KR100990911B1 - Anti-lock brake control method - Google Patents

Abstract

According to the present invention, in the ABS control when the vehicle is turning, ABS control is performed on the turning outer wheel based on the first body speed estimated from the wheel speed of the turning outer wheel, and the turning inner wheel has relatively low road friction. For the ABS control at the time of turning the vehicle by performing the ABS control based on the compensated second body speed after compensating the second body speed estimated from the wheel speed of the turning inner wheel using the first body speed. Improves steering and turning stability of the vehicle.

To this end, the present invention detects the wheel speed of the turning outer wheel and the wheel speed of the turning inner wheel, respectively, in ABS control during vehicle turning, estimates the first vehicle body speed from the detected wheel speed of the turning inner wheel, The second body speed is estimated from the wheel speed of the turning outer wheel, and the estimated first body speed is compensated on the basis of the preset reference speed so as to correspond to the estimated second body speed. ABS control so that the wheel slip estimated from the secondary body speed reaches the target slip, and ABS control so that the wheel slip estimated from the compensated first body speed reaches the target slip for the turning inner wheel.

Description

CONTROL METHOD FOR ANTI-LOCK BRAKE CONTROL SYSTEM}

1 is a hydraulic circuit diagram of an antilock brake system according to the present invention.

2 is a control flowchart of an antilock brake control method according to the present invention.

FIG. 3 is a view for explaining a vehicle speed Vin by the inner wheel of the turning and a vehicle speed Vout by the outer wheel of the turning when the ABS control is operated while turning the vehicle in FIG. 2.

FIG. 4 is a speed difference (?? V) between the vehicle body speed Vout by the turning outer wheel and the vehicle speed Vin by the turning inner wheel when the ABS control is operated in the normal turning of the vehicle in FIG. It is a graph for explaining the relationship between the vehicle body speed Vout by the outer wheel.

[Description of the Reference Numerals]

MC: Master cylinder

PC1 ~ PC4: Normally open inlet valve

PC5 ~ PC8: Normally closed outlet valve

WS1 ~ WS4: Wheel speed sensor 10: Electronic control unit (ECU)

The present invention relates to an anti-lock brake control method, and more particularly to an anti-lock brake control method that can further improve the steering and turning stability of the vehicle during anti-lock brake control (ABS) when turning the vehicle. .

In general, an anti-lock brake system (hereinafter referred to as ABS) detects slippage (slip) of wheels caused by sudden braking or by braking on slippery road surfaces, and accordingly the wheel cylinder of each wheel. It is a system that controls the vehicle so that the vehicle can be stopped at the shortest distance while securing proper cornering force and maintaining steering stability by reducing, maintaining or increasing the brake hydraulic pressure applied.

The antilock brake system performs ABS control when the slip value of the wheel, which is calculated based on the wheel speed detected from the wheel speed sensor and the body speed estimated according to the wheel speed, reaches a preset slip value.

Conventionally, when controlling ABS while the vehicle is turning, the body speed is estimated from the wheel speed of the turning outer wheel, and the ABS control is performed so that the amount of each wheel slip for the inner and outer turning wheels reaches the target slip amount based on the body speed. Perform At this time, the value obtained by subtracting the estimated body speed from the wheel speed from the wheel speed detected by the wheel speed sensor provided in each wheel by the body speed is defined as the slip amount.

In general, when the vehicle is turning, the load movement occurs from the inside of the turning radius of the vehicle to the outside, so that the turning inner wheel has a lower road traction than the turning outer wheel. A relatively large slip amount occurs even if it is added.

However, conventionally, such a phenomenon is not taken into account, and the same is true for the turning inner wheel based on the body speed estimated from the wheel speed of the turning outer wheel which is relatively faster than the wheel speed of the turning inner wheel during ABS control. Since the slip control is performed, steering and turning stability of the vehicle are relatively poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an anti-lock brake control method which can further improve steering and turning stability of the vehicle during ABS control when the vehicle is turning.

