proceeds to step 104. Step 104 is a step of detecting the state of wheel speed change,
The maximum wheel rotation speed is stored and used as the initial value of the vehicle speed prediction characteristic, and is used from the second cycle onwards. That is, at the beginning of braking, the rotational speed of the wheels does not increase, so the process proceeds to step 106. Step 106 is a step for providing the predicted characteristics of the vehicle speed after braking, and is a step for providing information to a timer interrupt routine that subtracts a predetermined amount at regular intervals according to a preset deceleration. do. As a result, the reference vehicle speed is obtained after a certain period of time has passed. Then, in the next step 108, the reference vehicle speed and the actual wheel rotation speed are compared. In normal cases,
If the wheel rotation speed is smaller than the reference vehicle speed, step 11
0 and compares the difference between the reference speed and the wheel rotational speed with a preset value. While it is smaller than the set value, the process returns to step 102 and the above loop is executed as time passes. As time passes and the slip rate increases,
In step 110, the difference between the reference vehicle speed and the wheel rotation speed becomes larger than the set value, and the process proceeds to step 112, where the actuator 46 is turned on and the brake is released.

Next, the process proceeds to step 114, where the solenoid timer is started and the operating time of the actuator 46 is set to H1. This time at 4 o'clock is processed by an interrupt routine at fixed time intervals, which will be described later.

The next step 116 is to compare the time measured by the solenoid timer (that is, the actuator operating time) with the set time. If the set time is not reached, the process returns to step 102 and step 103, step 112, step 11
Repeat loop 6. When the time indicated by the solenoid timer is determined to be longer than the set time, the road surface is low μ.
In the next step 118,
Reset the deceleration of the reference vehicle speed to a constant for low μ roads.

For this reason, the degree of deceleration of the reference vehicle speed applied from this point onwards becomes more gradual than before, and the vehicle speed characteristic is changed to that of a low μ road condition. The next step 120 serves to clear the solenoid timer and returns to step 102. and step 103.122.116.10
Repeat loop 2. As time passes, in step 122, when the wheel rotational speed recovers to be equal to the reference speed at that time, the process proceeds to step 124, and the actuator 46 is turned off. At this point, the brakes will be applied again. The next step 126 is a step for preparing for the next control cycle, in which the deceleration is reset to the initial high μ road constant. The process returns to step 102 via step 120. This time, since the actuator is off, the process proceeds to step 104. Even if the actuator is turned off and braking is applied, if the actual vehicle speed is higher than the reference vehicle speed, the wheel rotation speed will change due to the inertia of the control system.
It will rise for a while. and steps 104 and 130
．． By executing the loop 102, the maximum rotational speed of the wheels is stored, and this value is used as the initial value of the reference vehicle speed for the next control cycle.

As described above, the first cycle ends and the second cycle begins. and the cycle ending in step 102.1
The loop of 03.104.106.108.110.102 is repeated, that is, the car stops while maintaining the braking state.

In the above process, if the reference vehicle speed and wheel rotation speed match in step 122 before it is determined in step 116 that the actuator operating time is equal to or greater than the set value, the actuator is turned off in step 1241. . That is, the road surface is
It was determined that the road was a high μ road, and the deceleration was determined to be a high μ road.
A road constant is used, and in this case there is no intermediate switch to a low μ road constant.

The above is the main program for implementing this control method. FIG. 9 is a routine for generating a reference vehicle speed as a function of time. This routine is interrupted every 2.7a+sec by a timer built into the CPU.

Step 200 is a step for avoiding registers, etc., which is normally performed in interrupt processing. Ste.
Tube 202 performs step 106. of the main routine. If the reference vehicle speed is to be generated according to the information set in step 204, the process advances to step 204. In step 204, a timer corresponding to the deceleration is set. Here, the reference vehicle speed is generated with an accuracy of 1/h in minimum units. Therefore, in the case of a high μ road, the deceleration is set to 1G, so about 2
The reference vehicle speed is updated every 91 SeC. Therefore, in step 204, it is set to 29 Ilsec, as an example. In step 206, it is determined whether the update time of 2gm5ec has been reached, and if the update time has been reached, the reference vehicle speed is decreased by Ikl/h in step 210. Step 212
Now reset the timer mentioned above and move on to the next step. Step 208 is a process to prevent the reference vehicle speed from becoming negative. The next steps 214 and 216 are the steps to update the solenoid timer. Through this process, the solenoid timer is updated every 2.7m5ec. In the next step 218 and subsequent steps, the wheel rotational speed is constantly detected and a suspension device is devised. That is, the wheel rotation speed is measured by counting the number of square waves output from the waveform shaping section 32. To perform this count accurately, 86.4a+sec is required,
The design is such that the number of square waves created during that time corresponds to the speed at that time. Therefore, if it is configured with one counter, only the wheel rotation speed per 86.4IR8eC can be obtained. So NO31~N098
Eight counters are provided, each delaying the measurement start time every 10.8 m5ec. And 86°4m5ec
The measured values are No. 1 to No.

