KR101146578B1 - Control method of ABS - Google Patents

Abstract

The present invention relates to a control method of an anti-lock brake system of a vehicle, and an object of the present invention is to appropriately apply wheel pressure to a pressure level for generating maximum braking force according to a situation in which wheels are restored (accelerated) through linear flow control. The present invention provides a control method of an anti-lock brake system of a vehicle in which the structure is improved to improve the braking force of ABS by increasing pressure.

To this end, the present invention is a control method of the anti-lock brake system of the vehicle, when the anti-lock brake braking, it is determined whether the wheel speed reaches the inflection point that is increased without deceleration by the decompression of the wheel pressure, and the wheel speed is When the inflection point is reached, the road surface is determined by using the deceleration of the vehicle, the predetermined PWM duty ratio is provided to detect the boost slope corresponding to the determined road surface, and the pressure is increased by the detected boost slope and the wheel acceleration is increased. When it is determined that the wheel acceleration increases, it is determined whether the wheel acceleration increases higher than the preset reference acceleration, and when the wheel acceleration increases higher than the reference acceleration, the pressure is increased by the maximum boost slope.

ABS (Anti lock Brake System), Electronic Control Unit, LFC (Linear Flow Control)

Description

Control method of anti-lock brake system of vehicle {Control method of ABS}

1 is a schematic diagram illustrating a general ABS.

2 is a general ABS hydraulic circuit diagram.

3 is a control flowchart of an ABS control method according to a preferred embodiment of the present invention.

Description of the Related Art [0002]

10.Electronic control unit 20 ... Wheel speed sensing unit

30 Brake detection unit 30a Brake pedal

40.Hydraulic control means 50 ... Hydraulic module

51.Master cylinder 52 ... Normal open solenoid valve

53 ... Normal Close Solenoid Valve 54 ... Hydraulic Pump

55 Motor 60 Pulse Width Modulator

70 ... Memory

The present invention relates to a control method of an anti-lock brake system of a vehicle, and more particularly, to generate the maximum braking force of the wheel pressure according to a situation in which the wheel is recovered (accelerated) through linear flow control (LFC). The control method of the anti-lock brake system of the vehicle to properly boost up to the pressure level for.

In general, a vehicle is 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.

1 is a view showing a schematic configuration for explaining a general ABS.

As shown in FIG. 1, the electronic controller 10 analyzes the current wheel speeds transmitted from the wheel speed detector 20 and the current braking values transmitted from the brake detector 30 to determine the current driving situation. Generates an appropriate ABS control value suitable for the hydraulic control means 40 in accordance with the ABS control value controls the hydraulic module 50. That is, the electronic control apparatus 10 estimates the vehicle speed by using the wheel rotation speed detection sensor installed in the front and rear wheels of the vehicle during braking, and based on the deceleration and {(body speed-wheel speed) / body speed} × 100 ( %)} Estimates the current slip rate. The electronic control apparatus 10 predicts the occurrence of the fixed state of the vehicle by using the estimated data described above as an input variable, and closes the wheel speed to the vehicle body speed by reducing the brake pressure using the hydraulic control means 40 before. . Then, a series of operations of braking the wheels by increasing the brake pressure before the speed of the wheel exceeds a certain value is repeated to control to maintain the slip ratio of the braking vehicle in a desirable state.

2 is a view showing a general ABS hydraulic circuit diagram.

As shown in Fig. 2, the braking hydraulic pressure is formed in the master cylinder 51 by the operation of the brake pedal 30a by the driver, and the braking hydraulic pressure is the inlet of the front wheels FL, FR and the rear wheels RL, RR. Normally open solenoid valves (NO) 52 provided on the side and normal closed solenoid valves (NC) 53 provided on the outlet side are transmitted to the front and rear wheel cylinders FL, FR, RL and RR. In addition, a pair of hydraulic pumps 54 are connected to the low pressure accumulator LPA in which oil discharged from the wheel cylinder side is temporarily stored, and the hydraulic pump 54 is driven by the motor 55 to operate the low pressure accumulator LPA. The oil stored in the pump is delivered to the high pressure accumulator (HPA). The high pressure accumulator (HPA) attenuates pressure pulsations due to the operation of the pump 54. In this way, the braking pressure is transmitted to the wheel cylinder, and the braking force is exerted. At this time, if the friction with the road surface is insufficient, causing excessive slip ratio, and the wheel locking occurs, the ABS control unit closes the inlet solenoid valve (NO) of the wheel cylinder and exits. Open the side solenoid valve (NC) to depressurize, and then close both the inlet and outlet solenoid valves (NO) (NC) to maintain the braking pressure, then open the inlet solenoid valve (NO) and open the outlet solenoid valve ( ABS control is performed to close and boost the NC). The ABS control operation keeps the slip ratio in a certain range during braking and prevents locking of the wheels, so that sufficient frictional force is transmitted to the road surface and the braking distance can be shortened.

However, such a conventional ABS can simply or completely open the solenoid valve (NO) (NC) by switching the solenoid valve (NO) only when the slip ratio reaches within a certain range during braking or when a signal is detected that the wheel is fully recovered. There was a problem that the braking force of ABS is not sufficiently secured because the wheel pressure is increased by closing.

Therefore, there is a need for improving the braking force of ABS by increasing the wheel pressure by appropriately controlling the solenoid valves according to various situations such as road conditions and wheel recovery conditions.

Therefore, the present invention was devised to solve the above-mentioned problems, and the braking force of ABS by appropriately increasing the wheel pressure to a pressure level for generating the maximum braking force according to the situation where the wheel is recovered (accelerated) through linear flow control. It is an object of the present invention to provide a control method of an anti-lock brake system of a vehicle having an improved structure to improve the efficiency of the vehicle.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the claims.

According to the present invention for achieving the above object, in the control method of the anti-lock brake system of the vehicle, it is determined whether the wheel speed reaches the inflection point, which is an increase point without deceleration by the depressurization of the wheel pressure during anti-lock brake braking. When the wheel speed reaches the inflection point, the road surface is determined by using the deceleration of the vehicle, and a predetermined PWM duty ratio is provided to detect the boost slope corresponding to the determined road surface, and increase the detected slope. When the wheel acceleration is increased by determining whether the wheel acceleration is increased, it is determined whether the wheel acceleration is higher than the preset reference acceleration, and when the wheel acceleration is higher than the reference acceleration, the pressure is increased by the maximum boost slope.

When the wheel acceleration does not increase higher than the preset reference acceleration, the controller further determines whether to reach the stable region, and when reaching the stable region, increases the pressure to a predetermined lower slope than the increase slope according to the road surface.

When it does not reach the stable region, it is characterized in that the pressure is increased by the pressure gradient along the road surface.

When the wheel acceleration is maintained without increasing, the wheel pressure is maintained.

When the wheel acceleration is decelerated without increasing, the wheel pressure is reduced.

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

First, Figure 3 shows a control flow diagram for the anti-lock brake control method of a vehicle according to a preferred embodiment of the present invention.

Referring to FIG. 3 with reference to FIGS. 1 and 2, when the driver suddenly brakes in a dangerous situation, the wheel speed decreases rapidly, which is input to the electronic controller 10 through the wheel speed detection unit 20. do.

The microcomputer mounted on the electronic controller 10 calculates an appropriate speed value suitable for the current driving situation by using the wheel speed, and performs control according to the calculated speed value. If the slip generated due to the difference between the wheel speed and the body speed exceeds a predetermined threshold, the microcomputer controls the hydraulic module 50 to reduce the wheel pressure.

As a result, the wheel pressure is reduced and the brake speed is restored (increased) despite the braking state, and the wheel speed reaches a stable state in which the wheel speed reaches the vehicle speed and a certain slip.

At this time, in the present invention, it is determined whether the wheel speed reaches an inflection point which is a point where the wheel speed increases without being decelerated any more by the decompression of the wheel pressure (S300).

When the wheel speed reaches the inflection point, the road surface is determined using the deceleration of the vehicle (S301).

The road surface is a sliding surface, and the deceleration stage of the road surface may be determined using the deceleration of the vehicle. The deceleration stage of the road surface may be classified into at least three stages (low, medium, and high) according to the deceleration degree of the vehicle. For example, roads with relatively slow deceleration such as ice roads or downhill roads can be classified into "low" stages, and roads with relatively slow deceleration such as asphalt or hills can be categorized as "high" stages.

On the other hand, linear flow control (hereinafter referred to as LFC) instead of simply opening or closing completely the solenoid valve that controls the braking torque of the wheel by adjusting the brake fluid supplied to the wheel cylinder of each wheel. The pulse width modulation (PWM) method of controlling the duty ratio of the current supplied to the solenoid valve for each predetermined cycle is a method of smoothly increasing or decreasing the braking force of the wheel by adjusting the opening degree of the valve.

The anti-lock brake control method of the present invention applies the LFC control to ensure the stability of the control by adjusting the duty ratio of the cycle.

After determining the deceleration stage of the road surface as described above, the pulse width modulator 60 adjusts the PWM duty ratio provided to the normally open solenoid valve 52 to detect the increase in slope of the wheel pressure corresponding to the determined road surface. It is configured (S302).

That is, instead of opening the normally open solenoid valve 52 at the same time in the boosting mode through the PWM control, only a part of the opening is opened initially, and then a little more is opened so that the wheel pressure gradually increases linearly. The detection is divided into stages (high, medium, and low) corresponding to the deceleration stage of the completed road surface.

More specifically, for example, by setting and storing the boosting slope according to the deceleration stage of the road surface in the memory 70 connected to the electronic control apparatus 10, the slope of the boosting according to the determined deceleration stage of the road surface is preset. It can be detected easily.

After performing the above-described process of detecting the increase inclination, it is determined whether the wheel acceleration is increased (S303), and when it is determined that the wheel acceleration is increased, it is further determined whether the wheel acceleration is higher than a preset reference acceleration (S304). ).

Here, the reference acceleration is an acceleration that is a reference for measuring the degree of increase of the wheel acceleration, the reference acceleration is preferably stored in various values according to the structure and characteristics of the vehicle.

If the wheel acceleration is accelerated (recovered) more rapidly than the reference acceleration during the unit cycle, it is controlled to increase the pressure by the maximum boost slope (S305).

For example, when the wheel acceleration is 10g or more, it is switched to the maximum boosting slope mode, which is a mode in which the maximum boosting slope is boosted, so as to prevent overshoot due to rapid acceleration (recovery) of the wheel. However, the number of control cycles for maintaining the maximum boost slope mode is controlled so as not to exceed the number of decompression cycles.

When the wheel acceleration is accelerated to a predetermined reference acceleration or lower than the reference acceleration, it is further determined whether the stable acceleration is reached (S306).

 That is, it is determined whether the wheel speed reaches a stable area which reaches within a certain slip with the vehicle speed, and when the wheel speed reaches the stable area, the control is performed to increase the pressure by a predetermined lower slope than the increase slope according to the road surface (S307).

A predetermined lower slope than the boost slope according to the road surface is an inclination for maintaining the maximum braking pressure to secure the braking force, and thus the degree of inclination may be differently controlled according to the structure and the nature of the vehicle.

On the other hand, if it does not reach the stable region, the pressure is increased by the pressure gradient along the road surface (S308).

In step S303, the wheel acceleration does not increase and is determined to be kept constant (S309). When the wheel acceleration is kept constant, the wheel pressure is maintained (S310), and when the wheel acceleration is decelerated, the wheel pressure is decreased. The pressure is reduced (S311).

The degree of recovery of the wheel speed is detected through the speed difference of the wheels (speed difference between the previous cycle and the current cycle) and the wheel deceleration / acceleration, and the wheel speed difference is reduced to enter within a certain speed difference or the wheel acceleration is within a constant value. When entering, the current wheel pressure is maintained, and when the acceleration of the wheel is converted to a negative value, the wheel pressure is reduced again to recover the wheel speed.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this, The person of ordinary skill in the art to which this invention belongs, Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

According to the control method of the anti-lock brake system of the vehicle as described above, according to the situation where the wheel is recovered (accelerated) through the linear flow control by appropriately increasing the wheel pressure to a pressure level for generating the maximum braking force It creates the effect of improving the braking force of ABS.

Claims (5)

In the control method of the anti-lock brake system of the vehicle, When anti-lock brake braking, it is determined whether the wheel speed reaches the inflection point, which is an increase point without deceleration by the depressurization of the wheel pressure, When the wheel speed reaches the inflection point, using the deceleration of the vehicle to determine the deceleration step of the predetermined road surface according to the degree of deceleration, and provides a predetermined PWM duty ratio to increase the pressure corresponding to the deceleration step of the road surface determined Detect the slope and increase the pressure with the detected boost slope, If the wheel acceleration is increased by determining whether the wheel acceleration is increased, it is determined whether the wheel acceleration is higher than a predetermined reference acceleration, If the wheel acceleration is higher than the reference acceleration, the control method of the anti-lock brake system of the vehicle to increase by the maximum boost slope. The method of claim 1, When the wheel acceleration does not increase higher than the preset reference acceleration, it is further determined whether to reach the stable region, and when reaching the stable region, the pressure is increased by a predetermined lower slope than the increase slope according to the deceleration step of the road surface. Control method of vehicle anti-lock brake system. 3. The method of claim 2, If it does not reach the stable area, the control method of the anti-lock brake system of the vehicle, characterized in that for increasing the pressure in accordance with the deceleration step according to the deceleration step of the road surface. The method of claim 1, And if the wheel acceleration is maintained without increasing, the wheel pressure is maintained. The method of claim 4, wherein And decelerating the wheel pressure when the wheel acceleration is decelerated without increasing the wheel acceleration.

Images