The anti-lock brake control method of the present invention for achieving the above object is to detect the wheel speed of the turning outer wheel and the wheel speed of the turning inner wheel, respectively, in ABS control during vehicle turning, and the wheel of the detected turning outer wheel Estimating a first vehicle body speed from the speed, estimating a second vehicle body speed from the detected wheel speed of the turning inner wheel, and based on the reference speed preset to correspond to the estimated first vehicle body speed; Compensating secondary body speed, ABS controlling the wheel slip estimated from the estimated first body speed for the turning outer wheel to reach a target slip, and estimating from the compensated second body speed for the turning inner wheel It is characterized in that the ABS control so that the wheel slip to reach the target slip.

The second body speed is compensated by an average speed between the preset reference speed and the second body speed.

When the estimated second body speed is lower than the preset reference speed, the second body speed is compensated for.

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

1 is a hydraulic circuit diagram of an antilock brake system according to the present invention. As illustrated in FIG. 1, the master cylinder MC generates brake pressure by the operation of the vacuum booster VB by the pressing of the brake pedal BP.

This master cylinder (MC) has two chambers (MCP, MCS), the first chamber (MCP) and front wheel right wheel to control the brake hydraulic pressure transmitted from the master cylinder (MC) to the wheel cylinder (WFR, WRL) The normal open cut valve SC1 is provided in the hydraulic line MF between the wheel cylinders WFR and WRL respectively installed at the FR and the rear wheel left wheel RL.

In addition, the normal open inlet valves PC1 and PC2 are provided in the hydraulic lines MFr and MFl between the normal open cut valve SC1 and the wheel cylinders WFR and WRL. Further, the brake fluid is provided with normal closed outlet valves PC5 and PC6 on the outlet side of the wheel cylinders WFR and WRL. The low pressure accumulator RS1 temporarily storing the brake fluid discharged from the wheel cylinders WFR, WRL and the brake fluid stored in the low pressure accumulator RS1 are forced to the outlet side of the normal closed outlet valves PC5 and PC6. A hydraulic pump HP1 and a motor M for reflux are provided.

On the other hand, in the hydraulic circuit of the front wheel left wheel FL and the rear wheel right wheel RR, the respective components are configured in the same way as the hydraulic circuit of the front wheel right wheel FR and the rear wheel left wheel RL. For reference, reference numerals WS1 to WS4 denote wheel speed sensors.

The cut valves SC1 and SC2, the normally open inlet valves PC1 to PC4, the normal closed outlet valves PC5 to PC8, and the hydraulic pumps HP1 and HP2 in FIG. Is operated by

The anti-lock brake system having such a configuration is normally open inlet valves P1 to P4 in the state of closing the normal claw outlet valves P5 to P8 when the braking pressure provided to each wheel side is maintained during ABS control. In order to reduce the braking pressure provided on each wheel, the normal claw outlet valves P5 to P8 are opened. In addition, to increase the braking pressure on each wheel side, operate the motor M with the normal closed type outlet valves P5 to P8 closed and drive the hydraulic pumps HP1 and HP2. Open the valves P1 to P4.

In the present invention, as described above, in the ABS control while the vehicle is turning, the first body speed is estimated from the wheel speed of the turning outer wheel, and the amount of each wheel slip determined based on the first body speed is the target slip amount. Instead of the conventional method of performing ABS control irrespective of the turning inner and outer wheels so as to reach, the first and second body speeds are estimated separately by the turning inner and outer wheels, and the reliable outer outer wheels As for the conventional method, ABS control is performed on the basis of the first body speed estimated from the wheel speed of the turning outer wheel, and the wheel speed of the turning inner wheel is estimated for the turning outer wheel whose road friction is relatively low. After compensating the second body speed using the first body speed and performing ABS control based on the compensated second body speed, Even during control, steering and turning stability of the vehicle can be further improved.

In more detail, as shown in FIG. 2, first, in step S100, the electronic control unit ECU determines whether the vehicle is turning. The turning judgment of the vehicle can be known by processing information obtained from sensors for obtaining vehicle attitude information such as a yaw rate sensor and a lateral acceleration sensor or by using a speed difference between left and right wheels.