8 counters with a time delay of 10.811 SeO. Then, 10°8++s
The latest wheel rotation speed is measured for each ec.

Further, the read counters are cleared at each measurement start time.

Steps 218 to 228 represent the above processing. Step 230 functions to restore the avoided registers, which is a common method when returning from interrupt processing.

FIG. 10 shows a vehicle speed counting routine. This routine is started using the rising edge signal of the square wave outputted from the waveform shaping section 32 as an interrupt signal. After avoiding the register in step 300, in step 302, N011~No.

The vehicle speed counters 8 are each incremented by 1 unit, and in step 304, the registers are restored and the process returns to the main routine. Note that the vehicle speed counter used here refers to a register that measures the wheel rotation speed. As a result, the above-mentioned counter counts the number of square waves, and if the accumulated number after a certain period of time is detected, the wheel rotation speed is increased by 1q.

The above is the specific configuration of the software when the present control method is implemented by a digital computer. In the above, IG is used as the deceleration constant for high-μ roads, and O and IG are used as the correction deceleration constants, but these values can be selected more appropriately depending on the actual vehicle. Further, although only computer control has been specifically illustrated as a means for realizing the present control method, the gist of the present invention is characterized by the concept of the control method, and is limited only to the above-mentioned specific means. It's not a thing. For example, it would be easy for a person skilled in the art to construct it using an analog circuit.

In summary, in order to perform an anti-skid control method suitable for the road surface condition from the first control cycle, when the road surface is determined to be a low μ road, the present invention provides a The vehicle speed was calibrated using a smaller deceleration of 17 degrees, resulting in the same effect as the one controlled from the beginning with a pseudo-knit speed function for low-μ roads. . For this reason, the control method of the present invention
Significantly different from conventional methods, it is possible to perform optimal control according to road surface conditions from the beginning of braking. Therefore, according to the anti-skid control method according to the control method of the present invention, braking can be performed within a short braking distance regardless of the road surface condition.

[Brief explanation of drawings]

Figure 1 is a relationship diagram between friction coefficient and slip rate, Figure 2 is a diagram of the relationship between friction coefficient and slip rate.
Control characteristic diagram showing the conventional anti-skid control method, Part 3
4 is a control characteristic diagram for a low μ road, FIG. 4 is a control characteristic diagram for a high μ road, FIG. 5 is a control characteristic diagram showing a conventional control method, and FIG. 6 is a control characteristic diagram according to the method of the present invention. FIG. 7 is a block diagram in one embodiment of the method of the present invention, and FIGS. 8, 9, and 10 are flowcharts of computer software in one embodiment of the method of the present invention, respectively. 20...High μ road pseudo-vehicle speed characteristic, 21...Low μ road pseudo-vehicle speed characteristic 23...Corrected pseudo-vehicle speed characteristic, 22.24...Wheel rotation speed characteristic 30...Wheel rotation Speed sensor 46...Ac1 Actor Patent applicant Aisin Seiki Co., Ltd. Agent Patent attorney Sadamukai Okawa Patent attorney Shudo Fujitani Patent attorney Akio Maruyama Figure 3, Figure 4, Figure 10

Claims (2)

[Claims] (1) In predicting the vehicle speed after a till motion, the maximum wheel rotation speed is reduced by a constant deceleration to obtain a pseudo vehicle speed, and the pseudo vehicle speed is compared with the measured wheel rotation speed. At the time when the numerical values have a predetermined relationship,
Control the hydraulic control system to loosen the hydraulic pressure, and then
Anti-skid M in which one cycle is a process of controlling the control oil pressure to increase at a time when the relationship between the measured wheel rotation speed and the pseudo vehicle body speed has a predetermined relationship.
1117], when the period during which the control hydraulic pressure of the hydraulic control system is relaxed exceeds a predetermined set time, when predicting the subsequent vehicle speed, the pseudo vehicle speed at that time is set in the previous setting. to obtain a pseudo vehicle speed, and at a time when the relationship between the pseudo vehicle speed and the measured wheel rotation speed meets a predetermined relationship, the early control oil pressure is increased. Anti-skid control I7'J features an anti-skid control. (2) When predicting the vehicle speed after the preset time has elapsed, the smaller deceleration to be used is selected according to the difference between the simulated vehicle speed and the actual wheel rotation speed after the preset time has elapsed. Feature 1: The anti-skid control method according to claim 1, characterized in that: