KR100779466B1 - the Road surface condition judgement method when braking - Google Patents

Abstract

The present invention relates to a road surface determination method during braking, the first step of determining which one of the left and right sides of the front wheel exceeds the reference slip rate, and if it is determined that one side is out of the reference slip rate, A second step of calculating the behavior detection information of each wheel to determine whether the road surface condition is a split state, and a third step of determining whether the road surface is a split road surface based only on the behavior of the front wheel using the calculated information. And a fourth step of determining whether the split road surface is again determined by examining the behavior of the front wheel and the rear wheel by using the information calculated in the second step, when it is determined that the third step is not the split road surface. As a result, the state of the road surface changed during ABS control by detecting and detecting the state of the road surface more accurate during braking. Stable, it is possible to perform efficient braking force control.

Description

The road surface condition judgment method when braking}

1 is an overall flow chart illustrating a method of determining a vehicle name during braking according to an embodiment of the present invention.

FIG. 2A is a detailed flowchart of step 200 of FIG.

FIG. 2B is a detailed flowchart of step 300 of FIG.

FIG. 2C is a detailed flowchart of step 400 of FIG.

* Description of the symbols for the main functions of the drawings *

ΔSf: Difference in slip ratio of both wheels with respect to front wheels

ΔVf: Wheel lag of both wheels to front wheel

ΔSr: difference in slip ratio between both wheels

ΔVr: Wheel lag of both wheels to rear wheels

ΔSf1_thr: first threshold ΔVf1_thr: second threshold

ΔSf2_thr: third threshold ΔVf2_thr: fourth threshold

ΔSr2_thr: fifth threshold ΔVr2_thr: sixth threshold

The present invention relates to a method for determining road conditions during braking, and more particularly, to a method for determining road conditions during braking to quickly and accurately grasp road conditions to ensure stable braking efficiency of a vehicle regardless of changes in road conditions during braking. will be.

In general, automobiles are equipped with a brake system for stopping and speed control, and recently, an anti-lock brake system (hereinafter referred to as an anti-lock brake system) is used to improve the braking ability of the vehicle and to secure steering stability during braking. ABS is called).

ABS prevents the phenomenon by detecting the wheels during braking in advance to prevent the vehicle from slipping due to the failure to transfer the braking force to the road surface when braking during high-speed driving on roads with low braking friction coefficient. It is a system for doing so.

That is, the system estimates the vehicle speed by using the wheel speed sensor installed on the front and rear wheels of the vehicle, calculates the current slip rate and deceleration based on this, and sets the vehicle as the input variable. The slip rate is repeated by predicting the occurrence of the condition and reducing the brake pressure beforehand to bring the wheel speed closer to the vehicle speed and again increasing the brake pressure to brake the wheel before the wheel speed exceeds a certain value. By controlling to keep the vehicle in a desirable state, it is possible to prevent the vehicle from being in a state of steering loss and driving stability loss in advance due to the fixed state of the wheel and to improve the braking ability.

On the other hand, the friction coefficient between the wheel and the road surface changes according to the condition of the road surface, and compared with the road surface with a large friction coefficient, the wheel slippage is severe on the road surface with a small friction coefficient. easy to do. Therefore, even in ABS control, the braking pressure on the road surface with a small friction coefficient is generally smaller than that on a road surface with a small friction coefficient, because the control method is different on a road surface having a large friction coefficient and a road surface having a small friction coefficient.

For this reason, if the friction coefficient changes rapidly according to the road surface condition, the control state must be changed quickly. That is, during braking, if there is a sudden change from a road surface with a high friction coefficient to a low road surface, the braking force is large and it is easy to enter a fixed state, so the braking pressure should be drastically reduced.

Particularly problematic here is a case where there is a sudden road change on the split road surface during braking (for example, an asphalt road surface for one wheel and an ice road surface for the other wheel). In general, as the hydraulic control method according to the road surface change, a method of independently controlling the front wheel, which is the driving wheel, according to the road surface condition of the left and right wheels is used. On the basis of this, a select low method for depressurizing both of these small sides toward locking is already known. In the case of the selector low method, even if a split road surface cannot be detected, a certain degree of safety can be secured, but a problem arises in that the braking distance becomes long, and the control of the rear wheel is controlled by an independent control method to improve the braking force. In this case, the vehicle spins due to a sudden difference in braking pressure applied to the rear wheels.

Therefore, in order to compensate for the above, in order to perform appropriate control according to the change of road surface state, first, logic for accurately determining the change of the road state was required. In the past, the detection of the split road surface was performed by the behavior of the front wheels. Judging from the bay. That is, since only the behavior of the front wheels is judged, it is possible to quickly recognize the state of the road surface and perform appropriate control.

However, when the conventional logic does not detect a split road surface because it is insufficient to cover all of a lot of road conditions and driver's operation conditions (such as sudden braking and stepping deeply on the brake pedal) that are difficult to predict. In addition, a more accurate road surface determination method is required during braking.

Therefore, the present invention was devised in accordance with the request, and it is determined based on the behavior of the front wheel only to determine whether the road is split road surface, and even if it is determined that the road is not the split road surface, once again by looking at the behavior of the front wheel and the rear wheel again. An object of the present invention is to provide a road surface determination method during braking for determining whether a road is split.

In the braking road surface determination method according to the present invention for achieving the above object, a first step of determining which one of the left and right sides of the front wheel exceeds the reference slip rate, and as a result of which one side determines the reference slip rate If it is determined that the vehicle is out of the way, the second step of calculating the behavior detection information of each wheel to determine whether the road surface condition is a split state, and only the behavior of the front wheel is used based on the calculated information to determine whether the road is a split road surface. In the third step of determining and if it is determined that the split road surface is not the result of the third step, by using the information calculated in the second step to look at the behavior of the front wheel and the rear wheel again to determine whether the split road surface It comprises a fourth step.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an overall flowchart illustrating a method of determining a vehicle name during braking according to an exemplary embodiment of the present invention, FIG. 2A is a detailed flowchart of step 200 of FIG. 1, FIG. 2B is a detailed flowchart of step 300 of FIG. 1, 2C is a detailed flowchart of step 400 of FIG. 1.

Referring to the present invention in detail, first, when the driver operates the brake pedal for braking the vehicle, a braking hydraulic pressure is formed in the master cylinder, and the braking hydraulic pressure is transmitted to the wheel cylinders of the respective wheels to exert a braking force. Done. At this time, the control unit monitors the behavior of each wheel and determines which one of the left and right sides of the wheel exceeds the preset reference slip rate (S100).

If it is determined that the reference slip rate is not exceeded, it is determined that the current road condition is a uniform road surface. If it is determined that the reference slip rate is exceeded, the present road surface state is assumed to be a split road surface. Calculates wheel behavior information for each wheel to determine whether the road is a split road surface (S200).

As shown in FIG. 2A, the information calculated by the controller is a slip ratio difference and a wheel speed difference for each of the front and rear wheels. That is, the control unit calculates the body speed from the wheel speed of each wheel, calculates the slip ratio of each wheel using the wheel speed and the body speed, and uses both the calculated slip ratio and the wheel speed of both wheels for the front wheels. The slip rate difference ΔSf and the wheel speed difference ΔVf are calculated (S210). In addition, for the rear wheel, the slip ratio difference ΔSr and the wheel speed difference ΔVr of the two wheels with respect to the rear wheel are calculated through the same process as described above (S220).

On the other hand, the controller compares the information on the front wheel calculated in step 200 and each of the preset threshold value to determine whether the current road surface state is a split road surface (S300).

FIG. 2B illustrates this in detail. Referring to FIG. 2B, the controller determines whether the slip ratio difference ΔSf of both wheels for the front wheel is outside the preset first threshold value ΔSf1_thr and the wheel speed difference ΔVf for the front wheels. ) Is determined to deviate from the preset second threshold value ΔVf1_thr (S310 and S320). When the slip ratio difference and the wheel speed difference deviate from the respective threshold values, the process proceeds to step 500 to directly split the road surface state. If not, the process proceeds to step 400 for a more accurate determination and performs the split road surface determination step again. The reason why the split road surface is roughly determined roughly in step 300 is that when the slip ratio difference between the left and right wheels is large, it is necessary to quickly determine the split road surface using only the wheel behavior of the front wheel.                     