In addition, the ABS control start condition is determined in step S101.

If it is determined in step S101 that the ABS control start condition, in step S102, each wheel speed of the turning inner wheel is detected through the wheel speed sensor provided in the turning inner wheel. And, as shown in FIG. 3, the second vehicle body speed Vin by the turning inner wheel is estimated from each wheel speed of the turning inner wheel detected in step S103.

Further, in step S104, each wheel speed of the turning outer wheel is detected through the wheel speed sensor provided in the turning outer wheel. As shown in FIG. 3, the first vehicle body speed Vout due to the turning outer wheel is estimated from the second vehicle body speed from each wheel speed of the turning outer wheel detected in step S105.

Then, in step S106, the speed difference between these two (?? V = Vout-Vin) is obtained using the second vehicle body speed Vin estimated in step S103 and the first vehicle body speed Vout estimated in step S105. ), And in step S107, the reference body speed Vin_ref by the turning outer wheels preset for the same turning situation is determined through experiments corresponding to the first body speed Vout using the graph of FIG. . Then, in step S108, the speed difference (?? Vref = Vin_ref-Vin) between Vin-ref and Vin is determined.

If ?? V is greater than ?? Vref in step S109, the magnitude of ?? V is greater than ?? Vref, and in step S100, the second vehicle speed Vin is compensated with the compensated second vehicle speed Vin_compensated. . In this case, Vin_compensated is a value obtained by dividing the sum of Vin and Vin_ref by 2, that is, an average speed value of Vin and Vin_ref.

Afterwards, in step S111, ABS control is performed to reach the target slip for each wheel slip determined based on the compensated second body speed Vin_compensated for the turning inner wheel,

For the turning outer wheels, ABS control is performed to reach each target slip determined on the basis of the first vehicle body speed Vout.

For example, if the ABS control is activated when the vehicle is turning and the vehicle body speed by the turning inner wheel is 96 KPH and the first vehicle body speed Vout is 100 KPH, as shown in FIG. 4, the first vehicle body speed Vout is 100 KPH. If V is 2KPH, it is normal. For this purpose, the reference speed of the second body speed should be 98 KPH, but since the actually measured second body speed Vin is 96 KPH, it is necessary to compensate for the second body speed Vin. To this end, the present invention compensates the average vehicle speed Vin_compensated as the compensated second vehicle speed Vin_compensated to the average speed value 97KPH of Vin and Vin_ref, and compensates the compensated second vehicle speed Vin_compensated (97KPH). ABS control the turning inner wheels so that each wheel slip of the turning inner wheels determined on the basis of) reaches the target slip.

As described above in detail, in the ABS control at the time of turning the vehicle, the turning outer wheel is subjected to the ABS control based on the first body speed estimated from the wheel speed of the turning outer wheel, and the road frictional force is relatively lowered. As for the turning inner wheel, the ABS is carried out by compensating the second body speed estimated from the wheel speed of the turning inner wheel using the first body speed and then performing ABS control based on the compensated second body speed. Also in control, there is an effect of further improving steering and turning stability of the vehicle.

Claims (3)

In the ABS control at the time of turning the vehicle, the wheel speed of the turning outer wheel and the wheel speed of the turning inner wheel are respectively detected, Estimating a first vehicle body speed from the detected wheel speed of the turning outer wheel, estimating a second vehicle body speed from the detected wheel speed of the inner wheel turning, Compensating the estimated second body speed based on a reference speed preset to correspond to the estimated first body speed, The ABS control is performed such that the wheel slip estimated from the estimated first body speed reaches the target slip for the turning outer wheel, and the wheel slip estimated from the compensated second body speed is adjusted to the target slip for the turning inner wheel. ABS control to reach the anti-lock brake control method. The method of claim 1, wherein the second body speed is compensated by an average speed between the preset reference speed and the second body speed. The anti-lock brake control method according to claim 1 or 2, wherein the second vehicle body speed is compensated if the estimated second vehicle body speed is lower than the preset reference speed.

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