On the other hand, in the case of judging by using only the wheel behavior of the front wheel as described above, because the absolute value for the set threshold is set high, a lot of road conditions or operating conditions by the driver (deep braking, brake pedal deeply pressed) Case) is insufficient to cover all the cases, and to compensate for this, even if it is determined that the road is not the split road surface in step 300, the control unit performs the step of determining whether the road is the split road once again by examining the behavior of the front wheel and the rear wheel. It is made (S400).

FIG. 2C illustrates this in detail. Referring to FIG. 2C, the control unit may include a slip ratio difference ΔSf and a third threshold value ΔSf2_thr of the two wheels for the front wheel, and a wheel speed difference ΔVf value for the two wheels for the front wheel. The four thresholds (ΔVf2_thr) are compared and judged respectively, and the slip ratio difference (ΔSr) and fifth threshold value (ΔSr2_thr) and the wheel speed difference (ΔVr) value and the sixth threshold value of both wheels to the rear wheels are compared. (ΔVr2_thr) are compared and judged respectively (S410 to S440). As a result of the determination, when the slip ratio difference value and the wheel speed difference value deviate from each of the predetermined threshold values, it is determined as a split road surface (S500), otherwise, it is determined as a uniform road surface (S600).

Here, each absolute value of the first threshold value and the second threshold value set for the first determination of the step 300 is equal to the third threshold value and the fourth threshold value set for the second determination of the step 400. It is preferable to set larger than each absolute value for each. This is because, in the step of determining whether the road is split again, the setting threshold is lowered further, so that even in the case of determining that the road is not the split road in the first judgment step, another condition (such as braking and stepping deeply on the brake pedal) is considered. This can be determined by split road surface.

In addition, each absolute value of the third threshold value and the fourth threshold value for the front wheel set for the determination of the second step 400, the respective absolute value for the fifth threshold value and the sixth threshold value for the rear wheel It is preferable to set larger than each value. This is because the split road surface responsiveness to the rear wheels needs to be more sensitive than the front wheels to ensure the stability of the vehicle during braking.

As described above, according to the method for determining the road surface condition during braking according to the present invention, it is possible to perform stable and efficient braking force control even when the road surface changes during ABS control by determining and detecting the current state of the road surface more accurately during braking. have.

Claims (5)

In the method of determining the road surface condition during braking, A first step of determining which one of the left and right sides of the front wheel is out of the reference slip ratio; A second step of calculating the behavior detection information of each wheel to determine whether the road surface state is a split state when it is determined that one side is out of the reference slip ratio as a result of the determination; When determining whether the road is a split road surface based only on the behavior of the front wheel, the slip rate difference value and the first threshold value of the two wheels for the front wheel, and the wheel speed difference value and the second threshold value for both wheels for the front wheel are determined. A third step of comparing and judging each of said slip ratio difference and said wheel speed difference value when it is out of said predetermined threshold value; And if it is determined that the road is not the split road surface as a result of the third step, a fourth step of determining whether the road is the split road surface again using the information calculated in the second step is performed. How to determine the road surface conditions during braking characterized in that. The method of claim 1, The motion detection information of each wheel calculated in the second step is A method for determining a road surface condition during braking, characterized in that the difference between the slip ratio of the two wheels and the wheel speed difference and the wheel speed difference between the front wheels and the rear wheels. delete The method of claim 1, In the case of determining whether the road is split road again by examining the behavior of the front wheel and the rear wheel of the fourth step, The slip ratio difference value and the third threshold value of both wheels for the front wheels are compared and judged, respectively, and the slip ratio difference value and the fifth threshold value of both wheels for the rear wheels are compared. Comparing and judging the wheel speed difference value and the sixth threshold value of both wheels with respect to the rear wheels respectively, if the slip ratio difference value and the wheel speed difference value are outside the respective predetermined thresholds, it is determined as a split road surface. If it is determined that the road surface during braking, characterized in that the road surface during braking. The method of claim 4, wherein The first threshold value is greater than the third threshold value, The third threshold value is greater than the fifth threshold value, The second threshold value is greater than the fourth threshold value, and the fourth threshold value And a value is greater than the sixth threshold value.

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